1 \input texinfo @c -*-texinfo-*-
2 @c Copyright 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003, 2004, 2005
4 @c Free Software Foundation, Inc.
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
25 @c readline appendices use @vindex, @findex and @ftable,
26 @c annotate.texi and gdbmi use @findex.
30 @c !!set GDB manual's edition---not the same as GDB version!
31 @c This is updated by GNU Press.
34 @c !!set GDB edit command default editor
37 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
39 @c This is a dir.info fragment to support semi-automated addition of
40 @c manuals to an info tree.
41 @dircategory Software development
43 * Gdb: (gdb). The GNU debugger.
47 This file documents the @sc{gnu} debugger @value{GDBN}.
50 This is the @value{EDITION} Edition, of @cite{Debugging with
51 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
52 Version @value{GDBVN}.
54 Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,@*
55 1999, 2000, 2001, 2002, 2003, 2004, 2005@*
56 Free Software Foundation, Inc.
58 Permission is granted to copy, distribute and/or modify this document
59 under the terms of the GNU Free Documentation License, Version 1.1 or
60 any later version published by the Free Software Foundation; with the
61 Invariant Sections being ``Free Software'' and ``Free Software Needs
62 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
63 and with the Back-Cover Texts as in (a) below.
65 (a) The Free Software Foundation's Back-Cover Text is: ``You have
66 freedom to copy and modify this GNU Manual, like GNU software. Copies
67 published by the Free Software Foundation raise funds for GNU
72 @title Debugging with @value{GDBN}
73 @subtitle The @sc{gnu} Source-Level Debugger
75 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
76 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
80 \hfill (Send bugs and comments on @value{GDBN} to bug-gdb\@gnu.org.)\par
81 \hfill {\it Debugging with @value{GDBN}}\par
82 \hfill \TeX{}info \texinfoversion\par
86 @vskip 0pt plus 1filll
87 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
88 1996, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
89 Free Software Foundation, Inc.
91 Published by the Free Software Foundation @*
92 59 Temple Place - Suite 330, @*
93 Boston, MA 02111-1307 USA @*
96 Permission is granted to copy, distribute and/or modify this document
97 under the terms of the GNU Free Documentation License, Version 1.1 or
98 any later version published by the Free Software Foundation; with the
99 Invariant Sections being ``Free Software'' and ``Free Software Needs
100 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
101 and with the Back-Cover Texts as in (a) below.
103 (a) The Free Software Foundation's Back-Cover Text is: ``You have
104 freedom to copy and modify this GNU Manual, like GNU software. Copies
105 published by the Free Software Foundation raise funds for GNU
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN} Version
120 Copyright (C) 1988-2005 Free Software Foundation, Inc.
123 * Summary:: Summary of @value{GDBN}
124 * Sample Session:: A sample @value{GDBN} session
126 * Invocation:: Getting in and out of @value{GDBN}
127 * Commands:: @value{GDBN} commands
128 * Running:: Running programs under @value{GDBN}
129 * Stopping:: Stopping and continuing
130 * Stack:: Examining the stack
131 * Source:: Examining source files
132 * Data:: Examining data
133 * Macros:: Preprocessor Macros
134 * Tracepoints:: Debugging remote targets non-intrusively
135 * Overlays:: Debugging programs that use overlays
137 * Languages:: Using @value{GDBN} with different languages
139 * Symbols:: Examining the symbol table
140 * Altering:: Altering execution
141 * GDB Files:: @value{GDBN} files
142 * Targets:: Specifying a debugging target
143 * Remote Debugging:: Debugging remote programs
144 * Configurations:: Configuration-specific information
145 * Controlling GDB:: Controlling @value{GDBN}
146 * Sequences:: Canned sequences of commands
147 * TUI:: @value{GDBN} Text User Interface
148 * Interpreters:: Command Interpreters
149 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
150 * Annotations:: @value{GDBN}'s annotation interface.
151 * GDB/MI:: @value{GDBN}'s Machine Interface.
153 * GDB Bugs:: Reporting bugs in @value{GDBN}
154 * Formatting Documentation:: How to format and print @value{GDBN} documentation
156 * Command Line Editing:: Command Line Editing
157 * Using History Interactively:: Using History Interactively
158 * Installing GDB:: Installing GDB
159 * Maintenance Commands:: Maintenance Commands
160 * Remote Protocol:: GDB Remote Serial Protocol
161 * Agent Expressions:: The GDB Agent Expression Mechanism
162 * Copying:: GNU General Public License says
163 how you can copy and share GDB
164 * GNU Free Documentation License:: The license for this documentation
173 @unnumbered Summary of @value{GDBN}
175 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
176 going on ``inside'' another program while it executes---or what another
177 program was doing at the moment it crashed.
179 @value{GDBN} can do four main kinds of things (plus other things in support of
180 these) to help you catch bugs in the act:
184 Start your program, specifying anything that might affect its behavior.
187 Make your program stop on specified conditions.
190 Examine what has happened, when your program has stopped.
193 Change things in your program, so you can experiment with correcting the
194 effects of one bug and go on to learn about another.
197 You can use @value{GDBN} to debug programs written in C and C@t{++}.
198 For more information, see @ref{Supported languages,,Supported languages}.
199 For more information, see @ref{C,,C and C++}.
202 Support for Modula-2 is partial. For information on Modula-2, see
203 @ref{Modula-2,,Modula-2}.
206 Debugging Pascal programs which use sets, subranges, file variables, or
207 nested functions does not currently work. @value{GDBN} does not support
208 entering expressions, printing values, or similar features using Pascal
212 @value{GDBN} can be used to debug programs written in Fortran, although
213 it may be necessary to refer to some variables with a trailing
216 @value{GDBN} can be used to debug programs written in Objective-C,
217 using either the Apple/NeXT or the GNU Objective-C runtime.
220 * Free Software:: Freely redistributable software
221 * Contributors:: Contributors to GDB
225 @unnumberedsec Free software
227 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
228 General Public License
229 (GPL). The GPL gives you the freedom to copy or adapt a licensed
230 program---but every person getting a copy also gets with it the
231 freedom to modify that copy (which means that they must get access to
232 the source code), and the freedom to distribute further copies.
233 Typical software companies use copyrights to limit your freedoms; the
234 Free Software Foundation uses the GPL to preserve these freedoms.
236 Fundamentally, the General Public License is a license which says that
237 you have these freedoms and that you cannot take these freedoms away
240 @unnumberedsec Free Software Needs Free Documentation
242 The biggest deficiency in the free software community today is not in
243 the software---it is the lack of good free documentation that we can
244 include with the free software. Many of our most important
245 programs do not come with free reference manuals and free introductory
246 texts. Documentation is an essential part of any software package;
247 when an important free software package does not come with a free
248 manual and a free tutorial, that is a major gap. We have many such
251 Consider Perl, for instance. The tutorial manuals that people
252 normally use are non-free. How did this come about? Because the
253 authors of those manuals published them with restrictive terms---no
254 copying, no modification, source files not available---which exclude
255 them from the free software world.
257 That wasn't the first time this sort of thing happened, and it was far
258 from the last. Many times we have heard a GNU user eagerly describe a
259 manual that he is writing, his intended contribution to the community,
260 only to learn that he had ruined everything by signing a publication
261 contract to make it non-free.
263 Free documentation, like free software, is a matter of freedom, not
264 price. The problem with the non-free manual is not that publishers
265 charge a price for printed copies---that in itself is fine. (The Free
266 Software Foundation sells printed copies of manuals, too.) The
267 problem is the restrictions on the use of the manual. Free manuals
268 are available in source code form, and give you permission to copy and
269 modify. Non-free manuals do not allow this.
271 The criteria of freedom for a free manual are roughly the same as for
272 free software. Redistribution (including the normal kinds of
273 commercial redistribution) must be permitted, so that the manual can
274 accompany every copy of the program, both on-line and on paper.
276 Permission for modification of the technical content is crucial too.
277 When people modify the software, adding or changing features, if they
278 are conscientious they will change the manual too---so they can
279 provide accurate and clear documentation for the modified program. A
280 manual that leaves you no choice but to write a new manual to document
281 a changed version of the program is not really available to our
284 Some kinds of limits on the way modification is handled are
285 acceptable. For example, requirements to preserve the original
286 author's copyright notice, the distribution terms, or the list of
287 authors, are ok. It is also no problem to require modified versions
288 to include notice that they were modified. Even entire sections that
289 may not be deleted or changed are acceptable, as long as they deal
290 with nontechnical topics (like this one). These kinds of restrictions
291 are acceptable because they don't obstruct the community's normal use
294 However, it must be possible to modify all the @emph{technical}
295 content of the manual, and then distribute the result in all the usual
296 media, through all the usual channels. Otherwise, the restrictions
297 obstruct the use of the manual, it is not free, and we need another
298 manual to replace it.
300 Please spread the word about this issue. Our community continues to
301 lose manuals to proprietary publishing. If we spread the word that
302 free software needs free reference manuals and free tutorials, perhaps
303 the next person who wants to contribute by writing documentation will
304 realize, before it is too late, that only free manuals contribute to
305 the free software community.
307 If you are writing documentation, please insist on publishing it under
308 the GNU Free Documentation License or another free documentation
309 license. Remember that this decision requires your approval---you
310 don't have to let the publisher decide. Some commercial publishers
311 will use a free license if you insist, but they will not propose the
312 option; it is up to you to raise the issue and say firmly that this is
313 what you want. If the publisher you are dealing with refuses, please
314 try other publishers. If you're not sure whether a proposed license
315 is free, write to @email{licensing@@gnu.org}.
317 You can encourage commercial publishers to sell more free, copylefted
318 manuals and tutorials by buying them, and particularly by buying
319 copies from the publishers that paid for their writing or for major
320 improvements. Meanwhile, try to avoid buying non-free documentation
321 at all. Check the distribution terms of a manual before you buy it,
322 and insist that whoever seeks your business must respect your freedom.
323 Check the history of the book, and try to reward the publishers that
324 have paid or pay the authors to work on it.
326 The Free Software Foundation maintains a list of free documentation
327 published by other publishers, at
328 @url{http://www.fsf.org/doc/other-free-books.html}.
331 @unnumberedsec Contributors to @value{GDBN}
333 Richard Stallman was the original author of @value{GDBN}, and of many
334 other @sc{gnu} programs. Many others have contributed to its
335 development. This section attempts to credit major contributors. One
336 of the virtues of free software is that everyone is free to contribute
337 to it; with regret, we cannot actually acknowledge everyone here. The
338 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
339 blow-by-blow account.
341 Changes much prior to version 2.0 are lost in the mists of time.
344 @emph{Plea:} Additions to this section are particularly welcome. If you
345 or your friends (or enemies, to be evenhanded) have been unfairly
346 omitted from this list, we would like to add your names!
349 So that they may not regard their many labors as thankless, we
350 particularly thank those who shepherded @value{GDBN} through major
352 Andrew Cagney (releases 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
353 Jim Blandy (release 4.18);
354 Jason Molenda (release 4.17);
355 Stan Shebs (release 4.14);
356 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
357 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
358 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
359 Jim Kingdon (releases 3.5, 3.4, and 3.3);
360 and Randy Smith (releases 3.2, 3.1, and 3.0).
362 Richard Stallman, assisted at various times by Peter TerMaat, Chris
363 Hanson, and Richard Mlynarik, handled releases through 2.8.
365 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
366 in @value{GDBN}, with significant additional contributions from Per
367 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
368 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
369 much general update work leading to release 3.0).
371 @value{GDBN} uses the BFD subroutine library to examine multiple
372 object-file formats; BFD was a joint project of David V.
373 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
375 David Johnson wrote the original COFF support; Pace Willison did
376 the original support for encapsulated COFF.
378 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
380 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
381 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
383 Jean-Daniel Fekete contributed Sun 386i support.
384 Chris Hanson improved the HP9000 support.
385 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
386 David Johnson contributed Encore Umax support.
387 Jyrki Kuoppala contributed Altos 3068 support.
388 Jeff Law contributed HP PA and SOM support.
389 Keith Packard contributed NS32K support.
390 Doug Rabson contributed Acorn Risc Machine support.
391 Bob Rusk contributed Harris Nighthawk CX-UX support.
392 Chris Smith contributed Convex support (and Fortran debugging).
393 Jonathan Stone contributed Pyramid support.
394 Michael Tiemann contributed SPARC support.
395 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
396 Pace Willison contributed Intel 386 support.
397 Jay Vosburgh contributed Symmetry support.
398 Marko Mlinar contributed OpenRISC 1000 support.
400 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
402 Rich Schaefer and Peter Schauer helped with support of SunOS shared
405 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
406 about several machine instruction sets.
408 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
409 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
410 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
411 and RDI targets, respectively.
413 Brian Fox is the author of the readline libraries providing
414 command-line editing and command history.
416 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
417 Modula-2 support, and contributed the Languages chapter of this manual.
419 Fred Fish wrote most of the support for Unix System Vr4.
420 He also enhanced the command-completion support to cover C@t{++} overloaded
423 Hitachi America (now Renesas America), Ltd. sponsored the support for
424 H8/300, H8/500, and Super-H processors.
426 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
428 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
431 Toshiba sponsored the support for the TX39 Mips processor.
433 Matsushita sponsored the support for the MN10200 and MN10300 processors.
435 Fujitsu sponsored the support for SPARClite and FR30 processors.
437 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
440 Michael Snyder added support for tracepoints.
442 Stu Grossman wrote gdbserver.
444 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
445 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
447 The following people at the Hewlett-Packard Company contributed
448 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
449 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
450 compiler, and the Text User Interface (nee Terminal User Interface):
451 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
452 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
453 provided HP-specific information in this manual.
455 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
456 Robert Hoehne made significant contributions to the DJGPP port.
458 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
459 development since 1991. Cygnus engineers who have worked on @value{GDBN}
460 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
461 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
462 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
463 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
464 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
465 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
466 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
467 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
468 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
469 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
470 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
471 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
472 Zuhn have made contributions both large and small.
474 Jim Blandy added support for preprocessor macros, while working for Red
478 @chapter A Sample @value{GDBN} Session
480 You can use this manual at your leisure to read all about @value{GDBN}.
481 However, a handful of commands are enough to get started using the
482 debugger. This chapter illustrates those commands.
485 In this sample session, we emphasize user input like this: @b{input},
486 to make it easier to pick out from the surrounding output.
489 @c FIXME: this example may not be appropriate for some configs, where
490 @c FIXME...primary interest is in remote use.
492 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
493 processor) exhibits the following bug: sometimes, when we change its
494 quote strings from the default, the commands used to capture one macro
495 definition within another stop working. In the following short @code{m4}
496 session, we define a macro @code{foo} which expands to @code{0000}; we
497 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
498 same thing. However, when we change the open quote string to
499 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
500 procedure fails to define a new synonym @code{baz}:
509 @b{define(bar,defn(`foo'))}
513 @b{changequote(<QUOTE>,<UNQUOTE>)}
515 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
518 m4: End of input: 0: fatal error: EOF in string
522 Let us use @value{GDBN} to try to see what is going on.
525 $ @b{@value{GDBP} m4}
526 @c FIXME: this falsifies the exact text played out, to permit smallbook
527 @c FIXME... format to come out better.
528 @value{GDBN} is free software and you are welcome to distribute copies
529 of it under certain conditions; type "show copying" to see
531 There is absolutely no warranty for @value{GDBN}; type "show warranty"
534 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
539 @value{GDBN} reads only enough symbol data to know where to find the
540 rest when needed; as a result, the first prompt comes up very quickly.
541 We now tell @value{GDBN} to use a narrower display width than usual, so
542 that examples fit in this manual.
545 (@value{GDBP}) @b{set width 70}
549 We need to see how the @code{m4} built-in @code{changequote} works.
550 Having looked at the source, we know the relevant subroutine is
551 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
552 @code{break} command.
555 (@value{GDBP}) @b{break m4_changequote}
556 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
560 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
561 control; as long as control does not reach the @code{m4_changequote}
562 subroutine, the program runs as usual:
565 (@value{GDBP}) @b{run}
566 Starting program: /work/Editorial/gdb/gnu/m4/m4
574 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
575 suspends execution of @code{m4}, displaying information about the
576 context where it stops.
579 @b{changequote(<QUOTE>,<UNQUOTE>)}
581 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
583 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
587 Now we use the command @code{n} (@code{next}) to advance execution to
588 the next line of the current function.
592 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
597 @code{set_quotes} looks like a promising subroutine. We can go into it
598 by using the command @code{s} (@code{step}) instead of @code{next}.
599 @code{step} goes to the next line to be executed in @emph{any}
600 subroutine, so it steps into @code{set_quotes}.
604 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
606 530 if (lquote != def_lquote)
610 The display that shows the subroutine where @code{m4} is now
611 suspended (and its arguments) is called a stack frame display. It
612 shows a summary of the stack. We can use the @code{backtrace}
613 command (which can also be spelled @code{bt}), to see where we are
614 in the stack as a whole: the @code{backtrace} command displays a
615 stack frame for each active subroutine.
618 (@value{GDBP}) @b{bt}
619 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
621 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
623 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
624 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
626 #4 0x79dc in expand_input () at macro.c:40
627 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
631 We step through a few more lines to see what happens. The first two
632 times, we can use @samp{s}; the next two times we use @code{n} to avoid
633 falling into the @code{xstrdup} subroutine.
637 0x3b5c 532 if (rquote != def_rquote)
639 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
640 def_lquote : xstrdup(lq);
642 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
645 538 len_lquote = strlen(rquote);
649 The last line displayed looks a little odd; we can examine the variables
650 @code{lquote} and @code{rquote} to see if they are in fact the new left
651 and right quotes we specified. We use the command @code{p}
652 (@code{print}) to see their values.
655 (@value{GDBP}) @b{p lquote}
656 $1 = 0x35d40 "<QUOTE>"
657 (@value{GDBP}) @b{p rquote}
658 $2 = 0x35d50 "<UNQUOTE>"
662 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
663 To look at some context, we can display ten lines of source
664 surrounding the current line with the @code{l} (@code{list}) command.
670 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
672 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
675 538 len_lquote = strlen(rquote);
676 539 len_rquote = strlen(lquote);
683 Let us step past the two lines that set @code{len_lquote} and
684 @code{len_rquote}, and then examine the values of those variables.
688 539 len_rquote = strlen(lquote);
691 (@value{GDBP}) @b{p len_lquote}
693 (@value{GDBP}) @b{p len_rquote}
698 That certainly looks wrong, assuming @code{len_lquote} and
699 @code{len_rquote} are meant to be the lengths of @code{lquote} and
700 @code{rquote} respectively. We can set them to better values using
701 the @code{p} command, since it can print the value of
702 any expression---and that expression can include subroutine calls and
706 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
708 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
713 Is that enough to fix the problem of using the new quotes with the
714 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
715 executing with the @code{c} (@code{continue}) command, and then try the
716 example that caused trouble initially:
722 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
729 Success! The new quotes now work just as well as the default ones. The
730 problem seems to have been just the two typos defining the wrong
731 lengths. We allow @code{m4} exit by giving it an EOF as input:
735 Program exited normally.
739 The message @samp{Program exited normally.} is from @value{GDBN}; it
740 indicates @code{m4} has finished executing. We can end our @value{GDBN}
741 session with the @value{GDBN} @code{quit} command.
744 (@value{GDBP}) @b{quit}
748 @chapter Getting In and Out of @value{GDBN}
750 This chapter discusses how to start @value{GDBN}, and how to get out of it.
754 type @samp{@value{GDBP}} to start @value{GDBN}.
756 type @kbd{quit} or @kbd{C-d} to exit.
760 * Invoking GDB:: How to start @value{GDBN}
761 * Quitting GDB:: How to quit @value{GDBN}
762 * Shell Commands:: How to use shell commands inside @value{GDBN}
763 * Logging output:: How to log @value{GDBN}'s output to a file
767 @section Invoking @value{GDBN}
769 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
770 @value{GDBN} reads commands from the terminal until you tell it to exit.
772 You can also run @code{@value{GDBP}} with a variety of arguments and options,
773 to specify more of your debugging environment at the outset.
775 The command-line options described here are designed
776 to cover a variety of situations; in some environments, some of these
777 options may effectively be unavailable.
779 The most usual way to start @value{GDBN} is with one argument,
780 specifying an executable program:
783 @value{GDBP} @var{program}
787 You can also start with both an executable program and a core file
791 @value{GDBP} @var{program} @var{core}
794 You can, instead, specify a process ID as a second argument, if you want
795 to debug a running process:
798 @value{GDBP} @var{program} 1234
802 would attach @value{GDBN} to process @code{1234} (unless you also have a file
803 named @file{1234}; @value{GDBN} does check for a core file first).
805 Taking advantage of the second command-line argument requires a fairly
806 complete operating system; when you use @value{GDBN} as a remote
807 debugger attached to a bare board, there may not be any notion of
808 ``process'', and there is often no way to get a core dump. @value{GDBN}
809 will warn you if it is unable to attach or to read core dumps.
811 You can optionally have @code{@value{GDBP}} pass any arguments after the
812 executable file to the inferior using @code{--args}. This option stops
815 gdb --args gcc -O2 -c foo.c
817 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
818 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
820 You can run @code{@value{GDBP}} without printing the front material, which describes
821 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
828 You can further control how @value{GDBN} starts up by using command-line
829 options. @value{GDBN} itself can remind you of the options available.
839 to display all available options and briefly describe their use
840 (@samp{@value{GDBP} -h} is a shorter equivalent).
842 All options and command line arguments you give are processed
843 in sequential order. The order makes a difference when the
844 @samp{-x} option is used.
848 * File Options:: Choosing files
849 * Mode Options:: Choosing modes
853 @subsection Choosing files
855 When @value{GDBN} starts, it reads any arguments other than options as
856 specifying an executable file and core file (or process ID). This is
857 the same as if the arguments were specified by the @samp{-se} and
858 @samp{-c} (or @samp{-p} options respectively. (@value{GDBN} reads the
859 first argument that does not have an associated option flag as
860 equivalent to the @samp{-se} option followed by that argument; and the
861 second argument that does not have an associated option flag, if any, as
862 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
863 If the second argument begins with a decimal digit, @value{GDBN} will
864 first attempt to attach to it as a process, and if that fails, attempt
865 to open it as a corefile. If you have a corefile whose name begins with
866 a digit, you can prevent @value{GDBN} from treating it as a pid by
867 prefixing it with @file{./}, eg. @file{./12345}.
869 If @value{GDBN} has not been configured to included core file support,
870 such as for most embedded targets, then it will complain about a second
871 argument and ignore it.
873 Many options have both long and short forms; both are shown in the
874 following list. @value{GDBN} also recognizes the long forms if you truncate
875 them, so long as enough of the option is present to be unambiguous.
876 (If you prefer, you can flag option arguments with @samp{--} rather
877 than @samp{-}, though we illustrate the more usual convention.)
879 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
880 @c way, both those who look for -foo and --foo in the index, will find
884 @item -symbols @var{file}
886 @cindex @code{--symbols}
888 Read symbol table from file @var{file}.
890 @item -exec @var{file}
892 @cindex @code{--exec}
894 Use file @var{file} as the executable file to execute when appropriate,
895 and for examining pure data in conjunction with a core dump.
899 Read symbol table from file @var{file} and use it as the executable
902 @item -core @var{file}
904 @cindex @code{--core}
906 Use file @var{file} as a core dump to examine.
908 @item -c @var{number}
909 @item -pid @var{number}
910 @itemx -p @var{number}
913 Connect to process ID @var{number}, as with the @code{attach} command.
914 If there is no such process, @value{GDBN} will attempt to open a core
915 file named @var{number}.
917 @item -command @var{file}
919 @cindex @code{--command}
921 Execute @value{GDBN} commands from file @var{file}. @xref{Command
922 Files,, Command files}.
924 @item -directory @var{directory}
925 @itemx -d @var{directory}
926 @cindex @code{--directory}
928 Add @var{directory} to the path to search for source files.
932 @cindex @code{--mapped}
934 @emph{Warning: this option depends on operating system facilities that are not
935 supported on all systems.}@*
936 If memory-mapped files are available on your system through the @code{mmap}
937 system call, you can use this option
938 to have @value{GDBN} write the symbols from your
939 program into a reusable file in the current directory. If the program you are debugging is
940 called @file{/tmp/fred}, the mapped symbol file is @file{/tmp/fred.syms}.
941 Future @value{GDBN} debugging sessions notice the presence of this file,
942 and can quickly map in symbol information from it, rather than reading
943 the symbol table from the executable program.
945 The @file{.syms} file is specific to the host machine where @value{GDBN}
946 is run. It holds an exact image of the internal @value{GDBN} symbol
947 table. It cannot be shared across multiple host platforms.
951 @cindex @code{--readnow}
953 Read each symbol file's entire symbol table immediately, rather than
954 the default, which is to read it incrementally as it is needed.
955 This makes startup slower, but makes future operations faster.
959 You typically combine the @code{-mapped} and @code{-readnow} options in
960 order to build a @file{.syms} file that contains complete symbol
961 information. (@xref{Files,,Commands to specify files}, for information
962 on @file{.syms} files.) A simple @value{GDBN} invocation to do nothing
963 but build a @file{.syms} file for future use is:
966 gdb -batch -nx -mapped -readnow programname
970 @subsection Choosing modes
972 You can run @value{GDBN} in various alternative modes---for example, in
973 batch mode or quiet mode.
980 Do not execute commands found in any initialization files. Normally,
981 @value{GDBN} executes the commands in these files after all the command
982 options and arguments have been processed. @xref{Command Files,,Command
988 @cindex @code{--quiet}
989 @cindex @code{--silent}
991 ``Quiet''. Do not print the introductory and copyright messages. These
992 messages are also suppressed in batch mode.
995 @cindex @code{--batch}
996 Run in batch mode. Exit with status @code{0} after processing all the
997 command files specified with @samp{-x} (and all commands from
998 initialization files, if not inhibited with @samp{-n}). Exit with
999 nonzero status if an error occurs in executing the @value{GDBN} commands
1000 in the command files.
1002 Batch mode may be useful for running @value{GDBN} as a filter, for
1003 example to download and run a program on another computer; in order to
1004 make this more useful, the message
1007 Program exited normally.
1011 (which is ordinarily issued whenever a program running under
1012 @value{GDBN} control terminates) is not issued when running in batch
1017 @cindex @code{--nowindows}
1019 ``No windows''. If @value{GDBN} comes with a graphical user interface
1020 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1021 interface. If no GUI is available, this option has no effect.
1025 @cindex @code{--windows}
1027 If @value{GDBN} includes a GUI, then this option requires it to be
1030 @item -cd @var{directory}
1032 Run @value{GDBN} using @var{directory} as its working directory,
1033 instead of the current directory.
1037 @cindex @code{--fullname}
1039 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1040 subprocess. It tells @value{GDBN} to output the full file name and line
1041 number in a standard, recognizable fashion each time a stack frame is
1042 displayed (which includes each time your program stops). This
1043 recognizable format looks like two @samp{\032} characters, followed by
1044 the file name, line number and character position separated by colons,
1045 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1046 @samp{\032} characters as a signal to display the source code for the
1050 @cindex @code{--epoch}
1051 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1052 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1053 routines so as to allow Epoch to display values of expressions in a
1056 @item -annotate @var{level}
1057 @cindex @code{--annotate}
1058 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1059 effect is identical to using @samp{set annotate @var{level}}
1060 (@pxref{Annotations}). The annotation @var{level} controls how much
1061 information @value{GDBN} prints together with its prompt, values of
1062 expressions, source lines, and other types of output. Level 0 is the
1063 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1064 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1065 that control @value{GDBN}, and level 2 has been deprecated.
1067 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
1071 @cindex @code{--args}
1072 Change interpretation of command line so that arguments following the
1073 executable file are passed as command line arguments to the inferior.
1074 This option stops option processing.
1076 @item -baud @var{bps}
1078 @cindex @code{--baud}
1080 Set the line speed (baud rate or bits per second) of any serial
1081 interface used by @value{GDBN} for remote debugging.
1083 @item -l @var{timeout}
1085 Set the timeout (in seconds) of any communication used by @value{GDBN}
1086 for remote debugging.
1088 @item -tty @var{device}
1089 @itemx -t @var{device}
1090 @cindex @code{--tty}
1092 Run using @var{device} for your program's standard input and output.
1093 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1095 @c resolve the situation of these eventually
1097 @cindex @code{--tui}
1098 Activate the @dfn{Text User Interface} when starting. The Text User
1099 Interface manages several text windows on the terminal, showing
1100 source, assembly, registers and @value{GDBN} command outputs
1101 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1102 Text User Interface can be enabled by invoking the program
1103 @samp{gdbtui}. Do not use this option if you run @value{GDBN} from
1104 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1107 @c @cindex @code{--xdb}
1108 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1109 @c For information, see the file @file{xdb_trans.html}, which is usually
1110 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1113 @item -interpreter @var{interp}
1114 @cindex @code{--interpreter}
1115 Use the interpreter @var{interp} for interface with the controlling
1116 program or device. This option is meant to be set by programs which
1117 communicate with @value{GDBN} using it as a back end.
1118 @xref{Interpreters, , Command Interpreters}.
1120 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1121 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1122 The @sc{gdb/mi} Interface}) included since @var{GDBN} version 6.0. The
1123 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1124 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1125 @sc{gdb/mi} interfaces are no longer supported.
1128 @cindex @code{--write}
1129 Open the executable and core files for both reading and writing. This
1130 is equivalent to the @samp{set write on} command inside @value{GDBN}
1134 @cindex @code{--statistics}
1135 This option causes @value{GDBN} to print statistics about time and
1136 memory usage after it completes each command and returns to the prompt.
1139 @cindex @code{--version}
1140 This option causes @value{GDBN} to print its version number and
1141 no-warranty blurb, and exit.
1146 @section Quitting @value{GDBN}
1147 @cindex exiting @value{GDBN}
1148 @cindex leaving @value{GDBN}
1151 @kindex quit @r{[}@var{expression}@r{]}
1152 @kindex q @r{(@code{quit})}
1153 @item quit @r{[}@var{expression}@r{]}
1155 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1156 @code{q}), or type an end-of-file character (usually @kbd{C-d}). If you
1157 do not supply @var{expression}, @value{GDBN} will terminate normally;
1158 otherwise it will terminate using the result of @var{expression} as the
1163 An interrupt (often @kbd{C-c}) does not exit from @value{GDBN}, but rather
1164 terminates the action of any @value{GDBN} command that is in progress and
1165 returns to @value{GDBN} command level. It is safe to type the interrupt
1166 character at any time because @value{GDBN} does not allow it to take effect
1167 until a time when it is safe.
1169 If you have been using @value{GDBN} to control an attached process or
1170 device, you can release it with the @code{detach} command
1171 (@pxref{Attach, ,Debugging an already-running process}).
1173 @node Shell Commands
1174 @section Shell commands
1176 If you need to execute occasional shell commands during your
1177 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1178 just use the @code{shell} command.
1182 @cindex shell escape
1183 @item shell @var{command string}
1184 Invoke a standard shell to execute @var{command string}.
1185 If it exists, the environment variable @code{SHELL} determines which
1186 shell to run. Otherwise @value{GDBN} uses the default shell
1187 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1190 The utility @code{make} is often needed in development environments.
1191 You do not have to use the @code{shell} command for this purpose in
1196 @cindex calling make
1197 @item make @var{make-args}
1198 Execute the @code{make} program with the specified
1199 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1202 @node Logging output
1203 @section Logging output
1204 @cindex logging @value{GDBN} output
1205 @cindex save @value{GDBN} output to a file
1207 You may want to save the output of @value{GDBN} commands to a file.
1208 There are several commands to control @value{GDBN}'s logging.
1212 @item set logging on
1214 @item set logging off
1216 @cindex logging file name
1217 @item set logging file @var{file}
1218 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1219 @item set logging overwrite [on|off]
1220 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1221 you want @code{set logging on} to overwrite the logfile instead.
1222 @item set logging redirect [on|off]
1223 By default, @value{GDBN} output will go to both the terminal and the logfile.
1224 Set @code{redirect} if you want output to go only to the log file.
1225 @kindex show logging
1227 Show the current values of the logging settings.
1231 @chapter @value{GDBN} Commands
1233 You can abbreviate a @value{GDBN} command to the first few letters of the command
1234 name, if that abbreviation is unambiguous; and you can repeat certain
1235 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1236 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1237 show you the alternatives available, if there is more than one possibility).
1240 * Command Syntax:: How to give commands to @value{GDBN}
1241 * Completion:: Command completion
1242 * Help:: How to ask @value{GDBN} for help
1245 @node Command Syntax
1246 @section Command syntax
1248 A @value{GDBN} command is a single line of input. There is no limit on
1249 how long it can be. It starts with a command name, which is followed by
1250 arguments whose meaning depends on the command name. For example, the
1251 command @code{step} accepts an argument which is the number of times to
1252 step, as in @samp{step 5}. You can also use the @code{step} command
1253 with no arguments. Some commands do not allow any arguments.
1255 @cindex abbreviation
1256 @value{GDBN} command names may always be truncated if that abbreviation is
1257 unambiguous. Other possible command abbreviations are listed in the
1258 documentation for individual commands. In some cases, even ambiguous
1259 abbreviations are allowed; for example, @code{s} is specially defined as
1260 equivalent to @code{step} even though there are other commands whose
1261 names start with @code{s}. You can test abbreviations by using them as
1262 arguments to the @code{help} command.
1264 @cindex repeating commands
1265 @kindex RET @r{(repeat last command)}
1266 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1267 repeat the previous command. Certain commands (for example, @code{run})
1268 will not repeat this way; these are commands whose unintentional
1269 repetition might cause trouble and which you are unlikely to want to
1272 The @code{list} and @code{x} commands, when you repeat them with
1273 @key{RET}, construct new arguments rather than repeating
1274 exactly as typed. This permits easy scanning of source or memory.
1276 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1277 output, in a way similar to the common utility @code{more}
1278 (@pxref{Screen Size,,Screen size}). Since it is easy to press one
1279 @key{RET} too many in this situation, @value{GDBN} disables command
1280 repetition after any command that generates this sort of display.
1282 @kindex # @r{(a comment)}
1284 Any text from a @kbd{#} to the end of the line is a comment; it does
1285 nothing. This is useful mainly in command files (@pxref{Command
1286 Files,,Command files}).
1288 @cindex repeating command sequences
1289 @kindex C-o @r{(operate-and-get-next)}
1290 The @kbd{C-o} binding is useful for repeating a complex sequence of
1291 commands. This command accepts the current line, like @kbd{RET}, and
1292 then fetches the next line relative to the current line from the history
1296 @section Command completion
1299 @cindex word completion
1300 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1301 only one possibility; it can also show you what the valid possibilities
1302 are for the next word in a command, at any time. This works for @value{GDBN}
1303 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1305 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1306 of a word. If there is only one possibility, @value{GDBN} fills in the
1307 word, and waits for you to finish the command (or press @key{RET} to
1308 enter it). For example, if you type
1310 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1311 @c complete accuracy in these examples; space introduced for clarity.
1312 @c If texinfo enhancements make it unnecessary, it would be nice to
1313 @c replace " @key" by "@key" in the following...
1315 (@value{GDBP}) info bre @key{TAB}
1319 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1320 the only @code{info} subcommand beginning with @samp{bre}:
1323 (@value{GDBP}) info breakpoints
1327 You can either press @key{RET} at this point, to run the @code{info
1328 breakpoints} command, or backspace and enter something else, if
1329 @samp{breakpoints} does not look like the command you expected. (If you
1330 were sure you wanted @code{info breakpoints} in the first place, you
1331 might as well just type @key{RET} immediately after @samp{info bre},
1332 to exploit command abbreviations rather than command completion).
1334 If there is more than one possibility for the next word when you press
1335 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1336 characters and try again, or just press @key{TAB} a second time;
1337 @value{GDBN} displays all the possible completions for that word. For
1338 example, you might want to set a breakpoint on a subroutine whose name
1339 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1340 just sounds the bell. Typing @key{TAB} again displays all the
1341 function names in your program that begin with those characters, for
1345 (@value{GDBP}) b make_ @key{TAB}
1346 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1347 make_a_section_from_file make_environ
1348 make_abs_section make_function_type
1349 make_blockvector make_pointer_type
1350 make_cleanup make_reference_type
1351 make_command make_symbol_completion_list
1352 (@value{GDBP}) b make_
1356 After displaying the available possibilities, @value{GDBN} copies your
1357 partial input (@samp{b make_} in the example) so you can finish the
1360 If you just want to see the list of alternatives in the first place, you
1361 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1362 means @kbd{@key{META} ?}. You can type this either by holding down a
1363 key designated as the @key{META} shift on your keyboard (if there is
1364 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1366 @cindex quotes in commands
1367 @cindex completion of quoted strings
1368 Sometimes the string you need, while logically a ``word'', may contain
1369 parentheses or other characters that @value{GDBN} normally excludes from
1370 its notion of a word. To permit word completion to work in this
1371 situation, you may enclose words in @code{'} (single quote marks) in
1372 @value{GDBN} commands.
1374 The most likely situation where you might need this is in typing the
1375 name of a C@t{++} function. This is because C@t{++} allows function
1376 overloading (multiple definitions of the same function, distinguished
1377 by argument type). For example, when you want to set a breakpoint you
1378 may need to distinguish whether you mean the version of @code{name}
1379 that takes an @code{int} parameter, @code{name(int)}, or the version
1380 that takes a @code{float} parameter, @code{name(float)}. To use the
1381 word-completion facilities in this situation, type a single quote
1382 @code{'} at the beginning of the function name. This alerts
1383 @value{GDBN} that it may need to consider more information than usual
1384 when you press @key{TAB} or @kbd{M-?} to request word completion:
1387 (@value{GDBP}) b 'bubble( @kbd{M-?}
1388 bubble(double,double) bubble(int,int)
1389 (@value{GDBP}) b 'bubble(
1392 In some cases, @value{GDBN} can tell that completing a name requires using
1393 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1394 completing as much as it can) if you do not type the quote in the first
1398 (@value{GDBP}) b bub @key{TAB}
1399 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1400 (@value{GDBP}) b 'bubble(
1404 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1405 you have not yet started typing the argument list when you ask for
1406 completion on an overloaded symbol.
1408 For more information about overloaded functions, see @ref{C plus plus
1409 expressions, ,C@t{++} expressions}. You can use the command @code{set
1410 overload-resolution off} to disable overload resolution;
1411 see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
1415 @section Getting help
1416 @cindex online documentation
1419 You can always ask @value{GDBN} itself for information on its commands,
1420 using the command @code{help}.
1423 @kindex h @r{(@code{help})}
1426 You can use @code{help} (abbreviated @code{h}) with no arguments to
1427 display a short list of named classes of commands:
1431 List of classes of commands:
1433 aliases -- Aliases of other commands
1434 breakpoints -- Making program stop at certain points
1435 data -- Examining data
1436 files -- Specifying and examining files
1437 internals -- Maintenance commands
1438 obscure -- Obscure features
1439 running -- Running the program
1440 stack -- Examining the stack
1441 status -- Status inquiries
1442 support -- Support facilities
1443 tracepoints -- Tracing of program execution without@*
1444 stopping the program
1445 user-defined -- User-defined commands
1447 Type "help" followed by a class name for a list of
1448 commands in that class.
1449 Type "help" followed by command name for full
1451 Command name abbreviations are allowed if unambiguous.
1454 @c the above line break eliminates huge line overfull...
1456 @item help @var{class}
1457 Using one of the general help classes as an argument, you can get a
1458 list of the individual commands in that class. For example, here is the
1459 help display for the class @code{status}:
1462 (@value{GDBP}) help status
1467 @c Line break in "show" line falsifies real output, but needed
1468 @c to fit in smallbook page size.
1469 info -- Generic command for showing things
1470 about the program being debugged
1471 show -- Generic command for showing things
1474 Type "help" followed by command name for full
1476 Command name abbreviations are allowed if unambiguous.
1480 @item help @var{command}
1481 With a command name as @code{help} argument, @value{GDBN} displays a
1482 short paragraph on how to use that command.
1485 @item apropos @var{args}
1486 The @code{apropos} command searches through all of the @value{GDBN}
1487 commands, and their documentation, for the regular expression specified in
1488 @var{args}. It prints out all matches found. For example:
1499 set symbol-reloading -- Set dynamic symbol table reloading
1500 multiple times in one run
1501 show symbol-reloading -- Show dynamic symbol table reloading
1502 multiple times in one run
1507 @item complete @var{args}
1508 The @code{complete @var{args}} command lists all the possible completions
1509 for the beginning of a command. Use @var{args} to specify the beginning of the
1510 command you want completed. For example:
1516 @noindent results in:
1527 @noindent This is intended for use by @sc{gnu} Emacs.
1530 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1531 and @code{show} to inquire about the state of your program, or the state
1532 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1533 manual introduces each of them in the appropriate context. The listings
1534 under @code{info} and under @code{show} in the Index point to
1535 all the sub-commands. @xref{Index}.
1540 @kindex i @r{(@code{info})}
1542 This command (abbreviated @code{i}) is for describing the state of your
1543 program. For example, you can list the arguments given to your program
1544 with @code{info args}, list the registers currently in use with @code{info
1545 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1546 You can get a complete list of the @code{info} sub-commands with
1547 @w{@code{help info}}.
1551 You can assign the result of an expression to an environment variable with
1552 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1553 @code{set prompt $}.
1557 In contrast to @code{info}, @code{show} is for describing the state of
1558 @value{GDBN} itself.
1559 You can change most of the things you can @code{show}, by using the
1560 related command @code{set}; for example, you can control what number
1561 system is used for displays with @code{set radix}, or simply inquire
1562 which is currently in use with @code{show radix}.
1565 To display all the settable parameters and their current
1566 values, you can use @code{show} with no arguments; you may also use
1567 @code{info set}. Both commands produce the same display.
1568 @c FIXME: "info set" violates the rule that "info" is for state of
1569 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1570 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1574 Here are three miscellaneous @code{show} subcommands, all of which are
1575 exceptional in lacking corresponding @code{set} commands:
1578 @kindex show version
1579 @cindex @value{GDBN} version number
1581 Show what version of @value{GDBN} is running. You should include this
1582 information in @value{GDBN} bug-reports. If multiple versions of
1583 @value{GDBN} are in use at your site, you may need to determine which
1584 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1585 commands are introduced, and old ones may wither away. Also, many
1586 system vendors ship variant versions of @value{GDBN}, and there are
1587 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1588 The version number is the same as the one announced when you start
1591 @kindex show copying
1592 @kindex info copying
1593 @cindex display @value{GDBN} copyright
1596 Display information about permission for copying @value{GDBN}.
1598 @kindex show warranty
1599 @kindex info warranty
1601 @itemx info warranty
1602 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1603 if your version of @value{GDBN} comes with one.
1608 @chapter Running Programs Under @value{GDBN}
1610 When you run a program under @value{GDBN}, you must first generate
1611 debugging information when you compile it.
1613 You may start @value{GDBN} with its arguments, if any, in an environment
1614 of your choice. If you are doing native debugging, you may redirect
1615 your program's input and output, debug an already running process, or
1616 kill a child process.
1619 * Compilation:: Compiling for debugging
1620 * Starting:: Starting your program
1621 * Arguments:: Your program's arguments
1622 * Environment:: Your program's environment
1624 * Working Directory:: Your program's working directory
1625 * Input/Output:: Your program's input and output
1626 * Attach:: Debugging an already-running process
1627 * Kill Process:: Killing the child process
1629 * Threads:: Debugging programs with multiple threads
1630 * Processes:: Debugging programs with multiple processes
1634 @section Compiling for debugging
1636 In order to debug a program effectively, you need to generate
1637 debugging information when you compile it. This debugging information
1638 is stored in the object file; it describes the data type of each
1639 variable or function and the correspondence between source line numbers
1640 and addresses in the executable code.
1642 To request debugging information, specify the @samp{-g} option when you run
1645 Most compilers do not include information about preprocessor macros in
1646 the debugging information if you specify the @option{-g} flag alone,
1647 because this information is rather large. Version 3.1 of @value{NGCC},
1648 the @sc{gnu} C compiler, provides macro information if you specify the
1649 options @option{-gdwarf-2} and @option{-g3}; the former option requests
1650 debugging information in the Dwarf 2 format, and the latter requests
1651 ``extra information''. In the future, we hope to find more compact ways
1652 to represent macro information, so that it can be included with
1655 Many C compilers are unable to handle the @samp{-g} and @samp{-O}
1656 options together. Using those compilers, you cannot generate optimized
1657 executables containing debugging information.
1659 @value{NGCC}, the @sc{gnu} C compiler, supports @samp{-g} with or
1660 without @samp{-O}, making it possible to debug optimized code. We
1661 recommend that you @emph{always} use @samp{-g} whenever you compile a
1662 program. You may think your program is correct, but there is no sense
1663 in pushing your luck.
1665 @cindex optimized code, debugging
1666 @cindex debugging optimized code
1667 When you debug a program compiled with @samp{-g -O}, remember that the
1668 optimizer is rearranging your code; the debugger shows you what is
1669 really there. Do not be too surprised when the execution path does not
1670 exactly match your source file! An extreme example: if you define a
1671 variable, but never use it, @value{GDBN} never sees that
1672 variable---because the compiler optimizes it out of existence.
1674 Some things do not work as well with @samp{-g -O} as with just
1675 @samp{-g}, particularly on machines with instruction scheduling. If in
1676 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1677 please report it to us as a bug (including a test case!).
1678 @xref{Variables}, for more information about debugging optimized code.
1680 Older versions of the @sc{gnu} C compiler permitted a variant option
1681 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1682 format; if your @sc{gnu} C compiler has this option, do not use it.
1686 @section Starting your program
1692 @kindex r @r{(@code{run})}
1695 Use the @code{run} command to start your program under @value{GDBN}.
1696 You must first specify the program name (except on VxWorks) with an
1697 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1698 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1699 (@pxref{Files, ,Commands to specify files}).
1703 If you are running your program in an execution environment that
1704 supports processes, @code{run} creates an inferior process and makes
1705 that process run your program. (In environments without processes,
1706 @code{run} jumps to the start of your program.)
1708 The execution of a program is affected by certain information it
1709 receives from its superior. @value{GDBN} provides ways to specify this
1710 information, which you must do @emph{before} starting your program. (You
1711 can change it after starting your program, but such changes only affect
1712 your program the next time you start it.) This information may be
1713 divided into four categories:
1716 @item The @emph{arguments.}
1717 Specify the arguments to give your program as the arguments of the
1718 @code{run} command. If a shell is available on your target, the shell
1719 is used to pass the arguments, so that you may use normal conventions
1720 (such as wildcard expansion or variable substitution) in describing
1722 In Unix systems, you can control which shell is used with the
1723 @code{SHELL} environment variable.
1724 @xref{Arguments, ,Your program's arguments}.
1726 @item The @emph{environment.}
1727 Your program normally inherits its environment from @value{GDBN}, but you can
1728 use the @value{GDBN} commands @code{set environment} and @code{unset
1729 environment} to change parts of the environment that affect
1730 your program. @xref{Environment, ,Your program's environment}.
1732 @item The @emph{working directory.}
1733 Your program inherits its working directory from @value{GDBN}. You can set
1734 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1735 @xref{Working Directory, ,Your program's working directory}.
1737 @item The @emph{standard input and output.}
1738 Your program normally uses the same device for standard input and
1739 standard output as @value{GDBN} is using. You can redirect input and output
1740 in the @code{run} command line, or you can use the @code{tty} command to
1741 set a different device for your program.
1742 @xref{Input/Output, ,Your program's input and output}.
1745 @emph{Warning:} While input and output redirection work, you cannot use
1746 pipes to pass the output of the program you are debugging to another
1747 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1751 When you issue the @code{run} command, your program begins to execute
1752 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1753 of how to arrange for your program to stop. Once your program has
1754 stopped, you may call functions in your program, using the @code{print}
1755 or @code{call} commands. @xref{Data, ,Examining Data}.
1757 If the modification time of your symbol file has changed since the last
1758 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1759 table, and reads it again. When it does this, @value{GDBN} tries to retain
1760 your current breakpoints.
1765 @cindex run to main procedure
1766 The name of the main procedure can vary from language to language.
1767 With C or C@t{++}, the main procedure name is always @code{main}, but
1768 other languages such as Ada do not require a specific name for their
1769 main procedure. The debugger provides a convenient way to start the
1770 execution of the program and to stop at the beginning of the main
1771 procedure, depending on the language used.
1773 The @samp{start} command does the equivalent of setting a temporary
1774 breakpoint at the beginning of the main procedure and then invoking
1775 the @samp{run} command.
1777 @cindex elaboration phase
1778 Some programs contain an @dfn{elaboration} phase where some startup code is
1779 executed before the main procedure is called. This depends on the
1780 languages used to write your program. In C@t{++}, for instance,
1781 constructors for static and global objects are executed before
1782 @code{main} is called. It is therefore possible that the debugger stops
1783 before reaching the main procedure. However, the temporary breakpoint
1784 will remain to halt execution.
1786 Specify the arguments to give to your program as arguments to the
1787 @samp{start} command. These arguments will be given verbatim to the
1788 underlying @samp{run} command. Note that the same arguments will be
1789 reused if no argument is provided during subsequent calls to
1790 @samp{start} or @samp{run}.
1792 It is sometimes necessary to debug the program during elaboration. In
1793 these cases, using the @code{start} command would stop the execution of
1794 your program too late, as the program would have already completed the
1795 elaboration phase. Under these circumstances, insert breakpoints in your
1796 elaboration code before running your program.
1800 @section Your program's arguments
1802 @cindex arguments (to your program)
1803 The arguments to your program can be specified by the arguments of the
1805 They are passed to a shell, which expands wildcard characters and
1806 performs redirection of I/O, and thence to your program. Your
1807 @code{SHELL} environment variable (if it exists) specifies what shell
1808 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1809 the default shell (@file{/bin/sh} on Unix).
1811 On non-Unix systems, the program is usually invoked directly by
1812 @value{GDBN}, which emulates I/O redirection via the appropriate system
1813 calls, and the wildcard characters are expanded by the startup code of
1814 the program, not by the shell.
1816 @code{run} with no arguments uses the same arguments used by the previous
1817 @code{run}, or those set by the @code{set args} command.
1822 Specify the arguments to be used the next time your program is run. If
1823 @code{set args} has no arguments, @code{run} executes your program
1824 with no arguments. Once you have run your program with arguments,
1825 using @code{set args} before the next @code{run} is the only way to run
1826 it again without arguments.
1830 Show the arguments to give your program when it is started.
1834 @section Your program's environment
1836 @cindex environment (of your program)
1837 The @dfn{environment} consists of a set of environment variables and
1838 their values. Environment variables conventionally record such things as
1839 your user name, your home directory, your terminal type, and your search
1840 path for programs to run. Usually you set up environment variables with
1841 the shell and they are inherited by all the other programs you run. When
1842 debugging, it can be useful to try running your program with a modified
1843 environment without having to start @value{GDBN} over again.
1847 @item path @var{directory}
1848 Add @var{directory} to the front of the @code{PATH} environment variable
1849 (the search path for executables) that will be passed to your program.
1850 The value of @code{PATH} used by @value{GDBN} does not change.
1851 You may specify several directory names, separated by whitespace or by a
1852 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1853 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1854 is moved to the front, so it is searched sooner.
1856 You can use the string @samp{$cwd} to refer to whatever is the current
1857 working directory at the time @value{GDBN} searches the path. If you
1858 use @samp{.} instead, it refers to the directory where you executed the
1859 @code{path} command. @value{GDBN} replaces @samp{.} in the
1860 @var{directory} argument (with the current path) before adding
1861 @var{directory} to the search path.
1862 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1863 @c document that, since repeating it would be a no-op.
1867 Display the list of search paths for executables (the @code{PATH}
1868 environment variable).
1870 @kindex show environment
1871 @item show environment @r{[}@var{varname}@r{]}
1872 Print the value of environment variable @var{varname} to be given to
1873 your program when it starts. If you do not supply @var{varname},
1874 print the names and values of all environment variables to be given to
1875 your program. You can abbreviate @code{environment} as @code{env}.
1877 @kindex set environment
1878 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1879 Set environment variable @var{varname} to @var{value}. The value
1880 changes for your program only, not for @value{GDBN} itself. @var{value} may
1881 be any string; the values of environment variables are just strings, and
1882 any interpretation is supplied by your program itself. The @var{value}
1883 parameter is optional; if it is eliminated, the variable is set to a
1885 @c "any string" here does not include leading, trailing
1886 @c blanks. Gnu asks: does anyone care?
1888 For example, this command:
1895 tells the debugged program, when subsequently run, that its user is named
1896 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
1897 are not actually required.)
1899 @kindex unset environment
1900 @item unset environment @var{varname}
1901 Remove variable @var{varname} from the environment to be passed to your
1902 program. This is different from @samp{set env @var{varname} =};
1903 @code{unset environment} removes the variable from the environment,
1904 rather than assigning it an empty value.
1907 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
1909 by your @code{SHELL} environment variable if it exists (or
1910 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
1911 that runs an initialization file---such as @file{.cshrc} for C-shell, or
1912 @file{.bashrc} for BASH---any variables you set in that file affect
1913 your program. You may wish to move setting of environment variables to
1914 files that are only run when you sign on, such as @file{.login} or
1917 @node Working Directory
1918 @section Your program's working directory
1920 @cindex working directory (of your program)
1921 Each time you start your program with @code{run}, it inherits its
1922 working directory from the current working directory of @value{GDBN}.
1923 The @value{GDBN} working directory is initially whatever it inherited
1924 from its parent process (typically the shell), but you can specify a new
1925 working directory in @value{GDBN} with the @code{cd} command.
1927 The @value{GDBN} working directory also serves as a default for the commands
1928 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
1933 @cindex change working directory
1934 @item cd @var{directory}
1935 Set the @value{GDBN} working directory to @var{directory}.
1939 Print the @value{GDBN} working directory.
1942 It is generally impossible to find the current working directory of
1943 the process being debugged (since a program can change its directory
1944 during its run). If you work on a system where @value{GDBN} is
1945 configured with the @file{/proc} support, you can use the @code{info
1946 proc} command (@pxref{SVR4 Process Information}) to find out the
1947 current working directory of the debuggee.
1950 @section Your program's input and output
1955 By default, the program you run under @value{GDBN} does input and output to
1956 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
1957 to its own terminal modes to interact with you, but it records the terminal
1958 modes your program was using and switches back to them when you continue
1959 running your program.
1962 @kindex info terminal
1964 Displays information recorded by @value{GDBN} about the terminal modes your
1968 You can redirect your program's input and/or output using shell
1969 redirection with the @code{run} command. For example,
1976 starts your program, diverting its output to the file @file{outfile}.
1979 @cindex controlling terminal
1980 Another way to specify where your program should do input and output is
1981 with the @code{tty} command. This command accepts a file name as
1982 argument, and causes this file to be the default for future @code{run}
1983 commands. It also resets the controlling terminal for the child
1984 process, for future @code{run} commands. For example,
1991 directs that processes started with subsequent @code{run} commands
1992 default to do input and output on the terminal @file{/dev/ttyb} and have
1993 that as their controlling terminal.
1995 An explicit redirection in @code{run} overrides the @code{tty} command's
1996 effect on the input/output device, but not its effect on the controlling
1999 When you use the @code{tty} command or redirect input in the @code{run}
2000 command, only the input @emph{for your program} is affected. The input
2001 for @value{GDBN} still comes from your terminal.
2004 @section Debugging an already-running process
2009 @item attach @var{process-id}
2010 This command attaches to a running process---one that was started
2011 outside @value{GDBN}. (@code{info files} shows your active
2012 targets.) The command takes as argument a process ID. The usual way to
2013 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2014 or with the @samp{jobs -l} shell command.
2016 @code{attach} does not repeat if you press @key{RET} a second time after
2017 executing the command.
2020 To use @code{attach}, your program must be running in an environment
2021 which supports processes; for example, @code{attach} does not work for
2022 programs on bare-board targets that lack an operating system. You must
2023 also have permission to send the process a signal.
2025 When you use @code{attach}, the debugger finds the program running in
2026 the process first by looking in the current working directory, then (if
2027 the program is not found) by using the source file search path
2028 (@pxref{Source Path, ,Specifying source directories}). You can also use
2029 the @code{file} command to load the program. @xref{Files, ,Commands to
2032 The first thing @value{GDBN} does after arranging to debug the specified
2033 process is to stop it. You can examine and modify an attached process
2034 with all the @value{GDBN} commands that are ordinarily available when
2035 you start processes with @code{run}. You can insert breakpoints; you
2036 can step and continue; you can modify storage. If you would rather the
2037 process continue running, you may use the @code{continue} command after
2038 attaching @value{GDBN} to the process.
2043 When you have finished debugging the attached process, you can use the
2044 @code{detach} command to release it from @value{GDBN} control. Detaching
2045 the process continues its execution. After the @code{detach} command,
2046 that process and @value{GDBN} become completely independent once more, and you
2047 are ready to @code{attach} another process or start one with @code{run}.
2048 @code{detach} does not repeat if you press @key{RET} again after
2049 executing the command.
2052 If you exit @value{GDBN} or use the @code{run} command while you have an
2053 attached process, you kill that process. By default, @value{GDBN} asks
2054 for confirmation if you try to do either of these things; you can
2055 control whether or not you need to confirm by using the @code{set
2056 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
2060 @section Killing the child process
2065 Kill the child process in which your program is running under @value{GDBN}.
2068 This command is useful if you wish to debug a core dump instead of a
2069 running process. @value{GDBN} ignores any core dump file while your program
2072 On some operating systems, a program cannot be executed outside @value{GDBN}
2073 while you have breakpoints set on it inside @value{GDBN}. You can use the
2074 @code{kill} command in this situation to permit running your program
2075 outside the debugger.
2077 The @code{kill} command is also useful if you wish to recompile and
2078 relink your program, since on many systems it is impossible to modify an
2079 executable file while it is running in a process. In this case, when you
2080 next type @code{run}, @value{GDBN} notices that the file has changed, and
2081 reads the symbol table again (while trying to preserve your current
2082 breakpoint settings).
2085 @section Debugging programs with multiple threads
2087 @cindex threads of execution
2088 @cindex multiple threads
2089 @cindex switching threads
2090 In some operating systems, such as HP-UX and Solaris, a single program
2091 may have more than one @dfn{thread} of execution. The precise semantics
2092 of threads differ from one operating system to another, but in general
2093 the threads of a single program are akin to multiple processes---except
2094 that they share one address space (that is, they can all examine and
2095 modify the same variables). On the other hand, each thread has its own
2096 registers and execution stack, and perhaps private memory.
2098 @value{GDBN} provides these facilities for debugging multi-thread
2102 @item automatic notification of new threads
2103 @item @samp{thread @var{threadno}}, a command to switch among threads
2104 @item @samp{info threads}, a command to inquire about existing threads
2105 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2106 a command to apply a command to a list of threads
2107 @item thread-specific breakpoints
2111 @emph{Warning:} These facilities are not yet available on every
2112 @value{GDBN} configuration where the operating system supports threads.
2113 If your @value{GDBN} does not support threads, these commands have no
2114 effect. For example, a system without thread support shows no output
2115 from @samp{info threads}, and always rejects the @code{thread} command,
2119 (@value{GDBP}) info threads
2120 (@value{GDBP}) thread 1
2121 Thread ID 1 not known. Use the "info threads" command to
2122 see the IDs of currently known threads.
2124 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2125 @c doesn't support threads"?
2128 @cindex focus of debugging
2129 @cindex current thread
2130 The @value{GDBN} thread debugging facility allows you to observe all
2131 threads while your program runs---but whenever @value{GDBN} takes
2132 control, one thread in particular is always the focus of debugging.
2133 This thread is called the @dfn{current thread}. Debugging commands show
2134 program information from the perspective of the current thread.
2136 @cindex @code{New} @var{systag} message
2137 @cindex thread identifier (system)
2138 @c FIXME-implementors!! It would be more helpful if the [New...] message
2139 @c included GDB's numeric thread handle, so you could just go to that
2140 @c thread without first checking `info threads'.
2141 Whenever @value{GDBN} detects a new thread in your program, it displays
2142 the target system's identification for the thread with a message in the
2143 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2144 whose form varies depending on the particular system. For example, on
2145 LynxOS, you might see
2148 [New process 35 thread 27]
2152 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2153 the @var{systag} is simply something like @samp{process 368}, with no
2156 @c FIXME!! (1) Does the [New...] message appear even for the very first
2157 @c thread of a program, or does it only appear for the
2158 @c second---i.e.@: when it becomes obvious we have a multithread
2160 @c (2) *Is* there necessarily a first thread always? Or do some
2161 @c multithread systems permit starting a program with multiple
2162 @c threads ab initio?
2164 @cindex thread number
2165 @cindex thread identifier (GDB)
2166 For debugging purposes, @value{GDBN} associates its own thread
2167 number---always a single integer---with each thread in your program.
2170 @kindex info threads
2172 Display a summary of all threads currently in your
2173 program. @value{GDBN} displays for each thread (in this order):
2177 the thread number assigned by @value{GDBN}
2180 the target system's thread identifier (@var{systag})
2183 the current stack frame summary for that thread
2187 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2188 indicates the current thread.
2192 @c end table here to get a little more width for example
2195 (@value{GDBP}) info threads
2196 3 process 35 thread 27 0x34e5 in sigpause ()
2197 2 process 35 thread 23 0x34e5 in sigpause ()
2198 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2204 @cindex debugging multithreaded programs (on HP-UX)
2205 @cindex thread identifier (GDB), on HP-UX
2206 For debugging purposes, @value{GDBN} associates its own thread
2207 number---a small integer assigned in thread-creation order---with each
2208 thread in your program.
2210 @cindex @code{New} @var{systag} message, on HP-UX
2211 @cindex thread identifier (system), on HP-UX
2212 @c FIXME-implementors!! It would be more helpful if the [New...] message
2213 @c included GDB's numeric thread handle, so you could just go to that
2214 @c thread without first checking `info threads'.
2215 Whenever @value{GDBN} detects a new thread in your program, it displays
2216 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2217 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2218 whose form varies depending on the particular system. For example, on
2222 [New thread 2 (system thread 26594)]
2226 when @value{GDBN} notices a new thread.
2229 @kindex info threads (HP-UX)
2231 Display a summary of all threads currently in your
2232 program. @value{GDBN} displays for each thread (in this order):
2235 @item the thread number assigned by @value{GDBN}
2237 @item the target system's thread identifier (@var{systag})
2239 @item the current stack frame summary for that thread
2243 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2244 indicates the current thread.
2248 @c end table here to get a little more width for example
2251 (@value{GDBP}) info threads
2252 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2254 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2255 from /usr/lib/libc.2
2256 1 system thread 27905 0x7b003498 in _brk () \@*
2257 from /usr/lib/libc.2
2261 @kindex thread @var{threadno}
2262 @item thread @var{threadno}
2263 Make thread number @var{threadno} the current thread. The command
2264 argument @var{threadno} is the internal @value{GDBN} thread number, as
2265 shown in the first field of the @samp{info threads} display.
2266 @value{GDBN} responds by displaying the system identifier of the thread
2267 you selected, and its current stack frame summary:
2270 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2271 (@value{GDBP}) thread 2
2272 [Switching to process 35 thread 23]
2273 0x34e5 in sigpause ()
2277 As with the @samp{[New @dots{}]} message, the form of the text after
2278 @samp{Switching to} depends on your system's conventions for identifying
2281 @kindex thread apply
2282 @item thread apply [@var{threadno}] [@var{all}] @var{args}
2283 The @code{thread apply} command allows you to apply a command to one or
2284 more threads. Specify the numbers of the threads that you want affected
2285 with the command argument @var{threadno}. @var{threadno} is the internal
2286 @value{GDBN} thread number, as shown in the first field of the @samp{info
2287 threads} display. To apply a command to all threads, use
2288 @code{thread apply all} @var{args}.
2291 @cindex automatic thread selection
2292 @cindex switching threads automatically
2293 @cindex threads, automatic switching
2294 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2295 signal, it automatically selects the thread where that breakpoint or
2296 signal happened. @value{GDBN} alerts you to the context switch with a
2297 message of the form @samp{[Switching to @var{systag}]} to identify the
2300 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2301 more information about how @value{GDBN} behaves when you stop and start
2302 programs with multiple threads.
2304 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2305 watchpoints in programs with multiple threads.
2308 @section Debugging programs with multiple processes
2310 @cindex fork, debugging programs which call
2311 @cindex multiple processes
2312 @cindex processes, multiple
2313 On most systems, @value{GDBN} has no special support for debugging
2314 programs which create additional processes using the @code{fork}
2315 function. When a program forks, @value{GDBN} will continue to debug the
2316 parent process and the child process will run unimpeded. If you have
2317 set a breakpoint in any code which the child then executes, the child
2318 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2319 will cause it to terminate.
2321 However, if you want to debug the child process there is a workaround
2322 which isn't too painful. Put a call to @code{sleep} in the code which
2323 the child process executes after the fork. It may be useful to sleep
2324 only if a certain environment variable is set, or a certain file exists,
2325 so that the delay need not occur when you don't want to run @value{GDBN}
2326 on the child. While the child is sleeping, use the @code{ps} program to
2327 get its process ID. Then tell @value{GDBN} (a new invocation of
2328 @value{GDBN} if you are also debugging the parent process) to attach to
2329 the child process (@pxref{Attach}). From that point on you can debug
2330 the child process just like any other process which you attached to.
2332 On some systems, @value{GDBN} provides support for debugging programs that
2333 create additional processes using the @code{fork} or @code{vfork} functions.
2334 Currently, the only platforms with this feature are HP-UX (11.x and later
2335 only?) and GNU/Linux (kernel version 2.5.60 and later).
2337 By default, when a program forks, @value{GDBN} will continue to debug
2338 the parent process and the child process will run unimpeded.
2340 If you want to follow the child process instead of the parent process,
2341 use the command @w{@code{set follow-fork-mode}}.
2344 @kindex set follow-fork-mode
2345 @item set follow-fork-mode @var{mode}
2346 Set the debugger response to a program call of @code{fork} or
2347 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2348 process. The @var{mode} argument can be:
2352 The original process is debugged after a fork. The child process runs
2353 unimpeded. This is the default.
2356 The new process is debugged after a fork. The parent process runs
2361 @kindex show follow-fork-mode
2362 @item show follow-fork-mode
2363 Display the current debugger response to a @code{fork} or @code{vfork} call.
2366 If you ask to debug a child process and a @code{vfork} is followed by an
2367 @code{exec}, @value{GDBN} executes the new target up to the first
2368 breakpoint in the new target. If you have a breakpoint set on
2369 @code{main} in your original program, the breakpoint will also be set on
2370 the child process's @code{main}.
2372 When a child process is spawned by @code{vfork}, you cannot debug the
2373 child or parent until an @code{exec} call completes.
2375 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2376 call executes, the new target restarts. To restart the parent process,
2377 use the @code{file} command with the parent executable name as its
2380 You can use the @code{catch} command to make @value{GDBN} stop whenever
2381 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2382 Catchpoints, ,Setting catchpoints}.
2385 @chapter Stopping and Continuing
2387 The principal purposes of using a debugger are so that you can stop your
2388 program before it terminates; or so that, if your program runs into
2389 trouble, you can investigate and find out why.
2391 Inside @value{GDBN}, your program may stop for any of several reasons,
2392 such as a signal, a breakpoint, or reaching a new line after a
2393 @value{GDBN} command such as @code{step}. You may then examine and
2394 change variables, set new breakpoints or remove old ones, and then
2395 continue execution. Usually, the messages shown by @value{GDBN} provide
2396 ample explanation of the status of your program---but you can also
2397 explicitly request this information at any time.
2400 @kindex info program
2402 Display information about the status of your program: whether it is
2403 running or not, what process it is, and why it stopped.
2407 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2408 * Continuing and Stepping:: Resuming execution
2410 * Thread Stops:: Stopping and starting multi-thread programs
2414 @section Breakpoints, watchpoints, and catchpoints
2417 A @dfn{breakpoint} makes your program stop whenever a certain point in
2418 the program is reached. For each breakpoint, you can add conditions to
2419 control in finer detail whether your program stops. You can set
2420 breakpoints with the @code{break} command and its variants (@pxref{Set
2421 Breaks, ,Setting breakpoints}), to specify the place where your program
2422 should stop by line number, function name or exact address in the
2425 On some systems, you can set breakpoints in shared libraries before
2426 the executable is run. There is a minor limitation on HP-UX systems:
2427 you must wait until the executable is run in order to set breakpoints
2428 in shared library routines that are not called directly by the program
2429 (for example, routines that are arguments in a @code{pthread_create}
2433 @cindex memory tracing
2434 @cindex breakpoint on memory address
2435 @cindex breakpoint on variable modification
2436 A @dfn{watchpoint} is a special breakpoint that stops your program
2437 when the value of an expression changes. You must use a different
2438 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2439 watchpoints}), but aside from that, you can manage a watchpoint like
2440 any other breakpoint: you enable, disable, and delete both breakpoints
2441 and watchpoints using the same commands.
2443 You can arrange to have values from your program displayed automatically
2444 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2448 @cindex breakpoint on events
2449 A @dfn{catchpoint} is another special breakpoint that stops your program
2450 when a certain kind of event occurs, such as the throwing of a C@t{++}
2451 exception or the loading of a library. As with watchpoints, you use a
2452 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2453 catchpoints}), but aside from that, you can manage a catchpoint like any
2454 other breakpoint. (To stop when your program receives a signal, use the
2455 @code{handle} command; see @ref{Signals, ,Signals}.)
2457 @cindex breakpoint numbers
2458 @cindex numbers for breakpoints
2459 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2460 catchpoint when you create it; these numbers are successive integers
2461 starting with one. In many of the commands for controlling various
2462 features of breakpoints you use the breakpoint number to say which
2463 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2464 @dfn{disabled}; if disabled, it has no effect on your program until you
2467 @cindex breakpoint ranges
2468 @cindex ranges of breakpoints
2469 Some @value{GDBN} commands accept a range of breakpoints on which to
2470 operate. A breakpoint range is either a single breakpoint number, like
2471 @samp{5}, or two such numbers, in increasing order, separated by a
2472 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2473 all breakpoint in that range are operated on.
2476 * Set Breaks:: Setting breakpoints
2477 * Set Watchpoints:: Setting watchpoints
2478 * Set Catchpoints:: Setting catchpoints
2479 * Delete Breaks:: Deleting breakpoints
2480 * Disabling:: Disabling breakpoints
2481 * Conditions:: Break conditions
2482 * Break Commands:: Breakpoint command lists
2483 * Breakpoint Menus:: Breakpoint menus
2484 * Error in Breakpoints:: ``Cannot insert breakpoints''
2485 * Breakpoint related warnings:: ``Breakpoint address adjusted...''
2489 @subsection Setting breakpoints
2491 @c FIXME LMB what does GDB do if no code on line of breakpt?
2492 @c consider in particular declaration with/without initialization.
2494 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2497 @kindex b @r{(@code{break})}
2498 @vindex $bpnum@r{, convenience variable}
2499 @cindex latest breakpoint
2500 Breakpoints are set with the @code{break} command (abbreviated
2501 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2502 number of the breakpoint you've set most recently; see @ref{Convenience
2503 Vars,, Convenience variables}, for a discussion of what you can do with
2504 convenience variables.
2506 You have several ways to say where the breakpoint should go.
2509 @item break @var{function}
2510 Set a breakpoint at entry to function @var{function}.
2511 When using source languages that permit overloading of symbols, such as
2512 C@t{++}, @var{function} may refer to more than one possible place to break.
2513 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2515 @item break +@var{offset}
2516 @itemx break -@var{offset}
2517 Set a breakpoint some number of lines forward or back from the position
2518 at which execution stopped in the currently selected @dfn{stack frame}.
2519 (@xref{Frames, ,Frames}, for a description of stack frames.)
2521 @item break @var{linenum}
2522 Set a breakpoint at line @var{linenum} in the current source file.
2523 The current source file is the last file whose source text was printed.
2524 The breakpoint will stop your program just before it executes any of the
2527 @item break @var{filename}:@var{linenum}
2528 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2530 @item break @var{filename}:@var{function}
2531 Set a breakpoint at entry to function @var{function} found in file
2532 @var{filename}. Specifying a file name as well as a function name is
2533 superfluous except when multiple files contain similarly named
2536 @item break *@var{address}
2537 Set a breakpoint at address @var{address}. You can use this to set
2538 breakpoints in parts of your program which do not have debugging
2539 information or source files.
2542 When called without any arguments, @code{break} sets a breakpoint at
2543 the next instruction to be executed in the selected stack frame
2544 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2545 innermost, this makes your program stop as soon as control
2546 returns to that frame. This is similar to the effect of a
2547 @code{finish} command in the frame inside the selected frame---except
2548 that @code{finish} does not leave an active breakpoint. If you use
2549 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2550 the next time it reaches the current location; this may be useful
2553 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2554 least one instruction has been executed. If it did not do this, you
2555 would be unable to proceed past a breakpoint without first disabling the
2556 breakpoint. This rule applies whether or not the breakpoint already
2557 existed when your program stopped.
2559 @item break @dots{} if @var{cond}
2560 Set a breakpoint with condition @var{cond}; evaluate the expression
2561 @var{cond} each time the breakpoint is reached, and stop only if the
2562 value is nonzero---that is, if @var{cond} evaluates as true.
2563 @samp{@dots{}} stands for one of the possible arguments described
2564 above (or no argument) specifying where to break. @xref{Conditions,
2565 ,Break conditions}, for more information on breakpoint conditions.
2568 @item tbreak @var{args}
2569 Set a breakpoint enabled only for one stop. @var{args} are the
2570 same as for the @code{break} command, and the breakpoint is set in the same
2571 way, but the breakpoint is automatically deleted after the first time your
2572 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2575 @item hbreak @var{args}
2576 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2577 @code{break} command and the breakpoint is set in the same way, but the
2578 breakpoint requires hardware support and some target hardware may not
2579 have this support. The main purpose of this is EPROM/ROM code
2580 debugging, so you can set a breakpoint at an instruction without
2581 changing the instruction. This can be used with the new trap-generation
2582 provided by SPARClite DSU and most x86-based targets. These targets
2583 will generate traps when a program accesses some data or instruction
2584 address that is assigned to the debug registers. However the hardware
2585 breakpoint registers can take a limited number of breakpoints. For
2586 example, on the DSU, only two data breakpoints can be set at a time, and
2587 @value{GDBN} will reject this command if more than two are used. Delete
2588 or disable unused hardware breakpoints before setting new ones
2589 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2590 For remote targets, you can restrict the number of hardware
2591 breakpoints @value{GDBN} will use, see @ref{set remote
2592 hardware-breakpoint-limit}.
2596 @item thbreak @var{args}
2597 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2598 are the same as for the @code{hbreak} command and the breakpoint is set in
2599 the same way. However, like the @code{tbreak} command,
2600 the breakpoint is automatically deleted after the
2601 first time your program stops there. Also, like the @code{hbreak}
2602 command, the breakpoint requires hardware support and some target hardware
2603 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2604 See also @ref{Conditions, ,Break conditions}.
2607 @cindex regular expression
2608 @item rbreak @var{regex}
2609 Set breakpoints on all functions matching the regular expression
2610 @var{regex}. This command sets an unconditional breakpoint on all
2611 matches, printing a list of all breakpoints it set. Once these
2612 breakpoints are set, they are treated just like the breakpoints set with
2613 the @code{break} command. You can delete them, disable them, or make
2614 them conditional the same way as any other breakpoint.
2616 The syntax of the regular expression is the standard one used with tools
2617 like @file{grep}. Note that this is different from the syntax used by
2618 shells, so for instance @code{foo*} matches all functions that include
2619 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2620 @code{.*} leading and trailing the regular expression you supply, so to
2621 match only functions that begin with @code{foo}, use @code{^foo}.
2623 @cindex non-member C@t{++} functions, set breakpoint in
2624 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2625 breakpoints on overloaded functions that are not members of any special
2628 @cindex set breakpoints on all functions
2629 The @code{rbreak} command can be used to set breakpoints in
2630 @strong{all} the functions in a program, like this:
2633 (@value{GDBP}) rbreak .
2636 @kindex info breakpoints
2637 @cindex @code{$_} and @code{info breakpoints}
2638 @item info breakpoints @r{[}@var{n}@r{]}
2639 @itemx info break @r{[}@var{n}@r{]}
2640 @itemx info watchpoints @r{[}@var{n}@r{]}
2641 Print a table of all breakpoints, watchpoints, and catchpoints set and
2642 not deleted, with the following columns for each breakpoint:
2645 @item Breakpoint Numbers
2647 Breakpoint, watchpoint, or catchpoint.
2649 Whether the breakpoint is marked to be disabled or deleted when hit.
2650 @item Enabled or Disabled
2651 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2652 that are not enabled.
2654 Where the breakpoint is in your program, as a memory address. If the
2655 breakpoint is pending (see below for details) on a future load of a shared library, the address
2656 will be listed as @samp{<PENDING>}.
2658 Where the breakpoint is in the source for your program, as a file and
2659 line number. For a pending breakpoint, the original string passed to
2660 the breakpoint command will be listed as it cannot be resolved until
2661 the appropriate shared library is loaded in the future.
2665 If a breakpoint is conditional, @code{info break} shows the condition on
2666 the line following the affected breakpoint; breakpoint commands, if any,
2667 are listed after that. A pending breakpoint is allowed to have a condition
2668 specified for it. The condition is not parsed for validity until a shared
2669 library is loaded that allows the pending breakpoint to resolve to a
2673 @code{info break} with a breakpoint
2674 number @var{n} as argument lists only that breakpoint. The
2675 convenience variable @code{$_} and the default examining-address for
2676 the @code{x} command are set to the address of the last breakpoint
2677 listed (@pxref{Memory, ,Examining memory}).
2680 @code{info break} displays a count of the number of times the breakpoint
2681 has been hit. This is especially useful in conjunction with the
2682 @code{ignore} command. You can ignore a large number of breakpoint
2683 hits, look at the breakpoint info to see how many times the breakpoint
2684 was hit, and then run again, ignoring one less than that number. This
2685 will get you quickly to the last hit of that breakpoint.
2688 @value{GDBN} allows you to set any number of breakpoints at the same place in
2689 your program. There is nothing silly or meaningless about this. When
2690 the breakpoints are conditional, this is even useful
2691 (@pxref{Conditions, ,Break conditions}).
2693 @cindex pending breakpoints
2694 If a specified breakpoint location cannot be found, it may be due to the fact
2695 that the location is in a shared library that is yet to be loaded. In such
2696 a case, you may want @value{GDBN} to create a special breakpoint (known as
2697 a @dfn{pending breakpoint}) that
2698 attempts to resolve itself in the future when an appropriate shared library
2701 Pending breakpoints are useful to set at the start of your
2702 @value{GDBN} session for locations that you know will be dynamically loaded
2703 later by the program being debugged. When shared libraries are loaded,
2704 a check is made to see if the load resolves any pending breakpoint locations.
2705 If a pending breakpoint location gets resolved,
2706 a regular breakpoint is created and the original pending breakpoint is removed.
2708 @value{GDBN} provides some additional commands for controlling pending
2711 @kindex set breakpoint pending
2712 @kindex show breakpoint pending
2714 @item set breakpoint pending auto
2715 This is the default behavior. When @value{GDBN} cannot find the breakpoint
2716 location, it queries you whether a pending breakpoint should be created.
2718 @item set breakpoint pending on
2719 This indicates that an unrecognized breakpoint location should automatically
2720 result in a pending breakpoint being created.
2722 @item set breakpoint pending off
2723 This indicates that pending breakpoints are not to be created. Any
2724 unrecognized breakpoint location results in an error. This setting does
2725 not affect any pending breakpoints previously created.
2727 @item show breakpoint pending
2728 Show the current behavior setting for creating pending breakpoints.
2731 @cindex operations allowed on pending breakpoints
2732 Normal breakpoint operations apply to pending breakpoints as well. You may
2733 specify a condition for a pending breakpoint and/or commands to run when the
2734 breakpoint is reached. You can also enable or disable
2735 the pending breakpoint. When you specify a condition for a pending breakpoint,
2736 the parsing of the condition will be deferred until the point where the
2737 pending breakpoint location is resolved. Disabling a pending breakpoint
2738 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
2739 shared library load. When a pending breakpoint is re-enabled,
2740 @value{GDBN} checks to see if the location is already resolved.
2741 This is done because any number of shared library loads could have
2742 occurred since the time the breakpoint was disabled and one or more
2743 of these loads could resolve the location.
2745 @cindex negative breakpoint numbers
2746 @cindex internal @value{GDBN} breakpoints
2747 @value{GDBN} itself sometimes sets breakpoints in your program for
2748 special purposes, such as proper handling of @code{longjmp} (in C
2749 programs). These internal breakpoints are assigned negative numbers,
2750 starting with @code{-1}; @samp{info breakpoints} does not display them.
