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
1270 repeat. User-defined commands can disable this feature; see
1271 @ref{Define, dont-repeat}.
1273 The @code{list} and @code{x} commands, when you repeat them with
1274 @key{RET}, construct new arguments rather than repeating
1275 exactly as typed. This permits easy scanning of source or memory.
1277 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1278 output, in a way similar to the common utility @code{more}
1279 (@pxref{Screen Size,,Screen size}). Since it is easy to press one
1280 @key{RET} too many in this situation, @value{GDBN} disables command
1281 repetition after any command that generates this sort of display.
1283 @kindex # @r{(a comment)}
1285 Any text from a @kbd{#} to the end of the line is a comment; it does
1286 nothing. This is useful mainly in command files (@pxref{Command
1287 Files,,Command files}).
1289 @cindex repeating command sequences
1290 @kindex C-o @r{(operate-and-get-next)}
1291 The @kbd{C-o} binding is useful for repeating a complex sequence of
1292 commands. This command accepts the current line, like @kbd{RET}, and
1293 then fetches the next line relative to the current line from the history
1297 @section Command completion
1300 @cindex word completion
1301 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1302 only one possibility; it can also show you what the valid possibilities
1303 are for the next word in a command, at any time. This works for @value{GDBN}
1304 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1306 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1307 of a word. If there is only one possibility, @value{GDBN} fills in the
1308 word, and waits for you to finish the command (or press @key{RET} to
1309 enter it). For example, if you type
1311 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1312 @c complete accuracy in these examples; space introduced for clarity.
1313 @c If texinfo enhancements make it unnecessary, it would be nice to
1314 @c replace " @key" by "@key" in the following...
1316 (@value{GDBP}) info bre @key{TAB}
1320 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1321 the only @code{info} subcommand beginning with @samp{bre}:
1324 (@value{GDBP}) info breakpoints
1328 You can either press @key{RET} at this point, to run the @code{info
1329 breakpoints} command, or backspace and enter something else, if
1330 @samp{breakpoints} does not look like the command you expected. (If you
1331 were sure you wanted @code{info breakpoints} in the first place, you
1332 might as well just type @key{RET} immediately after @samp{info bre},
1333 to exploit command abbreviations rather than command completion).
1335 If there is more than one possibility for the next word when you press
1336 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1337 characters and try again, or just press @key{TAB} a second time;
1338 @value{GDBN} displays all the possible completions for that word. For
1339 example, you might want to set a breakpoint on a subroutine whose name
1340 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1341 just sounds the bell. Typing @key{TAB} again displays all the
1342 function names in your program that begin with those characters, for
1346 (@value{GDBP}) b make_ @key{TAB}
1347 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1348 make_a_section_from_file make_environ
1349 make_abs_section make_function_type
1350 make_blockvector make_pointer_type
1351 make_cleanup make_reference_type
1352 make_command make_symbol_completion_list
1353 (@value{GDBP}) b make_
1357 After displaying the available possibilities, @value{GDBN} copies your
1358 partial input (@samp{b make_} in the example) so you can finish the
1361 If you just want to see the list of alternatives in the first place, you
1362 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1363 means @kbd{@key{META} ?}. You can type this either by holding down a
1364 key designated as the @key{META} shift on your keyboard (if there is
1365 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1367 @cindex quotes in commands
1368 @cindex completion of quoted strings
1369 Sometimes the string you need, while logically a ``word'', may contain
1370 parentheses or other characters that @value{GDBN} normally excludes from
1371 its notion of a word. To permit word completion to work in this
1372 situation, you may enclose words in @code{'} (single quote marks) in
1373 @value{GDBN} commands.
1375 The most likely situation where you might need this is in typing the
1376 name of a C@t{++} function. This is because C@t{++} allows function
1377 overloading (multiple definitions of the same function, distinguished
1378 by argument type). For example, when you want to set a breakpoint you
1379 may need to distinguish whether you mean the version of @code{name}
1380 that takes an @code{int} parameter, @code{name(int)}, or the version
1381 that takes a @code{float} parameter, @code{name(float)}. To use the
1382 word-completion facilities in this situation, type a single quote
1383 @code{'} at the beginning of the function name. This alerts
1384 @value{GDBN} that it may need to consider more information than usual
1385 when you press @key{TAB} or @kbd{M-?} to request word completion:
1388 (@value{GDBP}) b 'bubble( @kbd{M-?}
1389 bubble(double,double) bubble(int,int)
1390 (@value{GDBP}) b 'bubble(
1393 In some cases, @value{GDBN} can tell that completing a name requires using
1394 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1395 completing as much as it can) if you do not type the quote in the first
1399 (@value{GDBP}) b bub @key{TAB}
1400 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1401 (@value{GDBP}) b 'bubble(
1405 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1406 you have not yet started typing the argument list when you ask for
1407 completion on an overloaded symbol.
1409 For more information about overloaded functions, see @ref{C plus plus
1410 expressions, ,C@t{++} expressions}. You can use the command @code{set
1411 overload-resolution off} to disable overload resolution;
1412 see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
1416 @section Getting help
1417 @cindex online documentation
1420 You can always ask @value{GDBN} itself for information on its commands,
1421 using the command @code{help}.
