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
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 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 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) 1988-2003 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++.
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 HP-UX (11.x and later only?), @value{GDBN} provides support for
2293 debugging programs that create additional processes using the
2294 @code{fork} or @code{vfork} function.
2296 By default, when a program forks, @value{GDBN} will continue to debug
2297 the parent process and the child process will run unimpeded.
2299 If you want to follow the child process instead of the parent process,
2300 use the command @w{@code{set follow-fork-mode}}.
2303 @kindex set follow-fork-mode
2304 @item set follow-fork-mode @var{mode}
2305 Set the debugger response to a program call of @code{fork} or
2306 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2307 process. The @var{mode} can be:
2311 The original process is debugged after a fork. The child process runs
2312 unimpeded. This is the default.
2315 The new process is debugged after a fork. The parent process runs
2319 The debugger will ask for one of the above choices.
2322 @item show follow-fork-mode
2323 Display the current debugger response to a @code{fork} or @code{vfork} call.
2326 If you ask to debug a child process and a @code{vfork} is followed by an
2327 @code{exec}, @value{GDBN} executes the new target up to the first
2328 breakpoint in the new target. If you have a breakpoint set on
2329 @code{main} in your original program, the breakpoint will also be set on
2330 the child process's @code{main}.
2332 When a child process is spawned by @code{vfork}, you cannot debug the
2333 child or parent until an @code{exec} call completes.
2335 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2336 call executes, the new target restarts. To restart the parent process,
2337 use the @code{file} command with the parent executable name as its
2340 You can use the @code{catch} command to make @value{GDBN} stop whenever
2341 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2342 Catchpoints, ,Setting catchpoints}.
2345 @chapter Stopping and Continuing
2347 The principal purposes of using a debugger are so that you can stop your
2348 program before it terminates; or so that, if your program runs into
2349 trouble, you can investigate and find out why.
2351 Inside @value{GDBN}, your program may stop for any of several reasons,
2352 such as a signal, a breakpoint, or reaching a new line after a
2353 @value{GDBN} command such as @code{step}. You may then examine and
2354 change variables, set new breakpoints or remove old ones, and then
2355 continue execution. Usually, the messages shown by @value{GDBN} provide
2356 ample explanation of the status of your program---but you can also
2357 explicitly request this information at any time.
2360 @kindex info program
2362 Display information about the status of your program: whether it is
2363 running or not, what process it is, and why it stopped.
2367 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2368 * Continuing and Stepping:: Resuming execution
2370 * Thread Stops:: Stopping and starting multi-thread programs
2374 @section Breakpoints, watchpoints, and catchpoints
2377 A @dfn{breakpoint} makes your program stop whenever a certain point in
2378 the program is reached. For each breakpoint, you can add conditions to
2379 control in finer detail whether your program stops. You can set
2380 breakpoints with the @code{break} command and its variants (@pxref{Set
2381 Breaks, ,Setting breakpoints}), to specify the place where your program
2382 should stop by line number, function name or exact address in the
2385 In HP-UX, SunOS 4.x, SVR4, and Alpha OSF/1 configurations, you can set
2386 breakpoints in shared libraries before the executable is run. There is
2387 a minor limitation on HP-UX systems: you must wait until the executable
2388 is run in order to set breakpoints in shared library routines that are
2389 not called directly by the program (for example, routines that are
2390 arguments in a @code{pthread_create} call).
2393 @cindex memory tracing
2394 @cindex breakpoint on memory address
2395 @cindex breakpoint on variable modification
2396 A @dfn{watchpoint} is a special breakpoint that stops your program
2397 when the value of an expression changes. You must use a different
2398 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2399 watchpoints}), but aside from that, you can manage a watchpoint like
2400 any other breakpoint: you enable, disable, and delete both breakpoints
2401 and watchpoints using the same commands.
2403 You can arrange to have values from your program displayed automatically
2404 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2408 @cindex breakpoint on events
2409 A @dfn{catchpoint} is another special breakpoint that stops your program
2410 when a certain kind of event occurs, such as the throwing of a C@t{++}
2411 exception or the loading of a library. As with watchpoints, you use a
2412 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2413 catchpoints}), but aside from that, you can manage a catchpoint like any
2414 other breakpoint. (To stop when your program receives a signal, use the
2415 @code{handle} command; see @ref{Signals, ,Signals}.)
2417 @cindex breakpoint numbers
2418 @cindex numbers for breakpoints
2419 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2420 catchpoint when you create it; these numbers are successive integers
2421 starting with one. In many of the commands for controlling various
2422 features of breakpoints you use the breakpoint number to say which
2423 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2424 @dfn{disabled}; if disabled, it has no effect on your program until you
2427 @cindex breakpoint ranges
2428 @cindex ranges of breakpoints
2429 Some @value{GDBN} commands accept a range of breakpoints on which to
2430 operate. A breakpoint range is either a single breakpoint number, like
2431 @samp{5}, or two such numbers, in increasing order, separated by a
2432 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2433 all breakpoint in that range are operated on.
2436 * Set Breaks:: Setting breakpoints
2437 * Set Watchpoints:: Setting watchpoints
2438 * Set Catchpoints:: Setting catchpoints
2439 * Delete Breaks:: Deleting breakpoints
2440 * Disabling:: Disabling breakpoints
2441 * Conditions:: Break conditions
2442 * Break Commands:: Breakpoint command lists
2443 * Breakpoint Menus:: Breakpoint menus
2444 * Error in Breakpoints:: ``Cannot insert breakpoints''
2445 * Breakpoint related warnings:: ``Breakpoint address adjusted...''
2449 @subsection Setting breakpoints
2451 @c FIXME LMB what does GDB do if no code on line of breakpt?
2452 @c consider in particular declaration with/without initialization.
2454 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2457 @kindex b @r{(@code{break})}
2458 @vindex $bpnum@r{, convenience variable}
2459 @cindex latest breakpoint
2460 Breakpoints are set with the @code{break} command (abbreviated
2461 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2462 number of the breakpoint you've set most recently; see @ref{Convenience
2463 Vars,, Convenience variables}, for a discussion of what you can do with
2464 convenience variables.
2466 You have several ways to say where the breakpoint should go.
2469 @item break @var{function}
2470 Set a breakpoint at entry to function @var{function}.
2471 When using source languages that permit overloading of symbols, such as
2472 C@t{++}, @var{function} may refer to more than one possible place to break.
2473 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2475 @item break +@var{offset}
2476 @itemx break -@var{offset}
2477 Set a breakpoint some number of lines forward or back from the position
2478 at which execution stopped in the currently selected @dfn{stack frame}.
2479 (@xref{Frames, ,Frames}, for a description of stack frames.)
2481 @item break @var{linenum}
2482 Set a breakpoint at line @var{linenum} in the current source file.
2483 The current source file is the last file whose source text was printed.
2484 The breakpoint will stop your program just before it executes any of the
2487 @item break @var{filename}:@var{linenum}
2488 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2490 @item break @var{filename}:@var{function}
2491 Set a breakpoint at entry to function @var{function} found in file
2492 @var{filename}. Specifying a file name as well as a function name is
2493 superfluous except when multiple files contain similarly named
2496 @item break *@var{address}
2497 Set a breakpoint at address @var{address}. You can use this to set
2498 breakpoints in parts of your program which do not have debugging
2499 information or source files.
2502 When called without any arguments, @code{break} sets a breakpoint at
2503 the next instruction to be executed in the selected stack frame
2504 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2505 innermost, this makes your program stop as soon as control
2506 returns to that frame. This is similar to the effect of a
2507 @code{finish} command in the frame inside the selected frame---except
2508 that @code{finish} does not leave an active breakpoint. If you use
2509 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2510 the next time it reaches the current location; this may be useful
2513 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2514 least one instruction has been executed. If it did not do this, you
2515 would be unable to proceed past a breakpoint without first disabling the
2516 breakpoint. This rule applies whether or not the breakpoint already
2517 existed when your program stopped.
2519 @item break @dots{} if @var{cond}
2520 Set a breakpoint with condition @var{cond}; evaluate the expression
2521 @var{cond} each time the breakpoint is reached, and stop only if the
2522 value is nonzero---that is, if @var{cond} evaluates as true.
2523 @samp{@dots{}} stands for one of the possible arguments described
2524 above (or no argument) specifying where to break. @xref{Conditions,
2525 ,Break conditions}, for more information on breakpoint conditions.
2528 @item tbreak @var{args}
2529 Set a breakpoint enabled only for one stop. @var{args} are the
2530 same as for the @code{break} command, and the breakpoint is set in the same
2531 way, but the breakpoint is automatically deleted after the first time your
2532 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2535 @item hbreak @var{args}
2536 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2537 @code{break} command and the breakpoint is set in the same way, but the
2538 breakpoint requires hardware support and some target hardware may not
2539 have this support. The main purpose of this is EPROM/ROM code
2540 debugging, so you can set a breakpoint at an instruction without
2541 changing the instruction. This can be used with the new trap-generation
2542 provided by SPARClite DSU and some x86-based targets. These targets
2543 will generate traps when a program accesses some data or instruction
2544 address that is assigned to the debug registers. However the hardware
2545 breakpoint registers can take a limited number of breakpoints. For
2546 example, on the DSU, only two data breakpoints can be set at a time, and
2547 @value{GDBN} will reject this command if more than two are used. Delete
2548 or disable unused hardware breakpoints before setting new ones
2549 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2550 @xref{set remote hardware-breakpoint-limit}.
2554 @item thbreak @var{args}
2555 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2556 are the same as for the @code{hbreak} command and the breakpoint is set in
2557 the same way. However, like the @code{tbreak} command,
2558 the breakpoint is automatically deleted after the
2559 first time your program stops there. Also, like the @code{hbreak}
2560 command, the breakpoint requires hardware support and some target hardware
2561 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2562 See also @ref{Conditions, ,Break conditions}.
2565 @cindex regular expression
2566 @item rbreak @var{regex}
2567 Set breakpoints on all functions matching the regular expression
2568 @var{regex}. This command sets an unconditional breakpoint on all
2569 matches, printing a list of all breakpoints it set. Once these
2570 breakpoints are set, they are treated just like the breakpoints set with
2571 the @code{break} command. You can delete them, disable them, or make
2572 them conditional the same way as any other breakpoint.
2574 The syntax of the regular expression is the standard one used with tools
2575 like @file{grep}. Note that this is different from the syntax used by
2576 shells, so for instance @code{foo*} matches all functions that include
2577 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2578 @code{.*} leading and trailing the regular expression you supply, so to
2579 match only functions that begin with @code{foo}, use @code{^foo}.
2581 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2582 breakpoints on overloaded functions that are not members of any special
2585 @kindex info breakpoints
2586 @cindex @code{$_} and @code{info breakpoints}
2587 @item info breakpoints @r{[}@var{n}@r{]}
2588 @itemx info break @r{[}@var{n}@r{]}
2589 @itemx info watchpoints @r{[}@var{n}@r{]}
2590 Print a table of all breakpoints, watchpoints, and catchpoints set and
2591 not deleted, with the following columns for each breakpoint:
2594 @item Breakpoint Numbers
2596 Breakpoint, watchpoint, or catchpoint.
2598 Whether the breakpoint is marked to be disabled or deleted when hit.
2599 @item Enabled or Disabled
2600 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2601 that are not enabled.
2603 Where the breakpoint is in your program, as a memory address.
2605 Where the breakpoint is in the source for your program, as a file and
2610 If a breakpoint is conditional, @code{info break} shows the condition on
2611 the line following the affected breakpoint; breakpoint commands, if any,
2612 are listed after that.
2615 @code{info break} with a breakpoint
2616 number @var{n} as argument lists only that breakpoint. The
2617 convenience variable @code{$_} and the default examining-address for
2618 the @code{x} command are set to the address of the last breakpoint
2619 listed (@pxref{Memory, ,Examining memory}).
2622 @code{info break} displays a count of the number of times the breakpoint
2623 has been hit. This is especially useful in conjunction with the
2624 @code{ignore} command. You can ignore a large number of breakpoint
2625 hits, look at the breakpoint info to see how many times the breakpoint
2626 was hit, and then run again, ignoring one less than that number. This
2627 will get you quickly to the last hit of that breakpoint.
2630 @value{GDBN} allows you to set any number of breakpoints at the same place in
2631 your program. There is nothing silly or meaningless about this. When
2632 the breakpoints are conditional, this is even useful
2633 (@pxref{Conditions, ,Break conditions}).
2635 @cindex negative breakpoint numbers
2636 @cindex internal @value{GDBN} breakpoints
2637 @value{GDBN} itself sometimes sets breakpoints in your program for
2638 special purposes, such as proper handling of @code{longjmp} (in C
2639 programs). These internal breakpoints are assigned negative numbers,
2640 starting with @code{-1}; @samp{info breakpoints} does not display them.
2641 You can see these breakpoints with the @value{GDBN} maintenance command
2642 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
2645 @node Set Watchpoints
2646 @subsection Setting watchpoints
2648 @cindex setting watchpoints
2649 @cindex software watchpoints
2650 @cindex hardware watchpoints
2651 You can use a watchpoint to stop execution whenever the value of an
2652 expression changes, without having to predict a particular place where
2655 Depending on your system, watchpoints may be implemented in software or
2656 hardware. @value{GDBN} does software watchpointing by single-stepping your
2657 program and testing the variable's value each time, which is hundreds of
2658 times slower than normal execution. (But this may still be worth it, to
2659 catch errors where you have no clue what part of your program is the
2662 On some systems, such as HP-UX, @sc{gnu}/Linux and some other x86-based targets,
2663 @value{GDBN} includes support for
2664 hardware watchpoints, which do not slow down the running of your
2669 @item watch @var{expr}
2670 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
2671 is written into by the program and its value changes.
2674 @item rwatch @var{expr}
2675 Set a watchpoint that will break when watch @var{expr} is read by the program.
2678 @item awatch @var{expr}
2679 Set a watchpoint that will break when @var{expr} is either read or written into
2682 @kindex info watchpoints
2683 @item info watchpoints
2684 This command prints a list of watchpoints, breakpoints, and catchpoints;
2685 it is the same as @code{info break}.
2688 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
2689 watchpoints execute very quickly, and the debugger reports a change in
2690 value at the exact instruction where the change occurs. If @value{GDBN}
2691 cannot set a hardware watchpoint, it sets a software watchpoint, which
2692 executes more slowly and reports the change in value at the next
2693 statement, not the instruction, after the change occurs.
2695 When you issue the @code{watch} command, @value{GDBN} reports
2698 Hardware watchpoint @var{num}: @var{expr}
2702 if it was able to set a hardware watchpoint.
2704 Currently, the @code{awatch} and @code{rwatch} commands can only set
2705 hardware watchpoints, because accesses to data that don't change the
2706 value of the watched expression cannot be detected without examining
2707 every instruction as it is being executed, and @value{GDBN} does not do
2708 that currently. If @value{GDBN} finds that it is unable to set a
2709 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
2710 will print a message like this:
2713 Expression cannot be implemented with read/access watchpoint.
2716 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
2717 data type of the watched expression is wider than what a hardware
2718 watchpoint on the target machine can handle. For example, some systems
2719 can only watch regions that are up to 4 bytes wide; on such systems you
2720 cannot set hardware watchpoints for an expression that yields a
2721 double-precision floating-point number (which is typically 8 bytes
2722 wide). As a work-around, it might be possible to break the large region
2723 into a series of smaller ones and watch them with separate watchpoints.
2725 If you set too many hardware watchpoints, @value{GDBN} might be unable
2726 to insert all of them when you resume the execution of your program.
2727 Since the precise number of active watchpoints is unknown until such
2728 time as the program is about to be resumed, @value{GDBN} might not be
2729 able to warn you about this when you set the watchpoints, and the
2730 warning will be printed only when the program is resumed:
2733 Hardware watchpoint @var{num}: Could not insert watchpoint
2737 If this happens, delete or disable some of the watchpoints.
2739 The SPARClite DSU will generate traps when a program accesses some data
2740 or instruction address that is assigned to the debug registers. For the
2741 data addresses, DSU facilitates the @code{watch} command. However the
2742 hardware breakpoint registers can only take two data watchpoints, and
2743 both watchpoints must be the same kind. For example, you can set two
2744 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
2745 @strong{or} two with @code{awatch} commands, but you cannot set one
2746 watchpoint with one command and the other with a different command.
2747 @value{GDBN} will reject the command if you try to mix watchpoints.
2748 Delete or disable unused watchpoint commands before setting new ones.
2750 If you call a function interactively using @code{print} or @code{call},
2751 any watchpoints you have set will be inactive until @value{GDBN} reaches another
2752 kind of breakpoint or the call completes.
2754 @value{GDBN} automatically deletes watchpoints that watch local
2755 (automatic) variables, or expressions that involve such variables, when
2756 they go out of scope, that is, when the execution leaves the block in
2757 which these variables were defined. In particular, when the program
2758 being debugged terminates, @emph{all} local variables go out of scope,
2759 and so only watchpoints that watch global variables remain set. If you
2760 rerun the program, you will need to set all such watchpoints again. One
2761 way of doing that would be to set a code breakpoint at the entry to the
2762 @code{main} function and when it breaks, set all the watchpoints.
2765 @cindex watchpoints and threads
2766 @cindex threads and watchpoints
2767 @emph{Warning:} In multi-thread programs, watchpoints have only limited
2768 usefulness. With the current watchpoint implementation, @value{GDBN}
2769 can only watch the value of an expression @emph{in a single thread}. If
2770 you are confident that the expression can only change due to the current
2771 thread's activity (and if you are also confident that no other thread
2772 can become current), then you can use watchpoints as usual. However,
2773 @value{GDBN} may not notice when a non-current thread's activity changes
2776 @c FIXME: this is almost identical to the previous paragraph.
2777 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
2778 have only limited usefulness. If @value{GDBN} creates a software
2779 watchpoint, it can only watch the value of an expression @emph{in a
2780 single thread}. If you are confident that the expression can only
2781 change due to the current thread's activity (and if you are also
2782 confident that no other thread can become current), then you can use
2783 software watchpoints as usual. However, @value{GDBN} may not notice
2784 when a non-current thread's activity changes the expression. (Hardware
2785 watchpoints, in contrast, watch an expression in all threads.)
2788 @xref{set remote hardware-watchpoint-limit}.
2790 @node Set Catchpoints
2791 @subsection Setting catchpoints
2792 @cindex catchpoints, setting
2793 @cindex exception handlers
2794 @cindex event handling
2796 You can use @dfn{catchpoints} to cause the debugger to stop for certain
2797 kinds of program events, such as C@t{++} exceptions or the loading of a
2798 shared library. Use the @code{catch} command to set a catchpoint.
2802 @item catch @var{event}
2803 Stop when @var{event} occurs. @var{event} can be any of the following:
2807 The throwing of a C@t{++} exception.
2811 The catching of a C@t{++} exception.
2815 A call to @code{exec}. This is currently only available for HP-UX.
2819 A call to @code{fork}. This is currently only available for HP-UX.
2823 A call to @code{vfork}. This is currently only available for HP-UX.
2826 @itemx load @var{libname}
2828 The dynamic loading of any shared library, or the loading of the library
2829 @var{libname}. This is currently only available for HP-UX.
2832 @itemx unload @var{libname}
2833 @kindex catch unload
2834 The unloading of any dynamically loaded shared library, or the unloading
2835 of the library @var{libname}. This is currently only available for HP-UX.
2838 @item tcatch @var{event}
2839 Set a catchpoint that is enabled only for one stop. The catchpoint is
2840 automatically deleted after the first time the event is caught.
2844 Use the @code{info break} command to list the current catchpoints.
2846 There are currently some limitations to C@t{++} exception handling
2847 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
2851 If you call a function interactively, @value{GDBN} normally returns
2852 control to you when the function has finished executing. If the call
2853 raises an exception, however, the call may bypass the mechanism that
2854 returns control to you and cause your program either to abort or to
2855 simply continue running until it hits a breakpoint, catches a signal
2856 that @value{GDBN} is listening for, or exits. This is the case even if
2857 you set a catchpoint for the exception; catchpoints on exceptions are
2858 disabled within interactive calls.
2861 You cannot raise an exception interactively.
2864 You cannot install an exception handler interactively.
2867 @cindex raise exceptions
2868 Sometimes @code{catch} is not the best way to debug exception handling:
2869 if you need to know exactly where an exception is raised, it is better to
2870 stop @emph{before} the exception handler is called, since that way you
2871 can see the stack before any unwinding takes place. If you set a
2872 breakpoint in an exception handler instead, it may not be easy to find
2873 out where the exception was raised.
2875 To stop just before an exception handler is called, you need some
2876 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
2877 raised by calling a library function named @code{__raise_exception}
2878 which has the following ANSI C interface:
2881 /* @var{addr} is where the exception identifier is stored.
2882 @var{id} is the exception identifier. */
2883 void __raise_exception (void **addr, void *id);
2887 To make the debugger catch all exceptions before any stack
2888 unwinding takes place, set a breakpoint on @code{__raise_exception}
2889 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
2891 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
2892 that depends on the value of @var{id}, you can stop your program when
2893 a specific exception is raised. You can use multiple conditional
2894 breakpoints to stop your program when any of a number of exceptions are
2899 @subsection Deleting breakpoints
2901 @cindex clearing breakpoints, watchpoints, catchpoints
2902 @cindex deleting breakpoints, watchpoints, catchpoints
2903 It is often necessary to eliminate a breakpoint, watchpoint, or
2904 catchpoint once it has done its job and you no longer want your program
2905 to stop there. This is called @dfn{deleting} the breakpoint. A
2906 breakpoint that has been deleted no longer exists; it is forgotten.
2908 With the @code{clear} command you can delete breakpoints according to
2909 where they are in your program. With the @code{delete} command you can
2910 delete individual breakpoints, watchpoints, or catchpoints by specifying
2911 their breakpoint numbers.
2913 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
2914 automatically ignores breakpoints on the first instruction to be executed
2915 when you continue execution without changing the execution address.
2920 Delete any breakpoints at the next instruction to be executed in the
2921 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
2922 the innermost frame is selected, this is a good way to delete a
2923 breakpoint where your program just stopped.
2925 @item clear @var{function}
2926 @itemx clear @var{filename}:@var{function}
2927 Delete any breakpoints set at entry to the function @var{function}.
2929 @item clear @var{linenum}
2930 @itemx clear @var{filename}:@var{linenum}
2931 Delete any breakpoints set at or within the code of the specified line.
2933 @cindex delete breakpoints
2935 @kindex d @r{(@code{delete})}
2936 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
2937 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
2938 ranges specified as arguments. If no argument is specified, delete all
2939 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
2940 confirm off}). You can abbreviate this command as @code{d}.
2944 @subsection Disabling breakpoints
2946 @kindex disable breakpoints
2947 @kindex enable breakpoints
2948 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
2949 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
2950 it had been deleted, but remembers the information on the breakpoint so
2951 that you can @dfn{enable} it again later.
2953 You disable and enable breakpoints, watchpoints, and catchpoints with
2954 the @code{enable} and @code{disable} commands, optionally specifying one
2955 or more breakpoint numbers as arguments. Use @code{info break} or
2956 @code{info watch} to print a list of breakpoints, watchpoints, and
2957 catchpoints if you do not know which numbers to use.
2959 A breakpoint, watchpoint, or catchpoint can have any of four different
2960 states of enablement:
2964 Enabled. The breakpoint stops your program. A breakpoint set
2965 with the @code{break} command starts out in this state.
2967 Disabled. The breakpoint has no effect on your program.
2969 Enabled once. The breakpoint stops your program, but then becomes
2972 Enabled for deletion. The breakpoint stops your program, but
2973 immediately after it does so it is deleted permanently. A breakpoint
2974 set with the @code{tbreak} command starts out in this state.
2977 You can use the following commands to enable or disable breakpoints,
2978 watchpoints, and catchpoints:
2981 @kindex disable breakpoints
2983 @kindex dis @r{(@code{disable})}
2984 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
2985 Disable the specified breakpoints---or all breakpoints, if none are
2986 listed. A disabled breakpoint has no effect but is not forgotten. All
2987 options such as ignore-counts, conditions and commands are remembered in
2988 case the breakpoint is enabled again later. You may abbreviate
2989 @code{disable} as @code{dis}.
2991 @kindex enable breakpoints
2993 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
2994 Enable the specified breakpoints (or all defined breakpoints). They
2995 become effective once again in stopping your program.
2997 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
2998 Enable the specified breakpoints temporarily. @value{GDBN} disables any
2999 of these breakpoints immediately after stopping your program.
3001 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3002 Enable the specified breakpoints to work once, then die. @value{GDBN}
3003 deletes any of these breakpoints as soon as your program stops there.
3006 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3007 @c confusing: tbreak is also initially enabled.
3008 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3009 ,Setting breakpoints}), breakpoints that you set are initially enabled;
3010 subsequently, they become disabled or enabled only when you use one of
3011 the commands above. (The command @code{until} can set and delete a
3012 breakpoint of its own, but it does not change the state of your other
3013 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3017 @subsection Break conditions
3018 @cindex conditional breakpoints
3019 @cindex breakpoint conditions
3021 @c FIXME what is scope of break condition expr? Context where wanted?
3022 @c in particular for a watchpoint?
3023 The simplest sort of breakpoint breaks every time your program reaches a
3024 specified place. You can also specify a @dfn{condition} for a
3025 breakpoint. A condition is just a Boolean expression in your
3026 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3027 a condition evaluates the expression each time your program reaches it,
3028 and your program stops only if the condition is @emph{true}.
3030 This is the converse of using assertions for program validation; in that
3031 situation, you want to stop when the assertion is violated---that is,
3032 when the condition is false. In C, if you want to test an assertion expressed
3033 by the condition @var{assert}, you should set the condition
3034 @samp{! @var{assert}} on the appropriate breakpoint.
3036 Conditions are also accepted for watchpoints; you may not need them,
3037 since a watchpoint is inspecting the value of an expression anyhow---but
3038 it might be simpler, say, to just set a watchpoint on a variable name,
3039 and specify a condition that tests whether the new value is an interesting
3042 Break conditions can have side effects, and may even call functions in
3043 your program. This can be useful, for example, to activate functions
3044 that log program progress, or to use your own print functions to
3045 format special data structures. The effects are completely predictable
3046 unless there is another enabled breakpoint at the same address. (In
3047 that case, @value{GDBN} might see the other breakpoint first and stop your
3048 program without checking the condition of this one.) Note that
3049 breakpoint commands are usually more convenient and flexible than break
3051 purpose of performing side effects when a breakpoint is reached
3052 (@pxref{Break Commands, ,Breakpoint command lists}).
3054 Break conditions can be specified when a breakpoint is set, by using
3055 @samp{if} in the arguments to the @code{break} command. @xref{Set
3056 Breaks, ,Setting breakpoints}. They can also be changed at any time
3057 with the @code{condition} command.
3059 You can also use the @code{if} keyword with the @code{watch} command.
3060 The @code{catch} command does not recognize the @code{if} keyword;
3061 @code{condition} is the only way to impose a further condition on a
3066 @item condition @var{bnum} @var{expression}
3067 Specify @var{expression} as the break condition for breakpoint,
3068 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3069 breakpoint @var{bnum} stops your program only if the value of
3070 @var{expression} is true (nonzero, in C). When you use
3071 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3072 syntactic correctness, and to determine whether symbols in it have
3073 referents in the context of your breakpoint. If @var{expression} uses
3074 symbols not referenced in the context of the breakpoint, @value{GDBN}
3075 prints an error message:
3078 No symbol "foo" in current context.
3083 not actually evaluate @var{expression} at the time the @code{condition}
3084 command (or a command that sets a breakpoint with a condition, like
3085 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3087 @item condition @var{bnum}
3088 Remove the condition from breakpoint number @var{bnum}. It becomes
3089 an ordinary unconditional breakpoint.
3092 @cindex ignore count (of breakpoint)
3093 A special case of a breakpoint condition is to stop only when the
3094 breakpoint has been reached a certain number of times. This is so
3095 useful that there is a special way to do it, using the @dfn{ignore
3096 count} of the breakpoint. Every breakpoint has an ignore count, which
3097 is an integer. Most of the time, the ignore count is zero, and
3098 therefore has no effect. But if your program reaches a breakpoint whose
3099 ignore count is positive, then instead of stopping, it just decrements
3100 the ignore count by one and continues. As a result, if the ignore count
3101 value is @var{n}, the breakpoint does not stop the next @var{n} times
3102 your program reaches it.
3106 @item ignore @var{bnum} @var{count}
3107 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3108 The next @var{count} times the breakpoint is reached, your program's
3109 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3112 To make the breakpoint stop the next time it is reached, specify
3115 When you use @code{continue} to resume execution of your program from a
3116 breakpoint, you can specify an ignore count directly as an argument to
3117 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3118 Stepping,,Continuing and stepping}.
3120 If a breakpoint has a positive ignore count and a condition, the
3121 condition is not checked. Once the ignore count reaches zero,
3122 @value{GDBN} resumes checking the condition.
3124 You could achieve the effect of the ignore count with a condition such
3125 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3126 is decremented each time. @xref{Convenience Vars, ,Convenience
3130 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3133 @node Break Commands
3134 @subsection Breakpoint command lists
3136 @cindex breakpoint commands
3137 You can give any breakpoint (or watchpoint or catchpoint) a series of
3138 commands to execute when your program stops due to that breakpoint. For
3139 example, you might want to print the values of certain expressions, or
3140 enable other breakpoints.
3145 @item commands @r{[}@var{bnum}@r{]}
3146 @itemx @dots{} @var{command-list} @dots{}
3148 Specify a list of commands for breakpoint number @var{bnum}. The commands
3149 themselves appear on the following lines. Type a line containing just
3150 @code{end} to terminate the commands.
3152 To remove all commands from a breakpoint, type @code{commands} and
3153 follow it immediately with @code{end}; that is, give no commands.
3155 With no @var{bnum} argument, @code{commands} refers to the last
3156 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3157 recently encountered).
3160 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3161 disabled within a @var{command-list}.
3163 You can use breakpoint commands to start your program up again. Simply
3164 use the @code{continue} command, or @code{step}, or any other command
3165 that resumes execution.
3167 Any other commands in the command list, after a command that resumes
3168 execution, are ignored. This is because any time you resume execution
3169 (even with a simple @code{next} or @code{step}), you may encounter
3170 another breakpoint---which could have its own command list, leading to
3171 ambiguities about which list to execute.
3174 If the first command you specify in a command list is @code{silent}, the
3175 usual message about stopping at a breakpoint is not printed. This may
3176 be desirable for breakpoints that are to print a specific message and
3177 then continue. If none of the remaining commands print anything, you
3178 see no sign that the breakpoint was reached. @code{silent} is
3179 meaningful only at the beginning of a breakpoint command list.
3181 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3182 print precisely controlled output, and are often useful in silent
3183 breakpoints. @xref{Output, ,Commands for controlled output}.
3185 For example, here is how you could use breakpoint commands to print the
3186 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3192 printf "x is %d\n",x
3197 One application for breakpoint commands is to compensate for one bug so
3198 you can test for another. Put a breakpoint just after the erroneous line
3199 of code, give it a condition to detect the case in which something
3200 erroneous has been done, and give it commands to assign correct values
3201 to any variables that need them. End with the @code{continue} command
3202 so that your program does not stop, and start with the @code{silent}
3203 command so that no output is produced. Here is an example:
3214 @node Breakpoint Menus
3215 @subsection Breakpoint menus
3217 @cindex symbol overloading
3219 Some programming languages (notably C@t{++} and Objective-C) permit a
3220 single function name
3221 to be defined several times, for application in different contexts.
3222 This is called @dfn{overloading}. When a function name is overloaded,
3223 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3224 a breakpoint. If you realize this is a problem, you can use
3225 something like @samp{break @var{function}(@var{types})} to specify which
3226 particular version of the function you want. Otherwise, @value{GDBN} offers
3227 you a menu of numbered choices for different possible breakpoints, and
3228 waits for your selection with the prompt @samp{>}. The first two
3229 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3230 sets a breakpoint at each definition of @var{function}, and typing
3231 @kbd{0} aborts the @code{break} command without setting any new
3234 For example, the following session excerpt shows an attempt to set a
3235 breakpoint at the overloaded symbol @code{String::after}.
3236 We choose three particular definitions of that function name:
3238 @c FIXME! This is likely to change to show arg type lists, at least
3241 (@value{GDBP}) b String::after
3244 [2] file:String.cc; line number:867
3245 [3] file:String.cc; line number:860
3246 [4] file:String.cc; line number:875
3247 [5] file:String.cc; line number:853
3248 [6] file:String.cc; line number:846
3249 [7] file:String.cc; line number:735
3251 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3252 Breakpoint 2 at 0xb344: file String.cc, line 875.
3253 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3254 Multiple breakpoints were set.
3255 Use the "delete" command to delete unwanted
3261 @c @ifclear BARETARGET
3262 @node Error in Breakpoints
3263 @subsection ``Cannot insert breakpoints''
3265 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3267 Under some operating systems, breakpoints cannot be used in a program if
3268 any other process is running that program. In this situation,
3269 attempting to run or continue a program with a breakpoint causes
3270 @value{GDBN} to print an error message:
3273 Cannot insert breakpoints.
3274 The same program may be running in another process.
3277 When this happens, you have three ways to proceed:
3281 Remove or disable the breakpoints, then continue.
3284 Suspend @value{GDBN}, and copy the file containing your program to a new
3285 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3286 that @value{GDBN} should run your program under that name.
3287 Then start your program again.
3290 Relink your program so that the text segment is nonsharable, using the
3291 linker option @samp{-N}. The operating system limitation may not apply
3292 to nonsharable executables.
3296 A similar message can be printed if you request too many active
3297 hardware-assisted breakpoints and watchpoints:
3299 @c FIXME: the precise wording of this message may change; the relevant
3300 @c source change is not committed yet (Sep 3, 1999).
3302 Stopped; cannot insert breakpoints.
3303 You may have requested too many hardware breakpoints and watchpoints.
3307 This message is printed when you attempt to resume the program, since
3308 only then @value{GDBN} knows exactly how many hardware breakpoints and
3309 watchpoints it needs to insert.
3311 When this message is printed, you need to disable or remove some of the
3312 hardware-assisted breakpoints and watchpoints, and then continue.
3314 @node Breakpoint related warnings
3315 @subsection ``Breakpoint address adjusted...''
3316 @cindex breakpoint address adjusted
3318 Some processor architectures place constraints on the addresses at
3319 which breakpoints may be placed. For architectures thus constrained,
3320 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3321 with the constraints dictated by the architecture.
3323 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3324 a VLIW architecture in which a number of RISC-like instructions may be
3325 bundled together for parallel execution. The FR-V architecture
3326 constrains the location of a breakpoint instruction within such a
3327 bundle to the instruction with the lowest address. @value{GDBN}
3328 honors this constraint by adjusting a breakpoint's address to the
3329 first in the bundle.
3331 It is not uncommon for optimized code to have bundles which contain
3332 instructions from different source statements, thus it may happen that
3333 a breakpoint's address will be adjusted from one source statement to
3334 another. Since this adjustment may significantly alter @value{GDBN}'s
3335 breakpoint related behavior from what the user expects, a warning is
3336 printed when the breakpoint is first set and also when the breakpoint
3339 A warning like the one below is printed when setting a breakpoint
3340 that's been subject to address adjustment:
3343 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3346 Such warnings are printed both for user settable and @value{GDBN}'s
3347 internal breakpoints. If you see one of these warnings, you should
3348 verify that a breakpoint set at the adjusted address will have the
3349 desired affect. If not, the breakpoint in question may be removed and
3350 other breakpoints may be set which will have the desired behavior.
3351 E.g., it may be sufficient to place the breakpoint at a later
3352 instruction. A conditional breakpoint may also be useful in some
3353 cases to prevent the breakpoint from triggering too often.
3355 @value{GDBN} will also issue a warning when stopping at one of these
3356 adjusted breakpoints:
3359 warning: Breakpoint 1 address previously adjusted from 0x00010414
3363 When this warning is encountered, it may be too late to take remedial
3364 action except in cases where the breakpoint is hit earlier or more
3365 frequently than expected.
3367 @node Continuing and Stepping
3368 @section Continuing and stepping
3372 @cindex resuming execution
3373 @dfn{Continuing} means resuming program execution until your program
3374 completes normally. In contrast, @dfn{stepping} means executing just
3375 one more ``step'' of your program, where ``step'' may mean either one
3376 line of source code, or one machine instruction (depending on what
3377 particular command you use). Either when continuing or when stepping,
3378 your program may stop even sooner, due to a breakpoint or a signal. (If
3379 it stops due to a signal, you may want to use @code{handle}, or use
3380 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3384 @kindex c @r{(@code{continue})}
3385 @kindex fg @r{(resume foreground execution)}
3386 @item continue @r{[}@var{ignore-count}@r{]}
3387 @itemx c @r{[}@var{ignore-count}@r{]}
3388 @itemx fg @r{[}@var{ignore-count}@r{]}
3389 Resume program execution, at the address where your program last stopped;
3390 any breakpoints set at that address are bypassed. The optional argument
3391 @var{ignore-count} allows you to specify a further number of times to
3392 ignore a breakpoint at this location; its effect is like that of
3393 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3395 The argument @var{ignore-count} is meaningful only when your program
3396 stopped due to a breakpoint. At other times, the argument to
3397 @code{continue} is ignored.
3399 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3400 debugged program is deemed to be the foreground program) are provided
3401 purely for convenience, and have exactly the same behavior as
3405 To resume execution at a different place, you can use @code{return}
3406 (@pxref{Returning, ,Returning from a function}) to go back to the
3407 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3408 different address}) to go to an arbitrary location in your program.
3410 A typical technique for using stepping is to set a breakpoint
3411 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3412 beginning of the function or the section of your program where a problem
3413 is believed to lie, run your program until it stops at that breakpoint,
3414 and then step through the suspect area, examining the variables that are
3415 interesting, until you see the problem happen.
3419 @kindex s @r{(@code{step})}
3421 Continue running your program until control reaches a different source
3422 line, then stop it and return control to @value{GDBN}. This command is
3423 abbreviated @code{s}.
3426 @c "without debugging information" is imprecise; actually "without line
3427 @c numbers in the debugging information". (gcc -g1 has debugging info but
3428 @c not line numbers). But it seems complex to try to make that
3429 @c distinction here.
3430 @emph{Warning:} If you use the @code{step} command while control is
3431 within a function that was compiled without debugging information,
3432 execution proceeds until control reaches a function that does have
3433 debugging information. Likewise, it will not step into a function which
3434 is compiled without debugging information. To step through functions
3435 without debugging information, use the @code{stepi} command, described
3439 The @code{step} command only stops at the first instruction of a source
3440 line. This prevents the multiple stops that could otherwise occur in
3441 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3442 to stop if a function that has debugging information is called within
3443 the line. In other words, @code{step} @emph{steps inside} any functions
3444 called within the line.
3446 Also, the @code{step} command only enters a function if there is line
3447 number information for the function. Otherwise it acts like the
3448 @code{next} command. This avoids problems when using @code{cc -gl}
3449 on MIPS machines. Previously, @code{step} entered subroutines if there
3450 was any debugging information about the routine.
3452 @item step @var{count}
3453 Continue running as in @code{step}, but do so @var{count} times. If a
3454 breakpoint is reached, or a signal not related to stepping occurs before
3455 @var{count} steps, stepping stops right away.
3458 @kindex n @r{(@code{next})}
3459 @item next @r{[}@var{count}@r{]}
3460 Continue to the next source line in the current (innermost) stack frame.
3461 This is similar to @code{step}, but function calls that appear within
3462 the line of code are executed without stopping. Execution stops when
3463 control reaches a different line of code at the original stack level
3464 that was executing when you gave the @code{next} command. This command
3465 is abbreviated @code{n}.
3467 An argument @var{count} is a repeat count, as for @code{step}.
3470 @c FIX ME!! Do we delete this, or is there a way it fits in with
3471 @c the following paragraph? --- Vctoria
3473 @c @code{next} within a function that lacks debugging information acts like
3474 @c @code{step}, but any function calls appearing within the code of the
3475 @c function are executed without stopping.
3477 The @code{next} command only stops at the first instruction of a
3478 source line. This prevents multiple stops that could otherwise occur in
3479 @code{switch} statements, @code{for} loops, etc.
3481 @kindex set step-mode
3483 @cindex functions without line info, and stepping
3484 @cindex stepping into functions with no line info
3485 @itemx set step-mode on
3486 The @code{set step-mode on} command causes the @code{step} command to
3487 stop at the first instruction of a function which contains no debug line
3488 information rather than stepping over it.
3490 This is useful in cases where you may be interested in inspecting the
3491 machine instructions of a function which has no symbolic info and do not
3492 want @value{GDBN} to automatically skip over this function.
3494 @item set step-mode off
3495 Causes the @code{step} command to step over any functions which contains no
3496 debug information. This is the default.
3500 Continue running until just after function in the selected stack frame
3501 returns. Print the returned value (if any).
3503 Contrast this with the @code{return} command (@pxref{Returning,
3504 ,Returning from a function}).
3507 @kindex u @r{(@code{until})}
3510 Continue running until a source line past the current line, in the
3511 current stack frame, is reached. This command is used to avoid single
3512 stepping through a loop more than once. It is like the @code{next}
3513 command, except that when @code{until} encounters a jump, it
3514 automatically continues execution until the program counter is greater
3515 than the address of the jump.
3517 This means that when you reach the end of a loop after single stepping
3518 though it, @code{until} makes your program continue execution until it
3519 exits the loop. In contrast, a @code{next} command at the end of a loop
3520 simply steps back to the beginning of the loop, which forces you to step
3521 through the next iteration.
3523 @code{until} always stops your program if it attempts to exit the current
3526 @code{until} may produce somewhat counterintuitive results if the order
3527 of machine code does not match the order of the source lines. For
3528 example, in the following excerpt from a debugging session, the @code{f}
3529 (@code{frame}) command shows that execution is stopped at line
3530 @code{206}; yet when we use @code{until}, we get to line @code{195}:
3534 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
3536 (@value{GDBP}) until
3537 195 for ( ; argc > 0; NEXTARG) @{
3540 This happened because, for execution efficiency, the compiler had
3541 generated code for the loop closure test at the end, rather than the
3542 start, of the loop---even though the test in a C @code{for}-loop is
3543 written before the body of the loop. The @code{until} command appeared
3544 to step back to the beginning of the loop when it advanced to this
3545 expression; however, it has not really gone to an earlier
3546 statement---not in terms of the actual machine code.
3548 @code{until} with no argument works by means of single
3549 instruction stepping, and hence is slower than @code{until} with an
3552 @item until @var{location}
3553 @itemx u @var{location}
3554 Continue running your program until either the specified location is
3555 reached, or the current stack frame returns. @var{location} is any of
3556 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
3557 ,Setting breakpoints}). This form of the command uses breakpoints, and
3558 hence is quicker than @code{until} without an argument. The specified
3559 location is actually reached only if it is in the current frame. This
3560 implies that @code{until} can be used to skip over recursive function
3561 invocations. For instance in the code below, if the current location is
3562 line @code{96}, issuing @code{until 99} will execute the program up to
3563 line @code{99} in the same invocation of factorial, i.e. after the inner
3564 invocations have returned.
3567 94 int factorial (int value)
3569 96 if (value > 1) @{
3570 97 value *= factorial (value - 1);
3577 @kindex advance @var{location}
3578 @itemx advance @var{location}
3579 Continue running the program up to the given location. An argument is
3580 required, anything of the same form as arguments for the @code{break}
3581 command. Execution will also stop upon exit from the current stack
3582 frame. This command is similar to @code{until}, but @code{advance} will
3583 not skip over recursive function calls, and the target location doesn't
3584 have to be in the same frame as the current one.
3588 @kindex si @r{(@code{stepi})}
3590 @itemx stepi @var{arg}
3592 Execute one machine instruction, then stop and return to the debugger.
3594 It is often useful to do @samp{display/i $pc} when stepping by machine
3595 instructions. This makes @value{GDBN} automatically display the next
3596 instruction to be executed, each time your program stops. @xref{Auto
3597 Display,, Automatic display}.
3599 An argument is a repeat count, as in @code{step}.
3603 @kindex ni @r{(@code{nexti})}
3605 @itemx nexti @var{arg}
3607 Execute one machine instruction, but if it is a function call,
3608 proceed until the function returns.
3610 An argument is a repeat count, as in @code{next}.
3617 A signal is an asynchronous event that can happen in a program. The
3618 operating system defines the possible kinds of signals, and gives each
3619 kind a name and a number. For example, in Unix @code{SIGINT} is the
3620 signal a program gets when you type an interrupt character (often @kbd{C-c});
3621 @code{SIGSEGV} is the signal a program gets from referencing a place in
3622 memory far away from all the areas in use; @code{SIGALRM} occurs when
3623 the alarm clock timer goes off (which happens only if your program has
3624 requested an alarm).
3626 @cindex fatal signals
3627 Some signals, including @code{SIGALRM}, are a normal part of the
3628 functioning of your program. Others, such as @code{SIGSEGV}, indicate
3629 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
3630 program has not specified in advance some other way to handle the signal.
3631 @code{SIGINT} does not indicate an error in your program, but it is normally
3632 fatal so it can carry out the purpose of the interrupt: to kill the program.
3634 @value{GDBN} has the ability to detect any occurrence of a signal in your
3635 program. You can tell @value{GDBN} in advance what to do for each kind of
3638 @cindex handling signals
3639 Normally, @value{GDBN} is set up to let the non-erroneous signals like
3640 @code{SIGALRM} be silently passed to your program
3641 (so as not to interfere with their role in the program's functioning)
3642 but to stop your program immediately whenever an error signal happens.
3643 You can change these settings with the @code{handle} command.
3646 @kindex info signals
3649 Print a table of all the kinds of signals and how @value{GDBN} has been told to
3650 handle each one. You can use this to see the signal numbers of all
3651 the defined types of signals.
3653 @code{info handle} is an alias for @code{info signals}.
3656 @item handle @var{signal} @var{keywords}@dots{}
3657 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
3658 can be the number of a signal or its name (with or without the
3659 @samp{SIG} at the beginning); a list of signal numbers of the form
3660 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
3661 known signals. The @var{keywords} say what change to make.
3665 The keywords allowed by the @code{handle} command can be abbreviated.
3666 Their full names are:
3670 @value{GDBN} should not stop your program when this signal happens. It may
3671 still print a message telling you that the signal has come in.
3674 @value{GDBN} should stop your program when this signal happens. This implies
3675 the @code{print} keyword as well.
3678 @value{GDBN} should print a message when this signal happens.
3681 @value{GDBN} should not mention the occurrence of the signal at all. This
3682 implies the @code{nostop} keyword as well.
3686 @value{GDBN} should allow your program to see this signal; your program
3687 can handle the signal, or else it may terminate if the signal is fatal
3688 and not handled. @code{pass} and @code{noignore} are synonyms.
3692 @value{GDBN} should not allow your program to see this signal.
3693 @code{nopass} and @code{ignore} are synonyms.
3697 When a signal stops your program, the signal is not visible to the
3699 continue. Your program sees the signal then, if @code{pass} is in
3700 effect for the signal in question @emph{at that time}. In other words,
3701 after @value{GDBN} reports a signal, you can use the @code{handle}
3702 command with @code{pass} or @code{nopass} to control whether your
3703 program sees that signal when you continue.
3705 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
3706 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
3707 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
3710 You can also use the @code{signal} command to prevent your program from
3711 seeing a signal, or cause it to see a signal it normally would not see,
3712 or to give it any signal at any time. For example, if your program stopped
3713 due to some sort of memory reference error, you might store correct
3714 values into the erroneous variables and continue, hoping to see more
3715 execution; but your program would probably terminate immediately as
3716 a result of the fatal signal once it saw the signal. To prevent this,
3717 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
3721 @section Stopping and starting multi-thread programs
3723 When your program has multiple threads (@pxref{Threads,, Debugging
3724 programs with multiple threads}), you can choose whether to set
3725 breakpoints on all threads, or on a particular thread.
3728 @cindex breakpoints and threads
3729 @cindex thread breakpoints
3730 @kindex break @dots{} thread @var{threadno}
3731 @item break @var{linespec} thread @var{threadno}
3732 @itemx break @var{linespec} thread @var{threadno} if @dots{}
3733 @var{linespec} specifies source lines; there are several ways of
3734 writing them, but the effect is always to specify some source line.
3736 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
3737 to specify that you only want @value{GDBN} to stop the program when a
3738 particular thread reaches this breakpoint. @var{threadno} is one of the
3739 numeric thread identifiers assigned by @value{GDBN}, shown in the first
3740 column of the @samp{info threads} display.
3742 If you do not specify @samp{thread @var{threadno}} when you set a
3743 breakpoint, the breakpoint applies to @emph{all} threads of your
3746 You can use the @code{thread} qualifier on conditional breakpoints as
3747 well; in this case, place @samp{thread @var{threadno}} before the
3748 breakpoint condition, like this:
3751 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
3756 @cindex stopped threads
3757 @cindex threads, stopped
3758 Whenever your program stops under @value{GDBN} for any reason,
3759 @emph{all} threads of execution stop, not just the current thread. This
3760 allows you to examine the overall state of the program, including
3761 switching between threads, without worrying that things may change
3764 @cindex thread breakpoints and system calls
3765 @cindex system calls and thread breakpoints
3766 @cindex premature return from system calls
3767 There is an unfortunate side effect. If one thread stops for a
3768 breakpoint, or for some other reason, and another thread is blocked in a
3769 system call, then the system call may return prematurely. This is a
3770 consequence of the interaction between multiple threads and the signals
3771 that @value{GDBN} uses to implement breakpoints and other events that
3774 To handle this problem, your program should check the return value of
3775 each system call and react appropriately. This is good programming
3778 For example, do not write code like this:
3784 The call to @code{sleep} will return early if a different thread stops
3785 at a breakpoint or for some other reason.
3787 Instead, write this:
3792 unslept = sleep (unslept);
3795 A system call is allowed to return early, so the system is still
3796 conforming to its specification. But @value{GDBN} does cause your
3797 multi-threaded program to behave differently than it would without
3800 Also, @value{GDBN} uses internal breakpoints in the thread library to
3801 monitor certain events such as thread creation and thread destruction.
3802 When such an event happens, a system call in another thread may return
3803 prematurely, even though your program does not appear to stop.
3805 @cindex continuing threads
3806 @cindex threads, continuing
3807 Conversely, whenever you restart the program, @emph{all} threads start
3808 executing. @emph{This is true even when single-stepping} with commands
3809 like @code{step} or @code{next}.
3811 In particular, @value{GDBN} cannot single-step all threads in lockstep.
3812 Since thread scheduling is up to your debugging target's operating
3813 system (not controlled by @value{GDBN}), other threads may
3814 execute more than one statement while the current thread completes a
3815 single step. Moreover, in general other threads stop in the middle of a
3816 statement, rather than at a clean statement boundary, when the program
3819 You might even find your program stopped in another thread after
3820 continuing or even single-stepping. This happens whenever some other
3821 thread runs into a breakpoint, a signal, or an exception before the
3822 first thread completes whatever you requested.
3824 On some OSes, you can lock the OS scheduler and thus allow only a single
3828 @item set scheduler-locking @var{mode}
3829 Set the scheduler locking mode. If it is @code{off}, then there is no
3830 locking and any thread may run at any time. If @code{on}, then only the
3831 current thread may run when the inferior is resumed. The @code{step}
3832 mode optimizes for single-stepping. It stops other threads from
3833 ``seizing the prompt'' by preempting the current thread while you are
3834 stepping. Other threads will only rarely (or never) get a chance to run
3835 when you step. They are more likely to run when you @samp{next} over a
3836 function call, and they are completely free to run when you use commands
3837 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
3838 thread hits a breakpoint during its timeslice, they will never steal the
3839 @value{GDBN} prompt away from the thread that you are debugging.
3841 @item show scheduler-locking
3842 Display the current scheduler locking mode.
3847 @chapter Examining the Stack
3849 When your program has stopped, the first thing you need to know is where it
3850 stopped and how it got there.
3853 Each time your program performs a function call, information about the call
3855 That information includes the location of the call in your program,
3856 the arguments of the call,
3857 and the local variables of the function being called.
3858 The information is saved in a block of data called a @dfn{stack frame}.
3859 The stack frames are allocated in a region of memory called the @dfn{call
3862 When your program stops, the @value{GDBN} commands for examining the
3863 stack allow you to see all of this information.
3865 @cindex selected frame
3866 One of the stack frames is @dfn{selected} by @value{GDBN} and many
3867 @value{GDBN} commands refer implicitly to the selected frame. In
3868 particular, whenever you ask @value{GDBN} for the value of a variable in
3869 your program, the value is found in the selected frame. There are
3870 special @value{GDBN} commands to select whichever frame you are
3871 interested in. @xref{Selection, ,Selecting a frame}.
3873 When your program stops, @value{GDBN} automatically selects the
3874 currently executing frame and describes it briefly, similar to the
3875 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
3878 * Frames:: Stack frames
3879 * Backtrace:: Backtraces
3880 * Selection:: Selecting a frame
3881 * Frame Info:: Information on a frame
3886 @section Stack frames
3888 @cindex frame, definition
3890 The call stack is divided up into contiguous pieces called @dfn{stack
3891 frames}, or @dfn{frames} for short; each frame is the data associated
3892 with one call to one function. The frame contains the arguments given
3893 to the function, the function's local variables, and the address at
3894 which the function is executing.
3896 @cindex initial frame
3897 @cindex outermost frame
3898 @cindex innermost frame
3899 When your program is started, the stack has only one frame, that of the
3900 function @code{main}. This is called the @dfn{initial} frame or the
3901 @dfn{outermost} frame. Each time a function is called, a new frame is
3902 made. Each time a function returns, the frame for that function invocation
3903 is eliminated. If a function is recursive, there can be many frames for
3904 the same function. The frame for the function in which execution is
3905 actually occurring is called the @dfn{innermost} frame. This is the most
3906 recently created of all the stack frames that still exist.
3908 @cindex frame pointer
3909 Inside your program, stack frames are identified by their addresses. A
3910 stack frame consists of many bytes, each of which has its own address; each
3911 kind of computer has a convention for choosing one byte whose
3912 address serves as the address of the frame. Usually this address is kept
3913 in a register called the @dfn{frame pointer register} while execution is
3914 going on in that frame.
3916 @cindex frame number
3917 @value{GDBN} assigns numbers to all existing stack frames, starting with
3918 zero for the innermost frame, one for the frame that called it,
3919 and so on upward. These numbers do not really exist in your program;
3920 they are assigned by @value{GDBN} to give you a way of designating stack
3921 frames in @value{GDBN} commands.
3923 @c The -fomit-frame-pointer below perennially causes hbox overflow
3924 @c underflow problems.
3925 @cindex frameless execution
3926 Some compilers provide a way to compile functions so that they operate
3927 without stack frames. (For example, the @value{GCC} option
3929 @samp{-fomit-frame-pointer}
3931 generates functions without a frame.)
3932 This is occasionally done with heavily used library functions to save
3933 the frame setup time. @value{GDBN} has limited facilities for dealing
3934 with these function invocations. If the innermost function invocation
3935 has no stack frame, @value{GDBN} nevertheless regards it as though
3936 it had a separate frame, which is numbered zero as usual, allowing
3937 correct tracing of the function call chain. However, @value{GDBN} has
3938 no provision for frameless functions elsewhere in the stack.
3941 @kindex frame@r{, command}
3942 @cindex current stack frame
3943 @item frame @var{args}
3944 The @code{frame} command allows you to move from one stack frame to another,
3945 and to print the stack frame you select. @var{args} may be either the
3946 address of the frame or the stack frame number. Without an argument,
3947 @code{frame} prints the current stack frame.
3949 @kindex select-frame
3950 @cindex selecting frame silently
3952 The @code{select-frame} command allows you to move from one stack frame
3953 to another without printing the frame. This is the silent version of
3962 @cindex stack traces
3963 A backtrace is a summary of how your program got where it is. It shows one
3964 line per frame, for many frames, starting with the currently executing
3965 frame (frame zero), followed by its caller (frame one), and on up the
3970 @kindex bt @r{(@code{backtrace})}
3973 Print a backtrace of the entire stack: one line per frame for all
3974 frames in the stack.
3976 You can stop the backtrace at any time by typing the system interrupt
3977 character, normally @kbd{C-c}.
3979 @item backtrace @var{n}
3981 Similar, but print only the innermost @var{n} frames.
3983 @item backtrace -@var{n}
3985 Similar, but print only the outermost @var{n} frames.
3990 @kindex info s @r{(@code{info stack})}
3991 The names @code{where} and @code{info stack} (abbreviated @code{info s})
3992 are additional aliases for @code{backtrace}.
3994 Each line in the backtrace shows the frame number and the function name.
3995 The program counter value is also shown---unless you use @code{set
3996 print address off}. The backtrace also shows the source file name and
3997 line number, as well as the arguments to the function. The program
3998 counter value is omitted if it is at the beginning of the code for that
4001 Here is an example of a backtrace. It was made with the command
4002 @samp{bt 3}, so it shows the innermost three frames.
4006 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4008 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4009 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4011 (More stack frames follow...)
4016 The display for frame zero does not begin with a program counter
4017 value, indicating that your program has stopped at the beginning of the
4018 code for line @code{993} of @code{builtin.c}.
4020 @kindex set backtrace past-main
4021 @kindex show backtrace past-main
4022 @kindex set backtrace limit
4023 @kindex show backtrace limit
4025 Most programs have a standard user entry point---a place where system
4026 libraries and startup code transition into user code. For C this is
4027 @code{main}. When @value{GDBN} finds the entry function in a backtrace
4028 it will terminate the backtrace, to avoid tracing into highly
4029 system-specific (and generally uninteresting) code.
4031 If you need to examine the startup code, or limit the number of levels
4032 in a backtrace, you can change this behavior:
4035 @item set backtrace past-main
4036 @itemx set backtrace past-main on
4037 Backtraces will continue past the user entry point.
4039 @item set backtrace past-main off
4040 Backtraces will stop when they encounter the user entry point. This is the
4043 @item show backtrace past-main
4044 Display the current user entry point backtrace policy.
4046 @item set backtrace limit @var{n}
4047 @itemx set backtrace limit 0
4048 @cindex backtrace limit
4049 Limit the backtrace to @var{n} levels. A value of zero means
4052 @item show backtrace limit
4053 Display the current limit on backtrace levels.
4057 @section Selecting a frame
4059 Most commands for examining the stack and other data in your program work on
4060 whichever stack frame is selected at the moment. Here are the commands for
4061 selecting a stack frame; all of them finish by printing a brief description
4062 of the stack frame just selected.
4065 @kindex frame@r{, selecting}
4066 @kindex f @r{(@code{frame})}
4069 Select frame number @var{n}. Recall that frame zero is the innermost
4070 (currently executing) frame, frame one is the frame that called the
4071 innermost one, and so on. The highest-numbered frame is the one for
4074 @item frame @var{addr}
4076 Select the frame at address @var{addr}. This is useful mainly if the
4077 chaining of stack frames has been damaged by a bug, making it
4078 impossible for @value{GDBN} to assign numbers properly to all frames. In
4079 addition, this can be useful when your program has multiple stacks and
4080 switches between them.
4082 On the SPARC architecture, @code{frame} needs two addresses to
4083 select an arbitrary frame: a frame pointer and a stack pointer.
4085 On the MIPS and Alpha architecture, it needs two addresses: a stack
4086 pointer and a program counter.
4088 On the 29k architecture, it needs three addresses: a register stack
4089 pointer, a program counter, and a memory stack pointer.
4090 @c note to future updaters: this is conditioned on a flag
4091 @c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date
4092 @c as of 27 Jan 1994.
4096 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4097 advances toward the outermost frame, to higher frame numbers, to frames
4098 that have existed longer. @var{n} defaults to one.
4101 @kindex do @r{(@code{down})}
4103 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4104 advances toward the innermost frame, to lower frame numbers, to frames
4105 that were created more recently. @var{n} defaults to one. You may
4106 abbreviate @code{down} as @code{do}.
4109 All of these commands end by printing two lines of output describing the
4110 frame. The first line shows the frame number, the function name, the
4111 arguments, and the source file and line number of execution in that
4112 frame. The second line shows the text of that source line.
4120 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4122 10 read_input_file (argv[i]);
4126 After such a printout, the @code{list} command with no arguments
4127 prints ten lines centered on the point of execution in the frame.
4128 You can also edit the program at the point of execution with your favorite
4129 editing program by typing @code{edit}.
4130 @xref{List, ,Printing source lines},
4134 @kindex down-silently
4136 @item up-silently @var{n}
4137 @itemx down-silently @var{n}
4138 These two commands are variants of @code{up} and @code{down},
4139 respectively; they differ in that they do their work silently, without
4140 causing display of the new frame. They are intended primarily for use
4141 in @value{GDBN} command scripts, where the output might be unnecessary and
4146 @section Information about a frame
4148 There are several other commands to print information about the selected
4154 When used without any argument, this command does not change which
4155 frame is selected, but prints a brief description of the currently
4156 selected stack frame. It can be abbreviated @code{f}. With an
4157 argument, this command is used to select a stack frame.
4158 @xref{Selection, ,Selecting a frame}.
4161 @kindex info f @r{(@code{info frame})}
4164 This command prints a verbose description of the selected stack frame,
4169 the address of the frame
4171 the address of the next frame down (called by this frame)
4173 the address of the next frame up (caller of this frame)
4175 the language in which the source code corresponding to this frame is written
4177 the address of the frame's arguments
4179 the address of the frame's local variables
4181 the program counter saved in it (the address of execution in the caller frame)
4183 which registers were saved in the frame
4186 @noindent The verbose description is useful when
4187 something has gone wrong that has made the stack format fail to fit
4188 the usual conventions.
4190 @item info frame @var{addr}
4191 @itemx info f @var{addr}
4192 Print a verbose description of the frame at address @var{addr}, without
4193 selecting that frame. The selected frame remains unchanged by this
4194 command. This requires the same kind of address (more than one for some
4195 architectures) that you specify in the @code{frame} command.
4196 @xref{Selection, ,Selecting a frame}.
4200 Print the arguments of the selected frame, each on a separate line.
4204 Print the local variables of the selected frame, each on a separate
4205 line. These are all variables (declared either static or automatic)
4206 accessible at the point of execution of the selected frame.
4209 @cindex catch exceptions, list active handlers
4210 @cindex exception handlers, how to list
4212 Print a list of all the exception handlers that are active in the
4213 current stack frame at the current point of execution. To see other
4214 exception handlers, visit the associated frame (using the @code{up},
4215 @code{down}, or @code{frame} commands); then type @code{info catch}.
4216 @xref{Set Catchpoints, , Setting catchpoints}.
4222 @chapter Examining Source Files
4224 @value{GDBN} can print parts of your program's source, since the debugging
4225 information recorded in the program tells @value{GDBN} what source files were
4226 used to build it. When your program stops, @value{GDBN} spontaneously prints
4227 the line where it stopped. Likewise, when you select a stack frame
4228 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4229 execution in that frame has stopped. You can print other portions of
4230 source files by explicit command.
4232 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4233 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4234 @value{GDBN} under @sc{gnu} Emacs}.
4237 * List:: Printing source lines
4238 * Edit:: Editing source files
4239 * Search:: Searching source files
4240 * Source Path:: Specifying source directories
4241 * Machine Code:: Source and machine code
4245 @section Printing source lines
4248 @kindex l @r{(@code{list})}
4249 To print lines from a source file, use the @code{list} command
4250 (abbreviated @code{l}). By default, ten lines are printed.
4251 There are several ways to specify what part of the file you want to print.
4253 Here are the forms of the @code{list} command most commonly used:
4256 @item list @var{linenum}
4257 Print lines centered around line number @var{linenum} in the
4258 current source file.
4260 @item list @var{function}
4261 Print lines centered around the beginning of function
4265 Print more lines. If the last lines printed were printed with a
4266 @code{list} command, this prints lines following the last lines
4267 printed; however, if the last line printed was a solitary line printed
4268 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4269 Stack}), this prints lines centered around that line.
4272 Print lines just before the lines last printed.
4275 By default, @value{GDBN} prints ten source lines with any of these forms of
4276 the @code{list} command. You can change this using @code{set listsize}:
4279 @kindex set listsize
4280 @item set listsize @var{count}
4281 Make the @code{list} command display @var{count} source lines (unless
4282 the @code{list} argument explicitly specifies some other number).