2751 You can see these breakpoints with the @value{GDBN} maintenance command
2752 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
2755 @node Set Watchpoints
2756 @subsection Setting watchpoints
2758 @cindex setting watchpoints
2759 You can use a watchpoint to stop execution whenever the value of an
2760 expression changes, without having to predict a particular place where
2763 @cindex software watchpoints
2764 @cindex hardware watchpoints
2765 Depending on your system, watchpoints may be implemented in software or
2766 hardware. @value{GDBN} does software watchpointing by single-stepping your
2767 program and testing the variable's value each time, which is hundreds of
2768 times slower than normal execution. (But this may still be worth it, to
2769 catch errors where you have no clue what part of your program is the
2772 On some systems, such as HP-UX, @sc{gnu}/Linux and most other
2773 x86-based targets, @value{GDBN} includes support for hardware
2774 watchpoints, which do not slow down the running of your program.
2778 @item watch @var{expr}
2779 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
2780 is written into by the program and its value changes.
2783 @item rwatch @var{expr}
2784 Set a watchpoint that will break when the value of @var{expr} is read
2788 @item awatch @var{expr}
2789 Set a watchpoint that will break when @var{expr} is either read from
2790 or written into by the program.
2792 @kindex info watchpoints
2793 @item info watchpoints
2794 This command prints a list of watchpoints, breakpoints, and catchpoints;
2795 it is the same as @code{info break} (@pxref{Set Breaks}).
2798 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
2799 watchpoints execute very quickly, and the debugger reports a change in
2800 value at the exact instruction where the change occurs. If @value{GDBN}
2801 cannot set a hardware watchpoint, it sets a software watchpoint, which
2802 executes more slowly and reports the change in value at the next
2803 @emph{statement}, not the instruction, after the change occurs.
2805 @vindex can-use-hw-watchpoints
2806 @cindex use only software watchpoints
2807 You can force @value{GDBN} to use only software watchpoints with the
2808 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
2809 zero, @value{GDBN} will never try to use hardware watchpoints, even if
2810 the underlying system supports them. (Note that hardware-assisted
2811 watchpoints that were set @emph{before} setting
2812 @code{can-use-hw-watchpoints} to zero will still use the hardware
2813 mechanism of watching expressiion values.)
2816 @item set can-use-hw-watchpoints
2817 @kindex set can-use-hw-watchpoints
2818 Set whether or not to use hardware watchpoints.
2820 @item show can-use-hw-watchpoints
2821 @kindex show can-use-hw-watchpoints
2822 Show the current mode of using hardware watchpoints.
2825 For remote targets, you can restrict the number of hardware
2826 watchpoints @value{GDBN} will use, see @ref{set remote
2827 hardware-breakpoint-limit}.
2829 When you issue the @code{watch} command, @value{GDBN} reports
2832 Hardware watchpoint @var{num}: @var{expr}
2836 if it was able to set a hardware watchpoint.
2838 Currently, the @code{awatch} and @code{rwatch} commands can only set
2839 hardware watchpoints, because accesses to data that don't change the
2840 value of the watched expression cannot be detected without examining
2841 every instruction as it is being executed, and @value{GDBN} does not do
2842 that currently. If @value{GDBN} finds that it is unable to set a
2843 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
2844 will print a message like this:
2847 Expression cannot be implemented with read/access watchpoint.
2850 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
2851 data type of the watched expression is wider than what a hardware
2852 watchpoint on the target machine can handle. For example, some systems
2853 can only watch regions that are up to 4 bytes wide; on such systems you
2854 cannot set hardware watchpoints for an expression that yields a
2855 double-precision floating-point number (which is typically 8 bytes
2856 wide). As a work-around, it might be possible to break the large region
2857 into a series of smaller ones and watch them with separate watchpoints.
2859 If you set too many hardware watchpoints, @value{GDBN} might be unable
2860 to insert all of them when you resume the execution of your program.
2861 Since the precise number of active watchpoints is unknown until such
2862 time as the program is about to be resumed, @value{GDBN} might not be
2863 able to warn you about this when you set the watchpoints, and the
2864 warning will be printed only when the program is resumed:
2867 Hardware watchpoint @var{num}: Could not insert watchpoint
2871 If this happens, delete or disable some of the watchpoints.
2873 The SPARClite DSU will generate traps when a program accesses some data
2874 or instruction address that is assigned to the debug registers. For the
2875 data addresses, DSU facilitates the @code{watch} command. However the
2876 hardware breakpoint registers can only take two data watchpoints, and
2877 both watchpoints must be the same kind. For example, you can set two
2878 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
2879 @strong{or} two with @code{awatch} commands, but you cannot set one
2880 watchpoint with one command and the other with a different command.
2881 @value{GDBN} will reject the command if you try to mix watchpoints.
2882 Delete or disable unused watchpoint commands before setting new ones.
2884 If you call a function interactively using @code{print} or @code{call},
2885 any watchpoints you have set will be inactive until @value{GDBN} reaches another
2886 kind of breakpoint or the call completes.
2888 @value{GDBN} automatically deletes watchpoints that watch local
2889 (automatic) variables, or expressions that involve such variables, when
2890 they go out of scope, that is, when the execution leaves the block in
2891 which these variables were defined. In particular, when the program
2892 being debugged terminates, @emph{all} local variables go out of scope,
2893 and so only watchpoints that watch global variables remain set. If you
2894 rerun the program, you will need to set all such watchpoints again. One
2895 way of doing that would be to set a code breakpoint at the entry to the
2896 @code{main} function and when it breaks, set all the watchpoints.
2899 @cindex watchpoints and threads
2900 @cindex threads and watchpoints
2901 @emph{Warning:} In multi-thread programs, watchpoints have only limited
2902 usefulness. With the current watchpoint implementation, @value{GDBN}
2903 can only watch the value of an expression @emph{in a single thread}. If
2904 you are confident that the expression can only change due to the current
2905 thread's activity (and if you are also confident that no other thread
2906 can become current), then you can use watchpoints as usual. However,
2907 @value{GDBN} may not notice when a non-current thread's activity changes
2910 @c FIXME: this is almost identical to the previous paragraph.
2911 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
2912 have only limited usefulness. If @value{GDBN} creates a software
2913 watchpoint, it can only watch the value of an expression @emph{in a
2914 single thread}. If you are confident that the expression can only
2915 change due to the current thread's activity (and if you are also
2916 confident that no other thread can become current), then you can use
2917 software watchpoints as usual. However, @value{GDBN} may not notice
2918 when a non-current thread's activity changes the expression. (Hardware
2919 watchpoints, in contrast, watch an expression in all threads.)
2922 @xref{set remote hardware-watchpoint-limit}.
2924 @node Set Catchpoints
2925 @subsection Setting catchpoints
2926 @cindex catchpoints, setting
2927 @cindex exception handlers
2928 @cindex event handling
2930 You can use @dfn{catchpoints} to cause the debugger to stop for certain
2931 kinds of program events, such as C@t{++} exceptions or the loading of a
2932 shared library. Use the @code{catch} command to set a catchpoint.
2936 @item catch @var{event}
2937 Stop when @var{event} occurs. @var{event} can be any of the following:
2940 @cindex stop on C@t{++} exceptions
2941 The throwing of a C@t{++} exception.
2944 The catching of a C@t{++} exception.
2947 @cindex break on fork/exec
2948 A call to @code{exec}. This is currently only available for HP-UX.
2951 A call to @code{fork}. This is currently only available for HP-UX.
2954 A call to @code{vfork}. This is currently only available for HP-UX.
2957 @itemx load @var{libname}
2958 @cindex break on load/unload of shared library
2959 The dynamic loading of any shared library, or the loading of the library
2960 @var{libname}. This is currently only available for HP-UX.
2963 @itemx unload @var{libname}
2964 The unloading of any dynamically loaded shared library, or the unloading
2965 of the library @var{libname}. This is currently only available for HP-UX.
2968 @item tcatch @var{event}
2969 Set a catchpoint that is enabled only for one stop. The catchpoint is
2970 automatically deleted after the first time the event is caught.
2974 Use the @code{info break} command to list the current catchpoints.
2976 There are currently some limitations to C@t{++} exception handling
2977 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
2981 If you call a function interactively, @value{GDBN} normally returns
2982 control to you when the function has finished executing. If the call
2983 raises an exception, however, the call may bypass the mechanism that
2984 returns control to you and cause your program either to abort or to
2985 simply continue running until it hits a breakpoint, catches a signal
2986 that @value{GDBN} is listening for, or exits. This is the case even if
2987 you set a catchpoint for the exception; catchpoints on exceptions are
2988 disabled within interactive calls.
2991 You cannot raise an exception interactively.
2994 You cannot install an exception handler interactively.
2997 @cindex raise exceptions
2998 Sometimes @code{catch} is not the best way to debug exception handling:
2999 if you need to know exactly where an exception is raised, it is better to
3000 stop @emph{before} the exception handler is called, since that way you
3001 can see the stack before any unwinding takes place. If you set a
3002 breakpoint in an exception handler instead, it may not be easy to find
3003 out where the exception was raised.
3005 To stop just before an exception handler is called, you need some
3006 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3007 raised by calling a library function named @code{__raise_exception}
3008 which has the following ANSI C interface:
3011 /* @var{addr} is where the exception identifier is stored.
3012 @var{id} is the exception identifier. */
3013 void __raise_exception (void **addr, void *id);
3017 To make the debugger catch all exceptions before any stack
3018 unwinding takes place, set a breakpoint on @code{__raise_exception}
3019 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
3021 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
3022 that depends on the value of @var{id}, you can stop your program when
3023 a specific exception is raised. You can use multiple conditional
3024 breakpoints to stop your program when any of a number of exceptions are
3029 @subsection Deleting breakpoints
3031 @cindex clearing breakpoints, watchpoints, catchpoints
3032 @cindex deleting breakpoints, watchpoints, catchpoints
3033 It is often necessary to eliminate a breakpoint, watchpoint, or
3034 catchpoint once it has done its job and you no longer want your program
3035 to stop there. This is called @dfn{deleting} the breakpoint. A
3036 breakpoint that has been deleted no longer exists; it is forgotten.
3038 With the @code{clear} command you can delete breakpoints according to
3039 where they are in your program. With the @code{delete} command you can
3040 delete individual breakpoints, watchpoints, or catchpoints by specifying
3041 their breakpoint numbers.
3043 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3044 automatically ignores breakpoints on the first instruction to be executed
3045 when you continue execution without changing the execution address.
3050 Delete any breakpoints at the next instruction to be executed in the
3051 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
3052 the innermost frame is selected, this is a good way to delete a
3053 breakpoint where your program just stopped.
3055 @item clear @var{function}
3056 @itemx clear @var{filename}:@var{function}
3057 Delete any breakpoints set at entry to the named @var{function}.
3059 @item clear @var{linenum}
3060 @itemx clear @var{filename}:@var{linenum}
3061 Delete any breakpoints set at or within the code of the specified
3062 @var{linenum} of the specified @var{filename}.
3064 @cindex delete breakpoints
3066 @kindex d @r{(@code{delete})}
3067 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3068 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3069 ranges specified as arguments. If no argument is specified, delete all
3070 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3071 confirm off}). You can abbreviate this command as @code{d}.
3075 @subsection Disabling breakpoints
3077 @cindex enable/disable a breakpoint
3078 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3079 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3080 it had been deleted, but remembers the information on the breakpoint so
3081 that you can @dfn{enable} it again later.
3083 You disable and enable breakpoints, watchpoints, and catchpoints with
3084 the @code{enable} and @code{disable} commands, optionally specifying one
3085 or more breakpoint numbers as arguments. Use @code{info break} or
3086 @code{info watch} to print a list of breakpoints, watchpoints, and
3087 catchpoints if you do not know which numbers to use.
3089 A breakpoint, watchpoint, or catchpoint can have any of four different
3090 states of enablement:
3094 Enabled. The breakpoint stops your program. A breakpoint set
3095 with the @code{break} command starts out in this state.
3097 Disabled. The breakpoint has no effect on your program.
3099 Enabled once. The breakpoint stops your program, but then becomes
3102 Enabled for deletion. The breakpoint stops your program, but
3103 immediately after it does so it is deleted permanently. A breakpoint
3104 set with the @code{tbreak} command starts out in this state.
3107 You can use the following commands to enable or disable breakpoints,
3108 watchpoints, and catchpoints:
3112 @kindex dis @r{(@code{disable})}
3113 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3114 Disable the specified breakpoints---or all breakpoints, if none are
3115 listed. A disabled breakpoint has no effect but is not forgotten. All
3116 options such as ignore-counts, conditions and commands are remembered in
3117 case the breakpoint is enabled again later. You may abbreviate
3118 @code{disable} as @code{dis}.
3121 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3122 Enable the specified breakpoints (or all defined breakpoints). They
3123 become effective once again in stopping your program.
3125 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3126 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3127 of these breakpoints immediately after stopping your program.
3129 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3130 Enable the specified breakpoints to work once, then die. @value{GDBN}
3131 deletes any of these breakpoints as soon as your program stops there.
3132 Breakpoints set by the @code{tbreak} command start out in this state.
3135 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3136 @c confusing: tbreak is also initially enabled.
3137 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3138 ,Setting breakpoints}), breakpoints that you set are initially enabled;
3139 subsequently, they become disabled or enabled only when you use one of
3140 the commands above. (The command @code{until} can set and delete a
3141 breakpoint of its own, but it does not change the state of your other
3142 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3146 @subsection Break conditions
3147 @cindex conditional breakpoints
3148 @cindex breakpoint conditions
3150 @c FIXME what is scope of break condition expr? Context where wanted?
3151 @c in particular for a watchpoint?
3152 The simplest sort of breakpoint breaks every time your program reaches a
3153 specified place. You can also specify a @dfn{condition} for a
3154 breakpoint. A condition is just a Boolean expression in your
3155 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3156 a condition evaluates the expression each time your program reaches it,
3157 and your program stops only if the condition is @emph{true}.
3159 This is the converse of using assertions for program validation; in that
3160 situation, you want to stop when the assertion is violated---that is,
3161 when the condition is false. In C, if you want to test an assertion expressed
3162 by the condition @var{assert}, you should set the condition
3163 @samp{! @var{assert}} on the appropriate breakpoint.
3165 Conditions are also accepted for watchpoints; you may not need them,
3166 since a watchpoint is inspecting the value of an expression anyhow---but
3167 it might be simpler, say, to just set a watchpoint on a variable name,
3168 and specify a condition that tests whether the new value is an interesting
3171 Break conditions can have side effects, and may even call functions in
3172 your program. This can be useful, for example, to activate functions
3173 that log program progress, or to use your own print functions to
3174 format special data structures. The effects are completely predictable
3175 unless there is another enabled breakpoint at the same address. (In
3176 that case, @value{GDBN} might see the other breakpoint first and stop your
3177 program without checking the condition of this one.) Note that
3178 breakpoint commands are usually more convenient and flexible than break
3180 purpose of performing side effects when a breakpoint is reached
3181 (@pxref{Break Commands, ,Breakpoint command lists}).
3183 Break conditions can be specified when a breakpoint is set, by using
3184 @samp{if} in the arguments to the @code{break} command. @xref{Set
3185 Breaks, ,Setting breakpoints}. They can also be changed at any time
3186 with the @code{condition} command.
3188 You can also use the @code{if} keyword with the @code{watch} command.
3189 The @code{catch} command does not recognize the @code{if} keyword;
3190 @code{condition} is the only way to impose a further condition on a
3195 @item condition @var{bnum} @var{expression}
3196 Specify @var{expression} as the break condition for breakpoint,
3197 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3198 breakpoint @var{bnum} stops your program only if the value of
3199 @var{expression} is true (nonzero, in C). When you use
3200 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3201 syntactic correctness, and to determine whether symbols in it have
3202 referents in the context of your breakpoint. If @var{expression} uses
3203 symbols not referenced in the context of the breakpoint, @value{GDBN}
3204 prints an error message:
3207 No symbol "foo" in current context.
3212 not actually evaluate @var{expression} at the time the @code{condition}
3213 command (or a command that sets a breakpoint with a condition, like
3214 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3216 @item condition @var{bnum}
3217 Remove the condition from breakpoint number @var{bnum}. It becomes
3218 an ordinary unconditional breakpoint.
3221 @cindex ignore count (of breakpoint)
3222 A special case of a breakpoint condition is to stop only when the
3223 breakpoint has been reached a certain number of times. This is so
3224 useful that there is a special way to do it, using the @dfn{ignore
3225 count} of the breakpoint. Every breakpoint has an ignore count, which
3226 is an integer. Most of the time, the ignore count is zero, and
3227 therefore has no effect. But if your program reaches a breakpoint whose
3228 ignore count is positive, then instead of stopping, it just decrements
3229 the ignore count by one and continues. As a result, if the ignore count
3230 value is @var{n}, the breakpoint does not stop the next @var{n} times
3231 your program reaches it.
3235 @item ignore @var{bnum} @var{count}
3236 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3237 The next @var{count} times the breakpoint is reached, your program's
3238 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3241 To make the breakpoint stop the next time it is reached, specify
3244 When you use @code{continue} to resume execution of your program from a
3245 breakpoint, you can specify an ignore count directly as an argument to
3246 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3247 Stepping,,Continuing and stepping}.
3249 If a breakpoint has a positive ignore count and a condition, the
3250 condition is not checked. Once the ignore count reaches zero,
3251 @value{GDBN} resumes checking the condition.
3253 You could achieve the effect of the ignore count with a condition such
3254 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3255 is decremented each time. @xref{Convenience Vars, ,Convenience
3259 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3262 @node Break Commands
3263 @subsection Breakpoint command lists
3265 @cindex breakpoint commands
3266 You can give any breakpoint (or watchpoint or catchpoint) a series of
3267 commands to execute when your program stops due to that breakpoint. For
3268 example, you might want to print the values of certain expressions, or
3269 enable other breakpoints.
3274 @item commands @r{[}@var{bnum}@r{]}
3275 @itemx @dots{} @var{command-list} @dots{}
3277 Specify a list of commands for breakpoint number @var{bnum}. The commands
3278 themselves appear on the following lines. Type a line containing just
3279 @code{end} to terminate the commands.
3281 To remove all commands from a breakpoint, type @code{commands} and
3282 follow it immediately with @code{end}; that is, give no commands.
3284 With no @var{bnum} argument, @code{commands} refers to the last
3285 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3286 recently encountered).
3289 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3290 disabled within a @var{command-list}.
3292 You can use breakpoint commands to start your program up again. Simply
3293 use the @code{continue} command, or @code{step}, or any other command
3294 that resumes execution.
3296 Any other commands in the command list, after a command that resumes
3297 execution, are ignored. This is because any time you resume execution
3298 (even with a simple @code{next} or @code{step}), you may encounter
3299 another breakpoint---which could have its own command list, leading to
3300 ambiguities about which list to execute.
3303 If the first command you specify in a command list is @code{silent}, the
3304 usual message about stopping at a breakpoint is not printed. This may
3305 be desirable for breakpoints that are to print a specific message and
3306 then continue. If none of the remaining commands print anything, you
3307 see no sign that the breakpoint was reached. @code{silent} is
3308 meaningful only at the beginning of a breakpoint command list.
3310 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3311 print precisely controlled output, and are often useful in silent
3312 breakpoints. @xref{Output, ,Commands for controlled output}.
3314 For example, here is how you could use breakpoint commands to print the
3315 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3321 printf "x is %d\n",x
3326 One application for breakpoint commands is to compensate for one bug so
3327 you can test for another. Put a breakpoint just after the erroneous line
3328 of code, give it a condition to detect the case in which something
3329 erroneous has been done, and give it commands to assign correct values
3330 to any variables that need them. End with the @code{continue} command
3331 so that your program does not stop, and start with the @code{silent}
3332 command so that no output is produced. Here is an example:
3343 @node Breakpoint Menus
3344 @subsection Breakpoint menus
3346 @cindex symbol overloading
3348 Some programming languages (notably C@t{++} and Objective-C) permit a
3349 single function name
3350 to be defined several times, for application in different contexts.
3351 This is called @dfn{overloading}. When a function name is overloaded,
3352 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3353 a breakpoint. If you realize this is a problem, you can use
3354 something like @samp{break @var{function}(@var{types})} to specify which
3355 particular version of the function you want. Otherwise, @value{GDBN} offers
3356 you a menu of numbered choices for different possible breakpoints, and
3357 waits for your selection with the prompt @samp{>}. The first two
3358 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3359 sets a breakpoint at each definition of @var{function}, and typing
3360 @kbd{0} aborts the @code{break} command without setting any new
3363 For example, the following session excerpt shows an attempt to set a
3364 breakpoint at the overloaded symbol @code{String::after}.
3365 We choose three particular definitions of that function name:
3367 @c FIXME! This is likely to change to show arg type lists, at least
3370 (@value{GDBP}) b String::after
3373 [2] file:String.cc; line number:867
3374 [3] file:String.cc; line number:860
3375 [4] file:String.cc; line number:875
3376 [5] file:String.cc; line number:853
3377 [6] file:String.cc; line number:846
3378 [7] file:String.cc; line number:735
3380 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3381 Breakpoint 2 at 0xb344: file String.cc, line 875.
3382 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3383 Multiple breakpoints were set.
3384 Use the "delete" command to delete unwanted
3390 @c @ifclear BARETARGET
3391 @node Error in Breakpoints
3392 @subsection ``Cannot insert breakpoints''
3394 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3396 Under some operating systems, breakpoints cannot be used in a program if
3397 any other process is running that program. In this situation,
3398 attempting to run or continue a program with a breakpoint causes
3399 @value{GDBN} to print an error message:
3402 Cannot insert breakpoints.
3403 The same program may be running in another process.
3406 When this happens, you have three ways to proceed:
3410 Remove or disable the breakpoints, then continue.
3413 Suspend @value{GDBN}, and copy the file containing your program to a new
3414 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3415 that @value{GDBN} should run your program under that name.
3416 Then start your program again.
3419 Relink your program so that the text segment is nonsharable, using the
3420 linker option @samp{-N}. The operating system limitation may not apply
3421 to nonsharable executables.
3425 A similar message can be printed if you request too many active
3426 hardware-assisted breakpoints and watchpoints:
3428 @c FIXME: the precise wording of this message may change; the relevant
3429 @c source change is not committed yet (Sep 3, 1999).
3431 Stopped; cannot insert breakpoints.
3432 You may have requested too many hardware breakpoints and watchpoints.
3436 This message is printed when you attempt to resume the program, since
3437 only then @value{GDBN} knows exactly how many hardware breakpoints and
3438 watchpoints it needs to insert.
3440 When this message is printed, you need to disable or remove some of the
3441 hardware-assisted breakpoints and watchpoints, and then continue.
3443 @node Breakpoint related warnings
3444 @subsection ``Breakpoint address adjusted...''
3445 @cindex breakpoint address adjusted
3447 Some processor architectures place constraints on the addresses at
3448 which breakpoints may be placed. For architectures thus constrained,
3449 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3450 with the constraints dictated by the architecture.
3452 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3453 a VLIW architecture in which a number of RISC-like instructions may be
3454 bundled together for parallel execution. The FR-V architecture
3455 constrains the location of a breakpoint instruction within such a
3456 bundle to the instruction with the lowest address. @value{GDBN}
3457 honors this constraint by adjusting a breakpoint's address to the
3458 first in the bundle.
3460 It is not uncommon for optimized code to have bundles which contain
3461 instructions from different source statements, thus it may happen that
3462 a breakpoint's address will be adjusted from one source statement to
3463 another. Since this adjustment may significantly alter @value{GDBN}'s
3464 breakpoint related behavior from what the user expects, a warning is
3465 printed when the breakpoint is first set and also when the breakpoint
3468 A warning like the one below is printed when setting a breakpoint
3469 that's been subject to address adjustment:
3472 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3475 Such warnings are printed both for user settable and @value{GDBN}'s
3476 internal breakpoints. If you see one of these warnings, you should
3477 verify that a breakpoint set at the adjusted address will have the
3478 desired affect. If not, the breakpoint in question may be removed and
3479 other breakpoints may be set which will have the desired behavior.
3480 E.g., it may be sufficient to place the breakpoint at a later
3481 instruction. A conditional breakpoint may also be useful in some
3482 cases to prevent the breakpoint from triggering too often.
3484 @value{GDBN} will also issue a warning when stopping at one of these
3485 adjusted breakpoints:
3488 warning: Breakpoint 1 address previously adjusted from 0x00010414
3492 When this warning is encountered, it may be too late to take remedial
3493 action except in cases where the breakpoint is hit earlier or more
3494 frequently than expected.
3496 @node Continuing and Stepping
3497 @section Continuing and stepping
3501 @cindex resuming execution
3502 @dfn{Continuing} means resuming program execution until your program
3503 completes normally. In contrast, @dfn{stepping} means executing just
3504 one more ``step'' of your program, where ``step'' may mean either one
3505 line of source code, or one machine instruction (depending on what
3506 particular command you use). Either when continuing or when stepping,
3507 your program may stop even sooner, due to a breakpoint or a signal. (If
3508 it stops due to a signal, you may want to use @code{handle}, or use
3509 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3513 @kindex c @r{(@code{continue})}
3514 @kindex fg @r{(resume foreground execution)}
3515 @item continue @r{[}@var{ignore-count}@r{]}
3516 @itemx c @r{[}@var{ignore-count}@r{]}
3517 @itemx fg @r{[}@var{ignore-count}@r{]}
3518 Resume program execution, at the address where your program last stopped;
3519 any breakpoints set at that address are bypassed. The optional argument
3520 @var{ignore-count} allows you to specify a further number of times to
3521 ignore a breakpoint at this location; its effect is like that of
3522 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3524 The argument @var{ignore-count} is meaningful only when your program
3525 stopped due to a breakpoint. At other times, the argument to
3526 @code{continue} is ignored.
3528 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3529 debugged program is deemed to be the foreground program) are provided
3530 purely for convenience, and have exactly the same behavior as
3534 To resume execution at a different place, you can use @code{return}
3535 (@pxref{Returning, ,Returning from a function}) to go back to the
3536 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3537 different address}) to go to an arbitrary location in your program.
3539 A typical technique for using stepping is to set a breakpoint
3540 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3541 beginning of the function or the section of your program where a problem
3542 is believed to lie, run your program until it stops at that breakpoint,
3543 and then step through the suspect area, examining the variables that are
3544 interesting, until you see the problem happen.
3548 @kindex s @r{(@code{step})}
3550 Continue running your program until control reaches a different source
3551 line, then stop it and return control to @value{GDBN}. This command is
3552 abbreviated @code{s}.
3555 @c "without debugging information" is imprecise; actually "without line
3556 @c numbers in the debugging information". (gcc -g1 has debugging info but
3557 @c not line numbers). But it seems complex to try to make that
3558 @c distinction here.
3559 @emph{Warning:} If you use the @code{step} command while control is
3560 within a function that was compiled without debugging information,
3561 execution proceeds until control reaches a function that does have
3562 debugging information. Likewise, it will not step into a function which
3563 is compiled without debugging information. To step through functions
3564 without debugging information, use the @code{stepi} command, described
3568 The @code{step} command only stops at the first instruction of a source
3569 line. This prevents the multiple stops that could otherwise occur in
3570 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3571 to stop if a function that has debugging information is called within
3572 the line. In other words, @code{step} @emph{steps inside} any functions
3573 called within the line.
3575 Also, the @code{step} command only enters a function if there is line
3576 number information for the function. Otherwise it acts like the
3577 @code{next} command. This avoids problems when using @code{cc -gl}
3578 on MIPS machines. Previously, @code{step} entered subroutines if there
3579 was any debugging information about the routine.
3581 @item step @var{count}
3582 Continue running as in @code{step}, but do so @var{count} times. If a
3583 breakpoint is reached, or a signal not related to stepping occurs before
3584 @var{count} steps, stepping stops right away.
3587 @kindex n @r{(@code{next})}
3588 @item next @r{[}@var{count}@r{]}
3589 Continue to the next source line in the current (innermost) stack frame.
3590 This is similar to @code{step}, but function calls that appear within
3591 the line of code are executed without stopping. Execution stops when
3592 control reaches a different line of code at the original stack level
3593 that was executing when you gave the @code{next} command. This command
3594 is abbreviated @code{n}.
3596 An argument @var{count} is a repeat count, as for @code{step}.
3599 @c FIX ME!! Do we delete this, or is there a way it fits in with
3600 @c the following paragraph? --- Vctoria
3602 @c @code{next} within a function that lacks debugging information acts like
3603 @c @code{step}, but any function calls appearing within the code of the
3604 @c function are executed without stopping.
3606 The @code{next} command only stops at the first instruction of a
3607 source line. This prevents multiple stops that could otherwise occur in
3608 @code{switch} statements, @code{for} loops, etc.
3610 @kindex set step-mode
3612 @cindex functions without line info, and stepping
3613 @cindex stepping into functions with no line info
3614 @itemx set step-mode on
3615 The @code{set step-mode on} command causes the @code{step} command to
3616 stop at the first instruction of a function which contains no debug line
3617 information rather than stepping over it.
3619 This is useful in cases where you may be interested in inspecting the
3620 machine instructions of a function which has no symbolic info and do not
3621 want @value{GDBN} to automatically skip over this function.
3623 @item set step-mode off
3624 Causes the @code{step} command to step over any functions which contains no
3625 debug information. This is the default.
3627 @item show step-mode
3628 Show whether @value{GDBN} will stop in or step over functions without
3629 source line debug information.
3633 Continue running until just after function in the selected stack frame
3634 returns. Print the returned value (if any).
3636 Contrast this with the @code{return} command (@pxref{Returning,
3637 ,Returning from a function}).
3640 @kindex u @r{(@code{until})}
3641 @cindex run until specified location
3644 Continue running until a source line past the current line, in the
3645 current stack frame, is reached. This command is used to avoid single
3646 stepping through a loop more than once. It is like the @code{next}
3647 command, except that when @code{until} encounters a jump, it
3648 automatically continues execution until the program counter is greater
3649 than the address of the jump.
3651 This means that when you reach the end of a loop after single stepping
3652 though it, @code{until} makes your program continue execution until it
3653 exits the loop. In contrast, a @code{next} command at the end of a loop
3654 simply steps back to the beginning of the loop, which forces you to step
3655 through the next iteration.
3657 @code{until} always stops your program if it attempts to exit the current
3660 @code{until} may produce somewhat counterintuitive results if the order
3661 of machine code does not match the order of the source lines. For
3662 example, in the following excerpt from a debugging session, the @code{f}
3663 (@code{frame}) command shows that execution is stopped at line
3664 @code{206}; yet when we use @code{until}, we get to line @code{195}:
3668 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
3670 (@value{GDBP}) until
3671 195 for ( ; argc > 0; NEXTARG) @{
3674 This happened because, for execution efficiency, the compiler had
3675 generated code for the loop closure test at the end, rather than the
3676 start, of the loop---even though the test in a C @code{for}-loop is
3677 written before the body of the loop. The @code{until} command appeared
3678 to step back to the beginning of the loop when it advanced to this
3679 expression; however, it has not really gone to an earlier
3680 statement---not in terms of the actual machine code.
3682 @code{until} with no argument works by means of single
3683 instruction stepping, and hence is slower than @code{until} with an
3686 @item until @var{location}
3687 @itemx u @var{location}
3688 Continue running your program until either the specified location is
3689 reached, or the current stack frame returns. @var{location} is any of
3690 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
3691 ,Setting breakpoints}). This form of the command uses breakpoints, and
3692 hence is quicker than @code{until} without an argument. The specified
3693 location is actually reached only if it is in the current frame. This
3694 implies that @code{until} can be used to skip over recursive function
3695 invocations. For instance in the code below, if the current location is
3696 line @code{96}, issuing @code{until 99} will execute the program up to
3697 line @code{99} in the same invocation of factorial, i.e. after the inner
3698 invocations have returned.
3701 94 int factorial (int value)
3703 96 if (value > 1) @{
3704 97 value *= factorial (value - 1);
3711 @kindex advance @var{location}
3712 @itemx advance @var{location}
3713 Continue running the program up to the given @var{location}. An argument is
3714 required, which should be of the same form as arguments for the @code{break}
3715 command. Execution will also stop upon exit from the current stack
3716 frame. This command is similar to @code{until}, but @code{advance} will
3717 not skip over recursive function calls, and the target location doesn't
3718 have to be in the same frame as the current one.
3722 @kindex si @r{(@code{stepi})}
3724 @itemx stepi @var{arg}
3726 Execute one machine instruction, then stop and return to the debugger.
3728 It is often useful to do @samp{display/i $pc} when stepping by machine
3729 instructions. This makes @value{GDBN} automatically display the next
3730 instruction to be executed, each time your program stops. @xref{Auto
3731 Display,, Automatic display}.
3733 An argument is a repeat count, as in @code{step}.
3737 @kindex ni @r{(@code{nexti})}
3739 @itemx nexti @var{arg}
3741 Execute one machine instruction, but if it is a function call,
3742 proceed until the function returns.
3744 An argument is a repeat count, as in @code{next}.
3751 A signal is an asynchronous event that can happen in a program. The
3752 operating system defines the possible kinds of signals, and gives each
3753 kind a name and a number. For example, in Unix @code{SIGINT} is the
3754 signal a program gets when you type an interrupt character (often @kbd{C-c});
3755 @code{SIGSEGV} is the signal a program gets from referencing a place in
3756 memory far away from all the areas in use; @code{SIGALRM} occurs when
3757 the alarm clock timer goes off (which happens only if your program has
3758 requested an alarm).
3760 @cindex fatal signals
3761 Some signals, including @code{SIGALRM}, are a normal part of the
3762 functioning of your program. Others, such as @code{SIGSEGV}, indicate
3763 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
3764 program has not specified in advance some other way to handle the signal.
3765 @code{SIGINT} does not indicate an error in your program, but it is normally
3766 fatal so it can carry out the purpose of the interrupt: to kill the program.
3768 @value{GDBN} has the ability to detect any occurrence of a signal in your
3769 program. You can tell @value{GDBN} in advance what to do for each kind of
3772 @cindex handling signals
3773 Normally, @value{GDBN} is set up to let the non-erroneous signals like
3774 @code{SIGALRM} be silently passed to your program
3775 (so as not to interfere with their role in the program's functioning)
3776 but to stop your program immediately whenever an error signal happens.
3777 You can change these settings with the @code{handle} command.
3780 @kindex info signals
3784 Print a table of all the kinds of signals and how @value{GDBN} has been told to
3785 handle each one. You can use this to see the signal numbers of all
3786 the defined types of signals.
3788 @code{info handle} is an alias for @code{info signals}.
3791 @item handle @var{signal} @var{keywords}@dots{}
3792 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
3793 can be the number of a signal or its name (with or without the
3794 @samp{SIG} at the beginning); a list of signal numbers of the form
3795 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
3796 known signals. The @var{keywords} say what change to make.
3800 The keywords allowed by the @code{handle} command can be abbreviated.
3801 Their full names are:
3805 @value{GDBN} should not stop your program when this signal happens. It may
3806 still print a message telling you that the signal has come in.
3809 @value{GDBN} should stop your program when this signal happens. This implies
3810 the @code{print} keyword as well.
3813 @value{GDBN} should print a message when this signal happens.
3816 @value{GDBN} should not mention the occurrence of the signal at all. This
3817 implies the @code{nostop} keyword as well.
3821 @value{GDBN} should allow your program to see this signal; your program
3822 can handle the signal, or else it may terminate if the signal is fatal
3823 and not handled. @code{pass} and @code{noignore} are synonyms.
3827 @value{GDBN} should not allow your program to see this signal.
3828 @code{nopass} and @code{ignore} are synonyms.
3832 When a signal stops your program, the signal is not visible to the
3834 continue. Your program sees the signal then, if @code{pass} is in
3835 effect for the signal in question @emph{at that time}. In other words,
3836 after @value{GDBN} reports a signal, you can use the @code{handle}
3837 command with @code{pass} or @code{nopass} to control whether your
3838 program sees that signal when you continue.
3840 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
3841 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
3842 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
3845 You can also use the @code{signal} command to prevent your program from
3846 seeing a signal, or cause it to see a signal it normally would not see,
3847 or to give it any signal at any time. For example, if your program stopped
3848 due to some sort of memory reference error, you might store correct
3849 values into the erroneous variables and continue, hoping to see more
3850 execution; but your program would probably terminate immediately as
3851 a result of the fatal signal once it saw the signal. To prevent this,
3852 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
3856 @section Stopping and starting multi-thread programs
3858 When your program has multiple threads (@pxref{Threads,, Debugging
3859 programs with multiple threads}), you can choose whether to set
3860 breakpoints on all threads, or on a particular thread.
3863 @cindex breakpoints and threads
3864 @cindex thread breakpoints
3865 @kindex break @dots{} thread @var{threadno}
3866 @item break @var{linespec} thread @var{threadno}
3867 @itemx break @var{linespec} thread @var{threadno} if @dots{}
3868 @var{linespec} specifies source lines; there are several ways of
3869 writing them, but the effect is always to specify some source line.
3871 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
3872 to specify that you only want @value{GDBN} to stop the program when a
3873 particular thread reaches this breakpoint. @var{threadno} is one of the
3874 numeric thread identifiers assigned by @value{GDBN}, shown in the first
3875 column of the @samp{info threads} display.
3877 If you do not specify @samp{thread @var{threadno}} when you set a
3878 breakpoint, the breakpoint applies to @emph{all} threads of your
3881 You can use the @code{thread} qualifier on conditional breakpoints as
3882 well; in this case, place @samp{thread @var{threadno}} before the
3883 breakpoint condition, like this:
3886 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
3891 @cindex stopped threads
3892 @cindex threads, stopped
3893 Whenever your program stops under @value{GDBN} for any reason,
3894 @emph{all} threads of execution stop, not just the current thread. This
3895 allows you to examine the overall state of the program, including
3896 switching between threads, without worrying that things may change
3899 @cindex thread breakpoints and system calls
3900 @cindex system calls and thread breakpoints
3901 @cindex premature return from system calls
3902 There is an unfortunate side effect. If one thread stops for a
3903 breakpoint, or for some other reason, and another thread is blocked in a
3904 system call, then the system call may return prematurely. This is a
3905 consequence of the interaction between multiple threads and the signals
3906 that @value{GDBN} uses to implement breakpoints and other events that
3909 To handle this problem, your program should check the return value of
3910 each system call and react appropriately. This is good programming
3913 For example, do not write code like this:
3919 The call to @code{sleep} will return early if a different thread stops
3920 at a breakpoint or for some other reason.
3922 Instead, write this:
3927 unslept = sleep (unslept);
3930 A system call is allowed to return early, so the system is still
3931 conforming to its specification. But @value{GDBN} does cause your
3932 multi-threaded program to behave differently than it would without
3935 Also, @value{GDBN} uses internal breakpoints in the thread library to
3936 monitor certain events such as thread creation and thread destruction.
3937 When such an event happens, a system call in another thread may return
3938 prematurely, even though your program does not appear to stop.
3940 @cindex continuing threads
3941 @cindex threads, continuing
3942 Conversely, whenever you restart the program, @emph{all} threads start
3943 executing. @emph{This is true even when single-stepping} with commands
3944 like @code{step} or @code{next}.
3946 In particular, @value{GDBN} cannot single-step all threads in lockstep.
3947 Since thread scheduling is up to your debugging target's operating
3948 system (not controlled by @value{GDBN}), other threads may
3949 execute more than one statement while the current thread completes a
3950 single step. Moreover, in general other threads stop in the middle of a
3951 statement, rather than at a clean statement boundary, when the program
3954 You might even find your program stopped in another thread after
3955 continuing or even single-stepping. This happens whenever some other
3956 thread runs into a breakpoint, a signal, or an exception before the
3957 first thread completes whatever you requested.
3959 On some OSes, you can lock the OS scheduler and thus allow only a single
3963 @item set scheduler-locking @var{mode}
3964 @cindex scheduler locking mode
3965 @cindex lock scheduler
3966 Set the scheduler locking mode. If it is @code{off}, then there is no
3967 locking and any thread may run at any time. If @code{on}, then only the
3968 current thread may run when the inferior is resumed. The @code{step}
3969 mode optimizes for single-stepping. It stops other threads from
3970 ``seizing the prompt'' by preempting the current thread while you are
3971 stepping. Other threads will only rarely (or never) get a chance to run
3972 when you step. They are more likely to run when you @samp{next} over a
3973 function call, and they are completely free to run when you use commands
3974 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
3975 thread hits a breakpoint during its timeslice, they will never steal the
3976 @value{GDBN} prompt away from the thread that you are debugging.
3978 @item show scheduler-locking
3979 Display the current scheduler locking mode.
3984 @chapter Examining the Stack
3986 When your program has stopped, the first thing you need to know is where it
3987 stopped and how it got there.
3990 Each time your program performs a function call, information about the call
3992 That information includes the location of the call in your program,
3993 the arguments of the call,
3994 and the local variables of the function being called.
3995 The information is saved in a block of data called a @dfn{stack frame}.
3996 The stack frames are allocated in a region of memory called the @dfn{call
3999 When your program stops, the @value{GDBN} commands for examining the
4000 stack allow you to see all of this information.
4002 @cindex selected frame
4003 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4004 @value{GDBN} commands refer implicitly to the selected frame. In
4005 particular, whenever you ask @value{GDBN} for the value of a variable in
4006 your program, the value is found in the selected frame. There are
4007 special @value{GDBN} commands to select whichever frame you are
4008 interested in. @xref{Selection, ,Selecting a frame}.
4010 When your program stops, @value{GDBN} automatically selects the
4011 currently executing frame and describes it briefly, similar to the
4012 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
4015 * Frames:: Stack frames
4016 * Backtrace:: Backtraces
4017 * Selection:: Selecting a frame
4018 * Frame Info:: Information on a frame
4023 @section Stack frames
4025 @cindex frame, definition
4027 The call stack is divided up into contiguous pieces called @dfn{stack
4028 frames}, or @dfn{frames} for short; each frame is the data associated
4029 with one call to one function. The frame contains the arguments given
4030 to the function, the function's local variables, and the address at
4031 which the function is executing.
4033 @cindex initial frame
4034 @cindex outermost frame
4035 @cindex innermost frame
4036 When your program is started, the stack has only one frame, that of the
4037 function @code{main}. This is called the @dfn{initial} frame or the
4038 @dfn{outermost} frame. Each time a function is called, a new frame is
4039 made. Each time a function returns, the frame for that function invocation
4040 is eliminated. If a function is recursive, there can be many frames for
4041 the same function. The frame for the function in which execution is
4042 actually occurring is called the @dfn{innermost} frame. This is the most
4043 recently created of all the stack frames that still exist.
4045 @cindex frame pointer
4046 Inside your program, stack frames are identified by their addresses. A
4047 stack frame consists of many bytes, each of which has its own address; each
4048 kind of computer has a convention for choosing one byte whose
4049 address serves as the address of the frame. Usually this address is kept
4050 in a register called the @dfn{frame pointer register} while execution is
4051 going on in that frame.
4053 @cindex frame number
4054 @value{GDBN} assigns numbers to all existing stack frames, starting with
4055 zero for the innermost frame, one for the frame that called it,
4056 and so on upward. These numbers do not really exist in your program;
4057 they are assigned by @value{GDBN} to give you a way of designating stack
4058 frames in @value{GDBN} commands.
4060 @c The -fomit-frame-pointer below perennially causes hbox overflow
4061 @c underflow problems.
4062 @cindex frameless execution
4063 Some compilers provide a way to compile functions so that they operate
4064 without stack frames. (For example, the @value{GCC} option
4066 @samp{-fomit-frame-pointer}
4068 generates functions without a frame.)
4069 This is occasionally done with heavily used library functions to save
4070 the frame setup time. @value{GDBN} has limited facilities for dealing
4071 with these function invocations. If the innermost function invocation
4072 has no stack frame, @value{GDBN} nevertheless regards it as though
4073 it had a separate frame, which is numbered zero as usual, allowing
4074 correct tracing of the function call chain. However, @value{GDBN} has
4075 no provision for frameless functions elsewhere in the stack.
4078 @kindex frame@r{, command}
4079 @cindex current stack frame
4080 @item frame @var{args}
4081 The @code{frame} command allows you to move from one stack frame to another,
4082 and to print the stack frame you select. @var{args} may be either the
4083 address of the frame or the stack frame number. Without an argument,
4084 @code{frame} prints the current stack frame.
4086 @kindex select-frame
4087 @cindex selecting frame silently
4089 The @code{select-frame} command allows you to move from one stack frame
4090 to another without printing the frame. This is the silent version of
4098 @cindex call stack traces
4099 A backtrace is a summary of how your program got where it is. It shows one
4100 line per frame, for many frames, starting with the currently executing
4101 frame (frame zero), followed by its caller (frame one), and on up the
4106 @kindex bt @r{(@code{backtrace})}
4109 Print a backtrace of the entire stack: one line per frame for all
4110 frames in the stack.
4112 You can stop the backtrace at any time by typing the system interrupt
4113 character, normally @kbd{C-c}.
4115 @item backtrace @var{n}
4117 Similar, but print only the innermost @var{n} frames.
4119 @item backtrace -@var{n}
4121 Similar, but print only the outermost @var{n} frames.
4126 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4127 are additional aliases for @code{backtrace}.
4129 Each line in the backtrace shows the frame number and the function name.
4130 The program counter value is also shown---unless you use @code{set
4131 print address off}. The backtrace also shows the source file name and
4132 line number, as well as the arguments to the function. The program
4133 counter value is omitted if it is at the beginning of the code for that
4136 Here is an example of a backtrace. It was made with the command
4137 @samp{bt 3}, so it shows the innermost three frames.
4141 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4143 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4144 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4146 (More stack frames follow...)
4151 The display for frame zero does not begin with a program counter
4152 value, indicating that your program has stopped at the beginning of the
4153 code for line @code{993} of @code{builtin.c}.
4155 @cindex backtrace beyond @code{main} function
4156 @cindex program entry point
4157 @cindex startup code, and backtrace
4158 Most programs have a standard user entry point---a place where system
4159 libraries and startup code transition into user code. For C this is
4160 @code{main}. When @value{GDBN} finds the entry function in a backtrace
4161 it will terminate the backtrace, to avoid tracing into highly
4162 system-specific (and generally uninteresting) code.
4164 If you need to examine the startup code, or limit the number of levels
4165 in a backtrace, you can change this behavior:
4168 @item set backtrace past-main
4169 @itemx set backtrace past-main on
4170 @kindex set backtrace
4171 Backtraces will continue past the user entry point.
4173 @item set backtrace past-main off
4174 Backtraces will stop when they encounter the user entry point. This is the
4177 @item show backtrace past-main
4178 @kindex show backtrace
4179 Display the current user entry point backtrace policy.
4181 @item set backtrace past-entry
4182 @itemx set backtrace past-entry on
4183 Backtraces will continue past the internal entry point of an application.
4184 This entry point is encoded by the linker when the application is built,
4185 and is likely before the user entry point @code{main} (or equivalent) is called.
4187 @item set backtrace past-entry off
4188 Backtraces will stop when they encouter the internal entry point of an
4189 application. This is the default.
4191 @item show backtrace past-entry
4192 Display the current internal entry point backtrace policy.
4194 @item set backtrace limit @var{n}
4195 @itemx set backtrace limit 0
4196 @cindex backtrace limit
4197 Limit the backtrace to @var{n} levels. A value of zero means
4200 @item show backtrace limit
4201 Display the current limit on backtrace levels.
4205 @section Selecting a frame
4207 Most commands for examining the stack and other data in your program work on
4208 whichever stack frame is selected at the moment. Here are the commands for
4209 selecting a stack frame; all of them finish by printing a brief description
4210 of the stack frame just selected.
4213 @kindex frame@r{, selecting}
4214 @kindex f @r{(@code{frame})}
4217 Select frame number @var{n}. Recall that frame zero is the innermost
4218 (currently executing) frame, frame one is the frame that called the
4219 innermost one, and so on. The highest-numbered frame is the one for
4222 @item frame @var{addr}
4224 Select the frame at address @var{addr}. This is useful mainly if the
4225 chaining of stack frames has been damaged by a bug, making it
4226 impossible for @value{GDBN} to assign numbers properly to all frames. In
4227 addition, this can be useful when your program has multiple stacks and
4228 switches between them.
4230 On the SPARC architecture, @code{frame} needs two addresses to
4231 select an arbitrary frame: a frame pointer and a stack pointer.
4233 On the MIPS and Alpha architecture, it needs two addresses: a stack
4234 pointer and a program counter.
4236 On the 29k architecture, it needs three addresses: a register stack
4237 pointer, a program counter, and a memory stack pointer.
4238 @c note to future updaters: this is conditioned on a flag
4239 @c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date
4240 @c as of 27 Jan 1994.
4244 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4245 advances toward the outermost frame, to higher frame numbers, to frames
4246 that have existed longer. @var{n} defaults to one.
4249 @kindex do @r{(@code{down})}
4251 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4252 advances toward the innermost frame, to lower frame numbers, to frames
4253 that were created more recently. @var{n} defaults to one. You may
4254 abbreviate @code{down} as @code{do}.
4257 All of these commands end by printing two lines of output describing the
4258 frame. The first line shows the frame number, the function name, the
4259 arguments, and the source file and line number of execution in that
4260 frame. The second line shows the text of that source line.
4268 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4270 10 read_input_file (argv[i]);
4274 After such a printout, the @code{list} command with no arguments
4275 prints ten lines centered on the point of execution in the frame.
4276 You can also edit the program at the point of execution with your favorite
4277 editing program by typing @code{edit}.
4278 @xref{List, ,Printing source lines},
4282 @kindex down-silently
4284 @item up-silently @var{n}
4285 @itemx down-silently @var{n}
4286 These two commands are variants of @code{up} and @code{down},
4287 respectively; they differ in that they do their work silently, without
4288 causing display of the new frame. They are intended primarily for use
4289 in @value{GDBN} command scripts, where the output might be unnecessary and
4294 @section Information about a frame
4296 There are several other commands to print information about the selected
4302 When used without any argument, this command does not change which
4303 frame is selected, but prints a brief description of the currently
4304 selected stack frame. It can be abbreviated @code{f}. With an
4305 argument, this command is used to select a stack frame.
4306 @xref{Selection, ,Selecting a frame}.
4309 @kindex info f @r{(@code{info frame})}
4312 This command prints a verbose description of the selected stack frame,
4317 the address of the frame
4319 the address of the next frame down (called by this frame)
4321 the address of the next frame up (caller of this frame)
4323 the language in which the source code corresponding to this frame is written
4325 the address of the frame's arguments
4327 the address of the frame's local variables
4329 the program counter saved in it (the address of execution in the caller frame)
4331 which registers were saved in the frame
4334 @noindent The verbose description is useful when
4335 something has gone wrong that has made the stack format fail to fit
4336 the usual conventions.
4338 @item info frame @var{addr}
4339 @itemx info f @var{addr}
4340 Print a verbose description of the frame at address @var{addr}, without
4341 selecting that frame. The selected frame remains unchanged by this
4342 command. This requires the same kind of address (more than one for some
4343 architectures) that you specify in the @code{frame} command.
4344 @xref{Selection, ,Selecting a frame}.
4348 Print the arguments of the selected frame, each on a separate line.
4352 Print the local variables of the selected frame, each on a separate
4353 line. These are all variables (declared either static or automatic)
4354 accessible at the point of execution of the selected frame.
4357 @cindex catch exceptions, list active handlers
4358 @cindex exception handlers, how to list
4360 Print a list of all the exception handlers that are active in the
4361 current stack frame at the current point of execution. To see other
4362 exception handlers, visit the associated frame (using the @code{up},
4363 @code{down}, or @code{frame} commands); then type @code{info catch}.
4364 @xref{Set Catchpoints, , Setting catchpoints}.
4370 @chapter Examining Source Files
4372 @value{GDBN} can print parts of your program's source, since the debugging
4373 information recorded in the program tells @value{GDBN} what source files were
4374 used to build it. When your program stops, @value{GDBN} spontaneously prints
4375 the line where it stopped. Likewise, when you select a stack frame
4376 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4377 execution in that frame has stopped. You can print other portions of
4378 source files by explicit command.
4380 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4381 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4382 @value{GDBN} under @sc{gnu} Emacs}.
4385 * List:: Printing source lines
4386 * Edit:: Editing source files
4387 * Search:: Searching source files
4388 * Source Path:: Specifying source directories
4389 * Machine Code:: Source and machine code
4393 @section Printing source lines
4396 @kindex l @r{(@code{list})}
4397 To print lines from a source file, use the @code{list} command
4398 (abbreviated @code{l}). By default, ten lines are printed.
4399 There are several ways to specify what part of the file you want to print.
4401 Here are the forms of the @code{list} command most commonly used:
4404 @item list @var{linenum}
4405 Print lines centered around line number @var{linenum} in the
4406 current source file.
4408 @item list @var{function}
4409 Print lines centered around the beginning of function
4413 Print more lines. If the last lines printed were printed with a
4414 @code{list} command, this prints lines following the last lines
4415 printed; however, if the last line printed was a solitary line printed
4416 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4417 Stack}), this prints lines centered around that line.
4420 Print lines just before the lines last printed.
4423 @cindex @code{list}, how many lines to display
4424 By default, @value{GDBN} prints ten source lines with any of these forms of
4425 the @code{list} command. You can change this using @code{set listsize}:
4428 @kindex set listsize
4429 @item set listsize @var{count}
4430 Make the @code{list} command display @var{count} source lines (unless
4431 the @code{list} argument explicitly specifies some other number).
4433 @kindex show listsize
4435 Display the number of lines that @code{list} prints.
4438 Repeating a @code{list} command with @key{RET} discards the argument,
4439 so it is equivalent to typing just @code{list}. This is more useful
4440 than listing the same lines again. An exception is made for an
4441 argument of @samp{-}; that argument is preserved in repetition so that
4442 each repetition moves up in the source file.
4445 In general, the @code{list} command expects you to supply zero, one or two
4446 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4447 of writing them, but the effect is always to specify some source line.
4448 Here is a complete description of the possible arguments for @code{list}:
4451 @item list @var{linespec}
4452 Print lines centered around the line specified by @var{linespec}.
4454 @item list @var{first},@var{last}
4455 Print lines from @var{first} to @var{last}. Both arguments are
4458 @item list ,@var{last}
4459 Print lines ending with @var{last}.
4461 @item list @var{first},
4462 Print lines starting with @var{first}.
4465 Print lines just after the lines last printed.
4468 Print lines just before the lines last printed.
4471 As described in the preceding table.
4474 Here are the ways of specifying a single source line---all the
4479 Specifies line @var{number} of the current source file.
4480 When a @code{list} command has two linespecs, this refers to
4481 the same source file as the first linespec.
4484 Specifies the line @var{offset} lines after the last line printed.
4485 When used as the second linespec in a @code{list} command that has
4486 two, this specifies the line @var{offset} lines down from the
4490 Specifies the line @var{offset} lines before the last line printed.
4492 @item @var{filename}:@var{number}
4493 Specifies line @var{number} in the source file @var{filename}.
4495 @item @var{function}
4496 Specifies the line that begins the body of the function @var{function}.
4497 For example: in C, this is the line with the open brace.
4499 @item @var{filename}:@var{function}
4500 Specifies the line of the open-brace that begins the body of the
4501 function @var{function} in the file @var{filename}. You only need the
4502 file name with a function name to avoid ambiguity when there are
4503 identically named functions in different source files.
4505 @item *@var{address}
4506 Specifies the line containing the program address @var{address}.
4507 @var{address} may be any expression.
4511 @section Editing source files
4512 @cindex editing source files
4515 @kindex e @r{(@code{edit})}
4516 To edit the lines in a source file, use the @code{edit} command.
4517 The editing program of your choice
4518 is invoked with the current line set to
4519 the active line in the program.
4520 Alternatively, there are several ways to specify what part of the file you
4521 want to print if you want to see other parts of the program.
4523 Here are the forms of the @code{edit} command most commonly used:
4527 Edit the current source file at the active line number in the program.
4529 @item edit @var{number}
4530 Edit the current source file with @var{number} as the active line number.
4532 @item edit @var{function}
4533 Edit the file containing @var{function} at the beginning of its definition.
4535 @item edit @var{filename}:@var{number}
4536 Specifies line @var{number} in the source file @var{filename}.
4538 @item edit @var{filename}:@var{function}
4539 Specifies the line that begins the body of the
4540 function @var{function} in the file @var{filename}. You only need the
4541 file name with a function name to avoid ambiguity when there are
4542 identically named functions in different source files.
4544 @item edit *@var{address}
4545 Specifies the line containing the program address @var{address}.
4546 @var{address} may be any expression.
4549 @subsection Choosing your editor
4550 You can customize @value{GDBN} to use any editor you want
4552 The only restriction is that your editor (say @code{ex}), recognizes the
4553 following command-line syntax:
4555 ex +@var{number} file
4557 The optional numeric value +@var{number} specifies the number of the line in
4558 the file where to start editing.}.
4559 By default, it is @file{@value{EDITOR}}, but you can change this
4560 by setting the environment variable @code{EDITOR} before using
4561 @value{GDBN}. For example, to configure @value{GDBN} to use the
4562 @code{vi} editor, you could use these commands with the @code{sh} shell:
4568 or in the @code{csh} shell,
4570 setenv EDITOR /usr/bin/vi
4575 @section Searching source files
4576 @cindex searching source files
4578 There are two commands for searching through the current source file for a
4583 @kindex forward-search
4584 @item forward-search @var{regexp}
4585 @itemx search @var{regexp}
4586 The command @samp{forward-search @var{regexp}} checks each line,
4587 starting with the one following the last line listed, for a match for
4588 @var{regexp}. It lists the line that is found. You can use the
4589 synonym @samp{search @var{regexp}} or abbreviate the command name as
4592 @kindex reverse-search
4593 @item reverse-search @var{regexp}
4594 The command @samp{reverse-search @var{regexp}} checks each line, starting
4595 with the one before the last line listed and going backward, for a match
4596 for @var{regexp}. It lists the line that is found. You can abbreviate
4597 this command as @code{rev}.
4601 @section Specifying source directories
4604 @cindex directories for source files
4605 Executable programs sometimes do not record the directories of the source
4606 files from which they were compiled, just the names. Even when they do,
4607 the directories could be moved between the compilation and your debugging
4608 session. @value{GDBN} has a list of directories to search for source files;
4609 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4610 it tries all the directories in the list, in the order they are present
4611 in the list, until it finds a file with the desired name.
4613 For example, suppose an executable references the file
4614 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
4615 @file{/mnt/cross}. The file is first looked up literally; if this
4616 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
4617 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
4618 message is printed. @value{GDBN} does not look up the parts of the
4619 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
4620 Likewise, the subdirectories of the source path are not searched: if
4621 the source path is @file{/mnt/cross}, and the binary refers to
4622 @file{foo.c}, @value{GDBN} would not find it under
4623 @file{/mnt/cross/usr/src/foo-1.0/lib}.
4625 Plain file names, relative file names with leading directories, file
4626 names containing dots, etc.@: are all treated as described above; for
4627 instance, if the source path is @file{/mnt/cross}, and the source file
4628 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
4629 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
4630 that---@file{/mnt/cross/foo.c}.
4632 Note that the executable search path is @emph{not} used to locate the
4633 source files. Neither is the current working directory, unless it
4634 happens to be in the source path.
4636 Whenever you reset or rearrange the source path, @value{GDBN} clears out
4637 any information it has cached about where source files are found and where
4638 each line is in the file.
4642 When you start @value{GDBN}, its source path includes only @samp{cdir}
4643 and @samp{cwd}, in that order.
4644 To add other directories, use the @code{directory} command.
4647 @item directory @var{dirname} @dots{}
4648 @item dir @var{dirname} @dots{}
4649 Add directory @var{dirname} to the front of the source path. Several
4650 directory names may be given to this command, separated by @samp{:}
4651 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4652 part of absolute file names) or
4653 whitespace. You may specify a directory that is already in the source
4654 path; this moves it forward, so @value{GDBN} searches it sooner.
4658 @vindex $cdir@r{, convenience variable}
4659 @vindex $cwdr@r{, convenience variable}
4660 @cindex compilation directory
4661 @cindex current directory
4662 @cindex working directory
4663 @cindex directory, current
4664 @cindex directory, compilation
4665 You can use the string @samp{$cdir} to refer to the compilation
4666 directory (if one is recorded), and @samp{$cwd} to refer to the current
4667 working directory. @samp{$cwd} is not the same as @samp{.}---the former
4668 tracks the current working directory as it changes during your @value{GDBN}
4669 session, while the latter is immediately expanded to the current
4670 directory at the time you add an entry to the source path.
4673 Reset the source path to empty again. This requires confirmation.
4675 @c RET-repeat for @code{directory} is explicitly disabled, but since
4676 @c repeating it would be a no-op we do not say that. (thanks to RMS)
4678 @item show directories
4679 @kindex show directories
4680 Print the source path: show which directories it contains.
4683 If your source path is cluttered with directories that are no longer of
4684 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4685 versions of source. You can correct the situation as follows:
4689 Use @code{directory} with no argument to reset the source path to empty.
4692 Use @code{directory} with suitable arguments to reinstall the
4693 directories you want in the source path. You can add all the
4694 directories in one command.
4698 @section Source and machine code
4699 @cindex source line and its code address
4701 You can use the command @code{info line} to map source lines to program
4702 addresses (and vice versa), and the command @code{disassemble} to display
4703 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
4704 mode, the @code{info line} command causes the arrow to point to the
4705 line specified. Also, @code{info line} prints addresses in symbolic form as
4710 @item info line @var{linespec}
4711 Print the starting and ending addresses of the compiled code for
4712 source line @var{linespec}. You can specify source lines in any of
4713 the ways understood by the @code{list} command (@pxref{List, ,Printing
4717 For example, we can use @code{info line} to discover the location of
4718 the object code for the first line of function
4719 @code{m4_changequote}:
4721 @c FIXME: I think this example should also show the addresses in
4722 @c symbolic form, as they usually would be displayed.
4724 (@value{GDBP}) info line m4_changequote
4725 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4729 @cindex code address and its source line
4730 We can also inquire (using @code{*@var{addr}} as the form for
4731 @var{linespec}) what source line covers a particular address:
4733 (@value{GDBP}) info line *0x63ff
4734 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4737 @cindex @code{$_} and @code{info line}
4738 @cindex @code{x} command, default address
4739 @kindex x@r{(examine), and} info line
4740 After @code{info line}, the default address for the @code{x} command
4741 is changed to the starting address of the line, so that @samp{x/i} is
4742 sufficient to begin examining the machine code (@pxref{Memory,
4743 ,Examining memory}). Also, this address is saved as the value of the
4744 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4749 @cindex assembly instructions
4750 @cindex instructions, assembly
4751 @cindex machine instructions
4752 @cindex listing machine instructions
4754 This specialized command dumps a range of memory as machine
4755 instructions. The default memory range is the function surrounding the
4756 program counter of the selected frame. A single argument to this
4757 command is a program counter value; @value{GDBN} dumps the function
4758 surrounding this value. Two arguments specify a range of addresses
4759 (first inclusive, second exclusive) to dump.
4762 The following example shows the disassembly of a range of addresses of
4763 HP PA-RISC 2.0 code:
4766 (@value{GDBP}) disas 0x32c4 0x32e4
4767 Dump of assembler code from 0x32c4 to 0x32e4:
4768 0x32c4 <main+204>: addil 0,dp
4769 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
4770 0x32cc <main+212>: ldil 0x3000,r31
4771 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
4772 0x32d4 <main+220>: ldo 0(r31),rp
4773 0x32d8 <main+224>: addil -0x800,dp
4774 0x32dc <main+228>: ldo 0x588(r1),r26
4775 0x32e0 <main+232>: ldil 0x3000,r31
4776 End of assembler dump.
4779 Some architectures have more than one commonly-used set of instruction
4780 mnemonics or other syntax.
4783 @kindex set disassembly-flavor
4784 @cindex Intel disassembly flavor
4785 @cindex AT&T disassembly flavor
4786 @item set disassembly-flavor @var{instruction-set}
4787 Select the instruction set to use when disassembling the
4788 program via the @code{disassemble} or @code{x/i} commands.
4790 Currently this command is only defined for the Intel x86 family. You
4791 can set @var{instruction-set} to either @code{intel} or @code{att}.
4792 The default is @code{att}, the AT&T flavor used by default by Unix
4793 assemblers for x86-based targets.
4795 @kindex show disassembly-flavor
4796 @item show disassembly-flavor
4797 Show the current setting of the disassembly flavor.
4802 @chapter Examining Data
4804 @cindex printing data
4805 @cindex examining data
4808 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
4809 @c document because it is nonstandard... Under Epoch it displays in a
4810 @c different window or something like that.
4811 The usual way to examine data in your program is with the @code{print}
4812 command (abbreviated @code{p}), or its synonym @code{inspect}. It
4813 evaluates and prints the value of an expression of the language your
4814 program is written in (@pxref{Languages, ,Using @value{GDBN} with
4815 Different Languages}).
4818 @item print @var{expr}
4819 @itemx print /@var{f} @var{expr}
4820 @var{expr} is an expression (in the source language). By default the
4821 value of @var{expr} is printed in a format appropriate to its data type;
4822 you can choose a different format by specifying @samp{/@var{f}}, where
4823 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
4827 @itemx print /@var{f}
4828 @cindex reprint the last value
4829 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
4830 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
4831 conveniently inspect the same value in an alternative format.
4834 A more low-level way of examining data is with the @code{x} command.
4835 It examines data in memory at a specified address and prints it in a
4836 specified format. @xref{Memory, ,Examining memory}.
4838 If you are interested in information about types, or about how the
4839 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
4840 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
4844 * Expressions:: Expressions
4845 * Variables:: Program variables
4846 * Arrays:: Artificial arrays
4847 * Output Formats:: Output formats
4848 * Memory:: Examining memory
4849 * Auto Display:: Automatic display
4850 * Print Settings:: Print settings
4851 * Value History:: Value history
4852 * Convenience Vars:: Convenience variables
4853 * Registers:: Registers
4854 * Floating Point Hardware:: Floating point hardware
4855 * Vector Unit:: Vector Unit
4856 * OS Information:: Auxiliary data provided by operating system
4857 * Memory Region Attributes:: Memory region attributes
4858 * Dump/Restore Files:: Copy between memory and a file
4859 * Core File Generation:: Cause a program dump its core
4860 * Character Sets:: Debugging programs that use a different
4861 character set than GDB does
4862 * Caching Remote Data:: Data caching for remote targets
4866 @section Expressions
4869 @code{print} and many other @value{GDBN} commands accept an expression and
4870 compute its value. Any kind of constant, variable or operator defined
4871 by the programming language you are using is valid in an expression in
4872 @value{GDBN}. This includes conditional expressions, function calls,
4873 casts, and string constants. It also includes preprocessor macros, if
4874 you compiled your program to include this information; see
4877 @cindex arrays in expressions
4878 @value{GDBN} supports array constants in expressions input by
4879 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
4880 you can use the command @code{print @{1, 2, 3@}} to build up an array in
4881 memory that is @code{malloc}ed in the target program.
4883 Because C is so widespread, most of the expressions shown in examples in
4884 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
4885 Languages}, for information on how to use expressions in other
4888 In this section, we discuss operators that you can use in @value{GDBN}
4889 expressions regardless of your programming language.
4891 @cindex casts, in expressions
4892 Casts are supported in all languages, not just in C, because it is so
4893 useful to cast a number into a pointer in order to examine a structure
4894 at that address in memory.
4895 @c FIXME: casts supported---Mod2 true?
4897 @value{GDBN} supports these operators, in addition to those common
4898 to programming languages:
4902 @samp{@@} is a binary operator for treating parts of memory as arrays.
4903 @xref{Arrays, ,Artificial arrays}, for more information.
4906 @samp{::} allows you to specify a variable in terms of the file or
4907 function where it is defined. @xref{Variables, ,Program variables}.
4909 @cindex @{@var{type}@}
4910 @cindex type casting memory
4911 @cindex memory, viewing as typed object
4912 @cindex casts, to view memory
4913 @item @{@var{type}@} @var{addr}
4914 Refers to an object of type @var{type} stored at address @var{addr} in
4915 memory. @var{addr} may be any expression whose value is an integer or
4916 pointer (but parentheses are required around binary operators, just as in
4917 a cast). This construct is allowed regardless of what kind of data is
4918 normally supposed to reside at @var{addr}.
4922 @section Program variables
4924 The most common kind of expression to use is the name of a variable
4927 Variables in expressions are understood in the selected stack frame
4928 (@pxref{Selection, ,Selecting a frame}); they must be either:
4932 global (or file-static)
4939 visible according to the scope rules of the
4940 programming language from the point of execution in that frame
4943 @noindent This means that in the function
4958 you can examine and use the variable @code{a} whenever your program is
4959 executing within the function @code{foo}, but you can only use or
4960 examine the variable @code{b} while your program is executing inside
4961 the block where @code{b} is declared.
4963 @cindex variable name conflict
4964 There is an exception: you can refer to a variable or function whose
4965 scope is a single source file even if the current execution point is not
4966 in this file. But it is possible to have more than one such variable or
4967 function with the same name (in different source files). If that
4968 happens, referring to that name has unpredictable effects. If you wish,
4969 you can specify a static variable in a particular function or file,
4970 using the colon-colon (@code{::}) notation:
4972 @cindex colon-colon, context for variables/functions
4974 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
4975 @cindex @code{::}, context for variables/functions
4978 @var{file}::@var{variable}
4979 @var{function}::@var{variable}
4983 Here @var{file} or @var{function} is the name of the context for the
4984 static @var{variable}. In the case of file names, you can use quotes to
4985 make sure @value{GDBN} parses the file name as a single word---for example,
4986 to print a global value of @code{x} defined in @file{f2.c}:
4989 (@value{GDBP}) p 'f2.c'::x
4992 @cindex C@t{++} scope resolution
4993 This use of @samp{::} is very rarely in conflict with the very similar
4994 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
4995 scope resolution operator in @value{GDBN} expressions.
4996 @c FIXME: Um, so what happens in one of those rare cases where it's in
4999 @cindex wrong values
5000 @cindex variable values, wrong
5001 @cindex function entry/exit, wrong values of variables
5002 @cindex optimized code, wrong values of variables
5004 @emph{Warning:} Occasionally, a local variable may appear to have the
5005 wrong value at certain points in a function---just after entry to a new
5006 scope, and just before exit.
5008 You may see this problem when you are stepping by machine instructions.
5009 This is because, on most machines, it takes more than one instruction to
5010 set up a stack frame (including local variable definitions); if you are
5011 stepping by machine instructions, variables may appear to have the wrong
5012 values until the stack frame is completely built. On exit, it usually
5013 also takes more than one machine instruction to destroy a stack frame;
5014 after you begin stepping through that group of instructions, local
5015 variable definitions may be gone.
5017 This may also happen when the compiler does significant optimizations.
5018 To be sure of always seeing accurate values, turn off all optimization
5021 @cindex ``No symbol "foo" in current context''
5022 Another possible effect of compiler optimizations is to optimize
5023 unused variables out of existence, or assign variables to registers (as
5024 opposed to memory addresses). Depending on the support for such cases
5025 offered by the debug info format used by the compiler, @value{GDBN}
5026 might not be able to display values for such local variables. If that
5027 happens, @value{GDBN} will print a message like this:
5030 No symbol "foo" in current context.
5033 To solve such problems, either recompile without optimizations, or use a
5034 different debug info format, if the compiler supports several such
5035 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5036 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5037 produces debug info in a format that is superior to formats such as
5038 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5039 an effective form for debug info. @xref{Debugging Options,,Options
5040 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
5041 @xref{C, , Debugging C++}, for more info about debug info formats
5042 that are best suited to C@t{++} programs.
5045 @section Artificial arrays
5047 @cindex artificial array
5049 @kindex @@@r{, referencing memory as an array}
5050 It is often useful to print out several successive objects of the
5051 same type in memory; a section of an array, or an array of
5052 dynamically determined size for which only a pointer exists in the
5055 You can do this by referring to a contiguous span of memory as an
5056 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5057 operand of @samp{@@} should be the first element of the desired array
5058 and be an individual object. The right operand should be the desired length
5059 of the array. The result is an array value whose elements are all of
5060 the type of the left argument. The first element is actually the left
5061 argument; the second element comes from bytes of memory immediately
5062 following those that hold the first element, and so on. Here is an
5063 example. If a program says
5066 int *array = (int *) malloc (len * sizeof (int));
5070 you can print the contents of @code{array} with
5076 The left operand of @samp{@@} must reside in memory. Array values made
5077 with @samp{@@} in this way behave just like other arrays in terms of
5078 subscripting, and are coerced to pointers when used in expressions.
5079 Artificial arrays most often appear in expressions via the value history
5080 (@pxref{Value History, ,Value history}), after printing one out.
5082 Another way to create an artificial array is to use a cast.
5083 This re-interprets a value as if it were an array.
5084 The value need not be in memory:
5086 (@value{GDBP}) p/x (short[2])0x12345678
5087 $1 = @{0x1234, 0x5678@}
5090 As a convenience, if you leave the array length out (as in
5091 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5092 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5094 (@value{GDBP}) p/x (short[])0x12345678
5095 $2 = @{0x1234, 0x5678@}
5098 Sometimes the artificial array mechanism is not quite enough; in
5099 moderately complex data structures, the elements of interest may not
5100 actually be adjacent---for example, if you are interested in the values
5101 of pointers in an array. One useful work-around in this situation is
5102 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5103 variables}) as a counter in an expression that prints the first
5104 interesting value, and then repeat that expression via @key{RET}. For
5105 instance, suppose you have an array @code{dtab} of pointers to
5106 structures, and you are interested in the values of a field @code{fv}
5107 in each structure. Here is an example of what you might type:
5117 @node Output Formats
5118 @section Output formats
5120 @cindex formatted output
5121 @cindex output formats
5122 By default, @value{GDBN} prints a value according to its data type. Sometimes
5123 this is not what you want. For example, you might want to print a number
5124 in hex, or a pointer in decimal. Or you might want to view data in memory
5125 at a certain address as a character string or as an instruction. To do
5126 these things, specify an @dfn{output format} when you print a value.
5128 The simplest use of output formats is to say how to print a value
5129 already computed. This is done by starting the arguments of the
5130 @code{print} command with a slash and a format letter. The format
5131 letters supported are:
5135 Regard the bits of the value as an integer, and print the integer in
5139 Print as integer in signed decimal.
5142 Print as integer in unsigned decimal.
5145 Print as integer in octal.
5148 Print as integer in binary. The letter @samp{t} stands for ``two''.
5149 @footnote{@samp{b} cannot be used because these format letters are also
5150 used with the @code{x} command, where @samp{b} stands for ``byte'';
5151 see @ref{Memory,,Examining memory}.}
5154 @cindex unknown address, locating
5155 @cindex locate address
5156 Print as an address, both absolute in hexadecimal and as an offset from
5157 the nearest preceding symbol. You can use this format used to discover
5158 where (in what function) an unknown address is located:
5161 (@value{GDBP}) p/a 0x54320
5162 $3 = 0x54320 <_initialize_vx+396>
5166 The command @code{info symbol 0x54320} yields similar results.
5167 @xref{Symbols, info symbol}.
5170 Regard as an integer and print it as a character constant.
5173 Regard the bits of the value as a floating point number and print
5174 using typical floating point syntax.
5177 For example, to print the program counter in hex (@pxref{Registers}), type
5184 Note that no space is required before the slash; this is because command
5185 names in @value{GDBN} cannot contain a slash.
5187 To reprint the last value in the value history with a different format,
5188 you can use the @code{print} command with just a format and no
5189 expression. For example, @samp{p/x} reprints the last value in hex.
5192 @section Examining memory
5194 You can use the command @code{x} (for ``examine'') to examine memory in
5195 any of several formats, independently of your program's data types.
5197 @cindex examining memory
5199 @kindex x @r{(examine memory)}
5200 @item x/@var{nfu} @var{addr}
5203 Use the @code{x} command to examine memory.
5206 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5207 much memory to display and how to format it; @var{addr} is an
5208 expression giving the address where you want to start displaying memory.
5209 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5210 Several commands set convenient defaults for @var{addr}.
5213 @item @var{n}, the repeat count
5214 The repeat count is a decimal integer; the default is 1. It specifies
5215 how much memory (counting by units @var{u}) to display.
5216 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5219 @item @var{f}, the display format
5220 The display format is one of the formats used by @code{print},
5221 @samp{s} (null-terminated string), or @samp{i} (machine instruction).
5222 The default is @samp{x} (hexadecimal) initially.
5223 The default changes each time you use either @code{x} or @code{print}.
5225 @item @var{u}, the unit size
5226 The unit size is any of
5232 Halfwords (two bytes).
5234 Words (four bytes). This is the initial default.
5236 Giant words (eight bytes).
5239 Each time you specify a unit size with @code{x}, that size becomes the
5240 default unit the next time you use @code{x}. (For the @samp{s} and
5241 @samp{i} formats, the unit size is ignored and is normally not written.)
5243 @item @var{addr}, starting display address
5244 @var{addr} is the address where you want @value{GDBN} to begin displaying
5245 memory. The expression need not have a pointer value (though it may);
5246 it is always interpreted as an integer address of a byte of memory.
5247 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5248 @var{addr} is usually just after the last address examined---but several
5249 other commands also set the default address: @code{info breakpoints} (to
5250 the address of the last breakpoint listed), @code{info line} (to the
5251 starting address of a line), and @code{print} (if you use it to display
5252 a value from memory).
5255 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5256 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5257 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5258 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5259 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5261 Since the letters indicating unit sizes are all distinct from the
5262 letters specifying output formats, you do not have to remember whether
5263 unit size or format comes first; either order works. The output
5264 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5265 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5267 Even though the unit size @var{u} is ignored for the formats @samp{s}
5268 and @samp{i}, you might still want to use a count @var{n}; for example,
5269 @samp{3i} specifies that you want to see three machine instructions,
5270 including any operands. The command @code{disassemble} gives an
5271 alternative way of inspecting machine instructions; see @ref{Machine
5272 Code,,Source and machine code}.
5274 All the defaults for the arguments to @code{x} are designed to make it
5275 easy to continue scanning memory with minimal specifications each time
5276 you use @code{x}. For example, after you have inspected three machine
5277 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5278 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5279 the repeat count @var{n} is used again; the other arguments default as
5280 for successive uses of @code{x}.
5282 @cindex @code{$_}, @code{$__}, and value history
5283 The addresses and contents printed by the @code{x} command are not saved
5284 in the value history because there is often too much of them and they
5285 would get in the way. Instead, @value{GDBN} makes these values available for
5286 subsequent use in expressions as values of the convenience variables
5287 @code{$_} and @code{$__}. After an @code{x} command, the last address
5288 examined is available for use in expressions in the convenience variable
5289 @code{$_}. The contents of that address, as examined, are available in
5290 the convenience variable @code{$__}.
5292 If the @code{x} command has a repeat count, the address and contents saved
5293 are from the last memory unit printed; this is not the same as the last
5294 address printed if several units were printed on the last line of output.
5296 @cindex remote memory comparison
5297 @cindex verify remote memory image
5298 When you are debugging a program running on a remote target machine
5299 (@pxref{Remote}), you may wish to verify the program's image in the
5300 remote machine's memory against the executable file you downloaded to
5301 the target. The @code{compare-sections} command is provided for such
5305 @kindex compare-sections
5306 @item compare-sections @r{[}@var{section-name}@r{]}
5307 Compare the data of a loadable section @var{section-name} in the
5308 executable file of the program being debugged with the same section in
5309 the remote machine's memory, and report any mismatches. With no
5310 arguments, compares all loadable sections. This command's
5311 availability depends on the target's support for the @code{"qCRC"}
5316 @section Automatic display
5317 @cindex automatic display
5318 @cindex display of expressions
5320 If you find that you want to print the value of an expression frequently
5321 (to see how it changes), you might want to add it to the @dfn{automatic
5322 display list} so that @value{GDBN} prints its value each time your program stops.
5323 Each expression added to the list is given a number to identify it;
5324 to remove an expression from the list, you specify that number.
5325 The automatic display looks like this:
5329 3: bar[5] = (struct hack *) 0x3804
5333 This display shows item numbers, expressions and their current values. As with
5334 displays you request manually using @code{x} or @code{print}, you can
5335 specify the output format you prefer; in fact, @code{display} decides
5336 whether to use @code{print} or @code{x} depending on how elaborate your
5337 format specification is---it uses @code{x} if you specify a unit size,
5338 or one of the two formats (@samp{i} and @samp{s}) that are only
5339 supported by @code{x}; otherwise it uses @code{print}.
5343 @item display @var{expr}
5344 Add the expression @var{expr} to the list of expressions to display
5345 each time your program stops. @xref{Expressions, ,Expressions}.
5347 @code{display} does not repeat if you press @key{RET} again after using it.
5349 @item display/@var{fmt} @var{expr}
5350 For @var{fmt} specifying only a display format and not a size or
5351 count, add the expression @var{expr} to the auto-display list but
5352 arrange to display it each time in the specified format @var{fmt}.
5353 @xref{Output Formats,,Output formats}.
5355 @item display/@var{fmt} @var{addr}
5356 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5357 number of units, add the expression @var{addr} as a memory address to
5358 be examined each time your program stops. Examining means in effect
5359 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5362 For example, @samp{display/i $pc} can be helpful, to see the machine
5363 instruction about to be executed each time execution stops (@samp{$pc}
5364 is a common name for the program counter; @pxref{Registers, ,Registers}).
5367 @kindex delete display
5369 @item undisplay @var{dnums}@dots{}
5370 @itemx delete display @var{dnums}@dots{}
5371 Remove item numbers @var{dnums} from the list of expressions to display.
5373 @code{undisplay} does not repeat if you press @key{RET} after using it.