1424 @kindex h @r{(@code{help})}
1427 You can use @code{help} (abbreviated @code{h}) with no arguments to
1428 display a short list of named classes of commands:
1432 List of classes of commands:
1434 aliases -- Aliases of other commands
1435 breakpoints -- Making program stop at certain points
1436 data -- Examining data
1437 files -- Specifying and examining files
1438 internals -- Maintenance commands
1439 obscure -- Obscure features
1440 running -- Running the program
1441 stack -- Examining the stack
1442 status -- Status inquiries
1443 support -- Support facilities
1444 tracepoints -- Tracing of program execution without@*
1445 stopping the program
1446 user-defined -- User-defined commands
1448 Type "help" followed by a class name for a list of
1449 commands in that class.
1450 Type "help" followed by command name for full
1452 Command name abbreviations are allowed if unambiguous.
1455 @c the above line break eliminates huge line overfull...
1457 @item help @var{class}
1458 Using one of the general help classes as an argument, you can get a
1459 list of the individual commands in that class. For example, here is the
1460 help display for the class @code{status}:
1463 (@value{GDBP}) help status
1468 @c Line break in "show" line falsifies real output, but needed
1469 @c to fit in smallbook page size.
1470 info -- Generic command for showing things
1471 about the program being debugged
1472 show -- Generic command for showing things
1475 Type "help" followed by command name for full
1477 Command name abbreviations are allowed if unambiguous.
1481 @item help @var{command}
1482 With a command name as @code{help} argument, @value{GDBN} displays a
1483 short paragraph on how to use that command.
1486 @item apropos @var{args}
1487 The @code{apropos} command searches through all of the @value{GDBN}
1488 commands, and their documentation, for the regular expression specified in
1489 @var{args}. It prints out all matches found. For example:
1500 set symbol-reloading -- Set dynamic symbol table reloading
1501 multiple times in one run
1502 show symbol-reloading -- Show dynamic symbol table reloading
1503 multiple times in one run
1508 @item complete @var{args}
1509 The @code{complete @var{args}} command lists all the possible completions
1510 for the beginning of a command. Use @var{args} to specify the beginning of the
1511 command you want completed. For example:
1517 @noindent results in:
1528 @noindent This is intended for use by @sc{gnu} Emacs.
1531 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1532 and @code{show} to inquire about the state of your program, or the state
1533 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1534 manual introduces each of them in the appropriate context. The listings
1535 under @code{info} and under @code{show} in the Index point to
1536 all the sub-commands. @xref{Index}.
1541 @kindex i @r{(@code{info})}
1543 This command (abbreviated @code{i}) is for describing the state of your
1544 program. For example, you can list the arguments given to your program
1545 with @code{info args}, list the registers currently in use with @code{info
1546 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1547 You can get a complete list of the @code{info} sub-commands with
1548 @w{@code{help info}}.
1552 You can assign the result of an expression to an environment variable with
1553 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1554 @code{set prompt $}.
1558 In contrast to @code{info}, @code{show} is for describing the state of
1559 @value{GDBN} itself.
1560 You can change most of the things you can @code{show}, by using the
1561 related command @code{set}; for example, you can control what number
1562 system is used for displays with @code{set radix}, or simply inquire
1563 which is currently in use with @code{show radix}.
1566 To display all the settable parameters and their current
1567 values, you can use @code{show} with no arguments; you may also use
1568 @code{info set}. Both commands produce the same display.
1569 @c FIXME: "info set" violates the rule that "info" is for state of
1570 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1571 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1575 Here are three miscellaneous @code{show} subcommands, all of which are
1576 exceptional in lacking corresponding @code{set} commands:
1579 @kindex show version
1580 @cindex @value{GDBN} version number
1582 Show what version of @value{GDBN} is running. You should include this
1583 information in @value{GDBN} bug-reports. If multiple versions of
1584 @value{GDBN} are in use at your site, you may need to determine which
1585 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1586 commands are introduced, and old ones may wither away. Also, many
1587 system vendors ship variant versions of @value{GDBN}, and there are
1588 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1589 The version number is the same as the one announced when you start
1592 @kindex show copying
1593 @kindex info copying
1594 @cindex display @value{GDBN} copyright
1597 Display information about permission for copying @value{GDBN}.
1599 @kindex show warranty
1600 @kindex info warranty
1602 @itemx info warranty
1603 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1604 if your version of @value{GDBN} comes with one.
1609 @chapter Running Programs Under @value{GDBN}
1611 When you run a program under @value{GDBN}, you must first generate
1612 debugging information when you compile it.
1614 You may start @value{GDBN} with its arguments, if any, in an environment
1615 of your choice. If you are doing native debugging, you may redirect
1616 your program's input and output, debug an already running process, or
1617 kill a child process.