4284 @kindex show listsize
4286 Display the number of lines that @code{list} prints.
4289 Repeating a @code{list} command with @key{RET} discards the argument,
4290 so it is equivalent to typing just @code{list}. This is more useful
4291 than listing the same lines again. An exception is made for an
4292 argument of @samp{-}; that argument is preserved in repetition so that
4293 each repetition moves up in the source file.
4296 In general, the @code{list} command expects you to supply zero, one or two
4297 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4298 of writing them, but the effect is always to specify some source line.
4299 Here is a complete description of the possible arguments for @code{list}:
4302 @item list @var{linespec}
4303 Print lines centered around the line specified by @var{linespec}.
4305 @item list @var{first},@var{last}
4306 Print lines from @var{first} to @var{last}. Both arguments are
4309 @item list ,@var{last}
4310 Print lines ending with @var{last}.
4312 @item list @var{first},
4313 Print lines starting with @var{first}.
4316 Print lines just after the lines last printed.
4319 Print lines just before the lines last printed.
4322 As described in the preceding table.
4325 Here are the ways of specifying a single source line---all the
4330 Specifies line @var{number} of the current source file.
4331 When a @code{list} command has two linespecs, this refers to
4332 the same source file as the first linespec.
4335 Specifies the line @var{offset} lines after the last line printed.
4336 When used as the second linespec in a @code{list} command that has
4337 two, this specifies the line @var{offset} lines down from the
4341 Specifies the line @var{offset} lines before the last line printed.
4343 @item @var{filename}:@var{number}
4344 Specifies line @var{number} in the source file @var{filename}.
4346 @item @var{function}
4347 Specifies the line that begins the body of the function @var{function}.
4348 For example: in C, this is the line with the open brace.
4350 @item @var{filename}:@var{function}
4351 Specifies the line of the open-brace that begins the body of the
4352 function @var{function} in the file @var{filename}. You only need the
4353 file name with a function name to avoid ambiguity when there are
4354 identically named functions in different source files.
4356 @item *@var{address}
4357 Specifies the line containing the program address @var{address}.
4358 @var{address} may be any expression.
4362 @section Editing source files
4363 @cindex editing source files
4366 @kindex e @r{(@code{edit})}
4367 To edit the lines in a source file, use the @code{edit} command.
4368 The editing program of your choice
4369 is invoked with the current line set to
4370 the active line in the program.
4371 Alternatively, there are several ways to specify what part of the file you
4372 want to print if you want to see other parts of the program.
4374 Here are the forms of the @code{edit} command most commonly used:
4378 Edit the current source file at the active line number in the program.
4380 @item edit @var{number}
4381 Edit the current source file with @var{number} as the active line number.
4383 @item edit @var{function}
4384 Edit the file containing @var{function} at the beginning of its definition.
4386 @item edit @var{filename}:@var{number}
4387 Specifies line @var{number} in the source file @var{filename}.
4389 @item edit @var{filename}:@var{function}
4390 Specifies the line that begins the body of the
4391 function @var{function} in the file @var{filename}. You only need the
4392 file name with a function name to avoid ambiguity when there are
4393 identically named functions in different source files.
4395 @item edit *@var{address}
4396 Specifies the line containing the program address @var{address}.
4397 @var{address} may be any expression.
4400 @subsection Choosing your editor
4401 You can customize @value{GDBN} to use any editor you want
4403 The only restriction is that your editor (say @code{ex}), recognizes the
4404 following command-line syntax:
4406 ex +@var{number} file
4408 The optional numeric value +@var{number} designates the active line in
4409 the file.}. By default, it is @value{EDITOR}, but you can change this
4410 by setting the environment variable @code{EDITOR} before using
4411 @value{GDBN}. For example, to configure @value{GDBN} to use the
4412 @code{vi} editor, you could use these commands with the @code{sh} shell:
4418 or in the @code{csh} shell,
4420 setenv EDITOR /usr/bin/vi
4425 @section Searching source files
4427 @kindex reverse-search
4429 There are two commands for searching through the current source file for a
4434 @kindex forward-search
4435 @item forward-search @var{regexp}
4436 @itemx search @var{regexp}
4437 The command @samp{forward-search @var{regexp}} checks each line,
4438 starting with the one following the last line listed, for a match for
4439 @var{regexp}. It lists the line that is found. You can use the
4440 synonym @samp{search @var{regexp}} or abbreviate the command name as
4443 @item reverse-search @var{regexp}
4444 The command @samp{reverse-search @var{regexp}} checks each line, starting
4445 with the one before the last line listed and going backward, for a match
4446 for @var{regexp}. It lists the line that is found. You can abbreviate
4447 this command as @code{rev}.
4451 @section Specifying source directories
4454 @cindex directories for source files
4455 Executable programs sometimes do not record the directories of the source
4456 files from which they were compiled, just the names. Even when they do,
4457 the directories could be moved between the compilation and your debugging
4458 session. @value{GDBN} has a list of directories to search for source files;
4459 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4460 it tries all the directories in the list, in the order they are present
4461 in the list, until it finds a file with the desired name. Note that
4462 the executable search path is @emph{not} used for this purpose. Neither is
4463 the current working directory, unless it happens to be in the source
4466 If @value{GDBN} cannot find a source file in the source path, and the
4467 object program records a directory, @value{GDBN} tries that directory
4468 too. If the source path is empty, and there is no record of the
4469 compilation directory, @value{GDBN} looks in the current directory as a
4472 Whenever you reset or rearrange the source path, @value{GDBN} clears out
4473 any information it has cached about where source files are found and where
4474 each line is in the file.
4478 When you start @value{GDBN}, its source path includes only @samp{cdir}
4479 and @samp{cwd}, in that order.
4480 To add other directories, use the @code{directory} command.
4483 @item directory @var{dirname} @dots{}
4484 @item dir @var{dirname} @dots{}
4485 Add directory @var{dirname} to the front of the source path. Several
4486 directory names may be given to this command, separated by @samp{:}
4487 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4488 part of absolute file names) or
4489 whitespace. You may specify a directory that is already in the source
4490 path; this moves it forward, so @value{GDBN} searches it sooner.
4494 @vindex $cdir@r{, convenience variable}
4495 @vindex $cwdr@r{, convenience variable}
4496 @cindex compilation directory
4497 @cindex current directory
4498 @cindex working directory
4499 @cindex directory, current
4500 @cindex directory, compilation
4501 You can use the string @samp{$cdir} to refer to the compilation
4502 directory (if one is recorded), and @samp{$cwd} to refer to the current
4503 working directory. @samp{$cwd} is not the same as @samp{.}---the former
4504 tracks the current working directory as it changes during your @value{GDBN}
4505 session, while the latter is immediately expanded to the current
4506 directory at the time you add an entry to the source path.
4509 Reset the source path to empty again. This requires confirmation.
4511 @c RET-repeat for @code{directory} is explicitly disabled, but since
4512 @c repeating it would be a no-op we do not say that. (thanks to RMS)
4514 @item show directories
4515 @kindex show directories
4516 Print the source path: show which directories it contains.
4519 If your source path is cluttered with directories that are no longer of
4520 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4521 versions of source. You can correct the situation as follows:
4525 Use @code{directory} with no argument to reset the source path to empty.
4528 Use @code{directory} with suitable arguments to reinstall the
4529 directories you want in the source path. You can add all the
4530 directories in one command.
4534 @section Source and machine code
4536 You can use the command @code{info line} to map source lines to program
4537 addresses (and vice versa), and the command @code{disassemble} to display
4538 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
4539 mode, the @code{info line} command causes the arrow to point to the
4540 line specified. Also, @code{info line} prints addresses in symbolic form as
4545 @item info line @var{linespec}
4546 Print the starting and ending addresses of the compiled code for
4547 source line @var{linespec}. You can specify source lines in any of
4548 the ways understood by the @code{list} command (@pxref{List, ,Printing
4552 For example, we can use @code{info line} to discover the location of
4553 the object code for the first line of function
4554 @code{m4_changequote}:
4556 @c FIXME: I think this example should also show the addresses in
4557 @c symbolic form, as they usually would be displayed.
4559 (@value{GDBP}) info line m4_changequote
4560 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4564 We can also inquire (using @code{*@var{addr}} as the form for
4565 @var{linespec}) what source line covers a particular address:
4567 (@value{GDBP}) info line *0x63ff
4568 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4571 @cindex @code{$_} and @code{info line}
4572 @kindex x@r{(examine), and} info line
4573 After @code{info line}, the default address for the @code{x} command
4574 is changed to the starting address of the line, so that @samp{x/i} is
4575 sufficient to begin examining the machine code (@pxref{Memory,
4576 ,Examining memory}). Also, this address is saved as the value of the
4577 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4582 @cindex assembly instructions
4583 @cindex instructions, assembly
4584 @cindex machine instructions
4585 @cindex listing machine instructions
4587 This specialized command dumps a range of memory as machine
4588 instructions. The default memory range is the function surrounding the
4589 program counter of the selected frame. A single argument to this
4590 command is a program counter value; @value{GDBN} dumps the function
4591 surrounding this value. Two arguments specify a range of addresses
4592 (first inclusive, second exclusive) to dump.
4595 The following example shows the disassembly of a range of addresses of
4596 HP PA-RISC 2.0 code:
4599 (@value{GDBP}) disas 0x32c4 0x32e4
4600 Dump of assembler code from 0x32c4 to 0x32e4:
4601 0x32c4 <main+204>: addil 0,dp
4602 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
4603 0x32cc <main+212>: ldil 0x3000,r31
4604 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
4605 0x32d4 <main+220>: ldo 0(r31),rp
4606 0x32d8 <main+224>: addil -0x800,dp
4607 0x32dc <main+228>: ldo 0x588(r1),r26
4608 0x32e0 <main+232>: ldil 0x3000,r31
4609 End of assembler dump.
4612 Some architectures have more than one commonly-used set of instruction
4613 mnemonics or other syntax.
4616 @kindex set disassembly-flavor
4617 @cindex assembly instructions
4618 @cindex instructions, assembly
4619 @cindex machine instructions
4620 @cindex listing machine instructions
4621 @cindex Intel disassembly flavor
4622 @cindex AT&T disassembly flavor
4623 @item set disassembly-flavor @var{instruction-set}
4624 Select the instruction set to use when disassembling the
4625 program via the @code{disassemble} or @code{x/i} commands.
4627 Currently this command is only defined for the Intel x86 family. You
4628 can set @var{instruction-set} to either @code{intel} or @code{att}.
4629 The default is @code{att}, the AT&T flavor used by default by Unix
4630 assemblers for x86-based targets.
4635 @chapter Examining Data
4637 @cindex printing data
4638 @cindex examining data
4641 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
4642 @c document because it is nonstandard... Under Epoch it displays in a
4643 @c different window or something like that.
4644 The usual way to examine data in your program is with the @code{print}
4645 command (abbreviated @code{p}), or its synonym @code{inspect}. It
4646 evaluates and prints the value of an expression of the language your
4647 program is written in (@pxref{Languages, ,Using @value{GDBN} with
4648 Different Languages}).
4651 @item print @var{expr}
4652 @itemx print /@var{f} @var{expr}
4653 @var{expr} is an expression (in the source language). By default the
4654 value of @var{expr} is printed in a format appropriate to its data type;
4655 you can choose a different format by specifying @samp{/@var{f}}, where
4656 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
4660 @itemx print /@var{f}
4661 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
4662 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
4663 conveniently inspect the same value in an alternative format.
4666 A more low-level way of examining data is with the @code{x} command.
4667 It examines data in memory at a specified address and prints it in a
4668 specified format. @xref{Memory, ,Examining memory}.
4670 If you are interested in information about types, or about how the
4671 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
4672 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
4676 * Expressions:: Expressions
4677 * Variables:: Program variables
4678 * Arrays:: Artificial arrays
4679 * Output Formats:: Output formats
4680 * Memory:: Examining memory
4681 * Auto Display:: Automatic display
4682 * Print Settings:: Print settings
4683 * Value History:: Value history
4684 * Convenience Vars:: Convenience variables
4685 * Registers:: Registers
4686 * Floating Point Hardware:: Floating point hardware
4687 * Vector Unit:: Vector Unit
4688 * Memory Region Attributes:: Memory region attributes
4689 * Dump/Restore Files:: Copy between memory and a file
4690 * Character Sets:: Debugging programs that use a different
4691 character set than GDB does
4695 @section Expressions
4698 @code{print} and many other @value{GDBN} commands accept an expression and
4699 compute its value. Any kind of constant, variable or operator defined
4700 by the programming language you are using is valid in an expression in
4701 @value{GDBN}. This includes conditional expressions, function calls,
4702 casts, and string constants. It also includes preprocessor macros, if
4703 you compiled your program to include this information; see
4706 @value{GDBN} supports array constants in expressions input by
4707 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
4708 you can use the command @code{print @{1, 2, 3@}} to build up an array in
4709 memory that is @code{malloc}ed in the target program.
4711 Because C is so widespread, most of the expressions shown in examples in
4712 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
4713 Languages}, for information on how to use expressions in other
4716 In this section, we discuss operators that you can use in @value{GDBN}
4717 expressions regardless of your programming language.
4719 Casts are supported in all languages, not just in C, because it is so
4720 useful to cast a number into a pointer in order to examine a structure
4721 at that address in memory.
4722 @c FIXME: casts supported---Mod2 true?
4724 @value{GDBN} supports these operators, in addition to those common
4725 to programming languages:
4729 @samp{@@} is a binary operator for treating parts of memory as arrays.
4730 @xref{Arrays, ,Artificial arrays}, for more information.
4733 @samp{::} allows you to specify a variable in terms of the file or
4734 function where it is defined. @xref{Variables, ,Program variables}.
4736 @cindex @{@var{type}@}
4737 @cindex type casting memory
4738 @cindex memory, viewing as typed object
4739 @cindex casts, to view memory
4740 @item @{@var{type}@} @var{addr}
4741 Refers to an object of type @var{type} stored at address @var{addr} in
4742 memory. @var{addr} may be any expression whose value is an integer or
4743 pointer (but parentheses are required around binary operators, just as in
4744 a cast). This construct is allowed regardless of what kind of data is
4745 normally supposed to reside at @var{addr}.
4749 @section Program variables
4751 The most common kind of expression to use is the name of a variable
4754 Variables in expressions are understood in the selected stack frame
4755 (@pxref{Selection, ,Selecting a frame}); they must be either:
4759 global (or file-static)
4766 visible according to the scope rules of the
4767 programming language from the point of execution in that frame
4770 @noindent This means that in the function
4785 you can examine and use the variable @code{a} whenever your program is
4786 executing within the function @code{foo}, but you can only use or
4787 examine the variable @code{b} while your program is executing inside
4788 the block where @code{b} is declared.
4790 @cindex variable name conflict
4791 There is an exception: you can refer to a variable or function whose
4792 scope is a single source file even if the current execution point is not
4793 in this file. But it is possible to have more than one such variable or
4794 function with the same name (in different source files). If that
4795 happens, referring to that name has unpredictable effects. If you wish,
4796 you can specify a static variable in a particular function or file,
4797 using the colon-colon notation:
4799 @cindex colon-colon, context for variables/functions
4801 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
4802 @cindex @code{::}, context for variables/functions
4805 @var{file}::@var{variable}
4806 @var{function}::@var{variable}
4810 Here @var{file} or @var{function} is the name of the context for the
4811 static @var{variable}. In the case of file names, you can use quotes to
4812 make sure @value{GDBN} parses the file name as a single word---for example,
4813 to print a global value of @code{x} defined in @file{f2.c}:
4816 (@value{GDBP}) p 'f2.c'::x
4819 @cindex C@t{++} scope resolution
4820 This use of @samp{::} is very rarely in conflict with the very similar
4821 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
4822 scope resolution operator in @value{GDBN} expressions.
4823 @c FIXME: Um, so what happens in one of those rare cases where it's in
4826 @cindex wrong values
4827 @cindex variable values, wrong
4829 @emph{Warning:} Occasionally, a local variable may appear to have the
4830 wrong value at certain points in a function---just after entry to a new
4831 scope, and just before exit.
4833 You may see this problem when you are stepping by machine instructions.
4834 This is because, on most machines, it takes more than one instruction to
4835 set up a stack frame (including local variable definitions); if you are
4836 stepping by machine instructions, variables may appear to have the wrong
4837 values until the stack frame is completely built. On exit, it usually
4838 also takes more than one machine instruction to destroy a stack frame;
4839 after you begin stepping through that group of instructions, local
4840 variable definitions may be gone.
4842 This may also happen when the compiler does significant optimizations.
4843 To be sure of always seeing accurate values, turn off all optimization
4846 @cindex ``No symbol "foo" in current context''
4847 Another possible effect of compiler optimizations is to optimize
4848 unused variables out of existence, or assign variables to registers (as
4849 opposed to memory addresses). Depending on the support for such cases
4850 offered by the debug info format used by the compiler, @value{GDBN}
4851 might not be able to display values for such local variables. If that
4852 happens, @value{GDBN} will print a message like this:
4855 No symbol "foo" in current context.
4858 To solve such problems, either recompile without optimizations, or use a
4859 different debug info format, if the compiler supports several such
4860 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler
4861 usually supports the @option{-gstabs+} option. @option{-gstabs+}
4862 produces debug info in a format that is superior to formats such as
4863 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
4864 an effective form for debug info. @xref{Debugging Options,,Options
4865 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
4869 @section Artificial arrays
4871 @cindex artificial array
4872 @kindex @@@r{, referencing memory as an array}
4873 It is often useful to print out several successive objects of the
4874 same type in memory; a section of an array, or an array of
4875 dynamically determined size for which only a pointer exists in the
4878 You can do this by referring to a contiguous span of memory as an
4879 @dfn{artificial array}, using the binary operator @samp{@@}. The left
4880 operand of @samp{@@} should be the first element of the desired array
4881 and be an individual object. The right operand should be the desired length
4882 of the array. The result is an array value whose elements are all of
4883 the type of the left argument. The first element is actually the left
4884 argument; the second element comes from bytes of memory immediately
4885 following those that hold the first element, and so on. Here is an
4886 example. If a program says
4889 int *array = (int *) malloc (len * sizeof (int));
4893 you can print the contents of @code{array} with
4899 The left operand of @samp{@@} must reside in memory. Array values made
4900 with @samp{@@} in this way behave just like other arrays in terms of
4901 subscripting, and are coerced to pointers when used in expressions.
4902 Artificial arrays most often appear in expressions via the value history
4903 (@pxref{Value History, ,Value history}), after printing one out.
4905 Another way to create an artificial array is to use a cast.
4906 This re-interprets a value as if it were an array.
4907 The value need not be in memory:
4909 (@value{GDBP}) p/x (short[2])0x12345678
4910 $1 = @{0x1234, 0x5678@}
4913 As a convenience, if you leave the array length out (as in
4914 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
4915 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
4917 (@value{GDBP}) p/x (short[])0x12345678
4918 $2 = @{0x1234, 0x5678@}
4921 Sometimes the artificial array mechanism is not quite enough; in
4922 moderately complex data structures, the elements of interest may not
4923 actually be adjacent---for example, if you are interested in the values
4924 of pointers in an array. One useful work-around in this situation is
4925 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
4926 variables}) as a counter in an expression that prints the first
4927 interesting value, and then repeat that expression via @key{RET}. For
4928 instance, suppose you have an array @code{dtab} of pointers to
4929 structures, and you are interested in the values of a field @code{fv}
4930 in each structure. Here is an example of what you might type:
4940 @node Output Formats
4941 @section Output formats
4943 @cindex formatted output
4944 @cindex output formats
4945 By default, @value{GDBN} prints a value according to its data type. Sometimes
4946 this is not what you want. For example, you might want to print a number
4947 in hex, or a pointer in decimal. Or you might want to view data in memory
4948 at a certain address as a character string or as an instruction. To do
4949 these things, specify an @dfn{output format} when you print a value.
4951 The simplest use of output formats is to say how to print a value
4952 already computed. This is done by starting the arguments of the
4953 @code{print} command with a slash and a format letter. The format
4954 letters supported are:
4958 Regard the bits of the value as an integer, and print the integer in
4962 Print as integer in signed decimal.
4965 Print as integer in unsigned decimal.
4968 Print as integer in octal.
4971 Print as integer in binary. The letter @samp{t} stands for ``two''.
4972 @footnote{@samp{b} cannot be used because these format letters are also
4973 used with the @code{x} command, where @samp{b} stands for ``byte'';
4974 see @ref{Memory,,Examining memory}.}
4977 @cindex unknown address, locating
4978 @cindex locate address
4979 Print as an address, both absolute in hexadecimal and as an offset from
4980 the nearest preceding symbol. You can use this format used to discover
4981 where (in what function) an unknown address is located:
4984 (@value{GDBP}) p/a 0x54320
4985 $3 = 0x54320 <_initialize_vx+396>
4989 The command @code{info symbol 0x54320} yields similar results.
4990 @xref{Symbols, info symbol}.
4993 Regard as an integer and print it as a character constant.
4996 Regard the bits of the value as a floating point number and print
4997 using typical floating point syntax.
5000 For example, to print the program counter in hex (@pxref{Registers}), type
5007 Note that no space is required before the slash; this is because command
5008 names in @value{GDBN} cannot contain a slash.
5010 To reprint the last value in the value history with a different format,
5011 you can use the @code{print} command with just a format and no
5012 expression. For example, @samp{p/x} reprints the last value in hex.
5015 @section Examining memory
5017 You can use the command @code{x} (for ``examine'') to examine memory in
5018 any of several formats, independently of your program's data types.
5020 @cindex examining memory
5022 @kindex x @r{(examine memory)}
5023 @item x/@var{nfu} @var{addr}
5026 Use the @code{x} command to examine memory.
5029 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5030 much memory to display and how to format it; @var{addr} is an
5031 expression giving the address where you want to start displaying memory.
5032 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5033 Several commands set convenient defaults for @var{addr}.
5036 @item @var{n}, the repeat count
5037 The repeat count is a decimal integer; the default is 1. It specifies
5038 how much memory (counting by units @var{u}) to display.
5039 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5042 @item @var{f}, the display format
5043 The display format is one of the formats used by @code{print},
5044 @samp{s} (null-terminated string), or @samp{i} (machine instruction).
5045 The default is @samp{x} (hexadecimal) initially.
5046 The default changes each time you use either @code{x} or @code{print}.
5048 @item @var{u}, the unit size
5049 The unit size is any of
5055 Halfwords (two bytes).
5057 Words (four bytes). This is the initial default.
5059 Giant words (eight bytes).
5062 Each time you specify a unit size with @code{x}, that size becomes the
5063 default unit the next time you use @code{x}. (For the @samp{s} and
5064 @samp{i} formats, the unit size is ignored and is normally not written.)
5066 @item @var{addr}, starting display address
5067 @var{addr} is the address where you want @value{GDBN} to begin displaying
5068 memory. The expression need not have a pointer value (though it may);
5069 it is always interpreted as an integer address of a byte of memory.
5070 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5071 @var{addr} is usually just after the last address examined---but several
5072 other commands also set the default address: @code{info breakpoints} (to
5073 the address of the last breakpoint listed), @code{info line} (to the
5074 starting address of a line), and @code{print} (if you use it to display
5075 a value from memory).
5078 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5079 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5080 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5081 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5082 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5084 Since the letters indicating unit sizes are all distinct from the
5085 letters specifying output formats, you do not have to remember whether
5086 unit size or format comes first; either order works. The output
5087 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5088 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5090 Even though the unit size @var{u} is ignored for the formats @samp{s}
5091 and @samp{i}, you might still want to use a count @var{n}; for example,
5092 @samp{3i} specifies that you want to see three machine instructions,
5093 including any operands. The command @code{disassemble} gives an
5094 alternative way of inspecting machine instructions; see @ref{Machine
5095 Code,,Source and machine code}.
5097 All the defaults for the arguments to @code{x} are designed to make it
5098 easy to continue scanning memory with minimal specifications each time
5099 you use @code{x}. For example, after you have inspected three machine
5100 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5101 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5102 the repeat count @var{n} is used again; the other arguments default as
5103 for successive uses of @code{x}.
5105 @cindex @code{$_}, @code{$__}, and value history
5106 The addresses and contents printed by the @code{x} command are not saved
5107 in the value history because there is often too much of them and they
5108 would get in the way. Instead, @value{GDBN} makes these values available for
5109 subsequent use in expressions as values of the convenience variables
5110 @code{$_} and @code{$__}. After an @code{x} command, the last address
5111 examined is available for use in expressions in the convenience variable
5112 @code{$_}. The contents of that address, as examined, are available in
5113 the convenience variable @code{$__}.
5115 If the @code{x} command has a repeat count, the address and contents saved
5116 are from the last memory unit printed; this is not the same as the last
5117 address printed if several units were printed on the last line of output.
5120 @section Automatic display
5121 @cindex automatic display
5122 @cindex display of expressions
5124 If you find that you want to print the value of an expression frequently
5125 (to see how it changes), you might want to add it to the @dfn{automatic
5126 display list} so that @value{GDBN} prints its value each time your program stops.
5127 Each expression added to the list is given a number to identify it;
5128 to remove an expression from the list, you specify that number.
5129 The automatic display looks like this:
5133 3: bar[5] = (struct hack *) 0x3804
5137 This display shows item numbers, expressions and their current values. As with
5138 displays you request manually using @code{x} or @code{print}, you can
5139 specify the output format you prefer; in fact, @code{display} decides
5140 whether to use @code{print} or @code{x} depending on how elaborate your
5141 format specification is---it uses @code{x} if you specify a unit size,
5142 or one of the two formats (@samp{i} and @samp{s}) that are only
5143 supported by @code{x}; otherwise it uses @code{print}.
5147 @item display @var{expr}
5148 Add the expression @var{expr} to the list of expressions to display
5149 each time your program stops. @xref{Expressions, ,Expressions}.
5151 @code{display} does not repeat if you press @key{RET} again after using it.
5153 @item display/@var{fmt} @var{expr}
5154 For @var{fmt} specifying only a display format and not a size or
5155 count, add the expression @var{expr} to the auto-display list but
5156 arrange to display it each time in the specified format @var{fmt}.
5157 @xref{Output Formats,,Output formats}.
5159 @item display/@var{fmt} @var{addr}
5160 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5161 number of units, add the expression @var{addr} as a memory address to
5162 be examined each time your program stops. Examining means in effect
5163 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5166 For example, @samp{display/i $pc} can be helpful, to see the machine
5167 instruction about to be executed each time execution stops (@samp{$pc}
5168 is a common name for the program counter; @pxref{Registers, ,Registers}).
5171 @kindex delete display
5173 @item undisplay @var{dnums}@dots{}
5174 @itemx delete display @var{dnums}@dots{}
5175 Remove item numbers @var{dnums} from the list of expressions to display.
5177 @code{undisplay} does not repeat if you press @key{RET} after using it.
5178 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5180 @kindex disable display
5181 @item disable display @var{dnums}@dots{}
5182 Disable the display of item numbers @var{dnums}. A disabled display
5183 item is not printed automatically, but is not forgotten. It may be
5184 enabled again later.
5186 @kindex enable display
5187 @item enable display @var{dnums}@dots{}
5188 Enable display of item numbers @var{dnums}. It becomes effective once
5189 again in auto display of its expression, until you specify otherwise.
5192 Display the current values of the expressions on the list, just as is
5193 done when your program stops.
5195 @kindex info display
5197 Print the list of expressions previously set up to display
5198 automatically, each one with its item number, but without showing the
5199 values. This includes disabled expressions, which are marked as such.
5200 It also includes expressions which would not be displayed right now
5201 because they refer to automatic variables not currently available.
5204 If a display expression refers to local variables, then it does not make
5205 sense outside the lexical context for which it was set up. Such an
5206 expression is disabled when execution enters a context where one of its
5207 variables is not defined. For example, if you give the command
5208 @code{display last_char} while inside a function with an argument
5209 @code{last_char}, @value{GDBN} displays this argument while your program
5210 continues to stop inside that function. When it stops elsewhere---where
5211 there is no variable @code{last_char}---the display is disabled
5212 automatically. The next time your program stops where @code{last_char}
5213 is meaningful, you can enable the display expression once again.
5215 @node Print Settings
5216 @section Print settings
5218 @cindex format options
5219 @cindex print settings
5220 @value{GDBN} provides the following ways to control how arrays, structures,
5221 and symbols are printed.
5224 These settings are useful for debugging programs in any language:
5227 @kindex set print address
5228 @item set print address
5229 @itemx set print address on
5230 @value{GDBN} prints memory addresses showing the location of stack
5231 traces, structure values, pointer values, breakpoints, and so forth,
5232 even when it also displays the contents of those addresses. The default
5233 is @code{on}. For example, this is what a stack frame display looks like with
5234 @code{set print address on}:
5239 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5241 530 if (lquote != def_lquote)
5245 @item set print address off
5246 Do not print addresses when displaying their contents. For example,
5247 this is the same stack frame displayed with @code{set print address off}:
5251 (@value{GDBP}) set print addr off
5253 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5254 530 if (lquote != def_lquote)
5258 You can use @samp{set print address off} to eliminate all machine
5259 dependent displays from the @value{GDBN} interface. For example, with
5260 @code{print address off}, you should get the same text for backtraces on
5261 all machines---whether or not they involve pointer arguments.
5263 @kindex show print address
5264 @item show print address
5265 Show whether or not addresses are to be printed.
5268 When @value{GDBN} prints a symbolic address, it normally prints the
5269 closest earlier symbol plus an offset. If that symbol does not uniquely
5270 identify the address (for example, it is a name whose scope is a single
5271 source file), you may need to clarify. One way to do this is with
5272 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5273 you can set @value{GDBN} to print the source file and line number when
5274 it prints a symbolic address:
5277 @kindex set print symbol-filename
5278 @item set print symbol-filename on
5279 Tell @value{GDBN} to print the source file name and line number of a
5280 symbol in the symbolic form of an address.
5282 @item set print symbol-filename off
5283 Do not print source file name and line number of a symbol. This is the
5286 @kindex show print symbol-filename
5287 @item show print symbol-filename
5288 Show whether or not @value{GDBN} will print the source file name and
5289 line number of a symbol in the symbolic form of an address.
5292 Another situation where it is helpful to show symbol filenames and line
5293 numbers is when disassembling code; @value{GDBN} shows you the line
5294 number and source file that corresponds to each instruction.
5296 Also, you may wish to see the symbolic form only if the address being
5297 printed is reasonably close to the closest earlier symbol:
5300 @kindex set print max-symbolic-offset
5301 @item set print max-symbolic-offset @var{max-offset}
5302 Tell @value{GDBN} to only display the symbolic form of an address if the
5303 offset between the closest earlier symbol and the address is less than
5304 @var{max-offset}. The default is 0, which tells @value{GDBN}
5305 to always print the symbolic form of an address if any symbol precedes it.
5307 @kindex show print max-symbolic-offset
5308 @item show print max-symbolic-offset
5309 Ask how large the maximum offset is that @value{GDBN} prints in a
5313 @cindex wild pointer, interpreting
5314 @cindex pointer, finding referent
5315 If you have a pointer and you are not sure where it points, try
5316 @samp{set print symbol-filename on}. Then you can determine the name
5317 and source file location of the variable where it points, using
5318 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5319 For example, here @value{GDBN} shows that a variable @code{ptt} points
5320 at another variable @code{t}, defined in @file{hi2.c}:
5323 (@value{GDBP}) set print symbol-filename on
5324 (@value{GDBP}) p/a ptt
5325 $4 = 0xe008 <t in hi2.c>
5329 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5330 does not show the symbol name and filename of the referent, even with
5331 the appropriate @code{set print} options turned on.
5334 Other settings control how different kinds of objects are printed:
5337 @kindex set print array
5338 @item set print array
5339 @itemx set print array on
5340 Pretty print arrays. This format is more convenient to read,
5341 but uses more space. The default is off.
5343 @item set print array off
5344 Return to compressed format for arrays.
5346 @kindex show print array
5347 @item show print array
5348 Show whether compressed or pretty format is selected for displaying
5351 @kindex set print elements
5352 @item set print elements @var{number-of-elements}
5353 Set a limit on how many elements of an array @value{GDBN} will print.
5354 If @value{GDBN} is printing a large array, it stops printing after it has
5355 printed the number of elements set by the @code{set print elements} command.
5356 This limit also applies to the display of strings.
5357 When @value{GDBN} starts, this limit is set to 200.
5358 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5360 @kindex show print elements
5361 @item show print elements
5362 Display the number of elements of a large array that @value{GDBN} will print.
5363 If the number is 0, then the printing is unlimited.
5365 @kindex set print null-stop
5366 @item set print null-stop
5367 Cause @value{GDBN} to stop printing the characters of an array when the first
5368 @sc{null} is encountered. This is useful when large arrays actually
5369 contain only short strings.
5372 @kindex set print pretty
5373 @item set print pretty on
5374 Cause @value{GDBN} to print structures in an indented format with one member
5375 per line, like this:
5390 @item set print pretty off
5391 Cause @value{GDBN} to print structures in a compact format, like this:
5395 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5396 meat = 0x54 "Pork"@}
5401 This is the default format.
5403 @kindex show print pretty
5404 @item show print pretty
5405 Show which format @value{GDBN} is using to print structures.
5407 @kindex set print sevenbit-strings
5408 @item set print sevenbit-strings on
5409 Print using only seven-bit characters; if this option is set,
5410 @value{GDBN} displays any eight-bit characters (in strings or
5411 character values) using the notation @code{\}@var{nnn}. This setting is
5412 best if you are working in English (@sc{ascii}) and you use the
5413 high-order bit of characters as a marker or ``meta'' bit.
5415 @item set print sevenbit-strings off
5416 Print full eight-bit characters. This allows the use of more
5417 international character sets, and is the default.
5419 @kindex show print sevenbit-strings
5420 @item show print sevenbit-strings
5421 Show whether or not @value{GDBN} is printing only seven-bit characters.
5423 @kindex set print union
5424 @item set print union on
5425 Tell @value{GDBN} to print unions which are contained in structures. This
5426 is the default setting.
5428 @item set print union off
5429 Tell @value{GDBN} not to print unions which are contained in structures.
5431 @kindex show print union
5432 @item show print union
5433 Ask @value{GDBN} whether or not it will print unions which are contained in
5436 For example, given the declarations
5439 typedef enum @{Tree, Bug@} Species;
5440 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5441 typedef enum @{Caterpillar, Cocoon, Butterfly@}
5452 struct thing foo = @{Tree, @{Acorn@}@};
5456 with @code{set print union on} in effect @samp{p foo} would print
5459 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5463 and with @code{set print union off} in effect it would print
5466 $1 = @{it = Tree, form = @{...@}@}
5472 These settings are of interest when debugging C@t{++} programs:
5476 @kindex set print demangle
5477 @item set print demangle
5478 @itemx set print demangle on
5479 Print C@t{++} names in their source form rather than in the encoded
5480 (``mangled'') form passed to the assembler and linker for type-safe
5481 linkage. The default is on.
5483 @kindex show print demangle
5484 @item show print demangle
5485 Show whether C@t{++} names are printed in mangled or demangled form.
5487 @kindex set print asm-demangle
5488 @item set print asm-demangle
5489 @itemx set print asm-demangle on
5490 Print C@t{++} names in their source form rather than their mangled form, even
5491 in assembler code printouts such as instruction disassemblies.
5494 @kindex show print asm-demangle
5495 @item show print asm-demangle
5496 Show whether C@t{++} names in assembly listings are printed in mangled
5499 @kindex set demangle-style
5500 @cindex C@t{++} symbol decoding style
5501 @cindex symbol decoding style, C@t{++}
5502 @item set demangle-style @var{style}
5503 Choose among several encoding schemes used by different compilers to
5504 represent C@t{++} names. The choices for @var{style} are currently:
5508 Allow @value{GDBN} to choose a decoding style by inspecting your program.
5511 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
5512 This is the default.
5515 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
5518 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
5521 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
5522 @strong{Warning:} this setting alone is not sufficient to allow
5523 debugging @code{cfront}-generated executables. @value{GDBN} would
5524 require further enhancement to permit that.
5527 If you omit @var{style}, you will see a list of possible formats.
5529 @kindex show demangle-style
5530 @item show demangle-style
5531 Display the encoding style currently in use for decoding C@t{++} symbols.
5533 @kindex set print object
5534 @item set print object
5535 @itemx set print object on
5536 When displaying a pointer to an object, identify the @emph{actual}
5537 (derived) type of the object rather than the @emph{declared} type, using
5538 the virtual function table.
5540 @item set print object off
5541 Display only the declared type of objects, without reference to the
5542 virtual function table. This is the default setting.
5544 @kindex show print object
5545 @item show print object
5546 Show whether actual, or declared, object types are displayed.
5548 @kindex set print static-members
5549 @item set print static-members
5550 @itemx set print static-members on
5551 Print static members when displaying a C@t{++} object. The default is on.
5553 @item set print static-members off
5554 Do not print static members when displaying a C@t{++} object.
5556 @kindex show print static-members
5557 @item show print static-members
5558 Show whether C@t{++} static members are printed, or not.
5560 @c These don't work with HP ANSI C++ yet.
5561 @kindex set print vtbl
5562 @item set print vtbl
5563 @itemx set print vtbl on
5564 Pretty print C@t{++} virtual function tables. The default is off.
5565 (The @code{vtbl} commands do not work on programs compiled with the HP
5566 ANSI C@t{++} compiler (@code{aCC}).)
5568 @item set print vtbl off
5569 Do not pretty print C@t{++} virtual function tables.
5571 @kindex show print vtbl
5572 @item show print vtbl
5573 Show whether C@t{++} virtual function tables are pretty printed, or not.
5577 @section Value history
5579 @cindex value history
5580 Values printed by the @code{print} command are saved in the @value{GDBN}
5581 @dfn{value history}. This allows you to refer to them in other expressions.
5582 Values are kept until the symbol table is re-read or discarded
5583 (for example with the @code{file} or @code{symbol-file} commands).
5584 When the symbol table changes, the value history is discarded,
5585 since the values may contain pointers back to the types defined in the
5590 @cindex history number
5591 The values printed are given @dfn{history numbers} by which you can
5592 refer to them. These are successive integers starting with one.
5593 @code{print} shows you the history number assigned to a value by
5594 printing @samp{$@var{num} = } before the value; here @var{num} is the
5597 To refer to any previous value, use @samp{$} followed by the value's
5598 history number. The way @code{print} labels its output is designed to
5599 remind you of this. Just @code{$} refers to the most recent value in
5600 the history, and @code{$$} refers to the value before that.
5601 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
5602 is the value just prior to @code{$$}, @code{$$1} is equivalent to
5603 @code{$$}, and @code{$$0} is equivalent to @code{$}.
5605 For example, suppose you have just printed a pointer to a structure and
5606 want to see the contents of the structure. It suffices to type
5612 If you have a chain of structures where the component @code{next} points
5613 to the next one, you can print the contents of the next one with this:
5620 You can print successive links in the chain by repeating this
5621 command---which you can do by just typing @key{RET}.
5623 Note that the history records values, not expressions. If the value of
5624 @code{x} is 4 and you type these commands:
5632 then the value recorded in the value history by the @code{print} command
5633 remains 4 even though the value of @code{x} has changed.
5638 Print the last ten values in the value history, with their item numbers.
5639 This is like @samp{p@ $$9} repeated ten times, except that @code{show
5640 values} does not change the history.
5642 @item show values @var{n}
5643 Print ten history values centered on history item number @var{n}.
5646 Print ten history values just after the values last printed. If no more
5647 values are available, @code{show values +} produces no display.
5650 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
5651 same effect as @samp{show values +}.
5653 @node Convenience Vars
5654 @section Convenience variables
5656 @cindex convenience variables
5657 @value{GDBN} provides @dfn{convenience variables} that you can use within
5658 @value{GDBN} to hold on to a value and refer to it later. These variables
5659 exist entirely within @value{GDBN}; they are not part of your program, and
5660 setting a convenience variable has no direct effect on further execution
5661 of your program. That is why you can use them freely.
5663 Convenience variables are prefixed with @samp{$}. Any name preceded by
5664 @samp{$} can be used for a convenience variable, unless it is one of
5665 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
5666 (Value history references, in contrast, are @emph{numbers} preceded
5667 by @samp{$}. @xref{Value History, ,Value history}.)
5669 You can save a value in a convenience variable with an assignment
5670 expression, just as you would set a variable in your program.
5674 set $foo = *object_ptr
5678 would save in @code{$foo} the value contained in the object pointed to by
5681 Using a convenience variable for the first time creates it, but its
5682 value is @code{void} until you assign a new value. You can alter the
5683 value with another assignment at any time.
5685 Convenience variables have no fixed types. You can assign a convenience
5686 variable any type of value, including structures and arrays, even if
5687 that variable already has a value of a different type. The convenience
5688 variable, when used as an expression, has the type of its current value.
5691 @kindex show convenience
5692 @item show convenience
5693 Print a list of convenience variables used so far, and their values.
5694 Abbreviated @code{show conv}.
5697 One of the ways to use a convenience variable is as a counter to be
5698 incremented or a pointer to be advanced. For example, to print
5699 a field from successive elements of an array of structures:
5703 print bar[$i++]->contents
5707 Repeat that command by typing @key{RET}.
5709 Some convenience variables are created automatically by @value{GDBN} and given
5710 values likely to be useful.
5713 @vindex $_@r{, convenience variable}
5715 The variable @code{$_} is automatically set by the @code{x} command to
5716 the last address examined (@pxref{Memory, ,Examining memory}). Other
5717 commands which provide a default address for @code{x} to examine also
5718 set @code{$_} to that address; these commands include @code{info line}
5719 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
5720 except when set by the @code{x} command, in which case it is a pointer
5721 to the type of @code{$__}.
5723 @vindex $__@r{, convenience variable}
5725 The variable @code{$__} is automatically set by the @code{x} command
5726 to the value found in the last address examined. Its type is chosen
5727 to match the format in which the data was printed.
5730 @vindex $_exitcode@r{, convenience variable}
5731 The variable @code{$_exitcode} is automatically set to the exit code when
5732 the program being debugged terminates.
5735 On HP-UX systems, if you refer to a function or variable name that
5736 begins with a dollar sign, @value{GDBN} searches for a user or system
5737 name first, before it searches for a convenience variable.
5743 You can refer to machine register contents, in expressions, as variables
5744 with names starting with @samp{$}. The names of registers are different
5745 for each machine; use @code{info registers} to see the names used on
5749 @kindex info registers
5750 @item info registers
5751 Print the names and values of all registers except floating-point
5752 and vector registers (in the selected stack frame).
5754 @kindex info all-registers
5755 @cindex floating point registers
5756 @item info all-registers
5757 Print the names and values of all registers, including floating-point
5758 and vector registers (in the selected stack frame).
5760 @item info registers @var{regname} @dots{}
5761 Print the @dfn{relativized} value of each specified register @var{regname}.
5762 As discussed in detail below, register values are normally relative to
5763 the selected stack frame. @var{regname} may be any register name valid on
5764 the machine you are using, with or without the initial @samp{$}.
5767 @value{GDBN} has four ``standard'' register names that are available (in
5768 expressions) on most machines---whenever they do not conflict with an
5769 architecture's canonical mnemonics for registers. The register names
5770 @code{$pc} and @code{$sp} are used for the program counter register and
5771 the stack pointer. @code{$fp} is used for a register that contains a
5772 pointer to the current stack frame, and @code{$ps} is used for a
5773 register that contains the processor status. For example,
5774 you could print the program counter in hex with
5781 or print the instruction to be executed next with
5788 or add four to the stack pointer@footnote{This is a way of removing
5789 one word from the stack, on machines where stacks grow downward in
5790 memory (most machines, nowadays). This assumes that the innermost
5791 stack frame is selected; setting @code{$sp} is not allowed when other
5792 stack frames are selected. To pop entire frames off the stack,
5793 regardless of machine architecture, use @code{return};
5794 see @ref{Returning, ,Returning from a function}.} with
5800 Whenever possible, these four standard register names are available on
5801 your machine even though the machine has different canonical mnemonics,
5802 so long as there is no conflict. The @code{info registers} command
5803 shows the canonical names. For example, on the SPARC, @code{info
5804 registers} displays the processor status register as @code{$psr} but you
5805 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
5806 is an alias for the @sc{eflags} register.
5808 @value{GDBN} always considers the contents of an ordinary register as an
5809 integer when the register is examined in this way. Some machines have
5810 special registers which can hold nothing but floating point; these
5811 registers are considered to have floating point values. There is no way
5812 to refer to the contents of an ordinary register as floating point value
5813 (although you can @emph{print} it as a floating point value with
5814 @samp{print/f $@var{regname}}).
5816 Some registers have distinct ``raw'' and ``virtual'' data formats. This
5817 means that the data format in which the register contents are saved by
5818 the operating system is not the same one that your program normally
5819 sees. For example, the registers of the 68881 floating point
5820 coprocessor are always saved in ``extended'' (raw) format, but all C
5821 programs expect to work with ``double'' (virtual) format. In such
5822 cases, @value{GDBN} normally works with the virtual format only (the format
5823 that makes sense for your program), but the @code{info registers} command
5824 prints the data in both formats.
5826 Normally, register values are relative to the selected stack frame
5827 (@pxref{Selection, ,Selecting a frame}). This means that you get the
5828 value that the register would contain if all stack frames farther in
5829 were exited and their saved registers restored. In order to see the
5830 true contents of hardware registers, you must select the innermost
5831 frame (with @samp{frame 0}).
5833 However, @value{GDBN} must deduce where registers are saved, from the machine
5834 code generated by your compiler. If some registers are not saved, or if
5835 @value{GDBN} is unable to locate the saved registers, the selected stack
5836 frame makes no difference.
5838 @node Floating Point Hardware
5839 @section Floating point hardware
5840 @cindex floating point
5842 Depending on the configuration, @value{GDBN} may be able to give
5843 you more information about the status of the floating point hardware.
5848 Display hardware-dependent information about the floating
5849 point unit. The exact contents and layout vary depending on the
5850 floating point chip. Currently, @samp{info float} is supported on
5851 the ARM and x86 machines.
5855 @section Vector Unit
5858 Depending on the configuration, @value{GDBN} may be able to give you
5859 more information about the status of the vector unit.
5864 Display information about the vector unit. The exact contents and
5865 layout vary depending on the hardware.
5868 @node Memory Region Attributes
5869 @section Memory region attributes
5870 @cindex memory region attributes
5872 @dfn{Memory region attributes} allow you to describe special handling
5873 required by regions of your target's memory. @value{GDBN} uses attributes
5874 to determine whether to allow certain types of memory accesses; whether to
5875 use specific width accesses; and whether to cache target memory.
5877 Defined memory regions can be individually enabled and disabled. When a
5878 memory region is disabled, @value{GDBN} uses the default attributes when
5879 accessing memory in that region. Similarly, if no memory regions have
5880 been defined, @value{GDBN} uses the default attributes when accessing
5883 When a memory region is defined, it is given a number to identify it;
5884 to enable, disable, or remove a memory region, you specify that number.
5888 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
5889 Define memory region bounded by @var{lower} and @var{upper} with
5890 attributes @var{attributes}@dots{}. Note that @var{upper} == 0 is a
5891 special case: it is treated as the the target's maximum memory address.
5892 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
5895 @item delete mem @var{nums}@dots{}
5896 Remove memory regions @var{nums}@dots{}.
5899 @item disable mem @var{nums}@dots{}
5900 Disable memory regions @var{nums}@dots{}.
5901 A disabled memory region is not forgotten.
5902 It may be enabled again later.
5905 @item enable mem @var{nums}@dots{}
5906 Enable memory regions @var{nums}@dots{}.
5910 Print a table of all defined memory regions, with the following columns
5914 @item Memory Region Number
5915 @item Enabled or Disabled.
5916 Enabled memory regions are marked with @samp{y}.
5917 Disabled memory regions are marked with @samp{n}.
5920 The address defining the inclusive lower bound of the memory region.
5923 The address defining the exclusive upper bound of the memory region.
5926 The list of attributes set for this memory region.
5931 @subsection Attributes
5933 @subsubsection Memory Access Mode
5934 The access mode attributes set whether @value{GDBN} may make read or
5935 write accesses to a memory region.
5937 While these attributes prevent @value{GDBN} from performing invalid
5938 memory accesses, they do nothing to prevent the target system, I/O DMA,
5939 etc. from accessing memory.
5943 Memory is read only.
5945 Memory is write only.
5947 Memory is read/write. This is the default.
5950 @subsubsection Memory Access Size
5951 The acccess size attributes tells @value{GDBN} to use specific sized
5952 accesses in the memory region. Often memory mapped device registers
5953 require specific sized accesses. If no access size attribute is
5954 specified, @value{GDBN} may use accesses of any size.
5958 Use 8 bit memory accesses.
5960 Use 16 bit memory accesses.
5962 Use 32 bit memory accesses.
5964 Use 64 bit memory accesses.
5967 @c @subsubsection Hardware/Software Breakpoints
5968 @c The hardware/software breakpoint attributes set whether @value{GDBN}
5969 @c will use hardware or software breakpoints for the internal breakpoints
5970 @c used by the step, next, finish, until, etc. commands.
5974 @c Always use hardware breakpoints
5975 @c @item swbreak (default)
5978 @subsubsection Data Cache
5979 The data cache attributes set whether @value{GDBN} will cache target
5980 memory. While this generally improves performance by reducing debug
5981 protocol overhead, it can lead to incorrect results because @value{GDBN}
5982 does not know about volatile variables or memory mapped device
5987 Enable @value{GDBN} to cache target memory.
5989 Disable @value{GDBN} from caching target memory. This is the default.
5992 @c @subsubsection Memory Write Verification
5993 @c The memory write verification attributes set whether @value{GDBN}
5994 @c will re-reads data after each write to verify the write was successful.
5998 @c @item noverify (default)
6001 @node Dump/Restore Files
6002 @section Copy between memory and a file
6003 @cindex dump/restore files
6004 @cindex append data to a file
6005 @cindex dump data to a file
6006 @cindex restore data from a file
6008 You can use the commands @code{dump}, @code{append}, and
6009 @code{restore} to copy data between target memory and a file. The
6010 @code{dump} and @code{append} commands write data to a file, and the
6011 @code{restore} command reads data from a file back into the inferior's
6012 memory. Files may be in binary, Motorola S-record, Intel hex, or
6013 Tektronix Hex format; however, @value{GDBN} can only append to binary
6019 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6020 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6021 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6022 or the value of @var{expr}, to @var{filename} in the given format.
6024 The @var{format} parameter may be any one of:
6031 Motorola S-record format.
6033 Tektronix Hex format.
6036 @value{GDBN} uses the same definitions of these formats as the
6037 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
6038 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
6042 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6043 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
6044 Append the contents of memory from @var{start_addr} to @var{end_addr},
6045 or the value of @var{expr}, to @var{filename}, in raw binary form.
6046 (@value{GDBN} can only append data to files in raw binary form.)
6049 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
6050 Restore the contents of file @var{filename} into memory. The
6051 @code{restore} command can automatically recognize any known @sc{bfd}
6052 file format, except for raw binary. To restore a raw binary file you
6053 must specify the optional keyword @code{binary} after the filename.
6055 If @var{bias} is non-zero, its value will be added to the addresses
6056 contained in the file. Binary files always start at address zero, so
6057 they will be restored at address @var{bias}. Other bfd files have
6058 a built-in location; they will be restored at offset @var{bias}
6061 If @var{start} and/or @var{end} are non-zero, then only data between
6062 file offset @var{start} and file offset @var{end} will be restored.
6063 These offsets are relative to the addresses in the file, before
6064 the @var{bias} argument is applied.
6068 @node Character Sets
6069 @section Character Sets
6070 @cindex character sets
6072 @cindex translating between character sets
6073 @cindex host character set
6074 @cindex target character set
6076 If the program you are debugging uses a different character set to
6077 represent characters and strings than the one @value{GDBN} uses itself,
6078 @value{GDBN} can automatically translate between the character sets for
6079 you. The character set @value{GDBN} uses we call the @dfn{host
6080 character set}; the one the inferior program uses we call the
6081 @dfn{target character set}.
6083 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
6084 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
6085 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
6086 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
6087 then the host character set is Latin-1, and the target character set is
6088 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
6089 target-charset EBCDIC-US}, then @value{GDBN} translates between
6090 @sc{ebcdic} and Latin 1 as you print character or string values, or use
6091 character and string literals in expressions.
6093 @value{GDBN} has no way to automatically recognize which character set
6094 the inferior program uses; you must tell it, using the @code{set
6095 target-charset} command, described below.
6097 Here are the commands for controlling @value{GDBN}'s character set
6101 @item set target-charset @var{charset}
6102 @kindex set target-charset
6103 Set the current target character set to @var{charset}. We list the
6104 character set names @value{GDBN} recognizes below, but if you type
6105 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6106 list the target character sets it supports.
6110 @item set host-charset @var{charset}
6111 @kindex set host-charset
6112 Set the current host character set to @var{charset}.
6114 By default, @value{GDBN} uses a host character set appropriate to the
6115 system it is running on; you can override that default using the
6116 @code{set host-charset} command.
6118 @value{GDBN} can only use certain character sets as its host character
6119 set. We list the character set names @value{GDBN} recognizes below, and
6120 indicate which can be host character sets, but if you type
6121 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6122 list the host character sets it supports.
6124 @item set charset @var{charset}
6126 Set the current host and target character sets to @var{charset}. As
6127 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
6128 @value{GDBN} will list the name of the character sets that can be used
6129 for both host and target.
6133 @kindex show charset
6134 Show the names of the current host and target charsets.
6136 @itemx show host-charset
6137 @kindex show host-charset
6138 Show the name of the current host charset.
6140 @itemx show target-charset
6141 @kindex show target-charset
6142 Show the name of the current target charset.
6146 @value{GDBN} currently includes support for the following character
6152 @cindex ASCII character set
6153 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6157 @cindex ISO 8859-1 character set
6158 @cindex ISO Latin 1 character set
6159 The ISO Latin 1 character set. This extends @sc{ascii} with accented
6160 characters needed for French, German, and Spanish. @value{GDBN} can use
6161 this as its host character set.
6165 @cindex EBCDIC character set
6166 @cindex IBM1047 character set
6167 Variants of the @sc{ebcdic} character set, used on some of IBM's
6168 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6169 @value{GDBN} cannot use these as its host character set.
6173 Note that these are all single-byte character sets. More work inside
6174 GDB is needed to support multi-byte or variable-width character
6175 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6177 Here is an example of @value{GDBN}'s character set support in action.
6178 Assume that the following source code has been placed in the file
6179 @file{charset-test.c}:
6185 = @{72, 101, 108, 108, 111, 44, 32, 119,
6186 111, 114, 108, 100, 33, 10, 0@};
6187 char ibm1047_hello[]
6188 = @{200, 133, 147, 147, 150, 107, 64, 166,
6189 150, 153, 147, 132, 90, 37, 0@};
6193 printf ("Hello, world!\n");
6197 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6198 containing the string @samp{Hello, world!} followed by a newline,
6199 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6201 We compile the program, and invoke the debugger on it:
6204 $ gcc -g charset-test.c -o charset-test
6205 $ gdb -nw charset-test
6206 GNU gdb 2001-12-19-cvs
6207 Copyright 2001 Free Software Foundation, Inc.
6212 We can use the @code{show charset} command to see what character sets
6213 @value{GDBN} is currently using to interpret and display characters and
6218 The current host and target character set is `ISO-8859-1'.
6222 For the sake of printing this manual, let's use @sc{ascii} as our
6223 initial character set:
6225 (gdb) set charset ASCII
6227 The current host and target character set is `ASCII'.
6231 Let's assume that @sc{ascii} is indeed the correct character set for our
6232 host system --- in other words, let's assume that if @value{GDBN} prints
6233 characters using the @sc{ascii} character set, our terminal will display
6234 them properly. Since our current target character set is also
6235 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
6238 (gdb) print ascii_hello
6239 $1 = 0x401698 "Hello, world!\n"
6240 (gdb) print ascii_hello[0]
6245 @value{GDBN} uses the target character set for character and string
6246 literals you use in expressions:
6254 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
6257 @value{GDBN} relies on the user to tell it which character set the
6258 target program uses. If we print @code{ibm1047_hello} while our target
6259 character set is still @sc{ascii}, we get jibberish:
6262 (gdb) print ibm1047_hello
6263 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
6264 (gdb) print ibm1047_hello[0]
6269 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
6270 @value{GDBN} tells us the character sets it supports:
6273 (gdb) set target-charset
6274 ASCII EBCDIC-US IBM1047 ISO-8859-1
6275 (gdb) set target-charset
6278 We can select @sc{ibm1047} as our target character set, and examine the
6279 program's strings again. Now the @sc{ascii} string is wrong, but
6280 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
6281 target character set, @sc{ibm1047}, to the host character set,
6282 @sc{ascii}, and they display correctly:
6285 (gdb) set target-charset IBM1047
6287 The current host character set is `ASCII'.
6288 The current target character set is `IBM1047'.
6289 (gdb) print ascii_hello
6290 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
6291 (gdb) print ascii_hello[0]
6293 (gdb) print ibm1047_hello
6294 $8 = 0x4016a8 "Hello, world!\n"
6295 (gdb) print ibm1047_hello[0]
6300 As above, @value{GDBN} uses the target character set for character and
6301 string literals you use in expressions:
6309 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
6314 @chapter C Preprocessor Macros
6316 Some languages, such as C and C++, provide a way to define and invoke
6317 ``preprocessor macros'' which expand into strings of tokens.
6318 @value{GDBN} can evaluate expressions containing macro invocations, show
6319 the result of macro expansion, and show a macro's definition, including
6320 where it was defined.
6322 You may need to compile your program specially to provide @value{GDBN}
6323 with information about preprocessor macros. Most compilers do not
6324 include macros in their debugging information, even when you compile
6325 with the @option{-g} flag. @xref{Compilation}.
6327 A program may define a macro at one point, remove that definition later,
6328 and then provide a different definition after that. Thus, at different
6329 points in the program, a macro may have different definitions, or have
6330 no definition at all. If there is a current stack frame, @value{GDBN}
6331 uses the macros in scope at that frame's source code line. Otherwise,
6332 @value{GDBN} uses the macros in scope at the current listing location;
6335 At the moment, @value{GDBN} does not support the @code{##}
6336 token-splicing operator, the @code{#} stringification operator, or
6337 variable-arity macros.
6339 Whenever @value{GDBN} evaluates an expression, it always expands any
6340 macro invocations present in the expression. @value{GDBN} also provides
6341 the following commands for working with macros explicitly.
6345 @kindex macro expand
6346 @cindex macro expansion, showing the results of preprocessor
6347 @cindex preprocessor macro expansion, showing the results of
6348 @cindex expanding preprocessor macros
6349 @item macro expand @var{expression}
6350 @itemx macro exp @var{expression}
6351 Show the results of expanding all preprocessor macro invocations in
6352 @var{expression}. Since @value{GDBN} simply expands macros, but does
6353 not parse the result, @var{expression} need not be a valid expression;
6354 it can be any string of tokens.
6356 @kindex macro expand-once
6357 @item macro expand-once @var{expression}
6358 @itemx macro exp1 @var{expression}
6359 @i{(This command is not yet implemented.)} Show the results of
6360 expanding those preprocessor macro invocations that appear explicitly in
6361 @var{expression}. Macro invocations appearing in that expansion are
6362 left unchanged. This command allows you to see the effect of a
6363 particular macro more clearly, without being confused by further
6364 expansions. Since @value{GDBN} simply expands macros, but does not
6365 parse the result, @var{expression} need not be a valid expression; it
6366 can be any string of tokens.
6369 @cindex macro definition, showing
6370 @cindex definition, showing a macro's
6371 @item info macro @var{macro}
6372 Show the definition of the macro named @var{macro}, and describe the
6373 source location where that definition was established.
6375 @kindex macro define
6376 @cindex user-defined macros
6377 @cindex defining macros interactively
6378 @cindex macros, user-defined
6379 @item macro define @var{macro} @var{replacement-list}
6380 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
6381 @i{(This command is not yet implemented.)} Introduce a definition for a
6382 preprocessor macro named @var{macro}, invocations of which are replaced
6383 by the tokens given in @var{replacement-list}. The first form of this
6384 command defines an ``object-like'' macro, which takes no arguments; the
6385 second form defines a ``function-like'' macro, which takes the arguments
6386 given in @var{arglist}.
6388 A definition introduced by this command is in scope in every expression
6389 evaluated in @value{GDBN}, until it is removed with the @command{macro
6390 undef} command, described below. The definition overrides all
6391 definitions for @var{macro} present in the program being debugged, as
6392 well as any previous user-supplied definition.
6395 @item macro undef @var{macro}
6396 @i{(This command is not yet implemented.)} Remove any user-supplied
6397 definition for the macro named @var{macro}. This command only affects
6398 definitions provided with the @command{macro define} command, described
6399 above; it cannot remove definitions present in the program being
6404 @cindex macros, example of debugging with
6405 Here is a transcript showing the above commands in action. First, we
6406 show our source files:
6414 #define ADD(x) (M + x)
6419 printf ("Hello, world!\n");
6421 printf ("We're so creative.\n");
6423 printf ("Goodbye, world!\n");
6430 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
6431 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
6432 compiler includes information about preprocessor macros in the debugging
6436 $ gcc -gdwarf-2 -g3 sample.c -o sample
6440 Now, we start @value{GDBN} on our sample program:
6444 GNU gdb 2002-05-06-cvs
6445 Copyright 2002 Free Software Foundation, Inc.
6446 GDB is free software, @dots{}
6450 We can expand macros and examine their definitions, even when the
6451 program is not running. @value{GDBN} uses the current listing position
6452 to decide which macro definitions are in scope:
6458 5 #define ADD(x) (M + x)
6463 10 printf ("Hello, world!\n");
6465 12 printf ("We're so creative.\n");
6466 (gdb) info macro ADD
6467 Defined at /home/jimb/gdb/macros/play/sample.c:5
6468 #define ADD(x) (M + x)
6470 Defined at /home/jimb/gdb/macros/play/sample.h:1
6471 included at /home/jimb/gdb/macros/play/sample.c:2
6473 (gdb) macro expand ADD(1)
6474 expands to: (42 + 1)
6475 (gdb) macro expand-once ADD(1)
6476 expands to: once (M + 1)
6480 In the example above, note that @command{macro expand-once} expands only
6481 the macro invocation explicit in the original text --- the invocation of
6482 @code{ADD} --- but does not expand the invocation of the macro @code{M},
6483 which was introduced by @code{ADD}.
6485 Once the program is running, GDB uses the macro definitions in force at
6486 the source line of the current stack frame:
6490 Breakpoint 1 at 0x8048370: file sample.c, line 10.
6492 Starting program: /home/jimb/gdb/macros/play/sample
6494 Breakpoint 1, main () at sample.c:10
6495 10 printf ("Hello, world!\n");
6499 At line 10, the definition of the macro @code{N} at line 9 is in force:
6503 Defined at /home/jimb/gdb/macros/play/sample.c:9
6505 (gdb) macro expand N Q M
6512 As we step over directives that remove @code{N}'s definition, and then
6513 give it a new definition, @value{GDBN} finds the definition (or lack
6514 thereof) in force at each point:
6519 12 printf ("We're so creative.\n");
6521 The symbol `N' has no definition as a C/C++ preprocessor macro
6522 at /home/jimb/gdb/macros/play/sample.c:12
6525 14 printf ("Goodbye, world!\n");
6527 Defined at /home/jimb/gdb/macros/play/sample.c:13
6529 (gdb) macro expand N Q M
6530 expands to: 1729 < 42
6538 @chapter Tracepoints
6539 @c This chapter is based on the documentation written by Michael
6540 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
6543 In some applications, it is not feasible for the debugger to interrupt
6544 the program's execution long enough for the developer to learn
6545 anything helpful about its behavior. If the program's correctness
6546 depends on its real-time behavior, delays introduced by a debugger
6547 might cause the program to change its behavior drastically, or perhaps
6548 fail, even when the code itself is correct. It is useful to be able
6549 to observe the program's behavior without interrupting it.
6551 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
6552 specify locations in the program, called @dfn{tracepoints}, and
6553 arbitrary expressions to evaluate when those tracepoints are reached.
6554 Later, using the @code{tfind} command, you can examine the values
6555 those expressions had when the program hit the tracepoints. The
6556 expressions may also denote objects in memory---structures or arrays,
6557 for example---whose values @value{GDBN} should record; while visiting
6558 a particular tracepoint, you may inspect those objects as if they were
6559 in memory at that moment. However, because @value{GDBN} records these
6560 values without interacting with you, it can do so quickly and
6561 unobtrusively, hopefully not disturbing the program's behavior.