5374 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5376 @kindex disable display
5377 @item disable display @var{dnums}@dots{}
5378 Disable the display of item numbers @var{dnums}. A disabled display
5379 item is not printed automatically, but is not forgotten. It may be
5380 enabled again later.
5382 @kindex enable display
5383 @item enable display @var{dnums}@dots{}
5384 Enable display of item numbers @var{dnums}. It becomes effective once
5385 again in auto display of its expression, until you specify otherwise.
5388 Display the current values of the expressions on the list, just as is
5389 done when your program stops.
5391 @kindex info display
5393 Print the list of expressions previously set up to display
5394 automatically, each one with its item number, but without showing the
5395 values. This includes disabled expressions, which are marked as such.
5396 It also includes expressions which would not be displayed right now
5397 because they refer to automatic variables not currently available.
5400 @cindex display disabled out of scope
5401 If a display expression refers to local variables, then it does not make
5402 sense outside the lexical context for which it was set up. Such an
5403 expression is disabled when execution enters a context where one of its
5404 variables is not defined. For example, if you give the command
5405 @code{display last_char} while inside a function with an argument
5406 @code{last_char}, @value{GDBN} displays this argument while your program
5407 continues to stop inside that function. When it stops elsewhere---where
5408 there is no variable @code{last_char}---the display is disabled
5409 automatically. The next time your program stops where @code{last_char}
5410 is meaningful, you can enable the display expression once again.
5412 @node Print Settings
5413 @section Print settings
5415 @cindex format options
5416 @cindex print settings
5417 @value{GDBN} provides the following ways to control how arrays, structures,
5418 and symbols are printed.
5421 These settings are useful for debugging programs in any language:
5425 @item set print address
5426 @itemx set print address on
5427 @cindex print/don't print memory addresses
5428 @value{GDBN} prints memory addresses showing the location of stack
5429 traces, structure values, pointer values, breakpoints, and so forth,
5430 even when it also displays the contents of those addresses. The default
5431 is @code{on}. For example, this is what a stack frame display looks like with
5432 @code{set print address on}:
5437 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5439 530 if (lquote != def_lquote)
5443 @item set print address off
5444 Do not print addresses when displaying their contents. For example,
5445 this is the same stack frame displayed with @code{set print address off}:
5449 (@value{GDBP}) set print addr off
5451 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5452 530 if (lquote != def_lquote)
5456 You can use @samp{set print address off} to eliminate all machine
5457 dependent displays from the @value{GDBN} interface. For example, with
5458 @code{print address off}, you should get the same text for backtraces on
5459 all machines---whether or not they involve pointer arguments.
5462 @item show print address
5463 Show whether or not addresses are to be printed.
5466 When @value{GDBN} prints a symbolic address, it normally prints the
5467 closest earlier symbol plus an offset. If that symbol does not uniquely
5468 identify the address (for example, it is a name whose scope is a single
5469 source file), you may need to clarify. One way to do this is with
5470 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5471 you can set @value{GDBN} to print the source file and line number when
5472 it prints a symbolic address:
5475 @item set print symbol-filename on
5476 @cindex source file and line of a symbol
5477 @cindex symbol, source file and line
5478 Tell @value{GDBN} to print the source file name and line number of a
5479 symbol in the symbolic form of an address.
5481 @item set print symbol-filename off
5482 Do not print source file name and line number of a symbol. This is the
5485 @item show print symbol-filename
5486 Show whether or not @value{GDBN} will print the source file name and
5487 line number of a symbol in the symbolic form of an address.
5490 Another situation where it is helpful to show symbol filenames and line
5491 numbers is when disassembling code; @value{GDBN} shows you the line
5492 number and source file that corresponds to each instruction.
5494 Also, you may wish to see the symbolic form only if the address being
5495 printed is reasonably close to the closest earlier symbol:
5498 @item set print max-symbolic-offset @var{max-offset}
5499 @cindex maximum value for offset of closest symbol
5500 Tell @value{GDBN} to only display the symbolic form of an address if the
5501 offset between the closest earlier symbol and the address is less than
5502 @var{max-offset}. The default is 0, which tells @value{GDBN}
5503 to always print the symbolic form of an address if any symbol precedes it.
5505 @item show print max-symbolic-offset
5506 Ask how large the maximum offset is that @value{GDBN} prints in a
5510 @cindex wild pointer, interpreting
5511 @cindex pointer, finding referent
5512 If you have a pointer and you are not sure where it points, try
5513 @samp{set print symbol-filename on}. Then you can determine the name
5514 and source file location of the variable where it points, using
5515 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5516 For example, here @value{GDBN} shows that a variable @code{ptt} points
5517 at another variable @code{t}, defined in @file{hi2.c}:
5520 (@value{GDBP}) set print symbol-filename on
5521 (@value{GDBP}) p/a ptt
5522 $4 = 0xe008 <t in hi2.c>
5526 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5527 does not show the symbol name and filename of the referent, even with
5528 the appropriate @code{set print} options turned on.
5531 Other settings control how different kinds of objects are printed:
5534 @item set print array
5535 @itemx set print array on
5536 @cindex pretty print arrays
5537 Pretty print arrays. This format is more convenient to read,
5538 but uses more space. The default is off.
5540 @item set print array off
5541 Return to compressed format for arrays.
5543 @item show print array
5544 Show whether compressed or pretty format is selected for displaying
5547 @item set print elements @var{number-of-elements}
5548 @cindex number of array elements to print
5549 @cindex limit on number of printed array elements
5550 Set a limit on how many elements of an array @value{GDBN} will print.
5551 If @value{GDBN} is printing a large array, it stops printing after it has
5552 printed the number of elements set by the @code{set print elements} command.
5553 This limit also applies to the display of strings.
5554 When @value{GDBN} starts, this limit is set to 200.
5555 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5557 @item show print elements
5558 Display the number of elements of a large array that @value{GDBN} will print.
5559 If the number is 0, then the printing is unlimited.
5561 @item set print repeats
5562 @cindex repeated array elements
5563 Set the threshold for suppressing display of repeated array
5564 elelments. When the number of consecutive identical elements of an
5565 array exceeds the threshold, @value{GDBN} prints the string
5566 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
5567 identical repetitions, instead of displaying the identical elements
5568 themselves. Setting the threshold to zero will cause all elements to
5569 be individually printed. The default threshold is 10.
5571 @item show print repeats
5572 Display the current threshold for printing repeated identical
5575 @item set print null-stop
5576 @cindex @sc{null} elements in arrays
5577 Cause @value{GDBN} to stop printing the characters of an array when the first
5578 @sc{null} is encountered. This is useful when large arrays actually
5579 contain only short strings.
5582 @item show print null-stop
5583 Show whether @value{GDBN} stops printing an array on the first
5584 @sc{null} character.
5586 @item set print pretty on
5587 @cindex print structures in indented form
5588 @cindex indentation in structure display
5589 Cause @value{GDBN} to print structures in an indented format with one member
5590 per line, like this:
5605 @item set print pretty off
5606 Cause @value{GDBN} to print structures in a compact format, like this:
5610 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5611 meat = 0x54 "Pork"@}
5616 This is the default format.
5618 @item show print pretty
5619 Show which format @value{GDBN} is using to print structures.
5621 @item set print sevenbit-strings on
5622 @cindex eight-bit characters in strings
5623 @cindex octal escapes in strings
5624 Print using only seven-bit characters; if this option is set,
5625 @value{GDBN} displays any eight-bit characters (in strings or
5626 character values) using the notation @code{\}@var{nnn}. This setting is
5627 best if you are working in English (@sc{ascii}) and you use the
5628 high-order bit of characters as a marker or ``meta'' bit.
5630 @item set print sevenbit-strings off
5631 Print full eight-bit characters. This allows the use of more
5632 international character sets, and is the default.
5634 @item show print sevenbit-strings
5635 Show whether or not @value{GDBN} is printing only seven-bit characters.
5637 @item set print union on
5638 @cindex unions in structures, printing
5639 Tell @value{GDBN} to print unions which are contained in structures
5640 and other unions. This is the default setting.
5642 @item set print union off
5643 Tell @value{GDBN} not to print unions which are contained in
5644 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
5647 @item show print union
5648 Ask @value{GDBN} whether or not it will print unions which are contained in
5649 structures and other unions.
5651 For example, given the declarations
5654 typedef enum @{Tree, Bug@} Species;
5655 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5656 typedef enum @{Caterpillar, Cocoon, Butterfly@}
5667 struct thing foo = @{Tree, @{Acorn@}@};
5671 with @code{set print union on} in effect @samp{p foo} would print
5674 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5678 and with @code{set print union off} in effect it would print
5681 $1 = @{it = Tree, form = @{...@}@}
5685 @code{set print union} affects programs written in C-like languages
5691 These settings are of interest when debugging C@t{++} programs:
5694 @cindex demangling C@t{++} names
5695 @item set print demangle
5696 @itemx set print demangle on
5697 Print C@t{++} names in their source form rather than in the encoded
5698 (``mangled'') form passed to the assembler and linker for type-safe
5699 linkage. The default is on.
5701 @item show print demangle
5702 Show whether C@t{++} names are printed in mangled or demangled form.
5704 @item set print asm-demangle
5705 @itemx set print asm-demangle on
5706 Print C@t{++} names in their source form rather than their mangled form, even
5707 in assembler code printouts such as instruction disassemblies.
5710 @item show print asm-demangle
5711 Show whether C@t{++} names in assembly listings are printed in mangled
5714 @cindex C@t{++} symbol decoding style
5715 @cindex symbol decoding style, C@t{++}
5716 @kindex set demangle-style
5717 @item set demangle-style @var{style}
5718 Choose among several encoding schemes used by different compilers to
5719 represent C@t{++} names. The choices for @var{style} are currently:
5723 Allow @value{GDBN} to choose a decoding style by inspecting your program.
5726 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
5727 This is the default.
5730 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
5733 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
5736 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
5737 @strong{Warning:} this setting alone is not sufficient to allow
5738 debugging @code{cfront}-generated executables. @value{GDBN} would
5739 require further enhancement to permit that.
5742 If you omit @var{style}, you will see a list of possible formats.
5744 @item show demangle-style
5745 Display the encoding style currently in use for decoding C@t{++} symbols.
5747 @item set print object
5748 @itemx set print object on
5749 @cindex derived type of an object, printing
5750 @cindex display derived types
5751 When displaying a pointer to an object, identify the @emph{actual}
5752 (derived) type of the object rather than the @emph{declared} type, using
5753 the virtual function table.
5755 @item set print object off
5756 Display only the declared type of objects, without reference to the
5757 virtual function table. This is the default setting.
5759 @item show print object
5760 Show whether actual, or declared, object types are displayed.
5762 @item set print static-members
5763 @itemx set print static-members on
5764 @cindex static members of C@t{++} objects
5765 Print static members when displaying a C@t{++} object. The default is on.
5767 @item set print static-members off
5768 Do not print static members when displaying a C@t{++} object.
5770 @item show print static-members
5771 Show whether C@t{++} static members are printed or not.
5773 @item set print pascal_static-members
5774 @itemx set print pascal_static-members on
5775 @cindex static members of Pacal objects
5776 @cindex Pacal objects, static members display
5777 Print static members when displaying a Pascal object. The default is on.
5779 @item set print pascal_static-members off
5780 Do not print static members when displaying a Pascal object.
5782 @item show print pascal_static-members
5783 Show whether Pascal static members are printed or not.
5785 @c These don't work with HP ANSI C++ yet.
5786 @item set print vtbl
5787 @itemx set print vtbl on
5788 @cindex pretty print C@t{++} virtual function tables
5789 @cindex virtual functions (C@t{++}) display
5790 @cindex VTBL display
5791 Pretty print C@t{++} virtual function tables. The default is off.
5792 (The @code{vtbl} commands do not work on programs compiled with the HP
5793 ANSI C@t{++} compiler (@code{aCC}).)
5795 @item set print vtbl off
5796 Do not pretty print C@t{++} virtual function tables.
5798 @item show print vtbl
5799 Show whether C@t{++} virtual function tables are pretty printed, or not.
5803 @section Value history
5805 @cindex value history
5806 @cindex history of values printed by @value{GDBN}
5807 Values printed by the @code{print} command are saved in the @value{GDBN}
5808 @dfn{value history}. This allows you to refer to them in other expressions.
5809 Values are kept until the symbol table is re-read or discarded
5810 (for example with the @code{file} or @code{symbol-file} commands).
5811 When the symbol table changes, the value history is discarded,
5812 since the values may contain pointers back to the types defined in the
5817 @cindex history number
5818 The values printed are given @dfn{history numbers} by which you can
5819 refer to them. These are successive integers starting with one.
5820 @code{print} shows you the history number assigned to a value by
5821 printing @samp{$@var{num} = } before the value; here @var{num} is the
5824 To refer to any previous value, use @samp{$} followed by the value's
5825 history number. The way @code{print} labels its output is designed to
5826 remind you of this. Just @code{$} refers to the most recent value in
5827 the history, and @code{$$} refers to the value before that.
5828 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
5829 is the value just prior to @code{$$}, @code{$$1} is equivalent to
5830 @code{$$}, and @code{$$0} is equivalent to @code{$}.
5832 For example, suppose you have just printed a pointer to a structure and
5833 want to see the contents of the structure. It suffices to type
5839 If you have a chain of structures where the component @code{next} points
5840 to the next one, you can print the contents of the next one with this:
5847 You can print successive links in the chain by repeating this
5848 command---which you can do by just typing @key{RET}.
5850 Note that the history records values, not expressions. If the value of
5851 @code{x} is 4 and you type these commands:
5859 then the value recorded in the value history by the @code{print} command
5860 remains 4 even though the value of @code{x} has changed.
5865 Print the last ten values in the value history, with their item numbers.
5866 This is like @samp{p@ $$9} repeated ten times, except that @code{show
5867 values} does not change the history.
5869 @item show values @var{n}
5870 Print ten history values centered on history item number @var{n}.
5873 Print ten history values just after the values last printed. If no more
5874 values are available, @code{show values +} produces no display.
5877 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
5878 same effect as @samp{show values +}.
5880 @node Convenience Vars
5881 @section Convenience variables
5883 @cindex convenience variables
5884 @cindex user-defined variables
5885 @value{GDBN} provides @dfn{convenience variables} that you can use within
5886 @value{GDBN} to hold on to a value and refer to it later. These variables
5887 exist entirely within @value{GDBN}; they are not part of your program, and
5888 setting a convenience variable has no direct effect on further execution
5889 of your program. That is why you can use them freely.
5891 Convenience variables are prefixed with @samp{$}. Any name preceded by
5892 @samp{$} can be used for a convenience variable, unless it is one of
5893 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
5894 (Value history references, in contrast, are @emph{numbers} preceded
5895 by @samp{$}. @xref{Value History, ,Value history}.)
5897 You can save a value in a convenience variable with an assignment
5898 expression, just as you would set a variable in your program.
5902 set $foo = *object_ptr
5906 would save in @code{$foo} the value contained in the object pointed to by
5909 Using a convenience variable for the first time creates it, but its
5910 value is @code{void} until you assign a new value. You can alter the
5911 value with another assignment at any time.
5913 Convenience variables have no fixed types. You can assign a convenience
5914 variable any type of value, including structures and arrays, even if
5915 that variable already has a value of a different type. The convenience
5916 variable, when used as an expression, has the type of its current value.
5919 @kindex show convenience
5920 @cindex show all user variables
5921 @item show convenience
5922 Print a list of convenience variables used so far, and their values.
5923 Abbreviated @code{show conv}.
5926 One of the ways to use a convenience variable is as a counter to be
5927 incremented or a pointer to be advanced. For example, to print
5928 a field from successive elements of an array of structures:
5932 print bar[$i++]->contents
5936 Repeat that command by typing @key{RET}.
5938 Some convenience variables are created automatically by @value{GDBN} and given
5939 values likely to be useful.
5942 @vindex $_@r{, convenience variable}
5944 The variable @code{$_} is automatically set by the @code{x} command to
5945 the last address examined (@pxref{Memory, ,Examining memory}). Other
5946 commands which provide a default address for @code{x} to examine also
5947 set @code{$_} to that address; these commands include @code{info line}
5948 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
5949 except when set by the @code{x} command, in which case it is a pointer
5950 to the type of @code{$__}.
5952 @vindex $__@r{, convenience variable}
5954 The variable @code{$__} is automatically set by the @code{x} command
5955 to the value found in the last address examined. Its type is chosen
5956 to match the format in which the data was printed.
5959 @vindex $_exitcode@r{, convenience variable}
5960 The variable @code{$_exitcode} is automatically set to the exit code when
5961 the program being debugged terminates.
5964 On HP-UX systems, if you refer to a function or variable name that
5965 begins with a dollar sign, @value{GDBN} searches for a user or system
5966 name first, before it searches for a convenience variable.
5972 You can refer to machine register contents, in expressions, as variables
5973 with names starting with @samp{$}. The names of registers are different
5974 for each machine; use @code{info registers} to see the names used on
5978 @kindex info registers
5979 @item info registers
5980 Print the names and values of all registers except floating-point
5981 and vector registers (in the selected stack frame).
5983 @kindex info all-registers
5984 @cindex floating point registers
5985 @item info all-registers
5986 Print the names and values of all registers, including floating-point
5987 and vector registers (in the selected stack frame).
5989 @item info registers @var{regname} @dots{}
5990 Print the @dfn{relativized} value of each specified register @var{regname}.
5991 As discussed in detail below, register values are normally relative to
5992 the selected stack frame. @var{regname} may be any register name valid on
5993 the machine you are using, with or without the initial @samp{$}.
5996 @value{GDBN} has four ``standard'' register names that are available (in
5997 expressions) on most machines---whenever they do not conflict with an
5998 architecture's canonical mnemonics for registers. The register names
5999 @code{$pc} and @code{$sp} are used for the program counter register and
6000 the stack pointer. @code{$fp} is used for a register that contains a
6001 pointer to the current stack frame, and @code{$ps} is used for a
6002 register that contains the processor status. For example,
6003 you could print the program counter in hex with
6010 or print the instruction to be executed next with
6017 or add four to the stack pointer@footnote{This is a way of removing
6018 one word from the stack, on machines where stacks grow downward in
6019 memory (most machines, nowadays). This assumes that the innermost
6020 stack frame is selected; setting @code{$sp} is not allowed when other
6021 stack frames are selected. To pop entire frames off the stack,
6022 regardless of machine architecture, use @code{return};
6023 see @ref{Returning, ,Returning from a function}.} with
6029 Whenever possible, these four standard register names are available on
6030 your machine even though the machine has different canonical mnemonics,
6031 so long as there is no conflict. The @code{info registers} command
6032 shows the canonical names. For example, on the SPARC, @code{info
6033 registers} displays the processor status register as @code{$psr} but you
6034 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6035 is an alias for the @sc{eflags} register.
6037 @value{GDBN} always considers the contents of an ordinary register as an
6038 integer when the register is examined in this way. Some machines have
6039 special registers which can hold nothing but floating point; these
6040 registers are considered to have floating point values. There is no way
6041 to refer to the contents of an ordinary register as floating point value
6042 (although you can @emph{print} it as a floating point value with
6043 @samp{print/f $@var{regname}}).
6045 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6046 means that the data format in which the register contents are saved by
6047 the operating system is not the same one that your program normally
6048 sees. For example, the registers of the 68881 floating point
6049 coprocessor are always saved in ``extended'' (raw) format, but all C
6050 programs expect to work with ``double'' (virtual) format. In such
6051 cases, @value{GDBN} normally works with the virtual format only (the format
6052 that makes sense for your program), but the @code{info registers} command
6053 prints the data in both formats.
6055 Normally, register values are relative to the selected stack frame
6056 (@pxref{Selection, ,Selecting a frame}). This means that you get the
6057 value that the register would contain if all stack frames farther in
6058 were exited and their saved registers restored. In order to see the
6059 true contents of hardware registers, you must select the innermost
6060 frame (with @samp{frame 0}).
6062 However, @value{GDBN} must deduce where registers are saved, from the machine
6063 code generated by your compiler. If some registers are not saved, or if
6064 @value{GDBN} is unable to locate the saved registers, the selected stack
6065 frame makes no difference.
6067 @node Floating Point Hardware
6068 @section Floating point hardware
6069 @cindex floating point
6071 Depending on the configuration, @value{GDBN} may be able to give
6072 you more information about the status of the floating point hardware.
6077 Display hardware-dependent information about the floating
6078 point unit. The exact contents and layout vary depending on the
6079 floating point chip. Currently, @samp{info float} is supported on
6080 the ARM and x86 machines.
6084 @section Vector Unit
6087 Depending on the configuration, @value{GDBN} may be able to give you
6088 more information about the status of the vector unit.
6093 Display information about the vector unit. The exact contents and
6094 layout vary depending on the hardware.
6097 @node OS Information
6098 @section Operating system auxiliary information
6099 @cindex OS information
6101 @value{GDBN} provides interfaces to useful OS facilities that can help
6102 you debug your program.
6104 @cindex @code{ptrace} system call
6105 @cindex @code{struct user} contents
6106 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
6107 machines), it interfaces with the inferior via the @code{ptrace}
6108 system call. The operating system creates a special sata structure,
6109 called @code{struct user}, for this interface. You can use the
6110 command @code{info udot} to display the contents of this data
6116 Display the contents of the @code{struct user} maintained by the OS
6117 kernel for the program being debugged. @value{GDBN} displays the
6118 contents of @code{struct user} as a list of hex numbers, similar to
6119 the @code{examine} command.
6122 @cindex auxiliary vector
6123 @cindex vector, auxiliary
6124 Some operating systems supply an @dfn{auxiliary vector} to programs at
6125 startup. This is akin to the arguments and environment that you
6126 specify for a program, but contains a system-dependent variety of
6127 binary values that tell system libraries important details about the
6128 hardware, operating system, and process. Each value's purpose is
6129 identified by an integer tag; the meanings are well-known but system-specific.
6130 Depending on the configuration and operating system facilities,
6131 @value{GDBN} may be able to show you this information. For remote
6132 targets, this functionality may further depend on the remote stub's
6133 support of the @samp{qPart:auxv:read} packet, see @ref{Remote
6134 configuration, auxiliary vector}.
6139 Display the auxiliary vector of the inferior, which can be either a
6140 live process or a core dump file. @value{GDBN} prints each tag value
6141 numerically, and also shows names and text descriptions for recognized
6142 tags. Some values in the vector are numbers, some bit masks, and some
6143 pointers to strings or other data. @value{GDBN} displays each value in the
6144 most appropriate form for a recognized tag, and in hexadecimal for
6145 an unrecognized tag.
6149 @node Memory Region Attributes
6150 @section Memory region attributes
6151 @cindex memory region attributes
6153 @dfn{Memory region attributes} allow you to describe special handling
6154 required by regions of your target's memory. @value{GDBN} uses attributes
6155 to determine whether to allow certain types of memory accesses; whether to
6156 use specific width accesses; and whether to cache target memory.
6158 Defined memory regions can be individually enabled and disabled. When a
6159 memory region is disabled, @value{GDBN} uses the default attributes when
6160 accessing memory in that region. Similarly, if no memory regions have
6161 been defined, @value{GDBN} uses the default attributes when accessing
6164 When a memory region is defined, it is given a number to identify it;
6165 to enable, disable, or remove a memory region, you specify that number.
6169 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6170 Define a memory region bounded by @var{lower} and @var{upper} with
6171 attributes @var{attributes}@dots{}, and add it to the list of regions
6172 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
6173 case: it is treated as the the target's maximum memory address.
6174 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6177 @item delete mem @var{nums}@dots{}
6178 Remove memory regions @var{nums}@dots{} from the list of regions
6179 monitored by @value{GDBN}.
6182 @item disable mem @var{nums}@dots{}
6183 Disable monitoring of memory regions @var{nums}@dots{}.
6184 A disabled memory region is not forgotten.
6185 It may be enabled again later.
6188 @item enable mem @var{nums}@dots{}
6189 Enable monitoring of memory regions @var{nums}@dots{}.
6193 Print a table of all defined memory regions, with the following columns
6197 @item Memory Region Number
6198 @item Enabled or Disabled.
6199 Enabled memory regions are marked with @samp{y}.
6200 Disabled memory regions are marked with @samp{n}.
6203 The address defining the inclusive lower bound of the memory region.
6206 The address defining the exclusive upper bound of the memory region.
6209 The list of attributes set for this memory region.
6214 @subsection Attributes
6216 @subsubsection Memory Access Mode
6217 The access mode attributes set whether @value{GDBN} may make read or
6218 write accesses to a memory region.
6220 While these attributes prevent @value{GDBN} from performing invalid
6221 memory accesses, they do nothing to prevent the target system, I/O DMA,
6222 etc. from accessing memory.
6226 Memory is read only.
6228 Memory is write only.
6230 Memory is read/write. This is the default.
6233 @subsubsection Memory Access Size
6234 The acccess size attributes tells @value{GDBN} to use specific sized
6235 accesses in the memory region. Often memory mapped device registers
6236 require specific sized accesses. If no access size attribute is
6237 specified, @value{GDBN} may use accesses of any size.
6241 Use 8 bit memory accesses.
6243 Use 16 bit memory accesses.
6245 Use 32 bit memory accesses.
6247 Use 64 bit memory accesses.
6250 @c @subsubsection Hardware/Software Breakpoints
6251 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6252 @c will use hardware or software breakpoints for the internal breakpoints
6253 @c used by the step, next, finish, until, etc. commands.
6257 @c Always use hardware breakpoints
6258 @c @item swbreak (default)
6261 @subsubsection Data Cache
6262 The data cache attributes set whether @value{GDBN} will cache target
6263 memory. While this generally improves performance by reducing debug
6264 protocol overhead, it can lead to incorrect results because @value{GDBN}
6265 does not know about volatile variables or memory mapped device
6270 Enable @value{GDBN} to cache target memory.
6272 Disable @value{GDBN} from caching target memory. This is the default.
6275 @c @subsubsection Memory Write Verification
6276 @c The memory write verification attributes set whether @value{GDBN}
6277 @c will re-reads data after each write to verify the write was successful.
6281 @c @item noverify (default)
6284 @node Dump/Restore Files
6285 @section Copy between memory and a file
6286 @cindex dump/restore files
6287 @cindex append data to a file
6288 @cindex dump data to a file
6289 @cindex restore data from a file
6291 You can use the commands @code{dump}, @code{append}, and
6292 @code{restore} to copy data between target memory and a file. The
6293 @code{dump} and @code{append} commands write data to a file, and the
6294 @code{restore} command reads data from a file back into the inferior's
6295 memory. Files may be in binary, Motorola S-record, Intel hex, or
6296 Tektronix Hex format; however, @value{GDBN} can only append to binary
6302 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6303 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6304 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6305 or the value of @var{expr}, to @var{filename} in the given format.
6307 The @var{format} parameter may be any one of:
6314 Motorola S-record format.
6316 Tektronix Hex format.
6319 @value{GDBN} uses the same definitions of these formats as the
6320 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
6321 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
6325 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6326 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
6327 Append the contents of memory from @var{start_addr} to @var{end_addr},
6328 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
6329 (@value{GDBN} can only append data to files in raw binary form.)
6332 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
6333 Restore the contents of file @var{filename} into memory. The
6334 @code{restore} command can automatically recognize any known @sc{bfd}
6335 file format, except for raw binary. To restore a raw binary file you
6336 must specify the optional keyword @code{binary} after the filename.
6338 If @var{bias} is non-zero, its value will be added to the addresses
6339 contained in the file. Binary files always start at address zero, so
6340 they will be restored at address @var{bias}. Other bfd files have
6341 a built-in location; they will be restored at offset @var{bias}
6344 If @var{start} and/or @var{end} are non-zero, then only data between
6345 file offset @var{start} and file offset @var{end} will be restored.
6346 These offsets are relative to the addresses in the file, before
6347 the @var{bias} argument is applied.
6351 @node Core File Generation
6352 @section How to Produce a Core File from Your Program
6353 @cindex dump core from inferior
6355 A @dfn{core file} or @dfn{core dump} is a file that records the memory
6356 image of a running process and its process status (register values
6357 etc.). Its primary use is post-mortem debugging of a program that
6358 crashed while it ran outside a debugger. A program that crashes
6359 automatically produces a core file, unless this feature is disabled by
6360 the user. @xref{Files}, for information on invoking @value{GDBN} in
6361 the post-mortem debugging mode.
6363 Occasionally, you may wish to produce a core file of the program you
6364 are debugging in order to preserve a snapshot of its state.
6365 @value{GDBN} has a special command for that.
6369 @kindex generate-core-file
6370 @item generate-core-file [@var{file}]
6371 @itemx gcore [@var{file}]
6372 Produce a core dump of the inferior process. The optional argument
6373 @var{file} specifies the file name where to put the core dump. If not
6374 specified, the file name defaults to @file{core.@var{pid}}, where
6375 @var{pid} is the inferior process ID.
6377 Note that this command is implemented only for some systems (as of
6378 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
6381 @node Character Sets
6382 @section Character Sets
6383 @cindex character sets
6385 @cindex translating between character sets
6386 @cindex host character set
6387 @cindex target character set
6389 If the program you are debugging uses a different character set to
6390 represent characters and strings than the one @value{GDBN} uses itself,
6391 @value{GDBN} can automatically translate between the character sets for
6392 you. The character set @value{GDBN} uses we call the @dfn{host
6393 character set}; the one the inferior program uses we call the
6394 @dfn{target character set}.
6396 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
6397 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
6398 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
6399 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
6400 then the host character set is Latin-1, and the target character set is
6401 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
6402 target-charset EBCDIC-US}, then @value{GDBN} translates between
6403 @sc{ebcdic} and Latin 1 as you print character or string values, or use
6404 character and string literals in expressions.
6406 @value{GDBN} has no way to automatically recognize which character set
6407 the inferior program uses; you must tell it, using the @code{set
6408 target-charset} command, described below.
6410 Here are the commands for controlling @value{GDBN}'s character set
6414 @item set target-charset @var{charset}
6415 @kindex set target-charset
6416 Set the current target character set to @var{charset}. We list the
6417 character set names @value{GDBN} recognizes below, but if you type
6418 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6419 list the target character sets it supports.
6423 @item set host-charset @var{charset}
6424 @kindex set host-charset
6425 Set the current host character set to @var{charset}.
6427 By default, @value{GDBN} uses a host character set appropriate to the
6428 system it is running on; you can override that default using the
6429 @code{set host-charset} command.
6431 @value{GDBN} can only use certain character sets as its host character
6432 set. We list the character set names @value{GDBN} recognizes below, and
6433 indicate which can be host character sets, but if you type
6434 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6435 list the host character sets it supports.
6437 @item set charset @var{charset}
6439 Set the current host and target character sets to @var{charset}. As
6440 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
6441 @value{GDBN} will list the name of the character sets that can be used
6442 for both host and target.
6446 @kindex show charset
6447 Show the names of the current host and target charsets.
6449 @itemx show host-charset
6450 @kindex show host-charset
6451 Show the name of the current host charset.
6453 @itemx show target-charset
6454 @kindex show target-charset
6455 Show the name of the current target charset.
6459 @value{GDBN} currently includes support for the following character
6465 @cindex ASCII character set
6466 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6470 @cindex ISO 8859-1 character set
6471 @cindex ISO Latin 1 character set
6472 The ISO Latin 1 character set. This extends @sc{ascii} with accented
6473 characters needed for French, German, and Spanish. @value{GDBN} can use
6474 this as its host character set.
6478 @cindex EBCDIC character set
6479 @cindex IBM1047 character set
6480 Variants of the @sc{ebcdic} character set, used on some of IBM's
6481 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6482 @value{GDBN} cannot use these as its host character set.
6486 Note that these are all single-byte character sets. More work inside
6487 GDB is needed to support multi-byte or variable-width character
6488 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6490 Here is an example of @value{GDBN}'s character set support in action.
6491 Assume that the following source code has been placed in the file
6492 @file{charset-test.c}:
6498 = @{72, 101, 108, 108, 111, 44, 32, 119,
6499 111, 114, 108, 100, 33, 10, 0@};
6500 char ibm1047_hello[]
6501 = @{200, 133, 147, 147, 150, 107, 64, 166,
6502 150, 153, 147, 132, 90, 37, 0@};
6506 printf ("Hello, world!\n");
6510 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6511 containing the string @samp{Hello, world!} followed by a newline,
6512 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6514 We compile the program, and invoke the debugger on it:
6517 $ gcc -g charset-test.c -o charset-test
6518 $ gdb -nw charset-test
6519 GNU gdb 2001-12-19-cvs
6520 Copyright 2001 Free Software Foundation, Inc.
6525 We can use the @code{show charset} command to see what character sets
6526 @value{GDBN} is currently using to interpret and display characters and
6530 (@value{GDBP}) show charset
6531 The current host and target character set is `ISO-8859-1'.
6535 For the sake of printing this manual, let's use @sc{ascii} as our
6536 initial character set:
6538 (@value{GDBP}) set charset ASCII
6539 (@value{GDBP}) show charset
6540 The current host and target character set is `ASCII'.
6544 Let's assume that @sc{ascii} is indeed the correct character set for our
6545 host system --- in other words, let's assume that if @value{GDBN} prints
6546 characters using the @sc{ascii} character set, our terminal will display
6547 them properly. Since our current target character set is also
6548 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
6551 (@value{GDBP}) print ascii_hello
6552 $1 = 0x401698 "Hello, world!\n"
6553 (@value{GDBP}) print ascii_hello[0]
6558 @value{GDBN} uses the target character set for character and string
6559 literals you use in expressions:
6562 (@value{GDBP}) print '+'
6567 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
6570 @value{GDBN} relies on the user to tell it which character set the
6571 target program uses. If we print @code{ibm1047_hello} while our target
6572 character set is still @sc{ascii}, we get jibberish:
6575 (@value{GDBP}) print ibm1047_hello
6576 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
6577 (@value{GDBP}) print ibm1047_hello[0]
6582 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
6583 @value{GDBN} tells us the character sets it supports:
6586 (@value{GDBP}) set target-charset
6587 ASCII EBCDIC-US IBM1047 ISO-8859-1
6588 (@value{GDBP}) set target-charset
6591 We can select @sc{ibm1047} as our target character set, and examine the
6592 program's strings again. Now the @sc{ascii} string is wrong, but
6593 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
6594 target character set, @sc{ibm1047}, to the host character set,
6595 @sc{ascii}, and they display correctly:
6598 (@value{GDBP}) set target-charset IBM1047
6599 (@value{GDBP}) show charset
6600 The current host character set is `ASCII'.
6601 The current target character set is `IBM1047'.
6602 (@value{GDBP}) print ascii_hello
6603 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
6604 (@value{GDBP}) print ascii_hello[0]
6606 (@value{GDBP}) print ibm1047_hello
6607 $8 = 0x4016a8 "Hello, world!\n"
6608 (@value{GDBP}) print ibm1047_hello[0]
6613 As above, @value{GDBN} uses the target character set for character and
6614 string literals you use in expressions:
6617 (@value{GDBP}) print '+'
6622 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
6625 @node Caching Remote Data
6626 @section Caching Data of Remote Targets
6627 @cindex caching data of remote targets
6629 @value{GDBN} can cache data exchanged between the debugger and a
6630 remote target (@pxref{Remote}). Such caching generally improves
6631 performance, because it reduces the overhead of the remote protocol by
6632 bundling memory reads and writes into large chunks. Unfortunately,
6633 @value{GDBN} does not currently know anything about volatile
6634 registers, and thus data caching will produce incorrect results when
6635 volatile registers are in use.
6638 @kindex set remotecache
6639 @item set remotecache on
6640 @itemx set remotecache off
6641 Set caching state for remote targets. When @code{ON}, use data
6642 caching. By default, this option is @code{OFF}.
6644 @kindex show remotecache
6645 @item show remotecache
6646 Show the current state of data caching for remote targets.
6650 Print the information about the data cache performance. The
6651 information displayed includes: the dcache width and depth; and for
6652 each cache line, how many times it was referenced, and its data and
6653 state (dirty, bad, ok, etc.). This command is useful for debugging
6654 the data cache operation.
6659 @chapter C Preprocessor Macros
6661 Some languages, such as C and C@t{++}, provide a way to define and invoke
6662 ``preprocessor macros'' which expand into strings of tokens.
6663 @value{GDBN} can evaluate expressions containing macro invocations, show
6664 the result of macro expansion, and show a macro's definition, including
6665 where it was defined.
6667 You may need to compile your program specially to provide @value{GDBN}
6668 with information about preprocessor macros. Most compilers do not
6669 include macros in their debugging information, even when you compile
6670 with the @option{-g} flag. @xref{Compilation}.
6672 A program may define a macro at one point, remove that definition later,
6673 and then provide a different definition after that. Thus, at different
6674 points in the program, a macro may have different definitions, or have
6675 no definition at all. If there is a current stack frame, @value{GDBN}
6676 uses the macros in scope at that frame's source code line. Otherwise,
6677 @value{GDBN} uses the macros in scope at the current listing location;
6680 At the moment, @value{GDBN} does not support the @code{##}
6681 token-splicing operator, the @code{#} stringification operator, or
6682 variable-arity macros.
6684 Whenever @value{GDBN} evaluates an expression, it always expands any
6685 macro invocations present in the expression. @value{GDBN} also provides
6686 the following commands for working with macros explicitly.
6690 @kindex macro expand
6691 @cindex macro expansion, showing the results of preprocessor
6692 @cindex preprocessor macro expansion, showing the results of
6693 @cindex expanding preprocessor macros
6694 @item macro expand @var{expression}
6695 @itemx macro exp @var{expression}
6696 Show the results of expanding all preprocessor macro invocations in
6697 @var{expression}. Since @value{GDBN} simply expands macros, but does
6698 not parse the result, @var{expression} need not be a valid expression;
6699 it can be any string of tokens.
6702 @item macro expand-once @var{expression}
6703 @itemx macro exp1 @var{expression}
6704 @cindex expand macro once
6705 @i{(This command is not yet implemented.)} Show the results of
6706 expanding those preprocessor macro invocations that appear explicitly in
6707 @var{expression}. Macro invocations appearing in that expansion are
6708 left unchanged. This command allows you to see the effect of a
6709 particular macro more clearly, without being confused by further
6710 expansions. Since @value{GDBN} simply expands macros, but does not
6711 parse the result, @var{expression} need not be a valid expression; it
6712 can be any string of tokens.
6715 @cindex macro definition, showing
6716 @cindex definition, showing a macro's
6717 @item info macro @var{macro}
6718 Show the definition of the macro named @var{macro}, and describe the
6719 source location where that definition was established.
6721 @kindex macro define
6722 @cindex user-defined macros
6723 @cindex defining macros interactively
6724 @cindex macros, user-defined
6725 @item macro define @var{macro} @var{replacement-list}
6726 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
6727 @i{(This command is not yet implemented.)} Introduce a definition for a
6728 preprocessor macro named @var{macro}, invocations of which are replaced
6729 by the tokens given in @var{replacement-list}. The first form of this
6730 command defines an ``object-like'' macro, which takes no arguments; the
6731 second form defines a ``function-like'' macro, which takes the arguments
6732 given in @var{arglist}.
6734 A definition introduced by this command is in scope in every expression
6735 evaluated in @value{GDBN}, until it is removed with the @command{macro
6736 undef} command, described below. The definition overrides all
6737 definitions for @var{macro} present in the program being debugged, as
6738 well as any previous user-supplied definition.
6741 @item macro undef @var{macro}
6742 @i{(This command is not yet implemented.)} Remove any user-supplied
6743 definition for the macro named @var{macro}. This command only affects
6744 definitions provided with the @command{macro define} command, described
6745 above; it cannot remove definitions present in the program being
6750 @i{(This command is not yet implemented.)} List all the macros
6751 defined using the @code{macro define} command.
6754 @cindex macros, example of debugging with
6755 Here is a transcript showing the above commands in action. First, we
6756 show our source files:
6764 #define ADD(x) (M + x)
6769 printf ("Hello, world!\n");
6771 printf ("We're so creative.\n");
6773 printf ("Goodbye, world!\n");
6780 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
6781 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
6782 compiler includes information about preprocessor macros in the debugging
6786 $ gcc -gdwarf-2 -g3 sample.c -o sample
6790 Now, we start @value{GDBN} on our sample program:
6794 GNU gdb 2002-05-06-cvs
6795 Copyright 2002 Free Software Foundation, Inc.
6796 GDB is free software, @dots{}
6800 We can expand macros and examine their definitions, even when the
6801 program is not running. @value{GDBN} uses the current listing position
6802 to decide which macro definitions are in scope:
6805 (@value{GDBP}) list main
6808 5 #define ADD(x) (M + x)
6813 10 printf ("Hello, world!\n");
6815 12 printf ("We're so creative.\n");
6816 (@value{GDBP}) info macro ADD
6817 Defined at /home/jimb/gdb/macros/play/sample.c:5
6818 #define ADD(x) (M + x)
6819 (@value{GDBP}) info macro Q
6820 Defined at /home/jimb/gdb/macros/play/sample.h:1
6821 included at /home/jimb/gdb/macros/play/sample.c:2
6823 (@value{GDBP}) macro expand ADD(1)
6824 expands to: (42 + 1)
6825 (@value{GDBP}) macro expand-once ADD(1)
6826 expands to: once (M + 1)
6830 In the example above, note that @command{macro expand-once} expands only
6831 the macro invocation explicit in the original text --- the invocation of
6832 @code{ADD} --- but does not expand the invocation of the macro @code{M},
6833 which was introduced by @code{ADD}.
6835 Once the program is running, GDB uses the macro definitions in force at
6836 the source line of the current stack frame:
6839 (@value{GDBP}) break main
6840 Breakpoint 1 at 0x8048370: file sample.c, line 10.
6842 Starting program: /home/jimb/gdb/macros/play/sample
6844 Breakpoint 1, main () at sample.c:10
6845 10 printf ("Hello, world!\n");
6849 At line 10, the definition of the macro @code{N} at line 9 is in force:
6852 (@value{GDBP}) info macro N
6853 Defined at /home/jimb/gdb/macros/play/sample.c:9
6855 (@value{GDBP}) macro expand N Q M
6857 (@value{GDBP}) print N Q M
6862 As we step over directives that remove @code{N}'s definition, and then
6863 give it a new definition, @value{GDBN} finds the definition (or lack
6864 thereof) in force at each point:
6869 12 printf ("We're so creative.\n");
6870 (@value{GDBP}) info macro N
6871 The symbol `N' has no definition as a C/C++ preprocessor macro
6872 at /home/jimb/gdb/macros/play/sample.c:12
6875 14 printf ("Goodbye, world!\n");
6876 (@value{GDBP}) info macro N
6877 Defined at /home/jimb/gdb/macros/play/sample.c:13
6879 (@value{GDBP}) macro expand N Q M
6880 expands to: 1729 < 42
6881 (@value{GDBP}) print N Q M
6888 @chapter Tracepoints
6889 @c This chapter is based on the documentation written by Michael
6890 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
6893 In some applications, it is not feasible for the debugger to interrupt
6894 the program's execution long enough for the developer to learn
6895 anything helpful about its behavior. If the program's correctness
6896 depends on its real-time behavior, delays introduced by a debugger
6897 might cause the program to change its behavior drastically, or perhaps
6898 fail, even when the code itself is correct. It is useful to be able
6899 to observe the program's behavior without interrupting it.
6901 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
6902 specify locations in the program, called @dfn{tracepoints}, and
6903 arbitrary expressions to evaluate when those tracepoints are reached.
6904 Later, using the @code{tfind} command, you can examine the values
6905 those expressions had when the program hit the tracepoints. The
6906 expressions may also denote objects in memory---structures or arrays,
6907 for example---whose values @value{GDBN} should record; while visiting
6908 a particular tracepoint, you may inspect those objects as if they were
6909 in memory at that moment. However, because @value{GDBN} records these
6910 values without interacting with you, it can do so quickly and
6911 unobtrusively, hopefully not disturbing the program's behavior.
6913 The tracepoint facility is currently available only for remote
6914 targets. @xref{Targets}. In addition, your remote target must know how
6915 to collect trace data. This functionality is implemented in the remote
6916 stub; however, none of the stubs distributed with @value{GDBN} support
6917 tracepoints as of this writing.
6919 This chapter describes the tracepoint commands and features.
6923 * Analyze Collected Data::
6924 * Tracepoint Variables::
6927 @node Set Tracepoints
6928 @section Commands to Set Tracepoints
6930 Before running such a @dfn{trace experiment}, an arbitrary number of
6931 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
6932 tracepoint has a number assigned to it by @value{GDBN}. Like with
6933 breakpoints, tracepoint numbers are successive integers starting from
6934 one. Many of the commands associated with tracepoints take the
6935 tracepoint number as their argument, to identify which tracepoint to
6938 For each tracepoint, you can specify, in advance, some arbitrary set
6939 of data that you want the target to collect in the trace buffer when
6940 it hits that tracepoint. The collected data can include registers,
6941 local variables, or global data. Later, you can use @value{GDBN}
6942 commands to examine the values these data had at the time the
6945 This section describes commands to set tracepoints and associated
6946 conditions and actions.
6949 * Create and Delete Tracepoints::
6950 * Enable and Disable Tracepoints::
6951 * Tracepoint Passcounts::
6952 * Tracepoint Actions::
6953 * Listing Tracepoints::
6954 * Starting and Stopping Trace Experiment::
6957 @node Create and Delete Tracepoints
6958 @subsection Create and Delete Tracepoints
6961 @cindex set tracepoint
6964 The @code{trace} command is very similar to the @code{break} command.
6965 Its argument can be a source line, a function name, or an address in
6966 the target program. @xref{Set Breaks}. The @code{trace} command
6967 defines a tracepoint, which is a point in the target program where the
6968 debugger will briefly stop, collect some data, and then allow the
6969 program to continue. Setting a tracepoint or changing its commands
6970 doesn't take effect until the next @code{tstart} command; thus, you
6971 cannot change the tracepoint attributes once a trace experiment is
6974 Here are some examples of using the @code{trace} command:
6977 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
6979 (@value{GDBP}) @b{trace +2} // 2 lines forward
6981 (@value{GDBP}) @b{trace my_function} // first source line of function
6983 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
6985 (@value{GDBP}) @b{trace *0x2117c4} // an address
6989 You can abbreviate @code{trace} as @code{tr}.
6992 @cindex last tracepoint number
6993 @cindex recent tracepoint number
6994 @cindex tracepoint number
6995 The convenience variable @code{$tpnum} records the tracepoint number
6996 of the most recently set tracepoint.
6998 @kindex delete tracepoint
6999 @cindex tracepoint deletion
7000 @item delete tracepoint @r{[}@var{num}@r{]}
7001 Permanently delete one or more tracepoints. With no argument, the
7002 default is to delete all tracepoints.
7007 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
7009 (@value{GDBP}) @b{delete trace} // remove all tracepoints
7013 You can abbreviate this command as @code{del tr}.
7016 @node Enable and Disable Tracepoints
7017 @subsection Enable and Disable Tracepoints
7020 @kindex disable tracepoint
7021 @item disable tracepoint @r{[}@var{num}@r{]}
7022 Disable tracepoint @var{num}, or all tracepoints if no argument
7023 @var{num} is given. A disabled tracepoint will have no effect during
7024 the next trace experiment, but it is not forgotten. You can re-enable
7025 a disabled tracepoint using the @code{enable tracepoint} command.
7027 @kindex enable tracepoint
7028 @item enable tracepoint @r{[}@var{num}@r{]}
7029 Enable tracepoint @var{num}, or all tracepoints. The enabled
7030 tracepoints will become effective the next time a trace experiment is
7034 @node Tracepoint Passcounts
7035 @subsection Tracepoint Passcounts
7039 @cindex tracepoint pass count
7040 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
7041 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
7042 automatically stop a trace experiment. If a tracepoint's passcount is
7043 @var{n}, then the trace experiment will be automatically stopped on
7044 the @var{n}'th time that tracepoint is hit. If the tracepoint number
7045 @var{num} is not specified, the @code{passcount} command sets the
7046 passcount of the most recently defined tracepoint. If no passcount is
7047 given, the trace experiment will run until stopped explicitly by the
7053 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
7054 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
7056 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
7057 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
7058 (@value{GDBP}) @b{trace foo}
7059 (@value{GDBP}) @b{pass 3}
7060 (@value{GDBP}) @b{trace bar}
7061 (@value{GDBP}) @b{pass 2}
7062 (@value{GDBP}) @b{trace baz}
7063 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
7064 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
7065 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
7066 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
7070 @node Tracepoint Actions
7071 @subsection Tracepoint Action Lists
7075 @cindex tracepoint actions
7076 @item actions @r{[}@var{num}@r{]}
7077 This command will prompt for a list of actions to be taken when the
7078 tracepoint is hit. If the tracepoint number @var{num} is not
7079 specified, this command sets the actions for the one that was most
7080 recently defined (so that you can define a tracepoint and then say
7081 @code{actions} without bothering about its number). You specify the
7082 actions themselves on the following lines, one action at a time, and
7083 terminate the actions list with a line containing just @code{end}. So
7084 far, the only defined actions are @code{collect} and
7085 @code{while-stepping}.
7087 @cindex remove actions from a tracepoint
7088 To remove all actions from a tracepoint, type @samp{actions @var{num}}
7089 and follow it immediately with @samp{end}.
7092 (@value{GDBP}) @b{collect @var{data}} // collect some data
7094 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
7096 (@value{GDBP}) @b{end} // signals the end of actions.
7099 In the following example, the action list begins with @code{collect}
7100 commands indicating the things to be collected when the tracepoint is
7101 hit. Then, in order to single-step and collect additional data
7102 following the tracepoint, a @code{while-stepping} command is used,
7103 followed by the list of things to be collected while stepping. The
7104 @code{while-stepping} command is terminated by its own separate
7105 @code{end} command. Lastly, the action list is terminated by an
7109 (@value{GDBP}) @b{trace foo}
7110 (@value{GDBP}) @b{actions}
7111 Enter actions for tracepoint 1, one per line:
7120 @kindex collect @r{(tracepoints)}
7121 @item collect @var{expr1}, @var{expr2}, @dots{}
7122 Collect values of the given expressions when the tracepoint is hit.
7123 This command accepts a comma-separated list of any valid expressions.
7124 In addition to global, static, or local variables, the following
7125 special arguments are supported:
7129 collect all registers
7132 collect all function arguments
7135 collect all local variables.
7138 You can give several consecutive @code{collect} commands, each one
7139 with a single argument, or one @code{collect} command with several
7140 arguments separated by commas: the effect is the same.
7142 The command @code{info scope} (@pxref{Symbols, info scope}) is
7143 particularly useful for figuring out what data to collect.
7145 @kindex while-stepping @r{(tracepoints)}
7146 @item while-stepping @var{n}
7147 Perform @var{n} single-step traces after the tracepoint, collecting
7148 new data at each step. The @code{while-stepping} command is
7149 followed by the list of what to collect while stepping (followed by
7150 its own @code{end} command):
7154 > collect $regs, myglobal
7160 You may abbreviate @code{while-stepping} as @code{ws} or
7164 @node Listing Tracepoints
7165 @subsection Listing Tracepoints
7168 @kindex info tracepoints
7170 @cindex information about tracepoints
7171 @item info tracepoints @r{[}@var{num}@r{]}
7172 Display information about the tracepoint @var{num}. If you don't specify
7173 a tracepoint number, displays information about all the tracepoints
7174 defined so far. For each tracepoint, the following information is
7181 whether it is enabled or disabled
7185 its passcount as given by the @code{passcount @var{n}} command
7187 its step count as given by the @code{while-stepping @var{n}} command
7189 where in the source files is the tracepoint set
7191 its action list as given by the @code{actions} command
7195 (@value{GDBP}) @b{info trace}
7196 Num Enb Address PassC StepC What
7197 1 y 0x002117c4 0 0 <gdb_asm>
7198 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
7199 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
7204 This command can be abbreviated @code{info tp}.
7207 @node Starting and Stopping Trace Experiment
7208 @subsection Starting and Stopping Trace Experiment
7212 @cindex start a new trace experiment
7213 @cindex collected data discarded
7215 This command takes no arguments. It starts the trace experiment, and
7216 begins collecting data. This has the side effect of discarding all
7217 the data collected in the trace buffer during the previous trace
7221 @cindex stop a running trace experiment
7223 This command takes no arguments. It ends the trace experiment, and
7224 stops collecting data.
7226 @strong{Note}: a trace experiment and data collection may stop
7227 automatically if any tracepoint's passcount is reached
7228 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
7231 @cindex status of trace data collection
7232 @cindex trace experiment, status of
7234 This command displays the status of the current trace data
7238 Here is an example of the commands we described so far:
7241 (@value{GDBP}) @b{trace gdb_c_test}
7242 (@value{GDBP}) @b{actions}
7243 Enter actions for tracepoint #1, one per line.
7244 > collect $regs,$locals,$args
7249 (@value{GDBP}) @b{tstart}
7250 [time passes @dots{}]
7251 (@value{GDBP}) @b{tstop}
7255 @node Analyze Collected Data
7256 @section Using the collected data
7258 After the tracepoint experiment ends, you use @value{GDBN} commands
7259 for examining the trace data. The basic idea is that each tracepoint
7260 collects a trace @dfn{snapshot} every time it is hit and another
7261 snapshot every time it single-steps. All these snapshots are
7262 consecutively numbered from zero and go into a buffer, and you can
7263 examine them later. The way you examine them is to @dfn{focus} on a
7264 specific trace snapshot. When the remote stub is focused on a trace
7265 snapshot, it will respond to all @value{GDBN} requests for memory and
7266 registers by reading from the buffer which belongs to that snapshot,
7267 rather than from @emph{real} memory or registers of the program being
7268 debugged. This means that @strong{all} @value{GDBN} commands
7269 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
7270 behave as if we were currently debugging the program state as it was
7271 when the tracepoint occurred. Any requests for data that are not in
7272 the buffer will fail.
7275 * tfind:: How to select a trace snapshot
7276 * tdump:: How to display all data for a snapshot
7277 * save-tracepoints:: How to save tracepoints for a future run
7281 @subsection @code{tfind @var{n}}
7284 @cindex select trace snapshot
7285 @cindex find trace snapshot
7286 The basic command for selecting a trace snapshot from the buffer is
7287 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
7288 counting from zero. If no argument @var{n} is given, the next
7289 snapshot is selected.
7291 Here are the various forms of using the @code{tfind} command.
7295 Find the first snapshot in the buffer. This is a synonym for
7296 @code{tfind 0} (since 0 is the number of the first snapshot).
7299 Stop debugging trace snapshots, resume @emph{live} debugging.
7302 Same as @samp{tfind none}.
7305 No argument means find the next trace snapshot.
7308 Find the previous trace snapshot before the current one. This permits
7309 retracing earlier steps.
7311 @item tfind tracepoint @var{num}
7312 Find the next snapshot associated with tracepoint @var{num}. Search
7313 proceeds forward from the last examined trace snapshot. If no
7314 argument @var{num} is given, it means find the next snapshot collected
7315 for the same tracepoint as the current snapshot.
7317 @item tfind pc @var{addr}
7318 Find the next snapshot associated with the value @var{addr} of the
7319 program counter. Search proceeds forward from the last examined trace
7320 snapshot. If no argument @var{addr} is given, it means find the next
7321 snapshot with the same value of PC as the current snapshot.
7323 @item tfind outside @var{addr1}, @var{addr2}
7324 Find the next snapshot whose PC is outside the given range of
7327 @item tfind range @var{addr1}, @var{addr2}
7328 Find the next snapshot whose PC is between @var{addr1} and
7329 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
7331 @item tfind line @r{[}@var{file}:@r{]}@var{n}
7332 Find the next snapshot associated with the source line @var{n}. If
7333 the optional argument @var{file} is given, refer to line @var{n} in
7334 that source file. Search proceeds forward from the last examined
7335 trace snapshot. If no argument @var{n} is given, it means find the
7336 next line other than the one currently being examined; thus saying
7337 @code{tfind line} repeatedly can appear to have the same effect as
7338 stepping from line to line in a @emph{live} debugging session.
7341 The default arguments for the @code{tfind} commands are specifically
7342 designed to make it easy to scan through the trace buffer. For
7343 instance, @code{tfind} with no argument selects the next trace
7344 snapshot, and @code{tfind -} with no argument selects the previous
7345 trace snapshot. So, by giving one @code{tfind} command, and then
7346 simply hitting @key{RET} repeatedly you can examine all the trace
7347 snapshots in order. Or, by saying @code{tfind -} and then hitting
7348 @key{RET} repeatedly you can examine the snapshots in reverse order.
7349 The @code{tfind line} command with no argument selects the snapshot
7350 for the next source line executed. The @code{tfind pc} command with
7351 no argument selects the next snapshot with the same program counter
7352 (PC) as the current frame. The @code{tfind tracepoint} command with
7353 no argument selects the next trace snapshot collected by the same
7354 tracepoint as the current one.
7356 In addition to letting you scan through the trace buffer manually,
7357 these commands make it easy to construct @value{GDBN} scripts that
7358 scan through the trace buffer and print out whatever collected data
7359 you are interested in. Thus, if we want to examine the PC, FP, and SP
7360 registers from each trace frame in the buffer, we can say this:
7363 (@value{GDBP}) @b{tfind start}
7364 (@value{GDBP}) @b{while ($trace_frame != -1)}
7365 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
7366 $trace_frame, $pc, $sp, $fp
7370 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
7371 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
7372 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
7373 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
7374 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
7375 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
7376 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
7377 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
7378 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
7379 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
7380 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
7383 Or, if we want to examine the variable @code{X} at each source line in
7387 (@value{GDBP}) @b{tfind start}
7388 (@value{GDBP}) @b{while ($trace_frame != -1)}
7389 > printf "Frame %d, X == %d\n", $trace_frame, X
7399 @subsection @code{tdump}
7401 @cindex dump all data collected at tracepoint
7402 @cindex tracepoint data, display
7404 This command takes no arguments. It prints all the data collected at
7405 the current trace snapshot.
7408 (@value{GDBP}) @b{trace 444}
7409 (@value{GDBP}) @b{actions}
7410 Enter actions for tracepoint #2, one per line:
7411 > collect $regs, $locals, $args, gdb_long_test
7414 (@value{GDBP}) @b{tstart}
7416 (@value{GDBP}) @b{tfind line 444}
7417 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
7419 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
7421 (@value{GDBP}) @b{tdump}
7422 Data collected at tracepoint 2, trace frame 1:
7423 d0 0xc4aa0085 -995491707
7427 d4 0x71aea3d 119204413
7432 a1 0x3000668 50333288
7435 a4 0x3000698 50333336
7437 fp 0x30bf3c 0x30bf3c
7438 sp 0x30bf34 0x30bf34
7440 pc 0x20b2c8 0x20b2c8
7444 p = 0x20e5b4 "gdb-test"
7451 gdb_long_test = 17 '\021'
7456 @node save-tracepoints
7457 @subsection @code{save-tracepoints @var{filename}}
7458 @kindex save-tracepoints
7459 @cindex save tracepoints for future sessions
7461 This command saves all current tracepoint definitions together with
7462 their actions and passcounts, into a file @file{@var{filename}}
7463 suitable for use in a later debugging session. To read the saved
7464 tracepoint definitions, use the @code{source} command (@pxref{Command
7467 @node Tracepoint Variables
7468 @section Convenience Variables for Tracepoints
7469 @cindex tracepoint variables
7470 @cindex convenience variables for tracepoints
7473 @vindex $trace_frame
7474 @item (int) $trace_frame
7475 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
7476 snapshot is selected.
7479 @item (int) $tracepoint
7480 The tracepoint for the current trace snapshot.
7483 @item (int) $trace_line
7484 The line number for the current trace snapshot.
7487 @item (char []) $trace_file
7488 The source file for the current trace snapshot.
7491 @item (char []) $trace_func
7492 The name of the function containing @code{$tracepoint}.
7495 Note: @code{$trace_file} is not suitable for use in @code{printf},
7496 use @code{output} instead.
7498 Here's a simple example of using these convenience variables for
7499 stepping through all the trace snapshots and printing some of their
7503 (@value{GDBP}) @b{tfind start}
7505 (@value{GDBP}) @b{while $trace_frame != -1}
7506 > output $trace_file
7507 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7513 @chapter Debugging Programs That Use Overlays
7516 If your program is too large to fit completely in your target system's
7517 memory, you can sometimes use @dfn{overlays} to work around this
7518 problem. @value{GDBN} provides some support for debugging programs that
7522 * How Overlays Work:: A general explanation of overlays.
7523 * Overlay Commands:: Managing overlays in @value{GDBN}.
7524 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7525 mapped by asking the inferior.
7526 * Overlay Sample Program:: A sample program using overlays.
7529 @node How Overlays Work
7530 @section How Overlays Work
7531 @cindex mapped overlays
7532 @cindex unmapped overlays
7533 @cindex load address, overlay's
7534 @cindex mapped address
7535 @cindex overlay area
7537 Suppose you have a computer whose instruction address space is only 64
7538 kilobytes long, but which has much more memory which can be accessed by
7539 other means: special instructions, segment registers, or memory
7540 management hardware, for example. Suppose further that you want to
7541 adapt a program which is larger than 64 kilobytes to run on this system.
7543 One solution is to identify modules of your program which are relatively
7544 independent, and need not call each other directly; call these modules
7545 @dfn{overlays}. Separate the overlays from the main program, and place
7546 their machine code in the larger memory. Place your main program in
7547 instruction memory, but leave at least enough space there to hold the
7548 largest overlay as well.
7550 Now, to call a function located in an overlay, you must first copy that
7551 overlay's machine code from the large memory into the space set aside
7552 for it in the instruction memory, and then jump to its entry point
7555 @c NB: In the below the mapped area's size is greater or equal to the
7556 @c size of all overlays. This is intentional to remind the developer
7557 @c that overlays don't necessarily need to be the same size.
7561 Data Instruction Larger
7562 Address Space Address Space Address Space
7563 +-----------+ +-----------+ +-----------+
7565 +-----------+ +-----------+ +-----------+<-- overlay 1
7566 | program | | main | .----| overlay 1 | load address
7567 | variables | | program | | +-----------+
7568 | and heap | | | | | |
7569 +-----------+ | | | +-----------+<-- overlay 2
7570 | | +-----------+ | | | load address
7571 +-----------+ | | | .-| overlay 2 |
7573 mapped --->+-----------+ | | +-----------+
7575 | overlay | <-' | | |
7576 | area | <---' +-----------+<-- overlay 3
7577 | | <---. | | load address
7578 +-----------+ `--| overlay 3 |
7585 @anchor{A code overlay}A code overlay
7589 The diagram (@pxref{A code overlay}) shows a system with separate data
7590 and instruction address spaces. To map an overlay, the program copies
7591 its code from the larger address space to the instruction address space.
7592 Since the overlays shown here all use the same mapped address, only one
7593 may be mapped at a time. For a system with a single address space for
7594 data and instructions, the diagram would be similar, except that the
7595 program variables and heap would share an address space with the main
7596 program and the overlay area.
7598 An overlay loaded into instruction memory and ready for use is called a
7599 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
7600 instruction memory. An overlay not present (or only partially present)
7601 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
7602 is its address in the larger memory. The mapped address is also called
7603 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
7604 called the @dfn{load memory address}, or @dfn{LMA}.
7606 Unfortunately, overlays are not a completely transparent way to adapt a
7607 program to limited instruction memory. They introduce a new set of
7608 global constraints you must keep in mind as you design your program:
7613 Before calling or returning to a function in an overlay, your program
7614 must make sure that overlay is actually mapped. Otherwise, the call or
7615 return will transfer control to the right address, but in the wrong
7616 overlay, and your program will probably crash.
7619 If the process of mapping an overlay is expensive on your system, you
7620 will need to choose your overlays carefully to minimize their effect on
7621 your program's performance.
7624 The executable file you load onto your system must contain each
7625 overlay's instructions, appearing at the overlay's load address, not its
7626 mapped address. However, each overlay's instructions must be relocated
7627 and its symbols defined as if the overlay were at its mapped address.
7628 You can use GNU linker scripts to specify different load and relocation
7629 addresses for pieces of your program; see @ref{Overlay Description,,,
7630 ld.info, Using ld: the GNU linker}.
7633 The procedure for loading executable files onto your system must be able
7634 to load their contents into the larger address space as well as the
7635 instruction and data spaces.
7639 The overlay system described above is rather simple, and could be
7640 improved in many ways:
7645 If your system has suitable bank switch registers or memory management
7646 hardware, you could use those facilities to make an overlay's load area
7647 contents simply appear at their mapped address in instruction space.
7648 This would probably be faster than copying the overlay to its mapped
7649 area in the usual way.
7652 If your overlays are small enough, you could set aside more than one
7653 overlay area, and have more than one overlay mapped at a time.
7656 You can use overlays to manage data, as well as instructions. In
7657 general, data overlays are even less transparent to your design than
7658 code overlays: whereas code overlays only require care when you call or
7659 return to functions, data overlays require care every time you access
7660 the data. Also, if you change the contents of a data overlay, you
7661 must copy its contents back out to its load address before you can copy a
7662 different data overlay into the same mapped area.
7667 @node Overlay Commands
7668 @section Overlay Commands
7670 To use @value{GDBN}'s overlay support, each overlay in your program must
7671 correspond to a separate section of the executable file. The section's
7672 virtual memory address and load memory address must be the overlay's
7673 mapped and load addresses. Identifying overlays with sections allows
7674 @value{GDBN} to determine the appropriate address of a function or
7675 variable, depending on whether the overlay is mapped or not.
7677 @value{GDBN}'s overlay commands all start with the word @code{overlay};
7678 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
7683 Disable @value{GDBN}'s overlay support. When overlay support is
7684 disabled, @value{GDBN} assumes that all functions and variables are
7685 always present at their mapped addresses. By default, @value{GDBN}'s
7686 overlay support is disabled.
7688 @item overlay manual
7689 @cindex manual overlay debugging
7690 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
7691 relies on you to tell it which overlays are mapped, and which are not,
7692 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
7693 commands described below.
7695 @item overlay map-overlay @var{overlay}
7696 @itemx overlay map @var{overlay}
7697 @cindex map an overlay
7698 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
7699 be the name of the object file section containing the overlay. When an
7700 overlay is mapped, @value{GDBN} assumes it can find the overlay's
7701 functions and variables at their mapped addresses. @value{GDBN} assumes
7702 that any other overlays whose mapped ranges overlap that of
7703 @var{overlay} are now unmapped.
7705 @item overlay unmap-overlay @var{overlay}
7706 @itemx overlay unmap @var{overlay}
7707 @cindex unmap an overlay
7708 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
7709 must be the name of the object file section containing the overlay.
7710 When an overlay is unmapped, @value{GDBN} assumes it can find the
7711 overlay's functions and variables at their load addresses.
7714 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
7715 consults a data structure the overlay manager maintains in the inferior
7716 to see which overlays are mapped. For details, see @ref{Automatic
7719 @item overlay load-target
7721 @cindex reloading the overlay table
7722 Re-read the overlay table from the inferior. Normally, @value{GDBN}
7723 re-reads the table @value{GDBN} automatically each time the inferior
7724 stops, so this command should only be necessary if you have changed the
7725 overlay mapping yourself using @value{GDBN}. This command is only
7726 useful when using automatic overlay debugging.
7728 @item overlay list-overlays
7730 @cindex listing mapped overlays
7731 Display a list of the overlays currently mapped, along with their mapped
7732 addresses, load addresses, and sizes.
7736 Normally, when @value{GDBN} prints a code address, it includes the name
7737 of the function the address falls in:
7740 (@value{GDBP}) print main
7741 $3 = @{int ()@} 0x11a0 <main>
7744 When overlay debugging is enabled, @value{GDBN} recognizes code in
7745 unmapped overlays, and prints the names of unmapped functions with
7746 asterisks around them. For example, if @code{foo} is a function in an
7747 unmapped overlay, @value{GDBN} prints it this way:
7750 (@value{GDBP}) overlay list
7751 No sections are mapped.
7752 (@value{GDBP}) print foo
7753 $5 = @{int (int)@} 0x100000 <*foo*>
7756 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
7760 (@value{GDBP}) overlay list
7761 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
7762 mapped at 0x1016 - 0x104a
7763 (@value{GDBP}) print foo
7764 $6 = @{int (int)@} 0x1016 <foo>
7767 When overlay debugging is enabled, @value{GDBN} can find the correct
7768 address for functions and variables in an overlay, whether or not the
7769 overlay is mapped. This allows most @value{GDBN} commands, like
7770 @code{break} and @code{disassemble}, to work normally, even on unmapped
7771 code. However, @value{GDBN}'s breakpoint support has some limitations:
7775 @cindex breakpoints in overlays
7776 @cindex overlays, setting breakpoints in
7777 You can set breakpoints in functions in unmapped overlays, as long as
7778 @value{GDBN} can write to the overlay at its load address.
7780 @value{GDBN} can not set hardware or simulator-based breakpoints in
7781 unmapped overlays. However, if you set a breakpoint at the end of your
7782 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
7783 you are using manual overlay management), @value{GDBN} will re-set its
7784 breakpoints properly.
7788 @node Automatic Overlay Debugging
7789 @section Automatic Overlay Debugging
7790 @cindex automatic overlay debugging
7792 @value{GDBN} can automatically track which overlays are mapped and which
7793 are not, given some simple co-operation from the overlay manager in the
7794 inferior. If you enable automatic overlay debugging with the
7795 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
7796 looks in the inferior's memory for certain variables describing the
7797 current state of the overlays.
7799 Here are the variables your overlay manager must define to support
7800 @value{GDBN}'s automatic overlay debugging:
7804 @item @code{_ovly_table}:
7805 This variable must be an array of the following structures:
7810 /* The overlay's mapped address. */
7813 /* The size of the overlay, in bytes. */
7816 /* The overlay's load address. */
7819 /* Non-zero if the overlay is currently mapped;
7821 unsigned long mapped;
7825 @item @code{_novlys}:
7826 This variable must be a four-byte signed integer, holding the total
7827 number of elements in @code{_ovly_table}.
7831 To decide whether a particular overlay is mapped or not, @value{GDBN}
7832 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
7833 @code{lma} members equal the VMA and LMA of the overlay's section in the
7834 executable file. When @value{GDBN} finds a matching entry, it consults
7835 the entry's @code{mapped} member to determine whether the overlay is
7838 In addition, your overlay manager may define a function called
7839 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
7840 will silently set a breakpoint there. If the overlay manager then
7841 calls this function whenever it has changed the overlay table, this
7842 will enable @value{GDBN} to accurately keep track of which overlays
7843 are in program memory, and update any breakpoints that may be set
7844 in overlays. This will allow breakpoints to work even if the
7845 overlays are kept in ROM or other non-writable memory while they
7846 are not being executed.
7848 @node Overlay Sample Program
7849 @section Overlay Sample Program
7850 @cindex overlay example program
7852 When linking a program which uses overlays, you must place the overlays
7853 at their load addresses, while relocating them to run at their mapped
7854 addresses. To do this, you must write a linker script (@pxref{Overlay
7855 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
7856 since linker scripts are specific to a particular host system, target
7857 architecture, and target memory layout, this manual cannot provide
7858 portable sample code demonstrating @value{GDBN}'s overlay support.
7860 However, the @value{GDBN} source distribution does contain an overlaid
7861 program, with linker scripts for a few systems, as part of its test
7862 suite. The program consists of the following files from
7863 @file{gdb/testsuite/gdb.base}:
7867 The main program file.
7869 A simple overlay manager, used by @file{overlays.c}.
7874 Overlay modules, loaded and used by @file{overlays.c}.
7877 Linker scripts for linking the test program on the @code{d10v-elf}
7878 and @code{m32r-elf} targets.
7881 You can build the test program using the @code{d10v-elf} GCC
7882 cross-compiler like this:
7885 $ d10v-elf-gcc -g -c overlays.c
7886 $ d10v-elf-gcc -g -c ovlymgr.c
7887 $ d10v-elf-gcc -g -c foo.c
7888 $ d10v-elf-gcc -g -c bar.c
7889 $ d10v-elf-gcc -g -c baz.c
7890 $ d10v-elf-gcc -g -c grbx.c
7891 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
7892 baz.o grbx.o -Wl,-Td10v.ld -o overlays
7895 The build process is identical for any other architecture, except that
7896 you must substitute the appropriate compiler and linker script for the
7897 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
7901 @chapter Using @value{GDBN} with Different Languages
7904 Although programming languages generally have common aspects, they are
7905 rarely expressed in the same manner. For instance, in ANSI C,
7906 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
7907 Modula-2, it is accomplished by @code{p^}. Values can also be
7908 represented (and displayed) differently. Hex numbers in C appear as
7909 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
7911 @cindex working language
7912 Language-specific information is built into @value{GDBN} for some languages,
7913 allowing you to express operations like the above in your program's
7914 native language, and allowing @value{GDBN} to output values in a manner
7915 consistent with the syntax of your program's native language. The
7916 language you use to build expressions is called the @dfn{working
7920 * Setting:: Switching between source languages
7921 * Show:: Displaying the language
7922 * Checks:: Type and range checks
7923 * Supported languages:: Supported languages
7924 * Unsupported languages:: Unsupported languages
7928 @section Switching between source languages
7930 There are two ways to control the working language---either have @value{GDBN}
7931 set it automatically, or select it manually yourself. You can use the
7932 @code{set language} command for either purpose. On startup, @value{GDBN}
7933 defaults to setting the language automatically. The working language is
7934 used to determine how expressions you type are interpreted, how values
7937 In addition to the working language, every source file that
7938 @value{GDBN} knows about has its own working language. For some object
7939 file formats, the compiler might indicate which language a particular
7940 source file is in. However, most of the time @value{GDBN} infers the
7941 language from the name of the file. The language of a source file
7942 controls whether C@t{++} names are demangled---this way @code{backtrace} can
7943 show each frame appropriately for its own language. There is no way to
7944 set the language of a source file from within @value{GDBN}, but you can
7945 set the language associated with a filename extension. @xref{Show, ,
7946 Displaying the language}.
7948 This is most commonly a problem when you use a program, such
7949 as @code{cfront} or @code{f2c}, that generates C but is written in
7950 another language. In that case, make the
7951 program use @code{#line} directives in its C output; that way
7952 @value{GDBN} will know the correct language of the source code of the original
7953 program, and will display that source code, not the generated C code.
7956 * Filenames:: Filename extensions and languages.
7957 * Manually:: Setting the working language manually
7958 * Automatically:: Having @value{GDBN} infer the source language
7962 @subsection List of filename extensions and languages
7964 If a source file name ends in one of the following extensions, then
7965 @value{GDBN} infers that its language is the one indicated.
7986 Objective-C source file
7993 Modula-2 source file
7997 Assembler source file. This actually behaves almost like C, but
7998 @value{GDBN} does not skip over function prologues when stepping.
8001 In addition, you may set the language associated with a filename
8002 extension. @xref{Show, , Displaying the language}.
8005 @subsection Setting the working language
8007 If you allow @value{GDBN} to set the language automatically,
8008 expressions are interpreted the same way in your debugging session and
8011 @kindex set language
8012 If you wish, you may set the language manually. To do this, issue the
8013 command @samp{set language @var{lang}}, where @var{lang} is the name of
8015 @code{c} or @code{modula-2}.
8016 For a list of the supported languages, type @samp{set language}.
8018 Setting the language manually prevents @value{GDBN} from updating the working
8019 language automatically. This can lead to confusion if you try
8020 to debug a program when the working language is not the same as the
8021 source language, when an expression is acceptable to both
8022 languages---but means different things. For instance, if the current
8023 source file were written in C, and @value{GDBN} was parsing Modula-2, a
8031 might not have the effect you intended. In C, this means to add
8032 @code{b} and @code{c} and place the result in @code{a}. The result
8033 printed would be the value of @code{a}. In Modula-2, this means to compare
8034 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
8037 @subsection Having @value{GDBN} infer the source language
8039 To have @value{GDBN} set the working language automatically, use
8040 @samp{set language local} or @samp{set language auto}. @value{GDBN}
8041 then infers the working language. That is, when your program stops in a
8042 frame (usually by encountering a breakpoint), @value{GDBN} sets the
8043 working language to the language recorded for the function in that
8044 frame. If the language for a frame is unknown (that is, if the function
8045 or block corresponding to the frame was defined in a source file that
8046 does not have a recognized extension), the current working language is
8047 not changed, and @value{GDBN} issues a warning.
8049 This may not seem necessary for most programs, which are written
8050 entirely in one source language. However, program modules and libraries
8051 written in one source language can be used by a main program written in
8052 a different source language. Using @samp{set language auto} in this
8053 case frees you from having to set the working language manually.
8056 @section Displaying the language
8058 The following commands help you find out which language is the
8059 working language, and also what language source files were written in.
8063 @kindex show language
8064 Display the current working language. This is the
8065 language you can use with commands such as @code{print} to
8066 build and compute expressions that may involve variables in your program.
8069 @kindex info frame@r{, show the source language}
8070 Display the source language for this frame. This language becomes the
8071 working language if you use an identifier from this frame.
8072 @xref{Frame Info, ,Information about a frame}, to identify the other
8073 information listed here.
8076 @kindex info source@r{, show the source language}
8077 Display the source language of this source file.
8078 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
8079 information listed here.
8082 In unusual circumstances, you may have source files with extensions
8083 not in the standard list. You can then set the extension associated
8084 with a language explicitly:
8087 @item set extension-language @var{ext} @var{language}
8088 @kindex set extension-language
8089 Tell @value{GDBN} that source files with extension @var{ext} are to be
8090 assumed as written in the source language @var{language}.
8092 @item info extensions
8093 @kindex info extensions
8094 List all the filename extensions and the associated languages.
8098 @section Type and range checking
8101 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
8102 checking are included, but they do not yet have any effect. This
8103 section documents the intended facilities.
8105 @c FIXME remove warning when type/range code added
8107 Some languages are designed to guard you against making seemingly common
8108 errors through a series of compile- and run-time checks. These include
8109 checking the type of arguments to functions and operators, and making
8110 sure mathematical overflows are caught at run time. Checks such as
8111 these help to ensure a program's correctness once it has been compiled
8112 by eliminating type mismatches, and providing active checks for range
8113 errors when your program is running.
8115 @value{GDBN} can check for conditions like the above if you wish.
8116 Although @value{GDBN} does not check the statements in your program,
8117 it can check expressions entered directly into @value{GDBN} for
8118 evaluation via the @code{print} command, for example. As with the
8119 working language, @value{GDBN} can also decide whether or not to check
8120 automatically based on your program's source language.
8121 @xref{Supported languages, ,Supported languages}, for the default
8122 settings of supported languages.
8125 * Type Checking:: An overview of type checking
8126 * Range Checking:: An overview of range checking
8129 @cindex type checking
8130 @cindex checks, type
8132 @subsection An overview of type checking
8134 Some languages, such as Modula-2, are strongly typed, meaning that the
8135 arguments to operators and functions have to be of the correct type,
8136 otherwise an error occurs. These checks prevent type mismatch
8137 errors from ever causing any run-time problems. For example,
8145 The second example fails because the @code{CARDINAL} 1 is not
8146 type-compatible with the @code{REAL} 2.3.
8148 For the expressions you use in @value{GDBN} commands, you can tell the
8149 @value{GDBN} type checker to skip checking;
8150 to treat any mismatches as errors and abandon the expression;
8151 or to only issue warnings when type mismatches occur,
8152 but evaluate the expression anyway. When you choose the last of
8153 these, @value{GDBN} evaluates expressions like the second example above, but
8154 also issues a warning.
8156 Even if you turn type checking off, there may be other reasons
8157 related to type that prevent @value{GDBN} from evaluating an expression.
8158 For instance, @value{GDBN} does not know how to add an @code{int} and
8159 a @code{struct foo}. These particular type errors have nothing to do
8160 with the language in use, and usually arise from expressions, such as
8161 the one described above, which make little sense to evaluate anyway.
8163 Each language defines to what degree it is strict about type. For
8164 instance, both Modula-2 and C require the arguments to arithmetical
8165 operators to be numbers. In C, enumerated types and pointers can be
8166 represented as numbers, so that they are valid arguments to mathematical
8167 operators. @xref{Supported languages, ,Supported languages}, for further
8168 details on specific languages.
8170 @value{GDBN} provides some additional commands for controlling the type checker:
8172 @kindex set check type
8173 @kindex show check type
8175 @item set check type auto
8176 Set type checking on or off based on the current working language.
8177 @xref{Supported languages, ,Supported languages}, for the default settings for
8180 @item set check type on
8181 @itemx set check type off
8182 Set type checking on or off, overriding the default setting for the
8183 current working language. Issue a warning if the setting does not
8184 match the language default. If any type mismatches occur in
8185 evaluating an expression while type checking is on, @value{GDBN} prints a
8186 message and aborts evaluation of the expression.
8188 @item set check type warn
8189 Cause the type checker to issue warnings, but to always attempt to
8190 evaluate the expression. Evaluating the expression may still
8191 be impossible for other reasons. For example, @value{GDBN} cannot add
8192 numbers and structures.
8195 Show the current setting of the type checker, and whether or not @value{GDBN}
8196 is setting it automatically.