1620 * Compilation:: Compiling for debugging
1621 * Starting:: Starting your program
1622 * Arguments:: Your program's arguments
1623 * Environment:: Your program's environment
1625 * Working Directory:: Your program's working directory
1626 * Input/Output:: Your program's input and output
1627 * Attach:: Debugging an already-running process
1628 * Kill Process:: Killing the child process
1630 * Threads:: Debugging programs with multiple threads
1631 * Processes:: Debugging programs with multiple processes
1635 @section Compiling for debugging
1637 In order to debug a program effectively, you need to generate
1638 debugging information when you compile it. This debugging information
1639 is stored in the object file; it describes the data type of each
1640 variable or function and the correspondence between source line numbers
1641 and addresses in the executable code.
1643 To request debugging information, specify the @samp{-g} option when you run
1646 Most compilers do not include information about preprocessor macros in
1647 the debugging information if you specify the @option{-g} flag alone,
1648 because this information is rather large. Version 3.1 of @value{NGCC},
1649 the @sc{gnu} C compiler, provides macro information if you specify the
1650 options @option{-gdwarf-2} and @option{-g3}; the former option requests
1651 debugging information in the Dwarf 2 format, and the latter requests
1652 ``extra information''. In the future, we hope to find more compact ways
1653 to represent macro information, so that it can be included with
1656 Many C compilers are unable to handle the @samp{-g} and @samp{-O}
1657 options together. Using those compilers, you cannot generate optimized
1658 executables containing debugging information.
1660 @value{NGCC}, the @sc{gnu} C compiler, supports @samp{-g} with or
1661 without @samp{-O}, making it possible to debug optimized code. We
1662 recommend that you @emph{always} use @samp{-g} whenever you compile a
1663 program. You may think your program is correct, but there is no sense
1664 in pushing your luck.
1666 @cindex optimized code, debugging
1667 @cindex debugging optimized code
1668 When you debug a program compiled with @samp{-g -O}, remember that the
1669 optimizer is rearranging your code; the debugger shows you what is
1670 really there. Do not be too surprised when the execution path does not
1671 exactly match your source file! An extreme example: if you define a
1672 variable, but never use it, @value{GDBN} never sees that
1673 variable---because the compiler optimizes it out of existence.
1675 Some things do not work as well with @samp{-g -O} as with just
1676 @samp{-g}, particularly on machines with instruction scheduling. If in
1677 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1678 please report it to us as a bug (including a test case!).
1679 @xref{Variables}, for more information about debugging optimized code.
1681 Older versions of the @sc{gnu} C compiler permitted a variant option
1682 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1683 format; if your @sc{gnu} C compiler has this option, do not use it.
1687 @section Starting your program
1693 @kindex r @r{(@code{run})}
1696 Use the @code{run} command to start your program under @value{GDBN}.
1697 You must first specify the program name (except on VxWorks) with an
1698 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1699 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1700 (@pxref{Files, ,Commands to specify files}).
1704 If you are running your program in an execution environment that
1705 supports processes, @code{run} creates an inferior process and makes
1706 that process run your program. (In environments without processes,
1707 @code{run} jumps to the start of your program.)
1709 The execution of a program is affected by certain information it
1710 receives from its superior. @value{GDBN} provides ways to specify this
1711 information, which you must do @emph{before} starting your program. (You
1712 can change it after starting your program, but such changes only affect
1713 your program the next time you start it.) This information may be
1714 divided into four categories:
1717 @item The @emph{arguments.}
1718 Specify the arguments to give your program as the arguments of the
1719 @code{run} command. If a shell is available on your target, the shell
1720 is used to pass the arguments, so that you may use normal conventions
1721 (such as wildcard expansion or variable substitution) in describing
1723 In Unix systems, you can control which shell is used with the
1724 @code{SHELL} environment variable.
1725 @xref{Arguments, ,Your program's arguments}.
1727 @item The @emph{environment.}
1728 Your program normally inherits its environment from @value{GDBN}, but you can
1729 use the @value{GDBN} commands @code{set environment} and @code{unset
1730 environment} to change parts of the environment that affect
1731 your program. @xref{Environment, ,Your program's environment}.
1733 @item The @emph{working directory.}
1734 Your program inherits its working directory from @value{GDBN}. You can set
1735 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1736 @xref{Working Directory, ,Your program's working directory}.
1738 @item The @emph{standard input and output.}
1739 Your program normally uses the same device for standard input and
1740 standard output as @value{GDBN} is using. You can redirect input and output
1741 in the @code{run} command line, or you can use the @code{tty} command to
1742 set a different device for your program.
1743 @xref{Input/Output, ,Your program's input and output}.
1746 @emph{Warning:} While input and output redirection work, you cannot use
1747 pipes to pass the output of the program you are debugging to another
1748 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1752 When you issue the @code{run} command, your program begins to execute
1753 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1754 of how to arrange for your program to stop. Once your program has
1755 stopped, you may call functions in your program, using the @code{print}
1756 or @code{call} commands. @xref{Data, ,Examining Data}.
1758 If the modification time of your symbol file has changed since the last
1759 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1760 table, and reads it again. When it does this, @value{GDBN} tries to retain
1761 your current breakpoints.