6563 The tracepoint facility is currently available only for remote
6564 targets. @xref{Targets}. In addition, your remote target must know how
6565 to collect trace data. This functionality is implemented in the remote
6566 stub; however, none of the stubs distributed with @value{GDBN} support
6567 tracepoints as of this writing.
6569 This chapter describes the tracepoint commands and features.
6573 * Analyze Collected Data::
6574 * Tracepoint Variables::
6577 @node Set Tracepoints
6578 @section Commands to Set Tracepoints
6580 Before running such a @dfn{trace experiment}, an arbitrary number of
6581 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
6582 tracepoint has a number assigned to it by @value{GDBN}. Like with
6583 breakpoints, tracepoint numbers are successive integers starting from
6584 one. Many of the commands associated with tracepoints take the
6585 tracepoint number as their argument, to identify which tracepoint to
6588 For each tracepoint, you can specify, in advance, some arbitrary set
6589 of data that you want the target to collect in the trace buffer when
6590 it hits that tracepoint. The collected data can include registers,
6591 local variables, or global data. Later, you can use @value{GDBN}
6592 commands to examine the values these data had at the time the
6595 This section describes commands to set tracepoints and associated
6596 conditions and actions.
6599 * Create and Delete Tracepoints::
6600 * Enable and Disable Tracepoints::
6601 * Tracepoint Passcounts::
6602 * Tracepoint Actions::
6603 * Listing Tracepoints::
6604 * Starting and Stopping Trace Experiment::
6607 @node Create and Delete Tracepoints
6608 @subsection Create and Delete Tracepoints
6611 @cindex set tracepoint
6614 The @code{trace} command is very similar to the @code{break} command.
6615 Its argument can be a source line, a function name, or an address in
6616 the target program. @xref{Set Breaks}. The @code{trace} command
6617 defines a tracepoint, which is a point in the target program where the
6618 debugger will briefly stop, collect some data, and then allow the
6619 program to continue. Setting a tracepoint or changing its commands
6620 doesn't take effect until the next @code{tstart} command; thus, you
6621 cannot change the tracepoint attributes once a trace experiment is
6624 Here are some examples of using the @code{trace} command:
6627 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
6629 (@value{GDBP}) @b{trace +2} // 2 lines forward
6631 (@value{GDBP}) @b{trace my_function} // first source line of function
6633 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
6635 (@value{GDBP}) @b{trace *0x2117c4} // an address
6639 You can abbreviate @code{trace} as @code{tr}.
6642 @cindex last tracepoint number
6643 @cindex recent tracepoint number
6644 @cindex tracepoint number
6645 The convenience variable @code{$tpnum} records the tracepoint number
6646 of the most recently set tracepoint.
6648 @kindex delete tracepoint
6649 @cindex tracepoint deletion
6650 @item delete tracepoint @r{[}@var{num}@r{]}
6651 Permanently delete one or more tracepoints. With no argument, the
6652 default is to delete all tracepoints.
6657 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
6659 (@value{GDBP}) @b{delete trace} // remove all tracepoints
6663 You can abbreviate this command as @code{del tr}.
6666 @node Enable and Disable Tracepoints
6667 @subsection Enable and Disable Tracepoints
6670 @kindex disable tracepoint
6671 @item disable tracepoint @r{[}@var{num}@r{]}
6672 Disable tracepoint @var{num}, or all tracepoints if no argument
6673 @var{num} is given. A disabled tracepoint will have no effect during
6674 the next trace experiment, but it is not forgotten. You can re-enable
6675 a disabled tracepoint using the @code{enable tracepoint} command.
6677 @kindex enable tracepoint
6678 @item enable tracepoint @r{[}@var{num}@r{]}
6679 Enable tracepoint @var{num}, or all tracepoints. The enabled
6680 tracepoints will become effective the next time a trace experiment is
6684 @node Tracepoint Passcounts
6685 @subsection Tracepoint Passcounts
6689 @cindex tracepoint pass count
6690 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
6691 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
6692 automatically stop a trace experiment. If a tracepoint's passcount is
6693 @var{n}, then the trace experiment will be automatically stopped on
6694 the @var{n}'th time that tracepoint is hit. If the tracepoint number
6695 @var{num} is not specified, the @code{passcount} command sets the
6696 passcount of the most recently defined tracepoint. If no passcount is
6697 given, the trace experiment will run until stopped explicitly by the
6703 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
6704 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
6706 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
6707 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
6708 (@value{GDBP}) @b{trace foo}
6709 (@value{GDBP}) @b{pass 3}
6710 (@value{GDBP}) @b{trace bar}
6711 (@value{GDBP}) @b{pass 2}
6712 (@value{GDBP}) @b{trace baz}
6713 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
6714 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
6715 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
6716 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
6720 @node Tracepoint Actions
6721 @subsection Tracepoint Action Lists
6725 @cindex tracepoint actions
6726 @item actions @r{[}@var{num}@r{]}
6727 This command will prompt for a list of actions to be taken when the
6728 tracepoint is hit. If the tracepoint number @var{num} is not
6729 specified, this command sets the actions for the one that was most
6730 recently defined (so that you can define a tracepoint and then say
6731 @code{actions} without bothering about its number). You specify the
6732 actions themselves on the following lines, one action at a time, and
6733 terminate the actions list with a line containing just @code{end}. So
6734 far, the only defined actions are @code{collect} and
6735 @code{while-stepping}.
6737 @cindex remove actions from a tracepoint
6738 To remove all actions from a tracepoint, type @samp{actions @var{num}}
6739 and follow it immediately with @samp{end}.
6742 (@value{GDBP}) @b{collect @var{data}} // collect some data
6744 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
6746 (@value{GDBP}) @b{end} // signals the end of actions.
6749 In the following example, the action list begins with @code{collect}
6750 commands indicating the things to be collected when the tracepoint is
6751 hit. Then, in order to single-step and collect additional data
6752 following the tracepoint, a @code{while-stepping} command is used,
6753 followed by the list of things to be collected while stepping. The
6754 @code{while-stepping} command is terminated by its own separate
6755 @code{end} command. Lastly, the action list is terminated by an
6759 (@value{GDBP}) @b{trace foo}
6760 (@value{GDBP}) @b{actions}
6761 Enter actions for tracepoint 1, one per line:
6770 @kindex collect @r{(tracepoints)}
6771 @item collect @var{expr1}, @var{expr2}, @dots{}
6772 Collect values of the given expressions when the tracepoint is hit.
6773 This command accepts a comma-separated list of any valid expressions.
6774 In addition to global, static, or local variables, the following
6775 special arguments are supported:
6779 collect all registers
6782 collect all function arguments
6785 collect all local variables.
6788 You can give several consecutive @code{collect} commands, each one
6789 with a single argument, or one @code{collect} command with several
6790 arguments separated by commas: the effect is the same.
6792 The command @code{info scope} (@pxref{Symbols, info scope}) is
6793 particularly useful for figuring out what data to collect.
6795 @kindex while-stepping @r{(tracepoints)}
6796 @item while-stepping @var{n}
6797 Perform @var{n} single-step traces after the tracepoint, collecting
6798 new data at each step. The @code{while-stepping} command is
6799 followed by the list of what to collect while stepping (followed by
6800 its own @code{end} command):
6804 > collect $regs, myglobal
6810 You may abbreviate @code{while-stepping} as @code{ws} or
6814 @node Listing Tracepoints
6815 @subsection Listing Tracepoints
6818 @kindex info tracepoints
6819 @cindex information about tracepoints
6820 @item info tracepoints @r{[}@var{num}@r{]}
6821 Display information about the tracepoint @var{num}. If you don't specify
6822 a tracepoint number, displays information about all the tracepoints
6823 defined so far. For each tracepoint, the following information is
6830 whether it is enabled or disabled
6834 its passcount as given by the @code{passcount @var{n}} command
6836 its step count as given by the @code{while-stepping @var{n}} command
6838 where in the source files is the tracepoint set
6840 its action list as given by the @code{actions} command
6844 (@value{GDBP}) @b{info trace}
6845 Num Enb Address PassC StepC What
6846 1 y 0x002117c4 0 0 <gdb_asm>
6847 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
6848 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
6853 This command can be abbreviated @code{info tp}.
6856 @node Starting and Stopping Trace Experiment
6857 @subsection Starting and Stopping Trace Experiment
6861 @cindex start a new trace experiment
6862 @cindex collected data discarded
6864 This command takes no arguments. It starts the trace experiment, and
6865 begins collecting data. This has the side effect of discarding all
6866 the data collected in the trace buffer during the previous trace
6870 @cindex stop a running trace experiment
6872 This command takes no arguments. It ends the trace experiment, and
6873 stops collecting data.
6875 @strong{Note:} a trace experiment and data collection may stop
6876 automatically if any tracepoint's passcount is reached
6877 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
6880 @cindex status of trace data collection
6881 @cindex trace experiment, status of
6883 This command displays the status of the current trace data
6887 Here is an example of the commands we described so far:
6890 (@value{GDBP}) @b{trace gdb_c_test}
6891 (@value{GDBP}) @b{actions}
6892 Enter actions for tracepoint #1, one per line.
6893 > collect $regs,$locals,$args
6898 (@value{GDBP}) @b{tstart}
6899 [time passes @dots{}]
6900 (@value{GDBP}) @b{tstop}
6904 @node Analyze Collected Data
6905 @section Using the collected data
6907 After the tracepoint experiment ends, you use @value{GDBN} commands
6908 for examining the trace data. The basic idea is that each tracepoint
6909 collects a trace @dfn{snapshot} every time it is hit and another
6910 snapshot every time it single-steps. All these snapshots are
6911 consecutively numbered from zero and go into a buffer, and you can
6912 examine them later. The way you examine them is to @dfn{focus} on a
6913 specific trace snapshot. When the remote stub is focused on a trace
6914 snapshot, it will respond to all @value{GDBN} requests for memory and
6915 registers by reading from the buffer which belongs to that snapshot,
6916 rather than from @emph{real} memory or registers of the program being
6917 debugged. This means that @strong{all} @value{GDBN} commands
6918 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
6919 behave as if we were currently debugging the program state as it was
6920 when the tracepoint occurred. Any requests for data that are not in
6921 the buffer will fail.
6924 * tfind:: How to select a trace snapshot
6925 * tdump:: How to display all data for a snapshot
6926 * save-tracepoints:: How to save tracepoints for a future run
6930 @subsection @code{tfind @var{n}}
6933 @cindex select trace snapshot
6934 @cindex find trace snapshot
6935 The basic command for selecting a trace snapshot from the buffer is
6936 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
6937 counting from zero. If no argument @var{n} is given, the next
6938 snapshot is selected.
6940 Here are the various forms of using the @code{tfind} command.
6944 Find the first snapshot in the buffer. This is a synonym for
6945 @code{tfind 0} (since 0 is the number of the first snapshot).
6948 Stop debugging trace snapshots, resume @emph{live} debugging.
6951 Same as @samp{tfind none}.
6954 No argument means find the next trace snapshot.
6957 Find the previous trace snapshot before the current one. This permits
6958 retracing earlier steps.
6960 @item tfind tracepoint @var{num}
6961 Find the next snapshot associated with tracepoint @var{num}. Search
6962 proceeds forward from the last examined trace snapshot. If no
6963 argument @var{num} is given, it means find the next snapshot collected
6964 for the same tracepoint as the current snapshot.
6966 @item tfind pc @var{addr}
6967 Find the next snapshot associated with the value @var{addr} of the
6968 program counter. Search proceeds forward from the last examined trace
6969 snapshot. If no argument @var{addr} is given, it means find the next
6970 snapshot with the same value of PC as the current snapshot.
6972 @item tfind outside @var{addr1}, @var{addr2}
6973 Find the next snapshot whose PC is outside the given range of
6976 @item tfind range @var{addr1}, @var{addr2}
6977 Find the next snapshot whose PC is between @var{addr1} and
6978 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
6980 @item tfind line @r{[}@var{file}:@r{]}@var{n}
6981 Find the next snapshot associated with the source line @var{n}. If
6982 the optional argument @var{file} is given, refer to line @var{n} in
6983 that source file. Search proceeds forward from the last examined
6984 trace snapshot. If no argument @var{n} is given, it means find the
6985 next line other than the one currently being examined; thus saying
6986 @code{tfind line} repeatedly can appear to have the same effect as
6987 stepping from line to line in a @emph{live} debugging session.
6990 The default arguments for the @code{tfind} commands are specifically
6991 designed to make it easy to scan through the trace buffer. For
6992 instance, @code{tfind} with no argument selects the next trace
6993 snapshot, and @code{tfind -} with no argument selects the previous
6994 trace snapshot. So, by giving one @code{tfind} command, and then
6995 simply hitting @key{RET} repeatedly you can examine all the trace
6996 snapshots in order. Or, by saying @code{tfind -} and then hitting
6997 @key{RET} repeatedly you can examine the snapshots in reverse order.
6998 The @code{tfind line} command with no argument selects the snapshot
6999 for the next source line executed. The @code{tfind pc} command with
7000 no argument selects the next snapshot with the same program counter
7001 (PC) as the current frame. The @code{tfind tracepoint} command with
7002 no argument selects the next trace snapshot collected by the same
7003 tracepoint as the current one.
7005 In addition to letting you scan through the trace buffer manually,
7006 these commands make it easy to construct @value{GDBN} scripts that
7007 scan through the trace buffer and print out whatever collected data
7008 you are interested in. Thus, if we want to examine the PC, FP, and SP
7009 registers from each trace frame in the buffer, we can say this:
7012 (@value{GDBP}) @b{tfind start}
7013 (@value{GDBP}) @b{while ($trace_frame != -1)}
7014 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
7015 $trace_frame, $pc, $sp, $fp
7019 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
7020 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
7021 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
7022 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
7023 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
7024 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
7025 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
7026 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
7027 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
7028 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
7029 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
7032 Or, if we want to examine the variable @code{X} at each source line in
7036 (@value{GDBP}) @b{tfind start}
7037 (@value{GDBP}) @b{while ($trace_frame != -1)}
7038 > printf "Frame %d, X == %d\n", $trace_frame, X
7048 @subsection @code{tdump}
7050 @cindex dump all data collected at tracepoint
7051 @cindex tracepoint data, display
7053 This command takes no arguments. It prints all the data collected at
7054 the current trace snapshot.
7057 (@value{GDBP}) @b{trace 444}
7058 (@value{GDBP}) @b{actions}
7059 Enter actions for tracepoint #2, one per line:
7060 > collect $regs, $locals, $args, gdb_long_test
7063 (@value{GDBP}) @b{tstart}
7065 (@value{GDBP}) @b{tfind line 444}
7066 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
7068 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
7070 (@value{GDBP}) @b{tdump}
7071 Data collected at tracepoint 2, trace frame 1:
7072 d0 0xc4aa0085 -995491707
7076 d4 0x71aea3d 119204413
7081 a1 0x3000668 50333288
7084 a4 0x3000698 50333336
7086 fp 0x30bf3c 0x30bf3c
7087 sp 0x30bf34 0x30bf34
7089 pc 0x20b2c8 0x20b2c8
7093 p = 0x20e5b4 "gdb-test"
7100 gdb_long_test = 17 '\021'
7105 @node save-tracepoints
7106 @subsection @code{save-tracepoints @var{filename}}
7107 @kindex save-tracepoints
7108 @cindex save tracepoints for future sessions
7110 This command saves all current tracepoint definitions together with
7111 their actions and passcounts, into a file @file{@var{filename}}
7112 suitable for use in a later debugging session. To read the saved
7113 tracepoint definitions, use the @code{source} command (@pxref{Command
7116 @node Tracepoint Variables
7117 @section Convenience Variables for Tracepoints
7118 @cindex tracepoint variables
7119 @cindex convenience variables for tracepoints
7122 @vindex $trace_frame
7123 @item (int) $trace_frame
7124 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
7125 snapshot is selected.
7128 @item (int) $tracepoint
7129 The tracepoint for the current trace snapshot.
7132 @item (int) $trace_line
7133 The line number for the current trace snapshot.
7136 @item (char []) $trace_file
7137 The source file for the current trace snapshot.
7140 @item (char []) $trace_func
7141 The name of the function containing @code{$tracepoint}.
7144 Note: @code{$trace_file} is not suitable for use in @code{printf},
7145 use @code{output} instead.
7147 Here's a simple example of using these convenience variables for
7148 stepping through all the trace snapshots and printing some of their
7152 (@value{GDBP}) @b{tfind start}
7154 (@value{GDBP}) @b{while $trace_frame != -1}
7155 > output $trace_file
7156 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7162 @chapter Debugging Programs That Use Overlays
7165 If your program is too large to fit completely in your target system's
7166 memory, you can sometimes use @dfn{overlays} to work around this
7167 problem. @value{GDBN} provides some support for debugging programs that
7171 * How Overlays Work:: A general explanation of overlays.
7172 * Overlay Commands:: Managing overlays in @value{GDBN}.
7173 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7174 mapped by asking the inferior.
7175 * Overlay Sample Program:: A sample program using overlays.
7178 @node How Overlays Work
7179 @section How Overlays Work
7180 @cindex mapped overlays
7181 @cindex unmapped overlays
7182 @cindex load address, overlay's
7183 @cindex mapped address
7184 @cindex overlay area
7186 Suppose you have a computer whose instruction address space is only 64
7187 kilobytes long, but which has much more memory which can be accessed by
7188 other means: special instructions, segment registers, or memory
7189 management hardware, for example. Suppose further that you want to
7190 adapt a program which is larger than 64 kilobytes to run on this system.
7192 One solution is to identify modules of your program which are relatively
7193 independent, and need not call each other directly; call these modules
7194 @dfn{overlays}. Separate the overlays from the main program, and place
7195 their machine code in the larger memory. Place your main program in
7196 instruction memory, but leave at least enough space there to hold the
7197 largest overlay as well.
7199 Now, to call a function located in an overlay, you must first copy that
7200 overlay's machine code from the large memory into the space set aside
7201 for it in the instruction memory, and then jump to its entry point
7204 @c NB: In the below the mapped area's size is greater or equal to the
7205 @c size of all overlays. This is intentional to remind the developer
7206 @c that overlays don't necessarily need to be the same size.
7210 Data Instruction Larger
7211 Address Space Address Space Address Space
7212 +-----------+ +-----------+ +-----------+
7214 +-----------+ +-----------+ +-----------+<-- overlay 1
7215 | program | | main | .----| overlay 1 | load address
7216 | variables | | program | | +-----------+
7217 | and heap | | | | | |
7218 +-----------+ | | | +-----------+<-- overlay 2
7219 | | +-----------+ | | | load address
7220 +-----------+ | | | .-| overlay 2 |
7222 mapped --->+-----------+ | | +-----------+
7224 | overlay | <-' | | |
7225 | area | <---' +-----------+<-- overlay 3
7226 | | <---. | | load address
7227 +-----------+ `--| overlay 3 |
7234 @anchor{A code overlay}A code overlay
7238 The diagram (@pxref{A code overlay}) shows a system with separate data
7239 and instruction address spaces. To map an overlay, the program copies
7240 its code from the larger address space to the instruction address space.
7241 Since the overlays shown here all use the same mapped address, only one
7242 may be mapped at a time. For a system with a single address space for
7243 data and instructions, the diagram would be similar, except that the
7244 program variables and heap would share an address space with the main
7245 program and the overlay area.
7247 An overlay loaded into instruction memory and ready for use is called a
7248 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
7249 instruction memory. An overlay not present (or only partially present)
7250 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
7251 is its address in the larger memory. The mapped address is also called
7252 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
7253 called the @dfn{load memory address}, or @dfn{LMA}.
7255 Unfortunately, overlays are not a completely transparent way to adapt a
7256 program to limited instruction memory. They introduce a new set of
7257 global constraints you must keep in mind as you design your program:
7262 Before calling or returning to a function in an overlay, your program
7263 must make sure that overlay is actually mapped. Otherwise, the call or
7264 return will transfer control to the right address, but in the wrong
7265 overlay, and your program will probably crash.
7268 If the process of mapping an overlay is expensive on your system, you
7269 will need to choose your overlays carefully to minimize their effect on
7270 your program's performance.
7273 The executable file you load onto your system must contain each
7274 overlay's instructions, appearing at the overlay's load address, not its
7275 mapped address. However, each overlay's instructions must be relocated
7276 and its symbols defined as if the overlay were at its mapped address.
7277 You can use GNU linker scripts to specify different load and relocation
7278 addresses for pieces of your program; see @ref{Overlay Description,,,
7279 ld.info, Using ld: the GNU linker}.
7282 The procedure for loading executable files onto your system must be able
7283 to load their contents into the larger address space as well as the
7284 instruction and data spaces.
7288 The overlay system described above is rather simple, and could be
7289 improved in many ways:
7294 If your system has suitable bank switch registers or memory management
7295 hardware, you could use those facilities to make an overlay's load area
7296 contents simply appear at their mapped address in instruction space.
7297 This would probably be faster than copying the overlay to its mapped
7298 area in the usual way.
7301 If your overlays are small enough, you could set aside more than one
7302 overlay area, and have more than one overlay mapped at a time.
7305 You can use overlays to manage data, as well as instructions. In
7306 general, data overlays are even less transparent to your design than
7307 code overlays: whereas code overlays only require care when you call or
7308 return to functions, data overlays require care every time you access
7309 the data. Also, if you change the contents of a data overlay, you
7310 must copy its contents back out to its load address before you can copy a
7311 different data overlay into the same mapped area.
7316 @node Overlay Commands
7317 @section Overlay Commands
7319 To use @value{GDBN}'s overlay support, each overlay in your program must
7320 correspond to a separate section of the executable file. The section's
7321 virtual memory address and load memory address must be the overlay's
7322 mapped and load addresses. Identifying overlays with sections allows
7323 @value{GDBN} to determine the appropriate address of a function or
7324 variable, depending on whether the overlay is mapped or not.
7326 @value{GDBN}'s overlay commands all start with the word @code{overlay};
7327 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
7332 Disable @value{GDBN}'s overlay support. When overlay support is
7333 disabled, @value{GDBN} assumes that all functions and variables are
7334 always present at their mapped addresses. By default, @value{GDBN}'s
7335 overlay support is disabled.
7337 @item overlay manual
7338 @kindex overlay manual
7339 @cindex manual overlay debugging
7340 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
7341 relies on you to tell it which overlays are mapped, and which are not,
7342 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
7343 commands described below.
7345 @item overlay map-overlay @var{overlay}
7346 @itemx overlay map @var{overlay}
7347 @kindex overlay map-overlay
7348 @cindex map an overlay
7349 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
7350 be the name of the object file section containing the overlay. When an
7351 overlay is mapped, @value{GDBN} assumes it can find the overlay's
7352 functions and variables at their mapped addresses. @value{GDBN} assumes
7353 that any other overlays whose mapped ranges overlap that of
7354 @var{overlay} are now unmapped.
7356 @item overlay unmap-overlay @var{overlay}
7357 @itemx overlay unmap @var{overlay}
7358 @kindex overlay unmap-overlay
7359 @cindex unmap an overlay
7360 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
7361 must be the name of the object file section containing the overlay.
7362 When an overlay is unmapped, @value{GDBN} assumes it can find the
7363 overlay's functions and variables at their load addresses.
7366 @kindex overlay auto
7367 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
7368 consults a data structure the overlay manager maintains in the inferior
7369 to see which overlays are mapped. For details, see @ref{Automatic
7372 @item overlay load-target
7374 @kindex overlay load-target
7375 @cindex reloading the overlay table
7376 Re-read the overlay table from the inferior. Normally, @value{GDBN}
7377 re-reads the table @value{GDBN} automatically each time the inferior
7378 stops, so this command should only be necessary if you have changed the
7379 overlay mapping yourself using @value{GDBN}. This command is only
7380 useful when using automatic overlay debugging.
7382 @item overlay list-overlays
7384 @cindex listing mapped overlays
7385 Display a list of the overlays currently mapped, along with their mapped
7386 addresses, load addresses, and sizes.
7390 Normally, when @value{GDBN} prints a code address, it includes the name
7391 of the function the address falls in:
7395 $3 = @{int ()@} 0x11a0 <main>
7398 When overlay debugging is enabled, @value{GDBN} recognizes code in
7399 unmapped overlays, and prints the names of unmapped functions with
7400 asterisks around them. For example, if @code{foo} is a function in an
7401 unmapped overlay, @value{GDBN} prints it this way:
7405 No sections are mapped.
7407 $5 = @{int (int)@} 0x100000 <*foo*>
7410 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
7415 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
7416 mapped at 0x1016 - 0x104a
7418 $6 = @{int (int)@} 0x1016 <foo>
7421 When overlay debugging is enabled, @value{GDBN} can find the correct
7422 address for functions and variables in an overlay, whether or not the
7423 overlay is mapped. This allows most @value{GDBN} commands, like
7424 @code{break} and @code{disassemble}, to work normally, even on unmapped
7425 code. However, @value{GDBN}'s breakpoint support has some limitations:
7429 @cindex breakpoints in overlays
7430 @cindex overlays, setting breakpoints in
7431 You can set breakpoints in functions in unmapped overlays, as long as
7432 @value{GDBN} can write to the overlay at its load address.
7434 @value{GDBN} can not set hardware or simulator-based breakpoints in
7435 unmapped overlays. However, if you set a breakpoint at the end of your
7436 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
7437 you are using manual overlay management), @value{GDBN} will re-set its
7438 breakpoints properly.
7442 @node Automatic Overlay Debugging
7443 @section Automatic Overlay Debugging
7444 @cindex automatic overlay debugging
7446 @value{GDBN} can automatically track which overlays are mapped and which
7447 are not, given some simple co-operation from the overlay manager in the
7448 inferior. If you enable automatic overlay debugging with the
7449 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
7450 looks in the inferior's memory for certain variables describing the
7451 current state of the overlays.
7453 Here are the variables your overlay manager must define to support
7454 @value{GDBN}'s automatic overlay debugging:
7458 @item @code{_ovly_table}:
7459 This variable must be an array of the following structures:
7464 /* The overlay's mapped address. */
7467 /* The size of the overlay, in bytes. */
7470 /* The overlay's load address. */
7473 /* Non-zero if the overlay is currently mapped;
7475 unsigned long mapped;
7479 @item @code{_novlys}:
7480 This variable must be a four-byte signed integer, holding the total
7481 number of elements in @code{_ovly_table}.
7485 To decide whether a particular overlay is mapped or not, @value{GDBN}
7486 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
7487 @code{lma} members equal the VMA and LMA of the overlay's section in the
7488 executable file. When @value{GDBN} finds a matching entry, it consults
7489 the entry's @code{mapped} member to determine whether the overlay is
7492 In addition, your overlay manager may define a function called
7493 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
7494 will silently set a breakpoint there. If the overlay manager then
7495 calls this function whenever it has changed the overlay table, this
7496 will enable @value{GDBN} to accurately keep track of which overlays
7497 are in program memory, and update any breakpoints that may be set
7498 in overlays. This will allow breakpoints to work even if the
7499 overlays are kept in ROM or other non-writable memory while they
7500 are not being executed.
7502 @node Overlay Sample Program
7503 @section Overlay Sample Program
7504 @cindex overlay example program
7506 When linking a program which uses overlays, you must place the overlays
7507 at their load addresses, while relocating them to run at their mapped
7508 addresses. To do this, you must write a linker script (@pxref{Overlay
7509 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
7510 since linker scripts are specific to a particular host system, target
7511 architecture, and target memory layout, this manual cannot provide
7512 portable sample code demonstrating @value{GDBN}'s overlay support.
7514 However, the @value{GDBN} source distribution does contain an overlaid
7515 program, with linker scripts for a few systems, as part of its test
7516 suite. The program consists of the following files from
7517 @file{gdb/testsuite/gdb.base}:
7521 The main program file.
7523 A simple overlay manager, used by @file{overlays.c}.
7528 Overlay modules, loaded and used by @file{overlays.c}.
7531 Linker scripts for linking the test program on the @code{d10v-elf}
7532 and @code{m32r-elf} targets.
7535 You can build the test program using the @code{d10v-elf} GCC
7536 cross-compiler like this:
7539 $ d10v-elf-gcc -g -c overlays.c
7540 $ d10v-elf-gcc -g -c ovlymgr.c
7541 $ d10v-elf-gcc -g -c foo.c
7542 $ d10v-elf-gcc -g -c bar.c
7543 $ d10v-elf-gcc -g -c baz.c
7544 $ d10v-elf-gcc -g -c grbx.c
7545 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
7546 baz.o grbx.o -Wl,-Td10v.ld -o overlays
7549 The build process is identical for any other architecture, except that
7550 you must substitute the appropriate compiler and linker script for the
7551 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
7555 @chapter Using @value{GDBN} with Different Languages
7558 Although programming languages generally have common aspects, they are
7559 rarely expressed in the same manner. For instance, in ANSI C,
7560 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
7561 Modula-2, it is accomplished by @code{p^}. Values can also be
7562 represented (and displayed) differently. Hex numbers in C appear as
7563 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
7565 @cindex working language
7566 Language-specific information is built into @value{GDBN} for some languages,
7567 allowing you to express operations like the above in your program's
7568 native language, and allowing @value{GDBN} to output values in a manner
7569 consistent with the syntax of your program's native language. The
7570 language you use to build expressions is called the @dfn{working
7574 * Setting:: Switching between source languages
7575 * Show:: Displaying the language
7576 * Checks:: Type and range checks
7577 * Support:: Supported languages
7578 * Unsupported languages:: Unsupported languages
7582 @section Switching between source languages
7584 There are two ways to control the working language---either have @value{GDBN}
7585 set it automatically, or select it manually yourself. You can use the
7586 @code{set language} command for either purpose. On startup, @value{GDBN}
7587 defaults to setting the language automatically. The working language is
7588 used to determine how expressions you type are interpreted, how values
7591 In addition to the working language, every source file that
7592 @value{GDBN} knows about has its own working language. For some object
7593 file formats, the compiler might indicate which language a particular
7594 source file is in. However, most of the time @value{GDBN} infers the
7595 language from the name of the file. The language of a source file
7596 controls whether C@t{++} names are demangled---this way @code{backtrace} can
7597 show each frame appropriately for its own language. There is no way to
7598 set the language of a source file from within @value{GDBN}, but you can
7599 set the language associated with a filename extension. @xref{Show, ,
7600 Displaying the language}.
7602 This is most commonly a problem when you use a program, such
7603 as @code{cfront} or @code{f2c}, that generates C but is written in
7604 another language. In that case, make the
7605 program use @code{#line} directives in its C output; that way
7606 @value{GDBN} will know the correct language of the source code of the original
7607 program, and will display that source code, not the generated C code.
7610 * Filenames:: Filename extensions and languages.
7611 * Manually:: Setting the working language manually
7612 * Automatically:: Having @value{GDBN} infer the source language
7616 @subsection List of filename extensions and languages
7618 If a source file name ends in one of the following extensions, then
7619 @value{GDBN} infers that its language is the one indicated.
7635 Objective-C source file
7642 Modula-2 source file
7646 Assembler source file. This actually behaves almost like C, but
7647 @value{GDBN} does not skip over function prologues when stepping.
7650 In addition, you may set the language associated with a filename
7651 extension. @xref{Show, , Displaying the language}.
7654 @subsection Setting the working language
7656 If you allow @value{GDBN} to set the language automatically,
7657 expressions are interpreted the same way in your debugging session and
7660 @kindex set language
7661 If you wish, you may set the language manually. To do this, issue the
7662 command @samp{set language @var{lang}}, where @var{lang} is the name of
7664 @code{c} or @code{modula-2}.
7665 For a list of the supported languages, type @samp{set language}.
7667 Setting the language manually prevents @value{GDBN} from updating the working
7668 language automatically. This can lead to confusion if you try
7669 to debug a program when the working language is not the same as the
7670 source language, when an expression is acceptable to both
7671 languages---but means different things. For instance, if the current
7672 source file were written in C, and @value{GDBN} was parsing Modula-2, a
7680 might not have the effect you intended. In C, this means to add
7681 @code{b} and @code{c} and place the result in @code{a}. The result
7682 printed would be the value of @code{a}. In Modula-2, this means to compare
7683 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
7686 @subsection Having @value{GDBN} infer the source language
7688 To have @value{GDBN} set the working language automatically, use
7689 @samp{set language local} or @samp{set language auto}. @value{GDBN}
7690 then infers the working language. That is, when your program stops in a
7691 frame (usually by encountering a breakpoint), @value{GDBN} sets the
7692 working language to the language recorded for the function in that
7693 frame. If the language for a frame is unknown (that is, if the function
7694 or block corresponding to the frame was defined in a source file that
7695 does not have a recognized extension), the current working language is
7696 not changed, and @value{GDBN} issues a warning.
7698 This may not seem necessary for most programs, which are written
7699 entirely in one source language. However, program modules and libraries
7700 written in one source language can be used by a main program written in
7701 a different source language. Using @samp{set language auto} in this
7702 case frees you from having to set the working language manually.
7705 @section Displaying the language
7707 The following commands help you find out which language is the
7708 working language, and also what language source files were written in.
7710 @kindex show language
7711 @kindex info frame@r{, show the source language}
7712 @kindex info source@r{, show the source language}
7715 Display the current working language. This is the
7716 language you can use with commands such as @code{print} to
7717 build and compute expressions that may involve variables in your program.
7720 Display the source language for this frame. This language becomes the
7721 working language if you use an identifier from this frame.
7722 @xref{Frame Info, ,Information about a frame}, to identify the other
7723 information listed here.
7726 Display the source language of this source file.
7727 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
7728 information listed here.
7731 In unusual circumstances, you may have source files with extensions
7732 not in the standard list. You can then set the extension associated
7733 with a language explicitly:
7735 @kindex set extension-language
7736 @kindex info extensions
7738 @item set extension-language @var{.ext} @var{language}
7739 Set source files with extension @var{.ext} to be assumed to be in
7740 the source language @var{language}.
7742 @item info extensions
7743 List all the filename extensions and the associated languages.
7747 @section Type and range checking
7750 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
7751 checking are included, but they do not yet have any effect. This
7752 section documents the intended facilities.
7754 @c FIXME remove warning when type/range code added
7756 Some languages are designed to guard you against making seemingly common
7757 errors through a series of compile- and run-time checks. These include
7758 checking the type of arguments to functions and operators, and making
7759 sure mathematical overflows are caught at run time. Checks such as
7760 these help to ensure a program's correctness once it has been compiled
7761 by eliminating type mismatches, and providing active checks for range
7762 errors when your program is running.
7764 @value{GDBN} can check for conditions like the above if you wish.
7765 Although @value{GDBN} does not check the statements in your program, it
7766 can check expressions entered directly into @value{GDBN} for evaluation via
7767 the @code{print} command, for example. As with the working language,
7768 @value{GDBN} can also decide whether or not to check automatically based on
7769 your program's source language. @xref{Support, ,Supported languages},
7770 for the default settings of supported languages.
7773 * Type Checking:: An overview of type checking
7774 * Range Checking:: An overview of range checking
7777 @cindex type checking
7778 @cindex checks, type
7780 @subsection An overview of type checking
7782 Some languages, such as Modula-2, are strongly typed, meaning that the
7783 arguments to operators and functions have to be of the correct type,
7784 otherwise an error occurs. These checks prevent type mismatch
7785 errors from ever causing any run-time problems. For example,
7793 The second example fails because the @code{CARDINAL} 1 is not
7794 type-compatible with the @code{REAL} 2.3.
7796 For the expressions you use in @value{GDBN} commands, you can tell the
7797 @value{GDBN} type checker to skip checking;
7798 to treat any mismatches as errors and abandon the expression;
7799 or to only issue warnings when type mismatches occur,
7800 but evaluate the expression anyway. When you choose the last of
7801 these, @value{GDBN} evaluates expressions like the second example above, but
7802 also issues a warning.
7804 Even if you turn type checking off, there may be other reasons
7805 related to type that prevent @value{GDBN} from evaluating an expression.
7806 For instance, @value{GDBN} does not know how to add an @code{int} and
7807 a @code{struct foo}. These particular type errors have nothing to do
7808 with the language in use, and usually arise from expressions, such as
7809 the one described above, which make little sense to evaluate anyway.
7811 Each language defines to what degree it is strict about type. For
7812 instance, both Modula-2 and C require the arguments to arithmetical
7813 operators to be numbers. In C, enumerated types and pointers can be
7814 represented as numbers, so that they are valid arguments to mathematical
7815 operators. @xref{Support, ,Supported languages}, for further
7816 details on specific languages.
7818 @value{GDBN} provides some additional commands for controlling the type checker:
7820 @kindex set check@r{, type}
7821 @kindex set check type
7822 @kindex show check type
7824 @item set check type auto
7825 Set type checking on or off based on the current working language.
7826 @xref{Support, ,Supported languages}, for the default settings for
7829 @item set check type on
7830 @itemx set check type off
7831 Set type checking on or off, overriding the default setting for the
7832 current working language. Issue a warning if the setting does not
7833 match the language default. If any type mismatches occur in
7834 evaluating an expression while type checking is on, @value{GDBN} prints a
7835 message and aborts evaluation of the expression.
7837 @item set check type warn
7838 Cause the type checker to issue warnings, but to always attempt to
7839 evaluate the expression. Evaluating the expression may still
7840 be impossible for other reasons. For example, @value{GDBN} cannot add
7841 numbers and structures.
7844 Show the current setting of the type checker, and whether or not @value{GDBN}
7845 is setting it automatically.
7848 @cindex range checking
7849 @cindex checks, range
7850 @node Range Checking
7851 @subsection An overview of range checking
7853 In some languages (such as Modula-2), it is an error to exceed the
7854 bounds of a type; this is enforced with run-time checks. Such range
7855 checking is meant to ensure program correctness by making sure
7856 computations do not overflow, or indices on an array element access do
7857 not exceed the bounds of the array.
7859 For expressions you use in @value{GDBN} commands, you can tell
7860 @value{GDBN} to treat range errors in one of three ways: ignore them,
7861 always treat them as errors and abandon the expression, or issue
7862 warnings but evaluate the expression anyway.
7864 A range error can result from numerical overflow, from exceeding an
7865 array index bound, or when you type a constant that is not a member
7866 of any type. Some languages, however, do not treat overflows as an
7867 error. In many implementations of C, mathematical overflow causes the
7868 result to ``wrap around'' to lower values---for example, if @var{m} is
7869 the largest integer value, and @var{s} is the smallest, then
7872 @var{m} + 1 @result{} @var{s}
7875 This, too, is specific to individual languages, and in some cases
7876 specific to individual compilers or machines. @xref{Support, ,
7877 Supported languages}, for further details on specific languages.
7879 @value{GDBN} provides some additional commands for controlling the range checker:
7881 @kindex set check@r{, range}
7882 @kindex set check range
7883 @kindex show check range
7885 @item set check range auto
7886 Set range checking on or off based on the current working language.
7887 @xref{Support, ,Supported languages}, for the default settings for
7890 @item set check range on
7891 @itemx set check range off
7892 Set range checking on or off, overriding the default setting for the
7893 current working language. A warning is issued if the setting does not
7894 match the language default. If a range error occurs and range checking is on,
7895 then a message is printed and evaluation of the expression is aborted.
7897 @item set check range warn
7898 Output messages when the @value{GDBN} range checker detects a range error,
7899 but attempt to evaluate the expression anyway. Evaluating the
7900 expression may still be impossible for other reasons, such as accessing
7901 memory that the process does not own (a typical example from many Unix
7905 Show the current setting of the range checker, and whether or not it is
7906 being set automatically by @value{GDBN}.
7910 @section Supported languages
7912 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, assembly, and Modula-2.
7913 @c This is false ...
7914 Some @value{GDBN} features may be used in expressions regardless of the
7915 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
7916 and the @samp{@{type@}addr} construct (@pxref{Expressions,
7917 ,Expressions}) can be used with the constructs of any supported
7920 The following sections detail to what degree each source language is
7921 supported by @value{GDBN}. These sections are not meant to be language
7922 tutorials or references, but serve only as a reference guide to what the
7923 @value{GDBN} expression parser accepts, and what input and output
7924 formats should look like for different languages. There are many good
7925 books written on each of these languages; please look to these for a
7926 language reference or tutorial.
7930 * Objective-C:: Objective-C
7931 * Modula-2:: Modula-2
7935 @subsection C and C@t{++}
7937 @cindex C and C@t{++}
7938 @cindex expressions in C or C@t{++}
7940 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
7941 to both languages. Whenever this is the case, we discuss those languages
7945 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
7946 @cindex @sc{gnu} C@t{++}
7947 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
7948 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
7949 effectively, you must compile your C@t{++} programs with a supported
7950 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
7951 compiler (@code{aCC}).
7953 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
7954 format; if it doesn't work on your system, try the stabs+ debugging
7955 format. You can select those formats explicitly with the @code{g++}
7956 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
7957 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
7958 CC, gcc.info, Using @sc{gnu} CC}.
7961 * C Operators:: C and C@t{++} operators
7962 * C Constants:: C and C@t{++} constants
7963 * C plus plus expressions:: C@t{++} expressions
7964 * C Defaults:: Default settings for C and C@t{++}
7965 * C Checks:: C and C@t{++} type and range checks
7966 * Debugging C:: @value{GDBN} and C
7967 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
7971 @subsubsection C and C@t{++} operators
7973 @cindex C and C@t{++} operators
7975 Operators must be defined on values of specific types. For instance,
7976 @code{+} is defined on numbers, but not on structures. Operators are
7977 often defined on groups of types.
7979 For the purposes of C and C@t{++}, the following definitions hold:
7984 @emph{Integral types} include @code{int} with any of its storage-class
7985 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
7988 @emph{Floating-point types} include @code{float}, @code{double}, and
7989 @code{long double} (if supported by the target platform).
7992 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
7995 @emph{Scalar types} include all of the above.
8000 The following operators are supported. They are listed here
8001 in order of increasing precedence:
8005 The comma or sequencing operator. Expressions in a comma-separated list
8006 are evaluated from left to right, with the result of the entire
8007 expression being the last expression evaluated.
8010 Assignment. The value of an assignment expression is the value
8011 assigned. Defined on scalar types.
8014 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
8015 and translated to @w{@code{@var{a} = @var{a op b}}}.
8016 @w{@code{@var{op}=}} and @code{=} have the same precedence.
8017 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
8018 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
8021 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
8022 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
8026 Logical @sc{or}. Defined on integral types.
8029 Logical @sc{and}. Defined on integral types.
8032 Bitwise @sc{or}. Defined on integral types.
8035 Bitwise exclusive-@sc{or}. Defined on integral types.
8038 Bitwise @sc{and}. Defined on integral types.
8041 Equality and inequality. Defined on scalar types. The value of these
8042 expressions is 0 for false and non-zero for true.
8044 @item <@r{, }>@r{, }<=@r{, }>=
8045 Less than, greater than, less than or equal, greater than or equal.
8046 Defined on scalar types. The value of these expressions is 0 for false
8047 and non-zero for true.
8050 left shift, and right shift. Defined on integral types.
8053 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8056 Addition and subtraction. Defined on integral types, floating-point types and
8059 @item *@r{, }/@r{, }%
8060 Multiplication, division, and modulus. Multiplication and division are
8061 defined on integral and floating-point types. Modulus is defined on
8065 Increment and decrement. When appearing before a variable, the
8066 operation is performed before the variable is used in an expression;
8067 when appearing after it, the variable's value is used before the
8068 operation takes place.
8071 Pointer dereferencing. Defined on pointer types. Same precedence as
8075 Address operator. Defined on variables. Same precedence as @code{++}.
8077 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
8078 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
8079 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
8080 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
8084 Negative. Defined on integral and floating-point types. Same
8085 precedence as @code{++}.
8088 Logical negation. Defined on integral types. Same precedence as
8092 Bitwise complement operator. Defined on integral types. Same precedence as
8097 Structure member, and pointer-to-structure member. For convenience,
8098 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
8099 pointer based on the stored type information.
8100 Defined on @code{struct} and @code{union} data.
8103 Dereferences of pointers to members.
8106 Array indexing. @code{@var{a}[@var{i}]} is defined as
8107 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
8110 Function parameter list. Same precedence as @code{->}.
8113 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
8114 and @code{class} types.
8117 Doubled colons also represent the @value{GDBN} scope operator
8118 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
8122 If an operator is redefined in the user code, @value{GDBN} usually
8123 attempts to invoke the redefined version instead of using the operator's
8131 @subsubsection C and C@t{++} constants
8133 @cindex C and C@t{++} constants
8135 @value{GDBN} allows you to express the constants of C and C@t{++} in the
8140 Integer constants are a sequence of digits. Octal constants are
8141 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
8142 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
8143 @samp{l}, specifying that the constant should be treated as a
8147 Floating point constants are a sequence of digits, followed by a decimal
8148 point, followed by a sequence of digits, and optionally followed by an
8149 exponent. An exponent is of the form:
8150 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8151 sequence of digits. The @samp{+} is optional for positive exponents.
8152 A floating-point constant may also end with a letter @samp{f} or
8153 @samp{F}, specifying that the constant should be treated as being of
8154 the @code{float} (as opposed to the default @code{double}) type; or with
8155 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8159 Enumerated constants consist of enumerated identifiers, or their
8160 integral equivalents.
8163 Character constants are a single character surrounded by single quotes
8164 (@code{'}), or a number---the ordinal value of the corresponding character
8165 (usually its @sc{ascii} value). Within quotes, the single character may
8166 be represented by a letter or by @dfn{escape sequences}, which are of
8167 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8168 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8169 @samp{@var{x}} is a predefined special character---for example,
8170 @samp{\n} for newline.
8173 String constants are a sequence of character constants surrounded by
8174 double quotes (@code{"}). Any valid character constant (as described
8175 above) may appear. Double quotes within the string must be preceded by
8176 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8180 Pointer constants are an integral value. You can also write pointers
8181 to constants using the C operator @samp{&}.
8184 Array constants are comma-separated lists surrounded by braces @samp{@{}
8185 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8186 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8187 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8191 * C plus plus expressions::
8198 @node C plus plus expressions
8199 @subsubsection C@t{++} expressions
8201 @cindex expressions in C@t{++}
8202 @value{GDBN} expression handling can interpret most C@t{++} expressions.
8204 @cindex debugging C@t{++} programs
8205 @cindex C@t{++} compilers
8206 @cindex debug formats and C@t{++}
8207 @cindex @value{NGCC} and C@t{++}
8209 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
8210 proper compiler and the proper debug format. Currently, @value{GDBN}
8211 works best when debugging C@t{++} code that is compiled with
8212 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
8213 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
8214 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
8215 stabs+ as their default debug format, so you usually don't need to
8216 specify a debug format explicitly. Other compilers and/or debug formats
8217 are likely to work badly or not at all when using @value{GDBN} to debug
8223 @cindex member functions
8225 Member function calls are allowed; you can use expressions like
8228 count = aml->GetOriginal(x, y)
8231 @vindex this@r{, inside C@t{++} member functions}
8232 @cindex namespace in C@t{++}
8234 While a member function is active (in the selected stack frame), your
8235 expressions have the same namespace available as the member function;
8236 that is, @value{GDBN} allows implicit references to the class instance
8237 pointer @code{this} following the same rules as C@t{++}.
8239 @cindex call overloaded functions
8240 @cindex overloaded functions, calling
8241 @cindex type conversions in C@t{++}
8243 You can call overloaded functions; @value{GDBN} resolves the function
8244 call to the right definition, with some restrictions. @value{GDBN} does not
8245 perform overload resolution involving user-defined type conversions,
8246 calls to constructors, or instantiations of templates that do not exist
8247 in the program. It also cannot handle ellipsis argument lists or
8250 It does perform integral conversions and promotions, floating-point
8251 promotions, arithmetic conversions, pointer conversions, conversions of
8252 class objects to base classes, and standard conversions such as those of
8253 functions or arrays to pointers; it requires an exact match on the
8254 number of function arguments.
8256 Overload resolution is always performed, unless you have specified
8257 @code{set overload-resolution off}. @xref{Debugging C plus plus,
8258 ,@value{GDBN} features for C@t{++}}.
8260 You must specify @code{set overload-resolution off} in order to use an
8261 explicit function signature to call an overloaded function, as in
8263 p 'foo(char,int)'('x', 13)
8266 The @value{GDBN} command-completion facility can simplify this;
8267 see @ref{Completion, ,Command completion}.
8269 @cindex reference declarations
8271 @value{GDBN} understands variables declared as C@t{++} references; you can use
8272 them in expressions just as you do in C@t{++} source---they are automatically
8275 In the parameter list shown when @value{GDBN} displays a frame, the values of
8276 reference variables are not displayed (unlike other variables); this
8277 avoids clutter, since references are often used for large structures.
8278 The @emph{address} of a reference variable is always shown, unless
8279 you have specified @samp{set print address off}.
8282 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
8283 expressions can use it just as expressions in your program do. Since
8284 one scope may be defined in another, you can use @code{::} repeatedly if
8285 necessary, for example in an expression like
8286 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
8287 resolving name scope by reference to source files, in both C and C@t{++}
8288 debugging (@pxref{Variables, ,Program variables}).
8291 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
8292 calling virtual functions correctly, printing out virtual bases of
8293 objects, calling functions in a base subobject, casting objects, and
8294 invoking user-defined operators.
8297 @subsubsection C and C@t{++} defaults
8299 @cindex C and C@t{++} defaults
8301 If you allow @value{GDBN} to set type and range checking automatically, they
8302 both default to @code{off} whenever the working language changes to
8303 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
8304 selects the working language.
8306 If you allow @value{GDBN} to set the language automatically, it
8307 recognizes source files whose names end with @file{.c}, @file{.C}, or
8308 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
8309 these files, it sets the working language to C or C@t{++}.
8310 @xref{Automatically, ,Having @value{GDBN} infer the source language},
8311 for further details.
8313 @c Type checking is (a) primarily motivated by Modula-2, and (b)
8314 @c unimplemented. If (b) changes, it might make sense to let this node
8315 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
8318 @subsubsection C and C@t{++} type and range checks
8320 @cindex C and C@t{++} checks
8322 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
8323 is not used. However, if you turn type checking on, @value{GDBN}
8324 considers two variables type equivalent if:
8328 The two variables are structured and have the same structure, union, or
8332 The two variables have the same type name, or types that have been
8333 declared equivalent through @code{typedef}.
8336 @c leaving this out because neither J Gilmore nor R Pesch understand it.
8339 The two @code{struct}, @code{union}, or @code{enum} variables are
8340 declared in the same declaration. (Note: this may not be true for all C
8345 Range checking, if turned on, is done on mathematical operations. Array
8346 indices are not checked, since they are often used to index a pointer
8347 that is not itself an array.
8350 @subsubsection @value{GDBN} and C
8352 The @code{set print union} and @code{show print union} commands apply to
8353 the @code{union} type. When set to @samp{on}, any @code{union} that is
8354 inside a @code{struct} or @code{class} is also printed. Otherwise, it
8355 appears as @samp{@{...@}}.
8357 The @code{@@} operator aids in the debugging of dynamic arrays, formed
8358 with pointers and a memory allocation function. @xref{Expressions,
8362 * Debugging C plus plus::
8365 @node Debugging C plus plus
8366 @subsubsection @value{GDBN} features for C@t{++}
8368 @cindex commands for C@t{++}
8370 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
8371 designed specifically for use with C@t{++}. Here is a summary:
8374 @cindex break in overloaded functions
8375 @item @r{breakpoint menus}
8376 When you want a breakpoint in a function whose name is overloaded,
8377 @value{GDBN} breakpoint menus help you specify which function definition
8378 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
8380 @cindex overloading in C@t{++}
8381 @item rbreak @var{regex}
8382 Setting breakpoints using regular expressions is helpful for setting
8383 breakpoints on overloaded functions that are not members of any special
8385 @xref{Set Breaks, ,Setting breakpoints}.
8387 @cindex C@t{++} exception handling
8390 Debug C@t{++} exception handling using these commands. @xref{Set
8391 Catchpoints, , Setting catchpoints}.
8394 @item ptype @var{typename}
8395 Print inheritance relationships as well as other information for type
8397 @xref{Symbols, ,Examining the Symbol Table}.
8399 @cindex C@t{++} symbol display
8400 @item set print demangle
8401 @itemx show print demangle
8402 @itemx set print asm-demangle
8403 @itemx show print asm-demangle
8404 Control whether C@t{++} symbols display in their source form, both when
8405 displaying code as C@t{++} source and when displaying disassemblies.
8406 @xref{Print Settings, ,Print settings}.
8408 @item set print object
8409 @itemx show print object
8410 Choose whether to print derived (actual) or declared types of objects.
8411 @xref{Print Settings, ,Print settings}.
8413 @item set print vtbl
8414 @itemx show print vtbl
8415 Control the format for printing virtual function tables.
8416 @xref{Print Settings, ,Print settings}.
8417 (The @code{vtbl} commands do not work on programs compiled with the HP
8418 ANSI C@t{++} compiler (@code{aCC}).)
8420 @kindex set overload-resolution
8421 @cindex overloaded functions, overload resolution
8422 @item set overload-resolution on
8423 Enable overload resolution for C@t{++} expression evaluation. The default
8424 is on. For overloaded functions, @value{GDBN} evaluates the arguments
8425 and searches for a function whose signature matches the argument types,
8426 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
8427 expressions}, for details). If it cannot find a match, it emits a
8430 @item set overload-resolution off
8431 Disable overload resolution for C@t{++} expression evaluation. For
8432 overloaded functions that are not class member functions, @value{GDBN}
8433 chooses the first function of the specified name that it finds in the
8434 symbol table, whether or not its arguments are of the correct type. For
8435 overloaded functions that are class member functions, @value{GDBN}
8436 searches for a function whose signature @emph{exactly} matches the
8439 @item @r{Overloaded symbol names}
8440 You can specify a particular definition of an overloaded symbol, using
8441 the same notation that is used to declare such symbols in C@t{++}: type
8442 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
8443 also use the @value{GDBN} command-line word completion facilities to list the
8444 available choices, or to finish the type list for you.
8445 @xref{Completion,, Command completion}, for details on how to do this.
8449 @subsection Objective-C
8452 This section provides information about some commands and command
8453 options that are useful for debugging Objective-C code.
8456 * Method Names in Commands::
8457 * The Print Command with Objective-C::
8460 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
8461 @subsubsection Method Names in Commands
8463 The following commands have been extended to accept Objective-C method
8464 names as line specifications:
8466 @kindex clear@r{, and Objective-C}
8467 @kindex break@r{, and Objective-C}
8468 @kindex info line@r{, and Objective-C}
8469 @kindex jump@r{, and Objective-C}
8470 @kindex list@r{, and Objective-C}
8474 @item @code{info line}
8479 A fully qualified Objective-C method name is specified as
8482 -[@var{Class} @var{methodName}]
8485 where the minus sign is used to indicate an instance method and a plus
8486 sign (not shown) is used to indicate a class method. The
8487 class name @var{Class} and method name @var{methoName} are enclosed in
8488 brackets, similar to the way messages are specified in Objective-C source
8489 code. For example, to set a breakpoint at the @code{create} instance method of
8490 class @code{Fruit} in the program currently being debugged, enter:
8493 break -[Fruit create]
8496 To list ten program lines around the @code{initialize} class method,
8500 list +[NSText initialize]
8503 In the current version of GDB, the plus or minus sign is required. In
8504 future versions of GDB, the plus or minus sign will be optional, but you
8505 can use it to narrow the search. It is also possible to specify just a
8512 You must specify the complete method name, including any colons. If
8513 your program's source files contain more than one @code{create} method,
8514 you'll be presented with a numbered list of classes that implement that
8515 method. Indicate your choice by number, or type @samp{0} to exit if
8518 As another example, to clear a breakpoint established at the
8519 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
8522 clear -[NSWindow makeKeyAndOrderFront:]
8525 @node The Print Command with Objective-C
8526 @subsubsection The Print Command With Objective-C
8528 The print command has also been extended to accept methods. For example:
8531 print -[object hash]
8534 @cindex print an Objective-C object description
8535 will tell gdb to send the -hash message to object and print the
8536 result. Also an additional command has been added, @code{print-object}
8537 or @code{po} for short, which is meant to print the description of an
8538 object. However, this command may only work with certain Objective-C
8539 libraries that have a particular hook function, called
8540 @code{_NSPrintForDebugger} defined.
8542 @node Modula-2, , Objective-C, Support
8543 @subsection Modula-2
8545 @cindex Modula-2, @value{GDBN} support
8547 The extensions made to @value{GDBN} to support Modula-2 only support
8548 output from the @sc{gnu} Modula-2 compiler (which is currently being
8549 developed). Other Modula-2 compilers are not currently supported, and
8550 attempting to debug executables produced by them is most likely
8551 to give an error as @value{GDBN} reads in the executable's symbol
8554 @cindex expressions in Modula-2
8556 * M2 Operators:: Built-in operators
8557 * Built-In Func/Proc:: Built-in functions and procedures
8558 * M2 Constants:: Modula-2 constants
8559 * M2 Defaults:: Default settings for Modula-2
8560 * Deviations:: Deviations from standard Modula-2
8561 * M2 Checks:: Modula-2 type and range checks
8562 * M2 Scope:: The scope operators @code{::} and @code{.}
8563 * GDB/M2:: @value{GDBN} and Modula-2
8567 @subsubsection Operators
8568 @cindex Modula-2 operators
8570 Operators must be defined on values of specific types. For instance,
8571 @code{+} is defined on numbers, but not on structures. Operators are
8572 often defined on groups of types. For the purposes of Modula-2, the
8573 following definitions hold:
8578 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
8582 @emph{Character types} consist of @code{CHAR} and its subranges.
8585 @emph{Floating-point types} consist of @code{REAL}.
8588 @emph{Pointer types} consist of anything declared as @code{POINTER TO
8592 @emph{Scalar types} consist of all of the above.
8595 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
8598 @emph{Boolean types} consist of @code{BOOLEAN}.
8602 The following operators are supported, and appear in order of
8603 increasing precedence:
8607 Function argument or array index separator.
8610 Assignment. The value of @var{var} @code{:=} @var{value} is
8614 Less than, greater than on integral, floating-point, or enumerated
8618 Less than or equal to, greater than or equal to
8619 on integral, floating-point and enumerated types, or set inclusion on
8620 set types. Same precedence as @code{<}.
8622 @item =@r{, }<>@r{, }#
8623 Equality and two ways of expressing inequality, valid on scalar types.
8624 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
8625 available for inequality, since @code{#} conflicts with the script
8629 Set membership. Defined on set types and the types of their members.
8630 Same precedence as @code{<}.
8633 Boolean disjunction. Defined on boolean types.
8636 Boolean conjunction. Defined on boolean types.
8639 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8642 Addition and subtraction on integral and floating-point types, or union
8643 and difference on set types.
8646 Multiplication on integral and floating-point types, or set intersection
8650 Division on floating-point types, or symmetric set difference on set
8651 types. Same precedence as @code{*}.
8654 Integer division and remainder. Defined on integral types. Same
8655 precedence as @code{*}.
8658 Negative. Defined on @code{INTEGER} and @code{REAL} data.
8661 Pointer dereferencing. Defined on pointer types.
8664 Boolean negation. Defined on boolean types. Same precedence as
8668 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
8669 precedence as @code{^}.
8672 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
8675 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
8679 @value{GDBN} and Modula-2 scope operators.
8683 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
8684 treats the use of the operator @code{IN}, or the use of operators
8685 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
8686 @code{<=}, and @code{>=} on sets as an error.
8690 @node Built-In Func/Proc
8691 @subsubsection Built-in functions and procedures
8692 @cindex Modula-2 built-ins
8694 Modula-2 also makes available several built-in procedures and functions.
8695 In describing these, the following metavariables are used:
8700 represents an @code{ARRAY} variable.
8703 represents a @code{CHAR} constant or variable.
8706 represents a variable or constant of integral type.
8709 represents an identifier that belongs to a set. Generally used in the
8710 same function with the metavariable @var{s}. The type of @var{s} should
8711 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
8714 represents a variable or constant of integral or floating-point type.
8717 represents a variable or constant of floating-point type.
8723 represents a variable.
8726 represents a variable or constant of one of many types. See the
8727 explanation of the function for details.
8730 All Modula-2 built-in procedures also return a result, described below.
8734 Returns the absolute value of @var{n}.
8737 If @var{c} is a lower case letter, it returns its upper case
8738 equivalent, otherwise it returns its argument.
8741 Returns the character whose ordinal value is @var{i}.
8744 Decrements the value in the variable @var{v} by one. Returns the new value.
8746 @item DEC(@var{v},@var{i})
8747 Decrements the value in the variable @var{v} by @var{i}. Returns the
8750 @item EXCL(@var{m},@var{s})
8751 Removes the element @var{m} from the set @var{s}. Returns the new
8754 @item FLOAT(@var{i})
8755 Returns the floating point equivalent of the integer @var{i}.
8758 Returns the index of the last member of @var{a}.
8761 Increments the value in the variable @var{v} by one. Returns the new value.
8763 @item INC(@var{v},@var{i})
8764 Increments the value in the variable @var{v} by @var{i}. Returns the
8767 @item INCL(@var{m},@var{s})
8768 Adds the element @var{m} to the set @var{s} if it is not already
8769 there. Returns the new set.
8772 Returns the maximum value of the type @var{t}.
8775 Returns the minimum value of the type @var{t}.
8778 Returns boolean TRUE if @var{i} is an odd number.
8781 Returns the ordinal value of its argument. For example, the ordinal
8782 value of a character is its @sc{ascii} value (on machines supporting the
8783 @sc{ascii} character set). @var{x} must be of an ordered type, which include
8784 integral, character and enumerated types.
8787 Returns the size of its argument. @var{x} can be a variable or a type.
8789 @item TRUNC(@var{r})
8790 Returns the integral part of @var{r}.
8792 @item VAL(@var{t},@var{i})
8793 Returns the member of the type @var{t} whose ordinal value is @var{i}.
8797 @emph{Warning:} Sets and their operations are not yet supported, so
8798 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
8802 @cindex Modula-2 constants
8804 @subsubsection Constants
8806 @value{GDBN} allows you to express the constants of Modula-2 in the following
8812 Integer constants are simply a sequence of digits. When used in an
8813 expression, a constant is interpreted to be type-compatible with the
8814 rest of the expression. Hexadecimal integers are specified by a
8815 trailing @samp{H}, and octal integers by a trailing @samp{B}.
8818 Floating point constants appear as a sequence of digits, followed by a
8819 decimal point and another sequence of digits. An optional exponent can
8820 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
8821 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
8822 digits of the floating point constant must be valid decimal (base 10)
8826 Character constants consist of a single character enclosed by a pair of
8827 like quotes, either single (@code{'}) or double (@code{"}). They may
8828 also be expressed by their ordinal value (their @sc{ascii} value, usually)
8829 followed by a @samp{C}.
8832 String constants consist of a sequence of characters enclosed by a
8833 pair of like quotes, either single (@code{'}) or double (@code{"}).
8834 Escape sequences in the style of C are also allowed. @xref{C
8835 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
8839 Enumerated constants consist of an enumerated identifier.
8842 Boolean constants consist of the identifiers @code{TRUE} and
8846 Pointer constants consist of integral values only.
8849 Set constants are not yet supported.
8853 @subsubsection Modula-2 defaults
8854 @cindex Modula-2 defaults
8856 If type and range checking are set automatically by @value{GDBN}, they
8857 both default to @code{on} whenever the working language changes to
8858 Modula-2. This happens regardless of whether you or @value{GDBN}
8859 selected the working language.
8861 If you allow @value{GDBN} to set the language automatically, then entering
8862 code compiled from a file whose name ends with @file{.mod} sets the
8863 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
8864 the language automatically}, for further details.
8867 @subsubsection Deviations from standard Modula-2
8868 @cindex Modula-2, deviations from
8870 A few changes have been made to make Modula-2 programs easier to debug.
8871 This is done primarily via loosening its type strictness:
8875 Unlike in standard Modula-2, pointer constants can be formed by
8876 integers. This allows you to modify pointer variables during
8877 debugging. (In standard Modula-2, the actual address contained in a
8878 pointer variable is hidden from you; it can only be modified
8879 through direct assignment to another pointer variable or expression that
8880 returned a pointer.)
8883 C escape sequences can be used in strings and characters to represent
8884 non-printable characters. @value{GDBN} prints out strings with these
8885 escape sequences embedded. Single non-printable characters are
8886 printed using the @samp{CHR(@var{nnn})} format.