8199 @cindex range checking
8200 @cindex checks, range
8201 @node Range Checking
8202 @subsection An overview of range checking
8204 In some languages (such as Modula-2), it is an error to exceed the
8205 bounds of a type; this is enforced with run-time checks. Such range
8206 checking is meant to ensure program correctness by making sure
8207 computations do not overflow, or indices on an array element access do
8208 not exceed the bounds of the array.
8210 For expressions you use in @value{GDBN} commands, you can tell
8211 @value{GDBN} to treat range errors in one of three ways: ignore them,
8212 always treat them as errors and abandon the expression, or issue
8213 warnings but evaluate the expression anyway.
8215 A range error can result from numerical overflow, from exceeding an
8216 array index bound, or when you type a constant that is not a member
8217 of any type. Some languages, however, do not treat overflows as an
8218 error. In many implementations of C, mathematical overflow causes the
8219 result to ``wrap around'' to lower values---for example, if @var{m} is
8220 the largest integer value, and @var{s} is the smallest, then
8223 @var{m} + 1 @result{} @var{s}
8226 This, too, is specific to individual languages, and in some cases
8227 specific to individual compilers or machines. @xref{Supported languages, ,
8228 Supported languages}, for further details on specific languages.
8230 @value{GDBN} provides some additional commands for controlling the range checker:
8232 @kindex set check range
8233 @kindex show check range
8235 @item set check range auto
8236 Set range checking on or off based on the current working language.
8237 @xref{Supported languages, ,Supported languages}, for the default settings for
8240 @item set check range on
8241 @itemx set check range off
8242 Set range checking on or off, overriding the default setting for the
8243 current working language. A warning is issued if the setting does not
8244 match the language default. If a range error occurs and range checking is on,
8245 then a message is printed and evaluation of the expression is aborted.
8247 @item set check range warn
8248 Output messages when the @value{GDBN} range checker detects a range error,
8249 but attempt to evaluate the expression anyway. Evaluating the
8250 expression may still be impossible for other reasons, such as accessing
8251 memory that the process does not own (a typical example from many Unix
8255 Show the current setting of the range checker, and whether or not it is
8256 being set automatically by @value{GDBN}.
8259 @node Supported languages
8260 @section Supported languages
8262 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
8263 assembly, Modula-2, and Ada.
8264 @c This is false ...
8265 Some @value{GDBN} features may be used in expressions regardless of the
8266 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
8267 and the @samp{@{type@}addr} construct (@pxref{Expressions,
8268 ,Expressions}) can be used with the constructs of any supported
8271 The following sections detail to what degree each source language is
8272 supported by @value{GDBN}. These sections are not meant to be language
8273 tutorials or references, but serve only as a reference guide to what the
8274 @value{GDBN} expression parser accepts, and what input and output
8275 formats should look like for different languages. There are many good
8276 books written on each of these languages; please look to these for a
8277 language reference or tutorial.
8281 * Objective-C:: Objective-C
8284 * Modula-2:: Modula-2
8289 @subsection C and C@t{++}
8291 @cindex C and C@t{++}
8292 @cindex expressions in C or C@t{++}
8294 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
8295 to both languages. Whenever this is the case, we discuss those languages
8299 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
8300 @cindex @sc{gnu} C@t{++}
8301 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
8302 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
8303 effectively, you must compile your C@t{++} programs with a supported
8304 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
8305 compiler (@code{aCC}).
8307 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
8308 format; if it doesn't work on your system, try the stabs+ debugging
8309 format. You can select those formats explicitly with the @code{g++}
8310 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
8311 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
8312 CC, gcc.info, Using @sc{gnu} CC}.
8315 * C Operators:: C and C@t{++} operators
8316 * C Constants:: C and C@t{++} constants
8317 * C plus plus expressions:: C@t{++} expressions
8318 * C Defaults:: Default settings for C and C@t{++}
8319 * C Checks:: C and C@t{++} type and range checks
8320 * Debugging C:: @value{GDBN} and C
8321 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
8325 @subsubsection C and C@t{++} operators
8327 @cindex C and C@t{++} operators
8329 Operators must be defined on values of specific types. For instance,
8330 @code{+} is defined on numbers, but not on structures. Operators are
8331 often defined on groups of types.
8333 For the purposes of C and C@t{++}, the following definitions hold:
8338 @emph{Integral types} include @code{int} with any of its storage-class
8339 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
8342 @emph{Floating-point types} include @code{float}, @code{double}, and
8343 @code{long double} (if supported by the target platform).
8346 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
8349 @emph{Scalar types} include all of the above.
8354 The following operators are supported. They are listed here
8355 in order of increasing precedence:
8359 The comma or sequencing operator. Expressions in a comma-separated list
8360 are evaluated from left to right, with the result of the entire
8361 expression being the last expression evaluated.
8364 Assignment. The value of an assignment expression is the value
8365 assigned. Defined on scalar types.
8368 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
8369 and translated to @w{@code{@var{a} = @var{a op b}}}.
8370 @w{@code{@var{op}=}} and @code{=} have the same precedence.
8371 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
8372 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
8375 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
8376 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
8380 Logical @sc{or}. Defined on integral types.
8383 Logical @sc{and}. Defined on integral types.
8386 Bitwise @sc{or}. Defined on integral types.
8389 Bitwise exclusive-@sc{or}. Defined on integral types.
8392 Bitwise @sc{and}. Defined on integral types.
8395 Equality and inequality. Defined on scalar types. The value of these
8396 expressions is 0 for false and non-zero for true.
8398 @item <@r{, }>@r{, }<=@r{, }>=
8399 Less than, greater than, less than or equal, greater than or equal.
8400 Defined on scalar types. The value of these expressions is 0 for false
8401 and non-zero for true.
8404 left shift, and right shift. Defined on integral types.
8407 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8410 Addition and subtraction. Defined on integral types, floating-point types and
8413 @item *@r{, }/@r{, }%
8414 Multiplication, division, and modulus. Multiplication and division are
8415 defined on integral and floating-point types. Modulus is defined on
8419 Increment and decrement. When appearing before a variable, the
8420 operation is performed before the variable is used in an expression;
8421 when appearing after it, the variable's value is used before the
8422 operation takes place.
8425 Pointer dereferencing. Defined on pointer types. Same precedence as
8429 Address operator. Defined on variables. Same precedence as @code{++}.
8431 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
8432 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
8433 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
8434 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
8438 Negative. Defined on integral and floating-point types. Same
8439 precedence as @code{++}.
8442 Logical negation. Defined on integral types. Same precedence as
8446 Bitwise complement operator. Defined on integral types. Same precedence as
8451 Structure member, and pointer-to-structure member. For convenience,
8452 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
8453 pointer based on the stored type information.
8454 Defined on @code{struct} and @code{union} data.
8457 Dereferences of pointers to members.
8460 Array indexing. @code{@var{a}[@var{i}]} is defined as
8461 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
8464 Function parameter list. Same precedence as @code{->}.
8467 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
8468 and @code{class} types.
8471 Doubled colons also represent the @value{GDBN} scope operator
8472 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
8476 If an operator is redefined in the user code, @value{GDBN} usually
8477 attempts to invoke the redefined version instead of using the operator's
8485 @subsubsection C and C@t{++} constants
8487 @cindex C and C@t{++} constants
8489 @value{GDBN} allows you to express the constants of C and C@t{++} in the
8494 Integer constants are a sequence of digits. Octal constants are
8495 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
8496 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
8497 @samp{l}, specifying that the constant should be treated as a
8501 Floating point constants are a sequence of digits, followed by a decimal
8502 point, followed by a sequence of digits, and optionally followed by an
8503 exponent. An exponent is of the form:
8504 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8505 sequence of digits. The @samp{+} is optional for positive exponents.
8506 A floating-point constant may also end with a letter @samp{f} or
8507 @samp{F}, specifying that the constant should be treated as being of
8508 the @code{float} (as opposed to the default @code{double}) type; or with
8509 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8513 Enumerated constants consist of enumerated identifiers, or their
8514 integral equivalents.
8517 Character constants are a single character surrounded by single quotes
8518 (@code{'}), or a number---the ordinal value of the corresponding character
8519 (usually its @sc{ascii} value). Within quotes, the single character may
8520 be represented by a letter or by @dfn{escape sequences}, which are of
8521 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8522 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8523 @samp{@var{x}} is a predefined special character---for example,
8524 @samp{\n} for newline.
8527 String constants are a sequence of character constants surrounded by
8528 double quotes (@code{"}). Any valid character constant (as described
8529 above) may appear. Double quotes within the string must be preceded by
8530 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8534 Pointer constants are an integral value. You can also write pointers
8535 to constants using the C operator @samp{&}.
8538 Array constants are comma-separated lists surrounded by braces @samp{@{}
8539 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8540 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8541 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8545 * C plus plus expressions::
8552 @node C plus plus expressions
8553 @subsubsection C@t{++} expressions
8555 @cindex expressions in C@t{++}
8556 @value{GDBN} expression handling can interpret most C@t{++} expressions.
8558 @cindex debugging C@t{++} programs
8559 @cindex C@t{++} compilers
8560 @cindex debug formats and C@t{++}
8561 @cindex @value{NGCC} and C@t{++}
8563 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
8564 proper compiler and the proper debug format. Currently, @value{GDBN}
8565 works best when debugging C@t{++} code that is compiled with
8566 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
8567 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
8568 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
8569 stabs+ as their default debug format, so you usually don't need to
8570 specify a debug format explicitly. Other compilers and/or debug formats
8571 are likely to work badly or not at all when using @value{GDBN} to debug
8577 @cindex member functions
8579 Member function calls are allowed; you can use expressions like
8582 count = aml->GetOriginal(x, y)
8585 @vindex this@r{, inside C@t{++} member functions}
8586 @cindex namespace in C@t{++}
8588 While a member function is active (in the selected stack frame), your
8589 expressions have the same namespace available as the member function;
8590 that is, @value{GDBN} allows implicit references to the class instance
8591 pointer @code{this} following the same rules as C@t{++}.
8593 @cindex call overloaded functions
8594 @cindex overloaded functions, calling
8595 @cindex type conversions in C@t{++}
8597 You can call overloaded functions; @value{GDBN} resolves the function
8598 call to the right definition, with some restrictions. @value{GDBN} does not
8599 perform overload resolution involving user-defined type conversions,
8600 calls to constructors, or instantiations of templates that do not exist
8601 in the program. It also cannot handle ellipsis argument lists or
8604 It does perform integral conversions and promotions, floating-point
8605 promotions, arithmetic conversions, pointer conversions, conversions of
8606 class objects to base classes, and standard conversions such as those of
8607 functions or arrays to pointers; it requires an exact match on the
8608 number of function arguments.
8610 Overload resolution is always performed, unless you have specified
8611 @code{set overload-resolution off}. @xref{Debugging C plus plus,
8612 ,@value{GDBN} features for C@t{++}}.
8614 You must specify @code{set overload-resolution off} in order to use an
8615 explicit function signature to call an overloaded function, as in
8617 p 'foo(char,int)'('x', 13)
8620 The @value{GDBN} command-completion facility can simplify this;
8621 see @ref{Completion, ,Command completion}.
8623 @cindex reference declarations
8625 @value{GDBN} understands variables declared as C@t{++} references; you can use
8626 them in expressions just as you do in C@t{++} source---they are automatically
8629 In the parameter list shown when @value{GDBN} displays a frame, the values of
8630 reference variables are not displayed (unlike other variables); this
8631 avoids clutter, since references are often used for large structures.
8632 The @emph{address} of a reference variable is always shown, unless
8633 you have specified @samp{set print address off}.
8636 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
8637 expressions can use it just as expressions in your program do. Since
8638 one scope may be defined in another, you can use @code{::} repeatedly if
8639 necessary, for example in an expression like
8640 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
8641 resolving name scope by reference to source files, in both C and C@t{++}
8642 debugging (@pxref{Variables, ,Program variables}).
8645 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
8646 calling virtual functions correctly, printing out virtual bases of
8647 objects, calling functions in a base subobject, casting objects, and
8648 invoking user-defined operators.
8651 @subsubsection C and C@t{++} defaults
8653 @cindex C and C@t{++} defaults
8655 If you allow @value{GDBN} to set type and range checking automatically, they
8656 both default to @code{off} whenever the working language changes to
8657 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
8658 selects the working language.
8660 If you allow @value{GDBN} to set the language automatically, it
8661 recognizes source files whose names end with @file{.c}, @file{.C}, or
8662 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
8663 these files, it sets the working language to C or C@t{++}.
8664 @xref{Automatically, ,Having @value{GDBN} infer the source language},
8665 for further details.
8667 @c Type checking is (a) primarily motivated by Modula-2, and (b)
8668 @c unimplemented. If (b) changes, it might make sense to let this node
8669 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
8672 @subsubsection C and C@t{++} type and range checks
8674 @cindex C and C@t{++} checks
8676 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
8677 is not used. However, if you turn type checking on, @value{GDBN}
8678 considers two variables type equivalent if:
8682 The two variables are structured and have the same structure, union, or
8686 The two variables have the same type name, or types that have been
8687 declared equivalent through @code{typedef}.
8690 @c leaving this out because neither J Gilmore nor R Pesch understand it.
8693 The two @code{struct}, @code{union}, or @code{enum} variables are
8694 declared in the same declaration. (Note: this may not be true for all C
8699 Range checking, if turned on, is done on mathematical operations. Array
8700 indices are not checked, since they are often used to index a pointer
8701 that is not itself an array.
8704 @subsubsection @value{GDBN} and C
8706 The @code{set print union} and @code{show print union} commands apply to
8707 the @code{union} type. When set to @samp{on}, any @code{union} that is
8708 inside a @code{struct} or @code{class} is also printed. Otherwise, it
8709 appears as @samp{@{...@}}.
8711 The @code{@@} operator aids in the debugging of dynamic arrays, formed
8712 with pointers and a memory allocation function. @xref{Expressions,
8716 * Debugging C plus plus::
8719 @node Debugging C plus plus
8720 @subsubsection @value{GDBN} features for C@t{++}
8722 @cindex commands for C@t{++}
8724 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
8725 designed specifically for use with C@t{++}. Here is a summary:
8728 @cindex break in overloaded functions
8729 @item @r{breakpoint menus}
8730 When you want a breakpoint in a function whose name is overloaded,
8731 @value{GDBN} breakpoint menus help you specify which function definition
8732 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
8734 @cindex overloading in C@t{++}
8735 @item rbreak @var{regex}
8736 Setting breakpoints using regular expressions is helpful for setting
8737 breakpoints on overloaded functions that are not members of any special
8739 @xref{Set Breaks, ,Setting breakpoints}.
8741 @cindex C@t{++} exception handling
8744 Debug C@t{++} exception handling using these commands. @xref{Set
8745 Catchpoints, , Setting catchpoints}.
8748 @item ptype @var{typename}
8749 Print inheritance relationships as well as other information for type
8751 @xref{Symbols, ,Examining the Symbol Table}.
8753 @cindex C@t{++} symbol display
8754 @item set print demangle
8755 @itemx show print demangle
8756 @itemx set print asm-demangle
8757 @itemx show print asm-demangle
8758 Control whether C@t{++} symbols display in their source form, both when
8759 displaying code as C@t{++} source and when displaying disassemblies.
8760 @xref{Print Settings, ,Print settings}.
8762 @item set print object
8763 @itemx show print object
8764 Choose whether to print derived (actual) or declared types of objects.
8765 @xref{Print Settings, ,Print settings}.
8767 @item set print vtbl
8768 @itemx show print vtbl
8769 Control the format for printing virtual function tables.
8770 @xref{Print Settings, ,Print settings}.
8771 (The @code{vtbl} commands do not work on programs compiled with the HP
8772 ANSI C@t{++} compiler (@code{aCC}).)
8774 @kindex set overload-resolution
8775 @cindex overloaded functions, overload resolution
8776 @item set overload-resolution on
8777 Enable overload resolution for C@t{++} expression evaluation. The default
8778 is on. For overloaded functions, @value{GDBN} evaluates the arguments
8779 and searches for a function whose signature matches the argument types,
8780 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
8781 expressions}, for details). If it cannot find a match, it emits a
8784 @item set overload-resolution off
8785 Disable overload resolution for C@t{++} expression evaluation. For
8786 overloaded functions that are not class member functions, @value{GDBN}
8787 chooses the first function of the specified name that it finds in the
8788 symbol table, whether or not its arguments are of the correct type. For
8789 overloaded functions that are class member functions, @value{GDBN}
8790 searches for a function whose signature @emph{exactly} matches the
8793 @kindex show overload-resolution
8794 @item show overload-resolution
8795 Show the current setting of overload resolution.
8797 @item @r{Overloaded symbol names}
8798 You can specify a particular definition of an overloaded symbol, using
8799 the same notation that is used to declare such symbols in C@t{++}: type
8800 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
8801 also use the @value{GDBN} command-line word completion facilities to list the
8802 available choices, or to finish the type list for you.
8803 @xref{Completion,, Command completion}, for details on how to do this.
8807 @subsection Objective-C
8810 This section provides information about some commands and command
8811 options that are useful for debugging Objective-C code. See also
8812 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
8813 few more commands specific to Objective-C support.
8816 * Method Names in Commands::
8817 * The Print Command with Objective-C::
8820 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
8821 @subsubsection Method Names in Commands
8823 The following commands have been extended to accept Objective-C method
8824 names as line specifications:
8826 @kindex clear@r{, and Objective-C}
8827 @kindex break@r{, and Objective-C}
8828 @kindex info line@r{, and Objective-C}
8829 @kindex jump@r{, and Objective-C}
8830 @kindex list@r{, and Objective-C}
8834 @item @code{info line}
8839 A fully qualified Objective-C method name is specified as
8842 -[@var{Class} @var{methodName}]
8845 where the minus sign is used to indicate an instance method and a
8846 plus sign (not shown) is used to indicate a class method. The class
8847 name @var{Class} and method name @var{methodName} are enclosed in
8848 brackets, similar to the way messages are specified in Objective-C
8849 source code. For example, to set a breakpoint at the @code{create}
8850 instance method of class @code{Fruit} in the program currently being
8854 break -[Fruit create]
8857 To list ten program lines around the @code{initialize} class method,
8861 list +[NSText initialize]
8864 In the current version of @value{GDBN}, the plus or minus sign is
8865 required. In future versions of @value{GDBN}, the plus or minus
8866 sign will be optional, but you can use it to narrow the search. It
8867 is also possible to specify just a method name:
8873 You must specify the complete method name, including any colons. If
8874 your program's source files contain more than one @code{create} method,
8875 you'll be presented with a numbered list of classes that implement that
8876 method. Indicate your choice by number, or type @samp{0} to exit if
8879 As another example, to clear a breakpoint established at the
8880 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
8883 clear -[NSWindow makeKeyAndOrderFront:]
8886 @node The Print Command with Objective-C
8887 @subsubsection The Print Command With Objective-C
8888 @cindex Objective-C, print objects
8889 @kindex print-object
8890 @kindex po @r{(@code{print-object})}
8892 The print command has also been extended to accept methods. For example:
8895 print -[@var{object} hash]
8898 @cindex print an Objective-C object description
8899 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
8901 will tell @value{GDBN} to send the @code{hash} message to @var{object}
8902 and print the result. Also, an additional command has been added,
8903 @code{print-object} or @code{po} for short, which is meant to print
8904 the description of an object. However, this command may only work
8905 with certain Objective-C libraries that have a particular hook
8906 function, @code{_NSPrintForDebugger}, defined.
8910 @cindex Fortran-specific support in @value{GDBN}
8913 @cindex @code{COMMON} blocks, Fortran
8915 @item info common @r{[}@var{common-name}@r{]}
8916 This command prints the values contained in the Fortran @code{COMMON}
8917 block whose name is @var{common-name}. With no argument, the names of
8918 all @code{COMMON} blocks visible at current program location are
8922 Fortran symbols are usually case-insensitive, so @value{GDBN} by
8923 default uses case-insensitive matches for Fortran symbols. You can
8924 change that with the @samp{set case-insensitive} command, see
8925 @ref{Symbols}, for the details.
8930 @cindex Pascal support in @value{GDBN}, limitations
8931 Debugging Pascal programs which use sets, subranges, file variables, or
8932 nested functions does not currently work. @value{GDBN} does not support
8933 entering expressions, printing values, or similar features using Pascal
8936 The Pascal-specific command @code{set print pascal_static-members}
8937 controls whether static members of Pascal objects are displayed.
8938 @xref{Print Settings, pascal_static-members}.
8941 @subsection Modula-2
8943 @cindex Modula-2, @value{GDBN} support
8945 The extensions made to @value{GDBN} to support Modula-2 only support
8946 output from the @sc{gnu} Modula-2 compiler (which is currently being
8947 developed). Other Modula-2 compilers are not currently supported, and
8948 attempting to debug executables produced by them is most likely
8949 to give an error as @value{GDBN} reads in the executable's symbol
8952 @cindex expressions in Modula-2
8954 * M2 Operators:: Built-in operators
8955 * Built-In Func/Proc:: Built-in functions and procedures
8956 * M2 Constants:: Modula-2 constants
8957 * M2 Defaults:: Default settings for Modula-2
8958 * Deviations:: Deviations from standard Modula-2
8959 * M2 Checks:: Modula-2 type and range checks
8960 * M2 Scope:: The scope operators @code{::} and @code{.}
8961 * GDB/M2:: @value{GDBN} and Modula-2
8965 @subsubsection Operators
8966 @cindex Modula-2 operators
8968 Operators must be defined on values of specific types. For instance,
8969 @code{+} is defined on numbers, but not on structures. Operators are
8970 often defined on groups of types. For the purposes of Modula-2, the
8971 following definitions hold:
8976 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
8980 @emph{Character types} consist of @code{CHAR} and its subranges.
8983 @emph{Floating-point types} consist of @code{REAL}.
8986 @emph{Pointer types} consist of anything declared as @code{POINTER TO
8990 @emph{Scalar types} consist of all of the above.
8993 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
8996 @emph{Boolean types} consist of @code{BOOLEAN}.
9000 The following operators are supported, and appear in order of
9001 increasing precedence:
9005 Function argument or array index separator.
9008 Assignment. The value of @var{var} @code{:=} @var{value} is
9012 Less than, greater than on integral, floating-point, or enumerated
9016 Less than or equal to, greater than or equal to
9017 on integral, floating-point and enumerated types, or set inclusion on
9018 set types. Same precedence as @code{<}.
9020 @item =@r{, }<>@r{, }#
9021 Equality and two ways of expressing inequality, valid on scalar types.
9022 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
9023 available for inequality, since @code{#} conflicts with the script
9027 Set membership. Defined on set types and the types of their members.
9028 Same precedence as @code{<}.
9031 Boolean disjunction. Defined on boolean types.
9034 Boolean conjunction. Defined on boolean types.
9037 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9040 Addition and subtraction on integral and floating-point types, or union
9041 and difference on set types.
9044 Multiplication on integral and floating-point types, or set intersection
9048 Division on floating-point types, or symmetric set difference on set
9049 types. Same precedence as @code{*}.
9052 Integer division and remainder. Defined on integral types. Same
9053 precedence as @code{*}.
9056 Negative. Defined on @code{INTEGER} and @code{REAL} data.
9059 Pointer dereferencing. Defined on pointer types.
9062 Boolean negation. Defined on boolean types. Same precedence as
9066 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
9067 precedence as @code{^}.
9070 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
9073 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
9077 @value{GDBN} and Modula-2 scope operators.
9081 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
9082 treats the use of the operator @code{IN}, or the use of operators
9083 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
9084 @code{<=}, and @code{>=} on sets as an error.
9088 @node Built-In Func/Proc
9089 @subsubsection Built-in functions and procedures
9090 @cindex Modula-2 built-ins
9092 Modula-2 also makes available several built-in procedures and functions.
9093 In describing these, the following metavariables are used:
9098 represents an @code{ARRAY} variable.
9101 represents a @code{CHAR} constant or variable.
9104 represents a variable or constant of integral type.
9107 represents an identifier that belongs to a set. Generally used in the
9108 same function with the metavariable @var{s}. The type of @var{s} should
9109 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
9112 represents a variable or constant of integral or floating-point type.
9115 represents a variable or constant of floating-point type.
9121 represents a variable.
9124 represents a variable or constant of one of many types. See the
9125 explanation of the function for details.
9128 All Modula-2 built-in procedures also return a result, described below.
9132 Returns the absolute value of @var{n}.
9135 If @var{c} is a lower case letter, it returns its upper case
9136 equivalent, otherwise it returns its argument.
9139 Returns the character whose ordinal value is @var{i}.
9142 Decrements the value in the variable @var{v} by one. Returns the new value.
9144 @item DEC(@var{v},@var{i})
9145 Decrements the value in the variable @var{v} by @var{i}. Returns the
9148 @item EXCL(@var{m},@var{s})
9149 Removes the element @var{m} from the set @var{s}. Returns the new
9152 @item FLOAT(@var{i})
9153 Returns the floating point equivalent of the integer @var{i}.
9156 Returns the index of the last member of @var{a}.
9159 Increments the value in the variable @var{v} by one. Returns the new value.
9161 @item INC(@var{v},@var{i})
9162 Increments the value in the variable @var{v} by @var{i}. Returns the
9165 @item INCL(@var{m},@var{s})
9166 Adds the element @var{m} to the set @var{s} if it is not already
9167 there. Returns the new set.
9170 Returns the maximum value of the type @var{t}.
9173 Returns the minimum value of the type @var{t}.
9176 Returns boolean TRUE if @var{i} is an odd number.
9179 Returns the ordinal value of its argument. For example, the ordinal
9180 value of a character is its @sc{ascii} value (on machines supporting the
9181 @sc{ascii} character set). @var{x} must be of an ordered type, which include
9182 integral, character and enumerated types.
9185 Returns the size of its argument. @var{x} can be a variable or a type.
9187 @item TRUNC(@var{r})
9188 Returns the integral part of @var{r}.
9190 @item VAL(@var{t},@var{i})
9191 Returns the member of the type @var{t} whose ordinal value is @var{i}.
9195 @emph{Warning:} Sets and their operations are not yet supported, so
9196 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
9200 @cindex Modula-2 constants
9202 @subsubsection Constants
9204 @value{GDBN} allows you to express the constants of Modula-2 in the following
9210 Integer constants are simply a sequence of digits. When used in an
9211 expression, a constant is interpreted to be type-compatible with the
9212 rest of the expression. Hexadecimal integers are specified by a
9213 trailing @samp{H}, and octal integers by a trailing @samp{B}.
9216 Floating point constants appear as a sequence of digits, followed by a
9217 decimal point and another sequence of digits. An optional exponent can
9218 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
9219 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
9220 digits of the floating point constant must be valid decimal (base 10)
9224 Character constants consist of a single character enclosed by a pair of
9225 like quotes, either single (@code{'}) or double (@code{"}). They may
9226 also be expressed by their ordinal value (their @sc{ascii} value, usually)
9227 followed by a @samp{C}.
9230 String constants consist of a sequence of characters enclosed by a
9231 pair of like quotes, either single (@code{'}) or double (@code{"}).
9232 Escape sequences in the style of C are also allowed. @xref{C
9233 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
9237 Enumerated constants consist of an enumerated identifier.
9240 Boolean constants consist of the identifiers @code{TRUE} and
9244 Pointer constants consist of integral values only.
9247 Set constants are not yet supported.
9251 @subsubsection Modula-2 defaults
9252 @cindex Modula-2 defaults
9254 If type and range checking are set automatically by @value{GDBN}, they
9255 both default to @code{on} whenever the working language changes to
9256 Modula-2. This happens regardless of whether you or @value{GDBN}
9257 selected the working language.
9259 If you allow @value{GDBN} to set the language automatically, then entering
9260 code compiled from a file whose name ends with @file{.mod} sets the
9261 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
9262 the language automatically}, for further details.
9265 @subsubsection Deviations from standard Modula-2
9266 @cindex Modula-2, deviations from
9268 A few changes have been made to make Modula-2 programs easier to debug.
9269 This is done primarily via loosening its type strictness:
9273 Unlike in standard Modula-2, pointer constants can be formed by
9274 integers. This allows you to modify pointer variables during
9275 debugging. (In standard Modula-2, the actual address contained in a
9276 pointer variable is hidden from you; it can only be modified
9277 through direct assignment to another pointer variable or expression that
9278 returned a pointer.)
9281 C escape sequences can be used in strings and characters to represent
9282 non-printable characters. @value{GDBN} prints out strings with these
9283 escape sequences embedded. Single non-printable characters are
9284 printed using the @samp{CHR(@var{nnn})} format.
9287 The assignment operator (@code{:=}) returns the value of its right-hand
9291 All built-in procedures both modify @emph{and} return their argument.
9295 @subsubsection Modula-2 type and range checks
9296 @cindex Modula-2 checks
9299 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
9302 @c FIXME remove warning when type/range checks added
9304 @value{GDBN} considers two Modula-2 variables type equivalent if:
9308 They are of types that have been declared equivalent via a @code{TYPE
9309 @var{t1} = @var{t2}} statement
9312 They have been declared on the same line. (Note: This is true of the
9313 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
9316 As long as type checking is enabled, any attempt to combine variables
9317 whose types are not equivalent is an error.
9319 Range checking is done on all mathematical operations, assignment, array
9320 index bounds, and all built-in functions and procedures.
9323 @subsubsection The scope operators @code{::} and @code{.}
9325 @cindex @code{.}, Modula-2 scope operator
9326 @cindex colon, doubled as scope operator
9328 @vindex colon-colon@r{, in Modula-2}
9329 @c Info cannot handle :: but TeX can.
9332 @vindex ::@r{, in Modula-2}
9335 There are a few subtle differences between the Modula-2 scope operator
9336 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
9341 @var{module} . @var{id}
9342 @var{scope} :: @var{id}
9346 where @var{scope} is the name of a module or a procedure,
9347 @var{module} the name of a module, and @var{id} is any declared
9348 identifier within your program, except another module.
9350 Using the @code{::} operator makes @value{GDBN} search the scope
9351 specified by @var{scope} for the identifier @var{id}. If it is not
9352 found in the specified scope, then @value{GDBN} searches all scopes
9353 enclosing the one specified by @var{scope}.
9355 Using the @code{.} operator makes @value{GDBN} search the current scope for
9356 the identifier specified by @var{id} that was imported from the
9357 definition module specified by @var{module}. With this operator, it is
9358 an error if the identifier @var{id} was not imported from definition
9359 module @var{module}, or if @var{id} is not an identifier in
9363 @subsubsection @value{GDBN} and Modula-2
9365 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
9366 Five subcommands of @code{set print} and @code{show print} apply
9367 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
9368 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
9369 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
9370 analogue in Modula-2.
9372 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
9373 with any language, is not useful with Modula-2. Its
9374 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
9375 created in Modula-2 as they can in C or C@t{++}. However, because an
9376 address can be specified by an integral constant, the construct
9377 @samp{@{@var{type}@}@var{adrexp}} is still useful.
9379 @cindex @code{#} in Modula-2
9380 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
9381 interpreted as the beginning of a comment. Use @code{<>} instead.
9387 The extensions made to @value{GDBN} for Ada only support
9388 output from the @sc{gnu} Ada (GNAT) compiler.
9389 Other Ada compilers are not currently supported, and
9390 attempting to debug executables produced by them is most likely
9394 @cindex expressions in Ada
9396 * Ada Mode Intro:: General remarks on the Ada syntax
9397 and semantics supported by Ada mode
9399 * Omissions from Ada:: Restrictions on the Ada expression syntax.
9400 * Additions to Ada:: Extensions of the Ada expression syntax.
9401 * Stopping Before Main Program:: Debugging the program during elaboration.
9402 * Ada Glitches:: Known peculiarities of Ada mode.
9405 @node Ada Mode Intro
9406 @subsubsection Introduction
9407 @cindex Ada mode, general
9409 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
9410 syntax, with some extensions.
9411 The philosophy behind the design of this subset is
9415 That @value{GDBN} should provide basic literals and access to operations for
9416 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
9417 leaving more sophisticated computations to subprograms written into the
9418 program (which therefore may be called from @value{GDBN}).
9421 That type safety and strict adherence to Ada language restrictions
9422 are not particularly important to the @value{GDBN} user.
9425 That brevity is important to the @value{GDBN} user.
9428 Thus, for brevity, the debugger acts as if there were
9429 implicit @code{with} and @code{use} clauses in effect for all user-written
9430 packages, making it unnecessary to fully qualify most names with
9431 their packages, regardless of context. Where this causes ambiguity,
9432 @value{GDBN} asks the user's intent.
9434 The debugger will start in Ada mode if it detects an Ada main program.
9435 As for other languages, it will enter Ada mode when stopped in a program that
9436 was translated from an Ada source file.
9438 While in Ada mode, you may use `@t{--}' for comments. This is useful
9439 mostly for documenting command files. The standard @value{GDBN} comment
9440 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
9441 middle (to allow based literals).
9443 The debugger supports limited overloading. Given a subprogram call in which
9444 the function symbol has multiple definitions, it will use the number of
9445 actual parameters and some information about their types to attempt to narrow
9446 the set of definitions. It also makes very limited use of context, preferring
9447 procedures to functions in the context of the @code{call} command, and
9448 functions to procedures elsewhere.
9450 @node Omissions from Ada
9451 @subsubsection Omissions from Ada
9452 @cindex Ada, omissions from
9454 Here are the notable omissions from the subset:
9458 Only a subset of the attributes are supported:
9462 @t{'First}, @t{'Last}, and @t{'Length}
9463 on array objects (not on types and subtypes).
9466 @t{'Min} and @t{'Max}.
9469 @t{'Pos} and @t{'Val}.
9475 @t{'Range} on array objects (not subtypes), but only as the right
9476 operand of the membership (@code{in}) operator.
9479 @t{'Access}, @t{'Unchecked_Access}, and
9480 @t{'Unrestricted_Access} (a GNAT extension).
9488 @code{Characters.Latin_1} are not available and
9489 concatenation is not implemented. Thus, escape characters in strings are
9490 not currently available.
9493 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
9494 equality of representations. They will generally work correctly
9495 for strings and arrays whose elements have integer or enumeration types.
9496 They may not work correctly for arrays whose element
9497 types have user-defined equality, for arrays of real values
9498 (in particular, IEEE-conformant floating point, because of negative
9499 zeroes and NaNs), and for arrays whose elements contain unused bits with
9500 indeterminate values.
9503 The other component-by-component array operations (@code{and}, @code{or},
9504 @code{xor}, @code{not}, and relational tests other than equality)
9505 are not implemented.
9508 There are no record or array aggregates.
9511 Calls to dispatching subprograms are not implemented.
9514 The overloading algorithm is much more limited (i.e., less selective)
9515 than that of real Ada. It makes only limited use of the context in which a subexpression
9516 appears to resolve its meaning, and it is much looser in its rules for allowing
9517 type matches. As a result, some function calls will be ambiguous, and the user
9518 will be asked to choose the proper resolution.
9521 The @code{new} operator is not implemented.
9524 Entry calls are not implemented.
9527 Aside from printing, arithmetic operations on the native VAX floating-point
9528 formats are not supported.
9531 It is not possible to slice a packed array.
9534 @node Additions to Ada
9535 @subsubsection Additions to Ada
9536 @cindex Ada, deviations from
9538 As it does for other languages, @value{GDBN} makes certain generic
9539 extensions to Ada (@pxref{Expressions}):
9543 If the expression @var{E} is a variable residing in memory
9544 (typically a local variable or array element) and @var{N} is
9545 a positive integer, then @code{@var{E}@@@var{N}} displays the values of
9546 @var{E} and the @var{N}-1 adjacent variables following it in memory as an array.
9547 In Ada, this operator is generally not necessary, since its prime use
9548 is in displaying parts of an array, and slicing will usually do this in Ada.
9549 However, there are occasional uses when debugging programs
9550 in which certain debugging information has been optimized away.
9553 @code{@var{B}::@var{var}} means ``the variable named @var{var} that appears
9554 in function or file @var{B}.'' When @var{B} is a file name, you must typically
9555 surround it in single quotes.
9558 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
9559 @var{type} that appears at address @var{addr}.''
9562 A name starting with @samp{$} is a convenience variable
9563 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
9566 In addition, @value{GDBN} provides a few other shortcuts and outright additions specific
9571 The assignment statement is allowed as an expression, returning
9572 its right-hand operand as its value. Thus, you may enter
9576 print A(tmp := y + 1)
9580 The semicolon is allowed as an ``operator,'' returning as its value
9581 the value of its right-hand operand.
9582 This allows, for example,
9583 complex conditional breaks:
9587 condition 1 (report(i); k += 1; A(k) > 100)
9591 Rather than use catenation and symbolic character names to introduce special
9592 characters into strings, one may instead use a special bracket notation,
9593 which is also used to print strings. A sequence of characters of the form
9594 @samp{["@var{XX}"]} within a string or character literal denotes the
9595 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
9596 sequence of characters @samp{["""]} also denotes a single quotation mark
9597 in strings. For example,
9599 "One line.["0a"]Next line.["0a"]"
9602 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF}) after each
9606 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
9607 @t{'Max} is optional (and is ignored in any case). For example, it is valid
9615 When printing arrays, @value{GDBN} uses positional notation when the
9616 array has a lower bound of 1, and uses a modified named notation otherwise.
9617 For example, a one-dimensional array of three integers with a lower bound of 3 might print as
9624 That is, in contrast to valid Ada, only the first component has a @code{=>}
9628 You may abbreviate attributes in expressions with any unique,
9629 multi-character subsequence of
9630 their names (an exact match gets preference).
9631 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
9632 in place of @t{a'length}.
9635 @cindex quoting Ada internal identifiers
9636 Since Ada is case-insensitive, the debugger normally maps identifiers you type
9637 to lower case. The GNAT compiler uses upper-case characters for
9638 some of its internal identifiers, which are normally of no interest to users.
9639 For the rare occasions when you actually have to look at them,
9640 enclose them in angle brackets to avoid the lower-case mapping.
9643 @value{GDBP} print <JMPBUF_SAVE>[0]
9647 Printing an object of class-wide type or dereferencing an
9648 access-to-class-wide value will display all the components of the object's
9649 specific type (as indicated by its run-time tag). Likewise, component
9650 selection on such a value will operate on the specific type of the
9655 @node Stopping Before Main Program
9656 @subsubsection Stopping at the Very Beginning
9658 @cindex breakpointing Ada elaboration code
9659 It is sometimes necessary to debug the program during elaboration, and
9660 before reaching the main procedure.
9661 As defined in the Ada Reference
9662 Manual, the elaboration code is invoked from a procedure called
9663 @code{adainit}. To run your program up to the beginning of
9664 elaboration, simply use the following two commands:
9665 @code{tbreak adainit} and @code{run}.
9668 @subsubsection Known Peculiarities of Ada Mode
9669 @cindex Ada, problems
9671 Besides the omissions listed previously (@pxref{Omissions from Ada}),
9672 we know of several problems with and limitations of Ada mode in
9674 some of which will be fixed with planned future releases of the debugger
9675 and the GNU Ada compiler.
9679 Currently, the debugger
9680 has insufficient information to determine whether certain pointers represent
9681 pointers to objects or the objects themselves.
9682 Thus, the user may have to tack an extra @code{.all} after an expression
9683 to get it printed properly.
9686 Static constants that the compiler chooses not to materialize as objects in
9687 storage are invisible to the debugger.
9690 Named parameter associations in function argument lists are ignored (the
9691 argument lists are treated as positional).
9694 Many useful library packages are currently invisible to the debugger.
9697 Fixed-point arithmetic, conversions, input, and output is carried out using
9698 floating-point arithmetic, and may give results that only approximate those on
9702 The type of the @t{'Address} attribute may not be @code{System.Address}.
9705 The GNAT compiler never generates the prefix @code{Standard} for any of
9706 the standard symbols defined by the Ada language. @value{GDBN} knows about
9707 this: it will strip the prefix from names when you use it, and will never
9708 look for a name you have so qualified among local symbols, nor match against
9709 symbols in other packages or subprograms. If you have
9710 defined entities anywhere in your program other than parameters and
9711 local variables whose simple names match names in @code{Standard},
9712 GNAT's lack of qualification here can cause confusion. When this happens,
9713 you can usually resolve the confusion
9714 by qualifying the problematic names with package
9715 @code{Standard} explicitly.
9718 @node Unsupported languages
9719 @section Unsupported languages
9721 @cindex unsupported languages
9722 @cindex minimal language
9723 In addition to the other fully-supported programming languages,
9724 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
9725 It does not represent a real programming language, but provides a set
9726 of capabilities close to what the C or assembly languages provide.
9727 This should allow most simple operations to be performed while debugging
9728 an application that uses a language currently not supported by @value{GDBN}.
9730 If the language is set to @code{auto}, @value{GDBN} will automatically
9731 select this language if the current frame corresponds to an unsupported
9735 @chapter Examining the Symbol Table
9737 The commands described in this chapter allow you to inquire about the
9738 symbols (names of variables, functions and types) defined in your
9739 program. This information is inherent in the text of your program and
9740 does not change as your program executes. @value{GDBN} finds it in your
9741 program's symbol table, in the file indicated when you started @value{GDBN}
9742 (@pxref{File Options, ,Choosing files}), or by one of the
9743 file-management commands (@pxref{Files, ,Commands to specify files}).
9745 @cindex symbol names
9746 @cindex names of symbols
9747 @cindex quoting names
9748 Occasionally, you may need to refer to symbols that contain unusual
9749 characters, which @value{GDBN} ordinarily treats as word delimiters. The
9750 most frequent case is in referring to static variables in other
9751 source files (@pxref{Variables,,Program variables}). File names
9752 are recorded in object files as debugging symbols, but @value{GDBN} would
9753 ordinarily parse a typical file name, like @file{foo.c}, as the three words
9754 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
9755 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
9762 looks up the value of @code{x} in the scope of the file @file{foo.c}.
9765 @cindex case-insensitive symbol names
9766 @cindex case sensitivity in symbol names
9767 @kindex set case-sensitive
9768 @item set case-sensitive on
9769 @itemx set case-sensitive off
9770 @itemx set case-sensitive auto
9771 Normally, when @value{GDBN} looks up symbols, it matches their names
9772 with case sensitivity determined by the current source language.
9773 Occasionally, you may wish to control that. The command @code{set
9774 case-sensitive} lets you do that by specifying @code{on} for
9775 case-sensitive matches or @code{off} for case-insensitive ones. If
9776 you specify @code{auto}, case sensitivity is reset to the default
9777 suitable for the source language. The default is case-sensitive
9778 matches for all languages except for Fortran, for which the default is
9779 case-insensitive matches.
9781 @kindex show case-sensitive
9782 @item show case-sensitive
9783 This command shows the current setting of case sensitivity for symbols
9786 @kindex info address
9787 @cindex address of a symbol
9788 @item info address @var{symbol}
9789 Describe where the data for @var{symbol} is stored. For a register
9790 variable, this says which register it is kept in. For a non-register
9791 local variable, this prints the stack-frame offset at which the variable
9794 Note the contrast with @samp{print &@var{symbol}}, which does not work
9795 at all for a register variable, and for a stack local variable prints
9796 the exact address of the current instantiation of the variable.
9799 @cindex symbol from address
9800 @cindex closest symbol and offset for an address
9801 @item info symbol @var{addr}
9802 Print the name of a symbol which is stored at the address @var{addr}.
9803 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
9804 nearest symbol and an offset from it:
9807 (@value{GDBP}) info symbol 0x54320
9808 _initialize_vx + 396 in section .text
9812 This is the opposite of the @code{info address} command. You can use
9813 it to find out the name of a variable or a function given its address.
9816 @item whatis @var{expr}
9817 Print the data type of expression @var{expr}. @var{expr} is not
9818 actually evaluated, and any side-effecting operations (such as
9819 assignments or function calls) inside it do not take place.
9820 @xref{Expressions, ,Expressions}.
9823 Print the data type of @code{$}, the last value in the value history.
9826 @item ptype @var{typename}
9827 Print a description of data type @var{typename}. @var{typename} may be
9828 the name of a type, or for C code it may have the form @samp{class
9829 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
9830 @var{union-tag}} or @samp{enum @var{enum-tag}}.
9832 @item ptype @var{expr}
9834 Print a description of the type of expression @var{expr}. @code{ptype}
9835 differs from @code{whatis} by printing a detailed description, instead
9836 of just the name of the type.
9838 For example, for this variable declaration:
9841 struct complex @{double real; double imag;@} v;
9845 the two commands give this output:
9849 (@value{GDBP}) whatis v
9850 type = struct complex
9851 (@value{GDBP}) ptype v
9852 type = struct complex @{
9860 As with @code{whatis}, using @code{ptype} without an argument refers to
9861 the type of @code{$}, the last value in the value history.
9864 @item info types @var{regexp}
9866 Print a brief description of all types whose names match the regular
9867 expression @var{regexp} (or all types in your program, if you supply
9868 no argument). Each complete typename is matched as though it were a
9869 complete line; thus, @samp{i type value} gives information on all
9870 types in your program whose names include the string @code{value}, but
9871 @samp{i type ^value$} gives information only on types whose complete
9872 name is @code{value}.
9874 This command differs from @code{ptype} in two ways: first, like
9875 @code{whatis}, it does not print a detailed description; second, it
9876 lists all source files where a type is defined.
9879 @cindex local variables
9880 @item info scope @var{location}
9881 List all the variables local to a particular scope. This command
9882 accepts a @var{location} argument---a function name, a source line, or
9883 an address preceded by a @samp{*}, and prints all the variables local
9884 to the scope defined by that location. For example:
9887 (@value{GDBP}) @b{info scope command_line_handler}
9888 Scope for command_line_handler:
9889 Symbol rl is an argument at stack/frame offset 8, length 4.
9890 Symbol linebuffer is in static storage at address 0x150a18, length 4.
9891 Symbol linelength is in static storage at address 0x150a1c, length 4.
9892 Symbol p is a local variable in register $esi, length 4.
9893 Symbol p1 is a local variable in register $ebx, length 4.
9894 Symbol nline is a local variable in register $edx, length 4.
9895 Symbol repeat is a local variable at frame offset -8, length 4.
9899 This command is especially useful for determining what data to collect
9900 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
9905 Show information about the current source file---that is, the source file for
9906 the function containing the current point of execution:
9909 the name of the source file, and the directory containing it,
9911 the directory it was compiled in,
9913 its length, in lines,
9915 which programming language it is written in,
9917 whether the executable includes debugging information for that file, and
9918 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
9920 whether the debugging information includes information about
9921 preprocessor macros.
9925 @kindex info sources
9927 Print the names of all source files in your program for which there is
9928 debugging information, organized into two lists: files whose symbols
9929 have already been read, and files whose symbols will be read when needed.
9931 @kindex info functions
9932 @item info functions
9933 Print the names and data types of all defined functions.
9935 @item info functions @var{regexp}
9936 Print the names and data types of all defined functions
9937 whose names contain a match for regular expression @var{regexp}.
9938 Thus, @samp{info fun step} finds all functions whose names
9939 include @code{step}; @samp{info fun ^step} finds those whose names
9940 start with @code{step}. If a function name contains characters
9941 that conflict with the regular expression language (eg.
9942 @samp{operator*()}), they may be quoted with a backslash.
9944 @kindex info variables
9945 @item info variables
9946 Print the names and data types of all variables that are declared
9947 outside of functions (i.e.@: excluding local variables).
9949 @item info variables @var{regexp}
9950 Print the names and data types of all variables (except for local
9951 variables) whose names contain a match for regular expression
9954 @kindex info classes
9955 @cindex Objective-C, classes and selectors
9957 @itemx info classes @var{regexp}
9958 Display all Objective-C classes in your program, or
9959 (with the @var{regexp} argument) all those matching a particular regular
9962 @kindex info selectors
9963 @item info selectors
9964 @itemx info selectors @var{regexp}
9965 Display all Objective-C selectors in your program, or
9966 (with the @var{regexp} argument) all those matching a particular regular
9970 This was never implemented.
9971 @kindex info methods
9973 @itemx info methods @var{regexp}
9974 The @code{info methods} command permits the user to examine all defined
9975 methods within C@t{++} program, or (with the @var{regexp} argument) a
9976 specific set of methods found in the various C@t{++} classes. Many
9977 C@t{++} classes provide a large number of methods. Thus, the output
9978 from the @code{ptype} command can be overwhelming and hard to use. The
9979 @code{info-methods} command filters the methods, printing only those
9980 which match the regular-expression @var{regexp}.
9983 @cindex reloading symbols
9984 Some systems allow individual object files that make up your program to
9985 be replaced without stopping and restarting your program. For example,
9986 in VxWorks you can simply recompile a defective object file and keep on
9987 running. If you are running on one of these systems, you can allow
9988 @value{GDBN} to reload the symbols for automatically relinked modules:
9991 @kindex set symbol-reloading
9992 @item set symbol-reloading on
9993 Replace symbol definitions for the corresponding source file when an
9994 object file with a particular name is seen again.
9996 @item set symbol-reloading off
9997 Do not replace symbol definitions when encountering object files of the
9998 same name more than once. This is the default state; if you are not
9999 running on a system that permits automatic relinking of modules, you
10000 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
10001 may discard symbols when linking large programs, that may contain
10002 several modules (from different directories or libraries) with the same
10005 @kindex show symbol-reloading
10006 @item show symbol-reloading
10007 Show the current @code{on} or @code{off} setting.
10010 @cindex opaque data types
10011 @kindex set opaque-type-resolution
10012 @item set opaque-type-resolution on
10013 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
10014 declared as a pointer to a @code{struct}, @code{class}, or
10015 @code{union}---for example, @code{struct MyType *}---that is used in one
10016 source file although the full declaration of @code{struct MyType} is in
10017 another source file. The default is on.
10019 A change in the setting of this subcommand will not take effect until
10020 the next time symbols for a file are loaded.
10022 @item set opaque-type-resolution off
10023 Tell @value{GDBN} not to resolve opaque types. In this case, the type
10024 is printed as follows:
10026 @{<no data fields>@}
10029 @kindex show opaque-type-resolution
10030 @item show opaque-type-resolution
10031 Show whether opaque types are resolved or not.
10033 @kindex maint print symbols
10034 @cindex symbol dump
10035 @kindex maint print psymbols
10036 @cindex partial symbol dump
10037 @item maint print symbols @var{filename}
10038 @itemx maint print psymbols @var{filename}
10039 @itemx maint print msymbols @var{filename}
10040 Write a dump of debugging symbol data into the file @var{filename}.
10041 These commands are used to debug the @value{GDBN} symbol-reading code. Only
10042 symbols with debugging data are included. If you use @samp{maint print
10043 symbols}, @value{GDBN} includes all the symbols for which it has already
10044 collected full details: that is, @var{filename} reflects symbols for
10045 only those files whose symbols @value{GDBN} has read. You can use the
10046 command @code{info sources} to find out which files these are. If you
10047 use @samp{maint print psymbols} instead, the dump shows information about
10048 symbols that @value{GDBN} only knows partially---that is, symbols defined in
10049 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
10050 @samp{maint print msymbols} dumps just the minimal symbol information
10051 required for each object file from which @value{GDBN} has read some symbols.
10052 @xref{Files, ,Commands to specify files}, for a discussion of how
10053 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
10055 @kindex maint info symtabs
10056 @kindex maint info psymtabs
10057 @cindex listing @value{GDBN}'s internal symbol tables
10058 @cindex symbol tables, listing @value{GDBN}'s internal
10059 @cindex full symbol tables, listing @value{GDBN}'s internal
10060 @cindex partial symbol tables, listing @value{GDBN}'s internal
10061 @item maint info symtabs @r{[} @var{regexp} @r{]}
10062 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
10064 List the @code{struct symtab} or @code{struct partial_symtab}
10065 structures whose names match @var{regexp}. If @var{regexp} is not
10066 given, list them all. The output includes expressions which you can
10067 copy into a @value{GDBN} debugging this one to examine a particular
10068 structure in more detail. For example:
10071 (@value{GDBP}) maint info psymtabs dwarf2read
10072 @{ objfile /home/gnu/build/gdb/gdb
10073 ((struct objfile *) 0x82e69d0)
10074 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
10075 ((struct partial_symtab *) 0x8474b10)
10078 text addresses 0x814d3c8 -- 0x8158074
10079 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
10080 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
10081 dependencies (none)
10084 (@value{GDBP}) maint info symtabs
10088 We see that there is one partial symbol table whose filename contains
10089 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
10090 and we see that @value{GDBN} has not read in any symtabs yet at all.
10091 If we set a breakpoint on a function, that will cause @value{GDBN} to
10092 read the symtab for the compilation unit containing that function:
10095 (@value{GDBP}) break dwarf2_psymtab_to_symtab
10096 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
10098 (@value{GDBP}) maint info symtabs
10099 @{ objfile /home/gnu/build/gdb/gdb
10100 ((struct objfile *) 0x82e69d0)
10101 @{ symtab /home/gnu/src/gdb/dwarf2read.c
10102 ((struct symtab *) 0x86c1f38)
10105 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
10106 debugformat DWARF 2
10115 @chapter Altering Execution
10117 Once you think you have found an error in your program, you might want to
10118 find out for certain whether correcting the apparent error would lead to
10119 correct results in the rest of the run. You can find the answer by
10120 experiment, using the @value{GDBN} features for altering execution of the
10123 For example, you can store new values into variables or memory
10124 locations, give your program a signal, restart it at a different
10125 address, or even return prematurely from a function.
10128 * Assignment:: Assignment to variables
10129 * Jumping:: Continuing at a different address
10130 * Signaling:: Giving your program a signal
10131 * Returning:: Returning from a function
10132 * Calling:: Calling your program's functions
10133 * Patching:: Patching your program
10137 @section Assignment to variables
10140 @cindex setting variables
10141 To alter the value of a variable, evaluate an assignment expression.
10142 @xref{Expressions, ,Expressions}. For example,
10149 stores the value 4 into the variable @code{x}, and then prints the
10150 value of the assignment expression (which is 4).
10151 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
10152 information on operators in supported languages.
10154 @kindex set variable
10155 @cindex variables, setting
10156 If you are not interested in seeing the value of the assignment, use the
10157 @code{set} command instead of the @code{print} command. @code{set} is
10158 really the same as @code{print} except that the expression's value is
10159 not printed and is not put in the value history (@pxref{Value History,
10160 ,Value history}). The expression is evaluated only for its effects.
10162 If the beginning of the argument string of the @code{set} command
10163 appears identical to a @code{set} subcommand, use the @code{set
10164 variable} command instead of just @code{set}. This command is identical
10165 to @code{set} except for its lack of subcommands. For example, if your
10166 program has a variable @code{width}, you get an error if you try to set
10167 a new value with just @samp{set width=13}, because @value{GDBN} has the
10168 command @code{set width}:
10171 (@value{GDBP}) whatis width
10173 (@value{GDBP}) p width
10175 (@value{GDBP}) set width=47
10176 Invalid syntax in expression.
10180 The invalid expression, of course, is @samp{=47}. In
10181 order to actually set the program's variable @code{width}, use
10184 (@value{GDBP}) set var width=47
10187 Because the @code{set} command has many subcommands that can conflict
10188 with the names of program variables, it is a good idea to use the
10189 @code{set variable} command instead of just @code{set}. For example, if
10190 your program has a variable @code{g}, you run into problems if you try
10191 to set a new value with just @samp{set g=4}, because @value{GDBN} has
10192 the command @code{set gnutarget}, abbreviated @code{set g}:
10196 (@value{GDBP}) whatis g
10200 (@value{GDBP}) set g=4
10204 The program being debugged has been started already.
10205 Start it from the beginning? (y or n) y
10206 Starting program: /home/smith/cc_progs/a.out
10207 "/home/smith/cc_progs/a.out": can't open to read symbols:
10208 Invalid bfd target.
10209 (@value{GDBP}) show g
10210 The current BFD target is "=4".
10215 The program variable @code{g} did not change, and you silently set the
10216 @code{gnutarget} to an invalid value. In order to set the variable
10220 (@value{GDBP}) set var g=4
10223 @value{GDBN} allows more implicit conversions in assignments than C; you can
10224 freely store an integer value into a pointer variable or vice versa,
10225 and you can convert any structure to any other structure that is the
10226 same length or shorter.
10227 @comment FIXME: how do structs align/pad in these conversions?
10228 @comment /doc@cygnus.com 18dec1990
10230 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
10231 construct to generate a value of specified type at a specified address
10232 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
10233 to memory location @code{0x83040} as an integer (which implies a certain size
10234 and representation in memory), and
10237 set @{int@}0x83040 = 4
10241 stores the value 4 into that memory location.
10244 @section Continuing at a different address
10246 Ordinarily, when you continue your program, you do so at the place where
10247 it stopped, with the @code{continue} command. You can instead continue at
10248 an address of your own choosing, with the following commands:
10252 @item jump @var{linespec}
10253 Resume execution at line @var{linespec}. Execution stops again
10254 immediately if there is a breakpoint there. @xref{List, ,Printing
10255 source lines}, for a description of the different forms of
10256 @var{linespec}. It is common practice to use the @code{tbreak} command
10257 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
10260 The @code{jump} command does not change the current stack frame, or
10261 the stack pointer, or the contents of any memory location or any
10262 register other than the program counter. If line @var{linespec} is in
10263 a different function from the one currently executing, the results may
10264 be bizarre if the two functions expect different patterns of arguments or
10265 of local variables. For this reason, the @code{jump} command requests
10266 confirmation if the specified line is not in the function currently
10267 executing. However, even bizarre results are predictable if you are
10268 well acquainted with the machine-language code of your program.
10270 @item jump *@var{address}
10271 Resume execution at the instruction at address @var{address}.
10274 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
10275 On many systems, you can get much the same effect as the @code{jump}
10276 command by storing a new value into the register @code{$pc}. The
10277 difference is that this does not start your program running; it only
10278 changes the address of where it @emph{will} run when you continue. For
10286 makes the next @code{continue} command or stepping command execute at
10287 address @code{0x485}, rather than at the address where your program stopped.
10288 @xref{Continuing and Stepping, ,Continuing and stepping}.
10290 The most common occasion to use the @code{jump} command is to back
10291 up---perhaps with more breakpoints set---over a portion of a program
10292 that has already executed, in order to examine its execution in more
10297 @section Giving your program a signal
10298 @cindex deliver a signal to a program
10302 @item signal @var{signal}
10303 Resume execution where your program stopped, but immediately give it the
10304 signal @var{signal}. @var{signal} can be the name or the number of a
10305 signal. For example, on many systems @code{signal 2} and @code{signal
10306 SIGINT} are both ways of sending an interrupt signal.
10308 Alternatively, if @var{signal} is zero, continue execution without
10309 giving a signal. This is useful when your program stopped on account of
10310 a signal and would ordinary see the signal when resumed with the
10311 @code{continue} command; @samp{signal 0} causes it to resume without a
10314 @code{signal} does not repeat when you press @key{RET} a second time
10315 after executing the command.
10319 Invoking the @code{signal} command is not the same as invoking the
10320 @code{kill} utility from the shell. Sending a signal with @code{kill}
10321 causes @value{GDBN} to decide what to do with the signal depending on
10322 the signal handling tables (@pxref{Signals}). The @code{signal} command
10323 passes the signal directly to your program.
10327 @section Returning from a function
10330 @cindex returning from a function
10333 @itemx return @var{expression}
10334 You can cancel execution of a function call with the @code{return}
10335 command. If you give an
10336 @var{expression} argument, its value is used as the function's return
10340 When you use @code{return}, @value{GDBN} discards the selected stack frame
10341 (and all frames within it). You can think of this as making the
10342 discarded frame return prematurely. If you wish to specify a value to
10343 be returned, give that value as the argument to @code{return}.
10345 This pops the selected stack frame (@pxref{Selection, ,Selecting a
10346 frame}), and any other frames inside of it, leaving its caller as the
10347 innermost remaining frame. That frame becomes selected. The
10348 specified value is stored in the registers used for returning values
10351 The @code{return} command does not resume execution; it leaves the
10352 program stopped in the state that would exist if the function had just
10353 returned. In contrast, the @code{finish} command (@pxref{Continuing
10354 and Stepping, ,Continuing and stepping}) resumes execution until the
10355 selected stack frame returns naturally.
10358 @section Calling program functions
10361 @cindex calling functions
10362 @cindex inferior functions, calling
10363 @item print @var{expr}
10364 Evaluate the expression @var{expr} and display the resuling value.
10365 @var{expr} may include calls to functions in the program being
10369 @item call @var{expr}
10370 Evaluate the expression @var{expr} without displaying @code{void}
10373 You can use this variant of the @code{print} command if you want to
10374 execute a function from your program that does not return anything
10375 (a.k.a.@: @dfn{a void function}), but without cluttering the output
10376 with @code{void} returned values that @value{GDBN} will otherwise
10377 print. If the result is not void, it is printed and saved in the
10381 It is possible for the function you call via the @code{print} or
10382 @code{call} command to generate a signal (e.g., if there's a bug in
10383 the function, or if you passed it incorrect arguments). What happens
10384 in that case is controlled by the @code{set unwindonsignal} command.
10387 @item set unwindonsignal
10388 @kindex set unwindonsignal
10389 @cindex unwind stack in called functions
10390 @cindex call dummy stack unwinding
10391 Set unwinding of the stack if a signal is received while in a function
10392 that @value{GDBN} called in the program being debugged. If set to on,
10393 @value{GDBN} unwinds the stack it created for the call and restores
10394 the context to what it was before the call. If set to off (the
10395 default), @value{GDBN} stops in the frame where the signal was
10398 @item show unwindonsignal
10399 @kindex show unwindonsignal
10400 Show the current setting of stack unwinding in the functions called by
10404 @cindex weak alias functions
10405 Sometimes, a function you wish to call is actually a @dfn{weak alias}
10406 for another function. In such case, @value{GDBN} might not pick up
10407 the type information, including the types of the function arguments,
10408 which causes @value{GDBN} to call the inferior function incorrectly.
10409 As a result, the called function will function erroneously and may
10410 even crash. A solution to that is to use the name of the aliased
10414 @section Patching programs
10416 @cindex patching binaries
10417 @cindex writing into executables
10418 @cindex writing into corefiles
10420 By default, @value{GDBN} opens the file containing your program's
10421 executable code (or the corefile) read-only. This prevents accidental
10422 alterations to machine code; but it also prevents you from intentionally
10423 patching your program's binary.
10425 If you'd like to be able to patch the binary, you can specify that
10426 explicitly with the @code{set write} command. For example, you might
10427 want to turn on internal debugging flags, or even to make emergency
10433 @itemx set write off
10434 If you specify @samp{set write on}, @value{GDBN} opens executable and
10435 core files for both reading and writing; if you specify @samp{set write
10436 off} (the default), @value{GDBN} opens them read-only.
10438 If you have already loaded a file, you must load it again (using the
10439 @code{exec-file} or @code{core-file} command) after changing @code{set
10440 write}, for your new setting to take effect.
10444 Display whether executable files and core files are opened for writing
10445 as well as reading.
10449 @chapter @value{GDBN} Files
10451 @value{GDBN} needs to know the file name of the program to be debugged,
10452 both in order to read its symbol table and in order to start your
10453 program. To debug a core dump of a previous run, you must also tell
10454 @value{GDBN} the name of the core dump file.
10457 * Files:: Commands to specify files
10458 * Separate Debug Files:: Debugging information in separate files
10459 * Symbol Errors:: Errors reading symbol files
10463 @section Commands to specify files
10465 @cindex symbol table
10466 @cindex core dump file
10468 You may want to specify executable and core dump file names. The usual
10469 way to do this is at start-up time, using the arguments to
10470 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
10471 Out of @value{GDBN}}).
10473 Occasionally it is necessary to change to a different file during a
10474 @value{GDBN} session. Or you may run @value{GDBN} and forget to specify
10475 a file you want to use. In these situations the @value{GDBN} commands
10476 to specify new files are useful.
10479 @cindex executable file
10481 @item file @var{filename}
10482 Use @var{filename} as the program to be debugged. It is read for its
10483 symbols and for the contents of pure memory. It is also the program
10484 executed when you use the @code{run} command. If you do not specify a
10485 directory and the file is not found in the @value{GDBN} working directory,
10486 @value{GDBN} uses the environment variable @code{PATH} as a list of
10487 directories to search, just as the shell does when looking for a program
10488 to run. You can change the value of this variable, for both @value{GDBN}
10489 and your program, using the @code{path} command.
10491 On systems with memory-mapped files, an auxiliary file named
10492 @file{@var{filename}.syms} may hold symbol table information for
10493 @var{filename}. If so, @value{GDBN} maps in the symbol table from
10494 @file{@var{filename}.syms}, starting up more quickly. See the
10495 descriptions of the file options @samp{-mapped} and @samp{-readnow}
10496 (available on the command line, see @ref{File Options, , -readnow},
10497 and with the commands @code{file}, @code{symbol-file}, or
10498 @code{add-symbol-file}, described below), for more information.
10501 @code{file} with no argument makes @value{GDBN} discard any information it
10502 has on both executable file and the symbol table.
10505 @item exec-file @r{[} @var{filename} @r{]}
10506 Specify that the program to be run (but not the symbol table) is found
10507 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
10508 if necessary to locate your program. Omitting @var{filename} means to
10509 discard information on the executable file.
10511 @kindex symbol-file
10512 @item symbol-file @r{[} @var{filename} @r{]}
10513 Read symbol table information from file @var{filename}. @code{PATH} is
10514 searched when necessary. Use the @code{file} command to get both symbol
10515 table and program to run from the same file.
10517 @code{symbol-file} with no argument clears out @value{GDBN} information on your
10518 program's symbol table.
10520 The @code{symbol-file} command causes @value{GDBN} to forget the contents
10521 of its convenience variables, the value history, and all breakpoints and
10522 auto-display expressions. This is because they may contain pointers to
10523 the internal data recording symbols and data types, which are part of
10524 the old symbol table data being discarded inside @value{GDBN}.
10526 @code{symbol-file} does not repeat if you press @key{RET} again after
10529 When @value{GDBN} is configured for a particular environment, it
10530 understands debugging information in whatever format is the standard
10531 generated for that environment; you may use either a @sc{gnu} compiler, or
10532 other compilers that adhere to the local conventions.
10533 Best results are usually obtained from @sc{gnu} compilers; for example,
10534 using @code{@value{GCC}} you can generate debugging information for
10537 For most kinds of object files, with the exception of old SVR3 systems
10538 using COFF, the @code{symbol-file} command does not normally read the
10539 symbol table in full right away. Instead, it scans the symbol table
10540 quickly to find which source files and which symbols are present. The
10541 details are read later, one source file at a time, as they are needed.
10543 The purpose of this two-stage reading strategy is to make @value{GDBN}
10544 start up faster. For the most part, it is invisible except for
10545 occasional pauses while the symbol table details for a particular source
10546 file are being read. (The @code{set verbose} command can turn these
10547 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
10548 warnings and messages}.)
10550 We have not implemented the two-stage strategy for COFF yet. When the
10551 symbol table is stored in COFF format, @code{symbol-file} reads the
10552 symbol table data in full right away. Note that ``stabs-in-COFF''
10553 still does the two-stage strategy, since the debug info is actually
10557 @cindex reading symbols immediately
10558 @cindex symbols, reading immediately
10560 @cindex memory-mapped symbol file
10561 @cindex saving symbol table
10562 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10563 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10564 You can override the @value{GDBN} two-stage strategy for reading symbol
10565 tables by using the @samp{-readnow} option with any of the commands that
10566 load symbol table information, if you want to be sure @value{GDBN} has the
10567 entire symbol table available.
10569 If memory-mapped files are available on your system through the
10570 @code{mmap} system call, you can use another option, @samp{-mapped}, to
10571 cause @value{GDBN} to write the symbols for your program into a reusable
10572 file. Future @value{GDBN} debugging sessions map in symbol information
10573 from this auxiliary symbol file (if the program has not changed), rather
10574 than spending time reading the symbol table from the executable
10575 program. Using the @samp{-mapped} option has the same effect as
10576 starting @value{GDBN} with the @samp{-mapped} command-line option.
10578 You can use both options together, to make sure the auxiliary symbol
10579 file has all the symbol information for your program.
10581 The auxiliary symbol file for a program called @var{myprog} is called
10582 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
10583 than the corresponding executable), @value{GDBN} always attempts to use
10584 it when you debug @var{myprog}; no special options or commands are
10587 The @file{.syms} file is specific to the host machine where you run
10588 @value{GDBN}. It holds an exact image of the internal @value{GDBN}
10589 symbol table. It cannot be shared across multiple host platforms.
10591 @c FIXME: for now no mention of directories, since this seems to be in
10592 @c flux. 13mar1992 status is that in theory GDB would look either in
10593 @c current dir or in same dir as myprog; but issues like competing
10594 @c GDB's, or clutter in system dirs, mean that in practice right now
10595 @c only current dir is used. FFish says maybe a special GDB hierarchy
10596 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
10600 @item core-file @r{[}@var{filename}@r{]}
10602 Specify the whereabouts of a core dump file to be used as the ``contents
10603 of memory''. Traditionally, core files contain only some parts of the
10604 address space of the process that generated them; @value{GDBN} can access the
10605 executable file itself for other parts.
10607 @code{core-file} with no argument specifies that no core file is
10610 Note that the core file is ignored when your program is actually running
10611 under @value{GDBN}. So, if you have been running your program and you
10612 wish to debug a core file instead, you must kill the subprocess in which
10613 the program is running. To do this, use the @code{kill} command
10614 (@pxref{Kill Process, ,Killing the child process}).
10616 @kindex add-symbol-file
10617 @cindex dynamic linking
10618 @item add-symbol-file @var{filename} @var{address}
10619 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10620 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
10621 The @code{add-symbol-file} command reads additional symbol table
10622 information from the file @var{filename}. You would use this command
10623 when @var{filename} has been dynamically loaded (by some other means)
10624 into the program that is running. @var{address} should be the memory
10625 address at which the file has been loaded; @value{GDBN} cannot figure
10626 this out for itself. You can additionally specify an arbitrary number
10627 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
10628 section name and base address for that section. You can specify any
10629 @var{address} as an expression.
10631 The symbol table of the file @var{filename} is added to the symbol table
10632 originally read with the @code{symbol-file} command. You can use the
10633 @code{add-symbol-file} command any number of times; the new symbol data
10634 thus read keeps adding to the old. To discard all old symbol data
10635 instead, use the @code{symbol-file} command without any arguments.
10637 @cindex relocatable object files, reading symbols from
10638 @cindex object files, relocatable, reading symbols from
10639 @cindex reading symbols from relocatable object files
10640 @cindex symbols, reading from relocatable object files
10641 @cindex @file{.o} files, reading symbols from
10642 Although @var{filename} is typically a shared library file, an
10643 executable file, or some other object file which has been fully
10644 relocated for loading into a process, you can also load symbolic
10645 information from relocatable @file{.o} files, as long as:
10649 the file's symbolic information refers only to linker symbols defined in
10650 that file, not to symbols defined by other object files,
10652 every section the file's symbolic information refers to has actually
10653 been loaded into the inferior, as it appears in the file, and
10655 you can determine the address at which every section was loaded, and
10656 provide these to the @code{add-symbol-file} command.
10660 Some embedded operating systems, like Sun Chorus and VxWorks, can load
10661 relocatable files into an already running program; such systems
10662 typically make the requirements above easy to meet. However, it's
10663 important to recognize that many native systems use complex link
10664 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
10665 assembly, for example) that make the requirements difficult to meet. In
10666 general, one cannot assume that using @code{add-symbol-file} to read a
10667 relocatable object file's symbolic information will have the same effect
10668 as linking the relocatable object file into the program in the normal
10671 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
10673 You can use the @samp{-mapped} and @samp{-readnow} options just as with
10674 the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
10675 table information for @var{filename}.
10677 @kindex add-shared-symbol-files
10679 @item add-shared-symbol-files @var{library-file}
10680 @itemx assf @var{library-file}
10681 The @code{add-shared-symbol-files} command can currently be used only
10682 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
10683 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
10684 @value{GDBN} automatically looks for shared libraries, however if
10685 @value{GDBN} does not find yours, you can invoke
10686 @code{add-shared-symbol-files}. It takes one argument: the shared
10687 library's file name. @code{assf} is a shorthand alias for
10688 @code{add-shared-symbol-files}.
10691 @item section @var{section} @var{addr}
10692 The @code{section} command changes the base address of the named
10693 @var{section} of the exec file to @var{addr}. This can be used if the
10694 exec file does not contain section addresses, (such as in the
10695 @code{a.out} format), or when the addresses specified in the file
10696 itself are wrong. Each section must be changed separately. The
10697 @code{info files} command, described below, lists all the sections and
10701 @kindex info target
10704 @code{info files} and @code{info target} are synonymous; both print the
10705 current target (@pxref{Targets, ,Specifying a Debugging Target}),
10706 including the names of the executable and core dump files currently in
10707 use by @value{GDBN}, and the files from which symbols were loaded. The
10708 command @code{help target} lists all possible targets rather than
10711 @kindex maint info sections
10712 @item maint info sections
10713 Another command that can give you extra information about program sections
10714 is @code{maint info sections}. In addition to the section information
10715 displayed by @code{info files}, this command displays the flags and file
10716 offset of each section in the executable and core dump files. In addition,
10717 @code{maint info sections} provides the following command options (which
10718 may be arbitrarily combined):
10722 Display sections for all loaded object files, including shared libraries.
10723 @item @var{sections}
10724 Display info only for named @var{sections}.
10725 @item @var{section-flags}
10726 Display info only for sections for which @var{section-flags} are true.
10727 The section flags that @value{GDBN} currently knows about are:
10730 Section will have space allocated in the process when loaded.
10731 Set for all sections except those containing debug information.
10733 Section will be loaded from the file into the child process memory.
10734 Set for pre-initialized code and data, clear for @code{.bss} sections.
10736 Section needs to be relocated before loading.
10738 Section cannot be modified by the child process.
10740 Section contains executable code only.
10742 Section contains data only (no executable code).
10744 Section will reside in ROM.
10746 Section contains data for constructor/destructor lists.
10748 Section is not empty.
10750 An instruction to the linker to not output the section.
10751 @item COFF_SHARED_LIBRARY
10752 A notification to the linker that the section contains
10753 COFF shared library information.
10755 Section contains common symbols.
10758 @kindex set trust-readonly-sections
10759 @cindex read-only sections
10760 @item set trust-readonly-sections on
10761 Tell @value{GDBN} that readonly sections in your object file
10762 really are read-only (i.e.@: that their contents will not change).
10763 In that case, @value{GDBN} can fetch values from these sections
10764 out of the object file, rather than from the target program.
10765 For some targets (notably embedded ones), this can be a significant
10766 enhancement to debugging performance.
10768 The default is off.
10770 @item set trust-readonly-sections off
10771 Tell @value{GDBN} not to trust readonly sections. This means that
10772 the contents of the section might change while the program is running,
10773 and must therefore be fetched from the target when needed.
10775 @item show trust-readonly-sections
10776 Show the current setting of trusting readonly sections.
10779 All file-specifying commands allow both absolute and relative file names
10780 as arguments. @value{GDBN} always converts the file name to an absolute file
10781 name and remembers it that way.
10783 @cindex shared libraries
10784 @value{GDBN} supports GNU/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
10785 and IBM RS/6000 AIX shared libraries.
10787 @value{GDBN} automatically loads symbol definitions from shared libraries
10788 when you use the @code{run} command, or when you examine a core file.
10789 (Before you issue the @code{run} command, @value{GDBN} does not understand
10790 references to a function in a shared library, however---unless you are
10791 debugging a core file).
10793 On HP-UX, if the program loads a library explicitly, @value{GDBN}
10794 automatically loads the symbols at the time of the @code{shl_load} call.
10796 @c FIXME: some @value{GDBN} release may permit some refs to undef
10797 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
10798 @c FIXME...lib; check this from time to time when updating manual
10800 There are times, however, when you may wish to not automatically load
10801 symbol definitions from shared libraries, such as when they are
10802 particularly large or there are many of them.
10804 To control the automatic loading of shared library symbols, use the
10808 @kindex set auto-solib-add
10809 @item set auto-solib-add @var{mode}
10810 If @var{mode} is @code{on}, symbols from all shared object libraries
10811 will be loaded automatically when the inferior begins execution, you
10812 attach to an independently started inferior, or when the dynamic linker
10813 informs @value{GDBN} that a new library has been loaded. If @var{mode}
10814 is @code{off}, symbols must be loaded manually, using the
10815 @code{sharedlibrary} command. The default value is @code{on}.
10817 @cindex memory used for symbol tables
10818 If your program uses lots of shared libraries with debug info that
10819 takes large amounts of memory, you can decrease the @value{GDBN}
10820 memory footprint by preventing it from automatically loading the
10821 symbols from shared libraries. To that end, type @kbd{set
10822 auto-solib-add off} before running the inferior, then load each
10823 library whose debug symbols you do need with @kbd{sharedlibrary
10824 @var{regexp}}, where @var{regexp} is a regular expresion that matches
10825 the libraries whose symbols you want to be loaded.
10827 @kindex show auto-solib-add
10828 @item show auto-solib-add
10829 Display the current autoloading mode.
10832 To explicitly load shared library symbols, use the @code{sharedlibrary}
10836 @kindex info sharedlibrary
10839 @itemx info sharedlibrary
10840 Print the names of the shared libraries which are currently loaded.
10842 @kindex sharedlibrary
10844 @item sharedlibrary @var{regex}
10845 @itemx share @var{regex}
10846 Load shared object library symbols for files matching a
10847 Unix regular expression.
10848 As with files loaded automatically, it only loads shared libraries
10849 required by your program for a core file or after typing @code{run}. If
10850 @var{regex} is omitted all shared libraries required by your program are
10854 On some systems, such as HP-UX systems, @value{GDBN} supports
10855 autoloading shared library symbols until a limiting threshold size is
10856 reached. This provides the benefit of allowing autoloading to remain on
10857 by default, but avoids autoloading excessively large shared libraries,
10858 up to a threshold that is initially set, but which you can modify if you
10861 Beyond that threshold, symbols from shared libraries must be explicitly
10862 loaded. To load these symbols, use the command @code{sharedlibrary
10863 @var{filename}}. The base address of the shared library is determined
10864 automatically by @value{GDBN} and need not be specified.
10866 To display or set the threshold, use the commands:
10869 @kindex set auto-solib-limit
10870 @item set auto-solib-limit @var{threshold}
10871 Set the autoloading size threshold, in an integral number of megabytes.
10872 If @var{threshold} is nonzero and shared library autoloading is enabled,
10873 symbols from all shared object libraries will be loaded until the total
10874 size of the loaded shared library symbols exceeds this threshold.
10875 Otherwise, symbols must be loaded manually, using the
10876 @code{sharedlibrary} command. The default threshold is 100 (i.e.@: 100
10879 @kindex show auto-solib-limit
10880 @item show auto-solib-limit
10881 Display the current autoloading size threshold, in megabytes.
10884 Sometimes you may wish that @value{GDBN} stops and gives you control
10885 when any of shared library events happen. Use the @code{set
10886 stop-on-solib-events} command for this:
10889 @item set stop-on-solib-events
10890 @kindex set stop-on-solib-events
10891 This command controls whether @value{GDBN} should give you control
10892 when the dynamic linker notifies it about some shared library event.
10893 The most common event of interest is loading or unloading of a new
10896 @item show stop-on-solib-events
10897 @kindex show stop-on-solib-events
10898 Show whether @value{GDBN} stops and gives you control when shared
10899 library events happen.
10902 Shared libraries are also supported in many cross or remote debugging
10903 configurations. A copy of the target's libraries need to be present on the
10904 host system; they need to be the same as the target libraries, although the
10905 copies on the target can be stripped as long as the copies on the host are
10908 You need to tell @value{GDBN} where the target libraries are, so that it can
10909 load the correct copies---otherwise, it may try to load the host's libraries.
10910 @value{GDBN} has two variables to specify the search directories for target
10914 @kindex set solib-absolute-prefix
10915 @item set solib-absolute-prefix @var{path}
10916 If this variable is set, @var{path} will be used as a prefix for any
10917 absolute shared library paths; many runtime loaders store the absolute
10918 paths to the shared library in the target program's memory. If you use
10919 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
10920 out in the same way that they are on the target, with e.g.@: a
10921 @file{/usr/lib} hierarchy under @var{path}.
10923 You can set the default value of @samp{solib-absolute-prefix} by using the
10924 configure-time @samp{--with-sysroot} option.
10926 @kindex show solib-absolute-prefix
10927 @item show solib-absolute-prefix
10928 Display the current shared library prefix.
10930 @kindex set solib-search-path
10931 @item set solib-search-path @var{path}
10932 If this variable is set, @var{path} is a colon-separated list of directories
10933 to search for shared libraries. @samp{solib-search-path} is used after
10934 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
10935 the library is relative instead of absolute. If you want to use
10936 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
10937 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
10938 @value{GDBN} from finding your host's libraries.
10940 @kindex show solib-search-path
10941 @item show solib-search-path
10942 Display the current shared library search path.
10946 @node Separate Debug Files
10947 @section Debugging Information in Separate Files
10948 @cindex separate debugging information files
10949 @cindex debugging information in separate files
10950 @cindex @file{.debug} subdirectories
10951 @cindex debugging information directory, global
10952 @cindex global debugging information directory
10954 @value{GDBN} allows you to put a program's debugging information in a
10955 file separate from the executable itself, in a way that allows
10956 @value{GDBN} to find and load the debugging information automatically.