1766 @cindex run to main procedure
1767 The name of the main procedure can vary from language to language.
1768 With C or C@t{++}, the main procedure name is always @code{main}, but
1769 other languages such as Ada do not require a specific name for their
1770 main procedure. The debugger provides a convenient way to start the
1771 execution of the program and to stop at the beginning of the main
1772 procedure, depending on the language used.
1774 The @samp{start} command does the equivalent of setting a temporary
1775 breakpoint at the beginning of the main procedure and then invoking
1776 the @samp{run} command.
1778 @cindex elaboration phase
1779 Some programs contain an @dfn{elaboration} phase where some startup code is
1780 executed before the main procedure is called. This depends on the
1781 languages used to write your program. In C@t{++}, for instance,
1782 constructors for static and global objects are executed before
1783 @code{main} is called. It is therefore possible that the debugger stops
1784 before reaching the main procedure. However, the temporary breakpoint
1785 will remain to halt execution.
1787 Specify the arguments to give to your program as arguments to the
1788 @samp{start} command. These arguments will be given verbatim to the
1789 underlying @samp{run} command. Note that the same arguments will be
1790 reused if no argument is provided during subsequent calls to
1791 @samp{start} or @samp{run}.
1793 It is sometimes necessary to debug the program during elaboration. In
1794 these cases, using the @code{start} command would stop the execution of
1795 your program too late, as the program would have already completed the
1796 elaboration phase. Under these circumstances, insert breakpoints in your
1797 elaboration code before running your program.
1801 @section Your program's arguments
1803 @cindex arguments (to your program)
1804 The arguments to your program can be specified by the arguments of the
1806 They are passed to a shell, which expands wildcard characters and
1807 performs redirection of I/O, and thence to your program. Your
1808 @code{SHELL} environment variable (if it exists) specifies what shell
1809 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1810 the default shell (@file{/bin/sh} on Unix).
1812 On non-Unix systems, the program is usually invoked directly by
1813 @value{GDBN}, which emulates I/O redirection via the appropriate system
1814 calls, and the wildcard characters are expanded by the startup code of
1815 the program, not by the shell.
1817 @code{run} with no arguments uses the same arguments used by the previous
1818 @code{run}, or those set by the @code{set args} command.
1823 Specify the arguments to be used the next time your program is run. If
1824 @code{set args} has no arguments, @code{run} executes your program
1825 with no arguments. Once you have run your program with arguments,
1826 using @code{set args} before the next @code{run} is the only way to run
1827 it again without arguments.
1831 Show the arguments to give your program when it is started.
1835 @section Your program's environment
1837 @cindex environment (of your program)
1838 The @dfn{environment} consists of a set of environment variables and
1839 their values. Environment variables conventionally record such things as
1840 your user name, your home directory, your terminal type, and your search
1841 path for programs to run. Usually you set up environment variables with
1842 the shell and they are inherited by all the other programs you run. When
1843 debugging, it can be useful to try running your program with a modified
1844 environment without having to start @value{GDBN} over again.
1848 @item path @var{directory}
1849 Add @var{directory} to the front of the @code{PATH} environment variable
1850 (the search path for executables) that will be passed to your program.
1851 The value of @code{PATH} used by @value{GDBN} does not change.
1852 You may specify several directory names, separated by whitespace or by a
1853 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1854 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1855 is moved to the front, so it is searched sooner.
1857 You can use the string @samp{$cwd} to refer to whatever is the current
1858 working directory at the time @value{GDBN} searches the path. If you
1859 use @samp{.} instead, it refers to the directory where you executed the
1860 @code{path} command. @value{GDBN} replaces @samp{.} in the
1861 @var{directory} argument (with the current path) before adding
1862 @var{directory} to the search path.
1863 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1864 @c document that, since repeating it would be a no-op.
1868 Display the list of search paths for executables (the @code{PATH}
1869 environment variable).
1871 @kindex show environment
1872 @item show environment @r{[}@var{varname}@r{]}
1873 Print the value of environment variable @var{varname} to be given to
1874 your program when it starts. If you do not supply @var{varname},
1875 print the names and values of all environment variables to be given to
1876 your program. You can abbreviate @code{environment} as @code{env}.
1878 @kindex set environment
1879 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1880 Set environment variable @var{varname} to @var{value}. The value
1881 changes for your program only, not for @value{GDBN} itself. @var{value} may
1882 be any string; the values of environment variables are just strings, and
1883 any interpretation is supplied by your program itself. The @var{value}
1884 parameter is optional; if it is eliminated, the variable is set to a
1886 @c "any string" here does not include leading, trailing
1887 @c blanks. Gnu asks: does anyone care?
1889 For example, this command:
1896 tells the debugged program, when subsequently run, that its user is named
1897 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
1898 are not actually required.)
1900 @kindex unset environment
1901 @item unset environment @var{varname}
1902 Remove variable @var{varname} from the environment to be passed to your
1903 program. This is different from @samp{set env @var{varname} =};
1904 @code{unset environment} removes the variable from the environment,
1905 rather than assigning it an empty value.