8889 The assignment operator (@code{:=}) returns the value of its right-hand
8893 All built-in procedures both modify @emph{and} return their argument.
8897 @subsubsection Modula-2 type and range checks
8898 @cindex Modula-2 checks
8901 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
8904 @c FIXME remove warning when type/range checks added
8906 @value{GDBN} considers two Modula-2 variables type equivalent if:
8910 They are of types that have been declared equivalent via a @code{TYPE
8911 @var{t1} = @var{t2}} statement
8914 They have been declared on the same line. (Note: This is true of the
8915 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
8918 As long as type checking is enabled, any attempt to combine variables
8919 whose types are not equivalent is an error.
8921 Range checking is done on all mathematical operations, assignment, array
8922 index bounds, and all built-in functions and procedures.
8925 @subsubsection The scope operators @code{::} and @code{.}
8927 @cindex @code{.}, Modula-2 scope operator
8928 @cindex colon, doubled as scope operator
8930 @vindex colon-colon@r{, in Modula-2}
8931 @c Info cannot handle :: but TeX can.
8934 @vindex ::@r{, in Modula-2}
8937 There are a few subtle differences between the Modula-2 scope operator
8938 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
8943 @var{module} . @var{id}
8944 @var{scope} :: @var{id}
8948 where @var{scope} is the name of a module or a procedure,
8949 @var{module} the name of a module, and @var{id} is any declared
8950 identifier within your program, except another module.
8952 Using the @code{::} operator makes @value{GDBN} search the scope
8953 specified by @var{scope} for the identifier @var{id}. If it is not
8954 found in the specified scope, then @value{GDBN} searches all scopes
8955 enclosing the one specified by @var{scope}.
8957 Using the @code{.} operator makes @value{GDBN} search the current scope for
8958 the identifier specified by @var{id} that was imported from the
8959 definition module specified by @var{module}. With this operator, it is
8960 an error if the identifier @var{id} was not imported from definition
8961 module @var{module}, or if @var{id} is not an identifier in
8965 @subsubsection @value{GDBN} and Modula-2
8967 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
8968 Five subcommands of @code{set print} and @code{show print} apply
8969 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
8970 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
8971 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
8972 analogue in Modula-2.
8974 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
8975 with any language, is not useful with Modula-2. Its
8976 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
8977 created in Modula-2 as they can in C or C@t{++}. However, because an
8978 address can be specified by an integral constant, the construct
8979 @samp{@{@var{type}@}@var{adrexp}} is still useful.
8981 @cindex @code{#} in Modula-2
8982 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
8983 interpreted as the beginning of a comment. Use @code{<>} instead.
8985 @node Unsupported languages
8986 @section Unsupported languages
8988 @cindex unsupported languages
8989 @cindex minimal language
8990 In addition to the other fully-supported programming languages,
8991 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
8992 It does not represent a real programming language, but provides a set
8993 of capabilities close to what the C or assembly languages provide.
8994 This should allow most simple operations to be performed while debugging
8995 an application that uses a language currently not supported by @value{GDBN}.
8997 If the language is set to @code{auto}, @value{GDBN} will automatically
8998 select this language if the current frame corresponds to an unsupported
9002 @chapter Examining the Symbol Table
9004 The commands described in this chapter allow you to inquire about the
9005 symbols (names of variables, functions and types) defined in your
9006 program. This information is inherent in the text of your program and
9007 does not change as your program executes. @value{GDBN} finds it in your
9008 program's symbol table, in the file indicated when you started @value{GDBN}
9009 (@pxref{File Options, ,Choosing files}), or by one of the
9010 file-management commands (@pxref{Files, ,Commands to specify files}).
9012 @cindex symbol names
9013 @cindex names of symbols
9014 @cindex quoting names
9015 Occasionally, you may need to refer to symbols that contain unusual
9016 characters, which @value{GDBN} ordinarily treats as word delimiters. The
9017 most frequent case is in referring to static variables in other
9018 source files (@pxref{Variables,,Program variables}). File names
9019 are recorded in object files as debugging symbols, but @value{GDBN} would
9020 ordinarily parse a typical file name, like @file{foo.c}, as the three words
9021 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
9022 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
9029 looks up the value of @code{x} in the scope of the file @file{foo.c}.
9032 @kindex info address
9033 @cindex address of a symbol
9034 @item info address @var{symbol}
9035 Describe where the data for @var{symbol} is stored. For a register
9036 variable, this says which register it is kept in. For a non-register
9037 local variable, this prints the stack-frame offset at which the variable
9040 Note the contrast with @samp{print &@var{symbol}}, which does not work
9041 at all for a register variable, and for a stack local variable prints
9042 the exact address of the current instantiation of the variable.
9045 @cindex symbol from address
9046 @item info symbol @var{addr}
9047 Print the name of a symbol which is stored at the address @var{addr}.
9048 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
9049 nearest symbol and an offset from it:
9052 (@value{GDBP}) info symbol 0x54320
9053 _initialize_vx + 396 in section .text
9057 This is the opposite of the @code{info address} command. You can use
9058 it to find out the name of a variable or a function given its address.
9061 @item whatis @var{expr}
9062 Print the data type of expression @var{expr}. @var{expr} is not
9063 actually evaluated, and any side-effecting operations (such as
9064 assignments or function calls) inside it do not take place.
9065 @xref{Expressions, ,Expressions}.
9068 Print the data type of @code{$}, the last value in the value history.
9071 @item ptype @var{typename}
9072 Print a description of data type @var{typename}. @var{typename} may be
9073 the name of a type, or for C code it may have the form @samp{class
9074 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
9075 @var{union-tag}} or @samp{enum @var{enum-tag}}.
9077 @item ptype @var{expr}
9079 Print a description of the type of expression @var{expr}. @code{ptype}
9080 differs from @code{whatis} by printing a detailed description, instead
9081 of just the name of the type.
9083 For example, for this variable declaration:
9086 struct complex @{double real; double imag;@} v;
9090 the two commands give this output:
9094 (@value{GDBP}) whatis v
9095 type = struct complex
9096 (@value{GDBP}) ptype v
9097 type = struct complex @{
9105 As with @code{whatis}, using @code{ptype} without an argument refers to
9106 the type of @code{$}, the last value in the value history.
9109 @item info types @var{regexp}
9111 Print a brief description of all types whose names match @var{regexp}
9112 (or all types in your program, if you supply no argument). Each
9113 complete typename is matched as though it were a complete line; thus,
9114 @samp{i type value} gives information on all types in your program whose
9115 names include the string @code{value}, but @samp{i type ^value$} gives
9116 information only on types whose complete name is @code{value}.
9118 This command differs from @code{ptype} in two ways: first, like
9119 @code{whatis}, it does not print a detailed description; second, it
9120 lists all source files where a type is defined.
9123 @cindex local variables
9124 @item info scope @var{addr}
9125 List all the variables local to a particular scope. This command
9126 accepts a location---a function name, a source line, or an address
9127 preceded by a @samp{*}, and prints all the variables local to the
9128 scope defined by that location. For example:
9131 (@value{GDBP}) @b{info scope command_line_handler}
9132 Scope for command_line_handler:
9133 Symbol rl is an argument at stack/frame offset 8, length 4.
9134 Symbol linebuffer is in static storage at address 0x150a18, length 4.
9135 Symbol linelength is in static storage at address 0x150a1c, length 4.
9136 Symbol p is a local variable in register $esi, length 4.
9137 Symbol p1 is a local variable in register $ebx, length 4.
9138 Symbol nline is a local variable in register $edx, length 4.
9139 Symbol repeat is a local variable at frame offset -8, length 4.
9143 This command is especially useful for determining what data to collect
9144 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
9149 Show information about the current source file---that is, the source file for
9150 the function containing the current point of execution:
9153 the name of the source file, and the directory containing it,
9155 the directory it was compiled in,
9157 its length, in lines,
9159 which programming language it is written in,
9161 whether the executable includes debugging information for that file, and
9162 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
9164 whether the debugging information includes information about
9165 preprocessor macros.
9169 @kindex info sources
9171 Print the names of all source files in your program for which there is
9172 debugging information, organized into two lists: files whose symbols
9173 have already been read, and files whose symbols will be read when needed.
9175 @kindex info functions
9176 @item info functions
9177 Print the names and data types of all defined functions.
9179 @item info functions @var{regexp}
9180 Print the names and data types of all defined functions
9181 whose names contain a match for regular expression @var{regexp}.
9182 Thus, @samp{info fun step} finds all functions whose names
9183 include @code{step}; @samp{info fun ^step} finds those whose names
9184 start with @code{step}. If a function name contains characters
9185 that conflict with the regular expression language (eg.
9186 @samp{operator*()}), they may be quoted with a backslash.
9188 @kindex info variables
9189 @item info variables
9190 Print the names and data types of all variables that are declared
9191 outside of functions (i.e.@: excluding local variables).
9193 @item info variables @var{regexp}
9194 Print the names and data types of all variables (except for local
9195 variables) whose names contain a match for regular expression
9198 @kindex info classes
9200 @itemx info classes @var{regexp}
9201 Display all Objective-C classes in your program, or
9202 (with the @var{regexp} argument) all those matching a particular regular
9205 @kindex info selectors
9206 @item info selectors
9207 @itemx info selectors @var{regexp}
9208 Display all Objective-C selectors in your program, or
9209 (with the @var{regexp} argument) all those matching a particular regular
9213 This was never implemented.
9214 @kindex info methods
9216 @itemx info methods @var{regexp}
9217 The @code{info methods} command permits the user to examine all defined
9218 methods within C@t{++} program, or (with the @var{regexp} argument) a
9219 specific set of methods found in the various C@t{++} classes. Many
9220 C@t{++} classes provide a large number of methods. Thus, the output
9221 from the @code{ptype} command can be overwhelming and hard to use. The
9222 @code{info-methods} command filters the methods, printing only those
9223 which match the regular-expression @var{regexp}.
9226 @cindex reloading symbols
9227 Some systems allow individual object files that make up your program to
9228 be replaced without stopping and restarting your program. For example,
9229 in VxWorks you can simply recompile a defective object file and keep on
9230 running. If you are running on one of these systems, you can allow
9231 @value{GDBN} to reload the symbols for automatically relinked modules:
9234 @kindex set symbol-reloading
9235 @item set symbol-reloading on
9236 Replace symbol definitions for the corresponding source file when an
9237 object file with a particular name is seen again.
9239 @item set symbol-reloading off
9240 Do not replace symbol definitions when encountering object files of the
9241 same name more than once. This is the default state; if you are not
9242 running on a system that permits automatic relinking of modules, you
9243 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
9244 may discard symbols when linking large programs, that may contain
9245 several modules (from different directories or libraries) with the same
9248 @kindex show symbol-reloading
9249 @item show symbol-reloading
9250 Show the current @code{on} or @code{off} setting.
9253 @kindex set opaque-type-resolution
9254 @item set opaque-type-resolution on
9255 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
9256 declared as a pointer to a @code{struct}, @code{class}, or
9257 @code{union}---for example, @code{struct MyType *}---that is used in one
9258 source file although the full declaration of @code{struct MyType} is in
9259 another source file. The default is on.
9261 A change in the setting of this subcommand will not take effect until
9262 the next time symbols for a file are loaded.
9264 @item set opaque-type-resolution off
9265 Tell @value{GDBN} not to resolve opaque types. In this case, the type
9266 is printed as follows:
9268 @{<no data fields>@}
9271 @kindex show opaque-type-resolution
9272 @item show opaque-type-resolution
9273 Show whether opaque types are resolved or not.
9275 @kindex maint print symbols
9277 @kindex maint print psymbols
9278 @cindex partial symbol dump
9279 @item maint print symbols @var{filename}
9280 @itemx maint print psymbols @var{filename}
9281 @itemx maint print msymbols @var{filename}
9282 Write a dump of debugging symbol data into the file @var{filename}.
9283 These commands are used to debug the @value{GDBN} symbol-reading code. Only
9284 symbols with debugging data are included. If you use @samp{maint print
9285 symbols}, @value{GDBN} includes all the symbols for which it has already
9286 collected full details: that is, @var{filename} reflects symbols for
9287 only those files whose symbols @value{GDBN} has read. You can use the
9288 command @code{info sources} to find out which files these are. If you
9289 use @samp{maint print psymbols} instead, the dump shows information about
9290 symbols that @value{GDBN} only knows partially---that is, symbols defined in
9291 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
9292 @samp{maint print msymbols} dumps just the minimal symbol information
9293 required for each object file from which @value{GDBN} has read some symbols.
9294 @xref{Files, ,Commands to specify files}, for a discussion of how
9295 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
9297 @kindex maint info symtabs
9298 @kindex maint info psymtabs
9299 @cindex listing @value{GDBN}'s internal symbol tables
9300 @cindex symbol tables, listing @value{GDBN}'s internal
9301 @cindex full symbol tables, listing @value{GDBN}'s internal
9302 @cindex partial symbol tables, listing @value{GDBN}'s internal
9303 @item maint info symtabs @r{[} @var{regexp} @r{]}
9304 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
9306 List the @code{struct symtab} or @code{struct partial_symtab}
9307 structures whose names match @var{regexp}. If @var{regexp} is not
9308 given, list them all. The output includes expressions which you can
9309 copy into a @value{GDBN} debugging this one to examine a particular
9310 structure in more detail. For example:
9313 (@value{GDBP}) maint info psymtabs dwarf2read
9314 @{ objfile /home/gnu/build/gdb/gdb
9315 ((struct objfile *) 0x82e69d0)
9316 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
9317 ((struct partial_symtab *) 0x8474b10)
9320 text addresses 0x814d3c8 -- 0x8158074
9321 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
9322 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
9326 (@value{GDBP}) maint info symtabs
9330 We see that there is one partial symbol table whose filename contains
9331 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
9332 and we see that @value{GDBN} has not read in any symtabs yet at all.
9333 If we set a breakpoint on a function, that will cause @value{GDBN} to
9334 read the symtab for the compilation unit containing that function:
9337 (@value{GDBP}) break dwarf2_psymtab_to_symtab
9338 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
9340 (@value{GDBP}) maint info symtabs
9341 @{ objfile /home/gnu/build/gdb/gdb
9342 ((struct objfile *) 0x82e69d0)
9343 @{ symtab /home/gnu/src/gdb/dwarf2read.c
9344 ((struct symtab *) 0x86c1f38)
9347 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
9357 @chapter Altering Execution
9359 Once you think you have found an error in your program, you might want to
9360 find out for certain whether correcting the apparent error would lead to
9361 correct results in the rest of the run. You can find the answer by
9362 experiment, using the @value{GDBN} features for altering execution of the
9365 For example, you can store new values into variables or memory
9366 locations, give your program a signal, restart it at a different
9367 address, or even return prematurely from a function.
9370 * Assignment:: Assignment to variables
9371 * Jumping:: Continuing at a different address
9372 * Signaling:: Giving your program a signal
9373 * Returning:: Returning from a function
9374 * Calling:: Calling your program's functions
9375 * Patching:: Patching your program
9379 @section Assignment to variables
9382 @cindex setting variables
9383 To alter the value of a variable, evaluate an assignment expression.
9384 @xref{Expressions, ,Expressions}. For example,
9391 stores the value 4 into the variable @code{x}, and then prints the
9392 value of the assignment expression (which is 4).
9393 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
9394 information on operators in supported languages.
9396 @kindex set variable
9397 @cindex variables, setting
9398 If you are not interested in seeing the value of the assignment, use the
9399 @code{set} command instead of the @code{print} command. @code{set} is
9400 really the same as @code{print} except that the expression's value is
9401 not printed and is not put in the value history (@pxref{Value History,
9402 ,Value history}). The expression is evaluated only for its effects.
9404 If the beginning of the argument string of the @code{set} command
9405 appears identical to a @code{set} subcommand, use the @code{set
9406 variable} command instead of just @code{set}. This command is identical
9407 to @code{set} except for its lack of subcommands. For example, if your
9408 program has a variable @code{width}, you get an error if you try to set
9409 a new value with just @samp{set width=13}, because @value{GDBN} has the
9410 command @code{set width}:
9413 (@value{GDBP}) whatis width
9415 (@value{GDBP}) p width
9417 (@value{GDBP}) set width=47
9418 Invalid syntax in expression.
9422 The invalid expression, of course, is @samp{=47}. In
9423 order to actually set the program's variable @code{width}, use
9426 (@value{GDBP}) set var width=47
9429 Because the @code{set} command has many subcommands that can conflict
9430 with the names of program variables, it is a good idea to use the
9431 @code{set variable} command instead of just @code{set}. For example, if
9432 your program has a variable @code{g}, you run into problems if you try
9433 to set a new value with just @samp{set g=4}, because @value{GDBN} has
9434 the command @code{set gnutarget}, abbreviated @code{set g}:
9438 (@value{GDBP}) whatis g
9442 (@value{GDBP}) set g=4
9446 The program being debugged has been started already.
9447 Start it from the beginning? (y or n) y
9448 Starting program: /home/smith/cc_progs/a.out
9449 "/home/smith/cc_progs/a.out": can't open to read symbols:
9451 (@value{GDBP}) show g
9452 The current BFD target is "=4".
9457 The program variable @code{g} did not change, and you silently set the
9458 @code{gnutarget} to an invalid value. In order to set the variable
9462 (@value{GDBP}) set var g=4
9465 @value{GDBN} allows more implicit conversions in assignments than C; you can
9466 freely store an integer value into a pointer variable or vice versa,
9467 and you can convert any structure to any other structure that is the
9468 same length or shorter.
9469 @comment FIXME: how do structs align/pad in these conversions?
9470 @comment /doc@cygnus.com 18dec1990
9472 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
9473 construct to generate a value of specified type at a specified address
9474 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
9475 to memory location @code{0x83040} as an integer (which implies a certain size
9476 and representation in memory), and
9479 set @{int@}0x83040 = 4
9483 stores the value 4 into that memory location.
9486 @section Continuing at a different address
9488 Ordinarily, when you continue your program, you do so at the place where
9489 it stopped, with the @code{continue} command. You can instead continue at
9490 an address of your own choosing, with the following commands:
9494 @item jump @var{linespec}
9495 Resume execution at line @var{linespec}. Execution stops again
9496 immediately if there is a breakpoint there. @xref{List, ,Printing
9497 source lines}, for a description of the different forms of
9498 @var{linespec}. It is common practice to use the @code{tbreak} command
9499 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
9502 The @code{jump} command does not change the current stack frame, or
9503 the stack pointer, or the contents of any memory location or any
9504 register other than the program counter. If line @var{linespec} is in
9505 a different function from the one currently executing, the results may
9506 be bizarre if the two functions expect different patterns of arguments or
9507 of local variables. For this reason, the @code{jump} command requests
9508 confirmation if the specified line is not in the function currently
9509 executing. However, even bizarre results are predictable if you are
9510 well acquainted with the machine-language code of your program.
9512 @item jump *@var{address}
9513 Resume execution at the instruction at address @var{address}.
9516 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
9517 On many systems, you can get much the same effect as the @code{jump}
9518 command by storing a new value into the register @code{$pc}. The
9519 difference is that this does not start your program running; it only
9520 changes the address of where it @emph{will} run when you continue. For
9528 makes the next @code{continue} command or stepping command execute at
9529 address @code{0x485}, rather than at the address where your program stopped.
9530 @xref{Continuing and Stepping, ,Continuing and stepping}.
9532 The most common occasion to use the @code{jump} command is to back
9533 up---perhaps with more breakpoints set---over a portion of a program
9534 that has already executed, in order to examine its execution in more
9539 @section Giving your program a signal
9543 @item signal @var{signal}
9544 Resume execution where your program stopped, but immediately give it the
9545 signal @var{signal}. @var{signal} can be the name or the number of a
9546 signal. For example, on many systems @code{signal 2} and @code{signal
9547 SIGINT} are both ways of sending an interrupt signal.
9549 Alternatively, if @var{signal} is zero, continue execution without
9550 giving a signal. This is useful when your program stopped on account of
9551 a signal and would ordinary see the signal when resumed with the
9552 @code{continue} command; @samp{signal 0} causes it to resume without a
9555 @code{signal} does not repeat when you press @key{RET} a second time
9556 after executing the command.
9560 Invoking the @code{signal} command is not the same as invoking the
9561 @code{kill} utility from the shell. Sending a signal with @code{kill}
9562 causes @value{GDBN} to decide what to do with the signal depending on
9563 the signal handling tables (@pxref{Signals}). The @code{signal} command
9564 passes the signal directly to your program.
9568 @section Returning from a function
9571 @cindex returning from a function
9574 @itemx return @var{expression}
9575 You can cancel execution of a function call with the @code{return}
9576 command. If you give an
9577 @var{expression} argument, its value is used as the function's return
9581 When you use @code{return}, @value{GDBN} discards the selected stack frame
9582 (and all frames within it). You can think of this as making the
9583 discarded frame return prematurely. If you wish to specify a value to
9584 be returned, give that value as the argument to @code{return}.
9586 This pops the selected stack frame (@pxref{Selection, ,Selecting a
9587 frame}), and any other frames inside of it, leaving its caller as the
9588 innermost remaining frame. That frame becomes selected. The
9589 specified value is stored in the registers used for returning values
9592 The @code{return} command does not resume execution; it leaves the
9593 program stopped in the state that would exist if the function had just
9594 returned. In contrast, the @code{finish} command (@pxref{Continuing
9595 and Stepping, ,Continuing and stepping}) resumes execution until the
9596 selected stack frame returns naturally.
9599 @section Calling program functions
9601 @cindex calling functions
9604 @item call @var{expr}
9605 Evaluate the expression @var{expr} without displaying @code{void}
9609 You can use this variant of the @code{print} command if you want to
9610 execute a function from your program, but without cluttering the output
9611 with @code{void} returned values. If the result is not void, it
9612 is printed and saved in the value history.
9615 @section Patching programs
9617 @cindex patching binaries
9618 @cindex writing into executables
9619 @cindex writing into corefiles
9621 By default, @value{GDBN} opens the file containing your program's
9622 executable code (or the corefile) read-only. This prevents accidental
9623 alterations to machine code; but it also prevents you from intentionally
9624 patching your program's binary.
9626 If you'd like to be able to patch the binary, you can specify that
9627 explicitly with the @code{set write} command. For example, you might
9628 want to turn on internal debugging flags, or even to make emergency
9634 @itemx set write off
9635 If you specify @samp{set write on}, @value{GDBN} opens executable and
9636 core files for both reading and writing; if you specify @samp{set write
9637 off} (the default), @value{GDBN} opens them read-only.
9639 If you have already loaded a file, you must load it again (using the
9640 @code{exec-file} or @code{core-file} command) after changing @code{set
9641 write}, for your new setting to take effect.
9645 Display whether executable files and core files are opened for writing
9650 @chapter @value{GDBN} Files
9652 @value{GDBN} needs to know the file name of the program to be debugged,
9653 both in order to read its symbol table and in order to start your
9654 program. To debug a core dump of a previous run, you must also tell
9655 @value{GDBN} the name of the core dump file.
9658 * Files:: Commands to specify files
9659 * Separate Debug Files:: Debugging information in separate files
9660 * Symbol Errors:: Errors reading symbol files
9664 @section Commands to specify files
9666 @cindex symbol table
9667 @cindex core dump file
9669 You may want to specify executable and core dump file names. The usual
9670 way to do this is at start-up time, using the arguments to
9671 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
9672 Out of @value{GDBN}}).
9674 Occasionally it is necessary to change to a different file during a
9675 @value{GDBN} session. Or you may run @value{GDBN} and forget to specify
9676 a file you want to use. In these situations the @value{GDBN} commands
9677 to specify new files are useful.
9680 @cindex executable file
9682 @item file @var{filename}
9683 Use @var{filename} as the program to be debugged. It is read for its
9684 symbols and for the contents of pure memory. It is also the program
9685 executed when you use the @code{run} command. If you do not specify a
9686 directory and the file is not found in the @value{GDBN} working directory,
9687 @value{GDBN} uses the environment variable @code{PATH} as a list of
9688 directories to search, just as the shell does when looking for a program
9689 to run. You can change the value of this variable, for both @value{GDBN}
9690 and your program, using the @code{path} command.
9692 On systems with memory-mapped files, an auxiliary file named
9693 @file{@var{filename}.syms} may hold symbol table information for
9694 @var{filename}. If so, @value{GDBN} maps in the symbol table from
9695 @file{@var{filename}.syms}, starting up more quickly. See the
9696 descriptions of the file options @samp{-mapped} and @samp{-readnow}
9697 (available on the command line, and with the commands @code{file},
9698 @code{symbol-file}, or @code{add-symbol-file}, described below),
9699 for more information.
9702 @code{file} with no argument makes @value{GDBN} discard any information it
9703 has on both executable file and the symbol table.
9706 @item exec-file @r{[} @var{filename} @r{]}
9707 Specify that the program to be run (but not the symbol table) is found
9708 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
9709 if necessary to locate your program. Omitting @var{filename} means to
9710 discard information on the executable file.
9713 @item symbol-file @r{[} @var{filename} @r{]}
9714 Read symbol table information from file @var{filename}. @code{PATH} is
9715 searched when necessary. Use the @code{file} command to get both symbol
9716 table and program to run from the same file.
9718 @code{symbol-file} with no argument clears out @value{GDBN} information on your
9719 program's symbol table.
9721 The @code{symbol-file} command causes @value{GDBN} to forget the contents
9722 of its convenience variables, the value history, and all breakpoints and
9723 auto-display expressions. This is because they may contain pointers to
9724 the internal data recording symbols and data types, which are part of
9725 the old symbol table data being discarded inside @value{GDBN}.
9727 @code{symbol-file} does not repeat if you press @key{RET} again after
9730 When @value{GDBN} is configured for a particular environment, it
9731 understands debugging information in whatever format is the standard
9732 generated for that environment; you may use either a @sc{gnu} compiler, or
9733 other compilers that adhere to the local conventions.
9734 Best results are usually obtained from @sc{gnu} compilers; for example,
9735 using @code{@value{GCC}} you can generate debugging information for
9738 For most kinds of object files, with the exception of old SVR3 systems
9739 using COFF, the @code{symbol-file} command does not normally read the
9740 symbol table in full right away. Instead, it scans the symbol table
9741 quickly to find which source files and which symbols are present. The
9742 details are read later, one source file at a time, as they are needed.
9744 The purpose of this two-stage reading strategy is to make @value{GDBN}
9745 start up faster. For the most part, it is invisible except for
9746 occasional pauses while the symbol table details for a particular source
9747 file are being read. (The @code{set verbose} command can turn these
9748 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
9749 warnings and messages}.)
9751 We have not implemented the two-stage strategy for COFF yet. When the
9752 symbol table is stored in COFF format, @code{symbol-file} reads the
9753 symbol table data in full right away. Note that ``stabs-in-COFF''
9754 still does the two-stage strategy, since the debug info is actually
9758 @cindex reading symbols immediately
9759 @cindex symbols, reading immediately
9761 @cindex memory-mapped symbol file
9762 @cindex saving symbol table
9763 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9764 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9765 You can override the @value{GDBN} two-stage strategy for reading symbol
9766 tables by using the @samp{-readnow} option with any of the commands that
9767 load symbol table information, if you want to be sure @value{GDBN} has the
9768 entire symbol table available.
9770 If memory-mapped files are available on your system through the
9771 @code{mmap} system call, you can use another option, @samp{-mapped}, to
9772 cause @value{GDBN} to write the symbols for your program into a reusable
9773 file. Future @value{GDBN} debugging sessions map in symbol information
9774 from this auxiliary symbol file (if the program has not changed), rather
9775 than spending time reading the symbol table from the executable
9776 program. Using the @samp{-mapped} option has the same effect as
9777 starting @value{GDBN} with the @samp{-mapped} command-line option.
9779 You can use both options together, to make sure the auxiliary symbol
9780 file has all the symbol information for your program.
9782 The auxiliary symbol file for a program called @var{myprog} is called
9783 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
9784 than the corresponding executable), @value{GDBN} always attempts to use
9785 it when you debug @var{myprog}; no special options or commands are
9788 The @file{.syms} file is specific to the host machine where you run
9789 @value{GDBN}. It holds an exact image of the internal @value{GDBN}
9790 symbol table. It cannot be shared across multiple host platforms.
9792 @c FIXME: for now no mention of directories, since this seems to be in
9793 @c flux. 13mar1992 status is that in theory GDB would look either in
9794 @c current dir or in same dir as myprog; but issues like competing
9795 @c GDB's, or clutter in system dirs, mean that in practice right now
9796 @c only current dir is used. FFish says maybe a special GDB hierarchy
9797 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
9802 @item core-file @r{[} @var{filename} @r{]}
9803 Specify the whereabouts of a core dump file to be used as the ``contents
9804 of memory''. Traditionally, core files contain only some parts of the
9805 address space of the process that generated them; @value{GDBN} can access the
9806 executable file itself for other parts.
9808 @code{core-file} with no argument specifies that no core file is
9811 Note that the core file is ignored when your program is actually running
9812 under @value{GDBN}. So, if you have been running your program and you
9813 wish to debug a core file instead, you must kill the subprocess in which
9814 the program is running. To do this, use the @code{kill} command
9815 (@pxref{Kill Process, ,Killing the child process}).
9817 @kindex add-symbol-file
9818 @cindex dynamic linking
9819 @item add-symbol-file @var{filename} @var{address}
9820 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9821 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
9822 The @code{add-symbol-file} command reads additional symbol table
9823 information from the file @var{filename}. You would use this command
9824 when @var{filename} has been dynamically loaded (by some other means)
9825 into the program that is running. @var{address} should be the memory
9826 address at which the file has been loaded; @value{GDBN} cannot figure
9827 this out for itself. You can additionally specify an arbitrary number
9828 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
9829 section name and base address for that section. You can specify any
9830 @var{address} as an expression.
9832 The symbol table of the file @var{filename} is added to the symbol table
9833 originally read with the @code{symbol-file} command. You can use the
9834 @code{add-symbol-file} command any number of times; the new symbol data
9835 thus read keeps adding to the old. To discard all old symbol data
9836 instead, use the @code{symbol-file} command without any arguments.
9838 @cindex relocatable object files, reading symbols from
9839 @cindex object files, relocatable, reading symbols from
9840 @cindex reading symbols from relocatable object files
9841 @cindex symbols, reading from relocatable object files
9842 @cindex @file{.o} files, reading symbols from
9843 Although @var{filename} is typically a shared library file, an
9844 executable file, or some other object file which has been fully
9845 relocated for loading into a process, you can also load symbolic
9846 information from relocatable @file{.o} files, as long as:
9850 the file's symbolic information refers only to linker symbols defined in
9851 that file, not to symbols defined by other object files,
9853 every section the file's symbolic information refers to has actually
9854 been loaded into the inferior, as it appears in the file, and
9856 you can determine the address at which every section was loaded, and
9857 provide these to the @code{add-symbol-file} command.
9861 Some embedded operating systems, like Sun Chorus and VxWorks, can load
9862 relocatable files into an already running program; such systems
9863 typically make the requirements above easy to meet. However, it's
9864 important to recognize that many native systems use complex link
9865 procedures (@code{.linkonce} section factoring and C++ constructor table
9866 assembly, for example) that make the requirements difficult to meet. In
9867 general, one cannot assume that using @code{add-symbol-file} to read a
9868 relocatable object file's symbolic information will have the same effect
9869 as linking the relocatable object file into the program in the normal
9872 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
9874 You can use the @samp{-mapped} and @samp{-readnow} options just as with
9875 the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
9876 table information for @var{filename}.
9878 @kindex add-shared-symbol-file
9879 @item add-shared-symbol-file
9880 The @code{add-shared-symbol-file} command can be used only under Harris' CXUX
9881 operating system for the Motorola 88k. @value{GDBN} automatically looks for
9882 shared libraries, however if @value{GDBN} does not find yours, you can run
9883 @code{add-shared-symbol-file}. It takes no arguments.
9887 The @code{section} command changes the base address of section SECTION of
9888 the exec file to ADDR. This can be used if the exec file does not contain
9889 section addresses, (such as in the a.out format), or when the addresses
9890 specified in the file itself are wrong. Each section must be changed
9891 separately. The @code{info files} command, described below, lists all
9892 the sections and their addresses.
9898 @code{info files} and @code{info target} are synonymous; both print the
9899 current target (@pxref{Targets, ,Specifying a Debugging Target}),
9900 including the names of the executable and core dump files currently in
9901 use by @value{GDBN}, and the files from which symbols were loaded. The
9902 command @code{help target} lists all possible targets rather than
9905 @kindex maint info sections
9906 @item maint info sections
9907 Another command that can give you extra information about program sections
9908 is @code{maint info sections}. In addition to the section information
9909 displayed by @code{info files}, this command displays the flags and file
9910 offset of each section in the executable and core dump files. In addition,
9911 @code{maint info sections} provides the following command options (which
9912 may be arbitrarily combined):
9916 Display sections for all loaded object files, including shared libraries.
9917 @item @var{sections}
9918 Display info only for named @var{sections}.
9919 @item @var{section-flags}
9920 Display info only for sections for which @var{section-flags} are true.
9921 The section flags that @value{GDBN} currently knows about are:
9924 Section will have space allocated in the process when loaded.
9925 Set for all sections except those containing debug information.
9927 Section will be loaded from the file into the child process memory.
9928 Set for pre-initialized code and data, clear for @code{.bss} sections.
9930 Section needs to be relocated before loading.
9932 Section cannot be modified by the child process.
9934 Section contains executable code only.
9936 Section contains data only (no executable code).
9938 Section will reside in ROM.
9940 Section contains data for constructor/destructor lists.
9942 Section is not empty.
9944 An instruction to the linker to not output the section.
9945 @item COFF_SHARED_LIBRARY
9946 A notification to the linker that the section contains
9947 COFF shared library information.
9949 Section contains common symbols.
9952 @kindex set trust-readonly-sections
9953 @item set trust-readonly-sections on
9954 Tell @value{GDBN} that readonly sections in your object file
9955 really are read-only (i.e.@: that their contents will not change).
9956 In that case, @value{GDBN} can fetch values from these sections
9957 out of the object file, rather than from the target program.
9958 For some targets (notably embedded ones), this can be a significant
9959 enhancement to debugging performance.
9963 @item set trust-readonly-sections off
9964 Tell @value{GDBN} not to trust readonly sections. This means that
9965 the contents of the section might change while the program is running,
9966 and must therefore be fetched from the target when needed.
9969 All file-specifying commands allow both absolute and relative file names
9970 as arguments. @value{GDBN} always converts the file name to an absolute file
9971 name and remembers it that way.
9973 @cindex shared libraries
9974 @value{GDBN} supports HP-UX, SunOS, SVr4, Irix 5, and IBM RS/6000 shared
9977 @value{GDBN} automatically loads symbol definitions from shared libraries
9978 when you use the @code{run} command, or when you examine a core file.
9979 (Before you issue the @code{run} command, @value{GDBN} does not understand
9980 references to a function in a shared library, however---unless you are
9981 debugging a core file).
9983 On HP-UX, if the program loads a library explicitly, @value{GDBN}
9984 automatically loads the symbols at the time of the @code{shl_load} call.
9986 @c FIXME: some @value{GDBN} release may permit some refs to undef
9987 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
9988 @c FIXME...lib; check this from time to time when updating manual
9990 There are times, however, when you may wish to not automatically load
9991 symbol definitions from shared libraries, such as when they are
9992 particularly large or there are many of them.
9994 To control the automatic loading of shared library symbols, use the
9998 @kindex set auto-solib-add
9999 @item set auto-solib-add @var{mode}
10000 If @var{mode} is @code{on}, symbols from all shared object libraries
10001 will be loaded automatically when the inferior begins execution, you
10002 attach to an independently started inferior, or when the dynamic linker
10003 informs @value{GDBN} that a new library has been loaded. If @var{mode}
10004 is @code{off}, symbols must be loaded manually, using the
10005 @code{sharedlibrary} command. The default value is @code{on}.
10007 @kindex show auto-solib-add
10008 @item show auto-solib-add
10009 Display the current autoloading mode.
10012 To explicitly load shared library symbols, use the @code{sharedlibrary}
10016 @kindex info sharedlibrary
10019 @itemx info sharedlibrary
10020 Print the names of the shared libraries which are currently loaded.
10022 @kindex sharedlibrary
10024 @item sharedlibrary @var{regex}
10025 @itemx share @var{regex}
10026 Load shared object library symbols for files matching a
10027 Unix regular expression.
10028 As with files loaded automatically, it only loads shared libraries
10029 required by your program for a core file or after typing @code{run}. If
10030 @var{regex} is omitted all shared libraries required by your program are
10034 On some systems, such as HP-UX systems, @value{GDBN} supports
10035 autoloading shared library symbols until a limiting threshold size is
10036 reached. This provides the benefit of allowing autoloading to remain on
10037 by default, but avoids autoloading excessively large shared libraries,
10038 up to a threshold that is initially set, but which you can modify if you
10041 Beyond that threshold, symbols from shared libraries must be explicitly
10042 loaded. To load these symbols, use the command @code{sharedlibrary
10043 @var{filename}}. The base address of the shared library is determined
10044 automatically by @value{GDBN} and need not be specified.
10046 To display or set the threshold, use the commands:
10049 @kindex set auto-solib-limit
10050 @item set auto-solib-limit @var{threshold}
10051 Set the autoloading size threshold, in an integral number of megabytes.
10052 If @var{threshold} is nonzero and shared library autoloading is enabled,
10053 symbols from all shared object libraries will be loaded until the total
10054 size of the loaded shared library symbols exceeds this threshold.
10055 Otherwise, symbols must be loaded manually, using the
10056 @code{sharedlibrary} command. The default threshold is 100 (i.e.@: 100
10059 @kindex show auto-solib-limit
10060 @item show auto-solib-limit
10061 Display the current autoloading size threshold, in megabytes.
10064 Shared libraries are also supported in many cross or remote debugging
10065 configurations. A copy of the target's libraries need to be present on the
10066 host system; they need to be the same as the target libraries, although the
10067 copies on the target can be stripped as long as the copies on the host are
10070 You need to tell @value{GDBN} where the target libraries are, so that it can
10071 load the correct copies---otherwise, it may try to load the host's libraries.
10072 @value{GDBN} has two variables to specify the search directories for target
10076 @kindex set solib-absolute-prefix
10077 @item set solib-absolute-prefix @var{path}
10078 If this variable is set, @var{path} will be used as a prefix for any
10079 absolute shared library paths; many runtime loaders store the absolute
10080 paths to the shared library in the target program's memory. If you use
10081 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
10082 out in the same way that they are on the target, with e.g.@: a
10083 @file{/usr/lib} hierarchy under @var{path}.
10085 You can set the default value of @samp{solib-absolute-prefix} by using the
10086 configure-time @samp{--with-sysroot} option.
10088 @kindex show solib-absolute-prefix
10089 @item show solib-absolute-prefix
10090 Display the current shared library prefix.
10092 @kindex set solib-search-path
10093 @item set solib-search-path @var{path}
10094 If this variable is set, @var{path} is a colon-separated list of directories
10095 to search for shared libraries. @samp{solib-search-path} is used after
10096 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
10097 the library is relative instead of absolute. If you want to use
10098 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
10099 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
10100 @value{GDBN} from finding your host's libraries.
10102 @kindex show solib-search-path
10103 @item show solib-search-path
10104 Display the current shared library search path.
10108 @node Separate Debug Files
10109 @section Debugging Information in Separate Files
10110 @cindex separate debugging information files
10111 @cindex debugging information in separate files
10112 @cindex @file{.debug} subdirectories
10113 @cindex debugging information directory, global
10114 @cindex global debugging information directory
10116 @value{GDBN} allows you to put a program's debugging information in a
10117 file separate from the executable itself, in a way that allows
10118 @value{GDBN} to find and load the debugging information automatically.
10119 Since debugging information can be very large --- sometimes larger
10120 than the executable code itself --- some systems distribute debugging
10121 information for their executables in separate files, which users can
10122 install only when they need to debug a problem.
10124 If an executable's debugging information has been extracted to a
10125 separate file, the executable should contain a @dfn{debug link} giving
10126 the name of the debugging information file (with no directory
10127 components), and a checksum of its contents. (The exact form of a
10128 debug link is described below.) If the full name of the directory
10129 containing the executable is @var{execdir}, and the executable has a
10130 debug link that specifies the name @var{debugfile}, then @value{GDBN}
10131 will automatically search for the debugging information file in three
10136 the directory containing the executable file (that is, it will look
10137 for a file named @file{@var{execdir}/@var{debugfile}},
10139 a subdirectory of that directory named @file{.debug} (that is, the
10140 file @file{@var{execdir}/.debug/@var{debugfile}}, and
10142 a subdirectory of the global debug file directory that includes the
10143 executable's full path, and the name from the link (that is, the file
10144 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
10145 @var{globaldebugdir} is the global debug file directory, and
10146 @var{execdir} has been turned into a relative path).
10149 @value{GDBN} checks under each of these names for a debugging
10150 information file whose checksum matches that given in the link, and
10151 reads the debugging information from the first one it finds.
10153 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
10154 which has a link containing the name @file{ls.debug}, and the global
10155 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
10156 for debug information in @file{/usr/bin/ls.debug},
10157 @file{/usr/bin/.debug/ls.debug}, and
10158 @file{/usr/lib/debug/usr/bin/ls.debug}.
10160 You can set the global debugging info directory's name, and view the
10161 name @value{GDBN} is currently using.
10165 @kindex set debug-file-directory
10166 @item set debug-file-directory @var{directory}
10167 Set the directory which @value{GDBN} searches for separate debugging
10168 information files to @var{directory}.
10170 @kindex show debug-file-directory
10171 @item show debug-file-directory
10172 Show the directory @value{GDBN} searches for separate debugging
10177 @cindex @code{.gnu_debuglink} sections
10178 @cindex debug links
10179 A debug link is a special section of the executable file named
10180 @code{.gnu_debuglink}. The section must contain:
10184 A filename, with any leading directory components removed, followed by
10187 zero to three bytes of padding, as needed to reach the next four-byte
10188 boundary within the section, and
10190 a four-byte CRC checksum, stored in the same endianness used for the
10191 executable file itself. The checksum is computed on the debugging
10192 information file's full contents by the function given below, passing
10193 zero as the @var{crc} argument.
10196 Any executable file format can carry a debug link, as long as it can
10197 contain a section named @code{.gnu_debuglink} with the contents
10200 The debugging information file itself should be an ordinary
10201 executable, containing a full set of linker symbols, sections, and
10202 debugging information. The sections of the debugging information file
10203 should have the same names, addresses and sizes as the original file,
10204 but they need not contain any data --- much like a @code{.bss} section
10205 in an ordinary executable.
10207 As of December 2002, there is no standard GNU utility to produce
10208 separated executable / debugging information file pairs. Ulrich
10209 Drepper's @file{elfutils} package, starting with version 0.53,
10210 contains a version of the @code{strip} command such that the command
10211 @kbd{strip foo -f foo.debug} removes the debugging information from
10212 the executable file @file{foo}, places it in the file
10213 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
10215 Since there are many different ways to compute CRC's (different
10216 polynomials, reversals, byte ordering, etc.), the simplest way to
10217 describe the CRC used in @code{.gnu_debuglink} sections is to give the
10218 complete code for a function that computes it:
10220 @kindex @code{gnu_debuglink_crc32}
10223 gnu_debuglink_crc32 (unsigned long crc,
10224 unsigned char *buf, size_t len)
10226 static const unsigned long crc32_table[256] =
10228 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
10229 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
10230 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
10231 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
10232 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
10233 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
10234 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
10235 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
10236 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
10237 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
10238 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
10239 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
10240 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
10241 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
10242 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
10243 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
10244 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
10245 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
10246 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
10247 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
10248 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
10249 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
10250 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
10251 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
10252 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
10253 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
10254 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
10255 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
10256 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
10257 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
10258 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
10259 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
10260 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
10261 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
10262 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
10263 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
10264 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
10265 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
10266 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
10267 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
10268 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
10269 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
10270 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
10271 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
10272 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
10273 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
10274 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
10275 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
10276 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
10277 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
10278 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
10281 unsigned char *end;
10283 crc = ~crc & 0xffffffff;
10284 for (end = buf + len; buf < end; ++buf)
10285 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
10286 return ~crc & 0xffffffff;
10291 @node Symbol Errors
10292 @section Errors reading symbol files
10294 While reading a symbol file, @value{GDBN} occasionally encounters problems,
10295 such as symbol types it does not recognize, or known bugs in compiler
10296 output. By default, @value{GDBN} does not notify you of such problems, since
10297 they are relatively common and primarily of interest to people
10298 debugging compilers. If you are interested in seeing information
10299 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
10300 only one message about each such type of problem, no matter how many
10301 times the problem occurs; or you can ask @value{GDBN} to print more messages,
10302 to see how many times the problems occur, with the @code{set
10303 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
10306 The messages currently printed, and their meanings, include:
10309 @item inner block not inside outer block in @var{symbol}
10311 The symbol information shows where symbol scopes begin and end
10312 (such as at the start of a function or a block of statements). This
10313 error indicates that an inner scope block is not fully contained
10314 in its outer scope blocks.
10316 @value{GDBN} circumvents the problem by treating the inner block as if it had
10317 the same scope as the outer block. In the error message, @var{symbol}
10318 may be shown as ``@code{(don't know)}'' if the outer block is not a
10321 @item block at @var{address} out of order
10323 The symbol information for symbol scope blocks should occur in
10324 order of increasing addresses. This error indicates that it does not
10327 @value{GDBN} does not circumvent this problem, and has trouble
10328 locating symbols in the source file whose symbols it is reading. (You
10329 can often determine what source file is affected by specifying
10330 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
10333 @item bad block start address patched
10335 The symbol information for a symbol scope block has a start address
10336 smaller than the address of the preceding source line. This is known
10337 to occur in the SunOS 4.1.1 (and earlier) C compiler.
10339 @value{GDBN} circumvents the problem by treating the symbol scope block as
10340 starting on the previous source line.
10342 @item bad string table offset in symbol @var{n}
10345 Symbol number @var{n} contains a pointer into the string table which is
10346 larger than the size of the string table.
10348 @value{GDBN} circumvents the problem by considering the symbol to have the
10349 name @code{foo}, which may cause other problems if many symbols end up
10352 @item unknown symbol type @code{0x@var{nn}}
10354 The symbol information contains new data types that @value{GDBN} does
10355 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
10356 uncomprehended information, in hexadecimal.
10358 @value{GDBN} circumvents the error by ignoring this symbol information.
10359 This usually allows you to debug your program, though certain symbols
10360 are not accessible. If you encounter such a problem and feel like
10361 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
10362 on @code{complain}, then go up to the function @code{read_dbx_symtab}
10363 and examine @code{*bufp} to see the symbol.
10365 @item stub type has NULL name
10367 @value{GDBN} could not find the full definition for a struct or class.
10369 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
10370 The symbol information for a C@t{++} member function is missing some
10371 information that recent versions of the compiler should have output for
10374 @item info mismatch between compiler and debugger
10376 @value{GDBN} could not parse a type specification output by the compiler.
10381 @chapter Specifying a Debugging Target
10383 @cindex debugging target
10386 A @dfn{target} is the execution environment occupied by your program.
10388 Often, @value{GDBN} runs in the same host environment as your program;
10389 in that case, the debugging target is specified as a side effect when
10390 you use the @code{file} or @code{core} commands. When you need more
10391 flexibility---for example, running @value{GDBN} on a physically separate
10392 host, or controlling a standalone system over a serial port or a
10393 realtime system over a TCP/IP connection---you can use the @code{target}
10394 command to specify one of the target types configured for @value{GDBN}
10395 (@pxref{Target Commands, ,Commands for managing targets}).
10398 * Active Targets:: Active targets
10399 * Target Commands:: Commands for managing targets
10400 * Byte Order:: Choosing target byte order
10401 * Remote:: Remote debugging
10402 * KOD:: Kernel Object Display
10406 @node Active Targets
10407 @section Active targets
10409 @cindex stacking targets
10410 @cindex active targets
10411 @cindex multiple targets
10413 There are three classes of targets: processes, core files, and
10414 executable files. @value{GDBN} can work concurrently on up to three
10415 active targets, one in each class. This allows you to (for example)
10416 start a process and inspect its activity without abandoning your work on
10419 For example, if you execute @samp{gdb a.out}, then the executable file
10420 @code{a.out} is the only active target. If you designate a core file as
10421 well---presumably from a prior run that crashed and coredumped---then
10422 @value{GDBN} has two active targets and uses them in tandem, looking
10423 first in the corefile target, then in the executable file, to satisfy
10424 requests for memory addresses. (Typically, these two classes of target
10425 are complementary, since core files contain only a program's
10426 read-write memory---variables and so on---plus machine status, while
10427 executable files contain only the program text and initialized data.)
10429 When you type @code{run}, your executable file becomes an active process
10430 target as well. When a process target is active, all @value{GDBN}
10431 commands requesting memory addresses refer to that target; addresses in
10432 an active core file or executable file target are obscured while the
10433 process target is active.
10435 Use the @code{core-file} and @code{exec-file} commands to select a new
10436 core file or executable target (@pxref{Files, ,Commands to specify
10437 files}). To specify as a target a process that is already running, use
10438 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
10441 @node Target Commands
10442 @section Commands for managing targets
10445 @item target @var{type} @var{parameters}
10446 Connects the @value{GDBN} host environment to a target machine or
10447 process. A target is typically a protocol for talking to debugging
10448 facilities. You use the argument @var{type} to specify the type or
10449 protocol of the target machine.
10451 Further @var{parameters} are interpreted by the target protocol, but
10452 typically include things like device names or host names to connect
10453 with, process numbers, and baud rates.
10455 The @code{target} command does not repeat if you press @key{RET} again
10456 after executing the command.
10458 @kindex help target
10460 Displays the names of all targets available. To display targets
10461 currently selected, use either @code{info target} or @code{info files}
10462 (@pxref{Files, ,Commands to specify files}).
10464 @item help target @var{name}
10465 Describe a particular target, including any parameters necessary to
10468 @kindex set gnutarget
10469 @item set gnutarget @var{args}
10470 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
10471 knows whether it is reading an @dfn{executable},
10472 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
10473 with the @code{set gnutarget} command. Unlike most @code{target} commands,
10474 with @code{gnutarget} the @code{target} refers to a program, not a machine.
10477 @emph{Warning:} To specify a file format with @code{set gnutarget},
10478 you must know the actual BFD name.
10482 @xref{Files, , Commands to specify files}.
10484 @kindex show gnutarget
10485 @item show gnutarget
10486 Use the @code{show gnutarget} command to display what file format
10487 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
10488 @value{GDBN} will determine the file format for each file automatically,
10489 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
10492 Here are some common targets (available, or not, depending on the GDB
10496 @kindex target exec
10497 @item target exec @var{program}
10498 An executable file. @samp{target exec @var{program}} is the same as
10499 @samp{exec-file @var{program}}.
10501 @kindex target core
10502 @item target core @var{filename}
10503 A core dump file. @samp{target core @var{filename}} is the same as
10504 @samp{core-file @var{filename}}.
10506 @kindex target remote
10507 @item target remote @var{dev}
10508 Remote serial target in GDB-specific protocol. The argument @var{dev}
10509 specifies what serial device to use for the connection (e.g.
10510 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
10511 supports the @code{load} command. This is only useful if you have
10512 some other way of getting the stub to the target system, and you can put
10513 it somewhere in memory where it won't get clobbered by the download.
10517 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
10525 works; however, you cannot assume that a specific memory map, device
10526 drivers, or even basic I/O is available, although some simulators do
10527 provide these. For info about any processor-specific simulator details,
10528 see the appropriate section in @ref{Embedded Processors, ,Embedded
10533 Some configurations may include these targets as well:
10537 @kindex target nrom
10538 @item target nrom @var{dev}
10539 NetROM ROM emulator. This target only supports downloading.
10543 Different targets are available on different configurations of @value{GDBN};
10544 your configuration may have more or fewer targets.
10546 Many remote targets require you to download the executable's code
10547 once you've successfully established a connection.
10551 @kindex load @var{filename}
10552 @item load @var{filename}
10553 Depending on what remote debugging facilities are configured into
10554 @value{GDBN}, the @code{load} command may be available. Where it exists, it
10555 is meant to make @var{filename} (an executable) available for debugging
10556 on the remote system---by downloading, or dynamic linking, for example.
10557 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
10558 the @code{add-symbol-file} command.
10560 If your @value{GDBN} does not have a @code{load} command, attempting to
10561 execute it gets the error message ``@code{You can't do that when your
10562 target is @dots{}}''
10564 The file is loaded at whatever address is specified in the executable.
10565 For some object file formats, you can specify the load address when you
10566 link the program; for other formats, like a.out, the object file format
10567 specifies a fixed address.
10568 @c FIXME! This would be a good place for an xref to the GNU linker doc.
10570 @code{load} does not repeat if you press @key{RET} again after using it.
10574 @section Choosing target byte order
10576 @cindex choosing target byte order
10577 @cindex target byte order
10579 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
10580 offer the ability to run either big-endian or little-endian byte
10581 orders. Usually the executable or symbol will include a bit to
10582 designate the endian-ness, and you will not need to worry about
10583 which to use. However, you may still find it useful to adjust
10584 @value{GDBN}'s idea of processor endian-ness manually.
10587 @kindex set endian big
10588 @item set endian big
10589 Instruct @value{GDBN} to assume the target is big-endian.
10591 @kindex set endian little
10592 @item set endian little
10593 Instruct @value{GDBN} to assume the target is little-endian.
10595 @kindex set endian auto
10596 @item set endian auto
10597 Instruct @value{GDBN} to use the byte order associated with the
10601 Display @value{GDBN}'s current idea of the target byte order.
10605 Note that these commands merely adjust interpretation of symbolic
10606 data on the host, and that they have absolutely no effect on the
10610 @section Remote debugging
10611 @cindex remote debugging
10613 If you are trying to debug a program running on a machine that cannot run
10614 @value{GDBN} in the usual way, it is often useful to use remote debugging.
10615 For example, you might use remote debugging on an operating system kernel,
10616 or on a small system which does not have a general purpose operating system
10617 powerful enough to run a full-featured debugger.
10619 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
10620 to make this work with particular debugging targets. In addition,
10621 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
10622 but not specific to any particular target system) which you can use if you
10623 write the remote stubs---the code that runs on the remote system to
10624 communicate with @value{GDBN}.
10626 Other remote targets may be available in your
10627 configuration of @value{GDBN}; use @code{help target} to list them.
10630 @section Kernel Object Display
10632 @cindex kernel object display
10633 @cindex kernel object
10636 Some targets support kernel object display. Using this facility,
10637 @value{GDBN} communicates specially with the underlying operating system
10638 and can display information about operating system-level objects such as
10639 mutexes and other synchronization objects. Exactly which objects can be
10640 displayed is determined on a per-OS basis.
10642 Use the @code{set os} command to set the operating system. This tells
10643 @value{GDBN} which kernel object display module to initialize:
10646 (@value{GDBP}) set os cisco
10649 If @code{set os} succeeds, @value{GDBN} will display some information
10650 about the operating system, and will create a new @code{info} command
10651 which can be used to query the target. The @code{info} command is named
10652 after the operating system:
10655 (@value{GDBP}) info cisco
10656 List of Cisco Kernel Objects
10658 any Any and all objects
10661 Further subcommands can be used to query about particular objects known
10664 There is currently no way to determine whether a given operating system
10665 is supported other than to try it.
10668 @node Remote Debugging
10669 @chapter Debugging remote programs
10672 * Connecting:: Connecting to a remote target
10673 * Server:: Using the gdbserver program
10674 * NetWare:: Using the gdbserve.nlm program
10675 * Remote configuration:: Remote configuration
10676 * remote stub:: Implementing a remote stub
10680 @section Connecting to a remote target
10682 On the @value{GDBN} host machine, you will need an unstripped copy of
10683 your program, since @value{GDBN} needs symobl and debugging information.
10684 Start up @value{GDBN} as usual, using the name of the local copy of your
10685 program as the first argument.
10687 @cindex serial line, @code{target remote}
10688 If you're using a serial line, you may want to give @value{GDBN} the
10689 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
10690 before the @code{target} command.
10692 After that, use @code{target remote} to establish communications with
10693 the target machine. Its argument specifies how to communicate---either
10694 via a devicename attached to a direct serial line, or a TCP or UDP port
10695 (possibly to a terminal server which in turn has a serial line to the
10696 target). For example, to use a serial line connected to the device
10697 named @file{/dev/ttyb}:
10700 target remote /dev/ttyb
10703 @cindex TCP port, @code{target remote}
10704 To use a TCP connection, use an argument of the form
10705 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
10706 For example, to connect to port 2828 on a
10707 terminal server named @code{manyfarms}:
10710 target remote manyfarms:2828
10713 If your remote target is actually running on the same machine as
10714 your debugger session (e.g.@: a simulator of your target running on
10715 the same host), you can omit the hostname. For example, to connect
10716 to port 1234 on your local machine:
10719 target remote :1234
10723 Note that the colon is still required here.
10725 @cindex UDP port, @code{target remote}
10726 To use a UDP connection, use an argument of the form
10727 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
10728 on a terminal server named @code{manyfarms}:
10731 target remote udp:manyfarms:2828
10734 When using a UDP connection for remote debugging, you should keep in mind
10735 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
10736 busy or unreliable networks, which will cause havoc with your debugging
10739 Now you can use all the usual commands to examine and change data and to
10740 step and continue the remote program.
10742 @cindex interrupting remote programs
10743 @cindex remote programs, interrupting
10744 Whenever @value{GDBN} is waiting for the remote program, if you type the
10745 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
10746 program. This may or may not succeed, depending in part on the hardware
10747 and the serial drivers the remote system uses. If you type the
10748 interrupt character once again, @value{GDBN} displays this prompt:
10751 Interrupted while waiting for the program.
10752 Give up (and stop debugging it)? (y or n)
10755 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
10756 (If you decide you want to try again later, you can use @samp{target
10757 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
10758 goes back to waiting.
10761 @kindex detach (remote)
10763 When you have finished debugging the remote program, you can use the
10764 @code{detach} command to release it from @value{GDBN} control.
10765 Detaching from the target normally resumes its execution, but the results
10766 will depend on your particular remote stub. After the @code{detach}
10767 command, @value{GDBN} is free to connect to another target.
10771 The @code{disconnect} command behaves like @code{detach}, except that
10772 the target is generally not resumed. It will wait for @value{GDBN}
10773 (this instance or another one) to connect and continue debugging. After
10774 the @code{disconnect} command, @value{GDBN} is again free to connect to
10779 @section Using the @code{gdbserver} program
10782 @cindex remote connection without stubs
10783 @code{gdbserver} is a control program for Unix-like systems, which
10784 allows you to connect your program with a remote @value{GDBN} via
10785 @code{target remote}---but without linking in the usual debugging stub.
10787 @code{gdbserver} is not a complete replacement for the debugging stubs,
10788 because it requires essentially the same operating-system facilities
10789 that @value{GDBN} itself does. In fact, a system that can run
10790 @code{gdbserver} to connect to a remote @value{GDBN} could also run
10791 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
10792 because it is a much smaller program than @value{GDBN} itself. It is
10793 also easier to port than all of @value{GDBN}, so you may be able to get
10794 started more quickly on a new system by using @code{gdbserver}.
10795 Finally, if you develop code for real-time systems, you may find that
10796 the tradeoffs involved in real-time operation make it more convenient to
10797 do as much development work as possible on another system, for example
10798 by cross-compiling. You can use @code{gdbserver} to make a similar
10799 choice for debugging.
10801 @value{GDBN} and @code{gdbserver} communicate via either a serial line
10802 or a TCP connection, using the standard @value{GDBN} remote serial
10806 @item On the target machine,
10807 you need to have a copy of the program you want to debug.
10808 @code{gdbserver} does not need your program's symbol table, so you can
10809 strip the program if necessary to save space. @value{GDBN} on the host
10810 system does all the symbol handling.
10812 To use the server, you must tell it how to communicate with @value{GDBN};
10813 the name of your program; and the arguments for your program. The usual
10817 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
10820 @var{comm} is either a device name (to use a serial line) or a TCP
10821 hostname and portnumber. For example, to debug Emacs with the argument
10822 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
10826 target> gdbserver /dev/com1 emacs foo.txt
10829 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
10832 To use a TCP connection instead of a serial line:
10835 target> gdbserver host:2345 emacs foo.txt
10838 The only difference from the previous example is the first argument,
10839 specifying that you are communicating with the host @value{GDBN} via
10840 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
10841 expect a TCP connection from machine @samp{host} to local TCP port 2345.
10842 (Currently, the @samp{host} part is ignored.) You can choose any number
10843 you want for the port number as long as it does not conflict with any
10844 TCP ports already in use on the target system (for example, @code{23} is
10845 reserved for @code{telnet}).@footnote{If you choose a port number that
10846 conflicts with another service, @code{gdbserver} prints an error message
10847 and exits.} You must use the same port number with the host @value{GDBN}
10848 @code{target remote} command.
10850 On some targets, @code{gdbserver} can also attach to running programs.
10851 This is accomplished via the @code{--attach} argument. The syntax is:
10854 target> gdbserver @var{comm} --attach @var{pid}
10857 @var{pid} is the process ID of a currently running process. It isn't necessary
10858 to point @code{gdbserver} at a binary for the running process.
10861 @cindex attach to a program by name
10862 You can debug processes by name instead of process ID if your target has the
10863 @code{pidof} utility:
10866 target> gdbserver @var{comm} --attach `pidof @var{PROGRAM}`
10869 In case more than one copy of @var{PROGRAM} is running, or @var{PROGRAM}
10870 has multiple threads, most versions of @code{pidof} support the
10871 @code{-s} option to only return the first process ID.
10873 @item On the host machine,
10874 connect to your target (@pxref{Connecting,,Connecting to a remote target}).
10875 For TCP connections, you must start up @code{gdbserver} prior to using
10876 the @code{target remote} command. Otherwise you may get an error whose
10877 text depends on the host system, but which usually looks something like
10878 @samp{Connection refused}. You don't need to use the @code{load}
10879 command in @value{GDBN} when using gdbserver, since the program is
10880 already on the target.
10885 @section Using the @code{gdbserve.nlm} program
10887 @kindex gdbserve.nlm
10888 @code{gdbserve.nlm} is a control program for NetWare systems, which
10889 allows you to connect your program with a remote @value{GDBN} via
10890 @code{target remote}.
10892 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
10893 using the standard @value{GDBN} remote serial protocol.
10896 @item On the target machine,
10897 you need to have a copy of the program you want to debug.
10898 @code{gdbserve.nlm} does not need your program's symbol table, so you
10899 can strip the program if necessary to save space. @value{GDBN} on the
10900 host system does all the symbol handling.
10902 To use the server, you must tell it how to communicate with
10903 @value{GDBN}; the name of your program; and the arguments for your
10904 program. The syntax is:
10907 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
10908 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
10911 @var{board} and @var{port} specify the serial line; @var{baud} specifies
10912 the baud rate used by the connection. @var{port} and @var{node} default
10913 to 0, @var{baud} defaults to 9600@dmn{bps}.
10915 For example, to debug Emacs with the argument @samp{foo.txt}and
10916 communicate with @value{GDBN} over serial port number 2 or board 1
10917 using a 19200@dmn{bps} connection:
10920 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
10924 On the @value{GDBN} host machine, connect to your target (@pxref{Connecting,,
10925 Connecting to a remote target}).
10929 @node Remote configuration
10930 @section Remote configuration
10932 The following configuration options are available when debugging remote
10936 @kindex set remote hardware-watchpoint-limit
10937 @kindex set remote hardware-breakpoint-limit
10938 @anchor{set remote hardware-watchpoint-limit}
10939 @anchor{set remote hardware-breakpoint-limit}
10940 @item set remote hardware-watchpoint-limit @var{limit}
10941 @itemx set remote hardware-breakpoint-limit @var{limit}
10942 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
10943 watchpoints. A limit of -1, the default, is treated as unlimited.
10947 @section Implementing a remote stub
10949 @cindex debugging stub, example
10950 @cindex remote stub, example
10951 @cindex stub example, remote debugging
10952 The stub files provided with @value{GDBN} implement the target side of the
10953 communication protocol, and the @value{GDBN} side is implemented in the
10954 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
10955 these subroutines to communicate, and ignore the details. (If you're
10956 implementing your own stub file, you can still ignore the details: start
10957 with one of the existing stub files. @file{sparc-stub.c} is the best
10958 organized, and therefore the easiest to read.)