10957 Since debugging information can be very large --- sometimes larger
10958 than the executable code itself --- some systems distribute debugging
10959 information for their executables in separate files, which users can
10960 install only when they need to debug a problem.
10962 If an executable's debugging information has been extracted to a
10963 separate file, the executable should contain a @dfn{debug link} giving
10964 the name of the debugging information file (with no directory
10965 components), and a checksum of its contents. (The exact form of a
10966 debug link is described below.) If the full name of the directory
10967 containing the executable is @var{execdir}, and the executable has a
10968 debug link that specifies the name @var{debugfile}, then @value{GDBN}
10969 will automatically search for the debugging information file in three
10974 the directory containing the executable file (that is, it will look
10975 for a file named @file{@var{execdir}/@var{debugfile}},
10977 a subdirectory of that directory named @file{.debug} (that is, the
10978 file @file{@var{execdir}/.debug/@var{debugfile}}, and
10980 a subdirectory of the global debug file directory that includes the
10981 executable's full path, and the name from the link (that is, the file
10982 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
10983 @var{globaldebugdir} is the global debug file directory, and
10984 @var{execdir} has been turned into a relative path).
10987 @value{GDBN} checks under each of these names for a debugging
10988 information file whose checksum matches that given in the link, and
10989 reads the debugging information from the first one it finds.
10991 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
10992 which has a link containing the name @file{ls.debug}, and the global
10993 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
10994 for debug information in @file{/usr/bin/ls.debug},
10995 @file{/usr/bin/.debug/ls.debug}, and
10996 @file{/usr/lib/debug/usr/bin/ls.debug}.
10998 You can set the global debugging info directory's name, and view the
10999 name @value{GDBN} is currently using.
11003 @kindex set debug-file-directory
11004 @item set debug-file-directory @var{directory}
11005 Set the directory which @value{GDBN} searches for separate debugging
11006 information files to @var{directory}.
11008 @kindex show debug-file-directory
11009 @item show debug-file-directory
11010 Show the directory @value{GDBN} searches for separate debugging
11015 @cindex @code{.gnu_debuglink} sections
11016 @cindex debug links
11017 A debug link is a special section of the executable file named
11018 @code{.gnu_debuglink}. The section must contain:
11022 A filename, with any leading directory components removed, followed by
11025 zero to three bytes of padding, as needed to reach the next four-byte
11026 boundary within the section, and
11028 a four-byte CRC checksum, stored in the same endianness used for the
11029 executable file itself. The checksum is computed on the debugging
11030 information file's full contents by the function given below, passing
11031 zero as the @var{crc} argument.
11034 Any executable file format can carry a debug link, as long as it can
11035 contain a section named @code{.gnu_debuglink} with the contents
11038 The debugging information file itself should be an ordinary
11039 executable, containing a full set of linker symbols, sections, and
11040 debugging information. The sections of the debugging information file
11041 should have the same names, addresses and sizes as the original file,
11042 but they need not contain any data --- much like a @code{.bss} section
11043 in an ordinary executable.
11045 As of December 2002, there is no standard GNU utility to produce
11046 separated executable / debugging information file pairs. Ulrich
11047 Drepper's @file{elfutils} package, starting with version 0.53,
11048 contains a version of the @code{strip} command such that the command
11049 @kbd{strip foo -f foo.debug} removes the debugging information from
11050 the executable file @file{foo}, places it in the file
11051 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
11053 Since there are many different ways to compute CRC's (different
11054 polynomials, reversals, byte ordering, etc.), the simplest way to
11055 describe the CRC used in @code{.gnu_debuglink} sections is to give the
11056 complete code for a function that computes it:
11058 @kindex gnu_debuglink_crc32
11061 gnu_debuglink_crc32 (unsigned long crc,
11062 unsigned char *buf, size_t len)
11064 static const unsigned long crc32_table[256] =
11066 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
11067 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
11068 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
11069 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
11070 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
11071 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
11072 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
11073 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
11074 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
11075 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
11076 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
11077 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
11078 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
11079 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
11080 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
11081 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
11082 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
11083 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
11084 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
11085 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
11086 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
11087 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
11088 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
11089 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
11090 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
11091 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
11092 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
11093 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
11094 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
11095 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
11096 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
11097 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
11098 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
11099 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
11100 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
11101 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
11102 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
11103 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
11104 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
11105 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
11106 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
11107 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
11108 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
11109 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
11110 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
11111 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
11112 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
11113 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
11114 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
11115 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
11116 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
11119 unsigned char *end;
11121 crc = ~crc & 0xffffffff;
11122 for (end = buf + len; buf < end; ++buf)
11123 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
11124 return ~crc & 0xffffffff;
11129 @node Symbol Errors
11130 @section Errors reading symbol files
11132 While reading a symbol file, @value{GDBN} occasionally encounters problems,
11133 such as symbol types it does not recognize, or known bugs in compiler
11134 output. By default, @value{GDBN} does not notify you of such problems, since
11135 they are relatively common and primarily of interest to people
11136 debugging compilers. If you are interested in seeing information
11137 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
11138 only one message about each such type of problem, no matter how many
11139 times the problem occurs; or you can ask @value{GDBN} to print more messages,
11140 to see how many times the problems occur, with the @code{set
11141 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
11144 The messages currently printed, and their meanings, include:
11147 @item inner block not inside outer block in @var{symbol}
11149 The symbol information shows where symbol scopes begin and end
11150 (such as at the start of a function or a block of statements). This
11151 error indicates that an inner scope block is not fully contained
11152 in its outer scope blocks.
11154 @value{GDBN} circumvents the problem by treating the inner block as if it had
11155 the same scope as the outer block. In the error message, @var{symbol}
11156 may be shown as ``@code{(don't know)}'' if the outer block is not a
11159 @item block at @var{address} out of order
11161 The symbol information for symbol scope blocks should occur in
11162 order of increasing addresses. This error indicates that it does not
11165 @value{GDBN} does not circumvent this problem, and has trouble
11166 locating symbols in the source file whose symbols it is reading. (You
11167 can often determine what source file is affected by specifying
11168 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
11171 @item bad block start address patched
11173 The symbol information for a symbol scope block has a start address
11174 smaller than the address of the preceding source line. This is known
11175 to occur in the SunOS 4.1.1 (and earlier) C compiler.
11177 @value{GDBN} circumvents the problem by treating the symbol scope block as
11178 starting on the previous source line.
11180 @item bad string table offset in symbol @var{n}
11183 Symbol number @var{n} contains a pointer into the string table which is
11184 larger than the size of the string table.
11186 @value{GDBN} circumvents the problem by considering the symbol to have the
11187 name @code{foo}, which may cause other problems if many symbols end up
11190 @item unknown symbol type @code{0x@var{nn}}
11192 The symbol information contains new data types that @value{GDBN} does
11193 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
11194 uncomprehended information, in hexadecimal.
11196 @value{GDBN} circumvents the error by ignoring this symbol information.
11197 This usually allows you to debug your program, though certain symbols
11198 are not accessible. If you encounter such a problem and feel like
11199 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
11200 on @code{complain}, then go up to the function @code{read_dbx_symtab}
11201 and examine @code{*bufp} to see the symbol.
11203 @item stub type has NULL name
11205 @value{GDBN} could not find the full definition for a struct or class.
11207 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
11208 The symbol information for a C@t{++} member function is missing some
11209 information that recent versions of the compiler should have output for
11212 @item info mismatch between compiler and debugger
11214 @value{GDBN} could not parse a type specification output by the compiler.
11219 @chapter Specifying a Debugging Target
11221 @cindex debugging target
11222 A @dfn{target} is the execution environment occupied by your program.
11224 Often, @value{GDBN} runs in the same host environment as your program;
11225 in that case, the debugging target is specified as a side effect when
11226 you use the @code{file} or @code{core} commands. When you need more
11227 flexibility---for example, running @value{GDBN} on a physically separate
11228 host, or controlling a standalone system over a serial port or a
11229 realtime system over a TCP/IP connection---you can use the @code{target}
11230 command to specify one of the target types configured for @value{GDBN}
11231 (@pxref{Target Commands, ,Commands for managing targets}).
11233 @cindex target architecture
11234 It is possible to build @value{GDBN} for several different @dfn{target
11235 architectures}. When @value{GDBN} is built like that, you can choose
11236 one of the available architectures with the @kbd{set architecture}
11240 @kindex set architecture
11241 @kindex show architecture
11242 @item set architecture @var{arch}
11243 This command sets the current target architecture to @var{arch}. The
11244 value of @var{arch} can be @code{"auto"}, in addition to one of the
11245 supported architectures.
11247 @item show architecture
11248 Show the current target architecture.
11250 @item set processor
11252 @kindex set processor
11253 @kindex show processor
11254 These are alias commands for, respectively, @code{set architecture}
11255 and @code{show architecture}.
11259 * Active Targets:: Active targets
11260 * Target Commands:: Commands for managing targets
11261 * Byte Order:: Choosing target byte order
11262 * Remote:: Remote debugging
11263 * KOD:: Kernel Object Display
11267 @node Active Targets
11268 @section Active targets
11270 @cindex stacking targets
11271 @cindex active targets
11272 @cindex multiple targets
11274 There are three classes of targets: processes, core files, and
11275 executable files. @value{GDBN} can work concurrently on up to three
11276 active targets, one in each class. This allows you to (for example)
11277 start a process and inspect its activity without abandoning your work on
11280 For example, if you execute @samp{gdb a.out}, then the executable file
11281 @code{a.out} is the only active target. If you designate a core file as
11282 well---presumably from a prior run that crashed and coredumped---then
11283 @value{GDBN} has two active targets and uses them in tandem, looking
11284 first in the corefile target, then in the executable file, to satisfy
11285 requests for memory addresses. (Typically, these two classes of target
11286 are complementary, since core files contain only a program's
11287 read-write memory---variables and so on---plus machine status, while
11288 executable files contain only the program text and initialized data.)
11290 When you type @code{run}, your executable file becomes an active process
11291 target as well. When a process target is active, all @value{GDBN}
11292 commands requesting memory addresses refer to that target; addresses in
11293 an active core file or executable file target are obscured while the
11294 process target is active.
11296 Use the @code{core-file} and @code{exec-file} commands to select a new
11297 core file or executable target (@pxref{Files, ,Commands to specify
11298 files}). To specify as a target a process that is already running, use
11299 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
11302 @node Target Commands
11303 @section Commands for managing targets
11306 @item target @var{type} @var{parameters}
11307 Connects the @value{GDBN} host environment to a target machine or
11308 process. A target is typically a protocol for talking to debugging
11309 facilities. You use the argument @var{type} to specify the type or
11310 protocol of the target machine.
11312 Further @var{parameters} are interpreted by the target protocol, but
11313 typically include things like device names or host names to connect
11314 with, process numbers, and baud rates.
11316 The @code{target} command does not repeat if you press @key{RET} again
11317 after executing the command.
11319 @kindex help target
11321 Displays the names of all targets available. To display targets
11322 currently selected, use either @code{info target} or @code{info files}
11323 (@pxref{Files, ,Commands to specify files}).
11325 @item help target @var{name}
11326 Describe a particular target, including any parameters necessary to
11329 @kindex set gnutarget
11330 @item set gnutarget @var{args}
11331 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
11332 knows whether it is reading an @dfn{executable},
11333 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
11334 with the @code{set gnutarget} command. Unlike most @code{target} commands,
11335 with @code{gnutarget} the @code{target} refers to a program, not a machine.
11338 @emph{Warning:} To specify a file format with @code{set gnutarget},
11339 you must know the actual BFD name.
11343 @xref{Files, , Commands to specify files}.
11345 @kindex show gnutarget
11346 @item show gnutarget
11347 Use the @code{show gnutarget} command to display what file format
11348 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
11349 @value{GDBN} will determine the file format for each file automatically,
11350 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
11353 @cindex common targets
11354 Here are some common targets (available, or not, depending on the GDB
11359 @item target exec @var{program}
11360 @cindex executable file target
11361 An executable file. @samp{target exec @var{program}} is the same as
11362 @samp{exec-file @var{program}}.
11364 @item target core @var{filename}
11365 @cindex core dump file target
11366 A core dump file. @samp{target core @var{filename}} is the same as
11367 @samp{core-file @var{filename}}.
11369 @item target remote @var{dev}
11370 @cindex remote target
11371 Remote serial target in GDB-specific protocol. The argument @var{dev}
11372 specifies what serial device to use for the connection (e.g.
11373 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
11374 supports the @code{load} command. This is only useful if you have
11375 some other way of getting the stub to the target system, and you can put
11376 it somewhere in memory where it won't get clobbered by the download.
11379 @cindex built-in simulator target
11380 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
11388 works; however, you cannot assume that a specific memory map, device
11389 drivers, or even basic I/O is available, although some simulators do
11390 provide these. For info about any processor-specific simulator details,
11391 see the appropriate section in @ref{Embedded Processors, ,Embedded
11396 Some configurations may include these targets as well:
11400 @item target nrom @var{dev}
11401 @cindex NetROM ROM emulator target
11402 NetROM ROM emulator. This target only supports downloading.
11406 Different targets are available on different configurations of @value{GDBN};
11407 your configuration may have more or fewer targets.
11409 Many remote targets require you to download the executable's code once
11410 you've successfully established a connection. You may wish to control
11411 various aspects of this process, such as the size of the data chunks
11412 used by @value{GDBN} to download program parts to the remote target.
11415 @kindex set download-write-size
11416 @item set download-write-size @var{size}
11417 Set the write size used when downloading a program. Only used when
11418 downloading a program onto a remote target. Specify zero or a
11419 negative value to disable blocked writes. The actual size of each
11420 transfer is also limited by the size of the target packet and the
11423 @kindex show download-write-size
11424 @item show download-write-size
11425 @kindex show download-write-size
11426 Show the current value of the write size.
11429 @kindex set hash@r{, for remote monitors}
11430 @cindex hash mark while downloading
11431 This command controls whether a hash mark @samp{#} is displayed while
11432 downloading a file to the remote monitor. If on, a hash mark is
11433 displayed after each S-record is successfully downloaded to the
11437 @kindex show hash@r{, for remote monitors}
11438 Show the current status of displaying the hash mark.
11440 @item set debug monitor
11441 @kindex set debug monitor
11442 @cindex display remote monitor communications
11443 Enable or disable display of communications messages between
11444 @value{GDBN} and the remote monitor.
11446 @item show debug monitor
11447 @kindex show debug monitor
11448 Show the current status of displaying communications between
11449 @value{GDBN} and the remote monitor.
11454 @kindex load @var{filename}
11455 @item load @var{filename}
11456 Depending on what remote debugging facilities are configured into
11457 @value{GDBN}, the @code{load} command may be available. Where it exists, it
11458 is meant to make @var{filename} (an executable) available for debugging
11459 on the remote system---by downloading, or dynamic linking, for example.
11460 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
11461 the @code{add-symbol-file} command.
11463 If your @value{GDBN} does not have a @code{load} command, attempting to
11464 execute it gets the error message ``@code{You can't do that when your
11465 target is @dots{}}''
11467 The file is loaded at whatever address is specified in the executable.
11468 For some object file formats, you can specify the load address when you
11469 link the program; for other formats, like a.out, the object file format
11470 specifies a fixed address.
11471 @c FIXME! This would be a good place for an xref to the GNU linker doc.
11473 @code{load} does not repeat if you press @key{RET} again after using it.
11477 @section Choosing target byte order
11479 @cindex choosing target byte order
11480 @cindex target byte order
11482 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
11483 offer the ability to run either big-endian or little-endian byte
11484 orders. Usually the executable or symbol will include a bit to
11485 designate the endian-ness, and you will not need to worry about
11486 which to use. However, you may still find it useful to adjust
11487 @value{GDBN}'s idea of processor endian-ness manually.
11491 @item set endian big
11492 Instruct @value{GDBN} to assume the target is big-endian.
11494 @item set endian little
11495 Instruct @value{GDBN} to assume the target is little-endian.
11497 @item set endian auto
11498 Instruct @value{GDBN} to use the byte order associated with the
11502 Display @value{GDBN}'s current idea of the target byte order.
11506 Note that these commands merely adjust interpretation of symbolic
11507 data on the host, and that they have absolutely no effect on the
11511 @section Remote debugging
11512 @cindex remote debugging
11514 If you are trying to debug a program running on a machine that cannot run
11515 @value{GDBN} in the usual way, it is often useful to use remote debugging.
11516 For example, you might use remote debugging on an operating system kernel,
11517 or on a small system which does not have a general purpose operating system
11518 powerful enough to run a full-featured debugger.
11520 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
11521 to make this work with particular debugging targets. In addition,
11522 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
11523 but not specific to any particular target system) which you can use if you
11524 write the remote stubs---the code that runs on the remote system to
11525 communicate with @value{GDBN}.
11527 Other remote targets may be available in your
11528 configuration of @value{GDBN}; use @code{help target} to list them.
11531 @section Kernel Object Display
11532 @cindex kernel object display
11535 Some targets support kernel object display. Using this facility,
11536 @value{GDBN} communicates specially with the underlying operating system
11537 and can display information about operating system-level objects such as
11538 mutexes and other synchronization objects. Exactly which objects can be
11539 displayed is determined on a per-OS basis.
11542 Use the @code{set os} command to set the operating system. This tells
11543 @value{GDBN} which kernel object display module to initialize:
11546 (@value{GDBP}) set os cisco
11550 The associated command @code{show os} displays the operating system
11551 set with the @code{set os} command; if no operating system has been
11552 set, @code{show os} will display an empty string @samp{""}.
11554 If @code{set os} succeeds, @value{GDBN} will display some information
11555 about the operating system, and will create a new @code{info} command
11556 which can be used to query the target. The @code{info} command is named
11557 after the operating system:
11561 (@value{GDBP}) info cisco
11562 List of Cisco Kernel Objects
11564 any Any and all objects
11567 Further subcommands can be used to query about particular objects known
11570 There is currently no way to determine whether a given operating
11571 system is supported other than to try setting it with @kbd{set os
11572 @var{name}}, where @var{name} is the name of the operating system you
11576 @node Remote Debugging
11577 @chapter Debugging remote programs
11580 * Connecting:: Connecting to a remote target
11581 * Server:: Using the gdbserver program
11582 * NetWare:: Using the gdbserve.nlm program
11583 * Remote configuration:: Remote configuration
11584 * remote stub:: Implementing a remote stub
11588 @section Connecting to a remote target
11590 On the @value{GDBN} host machine, you will need an unstripped copy of
11591 your program, since @value{GDBN} needs symobl and debugging information.
11592 Start up @value{GDBN} as usual, using the name of the local copy of your
11593 program as the first argument.
11595 @cindex serial line, @code{target remote}
11596 If you're using a serial line, you may want to give @value{GDBN} the
11597 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
11598 (@pxref{Remote configuration, set remotebaud}) before the
11599 @code{target} command.
11601 After that, use @code{target remote} to establish communications with
11602 the target machine. Its argument specifies how to communicate---either
11603 via a devicename attached to a direct serial line, or a TCP or UDP port
11604 (possibly to a terminal server which in turn has a serial line to the
11605 target). For example, to use a serial line connected to the device
11606 named @file{/dev/ttyb}:
11609 target remote /dev/ttyb
11612 @cindex TCP port, @code{target remote}
11613 To use a TCP connection, use an argument of the form
11614 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
11615 For example, to connect to port 2828 on a
11616 terminal server named @code{manyfarms}:
11619 target remote manyfarms:2828
11622 If your remote target is actually running on the same machine as
11623 your debugger session (e.g.@: a simulator of your target running on
11624 the same host), you can omit the hostname. For example, to connect
11625 to port 1234 on your local machine:
11628 target remote :1234
11632 Note that the colon is still required here.
11634 @cindex UDP port, @code{target remote}
11635 To use a UDP connection, use an argument of the form
11636 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
11637 on a terminal server named @code{manyfarms}:
11640 target remote udp:manyfarms:2828
11643 When using a UDP connection for remote debugging, you should keep in mind
11644 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
11645 busy or unreliable networks, which will cause havoc with your debugging
11648 Now you can use all the usual commands to examine and change data and to
11649 step and continue the remote program.
11651 @cindex interrupting remote programs
11652 @cindex remote programs, interrupting
11653 Whenever @value{GDBN} is waiting for the remote program, if you type the
11654 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
11655 program. This may or may not succeed, depending in part on the hardware
11656 and the serial drivers the remote system uses. If you type the
11657 interrupt character once again, @value{GDBN} displays this prompt:
11660 Interrupted while waiting for the program.
11661 Give up (and stop debugging it)? (y or n)
11664 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
11665 (If you decide you want to try again later, you can use @samp{target
11666 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
11667 goes back to waiting.
11670 @kindex detach (remote)
11672 When you have finished debugging the remote program, you can use the
11673 @code{detach} command to release it from @value{GDBN} control.
11674 Detaching from the target normally resumes its execution, but the results
11675 will depend on your particular remote stub. After the @code{detach}
11676 command, @value{GDBN} is free to connect to another target.
11680 The @code{disconnect} command behaves like @code{detach}, except that
11681 the target is generally not resumed. It will wait for @value{GDBN}
11682 (this instance or another one) to connect and continue debugging. After
11683 the @code{disconnect} command, @value{GDBN} is again free to connect to
11686 @cindex send command to remote monitor
11688 @item monitor @var{cmd}
11689 This command allows you to send commands directly to the remote
11694 @section Using the @code{gdbserver} program
11697 @cindex remote connection without stubs
11698 @code{gdbserver} is a control program for Unix-like systems, which
11699 allows you to connect your program with a remote @value{GDBN} via
11700 @code{target remote}---but without linking in the usual debugging stub.
11702 @code{gdbserver} is not a complete replacement for the debugging stubs,
11703 because it requires essentially the same operating-system facilities
11704 that @value{GDBN} itself does. In fact, a system that can run
11705 @code{gdbserver} to connect to a remote @value{GDBN} could also run
11706 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
11707 because it is a much smaller program than @value{GDBN} itself. It is
11708 also easier to port than all of @value{GDBN}, so you may be able to get
11709 started more quickly on a new system by using @code{gdbserver}.
11710 Finally, if you develop code for real-time systems, you may find that
11711 the tradeoffs involved in real-time operation make it more convenient to
11712 do as much development work as possible on another system, for example
11713 by cross-compiling. You can use @code{gdbserver} to make a similar
11714 choice for debugging.
11716 @value{GDBN} and @code{gdbserver} communicate via either a serial line
11717 or a TCP connection, using the standard @value{GDBN} remote serial
11721 @item On the target machine,
11722 you need to have a copy of the program you want to debug.
11723 @code{gdbserver} does not need your program's symbol table, so you can
11724 strip the program if necessary to save space. @value{GDBN} on the host
11725 system does all the symbol handling.
11727 To use the server, you must tell it how to communicate with @value{GDBN};
11728 the name of your program; and the arguments for your program. The usual
11732 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
11735 @var{comm} is either a device name (to use a serial line) or a TCP
11736 hostname and portnumber. For example, to debug Emacs with the argument
11737 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
11741 target> gdbserver /dev/com1 emacs foo.txt
11744 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
11747 To use a TCP connection instead of a serial line:
11750 target> gdbserver host:2345 emacs foo.txt
11753 The only difference from the previous example is the first argument,
11754 specifying that you are communicating with the host @value{GDBN} via
11755 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
11756 expect a TCP connection from machine @samp{host} to local TCP port 2345.
11757 (Currently, the @samp{host} part is ignored.) You can choose any number
11758 you want for the port number as long as it does not conflict with any
11759 TCP ports already in use on the target system (for example, @code{23} is
11760 reserved for @code{telnet}).@footnote{If you choose a port number that
11761 conflicts with another service, @code{gdbserver} prints an error message
11762 and exits.} You must use the same port number with the host @value{GDBN}
11763 @code{target remote} command.
11765 On some targets, @code{gdbserver} can also attach to running programs.
11766 This is accomplished via the @code{--attach} argument. The syntax is:
11769 target> gdbserver @var{comm} --attach @var{pid}
11772 @var{pid} is the process ID of a currently running process. It isn't necessary
11773 to point @code{gdbserver} at a binary for the running process.
11776 @cindex attach to a program by name
11777 You can debug processes by name instead of process ID if your target has the
11778 @code{pidof} utility:
11781 target> gdbserver @var{comm} --attach `pidof @var{PROGRAM}`
11784 In case more than one copy of @var{PROGRAM} is running, or @var{PROGRAM}
11785 has multiple threads, most versions of @code{pidof} support the
11786 @code{-s} option to only return the first process ID.
11788 @item On the host machine,
11789 connect to your target (@pxref{Connecting,,Connecting to a remote target}).
11790 For TCP connections, you must start up @code{gdbserver} prior to using
11791 the @code{target remote} command. Otherwise you may get an error whose
11792 text depends on the host system, but which usually looks something like
11793 @samp{Connection refused}. You don't need to use the @code{load}
11794 command in @value{GDBN} when using gdbserver, since the program is
11795 already on the target.
11800 @section Using the @code{gdbserve.nlm} program
11802 @kindex gdbserve.nlm
11803 @code{gdbserve.nlm} is a control program for NetWare systems, which
11804 allows you to connect your program with a remote @value{GDBN} via
11805 @code{target remote}.
11807 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
11808 using the standard @value{GDBN} remote serial protocol.
11811 @item On the target machine,
11812 you need to have a copy of the program you want to debug.
11813 @code{gdbserve.nlm} does not need your program's symbol table, so you
11814 can strip the program if necessary to save space. @value{GDBN} on the
11815 host system does all the symbol handling.
11817 To use the server, you must tell it how to communicate with
11818 @value{GDBN}; the name of your program; and the arguments for your
11819 program. The syntax is:
11822 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
11823 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
11826 @var{board} and @var{port} specify the serial line; @var{baud} specifies
11827 the baud rate used by the connection. @var{port} and @var{node} default
11828 to 0, @var{baud} defaults to 9600@dmn{bps}.
11830 For example, to debug Emacs with the argument @samp{foo.txt}and
11831 communicate with @value{GDBN} over serial port number 2 or board 1
11832 using a 19200@dmn{bps} connection:
11835 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
11839 On the @value{GDBN} host machine, connect to your target (@pxref{Connecting,,
11840 Connecting to a remote target}).
11844 @node Remote configuration
11845 @section Remote configuration
11848 @kindex show remote
11849 This section documents the configuration options available when
11850 debugging remote programs. For the options related to the File I/O
11851 extensions of the remote protocol, see @ref{The system call,
11852 system-call-allowed}.
11855 @item set remoteaddresssize @var{bits}
11856 @cindex adress size for remote targets
11857 @cindex bits in remote address
11858 Set the maximum size of address in a memory packet to the specified
11859 number of bits. @value{GDBN} will mask off the address bits above
11860 that number, when it passes addresses to the remote target. The
11861 default value is the number of bits in the target's address.
11863 @item show remoteaddresssize
11864 Show the current value of remote address size in bits.
11866 @item set remotebaud @var{n}
11867 @cindex baud rate for remote targets
11868 Set the baud rate for the remote serial I/O to @var{n} baud. The
11869 value is used to set the speed of the serial port used for debugging
11872 @item show remotebaud
11873 Show the current speed of the remote connection.
11875 @item set remotebreak
11876 @cindex interrupt remote programs
11877 @cindex BREAK signal instead of Ctrl-C
11878 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
11879 when you press the @key{Ctrl-C} key to interrupt the program running
11880 on the remote. If set to off, @value{GDBN} sends the @samp{Strl-C}
11881 character instead. The default is off, since most remote systems
11882 expect to see @samp{Ctrl-C} as the interrupt signal.
11884 @item show remotebreak
11885 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
11886 interrupt the remote program.
11888 @item set remotedebug
11889 @cindex debug remote protocol
11890 @cindex remote protocol debugging
11891 @cindex display remote packets
11892 Control the debugging of the remote protocol. When enabled, each
11893 packet sent to or received from the remote target is displayed. The
11896 @item show remotedebug
11897 Show the current setting of the remote protocol debugging.
11899 @item set remotedevice @var{device}
11900 @cindex serial port name
11901 Set the name of the serial port through which to communicate to the
11902 remote target to @var{device}. This is the device used by
11903 @value{GDBN} to open the serial communications line to the remote
11904 target. There's no default, so you must set a valid port name for the
11905 remote serial communications to work. (Some varieties of the
11906 @code{target} command accept the port name as part of their
11909 @item show remotedevice
11910 Show the current name of the serial port.
11912 @item set remotelogbase @var{base}
11913 Set the base (a.k.a.@: radix) of logging serial protocol
11914 communications to @var{base}. Supported values of @var{base} are:
11915 @code{ascii}, @code{octal}, and @code{hex}. The default is
11918 @item show remotelogbase
11919 Show the current setting of the radix for logging remote serial
11922 @item set remotelogfile @var{file}
11923 @cindex record serial communications on file
11924 Record remote serial communications on the named @var{file}. The
11925 default is not to record at all.
11927 @item show remotelogfile.
11928 Show the current setting of the file name on which to record the
11929 serial communications.
11931 @item set remotetimeout @var{num}
11932 @cindex timeout for serial communications
11933 @cindex remote timeout
11934 Set the timeout limit to wait for the remote target to respond to
11935 @var{num} seconds. The default is 2 seconds.
11937 @item show remotetimeout
11938 Show the current number of seconds to wait for the remote target
11941 @cindex limit hardware breakpoints and watchpoints
11942 @cindex remote target, limit break- and watchpoints
11943 @anchor{set remote hardware-watchpoint-limit}
11944 @anchor{set remote hardware-breakpoint-limit}
11945 @item set remote hardware-watchpoint-limit @var{limit}
11946 @itemx set remote hardware-breakpoint-limit @var{limit}
11947 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
11948 watchpoints. A limit of -1, the default, is treated as unlimited.
11950 @item set remote fetch-register-packet
11951 @itemx set remote set-register-packet
11952 @itemx set remote P-packet
11953 @itemx set remote p-packet
11955 @cindex fetch registers from remote targets
11956 @cindex set registers in remote targets
11957 Determine whether @value{GDBN} can set and fetch registers from the
11958 remote target using the @samp{P} packets. The default depends on the
11959 remote stub's support of the @samp{P} packets (@value{GDBN} queries
11960 the stub when this packet is first required).
11962 @item show remote fetch-register-packet
11963 @itemx show remote set-register-packet
11964 @itemx show remote P-packet
11965 @itemx show remote p-packet
11966 Show the current setting of using the @samp{P} packets for setting and
11967 fetching registers from the remote target.
11969 @cindex binary downloads
11971 @item set remote binary-download-packet
11972 @itemx set remote X-packet
11973 Determine whether @value{GDBN} sends downloads in binary mode using
11974 the @samp{X} packets. The default is on.
11976 @item show remote binary-download-packet
11977 @itemx show remote X-packet
11978 Show the current setting of using the @samp{X} packets for binary
11981 @item set remote read-aux-vector-packet
11982 @cindex auxiliary vector of remote target
11983 @cindex @code{auxv}, and remote targets
11984 Set the use of the remote protocol's @samp{qPart:auxv:read} (target
11985 auxiliary vector read) request. This request is used to fetch the
11986 remote target's @dfn{auxiliary vector}, see @ref{OS Information,
11987 Auxiliary Vector}. The default setting depends on the remote stub's
11988 support of this request (@value{GDBN} queries the stub when this
11989 request is first required). @xref{General Query Packets, qPart}, for
11990 more information about this request.
11992 @item show remote read-aux-vector-packet
11993 Show the current setting of use of the @samp{qPart:auxv:read} request.
11995 @item set remote symbol-lookup-packet
11996 @cindex remote symbol lookup request
11997 Set the use of the remote protocol's @samp{qSymbol} (target symbol
11998 lookup) request. This request is used to communicate symbol
11999 information to the remote target, e.g., whenever a new shared library
12000 is loaded by the remote (@pxref{Files, shared libraries}). The
12001 default setting depends on the remote stub's support of this request
12002 (@value{GDBN} queries the stub when this request is first required).
12003 @xref{General Query Packets, qSymbol}, for more information about this
12006 @item show remote symbol-lookup-packet
12007 Show the current setting of use of the @samp{qSymbol} request.
12009 @item set remote verbose-resume-packet
12010 @cindex resume remote target
12011 @cindex signal thread, and remote targets
12012 @cindex single-step thread, and remote targets
12013 @cindex thread-specific operations on remote targets
12014 Set the use of the remote protocol's @samp{vCont} (descriptive resume)
12015 request. This request is used to resume specific threads in the
12016 remote target, and to single-step or signal them. The default setting
12017 depends on the remote stub's support of this request (@value{GDBN}
12018 queries the stub when this request is first required). This setting
12019 affects debugging of multithreaded programs: if @samp{vCont} cannot be
12020 used, @value{GDBN} might be unable to single-step a specific thread,
12021 especially under @code{set scheduler-locking off}; it is also
12022 impossible to pause a specific thread. @xref{Packets, vCont}, for
12025 @item show remote verbose-resume-packet
12026 Show the current setting of use of the @samp{vCont} request
12028 @item set remote software-breakpoint-packet
12029 @itemx set remote hardware-breakpoint-packet
12030 @itemx set remote write-watchpoint-packet
12031 @itemx set remote read-watchpoint-packet
12032 @itemx set remote access-watchpoint-packet
12033 @itemx set remote Z-packet
12035 @cindex remote hardware breakpoints and watchpoints
12036 These commands enable or disable the use of @samp{Z} packets for
12037 setting breakpoints and watchpoints in the remote target. The default
12038 depends on the remote stub's support of the @samp{Z} packets
12039 (@value{GDBN} queries the stub when each packet is first required).
12040 The command @code{set remote Z-packet}, kept for back-compatibility,
12041 turns on or off all the features that require the use of @samp{Z}
12044 @item show remote software-breakpoint-packet
12045 @itemx show remote hardware-breakpoint-packet
12046 @itemx show remote write-watchpoint-packet
12047 @itemx show remote read-watchpoint-packet
12048 @itemx show remote access-watchpoint-packet
12049 @itemx show remote Z-packet
12050 Show the current setting of @samp{Z} packets usage.
12054 @section Implementing a remote stub
12056 @cindex debugging stub, example
12057 @cindex remote stub, example
12058 @cindex stub example, remote debugging
12059 The stub files provided with @value{GDBN} implement the target side of the
12060 communication protocol, and the @value{GDBN} side is implemented in the
12061 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
12062 these subroutines to communicate, and ignore the details. (If you're
12063 implementing your own stub file, you can still ignore the details: start
12064 with one of the existing stub files. @file{sparc-stub.c} is the best
12065 organized, and therefore the easiest to read.)
12067 @cindex remote serial debugging, overview
12068 To debug a program running on another machine (the debugging
12069 @dfn{target} machine), you must first arrange for all the usual
12070 prerequisites for the program to run by itself. For example, for a C
12075 A startup routine to set up the C runtime environment; these usually
12076 have a name like @file{crt0}. The startup routine may be supplied by
12077 your hardware supplier, or you may have to write your own.
12080 A C subroutine library to support your program's
12081 subroutine calls, notably managing input and output.
12084 A way of getting your program to the other machine---for example, a
12085 download program. These are often supplied by the hardware
12086 manufacturer, but you may have to write your own from hardware
12090 The next step is to arrange for your program to use a serial port to
12091 communicate with the machine where @value{GDBN} is running (the @dfn{host}
12092 machine). In general terms, the scheme looks like this:
12096 @value{GDBN} already understands how to use this protocol; when everything
12097 else is set up, you can simply use the @samp{target remote} command
12098 (@pxref{Targets,,Specifying a Debugging Target}).
12100 @item On the target,
12101 you must link with your program a few special-purpose subroutines that
12102 implement the @value{GDBN} remote serial protocol. The file containing these
12103 subroutines is called a @dfn{debugging stub}.
12105 On certain remote targets, you can use an auxiliary program
12106 @code{gdbserver} instead of linking a stub into your program.
12107 @xref{Server,,Using the @code{gdbserver} program}, for details.
12110 The debugging stub is specific to the architecture of the remote
12111 machine; for example, use @file{sparc-stub.c} to debug programs on
12114 @cindex remote serial stub list
12115 These working remote stubs are distributed with @value{GDBN}:
12120 @cindex @file{i386-stub.c}
12123 For Intel 386 and compatible architectures.
12126 @cindex @file{m68k-stub.c}
12127 @cindex Motorola 680x0
12129 For Motorola 680x0 architectures.
12132 @cindex @file{sh-stub.c}
12135 For Renesas SH architectures.
12138 @cindex @file{sparc-stub.c}
12140 For @sc{sparc} architectures.
12142 @item sparcl-stub.c
12143 @cindex @file{sparcl-stub.c}
12146 For Fujitsu @sc{sparclite} architectures.
12150 The @file{README} file in the @value{GDBN} distribution may list other
12151 recently added stubs.
12154 * Stub Contents:: What the stub can do for you
12155 * Bootstrapping:: What you must do for the stub
12156 * Debug Session:: Putting it all together
12159 @node Stub Contents
12160 @subsection What the stub can do for you
12162 @cindex remote serial stub
12163 The debugging stub for your architecture supplies these three
12167 @item set_debug_traps
12168 @findex set_debug_traps
12169 @cindex remote serial stub, initialization
12170 This routine arranges for @code{handle_exception} to run when your
12171 program stops. You must call this subroutine explicitly near the
12172 beginning of your program.
12174 @item handle_exception
12175 @findex handle_exception
12176 @cindex remote serial stub, main routine
12177 This is the central workhorse, but your program never calls it
12178 explicitly---the setup code arranges for @code{handle_exception} to
12179 run when a trap is triggered.
12181 @code{handle_exception} takes control when your program stops during
12182 execution (for example, on a breakpoint), and mediates communications
12183 with @value{GDBN} on the host machine. This is where the communications
12184 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
12185 representative on the target machine. It begins by sending summary
12186 information on the state of your program, then continues to execute,
12187 retrieving and transmitting any information @value{GDBN} needs, until you
12188 execute a @value{GDBN} command that makes your program resume; at that point,
12189 @code{handle_exception} returns control to your own code on the target
12193 @cindex @code{breakpoint} subroutine, remote
12194 Use this auxiliary subroutine to make your program contain a
12195 breakpoint. Depending on the particular situation, this may be the only
12196 way for @value{GDBN} to get control. For instance, if your target
12197 machine has some sort of interrupt button, you won't need to call this;
12198 pressing the interrupt button transfers control to
12199 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
12200 simply receiving characters on the serial port may also trigger a trap;
12201 again, in that situation, you don't need to call @code{breakpoint} from
12202 your own program---simply running @samp{target remote} from the host
12203 @value{GDBN} session gets control.
12205 Call @code{breakpoint} if none of these is true, or if you simply want
12206 to make certain your program stops at a predetermined point for the
12207 start of your debugging session.
12210 @node Bootstrapping
12211 @subsection What you must do for the stub
12213 @cindex remote stub, support routines
12214 The debugging stubs that come with @value{GDBN} are set up for a particular
12215 chip architecture, but they have no information about the rest of your
12216 debugging target machine.
12218 First of all you need to tell the stub how to communicate with the
12222 @item int getDebugChar()
12223 @findex getDebugChar
12224 Write this subroutine to read a single character from the serial port.
12225 It may be identical to @code{getchar} for your target system; a
12226 different name is used to allow you to distinguish the two if you wish.
12228 @item void putDebugChar(int)
12229 @findex putDebugChar
12230 Write this subroutine to write a single character to the serial port.
12231 It may be identical to @code{putchar} for your target system; a
12232 different name is used to allow you to distinguish the two if you wish.
12235 @cindex control C, and remote debugging
12236 @cindex interrupting remote targets
12237 If you want @value{GDBN} to be able to stop your program while it is
12238 running, you need to use an interrupt-driven serial driver, and arrange
12239 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
12240 character). That is the character which @value{GDBN} uses to tell the
12241 remote system to stop.
12243 Getting the debugging target to return the proper status to @value{GDBN}
12244 probably requires changes to the standard stub; one quick and dirty way
12245 is to just execute a breakpoint instruction (the ``dirty'' part is that
12246 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
12248 Other routines you need to supply are:
12251 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
12252 @findex exceptionHandler
12253 Write this function to install @var{exception_address} in the exception
12254 handling tables. You need to do this because the stub does not have any
12255 way of knowing what the exception handling tables on your target system
12256 are like (for example, the processor's table might be in @sc{rom},
12257 containing entries which point to a table in @sc{ram}).
12258 @var{exception_number} is the exception number which should be changed;
12259 its meaning is architecture-dependent (for example, different numbers
12260 might represent divide by zero, misaligned access, etc). When this
12261 exception occurs, control should be transferred directly to
12262 @var{exception_address}, and the processor state (stack, registers,
12263 and so on) should be just as it is when a processor exception occurs. So if
12264 you want to use a jump instruction to reach @var{exception_address}, it
12265 should be a simple jump, not a jump to subroutine.
12267 For the 386, @var{exception_address} should be installed as an interrupt
12268 gate so that interrupts are masked while the handler runs. The gate
12269 should be at privilege level 0 (the most privileged level). The
12270 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
12271 help from @code{exceptionHandler}.
12273 @item void flush_i_cache()
12274 @findex flush_i_cache
12275 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
12276 instruction cache, if any, on your target machine. If there is no
12277 instruction cache, this subroutine may be a no-op.
12279 On target machines that have instruction caches, @value{GDBN} requires this
12280 function to make certain that the state of your program is stable.
12284 You must also make sure this library routine is available:
12287 @item void *memset(void *, int, int)
12289 This is the standard library function @code{memset} that sets an area of
12290 memory to a known value. If you have one of the free versions of
12291 @code{libc.a}, @code{memset} can be found there; otherwise, you must
12292 either obtain it from your hardware manufacturer, or write your own.
12295 If you do not use the GNU C compiler, you may need other standard
12296 library subroutines as well; this varies from one stub to another,
12297 but in general the stubs are likely to use any of the common library
12298 subroutines which @code{@value{GCC}} generates as inline code.
12301 @node Debug Session
12302 @subsection Putting it all together
12304 @cindex remote serial debugging summary
12305 In summary, when your program is ready to debug, you must follow these
12310 Make sure you have defined the supporting low-level routines
12311 (@pxref{Bootstrapping,,What you must do for the stub}):
12313 @code{getDebugChar}, @code{putDebugChar},
12314 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
12318 Insert these lines near the top of your program:
12326 For the 680x0 stub only, you need to provide a variable called
12327 @code{exceptionHook}. Normally you just use:
12330 void (*exceptionHook)() = 0;
12334 but if before calling @code{set_debug_traps}, you set it to point to a
12335 function in your program, that function is called when
12336 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
12337 error). The function indicated by @code{exceptionHook} is called with
12338 one parameter: an @code{int} which is the exception number.
12341 Compile and link together: your program, the @value{GDBN} debugging stub for
12342 your target architecture, and the supporting subroutines.
12345 Make sure you have a serial connection between your target machine and
12346 the @value{GDBN} host, and identify the serial port on the host.
12349 @c The "remote" target now provides a `load' command, so we should
12350 @c document that. FIXME.
12351 Download your program to your target machine (or get it there by
12352 whatever means the manufacturer provides), and start it.
12355 Start @value{GDBN} on the host, and connect to the target
12356 (@pxref{Connecting,,Connecting to a remote target}).
12360 @node Configurations
12361 @chapter Configuration-Specific Information
12363 While nearly all @value{GDBN} commands are available for all native and
12364 cross versions of the debugger, there are some exceptions. This chapter
12365 describes things that are only available in certain configurations.
12367 There are three major categories of configurations: native
12368 configurations, where the host and target are the same, embedded
12369 operating system configurations, which are usually the same for several
12370 different processor architectures, and bare embedded processors, which
12371 are quite different from each other.
12376 * Embedded Processors::
12383 This section describes details specific to particular native
12388 * BSD libkvm Interface:: Debugging BSD kernel memory images
12389 * SVR4 Process Information:: SVR4 process information
12390 * DJGPP Native:: Features specific to the DJGPP port
12391 * Cygwin Native:: Features specific to the Cygwin port
12392 * Hurd Native:: Features specific to @sc{gnu} Hurd
12393 * Neutrino:: Features specific to QNX Neutrino
12399 On HP-UX systems, if you refer to a function or variable name that
12400 begins with a dollar sign, @value{GDBN} searches for a user or system
12401 name first, before it searches for a convenience variable.
12404 @node BSD libkvm Interface
12405 @subsection BSD libkvm Interface
12408 @cindex kernel memory image
12409 @cindex kernel crash dump
12411 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
12412 interface that provides a uniform interface for accessing kernel virtual
12413 memory images, including live systems and crash dumps. @value{GDBN}
12414 uses this interface to allow you to debug live kernels and kernel crash
12415 dumps on many native BSD configurations. This is implemented as a
12416 special @code{kvm} debugging target. For debugging a live system, load
12417 the currently running kernel into @value{GDBN} and connect to the
12421 (@value{GDBP}) @b{target kvm}
12424 For debugging crash dumps, provide the file name of the crash dump as an
12428 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
12431 Once connected to the @code{kvm} target, the following commands are
12437 Set current context from the @dfn{Process Control Block} (PCB) address.
12440 Set current context from proc address. This command isn't available on
12441 modern FreeBSD systems.
12444 @node SVR4 Process Information
12445 @subsection SVR4 process information
12447 @cindex examine process image
12448 @cindex process info via @file{/proc}
12450 Many versions of SVR4 and compatible systems provide a facility called
12451 @samp{/proc} that can be used to examine the image of a running
12452 process using file-system subroutines. If @value{GDBN} is configured
12453 for an operating system with this facility, the command @code{info
12454 proc} is available to report information about the process running
12455 your program, or about any process running on your system. @code{info
12456 proc} works only on SVR4 systems that include the @code{procfs} code.
12457 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
12458 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
12464 @itemx info proc @var{process-id}
12465 Summarize available information about any running process. If a
12466 process ID is specified by @var{process-id}, display information about
12467 that process; otherwise display information about the program being
12468 debugged. The summary includes the debugged process ID, the command
12469 line used to invoke it, its current working directory, and its
12470 executable file's absolute file name.
12472 On some systems, @var{process-id} can be of the form
12473 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
12474 within a process. If the optional @var{pid} part is missing, it means
12475 a thread from the process being debugged (the leading @samp{/} still
12476 needs to be present, or else @value{GDBN} will interpret the number as
12477 a process ID rather than a thread ID).
12479 @item info proc mappings
12480 @cindex memory address space mappings
12481 Report the memory address space ranges accessible in the program, with
12482 information on whether the process has read, write, or execute access
12483 rights to each range. On @sc{gnu}/Linux systems, each memory range
12484 includes the object file which is mapped to that range, instead of the
12485 memory access rights to that range.
12487 @item info proc stat
12488 @itemx info proc status
12489 @cindex process detailed status information
12490 These subcommands are specific to @sc{gnu}/Linux systems. They show
12491 the process-related information, including the user ID and group ID;
12492 how many threads are there in the process; its virtual memory usage;
12493 the signals that are pending, blocked, and ignored; its TTY; its
12494 consumption of system and user time; its stack size; its @samp{nice}
12495 value; etc. For more information, see the @samp{proc(5)} man page
12496 (type @kbd{man 5 proc} from your shell prompt).
12498 @item info proc all
12499 Show all the information about the process described under all of the
12500 above @code{info proc} subcommands.
12503 @comment These sub-options of 'info proc' were not included when
12504 @comment procfs.c was re-written. Keep their descriptions around
12505 @comment against the day when someone finds the time to put them back in.
12506 @kindex info proc times
12507 @item info proc times
12508 Starting time, user CPU time, and system CPU time for your program and
12511 @kindex info proc id
12513 Report on the process IDs related to your program: its own process ID,
12514 the ID of its parent, the process group ID, and the session ID.
12517 @item set procfs-trace
12518 @kindex set procfs-trace
12519 @cindex @code{procfs} API calls
12520 This command enables and disables tracing of @code{procfs} API calls.
12522 @item show procfs-trace
12523 @kindex show procfs-trace
12524 Show the current state of @code{procfs} API call tracing.
12526 @item set procfs-file @var{file}
12527 @kindex set procfs-file
12528 Tell @value{GDBN} to write @code{procfs} API trace to the named
12529 @var{file}. @value{GDBN} appends the trace info to the previous
12530 contents of the file. The default is to display the trace on the
12533 @item show procfs-file
12534 @kindex show procfs-file
12535 Show the file to which @code{procfs} API trace is written.
12537 @item proc-trace-entry
12538 @itemx proc-trace-exit
12539 @itemx proc-untrace-entry
12540 @itemx proc-untrace-exit
12541 @kindex proc-trace-entry
12542 @kindex proc-trace-exit
12543 @kindex proc-untrace-entry
12544 @kindex proc-untrace-exit
12545 These commands enable and disable tracing of entries into and exits
12546 from the @code{syscall} interface.
12549 @kindex info pidlist
12550 @cindex process list, QNX Neutrino
12551 For QNX Neutrino only, this command displays the list of all the
12552 processes and all the threads within each process.
12555 @kindex info meminfo
12556 @cindex mapinfo list, QNX Neutrino
12557 For QNX Neutrino only, this command displays the list of all mapinfos.
12561 @subsection Features for Debugging @sc{djgpp} Programs
12562 @cindex @sc{djgpp} debugging
12563 @cindex native @sc{djgpp} debugging
12564 @cindex MS-DOS-specific commands
12566 @sc{djgpp} is the port of @sc{gnu} development tools to MS-DOS and
12567 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
12568 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
12569 top of real-mode DOS systems and their emulations.
12571 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
12572 defines a few commands specific to the @sc{djgpp} port. This
12573 subsection describes those commands.
12578 This is a prefix of @sc{djgpp}-specific commands which print
12579 information about the target system and important OS structures.
12582 @cindex MS-DOS system info
12583 @cindex free memory information (MS-DOS)
12584 @item info dos sysinfo
12585 This command displays assorted information about the underlying
12586 platform: the CPU type and features, the OS version and flavor, the
12587 DPMI version, and the available conventional and DPMI memory.
12592 @cindex segment descriptor tables
12593 @cindex descriptor tables display
12595 @itemx info dos ldt
12596 @itemx info dos idt
12597 These 3 commands display entries from, respectively, Global, Local,
12598 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
12599 tables are data structures which store a descriptor for each segment
12600 that is currently in use. The segment's selector is an index into a
12601 descriptor table; the table entry for that index holds the
12602 descriptor's base address and limit, and its attributes and access
12605 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
12606 segment (used for both data and the stack), and a DOS segment (which
12607 allows access to DOS/BIOS data structures and absolute addresses in
12608 conventional memory). However, the DPMI host will usually define
12609 additional segments in order to support the DPMI environment.
12611 @cindex garbled pointers
12612 These commands allow to display entries from the descriptor tables.
12613 Without an argument, all entries from the specified table are
12614 displayed. An argument, which should be an integer expression, means
12615 display a single entry whose index is given by the argument. For
12616 example, here's a convenient way to display information about the
12617 debugged program's data segment:
12620 @exdent @code{(@value{GDBP}) info dos ldt $ds}
12621 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
12625 This comes in handy when you want to see whether a pointer is outside
12626 the data segment's limit (i.e.@: @dfn{garbled}).
12628 @cindex page tables display (MS-DOS)
12630 @itemx info dos pte
12631 These two commands display entries from, respectively, the Page
12632 Directory and the Page Tables. Page Directories and Page Tables are
12633 data structures which control how virtual memory addresses are mapped
12634 into physical addresses. A Page Table includes an entry for every
12635 page of memory that is mapped into the program's address space; there
12636 may be several Page Tables, each one holding up to 4096 entries. A
12637 Page Directory has up to 4096 entries, one each for every Page Table
12638 that is currently in use.
12640 Without an argument, @kbd{info dos pde} displays the entire Page
12641 Directory, and @kbd{info dos pte} displays all the entries in all of
12642 the Page Tables. An argument, an integer expression, given to the
12643 @kbd{info dos pde} command means display only that entry from the Page
12644 Directory table. An argument given to the @kbd{info dos pte} command
12645 means display entries from a single Page Table, the one pointed to by
12646 the specified entry in the Page Directory.
12648 @cindex direct memory access (DMA) on MS-DOS
12649 These commands are useful when your program uses @dfn{DMA} (Direct
12650 Memory Access), which needs physical addresses to program the DMA
12653 These commands are supported only with some DPMI servers.
12655 @cindex physical address from linear address
12656 @item info dos address-pte @var{addr}
12657 This command displays the Page Table entry for a specified linear
12658 address. The argument linear address @var{addr} should already have the
12659 appropriate segment's base address added to it, because this command
12660 accepts addresses which may belong to @emph{any} segment. For
12661 example, here's how to display the Page Table entry for the page where
12662 the variable @code{i} is stored:
12665 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
12666 @exdent @code{Page Table entry for address 0x11a00d30:}
12667 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
12671 This says that @code{i} is stored at offset @code{0xd30} from the page
12672 whose physical base address is @code{0x02698000}, and prints all the
12673 attributes of that page.
12675 Note that you must cast the addresses of variables to a @code{char *},
12676 since otherwise the value of @code{__djgpp_base_address}, the base
12677 address of all variables and functions in a @sc{djgpp} program, will
12678 be added using the rules of C pointer arithmetics: if @code{i} is
12679 declared an @code{int}, @value{GDBN} will add 4 times the value of
12680 @code{__djgpp_base_address} to the address of @code{i}.
12682 Here's another example, it displays the Page Table entry for the
12686 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
12687 @exdent @code{Page Table entry for address 0x29110:}
12688 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
12692 (The @code{+ 3} offset is because the transfer buffer's address is the
12693 3rd member of the @code{_go32_info_block} structure.) The output of
12694 this command clearly shows that addresses in conventional memory are
12695 mapped 1:1, i.e.@: the physical and linear addresses are identical.
12697 This command is supported only with some DPMI servers.
12700 In addition to native debugging, the DJGPP port supports remote
12701 debugging via a serial data link. The following commands are specific
12702 to remote serial debugging in the DJGPP port of @value{GDBN}.
12705 @kindex set com1base
12706 @kindex set com1irq
12707 @kindex set com2base
12708 @kindex set com2irq
12709 @kindex set com3base
12710 @kindex set com3irq
12711 @kindex set com4base
12712 @kindex set com4irq
12713 @item set com1base @var{addr}
12714 This command sets the base I/O port address of the @file{COM1} serial
12717 @item set com1irq @var{irq}
12718 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
12719 for the @file{COM1} serial port.
12721 There are similar commands @samp{set com2base}, @samp{set com3irq},
12722 etc.@: for setting the port address and the @code{IRQ} lines for the
12725 @kindex show com1base
12726 @kindex show com1irq
12727 @kindex show com2base
12728 @kindex show com2irq
12729 @kindex show com3base
12730 @kindex show com3irq
12731 @kindex show com4base
12732 @kindex show com4irq
12733 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
12734 display the current settings of the base address and the @code{IRQ}
12735 lines used by the COM ports.
12739 @node Cygwin Native
12740 @subsection Features for Debugging MS Windows PE executables
12741 @cindex MS Windows debugging
12742 @cindex native Cygwin debugging
12743 @cindex Cygwin-specific commands
12745 @value{GDBN} supports native debugging of MS Windows programs, including
12746 DLLs with and without symbolic debugging information. There are various
12747 additional Cygwin-specific commands, described in this subsection. The
12748 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
12749 that have no debugging symbols.
12755 This is a prefix of MS Windows specific commands which print
12756 information about the target system and important OS structures.
12758 @item info w32 selector
12759 This command displays information returned by
12760 the Win32 API @code{GetThreadSelectorEntry} function.
12761 It takes an optional argument that is evaluated to
12762 a long value to give the information about this given selector.
12763 Without argument, this command displays information
12764 about the the six segment registers.
12768 This is a Cygwin specific alias of info shared.
12770 @kindex dll-symbols
12772 This command loads symbols from a dll similarly to
12773 add-sym command but without the need to specify a base address.
12775 @kindex set new-console
12776 @item set new-console @var{mode}
12777 If @var{mode} is @code{on} the debuggee will
12778 be started in a new console on next start.
12779 If @var{mode} is @code{off}i, the debuggee will
12780 be started in the same console as the debugger.
12782 @kindex show new-console
12783 @item show new-console
12784 Displays whether a new console is used
12785 when the debuggee is started.
12787 @kindex set new-group
12788 @item set new-group @var{mode}
12789 This boolean value controls whether the debuggee should
12790 start a new group or stay in the same group as the debugger.
12791 This affects the way the Windows OS handles
12794 @kindex show new-group
12795 @item show new-group
12796 Displays current value of new-group boolean.
12798 @kindex set debugevents
12799 @item set debugevents
12800 This boolean value adds debug output concerning events seen by the debugger.
12802 @kindex set debugexec
12803 @item set debugexec
12804 This boolean value adds debug output concerning execute events
12805 seen by the debugger.
12807 @kindex set debugexceptions
12808 @item set debugexceptions
12809 This boolean value adds debug ouptut concerning exception events
12810 seen by the debugger.
12812 @kindex set debugmemory
12813 @item set debugmemory
12814 This boolean value adds debug ouptut concerning memory events
12815 seen by the debugger.
12819 This boolean values specifies whether the debuggee is called
12820 via a shell or directly (default value is on).
12824 Displays if the debuggee will be started with a shell.
12829 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
12832 @node Non-debug DLL symbols
12833 @subsubsection Support for DLLs without debugging symbols
12834 @cindex DLLs with no debugging symbols
12835 @cindex Minimal symbols and DLLs
12837 Very often on windows, some of the DLLs that your program relies on do
12838 not include symbolic debugging information (for example,
12839 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
12840 symbols in a DLL, it relies on the minimal amount of symbolic
12841 information contained in the DLL's export table. This subsubsection
12842 describes working with such symbols, known internally to @value{GDBN} as
12843 ``minimal symbols''.
12845 Note that before the debugged program has started execution, no DLLs
12846 will have been loaded. The easiest way around this problem is simply to
12847 start the program --- either by setting a breakpoint or letting the
12848 program run once to completion. It is also possible to force
12849 @value{GDBN} to load a particular DLL before starting the executable ---
12850 see the shared library information in @pxref{Files} or the
12851 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
12852 explicitly loading symbols from a DLL with no debugging information will
12853 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
12854 which may adversely affect symbol lookup performance.
12856 @subsubsection DLL name prefixes
12858 In keeping with the naming conventions used by the Microsoft debugging
12859 tools, DLL export symbols are made available with a prefix based on the
12860 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
12861 also entered into the symbol table, so @code{CreateFileA} is often
12862 sufficient. In some cases there will be name clashes within a program
12863 (particularly if the executable itself includes full debugging symbols)
12864 necessitating the use of the fully qualified name when referring to the
12865 contents of the DLL. Use single-quotes around the name to avoid the
12866 exclamation mark (``!'') being interpreted as a language operator.
12868 Note that the internal name of the DLL may be all upper-case, even
12869 though the file name of the DLL is lower-case, or vice-versa. Since
12870 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
12871 some confusion. If in doubt, try the @code{info functions} and
12872 @code{info variables} commands or even @code{maint print msymbols} (see
12873 @pxref{Symbols}). Here's an example:
12876 (@value{GDBP}) info function CreateFileA
12877 All functions matching regular expression "CreateFileA":
12879 Non-debugging symbols:
12880 0x77e885f4 CreateFileA
12881 0x77e885f4 KERNEL32!CreateFileA
12885 (@value{GDBP}) info function !
12886 All functions matching regular expression "!":
12888 Non-debugging symbols:
12889 0x6100114c cygwin1!__assert
12890 0x61004034 cygwin1!_dll_crt0@@0
12891 0x61004240 cygwin1!dll_crt0(per_process *)
12895 @subsubsection Working with minimal symbols
12897 Symbols extracted from a DLL's export table do not contain very much
12898 type information. All that @value{GDBN} can do is guess whether a symbol
12899 refers to a function or variable depending on the linker section that
12900 contains the symbol. Also note that the actual contents of the memory
12901 contained in a DLL are not available unless the program is running. This
12902 means that you cannot examine the contents of a variable or disassemble
12903 a function within a DLL without a running program.
12905 Variables are generally treated as pointers and dereferenced
12906 automatically. For this reason, it is often necessary to prefix a
12907 variable name with the address-of operator (``&'') and provide explicit
12908 type information in the command. Here's an example of the type of
12912 (@value{GDBP}) print 'cygwin1!__argv'
12917 (@value{GDBP}) x 'cygwin1!__argv'
12918 0x10021610: "\230y\""
12921 And two possible solutions:
12924 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
12925 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
12929 (@value{GDBP}) x/2x &'cygwin1!__argv'
12930 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
12931 (@value{GDBP}) x/x 0x10021608
12932 0x10021608: 0x0022fd98
12933 (@value{GDBP}) x/s 0x0022fd98
12934 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
12937 Setting a break point within a DLL is possible even before the program
12938 starts execution. However, under these circumstances, @value{GDBN} can't
12939 examine the initial instructions of the function in order to skip the
12940 function's frame set-up code. You can work around this by using ``*&''
12941 to set the breakpoint at a raw memory address:
12944 (@value{GDBP}) break *&'python22!PyOS_Readline'
12945 Breakpoint 1 at 0x1e04eff0
12948 The author of these extensions is not entirely convinced that setting a
12949 break point within a shared DLL like @file{kernel32.dll} is completely
12953 @subsection Commands specific to @sc{gnu} Hurd systems
12954 @cindex @sc{gnu} Hurd debugging
12956 This subsection describes @value{GDBN} commands specific to the
12957 @sc{gnu} Hurd native debugging.
12962 @kindex set signals@r{, Hurd command}
12963 @kindex set sigs@r{, Hurd command}
12964 This command toggles the state of inferior signal interception by
12965 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
12966 affected by this command. @code{sigs} is a shorthand alias for
12971 @kindex show signals@r{, Hurd command}
12972 @kindex show sigs@r{, Hurd command}
12973 Show the current state of intercepting inferior's signals.
12975 @item set signal-thread
12976 @itemx set sigthread
12977 @kindex set signal-thread
12978 @kindex set sigthread
12979 This command tells @value{GDBN} which thread is the @code{libc} signal
12980 thread. That thread is run when a signal is delivered to a running
12981 process. @code{set sigthread} is the shorthand alias of @code{set
12984 @item show signal-thread
12985 @itemx show sigthread
12986 @kindex show signal-thread
12987 @kindex show sigthread
12988 These two commands show which thread will run when the inferior is
12989 delivered a signal.
12992 @kindex set stopped@r{, Hurd command}
12993 This commands tells @value{GDBN} that the inferior process is stopped,
12994 as with the @code{SIGSTOP} signal. The stopped process can be
12995 continued by delivering a signal to it.
12998 @kindex show stopped@r{, Hurd command}
12999 This command shows whether @value{GDBN} thinks the debuggee is
13002 @item set exceptions
13003 @kindex set exceptions@r{, Hurd command}
13004 Use this command to turn off trapping of exceptions in the inferior.
13005 When exception trapping is off, neither breakpoints nor
13006 single-stepping will work. To restore the default, set exception
13009 @item show exceptions
13010 @kindex show exceptions@r{, Hurd command}
13011 Show the current state of trapping exceptions in the inferior.
13013 @item set task pause
13014 @kindex set task@r{, Hurd commands}
13015 @cindex task attributes (@sc{gnu} Hurd)
13016 @cindex pause current task (@sc{gnu} Hurd)
13017 This command toggles task suspension when @value{GDBN} has control.
13018 Setting it to on takes effect immediately, and the task is suspended
13019 whenever @value{GDBN} gets control. Setting it to off will take
13020 effect the next time the inferior is continued. If this option is set
13021 to off, you can use @code{set thread default pause on} or @code{set
13022 thread pause on} (see below) to pause individual threads.
13024 @item show task pause
13025 @kindex show task@r{, Hurd commands}
13026 Show the current state of task suspension.
13028 @item set task detach-suspend-count
13029 @cindex task suspend count
13030 @cindex detach from task, @sc{gnu} Hurd
13031 This command sets the suspend count the task will be left with when
13032 @value{GDBN} detaches from it.
13034 @item show task detach-suspend-count
13035 Show the suspend count the task will be left with when detaching.
13037 @item set task exception-port
13038 @itemx set task excp
13039 @cindex task exception port, @sc{gnu} Hurd
13040 This command sets the task exception port to which @value{GDBN} will
13041 forward exceptions. The argument should be the value of the @dfn{send
13042 rights} of the task. @code{set task excp} is a shorthand alias.
13044 @item set noninvasive
13045 @cindex noninvasive task options
13046 This command switches @value{GDBN} to a mode that is the least
13047 invasive as far as interfering with the inferior is concerned. This
13048 is the same as using @code{set task pause}, @code{set exceptions}, and
13049 @code{set signals} to values opposite to the defaults.
13051 @item info send-rights
13052 @itemx info receive-rights
13053 @itemx info port-rights
13054 @itemx info port-sets
13055 @itemx info dead-names
13058 @cindex send rights, @sc{gnu} Hurd
13059 @cindex receive rights, @sc{gnu} Hurd
13060 @cindex port rights, @sc{gnu} Hurd
13061 @cindex port sets, @sc{gnu} Hurd
13062 @cindex dead names, @sc{gnu} Hurd
13063 These commands display information about, respectively, send rights,
13064 receive rights, port rights, port sets, and dead names of a task.
13065 There are also shorthand aliases: @code{info ports} for @code{info
13066 port-rights} and @code{info psets} for @code{info port-sets}.
13068 @item set thread pause
13069 @kindex set thread@r{, Hurd command}
13070 @cindex thread properties, @sc{gnu} Hurd
13071 @cindex pause current thread (@sc{gnu} Hurd)
13072 This command toggles current thread suspension when @value{GDBN} has
13073 control. Setting it to on takes effect immediately, and the current
13074 thread is suspended whenever @value{GDBN} gets control. Setting it to
13075 off will take effect the next time the inferior is continued.
13076 Normally, this command has no effect, since when @value{GDBN} has
13077 control, the whole task is suspended. However, if you used @code{set
13078 task pause off} (see above), this command comes in handy to suspend
13079 only the current thread.
13081 @item show thread pause
13082 @kindex show thread@r{, Hurd command}
13083 This command shows the state of current thread suspension.
13085 @item set thread run
13086 This comamnd sets whether the current thread is allowed to run.
13088 @item show thread run
13089 Show whether the current thread is allowed to run.
13091 @item set thread detach-suspend-count
13092 @cindex thread suspend count, @sc{gnu} Hurd
13093 @cindex detach from thread, @sc{gnu} Hurd
13094 This command sets the suspend count @value{GDBN} will leave on a
13095 thread when detaching. This number is relative to the suspend count
13096 found by @value{GDBN} when it notices the thread; use @code{set thread
13097 takeover-suspend-count} to force it to an absolute value.
13099 @item show thread detach-suspend-count
13100 Show the suspend count @value{GDBN} will leave on the thread when
13103 @item set thread exception-port
13104 @itemx set thread excp
13105 Set the thread exception port to which to forward exceptions. This
13106 overrides the port set by @code{set task exception-port} (see above).
13107 @code{set thread excp} is the shorthand alias.
13109 @item set thread takeover-suspend-count
13110 Normally, @value{GDBN}'s thread suspend counts are relative to the
13111 value @value{GDBN} finds when it notices each thread. This command
13112 changes the suspend counts to be absolute instead.
13114 @item set thread default
13115 @itemx show thread default
13116 @cindex thread default settings, @sc{gnu} Hurd
13117 Each of the above @code{set thread} commands has a @code{set thread
13118 default} counterpart (e.g., @code{set thread default pause}, @code{set
13119 thread default exception-port}, etc.). The @code{thread default}
13120 variety of commands sets the default thread properties for all
13121 threads; you can then change the properties of individual threads with
13122 the non-default commands.
13127 @subsection QNX Neutrino
13128 @cindex QNX Neutrino
13130 @value{GDBN} provides the following commands specific to the QNX
13134 @item set debug nto-debug
13135 @kindex set debug nto-debug
13136 When set to on, enables debugging messages specific to the QNX
13139 @item show debug nto-debug
13140 @kindex show debug nto-debug
13141 Show the current state of QNX Neutrino messages.
13146 @section Embedded Operating Systems
13148 This section describes configurations involving the debugging of
13149 embedded operating systems that are available for several different
13153 * VxWorks:: Using @value{GDBN} with VxWorks
13156 @value{GDBN} includes the ability to debug programs running on
13157 various real-time operating systems.
13160 @subsection Using @value{GDBN} with VxWorks
13166 @kindex target vxworks
13167 @item target vxworks @var{machinename}
13168 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
13169 is the target system's machine name or IP address.
13173 On VxWorks, @code{load} links @var{filename} dynamically on the
13174 current target system as well as adding its symbols in @value{GDBN}.
13176 @value{GDBN} enables developers to spawn and debug tasks running on networked
13177 VxWorks targets from a Unix host. Already-running tasks spawned from
13178 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
13179 both the Unix host and on the VxWorks target. The program
13180 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
13181 installed with the name @code{vxgdb}, to distinguish it from a
13182 @value{GDBN} for debugging programs on the host itself.)
13185 @item VxWorks-timeout @var{args}
13186 @kindex vxworks-timeout
13187 All VxWorks-based targets now support the option @code{vxworks-timeout}.
13188 This option is set by the user, and @var{args} represents the number of
13189 seconds @value{GDBN} waits for responses to rpc's. You might use this if
13190 your VxWorks target is a slow software simulator or is on the far side
13191 of a thin network line.
13194 The following information on connecting to VxWorks was current when
13195 this manual was produced; newer releases of VxWorks may use revised
13198 @findex INCLUDE_RDB
13199 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
13200 to include the remote debugging interface routines in the VxWorks
13201 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
13202 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
13203 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
13204 source debugging task @code{tRdbTask} when VxWorks is booted. For more
13205 information on configuring and remaking VxWorks, see the manufacturer's
13207 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
13209 Once you have included @file{rdb.a} in your VxWorks system image and set
13210 your Unix execution search path to find @value{GDBN}, you are ready to
13211 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
13212 @code{vxgdb}, depending on your installation).
13214 @value{GDBN} comes up showing the prompt:
13221 * VxWorks Connection:: Connecting to VxWorks
13222 * VxWorks Download:: VxWorks download
13223 * VxWorks Attach:: Running tasks
13226 @node VxWorks Connection
13227 @subsubsection Connecting to VxWorks
13229 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
13230 network. To connect to a target whose host name is ``@code{tt}'', type:
13233 (vxgdb) target vxworks tt
13237 @value{GDBN} displays messages like these:
13240 Attaching remote machine across net...
13245 @value{GDBN} then attempts to read the symbol tables of any object modules
13246 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
13247 these files by searching the directories listed in the command search
13248 path (@pxref{Environment, ,Your program's environment}); if it fails
13249 to find an object file, it displays a message such as:
13252 prog.o: No such file or directory.
13255 When this happens, add the appropriate directory to the search path with
13256 the @value{GDBN} command @code{path}, and execute the @code{target}
13259 @node VxWorks Download
13260 @subsubsection VxWorks download
13262 @cindex download to VxWorks
13263 If you have connected to the VxWorks target and you want to debug an
13264 object that has not yet been loaded, you can use the @value{GDBN}
13265 @code{load} command to download a file from Unix to VxWorks
13266 incrementally. The object file given as an argument to the @code{load}
13267 command is actually opened twice: first by the VxWorks target in order
13268 to download the code, then by @value{GDBN} in order to read the symbol
13269 table. This can lead to problems if the current working directories on
13270 the two systems differ. If both systems have NFS mounted the same
13271 filesystems, you can avoid these problems by using absolute paths.
13272 Otherwise, it is simplest to set the working directory on both systems
13273 to the directory in which the object file resides, and then to reference
13274 the file by its name, without any path. For instance, a program
13275 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
13276 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
13277 program, type this on VxWorks:
13280 -> cd "@var{vxpath}/vw/demo/rdb"
13284 Then, in @value{GDBN}, type:
13287 (vxgdb) cd @var{hostpath}/vw/demo/rdb
13288 (vxgdb) load prog.o
13291 @value{GDBN} displays a response similar to this:
13294 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
13297 You can also use the @code{load} command to reload an object module
13298 after editing and recompiling the corresponding source file. Note that
13299 this makes @value{GDBN} delete all currently-defined breakpoints,
13300 auto-displays, and convenience variables, and to clear the value
13301 history. (This is necessary in order to preserve the integrity of
13302 debugger's data structures that reference the target system's symbol
13305 @node VxWorks Attach
13306 @subsubsection Running tasks
13308 @cindex running VxWorks tasks
13309 You can also attach to an existing task using the @code{attach} command as
13313 (vxgdb) attach @var{task}
13317 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
13318 or suspended when you attach to it. Running tasks are suspended at
13319 the time of attachment.
13321 @node Embedded Processors
13322 @section Embedded Processors
13324 This section goes into details specific to particular embedded
13330 * H8/300:: Renesas H8/300
13331 * H8/500:: Renesas H8/500
13332 * M32R/D:: Renesas M32R/D
13333 * M68K:: Motorola M68K
13334 * MIPS Embedded:: MIPS Embedded
13335 * OpenRISC 1000:: OpenRisc 1000
13336 * PA:: HP PA Embedded
13339 * Sparclet:: Tsqware Sparclet
13340 * Sparclite:: Fujitsu Sparclite
13341 * ST2000:: Tandem ST2000
13342 * Z8000:: Zilog Z8000
13345 * Super-H:: Renesas Super-H
13354 @item target rdi @var{dev}
13355 ARM Angel monitor, via RDI library interface to ADP protocol. You may
13356 use this target to communicate with both boards running the Angel
13357 monitor, or with the EmbeddedICE JTAG debug device.
13360 @item target rdp @var{dev}
13365 @value{GDBN} provides the following ARM-specific commands:
13368 @item set arm disassembler
13370 This commands selects from a list of disassembly styles. The
13371 @code{"std"} style is the standard style.
13373 @item show arm disassembler
13375 Show the current disassembly style.
13377 @item set arm apcs32
13378 @cindex ARM 32-bit mode
13379 This command toggles ARM operation mode between 32-bit and 26-bit.
13381 @item show arm apcs32
13382 Display the current usage of the ARM 32-bit mode.
13384 @item set arm fpu @var{fputype}
13385 This command sets the ARM floating-point unit (FPU) type. The
13386 argument @var{fputype} can be one of these:
13390 Determine the FPU type by querying the OS ABI.
13392 Software FPU, with mixed-endian doubles on little-endian ARM
13395 GCC-compiled FPA co-processor.
13397 Software FPU with pure-endian doubles.
13403 Show the current type of the FPU.
13406 This command forces @value{GDBN} to use the specified ABI.
13409 Show the currently used ABI.
13411 @item set debug arm
13412 Toggle whether to display ARM-specific debugging messages from the ARM
13413 target support subsystem.
13415 @item show debug arm
13416 Show whether ARM-specific debugging messages are enabled.
13421 @subsection Renesas H8/300
13425 @kindex target hms@r{, with H8/300}
13426 @item target hms @var{dev}
13427 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
13428 Use special commands @code{device} and @code{speed} to control the serial
13429 line and the communications speed used.
13431 @kindex target e7000@r{, with H8/300}
13432 @item target e7000 @var{dev}
13433 E7000 emulator for Renesas H8 and SH.
13435 @kindex target sh3@r{, with H8/300}
13436 @kindex target sh3e@r{, with H8/300}
13437 @item target sh3 @var{dev}
13438 @itemx target sh3e @var{dev}
13439 Renesas SH-3 and SH-3E target systems.
13443 @cindex download to H8/300 or H8/500
13444 @cindex H8/300 or H8/500 download
13445 @cindex download to Renesas SH
13446 @cindex Renesas SH download
13447 When you select remote debugging to a Renesas SH, H8/300, or H8/500
13448 board, the @code{load} command downloads your program to the Renesas
13449 board and also opens it as the current executable target for
13450 @value{GDBN} on your host (like the @code{file} command).
13452 @value{GDBN} needs to know these things to talk to your
13453 Renesas SH, H8/300, or H8/500:
13457 that you want to use @samp{target hms}, the remote debugging interface
13458 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
13459 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
13460 the default when @value{GDBN} is configured specifically for the Renesas SH,
13461 H8/300, or H8/500.)
13464 what serial device connects your host to your Renesas board (the first
13465 serial device available on your host is the default).
13468 what speed to use over the serial device.
13472 * Renesas Boards:: Connecting to Renesas boards.
13473 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
13474 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
13477 @node Renesas Boards
13478 @subsubsection Connecting to Renesas boards
13480 @c only for Unix hosts
13482 @cindex serial device, Renesas micros
13483 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
13484 need to explicitly set the serial device. The default @var{port} is the
13485 first available port on your host. This is only necessary on Unix
13486 hosts, where it is typically something like @file{/dev/ttya}.
13489 @cindex serial line speed, Renesas micros
13490 @code{@value{GDBN}} has another special command to set the communications
13491 speed: @samp{speed @var{bps}}. This command also is only used from Unix
13492 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
13493 the DOS @code{mode} command (for instance,
13494 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
13496 The @samp{device} and @samp{speed} commands are available only when you
13497 use a Unix host to debug your Renesas microprocessor programs. If you
13499 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
13500 called @code{asynctsr} to communicate with the development board
13501 through a PC serial port. You must also use the DOS @code{mode} command
13502 to set up the serial port on the DOS side.
13504 The following sample session illustrates the steps needed to start a
13505 program under @value{GDBN} control on an H8/300. The example uses a
13506 sample H8/300 program called @file{t.x}. The procedure is the same for
13507 the Renesas SH and the H8/500.
13509 First hook up your development board. In this example, we use a
13510 board attached to serial port @code{COM2}; if you use a different serial
13511 port, substitute its name in the argument of the @code{mode} command.
13512 When you call @code{asynctsr}, the auxiliary comms program used by the
13513 debugger, you give it just the numeric part of the serial port's name;
13514 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
13518 C:\H8300\TEST> asynctsr 2
13519 C:\H8300\TEST> mode com2:9600,n,8,1,p
13521 Resident portion of MODE loaded
13523 COM2: 9600, n, 8, 1, p
13528 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
13529 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
13530 disable it, or even boot without it, to use @code{asynctsr} to control
13531 your development board.
13534 @kindex target hms@r{, and serial protocol}
13535 Now that serial communications are set up, and the development board is
13536 connected, you can start up @value{GDBN}. Call @code{@value{GDBN}} with
13537 the name of your program as the argument. @code{@value{GDBN}} prompts
13538 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
13539 commands to begin your debugging session: @samp{target hms} to specify
13540 cross-debugging to the Renesas board, and the @code{load} command to
13541 download your program to the board. @code{load} displays the names of
13542 the program's sections, and a @samp{*} for each 2K of data downloaded.
13543 (If you want to refresh @value{GDBN} data on symbols or on the
13544 executable file without downloading, use the @value{GDBN} commands
13545 @code{file} or @code{symbol-file}. These commands, and @code{load}
13546 itself, are described in @ref{Files,,Commands to specify files}.)
13549 (eg-C:\H8300\TEST) @value{GDBP} t.x
13550 @value{GDBN} is free software and you are welcome to distribute copies
13551 of it under certain conditions; type "show copying" to see
13553 There is absolutely no warranty for @value{GDBN}; type "show warranty"
13555 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
13556 (@value{GDBP}) target hms
13557 Connected to remote H8/300 HMS system.
13558 (@value{GDBP}) load t.x
13559 .text : 0x8000 .. 0xabde ***********
13560 .data : 0xabde .. 0xad30 *
13561 .stack : 0xf000 .. 0xf014 *
13564 At this point, you're ready to run or debug your program. From here on,
13565 you can use all the usual @value{GDBN} commands. The @code{break} command
13566 sets breakpoints; the @code{run} command starts your program;
13567 @code{print} or @code{x} display data; the @code{continue} command
13568 resumes execution after stopping at a breakpoint. You can use the
13569 @code{help} command at any time to find out more about @value{GDBN} commands.
13571 Remember, however, that @emph{operating system} facilities aren't
13572 available on your development board; for example, if your program hangs,
13573 you can't send an interrupt---but you can press the @sc{reset} switch!
13575 Use the @sc{reset} button on the development board
13578 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
13579 no way to pass an interrupt signal to the development board); and
13582 to return to the @value{GDBN} command prompt after your program finishes
13583 normally. The communications protocol provides no other way for @value{GDBN}
13584 to detect program completion.
13587 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
13588 development board as a ``normal exit'' of your program.
13591 @subsubsection Using the E7000 in-circuit emulator
13593 @kindex target e7000@r{, with Renesas ICE}
13594 You can use the E7000 in-circuit emulator to develop code for either the
13595 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
13596 e7000} command to connect @value{GDBN} to your E7000:
13599 @item target e7000 @var{port} @var{speed}
13600 Use this form if your E7000 is connected to a serial port. The
13601 @var{port} argument identifies what serial port to use (for example,
13602 @samp{com2}). The third argument is the line speed in bits per second
13603 (for example, @samp{9600}).