1908 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
1910 by your @code{SHELL} environment variable if it exists (or
1911 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
1912 that runs an initialization file---such as @file{.cshrc} for C-shell, or
1913 @file{.bashrc} for BASH---any variables you set in that file affect
1914 your program. You may wish to move setting of environment variables to
1915 files that are only run when you sign on, such as @file{.login} or
1918 @node Working Directory
1919 @section Your program's working directory
1921 @cindex working directory (of your program)
1922 Each time you start your program with @code{run}, it inherits its
1923 working directory from the current working directory of @value{GDBN}.
1924 The @value{GDBN} working directory is initially whatever it inherited
1925 from its parent process (typically the shell), but you can specify a new
1926 working directory in @value{GDBN} with the @code{cd} command.
1928 The @value{GDBN} working directory also serves as a default for the commands
1929 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
1934 @cindex change working directory
1935 @item cd @var{directory}
1936 Set the @value{GDBN} working directory to @var{directory}.
1940 Print the @value{GDBN} working directory.
1943 It is generally impossible to find the current working directory of
1944 the process being debugged (since a program can change its directory
1945 during its run). If you work on a system where @value{GDBN} is
1946 configured with the @file{/proc} support, you can use the @code{info
1947 proc} command (@pxref{SVR4 Process Information}) to find out the
1948 current working directory of the debuggee.
1951 @section Your program's input and output
1956 By default, the program you run under @value{GDBN} does input and output to
1957 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
1958 to its own terminal modes to interact with you, but it records the terminal
1959 modes your program was using and switches back to them when you continue
1960 running your program.
1963 @kindex info terminal
1965 Displays information recorded by @value{GDBN} about the terminal modes your
1969 You can redirect your program's input and/or output using shell
1970 redirection with the @code{run} command. For example,
1977 starts your program, diverting its output to the file @file{outfile}.
1980 @cindex controlling terminal
1981 Another way to specify where your program should do input and output is
1982 with the @code{tty} command. This command accepts a file name as
1983 argument, and causes this file to be the default for future @code{run}
1984 commands. It also resets the controlling terminal for the child
1985 process, for future @code{run} commands. For example,
1992 directs that processes started with subsequent @code{run} commands
1993 default to do input and output on the terminal @file{/dev/ttyb} and have
1994 that as their controlling terminal.
1996 An explicit redirection in @code{run} overrides the @code{tty} command's
1997 effect on the input/output device, but not its effect on the controlling
2000 When you use the @code{tty} command or redirect input in the @code{run}
2001 command, only the input @emph{for your program} is affected. The input
2002 for @value{GDBN} still comes from your terminal.
2005 @section Debugging an already-running process
2010 @item attach @var{process-id}
2011 This command attaches to a running process---one that was started
2012 outside @value{GDBN}. (@code{info files} shows your active
2013 targets.) The command takes as argument a process ID. The usual way to
2014 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2015 or with the @samp{jobs -l} shell command.
2017 @code{attach} does not repeat if you press @key{RET} a second time after
2018 executing the command.
2021 To use @code{attach}, your program must be running in an environment
2022 which supports processes; for example, @code{attach} does not work for
2023 programs on bare-board targets that lack an operating system. You must
2024 also have permission to send the process a signal.
2026 When you use @code{attach}, the debugger finds the program running in
2027 the process first by looking in the current working directory, then (if
2028 the program is not found) by using the source file search path
2029 (@pxref{Source Path, ,Specifying source directories}). You can also use
2030 the @code{file} command to load the program. @xref{Files, ,Commands to
2033 The first thing @value{GDBN} does after arranging to debug the specified
2034 process is to stop it. You can examine and modify an attached process
2035 with all the @value{GDBN} commands that are ordinarily available when
2036 you start processes with @code{run}. You can insert breakpoints; you
2037 can step and continue; you can modify storage. If you would rather the
2038 process continue running, you may use the @code{continue} command after
2039 attaching @value{GDBN} to the process.
2044 When you have finished debugging the attached process, you can use the
2045 @code{detach} command to release it from @value{GDBN} control. Detaching
2046 the process continues its execution. After the @code{detach} command,
2047 that process and @value{GDBN} become completely independent once more, and you
2048 are ready to @code{attach} another process or start one with @code{run}.
2049 @code{detach} does not repeat if you press @key{RET} again after
2050 executing the command.
2053 If you exit @value{GDBN} or use the @code{run} command while you have an
2054 attached process, you kill that process. By default, @value{GDBN} asks
2055 for confirmation if you try to do either of these things; you can
2056 control whether or not you need to confirm by using the @code{set
2057 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
2061 @section Killing the child process
2066 Kill the child process in which your program is running under @value{GDBN}.
2069 This command is useful if you wish to debug a core dump instead of a
2070 running process. @value{GDBN} ignores any core dump file while your program
2073 On some operating systems, a program cannot be executed outside @value{GDBN}
2074 while you have breakpoints set on it inside @value{GDBN}. You can use the
2075 @code{kill} command in this situation to permit running your program
2076 outside the debugger.