10960 @cindex remote serial debugging, overview
10961 To debug a program running on another machine (the debugging
10962 @dfn{target} machine), you must first arrange for all the usual
10963 prerequisites for the program to run by itself. For example, for a C
10968 A startup routine to set up the C runtime environment; these usually
10969 have a name like @file{crt0}. The startup routine may be supplied by
10970 your hardware supplier, or you may have to write your own.
10973 A C subroutine library to support your program's
10974 subroutine calls, notably managing input and output.
10977 A way of getting your program to the other machine---for example, a
10978 download program. These are often supplied by the hardware
10979 manufacturer, but you may have to write your own from hardware
10983 The next step is to arrange for your program to use a serial port to
10984 communicate with the machine where @value{GDBN} is running (the @dfn{host}
10985 machine). In general terms, the scheme looks like this:
10989 @value{GDBN} already understands how to use this protocol; when everything
10990 else is set up, you can simply use the @samp{target remote} command
10991 (@pxref{Targets,,Specifying a Debugging Target}).
10993 @item On the target,
10994 you must link with your program a few special-purpose subroutines that
10995 implement the @value{GDBN} remote serial protocol. The file containing these
10996 subroutines is called a @dfn{debugging stub}.
10998 On certain remote targets, you can use an auxiliary program
10999 @code{gdbserver} instead of linking a stub into your program.
11000 @xref{Server,,Using the @code{gdbserver} program}, for details.
11003 The debugging stub is specific to the architecture of the remote
11004 machine; for example, use @file{sparc-stub.c} to debug programs on
11007 @cindex remote serial stub list
11008 These working remote stubs are distributed with @value{GDBN}:
11013 @cindex @file{i386-stub.c}
11016 For Intel 386 and compatible architectures.
11019 @cindex @file{m68k-stub.c}
11020 @cindex Motorola 680x0
11022 For Motorola 680x0 architectures.
11025 @cindex @file{sh-stub.c}
11028 For Renesas SH architectures.
11031 @cindex @file{sparc-stub.c}
11033 For @sc{sparc} architectures.
11035 @item sparcl-stub.c
11036 @cindex @file{sparcl-stub.c}
11039 For Fujitsu @sc{sparclite} architectures.
11043 The @file{README} file in the @value{GDBN} distribution may list other
11044 recently added stubs.
11047 * Stub Contents:: What the stub can do for you
11048 * Bootstrapping:: What you must do for the stub
11049 * Debug Session:: Putting it all together
11052 @node Stub Contents
11053 @subsection What the stub can do for you
11055 @cindex remote serial stub
11056 The debugging stub for your architecture supplies these three
11060 @item set_debug_traps
11061 @kindex set_debug_traps
11062 @cindex remote serial stub, initialization
11063 This routine arranges for @code{handle_exception} to run when your
11064 program stops. You must call this subroutine explicitly near the
11065 beginning of your program.
11067 @item handle_exception
11068 @kindex handle_exception
11069 @cindex remote serial stub, main routine
11070 This is the central workhorse, but your program never calls it
11071 explicitly---the setup code arranges for @code{handle_exception} to
11072 run when a trap is triggered.
11074 @code{handle_exception} takes control when your program stops during
11075 execution (for example, on a breakpoint), and mediates communications
11076 with @value{GDBN} on the host machine. This is where the communications
11077 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
11078 representative on the target machine. It begins by sending summary
11079 information on the state of your program, then continues to execute,
11080 retrieving and transmitting any information @value{GDBN} needs, until you
11081 execute a @value{GDBN} command that makes your program resume; at that point,
11082 @code{handle_exception} returns control to your own code on the target
11086 @cindex @code{breakpoint} subroutine, remote
11087 Use this auxiliary subroutine to make your program contain a
11088 breakpoint. Depending on the particular situation, this may be the only
11089 way for @value{GDBN} to get control. For instance, if your target
11090 machine has some sort of interrupt button, you won't need to call this;
11091 pressing the interrupt button transfers control to
11092 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
11093 simply receiving characters on the serial port may also trigger a trap;
11094 again, in that situation, you don't need to call @code{breakpoint} from
11095 your own program---simply running @samp{target remote} from the host
11096 @value{GDBN} session gets control.
11098 Call @code{breakpoint} if none of these is true, or if you simply want
11099 to make certain your program stops at a predetermined point for the
11100 start of your debugging session.
11103 @node Bootstrapping
11104 @subsection What you must do for the stub
11106 @cindex remote stub, support routines
11107 The debugging stubs that come with @value{GDBN} are set up for a particular
11108 chip architecture, but they have no information about the rest of your
11109 debugging target machine.
11111 First of all you need to tell the stub how to communicate with the
11115 @item int getDebugChar()
11116 @kindex getDebugChar
11117 Write this subroutine to read a single character from the serial port.
11118 It may be identical to @code{getchar} for your target system; a
11119 different name is used to allow you to distinguish the two if you wish.
11121 @item void putDebugChar(int)
11122 @kindex putDebugChar
11123 Write this subroutine to write a single character to the serial port.
11124 It may be identical to @code{putchar} for your target system; a
11125 different name is used to allow you to distinguish the two if you wish.
11128 @cindex control C, and remote debugging
11129 @cindex interrupting remote targets
11130 If you want @value{GDBN} to be able to stop your program while it is
11131 running, you need to use an interrupt-driven serial driver, and arrange
11132 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
11133 character). That is the character which @value{GDBN} uses to tell the
11134 remote system to stop.
11136 Getting the debugging target to return the proper status to @value{GDBN}
11137 probably requires changes to the standard stub; one quick and dirty way
11138 is to just execute a breakpoint instruction (the ``dirty'' part is that
11139 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
11141 Other routines you need to supply are:
11144 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
11145 @kindex exceptionHandler
11146 Write this function to install @var{exception_address} in the exception
11147 handling tables. You need to do this because the stub does not have any
11148 way of knowing what the exception handling tables on your target system
11149 are like (for example, the processor's table might be in @sc{rom},
11150 containing entries which point to a table in @sc{ram}).
11151 @var{exception_number} is the exception number which should be changed;
11152 its meaning is architecture-dependent (for example, different numbers
11153 might represent divide by zero, misaligned access, etc). When this
11154 exception occurs, control should be transferred directly to
11155 @var{exception_address}, and the processor state (stack, registers,
11156 and so on) should be just as it is when a processor exception occurs. So if
11157 you want to use a jump instruction to reach @var{exception_address}, it
11158 should be a simple jump, not a jump to subroutine.
11160 For the 386, @var{exception_address} should be installed as an interrupt
11161 gate so that interrupts are masked while the handler runs. The gate
11162 should be at privilege level 0 (the most privileged level). The
11163 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
11164 help from @code{exceptionHandler}.
11166 @item void flush_i_cache()
11167 @kindex flush_i_cache
11168 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
11169 instruction cache, if any, on your target machine. If there is no
11170 instruction cache, this subroutine may be a no-op.
11172 On target machines that have instruction caches, @value{GDBN} requires this
11173 function to make certain that the state of your program is stable.
11177 You must also make sure this library routine is available:
11180 @item void *memset(void *, int, int)
11182 This is the standard library function @code{memset} that sets an area of
11183 memory to a known value. If you have one of the free versions of
11184 @code{libc.a}, @code{memset} can be found there; otherwise, you must
11185 either obtain it from your hardware manufacturer, or write your own.
11188 If you do not use the GNU C compiler, you may need other standard
11189 library subroutines as well; this varies from one stub to another,
11190 but in general the stubs are likely to use any of the common library
11191 subroutines which @code{@value{GCC}} generates as inline code.
11194 @node Debug Session
11195 @subsection Putting it all together
11197 @cindex remote serial debugging summary
11198 In summary, when your program is ready to debug, you must follow these
11203 Make sure you have defined the supporting low-level routines
11204 (@pxref{Bootstrapping,,What you must do for the stub}):
11206 @code{getDebugChar}, @code{putDebugChar},
11207 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
11211 Insert these lines near the top of your program:
11219 For the 680x0 stub only, you need to provide a variable called
11220 @code{exceptionHook}. Normally you just use:
11223 void (*exceptionHook)() = 0;
11227 but if before calling @code{set_debug_traps}, you set it to point to a
11228 function in your program, that function is called when
11229 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
11230 error). The function indicated by @code{exceptionHook} is called with
11231 one parameter: an @code{int} which is the exception number.
11234 Compile and link together: your program, the @value{GDBN} debugging stub for
11235 your target architecture, and the supporting subroutines.
11238 Make sure you have a serial connection between your target machine and
11239 the @value{GDBN} host, and identify the serial port on the host.
11242 @c The "remote" target now provides a `load' command, so we should
11243 @c document that. FIXME.
11244 Download your program to your target machine (or get it there by
11245 whatever means the manufacturer provides), and start it.
11248 Start @value{GDBN} on the host, and connect to the target
11249 (@pxref{Connecting,,Connecting to a remote target}).
11253 @node Configurations
11254 @chapter Configuration-Specific Information
11256 While nearly all @value{GDBN} commands are available for all native and
11257 cross versions of the debugger, there are some exceptions. This chapter
11258 describes things that are only available in certain configurations.
11260 There are three major categories of configurations: native
11261 configurations, where the host and target are the same, embedded
11262 operating system configurations, which are usually the same for several
11263 different processor architectures, and bare embedded processors, which
11264 are quite different from each other.
11269 * Embedded Processors::
11276 This section describes details specific to particular native
11281 * SVR4 Process Information:: SVR4 process information
11282 * DJGPP Native:: Features specific to the DJGPP port
11283 * Cygwin Native:: Features specific to the Cygwin port
11289 On HP-UX systems, if you refer to a function or variable name that
11290 begins with a dollar sign, @value{GDBN} searches for a user or system
11291 name first, before it searches for a convenience variable.
11293 @node SVR4 Process Information
11294 @subsection SVR4 process information
11297 @cindex process image
11299 Many versions of SVR4 provide a facility called @samp{/proc} that can be
11300 used to examine the image of a running process using file-system
11301 subroutines. If @value{GDBN} is configured for an operating system with
11302 this facility, the command @code{info proc} is available to report on
11303 several kinds of information about the process running your program.
11304 @code{info proc} works only on SVR4 systems that include the
11305 @code{procfs} code. This includes OSF/1 (Digital Unix), Solaris, Irix,
11306 and Unixware, but not HP-UX or @sc{gnu}/Linux, for example.
11311 Summarize available information about the process.
11313 @kindex info proc mappings
11314 @item info proc mappings
11315 Report on the address ranges accessible in the program, with information
11316 on whether your program may read, write, or execute each range.
11318 @comment These sub-options of 'info proc' were not included when
11319 @comment procfs.c was re-written. Keep their descriptions around
11320 @comment against the day when someone finds the time to put them back in.
11321 @kindex info proc times
11322 @item info proc times
11323 Starting time, user CPU time, and system CPU time for your program and
11326 @kindex info proc id
11328 Report on the process IDs related to your program: its own process ID,
11329 the ID of its parent, the process group ID, and the session ID.
11331 @kindex info proc status
11332 @item info proc status
11333 General information on the state of the process. If the process is
11334 stopped, this report includes the reason for stopping, and any signal
11337 @item info proc all
11338 Show all the above information about the process.
11343 @subsection Features for Debugging @sc{djgpp} Programs
11344 @cindex @sc{djgpp} debugging
11345 @cindex native @sc{djgpp} debugging
11346 @cindex MS-DOS-specific commands
11348 @sc{djgpp} is the port of @sc{gnu} development tools to MS-DOS and
11349 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
11350 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
11351 top of real-mode DOS systems and their emulations.
11353 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
11354 defines a few commands specific to the @sc{djgpp} port. This
11355 subsection describes those commands.
11360 This is a prefix of @sc{djgpp}-specific commands which print
11361 information about the target system and important OS structures.
11364 @cindex MS-DOS system info
11365 @cindex free memory information (MS-DOS)
11366 @item info dos sysinfo
11367 This command displays assorted information about the underlying
11368 platform: the CPU type and features, the OS version and flavor, the
11369 DPMI version, and the available conventional and DPMI memory.
11374 @cindex segment descriptor tables
11375 @cindex descriptor tables display
11377 @itemx info dos ldt
11378 @itemx info dos idt
11379 These 3 commands display entries from, respectively, Global, Local,
11380 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
11381 tables are data structures which store a descriptor for each segment
11382 that is currently in use. The segment's selector is an index into a
11383 descriptor table; the table entry for that index holds the
11384 descriptor's base address and limit, and its attributes and access
11387 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
11388 segment (used for both data and the stack), and a DOS segment (which
11389 allows access to DOS/BIOS data structures and absolute addresses in
11390 conventional memory). However, the DPMI host will usually define
11391 additional segments in order to support the DPMI environment.
11393 @cindex garbled pointers
11394 These commands allow to display entries from the descriptor tables.
11395 Without an argument, all entries from the specified table are
11396 displayed. An argument, which should be an integer expression, means
11397 display a single entry whose index is given by the argument. For
11398 example, here's a convenient way to display information about the
11399 debugged program's data segment:
11402 @exdent @code{(@value{GDBP}) info dos ldt $ds}
11403 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
11407 This comes in handy when you want to see whether a pointer is outside
11408 the data segment's limit (i.e.@: @dfn{garbled}).
11410 @cindex page tables display (MS-DOS)
11412 @itemx info dos pte
11413 These two commands display entries from, respectively, the Page
11414 Directory and the Page Tables. Page Directories and Page Tables are
11415 data structures which control how virtual memory addresses are mapped
11416 into physical addresses. A Page Table includes an entry for every
11417 page of memory that is mapped into the program's address space; there
11418 may be several Page Tables, each one holding up to 4096 entries. A
11419 Page Directory has up to 4096 entries, one each for every Page Table
11420 that is currently in use.
11422 Without an argument, @kbd{info dos pde} displays the entire Page
11423 Directory, and @kbd{info dos pte} displays all the entries in all of
11424 the Page Tables. An argument, an integer expression, given to the
11425 @kbd{info dos pde} command means display only that entry from the Page
11426 Directory table. An argument given to the @kbd{info dos pte} command
11427 means display entries from a single Page Table, the one pointed to by
11428 the specified entry in the Page Directory.
11430 @cindex direct memory access (DMA) on MS-DOS
11431 These commands are useful when your program uses @dfn{DMA} (Direct
11432 Memory Access), which needs physical addresses to program the DMA
11435 These commands are supported only with some DPMI servers.
11437 @cindex physical address from linear address
11438 @item info dos address-pte @var{addr}
11439 This command displays the Page Table entry for a specified linear
11440 address. The argument linear address @var{addr} should already have the
11441 appropriate segment's base address added to it, because this command
11442 accepts addresses which may belong to @emph{any} segment. For
11443 example, here's how to display the Page Table entry for the page where
11444 the variable @code{i} is stored:
11447 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
11448 @exdent @code{Page Table entry for address 0x11a00d30:}
11449 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
11453 This says that @code{i} is stored at offset @code{0xd30} from the page
11454 whose physical base address is @code{0x02698000}, and prints all the
11455 attributes of that page.
11457 Note that you must cast the addresses of variables to a @code{char *},
11458 since otherwise the value of @code{__djgpp_base_address}, the base
11459 address of all variables and functions in a @sc{djgpp} program, will
11460 be added using the rules of C pointer arithmetics: if @code{i} is
11461 declared an @code{int}, @value{GDBN} will add 4 times the value of
11462 @code{__djgpp_base_address} to the address of @code{i}.
11464 Here's another example, it displays the Page Table entry for the
11468 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
11469 @exdent @code{Page Table entry for address 0x29110:}
11470 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
11474 (The @code{+ 3} offset is because the transfer buffer's address is the
11475 3rd member of the @code{_go32_info_block} structure.) The output of
11476 this command clearly shows that addresses in conventional memory are
11477 mapped 1:1, i.e.@: the physical and linear addresses are identical.
11479 This command is supported only with some DPMI servers.
11482 @node Cygwin Native
11483 @subsection Features for Debugging MS Windows PE executables
11484 @cindex MS Windows debugging
11485 @cindex native Cygwin debugging
11486 @cindex Cygwin-specific commands
11488 @value{GDBN} supports native debugging of MS Windows programs, including
11489 DLLs with and without symbolic debugging information. There are various
11490 additional Cygwin-specific commands, described in this subsection. The
11491 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
11492 that have no debugging symbols.
11498 This is a prefix of MS Windows specific commands which print
11499 information about the target system and important OS structures.
11501 @item info w32 selector
11502 This command displays information returned by
11503 the Win32 API @code{GetThreadSelectorEntry} function.
11504 It takes an optional argument that is evaluated to
11505 a long value to give the information about this given selector.
11506 Without argument, this command displays information
11507 about the the six segment registers.
11511 This is a Cygwin specific alias of info shared.
11513 @kindex dll-symbols
11515 This command loads symbols from a dll similarly to
11516 add-sym command but without the need to specify a base address.
11518 @kindex set new-console
11519 @item set new-console @var{mode}
11520 If @var{mode} is @code{on} the debuggee will
11521 be started in a new console on next start.
11522 If @var{mode} is @code{off}i, the debuggee will
11523 be started in the same console as the debugger.
11525 @kindex show new-console
11526 @item show new-console
11527 Displays whether a new console is used
11528 when the debuggee is started.
11530 @kindex set new-group
11531 @item set new-group @var{mode}
11532 This boolean value controls whether the debuggee should
11533 start a new group or stay in the same group as the debugger.
11534 This affects the way the Windows OS handles
11537 @kindex show new-group
11538 @item show new-group
11539 Displays current value of new-group boolean.
11541 @kindex set debugevents
11542 @item set debugevents
11543 This boolean value adds debug output concerning events seen by the debugger.
11545 @kindex set debugexec
11546 @item set debugexec
11547 This boolean value adds debug output concerning execute events
11548 seen by the debugger.
11550 @kindex set debugexceptions
11551 @item set debugexceptions
11552 This boolean value adds debug ouptut concerning exception events
11553 seen by the debugger.
11555 @kindex set debugmemory
11556 @item set debugmemory
11557 This boolean value adds debug ouptut concerning memory events
11558 seen by the debugger.
11562 This boolean values specifies whether the debuggee is called
11563 via a shell or directly (default value is on).
11567 Displays if the debuggee will be started with a shell.
11572 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
11575 @node Non-debug DLL symbols
11576 @subsubsection Support for DLLs without debugging symbols
11577 @cindex DLLs with no debugging symbols
11578 @cindex Minimal symbols and DLLs
11580 Very often on windows, some of the DLLs that your program relies on do
11581 not include symbolic debugging information (for example,
11582 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
11583 symbols in a DLL, it relies on the minimal amount of symbolic
11584 information contained in the DLL's export table. This subsubsection
11585 describes working with such symbols, known internally to @value{GDBN} as
11586 ``minimal symbols''.
11588 Note that before the debugged program has started execution, no DLLs
11589 will have been loaded. The easiest way around this problem is simply to
11590 start the program --- either by setting a breakpoint or letting the
11591 program run once to completion. It is also possible to force
11592 @value{GDBN} to load a particular DLL before starting the executable ---
11593 see the shared library information in @pxref{Files} or the
11594 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
11595 explicitly loading symbols from a DLL with no debugging information will
11596 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
11597 which may adversely affect symbol lookup performance.
11599 @subsubsection DLL name prefixes
11601 In keeping with the naming conventions used by the Microsoft debugging
11602 tools, DLL export symbols are made available with a prefix based on the
11603 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
11604 also entered into the symbol table, so @code{CreateFileA} is often
11605 sufficient. In some cases there will be name clashes within a program
11606 (particularly if the executable itself includes full debugging symbols)
11607 necessitating the use of the fully qualified name when referring to the
11608 contents of the DLL. Use single-quotes around the name to avoid the
11609 exclamation mark (``!'') being interpreted as a language operator.
11611 Note that the internal name of the DLL may be all upper-case, even
11612 though the file name of the DLL is lower-case, or vice-versa. Since
11613 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
11614 some confusion. If in doubt, try the @code{info functions} and
11615 @code{info variables} commands or even @code{maint print msymbols} (see
11616 @pxref{Symbols}). Here's an example:
11619 (gdb) info function CreateFileA
11620 All functions matching regular expression "CreateFileA":
11622 Non-debugging symbols:
11623 0x77e885f4 CreateFileA
11624 0x77e885f4 KERNEL32!CreateFileA
11628 (gdb) info function !
11629 All functions matching regular expression "!":
11631 Non-debugging symbols:
11632 0x6100114c cygwin1!__assert
11633 0x61004034 cygwin1!_dll_crt0@@0
11634 0x61004240 cygwin1!dll_crt0(per_process *)
11638 @subsubsection Working with minimal symbols
11640 Symbols extracted from a DLL's export table do not contain very much
11641 type information. All that @value{GDBN} can do is guess whether a symbol
11642 refers to a function or variable depending on the linker section that
11643 contains the symbol. Also note that the actual contents of the memory
11644 contained in a DLL are not available unless the program is running. This
11645 means that you cannot examine the contents of a variable or disassemble
11646 a function within a DLL without a running program.
11648 Variables are generally treated as pointers and dereferenced
11649 automatically. For this reason, it is often necessary to prefix a
11650 variable name with the address-of operator (``&'') and provide explicit
11651 type information in the command. Here's an example of the type of
11655 (gdb) print 'cygwin1!__argv'
11660 (gdb) x 'cygwin1!__argv'
11661 0x10021610: "\230y\""
11664 And two possible solutions:
11667 (gdb) print ((char **)'cygwin1!__argv')[0]
11668 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
11672 (gdb) x/2x &'cygwin1!__argv'
11673 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
11674 (gdb) x/x 0x10021608
11675 0x10021608: 0x0022fd98
11676 (gdb) x/s 0x0022fd98
11677 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
11680 Setting a break point within a DLL is possible even before the program
11681 starts execution. However, under these circumstances, @value{GDBN} can't
11682 examine the initial instructions of the function in order to skip the
11683 function's frame set-up code. You can work around this by using ``*&''
11684 to set the breakpoint at a raw memory address:
11687 (gdb) break *&'python22!PyOS_Readline'
11688 Breakpoint 1 at 0x1e04eff0
11691 The author of these extensions is not entirely convinced that setting a
11692 break point within a shared DLL like @file{kernel32.dll} is completely
11696 @section Embedded Operating Systems
11698 This section describes configurations involving the debugging of
11699 embedded operating systems that are available for several different
11703 * VxWorks:: Using @value{GDBN} with VxWorks
11706 @value{GDBN} includes the ability to debug programs running on
11707 various real-time operating systems.
11710 @subsection Using @value{GDBN} with VxWorks
11716 @kindex target vxworks
11717 @item target vxworks @var{machinename}
11718 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
11719 is the target system's machine name or IP address.
11723 On VxWorks, @code{load} links @var{filename} dynamically on the
11724 current target system as well as adding its symbols in @value{GDBN}.
11726 @value{GDBN} enables developers to spawn and debug tasks running on networked
11727 VxWorks targets from a Unix host. Already-running tasks spawned from
11728 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
11729 both the Unix host and on the VxWorks target. The program
11730 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
11731 installed with the name @code{vxgdb}, to distinguish it from a
11732 @value{GDBN} for debugging programs on the host itself.)
11735 @item VxWorks-timeout @var{args}
11736 @kindex vxworks-timeout
11737 All VxWorks-based targets now support the option @code{vxworks-timeout}.
11738 This option is set by the user, and @var{args} represents the number of
11739 seconds @value{GDBN} waits for responses to rpc's. You might use this if
11740 your VxWorks target is a slow software simulator or is on the far side
11741 of a thin network line.
11744 The following information on connecting to VxWorks was current when
11745 this manual was produced; newer releases of VxWorks may use revised
11748 @kindex INCLUDE_RDB
11749 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
11750 to include the remote debugging interface routines in the VxWorks
11751 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
11752 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
11753 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
11754 source debugging task @code{tRdbTask} when VxWorks is booted. For more
11755 information on configuring and remaking VxWorks, see the manufacturer's
11757 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
11759 Once you have included @file{rdb.a} in your VxWorks system image and set
11760 your Unix execution search path to find @value{GDBN}, you are ready to
11761 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
11762 @code{vxgdb}, depending on your installation).
11764 @value{GDBN} comes up showing the prompt:
11771 * VxWorks Connection:: Connecting to VxWorks
11772 * VxWorks Download:: VxWorks download
11773 * VxWorks Attach:: Running tasks
11776 @node VxWorks Connection
11777 @subsubsection Connecting to VxWorks
11779 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
11780 network. To connect to a target whose host name is ``@code{tt}'', type:
11783 (vxgdb) target vxworks tt
11787 @value{GDBN} displays messages like these:
11790 Attaching remote machine across net...
11795 @value{GDBN} then attempts to read the symbol tables of any object modules
11796 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
11797 these files by searching the directories listed in the command search
11798 path (@pxref{Environment, ,Your program's environment}); if it fails
11799 to find an object file, it displays a message such as:
11802 prog.o: No such file or directory.
11805 When this happens, add the appropriate directory to the search path with
11806 the @value{GDBN} command @code{path}, and execute the @code{target}
11809 @node VxWorks Download
11810 @subsubsection VxWorks download
11812 @cindex download to VxWorks
11813 If you have connected to the VxWorks target and you want to debug an
11814 object that has not yet been loaded, you can use the @value{GDBN}
11815 @code{load} command to download a file from Unix to VxWorks
11816 incrementally. The object file given as an argument to the @code{load}
11817 command is actually opened twice: first by the VxWorks target in order
11818 to download the code, then by @value{GDBN} in order to read the symbol
11819 table. This can lead to problems if the current working directories on
11820 the two systems differ. If both systems have NFS mounted the same
11821 filesystems, you can avoid these problems by using absolute paths.
11822 Otherwise, it is simplest to set the working directory on both systems
11823 to the directory in which the object file resides, and then to reference
11824 the file by its name, without any path. For instance, a program
11825 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
11826 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
11827 program, type this on VxWorks:
11830 -> cd "@var{vxpath}/vw/demo/rdb"
11834 Then, in @value{GDBN}, type:
11837 (vxgdb) cd @var{hostpath}/vw/demo/rdb
11838 (vxgdb) load prog.o
11841 @value{GDBN} displays a response similar to this:
11844 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
11847 You can also use the @code{load} command to reload an object module
11848 after editing and recompiling the corresponding source file. Note that
11849 this makes @value{GDBN} delete all currently-defined breakpoints,
11850 auto-displays, and convenience variables, and to clear the value
11851 history. (This is necessary in order to preserve the integrity of
11852 debugger's data structures that reference the target system's symbol
11855 @node VxWorks Attach
11856 @subsubsection Running tasks
11858 @cindex running VxWorks tasks
11859 You can also attach to an existing task using the @code{attach} command as
11863 (vxgdb) attach @var{task}
11867 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
11868 or suspended when you attach to it. Running tasks are suspended at
11869 the time of attachment.
11871 @node Embedded Processors
11872 @section Embedded Processors
11874 This section goes into details specific to particular embedded
11880 * H8/300:: Renesas H8/300
11881 * H8/500:: Renesas H8/500
11882 * M32R/D:: Renesas M32R/D
11883 * M68K:: Motorola M68K
11884 * MIPS Embedded:: MIPS Embedded
11885 * OpenRISC 1000:: OpenRisc 1000
11886 * PA:: HP PA Embedded
11889 * Sparclet:: Tsqware Sparclet
11890 * Sparclite:: Fujitsu Sparclite
11891 * ST2000:: Tandem ST2000
11892 * Z8000:: Zilog Z8000
11901 @item target rdi @var{dev}
11902 ARM Angel monitor, via RDI library interface to ADP protocol. You may
11903 use this target to communicate with both boards running the Angel
11904 monitor, or with the EmbeddedICE JTAG debug device.
11907 @item target rdp @var{dev}
11913 @subsection Renesas H8/300
11917 @kindex target hms@r{, with H8/300}
11918 @item target hms @var{dev}
11919 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
11920 Use special commands @code{device} and @code{speed} to control the serial
11921 line and the communications speed used.
11923 @kindex target e7000@r{, with H8/300}
11924 @item target e7000 @var{dev}
11925 E7000 emulator for Renesas H8 and SH.
11927 @kindex target sh3@r{, with H8/300}
11928 @kindex target sh3e@r{, with H8/300}
11929 @item target sh3 @var{dev}
11930 @itemx target sh3e @var{dev}
11931 Renesas SH-3 and SH-3E target systems.
11935 @cindex download to H8/300 or H8/500
11936 @cindex H8/300 or H8/500 download
11937 @cindex download to Renesas SH
11938 @cindex Renesas SH download
11939 When you select remote debugging to a Renesas SH, H8/300, or H8/500
11940 board, the @code{load} command downloads your program to the Renesas
11941 board and also opens it as the current executable target for
11942 @value{GDBN} on your host (like the @code{file} command).
11944 @value{GDBN} needs to know these things to talk to your
11945 Renesas SH, H8/300, or H8/500:
11949 that you want to use @samp{target hms}, the remote debugging interface
11950 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
11951 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
11952 the default when @value{GDBN} is configured specifically for the Renesas SH,
11953 H8/300, or H8/500.)
11956 what serial device connects your host to your Renesas board (the first
11957 serial device available on your host is the default).
11960 what speed to use over the serial device.
11964 * Renesas Boards:: Connecting to Renesas boards.
11965 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
11966 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
11969 @node Renesas Boards
11970 @subsubsection Connecting to Renesas boards
11972 @c only for Unix hosts
11974 @cindex serial device, Renesas micros
11975 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
11976 need to explicitly set the serial device. The default @var{port} is the
11977 first available port on your host. This is only necessary on Unix
11978 hosts, where it is typically something like @file{/dev/ttya}.
11981 @cindex serial line speed, Renesas micros
11982 @code{@value{GDBN}} has another special command to set the communications
11983 speed: @samp{speed @var{bps}}. This command also is only used from Unix
11984 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
11985 the DOS @code{mode} command (for instance,
11986 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
11988 The @samp{device} and @samp{speed} commands are available only when you
11989 use a Unix host to debug your Renesas microprocessor programs. If you
11991 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
11992 called @code{asynctsr} to communicate with the development board
11993 through a PC serial port. You must also use the DOS @code{mode} command
11994 to set up the serial port on the DOS side.
11996 The following sample session illustrates the steps needed to start a
11997 program under @value{GDBN} control on an H8/300. The example uses a
11998 sample H8/300 program called @file{t.x}. The procedure is the same for
11999 the Renesas SH and the H8/500.
12001 First hook up your development board. In this example, we use a
12002 board attached to serial port @code{COM2}; if you use a different serial
12003 port, substitute its name in the argument of the @code{mode} command.
12004 When you call @code{asynctsr}, the auxiliary comms program used by the
12005 debugger, you give it just the numeric part of the serial port's name;
12006 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
12010 C:\H8300\TEST> asynctsr 2
12011 C:\H8300\TEST> mode com2:9600,n,8,1,p
12013 Resident portion of MODE loaded
12015 COM2: 9600, n, 8, 1, p
12020 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
12021 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
12022 disable it, or even boot without it, to use @code{asynctsr} to control
12023 your development board.
12026 @kindex target hms@r{, and serial protocol}
12027 Now that serial communications are set up, and the development board is
12028 connected, you can start up @value{GDBN}. Call @code{@value{GDBP}} with
12029 the name of your program as the argument. @code{@value{GDBN}} prompts
12030 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
12031 commands to begin your debugging session: @samp{target hms} to specify
12032 cross-debugging to the Renesas board, and the @code{load} command to
12033 download your program to the board. @code{load} displays the names of
12034 the program's sections, and a @samp{*} for each 2K of data downloaded.
12035 (If you want to refresh @value{GDBN} data on symbols or on the
12036 executable file without downloading, use the @value{GDBN} commands
12037 @code{file} or @code{symbol-file}. These commands, and @code{load}
12038 itself, are described in @ref{Files,,Commands to specify files}.)
12041 (eg-C:\H8300\TEST) @value{GDBP} t.x
12042 @value{GDBN} is free software and you are welcome to distribute copies
12043 of it under certain conditions; type "show copying" to see
12045 There is absolutely no warranty for @value{GDBN}; type "show warranty"
12047 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
12048 (@value{GDBP}) target hms
12049 Connected to remote H8/300 HMS system.
12050 (@value{GDBP}) load t.x
12051 .text : 0x8000 .. 0xabde ***********
12052 .data : 0xabde .. 0xad30 *
12053 .stack : 0xf000 .. 0xf014 *
12056 At this point, you're ready to run or debug your program. From here on,
12057 you can use all the usual @value{GDBN} commands. The @code{break} command
12058 sets breakpoints; the @code{run} command starts your program;
12059 @code{print} or @code{x} display data; the @code{continue} command
12060 resumes execution after stopping at a breakpoint. You can use the
12061 @code{help} command at any time to find out more about @value{GDBN} commands.
12063 Remember, however, that @emph{operating system} facilities aren't
12064 available on your development board; for example, if your program hangs,
12065 you can't send an interrupt---but you can press the @sc{reset} switch!
12067 Use the @sc{reset} button on the development board
12070 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
12071 no way to pass an interrupt signal to the development board); and
12074 to return to the @value{GDBN} command prompt after your program finishes
12075 normally. The communications protocol provides no other way for @value{GDBN}
12076 to detect program completion.
12079 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
12080 development board as a ``normal exit'' of your program.
12083 @subsubsection Using the E7000 in-circuit emulator
12085 @kindex target e7000@r{, with Renesas ICE}
12086 You can use the E7000 in-circuit emulator to develop code for either the
12087 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
12088 e7000} command to connect @value{GDBN} to your E7000:
12091 @item target e7000 @var{port} @var{speed}
12092 Use this form if your E7000 is connected to a serial port. The
12093 @var{port} argument identifies what serial port to use (for example,
12094 @samp{com2}). The third argument is the line speed in bits per second
12095 (for example, @samp{9600}).
12097 @item target e7000 @var{hostname}
12098 If your E7000 is installed as a host on a TCP/IP network, you can just
12099 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
12102 @node Renesas Special
12103 @subsubsection Special @value{GDBN} commands for Renesas micros
12105 Some @value{GDBN} commands are available only for the H8/300:
12109 @kindex set machine
12110 @kindex show machine
12111 @item set machine h8300
12112 @itemx set machine h8300h
12113 Condition @value{GDBN} for one of the two variants of the H8/300
12114 architecture with @samp{set machine}. You can use @samp{show machine}
12115 to check which variant is currently in effect.
12124 @kindex set memory @var{mod}
12125 @cindex memory models, H8/500
12126 @item set memory @var{mod}
12128 Specify which H8/500 memory model (@var{mod}) you are using with
12129 @samp{set memory}; check which memory model is in effect with @samp{show
12130 memory}. The accepted values for @var{mod} are @code{small},
12131 @code{big}, @code{medium}, and @code{compact}.
12136 @subsection Renesas M32R/D
12140 @kindex target m32r
12141 @item target m32r @var{dev}
12142 Renesas M32R/D ROM monitor.
12144 @kindex target m32rsdi
12145 @item target m32rsdi @var{dev}
12146 Renesas M32R SDI server, connected via parallel port to the board.
12153 The Motorola m68k configuration includes ColdFire support, and
12154 target command for the following ROM monitors.
12158 @kindex target abug
12159 @item target abug @var{dev}
12160 ABug ROM monitor for M68K.
12162 @kindex target cpu32bug
12163 @item target cpu32bug @var{dev}
12164 CPU32BUG monitor, running on a CPU32 (M68K) board.
12166 @kindex target dbug
12167 @item target dbug @var{dev}
12168 dBUG ROM monitor for Motorola ColdFire.
12171 @item target est @var{dev}
12172 EST-300 ICE monitor, running on a CPU32 (M68K) board.
12174 @kindex target rom68k
12175 @item target rom68k @var{dev}
12176 ROM 68K monitor, running on an M68K IDP board.
12182 @kindex target rombug
12183 @item target rombug @var{dev}
12184 ROMBUG ROM monitor for OS/9000.
12188 @node MIPS Embedded
12189 @subsection MIPS Embedded
12191 @cindex MIPS boards
12192 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
12193 MIPS board attached to a serial line. This is available when
12194 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
12197 Use these @value{GDBN} commands to specify the connection to your target board:
12200 @item target mips @var{port}
12201 @kindex target mips @var{port}
12202 To run a program on the board, start up @code{@value{GDBP}} with the
12203 name of your program as the argument. To connect to the board, use the
12204 command @samp{target mips @var{port}}, where @var{port} is the name of
12205 the serial port connected to the board. If the program has not already
12206 been downloaded to the board, you may use the @code{load} command to
12207 download it. You can then use all the usual @value{GDBN} commands.
12209 For example, this sequence connects to the target board through a serial
12210 port, and loads and runs a program called @var{prog} through the
12214 host$ @value{GDBP} @var{prog}
12215 @value{GDBN} is free software and @dots{}
12216 (@value{GDBP}) target mips /dev/ttyb
12217 (@value{GDBP}) load @var{prog}
12221 @item target mips @var{hostname}:@var{portnumber}
12222 On some @value{GDBN} host configurations, you can specify a TCP
12223 connection (for instance, to a serial line managed by a terminal
12224 concentrator) instead of a serial port, using the syntax
12225 @samp{@var{hostname}:@var{portnumber}}.
12227 @item target pmon @var{port}
12228 @kindex target pmon @var{port}
12231 @item target ddb @var{port}
12232 @kindex target ddb @var{port}
12233 NEC's DDB variant of PMON for Vr4300.
12235 @item target lsi @var{port}
12236 @kindex target lsi @var{port}
12237 LSI variant of PMON.
12239 @kindex target r3900
12240 @item target r3900 @var{dev}
12241 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
12243 @kindex target array
12244 @item target array @var{dev}
12245 Array Tech LSI33K RAID controller board.
12251 @value{GDBN} also supports these special commands for MIPS targets:
12254 @item set processor @var{args}
12255 @itemx show processor
12256 @kindex set processor @var{args}
12257 @kindex show processor
12258 Use the @code{set processor} command to set the type of MIPS
12259 processor when you want to access processor-type-specific registers.
12260 For example, @code{set processor @var{r3041}} tells @value{GDBN}
12261 to use the CPU registers appropriate for the 3041 chip.
12262 Use the @code{show processor} command to see what MIPS processor @value{GDBN}
12263 is using. Use the @code{info reg} command to see what registers
12264 @value{GDBN} is using.
12266 @item set mipsfpu double
12267 @itemx set mipsfpu single
12268 @itemx set mipsfpu none
12269 @itemx show mipsfpu
12270 @kindex set mipsfpu
12271 @kindex show mipsfpu
12272 @cindex MIPS remote floating point
12273 @cindex floating point, MIPS remote
12274 If your target board does not support the MIPS floating point
12275 coprocessor, you should use the command @samp{set mipsfpu none} (if you
12276 need this, you may wish to put the command in your @value{GDBN} init
12277 file). This tells @value{GDBN} how to find the return value of
12278 functions which return floating point values. It also allows
12279 @value{GDBN} to avoid saving the floating point registers when calling
12280 functions on the board. If you are using a floating point coprocessor
12281 with only single precision floating point support, as on the @sc{r4650}
12282 processor, use the command @samp{set mipsfpu single}. The default
12283 double precision floating point coprocessor may be selected using
12284 @samp{set mipsfpu double}.
12286 In previous versions the only choices were double precision or no
12287 floating point, so @samp{set mipsfpu on} will select double precision
12288 and @samp{set mipsfpu off} will select no floating point.
12290 As usual, you can inquire about the @code{mipsfpu} variable with
12291 @samp{show mipsfpu}.
12293 @item set remotedebug @var{n}
12294 @itemx show remotedebug
12295 @kindex set remotedebug@r{, MIPS protocol}
12296 @kindex show remotedebug@r{, MIPS protocol}
12297 @cindex @code{remotedebug}, MIPS protocol
12298 @cindex MIPS @code{remotedebug} protocol
12299 @c FIXME! For this to be useful, you must know something about the MIPS
12300 @c FIXME...protocol. Where is it described?
12301 You can see some debugging information about communications with the board
12302 by setting the @code{remotedebug} variable. If you set it to @code{1} using
12303 @samp{set remotedebug 1}, every packet is displayed. If you set it
12304 to @code{2}, every character is displayed. You can check the current value
12305 at any time with the command @samp{show remotedebug}.
12307 @item set timeout @var{seconds}
12308 @itemx set retransmit-timeout @var{seconds}
12309 @itemx show timeout
12310 @itemx show retransmit-timeout
12311 @cindex @code{timeout}, MIPS protocol
12312 @cindex @code{retransmit-timeout}, MIPS protocol
12313 @kindex set timeout
12314 @kindex show timeout
12315 @kindex set retransmit-timeout
12316 @kindex show retransmit-timeout
12317 You can control the timeout used while waiting for a packet, in the MIPS
12318 remote protocol, with the @code{set timeout @var{seconds}} command. The
12319 default is 5 seconds. Similarly, you can control the timeout used while
12320 waiting for an acknowledgement of a packet with the @code{set
12321 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
12322 You can inspect both values with @code{show timeout} and @code{show
12323 retransmit-timeout}. (These commands are @emph{only} available when
12324 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
12326 The timeout set by @code{set timeout} does not apply when @value{GDBN}
12327 is waiting for your program to stop. In that case, @value{GDBN} waits
12328 forever because it has no way of knowing how long the program is going
12329 to run before stopping.
12332 @node OpenRISC 1000
12333 @subsection OpenRISC 1000
12334 @cindex OpenRISC 1000
12336 @cindex or1k boards
12337 See OR1k Architecture document (@uref{www.opencores.org}) for more information
12338 about platform and commands.
12342 @kindex target jtag
12343 @item target jtag jtag://@var{host}:@var{port}
12345 Connects to remote JTAG server.
12346 JTAG remote server can be either an or1ksim or JTAG server,
12347 connected via parallel port to the board.
12349 Example: @code{target jtag jtag://localhost:9999}
12352 @item or1ksim @var{command}
12353 If connected to @code{or1ksim} OpenRISC 1000 Architectural
12354 Simulator, proprietary commands can be executed.
12356 @kindex info or1k spr
12357 @item info or1k spr
12358 Displays spr groups.
12360 @item info or1k spr @var{group}
12361 @itemx info or1k spr @var{groupno}
12362 Displays register names in selected group.
12364 @item info or1k spr @var{group} @var{register}
12365 @itemx info or1k spr @var{register}
12366 @itemx info or1k spr @var{groupno} @var{registerno}
12367 @itemx info or1k spr @var{registerno}
12368 Shows information about specified spr register.
12371 @item spr @var{group} @var{register} @var{value}
12372 @itemx spr @var{register @var{value}}
12373 @itemx spr @var{groupno} @var{registerno @var{value}}
12374 @itemx spr @var{registerno @var{value}}
12375 Writes @var{value} to specified spr register.
12378 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
12379 It is very similar to @value{GDBN} trace, except it does not interfere with normal
12380 program execution and is thus much faster. Hardware breakpoints/watchpoint
12381 triggers can be set using:
12384 Load effective address/data
12386 Store effective address/data
12388 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
12393 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
12394 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
12396 @code{htrace} commands:
12397 @cindex OpenRISC 1000 htrace
12400 @item hwatch @var{conditional}
12401 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
12402 or Data. For example:
12404 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
12406 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
12408 @kindex htrace info
12410 Display information about current HW trace configuration.
12412 @kindex htrace trigger
12413 @item htrace trigger @var{conditional}
12414 Set starting criteria for HW trace.
12416 @kindex htrace qualifier
12417 @item htrace qualifier @var{conditional}
12418 Set acquisition qualifier for HW trace.
12420 @kindex htrace stop
12421 @item htrace stop @var{conditional}
12422 Set HW trace stopping criteria.
12424 @kindex htrace record
12425 @item htrace record [@var{data}]*
12426 Selects the data to be recorded, when qualifier is met and HW trace was
12429 @kindex htrace enable
12430 @item htrace enable
12431 @kindex htrace disable
12432 @itemx htrace disable
12433 Enables/disables the HW trace.
12435 @kindex htrace rewind
12436 @item htrace rewind [@var{filename}]
12437 Clears currently recorded trace data.
12439 If filename is specified, new trace file is made and any newly collected data
12440 will be written there.
12442 @kindex htrace print
12443 @item htrace print [@var{start} [@var{len}]]
12444 Prints trace buffer, using current record configuration.
12446 @kindex htrace mode continuous
12447 @item htrace mode continuous
12448 Set continuous trace mode.
12450 @kindex htrace mode suspend
12451 @item htrace mode suspend
12452 Set suspend trace mode.
12457 @subsection PowerPC
12461 @kindex target dink32
12462 @item target dink32 @var{dev}
12463 DINK32 ROM monitor.
12465 @kindex target ppcbug
12466 @item target ppcbug @var{dev}
12467 @kindex target ppcbug1
12468 @item target ppcbug1 @var{dev}
12469 PPCBUG ROM monitor for PowerPC.
12472 @item target sds @var{dev}
12473 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
12478 @subsection HP PA Embedded
12482 @kindex target op50n
12483 @item target op50n @var{dev}
12484 OP50N monitor, running on an OKI HPPA board.
12486 @kindex target w89k
12487 @item target w89k @var{dev}
12488 W89K monitor, running on a Winbond HPPA board.
12493 @subsection Renesas SH
12497 @kindex target hms@r{, with Renesas SH}
12498 @item target hms @var{dev}
12499 A Renesas SH board attached via serial line to your host. Use special
12500 commands @code{device} and @code{speed} to control the serial line and
12501 the communications speed used.
12503 @kindex target e7000@r{, with Renesas SH}
12504 @item target e7000 @var{dev}
12505 E7000 emulator for Renesas SH.
12507 @kindex target sh3@r{, with SH}
12508 @kindex target sh3e@r{, with SH}
12509 @item target sh3 @var{dev}
12510 @item target sh3e @var{dev}
12511 Renesas SH-3 and SH-3E target systems.
12516 @subsection Tsqware Sparclet
12520 @value{GDBN} enables developers to debug tasks running on
12521 Sparclet targets from a Unix host.
12522 @value{GDBN} uses code that runs on
12523 both the Unix host and on the Sparclet target. The program
12524 @code{@value{GDBP}} is installed and executed on the Unix host.
12527 @item remotetimeout @var{args}
12528 @kindex remotetimeout
12529 @value{GDBN} supports the option @code{remotetimeout}.
12530 This option is set by the user, and @var{args} represents the number of
12531 seconds @value{GDBN} waits for responses.
12534 @cindex compiling, on Sparclet
12535 When compiling for debugging, include the options @samp{-g} to get debug
12536 information and @samp{-Ttext} to relocate the program to where you wish to
12537 load it on the target. You may also want to add the options @samp{-n} or
12538 @samp{-N} in order to reduce the size of the sections. Example:
12541 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
12544 You can use @code{objdump} to verify that the addresses are what you intended:
12547 sparclet-aout-objdump --headers --syms prog
12550 @cindex running, on Sparclet
12552 your Unix execution search path to find @value{GDBN}, you are ready to
12553 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
12554 (or @code{sparclet-aout-gdb}, depending on your installation).
12556 @value{GDBN} comes up showing the prompt:
12563 * Sparclet File:: Setting the file to debug
12564 * Sparclet Connection:: Connecting to Sparclet
12565 * Sparclet Download:: Sparclet download
12566 * Sparclet Execution:: Running and debugging
12569 @node Sparclet File
12570 @subsubsection Setting file to debug
12572 The @value{GDBN} command @code{file} lets you choose with program to debug.
12575 (gdbslet) file prog
12579 @value{GDBN} then attempts to read the symbol table of @file{prog}.
12580 @value{GDBN} locates
12581 the file by searching the directories listed in the command search
12583 If the file was compiled with debug information (option "-g"), source
12584 files will be searched as well.
12585 @value{GDBN} locates
12586 the source files by searching the directories listed in the directory search
12587 path (@pxref{Environment, ,Your program's environment}).
12589 to find a file, it displays a message such as:
12592 prog: No such file or directory.
12595 When this happens, add the appropriate directories to the search paths with
12596 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
12597 @code{target} command again.
12599 @node Sparclet Connection
12600 @subsubsection Connecting to Sparclet
12602 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
12603 To connect to a target on serial port ``@code{ttya}'', type:
12606 (gdbslet) target sparclet /dev/ttya
12607 Remote target sparclet connected to /dev/ttya
12608 main () at ../prog.c:3
12612 @value{GDBN} displays messages like these:
12618 @node Sparclet Download
12619 @subsubsection Sparclet download
12621 @cindex download to Sparclet
12622 Once connected to the Sparclet target,
12623 you can use the @value{GDBN}
12624 @code{load} command to download the file from the host to the target.
12625 The file name and load offset should be given as arguments to the @code{load}
12627 Since the file format is aout, the program must be loaded to the starting
12628 address. You can use @code{objdump} to find out what this value is. The load
12629 offset is an offset which is added to the VMA (virtual memory address)
12630 of each of the file's sections.
12631 For instance, if the program
12632 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
12633 and bss at 0x12010170, in @value{GDBN}, type:
12636 (gdbslet) load prog 0x12010000
12637 Loading section .text, size 0xdb0 vma 0x12010000
12640 If the code is loaded at a different address then what the program was linked
12641 to, you may need to use the @code{section} and @code{add-symbol-file} commands
12642 to tell @value{GDBN} where to map the symbol table.
12644 @node Sparclet Execution
12645 @subsubsection Running and debugging
12647 @cindex running and debugging Sparclet programs
12648 You can now begin debugging the task using @value{GDBN}'s execution control
12649 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
12650 manual for the list of commands.
12654 Breakpoint 1 at 0x12010000: file prog.c, line 3.
12656 Starting program: prog
12657 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
12658 3 char *symarg = 0;
12660 4 char *execarg = "hello!";
12665 @subsection Fujitsu Sparclite
12669 @kindex target sparclite
12670 @item target sparclite @var{dev}
12671 Fujitsu sparclite boards, used only for the purpose of loading.
12672 You must use an additional command to debug the program.
12673 For example: target remote @var{dev} using @value{GDBN} standard
12679 @subsection Tandem ST2000
12681 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
12684 To connect your ST2000 to the host system, see the manufacturer's
12685 manual. Once the ST2000 is physically attached, you can run:
12688 target st2000 @var{dev} @var{speed}
12692 to establish it as your debugging environment. @var{dev} is normally
12693 the name of a serial device, such as @file{/dev/ttya}, connected to the
12694 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
12695 connection (for example, to a serial line attached via a terminal
12696 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
12698 The @code{load} and @code{attach} commands are @emph{not} defined for
12699 this target; you must load your program into the ST2000 as you normally
12700 would for standalone operation. @value{GDBN} reads debugging information
12701 (such as symbols) from a separate, debugging version of the program
12702 available on your host computer.
12703 @c FIXME!! This is terribly vague; what little content is here is
12704 @c basically hearsay.
12706 @cindex ST2000 auxiliary commands
12707 These auxiliary @value{GDBN} commands are available to help you with the ST2000
12711 @item st2000 @var{command}
12712 @kindex st2000 @var{cmd}
12713 @cindex STDBUG commands (ST2000)
12714 @cindex commands to STDBUG (ST2000)
12715 Send a @var{command} to the STDBUG monitor. See the manufacturer's
12716 manual for available commands.
12719 @cindex connect (to STDBUG)
12720 Connect the controlling terminal to the STDBUG command monitor. When
12721 you are done interacting with STDBUG, typing either of two character
12722 sequences gets you back to the @value{GDBN} command prompt:
12723 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
12724 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
12728 @subsection Zilog Z8000
12731 @cindex simulator, Z8000
12732 @cindex Zilog Z8000 simulator
12734 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
12737 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
12738 unsegmented variant of the Z8000 architecture) or the Z8001 (the
12739 segmented variant). The simulator recognizes which architecture is
12740 appropriate by inspecting the object code.
12743 @item target sim @var{args}
12745 @kindex target sim@r{, with Z8000}
12746 Debug programs on a simulated CPU. If the simulator supports setup
12747 options, specify them via @var{args}.
12751 After specifying this target, you can debug programs for the simulated
12752 CPU in the same style as programs for your host computer; use the
12753 @code{file} command to load a new program image, the @code{run} command
12754 to run your program, and so on.
12756 As well as making available all the usual machine registers
12757 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
12758 additional items of information as specially named registers:
12763 Counts clock-ticks in the simulator.
12766 Counts instructions run in the simulator.
12769 Execution time in 60ths of a second.
12773 You can refer to these values in @value{GDBN} expressions with the usual
12774 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
12775 conditional breakpoint that suspends only after at least 5000
12776 simulated clock ticks.
12778 @node Architectures
12779 @section Architectures
12781 This section describes characteristics of architectures that affect
12782 all uses of @value{GDBN} with the architecture, both native and cross.
12795 @kindex set rstack_high_address
12796 @cindex AMD 29K register stack
12797 @cindex register stack, AMD29K
12798 @item set rstack_high_address @var{address}
12799 On AMD 29000 family processors, registers are saved in a separate
12800 @dfn{register stack}. There is no way for @value{GDBN} to determine the
12801 extent of this stack. Normally, @value{GDBN} just assumes that the
12802 stack is ``large enough''. This may result in @value{GDBN} referencing
12803 memory locations that do not exist. If necessary, you can get around
12804 this problem by specifying the ending address of the register stack with
12805 the @code{set rstack_high_address} command. The argument should be an
12806 address, which you probably want to precede with @samp{0x} to specify in
12809 @kindex show rstack_high_address
12810 @item show rstack_high_address
12811 Display the current limit of the register stack, on AMD 29000 family
12819 See the following section.
12824 @cindex stack on Alpha
12825 @cindex stack on MIPS
12826 @cindex Alpha stack
12828 Alpha- and MIPS-based computers use an unusual stack frame, which
12829 sometimes requires @value{GDBN} to search backward in the object code to
12830 find the beginning of a function.
12832 @cindex response time, MIPS debugging
12833 To improve response time (especially for embedded applications, where
12834 @value{GDBN} may be restricted to a slow serial line for this search)
12835 you may want to limit the size of this search, using one of these
12839 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
12840 @item set heuristic-fence-post @var{limit}
12841 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
12842 search for the beginning of a function. A value of @var{0} (the
12843 default) means there is no limit. However, except for @var{0}, the
12844 larger the limit the more bytes @code{heuristic-fence-post} must search
12845 and therefore the longer it takes to run.
12847 @item show heuristic-fence-post
12848 Display the current limit.
12852 These commands are available @emph{only} when @value{GDBN} is configured
12853 for debugging programs on Alpha or MIPS processors.
12856 @node Controlling GDB
12857 @chapter Controlling @value{GDBN}
12859 You can alter the way @value{GDBN} interacts with you by using the
12860 @code{set} command. For commands controlling how @value{GDBN} displays
12861 data, see @ref{Print Settings, ,Print settings}. Other settings are
12866 * Editing:: Command editing
12867 * History:: Command history
12868 * Screen Size:: Screen size
12869 * Numbers:: Numbers
12870 * ABI:: Configuring the current ABI
12871 * Messages/Warnings:: Optional warnings and messages
12872 * Debugging Output:: Optional messages about internal happenings
12880 @value{GDBN} indicates its readiness to read a command by printing a string
12881 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
12882 can change the prompt string with the @code{set prompt} command. For
12883 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
12884 the prompt in one of the @value{GDBN} sessions so that you can always tell
12885 which one you are talking to.
12887 @emph{Note:} @code{set prompt} does not add a space for you after the
12888 prompt you set. This allows you to set a prompt which ends in a space
12889 or a prompt that does not.
12893 @item set prompt @var{newprompt}
12894 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
12896 @kindex show prompt
12898 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
12902 @section Command editing
12904 @cindex command line editing
12906 @value{GDBN} reads its input commands via the @dfn{readline} interface. This
12907 @sc{gnu} library provides consistent behavior for programs which provide a
12908 command line interface to the user. Advantages are @sc{gnu} Emacs-style
12909 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
12910 substitution, and a storage and recall of command history across
12911 debugging sessions.
12913 You may control the behavior of command line editing in @value{GDBN} with the
12914 command @code{set}.
12917 @kindex set editing
12920 @itemx set editing on
12921 Enable command line editing (enabled by default).
12923 @item set editing off
12924 Disable command line editing.
12926 @kindex show editing
12928 Show whether command line editing is enabled.
12932 @section Command history
12934 @value{GDBN} can keep track of the commands you type during your
12935 debugging sessions, so that you can be certain of precisely what
12936 happened. Use these commands to manage the @value{GDBN} command
12940 @cindex history substitution
12941 @cindex history file
12942 @kindex set history filename
12943 @kindex GDBHISTFILE
12944 @item set history filename @var{fname}
12945 Set the name of the @value{GDBN} command history file to @var{fname}.
12946 This is the file where @value{GDBN} reads an initial command history
12947 list, and where it writes the command history from this session when it
12948 exits. You can access this list through history expansion or through
12949 the history command editing characters listed below. This file defaults
12950 to the value of the environment variable @code{GDBHISTFILE}, or to
12951 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
12954 @cindex history save
12955 @kindex set history save
12956 @item set history save
12957 @itemx set history save on
12958 Record command history in a file, whose name may be specified with the
12959 @code{set history filename} command. By default, this option is disabled.
12961 @item set history save off
12962 Stop recording command history in a file.
12964 @cindex history size
12965 @kindex set history size
12966 @item set history size @var{size}
12967 Set the number of commands which @value{GDBN} keeps in its history list.
12968 This defaults to the value of the environment variable
12969 @code{HISTSIZE}, or to 256 if this variable is not set.
12972 @cindex history expansion
12973 History expansion assigns special meaning to the character @kbd{!}.
12974 @ifset have-readline-appendices
12975 @xref{Event Designators}.
12978 Since @kbd{!} is also the logical not operator in C, history expansion
12979 is off by default. If you decide to enable history expansion with the
12980 @code{set history expansion on} command, you may sometimes need to
12981 follow @kbd{!} (when it is used as logical not, in an expression) with
12982 a space or a tab to prevent it from being expanded. The readline
12983 history facilities do not attempt substitution on the strings
12984 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
12986 The commands to control history expansion are:
12989 @kindex set history expansion
12990 @item set history expansion on
12991 @itemx set history expansion
12992 Enable history expansion. History expansion is off by default.
12994 @item set history expansion off
12995 Disable history expansion.
12997 The readline code comes with more complete documentation of
12998 editing and history expansion features. Users unfamiliar with @sc{gnu} Emacs
12999 or @code{vi} may wish to read it.
13000 @ifset have-readline-appendices
13001 @xref{Command Line Editing}.
13005 @kindex show history
13007 @itemx show history filename
13008 @itemx show history save
13009 @itemx show history size
13010 @itemx show history expansion
13011 These commands display the state of the @value{GDBN} history parameters.
13012 @code{show history} by itself displays all four states.
13018 @item show commands
13019 Display the last ten commands in the command history.
13021 @item show commands @var{n}
13022 Print ten commands centered on command number @var{n}.
13024 @item show commands +
13025 Print ten commands just after the commands last printed.
13029 @section Screen size
13030 @cindex size of screen
13031 @cindex pauses in output
13033 Certain commands to @value{GDBN} may produce large amounts of
13034 information output to the screen. To help you read all of it,
13035 @value{GDBN} pauses and asks you for input at the end of each page of
13036 output. Type @key{RET} when you want to continue the output, or @kbd{q}
13037 to discard the remaining output. Also, the screen width setting
13038 determines when to wrap lines of output. Depending on what is being
13039 printed, @value{GDBN} tries to break the line at a readable place,
13040 rather than simply letting it overflow onto the following line.
13042 Normally @value{GDBN} knows the size of the screen from the terminal
13043 driver software. For example, on Unix @value{GDBN} uses the termcap data base
13044 together with the value of the @code{TERM} environment variable and the
13045 @code{stty rows} and @code{stty cols} settings. If this is not correct,
13046 you can override it with the @code{set height} and @code{set
13053 @kindex show height
13054 @item set height @var{lpp}
13056 @itemx set width @var{cpl}
13058 These @code{set} commands specify a screen height of @var{lpp} lines and
13059 a screen width of @var{cpl} characters. The associated @code{show}
13060 commands display the current settings.
13062 If you specify a height of zero lines, @value{GDBN} does not pause during
13063 output no matter how long the output is. This is useful if output is to a
13064 file or to an editor buffer.
13066 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
13067 from wrapping its output.
13072 @cindex number representation
13073 @cindex entering numbers
13075 You can always enter numbers in octal, decimal, or hexadecimal in
13076 @value{GDBN} by the usual conventions: octal numbers begin with
13077 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
13078 begin with @samp{0x}. Numbers that begin with none of these are, by
13079 default, entered in base 10; likewise, the default display for
13080 numbers---when no particular format is specified---is base 10. You can
13081 change the default base for both input and output with the @code{set
13085 @kindex set input-radix
13086 @item set input-radix @var{base}
13087 Set the default base for numeric input. Supported choices
13088 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
13089 specified either unambiguously or using the current default radix; for
13099 sets the base to decimal. On the other hand, @samp{set radix 10}
13100 leaves the radix unchanged no matter what it was.
13102 @kindex set output-radix
13103 @item set output-radix @var{base}
13104 Set the default base for numeric display. Supported choices
13105 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
13106 specified either unambiguously or using the current default radix.
13108 @kindex show input-radix
13109 @item show input-radix
13110 Display the current default base for numeric input.
13112 @kindex show output-radix
13113 @item show output-radix
13114 Display the current default base for numeric display.
13118 @section Configuring the current ABI
13120 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
13121 application automatically. However, sometimes you need to override its
13122 conclusions. Use these commands to manage @value{GDBN}'s view of the
13129 One @value{GDBN} configuration can debug binaries for multiple operating
13130 system targets, either via remote debugging or native emulation.
13131 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
13132 but you can override its conclusion using the @code{set osabi} command.
13133 One example where this is useful is in debugging of binaries which use
13134 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
13135 not have the same identifying marks that the standard C library for your
13140 Show the OS ABI currently in use.
13143 With no argument, show the list of registered available OS ABI's.
13145 @item set osabi @var{abi}
13146 Set the current OS ABI to @var{abi}.
13149 @cindex float promotion
13150 @kindex set coerce-float-to-double
13152 Generally, the way that an argument of type @code{float} is passed to a
13153 function depends on whether the function is prototyped. For a prototyped
13154 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
13155 according to the architecture's convention for @code{float}. For unprototyped
13156 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
13157 @code{double} and then passed.
13159 Unfortunately, some forms of debug information do not reliably indicate whether
13160 a function is prototyped. If @value{GDBN} calls a function that is not marked
13161 as prototyped, it consults @kbd{set coerce-float-to-double}.
13164 @item set coerce-float-to-double
13165 @itemx set coerce-float-to-double on
13166 Arguments of type @code{float} will be promoted to @code{double} when passed
13167 to an unprototyped function. This is the default setting.
13169 @item set coerce-float-to-double off
13170 Arguments of type @code{float} will be passed directly to unprototyped
13175 @kindex show cp-abi
13176 @value{GDBN} needs to know the ABI used for your program's C@t{++}
13177 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
13178 used to build your application. @value{GDBN} only fully supports
13179 programs with a single C@t{++} ABI; if your program contains code using
13180 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
13181 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
13182 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
13183 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
13184 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
13185 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
13190 Show the C@t{++} ABI currently in use.
13193 With no argument, show the list of supported C@t{++} ABI's.
13195 @item set cp-abi @var{abi}
13196 @itemx set cp-abi auto
13197 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
13200 @node Messages/Warnings
13201 @section Optional warnings and messages
13203 By default, @value{GDBN} is silent about its inner workings. If you are
13204 running on a slow machine, you may want to use the @code{set verbose}
13205 command. This makes @value{GDBN} tell you when it does a lengthy
13206 internal operation, so you will not think it has crashed.
13208 Currently, the messages controlled by @code{set verbose} are those
13209 which announce that the symbol table for a source file is being read;
13210 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
13213 @kindex set verbose
13214 @item set verbose on
13215 Enables @value{GDBN} output of certain informational messages.
13217 @item set verbose off
13218 Disables @value{GDBN} output of certain informational messages.
13220 @kindex show verbose
13222 Displays whether @code{set verbose} is on or off.
13225 By default, if @value{GDBN} encounters bugs in the symbol table of an
13226 object file, it is silent; but if you are debugging a compiler, you may
13227 find this information useful (@pxref{Symbol Errors, ,Errors reading
13232 @kindex set complaints
13233 @item set complaints @var{limit}
13234 Permits @value{GDBN} to output @var{limit} complaints about each type of
13235 unusual symbols before becoming silent about the problem. Set
13236 @var{limit} to zero to suppress all complaints; set it to a large number
13237 to prevent complaints from being suppressed.