13605 @item target e7000 @var{hostname}
13606 If your E7000 is installed as a host on a TCP/IP network, you can just
13607 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
13610 @node Renesas Special
13611 @subsubsection Special @value{GDBN} commands for Renesas micros
13613 Some @value{GDBN} commands are available only for the H8/300:
13617 @kindex set machine
13618 @kindex show machine
13619 @item set machine h8300
13620 @itemx set machine h8300h
13621 Condition @value{GDBN} for one of the two variants of the H8/300
13622 architecture with @samp{set machine}. You can use @samp{show machine}
13623 to check which variant is currently in effect.
13632 @kindex set memory @var{mod}
13633 @cindex memory models, H8/500
13634 @item set memory @var{mod}
13636 Specify which H8/500 memory model (@var{mod}) you are using with
13637 @samp{set memory}; check which memory model is in effect with @samp{show
13638 memory}. The accepted values for @var{mod} are @code{small},
13639 @code{big}, @code{medium}, and @code{compact}.
13644 @subsection Renesas M32R/D
13647 @kindex target m32r
13648 @item target m32r @var{dev}
13649 Renesas M32R/D ROM monitor.
13651 @kindex target m32rsdi
13652 @item target m32rsdi @var{dev}
13653 Renesas M32R SDI server, connected via parallel port to the board.
13656 The following @value{GDBN} commands are specific to the M32R monitor:
13659 @item set download-path @var{path}
13660 @kindex set download-path
13661 @cindex find downloadable @sc{srec} files (M32R)
13662 Set the default path for finding donwloadable @sc{srec} files.
13664 @item show download-path
13665 @kindex show download-path
13666 Show the default path for downloadable @sc{srec} files.
13668 @item set board-address @var{addr}
13669 @kindex set board-address
13670 @cindex M32-EVA target board address
13671 Set the IP address for the M32R-EVA target board.
13673 @item show board-address
13674 @kindex show board-address
13675 Show the current IP address of the target board.
13677 @item set server-address @var{addr}
13678 @kindex set server-address
13679 @cindex download server address (M32R)
13680 Set the IP address for the download server, which is the @value{GDBN}'s
13683 @item show server-address
13684 @kindex show server-address
13685 Display the IP address of the download server.
13687 @item upload @r{[}@var{file}@r{]}
13688 @kindex upload@r{, M32R}
13689 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
13690 upload capability. If no @var{file} argument is given, the current
13691 executable file is uploaded.
13693 @item tload @r{[}@var{file}@r{]}
13694 @kindex tload@r{, M32R}
13695 Test the @code{upload} command.
13701 The Motorola m68k configuration includes ColdFire support, and
13702 target command for the following ROM monitors.
13706 @kindex target abug
13707 @item target abug @var{dev}
13708 ABug ROM monitor for M68K.
13710 @kindex target cpu32bug
13711 @item target cpu32bug @var{dev}
13712 CPU32BUG monitor, running on a CPU32 (M68K) board.
13714 @kindex target dbug
13715 @item target dbug @var{dev}
13716 dBUG ROM monitor for Motorola ColdFire.
13719 @item target est @var{dev}
13720 EST-300 ICE monitor, running on a CPU32 (M68K) board.
13722 @kindex target rom68k
13723 @item target rom68k @var{dev}
13724 ROM 68K monitor, running on an M68K IDP board.
13730 @kindex target rombug
13731 @item target rombug @var{dev}
13732 ROMBUG ROM monitor for OS/9000.
13736 @node MIPS Embedded
13737 @subsection MIPS Embedded
13739 @cindex MIPS boards
13740 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
13741 MIPS board attached to a serial line. This is available when
13742 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
13745 Use these @value{GDBN} commands to specify the connection to your target board:
13748 @item target mips @var{port}
13749 @kindex target mips @var{port}
13750 To run a program on the board, start up @code{@value{GDBP}} with the
13751 name of your program as the argument. To connect to the board, use the
13752 command @samp{target mips @var{port}}, where @var{port} is the name of
13753 the serial port connected to the board. If the program has not already
13754 been downloaded to the board, you may use the @code{load} command to
13755 download it. You can then use all the usual @value{GDBN} commands.
13757 For example, this sequence connects to the target board through a serial
13758 port, and loads and runs a program called @var{prog} through the
13762 host$ @value{GDBP} @var{prog}
13763 @value{GDBN} is free software and @dots{}
13764 (@value{GDBP}) target mips /dev/ttyb
13765 (@value{GDBP}) load @var{prog}
13769 @item target mips @var{hostname}:@var{portnumber}
13770 On some @value{GDBN} host configurations, you can specify a TCP
13771 connection (for instance, to a serial line managed by a terminal
13772 concentrator) instead of a serial port, using the syntax
13773 @samp{@var{hostname}:@var{portnumber}}.
13775 @item target pmon @var{port}
13776 @kindex target pmon @var{port}
13779 @item target ddb @var{port}
13780 @kindex target ddb @var{port}
13781 NEC's DDB variant of PMON for Vr4300.
13783 @item target lsi @var{port}
13784 @kindex target lsi @var{port}
13785 LSI variant of PMON.
13787 @kindex target r3900
13788 @item target r3900 @var{dev}
13789 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
13791 @kindex target array
13792 @item target array @var{dev}
13793 Array Tech LSI33K RAID controller board.
13799 @value{GDBN} also supports these special commands for MIPS targets:
13802 @item set mipsfpu double
13803 @itemx set mipsfpu single
13804 @itemx set mipsfpu none
13805 @itemx set mipsfpu auto
13806 @itemx show mipsfpu
13807 @kindex set mipsfpu
13808 @kindex show mipsfpu
13809 @cindex MIPS remote floating point
13810 @cindex floating point, MIPS remote
13811 If your target board does not support the MIPS floating point
13812 coprocessor, you should use the command @samp{set mipsfpu none} (if you
13813 need this, you may wish to put the command in your @value{GDBN} init
13814 file). This tells @value{GDBN} how to find the return value of
13815 functions which return floating point values. It also allows
13816 @value{GDBN} to avoid saving the floating point registers when calling
13817 functions on the board. If you are using a floating point coprocessor
13818 with only single precision floating point support, as on the @sc{r4650}
13819 processor, use the command @samp{set mipsfpu single}. The default
13820 double precision floating point coprocessor may be selected using
13821 @samp{set mipsfpu double}.
13823 In previous versions the only choices were double precision or no
13824 floating point, so @samp{set mipsfpu on} will select double precision
13825 and @samp{set mipsfpu off} will select no floating point.
13827 As usual, you can inquire about the @code{mipsfpu} variable with
13828 @samp{show mipsfpu}.
13830 @item set timeout @var{seconds}
13831 @itemx set retransmit-timeout @var{seconds}
13832 @itemx show timeout
13833 @itemx show retransmit-timeout
13834 @cindex @code{timeout}, MIPS protocol
13835 @cindex @code{retransmit-timeout}, MIPS protocol
13836 @kindex set timeout
13837 @kindex show timeout
13838 @kindex set retransmit-timeout
13839 @kindex show retransmit-timeout
13840 You can control the timeout used while waiting for a packet, in the MIPS
13841 remote protocol, with the @code{set timeout @var{seconds}} command. The
13842 default is 5 seconds. Similarly, you can control the timeout used while
13843 waiting for an acknowledgement of a packet with the @code{set
13844 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
13845 You can inspect both values with @code{show timeout} and @code{show
13846 retransmit-timeout}. (These commands are @emph{only} available when
13847 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
13849 The timeout set by @code{set timeout} does not apply when @value{GDBN}
13850 is waiting for your program to stop. In that case, @value{GDBN} waits
13851 forever because it has no way of knowing how long the program is going
13852 to run before stopping.
13855 @node OpenRISC 1000
13856 @subsection OpenRISC 1000
13857 @cindex OpenRISC 1000
13859 @cindex or1k boards
13860 See OR1k Architecture document (@uref{www.opencores.org}) for more information
13861 about platform and commands.
13865 @kindex target jtag
13866 @item target jtag jtag://@var{host}:@var{port}
13868 Connects to remote JTAG server.
13869 JTAG remote server can be either an or1ksim or JTAG server,
13870 connected via parallel port to the board.
13872 Example: @code{target jtag jtag://localhost:9999}
13875 @item or1ksim @var{command}
13876 If connected to @code{or1ksim} OpenRISC 1000 Architectural
13877 Simulator, proprietary commands can be executed.
13879 @kindex info or1k spr
13880 @item info or1k spr
13881 Displays spr groups.
13883 @item info or1k spr @var{group}
13884 @itemx info or1k spr @var{groupno}
13885 Displays register names in selected group.
13887 @item info or1k spr @var{group} @var{register}
13888 @itemx info or1k spr @var{register}
13889 @itemx info or1k spr @var{groupno} @var{registerno}
13890 @itemx info or1k spr @var{registerno}
13891 Shows information about specified spr register.
13894 @item spr @var{group} @var{register} @var{value}
13895 @itemx spr @var{register @var{value}}
13896 @itemx spr @var{groupno} @var{registerno @var{value}}
13897 @itemx spr @var{registerno @var{value}}
13898 Writes @var{value} to specified spr register.
13901 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
13902 It is very similar to @value{GDBN} trace, except it does not interfere with normal
13903 program execution and is thus much faster. Hardware breakpoints/watchpoint
13904 triggers can be set using:
13907 Load effective address/data
13909 Store effective address/data
13911 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
13916 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
13917 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
13919 @code{htrace} commands:
13920 @cindex OpenRISC 1000 htrace
13923 @item hwatch @var{conditional}
13924 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
13925 or Data. For example:
13927 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
13929 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
13933 Display information about current HW trace configuration.
13935 @item htrace trigger @var{conditional}
13936 Set starting criteria for HW trace.
13938 @item htrace qualifier @var{conditional}
13939 Set acquisition qualifier for HW trace.
13941 @item htrace stop @var{conditional}
13942 Set HW trace stopping criteria.
13944 @item htrace record [@var{data}]*
13945 Selects the data to be recorded, when qualifier is met and HW trace was
13948 @item htrace enable
13949 @itemx htrace disable
13950 Enables/disables the HW trace.
13952 @item htrace rewind [@var{filename}]
13953 Clears currently recorded trace data.
13955 If filename is specified, new trace file is made and any newly collected data
13956 will be written there.
13958 @item htrace print [@var{start} [@var{len}]]
13959 Prints trace buffer, using current record configuration.
13961 @item htrace mode continuous
13962 Set continuous trace mode.
13964 @item htrace mode suspend
13965 Set suspend trace mode.
13970 @subsection PowerPC
13974 @kindex target dink32
13975 @item target dink32 @var{dev}
13976 DINK32 ROM monitor.
13978 @kindex target ppcbug
13979 @item target ppcbug @var{dev}
13980 @kindex target ppcbug1
13981 @item target ppcbug1 @var{dev}
13982 PPCBUG ROM monitor for PowerPC.
13985 @item target sds @var{dev}
13986 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
13991 @subsection HP PA Embedded
13995 @kindex target op50n
13996 @item target op50n @var{dev}
13997 OP50N monitor, running on an OKI HPPA board.
13999 @kindex target w89k
14000 @item target w89k @var{dev}
14001 W89K monitor, running on a Winbond HPPA board.
14006 @subsection Renesas SH
14010 @kindex target hms@r{, with Renesas SH}
14011 @item target hms @var{dev}
14012 A Renesas SH board attached via serial line to your host. Use special
14013 commands @code{device} and @code{speed} to control the serial line and
14014 the communications speed used.
14016 @kindex target e7000@r{, with Renesas SH}
14017 @item target e7000 @var{dev}
14018 E7000 emulator for Renesas SH.
14020 @kindex target sh3@r{, with SH}
14021 @kindex target sh3e@r{, with SH}
14022 @item target sh3 @var{dev}
14023 @item target sh3e @var{dev}
14024 Renesas SH-3 and SH-3E target systems.
14029 @subsection Tsqware Sparclet
14033 @value{GDBN} enables developers to debug tasks running on
14034 Sparclet targets from a Unix host.
14035 @value{GDBN} uses code that runs on
14036 both the Unix host and on the Sparclet target. The program
14037 @code{@value{GDBP}} is installed and executed on the Unix host.
14040 @item remotetimeout @var{args}
14041 @kindex remotetimeout
14042 @value{GDBN} supports the option @code{remotetimeout}.
14043 This option is set by the user, and @var{args} represents the number of
14044 seconds @value{GDBN} waits for responses.
14047 @cindex compiling, on Sparclet
14048 When compiling for debugging, include the options @samp{-g} to get debug
14049 information and @samp{-Ttext} to relocate the program to where you wish to
14050 load it on the target. You may also want to add the options @samp{-n} or
14051 @samp{-N} in order to reduce the size of the sections. Example:
14054 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
14057 You can use @code{objdump} to verify that the addresses are what you intended:
14060 sparclet-aout-objdump --headers --syms prog
14063 @cindex running, on Sparclet
14065 your Unix execution search path to find @value{GDBN}, you are ready to
14066 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
14067 (or @code{sparclet-aout-gdb}, depending on your installation).
14069 @value{GDBN} comes up showing the prompt:
14076 * Sparclet File:: Setting the file to debug
14077 * Sparclet Connection:: Connecting to Sparclet
14078 * Sparclet Download:: Sparclet download
14079 * Sparclet Execution:: Running and debugging
14082 @node Sparclet File
14083 @subsubsection Setting file to debug
14085 The @value{GDBN} command @code{file} lets you choose with program to debug.
14088 (gdbslet) file prog
14092 @value{GDBN} then attempts to read the symbol table of @file{prog}.
14093 @value{GDBN} locates
14094 the file by searching the directories listed in the command search
14096 If the file was compiled with debug information (option "-g"), source
14097 files will be searched as well.
14098 @value{GDBN} locates
14099 the source files by searching the directories listed in the directory search
14100 path (@pxref{Environment, ,Your program's environment}).
14102 to find a file, it displays a message such as:
14105 prog: No such file or directory.
14108 When this happens, add the appropriate directories to the search paths with
14109 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
14110 @code{target} command again.
14112 @node Sparclet Connection
14113 @subsubsection Connecting to Sparclet
14115 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
14116 To connect to a target on serial port ``@code{ttya}'', type:
14119 (gdbslet) target sparclet /dev/ttya
14120 Remote target sparclet connected to /dev/ttya
14121 main () at ../prog.c:3
14125 @value{GDBN} displays messages like these:
14131 @node Sparclet Download
14132 @subsubsection Sparclet download
14134 @cindex download to Sparclet
14135 Once connected to the Sparclet target,
14136 you can use the @value{GDBN}
14137 @code{load} command to download the file from the host to the target.
14138 The file name and load offset should be given as arguments to the @code{load}
14140 Since the file format is aout, the program must be loaded to the starting
14141 address. You can use @code{objdump} to find out what this value is. The load
14142 offset is an offset which is added to the VMA (virtual memory address)
14143 of each of the file's sections.
14144 For instance, if the program
14145 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
14146 and bss at 0x12010170, in @value{GDBN}, type:
14149 (gdbslet) load prog 0x12010000
14150 Loading section .text, size 0xdb0 vma 0x12010000
14153 If the code is loaded at a different address then what the program was linked
14154 to, you may need to use the @code{section} and @code{add-symbol-file} commands
14155 to tell @value{GDBN} where to map the symbol table.
14157 @node Sparclet Execution
14158 @subsubsection Running and debugging
14160 @cindex running and debugging Sparclet programs
14161 You can now begin debugging the task using @value{GDBN}'s execution control
14162 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
14163 manual for the list of commands.
14167 Breakpoint 1 at 0x12010000: file prog.c, line 3.
14169 Starting program: prog
14170 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
14171 3 char *symarg = 0;
14173 4 char *execarg = "hello!";
14178 @subsection Fujitsu Sparclite
14182 @kindex target sparclite
14183 @item target sparclite @var{dev}
14184 Fujitsu sparclite boards, used only for the purpose of loading.
14185 You must use an additional command to debug the program.
14186 For example: target remote @var{dev} using @value{GDBN} standard
14192 @subsection Tandem ST2000
14194 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
14197 To connect your ST2000 to the host system, see the manufacturer's
14198 manual. Once the ST2000 is physically attached, you can run:
14201 target st2000 @var{dev} @var{speed}
14205 to establish it as your debugging environment. @var{dev} is normally
14206 the name of a serial device, such as @file{/dev/ttya}, connected to the
14207 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
14208 connection (for example, to a serial line attached via a terminal
14209 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
14211 The @code{load} and @code{attach} commands are @emph{not} defined for
14212 this target; you must load your program into the ST2000 as you normally
14213 would for standalone operation. @value{GDBN} reads debugging information
14214 (such as symbols) from a separate, debugging version of the program
14215 available on your host computer.
14216 @c FIXME!! This is terribly vague; what little content is here is
14217 @c basically hearsay.
14219 @cindex ST2000 auxiliary commands
14220 These auxiliary @value{GDBN} commands are available to help you with the ST2000
14224 @item st2000 @var{command}
14225 @kindex st2000 @var{cmd}
14226 @cindex STDBUG commands (ST2000)
14227 @cindex commands to STDBUG (ST2000)
14228 Send a @var{command} to the STDBUG monitor. See the manufacturer's
14229 manual for available commands.
14232 @cindex connect (to STDBUG)
14233 Connect the controlling terminal to the STDBUG command monitor. When
14234 you are done interacting with STDBUG, typing either of two character
14235 sequences gets you back to the @value{GDBN} command prompt:
14236 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
14237 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
14241 @subsection Zilog Z8000
14244 @cindex simulator, Z8000
14245 @cindex Zilog Z8000 simulator
14247 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
14250 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
14251 unsegmented variant of the Z8000 architecture) or the Z8001 (the
14252 segmented variant). The simulator recognizes which architecture is
14253 appropriate by inspecting the object code.
14256 @item target sim @var{args}
14258 @kindex target sim@r{, with Z8000}
14259 Debug programs on a simulated CPU. If the simulator supports setup
14260 options, specify them via @var{args}.
14264 After specifying this target, you can debug programs for the simulated
14265 CPU in the same style as programs for your host computer; use the
14266 @code{file} command to load a new program image, the @code{run} command
14267 to run your program, and so on.
14269 As well as making available all the usual machine registers
14270 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
14271 additional items of information as specially named registers:
14276 Counts clock-ticks in the simulator.
14279 Counts instructions run in the simulator.
14282 Execution time in 60ths of a second.
14286 You can refer to these values in @value{GDBN} expressions with the usual
14287 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
14288 conditional breakpoint that suspends only after at least 5000
14289 simulated clock ticks.
14292 @subsection Atmel AVR
14295 When configured for debugging the Atmel AVR, @value{GDBN} supports the
14296 following AVR-specific commands:
14299 @item info io_registers
14300 @kindex info io_registers@r{, AVR}
14301 @cindex I/O registers (Atmel AVR)
14302 This command displays information about the AVR I/O registers. For
14303 each register, @value{GDBN} prints its number and value.
14310 When configured for debugging CRIS, @value{GDBN} provides the
14311 following CRIS-specific commands:
14314 @item set cris-version @var{ver}
14315 @cindex CRIS version
14316 Set the current CRIS version to @var{ver}. The CRIS version affects
14317 register names and sizes. This command is useful in case
14318 autodetection of the CRIS version fails.
14320 @item show cris-version
14321 Show the current CRIS version.
14323 @item set cris-dwarf2-cfi
14324 @cindex DWARF-2 CFI and CRIS
14325 Set the usage of DWARF-2 CFI for CRIS debugging. The default is off
14326 if using @code{gcc-cris} whose version is below @code{R59}, otherwise
14329 @item show cris-dwarf2-cfi
14330 Show the current state of using DWARF-2 CFI.
14334 @subsection Renesas Super-H
14337 For the Renesas Super-H processor, @value{GDBN} provides these
14342 @kindex regs@r{, Super-H}
14343 Show the values of all Super-H registers.
14347 @node Architectures
14348 @section Architectures
14350 This section describes characteristics of architectures that affect
14351 all uses of @value{GDBN} with the architecture, both native and cross.
14358 * HPPA:: HP PA architecture
14362 @subsection x86 Architecture-specific issues.
14365 @item set struct-convention @var{mode}
14366 @kindex set struct-convention
14367 @cindex struct return convention
14368 @cindex struct/union returned in registers
14369 Set the convention used by the inferior to return @code{struct}s and
14370 @code{union}s from functions to @var{mode}. Possible values of
14371 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
14372 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
14373 are returned on the stack, while @code{"reg"} means that a
14374 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
14375 be returned in a register.
14377 @item show struct-convention
14378 @kindex show struct-convention
14379 Show the current setting of the convention to return @code{struct}s
14388 @kindex set rstack_high_address
14389 @cindex AMD 29K register stack
14390 @cindex register stack, AMD29K
14391 @item set rstack_high_address @var{address}
14392 On AMD 29000 family processors, registers are saved in a separate
14393 @dfn{register stack}. There is no way for @value{GDBN} to determine the
14394 extent of this stack. Normally, @value{GDBN} just assumes that the
14395 stack is ``large enough''. This may result in @value{GDBN} referencing
14396 memory locations that do not exist. If necessary, you can get around
14397 this problem by specifying the ending address of the register stack with
14398 the @code{set rstack_high_address} command. The argument should be an
14399 address, which you probably want to precede with @samp{0x} to specify in
14402 @kindex show rstack_high_address
14403 @item show rstack_high_address
14404 Display the current limit of the register stack, on AMD 29000 family
14412 See the following section.
14417 @cindex stack on Alpha
14418 @cindex stack on MIPS
14419 @cindex Alpha stack
14421 Alpha- and MIPS-based computers use an unusual stack frame, which
14422 sometimes requires @value{GDBN} to search backward in the object code to
14423 find the beginning of a function.
14425 @cindex response time, MIPS debugging
14426 To improve response time (especially for embedded applications, where
14427 @value{GDBN} may be restricted to a slow serial line for this search)
14428 you may want to limit the size of this search, using one of these
14432 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
14433 @item set heuristic-fence-post @var{limit}
14434 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
14435 search for the beginning of a function. A value of @var{0} (the
14436 default) means there is no limit. However, except for @var{0}, the
14437 larger the limit the more bytes @code{heuristic-fence-post} must search
14438 and therefore the longer it takes to run. You should only need to use
14439 this command when debugging a stripped executable.
14441 @item show heuristic-fence-post
14442 Display the current limit.
14446 These commands are available @emph{only} when @value{GDBN} is configured
14447 for debugging programs on Alpha or MIPS processors.
14449 Several MIPS-specific commands are available when debugging MIPS
14453 @item set mips saved-gpreg-size @var{size}
14454 @kindex set mips saved-gpreg-size
14455 @cindex MIPS GP register size on stack
14456 Set the size of MIPS general-purpose registers saved on the stack.
14457 The argument @var{size} can be one of the following:
14461 32-bit GP registers
14463 64-bit GP registers
14465 Use the target's default setting or autodetect the saved size from the
14466 information contained in the executable. This is the default
14469 @item show mips saved-gpreg-size
14470 @kindex show mips saved-gpreg-size
14471 Show the current size of MIPS GP registers on the stack.
14473 @item set mips stack-arg-size @var{size}
14474 @kindex set mips stack-arg-size
14475 @cindex MIPS stack space for arguments
14476 Set the amount of stack space reserved for arguments to functions.
14477 The argument can be one of @code{"32"}, @code{"64"} or @code{"auto"}
14480 @item set mips abi @var{arg}
14481 @kindex set mips abi
14482 @cindex set ABI for MIPS
14483 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
14484 values of @var{arg} are:
14488 The default ABI associated with the current binary (this is the
14499 @item show mips abi
14500 @kindex show mips abi
14501 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
14504 @itemx show mipsfpu
14505 @xref{MIPS Embedded, set mipsfpu}.
14507 @item set mips mask-address @var{arg}
14508 @kindex set mips mask-address
14509 @cindex MIPS addresses, masking
14510 This command determines whether the most-significant 32 bits of 64-bit
14511 MIPS addresses are masked off. The argument @var{arg} can be
14512 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
14513 setting, which lets @value{GDBN} determine the correct value.
14515 @item show mips mask-address
14516 @kindex show mips mask-address
14517 Show whether the upper 32 bits of MIPS addresses are masked off or
14520 @item set remote-mips64-transfers-32bit-regs
14521 @kindex set remote-mips64-transfers-32bit-regs
14522 This command controls compatibility with 64-bit MIPS targets that
14523 transfer data in 32-bit quantities. If you have an old MIPS 64 target
14524 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
14525 and 64 bits for other registers, set this option to @samp{on}.
14527 @item show remote-mips64-transfers-32bit-regs
14528 @kindex show remote-mips64-transfers-32bit-regs
14529 Show the current setting of compatibility with older MIPS 64 targets.
14531 @item set debug mips
14532 @kindex set debug mips
14533 This command turns on and off debugging messages for the MIPS-specific
14534 target code in @value{GDBN}.
14536 @item show debug mips
14537 @kindex show debug mips
14538 Show the current setting of MIPS debugging messages.
14544 @cindex HPPA support
14546 When @value{GDBN} is debugging te HP PA architecture, it provides the
14547 following special commands:
14550 @item set debug hppa
14551 @kindex set debug hppa
14552 THis command determines whether HPPA architecture specific debugging
14553 messages are to be displayed.
14555 @item show debug hppa
14556 Show whether HPPA debugging messages are displayed.
14558 @item maint print unwind @var{address}
14559 @kindex maint print unwind@r{, HPPA}
14560 This command displays the contents of the unwind table entry at the
14561 given @var{address}.
14566 @node Controlling GDB
14567 @chapter Controlling @value{GDBN}
14569 You can alter the way @value{GDBN} interacts with you by using the
14570 @code{set} command. For commands controlling how @value{GDBN} displays
14571 data, see @ref{Print Settings, ,Print settings}. Other settings are
14576 * Editing:: Command editing
14577 * History:: Command history
14578 * Screen Size:: Screen size
14579 * Numbers:: Numbers
14580 * ABI:: Configuring the current ABI
14581 * Messages/Warnings:: Optional warnings and messages
14582 * Debugging Output:: Optional messages about internal happenings
14590 @value{GDBN} indicates its readiness to read a command by printing a string
14591 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
14592 can change the prompt string with the @code{set prompt} command. For
14593 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
14594 the prompt in one of the @value{GDBN} sessions so that you can always tell
14595 which one you are talking to.
14597 @emph{Note:} @code{set prompt} does not add a space for you after the
14598 prompt you set. This allows you to set a prompt which ends in a space
14599 or a prompt that does not.
14603 @item set prompt @var{newprompt}
14604 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
14606 @kindex show prompt
14608 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
14612 @section Command editing
14614 @cindex command line editing
14616 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
14617 @sc{gnu} library provides consistent behavior for programs which provide a
14618 command line interface to the user. Advantages are @sc{gnu} Emacs-style
14619 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
14620 substitution, and a storage and recall of command history across
14621 debugging sessions.
14623 You may control the behavior of command line editing in @value{GDBN} with the
14624 command @code{set}.
14627 @kindex set editing
14630 @itemx set editing on
14631 Enable command line editing (enabled by default).
14633 @item set editing off
14634 Disable command line editing.
14636 @kindex show editing
14638 Show whether command line editing is enabled.
14641 @xref{Command Line Editing}, for more details about the Readline
14642 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
14643 encouraged to read that chapter.
14646 @section Command history
14647 @cindex command history
14649 @value{GDBN} can keep track of the commands you type during your
14650 debugging sessions, so that you can be certain of precisely what
14651 happened. Use these commands to manage the @value{GDBN} command
14654 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
14655 package, to provide the history facility. @xref{Using History
14656 Interactively}, for the detailed description of the History library.
14658 Here is the description of @value{GDBN} commands related to command
14662 @cindex history substitution
14663 @cindex history file
14664 @kindex set history filename
14665 @cindex @env{GDBHISTFILE}, environment variable
14666 @item set history filename @var{fname}
14667 Set the name of the @value{GDBN} command history file to @var{fname}.
14668 This is the file where @value{GDBN} reads an initial command history
14669 list, and where it writes the command history from this session when it
14670 exits. You can access this list through history expansion or through
14671 the history command editing characters listed below. This file defaults
14672 to the value of the environment variable @code{GDBHISTFILE}, or to
14673 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
14676 @cindex save command history
14677 @kindex set history save
14678 @item set history save
14679 @itemx set history save on
14680 Record command history in a file, whose name may be specified with the
14681 @code{set history filename} command. By default, this option is disabled.
14683 @item set history save off
14684 Stop recording command history in a file.
14686 @cindex history size
14687 @kindex set history size
14688 @item set history size @var{size}
14689 Set the number of commands which @value{GDBN} keeps in its history list.
14690 This defaults to the value of the environment variable
14691 @code{HISTSIZE}, or to 256 if this variable is not set.
14694 History expansion assigns special meaning to the character @kbd{!}.
14695 @xref{Event Designators}, for more details.
14697 @cindex history expansion, turn on/off
14698 Since @kbd{!} is also the logical not operator in C, history expansion
14699 is off by default. If you decide to enable history expansion with the
14700 @code{set history expansion on} command, you may sometimes need to
14701 follow @kbd{!} (when it is used as logical not, in an expression) with
14702 a space or a tab to prevent it from being expanded. The readline
14703 history facilities do not attempt substitution on the strings
14704 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
14706 The commands to control history expansion are:
14709 @item set history expansion on
14710 @itemx set history expansion
14711 @kindex set history expansion
14712 Enable history expansion. History expansion is off by default.
14714 @item set history expansion off
14715 Disable history expansion.
14718 @kindex show history
14720 @itemx show history filename
14721 @itemx show history save
14722 @itemx show history size
14723 @itemx show history expansion
14724 These commands display the state of the @value{GDBN} history parameters.
14725 @code{show history} by itself displays all four states.
14730 @kindex show commands
14731 @cindex show last commands
14732 @cindex display command history
14733 @item show commands
14734 Display the last ten commands in the command history.
14736 @item show commands @var{n}
14737 Print ten commands centered on command number @var{n}.
14739 @item show commands +
14740 Print ten commands just after the commands last printed.
14744 @section Screen size
14745 @cindex size of screen
14746 @cindex pauses in output
14748 Certain commands to @value{GDBN} may produce large amounts of
14749 information output to the screen. To help you read all of it,
14750 @value{GDBN} pauses and asks you for input at the end of each page of
14751 output. Type @key{RET} when you want to continue the output, or @kbd{q}
14752 to discard the remaining output. Also, the screen width setting
14753 determines when to wrap lines of output. Depending on what is being
14754 printed, @value{GDBN} tries to break the line at a readable place,
14755 rather than simply letting it overflow onto the following line.
14757 Normally @value{GDBN} knows the size of the screen from the terminal
14758 driver software. For example, on Unix @value{GDBN} uses the termcap data base
14759 together with the value of the @code{TERM} environment variable and the
14760 @code{stty rows} and @code{stty cols} settings. If this is not correct,
14761 you can override it with the @code{set height} and @code{set
14768 @kindex show height
14769 @item set height @var{lpp}
14771 @itemx set width @var{cpl}
14773 These @code{set} commands specify a screen height of @var{lpp} lines and
14774 a screen width of @var{cpl} characters. The associated @code{show}
14775 commands display the current settings.
14777 If you specify a height of zero lines, @value{GDBN} does not pause during
14778 output no matter how long the output is. This is useful if output is to a
14779 file or to an editor buffer.
14781 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
14782 from wrapping its output.
14784 @item set pagination on
14785 @itemx set pagination off
14786 @kindex set pagination
14787 Turn the output pagination on or off; the default is on. Turning
14788 pagination off is the alternative to @code{set height 0}.
14790 @item show pagination
14791 @kindex show pagination
14792 Show the current pagination mode.
14797 @cindex number representation
14798 @cindex entering numbers
14800 You can always enter numbers in octal, decimal, or hexadecimal in
14801 @value{GDBN} by the usual conventions: octal numbers begin with
14802 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
14803 begin with @samp{0x}. Numbers that begin with none of these are, by
14804 default, entered in base 10; likewise, the default display for
14805 numbers---when no particular format is specified---is base 10. You can
14806 change the default base for both input and output with the @code{set
14810 @kindex set input-radix
14811 @item set input-radix @var{base}
14812 Set the default base for numeric input. Supported choices
14813 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
14814 specified either unambiguously or using the current default radix; for
14818 set input-radix 012
14819 set input-radix 10.
14820 set input-radix 0xa
14824 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
14825 leaves the input radix unchanged, no matter what it was.
14827 @kindex set output-radix
14828 @item set output-radix @var{base}
14829 Set the default base for numeric display. Supported choices
14830 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
14831 specified either unambiguously or using the current default radix.
14833 @kindex show input-radix
14834 @item show input-radix
14835 Display the current default base for numeric input.
14837 @kindex show output-radix
14838 @item show output-radix
14839 Display the current default base for numeric display.
14841 @item set radix @r{[}@var{base}@r{]}
14845 These commands set and show the default base for both input and output
14846 of numbers. @code{set radix} sets the radix of input and output to
14847 the same base; without an argument, it resets the radix back to its
14848 default value of 10.
14853 @section Configuring the current ABI
14855 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
14856 application automatically. However, sometimes you need to override its
14857 conclusions. Use these commands to manage @value{GDBN}'s view of the
14864 One @value{GDBN} configuration can debug binaries for multiple operating
14865 system targets, either via remote debugging or native emulation.
14866 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
14867 but you can override its conclusion using the @code{set osabi} command.
14868 One example where this is useful is in debugging of binaries which use
14869 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
14870 not have the same identifying marks that the standard C library for your
14875 Show the OS ABI currently in use.
14878 With no argument, show the list of registered available OS ABI's.
14880 @item set osabi @var{abi}
14881 Set the current OS ABI to @var{abi}.
14884 @cindex float promotion
14886 Generally, the way that an argument of type @code{float} is passed to a
14887 function depends on whether the function is prototyped. For a prototyped
14888 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
14889 according to the architecture's convention for @code{float}. For unprototyped
14890 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
14891 @code{double} and then passed.
14893 Unfortunately, some forms of debug information do not reliably indicate whether
14894 a function is prototyped. If @value{GDBN} calls a function that is not marked
14895 as prototyped, it consults @kbd{set coerce-float-to-double}.
14898 @kindex set coerce-float-to-double
14899 @item set coerce-float-to-double
14900 @itemx set coerce-float-to-double on
14901 Arguments of type @code{float} will be promoted to @code{double} when passed
14902 to an unprototyped function. This is the default setting.
14904 @item set coerce-float-to-double off
14905 Arguments of type @code{float} will be passed directly to unprototyped
14908 @kindex show coerce-float-to-double
14909 @item show coerce-float-to-double
14910 Show the current setting of promoting @code{float} to @code{double}.
14914 @kindex show cp-abi
14915 @value{GDBN} needs to know the ABI used for your program's C@t{++}
14916 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
14917 used to build your application. @value{GDBN} only fully supports
14918 programs with a single C@t{++} ABI; if your program contains code using
14919 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
14920 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
14921 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
14922 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
14923 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
14924 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
14929 Show the C@t{++} ABI currently in use.
14932 With no argument, show the list of supported C@t{++} ABI's.
14934 @item set cp-abi @var{abi}
14935 @itemx set cp-abi auto
14936 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
14939 @node Messages/Warnings
14940 @section Optional warnings and messages
14942 @cindex verbose operation
14943 @cindex optional warnings
14944 By default, @value{GDBN} is silent about its inner workings. If you are
14945 running on a slow machine, you may want to use the @code{set verbose}
14946 command. This makes @value{GDBN} tell you when it does a lengthy
14947 internal operation, so you will not think it has crashed.
14949 Currently, the messages controlled by @code{set verbose} are those
14950 which announce that the symbol table for a source file is being read;
14951 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
14954 @kindex set verbose
14955 @item set verbose on
14956 Enables @value{GDBN} output of certain informational messages.
14958 @item set verbose off
14959 Disables @value{GDBN} output of certain informational messages.
14961 @kindex show verbose
14963 Displays whether @code{set verbose} is on or off.
14966 By default, if @value{GDBN} encounters bugs in the symbol table of an
14967 object file, it is silent; but if you are debugging a compiler, you may
14968 find this information useful (@pxref{Symbol Errors, ,Errors reading
14973 @kindex set complaints
14974 @item set complaints @var{limit}
14975 Permits @value{GDBN} to output @var{limit} complaints about each type of
14976 unusual symbols before becoming silent about the problem. Set
14977 @var{limit} to zero to suppress all complaints; set it to a large number
14978 to prevent complaints from being suppressed.
14980 @kindex show complaints
14981 @item show complaints
14982 Displays how many symbol complaints @value{GDBN} is permitted to produce.
14986 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
14987 lot of stupid questions to confirm certain commands. For example, if
14988 you try to run a program which is already running:
14992 The program being debugged has been started already.
14993 Start it from the beginning? (y or n)
14996 If you are willing to unflinchingly face the consequences of your own
14997 commands, you can disable this ``feature'':
15001 @kindex set confirm
15003 @cindex confirmation
15004 @cindex stupid questions
15005 @item set confirm off
15006 Disables confirmation requests.
15008 @item set confirm on
15009 Enables confirmation requests (the default).
15011 @kindex show confirm
15013 Displays state of confirmation requests.
15017 @node Debugging Output
15018 @section Optional messages about internal happenings
15019 @cindex optional debugging messages
15021 @value{GDBN} has commands that enable optional debugging messages from
15022 various @value{GDBN} subsystems; normally these commands are of
15023 interest to @value{GDBN} maintainers, or when reporting a bug. This
15024 section documents those commands.
15027 @kindex set exec-done-display
15028 @item set exec-done-display
15029 Turns on or off the notification of asynchronous commands'
15030 completion. When on, @value{GDBN} will print a message when an
15031 asynchronous command finishes its execution. The default is off.
15032 @kindex show exec-done-display
15033 @item show exec-done-display
15034 Displays the current setting of asynchronous command completion
15037 @cindex gdbarch debugging info
15038 @cindex architecture debugging info
15039 @item set debug arch
15040 Turns on or off display of gdbarch debugging info. The default is off
15042 @item show debug arch
15043 Displays the current state of displaying gdbarch debugging info.
15044 @item set debug aix-thread
15045 @cindex AIX threads
15046 Display debugging messages about inner workings of the AIX thread
15048 @item show debug aix-thread
15049 Show the current state of AIX thread debugging info display.
15050 @item set debug event
15051 @cindex event debugging info
15052 Turns on or off display of @value{GDBN} event debugging info. The
15054 @item show debug event
15055 Displays the current state of displaying @value{GDBN} event debugging
15057 @item set debug expression
15058 @cindex expression debugging info
15059 Turns on or off display of debugging info about @value{GDBN}
15060 expression parsing. The default is off.
15061 @item show debug expression
15062 Displays the current state of displaying debugging info about
15063 @value{GDBN} expression parsing.
15064 @item set debug frame
15065 @cindex frame debugging info
15066 Turns on or off display of @value{GDBN} frame debugging info. The
15068 @item show debug frame
15069 Displays the current state of displaying @value{GDBN} frame debugging
15071 @item set debug infrun
15072 @cindex inferior debugging info
15073 Turns on or off display of @value{GDBN} debugging info for running the inferior.
15074 The default is off. @file{infrun.c} contains GDB's runtime state machine used
15075 for implementing operations such as single-stepping the inferior.
15076 @item show debug infrun
15077 Displays the current state of @value{GDBN} inferior debugging.
15078 @item set debug lin-lwp
15079 @cindex @sc{gnu}/Linux LWP debug messages
15080 @cindex Linux lightweight processes
15081 Turns on or off debugging messages from the Linux LWP debug support.
15082 @item show debug lin-lwp
15083 Show the current state of Linux LWP debugging messages.
15084 @item set debug observer
15085 @cindex observer debugging info
15086 Turns on or off display of @value{GDBN} observer debugging. This
15087 includes info such as the notification of observable events.
15088 @item show debug observer
15089 Displays the current state of observer debugging.
15090 @item set debug overload
15091 @cindex C@t{++} overload debugging info
15092 Turns on or off display of @value{GDBN} C@t{++} overload debugging
15093 info. This includes info such as ranking of functions, etc. The default
15095 @item show debug overload
15096 Displays the current state of displaying @value{GDBN} C@t{++} overload
15098 @cindex packets, reporting on stdout
15099 @cindex serial connections, debugging
15100 @item set debug remote
15101 Turns on or off display of reports on all packets sent back and forth across
15102 the serial line to the remote machine. The info is printed on the
15103 @value{GDBN} standard output stream. The default is off.
15104 @item show debug remote
15105 Displays the state of display of remote packets.
15106 @item set debug serial
15107 Turns on or off display of @value{GDBN} serial debugging info. The
15109 @item show debug serial
15110 Displays the current state of displaying @value{GDBN} serial debugging
15112 @item set debug target
15113 @cindex target debugging info
15114 Turns on or off display of @value{GDBN} target debugging info. This info
15115 includes what is going on at the target level of GDB, as it happens. The
15116 default is 0. Set it to 1 to track events, and to 2 to also track the
15117 value of large memory transfers. Changes to this flag do not take effect
15118 until the next time you connect to a target or use the @code{run} command.
15119 @item show debug target
15120 Displays the current state of displaying @value{GDBN} target debugging
15122 @item set debug varobj
15123 @cindex variable object debugging info
15124 Turns on or off display of @value{GDBN} variable object debugging
15125 info. The default is off.
15126 @item show debug varobj
15127 Displays the current state of displaying @value{GDBN} variable object
15132 @chapter Canned Sequences of Commands
15134 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
15135 command lists}), @value{GDBN} provides two ways to store sequences of
15136 commands for execution as a unit: user-defined commands and command
15140 * Define:: User-defined commands
15141 * Hooks:: User-defined command hooks
15142 * Command Files:: Command files
15143 * Output:: Commands for controlled output
15147 @section User-defined commands
15149 @cindex user-defined command
15150 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
15151 which you assign a new name as a command. This is done with the
15152 @code{define} command. User commands may accept up to 10 arguments
15153 separated by whitespace. Arguments are accessed within the user command
15154 via @var{$arg0@dots{}$arg9}. A trivial example:
15158 print $arg0 + $arg1 + $arg2
15162 To execute the command use:
15169 This defines the command @code{adder}, which prints the sum of
15170 its three arguments. Note the arguments are text substitutions, so they may
15171 reference variables, use complex expressions, or even perform inferior
15177 @item define @var{commandname}
15178 Define a command named @var{commandname}. If there is already a command
15179 by that name, you are asked to confirm that you want to redefine it.
15181 The definition of the command is made up of other @value{GDBN} command lines,
15182 which are given following the @code{define} command. The end of these
15183 commands is marked by a line containing @code{end}.
15189 Takes a single argument, which is an expression to evaluate.
15190 It is followed by a series of commands that are executed
15191 only if the expression is true (nonzero).
15192 There can then optionally be a line @code{else}, followed
15193 by a series of commands that are only executed if the expression
15194 was false. The end of the list is marked by a line containing @code{end}.
15198 The syntax is similar to @code{if}: the command takes a single argument,
15199 which is an expression to evaluate, and must be followed by the commands to
15200 execute, one per line, terminated by an @code{end}.
15201 The commands are executed repeatedly as long as the expression
15205 @item document @var{commandname}
15206 Document the user-defined command @var{commandname}, so that it can be
15207 accessed by @code{help}. The command @var{commandname} must already be
15208 defined. This command reads lines of documentation just as @code{define}
15209 reads the lines of the command definition, ending with @code{end}.
15210 After the @code{document} command is finished, @code{help} on command
15211 @var{commandname} displays the documentation you have written.
15213 You may use the @code{document} command again to change the
15214 documentation of a command. Redefining the command with @code{define}
15215 does not change the documentation.
15217 @kindex help user-defined
15218 @item help user-defined
15219 List all user-defined commands, with the first line of the documentation
15224 @itemx show user @var{commandname}
15225 Display the @value{GDBN} commands used to define @var{commandname} (but
15226 not its documentation). If no @var{commandname} is given, display the
15227 definitions for all user-defined commands.
15229 @cindex infinite recusrion in user-defined commands
15230 @kindex show max-user-call-depth
15231 @kindex set max-user-call-depth
15232 @item show max-user-call-depth
15233 @itemx set max-user-call-depth
15234 The value of @code{max-user-call-depth} controls how many recursion
15235 levels are allowed in user-defined commands before GDB suspects an
15236 infinite recursion and aborts the command.
15240 When user-defined commands are executed, the
15241 commands of the definition are not printed. An error in any command
15242 stops execution of the user-defined command.
15244 If used interactively, commands that would ask for confirmation proceed
15245 without asking when used inside a user-defined command. Many @value{GDBN}
15246 commands that normally print messages to say what they are doing omit the
15247 messages when used in a user-defined command.
15250 @section User-defined command hooks
15251 @cindex command hooks
15252 @cindex hooks, for commands
15253 @cindex hooks, pre-command
15256 You may define @dfn{hooks}, which are a special kind of user-defined
15257 command. Whenever you run the command @samp{foo}, if the user-defined
15258 command @samp{hook-foo} exists, it is executed (with no arguments)
15259 before that command.
15261 @cindex hooks, post-command
15263 A hook may also be defined which is run after the command you executed.
15264 Whenever you run the command @samp{foo}, if the user-defined command
15265 @samp{hookpost-foo} exists, it is executed (with no arguments) after
15266 that command. Post-execution hooks may exist simultaneously with
15267 pre-execution hooks, for the same command.
15269 It is valid for a hook to call the command which it hooks. If this
15270 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
15272 @c It would be nice if hookpost could be passed a parameter indicating
15273 @c if the command it hooks executed properly or not. FIXME!
15275 @kindex stop@r{, a pseudo-command}
15276 In addition, a pseudo-command, @samp{stop} exists. Defining
15277 (@samp{hook-stop}) makes the associated commands execute every time
15278 execution stops in your program: before breakpoint commands are run,
15279 displays are printed, or the stack frame is printed.
15281 For example, to ignore @code{SIGALRM} signals while
15282 single-stepping, but treat them normally during normal execution,
15287 handle SIGALRM nopass
15291 handle SIGALRM pass
15294 define hook-continue
15295 handle SIGLARM pass
15299 As a further example, to hook at the begining and end of the @code{echo}
15300 command, and to add extra text to the beginning and end of the message,
15308 define hookpost-echo
15312 (@value{GDBP}) echo Hello World
15313 <<<---Hello World--->>>
15318 You can define a hook for any single-word command in @value{GDBN}, but
15319 not for command aliases; you should define a hook for the basic command
15320 name, e.g. @code{backtrace} rather than @code{bt}.
15321 @c FIXME! So how does Joe User discover whether a command is an alias
15323 If an error occurs during the execution of your hook, execution of
15324 @value{GDBN} commands stops and @value{GDBN} issues a prompt
15325 (before the command that you actually typed had a chance to run).
15327 If you try to define a hook which does not match any known command, you
15328 get a warning from the @code{define} command.
15330 @node Command Files
15331 @section Command files
15333 @cindex command files
15334 A command file for @value{GDBN} is a file of lines that are @value{GDBN}
15335 commands. Comments (lines starting with @kbd{#}) may also be included.
15336 An empty line in a command file does nothing; it does not mean to repeat
15337 the last command, as it would from the terminal.
15340 @cindex @file{.gdbinit}
15341 @cindex @file{gdb.ini}
15342 When you start @value{GDBN}, it automatically executes commands from its
15343 @dfn{init files}, normally called @file{.gdbinit}@footnote{The DJGPP
15344 port of @value{GDBN} uses the name @file{gdb.ini} instead, due to the
15345 limitations of file names imposed by DOS filesystems.}.
15346 During startup, @value{GDBN} does the following:
15350 Reads the init file (if any) in your home directory@footnote{On
15351 DOS/Windows systems, the home directory is the one pointed to by the
15352 @code{HOME} environment variable.}.
15355 Processes command line options and operands.
15358 Reads the init file (if any) in the current working directory.
15361 Reads command files specified by the @samp{-x} option.
15364 The init file in your home directory can set options (such as @samp{set
15365 complaints}) that affect subsequent processing of command line options
15366 and operands. Init files are not executed if you use the @samp{-nx}
15367 option (@pxref{Mode Options, ,Choosing modes}).
15369 @cindex init file name
15370 On some configurations of @value{GDBN}, the init file is known by a
15371 different name (these are typically environments where a specialized
15372 form of @value{GDBN} may need to coexist with other forms, hence a
15373 different name for the specialized version's init file). These are the
15374 environments with special init file names:
15376 @cindex @file{.vxgdbinit}
15379 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
15381 @cindex @file{.os68gdbinit}
15383 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
15385 @cindex @file{.esgdbinit}
15387 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
15390 You can also request the execution of a command file with the
15391 @code{source} command:
15395 @item source @var{filename}
15396 Execute the command file @var{filename}.
15399 The lines in a command file are executed sequentially. They are not
15400 printed as they are executed. An error in any command terminates
15401 execution of the command file and control is returned to the console.
15403 Commands that would ask for confirmation if used interactively proceed
15404 without asking when used in a command file. Many @value{GDBN} commands that
15405 normally print messages to say what they are doing omit the messages
15406 when called from command files.
15408 @value{GDBN} also accepts command input from standard input. In this
15409 mode, normal output goes to standard output and error output goes to
15410 standard error. Errors in a command file supplied on standard input do
15411 not terminate execution of the command file --- execution continues with
15415 gdb < cmds > log 2>&1
15418 (The syntax above will vary depending on the shell used.) This example
15419 will execute commands from the file @file{cmds}. All output and errors
15420 would be directed to @file{log}.
15423 @section Commands for controlled output
15425 During the execution of a command file or a user-defined command, normal
15426 @value{GDBN} output is suppressed; the only output that appears is what is
15427 explicitly printed by the commands in the definition. This section
15428 describes three commands useful for generating exactly the output you
15433 @item echo @var{text}
15434 @c I do not consider backslash-space a standard C escape sequence
15435 @c because it is not in ANSI.
15436 Print @var{text}. Nonprinting characters can be included in
15437 @var{text} using C escape sequences, such as @samp{\n} to print a
15438 newline. @strong{No newline is printed unless you specify one.}
15439 In addition to the standard C escape sequences, a backslash followed
15440 by a space stands for a space. This is useful for displaying a
15441 string with spaces at the beginning or the end, since leading and
15442 trailing spaces are otherwise trimmed from all arguments.
15443 To print @samp{@w{ }and foo =@w{ }}, use the command
15444 @samp{echo \@w{ }and foo = \@w{ }}.
15446 A backslash at the end of @var{text} can be used, as in C, to continue
15447 the command onto subsequent lines. For example,
15450 echo This is some text\n\
15451 which is continued\n\
15452 onto several lines.\n
15455 produces the same output as
15458 echo This is some text\n
15459 echo which is continued\n
15460 echo onto several lines.\n
15464 @item output @var{expression}
15465 Print the value of @var{expression} and nothing but that value: no
15466 newlines, no @samp{$@var{nn} = }. The value is not entered in the
15467 value history either. @xref{Expressions, ,Expressions}, for more information
15470 @item output/@var{fmt} @var{expression}
15471 Print the value of @var{expression} in format @var{fmt}. You can use
15472 the same formats as for @code{print}. @xref{Output Formats,,Output
15473 formats}, for more information.
15476 @item printf @var{string}, @var{expressions}@dots{}
15477 Print the values of the @var{expressions} under the control of
15478 @var{string}. The @var{expressions} are separated by commas and may be
15479 either numbers or pointers. Their values are printed as specified by
15480 @var{string}, exactly as if your program were to execute the C
15482 @c FIXME: the above implies that at least all ANSI C formats are
15483 @c supported, but it isn't true: %E and %G don't work (or so it seems).
15484 @c Either this is a bug, or the manual should document what formats are
15488 printf (@var{string}, @var{expressions}@dots{});
15491 For example, you can print two values in hex like this:
15494 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
15497 The only backslash-escape sequences that you can use in the format
15498 string are the simple ones that consist of backslash followed by a
15503 @chapter Command Interpreters
15504 @cindex command interpreters
15506 @value{GDBN} supports multiple command interpreters, and some command
15507 infrastructure to allow users or user interface writers to switch
15508 between interpreters or run commands in other interpreters.
15510 @value{GDBN} currently supports two command interpreters, the console
15511 interpreter (sometimes called the command-line interpreter or @sc{cli})
15512 and the machine interface interpreter (or @sc{gdb/mi}). This manual
15513 describes both of these interfaces in great detail.
15515 By default, @value{GDBN} will start with the console interpreter.
15516 However, the user may choose to start @value{GDBN} with another
15517 interpreter by specifying the @option{-i} or @option{--interpreter}
15518 startup options. Defined interpreters include:
15522 @cindex console interpreter
15523 The traditional console or command-line interpreter. This is the most often
15524 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
15525 @value{GDBN} will use this interpreter.
15528 @cindex mi interpreter
15529 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
15530 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
15531 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
15535 @cindex mi2 interpreter
15536 The current @sc{gdb/mi} interface.
15539 @cindex mi1 interpreter
15540 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
15544 @cindex invoke another interpreter
15545 The interpreter being used by @value{GDBN} may not be dynamically
15546 switched at runtime. Although possible, this could lead to a very
15547 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
15548 enters the command "interpreter-set console" in a console view,
15549 @value{GDBN} would switch to using the console interpreter, rendering
15550 the IDE inoperable!
15552 @kindex interpreter-exec
15553 Although you may only choose a single interpreter at startup, you may execute
15554 commands in any interpreter from the current interpreter using the appropriate
15555 command. If you are running the console interpreter, simply use the
15556 @code{interpreter-exec} command:
15559 interpreter-exec mi "-data-list-register-names"
15562 @sc{gdb/mi} has a similar command, although it is only available in versions of
15563 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
15566 @chapter @value{GDBN} Text User Interface
15568 @cindex Text User Interface
15571 * TUI Overview:: TUI overview
15572 * TUI Keys:: TUI key bindings
15573 * TUI Single Key Mode:: TUI single key mode
15574 * TUI Commands:: TUI specific commands
15575 * TUI Configuration:: TUI configuration variables
15578 The @value{GDBN} Text User Interface, TUI in short, is a terminal
15579 interface which uses the @code{curses} library to show the source
15580 file, the assembly output, the program registers and @value{GDBN}
15581 commands in separate text windows.
15583 The TUI is enabled by invoking @value{GDBN} using either
15585 @samp{gdbtui} or @samp{gdb -tui}.
15588 @section TUI overview
15590 The TUI has two display modes that can be switched while
15595 A curses (or TUI) mode in which it displays several text
15596 windows on the terminal.
15599 A standard mode which corresponds to the @value{GDBN} configured without
15603 In the TUI mode, @value{GDBN} can display several text window
15608 This window is the @value{GDBN} command window with the @value{GDBN}
15609 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
15610 managed using readline but through the TUI. The @emph{command}
15611 window is always visible.
15614 The source window shows the source file of the program. The current
15615 line as well as active breakpoints are displayed in this window.
15618 The assembly window shows the disassembly output of the program.
15621 This window shows the processor registers. It detects when
15622 a register is changed and when this is the case, registers that have
15623 changed are highlighted.
15627 The source and assembly windows show the current program position
15628 by highlighting the current line and marking them with the @samp{>} marker.
15629 Breakpoints are also indicated with two markers. A first one
15630 indicates the breakpoint type:
15634 Breakpoint which was hit at least once.
15637 Breakpoint which was never hit.
15640 Hardware breakpoint which was hit at least once.
15643 Hardware breakpoint which was never hit.
15647 The second marker indicates whether the breakpoint is enabled or not:
15651 Breakpoint is enabled.
15654 Breakpoint is disabled.
15658 The source, assembly and register windows are attached to the thread
15659 and the frame position. They are updated when the current thread
15660 changes, when the frame changes or when the program counter changes.
15661 These three windows are arranged by the TUI according to several
15662 layouts. The layout defines which of these three windows are visible.
15663 The following layouts are available:
15673 source and assembly
15676 source and registers
15679 assembly and registers
15683 On top of the command window a status line gives various information
15684 concerning the current process begin debugged. The status line is
15685 updated when the information it shows changes. The following fields
15690 Indicates the current gdb target
15691 (@pxref{Targets, ,Specifying a Debugging Target}).
15694 Gives information about the current process or thread number.
15695 When no process is being debugged, this field is set to @code{No process}.
15698 Gives the current function name for the selected frame.
15699 The name is demangled if demangling is turned on (@pxref{Print Settings}).
15700 When there is no symbol corresponding to the current program counter
15701 the string @code{??} is displayed.
15704 Indicates the current line number for the selected frame.
15705 When the current line number is not known the string @code{??} is displayed.
15708 Indicates the current program counter address.
15713 @section TUI Key Bindings
15714 @cindex TUI key bindings
15716 The TUI installs several key bindings in the readline keymaps
15717 (@pxref{Command Line Editing}).
15718 They allow to leave or enter in the TUI mode or they operate
15719 directly on the TUI layout and windows. The TUI also provides
15720 a @emph{SingleKey} keymap which binds several keys directly to
15721 @value{GDBN} commands. The following key bindings
15722 are installed for both TUI mode and the @value{GDBN} standard mode.
15731 Enter or leave the TUI mode. When the TUI mode is left,
15732 the curses window management is left and @value{GDBN} operates using
15733 its standard mode writing on the terminal directly. When the TUI
15734 mode is entered, the control is given back to the curses windows.
15735 The screen is then refreshed.
15739 Use a TUI layout with only one window. The layout will
15740 either be @samp{source} or @samp{assembly}. When the TUI mode
15741 is not active, it will switch to the TUI mode.
15743 Think of this key binding as the Emacs @kbd{C-x 1} binding.
15747 Use a TUI layout with at least two windows. When the current
15748 layout shows already two windows, a next layout with two windows is used.
15749 When a new layout is chosen, one window will always be common to the
15750 previous layout and the new one.
15752 Think of it as the Emacs @kbd{C-x 2} binding.
15756 Change the active window. The TUI associates several key bindings
15757 (like scrolling and arrow keys) to the active window. This command
15758 gives the focus to the next TUI window.
15760 Think of it as the Emacs @kbd{C-x o} binding.
15764 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
15765 (@pxref{TUI Single Key Mode}).
15769 The following key bindings are handled only by the TUI mode:
15774 Scroll the active window one page up.
15778 Scroll the active window one page down.
15782 Scroll the active window one line up.
15786 Scroll the active window one line down.
15790 Scroll the active window one column left.
15794 Scroll the active window one column right.
15798 Refresh the screen.
15802 In the TUI mode, the arrow keys are used by the active window
15803 for scrolling. This means they are available for readline when the
15804 active window is the command window. When the command window
15805 does not have the focus, it is necessary to use other readline
15806 key bindings such as @key{C-p}, @key{C-n}, @key{C-b} and @key{C-f}.
15808 @node TUI Single Key Mode
15809 @section TUI Single Key Mode
15810 @cindex TUI single key mode
15812 The TUI provides a @emph{SingleKey} mode in which it installs a particular
15813 key binding in the readline keymaps to connect single keys to
15817 @kindex c @r{(SingleKey TUI key)}
15821 @kindex d @r{(SingleKey TUI key)}
15825 @kindex f @r{(SingleKey TUI key)}
15829 @kindex n @r{(SingleKey TUI key)}
15833 @kindex q @r{(SingleKey TUI key)}
15835 exit the @emph{SingleKey} mode.
15837 @kindex r @r{(SingleKey TUI key)}
15841 @kindex s @r{(SingleKey TUI key)}
15845 @kindex u @r{(SingleKey TUI key)}
15849 @kindex v @r{(SingleKey TUI key)}
15853 @kindex w @r{(SingleKey TUI key)}
15859 Other keys temporarily switch to the @value{GDBN} command prompt.
15860 The key that was pressed is inserted in the editing buffer so that
15861 it is possible to type most @value{GDBN} commands without interaction
15862 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
15863 @emph{SingleKey} mode is restored. The only way to permanently leave
15864 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
15868 @section TUI specific commands
15869 @cindex TUI commands
15871 The TUI has specific commands to control the text windows.
15872 These commands are always available, that is they do not depend on
15873 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
15874 is in the standard mode, using these commands will automatically switch
15880 List and give the size of all displayed windows.
15884 Display the next layout.
15887 Display the previous layout.
15890 Display the source window only.
15893 Display the assembly window only.
15896 Display the source and assembly window.
15899 Display the register window together with the source or assembly window.
15901 @item focus next | prev | src | asm | regs | split
15903 Set the focus to the named window.
15904 This command allows to change the active window so that scrolling keys
15905 can be affected to another window.
15909 Refresh the screen. This is similar to using @key{C-L} key.
15911 @item tui reg float
15913 Show the floating point registers in the register window.
15915 @item tui reg general
15916 Show the general registers in the register window.
15919 Show the next register group. The list of register groups as well as
15920 their order is target specific. The predefined register groups are the
15921 following: @code{general}, @code{float}, @code{system}, @code{vector},
15922 @code{all}, @code{save}, @code{restore}.
15924 @item tui reg system
15925 Show the system registers in the register window.
15929 Update the source window and the current execution point.
15931 @item winheight @var{name} +@var{count}
15932 @itemx winheight @var{name} -@var{count}
15934 Change the height of the window @var{name} by @var{count}
15935 lines. Positive counts increase the height, while negative counts
15940 @node TUI Configuration
15941 @section TUI configuration variables
15942 @cindex TUI configuration variables
15944 The TUI has several configuration variables that control the
15945 appearance of windows on the terminal.
15948 @item set tui border-kind @var{kind}
15949 @kindex set tui border-kind
15950 Select the border appearance for the source, assembly and register windows.
15951 The possible values are the following:
15954 Use a space character to draw the border.
15957 Use ascii characters + - and | to draw the border.
15960 Use the Alternate Character Set to draw the border. The border is
15961 drawn using character line graphics if the terminal supports them.
15965 @item set tui active-border-mode @var{mode}
15966 @kindex set tui active-border-mode
15967 Select the attributes to display the border of the active window.
15968 The possible values are @code{normal}, @code{standout}, @code{reverse},
15969 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
15971 @item set tui border-mode @var{mode}
15972 @kindex set tui border-mode
15973 Select the attributes to display the border of other windows.
15974 The @var{mode} can be one of the following:
15977 Use normal attributes to display the border.
15983 Use reverse video mode.
15986 Use half bright mode.
15988 @item half-standout
15989 Use half bright and standout mode.
15992 Use extra bright or bold mode.
15994 @item bold-standout
15995 Use extra bright or bold and standout mode.
16002 @chapter Using @value{GDBN} under @sc{gnu} Emacs
16005 @cindex @sc{gnu} Emacs
16006 A special interface allows you to use @sc{gnu} Emacs to view (and
16007 edit) the source files for the program you are debugging with
16010 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
16011 executable file you want to debug as an argument. This command starts
16012 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
16013 created Emacs buffer.
16014 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
16016 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
16021 All ``terminal'' input and output goes through the Emacs buffer.
16024 This applies both to @value{GDBN} commands and their output, and to the input
16025 and output done by the program you are debugging.
16027 This is useful because it means that you can copy the text of previous
16028 commands and input them again; you can even use parts of the output
16031 All the facilities of Emacs' Shell mode are available for interacting
16032 with your program. In particular, you can send signals the usual
16033 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
16038 @value{GDBN} displays source code through Emacs.
16041 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
16042 source file for that frame and puts an arrow (@samp{=>}) at the
16043 left margin of the current line. Emacs uses a separate buffer for
16044 source display, and splits the screen to show both your @value{GDBN} session
16047 Explicit @value{GDBN} @code{list} or search commands still produce output as
16048 usual, but you probably have no reason to use them from Emacs.
16050 If you specify an absolute file name when prompted for the @kbd{M-x
16051 gdb} argument, then Emacs sets your current working directory to where
16052 your program resides. If you only specify the file name, then Emacs
16053 sets your current working directory to to the directory associated
16054 with the previous buffer. In this case, @value{GDBN} may find your
16055 program by searching your environment's @code{PATH} variable, but on
16056 some operating systems it might not find the source. So, although the
16057 @value{GDBN} input and output session proceeds normally, the auxiliary
16058 buffer does not display the current source and line of execution.
16060 The initial working directory of @value{GDBN} is printed on the top
16061 line of the @value{GDBN} I/O buffer and this serves as a default for
16062 the commands that specify files for @value{GDBN} to operate
16063 on. @xref{Files, ,Commands to specify files}.
16065 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
16066 need to call @value{GDBN} by a different name (for example, if you
16067 keep several configurations around, with different names) you can
16068 customize the Emacs variable @code{gud-gdb-command-name} to run the
16071 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
16072 addition to the standard Shell mode commands:
16076 Describe the features of Emacs' @value{GDBN} Mode.
16079 Execute to another source line, like the @value{GDBN} @code{step} command; also
16080 update the display window to show the current file and location.
16083 Execute to next source line in this function, skipping all function
16084 calls, like the @value{GDBN} @code{next} command. Then update the display window
16085 to show the current file and location.
16088 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
16089 display window accordingly.
16092 Execute until exit from the selected stack frame, like the @value{GDBN}
16093 @code{finish} command.
16096 Continue execution of your program, like the @value{GDBN} @code{continue}
16100 Go up the number of frames indicated by the numeric argument
16101 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
16102 like the @value{GDBN} @code{up} command.
16105 Go down the number of frames indicated by the numeric argument, like the
16106 @value{GDBN} @code{down} command.
16109 In any source file, the Emacs command @kbd{C-x SPC} (@code{gud-break})
16110 tells @value{GDBN} to set a breakpoint on the source line point is on.
16112 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
16113 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
16114 point to any frame in the stack and type @key{RET} to make it become the
16115 current frame and display the associated source in the source buffer.
16116 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
16119 If you accidentally delete the source-display buffer, an easy way to get
16120 it back is to type the command @code{f} in the @value{GDBN} buffer, to
16121 request a frame display; when you run under Emacs, this recreates
16122 the source buffer if necessary to show you the context of the current
16125 The source files displayed in Emacs are in ordinary Emacs buffers
16126 which are visiting the source files in the usual way. You can edit
16127 the files with these buffers if you wish; but keep in mind that @value{GDBN}
16128 communicates with Emacs in terms of line numbers. If you add or
16129 delete lines from the text, the line numbers that @value{GDBN} knows cease
16130 to correspond properly with the code.
16132 The description given here is for GNU Emacs version 21.3 and a more
16133 detailed description of its interaction with @value{GDBN} is given in
16134 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
16136 @c The following dropped because Epoch is nonstandard. Reactivate
16137 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
16139 @kindex Emacs Epoch environment
16143 Version 18 of @sc{gnu} Emacs has a built-in window system
16144 called the @code{epoch}
16145 environment. Users of this environment can use a new command,
16146 @code{inspect} which performs identically to @code{print} except that
16147 each value is printed in its own window.
16152 @chapter The @sc{gdb/mi} Interface
16154 @unnumberedsec Function and Purpose
16156 @cindex @sc{gdb/mi}, its purpose
16157 @sc{gdb/mi} is a line based machine oriented text interface to @value{GDBN}. It is
16158 specifically intended to support the development of systems which use
16159 the debugger as just one small component of a larger system.
16161 This chapter is a specification of the @sc{gdb/mi} interface. It is written
16162 in the form of a reference manual.
16164 Note that @sc{gdb/mi} is still under construction, so some of the
16165 features described below are incomplete and subject to change.
16167 @unnumberedsec Notation and Terminology
16169 @cindex notational conventions, for @sc{gdb/mi}
16170 This chapter uses the following notation:
16174 @code{|} separates two alternatives.
16177 @code{[ @var{something} ]} indicates that @var{something} is optional:
16178 it may or may not be given.
16181 @code{( @var{group} )*} means that @var{group} inside the parentheses
16182 may repeat zero or more times.
16185 @code{( @var{group} )+} means that @var{group} inside the parentheses
16186 may repeat one or more times.
16189 @code{"@var{string}"} means a literal @var{string}.
16193 @heading Dependencies
16196 @heading Acknowledgments
16198 In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
16202 * GDB/MI Command Syntax::
16203 * GDB/MI Compatibility with CLI::
16204 * GDB/MI Output Records::
16205 * GDB/MI Command Description Format::
16206 * GDB/MI Breakpoint Table Commands::
16207 * GDB/MI Data Manipulation::
16208 * GDB/MI Program Control::
16209 * GDB/MI Miscellaneous Commands::
16211 * GDB/MI Kod Commands::
16212 * GDB/MI Memory Overlay Commands::
16213 * GDB/MI Signal Handling Commands::
16215 * GDB/MI Stack Manipulation::
16216 * GDB/MI Symbol Query::
16217 * GDB/MI Target Manipulation::
16218 * GDB/MI Thread Commands::
16219 * GDB/MI Tracepoint Commands::
16220 * GDB/MI Variable Objects::
16223 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16224 @node GDB/MI Command Syntax
16225 @section @sc{gdb/mi} Command Syntax
16228 * GDB/MI Input Syntax::
16229 * GDB/MI Output Syntax::
16230 * GDB/MI Simple Examples::
16233 @node GDB/MI Input Syntax
16234 @subsection @sc{gdb/mi} Input Syntax
16236 @cindex input syntax for @sc{gdb/mi}
16237 @cindex @sc{gdb/mi}, input syntax
16239 @item @var{command} @expansion{}
16240 @code{@var{cli-command} | @var{mi-command}}
16242 @item @var{cli-command} @expansion{}
16243 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
16244 @var{cli-command} is any existing @value{GDBN} CLI command.
16246 @item @var{mi-command} @expansion{}
16247 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
16248 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
16250 @item @var{token} @expansion{}
16251 "any sequence of digits"
16253 @item @var{option} @expansion{}
16254 @code{"-" @var{parameter} [ " " @var{parameter} ]}
16256 @item @var{parameter} @expansion{}
16257 @code{@var{non-blank-sequence} | @var{c-string}}
16259 @item @var{operation} @expansion{}
16260 @emph{any of the operations described in this chapter}
16262 @item @var{non-blank-sequence} @expansion{}
16263 @emph{anything, provided it doesn't contain special characters such as
16264 "-", @var{nl}, """ and of course " "}
16266 @item @var{c-string} @expansion{}
16267 @code{""" @var{seven-bit-iso-c-string-content} """}
16269 @item @var{nl} @expansion{}
16278 The CLI commands are still handled by the @sc{mi} interpreter; their
16279 output is described below.
16282 The @code{@var{token}}, when present, is passed back when the command
16286 Some @sc{mi} commands accept optional arguments as part of the parameter
16287 list. Each option is identified by a leading @samp{-} (dash) and may be
16288 followed by an optional argument parameter. Options occur first in the
16289 parameter list and can be delimited from normal parameters using
16290 @samp{--} (this is useful when some parameters begin with a dash).
16297 We want easy access to the existing CLI syntax (for debugging).
16300 We want it to be easy to spot a @sc{mi} operation.
16303 @node GDB/MI Output Syntax
16304 @subsection @sc{gdb/mi} Output Syntax
16306 @cindex output syntax of @sc{gdb/mi}
16307 @cindex @sc{gdb/mi}, output syntax
16308 The output from @sc{gdb/mi} consists of zero or more out-of-band records
16309 followed, optionally, by a single result record. This result record
16310 is for the most recent command. The sequence of output records is
16311 terminated by @samp{(@value{GDBP})}.
16313 If an input command was prefixed with a @code{@var{token}} then the
16314 corresponding output for that command will also be prefixed by that same
16318 @item @var{output} @expansion{}
16319 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(@value{GDBP})" @var{nl}}
16321 @item @var{result-record} @expansion{}
16322 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
16324 @item @var{out-of-band-record} @expansion{}
16325 @code{@var{async-record} | @var{stream-record}}
16327 @item @var{async-record} @expansion{}
16328 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
16330 @item @var{exec-async-output} @expansion{}
16331 @code{[ @var{token} ] "*" @var{async-output}}
16333 @item @var{status-async-output} @expansion{}
16334 @code{[ @var{token} ] "+" @var{async-output}}
16336 @item @var{notify-async-output} @expansion{}
16337 @code{[ @var{token} ] "=" @var{async-output}}
16339 @item @var{async-output} @expansion{}
16340 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
16342 @item @var{result-class} @expansion{}
16343 @code{"done" | "running" | "connected" | "error" | "exit"}
16345 @item @var{async-class} @expansion{}
16346 @code{"stopped" | @var{others}} (where @var{others} will be added
16347 depending on the needs---this is still in development).
16349 @item @var{result} @expansion{}
16350 @code{ @var{variable} "=" @var{value}}
16352 @item @var{variable} @expansion{}
16353 @code{ @var{string} }
16355 @item @var{value} @expansion{}
16356 @code{ @var{const} | @var{tuple} | @var{list} }
16358 @item @var{const} @expansion{}
16359 @code{@var{c-string}}
16361 @item @var{tuple} @expansion{}
16362 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
16364 @item @var{list} @expansion{}
16365 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
16366 @var{result} ( "," @var{result} )* "]" }
16368 @item @var{stream-record} @expansion{}
16369 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
16371 @item @var{console-stream-output} @expansion{}
16372 @code{"~" @var{c-string}}
16374 @item @var{target-stream-output} @expansion{}
16375 @code{"@@" @var{c-string}}
16377 @item @var{log-stream-output} @expansion{}
16378 @code{"&" @var{c-string}}
16380 @item @var{nl} @expansion{}
16383 @item @var{token} @expansion{}
16384 @emph{any sequence of digits}.
16392 All output sequences end in a single line containing a period.
16395 The @code{@var{token}} is from the corresponding request. If an execution
16396 command is interrupted by the @samp{-exec-interrupt} command, the
16397 @var{token} associated with the @samp{*stopped} message is the one of the
16398 original execution command, not the one of the interrupt command.
16401 @cindex status output in @sc{gdb/mi}
16402 @var{status-async-output} contains on-going status information about the
16403 progress of a slow operation. It can be discarded. All status output is
16404 prefixed by @samp{+}.
16407 @cindex async output in @sc{gdb/mi}
16408 @var{exec-async-output} contains asynchronous state change on the target
16409 (stopped, started, disappeared). All async output is prefixed by
16413 @cindex notify output in @sc{gdb/mi}
16414 @var{notify-async-output} contains supplementary information that the
16415 client should handle (e.g., a new breakpoint information). All notify
16416 output is prefixed by @samp{=}.
16419 @cindex console output in @sc{gdb/mi}
16420 @var{console-stream-output} is output that should be displayed as is in the
16421 console. It is the textual response to a CLI command. All the console
16422 output is prefixed by @samp{~}.
16425 @cindex target output in @sc{gdb/mi}
16426 @var{target-stream-output} is the output produced by the target program.
16427 All the target output is prefixed by @samp{@@}.
16430 @cindex log output in @sc{gdb/mi}
16431 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
16432 instance messages that should be displayed as part of an error log. All
16433 the log output is prefixed by @samp{&}.
16436 @cindex list output in @sc{gdb/mi}
16437 New @sc{gdb/mi} commands should only output @var{lists} containing
16443 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
16444 details about the various output records.
16446 @node GDB/MI Simple Examples
16447 @subsection Simple Examples of @sc{gdb/mi} Interaction
16448 @cindex @sc{gdb/mi}, simple examples
16450 This subsection presents several simple examples of interaction using
16451 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
16452 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
16453 the output received from @sc{gdb/mi}.
16455 @subsubheading Target Stop
16456 @c Ummm... There is no "-stop" command. This assumes async, no?
16457 Here's an example of stopping the inferior process:
16468 <- *stop,reason="stop",address="0x123",source="a.c:123"
16472 @subsubheading Simple CLI Command
16474 Here's an example of a simple CLI command being passed through
16475 @sc{gdb/mi} and on to the CLI.
16485 @subsubheading Command With Side Effects
16488 -> -symbol-file xyz.exe
16489 <- *breakpoint,nr="3",address="0x123",source="a.c:123"
16493 @subsubheading A Bad Command
16495 Here's what happens if you pass a non-existent command:
16499 <- ^error,msg="Undefined MI command: rubbish"
16503 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16504 @node GDB/MI Compatibility with CLI
16505 @section @sc{gdb/mi} Compatibility with CLI
16507 @cindex compatibility, @sc{gdb/mi} and CLI
16508 @cindex @sc{gdb/mi}, compatibility with CLI
16509 To help users familiar with @value{GDBN}'s existing CLI interface, @sc{gdb/mi}
16510 accepts existing CLI commands. As specified by the syntax, such
16511 commands can be directly entered into the @sc{gdb/mi} interface and @value{GDBN} will
16514 This mechanism is provided as an aid to developers of @sc{gdb/mi}
16515 clients and not as a reliable interface into the CLI. Since the command
16516 is being interpreteted in an environment that assumes @sc{gdb/mi}
16517 behaviour, the exact output of such commands is likely to end up being
16518 an un-supported hybrid of @sc{gdb/mi} and CLI output.
16520 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16521 @node GDB/MI Output Records
16522 @section @sc{gdb/mi} Output Records
16525 * GDB/MI Result Records::
16526 * GDB/MI Stream Records::
16527 * GDB/MI Out-of-band Records::
16530 @node GDB/MI Result Records
16531 @subsection @sc{gdb/mi} Result Records
16533 @cindex result records in @sc{gdb/mi}
16534 @cindex @sc{gdb/mi}, result records
16535 In addition to a number of out-of-band notifications, the response to a
16536 @sc{gdb/mi} command includes one of the following result indications:
16540 @item "^done" [ "," @var{results} ]
16541 The synchronous operation was successful, @code{@var{results}} are the return
16546 @c Is this one correct? Should it be an out-of-band notification?
16547 The asynchronous operation was successfully started. The target is
16550 @item "^error" "," @var{c-string}
16552 The operation failed. The @code{@var{c-string}} contains the corresponding
16556 @node GDB/MI Stream Records
16557 @subsection @sc{gdb/mi} Stream Records
16559 @cindex @sc{gdb/mi}, stream records
16560 @cindex stream records in @sc{gdb/mi}
16561 @value{GDBN} internally maintains a number of output streams: the console, the
16562 target, and the log. The output intended for each of these streams is
16563 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
16565 Each stream record begins with a unique @dfn{prefix character} which
16566 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
16567 Syntax}). In addition to the prefix, each stream record contains a
16568 @code{@var{string-output}}. This is either raw text (with an implicit new
16569 line) or a quoted C string (which does not contain an implicit newline).
16572 @item "~" @var{string-output}
16573 The console output stream contains text that should be displayed in the
16574 CLI console window. It contains the textual responses to CLI commands.
16576 @item "@@" @var{string-output}
16577 The target output stream contains any textual output from the running
16580 @item "&" @var{string-output}
16581 The log stream contains debugging messages being produced by @value{GDBN}'s
16585 @node GDB/MI Out-of-band Records
16586 @subsection @sc{gdb/mi} Out-of-band Records
16588 @cindex out-of-band records in @sc{gdb/mi}
16589 @cindex @sc{gdb/mi}, out-of-band records
16590 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
16591 additional changes that have occurred. Those changes can either be a
16592 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
16593 target activity (e.g., target stopped).
16595 The following is a preliminary list of possible out-of-band records.
16602 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16603 @node GDB/MI Command Description Format
16604 @section @sc{gdb/mi} Command Description Format
16606 The remaining sections describe blocks of commands. Each block of
16607 commands is laid out in a fashion similar to this section.
16609 Note the the line breaks shown in the examples are here only for
16610 readability. They don't appear in the real output.
16611 Also note that the commands with a non-available example (N.A.@:) are
16612 not yet implemented.
16614 @subheading Motivation
16616 The motivation for this collection of commands.
16618 @subheading Introduction
16620 A brief introduction to this collection of commands as a whole.
16622 @subheading Commands
16624 For each command in the block, the following is described:
16626 @subsubheading Synopsis
16629 -command @var{args}@dots{}
16632 @subsubheading @value{GDBN} Command
16634 The corresponding @value{GDBN} CLI command.
16636 @subsubheading Result
16638 @subsubheading Out-of-band
16640 @subsubheading Notes
16642 @subsubheading Example
16645 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16646 @node GDB/MI Breakpoint Table Commands
16647 @section @sc{gdb/mi} Breakpoint table commands
16649 @cindex breakpoint commands for @sc{gdb/mi}
16650 @cindex @sc{gdb/mi}, breakpoint commands
16651 This section documents @sc{gdb/mi} commands for manipulating
16654 @subheading The @code{-break-after} Command
16655 @findex -break-after
16657 @subsubheading Synopsis
16660 -break-after @var{number} @var{count}
16663 The breakpoint number @var{number} is not in effect until it has been
16664 hit @var{count} times. To see how this is reflected in the output of
16665 the @samp{-break-list} command, see the description of the
16666 @samp{-break-list} command below.
16668 @subsubheading @value{GDBN} Command
16670 The corresponding @value{GDBN} command is @samp{ignore}.
16672 @subsubheading Example
16677 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",line="5"@}
16684 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
16685 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
16686 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
16687 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
16688 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
16689 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
16690 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
16691 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
16692 addr="0x000100d0",func="main",file="hello.c",line="5",times="0",
16698 @subheading The @code{-break-catch} Command
16699 @findex -break-catch
16701 @subheading The @code{-break-commands} Command
16702 @findex -break-commands
16706 @subheading The @code{-break-condition} Command
16707 @findex -break-condition
16709 @subsubheading Synopsis
16712 -break-condition @var{number} @var{expr}
16715 Breakpoint @var{number} will stop the program only if the condition in
16716 @var{expr} is true. The condition becomes part of the
16717 @samp{-break-list} output (see the description of the @samp{-break-list}
16720 @subsubheading @value{GDBN} Command
16722 The corresponding @value{GDBN} command is @samp{condition}.
16724 @subsubheading Example
16728 -break-condition 1 1
16732 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
16733 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
16734 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
16735 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
16736 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
16737 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
16738 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
16739 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
16740 addr="0x000100d0",func="main",file="hello.c",line="5",cond="1",
16741 times="0",ignore="3"@}]@}
16745 @subheading The @code{-break-delete} Command
16746 @findex -break-delete
16748 @subsubheading Synopsis
16751 -break-delete ( @var{breakpoint} )+
16754 Delete the breakpoint(s) whose number(s) are specified in the argument
16755 list. This is obviously reflected in the breakpoint list.