2078 The @code{kill} command is also useful if you wish to recompile and
2079 relink your program, since on many systems it is impossible to modify an
2080 executable file while it is running in a process. In this case, when you
2081 next type @code{run}, @value{GDBN} notices that the file has changed, and
2082 reads the symbol table again (while trying to preserve your current
2083 breakpoint settings).
2086 @section Debugging programs with multiple threads
2088 @cindex threads of execution
2089 @cindex multiple threads
2090 @cindex switching threads
2091 In some operating systems, such as HP-UX and Solaris, a single program
2092 may have more than one @dfn{thread} of execution. The precise semantics
2093 of threads differ from one operating system to another, but in general
2094 the threads of a single program are akin to multiple processes---except
2095 that they share one address space (that is, they can all examine and
2096 modify the same variables). On the other hand, each thread has its own
2097 registers and execution stack, and perhaps private memory.
2099 @value{GDBN} provides these facilities for debugging multi-thread
2103 @item automatic notification of new threads
2104 @item @samp{thread @var{threadno}}, a command to switch among threads
2105 @item @samp{info threads}, a command to inquire about existing threads
2106 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2107 a command to apply a command to a list of threads
2108 @item thread-specific breakpoints
2112 @emph{Warning:} These facilities are not yet available on every
2113 @value{GDBN} configuration where the operating system supports threads.
2114 If your @value{GDBN} does not support threads, these commands have no
2115 effect. For example, a system without thread support shows no output
2116 from @samp{info threads}, and always rejects the @code{thread} command,
2120 (@value{GDBP}) info threads
2121 (@value{GDBP}) thread 1
2122 Thread ID 1 not known. Use the "info threads" command to
2123 see the IDs of currently known threads.
2125 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2126 @c doesn't support threads"?
2129 @cindex focus of debugging
2130 @cindex current thread
2131 The @value{GDBN} thread debugging facility allows you to observe all
2132 threads while your program runs---but whenever @value{GDBN} takes
2133 control, one thread in particular is always the focus of debugging.
2134 This thread is called the @dfn{current thread}. Debugging commands show
2135 program information from the perspective of the current thread.
2137 @cindex @code{New} @var{systag} message
2138 @cindex thread identifier (system)
2139 @c FIXME-implementors!! It would be more helpful if the [New...] message
2140 @c included GDB's numeric thread handle, so you could just go to that
2141 @c thread without first checking `info threads'.
2142 Whenever @value{GDBN} detects a new thread in your program, it displays
2143 the target system's identification for the thread with a message in the
2144 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2145 whose form varies depending on the particular system. For example, on
2146 LynxOS, you might see
2149 [New process 35 thread 27]
2153 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2154 the @var{systag} is simply something like @samp{process 368}, with no
2157 @c FIXME!! (1) Does the [New...] message appear even for the very first
2158 @c thread of a program, or does it only appear for the
2159 @c second---i.e.@: when it becomes obvious we have a multithread
2161 @c (2) *Is* there necessarily a first thread always? Or do some
2162 @c multithread systems permit starting a program with multiple
2163 @c threads ab initio?
2165 @cindex thread number
2166 @cindex thread identifier (GDB)
2167 For debugging purposes, @value{GDBN} associates its own thread
2168 number---always a single integer---with each thread in your program.
2171 @kindex info threads
2173 Display a summary of all threads currently in your
2174 program. @value{GDBN} displays for each thread (in this order):
2178 the thread number assigned by @value{GDBN}
2181 the target system's thread identifier (@var{systag})
2184 the current stack frame summary for that thread
2188 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2189 indicates the current thread.
2193 @c end table here to get a little more width for example
2196 (@value{GDBP}) info threads
2197 3 process 35 thread 27 0x34e5 in sigpause ()
2198 2 process 35 thread 23 0x34e5 in sigpause ()
2199 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2205 @cindex debugging multithreaded programs (on HP-UX)
2206 @cindex thread identifier (GDB), on HP-UX
2207 For debugging purposes, @value{GDBN} associates its own thread
2208 number---a small integer assigned in thread-creation order---with each
2209 thread in your program.
2211 @cindex @code{New} @var{systag} message, on HP-UX
2212 @cindex thread identifier (system), on HP-UX
2213 @c FIXME-implementors!! It would be more helpful if the [New...] message
2214 @c included GDB's numeric thread handle, so you could just go to that
2215 @c thread without first checking `info threads'.
2216 Whenever @value{GDBN} detects a new thread in your program, it displays
2217 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2218 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2219 whose form varies depending on the particular system. For example, on
2223 [New thread 2 (system thread 26594)]
2227 when @value{GDBN} notices a new thread.
2230 @kindex info threads (HP-UX)
2232 Display a summary of all threads currently in your
2233 program. @value{GDBN} displays for each thread (in this order):
2236 @item the thread number assigned by @value{GDBN}
2238 @item the target system's thread identifier (@var{systag})
2240 @item the current stack frame summary for that thread
2244 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2245 indicates the current thread.