13239 @kindex show complaints
13240 @item show complaints
13241 Displays how many symbol complaints @value{GDBN} is permitted to produce.
13245 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
13246 lot of stupid questions to confirm certain commands. For example, if
13247 you try to run a program which is already running:
13251 The program being debugged has been started already.
13252 Start it from the beginning? (y or n)
13255 If you are willing to unflinchingly face the consequences of your own
13256 commands, you can disable this ``feature'':
13260 @kindex set confirm
13262 @cindex confirmation
13263 @cindex stupid questions
13264 @item set confirm off
13265 Disables confirmation requests.
13267 @item set confirm on
13268 Enables confirmation requests (the default).
13270 @kindex show confirm
13272 Displays state of confirmation requests.
13276 @node Debugging Output
13277 @section Optional messages about internal happenings
13279 @kindex set debug arch
13280 @item set debug arch
13281 Turns on or off display of gdbarch debugging info. The default is off
13282 @kindex show debug arch
13283 @item show debug arch
13284 Displays the current state of displaying gdbarch debugging info.
13285 @kindex set debug event
13286 @item set debug event
13287 Turns on or off display of @value{GDBN} event debugging info. The
13289 @kindex show debug event
13290 @item show debug event
13291 Displays the current state of displaying @value{GDBN} event debugging
13293 @kindex set debug expression
13294 @item set debug expression
13295 Turns on or off display of @value{GDBN} expression debugging info. The
13297 @kindex show debug expression
13298 @item show debug expression
13299 Displays the current state of displaying @value{GDBN} expression
13301 @kindex set debug frame
13302 @item set debug frame
13303 Turns on or off display of @value{GDBN} frame debugging info. The
13305 @kindex show debug frame
13306 @item show debug frame
13307 Displays the current state of displaying @value{GDBN} frame debugging
13309 @kindex set debug overload
13310 @item set debug overload
13311 Turns on or off display of @value{GDBN} C@t{++} overload debugging
13312 info. This includes info such as ranking of functions, etc. The default
13314 @kindex show debug overload
13315 @item show debug overload
13316 Displays the current state of displaying @value{GDBN} C@t{++} overload
13318 @kindex set debug remote
13319 @cindex packets, reporting on stdout
13320 @cindex serial connections, debugging
13321 @item set debug remote
13322 Turns on or off display of reports on all packets sent back and forth across
13323 the serial line to the remote machine. The info is printed on the
13324 @value{GDBN} standard output stream. The default is off.
13325 @kindex show debug remote
13326 @item show debug remote
13327 Displays the state of display of remote packets.
13328 @kindex set debug serial
13329 @item set debug serial
13330 Turns on or off display of @value{GDBN} serial debugging info. The
13332 @kindex show debug serial
13333 @item show debug serial
13334 Displays the current state of displaying @value{GDBN} serial debugging
13336 @kindex set debug target
13337 @item set debug target
13338 Turns on or off display of @value{GDBN} target debugging info. This info
13339 includes what is going on at the target level of GDB, as it happens. The
13341 @kindex show debug target
13342 @item show debug target
13343 Displays the current state of displaying @value{GDBN} target debugging
13345 @kindex set debug varobj
13346 @item set debug varobj
13347 Turns on or off display of @value{GDBN} variable object debugging
13348 info. The default is off.
13349 @kindex show debug varobj
13350 @item show debug varobj
13351 Displays the current state of displaying @value{GDBN} variable object
13356 @chapter Canned Sequences of Commands
13358 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
13359 command lists}), @value{GDBN} provides two ways to store sequences of
13360 commands for execution as a unit: user-defined commands and command
13364 * Define:: User-defined commands
13365 * Hooks:: User-defined command hooks
13366 * Command Files:: Command files
13367 * Output:: Commands for controlled output
13371 @section User-defined commands
13373 @cindex user-defined command
13374 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
13375 which you assign a new name as a command. This is done with the
13376 @code{define} command. User commands may accept up to 10 arguments
13377 separated by whitespace. Arguments are accessed within the user command
13378 via @var{$arg0@dots{}$arg9}. A trivial example:
13382 print $arg0 + $arg1 + $arg2
13386 To execute the command use:
13393 This defines the command @code{adder}, which prints the sum of
13394 its three arguments. Note the arguments are text substitutions, so they may
13395 reference variables, use complex expressions, or even perform inferior
13401 @item define @var{commandname}
13402 Define a command named @var{commandname}. If there is already a command
13403 by that name, you are asked to confirm that you want to redefine it.
13405 The definition of the command is made up of other @value{GDBN} command lines,
13406 which are given following the @code{define} command. The end of these
13407 commands is marked by a line containing @code{end}.
13412 Takes a single argument, which is an expression to evaluate.
13413 It is followed by a series of commands that are executed
13414 only if the expression is true (nonzero).
13415 There can then optionally be a line @code{else}, followed
13416 by a series of commands that are only executed if the expression
13417 was false. The end of the list is marked by a line containing @code{end}.
13421 The syntax is similar to @code{if}: the command takes a single argument,
13422 which is an expression to evaluate, and must be followed by the commands to
13423 execute, one per line, terminated by an @code{end}.
13424 The commands are executed repeatedly as long as the expression
13428 @item document @var{commandname}
13429 Document the user-defined command @var{commandname}, so that it can be
13430 accessed by @code{help}. The command @var{commandname} must already be
13431 defined. This command reads lines of documentation just as @code{define}
13432 reads the lines of the command definition, ending with @code{end}.
13433 After the @code{document} command is finished, @code{help} on command
13434 @var{commandname} displays the documentation you have written.
13436 You may use the @code{document} command again to change the
13437 documentation of a command. Redefining the command with @code{define}
13438 does not change the documentation.
13440 @kindex help user-defined
13441 @item help user-defined
13442 List all user-defined commands, with the first line of the documentation
13447 @itemx show user @var{commandname}
13448 Display the @value{GDBN} commands used to define @var{commandname} (but
13449 not its documentation). If no @var{commandname} is given, display the
13450 definitions for all user-defined commands.
13452 @kindex show max-user-call-depth
13453 @kindex set max-user-call-depth
13454 @item show max-user-call-depth
13455 @itemx set max-user-call-depth
13456 The value of @code{max-user-call-depth} controls how many recursion
13457 levels are allowed in user-defined commands before GDB suspects an
13458 infinite recursion and aborts the command.
13462 When user-defined commands are executed, the
13463 commands of the definition are not printed. An error in any command
13464 stops execution of the user-defined command.
13466 If used interactively, commands that would ask for confirmation proceed
13467 without asking when used inside a user-defined command. Many @value{GDBN}
13468 commands that normally print messages to say what they are doing omit the
13469 messages when used in a user-defined command.
13472 @section User-defined command hooks
13473 @cindex command hooks
13474 @cindex hooks, for commands
13475 @cindex hooks, pre-command
13479 You may define @dfn{hooks}, which are a special kind of user-defined
13480 command. Whenever you run the command @samp{foo}, if the user-defined
13481 command @samp{hook-foo} exists, it is executed (with no arguments)
13482 before that command.
13484 @cindex hooks, post-command
13487 A hook may also be defined which is run after the command you executed.
13488 Whenever you run the command @samp{foo}, if the user-defined command
13489 @samp{hookpost-foo} exists, it is executed (with no arguments) after
13490 that command. Post-execution hooks may exist simultaneously with
13491 pre-execution hooks, for the same command.
13493 It is valid for a hook to call the command which it hooks. If this
13494 occurs, the hook is not re-executed, thereby avoiding infinte recursion.
13496 @c It would be nice if hookpost could be passed a parameter indicating
13497 @c if the command it hooks executed properly or not. FIXME!
13499 @kindex stop@r{, a pseudo-command}
13500 In addition, a pseudo-command, @samp{stop} exists. Defining
13501 (@samp{hook-stop}) makes the associated commands execute every time
13502 execution stops in your program: before breakpoint commands are run,
13503 displays are printed, or the stack frame is printed.
13505 For example, to ignore @code{SIGALRM} signals while
13506 single-stepping, but treat them normally during normal execution,
13511 handle SIGALRM nopass
13515 handle SIGALRM pass
13518 define hook-continue
13519 handle SIGLARM pass
13523 As a further example, to hook at the begining and end of the @code{echo}
13524 command, and to add extra text to the beginning and end of the message,
13532 define hookpost-echo
13536 (@value{GDBP}) echo Hello World
13537 <<<---Hello World--->>>
13542 You can define a hook for any single-word command in @value{GDBN}, but
13543 not for command aliases; you should define a hook for the basic command
13544 name, e.g. @code{backtrace} rather than @code{bt}.
13545 @c FIXME! So how does Joe User discover whether a command is an alias
13547 If an error occurs during the execution of your hook, execution of
13548 @value{GDBN} commands stops and @value{GDBN} issues a prompt
13549 (before the command that you actually typed had a chance to run).
13551 If you try to define a hook which does not match any known command, you
13552 get a warning from the @code{define} command.
13554 @node Command Files
13555 @section Command files
13557 @cindex command files
13558 A command file for @value{GDBN} is a file of lines that are @value{GDBN}
13559 commands. Comments (lines starting with @kbd{#}) may also be included.
13560 An empty line in a command file does nothing; it does not mean to repeat
13561 the last command, as it would from the terminal.
13564 @cindex @file{.gdbinit}
13565 @cindex @file{gdb.ini}
13566 When you start @value{GDBN}, it automatically executes commands from its
13567 @dfn{init files}, normally called @file{.gdbinit}@footnote{The DJGPP
13568 port of @value{GDBN} uses the name @file{gdb.ini} instead, due to the
13569 limitations of file names imposed by DOS filesystems.}.
13570 During startup, @value{GDBN} does the following:
13574 Reads the init file (if any) in your home directory@footnote{On
13575 DOS/Windows systems, the home directory is the one pointed to by the
13576 @code{HOME} environment variable.}.
13579 Processes command line options and operands.
13582 Reads the init file (if any) in the current working directory.
13585 Reads command files specified by the @samp{-x} option.
13588 The init file in your home directory can set options (such as @samp{set
13589 complaints}) that affect subsequent processing of command line options
13590 and operands. Init files are not executed if you use the @samp{-nx}
13591 option (@pxref{Mode Options, ,Choosing modes}).
13593 @cindex init file name
13594 On some configurations of @value{GDBN}, the init file is known by a
13595 different name (these are typically environments where a specialized
13596 form of @value{GDBN} may need to coexist with other forms, hence a
13597 different name for the specialized version's init file). These are the
13598 environments with special init file names:
13600 @cindex @file{.vxgdbinit}
13603 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
13605 @cindex @file{.os68gdbinit}
13607 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
13609 @cindex @file{.esgdbinit}
13611 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
13614 You can also request the execution of a command file with the
13615 @code{source} command:
13619 @item source @var{filename}
13620 Execute the command file @var{filename}.
13623 The lines in a command file are executed sequentially. They are not
13624 printed as they are executed. An error in any command terminates
13625 execution of the command file and control is returned to the console.
13627 Commands that would ask for confirmation if used interactively proceed
13628 without asking when used in a command file. Many @value{GDBN} commands that
13629 normally print messages to say what they are doing omit the messages
13630 when called from command files.
13632 @value{GDBN} also accepts command input from standard input. In this
13633 mode, normal output goes to standard output and error output goes to
13634 standard error. Errors in a command file supplied on standard input do
13635 not terminate execution of the command file --- execution continues with
13639 gdb < cmds > log 2>&1
13642 (The syntax above will vary depending on the shell used.) This example
13643 will execute commands from the file @file{cmds}. All output and errors
13644 would be directed to @file{log}.
13647 @section Commands for controlled output
13649 During the execution of a command file or a user-defined command, normal
13650 @value{GDBN} output is suppressed; the only output that appears is what is
13651 explicitly printed by the commands in the definition. This section
13652 describes three commands useful for generating exactly the output you
13657 @item echo @var{text}
13658 @c I do not consider backslash-space a standard C escape sequence
13659 @c because it is not in ANSI.
13660 Print @var{text}. Nonprinting characters can be included in
13661 @var{text} using C escape sequences, such as @samp{\n} to print a
13662 newline. @strong{No newline is printed unless you specify one.}
13663 In addition to the standard C escape sequences, a backslash followed
13664 by a space stands for a space. This is useful for displaying a
13665 string with spaces at the beginning or the end, since leading and
13666 trailing spaces are otherwise trimmed from all arguments.
13667 To print @samp{@w{ }and foo =@w{ }}, use the command
13668 @samp{echo \@w{ }and foo = \@w{ }}.
13670 A backslash at the end of @var{text} can be used, as in C, to continue
13671 the command onto subsequent lines. For example,
13674 echo This is some text\n\
13675 which is continued\n\
13676 onto several lines.\n
13679 produces the same output as
13682 echo This is some text\n
13683 echo which is continued\n
13684 echo onto several lines.\n
13688 @item output @var{expression}
13689 Print the value of @var{expression} and nothing but that value: no
13690 newlines, no @samp{$@var{nn} = }. The value is not entered in the
13691 value history either. @xref{Expressions, ,Expressions}, for more information
13694 @item output/@var{fmt} @var{expression}
13695 Print the value of @var{expression} in format @var{fmt}. You can use
13696 the same formats as for @code{print}. @xref{Output Formats,,Output
13697 formats}, for more information.
13700 @item printf @var{string}, @var{expressions}@dots{}
13701 Print the values of the @var{expressions} under the control of
13702 @var{string}. The @var{expressions} are separated by commas and may be
13703 either numbers or pointers. Their values are printed as specified by
13704 @var{string}, exactly as if your program were to execute the C
13706 @c FIXME: the above implies that at least all ANSI C formats are
13707 @c supported, but it isn't true: %E and %G don't work (or so it seems).
13708 @c Either this is a bug, or the manual should document what formats are
13712 printf (@var{string}, @var{expressions}@dots{});
13715 For example, you can print two values in hex like this:
13718 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
13721 The only backslash-escape sequences that you can use in the format
13722 string are the simple ones that consist of backslash followed by a
13727 @chapter Command Interpreters
13728 @cindex command interpreters
13730 @value{GDBN} supports multiple command interpreters, and some command
13731 infrastructure to allow users or user interface writers to switch
13732 between interpreters or run commands in other interpreters.
13734 @value{GDBN} currently supports two command interpreters, the console
13735 interpreter (sometimes called the command-line interpreter or @sc{cli})
13736 and the machine interface interpreter (or @sc{gdb/mi}). This manual
13737 describes both of these interfaces in great detail.
13739 By default, @value{GDBN} will start with the console interpreter.
13740 However, the user may choose to start @value{GDBN} with another
13741 interpreter by specifying the @option{-i} or @option{--interpreter}
13742 startup options. Defined interpreters include:
13746 @cindex console interpreter
13747 The traditional console or command-line interpreter. This is the most often
13748 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
13749 @value{GDBN} will use this interpreter.
13752 @cindex mi interpreter
13753 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
13754 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
13755 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
13759 @cindex mi2 interpreter
13760 The current @sc{gdb/mi} interface.
13763 @cindex mi1 interpreter
13764 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
13768 @cindex invoke another interpreter
13769 The interpreter being used by @value{GDBN} may not be dynamically
13770 switched at runtime. Although possible, this could lead to a very
13771 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
13772 enters the command "interpreter-set console" in a console view,
13773 @value{GDBN} would switch to using the console interpreter, rendering
13774 the IDE inoperable!
13776 @kindex interpreter-exec
13777 Although you may only choose a single interpreter at startup, you may execute
13778 commands in any interpreter from the current interpreter using the appropriate
13779 command. If you are running the console interpreter, simply use the
13780 @code{interpreter-exec} command:
13783 interpreter-exec mi "-data-list-register-names"
13786 @sc{gdb/mi} has a similar command, although it is only available in versions of
13787 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
13790 @chapter @value{GDBN} Text User Interface
13794 * TUI Overview:: TUI overview
13795 * TUI Keys:: TUI key bindings
13796 * TUI Single Key Mode:: TUI single key mode
13797 * TUI Commands:: TUI specific commands
13798 * TUI Configuration:: TUI configuration variables
13801 The @value{GDBN} Text User Interface, TUI in short,
13802 is a terminal interface which uses the @code{curses} library
13803 to show the source file, the assembly output, the program registers
13804 and @value{GDBN} commands in separate text windows.
13805 The TUI is available only when @value{GDBN} is configured
13806 with the @code{--enable-tui} configure option (@pxref{Configure Options}).
13809 @section TUI overview
13811 The TUI has two display modes that can be switched while
13816 A curses (or TUI) mode in which it displays several text
13817 windows on the terminal.
13820 A standard mode which corresponds to the @value{GDBN} configured without
13824 In the TUI mode, @value{GDBN} can display several text window
13829 This window is the @value{GDBN} command window with the @value{GDBN}
13830 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
13831 managed using readline but through the TUI. The @emph{command}
13832 window is always visible.
13835 The source window shows the source file of the program. The current
13836 line as well as active breakpoints are displayed in this window.
13839 The assembly window shows the disassembly output of the program.
13842 This window shows the processor registers. It detects when
13843 a register is changed and when this is the case, registers that have
13844 changed are highlighted.
13848 The source and assembly windows show the current program position
13849 by highlighting the current line and marking them with the @samp{>} marker.
13850 Breakpoints are also indicated with two markers. A first one
13851 indicates the breakpoint type:
13855 Breakpoint which was hit at least once.
13858 Breakpoint which was never hit.
13861 Hardware breakpoint which was hit at least once.
13864 Hardware breakpoint which was never hit.
13868 The second marker indicates whether the breakpoint is enabled or not:
13872 Breakpoint is enabled.
13875 Breakpoint is disabled.
13879 The source, assembly and register windows are attached to the thread
13880 and the frame position. They are updated when the current thread
13881 changes, when the frame changes or when the program counter changes.
13882 These three windows are arranged by the TUI according to several
13883 layouts. The layout defines which of these three windows are visible.
13884 The following layouts are available:
13894 source and assembly
13897 source and registers
13900 assembly and registers
13904 On top of the command window a status line gives various information
13905 concerning the current process begin debugged. The status line is
13906 updated when the information it shows changes. The following fields
13911 Indicates the current gdb target
13912 (@pxref{Targets, ,Specifying a Debugging Target}).
13915 Gives information about the current process or thread number.
13916 When no process is being debugged, this field is set to @code{No process}.
13919 Gives the current function name for the selected frame.
13920 The name is demangled if demangling is turned on (@pxref{Print Settings}).
13921 When there is no symbol corresponding to the current program counter
13922 the string @code{??} is displayed.
13925 Indicates the current line number for the selected frame.
13926 When the current line number is not known the string @code{??} is displayed.
13929 Indicates the current program counter address.
13934 @section TUI Key Bindings
13935 @cindex TUI key bindings
13937 The TUI installs several key bindings in the readline keymaps
13938 (@pxref{Command Line Editing}).
13939 They allow to leave or enter in the TUI mode or they operate
13940 directly on the TUI layout and windows. The TUI also provides
13941 a @emph{SingleKey} keymap which binds several keys directly to
13942 @value{GDBN} commands. The following key bindings
13943 are installed for both TUI mode and the @value{GDBN} standard mode.
13952 Enter or leave the TUI mode. When the TUI mode is left,
13953 the curses window management is left and @value{GDBN} operates using
13954 its standard mode writing on the terminal directly. When the TUI
13955 mode is entered, the control is given back to the curses windows.
13956 The screen is then refreshed.
13960 Use a TUI layout with only one window. The layout will
13961 either be @samp{source} or @samp{assembly}. When the TUI mode
13962 is not active, it will switch to the TUI mode.
13964 Think of this key binding as the Emacs @kbd{C-x 1} binding.
13968 Use a TUI layout with at least two windows. When the current
13969 layout shows already two windows, a next layout with two windows is used.
13970 When a new layout is chosen, one window will always be common to the
13971 previous layout and the new one.
13973 Think of it as the Emacs @kbd{C-x 2} binding.
13977 Change the active window. The TUI associates several key bindings
13978 (like scrolling and arrow keys) to the active window. This command
13979 gives the focus to the next TUI window.
13981 Think of it as the Emacs @kbd{C-x o} binding.
13985 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
13986 (@pxref{TUI Single Key Mode}).
13990 The following key bindings are handled only by the TUI mode:
13995 Scroll the active window one page up.
13999 Scroll the active window one page down.
14003 Scroll the active window one line up.
14007 Scroll the active window one line down.
14011 Scroll the active window one column left.
14015 Scroll the active window one column right.
14019 Refresh the screen.
14023 In the TUI mode, the arrow keys are used by the active window
14024 for scrolling. This means they are available for readline when the
14025 active window is the command window. When the command window
14026 does not have the focus, it is necessary to use other readline
14027 key bindings such as @key{C-p}, @key{C-n}, @key{C-b} and @key{C-f}.
14029 @node TUI Single Key Mode
14030 @section TUI Single Key Mode
14031 @cindex TUI single key mode
14033 The TUI provides a @emph{SingleKey} mode in which it installs a particular
14034 key binding in the readline keymaps to connect single keys to
14038 @kindex c @r{(SingleKey TUI key)}
14042 @kindex d @r{(SingleKey TUI key)}
14046 @kindex f @r{(SingleKey TUI key)}
14050 @kindex n @r{(SingleKey TUI key)}
14054 @kindex q @r{(SingleKey TUI key)}
14056 exit the @emph{SingleKey} mode.
14058 @kindex r @r{(SingleKey TUI key)}
14062 @kindex s @r{(SingleKey TUI key)}
14066 @kindex u @r{(SingleKey TUI key)}
14070 @kindex v @r{(SingleKey TUI key)}
14074 @kindex w @r{(SingleKey TUI key)}
14080 Other keys temporarily switch to the @value{GDBN} command prompt.
14081 The key that was pressed is inserted in the editing buffer so that
14082 it is possible to type most @value{GDBN} commands without interaction
14083 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
14084 @emph{SingleKey} mode is restored. The only way to permanently leave
14085 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
14089 @section TUI specific commands
14090 @cindex TUI commands
14092 The TUI has specific commands to control the text windows.
14093 These commands are always available, that is they do not depend on
14094 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
14095 is in the standard mode, using these commands will automatically switch
14101 List and give the size of all displayed windows.
14104 @kindex layout next
14105 Display the next layout.
14108 @kindex layout prev
14109 Display the previous layout.
14113 Display the source window only.
14117 Display the assembly window only.
14120 @kindex layout split
14121 Display the source and assembly window.
14124 @kindex layout regs
14125 Display the register window together with the source or assembly window.
14127 @item focus next | prev | src | asm | regs | split
14129 Set the focus to the named window.
14130 This command allows to change the active window so that scrolling keys
14131 can be affected to another window.
14135 Refresh the screen. This is similar to using @key{C-L} key.
14139 Update the source window and the current execution point.
14141 @item winheight @var{name} +@var{count}
14142 @itemx winheight @var{name} -@var{count}
14144 Change the height of the window @var{name} by @var{count}
14145 lines. Positive counts increase the height, while negative counts
14150 @node TUI Configuration
14151 @section TUI configuration variables
14152 @cindex TUI configuration variables
14154 The TUI has several configuration variables that control the
14155 appearance of windows on the terminal.
14158 @item set tui border-kind @var{kind}
14159 @kindex set tui border-kind
14160 Select the border appearance for the source, assembly and register windows.
14161 The possible values are the following:
14164 Use a space character to draw the border.
14167 Use ascii characters + - and | to draw the border.
14170 Use the Alternate Character Set to draw the border. The border is
14171 drawn using character line graphics if the terminal supports them.
14175 @item set tui active-border-mode @var{mode}
14176 @kindex set tui active-border-mode
14177 Select the attributes to display the border of the active window.
14178 The possible values are @code{normal}, @code{standout}, @code{reverse},
14179 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
14181 @item set tui border-mode @var{mode}
14182 @kindex set tui border-mode
14183 Select the attributes to display the border of other windows.
14184 The @var{mode} can be one of the following:
14187 Use normal attributes to display the border.
14193 Use reverse video mode.
14196 Use half bright mode.
14198 @item half-standout
14199 Use half bright and standout mode.
14202 Use extra bright or bold mode.
14204 @item bold-standout
14205 Use extra bright or bold and standout mode.
14212 @chapter Using @value{GDBN} under @sc{gnu} Emacs
14215 @cindex @sc{gnu} Emacs
14216 A special interface allows you to use @sc{gnu} Emacs to view (and
14217 edit) the source files for the program you are debugging with
14220 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
14221 executable file you want to debug as an argument. This command starts
14222 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
14223 created Emacs buffer.
14224 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
14226 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
14231 All ``terminal'' input and output goes through the Emacs buffer.
14234 This applies both to @value{GDBN} commands and their output, and to the input
14235 and output done by the program you are debugging.
14237 This is useful because it means that you can copy the text of previous
14238 commands and input them again; you can even use parts of the output
14241 All the facilities of Emacs' Shell mode are available for interacting
14242 with your program. In particular, you can send signals the usual
14243 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
14248 @value{GDBN} displays source code through Emacs.
14251 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
14252 source file for that frame and puts an arrow (@samp{=>}) at the
14253 left margin of the current line. Emacs uses a separate buffer for
14254 source display, and splits the screen to show both your @value{GDBN} session
14257 Explicit @value{GDBN} @code{list} or search commands still produce output as
14258 usual, but you probably have no reason to use them from Emacs.
14260 If you specify an absolute file name when prompted for the @kbd{M-x
14261 gdb} argument, then Emacs sets your current working directory to where
14262 your program resides. If you only specify the file name, then Emacs
14263 sets your current working directory to to the directory associated
14264 with the previous buffer. In this case, @value{GDBN} may find your
14265 program by searching your environment's @code{PATH} variable, but on
14266 some operating systems it might not find the source. So, although the
14267 @value{GDBN} input and output session proceeds normally, the auxiliary
14268 buffer does not display the current source and line of execution.
14270 The initial working directory of @value{GDBN} is printed on the top
14271 line of the @value{GDBN} I/O buffer and this serves as a default for
14272 the commands that specify files for @value{GDBN} to operate
14273 on. @xref{Files, ,Commands to specify files}.
14275 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
14276 need to call @value{GDBN} by a different name (for example, if you
14277 keep several configurations around, with different names) you can
14278 customize the Emacs variable @code{gud-gdb-command-name} to run the
14281 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
14282 addition to the standard Shell mode commands:
14286 Describe the features of Emacs' @value{GDBN} Mode.
14289 Execute to another source line, like the @value{GDBN} @code{step} command; also
14290 update the display window to show the current file and location.
14293 Execute to next source line in this function, skipping all function
14294 calls, like the @value{GDBN} @code{next} command. Then update the display window
14295 to show the current file and location.
14298 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
14299 display window accordingly.
14302 Execute until exit from the selected stack frame, like the @value{GDBN}
14303 @code{finish} command.
14306 Continue execution of your program, like the @value{GDBN} @code{continue}
14310 Go up the number of frames indicated by the numeric argument
14311 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
14312 like the @value{GDBN} @code{up} command.
14315 Go down the number of frames indicated by the numeric argument, like the
14316 @value{GDBN} @code{down} command.
14319 In any source file, the Emacs command @kbd{C-x SPC} (@code{gud-break})
14320 tells @value{GDBN} to set a breakpoint on the source line point is on.
14322 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
14323 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
14324 point to any frame in the stack and type @key{RET} to make it become the
14325 current frame and display the associated source in the source buffer.
14326 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
14329 If you accidentally delete the source-display buffer, an easy way to get
14330 it back is to type the command @code{f} in the @value{GDBN} buffer, to
14331 request a frame display; when you run under Emacs, this recreates
14332 the source buffer if necessary to show you the context of the current
14335 The source files displayed in Emacs are in ordinary Emacs buffers
14336 which are visiting the source files in the usual way. You can edit
14337 the files with these buffers if you wish; but keep in mind that @value{GDBN}
14338 communicates with Emacs in terms of line numbers. If you add or
14339 delete lines from the text, the line numbers that @value{GDBN} knows cease
14340 to correspond properly with the code.
14342 The description given here is for GNU Emacs version 21.3 and a more
14343 detailed description of its interaction with @value{GDBN} is given in
14344 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
14346 @c The following dropped because Epoch is nonstandard. Reactivate
14347 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
14349 @kindex Emacs Epoch environment
14353 Version 18 of @sc{gnu} Emacs has a built-in window system
14354 called the @code{epoch}
14355 environment. Users of this environment can use a new command,
14356 @code{inspect} which performs identically to @code{print} except that
14357 each value is printed in its own window.
14362 @chapter The @sc{gdb/mi} Interface
14364 @unnumberedsec Function and Purpose
14366 @cindex @sc{gdb/mi}, its purpose
14367 @sc{gdb/mi} is a line based machine oriented text interface to @value{GDBN}. It is
14368 specifically intended to support the development of systems which use
14369 the debugger as just one small component of a larger system.
14371 This chapter is a specification of the @sc{gdb/mi} interface. It is written
14372 in the form of a reference manual.
14374 Note that @sc{gdb/mi} is still under construction, so some of the
14375 features described below are incomplete and subject to change.
14377 @unnumberedsec Notation and Terminology
14379 @cindex notational conventions, for @sc{gdb/mi}
14380 This chapter uses the following notation:
14384 @code{|} separates two alternatives.
14387 @code{[ @var{something} ]} indicates that @var{something} is optional:
14388 it may or may not be given.
14391 @code{( @var{group} )*} means that @var{group} inside the parentheses
14392 may repeat zero or more times.
14395 @code{( @var{group} )+} means that @var{group} inside the parentheses
14396 may repeat one or more times.
14399 @code{"@var{string}"} means a literal @var{string}.
14403 @heading Dependencies
14406 @heading Acknowledgments
14408 In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
14412 * GDB/MI Command Syntax::
14413 * GDB/MI Compatibility with CLI::
14414 * GDB/MI Output Records::
14415 * GDB/MI Command Description Format::
14416 * GDB/MI Breakpoint Table Commands::
14417 * GDB/MI Data Manipulation::
14418 * GDB/MI Program Control::
14419 * GDB/MI Miscellaneous Commands::
14421 * GDB/MI Kod Commands::
14422 * GDB/MI Memory Overlay Commands::
14423 * GDB/MI Signal Handling Commands::
14425 * GDB/MI Stack Manipulation::
14426 * GDB/MI Symbol Query::
14427 * GDB/MI Target Manipulation::
14428 * GDB/MI Thread Commands::
14429 * GDB/MI Tracepoint Commands::
14430 * GDB/MI Variable Objects::
14433 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14434 @node GDB/MI Command Syntax
14435 @section @sc{gdb/mi} Command Syntax
14438 * GDB/MI Input Syntax::
14439 * GDB/MI Output Syntax::
14440 * GDB/MI Simple Examples::
14443 @node GDB/MI Input Syntax
14444 @subsection @sc{gdb/mi} Input Syntax
14446 @cindex input syntax for @sc{gdb/mi}
14447 @cindex @sc{gdb/mi}, input syntax
14449 @item @var{command} @expansion{}
14450 @code{@var{cli-command} | @var{mi-command}}
14452 @item @var{cli-command} @expansion{}
14453 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
14454 @var{cli-command} is any existing @value{GDBN} CLI command.
14456 @item @var{mi-command} @expansion{}
14457 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
14458 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
14460 @item @var{token} @expansion{}
14461 "any sequence of digits"
14463 @item @var{option} @expansion{}
14464 @code{"-" @var{parameter} [ " " @var{parameter} ]}
14466 @item @var{parameter} @expansion{}
14467 @code{@var{non-blank-sequence} | @var{c-string}}
14469 @item @var{operation} @expansion{}
14470 @emph{any of the operations described in this chapter}
14472 @item @var{non-blank-sequence} @expansion{}
14473 @emph{anything, provided it doesn't contain special characters such as
14474 "-", @var{nl}, """ and of course " "}
14476 @item @var{c-string} @expansion{}
14477 @code{""" @var{seven-bit-iso-c-string-content} """}
14479 @item @var{nl} @expansion{}
14488 The CLI commands are still handled by the @sc{mi} interpreter; their
14489 output is described below.
14492 The @code{@var{token}}, when present, is passed back when the command
14496 Some @sc{mi} commands accept optional arguments as part of the parameter
14497 list. Each option is identified by a leading @samp{-} (dash) and may be
14498 followed by an optional argument parameter. Options occur first in the
14499 parameter list and can be delimited from normal parameters using
14500 @samp{--} (this is useful when some parameters begin with a dash).
14507 We want easy access to the existing CLI syntax (for debugging).
14510 We want it to be easy to spot a @sc{mi} operation.
14513 @node GDB/MI Output Syntax
14514 @subsection @sc{gdb/mi} Output Syntax
14516 @cindex output syntax of @sc{gdb/mi}
14517 @cindex @sc{gdb/mi}, output syntax
14518 The output from @sc{gdb/mi} consists of zero or more out-of-band records
14519 followed, optionally, by a single result record. This result record
14520 is for the most recent command. The sequence of output records is
14521 terminated by @samp{(@value{GDBP})}.
14523 If an input command was prefixed with a @code{@var{token}} then the
14524 corresponding output for that command will also be prefixed by that same
14528 @item @var{output} @expansion{}
14529 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
14531 @item @var{result-record} @expansion{}
14532 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
14534 @item @var{out-of-band-record} @expansion{}
14535 @code{@var{async-record} | @var{stream-record}}
14537 @item @var{async-record} @expansion{}
14538 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
14540 @item @var{exec-async-output} @expansion{}
14541 @code{[ @var{token} ] "*" @var{async-output}}
14543 @item @var{status-async-output} @expansion{}
14544 @code{[ @var{token} ] "+" @var{async-output}}
14546 @item @var{notify-async-output} @expansion{}
14547 @code{[ @var{token} ] "=" @var{async-output}}
14549 @item @var{async-output} @expansion{}
14550 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
14552 @item @var{result-class} @expansion{}
14553 @code{"done" | "running" | "connected" | "error" | "exit"}
14555 @item @var{async-class} @expansion{}
14556 @code{"stopped" | @var{others}} (where @var{others} will be added
14557 depending on the needs---this is still in development).
14559 @item @var{result} @expansion{}
14560 @code{ @var{variable} "=" @var{value}}
14562 @item @var{variable} @expansion{}
14563 @code{ @var{string} }
14565 @item @var{value} @expansion{}
14566 @code{ @var{const} | @var{tuple} | @var{list} }
14568 @item @var{const} @expansion{}
14569 @code{@var{c-string}}
14571 @item @var{tuple} @expansion{}
14572 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
14574 @item @var{list} @expansion{}
14575 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
14576 @var{result} ( "," @var{result} )* "]" }
14578 @item @var{stream-record} @expansion{}
14579 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
14581 @item @var{console-stream-output} @expansion{}
14582 @code{"~" @var{c-string}}
14584 @item @var{target-stream-output} @expansion{}
14585 @code{"@@" @var{c-string}}
14587 @item @var{log-stream-output} @expansion{}
14588 @code{"&" @var{c-string}}
14590 @item @var{nl} @expansion{}
14593 @item @var{token} @expansion{}
14594 @emph{any sequence of digits}.
14602 All output sequences end in a single line containing a period.
14605 The @code{@var{token}} is from the corresponding request. If an execution
14606 command is interrupted by the @samp{-exec-interrupt} command, the
14607 @var{token} associated with the @samp{*stopped} message is the one of the
14608 original execution command, not the one of the interrupt command.
14611 @cindex status output in @sc{gdb/mi}
14612 @var{status-async-output} contains on-going status information about the
14613 progress of a slow operation. It can be discarded. All status output is
14614 prefixed by @samp{+}.
14617 @cindex async output in @sc{gdb/mi}
14618 @var{exec-async-output} contains asynchronous state change on the target
14619 (stopped, started, disappeared). All async output is prefixed by
14623 @cindex notify output in @sc{gdb/mi}
14624 @var{notify-async-output} contains supplementary information that the
14625 client should handle (e.g., a new breakpoint information). All notify
14626 output is prefixed by @samp{=}.
14629 @cindex console output in @sc{gdb/mi}
14630 @var{console-stream-output} is output that should be displayed as is in the
14631 console. It is the textual response to a CLI command. All the console
14632 output is prefixed by @samp{~}.
14635 @cindex target output in @sc{gdb/mi}
14636 @var{target-stream-output} is the output produced by the target program.
14637 All the target output is prefixed by @samp{@@}.
14640 @cindex log output in @sc{gdb/mi}
14641 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
14642 instance messages that should be displayed as part of an error log. All
14643 the log output is prefixed by @samp{&}.
14646 @cindex list output in @sc{gdb/mi}
14647 New @sc{gdb/mi} commands should only output @var{lists} containing
14653 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
14654 details about the various output records.
14656 @node GDB/MI Simple Examples
14657 @subsection Simple Examples of @sc{gdb/mi} Interaction
14658 @cindex @sc{gdb/mi}, simple examples
14660 This subsection presents several simple examples of interaction using
14661 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
14662 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
14663 the output received from @sc{gdb/mi}.
14665 @subsubheading Target Stop
14666 @c Ummm... There is no "-stop" command. This assumes async, no?
14667 Here's an example of stopping the inferior process:
14678 <- *stop,reason="stop",address="0x123",source="a.c:123"
14682 @subsubheading Simple CLI Command
14684 Here's an example of a simple CLI command being passed through
14685 @sc{gdb/mi} and on to the CLI.
14695 @subsubheading Command With Side Effects
14698 -> -symbol-file xyz.exe
14699 <- *breakpoint,nr="3",address="0x123",source="a.c:123"
14703 @subsubheading A Bad Command
14705 Here's what happens if you pass a non-existent command:
14709 <- ^error,msg="Undefined MI command: rubbish"
14713 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14714 @node GDB/MI Compatibility with CLI
14715 @section @sc{gdb/mi} Compatibility with CLI
14717 @cindex compatibility, @sc{gdb/mi} and CLI
14718 @cindex @sc{gdb/mi}, compatibility with CLI
14719 To help users familiar with @value{GDBN}'s existing CLI interface, @sc{gdb/mi}
14720 accepts existing CLI commands. As specified by the syntax, such
14721 commands can be directly entered into the @sc{gdb/mi} interface and @value{GDBN} will
14724 This mechanism is provided as an aid to developers of @sc{gdb/mi}
14725 clients and not as a reliable interface into the CLI. Since the command
14726 is being interpreteted in an environment that assumes @sc{gdb/mi}
14727 behaviour, the exact output of such commands is likely to end up being
14728 an un-supported hybrid of @sc{gdb/mi} and CLI output.
14730 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14731 @node GDB/MI Output Records
14732 @section @sc{gdb/mi} Output Records
14735 * GDB/MI Result Records::
14736 * GDB/MI Stream Records::
14737 * GDB/MI Out-of-band Records::
14740 @node GDB/MI Result Records
14741 @subsection @sc{gdb/mi} Result Records
14743 @cindex result records in @sc{gdb/mi}
14744 @cindex @sc{gdb/mi}, result records
14745 In addition to a number of out-of-band notifications, the response to a
14746 @sc{gdb/mi} command includes one of the following result indications:
14750 @item "^done" [ "," @var{results} ]
14751 The synchronous operation was successful, @code{@var{results}} are the return
14756 @c Is this one correct? Should it be an out-of-band notification?
14757 The asynchronous operation was successfully started. The target is
14760 @item "^error" "," @var{c-string}
14762 The operation failed. The @code{@var{c-string}} contains the corresponding
14766 @node GDB/MI Stream Records
14767 @subsection @sc{gdb/mi} Stream Records
14769 @cindex @sc{gdb/mi}, stream records
14770 @cindex stream records in @sc{gdb/mi}
14771 @value{GDBN} internally maintains a number of output streams: the console, the
14772 target, and the log. The output intended for each of these streams is
14773 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
14775 Each stream record begins with a unique @dfn{prefix character} which
14776 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
14777 Syntax}). In addition to the prefix, each stream record contains a
14778 @code{@var{string-output}}. This is either raw text (with an implicit new
14779 line) or a quoted C string (which does not contain an implicit newline).
14782 @item "~" @var{string-output}
14783 The console output stream contains text that should be displayed in the
14784 CLI console window. It contains the textual responses to CLI commands.
14786 @item "@@" @var{string-output}
14787 The target output stream contains any textual output from the running
14790 @item "&" @var{string-output}
14791 The log stream contains debugging messages being produced by @value{GDBN}'s
14795 @node GDB/MI Out-of-band Records
14796 @subsection @sc{gdb/mi} Out-of-band Records
14798 @cindex out-of-band records in @sc{gdb/mi}
14799 @cindex @sc{gdb/mi}, out-of-band records
14800 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
14801 additional changes that have occurred. Those changes can either be a
14802 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
14803 target activity (e.g., target stopped).
14805 The following is a preliminary list of possible out-of-band records.
14812 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14813 @node GDB/MI Command Description Format
14814 @section @sc{gdb/mi} Command Description Format
14816 The remaining sections describe blocks of commands. Each block of
14817 commands is laid out in a fashion similar to this section.
14819 Note the the line breaks shown in the examples are here only for
14820 readability. They don't appear in the real output.
14821 Also note that the commands with a non-available example (N.A.@:) are
14822 not yet implemented.
14824 @subheading Motivation
14826 The motivation for this collection of commands.
14828 @subheading Introduction
14830 A brief introduction to this collection of commands as a whole.
14832 @subheading Commands
14834 For each command in the block, the following is described:
14836 @subsubheading Synopsis
14839 -command @var{args}@dots{}
14842 @subsubheading @value{GDBN} Command
14844 The corresponding @value{GDBN} CLI command.
14846 @subsubheading Result
14848 @subsubheading Out-of-band
14850 @subsubheading Notes
14852 @subsubheading Example
14855 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14856 @node GDB/MI Breakpoint Table Commands
14857 @section @sc{gdb/mi} Breakpoint table commands
14859 @cindex breakpoint commands for @sc{gdb/mi}
14860 @cindex @sc{gdb/mi}, breakpoint commands
14861 This section documents @sc{gdb/mi} commands for manipulating
14864 @subheading The @code{-break-after} Command
14865 @findex -break-after
14867 @subsubheading Synopsis
14870 -break-after @var{number} @var{count}
14873 The breakpoint number @var{number} is not in effect until it has been
14874 hit @var{count} times. To see how this is reflected in the output of
14875 the @samp{-break-list} command, see the description of the
14876 @samp{-break-list} command below.
14878 @subsubheading @value{GDBN} Command
14880 The corresponding @value{GDBN} command is @samp{ignore}.
14882 @subsubheading Example
14887 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",line="5"@}
14894 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
14895 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14896 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14897 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14898 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14899 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14900 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14901 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
14902 addr="0x000100d0",func="main",file="hello.c",line="5",times="0",
14908 @subheading The @code{-break-catch} Command
14909 @findex -break-catch
14911 @subheading The @code{-break-commands} Command
14912 @findex -break-commands
14916 @subheading The @code{-break-condition} Command
14917 @findex -break-condition
14919 @subsubheading Synopsis
14922 -break-condition @var{number} @var{expr}
14925 Breakpoint @var{number} will stop the program only if the condition in
14926 @var{expr} is true. The condition becomes part of the
14927 @samp{-break-list} output (see the description of the @samp{-break-list}
14930 @subsubheading @value{GDBN} Command
14932 The corresponding @value{GDBN} command is @samp{condition}.
14934 @subsubheading Example
14938 -break-condition 1 1
14942 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
14943 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14944 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14945 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14946 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14947 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14948 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14949 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
14950 addr="0x000100d0",func="main",file="hello.c",line="5",cond="1",
14951 times="0",ignore="3"@}]@}
14955 @subheading The @code{-break-delete} Command
14956 @findex -break-delete
14958 @subsubheading Synopsis
14961 -break-delete ( @var{breakpoint} )+
14964 Delete the breakpoint(s) whose number(s) are specified in the argument
14965 list. This is obviously reflected in the breakpoint list.
14967 @subsubheading @value{GDBN} command
14969 The corresponding @value{GDBN} command is @samp{delete}.
14971 @subsubheading Example
14979 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
14980 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14981 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14982 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14983 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14984 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14985 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14990 @subheading The @code{-break-disable} Command
14991 @findex -break-disable
14993 @subsubheading Synopsis
14996 -break-disable ( @var{breakpoint} )+
14999 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
15000 break list is now set to @samp{n} for the named @var{breakpoint}(s).
15002 @subsubheading @value{GDBN} Command
15004 The corresponding @value{GDBN} command is @samp{disable}.
15006 @subsubheading Example
15014 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15015 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15016 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15017 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15018 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15019 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15020 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15021 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
15022 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
15026 @subheading The @code{-break-enable} Command
15027 @findex -break-enable
15029 @subsubheading Synopsis
15032 -break-enable ( @var{breakpoint} )+
15035 Enable (previously disabled) @var{breakpoint}(s).
15037 @subsubheading @value{GDBN} Command
15039 The corresponding @value{GDBN} command is @samp{enable}.
15041 @subsubheading Example
15049 ^done,BreakpointTable=@{nr_rows="1",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"@}],
15056 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
15057 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
15061 @subheading The @code{-break-info} Command
15062 @findex -break-info
15064 @subsubheading Synopsis
15067 -break-info @var{breakpoint}
15071 Get information about a single breakpoint.
15073 @subsubheading @value{GDBN} command
15075 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
15077 @subsubheading Example
15080 @subheading The @code{-break-insert} Command
15081 @findex -break-insert
15083 @subsubheading Synopsis
15086 -break-insert [ -t ] [ -h ] [ -r ]
15087 [ -c @var{condition} ] [ -i @var{ignore-count} ]
15088 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
15092 If specified, @var{line}, can be one of:
15099 @item filename:linenum
15100 @item filename:function
15104 The possible optional parameters of this command are:
15108 Insert a tempoary breakpoint.
15110 Insert a hardware breakpoint.
15111 @item -c @var{condition}
15112 Make the breakpoint conditional on @var{condition}.
15113 @item -i @var{ignore-count}
15114 Initialize the @var{ignore-count}.
15116 Insert a regular breakpoint in all the functions whose names match the
15117 given regular expression. Other flags are not applicable to regular
15121 @subsubheading Result
15123 The result is in the form:
15126 ^done,bkptno="@var{number}",func="@var{funcname}",
15127 file="@var{filename}",line="@var{lineno}"
15131 where @var{number} is the @value{GDBN} number for this breakpoint, @var{funcname}
15132 is the name of the function where the breakpoint was inserted,
15133 @var{filename} is the name of the source file which contains this
15134 function, and @var{lineno} is the source line number within that file.
15136 Note: this format is open to change.
15137 @c An out-of-band breakpoint instead of part of the result?
15139 @subsubheading @value{GDBN} Command
15141 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
15142 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
15144 @subsubheading Example
15149 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
15151 -break-insert -t foo
15152 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",line="11"@}
15155 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15156 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15157 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15158 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15159 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15160 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15161 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15162 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15163 addr="0x0001072c", func="main",file="recursive2.c",line="4",times="0"@},
15164 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
15165 addr="0x00010774",func="foo",file="recursive2.c",line="11",times="0"@}]@}
15167 -break-insert -r foo.*
15168 ~int foo(int, int);
15169 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c",line="11"@}
15173 @subheading The @code{-break-list} Command
15174 @findex -break-list
15176 @subsubheading Synopsis
15182 Displays the list of inserted breakpoints, showing the following fields:
15186 number of the breakpoint
15188 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
15190 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
15193 is the breakpoint enabled or no: @samp{y} or @samp{n}
15195 memory location at which the breakpoint is set
15197 logical location of the breakpoint, expressed by function name, file
15200 number of times the breakpoint has been hit
15203 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
15204 @code{body} field is an empty list.
15206 @subsubheading @value{GDBN} Command
15208 The corresponding @value{GDBN} command is @samp{info break}.
15210 @subsubheading Example
15215 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15216 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15217 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15218 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15219 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15220 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15221 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15222 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15223 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
15224 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
15225 addr="0x00010114",func="foo",file="hello.c",line="13",times="0"@}]@}
15229 Here's an example of the result when there are no breakpoints:
15234 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
15235 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15236 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15237 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15238 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15239 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15240 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15245 @subheading The @code{-break-watch} Command
15246 @findex -break-watch
15248 @subsubheading Synopsis
15251 -break-watch [ -a | -r ]
15254 Create a watchpoint. With the @samp{-a} option it will create an
15255 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
15256 read from or on a write to the memory location. With the @samp{-r}
15257 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
15258 trigger only when the memory location is accessed for reading. Without
15259 either of the options, the watchpoint created is a regular watchpoint,
15260 i.e. it will trigger when the memory location is accessed for writing.
15261 @xref{Set Watchpoints, , Setting watchpoints}.
15263 Note that @samp{-break-list} will report a single list of watchpoints and
15264 breakpoints inserted.
15266 @subsubheading @value{GDBN} Command
15268 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
15271 @subsubheading Example
15273 Setting a watchpoint on a variable in the @code{main} function:
15278 ^done,wpt=@{number="2",exp="x"@}
15282 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
15283 value=@{old="-268439212",new="55"@},
15284 frame=@{func="main",args=[],file="recursive2.c",line="5"@}
15288 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
15289 the program execution twice: first for the variable changing value, then
15290 for the watchpoint going out of scope.
15295 ^done,wpt=@{number="5",exp="C"@}
15299 ^done,reason="watchpoint-trigger",
15300 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
15301 frame=@{func="callee4",args=[],
15302 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
15306 ^done,reason="watchpoint-scope",wpnum="5",
15307 frame=@{func="callee3",args=[@{name="strarg",
15308 value="0x11940 \"A string argument.\""@}],
15309 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
15313 Listing breakpoints and watchpoints, at different points in the program
15314 execution. Note that once the watchpoint goes out of scope, it is
15320 ^done,wpt=@{number="2",exp="C"@}
15323 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15324 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15325 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15326 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15327 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15328 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15329 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15330 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15331 addr="0x00010734",func="callee4",
15332 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
15333 bkpt=@{number="2",type="watchpoint",disp="keep",
15334 enabled="y",addr="",what="C",times="0"@}]@}
15338 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
15339 value=@{old="-276895068",new="3"@},
15340 frame=@{func="callee4",args=[],
15341 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
15344 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15345 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15346 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15347 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15348 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15349 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15350 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15351 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15352 addr="0x00010734",func="callee4",
15353 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
15354 bkpt=@{number="2",type="watchpoint",disp="keep",
15355 enabled="y",addr="",what="C",times="-5"@}]@}
15359 ^done,reason="watchpoint-scope",wpnum="2",
15360 frame=@{func="callee3",args=[@{name="strarg",
15361 value="0x11940 \"A string argument.\""@}],
15362 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
15365 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15366 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15367 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15368 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15369 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15370 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15371 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15372 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15373 addr="0x00010734",func="callee4",
15374 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@}]@}
15378 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15379 @node GDB/MI Data Manipulation
15380 @section @sc{gdb/mi} Data Manipulation
15382 @cindex data manipulation, in @sc{gdb/mi}
15383 @cindex @sc{gdb/mi}, data manipulation
15384 This section describes the @sc{gdb/mi} commands that manipulate data:
15385 examine memory and registers, evaluate expressions, etc.
15387 @c REMOVED FROM THE INTERFACE.
15388 @c @subheading -data-assign
15389 @c Change the value of a program variable. Plenty of side effects.
15390 @c @subsubheading GDB command
15392 @c @subsubheading Example
15395 @subheading The @code{-data-disassemble} Command
15396 @findex -data-disassemble
15398 @subsubheading Synopsis
15402 [ -s @var{start-addr} -e @var{end-addr} ]
15403 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
15411 @item @var{start-addr}
15412 is the beginning address (or @code{$pc})
15413 @item @var{end-addr}
15415 @item @var{filename}
15416 is the name of the file to disassemble
15417 @item @var{linenum}
15418 is the line number to disassemble around
15420 is the the number of disassembly lines to be produced. If it is -1,
15421 the whole function will be disassembled, in case no @var{end-addr} is
15422 specified. If @var{end-addr} is specified as a non-zero value, and
15423 @var{lines} is lower than the number of disassembly lines between
15424 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
15425 displayed; if @var{lines} is higher than the number of lines between
15426 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
15429 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
15433 @subsubheading Result
15435 The output for each instruction is composed of four fields:
15444 Note that whatever included in the instruction field, is not manipulated
15445 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
15447 @subsubheading @value{GDBN} Command
15449 There's no direct mapping from this command to the CLI.
15451 @subsubheading Example
15453 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
15457 -data-disassemble -s $pc -e "$pc + 20" -- 0
15460 @{address="0x000107c0",func-name="main",offset="4",
15461 inst="mov 2, %o0"@},
15462 @{address="0x000107c4",func-name="main",offset="8",
15463 inst="sethi %hi(0x11800), %o2"@},
15464 @{address="0x000107c8",func-name="main",offset="12",
15465 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
15466 @{address="0x000107cc",func-name="main",offset="16",
15467 inst="sethi %hi(0x11800), %o2"@},
15468 @{address="0x000107d0",func-name="main",offset="20",
15469 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
15473 Disassemble the whole @code{main} function. Line 32 is part of
15477 -data-disassemble -f basics.c -l 32 -- 0
15479 @{address="0x000107bc",func-name="main",offset="0",
15480 inst="save %sp, -112, %sp"@},
15481 @{address="0x000107c0",func-name="main",offset="4",
15482 inst="mov 2, %o0"@},
15483 @{address="0x000107c4",func-name="main",offset="8",
15484 inst="sethi %hi(0x11800), %o2"@},
15486 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
15487 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
15491 Disassemble 3 instructions from the start of @code{main}:
15495 -data-disassemble -f basics.c -l 32 -n 3 -- 0
15497 @{address="0x000107bc",func-name="main",offset="0",
15498 inst="save %sp, -112, %sp"@},
15499 @{address="0x000107c0",func-name="main",offset="4",
15500 inst="mov 2, %o0"@},
15501 @{address="0x000107c4",func-name="main",offset="8",
15502 inst="sethi %hi(0x11800), %o2"@}]
15506 Disassemble 3 instructions from the start of @code{main} in mixed mode:
15510 -data-disassemble -f basics.c -l 32 -n 3 -- 1
15512 src_and_asm_line=@{line="31",
15513 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
15514 testsuite/gdb.mi/basics.c",line_asm_insn=[
15515 @{address="0x000107bc",func-name="main",offset="0",
15516 inst="save %sp, -112, %sp"@}]@},
15517 src_and_asm_line=@{line="32",
15518 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
15519 testsuite/gdb.mi/basics.c",line_asm_insn=[
15520 @{address="0x000107c0",func-name="main",offset="4",
15521 inst="mov 2, %o0"@},
15522 @{address="0x000107c4",func-name="main",offset="8",
15523 inst="sethi %hi(0x11800), %o2"@}]@}]
15528 @subheading The @code{-data-evaluate-expression} Command
15529 @findex -data-evaluate-expression
15531 @subsubheading Synopsis
15534 -data-evaluate-expression @var{expr}
15537 Evaluate @var{expr} as an expression. The expression could contain an
15538 inferior function call. The function call will execute synchronously.
15539 If the expression contains spaces, it must be enclosed in double quotes.
15541 @subsubheading @value{GDBN} Command
15543 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
15544 @samp{call}. In @code{gdbtk} only, there's a corresponding
15545 @samp{gdb_eval} command.
15547 @subsubheading Example
15549 In the following example, the numbers that precede the commands are the
15550 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
15551 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
15555 211-data-evaluate-expression A
15558 311-data-evaluate-expression &A
15559 311^done,value="0xefffeb7c"
15561 411-data-evaluate-expression A+3
15564 511-data-evaluate-expression "A + 3"
15570 @subheading The @code{-data-list-changed-registers} Command
15571 @findex -data-list-changed-registers
15573 @subsubheading Synopsis
15576 -data-list-changed-registers
15579 Display a list of the registers that have changed.
15581 @subsubheading @value{GDBN} Command
15583 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
15584 has the corresponding command @samp{gdb_changed_register_list}.
15586 @subsubheading Example
15588 On a PPC MBX board:
15596 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
15597 args=[],file="try.c",line="5"@}
15599 -data-list-changed-registers
15600 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
15601 "10","11","13","14","15","16","17","18","19","20","21","22","23",
15602 "24","25","26","27","28","30","31","64","65","66","67","69"]
15607 @subheading The @code{-data-list-register-names} Command
15608 @findex -data-list-register-names
15610 @subsubheading Synopsis
15613 -data-list-register-names [ ( @var{regno} )+ ]
15616 Show a list of register names for the current target. If no arguments
15617 are given, it shows a list of the names of all the registers. If
15618 integer numbers are given as arguments, it will print a list of the
15619 names of the registers corresponding to the arguments. To ensure
15620 consistency between a register name and its number, the output list may
15621 include empty register names.
15623 @subsubheading @value{GDBN} Command
15625 @value{GDBN} does not have a command which corresponds to
15626 @samp{-data-list-register-names}. In @code{gdbtk} there is a
15627 corresponding command @samp{gdb_regnames}.
15629 @subsubheading Example
15631 For the PPC MBX board:
15634 -data-list-register-names
15635 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
15636 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
15637 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
15638 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
15639 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
15640 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
15641 "", "pc","ps","cr","lr","ctr","xer"]
15643 -data-list-register-names 1 2 3
15644 ^done,register-names=["r1","r2","r3"]
15648 @subheading The @code{-data-list-register-values} Command
15649 @findex -data-list-register-values
15651 @subsubheading Synopsis
15654 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
15657 Display the registers' contents. @var{fmt} is the format according to
15658 which the registers' contents are to be returned, followed by an optional
15659 list of numbers specifying the registers to display. A missing list of
15660 numbers indicates that the contents of all the registers must be returned.
15662 Allowed formats for @var{fmt} are:
15679 @subsubheading @value{GDBN} Command
15681 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
15682 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
15684 @subsubheading Example
15686 For a PPC MBX board (note: line breaks are for readability only, they
15687 don't appear in the actual output):
15691 -data-list-register-values r 64 65
15692 ^done,register-values=[@{number="64",value="0xfe00a300"@},
15693 @{number="65",value="0x00029002"@}]
15695 -data-list-register-values x
15696 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
15697 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
15698 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
15699 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
15700 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
15701 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
15702 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
15703 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
15704 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
15705 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
15706 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
15707 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
15708 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
15709 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
15710 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
15711 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
15712 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
15713 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
15714 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
15715 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
15716 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
15717 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
15718 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
15719 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
15720 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
15721 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
15722 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
15723 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
15724 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
15725 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
15726 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
15727 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
15728 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
15729 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
15730 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
15731 @{number="69",value="0x20002b03"@}]
15736 @subheading The @code{-data-read-memory} Command
15737 @findex -data-read-memory
15739 @subsubheading Synopsis
15742 -data-read-memory [ -o @var{byte-offset} ]
15743 @var{address} @var{word-format} @var{word-size}
15744 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
15751 @item @var{address}
15752 An expression specifying the address of the first memory word to be
15753 read. Complex expressions containing embedded white space should be
15754 quoted using the C convention.
15756 @item @var{word-format}
15757 The format to be used to print the memory words. The notation is the
15758 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
15761 @item @var{word-size}
15762 The size of each memory word in bytes.
15764 @item @var{nr-rows}
15765 The number of rows in the output table.
15767 @item @var{nr-cols}
15768 The number of columns in the output table.
15771 If present, indicates that each row should include an @sc{ascii} dump. The
15772 value of @var{aschar} is used as a padding character when a byte is not a
15773 member of the printable @sc{ascii} character set (printable @sc{ascii}
15774 characters are those whose code is between 32 and 126, inclusively).
15776 @item @var{byte-offset}
15777 An offset to add to the @var{address} before fetching memory.
15780 This command displays memory contents as a table of @var{nr-rows} by
15781 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
15782 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
15783 (returned as @samp{total-bytes}). Should less than the requested number
15784 of bytes be returned by the target, the missing words are identified
15785 using @samp{N/A}. The number of bytes read from the target is returned
15786 in @samp{nr-bytes} and the starting address used to read memory in
15789 The address of the next/previous row or page is available in
15790 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
15793 @subsubheading @value{GDBN} Command
15795 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
15796 @samp{gdb_get_mem} memory read command.
15798 @subsubheading Example
15800 Read six bytes of memory starting at @code{bytes+6} but then offset by
15801 @code{-6} bytes. Format as three rows of two columns. One byte per
15802 word. Display each word in hex.
15806 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
15807 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
15808 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
15809 prev-page="0x0000138a",memory=[
15810 @{addr="0x00001390",data=["0x00","0x01"]@},
15811 @{addr="0x00001392",data=["0x02","0x03"]@},
15812 @{addr="0x00001394",data=["0x04","0x05"]@}]
15816 Read two bytes of memory starting at address @code{shorts + 64} and
15817 display as a single word formatted in decimal.
15821 5-data-read-memory shorts+64 d 2 1 1
15822 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
15823 next-row="0x00001512",prev-row="0x0000150e",
15824 next-page="0x00001512",prev-page="0x0000150e",memory=[
15825 @{addr="0x00001510",data=["128"]@}]
15829 Read thirty two bytes of memory starting at @code{bytes+16} and format
15830 as eight rows of four columns. Include a string encoding with @samp{x}
15831 used as the non-printable character.
15835 4-data-read-memory bytes+16 x 1 8 4 x
15836 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
15837 next-row="0x000013c0",prev-row="0x0000139c",
15838 next-page="0x000013c0",prev-page="0x00001380",memory=[
15839 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
15840 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
15841 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
15842 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
15843 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
15844 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
15845 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
15846 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
15850 @subheading The @code{-display-delete} Command
15851 @findex -display-delete
15853 @subsubheading Synopsis
15856 -display-delete @var{number}
15859 Delete the display @var{number}.
15861 @subsubheading @value{GDBN} Command
15863 The corresponding @value{GDBN} command is @samp{delete display}.
15865 @subsubheading Example
15869 @subheading The @code{-display-disable} Command
15870 @findex -display-disable
15872 @subsubheading Synopsis
15875 -display-disable @var{number}
15878 Disable display @var{number}.
15880 @subsubheading @value{GDBN} Command
15882 The corresponding @value{GDBN} command is @samp{disable display}.
15884 @subsubheading Example
15888 @subheading The @code{-display-enable} Command
15889 @findex -display-enable
15891 @subsubheading Synopsis
15894 -display-enable @var{number}
15897 Enable display @var{number}.
15899 @subsubheading @value{GDBN} Command
15901 The corresponding @value{GDBN} command is @samp{enable display}.
15903 @subsubheading Example
15907 @subheading The @code{-display-insert} Command
15908 @findex -display-insert
15910 @subsubheading Synopsis
15913 -display-insert @var{expression}
15916 Display @var{expression} every time the program stops.
15918 @subsubheading @value{GDBN} Command
15920 The corresponding @value{GDBN} command is @samp{display}.
15922 @subsubheading Example
15926 @subheading The @code{-display-list} Command
15927 @findex -display-list
15929 @subsubheading Synopsis
15935 List the displays. Do not show the current values.
15937 @subsubheading @value{GDBN} Command
15939 The corresponding @value{GDBN} command is @samp{info display}.
15941 @subsubheading Example
15945 @subheading The @code{-environment-cd} Command
15946 @findex -environment-cd
15948 @subsubheading Synopsis
15951 -environment-cd @var{pathdir}
15954 Set @value{GDBN}'s working directory.
15956 @subsubheading @value{GDBN} Command
15958 The corresponding @value{GDBN} command is @samp{cd}.
15960 @subsubheading Example
15964 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
15970 @subheading The @code{-environment-directory} Command
15971 @findex -environment-directory
15973 @subsubheading Synopsis
15976 -environment-directory [ -r ] [ @var{pathdir} ]+
15979 Add directories @var{pathdir} to beginning of search path for source files.
15980 If the @samp{-r} option is used, the search path is reset to the default
15981 search path. If directories @var{pathdir} are supplied in addition to the
15982 @samp{-r} option, the search path is first reset and then addition
15984 Multiple directories may be specified, separated by blanks. Specifying
15985 multiple directories in a single command
15986 results in the directories added to the beginning of the
15987 search path in the same order they were presented in the command.
15988 If blanks are needed as
15989 part of a directory name, double-quotes should be used around
15990 the name. In the command output, the path will show up separated
15991 by the system directory-separator character. The directory-seperator
15992 character must not be used
15993 in any directory name.