16757 @subsubheading @value{GDBN} command
16759 The corresponding @value{GDBN} command is @samp{delete}.
16761 @subsubheading Example
16769 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
16770 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
16771 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
16772 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
16773 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
16774 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
16775 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
16780 @subheading The @code{-break-disable} Command
16781 @findex -break-disable
16783 @subsubheading Synopsis
16786 -break-disable ( @var{breakpoint} )+
16789 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
16790 break list is now set to @samp{n} for the named @var{breakpoint}(s).
16792 @subsubheading @value{GDBN} Command
16794 The corresponding @value{GDBN} command is @samp{disable}.
16796 @subsubheading Example
16804 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
16805 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
16806 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
16807 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
16808 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
16809 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
16810 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
16811 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
16812 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
16816 @subheading The @code{-break-enable} Command
16817 @findex -break-enable
16819 @subsubheading Synopsis
16822 -break-enable ( @var{breakpoint} )+
16825 Enable (previously disabled) @var{breakpoint}(s).
16827 @subsubheading @value{GDBN} Command
16829 The corresponding @value{GDBN} command is @samp{enable}.
16831 @subsubheading Example
16839 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
16840 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
16841 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
16842 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
16843 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
16844 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
16845 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
16846 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
16847 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
16851 @subheading The @code{-break-info} Command
16852 @findex -break-info
16854 @subsubheading Synopsis
16857 -break-info @var{breakpoint}
16861 Get information about a single breakpoint.
16863 @subsubheading @value{GDBN} command
16865 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
16867 @subsubheading Example
16870 @subheading The @code{-break-insert} Command
16871 @findex -break-insert
16873 @subsubheading Synopsis
16876 -break-insert [ -t ] [ -h ] [ -r ]
16877 [ -c @var{condition} ] [ -i @var{ignore-count} ]
16878 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
16882 If specified, @var{line}, can be one of:
16889 @item filename:linenum
16890 @item filename:function
16894 The possible optional parameters of this command are:
16898 Insert a tempoary breakpoint.
16900 Insert a hardware breakpoint.
16901 @item -c @var{condition}
16902 Make the breakpoint conditional on @var{condition}.
16903 @item -i @var{ignore-count}
16904 Initialize the @var{ignore-count}.
16906 Insert a regular breakpoint in all the functions whose names match the
16907 given regular expression. Other flags are not applicable to regular
16911 @subsubheading Result
16913 The result is in the form:
16916 ^done,bkptno="@var{number}",func="@var{funcname}",
16917 file="@var{filename}",line="@var{lineno}"
16921 where @var{number} is the @value{GDBN} number for this breakpoint, @var{funcname}
16922 is the name of the function where the breakpoint was inserted,
16923 @var{filename} is the name of the source file which contains this
16924 function, and @var{lineno} is the source line number within that file.
16926 Note: this format is open to change.
16927 @c An out-of-band breakpoint instead of part of the result?
16929 @subsubheading @value{GDBN} Command
16931 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
16932 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
16934 @subsubheading Example
16939 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
16941 -break-insert -t foo
16942 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",line="11"@}
16945 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
16946 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
16947 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
16948 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
16949 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
16950 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
16951 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
16952 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
16953 addr="0x0001072c", func="main",file="recursive2.c",line="4",times="0"@},
16954 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
16955 addr="0x00010774",func="foo",file="recursive2.c",line="11",times="0"@}]@}
16957 -break-insert -r foo.*
16958 ~int foo(int, int);
16959 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c",line="11"@}
16963 @subheading The @code{-break-list} Command
16964 @findex -break-list
16966 @subsubheading Synopsis
16972 Displays the list of inserted breakpoints, showing the following fields:
16976 number of the breakpoint
16978 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
16980 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
16983 is the breakpoint enabled or no: @samp{y} or @samp{n}
16985 memory location at which the breakpoint is set
16987 logical location of the breakpoint, expressed by function name, file
16990 number of times the breakpoint has been hit
16993 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
16994 @code{body} field is an empty list.
16996 @subsubheading @value{GDBN} Command
16998 The corresponding @value{GDBN} command is @samp{info break}.
17000 @subsubheading Example
17005 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17006 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17007 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17008 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17009 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17010 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17011 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17012 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17013 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
17014 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17015 addr="0x00010114",func="foo",file="hello.c",line="13",times="0"@}]@}
17019 Here's an example of the result when there are no breakpoints:
17024 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17025 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17026 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17027 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17028 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17029 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17030 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17035 @subheading The @code{-break-watch} Command
17036 @findex -break-watch
17038 @subsubheading Synopsis
17041 -break-watch [ -a | -r ]
17044 Create a watchpoint. With the @samp{-a} option it will create an
17045 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
17046 read from or on a write to the memory location. With the @samp{-r}
17047 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
17048 trigger only when the memory location is accessed for reading. Without
17049 either of the options, the watchpoint created is a regular watchpoint,
17050 i.e. it will trigger when the memory location is accessed for writing.
17051 @xref{Set Watchpoints, , Setting watchpoints}.
17053 Note that @samp{-break-list} will report a single list of watchpoints and
17054 breakpoints inserted.
17056 @subsubheading @value{GDBN} Command
17058 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
17061 @subsubheading Example
17063 Setting a watchpoint on a variable in the @code{main} function:
17068 ^done,wpt=@{number="2",exp="x"@}
17072 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
17073 value=@{old="-268439212",new="55"@},
17074 frame=@{func="main",args=[],file="recursive2.c",line="5"@}
17078 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
17079 the program execution twice: first for the variable changing value, then
17080 for the watchpoint going out of scope.
17085 ^done,wpt=@{number="5",exp="C"@}
17089 ^done,reason="watchpoint-trigger",
17090 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
17091 frame=@{func="callee4",args=[],
17092 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
17096 ^done,reason="watchpoint-scope",wpnum="5",
17097 frame=@{func="callee3",args=[@{name="strarg",
17098 value="0x11940 \"A string argument.\""@}],
17099 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
17103 Listing breakpoints and watchpoints, at different points in the program
17104 execution. Note that once the watchpoint goes out of scope, it is
17110 ^done,wpt=@{number="2",exp="C"@}
17113 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17114 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17115 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17116 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17117 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17118 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17119 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17120 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17121 addr="0x00010734",func="callee4",
17122 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
17123 bkpt=@{number="2",type="watchpoint",disp="keep",
17124 enabled="y",addr="",what="C",times="0"@}]@}
17128 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
17129 value=@{old="-276895068",new="3"@},
17130 frame=@{func="callee4",args=[],
17131 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
17134 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17135 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17136 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17137 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17138 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17139 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17140 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17141 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17142 addr="0x00010734",func="callee4",
17143 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
17144 bkpt=@{number="2",type="watchpoint",disp="keep",
17145 enabled="y",addr="",what="C",times="-5"@}]@}
17149 ^done,reason="watchpoint-scope",wpnum="2",
17150 frame=@{func="callee3",args=[@{name="strarg",
17151 value="0x11940 \"A string argument.\""@}],
17152 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
17155 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17156 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17157 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17158 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17159 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17160 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17161 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17162 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17163 addr="0x00010734",func="callee4",
17164 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@}]@}
17168 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17169 @node GDB/MI Data Manipulation
17170 @section @sc{gdb/mi} Data Manipulation
17172 @cindex data manipulation, in @sc{gdb/mi}
17173 @cindex @sc{gdb/mi}, data manipulation
17174 This section describes the @sc{gdb/mi} commands that manipulate data:
17175 examine memory and registers, evaluate expressions, etc.
17177 @c REMOVED FROM THE INTERFACE.
17178 @c @subheading -data-assign
17179 @c Change the value of a program variable. Plenty of side effects.
17180 @c @subsubheading GDB command
17182 @c @subsubheading Example
17185 @subheading The @code{-data-disassemble} Command
17186 @findex -data-disassemble
17188 @subsubheading Synopsis
17192 [ -s @var{start-addr} -e @var{end-addr} ]
17193 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
17201 @item @var{start-addr}
17202 is the beginning address (or @code{$pc})
17203 @item @var{end-addr}
17205 @item @var{filename}
17206 is the name of the file to disassemble
17207 @item @var{linenum}
17208 is the line number to disassemble around
17210 is the the number of disassembly lines to be produced. If it is -1,
17211 the whole function will be disassembled, in case no @var{end-addr} is
17212 specified. If @var{end-addr} is specified as a non-zero value, and
17213 @var{lines} is lower than the number of disassembly lines between
17214 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
17215 displayed; if @var{lines} is higher than the number of lines between
17216 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
17219 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
17223 @subsubheading Result
17225 The output for each instruction is composed of four fields:
17234 Note that whatever included in the instruction field, is not manipulated
17235 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
17237 @subsubheading @value{GDBN} Command
17239 There's no direct mapping from this command to the CLI.
17241 @subsubheading Example
17243 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
17247 -data-disassemble -s $pc -e "$pc + 20" -- 0
17250 @{address="0x000107c0",func-name="main",offset="4",
17251 inst="mov 2, %o0"@},
17252 @{address="0x000107c4",func-name="main",offset="8",
17253 inst="sethi %hi(0x11800), %o2"@},
17254 @{address="0x000107c8",func-name="main",offset="12",
17255 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
17256 @{address="0x000107cc",func-name="main",offset="16",
17257 inst="sethi %hi(0x11800), %o2"@},
17258 @{address="0x000107d0",func-name="main",offset="20",
17259 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
17263 Disassemble the whole @code{main} function. Line 32 is part of
17267 -data-disassemble -f basics.c -l 32 -- 0
17269 @{address="0x000107bc",func-name="main",offset="0",
17270 inst="save %sp, -112, %sp"@},
17271 @{address="0x000107c0",func-name="main",offset="4",
17272 inst="mov 2, %o0"@},
17273 @{address="0x000107c4",func-name="main",offset="8",
17274 inst="sethi %hi(0x11800), %o2"@},
17276 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
17277 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
17281 Disassemble 3 instructions from the start of @code{main}:
17285 -data-disassemble -f basics.c -l 32 -n 3 -- 0
17287 @{address="0x000107bc",func-name="main",offset="0",
17288 inst="save %sp, -112, %sp"@},
17289 @{address="0x000107c0",func-name="main",offset="4",
17290 inst="mov 2, %o0"@},
17291 @{address="0x000107c4",func-name="main",offset="8",
17292 inst="sethi %hi(0x11800), %o2"@}]
17296 Disassemble 3 instructions from the start of @code{main} in mixed mode:
17300 -data-disassemble -f basics.c -l 32 -n 3 -- 1
17302 src_and_asm_line=@{line="31",
17303 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
17304 testsuite/gdb.mi/basics.c",line_asm_insn=[
17305 @{address="0x000107bc",func-name="main",offset="0",
17306 inst="save %sp, -112, %sp"@}]@},
17307 src_and_asm_line=@{line="32",
17308 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
17309 testsuite/gdb.mi/basics.c",line_asm_insn=[
17310 @{address="0x000107c0",func-name="main",offset="4",
17311 inst="mov 2, %o0"@},
17312 @{address="0x000107c4",func-name="main",offset="8",
17313 inst="sethi %hi(0x11800), %o2"@}]@}]
17318 @subheading The @code{-data-evaluate-expression} Command
17319 @findex -data-evaluate-expression
17321 @subsubheading Synopsis
17324 -data-evaluate-expression @var{expr}
17327 Evaluate @var{expr} as an expression. The expression could contain an
17328 inferior function call. The function call will execute synchronously.
17329 If the expression contains spaces, it must be enclosed in double quotes.
17331 @subsubheading @value{GDBN} Command
17333 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
17334 @samp{call}. In @code{gdbtk} only, there's a corresponding
17335 @samp{gdb_eval} command.
17337 @subsubheading Example
17339 In the following example, the numbers that precede the commands are the
17340 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
17341 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
17345 211-data-evaluate-expression A
17348 311-data-evaluate-expression &A
17349 311^done,value="0xefffeb7c"
17351 411-data-evaluate-expression A+3
17354 511-data-evaluate-expression "A + 3"
17360 @subheading The @code{-data-list-changed-registers} Command
17361 @findex -data-list-changed-registers
17363 @subsubheading Synopsis
17366 -data-list-changed-registers
17369 Display a list of the registers that have changed.
17371 @subsubheading @value{GDBN} Command
17373 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
17374 has the corresponding command @samp{gdb_changed_register_list}.
17376 @subsubheading Example
17378 On a PPC MBX board:
17386 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
17387 args=[],file="try.c",line="5"@}
17389 -data-list-changed-registers
17390 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
17391 "10","11","13","14","15","16","17","18","19","20","21","22","23",
17392 "24","25","26","27","28","30","31","64","65","66","67","69"]
17397 @subheading The @code{-data-list-register-names} Command
17398 @findex -data-list-register-names
17400 @subsubheading Synopsis
17403 -data-list-register-names [ ( @var{regno} )+ ]
17406 Show a list of register names for the current target. If no arguments
17407 are given, it shows a list of the names of all the registers. If
17408 integer numbers are given as arguments, it will print a list of the
17409 names of the registers corresponding to the arguments. To ensure
17410 consistency between a register name and its number, the output list may
17411 include empty register names.
17413 @subsubheading @value{GDBN} Command
17415 @value{GDBN} does not have a command which corresponds to
17416 @samp{-data-list-register-names}. In @code{gdbtk} there is a
17417 corresponding command @samp{gdb_regnames}.
17419 @subsubheading Example
17421 For the PPC MBX board:
17424 -data-list-register-names
17425 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
17426 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
17427 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
17428 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
17429 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
17430 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
17431 "", "pc","ps","cr","lr","ctr","xer"]
17433 -data-list-register-names 1 2 3
17434 ^done,register-names=["r1","r2","r3"]
17438 @subheading The @code{-data-list-register-values} Command
17439 @findex -data-list-register-values
17441 @subsubheading Synopsis
17444 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
17447 Display the registers' contents. @var{fmt} is the format according to
17448 which the registers' contents are to be returned, followed by an optional
17449 list of numbers specifying the registers to display. A missing list of
17450 numbers indicates that the contents of all the registers must be returned.
17452 Allowed formats for @var{fmt} are:
17469 @subsubheading @value{GDBN} Command
17471 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
17472 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
17474 @subsubheading Example
17476 For a PPC MBX board (note: line breaks are for readability only, they
17477 don't appear in the actual output):
17481 -data-list-register-values r 64 65
17482 ^done,register-values=[@{number="64",value="0xfe00a300"@},
17483 @{number="65",value="0x00029002"@}]
17485 -data-list-register-values x
17486 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
17487 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
17488 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
17489 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
17490 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
17491 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
17492 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
17493 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
17494 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
17495 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
17496 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
17497 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
17498 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
17499 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
17500 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
17501 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
17502 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
17503 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
17504 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
17505 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
17506 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
17507 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
17508 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
17509 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
17510 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
17511 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
17512 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
17513 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
17514 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
17515 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
17516 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
17517 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
17518 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
17519 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
17520 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
17521 @{number="69",value="0x20002b03"@}]
17526 @subheading The @code{-data-read-memory} Command
17527 @findex -data-read-memory
17529 @subsubheading Synopsis
17532 -data-read-memory [ -o @var{byte-offset} ]
17533 @var{address} @var{word-format} @var{word-size}
17534 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
17541 @item @var{address}
17542 An expression specifying the address of the first memory word to be
17543 read. Complex expressions containing embedded white space should be
17544 quoted using the C convention.
17546 @item @var{word-format}
17547 The format to be used to print the memory words. The notation is the
17548 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
17551 @item @var{word-size}
17552 The size of each memory word in bytes.
17554 @item @var{nr-rows}
17555 The number of rows in the output table.
17557 @item @var{nr-cols}
17558 The number of columns in the output table.
17561 If present, indicates that each row should include an @sc{ascii} dump. The
17562 value of @var{aschar} is used as a padding character when a byte is not a
17563 member of the printable @sc{ascii} character set (printable @sc{ascii}
17564 characters are those whose code is between 32 and 126, inclusively).
17566 @item @var{byte-offset}
17567 An offset to add to the @var{address} before fetching memory.
17570 This command displays memory contents as a table of @var{nr-rows} by
17571 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
17572 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
17573 (returned as @samp{total-bytes}). Should less than the requested number
17574 of bytes be returned by the target, the missing words are identified
17575 using @samp{N/A}. The number of bytes read from the target is returned
17576 in @samp{nr-bytes} and the starting address used to read memory in
17579 The address of the next/previous row or page is available in
17580 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
17583 @subsubheading @value{GDBN} Command
17585 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
17586 @samp{gdb_get_mem} memory read command.
17588 @subsubheading Example
17590 Read six bytes of memory starting at @code{bytes+6} but then offset by
17591 @code{-6} bytes. Format as three rows of two columns. One byte per
17592 word. Display each word in hex.
17596 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
17597 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
17598 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
17599 prev-page="0x0000138a",memory=[
17600 @{addr="0x00001390",data=["0x00","0x01"]@},
17601 @{addr="0x00001392",data=["0x02","0x03"]@},
17602 @{addr="0x00001394",data=["0x04","0x05"]@}]
17606 Read two bytes of memory starting at address @code{shorts + 64} and
17607 display as a single word formatted in decimal.
17611 5-data-read-memory shorts+64 d 2 1 1
17612 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
17613 next-row="0x00001512",prev-row="0x0000150e",
17614 next-page="0x00001512",prev-page="0x0000150e",memory=[
17615 @{addr="0x00001510",data=["128"]@}]
17619 Read thirty two bytes of memory starting at @code{bytes+16} and format
17620 as eight rows of four columns. Include a string encoding with @samp{x}
17621 used as the non-printable character.
17625 4-data-read-memory bytes+16 x 1 8 4 x
17626 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
17627 next-row="0x000013c0",prev-row="0x0000139c",
17628 next-page="0x000013c0",prev-page="0x00001380",memory=[
17629 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
17630 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
17631 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
17632 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
17633 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
17634 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
17635 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
17636 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
17640 @subheading The @code{-display-delete} Command
17641 @findex -display-delete
17643 @subsubheading Synopsis
17646 -display-delete @var{number}
17649 Delete the display @var{number}.
17651 @subsubheading @value{GDBN} Command
17653 The corresponding @value{GDBN} command is @samp{delete display}.
17655 @subsubheading Example
17659 @subheading The @code{-display-disable} Command
17660 @findex -display-disable
17662 @subsubheading Synopsis
17665 -display-disable @var{number}
17668 Disable display @var{number}.
17670 @subsubheading @value{GDBN} Command
17672 The corresponding @value{GDBN} command is @samp{disable display}.
17674 @subsubheading Example
17678 @subheading The @code{-display-enable} Command
17679 @findex -display-enable
17681 @subsubheading Synopsis
17684 -display-enable @var{number}
17687 Enable display @var{number}.
17689 @subsubheading @value{GDBN} Command
17691 The corresponding @value{GDBN} command is @samp{enable display}.
17693 @subsubheading Example
17697 @subheading The @code{-display-insert} Command
17698 @findex -display-insert
17700 @subsubheading Synopsis
17703 -display-insert @var{expression}
17706 Display @var{expression} every time the program stops.
17708 @subsubheading @value{GDBN} Command
17710 The corresponding @value{GDBN} command is @samp{display}.
17712 @subsubheading Example
17716 @subheading The @code{-display-list} Command
17717 @findex -display-list
17719 @subsubheading Synopsis
17725 List the displays. Do not show the current values.
17727 @subsubheading @value{GDBN} Command
17729 The corresponding @value{GDBN} command is @samp{info display}.
17731 @subsubheading Example
17735 @subheading The @code{-environment-cd} Command
17736 @findex -environment-cd
17738 @subsubheading Synopsis
17741 -environment-cd @var{pathdir}
17744 Set @value{GDBN}'s working directory.
17746 @subsubheading @value{GDBN} Command
17748 The corresponding @value{GDBN} command is @samp{cd}.
17750 @subsubheading Example
17754 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
17760 @subheading The @code{-environment-directory} Command
17761 @findex -environment-directory
17763 @subsubheading Synopsis
17766 -environment-directory [ -r ] [ @var{pathdir} ]+
17769 Add directories @var{pathdir} to beginning of search path for source files.
17770 If the @samp{-r} option is used, the search path is reset to the default
17771 search path. If directories @var{pathdir} are supplied in addition to the
17772 @samp{-r} option, the search path is first reset and then addition
17774 Multiple directories may be specified, separated by blanks. Specifying
17775 multiple directories in a single command
17776 results in the directories added to the beginning of the
17777 search path in the same order they were presented in the command.
17778 If blanks are needed as
17779 part of a directory name, double-quotes should be used around
17780 the name. In the command output, the path will show up separated
17781 by the system directory-separator character. The directory-seperator
17782 character must not be used
17783 in any directory name.
17784 If no directories are specified, the current search path is displayed.
17786 @subsubheading @value{GDBN} Command
17788 The corresponding @value{GDBN} command is @samp{dir}.
17790 @subsubheading Example
17794 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
17795 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
17797 -environment-directory ""
17798 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
17800 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
17801 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
17803 -environment-directory -r
17804 ^done,source-path="$cdir:$cwd"
17809 @subheading The @code{-environment-path} Command
17810 @findex -environment-path
17812 @subsubheading Synopsis
17815 -environment-path [ -r ] [ @var{pathdir} ]+
17818 Add directories @var{pathdir} to beginning of search path for object files.
17819 If the @samp{-r} option is used, the search path is reset to the original
17820 search path that existed at gdb start-up. If directories @var{pathdir} are
17821 supplied in addition to the
17822 @samp{-r} option, the search path is first reset and then addition
17824 Multiple directories may be specified, separated by blanks. Specifying
17825 multiple directories in a single command
17826 results in the directories added to the beginning of the
17827 search path in the same order they were presented in the command.
17828 If blanks are needed as
17829 part of a directory name, double-quotes should be used around
17830 the name. In the command output, the path will show up separated
17831 by the system directory-separator character. The directory-seperator
17832 character must not be used
17833 in any directory name.
17834 If no directories are specified, the current path is displayed.
17837 @subsubheading @value{GDBN} Command
17839 The corresponding @value{GDBN} command is @samp{path}.
17841 @subsubheading Example
17846 ^done,path="/usr/bin"
17848 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
17849 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
17851 -environment-path -r /usr/local/bin
17852 ^done,path="/usr/local/bin:/usr/bin"
17857 @subheading The @code{-environment-pwd} Command
17858 @findex -environment-pwd
17860 @subsubheading Synopsis
17866 Show the current working directory.
17868 @subsubheading @value{GDBN} command
17870 The corresponding @value{GDBN} command is @samp{pwd}.
17872 @subsubheading Example
17877 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
17881 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17882 @node GDB/MI Program Control
17883 @section @sc{gdb/mi} Program control
17885 @subsubheading Program termination
17887 As a result of execution, the inferior program can run to completion, if
17888 it doesn't encounter any breakpoints. In this case the output will
17889 include an exit code, if the program has exited exceptionally.
17891 @subsubheading Examples
17894 Program exited normally:
17902 *stopped,reason="exited-normally"
17907 Program exited exceptionally:
17915 *stopped,reason="exited",exit-code="01"
17919 Another way the program can terminate is if it receives a signal such as
17920 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
17924 *stopped,reason="exited-signalled",signal-name="SIGINT",
17925 signal-meaning="Interrupt"
17929 @subheading The @code{-exec-abort} Command
17930 @findex -exec-abort
17932 @subsubheading Synopsis
17938 Kill the inferior running program.
17940 @subsubheading @value{GDBN} Command
17942 The corresponding @value{GDBN} command is @samp{kill}.
17944 @subsubheading Example
17948 @subheading The @code{-exec-arguments} Command
17949 @findex -exec-arguments
17951 @subsubheading Synopsis
17954 -exec-arguments @var{args}
17957 Set the inferior program arguments, to be used in the next
17960 @subsubheading @value{GDBN} Command
17962 The corresponding @value{GDBN} command is @samp{set args}.
17964 @subsubheading Example
17967 Don't have one around.
17970 @subheading The @code{-exec-continue} Command
17971 @findex -exec-continue
17973 @subsubheading Synopsis
17979 Asynchronous command. Resumes the execution of the inferior program
17980 until a breakpoint is encountered, or until the inferior exits.
17982 @subsubheading @value{GDBN} Command
17984 The corresponding @value{GDBN} corresponding is @samp{continue}.
17986 @subsubheading Example
17993 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
17994 file="hello.c",line="13"@}
17999 @subheading The @code{-exec-finish} Command
18000 @findex -exec-finish
18002 @subsubheading Synopsis
18008 Asynchronous command. Resumes the execution of the inferior program
18009 until the current function is exited. Displays the results returned by
18012 @subsubheading @value{GDBN} Command
18014 The corresponding @value{GDBN} command is @samp{finish}.
18016 @subsubheading Example
18018 Function returning @code{void}.
18025 *stopped,reason="function-finished",frame=@{func="main",args=[],
18026 file="hello.c",line="7"@}
18030 Function returning other than @code{void}. The name of the internal
18031 @value{GDBN} variable storing the result is printed, together with the
18038 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
18039 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
18040 file="recursive2.c",line="14"@},
18041 gdb-result-var="$1",return-value="0"
18046 @subheading The @code{-exec-interrupt} Command
18047 @findex -exec-interrupt
18049 @subsubheading Synopsis
18055 Asynchronous command. Interrupts the background execution of the target.
18056 Note how the token associated with the stop message is the one for the
18057 execution command that has been interrupted. The token for the interrupt
18058 itself only appears in the @samp{^done} output. If the user is trying to
18059 interrupt a non-running program, an error message will be printed.
18061 @subsubheading @value{GDBN} Command
18063 The corresponding @value{GDBN} command is @samp{interrupt}.
18065 @subsubheading Example
18076 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
18077 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",line="13"@}
18082 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
18087 @subheading The @code{-exec-next} Command
18090 @subsubheading Synopsis
18096 Asynchronous command. Resumes execution of the inferior program, stopping
18097 when the beginning of the next source line is reached.
18099 @subsubheading @value{GDBN} Command
18101 The corresponding @value{GDBN} command is @samp{next}.
18103 @subsubheading Example
18109 *stopped,reason="end-stepping-range",line="8",file="hello.c"
18114 @subheading The @code{-exec-next-instruction} Command
18115 @findex -exec-next-instruction
18117 @subsubheading Synopsis
18120 -exec-next-instruction
18123 Asynchronous command. Executes one machine instruction. If the
18124 instruction is a function call continues until the function returns. If
18125 the program stops at an instruction in the middle of a source line, the
18126 address will be printed as well.
18128 @subsubheading @value{GDBN} Command
18130 The corresponding @value{GDBN} command is @samp{nexti}.
18132 @subsubheading Example
18136 -exec-next-instruction
18140 *stopped,reason="end-stepping-range",
18141 addr="0x000100d4",line="5",file="hello.c"
18146 @subheading The @code{-exec-return} Command
18147 @findex -exec-return
18149 @subsubheading Synopsis
18155 Makes current function return immediately. Doesn't execute the inferior.
18156 Displays the new current frame.
18158 @subsubheading @value{GDBN} Command
18160 The corresponding @value{GDBN} command is @samp{return}.
18162 @subsubheading Example
18166 200-break-insert callee4
18167 200^done,bkpt=@{number="1",addr="0x00010734",
18168 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18173 000*stopped,reason="breakpoint-hit",bkptno="1",
18174 frame=@{func="callee4",args=[],
18175 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18181 111^done,frame=@{level="0",func="callee3",
18182 args=[@{name="strarg",
18183 value="0x11940 \"A string argument.\""@}],
18184 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18189 @subheading The @code{-exec-run} Command
18192 @subsubheading Synopsis
18198 Asynchronous command. Starts execution of the inferior from the
18199 beginning. The inferior executes until either a breakpoint is
18200 encountered or the program exits.
18202 @subsubheading @value{GDBN} Command
18204 The corresponding @value{GDBN} command is @samp{run}.
18206 @subsubheading Example
18211 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
18216 *stopped,reason="breakpoint-hit",bkptno="1",
18217 frame=@{func="main",args=[],file="recursive2.c",line="4"@}
18222 @subheading The @code{-exec-show-arguments} Command
18223 @findex -exec-show-arguments
18225 @subsubheading Synopsis
18228 -exec-show-arguments
18231 Print the arguments of the program.
18233 @subsubheading @value{GDBN} Command
18235 The corresponding @value{GDBN} command is @samp{show args}.
18237 @subsubheading Example
18240 @c @subheading -exec-signal
18242 @subheading The @code{-exec-step} Command
18245 @subsubheading Synopsis
18251 Asynchronous command. Resumes execution of the inferior program, stopping
18252 when the beginning of the next source line is reached, if the next
18253 source line is not a function call. If it is, stop at the first
18254 instruction of the called function.
18256 @subsubheading @value{GDBN} Command
18258 The corresponding @value{GDBN} command is @samp{step}.
18260 @subsubheading Example
18262 Stepping into a function:
18268 *stopped,reason="end-stepping-range",
18269 frame=@{func="foo",args=[@{name="a",value="10"@},
18270 @{name="b",value="0"@}],file="recursive2.c",line="11"@}
18280 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
18285 @subheading The @code{-exec-step-instruction} Command
18286 @findex -exec-step-instruction
18288 @subsubheading Synopsis
18291 -exec-step-instruction
18294 Asynchronous command. Resumes the inferior which executes one machine
18295 instruction. The output, once @value{GDBN} has stopped, will vary depending on
18296 whether we have stopped in the middle of a source line or not. In the
18297 former case, the address at which the program stopped will be printed as
18300 @subsubheading @value{GDBN} Command
18302 The corresponding @value{GDBN} command is @samp{stepi}.
18304 @subsubheading Example
18308 -exec-step-instruction
18312 *stopped,reason="end-stepping-range",
18313 frame=@{func="foo",args=[],file="try.c",line="10"@}
18315 -exec-step-instruction
18319 *stopped,reason="end-stepping-range",
18320 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",line="10"@}
18325 @subheading The @code{-exec-until} Command
18326 @findex -exec-until
18328 @subsubheading Synopsis
18331 -exec-until [ @var{location} ]
18334 Asynchronous command. Executes the inferior until the @var{location}
18335 specified in the argument is reached. If there is no argument, the inferior
18336 executes until a source line greater than the current one is reached.
18337 The reason for stopping in this case will be @samp{location-reached}.
18339 @subsubheading @value{GDBN} Command
18341 The corresponding @value{GDBN} command is @samp{until}.
18343 @subsubheading Example
18347 -exec-until recursive2.c:6
18351 *stopped,reason="location-reached",frame=@{func="main",args=[],
18352 file="recursive2.c",line="6"@}
18357 @subheading -file-clear
18358 Is this going away????
18362 @subheading The @code{-file-exec-and-symbols} Command
18363 @findex -file-exec-and-symbols
18365 @subsubheading Synopsis
18368 -file-exec-and-symbols @var{file}
18371 Specify the executable file to be debugged. This file is the one from
18372 which the symbol table is also read. If no file is specified, the
18373 command clears the executable and symbol information. If breakpoints
18374 are set when using this command with no arguments, @value{GDBN} will produce
18375 error messages. Otherwise, no output is produced, except a completion
18378 @subsubheading @value{GDBN} Command
18380 The corresponding @value{GDBN} command is @samp{file}.
18382 @subsubheading Example
18386 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18392 @subheading The @code{-file-exec-file} Command
18393 @findex -file-exec-file
18395 @subsubheading Synopsis
18398 -file-exec-file @var{file}
18401 Specify the executable file to be debugged. Unlike
18402 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
18403 from this file. If used without argument, @value{GDBN} clears the information
18404 about the executable file. No output is produced, except a completion
18407 @subsubheading @value{GDBN} Command
18409 The corresponding @value{GDBN} command is @samp{exec-file}.
18411 @subsubheading Example
18415 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18421 @subheading The @code{-file-list-exec-sections} Command
18422 @findex -file-list-exec-sections
18424 @subsubheading Synopsis
18427 -file-list-exec-sections
18430 List the sections of the current executable file.
18432 @subsubheading @value{GDBN} Command
18434 The @value{GDBN} command @samp{info file} shows, among the rest, the same
18435 information as this command. @code{gdbtk} has a corresponding command
18436 @samp{gdb_load_info}.
18438 @subsubheading Example
18442 @subheading The @code{-file-list-exec-source-file} Command
18443 @findex -file-list-exec-source-file
18445 @subsubheading Synopsis
18448 -file-list-exec-source-file
18451 List the line number, the current source file, and the absolute path
18452 to the current source file for the current executable.
18454 @subsubheading @value{GDBN} Command
18456 There's no @value{GDBN} command which directly corresponds to this one.
18458 @subsubheading Example
18462 123-file-list-exec-source-file
18463 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
18468 @subheading The @code{-file-list-exec-source-files} Command
18469 @findex -file-list-exec-source-files
18471 @subsubheading Synopsis
18474 -file-list-exec-source-files
18477 List the source files for the current executable.
18479 It will always output the filename, but only when GDB can find the absolute
18480 file name of a source file, will it output the fullname.
18482 @subsubheading @value{GDBN} Command
18484 There's no @value{GDBN} command which directly corresponds to this one.
18485 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
18487 @subsubheading Example
18490 -file-list-exec-source-files
18492 @{file=foo.c,fullname=/home/foo.c@},
18493 @{file=/home/bar.c,fullname=/home/bar.c@},
18494 @{file=gdb_could_not_find_fullpath.c@}]
18498 @subheading The @code{-file-list-shared-libraries} Command
18499 @findex -file-list-shared-libraries
18501 @subsubheading Synopsis
18504 -file-list-shared-libraries
18507 List the shared libraries in the program.
18509 @subsubheading @value{GDBN} Command
18511 The corresponding @value{GDBN} command is @samp{info shared}.
18513 @subsubheading Example
18517 @subheading The @code{-file-list-symbol-files} Command
18518 @findex -file-list-symbol-files
18520 @subsubheading Synopsis
18523 -file-list-symbol-files
18528 @subsubheading @value{GDBN} Command
18530 The corresponding @value{GDBN} command is @samp{info file} (part of it).
18532 @subsubheading Example
18536 @subheading The @code{-file-symbol-file} Command
18537 @findex -file-symbol-file
18539 @subsubheading Synopsis
18542 -file-symbol-file @var{file}
18545 Read symbol table info from the specified @var{file} argument. When
18546 used without arguments, clears @value{GDBN}'s symbol table info. No output is
18547 produced, except for a completion notification.
18549 @subsubheading @value{GDBN} Command
18551 The corresponding @value{GDBN} command is @samp{symbol-file}.
18553 @subsubheading Example
18557 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18562 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18563 @node GDB/MI Miscellaneous Commands
18564 @section Miscellaneous @value{GDBN} commands in @sc{gdb/mi}
18566 @c @subheading -gdb-complete
18568 @subheading The @code{-gdb-exit} Command
18571 @subsubheading Synopsis
18577 Exit @value{GDBN} immediately.
18579 @subsubheading @value{GDBN} Command
18581 Approximately corresponds to @samp{quit}.
18583 @subsubheading Example
18590 @subheading The @code{-gdb-set} Command
18593 @subsubheading Synopsis
18599 Set an internal @value{GDBN} variable.
18600 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
18602 @subsubheading @value{GDBN} Command
18604 The corresponding @value{GDBN} command is @samp{set}.
18606 @subsubheading Example
18616 @subheading The @code{-gdb-show} Command
18619 @subsubheading Synopsis
18625 Show the current value of a @value{GDBN} variable.
18627 @subsubheading @value{GDBN} command
18629 The corresponding @value{GDBN} command is @samp{show}.
18631 @subsubheading Example
18640 @c @subheading -gdb-source
18643 @subheading The @code{-gdb-version} Command
18644 @findex -gdb-version
18646 @subsubheading Synopsis
18652 Show version information for @value{GDBN}. Used mostly in testing.
18654 @subsubheading @value{GDBN} Command
18656 There's no equivalent @value{GDBN} command. @value{GDBN} by default shows this
18657 information when you start an interactive session.
18659 @subsubheading Example
18661 @c This example modifies the actual output from GDB to avoid overfull
18667 ~Copyright 2000 Free Software Foundation, Inc.
18668 ~GDB is free software, covered by the GNU General Public License, and
18669 ~you are welcome to change it and/or distribute copies of it under
18670 ~ certain conditions.
18671 ~Type "show copying" to see the conditions.
18672 ~There is absolutely no warranty for GDB. Type "show warranty" for
18674 ~This GDB was configured as
18675 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
18680 @subheading The @code{-interpreter-exec} Command
18681 @findex -interpreter-exec
18683 @subheading Synopsis
18686 -interpreter-exec @var{interpreter} @var{command}
18689 Execute the specified @var{command} in the given @var{interpreter}.
18691 @subheading @value{GDBN} Command
18693 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
18695 @subheading Example
18699 -interpreter-exec console "break main"
18700 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
18701 &"During symbol reading, bad structure-type format.\n"
18702 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
18708 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18709 @node GDB/MI Kod Commands
18710 @section @sc{gdb/mi} Kod Commands
18712 The Kod commands are not implemented.
18714 @c @subheading -kod-info
18716 @c @subheading -kod-list
18718 @c @subheading -kod-list-object-types
18720 @c @subheading -kod-show
18722 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18723 @node GDB/MI Memory Overlay Commands
18724 @section @sc{gdb/mi} Memory Overlay Commands
18726 The memory overlay commands are not implemented.
18728 @c @subheading -overlay-auto
18730 @c @subheading -overlay-list-mapping-state
18732 @c @subheading -overlay-list-overlays
18734 @c @subheading -overlay-map
18736 @c @subheading -overlay-off
18738 @c @subheading -overlay-on
18740 @c @subheading -overlay-unmap
18742 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18743 @node GDB/MI Signal Handling Commands
18744 @section @sc{gdb/mi} Signal Handling Commands
18746 Signal handling commands are not implemented.
18748 @c @subheading -signal-handle
18750 @c @subheading -signal-list-handle-actions
18752 @c @subheading -signal-list-signal-types
18756 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18757 @node GDB/MI Stack Manipulation
18758 @section @sc{gdb/mi} Stack Manipulation Commands
18761 @subheading The @code{-stack-info-frame} Command
18762 @findex -stack-info-frame
18764 @subsubheading Synopsis
18770 Get info on the current frame.
18772 @subsubheading @value{GDBN} Command
18774 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
18775 (without arguments).
18777 @subsubheading Example
18780 @subheading The @code{-stack-info-depth} Command
18781 @findex -stack-info-depth
18783 @subsubheading Synopsis
18786 -stack-info-depth [ @var{max-depth} ]
18789 Return the depth of the stack. If the integer argument @var{max-depth}
18790 is specified, do not count beyond @var{max-depth} frames.
18792 @subsubheading @value{GDBN} Command
18794 There's no equivalent @value{GDBN} command.
18796 @subsubheading Example
18798 For a stack with frame levels 0 through 11:
18805 -stack-info-depth 4
18808 -stack-info-depth 12
18811 -stack-info-depth 11
18814 -stack-info-depth 13
18819 @subheading The @code{-stack-list-arguments} Command
18820 @findex -stack-list-arguments
18822 @subsubheading Synopsis
18825 -stack-list-arguments @var{show-values}
18826 [ @var{low-frame} @var{high-frame} ]
18829 Display a list of the arguments for the frames between @var{low-frame}
18830 and @var{high-frame} (inclusive). If @var{low-frame} and
18831 @var{high-frame} are not provided, list the arguments for the whole call
18834 The @var{show-values} argument must have a value of 0 or 1. A value of
18835 0 means that only the names of the arguments are listed, a value of 1
18836 means that both names and values of the arguments are printed.
18838 @subsubheading @value{GDBN} Command
18840 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
18841 @samp{gdb_get_args} command which partially overlaps with the
18842 functionality of @samp{-stack-list-arguments}.
18844 @subsubheading Example
18851 frame=@{level="0",addr="0x00010734",func="callee4",
18852 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
18853 frame=@{level="1",addr="0x0001076c",func="callee3",
18854 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
18855 frame=@{level="2",addr="0x0001078c",func="callee2",
18856 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
18857 frame=@{level="3",addr="0x000107b4",func="callee1",
18858 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
18859 frame=@{level="4",addr="0x000107e0",func="main",
18860 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
18862 -stack-list-arguments 0
18865 frame=@{level="0",args=[]@},
18866 frame=@{level="1",args=[name="strarg"]@},
18867 frame=@{level="2",args=[name="intarg",name="strarg"]@},
18868 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
18869 frame=@{level="4",args=[]@}]
18871 -stack-list-arguments 1
18874 frame=@{level="0",args=[]@},
18876 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
18877 frame=@{level="2",args=[
18878 @{name="intarg",value="2"@},
18879 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
18880 @{frame=@{level="3",args=[
18881 @{name="intarg",value="2"@},
18882 @{name="strarg",value="0x11940 \"A string argument.\""@},
18883 @{name="fltarg",value="3.5"@}]@},
18884 frame=@{level="4",args=[]@}]
18886 -stack-list-arguments 0 2 2
18887 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
18889 -stack-list-arguments 1 2 2
18890 ^done,stack-args=[frame=@{level="2",
18891 args=[@{name="intarg",value="2"@},
18892 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
18896 @c @subheading -stack-list-exception-handlers
18899 @subheading The @code{-stack-list-frames} Command
18900 @findex -stack-list-frames
18902 @subsubheading Synopsis
18905 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
18908 List the frames currently on the stack. For each frame it displays the
18913 The frame number, 0 being the topmost frame, i.e. the innermost function.
18915 The @code{$pc} value for that frame.
18919 File name of the source file where the function lives.
18921 Line number corresponding to the @code{$pc}.
18924 If invoked without arguments, this command prints a backtrace for the
18925 whole stack. If given two integer arguments, it shows the frames whose
18926 levels are between the two arguments (inclusive). If the two arguments
18927 are equal, it shows the single frame at the corresponding level.
18929 @subsubheading @value{GDBN} Command
18931 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
18933 @subsubheading Example
18935 Full stack backtrace:
18941 [frame=@{level="0",addr="0x0001076c",func="foo",
18942 file="recursive2.c",line="11"@},
18943 frame=@{level="1",addr="0x000107a4",func="foo",
18944 file="recursive2.c",line="14"@},
18945 frame=@{level="2",addr="0x000107a4",func="foo",
18946 file="recursive2.c",line="14"@},
18947 frame=@{level="3",addr="0x000107a4",func="foo",
18948 file="recursive2.c",line="14"@},
18949 frame=@{level="4",addr="0x000107a4",func="foo",
18950 file="recursive2.c",line="14"@},
18951 frame=@{level="5",addr="0x000107a4",func="foo",
18952 file="recursive2.c",line="14"@},
18953 frame=@{level="6",addr="0x000107a4",func="foo",
18954 file="recursive2.c",line="14"@},
18955 frame=@{level="7",addr="0x000107a4",func="foo",
18956 file="recursive2.c",line="14"@},
18957 frame=@{level="8",addr="0x000107a4",func="foo",
18958 file="recursive2.c",line="14"@},
18959 frame=@{level="9",addr="0x000107a4",func="foo",
18960 file="recursive2.c",line="14"@},
18961 frame=@{level="10",addr="0x000107a4",func="foo",
18962 file="recursive2.c",line="14"@},
18963 frame=@{level="11",addr="0x00010738",func="main",
18964 file="recursive2.c",line="4"@}]
18968 Show frames between @var{low_frame} and @var{high_frame}:
18972 -stack-list-frames 3 5
18974 [frame=@{level="3",addr="0x000107a4",func="foo",
18975 file="recursive2.c",line="14"@},
18976 frame=@{level="4",addr="0x000107a4",func="foo",
18977 file="recursive2.c",line="14"@},
18978 frame=@{level="5",addr="0x000107a4",func="foo",
18979 file="recursive2.c",line="14"@}]
18983 Show a single frame:
18987 -stack-list-frames 3 3
18989 [frame=@{level="3",addr="0x000107a4",func="foo",
18990 file="recursive2.c",line="14"@}]
18995 @subheading The @code{-stack-list-locals} Command
18996 @findex -stack-list-locals
18998 @subsubheading Synopsis
19001 -stack-list-locals @var{print-values}
19004 Display the local variable names for the current frame. With an
19005 argument of 0 or @code{--no-values}, prints only the names of the variables.
19006 With argument of 1 or @code{--all-values}, prints also their values. With
19007 argument of 2 or @code{--simple-values}, prints the name, type and value for
19008 simple data types and the name and type for arrays, structures and
19009 unions. In this last case, the idea is that the user can see the
19010 value of simple data types immediately and he can create variable
19011 objects for other data types if he wishes to explore their values in
19014 @subsubheading @value{GDBN} Command
19016 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
19018 @subsubheading Example
19022 -stack-list-locals 0
19023 ^done,locals=[name="A",name="B",name="C"]
19025 -stack-list-locals --all-values
19026 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
19027 @{name="C",value="@{1, 2, 3@}"@}]
19028 -stack-list-locals --simple-values
19029 ^done,locals=[@{name="A",type="int",value="1"@},
19030 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
19035 @subheading The @code{-stack-select-frame} Command
19036 @findex -stack-select-frame
19038 @subsubheading Synopsis
19041 -stack-select-frame @var{framenum}
19044 Change the current frame. Select a different frame @var{framenum} on
19047 @subsubheading @value{GDBN} Command
19049 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
19050 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
19052 @subsubheading Example
19056 -stack-select-frame 2
19061 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19062 @node GDB/MI Symbol Query
19063 @section @sc{gdb/mi} Symbol Query Commands
19066 @subheading The @code{-symbol-info-address} Command
19067 @findex -symbol-info-address
19069 @subsubheading Synopsis
19072 -symbol-info-address @var{symbol}
19075 Describe where @var{symbol} is stored.
19077 @subsubheading @value{GDBN} Command
19079 The corresponding @value{GDBN} command is @samp{info address}.
19081 @subsubheading Example
19085 @subheading The @code{-symbol-info-file} Command
19086 @findex -symbol-info-file
19088 @subsubheading Synopsis
19094 Show the file for the symbol.
19096 @subsubheading @value{GDBN} Command
19098 There's no equivalent @value{GDBN} command. @code{gdbtk} has
19099 @samp{gdb_find_file}.
19101 @subsubheading Example
19105 @subheading The @code{-symbol-info-function} Command
19106 @findex -symbol-info-function
19108 @subsubheading Synopsis
19111 -symbol-info-function
19114 Show which function the symbol lives in.
19116 @subsubheading @value{GDBN} Command
19118 @samp{gdb_get_function} in @code{gdbtk}.
19120 @subsubheading Example
19124 @subheading The @code{-symbol-info-line} Command
19125 @findex -symbol-info-line
19127 @subsubheading Synopsis
19133 Show the core addresses of the code for a source line.
19135 @subsubheading @value{GDBN} Command
19137 The corresponding @value{GDBN} command is @samp{info line}.
19138 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
19140 @subsubheading Example
19144 @subheading The @code{-symbol-info-symbol} Command
19145 @findex -symbol-info-symbol
19147 @subsubheading Synopsis
19150 -symbol-info-symbol @var{addr}
19153 Describe what symbol is at location @var{addr}.
19155 @subsubheading @value{GDBN} Command
19157 The corresponding @value{GDBN} command is @samp{info symbol}.
19159 @subsubheading Example
19163 @subheading The @code{-symbol-list-functions} Command
19164 @findex -symbol-list-functions
19166 @subsubheading Synopsis
19169 -symbol-list-functions
19172 List the functions in the executable.
19174 @subsubheading @value{GDBN} Command
19176 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
19177 @samp{gdb_search} in @code{gdbtk}.
19179 @subsubheading Example
19183 @subheading The @code{-symbol-list-lines} Command
19184 @findex -symbol-list-lines
19186 @subsubheading Synopsis
19189 -symbol-list-lines @var{filename}
19192 Print the list of lines that contain code and their associated program
19193 addresses for the given source filename. The entries are sorted in
19194 ascending PC order.
19196 @subsubheading @value{GDBN} Command
19198 There is no corresponding @value{GDBN} command.
19200 @subsubheading Example
19203 -symbol-list-lines basics.c
19204 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
19209 @subheading The @code{-symbol-list-types} Command
19210 @findex -symbol-list-types
19212 @subsubheading Synopsis
19218 List all the type names.
19220 @subsubheading @value{GDBN} Command
19222 The corresponding commands are @samp{info types} in @value{GDBN},
19223 @samp{gdb_search} in @code{gdbtk}.
19225 @subsubheading Example
19229 @subheading The @code{-symbol-list-variables} Command
19230 @findex -symbol-list-variables
19232 @subsubheading Synopsis
19235 -symbol-list-variables
19238 List all the global and static variable names.
19240 @subsubheading @value{GDBN} Command
19242 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
19244 @subsubheading Example
19248 @subheading The @code{-symbol-locate} Command
19249 @findex -symbol-locate
19251 @subsubheading Synopsis
19257 @subsubheading @value{GDBN} Command
19259 @samp{gdb_loc} in @code{gdbtk}.
19261 @subsubheading Example
19265 @subheading The @code{-symbol-type} Command
19266 @findex -symbol-type
19268 @subsubheading Synopsis
19271 -symbol-type @var{variable}
19274 Show type of @var{variable}.
19276 @subsubheading @value{GDBN} Command
19278 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
19279 @samp{gdb_obj_variable}.
19281 @subsubheading Example
19285 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19286 @node GDB/MI Target Manipulation
19287 @section @sc{gdb/mi} Target Manipulation Commands
19290 @subheading The @code{-target-attach} Command
19291 @findex -target-attach
19293 @subsubheading Synopsis
19296 -target-attach @var{pid} | @var{file}
19299 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
19301 @subsubheading @value{GDBN} command
19303 The corresponding @value{GDBN} command is @samp{attach}.
19305 @subsubheading Example
19309 @subheading The @code{-target-compare-sections} Command
19310 @findex -target-compare-sections
19312 @subsubheading Synopsis
19315 -target-compare-sections [ @var{section} ]
19318 Compare data of section @var{section} on target to the exec file.
19319 Without the argument, all sections are compared.
19321 @subsubheading @value{GDBN} Command
19323 The @value{GDBN} equivalent is @samp{compare-sections}.
19325 @subsubheading Example
19329 @subheading The @code{-target-detach} Command
19330 @findex -target-detach
19332 @subsubheading Synopsis
19338 Disconnect from the remote target. There's no output.
19340 @subsubheading @value{GDBN} command
19342 The corresponding @value{GDBN} command is @samp{detach}.
19344 @subsubheading Example
19354 @subheading The @code{-target-disconnect} Command
19355 @findex -target-disconnect
19357 @subsubheading Synopsis
19363 Disconnect from the remote target. There's no output.
19365 @subsubheading @value{GDBN} command
19367 The corresponding @value{GDBN} command is @samp{disconnect}.
19369 @subsubheading Example
19379 @subheading The @code{-target-download} Command
19380 @findex -target-download
19382 @subsubheading Synopsis
19388 Loads the executable onto the remote target.
19389 It prints out an update message every half second, which includes the fields:
19393 The name of the section.
19395 The size of what has been sent so far for that section.
19397 The size of the section.
19399 The total size of what was sent so far (the current and the previous sections).
19401 The size of the overall executable to download.
19405 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
19406 @sc{gdb/mi} Output Syntax}).
19408 In addition, it prints the name and size of the sections, as they are
19409 downloaded. These messages include the following fields:
19413 The name of the section.
19415 The size of the section.
19417 The size of the overall executable to download.
19421 At the end, a summary is printed.
19423 @subsubheading @value{GDBN} Command
19425 The corresponding @value{GDBN} command is @samp{load}.
19427 @subsubheading Example
19429 Note: each status message appears on a single line. Here the messages
19430 have been broken down so that they can fit onto a page.
19435 +download,@{section=".text",section-size="6668",total-size="9880"@}
19436 +download,@{section=".text",section-sent="512",section-size="6668",
19437 total-sent="512",total-size="9880"@}
19438 +download,@{section=".text",section-sent="1024",section-size="6668",
19439 total-sent="1024",total-size="9880"@}
19440 +download,@{section=".text",section-sent="1536",section-size="6668",
19441 total-sent="1536",total-size="9880"@}
19442 +download,@{section=".text",section-sent="2048",section-size="6668",
19443 total-sent="2048",total-size="9880"@}
19444 +download,@{section=".text",section-sent="2560",section-size="6668",
19445 total-sent="2560",total-size="9880"@}
19446 +download,@{section=".text",section-sent="3072",section-size="6668",
19447 total-sent="3072",total-size="9880"@}
19448 +download,@{section=".text",section-sent="3584",section-size="6668",
19449 total-sent="3584",total-size="9880"@}
19450 +download,@{section=".text",section-sent="4096",section-size="6668",
19451 total-sent="4096",total-size="9880"@}
19452 +download,@{section=".text",section-sent="4608",section-size="6668",
19453 total-sent="4608",total-size="9880"@}
19454 +download,@{section=".text",section-sent="5120",section-size="6668",
19455 total-sent="5120",total-size="9880"@}
19456 +download,@{section=".text",section-sent="5632",section-size="6668",
19457 total-sent="5632",total-size="9880"@}
19458 +download,@{section=".text",section-sent="6144",section-size="6668",
19459 total-sent="6144",total-size="9880"@}
19460 +download,@{section=".text",section-sent="6656",section-size="6668",
19461 total-sent="6656",total-size="9880"@}
19462 +download,@{section=".init",section-size="28",total-size="9880"@}
19463 +download,@{section=".fini",section-size="28",total-size="9880"@}
19464 +download,@{section=".data",section-size="3156",total-size="9880"@}
19465 +download,@{section=".data",section-sent="512",section-size="3156",
19466 total-sent="7236",total-size="9880"@}
19467 +download,@{section=".data",section-sent="1024",section-size="3156",
19468 total-sent="7748",total-size="9880"@}
19469 +download,@{section=".data",section-sent="1536",section-size="3156",
19470 total-sent="8260",total-size="9880"@}
19471 +download,@{section=".data",section-sent="2048",section-size="3156",
19472 total-sent="8772",total-size="9880"@}
19473 +download,@{section=".data",section-sent="2560",section-size="3156",
19474 total-sent="9284",total-size="9880"@}
19475 +download,@{section=".data",section-sent="3072",section-size="3156",
19476 total-sent="9796",total-size="9880"@}
19477 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
19483 @subheading The @code{-target-exec-status} Command
19484 @findex -target-exec-status
19486 @subsubheading Synopsis
19489 -target-exec-status
19492 Provide information on the state of the target (whether it is running or
19493 not, for instance).
19495 @subsubheading @value{GDBN} Command
19497 There's no equivalent @value{GDBN} command.
19499 @subsubheading Example
19503 @subheading The @code{-target-list-available-targets} Command
19504 @findex -target-list-available-targets
19506 @subsubheading Synopsis
19509 -target-list-available-targets
19512 List the possible targets to connect to.
19514 @subsubheading @value{GDBN} Command
19516 The corresponding @value{GDBN} command is @samp{help target}.
19518 @subsubheading Example
19522 @subheading The @code{-target-list-current-targets} Command
19523 @findex -target-list-current-targets
19525 @subsubheading Synopsis
19528 -target-list-current-targets
19531 Describe the current target.
19533 @subsubheading @value{GDBN} Command
19535 The corresponding information is printed by @samp{info file} (among
19538 @subsubheading Example
19542 @subheading The @code{-target-list-parameters} Command
19543 @findex -target-list-parameters
19545 @subsubheading Synopsis
19548 -target-list-parameters
19553 @subsubheading @value{GDBN} Command
19557 @subsubheading Example
19561 @subheading The @code{-target-select} Command
19562 @findex -target-select
19564 @subsubheading Synopsis
19567 -target-select @var{type} @var{parameters @dots{}}
19570 Connect @value{GDBN} to the remote target. This command takes two args:
19574 The type of target, for instance @samp{async}, @samp{remote}, etc.
19575 @item @var{parameters}
19576 Device names, host names and the like. @xref{Target Commands, ,
19577 Commands for managing targets}, for more details.
19580 The output is a connection notification, followed by the address at
19581 which the target program is, in the following form:
19584 ^connected,addr="@var{address}",func="@var{function name}",
19585 args=[@var{arg list}]
19588 @subsubheading @value{GDBN} Command
19590 The corresponding @value{GDBN} command is @samp{target}.
19592 @subsubheading Example
19596 -target-select async /dev/ttya
19597 ^connected,addr="0xfe00a300",func="??",args=[]
19601 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19602 @node GDB/MI Thread Commands
19603 @section @sc{gdb/mi} Thread Commands
19606 @subheading The @code{-thread-info} Command
19607 @findex -thread-info
19609 @subsubheading Synopsis
19615 @subsubheading @value{GDBN} command
19619 @subsubheading Example
19623 @subheading The @code{-thread-list-all-threads} Command
19624 @findex -thread-list-all-threads
19626 @subsubheading Synopsis
19629 -thread-list-all-threads
19632 @subsubheading @value{GDBN} Command
19634 The equivalent @value{GDBN} command is @samp{info threads}.
19636 @subsubheading Example
19640 @subheading The @code{-thread-list-ids} Command
19641 @findex -thread-list-ids
19643 @subsubheading Synopsis
19649 Produces a list of the currently known @value{GDBN} thread ids. At the
19650 end of the list it also prints the total number of such threads.
19652 @subsubheading @value{GDBN} Command
19654 Part of @samp{info threads} supplies the same information.
19656 @subsubheading Example
19658 No threads present, besides the main process:
19663 ^done,thread-ids=@{@},number-of-threads="0"
19673 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
19674 number-of-threads="3"
19679 @subheading The @code{-thread-select} Command
19680 @findex -thread-select
19682 @subsubheading Synopsis
19685 -thread-select @var{threadnum}
19688 Make @var{threadnum} the current thread. It prints the number of the new
19689 current thread, and the topmost frame for that thread.
19691 @subsubheading @value{GDBN} Command
19693 The corresponding @value{GDBN} command is @samp{thread}.
19695 @subsubheading Example
19702 *stopped,reason="end-stepping-range",thread-id="2",line="187",
19703 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
19707 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
19708 number-of-threads="3"
19711 ^done,new-thread-id="3",
19712 frame=@{level="0",func="vprintf",
19713 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
19714 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
19718 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19719 @node GDB/MI Tracepoint Commands
19720 @section @sc{gdb/mi} Tracepoint Commands
19722 The tracepoint commands are not yet implemented.
19724 @c @subheading -trace-actions
19726 @c @subheading -trace-delete
19728 @c @subheading -trace-disable
19730 @c @subheading -trace-dump
19732 @c @subheading -trace-enable
19734 @c @subheading -trace-exists
19736 @c @subheading -trace-find
19738 @c @subheading -trace-frame-number
19740 @c @subheading -trace-info
19742 @c @subheading -trace-insert
19744 @c @subheading -trace-list
19746 @c @subheading -trace-pass-count
19748 @c @subheading -trace-save
19750 @c @subheading -trace-start
19752 @c @subheading -trace-stop
19755 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19756 @node GDB/MI Variable Objects
19757 @section @sc{gdb/mi} Variable Objects
19760 @subheading Motivation for Variable Objects in @sc{gdb/mi}
19762 For the implementation of a variable debugger window (locals, watched
19763 expressions, etc.), we are proposing the adaptation of the existing code
19764 used by @code{Insight}.
19766 The two main reasons for that are:
19770 It has been proven in practice (it is already on its second generation).
19773 It will shorten development time (needless to say how important it is
19777 The original interface was designed to be used by Tcl code, so it was
19778 slightly changed so it could be used through @sc{gdb/mi}. This section
19779 describes the @sc{gdb/mi} operations that will be available and gives some
19780 hints about their use.
19782 @emph{Note}: In addition to the set of operations described here, we
19783 expect the @sc{gui} implementation of a variable window to require, at
19784 least, the following operations:
19787 @item @code{-gdb-show} @code{output-radix}
19788 @item @code{-stack-list-arguments}
19789 @item @code{-stack-list-locals}
19790 @item @code{-stack-select-frame}
19793 @subheading Introduction to Variable Objects in @sc{gdb/mi}
19795 @cindex variable objects in @sc{gdb/mi}
19796 The basic idea behind variable objects is the creation of a named object
19797 to represent a variable, an expression, a memory location or even a CPU
19798 register. For each object created, a set of operations is available for
19799 examining or changing its properties.
19801 Furthermore, complex data types, such as C structures, are represented
19802 in a tree format. For instance, the @code{struct} type variable is the
19803 root and the children will represent the struct members. If a child
19804 is itself of a complex type, it will also have children of its own.
19805 Appropriate language differences are handled for C, C@t{++} and Java.
19807 When returning the actual values of the objects, this facility allows
19808 for the individual selection of the display format used in the result
19809 creation. It can be chosen among: binary, decimal, hexadecimal, octal
19810 and natural. Natural refers to a default format automatically
19811 chosen based on the variable type (like decimal for an @code{int}, hex
19812 for pointers, etc.).
19814 The following is the complete set of @sc{gdb/mi} operations defined to
19815 access this functionality:
19817 @multitable @columnfractions .4 .6
19818 @item @strong{Operation}
19819 @tab @strong{Description}
19821 @item @code{-var-create}
19822 @tab create a variable object
19823 @item @code{-var-delete}
19824 @tab delete the variable object and its children
19825 @item @code{-var-set-format}
19826 @tab set the display format of this variable
19827 @item @code{-var-show-format}
19828 @tab show the display format of this variable
19829 @item @code{-var-info-num-children}
19830 @tab tells how many children this object has
19831 @item @code{-var-list-children}
19832 @tab return a list of the object's children
19833 @item @code{-var-info-type}
19834 @tab show the type of this variable object
19835 @item @code{-var-info-expression}
19836 @tab print what this variable object represents
19837 @item @code{-var-show-attributes}
19838 @tab is this variable editable? does it exist here?
19839 @item @code{-var-evaluate-expression}
19840 @tab get the value of this variable
19841 @item @code{-var-assign}
19842 @tab set the value of this variable
19843 @item @code{-var-update}
19844 @tab update the variable and its children
19847 In the next subsection we describe each operation in detail and suggest
19848 how it can be used.
19850 @subheading Description And Use of Operations on Variable Objects
19852 @subheading The @code{-var-create} Command
19853 @findex -var-create
19855 @subsubheading Synopsis
19858 -var-create @{@var{name} | "-"@}
19859 @{@var{frame-addr} | "*"@} @var{expression}
19862 This operation creates a variable object, which allows the monitoring of
19863 a variable, the result of an expression, a memory cell or a CPU
19866 The @var{name} parameter is the string by which the object can be
19867 referenced. It must be unique. If @samp{-} is specified, the varobj
19868 system will generate a string ``varNNNNNN'' automatically. It will be
19869 unique provided that one does not specify @var{name} on that format.
19870 The command fails if a duplicate name is found.
19872 The frame under which the expression should be evaluated can be
19873 specified by @var{frame-addr}. A @samp{*} indicates that the current
19874 frame should be used.
19876 @var{expression} is any expression valid on the current language set (must not
19877 begin with a @samp{*}), or one of the following:
19881 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
19884 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
19887 @samp{$@var{regname}} --- a CPU register name
19890 @subsubheading Result
19892 This operation returns the name, number of children and the type of the
19893 object created. Type is returned as a string as the ones generated by
19894 the @value{GDBN} CLI:
19897 name="@var{name}",numchild="N",type="@var{type}"
19901 @subheading The @code{-var-delete} Command
19902 @findex -var-delete
19904 @subsubheading Synopsis
19907 -var-delete @var{name}
19910 Deletes a previously created variable object and all of its children.
19912 Returns an error if the object @var{name} is not found.
19915 @subheading The @code{-var-set-format} Command
19916 @findex -var-set-format
19918 @subsubheading Synopsis
19921 -var-set-format @var{name} @var{format-spec}
19924 Sets the output format for the value of the object @var{name} to be
19927 The syntax for the @var{format-spec} is as follows:
19930 @var{format-spec} @expansion{}
19931 @{binary | decimal | hexadecimal | octal | natural@}
19935 @subheading The @code{-var-show-format} Command
19936 @findex -var-show-format
19938 @subsubheading Synopsis
19941 -var-show-format @var{name}
19944 Returns the format used to display the value of the object @var{name}.
19947 @var{format} @expansion{}
19952 @subheading The @code{-var-info-num-children} Command
19953 @findex -var-info-num-children
19955 @subsubheading Synopsis
19958 -var-info-num-children @var{name}
19961 Returns the number of children of a variable object @var{name}:
19968 @subheading The @code{-var-list-children} Command
19969 @findex -var-list-children
19971 @subsubheading Synopsis
19974 -var-list-children [@var{print-values}] @var{name}
19977 Returns a list of the children of the specified variable object. With
19978 just the variable object name as an argument or with an optional
19979 preceding argument of 0 or @code{--no-values}, prints only the names of the
19980 variables. With an optional preceding argument of 1 or @code{--all-values},
19981 also prints their values.
19983 @subsubheading Example
19987 -var-list-children n
19988 numchild=@var{n},children=[@{name=@var{name},
19989 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
19991 -var-list-children --all-values n
19992 numchild=@var{n},children=[@{name=@var{name},
19993 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
19997 @subheading The @code{-var-info-type} Command
19998 @findex -var-info-type
20000 @subsubheading Synopsis
20003 -var-info-type @var{name}
20006 Returns the type of the specified variable @var{name}. The type is
20007 returned as a string in the same format as it is output by the
20011 type=@var{typename}
20015 @subheading The @code{-var-info-expression} Command
20016 @findex -var-info-expression
20018 @subsubheading Synopsis
20021 -var-info-expression @var{name}
20024 Returns what is represented by the variable object @var{name}:
20027 lang=@var{lang-spec},exp=@var{expression}
20031 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
20033 @subheading The @code{-var-show-attributes} Command
20034 @findex -var-show-attributes
20036 @subsubheading Synopsis
20039 -var-show-attributes @var{name}
20042 List attributes of the specified variable object @var{name}:
20045 status=@var{attr} [ ( ,@var{attr} )* ]
20049 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
20051 @subheading The @code{-var-evaluate-expression} Command
20052 @findex -var-evaluate-expression
20054 @subsubheading Synopsis
20057 -var-evaluate-expression @var{name}
20060 Evaluates the expression that is represented by the specified variable
20061 object and returns its value as a string in the current format specified
20068 Note that one must invoke @code{-var-list-children} for a variable
20069 before the value of a child variable can be evaluated.
20071 @subheading The @code{-var-assign} Command
20072 @findex -var-assign
20074 @subsubheading Synopsis
20077 -var-assign @var{name} @var{expression}
20080 Assigns the value of @var{expression} to the variable object specified
20081 by @var{name}. The object must be @samp{editable}. If the variable's
20082 value is altered by the assign, the variable will show up in any
20083 subsequent @code{-var-update} list.
20085 @subsubheading Example
20093 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
20097 @subheading The @code{-var-update} Command
20098 @findex -var-update
20100 @subsubheading Synopsis
20103 -var-update @{@var{name} | "*"@}
20106 Update the value of the variable object @var{name} by evaluating its
20107 expression after fetching all the new values from memory or registers.
20108 A @samp{*} causes all existing variable objects to be updated.
20112 @chapter @value{GDBN} Annotations
20114 This chapter describes annotations in @value{GDBN}. Annotations were
20115 designed to interface @value{GDBN} to graphical user interfaces or other
20116 similar programs which want to interact with @value{GDBN} at a
20117 relatively high level.
20119 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
20123 This is Edition @value{EDITION}, @value{DATE}.
20127 * Annotations Overview:: What annotations are; the general syntax.
20128 * Server Prefix:: Issuing a command without affecting user state.
20129 * Prompting:: Annotations marking @value{GDBN}'s need for input.
20130 * Errors:: Annotations for error messages.
20131 * Invalidation:: Some annotations describe things now invalid.
20132 * Annotations for Running::
20133 Whether the program is running, how it stopped, etc.
20134 * Source Annotations:: Annotations describing source code.
20137 @node Annotations Overview
20138 @section What is an Annotation?
20139 @cindex annotations
20141 Annotations start with a newline character, two @samp{control-z}
20142 characters, and the name of the annotation. If there is no additional
20143 information associated with this annotation, the name of the annotation
20144 is followed immediately by a newline. If there is additional
20145 information, the name of the annotation is followed by a space, the
20146 additional information, and a newline. The additional information
20147 cannot contain newline characters.
20149 Any output not beginning with a newline and two @samp{control-z}
20150 characters denotes literal output from @value{GDBN}. Currently there is
20151 no need for @value{GDBN} to output a newline followed by two
20152 @samp{control-z} characters, but if there was such a need, the
20153 annotations could be extended with an @samp{escape} annotation which
20154 means those three characters as output.
20156 The annotation @var{level}, which is specified using the
20157 @option{--annotate} command line option (@pxref{Mode Options}), controls
20158 how much information @value{GDBN} prints together with its prompt,
20159 values of expressions, source lines, and other types of output. Level 0
20160 is for no anntations, level 1 is for use when @value{GDBN} is run as a
20161 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
20162 for programs that control @value{GDBN}, and level 2 annotations have
20163 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
20164 Interface, annotate, GDB's Obsolete Annotations}).
20167 @kindex set annotate
20168 @item set annotate @var{level}
20169 The @value{GDB} command @code{set annotate} sets the level of
20170 annotations to the specified @var{level}.
20172 @item show annotate
20173 @kindex show annotate
20174 Show the current annotation level.
20177 This chapter describes level 3 annotations.
20179 A simple example of starting up @value{GDBN} with annotations is:
20182 $ @kbd{gdb --annotate=3}
20184 Copyright 2003 Free Software Foundation, Inc.
20185 GDB is free software, covered by the GNU General Public License,
20186 and you are welcome to change it and/or distribute copies of it
20187 under certain conditions.
20188 Type "show copying" to see the conditions.
20189 There is absolutely no warranty for GDB. Type "show warranty"
20191 This GDB was configured as "i386-pc-linux-gnu"
20202 Here @samp{quit} is input to @value{GDBN}; the rest is output from
20203 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
20204 denotes a @samp{control-z} character) are annotations; the rest is
20205 output from @value{GDBN}.
20207 @node Server Prefix
20208 @section The Server Prefix
20209 @cindex server prefix for annotations
20211 To issue a command to @value{GDBN} without affecting certain aspects of
20212 the state which is seen by users, prefix it with @samp{server }. This
20213 means that this command will not affect the command history, nor will it
20214 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
20215 pressed on a line by itself.
20217 The server prefix does not affect the recording of values into the value
20218 history; to print a value without recording it into the value history,
20219 use the @code{output} command instead of the @code{print} command.
20222 @section Annotation for @value{GDBN} Input
20224 @cindex annotations for prompts
20225 When @value{GDBN} prompts for input, it annotates this fact so it is possible
20226 to know when to send output, when the output from a given command is
20229 Different kinds of input each have a different @dfn{input type}. Each
20230 input type has three annotations: a @code{pre-} annotation, which
20231 denotes the beginning of any prompt which is being output, a plain
20232 annotation, which denotes the end of the prompt, and then a @code{post-}
20233 annotation which denotes the end of any echo which may (or may not) be
20234 associated with the input. For example, the @code{prompt} input type
20235 features the following annotations:
20243 The input types are
20248 @findex post-prompt
20250 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
20252 @findex pre-commands
20254 @findex post-commands
20256 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
20257 command. The annotations are repeated for each command which is input.
20259 @findex pre-overload-choice
20260 @findex overload-choice
20261 @findex post-overload-choice
20262 @item overload-choice
20263 When @value{GDBN} wants the user to select between various overloaded functions.
20269 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
20271 @findex pre-prompt-for-continue
20272 @findex prompt-for-continue
20273 @findex post-prompt-for-continue
20274 @item prompt-for-continue
20275 When @value{GDBN} is asking the user to press return to continue. Note: Don't
20276 expect this to work well; instead use @code{set height 0} to disable
20277 prompting. This is because the counting of lines is buggy in the
20278 presence of annotations.
20283 @cindex annotations for errors, warnings and interrupts
20290 This annotation occurs right before @value{GDBN} responds to an interrupt.
20297 This annotation occurs right before @value{GDBN} responds to an error.
20299 Quit and error annotations indicate that any annotations which @value{GDBN} was
20300 in the middle of may end abruptly. For example, if a
20301 @code{value-history-begin} annotation is followed by a @code{error}, one
20302 cannot expect to receive the matching @code{value-history-end}. One
20303 cannot expect not to receive it either, however; an error annotation
20304 does not necessarily mean that @value{GDBN} is immediately returning all the way
20307 @findex error-begin
20308 A quit or error annotation may be preceded by
20314 Any output between that and the quit or error annotation is the error
20317 Warning messages are not yet annotated.
20318 @c If we want to change that, need to fix warning(), type_error(),
20319 @c range_error(), and possibly other places.
20322 @section Invalidation Notices
20324 @cindex annotations for invalidation messages
20325 The following annotations say that certain pieces of state may have
20329 @findex frames-invalid
20330 @item ^Z^Zframes-invalid
20332 The frames (for example, output from the @code{backtrace} command) may
20335 @findex breakpoints-invalid
20336 @item ^Z^Zbreakpoints-invalid
20338 The breakpoints may have changed. For example, the user just added or
20339 deleted a breakpoint.
20342 @node Annotations for Running
20343 @section Running the Program
20344 @cindex annotations for running programs
20348 When the program starts executing due to a @value{GDBN} command such as
20349 @code{step} or @code{continue},
20355 is output. When the program stops,
20361 is output. Before the @code{stopped} annotation, a variety of
20362 annotations describe how the program stopped.
20366 @item ^Z^Zexited @var{exit-status}
20367 The program exited, and @var{exit-status} is the exit status (zero for
20368 successful exit, otherwise nonzero).
20371 @findex signal-name
20372 @findex signal-name-end
20373 @findex signal-string
20374 @findex signal-string-end
20375 @item ^Z^Zsignalled
20376 The program exited with a signal. After the @code{^Z^Zsignalled}, the
20377 annotation continues:
20383 ^Z^Zsignal-name-end
20387 ^Z^Zsignal-string-end
20392 where @var{name} is the name of the signal, such as @code{SIGILL} or
20393 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
20394 as @code{Illegal Instruction} or @code{Segmentation fault}.
20395 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
20396 user's benefit and have no particular format.
20400 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
20401 just saying that the program received the signal, not that it was
20402 terminated with it.
20405 @item ^Z^Zbreakpoint @var{number}
20406 The program hit breakpoint number @var{number}.
20409 @item ^Z^Zwatchpoint @var{number}
20410 The program hit watchpoint number @var{number}.
20413 @node Source Annotations
20414 @section Displaying Source
20415 @cindex annotations for source display
20418 The following annotation is used instead of displaying source code:
20421 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
20424 where @var{filename} is an absolute file name indicating which source
20425 file, @var{line} is the line number within that file (where 1 is the
20426 first line in the file), @var{character} is the character position
20427 within the file (where 0 is the first character in the file) (for most
20428 debug formats this will necessarily point to the beginning of a line),
20429 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
20430 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
20431 @var{addr} is the address in the target program associated with the
20432 source which is being displayed. @var{addr} is in the form @samp{0x}
20433 followed by one or more lowercase hex digits (note that this does not
20434 depend on the language).
20437 @chapter Reporting Bugs in @value{GDBN}
20438 @cindex bugs in @value{GDBN}
20439 @cindex reporting bugs in @value{GDBN}
20441 Your bug reports play an essential role in making @value{GDBN} reliable.
20443 Reporting a bug may help you by bringing a solution to your problem, or it
20444 may not. But in any case the principal function of a bug report is to help
20445 the entire community by making the next version of @value{GDBN} work better. Bug
20446 reports are your contribution to the maintenance of @value{GDBN}.
20448 In order for a bug report to serve its purpose, you must include the
20449 information that enables us to fix the bug.
20452 * Bug Criteria:: Have you found a bug?
20453 * Bug Reporting:: How to report bugs
20457 @section Have you found a bug?
20458 @cindex bug criteria
20460 If you are not sure whether you have found a bug, here are some guidelines:
20463 @cindex fatal signal
20464 @cindex debugger crash
20465 @cindex crash of debugger
20467 If the debugger gets a fatal signal, for any input whatever, that is a
20468 @value{GDBN} bug. Reliable debuggers never crash.
20470 @cindex error on valid input
20472 If @value{GDBN} produces an error message for valid input, that is a
20473 bug. (Note that if you're cross debugging, the problem may also be
20474 somewhere in the connection to the target.)
20476 @cindex invalid input
20478 If @value{GDBN} does not produce an error message for invalid input,
20479 that is a bug. However, you should note that your idea of
20480 ``invalid input'' might be our idea of ``an extension'' or ``support
20481 for traditional practice''.
20484 If you are an experienced user of debugging tools, your suggestions
20485 for improvement of @value{GDBN} are welcome in any case.
20488 @node Bug Reporting
20489 @section How to report bugs
20490 @cindex bug reports
20491 @cindex @value{GDBN} bugs, reporting
20493 A number of companies and individuals offer support for @sc{gnu} products.
20494 If you obtained @value{GDBN} from a support organization, we recommend you
20495 contact that organization first.
20497 You can find contact information for many support companies and
20498 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
20500 @c should add a web page ref...
20502 In any event, we also recommend that you submit bug reports for
20503 @value{GDBN}. The prefered method is to submit them directly using
20504 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
20505 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
20508 @strong{Do not send bug reports to @samp{info-gdb}, or to
20509 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
20510 not want to receive bug reports. Those that do have arranged to receive
20513 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
20514 serves as a repeater. The mailing list and the newsgroup carry exactly
20515 the same messages. Often people think of posting bug reports to the
20516 newsgroup instead of mailing them. This appears to work, but it has one
20517 problem which can be crucial: a newsgroup posting often lacks a mail
20518 path back to the sender. Thus, if we need to ask for more information,
20519 we may be unable to reach you. For this reason, it is better to send
20520 bug reports to the mailing list.
20522 The fundamental principle of reporting bugs usefully is this:
20523 @strong{report all the facts}. If you are not sure whether to state a
20524 fact or leave it out, state it!
20526 Often people omit facts because they think they know what causes the
20527 problem and assume that some details do not matter. Thus, you might
20528 assume that the name of the variable you use in an example does not matter.
20529 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
20530 stray memory reference which happens to fetch from the location where that
20531 name is stored in memory; perhaps, if the name were different, the contents
20532 of that location would fool the debugger into doing the right thing despite
20533 the bug. Play it safe and give a specific, complete example. That is the
20534 easiest thing for you to do, and the most helpful.
20536 Keep in mind that the purpose of a bug report is to enable us to fix the
20537 bug. It may be that the bug has been reported previously, but neither
20538 you nor we can know that unless your bug report is complete and
20541 Sometimes people give a few sketchy facts and ask, ``Does this ring a
20542 bell?'' Those bug reports are useless, and we urge everyone to
20543 @emph{refuse to respond to them} except to chide the sender to report
20546 To enable us to fix the bug, you should include all these things:
20550 The version of @value{GDBN}. @value{GDBN} announces it if you start
20551 with no arguments; you can also print it at any time using @code{show
20554 Without this, we will not know whether there is any point in looking for
20555 the bug in the current version of @value{GDBN}.
20558 The type of machine you are using, and the operating system name and
20562 What compiler (and its version) was used to compile @value{GDBN}---e.g.
20563 ``@value{GCC}--2.8.1''.
20566 What compiler (and its version) was used to compile the program you are
20567 debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
20568 C Compiler''. For GCC, you can say @code{gcc --version} to get this
20569 information; for other compilers, see the documentation for those
20573 The command arguments you gave the compiler to compile your example and
20574 observe the bug. For example, did you use @samp{-O}? To guarantee
20575 you will not omit something important, list them all. A copy of the
20576 Makefile (or the output from make) is sufficient.
20578 If we were to try to guess the arguments, we would probably guess wrong
20579 and then we might not encounter the bug.
20582 A complete input script, and all necessary source files, that will
20586 A description of what behavior you observe that you believe is
20587 incorrect. For example, ``It gets a fatal signal.''
20589 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
20590 will certainly notice it. But if the bug is incorrect output, we might
20591 not notice unless it is glaringly wrong. You might as well not give us
20592 a chance to make a mistake.
20594 Even if the problem you experience is a fatal signal, you should still
20595 say so explicitly. Suppose something strange is going on, such as, your
20596 copy of @value{GDBN} is out of synch, or you have encountered a bug in
20597 the C library on your system. (This has happened!) Your copy might
20598 crash and ours would not. If you told us to expect a crash, then when
20599 ours fails to crash, we would know that the bug was not happening for
20600 us. If you had not told us to expect a crash, then we would not be able
20601 to draw any conclusion from our observations.