2249 @c end table here to get a little more width for example
2252 (@value{GDBP}) info threads
2253 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2255 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2256 from /usr/lib/libc.2
2257 1 system thread 27905 0x7b003498 in _brk () \@*
2258 from /usr/lib/libc.2
2261 On Solaris, you can display more information about user threads with a
2262 Solaris-specific command:
2265 @item maint info sol-threads
2266 @kindex maint info sol-threads
2267 @cindex thread info (Solaris)
2268 Display info on Solaris user threads.
2272 @kindex thread @var{threadno}
2273 @item thread @var{threadno}
2274 Make thread number @var{threadno} the current thread. The command
2275 argument @var{threadno} is the internal @value{GDBN} thread number, as
2276 shown in the first field of the @samp{info threads} display.
2277 @value{GDBN} responds by displaying the system identifier of the thread
2278 you selected, and its current stack frame summary:
2281 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2282 (@value{GDBP}) thread 2
2283 [Switching to process 35 thread 23]
2284 0x34e5 in sigpause ()
2288 As with the @samp{[New @dots{}]} message, the form of the text after
2289 @samp{Switching to} depends on your system's conventions for identifying
2292 @kindex thread apply
2293 @item thread apply [@var{threadno}] [@var{all}] @var{args}
2294 The @code{thread apply} command allows you to apply a command to one or
2295 more threads. Specify the numbers of the threads that you want affected
2296 with the command argument @var{threadno}. @var{threadno} is the internal
2297 @value{GDBN} thread number, as shown in the first field of the @samp{info
2298 threads} display. To apply a command to all threads, use
2299 @code{thread apply all} @var{args}.
2302 @cindex automatic thread selection
2303 @cindex switching threads automatically
2304 @cindex threads, automatic switching
2305 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2306 signal, it automatically selects the thread where that breakpoint or
2307 signal happened. @value{GDBN} alerts you to the context switch with a
2308 message of the form @samp{[Switching to @var{systag}]} to identify the
2311 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2312 more information about how @value{GDBN} behaves when you stop and start
2313 programs with multiple threads.
2315 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2316 watchpoints in programs with multiple threads.
2319 @section Debugging programs with multiple processes
2321 @cindex fork, debugging programs which call
2322 @cindex multiple processes
2323 @cindex processes, multiple
2324 On most systems, @value{GDBN} has no special support for debugging
2325 programs which create additional processes using the @code{fork}
2326 function. When a program forks, @value{GDBN} will continue to debug the
2327 parent process and the child process will run unimpeded. If you have
2328 set a breakpoint in any code which the child then executes, the child
2329 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2330 will cause it to terminate.
2332 However, if you want to debug the child process there is a workaround
2333 which isn't too painful. Put a call to @code{sleep} in the code which
2334 the child process executes after the fork. It may be useful to sleep
2335 only if a certain environment variable is set, or a certain file exists,
2336 so that the delay need not occur when you don't want to run @value{GDBN}
2337 on the child. While the child is sleeping, use the @code{ps} program to
2338 get its process ID. Then tell @value{GDBN} (a new invocation of
2339 @value{GDBN} if you are also debugging the parent process) to attach to
2340 the child process (@pxref{Attach}). From that point on you can debug
2341 the child process just like any other process which you attached to.
2343 On some systems, @value{GDBN} provides support for debugging programs that
2344 create additional processes using the @code{fork} or @code{vfork} functions.
2345 Currently, the only platforms with this feature are HP-UX (11.x and later
2346 only?) and GNU/Linux (kernel version 2.5.60 and later).
2348 By default, when a program forks, @value{GDBN} will continue to debug
2349 the parent process and the child process will run unimpeded.
2351 If you want to follow the child process instead of the parent process,
2352 use the command @w{@code{set follow-fork-mode}}.
2355 @kindex set follow-fork-mode
2356 @item set follow-fork-mode @var{mode}
2357 Set the debugger response to a program call of @code{fork} or
2358 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2359 process. The @var{mode} argument can be:
2363 The original process is debugged after a fork. The child process runs
2364 unimpeded. This is the default.
2367 The new process is debugged after a fork. The parent process runs
2372 @kindex show follow-fork-mode
2373 @item show follow-fork-mode
2374 Display the current debugger response to a @code{fork} or @code{vfork} call.
2377 If you ask to debug a child process and a @code{vfork} is followed by an
2378 @code{exec}, @value{GDBN} executes the new target up to the first
2379 breakpoint in the new target. If you have a breakpoint set on
2380 @code{main} in your original program, the breakpoint will also be set on
2381 the child process's @code{main}.
2383 When a child process is spawned by @code{vfork}, you cannot debug the
2384 child or parent until an @code{exec} call completes.
2386 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2387 call executes, the new target restarts. To restart the parent process,
2388 use the @code{file} command with the parent executable name as its
2391 You can use the @code{catch} command to make @value{GDBN} stop whenever
2392 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2393 Catchpoints, ,Setting catchpoints}.
2396 @chapter Stopping and Continuing
2398 The principal purposes of using a debugger are so that you can stop your
2399 program before it terminates; or so that, if your program runs into
2400 trouble, you can investigate and find out why.