15994 If no directories are specified, the current search path is displayed.
15996 @subsubheading @value{GDBN} Command
15998 The corresponding @value{GDBN} command is @samp{dir}.
16000 @subsubheading Example
16004 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
16005 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
16007 -environment-directory ""
16008 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
16010 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
16011 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
16013 -environment-directory -r
16014 ^done,source-path="$cdir:$cwd"
16019 @subheading The @code{-environment-path} Command
16020 @findex -environment-path
16022 @subsubheading Synopsis
16025 -environment-path [ -r ] [ @var{pathdir} ]+
16028 Add directories @var{pathdir} to beginning of search path for object files.
16029 If the @samp{-r} option is used, the search path is reset to the original
16030 search path that existed at gdb start-up. If directories @var{pathdir} are
16031 supplied in addition to the
16032 @samp{-r} option, the search path is first reset and then addition
16034 Multiple directories may be specified, separated by blanks. Specifying
16035 multiple directories in a single command
16036 results in the directories added to the beginning of the
16037 search path in the same order they were presented in the command.
16038 If blanks are needed as
16039 part of a directory name, double-quotes should be used around
16040 the name. In the command output, the path will show up separated
16041 by the system directory-separator character. The directory-seperator
16042 character must not be used
16043 in any directory name.
16044 If no directories are specified, the current path is displayed.
16047 @subsubheading @value{GDBN} Command
16049 The corresponding @value{GDBN} command is @samp{path}.
16051 @subsubheading Example
16056 ^done,path="/usr/bin"
16058 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
16059 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
16061 -environment-path -r /usr/local/bin
16062 ^done,path="/usr/local/bin:/usr/bin"
16067 @subheading The @code{-environment-pwd} Command
16068 @findex -environment-pwd
16070 @subsubheading Synopsis
16076 Show the current working directory.
16078 @subsubheading @value{GDBN} command
16080 The corresponding @value{GDBN} command is @samp{pwd}.
16082 @subsubheading Example
16087 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
16091 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16092 @node GDB/MI Program Control
16093 @section @sc{gdb/mi} Program control
16095 @subsubheading Program termination
16097 As a result of execution, the inferior program can run to completion, if
16098 it doesn't encounter any breakpoints. In this case the output will
16099 include an exit code, if the program has exited exceptionally.
16101 @subsubheading Examples
16104 Program exited normally:
16112 *stopped,reason="exited-normally"
16117 Program exited exceptionally:
16125 *stopped,reason="exited",exit-code="01"
16129 Another way the program can terminate is if it receives a signal such as
16130 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
16134 *stopped,reason="exited-signalled",signal-name="SIGINT",
16135 signal-meaning="Interrupt"
16139 @subheading The @code{-exec-abort} Command
16140 @findex -exec-abort
16142 @subsubheading Synopsis
16148 Kill the inferior running program.
16150 @subsubheading @value{GDBN} Command
16152 The corresponding @value{GDBN} command is @samp{kill}.
16154 @subsubheading Example
16158 @subheading The @code{-exec-arguments} Command
16159 @findex -exec-arguments
16161 @subsubheading Synopsis
16164 -exec-arguments @var{args}
16167 Set the inferior program arguments, to be used in the next
16170 @subsubheading @value{GDBN} Command
16172 The corresponding @value{GDBN} command is @samp{set args}.
16174 @subsubheading Example
16177 Don't have one around.
16180 @subheading The @code{-exec-continue} Command
16181 @findex -exec-continue
16183 @subsubheading Synopsis
16189 Asynchronous command. Resumes the execution of the inferior program
16190 until a breakpoint is encountered, or until the inferior exits.
16192 @subsubheading @value{GDBN} Command
16194 The corresponding @value{GDBN} corresponding is @samp{continue}.
16196 @subsubheading Example
16203 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
16204 file="hello.c",line="13"@}
16209 @subheading The @code{-exec-finish} Command
16210 @findex -exec-finish
16212 @subsubheading Synopsis
16218 Asynchronous command. Resumes the execution of the inferior program
16219 until the current function is exited. Displays the results returned by
16222 @subsubheading @value{GDBN} Command
16224 The corresponding @value{GDBN} command is @samp{finish}.
16226 @subsubheading Example
16228 Function returning @code{void}.
16235 *stopped,reason="function-finished",frame=@{func="main",args=[],
16236 file="hello.c",line="7"@}
16240 Function returning other than @code{void}. The name of the internal
16241 @value{GDBN} variable storing the result is printed, together with the
16248 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
16249 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
16250 file="recursive2.c",line="14"@},
16251 gdb-result-var="$1",return-value="0"
16256 @subheading The @code{-exec-interrupt} Command
16257 @findex -exec-interrupt
16259 @subsubheading Synopsis
16265 Asynchronous command. Interrupts the background execution of the target.
16266 Note how the token associated with the stop message is the one for the
16267 execution command that has been interrupted. The token for the interrupt
16268 itself only appears in the @samp{^done} output. If the user is trying to
16269 interrupt a non-running program, an error message will be printed.
16271 @subsubheading @value{GDBN} Command
16273 The corresponding @value{GDBN} command is @samp{interrupt}.
16275 @subsubheading Example
16286 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
16287 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",line="13"@}
16292 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
16297 @subheading The @code{-exec-next} Command
16300 @subsubheading Synopsis
16306 Asynchronous command. Resumes execution of the inferior program, stopping
16307 when the beginning of the next source line is reached.
16309 @subsubheading @value{GDBN} Command
16311 The corresponding @value{GDBN} command is @samp{next}.
16313 @subsubheading Example
16319 *stopped,reason="end-stepping-range",line="8",file="hello.c"
16324 @subheading The @code{-exec-next-instruction} Command
16325 @findex -exec-next-instruction
16327 @subsubheading Synopsis
16330 -exec-next-instruction
16333 Asynchronous command. Executes one machine instruction. If the
16334 instruction is a function call continues until the function returns. If
16335 the program stops at an instruction in the middle of a source line, the
16336 address will be printed as well.
16338 @subsubheading @value{GDBN} Command
16340 The corresponding @value{GDBN} command is @samp{nexti}.
16342 @subsubheading Example
16346 -exec-next-instruction
16350 *stopped,reason="end-stepping-range",
16351 addr="0x000100d4",line="5",file="hello.c"
16356 @subheading The @code{-exec-return} Command
16357 @findex -exec-return
16359 @subsubheading Synopsis
16365 Makes current function return immediately. Doesn't execute the inferior.
16366 Displays the new current frame.
16368 @subsubheading @value{GDBN} Command
16370 The corresponding @value{GDBN} command is @samp{return}.
16372 @subsubheading Example
16376 200-break-insert callee4
16377 200^done,bkpt=@{number="1",addr="0x00010734",
16378 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
16383 000*stopped,reason="breakpoint-hit",bkptno="1",
16384 frame=@{func="callee4",args=[],
16385 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
16391 111^done,frame=@{level="0",func="callee3",
16392 args=[@{name="strarg",
16393 value="0x11940 \"A string argument.\""@}],
16394 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
16399 @subheading The @code{-exec-run} Command
16402 @subsubheading Synopsis
16408 Asynchronous command. Starts execution of the inferior from the
16409 beginning. The inferior executes until either a breakpoint is
16410 encountered or the program exits.
16412 @subsubheading @value{GDBN} Command
16414 The corresponding @value{GDBN} command is @samp{run}.
16416 @subsubheading Example
16421 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
16426 *stopped,reason="breakpoint-hit",bkptno="1",
16427 frame=@{func="main",args=[],file="recursive2.c",line="4"@}
16432 @subheading The @code{-exec-show-arguments} Command
16433 @findex -exec-show-arguments
16435 @subsubheading Synopsis
16438 -exec-show-arguments
16441 Print the arguments of the program.
16443 @subsubheading @value{GDBN} Command
16445 The corresponding @value{GDBN} command is @samp{show args}.
16447 @subsubheading Example
16450 @c @subheading -exec-signal
16452 @subheading The @code{-exec-step} Command
16455 @subsubheading Synopsis
16461 Asynchronous command. Resumes execution of the inferior program, stopping
16462 when the beginning of the next source line is reached, if the next
16463 source line is not a function call. If it is, stop at the first
16464 instruction of the called function.
16466 @subsubheading @value{GDBN} Command
16468 The corresponding @value{GDBN} command is @samp{step}.
16470 @subsubheading Example
16472 Stepping into a function:
16478 *stopped,reason="end-stepping-range",
16479 frame=@{func="foo",args=[@{name="a",value="10"@},
16480 @{name="b",value="0"@}],file="recursive2.c",line="11"@}
16490 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
16495 @subheading The @code{-exec-step-instruction} Command
16496 @findex -exec-step-instruction
16498 @subsubheading Synopsis
16501 -exec-step-instruction
16504 Asynchronous command. Resumes the inferior which executes one machine
16505 instruction. The output, once @value{GDBN} has stopped, will vary depending on
16506 whether we have stopped in the middle of a source line or not. In the
16507 former case, the address at which the program stopped will be printed as
16510 @subsubheading @value{GDBN} Command
16512 The corresponding @value{GDBN} command is @samp{stepi}.
16514 @subsubheading Example
16518 -exec-step-instruction
16522 *stopped,reason="end-stepping-range",
16523 frame=@{func="foo",args=[],file="try.c",line="10"@}
16525 -exec-step-instruction
16529 *stopped,reason="end-stepping-range",
16530 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",line="10"@}
16535 @subheading The @code{-exec-until} Command
16536 @findex -exec-until
16538 @subsubheading Synopsis
16541 -exec-until [ @var{location} ]
16544 Asynchronous command. Executes the inferior until the @var{location}
16545 specified in the argument is reached. If there is no argument, the inferior
16546 executes until a source line greater than the current one is reached.
16547 The reason for stopping in this case will be @samp{location-reached}.
16549 @subsubheading @value{GDBN} Command
16551 The corresponding @value{GDBN} command is @samp{until}.
16553 @subsubheading Example
16557 -exec-until recursive2.c:6
16561 *stopped,reason="location-reached",frame=@{func="main",args=[],
16562 file="recursive2.c",line="6"@}
16567 @subheading -file-clear
16568 Is this going away????
16572 @subheading The @code{-file-exec-and-symbols} Command
16573 @findex -file-exec-and-symbols
16575 @subsubheading Synopsis
16578 -file-exec-and-symbols @var{file}
16581 Specify the executable file to be debugged. This file is the one from
16582 which the symbol table is also read. If no file is specified, the
16583 command clears the executable and symbol information. If breakpoints
16584 are set when using this command with no arguments, @value{GDBN} will produce
16585 error messages. Otherwise, no output is produced, except a completion
16588 @subsubheading @value{GDBN} Command
16590 The corresponding @value{GDBN} command is @samp{file}.
16592 @subsubheading Example
16596 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
16602 @subheading The @code{-file-exec-file} Command
16603 @findex -file-exec-file
16605 @subsubheading Synopsis
16608 -file-exec-file @var{file}
16611 Specify the executable file to be debugged. Unlike
16612 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
16613 from this file. If used without argument, @value{GDBN} clears the information
16614 about the executable file. No output is produced, except a completion
16617 @subsubheading @value{GDBN} Command
16619 The corresponding @value{GDBN} command is @samp{exec-file}.
16621 @subsubheading Example
16625 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
16631 @subheading The @code{-file-list-exec-sections} Command
16632 @findex -file-list-exec-sections
16634 @subsubheading Synopsis
16637 -file-list-exec-sections
16640 List the sections of the current executable file.
16642 @subsubheading @value{GDBN} Command
16644 The @value{GDBN} command @samp{info file} shows, among the rest, the same
16645 information as this command. @code{gdbtk} has a corresponding command
16646 @samp{gdb_load_info}.
16648 @subsubheading Example
16652 @subheading The @code{-file-list-exec-source-file} Command
16653 @findex -file-list-exec-source-file
16655 @subsubheading Synopsis
16658 -file-list-exec-source-file
16661 List the line number, the current source file, and the absolute path
16662 to the current source file for the current executable.
16664 @subsubheading @value{GDBN} Command
16666 There's no @value{GDBN} command which directly corresponds to this one.
16668 @subsubheading Example
16672 123-file-list-exec-source-file
16673 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
16678 @subheading The @code{-file-list-exec-source-files} Command
16679 @findex -file-list-exec-source-files
16681 @subsubheading Synopsis
16684 -file-list-exec-source-files
16687 List the source files for the current executable.
16689 @subsubheading @value{GDBN} Command
16691 There's no @value{GDBN} command which directly corresponds to this one.
16692 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
16694 @subsubheading Example
16698 @subheading The @code{-file-list-shared-libraries} Command
16699 @findex -file-list-shared-libraries
16701 @subsubheading Synopsis
16704 -file-list-shared-libraries
16707 List the shared libraries in the program.
16709 @subsubheading @value{GDBN} Command
16711 The corresponding @value{GDBN} command is @samp{info shared}.
16713 @subsubheading Example
16717 @subheading The @code{-file-list-symbol-files} Command
16718 @findex -file-list-symbol-files
16720 @subsubheading Synopsis
16723 -file-list-symbol-files
16728 @subsubheading @value{GDBN} Command
16730 The corresponding @value{GDBN} command is @samp{info file} (part of it).
16732 @subsubheading Example
16736 @subheading The @code{-file-symbol-file} Command
16737 @findex -file-symbol-file
16739 @subsubheading Synopsis
16742 -file-symbol-file @var{file}
16745 Read symbol table info from the specified @var{file} argument. When
16746 used without arguments, clears @value{GDBN}'s symbol table info. No output is
16747 produced, except for a completion notification.
16749 @subsubheading @value{GDBN} Command
16751 The corresponding @value{GDBN} command is @samp{symbol-file}.
16753 @subsubheading Example
16757 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
16762 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16763 @node GDB/MI Miscellaneous Commands
16764 @section Miscellaneous @value{GDBN} commands in @sc{gdb/mi}
16766 @c @subheading -gdb-complete
16768 @subheading The @code{-gdb-exit} Command
16771 @subsubheading Synopsis
16777 Exit @value{GDBN} immediately.
16779 @subsubheading @value{GDBN} Command
16781 Approximately corresponds to @samp{quit}.
16783 @subsubheading Example
16790 @subheading The @code{-gdb-set} Command
16793 @subsubheading Synopsis
16799 Set an internal @value{GDBN} variable.
16800 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
16802 @subsubheading @value{GDBN} Command
16804 The corresponding @value{GDBN} command is @samp{set}.
16806 @subsubheading Example
16816 @subheading The @code{-gdb-show} Command
16819 @subsubheading Synopsis
16825 Show the current value of a @value{GDBN} variable.
16827 @subsubheading @value{GDBN} command
16829 The corresponding @value{GDBN} command is @samp{show}.
16831 @subsubheading Example
16840 @c @subheading -gdb-source
16843 @subheading The @code{-gdb-version} Command
16844 @findex -gdb-version
16846 @subsubheading Synopsis
16852 Show version information for @value{GDBN}. Used mostly in testing.
16854 @subsubheading @value{GDBN} Command
16856 There's no equivalent @value{GDBN} command. @value{GDBN} by default shows this
16857 information when you start an interactive session.
16859 @subsubheading Example
16861 @c This example modifies the actual output from GDB to avoid overfull
16867 ~Copyright 2000 Free Software Foundation, Inc.
16868 ~GDB is free software, covered by the GNU General Public License, and
16869 ~you are welcome to change it and/or distribute copies of it under
16870 ~ certain conditions.
16871 ~Type "show copying" to see the conditions.
16872 ~There is absolutely no warranty for GDB. Type "show warranty" for
16874 ~This GDB was configured as
16875 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
16880 @subheading The @code{-interpreter-exec} Command
16881 @findex -interpreter-exec
16883 @subheading Synopsis
16886 -interpreter-exec @var{interpreter} @var{command}
16889 Execute the specified @var{command} in the given @var{interpreter}.
16891 @subheading @value{GDBN} Command
16893 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
16895 @subheading Example
16899 -interpreter-exec console "break main"
16900 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
16901 &"During symbol reading, bad structure-type format.\n"
16902 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
16908 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16909 @node GDB/MI Kod Commands
16910 @section @sc{gdb/mi} Kod Commands
16912 The Kod commands are not implemented.
16914 @c @subheading -kod-info
16916 @c @subheading -kod-list
16918 @c @subheading -kod-list-object-types
16920 @c @subheading -kod-show
16922 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16923 @node GDB/MI Memory Overlay Commands
16924 @section @sc{gdb/mi} Memory Overlay Commands
16926 The memory overlay commands are not implemented.
16928 @c @subheading -overlay-auto
16930 @c @subheading -overlay-list-mapping-state
16932 @c @subheading -overlay-list-overlays
16934 @c @subheading -overlay-map
16936 @c @subheading -overlay-off
16938 @c @subheading -overlay-on
16940 @c @subheading -overlay-unmap
16942 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16943 @node GDB/MI Signal Handling Commands
16944 @section @sc{gdb/mi} Signal Handling Commands
16946 Signal handling commands are not implemented.
16948 @c @subheading -signal-handle
16950 @c @subheading -signal-list-handle-actions
16952 @c @subheading -signal-list-signal-types
16956 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16957 @node GDB/MI Stack Manipulation
16958 @section @sc{gdb/mi} Stack Manipulation Commands
16961 @subheading The @code{-stack-info-frame} Command
16962 @findex -stack-info-frame
16964 @subsubheading Synopsis
16970 Get info on the current frame.
16972 @subsubheading @value{GDBN} Command
16974 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
16975 (without arguments).
16977 @subsubheading Example
16980 @subheading The @code{-stack-info-depth} Command
16981 @findex -stack-info-depth
16983 @subsubheading Synopsis
16986 -stack-info-depth [ @var{max-depth} ]
16989 Return the depth of the stack. If the integer argument @var{max-depth}
16990 is specified, do not count beyond @var{max-depth} frames.
16992 @subsubheading @value{GDBN} Command
16994 There's no equivalent @value{GDBN} command.
16996 @subsubheading Example
16998 For a stack with frame levels 0 through 11:
17005 -stack-info-depth 4
17008 -stack-info-depth 12
17011 -stack-info-depth 11
17014 -stack-info-depth 13
17019 @subheading The @code{-stack-list-arguments} Command
17020 @findex -stack-list-arguments
17022 @subsubheading Synopsis
17025 -stack-list-arguments @var{show-values}
17026 [ @var{low-frame} @var{high-frame} ]
17029 Display a list of the arguments for the frames between @var{low-frame}
17030 and @var{high-frame} (inclusive). If @var{low-frame} and
17031 @var{high-frame} are not provided, list the arguments for the whole call
17034 The @var{show-values} argument must have a value of 0 or 1. A value of
17035 0 means that only the names of the arguments are listed, a value of 1
17036 means that both names and values of the arguments are printed.
17038 @subsubheading @value{GDBN} Command
17040 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
17041 @samp{gdb_get_args} command which partially overlaps with the
17042 functionality of @samp{-stack-list-arguments}.
17044 @subsubheading Example
17051 frame=@{level="0",addr="0x00010734",func="callee4",
17052 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
17053 frame=@{level="1",addr="0x0001076c",func="callee3",
17054 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
17055 frame=@{level="2",addr="0x0001078c",func="callee2",
17056 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
17057 frame=@{level="3",addr="0x000107b4",func="callee1",
17058 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
17059 frame=@{level="4",addr="0x000107e0",func="main",
17060 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
17062 -stack-list-arguments 0
17065 frame=@{level="0",args=[]@},
17066 frame=@{level="1",args=[name="strarg"]@},
17067 frame=@{level="2",args=[name="intarg",name="strarg"]@},
17068 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
17069 frame=@{level="4",args=[]@}]
17071 -stack-list-arguments 1
17074 frame=@{level="0",args=[]@},
17076 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
17077 frame=@{level="2",args=[
17078 @{name="intarg",value="2"@},
17079 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
17080 @{frame=@{level="3",args=[
17081 @{name="intarg",value="2"@},
17082 @{name="strarg",value="0x11940 \"A string argument.\""@},
17083 @{name="fltarg",value="3.5"@}]@},
17084 frame=@{level="4",args=[]@}]
17086 -stack-list-arguments 0 2 2
17087 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
17089 -stack-list-arguments 1 2 2
17090 ^done,stack-args=[frame=@{level="2",
17091 args=[@{name="intarg",value="2"@},
17092 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
17096 @c @subheading -stack-list-exception-handlers
17099 @subheading The @code{-stack-list-frames} Command
17100 @findex -stack-list-frames
17102 @subsubheading Synopsis
17105 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
17108 List the frames currently on the stack. For each frame it displays the
17113 The frame number, 0 being the topmost frame, i.e. the innermost function.
17115 The @code{$pc} value for that frame.
17119 File name of the source file where the function lives.
17121 Line number corresponding to the @code{$pc}.
17124 If invoked without arguments, this command prints a backtrace for the
17125 whole stack. If given two integer arguments, it shows the frames whose
17126 levels are between the two arguments (inclusive). If the two arguments
17127 are equal, it shows the single frame at the corresponding level.
17129 @subsubheading @value{GDBN} Command
17131 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
17133 @subsubheading Example
17135 Full stack backtrace:
17141 [frame=@{level="0",addr="0x0001076c",func="foo",
17142 file="recursive2.c",line="11"@},
17143 frame=@{level="1",addr="0x000107a4",func="foo",
17144 file="recursive2.c",line="14"@},
17145 frame=@{level="2",addr="0x000107a4",func="foo",
17146 file="recursive2.c",line="14"@},
17147 frame=@{level="3",addr="0x000107a4",func="foo",
17148 file="recursive2.c",line="14"@},
17149 frame=@{level="4",addr="0x000107a4",func="foo",
17150 file="recursive2.c",line="14"@},
17151 frame=@{level="5",addr="0x000107a4",func="foo",
17152 file="recursive2.c",line="14"@},
17153 frame=@{level="6",addr="0x000107a4",func="foo",
17154 file="recursive2.c",line="14"@},
17155 frame=@{level="7",addr="0x000107a4",func="foo",
17156 file="recursive2.c",line="14"@},
17157 frame=@{level="8",addr="0x000107a4",func="foo",
17158 file="recursive2.c",line="14"@},
17159 frame=@{level="9",addr="0x000107a4",func="foo",
17160 file="recursive2.c",line="14"@},
17161 frame=@{level="10",addr="0x000107a4",func="foo",
17162 file="recursive2.c",line="14"@},
17163 frame=@{level="11",addr="0x00010738",func="main",
17164 file="recursive2.c",line="4"@}]
17168 Show frames between @var{low_frame} and @var{high_frame}:
17172 -stack-list-frames 3 5
17174 [frame=@{level="3",addr="0x000107a4",func="foo",
17175 file="recursive2.c",line="14"@},
17176 frame=@{level="4",addr="0x000107a4",func="foo",
17177 file="recursive2.c",line="14"@},
17178 frame=@{level="5",addr="0x000107a4",func="foo",
17179 file="recursive2.c",line="14"@}]
17183 Show a single frame:
17187 -stack-list-frames 3 3
17189 [frame=@{level="3",addr="0x000107a4",func="foo",
17190 file="recursive2.c",line="14"@}]
17195 @subheading The @code{-stack-list-locals} Command
17196 @findex -stack-list-locals
17198 @subsubheading Synopsis
17201 -stack-list-locals @var{print-values}
17204 Display the local variable names for the current frame. With an
17205 argument of 0 prints only the names of the variables, with argument of 1
17206 prints also their values.
17208 @subsubheading @value{GDBN} Command
17210 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
17212 @subsubheading Example
17216 -stack-list-locals 0
17217 ^done,locals=[name="A",name="B",name="C"]
17219 -stack-list-locals 1
17220 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
17221 @{name="C",value="3"@}]
17226 @subheading The @code{-stack-select-frame} Command
17227 @findex -stack-select-frame
17229 @subsubheading Synopsis
17232 -stack-select-frame @var{framenum}
17235 Change the current frame. Select a different frame @var{framenum} on
17238 @subsubheading @value{GDBN} Command
17240 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
17241 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
17243 @subsubheading Example
17247 -stack-select-frame 2
17252 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17253 @node GDB/MI Symbol Query
17254 @section @sc{gdb/mi} Symbol Query Commands
17257 @subheading The @code{-symbol-info-address} Command
17258 @findex -symbol-info-address
17260 @subsubheading Synopsis
17263 -symbol-info-address @var{symbol}
17266 Describe where @var{symbol} is stored.
17268 @subsubheading @value{GDBN} Command
17270 The corresponding @value{GDBN} command is @samp{info address}.
17272 @subsubheading Example
17276 @subheading The @code{-symbol-info-file} Command
17277 @findex -symbol-info-file
17279 @subsubheading Synopsis
17285 Show the file for the symbol.
17287 @subsubheading @value{GDBN} Command
17289 There's no equivalent @value{GDBN} command. @code{gdbtk} has
17290 @samp{gdb_find_file}.
17292 @subsubheading Example
17296 @subheading The @code{-symbol-info-function} Command
17297 @findex -symbol-info-function
17299 @subsubheading Synopsis
17302 -symbol-info-function
17305 Show which function the symbol lives in.
17307 @subsubheading @value{GDBN} Command
17309 @samp{gdb_get_function} in @code{gdbtk}.
17311 @subsubheading Example
17315 @subheading The @code{-symbol-info-line} Command
17316 @findex -symbol-info-line
17318 @subsubheading Synopsis
17324 Show the core addresses of the code for a source line.
17326 @subsubheading @value{GDBN} Command
17328 The corresponding @value{GDBN} command is @samp{info line}.
17329 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
17331 @subsubheading Example
17335 @subheading The @code{-symbol-info-symbol} Command
17336 @findex -symbol-info-symbol
17338 @subsubheading Synopsis
17341 -symbol-info-symbol @var{addr}
17344 Describe what symbol is at location @var{addr}.
17346 @subsubheading @value{GDBN} Command
17348 The corresponding @value{GDBN} command is @samp{info symbol}.
17350 @subsubheading Example
17354 @subheading The @code{-symbol-list-functions} Command
17355 @findex -symbol-list-functions
17357 @subsubheading Synopsis
17360 -symbol-list-functions
17363 List the functions in the executable.
17365 @subsubheading @value{GDBN} Command
17367 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
17368 @samp{gdb_search} in @code{gdbtk}.
17370 @subsubheading Example
17374 @subheading The @code{-symbol-list-lines} Command
17375 @findex -symbol-list-lines
17377 @subsubheading Synopsis
17380 -symbol-list-lines @var{filename}
17383 Print the list of lines that contain code and their associated program
17384 addresses for the given source filename. The entries are sorted in
17385 ascending PC order.
17387 @subsubheading @value{GDBN} Command
17389 There is no corresponding @value{GDBN} command.
17391 @subsubheading Example
17394 -symbol-list-lines basics.c
17395 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
17400 @subheading The @code{-symbol-list-types} Command
17401 @findex -symbol-list-types
17403 @subsubheading Synopsis
17409 List all the type names.
17411 @subsubheading @value{GDBN} Command
17413 The corresponding commands are @samp{info types} in @value{GDBN},
17414 @samp{gdb_search} in @code{gdbtk}.
17416 @subsubheading Example
17420 @subheading The @code{-symbol-list-variables} Command
17421 @findex -symbol-list-variables
17423 @subsubheading Synopsis
17426 -symbol-list-variables
17429 List all the global and static variable names.
17431 @subsubheading @value{GDBN} Command
17433 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
17435 @subsubheading Example
17439 @subheading The @code{-symbol-locate} Command
17440 @findex -symbol-locate
17442 @subsubheading Synopsis
17448 @subsubheading @value{GDBN} Command
17450 @samp{gdb_loc} in @code{gdbtk}.
17452 @subsubheading Example
17456 @subheading The @code{-symbol-type} Command
17457 @findex -symbol-type
17459 @subsubheading Synopsis
17462 -symbol-type @var{variable}
17465 Show type of @var{variable}.
17467 @subsubheading @value{GDBN} Command
17469 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
17470 @samp{gdb_obj_variable}.
17472 @subsubheading Example
17476 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17477 @node GDB/MI Target Manipulation
17478 @section @sc{gdb/mi} Target Manipulation Commands
17481 @subheading The @code{-target-attach} Command
17482 @findex -target-attach
17484 @subsubheading Synopsis
17487 -target-attach @var{pid} | @var{file}
17490 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
17492 @subsubheading @value{GDBN} command
17494 The corresponding @value{GDBN} command is @samp{attach}.
17496 @subsubheading Example
17500 @subheading The @code{-target-compare-sections} Command
17501 @findex -target-compare-sections
17503 @subsubheading Synopsis
17506 -target-compare-sections [ @var{section} ]
17509 Compare data of section @var{section} on target to the exec file.
17510 Without the argument, all sections are compared.
17512 @subsubheading @value{GDBN} Command
17514 The @value{GDBN} equivalent is @samp{compare-sections}.
17516 @subsubheading Example
17520 @subheading The @code{-target-detach} Command
17521 @findex -target-detach
17523 @subsubheading Synopsis
17529 Disconnect from the remote target. There's no output.
17531 @subsubheading @value{GDBN} command
17533 The corresponding @value{GDBN} command is @samp{detach}.
17535 @subsubheading Example
17545 @subheading The @code{-target-disconnect} Command
17546 @findex -target-disconnect
17548 @subsubheading Synopsis
17554 Disconnect from the remote target. There's no output.
17556 @subsubheading @value{GDBN} command
17558 The corresponding @value{GDBN} command is @samp{disconnect}.
17560 @subsubheading Example
17570 @subheading The @code{-target-download} Command
17571 @findex -target-download
17573 @subsubheading Synopsis
17579 Loads the executable onto the remote target.
17580 It prints out an update message every half second, which includes the fields:
17584 The name of the section.
17586 The size of what has been sent so far for that section.
17588 The size of the section.
17590 The total size of what was sent so far (the current and the previous sections).
17592 The size of the overall executable to download.
17596 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
17597 @sc{gdb/mi} Output Syntax}).
17599 In addition, it prints the name and size of the sections, as they are
17600 downloaded. These messages include the following fields:
17604 The name of the section.
17606 The size of the section.
17608 The size of the overall executable to download.
17612 At the end, a summary is printed.
17614 @subsubheading @value{GDBN} Command
17616 The corresponding @value{GDBN} command is @samp{load}.
17618 @subsubheading Example
17620 Note: each status message appears on a single line. Here the messages
17621 have been broken down so that they can fit onto a page.
17626 +download,@{section=".text",section-size="6668",total-size="9880"@}
17627 +download,@{section=".text",section-sent="512",section-size="6668",
17628 total-sent="512",total-size="9880"@}
17629 +download,@{section=".text",section-sent="1024",section-size="6668",
17630 total-sent="1024",total-size="9880"@}
17631 +download,@{section=".text",section-sent="1536",section-size="6668",
17632 total-sent="1536",total-size="9880"@}
17633 +download,@{section=".text",section-sent="2048",section-size="6668",
17634 total-sent="2048",total-size="9880"@}
17635 +download,@{section=".text",section-sent="2560",section-size="6668",
17636 total-sent="2560",total-size="9880"@}
17637 +download,@{section=".text",section-sent="3072",section-size="6668",
17638 total-sent="3072",total-size="9880"@}
17639 +download,@{section=".text",section-sent="3584",section-size="6668",
17640 total-sent="3584",total-size="9880"@}
17641 +download,@{section=".text",section-sent="4096",section-size="6668",
17642 total-sent="4096",total-size="9880"@}
17643 +download,@{section=".text",section-sent="4608",section-size="6668",
17644 total-sent="4608",total-size="9880"@}
17645 +download,@{section=".text",section-sent="5120",section-size="6668",
17646 total-sent="5120",total-size="9880"@}
17647 +download,@{section=".text",section-sent="5632",section-size="6668",
17648 total-sent="5632",total-size="9880"@}
17649 +download,@{section=".text",section-sent="6144",section-size="6668",
17650 total-sent="6144",total-size="9880"@}
17651 +download,@{section=".text",section-sent="6656",section-size="6668",
17652 total-sent="6656",total-size="9880"@}
17653 +download,@{section=".init",section-size="28",total-size="9880"@}
17654 +download,@{section=".fini",section-size="28",total-size="9880"@}
17655 +download,@{section=".data",section-size="3156",total-size="9880"@}
17656 +download,@{section=".data",section-sent="512",section-size="3156",
17657 total-sent="7236",total-size="9880"@}
17658 +download,@{section=".data",section-sent="1024",section-size="3156",
17659 total-sent="7748",total-size="9880"@}
17660 +download,@{section=".data",section-sent="1536",section-size="3156",
17661 total-sent="8260",total-size="9880"@}
17662 +download,@{section=".data",section-sent="2048",section-size="3156",
17663 total-sent="8772",total-size="9880"@}
17664 +download,@{section=".data",section-sent="2560",section-size="3156",
17665 total-sent="9284",total-size="9880"@}
17666 +download,@{section=".data",section-sent="3072",section-size="3156",
17667 total-sent="9796",total-size="9880"@}
17668 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
17674 @subheading The @code{-target-exec-status} Command
17675 @findex -target-exec-status
17677 @subsubheading Synopsis
17680 -target-exec-status
17683 Provide information on the state of the target (whether it is running or
17684 not, for instance).
17686 @subsubheading @value{GDBN} Command
17688 There's no equivalent @value{GDBN} command.
17690 @subsubheading Example
17694 @subheading The @code{-target-list-available-targets} Command
17695 @findex -target-list-available-targets
17697 @subsubheading Synopsis
17700 -target-list-available-targets
17703 List the possible targets to connect to.
17705 @subsubheading @value{GDBN} Command
17707 The corresponding @value{GDBN} command is @samp{help target}.
17709 @subsubheading Example
17713 @subheading The @code{-target-list-current-targets} Command
17714 @findex -target-list-current-targets
17716 @subsubheading Synopsis
17719 -target-list-current-targets
17722 Describe the current target.
17724 @subsubheading @value{GDBN} Command
17726 The corresponding information is printed by @samp{info file} (among
17729 @subsubheading Example
17733 @subheading The @code{-target-list-parameters} Command
17734 @findex -target-list-parameters
17736 @subsubheading Synopsis
17739 -target-list-parameters
17744 @subsubheading @value{GDBN} Command
17748 @subsubheading Example
17752 @subheading The @code{-target-select} Command
17753 @findex -target-select
17755 @subsubheading Synopsis
17758 -target-select @var{type} @var{parameters @dots{}}
17761 Connect @value{GDBN} to the remote target. This command takes two args:
17765 The type of target, for instance @samp{async}, @samp{remote}, etc.
17766 @item @var{parameters}
17767 Device names, host names and the like. @xref{Target Commands, ,
17768 Commands for managing targets}, for more details.
17771 The output is a connection notification, followed by the address at
17772 which the target program is, in the following form:
17775 ^connected,addr="@var{address}",func="@var{function name}",
17776 args=[@var{arg list}]
17779 @subsubheading @value{GDBN} Command
17781 The corresponding @value{GDBN} command is @samp{target}.
17783 @subsubheading Example
17787 -target-select async /dev/ttya
17788 ^connected,addr="0xfe00a300",func="??",args=[]
17792 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17793 @node GDB/MI Thread Commands
17794 @section @sc{gdb/mi} Thread Commands
17797 @subheading The @code{-thread-info} Command
17798 @findex -thread-info
17800 @subsubheading Synopsis
17806 @subsubheading @value{GDBN} command
17810 @subsubheading Example
17814 @subheading The @code{-thread-list-all-threads} Command
17815 @findex -thread-list-all-threads
17817 @subsubheading Synopsis
17820 -thread-list-all-threads
17823 @subsubheading @value{GDBN} Command
17825 The equivalent @value{GDBN} command is @samp{info threads}.
17827 @subsubheading Example
17831 @subheading The @code{-thread-list-ids} Command
17832 @findex -thread-list-ids
17834 @subsubheading Synopsis
17840 Produces a list of the currently known @value{GDBN} thread ids. At the
17841 end of the list it also prints the total number of such threads.
17843 @subsubheading @value{GDBN} Command
17845 Part of @samp{info threads} supplies the same information.
17847 @subsubheading Example
17849 No threads present, besides the main process:
17854 ^done,thread-ids=@{@},number-of-threads="0"
17864 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
17865 number-of-threads="3"
17870 @subheading The @code{-thread-select} Command
17871 @findex -thread-select
17873 @subsubheading Synopsis
17876 -thread-select @var{threadnum}
17879 Make @var{threadnum} the current thread. It prints the number of the new
17880 current thread, and the topmost frame for that thread.
17882 @subsubheading @value{GDBN} Command
17884 The corresponding @value{GDBN} command is @samp{thread}.
17886 @subsubheading Example
17893 *stopped,reason="end-stepping-range",thread-id="2",line="187",
17894 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
17898 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
17899 number-of-threads="3"
17902 ^done,new-thread-id="3",
17903 frame=@{level="0",func="vprintf",
17904 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
17905 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
17909 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17910 @node GDB/MI Tracepoint Commands
17911 @section @sc{gdb/mi} Tracepoint Commands
17913 The tracepoint commands are not yet implemented.
17915 @c @subheading -trace-actions
17917 @c @subheading -trace-delete
17919 @c @subheading -trace-disable
17921 @c @subheading -trace-dump
17923 @c @subheading -trace-enable
17925 @c @subheading -trace-exists
17927 @c @subheading -trace-find
17929 @c @subheading -trace-frame-number
17931 @c @subheading -trace-info
17933 @c @subheading -trace-insert
17935 @c @subheading -trace-list
17937 @c @subheading -trace-pass-count
17939 @c @subheading -trace-save
17941 @c @subheading -trace-start
17943 @c @subheading -trace-stop
17946 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17947 @node GDB/MI Variable Objects
17948 @section @sc{gdb/mi} Variable Objects
17951 @subheading Motivation for Variable Objects in @sc{gdb/mi}
17953 For the implementation of a variable debugger window (locals, watched
17954 expressions, etc.), we are proposing the adaptation of the existing code
17955 used by @code{Insight}.
17957 The two main reasons for that are:
17961 It has been proven in practice (it is already on its second generation).
17964 It will shorten development time (needless to say how important it is
17968 The original interface was designed to be used by Tcl code, so it was
17969 slightly changed so it could be used through @sc{gdb/mi}. This section
17970 describes the @sc{gdb/mi} operations that will be available and gives some
17971 hints about their use.
17973 @emph{Note}: In addition to the set of operations described here, we
17974 expect the @sc{gui} implementation of a variable window to require, at
17975 least, the following operations:
17978 @item @code{-gdb-show} @code{output-radix}
17979 @item @code{-stack-list-arguments}
17980 @item @code{-stack-list-locals}
17981 @item @code{-stack-select-frame}
17984 @subheading Introduction to Variable Objects in @sc{gdb/mi}
17986 @cindex variable objects in @sc{gdb/mi}
17987 The basic idea behind variable objects is the creation of a named object
17988 to represent a variable, an expression, a memory location or even a CPU
17989 register. For each object created, a set of operations is available for
17990 examining or changing its properties.
17992 Furthermore, complex data types, such as C structures, are represented
17993 in a tree format. For instance, the @code{struct} type variable is the
17994 root and the children will represent the struct members. If a child
17995 is itself of a complex type, it will also have children of its own.
17996 Appropriate language differences are handled for C, C@t{++} and Java.
17998 When returning the actual values of the objects, this facility allows
17999 for the individual selection of the display format used in the result
18000 creation. It can be chosen among: binary, decimal, hexadecimal, octal
18001 and natural. Natural refers to a default format automatically
18002 chosen based on the variable type (like decimal for an @code{int}, hex
18003 for pointers, etc.).
18005 The following is the complete set of @sc{gdb/mi} operations defined to
18006 access this functionality:
18008 @multitable @columnfractions .4 .6
18009 @item @strong{Operation}
18010 @tab @strong{Description}
18012 @item @code{-var-create}
18013 @tab create a variable object
18014 @item @code{-var-delete}
18015 @tab delete the variable object and its children
18016 @item @code{-var-set-format}
18017 @tab set the display format of this variable
18018 @item @code{-var-show-format}
18019 @tab show the display format of this variable
18020 @item @code{-var-info-num-children}
18021 @tab tells how many children this object has
18022 @item @code{-var-list-children}
18023 @tab return a list of the object's children
18024 @item @code{-var-info-type}
18025 @tab show the type of this variable object
18026 @item @code{-var-info-expression}
18027 @tab print what this variable object represents
18028 @item @code{-var-show-attributes}
18029 @tab is this variable editable? does it exist here?
18030 @item @code{-var-evaluate-expression}
18031 @tab get the value of this variable
18032 @item @code{-var-assign}
18033 @tab set the value of this variable
18034 @item @code{-var-update}
18035 @tab update the variable and its children
18038 In the next subsection we describe each operation in detail and suggest
18039 how it can be used.
18041 @subheading Description And Use of Operations on Variable Objects
18043 @subheading The @code{-var-create} Command
18044 @findex -var-create
18046 @subsubheading Synopsis
18049 -var-create @{@var{name} | "-"@}
18050 @{@var{frame-addr} | "*"@} @var{expression}
18053 This operation creates a variable object, which allows the monitoring of
18054 a variable, the result of an expression, a memory cell or a CPU
18057 The @var{name} parameter is the string by which the object can be
18058 referenced. It must be unique. If @samp{-} is specified, the varobj
18059 system will generate a string ``varNNNNNN'' automatically. It will be
18060 unique provided that one does not specify @var{name} on that format.
18061 The command fails if a duplicate name is found.
18063 The frame under which the expression should be evaluated can be
18064 specified by @var{frame-addr}. A @samp{*} indicates that the current
18065 frame should be used.
18067 @var{expression} is any expression valid on the current language set (must not
18068 begin with a @samp{*}), or one of the following:
18072 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
18075 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
18078 @samp{$@var{regname}} --- a CPU register name
18081 @subsubheading Result
18083 This operation returns the name, number of children and the type of the
18084 object created. Type is returned as a string as the ones generated by
18085 the @value{GDBN} CLI:
18088 name="@var{name}",numchild="N",type="@var{type}"
18092 @subheading The @code{-var-delete} Command
18093 @findex -var-delete
18095 @subsubheading Synopsis
18098 -var-delete @var{name}
18101 Deletes a previously created variable object and all of its children.
18103 Returns an error if the object @var{name} is not found.
18106 @subheading The @code{-var-set-format} Command
18107 @findex -var-set-format
18109 @subsubheading Synopsis
18112 -var-set-format @var{name} @var{format-spec}
18115 Sets the output format for the value of the object @var{name} to be
18118 The syntax for the @var{format-spec} is as follows:
18121 @var{format-spec} @expansion{}
18122 @{binary | decimal | hexadecimal | octal | natural@}
18126 @subheading The @code{-var-show-format} Command
18127 @findex -var-show-format
18129 @subsubheading Synopsis
18132 -var-show-format @var{name}
18135 Returns the format used to display the value of the object @var{name}.
18138 @var{format} @expansion{}
18143 @subheading The @code{-var-info-num-children} Command
18144 @findex -var-info-num-children
18146 @subsubheading Synopsis
18149 -var-info-num-children @var{name}
18152 Returns the number of children of a variable object @var{name}:
18159 @subheading The @code{-var-list-children} Command
18160 @findex -var-list-children
18162 @subsubheading Synopsis
18165 -var-list-children @var{name}
18168 Returns a list of the children of the specified variable object:
18171 numchild=@var{n},children=[@{name=@var{name},
18172 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
18176 @subheading The @code{-var-info-type} Command
18177 @findex -var-info-type
18179 @subsubheading Synopsis
18182 -var-info-type @var{name}
18185 Returns the type of the specified variable @var{name}. The type is
18186 returned as a string in the same format as it is output by the
18190 type=@var{typename}
18194 @subheading The @code{-var-info-expression} Command
18195 @findex -var-info-expression
18197 @subsubheading Synopsis
18200 -var-info-expression @var{name}
18203 Returns what is represented by the variable object @var{name}:
18206 lang=@var{lang-spec},exp=@var{expression}
18210 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
18212 @subheading The @code{-var-show-attributes} Command
18213 @findex -var-show-attributes
18215 @subsubheading Synopsis
18218 -var-show-attributes @var{name}
18221 List attributes of the specified variable object @var{name}:
18224 status=@var{attr} [ ( ,@var{attr} )* ]
18228 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
18230 @subheading The @code{-var-evaluate-expression} Command
18231 @findex -var-evaluate-expression
18233 @subsubheading Synopsis
18236 -var-evaluate-expression @var{name}
18239 Evaluates the expression that is represented by the specified variable
18240 object and returns its value as a string in the current format specified
18247 Note that one must invoke @code{-var-list-children} for a variable
18248 before the value of a child variable can be evaluated.
18250 @subheading The @code{-var-assign} Command
18251 @findex -var-assign
18253 @subsubheading Synopsis
18256 -var-assign @var{name} @var{expression}
18259 Assigns the value of @var{expression} to the variable object specified
18260 by @var{name}. The object must be @samp{editable}. If the variable's
18261 value is altered by the assign, the variable will show up in any
18262 subsequent @code{-var-update} list.
18264 @subsubheading Example
18272 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
18276 @subheading The @code{-var-update} Command
18277 @findex -var-update
18279 @subsubheading Synopsis
18282 -var-update @{@var{name} | "*"@}
18285 Update the value of the variable object @var{name} by evaluating its
18286 expression after fetching all the new values from memory or registers.
18287 A @samp{*} causes all existing variable objects to be updated.
18291 @chapter @value{GDBN} Annotations
18293 This chapter describes annotations in @value{GDBN}. Annotations were
18294 designed to interface @value{GDBN} to graphical user interfaces or other
18295 similar programs which want to interact with @value{GDBN} at a
18296 relatively high level.
18298 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
18302 This is Edition @value{EDITION}, @value{DATE}.
18306 * Annotations Overview:: What annotations are; the general syntax.
18307 * Server Prefix:: Issuing a command without affecting user state.
18308 * Prompting:: Annotations marking @value{GDBN}'s need for input.
18309 * Errors:: Annotations for error messages.
18310 * Invalidation:: Some annotations describe things now invalid.
18311 * Annotations for Running::
18312 Whether the program is running, how it stopped, etc.
18313 * Source Annotations:: Annotations describing source code.
18316 @node Annotations Overview
18317 @section What is an Annotation?
18318 @cindex annotations
18320 Annotations start with a newline character, two @samp{control-z}
18321 characters, and the name of the annotation. If there is no additional
18322 information associated with this annotation, the name of the annotation
18323 is followed immediately by a newline. If there is additional
18324 information, the name of the annotation is followed by a space, the
18325 additional information, and a newline. The additional information
18326 cannot contain newline characters.
18328 Any output not beginning with a newline and two @samp{control-z}
18329 characters denotes literal output from @value{GDBN}. Currently there is
18330 no need for @value{GDBN} to output a newline followed by two
18331 @samp{control-z} characters, but if there was such a need, the
18332 annotations could be extended with an @samp{escape} annotation which
18333 means those three characters as output.
18335 The annotation @var{level}, which is specified using the
18336 @option{--annotate} command line option (@pxref{Mode Options}), controls
18337 how much information @value{GDBN} prints together with its prompt,
18338 values of expressions, source lines, and other types of output. Level 0
18339 is for no anntations, level 1 is for use when @value{GDBN} is run as a
18340 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
18341 for programs that control @value{GDBN}, and level 2 annotations have
18342 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
18343 Interface, annotate, GDB's Obsolete Annotations}). This chapter
18344 describes level 3 annotations.
18346 A simple example of starting up @value{GDBN} with annotations is:
18349 $ @kbd{gdb --annotate=3}
18351 Copyright 2003 Free Software Foundation, Inc.
18352 GDB is free software, covered by the GNU General Public License,
18353 and you are welcome to change it and/or distribute copies of it
18354 under certain conditions.
18355 Type "show copying" to see the conditions.
18356 There is absolutely no warranty for GDB. Type "show warranty"
18358 This GDB was configured as "i386-pc-linux-gnu"
18369 Here @samp{quit} is input to @value{GDBN}; the rest is output from
18370 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
18371 denotes a @samp{control-z} character) are annotations; the rest is
18372 output from @value{GDBN}.
18374 @node Server Prefix
18375 @section The Server Prefix
18376 @cindex server prefix for annotations
18378 To issue a command to @value{GDBN} without affecting certain aspects of
18379 the state which is seen by users, prefix it with @samp{server }. This
18380 means that this command will not affect the command history, nor will it
18381 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
18382 pressed on a line by itself.
18384 The server prefix does not affect the recording of values into the value
18385 history; to print a value without recording it into the value history,
18386 use the @code{output} command instead of the @code{print} command.
18389 @section Annotation for @value{GDBN} Input
18391 @cindex annotations for prompts
18392 When @value{GDBN} prompts for input, it annotates this fact so it is possible
18393 to know when to send output, when the output from a given command is
18396 Different kinds of input each have a different @dfn{input type}. Each
18397 input type has three annotations: a @code{pre-} annotation, which
18398 denotes the beginning of any prompt which is being output, a plain
18399 annotation, which denotes the end of the prompt, and then a @code{post-}
18400 annotation which denotes the end of any echo which may (or may not) be
18401 associated with the input. For example, the @code{prompt} input type
18402 features the following annotations:
18410 The input types are
18415 @findex post-prompt
18417 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
18419 @findex pre-commands
18421 @findex post-commands
18423 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
18424 command. The annotations are repeated for each command which is input.
18426 @findex pre-overload-choice
18427 @findex overload-choice
18428 @findex post-overload-choice
18429 @item overload-choice
18430 When @value{GDBN} wants the user to select between various overloaded functions.
18436 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
18438 @findex pre-prompt-for-continue
18439 @findex prompt-for-continue
18440 @findex post-prompt-for-continue
18441 @item prompt-for-continue
18442 When @value{GDBN} is asking the user to press return to continue. Note: Don't
18443 expect this to work well; instead use @code{set height 0} to disable
18444 prompting. This is because the counting of lines is buggy in the
18445 presence of annotations.
18450 @cindex annotations for errors, warnings and interrupts
18457 This annotation occurs right before @value{GDBN} responds to an interrupt.
18464 This annotation occurs right before @value{GDBN} responds to an error.
18466 Quit and error annotations indicate that any annotations which @value{GDBN} was
18467 in the middle of may end abruptly. For example, if a
18468 @code{value-history-begin} annotation is followed by a @code{error}, one
18469 cannot expect to receive the matching @code{value-history-end}. One
18470 cannot expect not to receive it either, however; an error annotation
18471 does not necessarily mean that @value{GDBN} is immediately returning all the way
18474 @findex error-begin
18475 A quit or error annotation may be preceded by
18481 Any output between that and the quit or error annotation is the error
18484 Warning messages are not yet annotated.
18485 @c If we want to change that, need to fix warning(), type_error(),
18486 @c range_error(), and possibly other places.
18489 @section Invalidation Notices
18491 @cindex annotations for invalidation messages
18492 The following annotations say that certain pieces of state may have
18496 @findex frames-invalid
18497 @item ^Z^Zframes-invalid
18499 The frames (for example, output from the @code{backtrace} command) may
18502 @findex breakpoints-invalid
18503 @item ^Z^Zbreakpoints-invalid
18505 The breakpoints may have changed. For example, the user just added or
18506 deleted a breakpoint.
18509 @node Annotations for Running
18510 @section Running the Program
18511 @cindex annotations for running programs
18515 When the program starts executing due to a @value{GDBN} command such as
18516 @code{step} or @code{continue},
18522 is output. When the program stops,
18528 is output. Before the @code{stopped} annotation, a variety of
18529 annotations describe how the program stopped.
18533 @item ^Z^Zexited @var{exit-status}
18534 The program exited, and @var{exit-status} is the exit status (zero for
18535 successful exit, otherwise nonzero).
18538 @findex signal-name
18539 @findex signal-name-end
18540 @findex signal-string
18541 @findex signal-string-end
18542 @item ^Z^Zsignalled
18543 The program exited with a signal. After the @code{^Z^Zsignalled}, the
18544 annotation continues:
18550 ^Z^Zsignal-name-end
18554 ^Z^Zsignal-string-end
18559 where @var{name} is the name of the signal, such as @code{SIGILL} or
18560 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
18561 as @code{Illegal Instruction} or @code{Segmentation fault}.
18562 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
18563 user's benefit and have no particular format.
18567 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
18568 just saying that the program received the signal, not that it was
18569 terminated with it.
18572 @item ^Z^Zbreakpoint @var{number}
18573 The program hit breakpoint number @var{number}.
18576 @item ^Z^Zwatchpoint @var{number}
18577 The program hit watchpoint number @var{number}.
18580 @node Source Annotations
18581 @section Displaying Source
18582 @cindex annotations for source display
18585 The following annotation is used instead of displaying source code:
18588 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
18591 where @var{filename} is an absolute file name indicating which source
18592 file, @var{line} is the line number within that file (where 1 is the
18593 first line in the file), @var{character} is the character position
18594 within the file (where 0 is the first character in the file) (for most
18595 debug formats this will necessarily point to the beginning of a line),
18596 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
18597 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
18598 @var{addr} is the address in the target program associated with the
18599 source which is being displayed. @var{addr} is in the form @samp{0x}
18600 followed by one or more lowercase hex digits (note that this does not
18601 depend on the language).
18604 @chapter Reporting Bugs in @value{GDBN}
18605 @cindex bugs in @value{GDBN}
18606 @cindex reporting bugs in @value{GDBN}
18608 Your bug reports play an essential role in making @value{GDBN} reliable.
18610 Reporting a bug may help you by bringing a solution to your problem, or it
18611 may not. But in any case the principal function of a bug report is to help
18612 the entire community by making the next version of @value{GDBN} work better. Bug
18613 reports are your contribution to the maintenance of @value{GDBN}.
18615 In order for a bug report to serve its purpose, you must include the
18616 information that enables us to fix the bug.
18619 * Bug Criteria:: Have you found a bug?
18620 * Bug Reporting:: How to report bugs
18624 @section Have you found a bug?
18625 @cindex bug criteria
18627 If you are not sure whether you have found a bug, here are some guidelines:
18630 @cindex fatal signal
18631 @cindex debugger crash
18632 @cindex crash of debugger
18634 If the debugger gets a fatal signal, for any input whatever, that is a
18635 @value{GDBN} bug. Reliable debuggers never crash.
18637 @cindex error on valid input
18639 If @value{GDBN} produces an error message for valid input, that is a
18640 bug. (Note that if you're cross debugging, the problem may also be
18641 somewhere in the connection to the target.)
18643 @cindex invalid input
18645 If @value{GDBN} does not produce an error message for invalid input,
18646 that is a bug. However, you should note that your idea of
18647 ``invalid input'' might be our idea of ``an extension'' or ``support
18648 for traditional practice''.
18651 If you are an experienced user of debugging tools, your suggestions
18652 for improvement of @value{GDBN} are welcome in any case.
18655 @node Bug Reporting
18656 @section How to report bugs
18657 @cindex bug reports
18658 @cindex @value{GDBN} bugs, reporting
18660 A number of companies and individuals offer support for @sc{gnu} products.
18661 If you obtained @value{GDBN} from a support organization, we recommend you
18662 contact that organization first.
18664 You can find contact information for many support companies and
18665 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
18667 @c should add a web page ref...
18669 In any event, we also recommend that you submit bug reports for
18670 @value{GDBN}. The prefered method is to submit them directly using
18671 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
18672 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
18675 @strong{Do not send bug reports to @samp{info-gdb}, or to
18676 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
18677 not want to receive bug reports. Those that do have arranged to receive
18680 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
18681 serves as a repeater. The mailing list and the newsgroup carry exactly
18682 the same messages. Often people think of posting bug reports to the
18683 newsgroup instead of mailing them. This appears to work, but it has one
18684 problem which can be crucial: a newsgroup posting often lacks a mail
18685 path back to the sender. Thus, if we need to ask for more information,
18686 we may be unable to reach you. For this reason, it is better to send
18687 bug reports to the mailing list.
18689 The fundamental principle of reporting bugs usefully is this:
18690 @strong{report all the facts}. If you are not sure whether to state a
18691 fact or leave it out, state it!
18693 Often people omit facts because they think they know what causes the
18694 problem and assume that some details do not matter. Thus, you might
18695 assume that the name of the variable you use in an example does not matter.
18696 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
18697 stray memory reference which happens to fetch from the location where that
18698 name is stored in memory; perhaps, if the name were different, the contents
18699 of that location would fool the debugger into doing the right thing despite
18700 the bug. Play it safe and give a specific, complete example. That is the
18701 easiest thing for you to do, and the most helpful.
18703 Keep in mind that the purpose of a bug report is to enable us to fix the
18704 bug. It may be that the bug has been reported previously, but neither
18705 you nor we can know that unless your bug report is complete and
18708 Sometimes people give a few sketchy facts and ask, ``Does this ring a
18709 bell?'' Those bug reports are useless, and we urge everyone to
18710 @emph{refuse to respond to them} except to chide the sender to report
18713 To enable us to fix the bug, you should include all these things:
18717 The version of @value{GDBN}. @value{GDBN} announces it if you start
18718 with no arguments; you can also print it at any time using @code{show
18721 Without this, we will not know whether there is any point in looking for
18722 the bug in the current version of @value{GDBN}.
18725 The type of machine you are using, and the operating system name and
18729 What compiler (and its version) was used to compile @value{GDBN}---e.g.
18730 ``@value{GCC}--2.8.1''.
18733 What compiler (and its version) was used to compile the program you are
18734 debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
18735 C Compiler''. For GCC, you can say @code{gcc --version} to get this
18736 information; for other compilers, see the documentation for those
18740 The command arguments you gave the compiler to compile your example and
18741 observe the bug. For example, did you use @samp{-O}? To guarantee
18742 you will not omit something important, list them all. A copy of the
18743 Makefile (or the output from make) is sufficient.
18745 If we were to try to guess the arguments, we would probably guess wrong
18746 and then we might not encounter the bug.
18749 A complete input script, and all necessary source files, that will
18753 A description of what behavior you observe that you believe is
18754 incorrect. For example, ``It gets a fatal signal.''
18756 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
18757 will certainly notice it. But if the bug is incorrect output, we might
18758 not notice unless it is glaringly wrong. You might as well not give us
18759 a chance to make a mistake.
18761 Even if the problem you experience is a fatal signal, you should still
18762 say so explicitly. Suppose something strange is going on, such as, your
18763 copy of @value{GDBN} is out of synch, or you have encountered a bug in
18764 the C library on your system. (This has happened!) Your copy might
18765 crash and ours would not. If you told us to expect a crash, then when
18766 ours fails to crash, we would know that the bug was not happening for
18767 us. If you had not told us to expect a crash, then we would not be able
18768 to draw any conclusion from our observations.
18771 If you wish to suggest changes to the @value{GDBN} source, send us context
18772 diffs. If you even discuss something in the @value{GDBN} source, refer to
18773 it by context, not by line number.
18775 The line numbers in our development sources will not match those in your
18776 sources. Your line numbers would convey no useful information to us.
18780 Here are some things that are not necessary:
18784 A description of the envelope of the bug.
18786 Often people who encounter a bug spend a lot of time investigating
18787 which changes to the input file will make the bug go away and which
18788 changes will not affect it.
18790 This is often time consuming and not very useful, because the way we
18791 will find the bug is by running a single example under the debugger
18792 with breakpoints, not by pure deduction from a series of examples.
18793 We recommend that you save your time for something else.
18795 Of course, if you can find a simpler example to report @emph{instead}
18796 of the original one, that is a convenience for us. Errors in the
18797 output will be easier to spot, running under the debugger will take
18798 less time, and so on.
18800 However, simplification is not vital; if you do not want to do this,
18801 report the bug anyway and send us the entire test case you used.
18804 A patch for the bug.
18806 A patch for the bug does help us if it is a good one. But do not omit
18807 the necessary information, such as the test case, on the assumption that
18808 a patch is all we need. We might see problems with your patch and decide
18809 to fix the problem another way, or we might not understand it at all.
18811 Sometimes with a program as complicated as @value{GDBN} it is very hard to
18812 construct an example that will make the program follow a certain path
18813 through the code. If you do not send us the example, we will not be able
18814 to construct one, so we will not be able to verify that the bug is fixed.
18816 And if we cannot understand what bug you are trying to fix, or why your
18817 patch should be an improvement, we will not install it. A test case will
18818 help us to understand.
18821 A guess about what the bug is or what it depends on.
18823 Such guesses are usually wrong. Even we cannot guess right about such
18824 things without first using the debugger to find the facts.
18827 @c The readline documentation is distributed with the readline code
18828 @c and consists of the two following files:
18830 @c inc-hist.texinfo
18831 @c Use -I with makeinfo to point to the appropriate directory,
18832 @c environment var TEXINPUTS with TeX.
18833 @include rluser.texinfo
18834 @include inc-hist.texinfo
18837 @node Formatting Documentation
18838 @appendix Formatting Documentation
18840 @cindex @value{GDBN} reference card
18841 @cindex reference card
18842 The @value{GDBN} 4 release includes an already-formatted reference card, ready
18843 for printing with PostScript or Ghostscript, in the @file{gdb}
18844 subdirectory of the main source directory@footnote{In
18845 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
18846 release.}. If you can use PostScript or Ghostscript with your printer,
18847 you can print the reference card immediately with @file{refcard.ps}.
18849 The release also includes the source for the reference card. You
18850 can format it, using @TeX{}, by typing:
18856 The @value{GDBN} reference card is designed to print in @dfn{landscape}
18857 mode on US ``letter'' size paper;
18858 that is, on a sheet 11 inches wide by 8.5 inches
18859 high. You will need to specify this form of printing as an option to
18860 your @sc{dvi} output program.
18862 @cindex documentation
18864 All the documentation for @value{GDBN} comes as part of the machine-readable
18865 distribution. The documentation is written in Texinfo format, which is
18866 a documentation system that uses a single source file to produce both
18867 on-line information and a printed manual. You can use one of the Info
18868 formatting commands to create the on-line version of the documentation
18869 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
18871 @value{GDBN} includes an already formatted copy of the on-line Info
18872 version of this manual in the @file{gdb} subdirectory. The main Info
18873 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
18874 subordinate files matching @samp{gdb.info*} in the same directory. If
18875 necessary, you can print out these files, or read them with any editor;
18876 but they are easier to read using the @code{info} subsystem in @sc{gnu}
18877 Emacs or the standalone @code{info} program, available as part of the
18878 @sc{gnu} Texinfo distribution.
18880 If you want to format these Info files yourself, you need one of the
18881 Info formatting programs, such as @code{texinfo-format-buffer} or
18884 If you have @code{makeinfo} installed, and are in the top level
18885 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
18886 version @value{GDBVN}), you can make the Info file by typing:
18893 If you want to typeset and print copies of this manual, you need @TeX{},
18894 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
18895 Texinfo definitions file.
18897 @TeX{} is a typesetting program; it does not print files directly, but
18898 produces output files called @sc{dvi} files. To print a typeset
18899 document, you need a program to print @sc{dvi} files. If your system
18900 has @TeX{} installed, chances are it has such a program. The precise
18901 command to use depends on your system; @kbd{lpr -d} is common; another
18902 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
18903 require a file name without any extension or a @samp{.dvi} extension.
18905 @TeX{} also requires a macro definitions file called
18906 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
18907 written in Texinfo format. On its own, @TeX{} cannot either read or
18908 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
18909 and is located in the @file{gdb-@var{version-number}/texinfo}
18912 If you have @TeX{} and a @sc{dvi} printer program installed, you can
18913 typeset and print this manual. First switch to the the @file{gdb}
18914 subdirectory of the main source directory (for example, to
18915 @file{gdb-@value{GDBVN}/gdb}) and type:
18921 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
18923 @node Installing GDB
18924 @appendix Installing @value{GDBN}
18925 @cindex configuring @value{GDBN}
18926 @cindex installation
18927 @cindex configuring @value{GDBN}, and source tree subdirectories
18929 @value{GDBN} comes with a @code{configure} script that automates the process
18930 of preparing @value{GDBN} for installation; you can then use @code{make} to
18931 build the @code{gdb} program.
18933 @c irrelevant in info file; it's as current as the code it lives with.
18934 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
18935 look at the @file{README} file in the sources; we may have improved the
18936 installation procedures since publishing this manual.}
18939 The @value{GDBN} distribution includes all the source code you need for
18940 @value{GDBN} in a single directory, whose name is usually composed by
18941 appending the version number to @samp{gdb}.