20604 @cindex recording a session script
20605 To collect all this information, you can use a session recording program
20606 such as @command{script}, which is available on many Unix systems.
20607 Just run your @value{GDBN} session inside @command{script} and then
20608 include the @file{typescript} file with your bug report.
20610 Another way to record a @value{GDBN} session is to run @value{GDBN}
20611 inside Emacs and then save the entire buffer to a file.
20614 If you wish to suggest changes to the @value{GDBN} source, send us context
20615 diffs. If you even discuss something in the @value{GDBN} source, refer to
20616 it by context, not by line number.
20618 The line numbers in our development sources will not match those in your
20619 sources. Your line numbers would convey no useful information to us.
20623 Here are some things that are not necessary:
20627 A description of the envelope of the bug.
20629 Often people who encounter a bug spend a lot of time investigating
20630 which changes to the input file will make the bug go away and which
20631 changes will not affect it.
20633 This is often time consuming and not very useful, because the way we
20634 will find the bug is by running a single example under the debugger
20635 with breakpoints, not by pure deduction from a series of examples.
20636 We recommend that you save your time for something else.
20638 Of course, if you can find a simpler example to report @emph{instead}
20639 of the original one, that is a convenience for us. Errors in the
20640 output will be easier to spot, running under the debugger will take
20641 less time, and so on.
20643 However, simplification is not vital; if you do not want to do this,
20644 report the bug anyway and send us the entire test case you used.
20647 A patch for the bug.
20649 A patch for the bug does help us if it is a good one. But do not omit
20650 the necessary information, such as the test case, on the assumption that
20651 a patch is all we need. We might see problems with your patch and decide
20652 to fix the problem another way, or we might not understand it at all.
20654 Sometimes with a program as complicated as @value{GDBN} it is very hard to
20655 construct an example that will make the program follow a certain path
20656 through the code. If you do not send us the example, we will not be able
20657 to construct one, so we will not be able to verify that the bug is fixed.
20659 And if we cannot understand what bug you are trying to fix, or why your
20660 patch should be an improvement, we will not install it. A test case will
20661 help us to understand.
20664 A guess about what the bug is or what it depends on.
20666 Such guesses are usually wrong. Even we cannot guess right about such
20667 things without first using the debugger to find the facts.
20670 @c The readline documentation is distributed with the readline code
20671 @c and consists of the two following files:
20673 @c inc-hist.texinfo
20674 @c Use -I with makeinfo to point to the appropriate directory,
20675 @c environment var TEXINPUTS with TeX.
20676 @include rluser.texinfo
20677 @include inc-hist.texinfo
20680 @node Formatting Documentation
20681 @appendix Formatting Documentation
20683 @cindex @value{GDBN} reference card
20684 @cindex reference card
20685 The @value{GDBN} 4 release includes an already-formatted reference card, ready
20686 for printing with PostScript or Ghostscript, in the @file{gdb}
20687 subdirectory of the main source directory@footnote{In
20688 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
20689 release.}. If you can use PostScript or Ghostscript with your printer,
20690 you can print the reference card immediately with @file{refcard.ps}.
20692 The release also includes the source for the reference card. You
20693 can format it, using @TeX{}, by typing:
20699 The @value{GDBN} reference card is designed to print in @dfn{landscape}
20700 mode on US ``letter'' size paper;
20701 that is, on a sheet 11 inches wide by 8.5 inches
20702 high. You will need to specify this form of printing as an option to
20703 your @sc{dvi} output program.
20705 @cindex documentation
20707 All the documentation for @value{GDBN} comes as part of the machine-readable
20708 distribution. The documentation is written in Texinfo format, which is
20709 a documentation system that uses a single source file to produce both
20710 on-line information and a printed manual. You can use one of the Info
20711 formatting commands to create the on-line version of the documentation
20712 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
20714 @value{GDBN} includes an already formatted copy of the on-line Info
20715 version of this manual in the @file{gdb} subdirectory. The main Info
20716 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
20717 subordinate files matching @samp{gdb.info*} in the same directory. If
20718 necessary, you can print out these files, or read them with any editor;
20719 but they are easier to read using the @code{info} subsystem in @sc{gnu}
20720 Emacs or the standalone @code{info} program, available as part of the
20721 @sc{gnu} Texinfo distribution.
20723 If you want to format these Info files yourself, you need one of the
20724 Info formatting programs, such as @code{texinfo-format-buffer} or
20727 If you have @code{makeinfo} installed, and are in the top level
20728 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
20729 version @value{GDBVN}), you can make the Info file by typing:
20736 If you want to typeset and print copies of this manual, you need @TeX{},
20737 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
20738 Texinfo definitions file.
20740 @TeX{} is a typesetting program; it does not print files directly, but
20741 produces output files called @sc{dvi} files. To print a typeset
20742 document, you need a program to print @sc{dvi} files. If your system
20743 has @TeX{} installed, chances are it has such a program. The precise
20744 command to use depends on your system; @kbd{lpr -d} is common; another
20745 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
20746 require a file name without any extension or a @samp{.dvi} extension.
20748 @TeX{} also requires a macro definitions file called
20749 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
20750 written in Texinfo format. On its own, @TeX{} cannot either read or
20751 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
20752 and is located in the @file{gdb-@var{version-number}/texinfo}
20755 If you have @TeX{} and a @sc{dvi} printer program installed, you can
20756 typeset and print this manual. First switch to the the @file{gdb}
20757 subdirectory of the main source directory (for example, to
20758 @file{gdb-@value{GDBVN}/gdb}) and type:
20764 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
20766 @node Installing GDB
20767 @appendix Installing @value{GDBN}
20768 @cindex configuring @value{GDBN}
20769 @cindex installation
20770 @cindex configuring @value{GDBN}, and source tree subdirectories
20772 @value{GDBN} comes with a @code{configure} script that automates the process
20773 of preparing @value{GDBN} for installation; you can then use @code{make} to
20774 build the @code{gdb} program.
20776 @c irrelevant in info file; it's as current as the code it lives with.
20777 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
20778 look at the @file{README} file in the sources; we may have improved the
20779 installation procedures since publishing this manual.}
20782 The @value{GDBN} distribution includes all the source code you need for
20783 @value{GDBN} in a single directory, whose name is usually composed by
20784 appending the version number to @samp{gdb}.
20786 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
20787 @file{gdb-@value{GDBVN}} directory. That directory contains:
20790 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
20791 script for configuring @value{GDBN} and all its supporting libraries
20793 @item gdb-@value{GDBVN}/gdb
20794 the source specific to @value{GDBN} itself
20796 @item gdb-@value{GDBVN}/bfd
20797 source for the Binary File Descriptor library
20799 @item gdb-@value{GDBVN}/include
20800 @sc{gnu} include files
20802 @item gdb-@value{GDBVN}/libiberty
20803 source for the @samp{-liberty} free software library
20805 @item gdb-@value{GDBVN}/opcodes
20806 source for the library of opcode tables and disassemblers
20808 @item gdb-@value{GDBVN}/readline
20809 source for the @sc{gnu} command-line interface
20811 @item gdb-@value{GDBVN}/glob
20812 source for the @sc{gnu} filename pattern-matching subroutine
20814 @item gdb-@value{GDBVN}/mmalloc
20815 source for the @sc{gnu} memory-mapped malloc package
20818 The simplest way to configure and build @value{GDBN} is to run @code{configure}
20819 from the @file{gdb-@var{version-number}} source directory, which in
20820 this example is the @file{gdb-@value{GDBVN}} directory.
20822 First switch to the @file{gdb-@var{version-number}} source directory
20823 if you are not already in it; then run @code{configure}. Pass the
20824 identifier for the platform on which @value{GDBN} will run as an
20830 cd gdb-@value{GDBVN}
20831 ./configure @var{host}
20836 where @var{host} is an identifier such as @samp{sun4} or
20837 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
20838 (You can often leave off @var{host}; @code{configure} tries to guess the
20839 correct value by examining your system.)
20841 Running @samp{configure @var{host}} and then running @code{make} builds the
20842 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
20843 libraries, then @code{gdb} itself. The configured source files, and the
20844 binaries, are left in the corresponding source directories.
20847 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
20848 system does not recognize this automatically when you run a different
20849 shell, you may need to run @code{sh} on it explicitly:
20852 sh configure @var{host}
20855 If you run @code{configure} from a directory that contains source
20856 directories for multiple libraries or programs, such as the
20857 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
20858 creates configuration files for every directory level underneath (unless
20859 you tell it not to, with the @samp{--norecursion} option).
20861 You should run the @code{configure} script from the top directory in the
20862 source tree, the @file{gdb-@var{version-number}} directory. If you run
20863 @code{configure} from one of the subdirectories, you will configure only
20864 that subdirectory. That is usually not what you want. In particular,
20865 if you run the first @code{configure} from the @file{gdb} subdirectory
20866 of the @file{gdb-@var{version-number}} directory, you will omit the
20867 configuration of @file{bfd}, @file{readline}, and other sibling
20868 directories of the @file{gdb} subdirectory. This leads to build errors
20869 about missing include files such as @file{bfd/bfd.h}.
20871 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
20872 However, you should make sure that the shell on your path (named by
20873 the @samp{SHELL} environment variable) is publicly readable. Remember
20874 that @value{GDBN} uses the shell to start your program---some systems refuse to
20875 let @value{GDBN} debug child processes whose programs are not readable.
20878 * Separate Objdir:: Compiling @value{GDBN} in another directory
20879 * Config Names:: Specifying names for hosts and targets
20880 * Configure Options:: Summary of options for configure
20883 @node Separate Objdir
20884 @section Compiling @value{GDBN} in another directory
20886 If you want to run @value{GDBN} versions for several host or target machines,
20887 you need a different @code{gdb} compiled for each combination of
20888 host and target. @code{configure} is designed to make this easy by
20889 allowing you to generate each configuration in a separate subdirectory,
20890 rather than in the source directory. If your @code{make} program
20891 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
20892 @code{make} in each of these directories builds the @code{gdb}
20893 program specified there.
20895 To build @code{gdb} in a separate directory, run @code{configure}
20896 with the @samp{--srcdir} option to specify where to find the source.
20897 (You also need to specify a path to find @code{configure}
20898 itself from your working directory. If the path to @code{configure}
20899 would be the same as the argument to @samp{--srcdir}, you can leave out
20900 the @samp{--srcdir} option; it is assumed.)
20902 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
20903 separate directory for a Sun 4 like this:
20907 cd gdb-@value{GDBVN}
20910 ../gdb-@value{GDBVN}/configure sun4
20915 When @code{configure} builds a configuration using a remote source
20916 directory, it creates a tree for the binaries with the same structure
20917 (and using the same names) as the tree under the source directory. In
20918 the example, you'd find the Sun 4 library @file{libiberty.a} in the
20919 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
20920 @file{gdb-sun4/gdb}.
20922 Make sure that your path to the @file{configure} script has just one
20923 instance of @file{gdb} in it. If your path to @file{configure} looks
20924 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
20925 one subdirectory of @value{GDBN}, not the whole package. This leads to
20926 build errors about missing include files such as @file{bfd/bfd.h}.
20928 One popular reason to build several @value{GDBN} configurations in separate
20929 directories is to configure @value{GDBN} for cross-compiling (where
20930 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
20931 programs that run on another machine---the @dfn{target}).
20932 You specify a cross-debugging target by
20933 giving the @samp{--target=@var{target}} option to @code{configure}.
20935 When you run @code{make} to build a program or library, you must run
20936 it in a configured directory---whatever directory you were in when you
20937 called @code{configure} (or one of its subdirectories).
20939 The @code{Makefile} that @code{configure} generates in each source
20940 directory also runs recursively. If you type @code{make} in a source
20941 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
20942 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
20943 will build all the required libraries, and then build GDB.
20945 When you have multiple hosts or targets configured in separate
20946 directories, you can run @code{make} on them in parallel (for example,
20947 if they are NFS-mounted on each of the hosts); they will not interfere
20951 @section Specifying names for hosts and targets
20953 The specifications used for hosts and targets in the @code{configure}
20954 script are based on a three-part naming scheme, but some short predefined
20955 aliases are also supported. The full naming scheme encodes three pieces
20956 of information in the following pattern:
20959 @var{architecture}-@var{vendor}-@var{os}
20962 For example, you can use the alias @code{sun4} as a @var{host} argument,
20963 or as the value for @var{target} in a @code{--target=@var{target}}
20964 option. The equivalent full name is @samp{sparc-sun-sunos4}.
20966 The @code{configure} script accompanying @value{GDBN} does not provide
20967 any query facility to list all supported host and target names or
20968 aliases. @code{configure} calls the Bourne shell script
20969 @code{config.sub} to map abbreviations to full names; you can read the
20970 script, if you wish, or you can use it to test your guesses on
20971 abbreviations---for example:
20974 % sh config.sub i386-linux
20976 % sh config.sub alpha-linux
20977 alpha-unknown-linux-gnu
20978 % sh config.sub hp9k700
20980 % sh config.sub sun4
20981 sparc-sun-sunos4.1.1
20982 % sh config.sub sun3
20983 m68k-sun-sunos4.1.1
20984 % sh config.sub i986v
20985 Invalid configuration `i986v': machine `i986v' not recognized
20989 @code{config.sub} is also distributed in the @value{GDBN} source
20990 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
20992 @node Configure Options
20993 @section @code{configure} options
20995 Here is a summary of the @code{configure} options and arguments that
20996 are most often useful for building @value{GDBN}. @code{configure} also has
20997 several other options not listed here. @inforef{What Configure
20998 Does,,configure.info}, for a full explanation of @code{configure}.
21001 configure @r{[}--help@r{]}
21002 @r{[}--prefix=@var{dir}@r{]}
21003 @r{[}--exec-prefix=@var{dir}@r{]}
21004 @r{[}--srcdir=@var{dirname}@r{]}
21005 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
21006 @r{[}--target=@var{target}@r{]}
21011 You may introduce options with a single @samp{-} rather than
21012 @samp{--} if you prefer; but you may abbreviate option names if you use
21017 Display a quick summary of how to invoke @code{configure}.
21019 @item --prefix=@var{dir}
21020 Configure the source to install programs and files under directory
21023 @item --exec-prefix=@var{dir}
21024 Configure the source to install programs under directory
21027 @c avoid splitting the warning from the explanation:
21029 @item --srcdir=@var{dirname}
21030 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
21031 @code{make} that implements the @code{VPATH} feature.}@*
21032 Use this option to make configurations in directories separate from the
21033 @value{GDBN} source directories. Among other things, you can use this to
21034 build (or maintain) several configurations simultaneously, in separate
21035 directories. @code{configure} writes configuration specific files in
21036 the current directory, but arranges for them to use the source in the
21037 directory @var{dirname}. @code{configure} creates directories under
21038 the working directory in parallel to the source directories below
21041 @item --norecursion
21042 Configure only the directory level where @code{configure} is executed; do not
21043 propagate configuration to subdirectories.
21045 @item --target=@var{target}
21046 Configure @value{GDBN} for cross-debugging programs running on the specified
21047 @var{target}. Without this option, @value{GDBN} is configured to debug
21048 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
21050 There is no convenient way to generate a list of all available targets.
21052 @item @var{host} @dots{}
21053 Configure @value{GDBN} to run on the specified @var{host}.
21055 There is no convenient way to generate a list of all available hosts.
21058 There are many other options available as well, but they are generally
21059 needed for special purposes only.
21061 @node Maintenance Commands
21062 @appendix Maintenance Commands
21063 @cindex maintenance commands
21064 @cindex internal commands
21066 In addition to commands intended for @value{GDBN} users, @value{GDBN}
21067 includes a number of commands intended for @value{GDBN} developers,
21068 that are not documented elsewhere in this manual. These commands are
21069 provided here for reference. (For commands that turn on debugging
21070 messages, see @ref{Debugging Output}.)
21073 @kindex maint agent
21074 @item maint agent @var{expression}
21075 Translate the given @var{expression} into remote agent bytecodes.
21076 This command is useful for debugging the Agent Expression mechanism
21077 (@pxref{Agent Expressions}).
21079 @kindex maint info breakpoints
21080 @item @anchor{maint info breakpoints}maint info breakpoints
21081 Using the same format as @samp{info breakpoints}, display both the
21082 breakpoints you've set explicitly, and those @value{GDBN} is using for
21083 internal purposes. Internal breakpoints are shown with negative
21084 breakpoint numbers. The type column identifies what kind of breakpoint
21089 Normal, explicitly set breakpoint.
21092 Normal, explicitly set watchpoint.
21095 Internal breakpoint, used to handle correctly stepping through
21096 @code{longjmp} calls.
21098 @item longjmp resume
21099 Internal breakpoint at the target of a @code{longjmp}.
21102 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
21105 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
21108 Shared library events.
21112 @kindex maint check-symtabs
21113 @item maint check-symtabs
21114 Check the consistency of psymtabs and symtabs.
21116 @kindex maint cplus first_component
21117 @item maint cplus first_component @var{name}
21118 Print the first C@t{++} class/namespace component of @var{name}.
21120 @kindex maint cplus namespace
21121 @item maint cplus namespace
21122 Print the list of possible C@t{++} namespaces.
21124 @kindex maint demangle
21125 @item maint demangle @var{name}
21126 Demangle a C@t{++} or Objective-C manled @var{name}.
21128 @kindex maint deprecate
21129 @kindex maint undeprecate
21130 @cindex deprecated commands
21131 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
21132 @itemx maint undeprecate @var{command}
21133 Deprecate or undeprecate the named @var{command}. Deprecated commands
21134 cause @value{GDBN} to issue a warning when you use them. The optional
21135 argument @var{replacement} says which newer command should be used in
21136 favor of the deprecated one; if it is given, @value{GDBN} will mention
21137 the replacement as part of the warning.
21139 @kindex maint dump-me
21140 @item maint dump-me
21141 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
21142 Cause a fatal signal in the debugger and force it to dump its core.
21143 This is supported only on systems which support aborting a program
21144 with the @code{SIGQUIT} signal.
21146 @kindex maint internal-error
21147 @kindex maint internal-warning
21148 @item maint internal-error @r{[}@var{message-text}@r{]}
21149 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
21150 Cause @value{GDBN} to call the internal function @code{internal_error}
21151 or @code{internal_warning} and hence behave as though an internal error
21152 or internal warning has been detected. In addition to reporting the
21153 internal problem, these functions give the user the opportunity to
21154 either quit @value{GDBN} or create a core file of the current
21155 @value{GDBN} session.
21157 These commands take an optional parameter @var{message-text} that is
21158 used as the text of the error or warning message.
21160 Here's an example of using @code{indernal-error}:
21163 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
21164 @dots{}/maint.c:121: internal-error: testing, 1, 2
21165 A problem internal to GDB has been detected. Further
21166 debugging may prove unreliable.
21167 Quit this debugging session? (y or n) @kbd{n}
21168 Create a core file? (y or n) @kbd{n}
21172 @kindex maint packet
21173 @item maint packet @var{text}
21174 If @value{GDBN} is talking to an inferior via the serial protocol,
21175 then this command sends the string @var{text} to the inferior, and
21176 displays the response packet. @value{GDBN} supplies the initial
21177 @samp{$} character, the terminating @samp{#} character, and the
21180 @kindex maint print architecture
21181 @item maint print architecture @r{[}@var{file}@r{]}
21182 Print the entire architecture configuration. The optional argument
21183 @var{file} names the file where the output goes.
21185 @kindex maint print dummy-frames
21186 @item maint print dummy-frames
21187 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
21190 (@value{GDBP}) @kbd{b add}
21192 (@value{GDBP}) @kbd{print add(2,3)}
21193 Breakpoint 2, add (a=2, b=3) at @dots{}
21195 The program being debugged stopped while in a function called from GDB.
21197 (@value{GDBP}) @kbd{maint print dummy-frames}
21198 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
21199 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
21200 call_lo=0x01014000 call_hi=0x01014001
21204 Takes an optional file parameter.
21206 @kindex maint print registers
21207 @kindex maint print raw-registers
21208 @kindex maint print cooked-registers
21209 @kindex maint print register-groups
21210 @item maint print registers @r{[}@var{file}@r{]}
21211 @itemx maint print raw-registers @r{[}@var{file}@r{]}
21212 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
21213 @itemx maint print register-groups @r{[}@var{file}@r{]}
21214 Print @value{GDBN}'s internal register data structures.
21216 The command @code{maint print raw-registers} includes the contents of
21217 the raw register cache; the command @code{maint print cooked-registers}
21218 includes the (cooked) value of all registers; and the command
21219 @code{maint print register-groups} includes the groups that each
21220 register is a member of. @xref{Registers,, Registers, gdbint,
21221 @value{GDBN} Internals}.
21223 These commands take an optional parameter, a file name to which to
21224 write the information.
21226 @kindex maint print reggroups
21227 @item maint print reggroups @r{[}@var{file}@r{]}
21228 Print @value{GDBN}'s internal register group data structures. The
21229 optional argument @var{file} tells to what file to write the
21232 The register groups info looks like this:
21235 (@value{GDBP}) @kbd{maint print reggroups}
21248 This command forces @value{GDBN} to flush its internal register cache.
21250 @kindex maint print objfiles
21251 @cindex info for known object files
21252 @item maint print objfiles
21253 Print a dump of all known object files. For each object file, this
21254 command prints its name, address in memory, and all of its psymtabs
21257 @kindex maint print statistics
21258 @cindex bcache statistics
21259 @item maint print statistics
21260 This command prints, for each object file in the program, various data
21261 about that object file followed by the byte cache (@dfn{bcache})
21262 statistics for the object file. The objfile data includes the number
21263 of minimal, partical, full, and stabs symbols, the number of types
21264 defined by the objfile, the number of as yet unexpanded psym tables,
21265 the number of line tables and string tables, and the amount of memory
21266 used by the various tables. The bcache statistics include the counts,
21267 sizes, and counts of duplicates of all and unique objects, max,
21268 average, and median entry size, total memory used and its overhead and
21269 savings, and various measures of the hash table size and chain
21272 @kindex maint print type
21273 @cindex type chain of a data type
21274 @item maint print type @var{expr}
21275 Print the type chain for a type specified by @var{expr}. The argument
21276 can be either a type name or a symbol. If it is a symbol, the type of
21277 that symbol is described. The type chain produced by this command is
21278 a recursive definition of the data type as stored in @value{GDBN}'s
21279 data structures, including its flags and contained types.
21281 @kindex maint set dwarf2 max-cache-age
21282 @kindex maint show dwarf2 max-cache-age
21283 @item maint set dwarf2 max-cache-age
21284 @itemx maint show dwarf2 max-cache-age
21285 Control the DWARF 2 compilation unit cache.
21287 @cindex DWARF 2 compilation units cache
21288 In object files with inter-compilation-unit references, such as those
21289 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
21290 reader needs to frequently refer to previously read compilation units.
21291 This setting controls how long a compilation unit will remain in the
21292 cache if it is not referenced. A higher limit means that cached
21293 compilation units will be stored in memory longer, and more total
21294 memory will be used. Setting it to zero disables caching, which will
21295 slow down @value{GDBN} startup, but reduce memory consumption.
21297 @kindex maint set profile
21298 @kindex maint show profile
21299 @cindex profiling GDB
21300 @item maint set profile
21301 @itemx maint show profile
21302 Control profiling of @value{GDBN}.
21304 Profiling will be disabled until you use the @samp{maint set profile}
21305 command to enable it. When you enable profiling, the system will begin
21306 collecting timing and execution count data; when you disable profiling or
21307 exit @value{GDBN}, the results will be written to a log file. Remember that
21308 if you use profiling, @value{GDBN} will overwrite the profiling log file
21309 (often called @file{gmon.out}). If you have a record of important profiling
21310 data in a @file{gmon.out} file, be sure to move it to a safe location.
21312 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
21313 compiled with the @samp{-pg} compiler option.
21315 @kindex maint show-debug-regs
21316 @cindex x86 hardware debug registers
21317 @item maint show-debug-regs
21318 Control whether to show variables that mirror the x86 hardware debug
21319 registers. Use @code{ON} to enable, @code{OFF} to disable. If
21320 enabled, the debug registers values are shown when GDB inserts or
21321 removes a hardware breakpoint or watchpoint, and when the inferior
21322 triggers a hardware-assisted breakpoint or watchpoint.
21324 @kindex maint space
21325 @cindex memory used by commands
21327 Control whether to display memory usage for each command. If set to a
21328 nonzero value, @value{GDBN} will display how much memory each command
21329 took, following the command's own output. This can also be requested
21330 by invoking @value{GDBN} with the @option{--statistics} command-line
21331 switch (@pxref{Mode Options}).
21334 @cindex time of command execution
21336 Control whether to display the execution time for each command. If
21337 set to a nonzero value, @value{GDBN} will display how much time it
21338 took to execute each command, following the command's own output.
21339 This can also be requested by invoking @value{GDBN} with the
21340 @option{--statistics} command-line switch (@pxref{Mode Options}).
21342 @kindex maint translate-address
21343 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
21344 Find the symbol stored at the location specified by the address
21345 @var{addr} and an optional section name @var{section}. If found,
21346 @value{GDBN} prints the name of the closest symbol and an offset from
21347 the symbol's location to the specified address. This is similar to
21348 the @code{info address} command (@pxref{Symbols}), except that this
21349 command also allows to find symbols in other sections.
21353 The following command is useful for non-interactive invocations of
21354 @value{GDBN}, such as in the test suite.
21357 @item set watchdog @var{nsec}
21358 @kindex set watchdog
21359 @cindex watchdog timer
21360 @cindex timeout for commands
21361 Set the maximum number of seconds @value{GDBN} will wait for the
21362 target operation to finish. If this time expires, @value{GDBN}
21363 reports and error and the command is aborted.
21365 @item show watchdog
21366 Show the current setting of the target wait timeout.
21369 @node Remote Protocol
21370 @appendix @value{GDBN} Remote Serial Protocol
21375 * Stop Reply Packets::
21376 * General Query Packets::
21377 * Register Packet Format::
21379 * File-I/O remote protocol extension::
21385 There may be occasions when you need to know something about the
21386 protocol---for example, if there is only one serial port to your target
21387 machine, you might want your program to do something special if it
21388 recognizes a packet meant for @value{GDBN}.
21390 In the examples below, @samp{->} and @samp{<-} are used to indicate
21391 transmitted and received data respectfully.
21393 @cindex protocol, @value{GDBN} remote serial
21394 @cindex serial protocol, @value{GDBN} remote
21395 @cindex remote serial protocol
21396 All @value{GDBN} commands and responses (other than acknowledgments) are
21397 sent as a @var{packet}. A @var{packet} is introduced with the character
21398 @samp{$}, the actual @var{packet-data}, and the terminating character
21399 @samp{#} followed by a two-digit @var{checksum}:
21402 @code{$}@var{packet-data}@code{#}@var{checksum}
21406 @cindex checksum, for @value{GDBN} remote
21408 The two-digit @var{checksum} is computed as the modulo 256 sum of all
21409 characters between the leading @samp{$} and the trailing @samp{#} (an
21410 eight bit unsigned checksum).
21412 Implementors should note that prior to @value{GDBN} 5.0 the protocol
21413 specification also included an optional two-digit @var{sequence-id}:
21416 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
21419 @cindex sequence-id, for @value{GDBN} remote
21421 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
21422 has never output @var{sequence-id}s. Stubs that handle packets added
21423 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
21425 @cindex acknowledgment, for @value{GDBN} remote
21426 When either the host or the target machine receives a packet, the first
21427 response expected is an acknowledgment: either @samp{+} (to indicate
21428 the package was received correctly) or @samp{-} (to request
21432 -> @code{$}@var{packet-data}@code{#}@var{checksum}
21437 The host (@value{GDBN}) sends @var{command}s, and the target (the
21438 debugging stub incorporated in your program) sends a @var{response}. In
21439 the case of step and continue @var{command}s, the response is only sent
21440 when the operation has completed (the target has again stopped).
21442 @var{packet-data} consists of a sequence of characters with the
21443 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
21446 Fields within the packet should be separated using @samp{,} @samp{;} or
21447 @cindex remote protocol, field separator
21448 @samp{:}. Except where otherwise noted all numbers are represented in
21449 @sc{hex} with leading zeros suppressed.
21451 Implementors should note that prior to @value{GDBN} 5.0, the character
21452 @samp{:} could not appear as the third character in a packet (as it
21453 would potentially conflict with the @var{sequence-id}).
21455 Response @var{data} can be run-length encoded to save space. A @samp{*}
21456 means that the next character is an @sc{ascii} encoding giving a repeat count
21457 which stands for that many repetitions of the character preceding the
21458 @samp{*}. The encoding is @code{n+29}, yielding a printable character
21459 where @code{n >=3} (which is where rle starts to win). The printable
21460 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
21461 value greater than 126 should not be used.
21468 means the same as "0000".
21470 The error response returned for some packets includes a two character
21471 error number. That number is not well defined.
21473 For any @var{command} not supported by the stub, an empty response
21474 (@samp{$#00}) should be returned. That way it is possible to extend the
21475 protocol. A newer @value{GDBN} can tell if a packet is supported based
21478 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
21479 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
21485 The following table provides a complete list of all currently defined
21486 @var{command}s and their corresponding response @var{data}.
21487 @xref{File-I/O remote protocol extension}, for details about the File
21488 I/O extension of the remote protocol.
21492 @item @code{!} --- extended mode
21493 @cindex @code{!} packet
21495 Enable extended mode. In extended mode, the remote server is made
21496 persistent. The @samp{R} packet is used to restart the program being
21502 The remote target both supports and has enabled extended mode.
21505 @item @code{?} --- last signal
21506 @cindex @code{?} packet
21508 Indicate the reason the target halted. The reply is the same as for
21512 @xref{Stop Reply Packets}, for the reply specifications.
21514 @item @code{a} --- reserved
21516 Reserved for future use.
21518 @item @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,@dots{}} --- set program arguments @strong{(reserved)}
21519 @cindex @code{A} packet
21521 Initialized @samp{argv[]} array passed into program. @var{arglen}
21522 specifies the number of bytes in the hex encoded byte stream @var{arg}.
21523 See @code{gdbserver} for more details.
21531 @item @code{b}@var{baud} --- set baud @strong{(deprecated)}
21532 @cindex @code{b} packet
21534 Change the serial line speed to @var{baud}.
21536 JTC: @emph{When does the transport layer state change? When it's
21537 received, or after the ACK is transmitted. In either case, there are
21538 problems if the command or the acknowledgment packet is dropped.}
21540 Stan: @emph{If people really wanted to add something like this, and get
21541 it working for the first time, they ought to modify ser-unix.c to send
21542 some kind of out-of-band message to a specially-setup stub and have the
21543 switch happen "in between" packets, so that from remote protocol's point
21544 of view, nothing actually happened.}
21546 @item @code{B}@var{addr},@var{mode} --- set breakpoint @strong{(deprecated)}
21547 @cindex @code{B} packet
21549 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
21550 breakpoint at @var{addr}.
21552 This packet has been replaced by the @samp{Z} and @samp{z} packets
21553 (@pxref{insert breakpoint or watchpoint packet}).
21555 @item @code{c}@var{addr} --- continue
21556 @cindex @code{c} packet
21558 @var{addr} is address to resume. If @var{addr} is omitted, resume at
21562 @xref{Stop Reply Packets}, for the reply specifications.
21564 @item @code{C}@var{sig}@code{;}@var{addr} --- continue with signal
21565 @cindex @code{C} packet
21567 Continue with signal @var{sig} (hex signal number). If
21568 @code{;}@var{addr} is omitted, resume at same address.
21571 @xref{Stop Reply Packets}, for the reply specifications.
21573 @item @code{d} --- toggle debug @strong{(deprecated)}
21574 @cindex @code{d} packet
21578 @item @code{D} --- detach
21579 @cindex @code{D} packet
21581 Detach @value{GDBN} from the remote system. Sent to the remote target
21582 before @value{GDBN} disconnects via the @code{detach} command.
21586 @item @emph{no response}
21587 @value{GDBN} does not check for any response after sending this packet.
21590 @item @code{e} --- reserved
21592 Reserved for future use.
21594 @item @code{E} --- reserved
21596 Reserved for future use.
21598 @item @code{f} --- reserved
21600 Reserved for future use.
21602 @item @code{F}@var{RC}@code{,}@var{EE}@code{,}@var{CF}@code{;}@var{XX} --- Reply to target's F packet.
21603 @cindex @code{F} packet
21605 This packet is send by @value{GDBN} as reply to a @code{F} request packet
21606 sent by the target. This is part of the File-I/O protocol extension.
21607 @xref{File-I/O remote protocol extension}, for the specification.
21609 @item @code{g} --- read registers
21610 @anchor{read registers packet}
21611 @cindex @code{g} packet
21613 Read general registers.
21617 @item @var{XX@dots{}}
21618 Each byte of register data is described by two hex digits. The bytes
21619 with the register are transmitted in target byte order. The size of
21620 each register and their position within the @samp{g} @var{packet} are
21621 determined by the @value{GDBN} internal macros
21622 @var{DEPRECATED_REGISTER_RAW_SIZE} and @var{REGISTER_NAME} macros. The
21623 specification of several standard @code{g} packets is specified below.
21628 @item @code{G}@var{XX@dots{}} --- write regs
21629 @cindex @code{G} packet
21631 @xref{read registers packet}, for a description of the @var{XX@dots{}}
21642 @item @code{h} --- reserved
21644 Reserved for future use.
21646 @item @code{H}@var{c}@var{t@dots{}} --- set thread
21647 @cindex @code{H} packet
21649 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
21650 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
21651 should be @samp{c} for step and continue operations, @samp{g} for other
21652 operations. The thread designator @var{t@dots{}} may be -1, meaning all
21653 the threads, a thread number, or zero which means pick any thread.
21664 @c 'H': How restrictive (or permissive) is the thread model. If a
21665 @c thread is selected and stopped, are other threads allowed
21666 @c to continue to execute? As I mentioned above, I think the
21667 @c semantics of each command when a thread is selected must be
21668 @c described. For example:
21670 @c 'g': If the stub supports threads and a specific thread is
21671 @c selected, returns the register block from that thread;
21672 @c otherwise returns current registers.
21674 @c 'G' If the stub supports threads and a specific thread is
21675 @c selected, sets the registers of the register block of
21676 @c that thread; otherwise sets current registers.
21678 @item @code{i}@var{addr}@code{,}@var{nnn} --- cycle step @strong{(draft)}
21679 @anchor{cycle step packet}
21680 @cindex @code{i} packet
21682 Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
21683 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
21684 step starting at that address.
21686 @item @code{I} --- signal then cycle step @strong{(reserved)}
21687 @cindex @code{I} packet
21689 @xref{step with signal packet}. @xref{cycle step packet}.
21691 @item @code{j} --- reserved
21693 Reserved for future use.
21695 @item @code{J} --- reserved
21697 Reserved for future use.
21699 @item @code{k} --- kill request
21700 @cindex @code{k} packet
21702 FIXME: @emph{There is no description of how to operate when a specific
21703 thread context has been selected (i.e.@: does 'k' kill only that
21706 @item @code{K} --- reserved
21708 Reserved for future use.
21710 @item @code{l} --- reserved
21712 Reserved for future use.
21714 @item @code{L} --- reserved
21716 Reserved for future use.
21718 @item @code{m}@var{addr}@code{,}@var{length} --- read memory
21719 @cindex @code{m} packet
21721 Read @var{length} bytes of memory starting at address @var{addr}.
21722 Neither @value{GDBN} nor the stub assume that sized memory transfers are
21723 assumed using word aligned accesses. FIXME: @emph{A word aligned memory
21724 transfer mechanism is needed.}
21728 @item @var{XX@dots{}}
21729 @var{XX@dots{}} is mem contents. Can be fewer bytes than requested if able
21730 to read only part of the data. Neither @value{GDBN} nor the stub assume
21731 that sized memory transfers are assumed using word aligned
21732 accesses. FIXME: @emph{A word aligned memory transfer mechanism is
21738 @item @code{M}@var{addr},@var{length}@code{:}@var{XX@dots{}} --- write mem
21739 @cindex @code{M} packet
21741 Write @var{length} bytes of memory starting at address @var{addr}.
21742 @var{XX@dots{}} is the data.
21749 for an error (this includes the case where only part of the data was
21753 @item @code{n} --- reserved
21755 Reserved for future use.
21757 @item @code{N} --- reserved
21759 Reserved for future use.
21761 @item @code{o} --- reserved
21763 Reserved for future use.
21765 @item @code{O} --- reserved
21767 @item @code{p}@var{hex number of register} --- read register packet
21768 @cindex @code{p} packet
21770 @xref{read registers packet}, for a description of how the returned
21771 register value is encoded.
21775 @item @var{XX@dots{}}
21776 the register's value
21780 Indicating an unrecognized @var{query}.
21783 @item @code{P}@var{n@dots{}}@code{=}@var{r@dots{}} --- write register
21784 @anchor{write register packet}
21785 @cindex @code{P} packet
21787 Write register @var{n@dots{}} with value @var{r@dots{}}, which contains two hex
21788 digits for each byte in the register (target byte order).
21798 @item @code{q}@var{query} --- general query
21799 @anchor{general query packet}
21800 @cindex @code{q} packet
21802 Request info about @var{query}. In general @value{GDBN} queries have a
21803 leading upper case letter. Custom vendor queries should use a company
21804 prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may optionally
21805 be followed by a @samp{,} or @samp{;} separated list. Stubs must ensure
21806 that they match the full @var{query} name.
21810 @item @var{XX@dots{}}
21811 Hex encoded data from query. The reply can not be empty.
21815 Indicating an unrecognized @var{query}.
21818 @item @code{Q}@var{var}@code{=}@var{val} --- general set
21819 @cindex @code{Q} packet
21821 Set value of @var{var} to @var{val}.
21823 @xref{general query packet}, for a discussion of naming conventions.
21825 @item @code{r} --- reset @strong{(deprecated)}
21826 @cindex @code{r} packet
21828 Reset the entire system.
21830 @item @code{R}@var{XX} --- remote restart
21831 @cindex @code{R} packet
21833 Restart the program being debugged. @var{XX}, while needed, is ignored.
21834 This packet is only available in extended mode.
21838 @item @emph{no reply}
21839 The @samp{R} packet has no reply.
21842 @item @code{s}@var{addr} --- step
21843 @cindex @code{s} packet
21845 @var{addr} is address to resume. If @var{addr} is omitted, resume at
21849 @xref{Stop Reply Packets}, for the reply specifications.
21851 @item @code{S}@var{sig}@code{;}@var{addr} --- step with signal
21852 @anchor{step with signal packet}
21853 @cindex @code{S} packet
21855 Like @samp{C} but step not continue.
21858 @xref{Stop Reply Packets}, for the reply specifications.
21860 @item @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} --- search
21861 @cindex @code{t} packet
21863 Search backwards starting at address @var{addr} for a match with pattern
21864 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
21865 @var{addr} must be at least 3 digits.
21867 @item @code{T}@var{XX} --- thread alive
21868 @cindex @code{T} packet
21870 Find out if the thread XX is alive.
21875 thread is still alive
21880 @item @code{u} --- reserved
21882 Reserved for future use.
21884 @item @code{U} --- reserved
21886 Reserved for future use.
21888 @item @code{v} --- verbose packet prefix
21890 Packets starting with @code{v} are identified by a multi-letter name,
21891 up to the first @code{;} or @code{?} (or the end of the packet).
21893 @item @code{vCont}[;@var{action}[@code{:}@var{tid}]]... --- extended resume
21894 @cindex @code{vCont} packet
21896 Resume the inferior. Different actions may be specified for each thread.
21897 If an action is specified with no @var{tid}, then it is applied to any
21898 threads that don't have a specific action specified; if no default action is
21899 specified then other threads should remain stopped. Specifying multiple
21900 default actions is an error; specifying no actions is also an error.
21901 Thread IDs are specified in hexadecimal. Currently supported actions are:
21907 Continue with signal @var{sig}. @var{sig} should be two hex digits.
21911 Step with signal @var{sig}. @var{sig} should be two hex digits.
21914 The optional @var{addr} argument normally associated with these packets is
21915 not supported in @code{vCont}.
21918 @xref{Stop Reply Packets}, for the reply specifications.
21920 @item @code{vCont?} --- extended resume query
21921 @cindex @code{vCont?} packet
21923 Query support for the @code{vCont} packet.
21927 @item @code{vCont}[;@var{action}]...
21928 The @code{vCont} packet is supported. Each @var{action} is a supported
21929 command in the @code{vCont} packet.
21931 The @code{vCont} packet is not supported.
21934 @item @code{V} --- reserved
21936 Reserved for future use.
21938 @item @code{w} --- reserved
21940 Reserved for future use.
21942 @item @code{W} --- reserved
21944 Reserved for future use.
21946 @item @code{x} --- reserved
21948 Reserved for future use.
21950 @item @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX@dots{}} --- write mem (binary)
21951 @cindex @code{X} packet
21953 @var{addr} is address, @var{length} is number of bytes, @var{XX@dots{}}
21954 is binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
21955 escaped using @code{0x7d}, and then XORed with @code{0x20}.
21956 For example, @code{0x7d} would be transmitted as @code{0x7d 0x5d}.
21966 @item @code{y} --- reserved
21968 Reserved for future use.
21970 @item @code{Y} reserved
21972 Reserved for future use.
21974 @item @code{z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- remove breakpoint or watchpoint @strong{(draft)}
21975 @itemx @code{Z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- insert breakpoint or watchpoint @strong{(draft)}
21976 @anchor{insert breakpoint or watchpoint packet}
21977 @cindex @code{z} packet
21978 @cindex @code{Z} packets
21980 Insert (@code{Z}) or remove (@code{z}) a @var{type} breakpoint or
21981 watchpoint starting at address @var{address} and covering the next
21982 @var{length} bytes.
21984 Each breakpoint and watchpoint packet @var{type} is documented
21987 @emph{Implementation notes: A remote target shall return an empty string
21988 for an unrecognized breakpoint or watchpoint packet @var{type}. A
21989 remote target shall support either both or neither of a given
21990 @code{Z}@var{type}@dots{} and @code{z}@var{type}@dots{} packet pair. To
21991 avoid potential problems with duplicate packets, the operations should
21992 be implemented in an idempotent way.}
21994 @item @code{z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- remove memory breakpoint @strong{(draft)}
21995 @item @code{Z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- insert memory breakpoint @strong{(draft)}
21996 @cindex @code{z0} packet
21997 @cindex @code{Z0} packet
21999 Insert (@code{Z0}) or remove (@code{z0}) a memory breakpoint at address
22000 @code{addr} of size @code{length}.
22002 A memory breakpoint is implemented by replacing the instruction at
22003 @var{addr} with a software breakpoint or trap instruction. The
22004 @code{length} is used by targets that indicates the size of the
22005 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
22006 @sc{mips} can insert either a 2 or 4 byte breakpoint).
22008 @emph{Implementation note: It is possible for a target to copy or move
22009 code that contains memory breakpoints (e.g., when implementing
22010 overlays). The behavior of this packet, in the presence of such a
22011 target, is not defined.}
22023 @item @code{z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- remove hardware breakpoint @strong{(draft)}
22024 @item @code{Z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- insert hardware breakpoint @strong{(draft)}
22025 @cindex @code{z1} packet
22026 @cindex @code{Z1} packet
22028 Insert (@code{Z1}) or remove (@code{z1}) a hardware breakpoint at
22029 address @code{addr} of size @code{length}.
22031 A hardware breakpoint is implemented using a mechanism that is not
22032 dependant on being able to modify the target's memory.
22034 @emph{Implementation note: A hardware breakpoint is not affected by code
22047 @item @code{z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- remove write watchpoint @strong{(draft)}
22048 @item @code{Z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- insert write watchpoint @strong{(draft)}
22049 @cindex @code{z2} packet
22050 @cindex @code{Z2} packet
22052 Insert (@code{Z2}) or remove (@code{z2}) a write watchpoint.
22064 @item @code{z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- remove read watchpoint @strong{(draft)}
22065 @item @code{Z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- insert read watchpoint @strong{(draft)}
22066 @cindex @code{z3} packet
22067 @cindex @code{Z3} packet
22069 Insert (@code{Z3}) or remove (@code{z3}) a read watchpoint.
22081 @item @code{z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- remove access watchpoint @strong{(draft)}
22082 @item @code{Z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- insert access watchpoint @strong{(draft)}
22083 @cindex @code{z4} packet
22084 @cindex @code{Z4} packet
22086 Insert (@code{Z4}) or remove (@code{z4}) an access watchpoint.
22100 @node Stop Reply Packets
22101 @section Stop Reply Packets
22102 @cindex stop reply packets
22104 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
22105 receive any of the below as a reply. In the case of the @samp{C},
22106 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
22107 when the target halts. In the below the exact meaning of @samp{signal
22108 number} is poorly defined. In general one of the UNIX signal numbering
22109 conventions is used.
22114 @var{AA} is the signal number
22116 @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
22117 @cindex @code{T} packet reply
22119 @var{AA} = two hex digit signal number; @var{n...} = register number
22120 (hex), @var{r...} = target byte ordered register contents, size defined
22121 by @code{DEPRECATED_REGISTER_RAW_SIZE}; @var{n...} = @samp{thread},
22122 @var{r...} = thread process ID, this is a hex integer; @var{n...} =
22123 (@samp{watch} | @samp{rwatch} | @samp{awatch}, @var{r...} = data
22124 address, this is a hex integer; @var{n...} = other string not starting
22125 with valid hex digit. @value{GDBN} should ignore this @var{n...},
22126 @var{r...} pair and go on to the next. This way we can extend the
22131 The process exited, and @var{AA} is the exit status. This is only
22132 applicable to certain targets.
22136 The process terminated with signal @var{AA}.
22138 @item O@var{XX@dots{}}
22140 @var{XX@dots{}} is hex encoding of @sc{ascii} data. This can happen at
22141 any time while the program is running and the debugger should continue
22142 to wait for @samp{W}, @samp{T}, etc.
22144 @item F@var{call-id}@code{,}@var{parameter@dots{}}
22146 @var{call-id} is the identifier which says which host system call should
22147 be called. This is just the name of the function. Translation into the
22148 correct system call is only applicable as it's defined in @value{GDBN}.
22149 @xref{File-I/O remote protocol extension}, for a list of implemented
22152 @var{parameter@dots{}} is a list of parameters as defined for this very
22155 The target replies with this packet when it expects @value{GDBN} to call
22156 a host system call on behalf of the target. @value{GDBN} replies with
22157 an appropriate @code{F} packet and keeps up waiting for the next reply
22158 packet from the target. The latest @samp{C}, @samp{c}, @samp{S} or
22159 @samp{s} action is expected to be continued.
22160 @xref{File-I/O remote protocol extension}, for more details.
22164 @node General Query Packets
22165 @section General Query Packets
22166 @cindex remote query requests
22168 The following set and query packets have already been defined.
22172 @item @code{q}@code{C} --- current thread
22173 @cindex current thread, remote request
22174 @cindex @code{qC} packet
22175 Return the current thread id.
22179 @item @code{QC}@var{pid}
22180 Where @var{pid} is an unsigned hexidecimal process id.
22182 Any other reply implies the old pid.
22185 @item @code{q}@code{fThreadInfo} -- all thread ids
22186 @cindex list active threads, remote request
22187 @cindex @code{qfThreadInfo} packet
22188 @code{q}@code{sThreadInfo}
22190 Obtain a list of active thread ids from the target (OS). Since there
22191 may be too many active threads to fit into one reply packet, this query
22192 works iteratively: it may require more than one query/reply sequence to
22193 obtain the entire list of threads. The first query of the sequence will
22194 be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
22195 sequence will be the @code{qs}@code{ThreadInfo} query.
22197 NOTE: replaces the @code{qL} query (see below).
22201 @item @code{m}@var{id}
22203 @item @code{m}@var{id},@var{id}@dots{}
22204 a comma-separated list of thread ids
22206 (lower case 'el') denotes end of list.
22209 In response to each query, the target will reply with a list of one or
22210 more thread ids, in big-endian unsigned hex, separated by commas.
22211 @value{GDBN} will respond to each reply with a request for more thread
22212 ids (using the @code{qs} form of the query), until the target responds
22213 with @code{l} (lower-case el, for @code{'last'}).
22215 @item @code{q}@code{ThreadExtraInfo}@code{,}@var{id} --- extra thread info
22216 @cindex thread attributes info, remote request
22217 @cindex @code{qThreadExtraInfo} packet
22218 Where @var{id} is a thread-id in big-endian hex. Obtain a printable
22219 string description of a thread's attributes from the target OS. This
22220 string may contain anything that the target OS thinks is interesting for
22221 @value{GDBN} to tell the user about the thread. The string is displayed
22222 in @value{GDBN}'s @samp{info threads} display. Some examples of
22223 possible thread extra info strings are ``Runnable'', or ``Blocked on
22228 @item @var{XX@dots{}}
22229 Where @var{XX@dots{}} is a hex encoding of @sc{ascii} data, comprising
22230 the printable string containing the extra information about the thread's
22234 @item @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} --- query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
22236 Obtain thread information from RTOS. Where: @var{startflag} (one hex
22237 digit) is one to indicate the first query and zero to indicate a
22238 subsequent query; @var{threadcount} (two hex digits) is the maximum
22239 number of threads the response packet can contain; and @var{nextthread}
22240 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
22241 returned in the response as @var{argthread}.
22243 NOTE: this query is replaced by the @code{q}@code{fThreadInfo} query
22248 @item @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread@dots{}}
22249 Where: @var{count} (two hex digits) is the number of threads being
22250 returned; @var{done} (one hex digit) is zero to indicate more threads
22251 and one indicates no further threads; @var{argthreadid} (eight hex
22252 digits) is @var{nextthread} from the request packet; @var{thread@dots{}}
22253 is a sequence of thread IDs from the target. @var{threadid} (eight hex
22254 digits). See @code{remote.c:parse_threadlist_response()}.
22257 @item @code{q}@code{CRC:}@var{addr}@code{,}@var{length} --- compute CRC of memory block
22258 @cindex CRC of memory block, remote request
22259 @cindex @code{qCRC} packet
22262 @item @code{E}@var{NN}
22263 An error (such as memory fault)
22264 @item @code{C}@var{CRC32}
22265 A 32 bit cyclic redundancy check of the specified memory region.
22268 @item @code{q}@code{Offsets} --- query sect offs
22269 @cindex section offsets, remote request
22270 @cindex @code{qOffsets} packet
22271 Get section offsets that the target used when re-locating the downloaded
22272 image. @emph{Note: while a @code{Bss} offset is included in the
22273 response, @value{GDBN} ignores this and instead applies the @code{Data}
22274 offset to the @code{Bss} section.}
22278 @item @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
22281 @item @code{q}@code{P}@var{mode}@var{threadid} --- thread info request
22282 @cindex thread information, remote request
22283 @cindex @code{qP} packet
22284 Returns information on @var{threadid}. Where: @var{mode} is a hex
22285 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
22292 See @code{remote.c:remote_unpack_thread_info_response()}.
22294 @item @code{q}@code{Rcmd,}@var{command} --- remote command
22295 @cindex execute remote command, remote request
22296 @cindex @code{qRcmd} packet
22297 @var{command} (hex encoded) is passed to the local interpreter for
22298 execution. Invalid commands should be reported using the output string.
22299 Before the final result packet, the target may also respond with a
22300 number of intermediate @code{O}@var{output} console output packets.
22301 @emph{Implementors should note that providing access to a stubs's
22302 interpreter may have security implications}.
22307 A command response with no output.
22309 A command response with the hex encoded output string @var{OUTPUT}.
22310 @item @code{E}@var{NN}
22311 Indicate a badly formed request.
22313 When @samp{q}@samp{Rcmd} is not recognized.
22316 @item @code{qSymbol::} --- symbol lookup
22317 @cindex symbol lookup, remote request
22318 @cindex @code{qSymbol} packet
22319 Notify the target that @value{GDBN} is prepared to serve symbol lookup
22320 requests. Accept requests from the target for the values of symbols.
22325 The target does not need to look up any (more) symbols.
22326 @item @code{qSymbol:}@var{sym_name}
22327 The target requests the value of symbol @var{sym_name} (hex encoded).
22328 @value{GDBN} may provide the value by using the
22329 @code{qSymbol:}@var{sym_value}:@var{sym_name} message, described below.
22332 @item @code{qSymbol:}@var{sym_value}:@var{sym_name} --- symbol value
22334 Set the value of @var{sym_name} to @var{sym_value}.
22336 @var{sym_name} (hex encoded) is the name of a symbol whose value the
22337 target has previously requested.
22339 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
22340 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
22346 The target does not need to look up any (more) symbols.
22347 @item @code{qSymbol:}@var{sym_name}
22348 The target requests the value of a new symbol @var{sym_name} (hex
22349 encoded). @value{GDBN} will continue to supply the values of symbols
22350 (if available), until the target ceases to request them.
22353 @item @code{qPart}:@var{object}:@code{read}:@var{annex}:@var{offset},@var{length} --- read special data
22354 @cindex read special object, remote request
22355 @cindex @code{qPart} packet
22356 Read uninterpreted bytes from the target's special data area
22357 identified by the keyword @code{object}.
22358 Request @var{length} bytes starting at @var{offset} bytes into the data.
22359 The content and encoding of @var{annex} is specific to the object;
22360 it can supply additional details about what data to access.
22362 Here are the specific requests of this form defined so far.
22363 All @samp{@code{qPart}:@var{object}:@code{read}:@dots{}}
22364 requests use the same reply formats, listed below.
22367 @item @code{qPart}:@code{auxv}:@code{read}::@var{offset},@var{length}
22368 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
22369 auxiliary vector}, and see @ref{Remote configuration,
22370 read-aux-vector-packet}. Note @var{annex} must be empty.
22376 The @var{offset} in the request is at the end of the data.
22377 There is no more data to be read.
22379 @item @var{XX@dots{}}
22380 Hex encoded data bytes read.
22381 This may be fewer bytes than the @var{length} in the request.
22384 The request was malformed, or @var{annex} was invalid.
22386 @item @code{E}@var{nn}
22387 The offset was invalid, or there was an error encountered reading the data.
22388 @var{nn} is a hex-encoded @code{errno} value.
22390 @item @code{""} (empty)
22391 An empty reply indicates the @var{object} or @var{annex} string was not
22392 recognized by the stub.
22395 @item @code{qPart}:@var{object}:@code{write}:@var{annex}:@var{offset}:@var{data@dots{}}
22396 @cindex write data into object, remote request
22397 Write uninterpreted bytes into the target's special data area
22398 identified by the keyword @code{object},
22399 starting at @var{offset} bytes into the data.
22400 @var{data@dots{}} is the hex-encoded data to be written.
22401 The content and encoding of @var{annex} is specific to the object;
22402 it can supply additional details about what data to access.
22404 No requests of this form are presently in use. This specification
22405 serves as a placeholder to document the common format that new
22406 specific request specifications ought to use.
22411 @var{nn} (hex encoded) is the number of bytes written.
22412 This may be fewer bytes than supplied in the request.
22415 The request was malformed, or @var{annex} was invalid.
22417 @item @code{E}@var{nn}
22418 The offset was invalid, or there was an error encountered writing the data.
22419 @var{nn} is a hex-encoded @code{errno} value.
22421 @item @code{""} (empty)
22422 An empty reply indicates the @var{object} or @var{annex} string was not
22423 recognized by the stub, or that the object does not support writing.
22426 @item @code{qPart}:@var{object}:@var{operation}:@dots{}
22427 Requests of this form may be added in the future. When a stub does
22428 not recognize the @var{object} keyword, or its support for
22429 @var{object} does not recognize the @var{operation} keyword,
22430 the stub must respond with an empty packet.
22432 @item @code{qGetTLSAddr}:@var{thread-id},@var{offset},@var{lm} --- get thread local storage address
22433 @cindex get thread-local storage address, remote request
22434 @cindex @code{qGetTLSAddr} packet
22435 Fetch the address associated with thread local storage specified
22436 by @var{thread-id}, @var{offset}, and @var{lm}.
22438 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
22439 thread for which to fetch the TLS address.
22441 @var{offset} is the (big endian, hex encoded) offset associated with the
22442 thread local variable. (This offset is obtained from the debug
22443 information associated with the variable.)
22445 @var{lm} is the (big endian, hex encoded) OS/ABI specific encoding of the
22446 the load module associated with the thread local storage. For example,
22447 a @sc{gnu}/Linux system will pass the link map address of the shared
22448 object associated with the thread local storage under consideration.
22449 Other operating environments may choose to represent the load module
22450 differently, so the precise meaning of this parameter will vary.
22454 @item @var{XX@dots{}}
22455 Hex encoded (big endian) bytes representing the address of the thread
22456 local storage requested.
22458 @item @code{E}@var{nn} (where @var{nn} are hex digits)
22461 @item @code{""} (empty)
22462 An empty reply indicates that @code{qGetTLSAddr} is not supported by the stub.
22467 @node Register Packet Format
22468 @section Register Packet Format
22470 The following @samp{g}/@samp{G} packets have previously been defined.
22471 In the below, some thirty-two bit registers are transferred as
22472 sixty-four bits. Those registers should be zero/sign extended (which?)
22473 to fill the space allocated. Register bytes are transfered in target
22474 byte order. The two nibbles within a register byte are transfered
22475 most-significant - least-significant.
22481 All registers are transfered as thirty-two bit quantities in the order:
22482 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
22483 registers; fsr; fir; fp.
22487 All registers are transfered as sixty-four bit quantities (including
22488 thirty-two bit registers such as @code{sr}). The ordering is the same
22496 Example sequence of a target being re-started. Notice how the restart
22497 does not get any direct output:
22502 @emph{target restarts}
22505 <- @code{T001:1234123412341234}
22509 Example sequence of a target being stepped by a single instruction:
22512 -> @code{G1445@dots{}}
22517 <- @code{T001:1234123412341234}
22521 <- @code{1455@dots{}}
22525 @node File-I/O remote protocol extension
22526 @section File-I/O remote protocol extension
22527 @cindex File-I/O remote protocol extension
22530 * File-I/O Overview::
22531 * Protocol basics::
22532 * The F request packet::
22533 * The F reply packet::
22534 * Memory transfer::
22535 * The Ctrl-C message::
22537 * The isatty call::
22538 * The system call::
22539 * List of supported calls::
22540 * Protocol specific representation of datatypes::
22542 * File-I/O Examples::
22545 @node File-I/O Overview
22546 @subsection File-I/O Overview
22547 @cindex file-i/o overview
22549 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
22550 target to use the host's file system and console I/O when calling various
22551 system calls. System calls on the target system are translated into a
22552 remote protocol packet to the host system which then performs the needed
22553 actions and returns with an adequate response packet to the target system.
22554 This simulates file system operations even on targets that lack file systems.
22556 The protocol is defined host- and target-system independent. It uses
22557 its own independent representation of datatypes and values. Both,
22558 @value{GDBN} and the target's @value{GDBN} stub are responsible for
22559 translating the system dependent values into the unified protocol values
22560 when data is transmitted.
22562 The communication is synchronous. A system call is possible only
22563 when GDB is waiting for the @samp{C}, @samp{c}, @samp{S} or @samp{s}
22564 packets. While @value{GDBN} handles the request for a system call,
22565 the target is stopped to allow deterministic access to the target's
22566 memory. Therefore File-I/O is not interuptible by target signals. It
22567 is possible to interrupt File-I/O by a user interrupt (Ctrl-C), though.
22569 The target's request to perform a host system call does not finish
22570 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
22571 after finishing the system call, the target returns to continuing the
22572 previous activity (continue, step). No additional continue or step
22573 request from @value{GDBN} is required.
22576 (@value{GDBP}) continue
22577 <- target requests 'system call X'
22578 target is stopped, @value{GDBN} executes system call
22579 -> GDB returns result
22580 ... target continues, GDB returns to wait for the target
22581 <- target hits breakpoint and sends a Txx packet
22584 The protocol is only used for files on the host file system and
22585 for I/O on the console. Character or block special devices, pipes,
22586 named pipes or sockets or any other communication method on the host
22587 system are not supported by this protocol.
22589 @node Protocol basics
22590 @subsection Protocol basics
22591 @cindex protocol basics, file-i/o
22593 The File-I/O protocol uses the @code{F} packet, as request as well
22594 as as reply packet. Since a File-I/O system call can only occur when
22595 @value{GDBN} is waiting for the continuing or stepping target, the
22596 File-I/O request is a reply that @value{GDBN} has to expect as a result
22597 of a former @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
22598 This @code{F} packet contains all information needed to allow @value{GDBN}
22599 to call the appropriate host system call:
22603 A unique identifier for the requested system call.
22606 All parameters to the system call. Pointers are given as addresses
22607 in the target memory address space. Pointers to strings are given as
22608 pointer/length pair. Numerical values are given as they are.
22609 Numerical control values are given in a protocol specific representation.
22613 At that point @value{GDBN} has to perform the following actions.
22617 If parameter pointer values are given, which point to data needed as input
22618 to a system call, @value{GDBN} requests this data from the target with a
22619 standard @code{m} packet request. This additional communication has to be
22620 expected by the target implementation and is handled as any other @code{m}
22624 @value{GDBN} translates all value from protocol representation to host
22625 representation as needed. Datatypes are coerced into the host types.
22628 @value{GDBN} calls the system call
22631 It then coerces datatypes back to protocol representation.
22634 If pointer parameters in the request packet point to buffer space in which
22635 a system call is expected to copy data to, the data is transmitted to the
22636 target using a @code{M} or @code{X} packet. This packet has to be expected
22637 by the target implementation and is handled as any other @code{M} or @code{X}
22642 Eventually @value{GDBN} replies with another @code{F} packet which contains all
22643 necessary information for the target to continue. This at least contains
22650 @code{errno}, if has been changed by the system call.
22657 After having done the needed type and value coercion, the target continues
22658 the latest continue or step action.
22660 @node The F request packet
22661 @subsection The @code{F} request packet
22662 @cindex file-i/o request packet
22663 @cindex @code{F} request packet
22665 The @code{F} request packet has the following format:
22670 @code{F}@var{call-id}@code{,}@var{parameter@dots{}}
22673 @var{call-id} is the identifier to indicate the host system call to be called.
22674 This is just the name of the function.
22676 @var{parameter@dots{}} are the parameters to the system call.
22680 Parameters are hexadecimal integer values, either the real values in case
22681 of scalar datatypes, as pointers to target buffer space in case of compound
22682 datatypes and unspecified memory areas or as pointer/length pairs in case
22683 of string parameters. These are appended to the call-id, each separated
22684 from its predecessor by a comma. All values are transmitted in ASCII
22685 string representation, pointer/length pairs separated by a slash.
22687 @node The F reply packet
22688 @subsection The @code{F} reply packet
22689 @cindex file-i/o reply packet
22690 @cindex @code{F} reply packet
22692 The @code{F} reply packet has the following format:
22697 @code{F}@var{retcode}@code{,}@var{errno}@code{,}@var{Ctrl-C flag}@code{;}@var{call specific attachment}
22700 @var{retcode} is the return code of the system call as hexadecimal value.
22702 @var{errno} is the errno set by the call, in protocol specific representation.
22703 This parameter can be omitted if the call was successful.
22705 @var{Ctrl-C flag} is only send if the user requested a break. In this
22706 case, @var{errno} must be send as well, even if the call was successful.
22707 The @var{Ctrl-C flag} itself consists of the character 'C':
22714 or, if the call was interupted before the host call has been performed:
22721 assuming 4 is the protocol specific representation of @code{EINTR}.
22725 @node Memory transfer
22726 @subsection Memory transfer
22727 @cindex memory transfer, in file-i/o protocol
22729 Structured data which is transferred using a memory read or write as e.g.@:
22730 a @code{struct stat} is expected to be in a protocol specific format with
22731 all scalar multibyte datatypes being big endian. This should be done by
22732 the target before the @code{F} packet is sent resp.@: by @value{GDBN} before
22733 it transfers memory to the target. Transferred pointers to structured
22734 data should point to the already coerced data at any time.
22736 @node The Ctrl-C message
22737 @subsection The Ctrl-C message
22738 @cindex ctrl-c message, in file-i/o protocol
22740 A special case is, if the @var{Ctrl-C flag} is set in the @value{GDBN}
22741 reply packet. In this case the target should behave, as if it had
22742 gotten a break message. The meaning for the target is ``system call
22743 interupted by @code{SIGINT}''. Consequentially, the target should actually stop
22744 (as with a break message) and return to @value{GDBN} with a @code{T02}
22745 packet. In this case, it's important for the target to know, in which
22746 state the system call was interrupted. Since this action is by design
22747 not an atomic operation, we have to differ between two cases:
22751 The system call hasn't been performed on the host yet.
22754 The system call on the host has been finished.
22758 These two states can be distinguished by the target by the value of the
22759 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
22760 call hasn't been performed. This is equivalent to the @code{EINTR} handling
22761 on POSIX systems. In any other case, the target may presume that the
22762 system call has been finished --- successful or not --- and should behave
22763 as if the break message arrived right after the system call.
22765 @value{GDBN} must behave reliable. If the system call has not been called
22766 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
22767 @code{errno} in the packet. If the system call on the host has been finished
22768 before the user requests a break, the full action must be finshed by
22769 @value{GDBN}. This requires sending @code{M} or @code{X} packets as they fit.
22770 The @code{F} packet may only be send when either nothing has happened
22771 or the full action has been completed.
22774 @subsection Console I/O
22775 @cindex console i/o as part of file-i/o
22777 By default and if not explicitely closed by the target system, the file
22778 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
22779 on the @value{GDBN} console is handled as any other file output operation
22780 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
22781 by @value{GDBN} so that after the target read request from file descriptor
22782 0 all following typing is buffered until either one of the following
22787 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, the
22789 system call is treated as finished.
22792 The user presses @kbd{Enter}. This is treated as end of input with a trailing
22796 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
22797 character, especially no Ctrl-D is appended to the input.
22801 If the user has typed more characters as fit in the buffer given to
22802 the read call, the trailing characters are buffered in @value{GDBN} until
22803 either another @code{read(0, @dots{})} is requested by the target or debugging
22804 is stopped on users request.
22806 @node The isatty call
22807 @subsection The isatty(3) call
22808 @cindex isatty call, file-i/o protocol
22810 A special case in this protocol is the library call @code{isatty} which
22811 is implemented as its own call inside of this protocol. It returns
22812 1 to the target if the file descriptor given as parameter is attached
22813 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
22814 would require implementing @code{ioctl} and would be more complex than
22817 @node The system call
22818 @subsection The system(3) call
22819 @cindex system call, file-i/o protocol
22821 The other special case in this protocol is the @code{system} call which
22822 is implemented as its own call, too. @value{GDBN} is taking over the full
22823 task of calling the necessary host calls to perform the @code{system}
22824 call. The return value of @code{system} is simplified before it's returned
22825 to the target. Basically, the only signal transmitted back is @code{EINTR}
22826 in case the user pressed @kbd{Ctrl-C}. Otherwise the return value consists
22827 entirely of the exit status of the called command.
22829 Due to security concerns, the @code{system} call is by default refused
22830 by @value{GDBN}. The user has to allow this call explicitly with the
22831 @kbd{set remote system-call-allowed 1} command.
22834 @item set remote system-call-allowed
22835 @kindex set remote system-call-allowed
22836 Control whether to allow the @code{system} calls in the File I/O
22837 protocol for the remote target. The default is zero (disabled).
22839 @item show remote system-call-allowed
22840 @kindex show remote system-call-allowed
22841 Show the current setting of system calls for the remote File I/O
22845 @node List of supported calls
22846 @subsection List of supported calls
22847 @cindex list of supported file-i/o calls
22864 @unnumberedsubsubsec open
22865 @cindex open, file-i/o system call
22869 int open(const char *pathname, int flags);
22870 int open(const char *pathname, int flags, mode_t mode);
22873 Fopen,pathptr/len,flags,mode
22877 @code{flags} is the bitwise or of the following values:
22881 If the file does not exist it will be created. The host
22882 rules apply as far as file ownership and time stamps
22886 When used with O_CREAT, if the file already exists it is
22887 an error and open() fails.
22890 If the file already exists and the open mode allows
22891 writing (O_RDWR or O_WRONLY is given) it will be
22892 truncated to length 0.
22895 The file is opened in append mode.
22898 The file is opened for reading only.
22901 The file is opened for writing only.
22904 The file is opened for reading and writing.
22907 Each other bit is silently ignored.
22912 @code{mode} is the bitwise or of the following values:
22916 User has read permission.
22919 User has write permission.
22922 Group has read permission.
22925 Group has write permission.
22928 Others have read permission.
22931 Others have write permission.
22934 Each other bit is silently ignored.
22939 @exdent Return value:
22940 open returns the new file descriptor or -1 if an error
22948 pathname already exists and O_CREAT and O_EXCL were used.
22951 pathname refers to a directory.
22954 The requested access is not allowed.
22957 pathname was too long.
22960 A directory component in pathname does not exist.
22963 pathname refers to a device, pipe, named pipe or socket.
22966 pathname refers to a file on a read-only filesystem and
22967 write access was requested.
22970 pathname is an invalid pointer value.
22973 No space on device to create the file.
22976 The process already has the maximum number of files open.
22979 The limit on the total number of files open on the system
22983 The call was interrupted by the user.
22987 @unnumberedsubsubsec close
22988 @cindex close, file-i/o system call
22997 @exdent Return value:
22998 close returns zero on success, or -1 if an error occurred.
23005 fd isn't a valid open file descriptor.
23008 The call was interrupted by the user.
23012 @unnumberedsubsubsec read
23013 @cindex read, file-i/o system call
23017 int read(int fd, void *buf, unsigned int count);
23020 Fread,fd,bufptr,count
23022 @exdent Return value:
23023 On success, the number of bytes read is returned.
23024 Zero indicates end of file. If count is zero, read
23025 returns zero as well. On error, -1 is returned.
23032 fd is not a valid file descriptor or is not open for
23036 buf is an invalid pointer value.
23039 The call was interrupted by the user.
23043 @unnumberedsubsubsec write
23044 @cindex write, file-i/o system call
23048 int write(int fd, const void *buf, unsigned int count);
23051 Fwrite,fd,bufptr,count
23053 @exdent Return value:
23054 On success, the number of bytes written are returned.
23055 Zero indicates nothing was written. On error, -1
23063 fd is not a valid file descriptor or is not open for
23067 buf is an invalid pointer value.
23070 An attempt was made to write a file that exceeds the
23071 host specific maximum file size allowed.
23074 No space on device to write the data.
23077 The call was interrupted by the user.
23081 @unnumberedsubsubsec lseek
23082 @cindex lseek, file-i/o system call
23086 long lseek (int fd, long offset, int flag);
23089 Flseek,fd,offset,flag
23092 @code{flag} is one of:
23096 The offset is set to offset bytes.
23099 The offset is set to its current location plus offset
23103 The offset is set to the size of the file plus offset
23108 @exdent Return value:
23109 On success, the resulting unsigned offset in bytes from
23110 the beginning of the file is returned. Otherwise, a
23111 value of -1 is returned.
23118 fd is not a valid open file descriptor.
23121 fd is associated with the @value{GDBN} console.
23124 flag is not a proper value.
23127 The call was interrupted by the user.
23131 @unnumberedsubsubsec rename
23132 @cindex rename, file-i/o system call
23136 int rename(const char *oldpath, const char *newpath);
23139 Frename,oldpathptr/len,newpathptr/len
23141 @exdent Return value:
23142 On success, zero is returned. On error, -1 is returned.
23149 newpath is an existing directory, but oldpath is not a
23153 newpath is a non-empty directory.
23156 oldpath or newpath is a directory that is in use by some
23160 An attempt was made to make a directory a subdirectory
23164 A component used as a directory in oldpath or new
23165 path is not a directory. Or oldpath is a directory
23166 and newpath exists but is not a directory.
23169 oldpathptr or newpathptr are invalid pointer values.
23172 No access to the file or the path of the file.
23176 oldpath or newpath was too long.
23179 A directory component in oldpath or newpath does not exist.
23182 The file is on a read-only filesystem.
23185 The device containing the file has no room for the new
23189 The call was interrupted by the user.
23193 @unnumberedsubsubsec unlink
23194 @cindex unlink, file-i/o system call
23198 int unlink(const char *pathname);
23201 Funlink,pathnameptr/len
23203 @exdent Return value:
23204 On success, zero is returned. On error, -1 is returned.
23211 No access to the file or the path of the file.
23214 The system does not allow unlinking of directories.
23217 The file pathname cannot be unlinked because it's
23218 being used by another process.
23221 pathnameptr is an invalid pointer value.
23224 pathname was too long.
23227 A directory component in pathname does not exist.
23230 A component of the path is not a directory.
23233 The file is on a read-only filesystem.
23236 The call was interrupted by the user.
23240 @unnumberedsubsubsec stat/fstat
23241 @cindex fstat, file-i/o system call
23242 @cindex stat, file-i/o system call
23246 int stat(const char *pathname, struct stat *buf);
23247 int fstat(int fd, struct stat *buf);
23250 Fstat,pathnameptr/len,bufptr
23253 @exdent Return value:
23254 On success, zero is returned. On error, -1 is returned.
23261 fd is not a valid open file.
23264 A directory component in pathname does not exist or the
23265 path is an empty string.
23268 A component of the path is not a directory.
23271 pathnameptr is an invalid pointer value.
23274 No access to the file or the path of the file.
23277 pathname was too long.
23280 The call was interrupted by the user.
23284 @unnumberedsubsubsec gettimeofday
23285 @cindex gettimeofday, file-i/o system call
23289 int gettimeofday(struct timeval *tv, void *tz);
23292 Fgettimeofday,tvptr,tzptr
23294 @exdent Return value:
23295 On success, 0 is returned, -1 otherwise.
23302 tz is a non-NULL pointer.
23305 tvptr and/or tzptr is an invalid pointer value.
23309 @unnumberedsubsubsec isatty
23310 @cindex isatty, file-i/o system call
23314 int isatty(int fd);
23319 @exdent Return value:
23320 Returns 1 if fd refers to the @value{GDBN} console, 0 otherwise.
23327 The call was interrupted by the user.
23331 @unnumberedsubsubsec system
23332 @cindex system, file-i/o system call
23336 int system(const char *command);
23339 Fsystem,commandptr/len
23341 @exdent Return value:
23342 The value returned is -1 on error and the return status
23343 of the command otherwise. Only the exit status of the
23344 command is returned, which is extracted from the hosts
23345 system return value by calling WEXITSTATUS(retval).
23346 In case /bin/sh could not be executed, 127 is returned.
23353 The call was interrupted by the user.
23356 @node Protocol specific representation of datatypes
23357 @subsection Protocol specific representation of datatypes
23358 @cindex protocol specific representation of datatypes, in file-i/o protocol
23361 * Integral datatypes::
23367 @node Integral datatypes
23368 @unnumberedsubsubsec Integral datatypes
23369 @cindex integral datatypes, in file-i/o protocol
23371 The integral datatypes used in the system calls are
23374 int@r{,} unsigned int@r{,} long@r{,} unsigned long@r{,} mode_t @r{and} time_t
23377 @code{Int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
23378 implemented as 32 bit values in this protocol.
23380 @code{Long} and @code{unsigned long} are implemented as 64 bit types.
23382 @xref{Limits}, for corresponding MIN and MAX values (similar to those
23383 in @file{limits.h}) to allow range checking on host and target.
23385 @code{time_t} datatypes are defined as seconds since the Epoch.
23387 All integral datatypes transferred as part of a memory read or write of a
23388 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
23391 @node Pointer values
23392 @unnumberedsubsubsec Pointer values
23393 @cindex pointer values, in file-i/o protocol
23395 Pointers to target data are transmitted as they are. An exception
23396 is made for pointers to buffers for which the length isn't
23397 transmitted as part of the function call, namely strings. Strings
23398 are transmitted as a pointer/length pair, both as hex values, e.g.@:
23405 which is a pointer to data of length 18 bytes at position 0x1aaf.
23406 The length is defined as the full string length in bytes, including
23407 the trailing null byte. Example:
23410 ``hello, world'' at address 0x123456
23421 @unnumberedsubsubsec struct stat
23422 @cindex struct stat, in file-i/o protocol
23424 The buffer of type struct stat used by the target and @value{GDBN} is defined
23429 unsigned int st_dev; /* device */
23430 unsigned int st_ino; /* inode */
23431 mode_t st_mode; /* protection */
23432 unsigned int st_nlink; /* number of hard links */
23433 unsigned int st_uid; /* user ID of owner */
23434 unsigned int st_gid; /* group ID of owner */
23435 unsigned int st_rdev; /* device type (if inode device) */
23436 unsigned long st_size; /* total size, in bytes */
23437 unsigned long st_blksize; /* blocksize for filesystem I/O */
23438 unsigned long st_blocks; /* number of blocks allocated */
23439 time_t st_atime; /* time of last access */
23440 time_t st_mtime; /* time of last modification */
23441 time_t st_ctime; /* time of last change */
23445 The integral datatypes are conforming to the definitions given in the
23446 approriate section (see @ref{Integral datatypes}, for details) so this
23447 structure is of size 64 bytes.
23449 The values of several fields have a restricted meaning and/or
23456 st_ino: No valid meaning for the target. Transmitted unchanged.
23458 st_mode: Valid mode bits are described in Appendix C. Any other
23459 bits have currently no meaning for the target.
23461 st_uid: No valid meaning for the target. Transmitted unchanged.
23463 st_gid: No valid meaning for the target. Transmitted unchanged.
23465 st_rdev: No valid meaning for the target. Transmitted unchanged.
23467 st_atime, st_mtime, st_ctime:
23468 These values have a host and file system dependent
23469 accuracy. Especially on Windows hosts the file systems
23470 don't support exact timing values.
23473 The target gets a struct stat of the above representation and is
23474 responsible to coerce it to the target representation before
23477 Note that due to size differences between the host and target
23478 representation of stat members, these members could eventually
23479 get truncated on the target.
23481 @node struct timeval
23482 @unnumberedsubsubsec struct timeval
23483 @cindex struct timeval, in file-i/o protocol
23485 The buffer of type struct timeval used by the target and @value{GDBN}
23486 is defined as follows:
23490 time_t tv_sec; /* second */
23491 long tv_usec; /* microsecond */
23495 The integral datatypes are conforming to the definitions given in the
23496 approriate section (see @ref{Integral datatypes}, for details) so this
23497 structure is of size 8 bytes.
23500 @subsection Constants
23501 @cindex constants, in file-i/o protocol
23503 The following values are used for the constants inside of the
23504 protocol. @value{GDBN} and target are resposible to translate these
23505 values before and after the call as needed.
23516 @unnumberedsubsubsec Open flags
23517 @cindex open flags, in file-i/o protocol
23519 All values are given in hexadecimal representation.
23531 @node mode_t values
23532 @unnumberedsubsubsec mode_t values
23533 @cindex mode_t values, in file-i/o protocol
23535 All values are given in octal representation.
23552 @unnumberedsubsubsec Errno values
23553 @cindex errno values, in file-i/o protocol
23555 All values are given in decimal representation.
23580 EUNKNOWN is used as a fallback error value if a host system returns
23581 any error value not in the list of supported error numbers.
23584 @unnumberedsubsubsec Lseek flags
23585 @cindex lseek flags, in file-i/o protocol
23594 @unnumberedsubsubsec Limits
23595 @cindex limits, in file-i/o protocol
23597 All values are given in decimal representation.
23600 INT_MIN -2147483648
23602 UINT_MAX 4294967295
23603 LONG_MIN -9223372036854775808
23604 LONG_MAX 9223372036854775807
23605 ULONG_MAX 18446744073709551615
23608 @node File-I/O Examples
23609 @subsection File-I/O Examples
23610 @cindex file-i/o examples
23612 Example sequence of a write call, file descriptor 3, buffer is at target
23613 address 0x1234, 6 bytes should be written:
23616 <- @code{Fwrite,3,1234,6}
23617 @emph{request memory read from target}
23620 @emph{return "6 bytes written"}
23624 Example sequence of a read call, file descriptor 3, buffer is at target
23625 address 0x1234, 6 bytes should be read:
23628 <- @code{Fread,3,1234,6}
23629 @emph{request memory write to target}
23630 -> @code{X1234,6:XXXXXX}
23631 @emph{return "6 bytes read"}
23635 Example sequence of a read call, call fails on the host due to invalid
23636 file descriptor (EBADF):
23639 <- @code{Fread,3,1234,6}
23643 Example sequence of a read call, user presses Ctrl-C before syscall on
23647 <- @code{Fread,3,1234,6}
23652 Example sequence of a read call, user presses Ctrl-C after syscall on
23656 <- @code{Fread,3,1234,6}
23657 -> @code{X1234,6:XXXXXX}
23661 @include agentexpr.texi
23675 % I think something like @colophon should be in texinfo. In the
23677 \long\def\colophon{\hbox to0pt{}\vfill
23678 \centerline{The body of this manual is set in}
23679 \centerline{\fontname\tenrm,}
23680 \centerline{with headings in {\bf\fontname\tenbf}}
23681 \centerline{and examples in {\tt\fontname\tentt}.}
23682 \centerline{{\it\fontname\tenit\/},}
23683 \centerline{{\bf\fontname\tenbf}, and}
23684 \centerline{{\sl\fontname\tensl\/}}
23685 \centerline{are used for emphasis.}\vfill}
23687 % Blame: doc@cygnus.com, 1991.