18943 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
18944 @file{gdb-@value{GDBVN}} directory. That directory contains:
18947 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
18948 script for configuring @value{GDBN} and all its supporting libraries
18950 @item gdb-@value{GDBVN}/gdb
18951 the source specific to @value{GDBN} itself
18953 @item gdb-@value{GDBVN}/bfd
18954 source for the Binary File Descriptor library
18956 @item gdb-@value{GDBVN}/include
18957 @sc{gnu} include files
18959 @item gdb-@value{GDBVN}/libiberty
18960 source for the @samp{-liberty} free software library
18962 @item gdb-@value{GDBVN}/opcodes
18963 source for the library of opcode tables and disassemblers
18965 @item gdb-@value{GDBVN}/readline
18966 source for the @sc{gnu} command-line interface
18968 @item gdb-@value{GDBVN}/glob
18969 source for the @sc{gnu} filename pattern-matching subroutine
18971 @item gdb-@value{GDBVN}/mmalloc
18972 source for the @sc{gnu} memory-mapped malloc package
18975 The simplest way to configure and build @value{GDBN} is to run @code{configure}
18976 from the @file{gdb-@var{version-number}} source directory, which in
18977 this example is the @file{gdb-@value{GDBVN}} directory.
18979 First switch to the @file{gdb-@var{version-number}} source directory
18980 if you are not already in it; then run @code{configure}. Pass the
18981 identifier for the platform on which @value{GDBN} will run as an
18987 cd gdb-@value{GDBVN}
18988 ./configure @var{host}
18993 where @var{host} is an identifier such as @samp{sun4} or
18994 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
18995 (You can often leave off @var{host}; @code{configure} tries to guess the
18996 correct value by examining your system.)
18998 Running @samp{configure @var{host}} and then running @code{make} builds the
18999 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
19000 libraries, then @code{gdb} itself. The configured source files, and the
19001 binaries, are left in the corresponding source directories.
19004 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
19005 system does not recognize this automatically when you run a different
19006 shell, you may need to run @code{sh} on it explicitly:
19009 sh configure @var{host}
19012 If you run @code{configure} from a directory that contains source
19013 directories for multiple libraries or programs, such as the
19014 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
19015 creates configuration files for every directory level underneath (unless
19016 you tell it not to, with the @samp{--norecursion} option).
19018 You should run the @code{configure} script from the top directory in the
19019 source tree, the @file{gdb-@var{version-number}} directory. If you run
19020 @code{configure} from one of the subdirectories, you will configure only
19021 that subdirectory. That is usually not what you want. In particular,
19022 if you run the first @code{configure} from the @file{gdb} subdirectory
19023 of the @file{gdb-@var{version-number}} directory, you will omit the
19024 configuration of @file{bfd}, @file{readline}, and other sibling
19025 directories of the @file{gdb} subdirectory. This leads to build errors
19026 about missing include files such as @file{bfd/bfd.h}.
19028 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
19029 However, you should make sure that the shell on your path (named by
19030 the @samp{SHELL} environment variable) is publicly readable. Remember
19031 that @value{GDBN} uses the shell to start your program---some systems refuse to
19032 let @value{GDBN} debug child processes whose programs are not readable.
19035 * Separate Objdir:: Compiling @value{GDBN} in another directory
19036 * Config Names:: Specifying names for hosts and targets
19037 * Configure Options:: Summary of options for configure
19040 @node Separate Objdir
19041 @section Compiling @value{GDBN} in another directory
19043 If you want to run @value{GDBN} versions for several host or target machines,
19044 you need a different @code{gdb} compiled for each combination of
19045 host and target. @code{configure} is designed to make this easy by
19046 allowing you to generate each configuration in a separate subdirectory,
19047 rather than in the source directory. If your @code{make} program
19048 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
19049 @code{make} in each of these directories builds the @code{gdb}
19050 program specified there.
19052 To build @code{gdb} in a separate directory, run @code{configure}
19053 with the @samp{--srcdir} option to specify where to find the source.
19054 (You also need to specify a path to find @code{configure}
19055 itself from your working directory. If the path to @code{configure}
19056 would be the same as the argument to @samp{--srcdir}, you can leave out
19057 the @samp{--srcdir} option; it is assumed.)
19059 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
19060 separate directory for a Sun 4 like this:
19064 cd gdb-@value{GDBVN}
19067 ../gdb-@value{GDBVN}/configure sun4
19072 When @code{configure} builds a configuration using a remote source
19073 directory, it creates a tree for the binaries with the same structure
19074 (and using the same names) as the tree under the source directory. In
19075 the example, you'd find the Sun 4 library @file{libiberty.a} in the
19076 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
19077 @file{gdb-sun4/gdb}.
19079 Make sure that your path to the @file{configure} script has just one
19080 instance of @file{gdb} in it. If your path to @file{configure} looks
19081 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
19082 one subdirectory of @value{GDBN}, not the whole package. This leads to
19083 build errors about missing include files such as @file{bfd/bfd.h}.
19085 One popular reason to build several @value{GDBN} configurations in separate
19086 directories is to configure @value{GDBN} for cross-compiling (where
19087 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
19088 programs that run on another machine---the @dfn{target}).
19089 You specify a cross-debugging target by
19090 giving the @samp{--target=@var{target}} option to @code{configure}.
19092 When you run @code{make} to build a program or library, you must run
19093 it in a configured directory---whatever directory you were in when you
19094 called @code{configure} (or one of its subdirectories).
19096 The @code{Makefile} that @code{configure} generates in each source
19097 directory also runs recursively. If you type @code{make} in a source
19098 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
19099 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
19100 will build all the required libraries, and then build GDB.
19102 When you have multiple hosts or targets configured in separate
19103 directories, you can run @code{make} on them in parallel (for example,
19104 if they are NFS-mounted on each of the hosts); they will not interfere
19108 @section Specifying names for hosts and targets
19110 The specifications used for hosts and targets in the @code{configure}
19111 script are based on a three-part naming scheme, but some short predefined
19112 aliases are also supported. The full naming scheme encodes three pieces
19113 of information in the following pattern:
19116 @var{architecture}-@var{vendor}-@var{os}
19119 For example, you can use the alias @code{sun4} as a @var{host} argument,
19120 or as the value for @var{target} in a @code{--target=@var{target}}
19121 option. The equivalent full name is @samp{sparc-sun-sunos4}.
19123 The @code{configure} script accompanying @value{GDBN} does not provide
19124 any query facility to list all supported host and target names or
19125 aliases. @code{configure} calls the Bourne shell script
19126 @code{config.sub} to map abbreviations to full names; you can read the
19127 script, if you wish, or you can use it to test your guesses on
19128 abbreviations---for example:
19131 % sh config.sub i386-linux
19133 % sh config.sub alpha-linux
19134 alpha-unknown-linux-gnu
19135 % sh config.sub hp9k700
19137 % sh config.sub sun4
19138 sparc-sun-sunos4.1.1
19139 % sh config.sub sun3
19140 m68k-sun-sunos4.1.1
19141 % sh config.sub i986v
19142 Invalid configuration `i986v': machine `i986v' not recognized
19146 @code{config.sub} is also distributed in the @value{GDBN} source
19147 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
19149 @node Configure Options
19150 @section @code{configure} options
19152 Here is a summary of the @code{configure} options and arguments that
19153 are most often useful for building @value{GDBN}. @code{configure} also has
19154 several other options not listed here. @inforef{What Configure
19155 Does,,configure.info}, for a full explanation of @code{configure}.
19158 configure @r{[}--help@r{]}
19159 @r{[}--prefix=@var{dir}@r{]}
19160 @r{[}--exec-prefix=@var{dir}@r{]}
19161 @r{[}--srcdir=@var{dirname}@r{]}
19162 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
19163 @r{[}--target=@var{target}@r{]}
19168 You may introduce options with a single @samp{-} rather than
19169 @samp{--} if you prefer; but you may abbreviate option names if you use
19174 Display a quick summary of how to invoke @code{configure}.
19176 @item --prefix=@var{dir}
19177 Configure the source to install programs and files under directory
19180 @item --exec-prefix=@var{dir}
19181 Configure the source to install programs under directory
19184 @c avoid splitting the warning from the explanation:
19186 @item --srcdir=@var{dirname}
19187 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
19188 @code{make} that implements the @code{VPATH} feature.}@*
19189 Use this option to make configurations in directories separate from the
19190 @value{GDBN} source directories. Among other things, you can use this to
19191 build (or maintain) several configurations simultaneously, in separate
19192 directories. @code{configure} writes configuration specific files in
19193 the current directory, but arranges for them to use the source in the
19194 directory @var{dirname}. @code{configure} creates directories under
19195 the working directory in parallel to the source directories below
19198 @item --norecursion
19199 Configure only the directory level where @code{configure} is executed; do not
19200 propagate configuration to subdirectories.
19202 @item --target=@var{target}
19203 Configure @value{GDBN} for cross-debugging programs running on the specified
19204 @var{target}. Without this option, @value{GDBN} is configured to debug
19205 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
19207 There is no convenient way to generate a list of all available targets.
19209 @item @var{host} @dots{}
19210 Configure @value{GDBN} to run on the specified @var{host}.
19212 There is no convenient way to generate a list of all available hosts.
19215 There are many other options available as well, but they are generally
19216 needed for special purposes only.
19218 @node Maintenance Commands
19219 @appendix Maintenance Commands
19220 @cindex maintenance commands
19221 @cindex internal commands
19223 In addition to commands intended for @value{GDBN} users, @value{GDBN}
19224 includes a number of commands intended for @value{GDBN} developers.
19225 These commands are provided here for reference.
19228 @kindex maint info breakpoints
19229 @item @anchor{maint info breakpoints}maint info breakpoints
19230 Using the same format as @samp{info breakpoints}, display both the
19231 breakpoints you've set explicitly, and those @value{GDBN} is using for
19232 internal purposes. Internal breakpoints are shown with negative
19233 breakpoint numbers. The type column identifies what kind of breakpoint
19238 Normal, explicitly set breakpoint.
19241 Normal, explicitly set watchpoint.
19244 Internal breakpoint, used to handle correctly stepping through
19245 @code{longjmp} calls.
19247 @item longjmp resume
19248 Internal breakpoint at the target of a @code{longjmp}.
19251 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
19254 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
19257 Shared library events.
19261 @kindex maint internal-error
19262 @kindex maint internal-warning
19263 @item maint internal-error
19264 @itemx maint internal-warning
19265 Cause @value{GDBN} to call the internal function @code{internal_error}
19266 or @code{internal_warning} and hence behave as though an internal error
19267 or internal warning has been detected. In addition to reporting the
19268 internal problem, these functions give the user the opportunity to
19269 either quit @value{GDBN} or create a core file of the current
19270 @value{GDBN} session.
19273 (gdb) @kbd{maint internal-error testing, 1, 2}
19274 @dots{}/maint.c:121: internal-error: testing, 1, 2
19275 A problem internal to GDB has been detected. Further
19276 debugging may prove unreliable.
19277 Quit this debugging session? (y or n) @kbd{n}
19278 Create a core file? (y or n) @kbd{n}
19282 Takes an optional parameter that is used as the text of the error or
19285 @kindex maint print dummy-frames
19286 @item maint print dummy-frames
19288 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
19293 (gdb) @kbd{print add(2,3)}
19294 Breakpoint 2, add (a=2, b=3) at @dots{}
19296 The program being debugged stopped while in a function called from GDB.
19298 (gdb) @kbd{maint print dummy-frames}
19299 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
19300 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
19301 call_lo=0x01014000 call_hi=0x01014001
19305 Takes an optional file parameter.
19307 @kindex maint print registers
19308 @kindex maint print raw-registers
19309 @kindex maint print cooked-registers
19310 @kindex maint print register-groups
19311 @item maint print registers
19312 @itemx maint print raw-registers
19313 @itemx maint print cooked-registers
19314 @itemx maint print register-groups
19315 Print @value{GDBN}'s internal register data structures.
19317 The command @code{maint print raw-registers} includes the contents of
19318 the raw register cache; the command @code{maint print cooked-registers}
19319 includes the (cooked) value of all registers; and the command
19320 @code{maint print register-groups} includes the groups that each
19321 register is a member of. @xref{Registers,, Registers, gdbint,
19322 @value{GDBN} Internals}.
19324 Takes an optional file parameter.
19326 @kindex maint print reggroups
19327 @item maint print reggroups
19328 Print @value{GDBN}'s internal register group data structures.
19330 Takes an optional file parameter.
19333 (gdb) @kbd{maint print reggroups}
19344 @kindex maint set profile
19345 @kindex maint show profile
19346 @cindex profiling GDB
19347 @item maint set profile
19348 @itemx maint show profile
19349 Control profiling of @value{GDBN}.
19351 Profiling will be disabled until you use the @samp{maint set profile}
19352 command to enable it. When you enable profiling, the system will begin
19353 collecting timing and execution count data; when you disable profiling or
19354 exit @value{GDBN}, the results will be written to a log file. Remember that
19355 if you use profiling, @value{GDBN} will overwrite the profiling log file
19356 (often called @file{gmon.out}). If you have a record of important profiling
19357 data in a @file{gmon.out} file, be sure to move it to a safe location.
19359 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
19360 compiled with the @samp{-pg} compiler option.
19365 @node Remote Protocol
19366 @appendix @value{GDBN} Remote Serial Protocol
19371 * Stop Reply Packets::
19372 * General Query Packets::
19373 * Register Packet Format::
19375 * File-I/O remote protocol extension::
19381 There may be occasions when you need to know something about the
19382 protocol---for example, if there is only one serial port to your target
19383 machine, you might want your program to do something special if it
19384 recognizes a packet meant for @value{GDBN}.
19386 In the examples below, @samp{->} and @samp{<-} are used to indicate
19387 transmitted and received data respectfully.
19389 @cindex protocol, @value{GDBN} remote serial
19390 @cindex serial protocol, @value{GDBN} remote
19391 @cindex remote serial protocol
19392 All @value{GDBN} commands and responses (other than acknowledgments) are
19393 sent as a @var{packet}. A @var{packet} is introduced with the character
19394 @samp{$}, the actual @var{packet-data}, and the terminating character
19395 @samp{#} followed by a two-digit @var{checksum}:
19398 @code{$}@var{packet-data}@code{#}@var{checksum}
19402 @cindex checksum, for @value{GDBN} remote
19404 The two-digit @var{checksum} is computed as the modulo 256 sum of all
19405 characters between the leading @samp{$} and the trailing @samp{#} (an
19406 eight bit unsigned checksum).
19408 Implementors should note that prior to @value{GDBN} 5.0 the protocol
19409 specification also included an optional two-digit @var{sequence-id}:
19412 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
19415 @cindex sequence-id, for @value{GDBN} remote
19417 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
19418 has never output @var{sequence-id}s. Stubs that handle packets added
19419 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
19421 @cindex acknowledgment, for @value{GDBN} remote
19422 When either the host or the target machine receives a packet, the first
19423 response expected is an acknowledgment: either @samp{+} (to indicate
19424 the package was received correctly) or @samp{-} (to request
19428 -> @code{$}@var{packet-data}@code{#}@var{checksum}
19433 The host (@value{GDBN}) sends @var{command}s, and the target (the
19434 debugging stub incorporated in your program) sends a @var{response}. In
19435 the case of step and continue @var{command}s, the response is only sent
19436 when the operation has completed (the target has again stopped).
19438 @var{packet-data} consists of a sequence of characters with the
19439 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
19442 Fields within the packet should be separated using @samp{,} @samp{;} or
19443 @cindex remote protocol, field separator
19444 @samp{:}. Except where otherwise noted all numbers are represented in
19445 @sc{hex} with leading zeros suppressed.
19447 Implementors should note that prior to @value{GDBN} 5.0, the character
19448 @samp{:} could not appear as the third character in a packet (as it
19449 would potentially conflict with the @var{sequence-id}).
19451 Response @var{data} can be run-length encoded to save space. A @samp{*}
19452 means that the next character is an @sc{ascii} encoding giving a repeat count
19453 which stands for that many repetitions of the character preceding the
19454 @samp{*}. The encoding is @code{n+29}, yielding a printable character
19455 where @code{n >=3} (which is where rle starts to win). The printable
19456 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
19457 value greater than 126 should not be used.
19459 Some remote systems have used a different run-length encoding mechanism
19460 loosely refered to as the cisco encoding. Following the @samp{*}
19461 character are two hex digits that indicate the size of the packet.
19468 means the same as "0000".
19470 The error response returned for some packets includes a two character
19471 error number. That number is not well defined.
19473 For any @var{command} not supported by the stub, an empty response
19474 (@samp{$#00}) should be returned. That way it is possible to extend the
19475 protocol. A newer @value{GDBN} can tell if a packet is supported based
19478 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
19479 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
19485 The following table provides a complete list of all currently defined
19486 @var{command}s and their corresponding response @var{data}.
19490 @item @code{!} --- extended mode
19491 @cindex @code{!} packet
19493 Enable extended mode. In extended mode, the remote server is made
19494 persistent. The @samp{R} packet is used to restart the program being
19500 The remote target both supports and has enabled extended mode.
19503 @item @code{?} --- last signal
19504 @cindex @code{?} packet
19506 Indicate the reason the target halted. The reply is the same as for
19510 @xref{Stop Reply Packets}, for the reply specifications.
19512 @item @code{a} --- reserved
19514 Reserved for future use.
19516 @item @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,@dots{}} --- set program arguments @strong{(reserved)}
19517 @cindex @code{A} packet
19519 Initialized @samp{argv[]} array passed into program. @var{arglen}
19520 specifies the number of bytes in the hex encoded byte stream @var{arg}.
19521 See @code{gdbserver} for more details.
19529 @item @code{b}@var{baud} --- set baud @strong{(deprecated)}
19530 @cindex @code{b} packet
19532 Change the serial line speed to @var{baud}.
19534 JTC: @emph{When does the transport layer state change? When it's
19535 received, or after the ACK is transmitted. In either case, there are
19536 problems if the command or the acknowledgment packet is dropped.}
19538 Stan: @emph{If people really wanted to add something like this, and get
19539 it working for the first time, they ought to modify ser-unix.c to send
19540 some kind of out-of-band message to a specially-setup stub and have the
19541 switch happen "in between" packets, so that from remote protocol's point
19542 of view, nothing actually happened.}
19544 @item @code{B}@var{addr},@var{mode} --- set breakpoint @strong{(deprecated)}
19545 @cindex @code{B} packet
19547 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
19548 breakpoint at @var{addr}.
19550 This packet has been replaced by the @samp{Z} and @samp{z} packets
19551 (@pxref{insert breakpoint or watchpoint packet}).
19553 @item @code{c}@var{addr} --- continue
19554 @cindex @code{c} packet
19556 @var{addr} is address to resume. If @var{addr} is omitted, resume at
19560 @xref{Stop Reply Packets}, for the reply specifications.
19562 @item @code{C}@var{sig}@code{;}@var{addr} --- continue with signal
19563 @cindex @code{C} packet
19565 Continue with signal @var{sig} (hex signal number). If
19566 @code{;}@var{addr} is omitted, resume at same address.
19569 @xref{Stop Reply Packets}, for the reply specifications.
19571 @item @code{d} --- toggle debug @strong{(deprecated)}
19572 @cindex @code{d} packet
19576 @item @code{D} --- detach
19577 @cindex @code{D} packet
19579 Detach @value{GDBN} from the remote system. Sent to the remote target
19580 before @value{GDBN} disconnects via the @code{detach} command.
19584 @item @emph{no response}
19585 @value{GDBN} does not check for any response after sending this packet.
19588 @item @code{e} --- reserved
19590 Reserved for future use.
19592 @item @code{E} --- reserved
19594 Reserved for future use.
19596 @item @code{f} --- reserved
19598 Reserved for future use.
19600 @item @code{F}@var{RC}@code{,}@var{EE}@code{,}@var{CF}@code{;}@var{XX} --- Reply to target's F packet.
19601 @cindex @code{F} packet
19603 This packet is send by @value{GDBN} as reply to a @code{F} request packet
19604 sent by the target. This is part of the File-I/O protocol extension.
19605 @xref{File-I/O remote protocol extension}, for the specification.
19607 @item @code{g} --- read registers
19608 @anchor{read registers packet}
19609 @cindex @code{g} packet
19611 Read general registers.
19615 @item @var{XX@dots{}}
19616 Each byte of register data is described by two hex digits. The bytes
19617 with the register are transmitted in target byte order. The size of
19618 each register and their position within the @samp{g} @var{packet} are
19619 determined by the @value{GDBN} internal macros
19620 @var{DEPRECATED_REGISTER_RAW_SIZE} and @var{REGISTER_NAME} macros. The
19621 specification of several standard @code{g} packets is specified below.
19626 @item @code{G}@var{XX@dots{}} --- write regs
19627 @cindex @code{G} packet
19629 @xref{read registers packet}, for a description of the @var{XX@dots{}}
19640 @item @code{h} --- reserved
19642 Reserved for future use.
19644 @item @code{H}@var{c}@var{t@dots{}} --- set thread
19645 @cindex @code{H} packet
19647 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
19648 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
19649 should be @samp{c} for step and continue operations, @samp{g} for other
19650 operations. The thread designator @var{t@dots{}} may be -1, meaning all
19651 the threads, a thread number, or zero which means pick any thread.
19662 @c 'H': How restrictive (or permissive) is the thread model. If a
19663 @c thread is selected and stopped, are other threads allowed
19664 @c to continue to execute? As I mentioned above, I think the
19665 @c semantics of each command when a thread is selected must be
19666 @c described. For example:
19668 @c 'g': If the stub supports threads and a specific thread is
19669 @c selected, returns the register block from that thread;
19670 @c otherwise returns current registers.
19672 @c 'G' If the stub supports threads and a specific thread is
19673 @c selected, sets the registers of the register block of
19674 @c that thread; otherwise sets current registers.
19676 @item @code{i}@var{addr}@code{,}@var{nnn} --- cycle step @strong{(draft)}
19677 @anchor{cycle step packet}
19678 @cindex @code{i} packet
19680 Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
19681 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
19682 step starting at that address.
19684 @item @code{I} --- signal then cycle step @strong{(reserved)}
19685 @cindex @code{I} packet
19687 @xref{step with signal packet}. @xref{cycle step packet}.
19689 @item @code{j} --- reserved
19691 Reserved for future use.
19693 @item @code{J} --- reserved
19695 Reserved for future use.
19697 @item @code{k} --- kill request
19698 @cindex @code{k} packet
19700 FIXME: @emph{There is no description of how to operate when a specific
19701 thread context has been selected (i.e.@: does 'k' kill only that
19704 @item @code{K} --- reserved
19706 Reserved for future use.
19708 @item @code{l} --- reserved
19710 Reserved for future use.
19712 @item @code{L} --- reserved
19714 Reserved for future use.
19716 @item @code{m}@var{addr}@code{,}@var{length} --- read memory
19717 @cindex @code{m} packet
19719 Read @var{length} bytes of memory starting at address @var{addr}.
19720 Neither @value{GDBN} nor the stub assume that sized memory transfers are
19721 assumed using word aligned accesses. FIXME: @emph{A word aligned memory
19722 transfer mechanism is needed.}
19726 @item @var{XX@dots{}}
19727 @var{XX@dots{}} is mem contents. Can be fewer bytes than requested if able
19728 to read only part of the data. Neither @value{GDBN} nor the stub assume
19729 that sized memory transfers are assumed using word aligned
19730 accesses. FIXME: @emph{A word aligned memory transfer mechanism is
19736 @item @code{M}@var{addr},@var{length}@code{:}@var{XX@dots{}} --- write mem
19737 @cindex @code{M} packet
19739 Write @var{length} bytes of memory starting at address @var{addr}.
19740 @var{XX@dots{}} is the data.
19747 for an error (this includes the case where only part of the data was
19751 @item @code{n} --- reserved
19753 Reserved for future use.
19755 @item @code{N} --- reserved
19757 Reserved for future use.
19759 @item @code{o} --- reserved
19761 Reserved for future use.
19763 @item @code{O} --- reserved
19765 Reserved for future use.
19767 @item @code{p}@var{n@dots{}} --- read reg @strong{(reserved)}
19768 @cindex @code{p} packet
19770 @xref{write register packet}.
19774 @item @var{r@dots{}.}
19775 The hex encoded value of the register in target byte order.
19778 @item @code{P}@var{n@dots{}}@code{=}@var{r@dots{}} --- write register
19779 @anchor{write register packet}
19780 @cindex @code{P} packet
19782 Write register @var{n@dots{}} with value @var{r@dots{}}, which contains two hex
19783 digits for each byte in the register (target byte order).
19793 @item @code{q}@var{query} --- general query
19794 @anchor{general query packet}
19795 @cindex @code{q} packet
19797 Request info about @var{query}. In general @value{GDBN} queries have a
19798 leading upper case letter. Custom vendor queries should use a company
19799 prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may optionally
19800 be followed by a @samp{,} or @samp{;} separated list. Stubs must ensure
19801 that they match the full @var{query} name.
19805 @item @var{XX@dots{}}
19806 Hex encoded data from query. The reply can not be empty.
19810 Indicating an unrecognized @var{query}.
19813 @item @code{Q}@var{var}@code{=}@var{val} --- general set
19814 @cindex @code{Q} packet
19816 Set value of @var{var} to @var{val}.
19818 @xref{general query packet}, for a discussion of naming conventions.
19820 @item @code{r} --- reset @strong{(deprecated)}
19821 @cindex @code{r} packet
19823 Reset the entire system.
19825 @item @code{R}@var{XX} --- remote restart
19826 @cindex @code{R} packet
19828 Restart the program being debugged. @var{XX}, while needed, is ignored.
19829 This packet is only available in extended mode.
19833 @item @emph{no reply}
19834 The @samp{R} packet has no reply.
19837 @item @code{s}@var{addr} --- step
19838 @cindex @code{s} packet
19840 @var{addr} is address to resume. If @var{addr} is omitted, resume at
19844 @xref{Stop Reply Packets}, for the reply specifications.
19846 @item @code{S}@var{sig}@code{;}@var{addr} --- step with signal
19847 @anchor{step with signal packet}
19848 @cindex @code{S} packet
19850 Like @samp{C} but step not continue.
19853 @xref{Stop Reply Packets}, for the reply specifications.
19855 @item @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} --- search
19856 @cindex @code{t} packet
19858 Search backwards starting at address @var{addr} for a match with pattern
19859 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
19860 @var{addr} must be at least 3 digits.
19862 @item @code{T}@var{XX} --- thread alive
19863 @cindex @code{T} packet
19865 Find out if the thread XX is alive.
19870 thread is still alive
19875 @item @code{u} --- reserved
19877 Reserved for future use.
19879 @item @code{U} --- reserved
19881 Reserved for future use.
19883 @item @code{v} --- verbose packet prefix
19885 Packets starting with @code{v} are identified by a multi-letter name,
19886 up to the first @code{;} or @code{?} (or the end of the packet).
19888 @item @code{vCont}[;@var{action}[@code{:}@var{tid}]]... --- extended resume
19889 @cindex @code{vCont} packet
19891 Resume the inferior. Different actions may be specified for each thread.
19892 If an action is specified with no @var{tid}, then it is applied to any
19893 threads that don't have a specific action specified; if no default action is
19894 specified then other threads should remain stopped. Specifying multiple
19895 default actions is an error; specifying no actions is also an error.
19896 Thread IDs are specified in hexadecimal. Currently supported actions are:
19902 Continue with signal @var{sig}. @var{sig} should be two hex digits.
19906 Step with signal @var{sig}. @var{sig} should be two hex digits.
19909 The optional @var{addr} argument normally associated with these packets is
19910 not supported in @code{vCont}.
19913 @xref{Stop Reply Packets}, for the reply specifications.
19915 @item @code{vCont?} --- extended resume query
19916 @cindex @code{vCont?} packet
19918 Query support for the @code{vCont} packet.
19922 @item @code{vCont}[;@var{action}]...
19923 The @code{vCont} packet is supported. Each @var{action} is a supported
19924 command in the @code{vCont} packet.
19926 The @code{vCont} packet is not supported.
19929 @item @code{V} --- reserved
19931 Reserved for future use.
19933 @item @code{w} --- reserved
19935 Reserved for future use.
19937 @item @code{W} --- reserved
19939 Reserved for future use.
19941 @item @code{x} --- reserved
19943 Reserved for future use.
19945 @item @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX@dots{}} --- write mem (binary)
19946 @cindex @code{X} packet
19948 @var{addr} is address, @var{length} is number of bytes, @var{XX@dots{}}
19949 is binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
19950 escaped using @code{0x7d}.
19960 @item @code{y} --- reserved
19962 Reserved for future use.
19964 @item @code{Y} reserved
19966 Reserved for future use.
19968 @item @code{z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- remove breakpoint or watchpoint @strong{(draft)}
19969 @itemx @code{Z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- insert breakpoint or watchpoint @strong{(draft)}
19970 @anchor{insert breakpoint or watchpoint packet}
19971 @cindex @code{z} packet
19972 @cindex @code{Z} packets
19974 Insert (@code{Z}) or remove (@code{z}) a @var{type} breakpoint or
19975 watchpoint starting at address @var{address} and covering the next
19976 @var{length} bytes.
19978 Each breakpoint and watchpoint packet @var{type} is documented
19981 @emph{Implementation notes: A remote target shall return an empty string
19982 for an unrecognized breakpoint or watchpoint packet @var{type}. A
19983 remote target shall support either both or neither of a given
19984 @code{Z}@var{type}@dots{} and @code{z}@var{type}@dots{} packet pair. To
19985 avoid potential problems with duplicate packets, the operations should
19986 be implemented in an idempotent way.}
19988 @item @code{z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- remove memory breakpoint @strong{(draft)}
19989 @item @code{Z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- insert memory breakpoint @strong{(draft)}
19990 @cindex @code{z0} packet
19991 @cindex @code{Z0} packet
19993 Insert (@code{Z0}) or remove (@code{z0}) a memory breakpoint at address
19994 @code{addr} of size @code{length}.
19996 A memory breakpoint is implemented by replacing the instruction at
19997 @var{addr} with a software breakpoint or trap instruction. The
19998 @code{length} is used by targets that indicates the size of the
19999 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
20000 @sc{mips} can insert either a 2 or 4 byte breakpoint).
20002 @emph{Implementation note: It is possible for a target to copy or move
20003 code that contains memory breakpoints (e.g., when implementing
20004 overlays). The behavior of this packet, in the presence of such a
20005 target, is not defined.}
20017 @item @code{z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- remove hardware breakpoint @strong{(draft)}
20018 @item @code{Z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- insert hardware breakpoint @strong{(draft)}
20019 @cindex @code{z1} packet
20020 @cindex @code{Z1} packet
20022 Insert (@code{Z1}) or remove (@code{z1}) a hardware breakpoint at
20023 address @code{addr} of size @code{length}.
20025 A hardware breakpoint is implemented using a mechanism that is not
20026 dependant on being able to modify the target's memory.
20028 @emph{Implementation note: A hardware breakpoint is not affected by code
20041 @item @code{z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- remove write watchpoint @strong{(draft)}
20042 @item @code{Z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- insert write watchpoint @strong{(draft)}
20043 @cindex @code{z2} packet
20044 @cindex @code{Z2} packet
20046 Insert (@code{Z2}) or remove (@code{z2}) a write watchpoint.
20058 @item @code{z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- remove read watchpoint @strong{(draft)}
20059 @item @code{Z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- insert read watchpoint @strong{(draft)}
20060 @cindex @code{z3} packet
20061 @cindex @code{Z3} packet
20063 Insert (@code{Z3}) or remove (@code{z3}) a read watchpoint.
20075 @item @code{z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- remove access watchpoint @strong{(draft)}
20076 @item @code{Z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- insert access watchpoint @strong{(draft)}
20077 @cindex @code{z4} packet
20078 @cindex @code{Z4} packet
20080 Insert (@code{Z4}) or remove (@code{z4}) an access watchpoint.
20094 @node Stop Reply Packets
20095 @section Stop Reply Packets
20096 @cindex stop reply packets
20098 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
20099 receive any of the below as a reply. In the case of the @samp{C},
20100 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
20101 when the target halts. In the below the exact meaning of @samp{signal
20102 number} is poorly defined. In general one of the UNIX signal numbering
20103 conventions is used.
20108 @var{AA} is the signal number
20110 @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
20111 @cindex @code{T} packet reply
20113 @var{AA} = two hex digit signal number; @var{n...} = register number
20114 (hex), @var{r...} = target byte ordered register contents, size defined
20115 by @code{DEPRECATED_REGISTER_RAW_SIZE}; @var{n...} = @samp{thread},
20116 @var{r...} = thread process ID, this is a hex integer; @var{n...} =
20117 (@samp{watch} | @samp{rwatch} | @samp{awatch}, @var{r...} = data
20118 address, this is a hex integer; @var{n...} = other string not starting
20119 with valid hex digit. @value{GDBN} should ignore this @var{n...},
20120 @var{r...} pair and go on to the next. This way we can extend the
20125 The process exited, and @var{AA} is the exit status. This is only
20126 applicable to certain targets.
20130 The process terminated with signal @var{AA}.
20132 @item N@var{AA};@var{t@dots{}};@var{d@dots{}};@var{b@dots{}} @strong{(obsolete)}
20134 @var{AA} = signal number; @var{t@dots{}} = address of symbol
20135 @code{_start}; @var{d@dots{}} = base of data section; @var{b@dots{}} =
20136 base of bss section. @emph{Note: only used by Cisco Systems targets.
20137 The difference between this reply and the @samp{qOffsets} query is that
20138 the @samp{N} packet may arrive spontaneously whereas the @samp{qOffsets}
20139 is a query initiated by the host debugger.}
20141 @item O@var{XX@dots{}}
20143 @var{XX@dots{}} is hex encoding of @sc{ascii} data. This can happen at
20144 any time while the program is running and the debugger should continue
20145 to wait for @samp{W}, @samp{T}, etc.
20147 @item F@var{call-id}@code{,}@var{parameter@dots{}}
20149 @var{call-id} is the identifier which says which host system call should
20150 be called. This is just the name of the function. Translation into the
20151 correct system call is only applicable as it's defined in @value{GDBN}.
20152 @xref{File-I/O remote protocol extension}, for a list of implemented
20155 @var{parameter@dots{}} is a list of parameters as defined for this very
20158 The target replies with this packet when it expects @value{GDBN} to call
20159 a host system call on behalf of the target. @value{GDBN} replies with
20160 an appropriate @code{F} packet and keeps up waiting for the next reply
20161 packet from the target. The latest @samp{C}, @samp{c}, @samp{S} or
20162 @samp{s} action is expected to be continued.
20163 @xref{File-I/O remote protocol extension}, for more details.
20167 @node General Query Packets
20168 @section General Query Packets
20170 The following set and query packets have already been defined.
20174 @item @code{q}@code{C} --- current thread
20176 Return the current thread id.
20180 @item @code{QC}@var{pid}
20181 Where @var{pid} is a HEX encoded 16 bit process id.
20183 Any other reply implies the old pid.
20186 @item @code{q}@code{fThreadInfo} -- all thread ids
20188 @code{q}@code{sThreadInfo}
20190 Obtain a list of active thread ids from the target (OS). Since there
20191 may be too many active threads to fit into one reply packet, this query
20192 works iteratively: it may require more than one query/reply sequence to
20193 obtain the entire list of threads. The first query of the sequence will
20194 be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
20195 sequence will be the @code{qs}@code{ThreadInfo} query.
20197 NOTE: replaces the @code{qL} query (see below).
20201 @item @code{m}@var{id}
20203 @item @code{m}@var{id},@var{id}@dots{}
20204 a comma-separated list of thread ids
20206 (lower case 'el') denotes end of list.
20209 In response to each query, the target will reply with a list of one or
20210 more thread ids, in big-endian hex, separated by commas. @value{GDBN}
20211 will respond to each reply with a request for more thread ids (using the
20212 @code{qs} form of the query), until the target responds with @code{l}
20213 (lower-case el, for @code{'last'}).
20215 @item @code{q}@code{ThreadExtraInfo}@code{,}@var{id} --- extra thread info
20217 Where @var{id} is a thread-id in big-endian hex. Obtain a printable
20218 string description of a thread's attributes from the target OS. This
20219 string may contain anything that the target OS thinks is interesting for
20220 @value{GDBN} to tell the user about the thread. The string is displayed
20221 in @value{GDBN}'s @samp{info threads} display. Some examples of
20222 possible thread extra info strings are ``Runnable'', or ``Blocked on
20227 @item @var{XX@dots{}}
20228 Where @var{XX@dots{}} is a hex encoding of @sc{ascii} data, comprising
20229 the printable string containing the extra information about the thread's
20233 @item @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} --- query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
20235 Obtain thread information from RTOS. Where: @var{startflag} (one hex
20236 digit) is one to indicate the first query and zero to indicate a
20237 subsequent query; @var{threadcount} (two hex digits) is the maximum
20238 number of threads the response packet can contain; and @var{nextthread}
20239 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
20240 returned in the response as @var{argthread}.
20242 NOTE: this query is replaced by the @code{q}@code{fThreadInfo} query
20247 @item @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread@dots{}}
20248 Where: @var{count} (two hex digits) is the number of threads being
20249 returned; @var{done} (one hex digit) is zero to indicate more threads
20250 and one indicates no further threads; @var{argthreadid} (eight hex
20251 digits) is @var{nextthread} from the request packet; @var{thread@dots{}}
20252 is a sequence of thread IDs from the target. @var{threadid} (eight hex
20253 digits). See @code{remote.c:parse_threadlist_response()}.
20256 @item @code{q}@code{CRC:}@var{addr}@code{,}@var{length} --- compute CRC of memory block
20260 @item @code{E}@var{NN}
20261 An error (such as memory fault)
20262 @item @code{C}@var{CRC32}
20263 A 32 bit cyclic redundancy check of the specified memory region.
20266 @item @code{q}@code{Offsets} --- query sect offs
20268 Get section offsets that the target used when re-locating the downloaded
20269 image. @emph{Note: while a @code{Bss} offset is included in the
20270 response, @value{GDBN} ignores this and instead applies the @code{Data}
20271 offset to the @code{Bss} section.}
20275 @item @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
20278 @item @code{q}@code{P}@var{mode}@var{threadid} --- thread info request
20280 Returns information on @var{threadid}. Where: @var{mode} is a hex
20281 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
20288 See @code{remote.c:remote_unpack_thread_info_response()}.
20290 @item @code{q}@code{Rcmd,}@var{command} --- remote command
20292 @var{command} (hex encoded) is passed to the local interpreter for
20293 execution. Invalid commands should be reported using the output string.
20294 Before the final result packet, the target may also respond with a
20295 number of intermediate @code{O}@var{output} console output packets.
20296 @emph{Implementors should note that providing access to a stubs's
20297 interpreter may have security implications}.
20302 A command response with no output.
20304 A command response with the hex encoded output string @var{OUTPUT}.
20305 @item @code{E}@var{NN}
20306 Indicate a badly formed request.
20308 When @samp{q}@samp{Rcmd} is not recognized.
20311 @item @code{qSymbol::} --- symbol lookup
20313 Notify the target that @value{GDBN} is prepared to serve symbol lookup
20314 requests. Accept requests from the target for the values of symbols.
20319 The target does not need to look up any (more) symbols.
20320 @item @code{qSymbol:}@var{sym_name}
20321 The target requests the value of symbol @var{sym_name} (hex encoded).
20322 @value{GDBN} may provide the value by using the
20323 @code{qSymbol:}@var{sym_value}:@var{sym_name} message, described below.
20326 @item @code{qSymbol:}@var{sym_value}:@var{sym_name} --- symbol value
20328 Set the value of @var{sym_name} to @var{sym_value}.
20330 @var{sym_name} (hex encoded) is the name of a symbol whose value the
20331 target has previously requested.
20333 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
20334 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
20340 The target does not need to look up any (more) symbols.
20341 @item @code{qSymbol:}@var{sym_name}
20342 The target requests the value of a new symbol @var{sym_name} (hex
20343 encoded). @value{GDBN} will continue to supply the values of symbols
20344 (if available), until the target ceases to request them.
20349 @node Register Packet Format
20350 @section Register Packet Format
20352 The following @samp{g}/@samp{G} packets have previously been defined.
20353 In the below, some thirty-two bit registers are transferred as
20354 sixty-four bits. Those registers should be zero/sign extended (which?)
20355 to fill the space allocated. Register bytes are transfered in target
20356 byte order. The two nibbles within a register byte are transfered
20357 most-significant - least-significant.
20363 All registers are transfered as thirty-two bit quantities in the order:
20364 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
20365 registers; fsr; fir; fp.
20369 All registers are transfered as sixty-four bit quantities (including
20370 thirty-two bit registers such as @code{sr}). The ordering is the same
20378 Example sequence of a target being re-started. Notice how the restart
20379 does not get any direct output:
20384 @emph{target restarts}
20387 <- @code{T001:1234123412341234}
20391 Example sequence of a target being stepped by a single instruction:
20394 -> @code{G1445@dots{}}
20399 <- @code{T001:1234123412341234}
20403 <- @code{1455@dots{}}
20407 @node File-I/O remote protocol extension
20408 @section File-I/O remote protocol extension
20409 @cindex File-I/O remote protocol extension
20412 * File-I/O Overview::
20413 * Protocol basics::
20414 * The F request packet::
20415 * The F reply packet::
20416 * Memory transfer::
20417 * The Ctrl-C message::
20419 * The isatty call::
20420 * The system call::
20421 * List of supported calls::
20422 * Protocol specific representation of datatypes::
20424 * File-I/O Examples::
20427 @node File-I/O Overview
20428 @subsection File-I/O Overview
20429 @cindex file-i/o overview
20431 The File I/O remote protocol extension (short: File-I/O) allows the
20432 target to use the hosts file system and console I/O when calling various
20433 system calls. System calls on the target system are translated into a
20434 remote protocol packet to the host system which then performs the needed
20435 actions and returns with an adequate response packet to the target system.
20436 This simulates file system operations even on targets that lack file systems.
20438 The protocol is defined host- and target-system independent. It uses
20439 it's own independent representation of datatypes and values. Both,
20440 @value{GDBN} and the target's @value{GDBN} stub are responsible for
20441 translating the system dependent values into the unified protocol values
20442 when data is transmitted.
20444 The communication is synchronous. A system call is possible only
20445 when GDB is waiting for the @samp{C}, @samp{c}, @samp{S} or @samp{s}
20446 packets. While @value{GDBN} handles the request for a system call,
20447 the target is stopped to allow deterministic access to the target's
20448 memory. Therefore File-I/O is not interuptible by target signals. It
20449 is possible to interrupt File-I/O by a user interrupt (Ctrl-C), though.
20451 The target's request to perform a host system call does not finish
20452 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
20453 after finishing the system call, the target returns to continuing the
20454 previous activity (continue, step). No additional continue or step
20455 request from @value{GDBN} is required.
20459 <- target requests 'system call X'
20460 target is stopped, @value{GDBN} executes system call
20461 -> GDB returns result
20462 ... target continues, GDB returns to wait for the target
20463 <- target hits breakpoint and sends a Txx packet
20466 The protocol is only used for files on the host file system and
20467 for I/O on the console. Character or block special devices, pipes,
20468 named pipes or sockets or any other communication method on the host
20469 system are not supported by this protocol.
20471 @node Protocol basics
20472 @subsection Protocol basics
20473 @cindex protocol basics, file-i/o
20475 The File-I/O protocol uses the @code{F} packet, as request as well
20476 as as reply packet. Since a File-I/O system call can only occur when
20477 @value{GDBN} is waiting for the continuing or stepping target, the
20478 File-I/O request is a reply that @value{GDBN} has to expect as a result
20479 of a former @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
20480 This @code{F} packet contains all information needed to allow @value{GDBN}
20481 to call the appropriate host system call:
20485 A unique identifier for the requested system call.
20488 All parameters to the system call. Pointers are given as addresses
20489 in the target memory address space. Pointers to strings are given as
20490 pointer/length pair. Numerical values are given as they are.
20491 Numerical control values are given in a protocol specific representation.
20495 At that point @value{GDBN} has to perform the following actions.
20499 If parameter pointer values are given, which point to data needed as input
20500 to a system call, @value{GDBN} requests this data from the target with a
20501 standard @code{m} packet request. This additional communication has to be
20502 expected by the target implementation and is handled as any other @code{m}
20506 @value{GDBN} translates all value from protocol representation to host
20507 representation as needed. Datatypes are coerced into the host types.
20510 @value{GDBN} calls the system call
20513 It then coerces datatypes back to protocol representation.
20516 If pointer parameters in the request packet point to buffer space in which
20517 a system call is expected to copy data to, the data is transmitted to the
20518 target using a @code{M} or @code{X} packet. This packet has to be expected
20519 by the target implementation and is handled as any other @code{M} or @code{X}
20524 Eventually @value{GDBN} replies with another @code{F} packet which contains all
20525 necessary information for the target to continue. This at least contains
20532 @code{errno}, if has been changed by the system call.
20539 After having done the needed type and value coercion, the target continues
20540 the latest continue or step action.
20542 @node The F request packet
20543 @subsection The @code{F} request packet
20544 @cindex file-i/o request packet
20545 @cindex @code{F} request packet
20547 The @code{F} request packet has the following format:
20552 @code{F}@var{call-id}@code{,}@var{parameter@dots{}}
20555 @var{call-id} is the identifier to indicate the host system call to be called.
20556 This is just the name of the function.
20558 @var{parameter@dots{}} are the parameters to the system call.
20562 Parameters are hexadecimal integer values, either the real values in case
20563 of scalar datatypes, as pointers to target buffer space in case of compound
20564 datatypes and unspecified memory areas or as pointer/length pairs in case
20565 of string parameters. These are appended to the call-id, each separated
20566 from its predecessor by a comma. All values are transmitted in ASCII
20567 string representation, pointer/length pairs separated by a slash.
20569 @node The F reply packet
20570 @subsection The @code{F} reply packet
20571 @cindex file-i/o reply packet
20572 @cindex @code{F} reply packet
20574 The @code{F} reply packet has the following format:
20579 @code{F}@var{retcode}@code{,}@var{errno}@code{,}@var{Ctrl-C flag}@code{;}@var{call specific attachment}
20582 @var{retcode} is the return code of the system call as hexadecimal value.
20584 @var{errno} is the errno set by the call, in protocol specific representation.
20585 This parameter can be omitted if the call was successful.
20587 @var{Ctrl-C flag} is only send if the user requested a break. In this
20588 case, @var{errno} must be send as well, even if the call was successful.
20589 The @var{Ctrl-C flag} itself consists of the character 'C':
20596 or, if the call was interupted before the host call has been performed:
20603 assuming 4 is the protocol specific representation of @code{EINTR}.
20607 @node Memory transfer
20608 @subsection Memory transfer
20609 @cindex memory transfer, in file-i/o protocol
20611 Structured data which is transferred using a memory read or write as e.g.@:
20612 a @code{struct stat} is expected to be in a protocol specific format with
20613 all scalar multibyte datatypes being big endian. This should be done by
20614 the target before the @code{F} packet is sent resp.@: by @value{GDBN} before
20615 it transfers memory to the target. Transferred pointers to structured
20616 data should point to the already coerced data at any time.
20618 @node The Ctrl-C message
20619 @subsection The Ctrl-C message
20620 @cindex ctrl-c message, in file-i/o protocol
20622 A special case is, if the @var{Ctrl-C flag} is set in the @value{GDBN}
20623 reply packet. In this case the target should behave, as if it had
20624 gotten a break message. The meaning for the target is ``system call
20625 interupted by @code{SIGINT}''. Consequentially, the target should actually stop
20626 (as with a break message) and return to @value{GDBN} with a @code{T02}
20627 packet. In this case, it's important for the target to know, in which
20628 state the system call was interrupted. Since this action is by design
20629 not an atomic operation, we have to differ between two cases:
20633 The system call hasn't been performed on the host yet.
20636 The system call on the host has been finished.
20640 These two states can be distinguished by the target by the value of the
20641 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
20642 call hasn't been performed. This is equivalent to the @code{EINTR} handling
20643 on POSIX systems. In any other case, the target may presume that the
20644 system call has been finished --- successful or not --- and should behave
20645 as if the break message arrived right after the system call.
20647 @value{GDBN} must behave reliable. If the system call has not been called
20648 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
20649 @code{errno} in the packet. If the system call on the host has been finished
20650 before the user requests a break, the full action must be finshed by
20651 @value{GDBN}. This requires sending @code{M} or @code{X} packets as they fit.
20652 The @code{F} packet may only be send when either nothing has happened
20653 or the full action has been completed.
20656 @subsection Console I/O
20657 @cindex console i/o as part of file-i/o
20659 By default and if not explicitely closed by the target system, the file
20660 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
20661 on the @value{GDBN} console is handled as any other file output operation
20662 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
20663 by @value{GDBN} so that after the target read request from file descriptor
20664 0 all following typing is buffered until either one of the following
20669 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, the
20671 system call is treated as finished.
20674 The user presses @kbd{Enter}. This is treated as end of input with a trailing
20678 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
20679 character, especially no Ctrl-D is appended to the input.
20683 If the user has typed more characters as fit in the buffer given to
20684 the read call, the trailing characters are buffered in @value{GDBN} until
20685 either another @code{read(0, @dots{})} is requested by the target or debugging
20686 is stopped on users request.
20688 @node The isatty call
20689 @subsection The isatty(3) call
20690 @cindex isatty call, file-i/o protocol
20692 A special case in this protocol is the library call @code{isatty} which
20693 is implemented as it's own call inside of this protocol. It returns
20694 1 to the target if the file descriptor given as parameter is attached
20695 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
20696 would require implementing @code{ioctl} and would be more complex than
20699 @node The system call
20700 @subsection The system(3) call
20701 @cindex system call, file-i/o protocol
20703 The other special case in this protocol is the @code{system} call which
20704 is implemented as it's own call, too. @value{GDBN} is taking over the full
20705 task of calling the necessary host calls to perform the @code{system}
20706 call. The return value of @code{system} is simplified before it's returned
20707 to the target. Basically, the only signal transmitted back is @code{EINTR}
20708 in case the user pressed @kbd{Ctrl-C}. Otherwise the return value consists
20709 entirely of the exit status of the called command.
20711 Due to security concerns, the @code{system} call is refused to be called
20712 by @value{GDBN} by default. The user has to allow this call explicitly by
20716 @kindex set remote system-call-allowed 1
20717 @item @code{set remote system-call-allowed 1}
20720 Disabling the @code{system} call is done by
20723 @kindex set remote system-call-allowed 0
20724 @item @code{set remote system-call-allowed 0}
20727 The current setting is shown by typing
20730 @kindex show remote system-call-allowed
20731 @item @code{show remote system-call-allowed}
20734 @node List of supported calls
20735 @subsection List of supported calls
20736 @cindex list of supported file-i/o calls
20753 @unnumberedsubsubsec open
20754 @cindex open, file-i/o system call
20758 int open(const char *pathname, int flags);
20759 int open(const char *pathname, int flags, mode_t mode);
20762 Fopen,pathptr/len,flags,mode
20766 @code{flags} is the bitwise or of the following values:
20770 If the file does not exist it will be created. The host
20771 rules apply as far as file ownership and time stamps
20775 When used with O_CREAT, if the file already exists it is
20776 an error and open() fails.
20779 If the file already exists and the open mode allows
20780 writing (O_RDWR or O_WRONLY is given) it will be
20781 truncated to length 0.
20784 The file is opened in append mode.
20787 The file is opened for reading only.
20790 The file is opened for writing only.
20793 The file is opened for reading and writing.
20796 Each other bit is silently ignored.
20801 @code{mode} is the bitwise or of the following values:
20805 User has read permission.
20808 User has write permission.
20811 Group has read permission.
20814 Group has write permission.
20817 Others have read permission.
20820 Others have write permission.
20823 Each other bit is silently ignored.
20828 @exdent Return value:
20829 open returns the new file descriptor or -1 if an error
20837 pathname already exists and O_CREAT and O_EXCL were used.
20840 pathname refers to a directory.
20843 The requested access is not allowed.
20846 pathname was too long.
20849 A directory component in pathname does not exist.
20852 pathname refers to a device, pipe, named pipe or socket.
20855 pathname refers to a file on a read-only filesystem and
20856 write access was requested.
20859 pathname is an invalid pointer value.
20862 No space on device to create the file.
20865 The process already has the maximum number of files open.
20868 The limit on the total number of files open on the system
20872 The call was interrupted by the user.
20876 @unnumberedsubsubsec close
20877 @cindex close, file-i/o system call
20886 @exdent Return value:
20887 close returns zero on success, or -1 if an error occurred.
20894 fd isn't a valid open file descriptor.
20897 The call was interrupted by the user.
20901 @unnumberedsubsubsec read
20902 @cindex read, file-i/o system call
20906 int read(int fd, void *buf, unsigned int count);
20909 Fread,fd,bufptr,count
20911 @exdent Return value:
20912 On success, the number of bytes read is returned.
20913 Zero indicates end of file. If count is zero, read
20914 returns zero as well. On error, -1 is returned.
20921 fd is not a valid file descriptor or is not open for
20925 buf is an invalid pointer value.
20928 The call was interrupted by the user.
20932 @unnumberedsubsubsec write
20933 @cindex write, file-i/o system call
20937 int write(int fd, const void *buf, unsigned int count);
20940 Fwrite,fd,bufptr,count
20942 @exdent Return value:
20943 On success, the number of bytes written are returned.
20944 Zero indicates nothing was written. On error, -1
20952 fd is not a valid file descriptor or is not open for
20956 buf is an invalid pointer value.
20959 An attempt was made to write a file that exceeds the
20960 host specific maximum file size allowed.
20963 No space on device to write the data.
20966 The call was interrupted by the user.
20970 @unnumberedsubsubsec lseek
20971 @cindex lseek, file-i/o system call
20975 long lseek (int fd, long offset, int flag);
20978 Flseek,fd,offset,flag
20981 @code{flag} is one of:
20985 The offset is set to offset bytes.
20988 The offset is set to its current location plus offset
20992 The offset is set to the size of the file plus offset
20997 @exdent Return value:
20998 On success, the resulting unsigned offset in bytes from
20999 the beginning of the file is returned. Otherwise, a
21000 value of -1 is returned.
21007 fd is not a valid open file descriptor.
21010 fd is associated with the @value{GDBN} console.
21013 flag is not a proper value.
21016 The call was interrupted by the user.
21020 @unnumberedsubsubsec rename
21021 @cindex rename, file-i/o system call
21025 int rename(const char *oldpath, const char *newpath);
21028 Frename,oldpathptr/len,newpathptr/len
21030 @exdent Return value:
21031 On success, zero is returned. On error, -1 is returned.
21038 newpath is an existing directory, but oldpath is not a
21042 newpath is a non-empty directory.
21045 oldpath or newpath is a directory that is in use by some
21049 An attempt was made to make a directory a subdirectory
21053 A component used as a directory in oldpath or new
21054 path is not a directory. Or oldpath is a directory
21055 and newpath exists but is not a directory.
21058 oldpathptr or newpathptr are invalid pointer values.
21061 No access to the file or the path of the file.
21065 oldpath or newpath was too long.
21068 A directory component in oldpath or newpath does not exist.
21071 The file is on a read-only filesystem.
21074 The device containing the file has no room for the new
21078 The call was interrupted by the user.
21082 @unnumberedsubsubsec unlink
21083 @cindex unlink, file-i/o system call
21087 int unlink(const char *pathname);
21090 Funlink,pathnameptr/len
21092 @exdent Return value:
21093 On success, zero is returned. On error, -1 is returned.
21100 No access to the file or the path of the file.
21103 The system does not allow unlinking of directories.
21106 The file pathname cannot be unlinked because it's
21107 being used by another process.
21110 pathnameptr is an invalid pointer value.
21113 pathname was too long.
21116 A directory component in pathname does not exist.
21119 A component of the path is not a directory.
21122 The file is on a read-only filesystem.
21125 The call was interrupted by the user.
21129 @unnumberedsubsubsec stat/fstat
21130 @cindex fstat, file-i/o system call
21131 @cindex stat, file-i/o system call
21135 int stat(const char *pathname, struct stat *buf);
21136 int fstat(int fd, struct stat *buf);
21139 Fstat,pathnameptr/len,bufptr
21142 @exdent Return value:
21143 On success, zero is returned. On error, -1 is returned.
21150 fd is not a valid open file.
21153 A directory component in pathname does not exist or the
21154 path is an empty string.
21157 A component of the path is not a directory.
21160 pathnameptr is an invalid pointer value.
21163 No access to the file or the path of the file.
21166 pathname was too long.
21169 The call was interrupted by the user.
21173 @unnumberedsubsubsec gettimeofday
21174 @cindex gettimeofday, file-i/o system call
21178 int gettimeofday(struct timeval *tv, void *tz);
21181 Fgettimeofday,tvptr,tzptr
21183 @exdent Return value:
21184 On success, 0 is returned, -1 otherwise.
21191 tz is a non-NULL pointer.
21194 tvptr and/or tzptr is an invalid pointer value.
21198 @unnumberedsubsubsec isatty
21199 @cindex isatty, file-i/o system call
21203 int isatty(int fd);
21208 @exdent Return value:
21209 Returns 1 if fd refers to the @value{GDBN} console, 0 otherwise.
21216 The call was interrupted by the user.
21220 @unnumberedsubsubsec system
21221 @cindex system, file-i/o system call
21225 int system(const char *command);
21228 Fsystem,commandptr/len
21230 @exdent Return value:
21231 The value returned is -1 on error and the return status
21232 of the command otherwise. Only the exit status of the
21233 command is returned, which is extracted from the hosts
21234 system return value by calling WEXITSTATUS(retval).
21235 In case /bin/sh could not be executed, 127 is returned.
21242 The call was interrupted by the user.
21245 @node Protocol specific representation of datatypes
21246 @subsection Protocol specific representation of datatypes
21247 @cindex protocol specific representation of datatypes, in file-i/o protocol
21250 * Integral datatypes::
21256 @node Integral datatypes
21257 @unnumberedsubsubsec Integral datatypes
21258 @cindex integral datatypes, in file-i/o protocol
21260 The integral datatypes used in the system calls are
21263 int@r{,} unsigned int@r{,} long@r{,} unsigned long@r{,} mode_t @r{and} time_t
21266 @code{Int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
21267 implemented as 32 bit values in this protocol.
21269 @code{Long} and @code{unsigned long} are implemented as 64 bit types.
21271 @xref{Limits}, for corresponding MIN and MAX values (similar to those
21272 in @file{limits.h}) to allow range checking on host and target.
21274 @code{time_t} datatypes are defined as seconds since the Epoch.
21276 All integral datatypes transferred as part of a memory read or write of a
21277 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
21280 @node Pointer values
21281 @unnumberedsubsubsec Pointer values
21282 @cindex pointer values, in file-i/o protocol
21284 Pointers to target data are transmitted as they are. An exception
21285 is made for pointers to buffers for which the length isn't
21286 transmitted as part of the function call, namely strings. Strings
21287 are transmitted as a pointer/length pair, both as hex values, e.g.@:
21294 which is a pointer to data of length 18 bytes at position 0x1aaf.
21295 The length is defined as the full string length in bytes, including
21296 the trailing null byte. Example:
21299 ``hello, world'' at address 0x123456
21310 @unnumberedsubsubsec struct stat
21311 @cindex struct stat, in file-i/o protocol
21313 The buffer of type struct stat used by the target and @value{GDBN} is defined
21318 unsigned int st_dev; /* device */
21319 unsigned int st_ino; /* inode */
21320 mode_t st_mode; /* protection */
21321 unsigned int st_nlink; /* number of hard links */
21322 unsigned int st_uid; /* user ID of owner */
21323 unsigned int st_gid; /* group ID of owner */
21324 unsigned int st_rdev; /* device type (if inode device) */
21325 unsigned long st_size; /* total size, in bytes */
21326 unsigned long st_blksize; /* blocksize for filesystem I/O */
21327 unsigned long st_blocks; /* number of blocks allocated */
21328 time_t st_atime; /* time of last access */
21329 time_t st_mtime; /* time of last modification */
21330 time_t st_ctime; /* time of last change */
21334 The integral datatypes are conforming to the definitions given in the
21335 approriate section (see @ref{Integral datatypes}, for details) so this
21336 structure is of size 64 bytes.
21338 The values of several fields have a restricted meaning and/or
21345 st_ino: No valid meaning for the target. Transmitted unchanged.
21347 st_mode: Valid mode bits are described in Appendix C. Any other
21348 bits have currently no meaning for the target.
21350 st_uid: No valid meaning for the target. Transmitted unchanged.
21352 st_gid: No valid meaning for the target. Transmitted unchanged.
21354 st_rdev: No valid meaning for the target. Transmitted unchanged.
21356 st_atime, st_mtime, st_ctime:
21357 These values have a host and file system dependent
21358 accuracy. Especially on Windows hosts the file systems
21359 don't support exact timing values.
21362 The target gets a struct stat of the above representation and is
21363 responsible to coerce it to the target representation before
21366 Note that due to size differences between the host and target
21367 representation of stat members, these members could eventually
21368 get truncated on the target.
21370 @node struct timeval
21371 @unnumberedsubsubsec struct timeval
21372 @cindex struct timeval, in file-i/o protocol
21374 The buffer of type struct timeval used by the target and @value{GDBN}
21375 is defined as follows:
21379 time_t tv_sec; /* second */
21380 long tv_usec; /* microsecond */
21384 The integral datatypes are conforming to the definitions given in the
21385 approriate section (see @ref{Integral datatypes}, for details) so this
21386 structure is of size 8 bytes.
21389 @subsection Constants
21390 @cindex constants, in file-i/o protocol
21392 The following values are used for the constants inside of the
21393 protocol. @value{GDBN} and target are resposible to translate these
21394 values before and after the call as needed.
21405 @unnumberedsubsubsec Open flags
21406 @cindex open flags, in file-i/o protocol
21408 All values are given in hexadecimal representation.
21420 @node mode_t values
21421 @unnumberedsubsubsec mode_t values
21422 @cindex mode_t values, in file-i/o protocol
21424 All values are given in octal representation.
21441 @unnumberedsubsubsec Errno values
21442 @cindex errno values, in file-i/o protocol
21444 All values are given in decimal representation.
21469 EUNKNOWN is used as a fallback error value if a host system returns
21470 any error value not in the list of supported error numbers.
21473 @unnumberedsubsubsec Lseek flags
21474 @cindex lseek flags, in file-i/o protocol
21483 @unnumberedsubsubsec Limits
21484 @cindex limits, in file-i/o protocol
21486 All values are given in decimal representation.
21489 INT_MIN -2147483648
21491 UINT_MAX 4294967295
21492 LONG_MIN -9223372036854775808
21493 LONG_MAX 9223372036854775807
21494 ULONG_MAX 18446744073709551615
21497 @node File-I/O Examples
21498 @subsection File-I/O Examples
21499 @cindex file-i/o examples
21501 Example sequence of a write call, file descriptor 3, buffer is at target
21502 address 0x1234, 6 bytes should be written:
21505 <- @code{Fwrite,3,1234,6}
21506 @emph{request memory read from target}
21509 @emph{return "6 bytes written"}
21513 Example sequence of a read call, file descriptor 3, buffer is at target
21514 address 0x1234, 6 bytes should be read:
21517 <- @code{Fread,3,1234,6}
21518 @emph{request memory write to target}
21519 -> @code{X1234,6:XXXXXX}
21520 @emph{return "6 bytes read"}
21524 Example sequence of a read call, call fails on the host due to invalid
21525 file descriptor (EBADF):
21528 <- @code{Fread,3,1234,6}
21532 Example sequence of a read call, user presses Ctrl-C before syscall on
21536 <- @code{Fread,3,1234,6}
21541 Example sequence of a read call, user presses Ctrl-C after syscall on
21545 <- @code{Fread,3,1234,6}
21546 -> @code{X1234,6:XXXXXX}
21550 @include agentexpr.texi
21562 % I think something like @colophon should be in texinfo. In the
21564 \long\def\colophon{\hbox to0pt{}\vfill
21565 \centerline{The body of this manual is set in}
21566 \centerline{\fontname\tenrm,}
21567 \centerline{with headings in {\bf\fontname\tenbf}}
21568 \centerline{and examples in {\tt\fontname\tentt}.}
21569 \centerline{{\it\fontname\tenit\/},}
21570 \centerline{{\bf\fontname\tenbf}, and}
21571 \centerline{{\sl\fontname\tensl\/}}
21572 \centerline{are used for emphasis.}\vfill}
21574 % Blame: doc@cygnus.com, 1991.