2402 Inside @value{GDBN}, your program may stop for any of several reasons,
2403 such as a signal, a breakpoint, or reaching a new line after a
2404 @value{GDBN} command such as @code{step}. You may then examine and
2405 change variables, set new breakpoints or remove old ones, and then
2406 continue execution. Usually, the messages shown by @value{GDBN} provide
2407 ample explanation of the status of your program---but you can also
2408 explicitly request this information at any time.
2411 @kindex info program
2413 Display information about the status of your program: whether it is
2414 running or not, what process it is, and why it stopped.
2418 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2419 * Continuing and Stepping:: Resuming execution
2421 * Thread Stops:: Stopping and starting multi-thread programs
2425 @section Breakpoints, watchpoints, and catchpoints
2428 A @dfn{breakpoint} makes your program stop whenever a certain point in
2429 the program is reached. For each breakpoint, you can add conditions to
2430 control in finer detail whether your program stops. You can set
2431 breakpoints with the @code{break} command and its variants (@pxref{Set
2432 Breaks, ,Setting breakpoints}), to specify the place where your program
2433 should stop by line number, function name or exact address in the
2436 On some systems, you can set breakpoints in shared libraries before
2437 the executable is run. There is a minor limitation on HP-UX systems:
2438 you must wait until the executable is run in order to set breakpoints
2439 in shared library routines that are not called directly by the program
2440 (for example, routines that are arguments in a @code{pthread_create}
2444 @cindex memory tracing
2445 @cindex breakpoint on memory address
2446 @cindex breakpoint on variable modification
2447 A @dfn{watchpoint} is a special breakpoint that stops your program
2448 when the value of an expression changes. You must use a different
2449 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2450 watchpoints}), but aside from that, you can manage a watchpoint like
2451 any other breakpoint: you enable, disable, and delete both breakpoints
2452 and watchpoints using the same commands.
2454 You can arrange to have values from your program displayed automatically
2455 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2459 @cindex breakpoint on events
2460 A @dfn{catchpoint} is another special breakpoint that stops your program
2461 when a certain kind of event occurs, such as the throwing of a C@t{++}
2462 exception or the loading of a library. As with watchpoints, you use a
2463 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2464 catchpoints}), but aside from that, you can manage a catchpoint like any
2465 other breakpoint. (To stop when your program receives a signal, use the
2466 @code{handle} command; see @ref{Signals, ,Signals}.)
2468 @cindex breakpoint numbers
2469 @cindex numbers for breakpoints
2470 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2471 catchpoint when you create it; these numbers are successive integers
2472 starting with one. In many of the commands for controlling various
2473 features of breakpoints you use the breakpoint number to say which
2474 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2475 @dfn{disabled}; if disabled, it has no effect on your program until you
2478 @cindex breakpoint ranges
2479 @cindex ranges of breakpoints
2480 Some @value{GDBN} commands accept a range of breakpoints on which to
2481 operate. A breakpoint range is either a single breakpoint number, like
2482 @samp{5}, or two such numbers, in increasing order, separated by a
2483 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2484 all breakpoint in that range are operated on.
2487 * Set Breaks:: Setting breakpoints
2488 * Set Watchpoints:: Setting watchpoints
2489 * Set Catchpoints:: Setting catchpoints
2490 * Delete Breaks:: Deleting breakpoints
2491 * Disabling:: Disabling breakpoints
2492 * Conditions:: Break conditions
2493 * Break Commands:: Breakpoint command lists
2494 * Breakpoint Menus:: Breakpoint menus
2495 * Error in Breakpoints:: ``Cannot insert breakpoints''
2496 * Breakpoint related warnings:: ``Breakpoint address adjusted...''
2500 @subsection Setting breakpoints
2502 @c FIXME LMB what does GDB do if no code on line of breakpt?
2503 @c consider in particular declaration with/without initialization.
2505 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2508 @kindex b @r{(@code{break})}
2509 @vindex $bpnum@r{, convenience variable}
2510 @cindex latest breakpoint
2511 Breakpoints are set with the @code{break} command (abbreviated
2512 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2513 number of the breakpoint you've set most recently; see @ref{Convenience
2514 Vars,, Convenience variables}, for a discussion of what you can do with
2515 convenience variables.
2517 You have several ways to say where the breakpoint should go.
2520 @item break @var{function}
2521 Set a breakpoint at entry to function @var{function}.
2522 When using source languages that permit overloading of symbols, such as
2523 C@t{++}, @var{function} may refer to more than one possible place to break.
2524 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2526 @item break +@var{offset}
2527 @itemx break -@var{offset}
2528 Set a breakpoint some number of lines forward or back from the position
2529 at which execution stopped in the currently selected @dfn{stack frame}.
2530 (@xref{Frames, ,Frames}, for a description of stack frames.)
2532 @item break @var{linenum}
2533 Set a breakpoint at line @var{linenum} in the current source file.
2534 The current source file is the last file whose source text was printed.
2535 The breakpoint will stop your program just before it executes any of the
2538 @item break @var{filename}:@var{linenum}
2539 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2541 @item break @var{filename}:@var{function}
2542 Set a breakpoint at entry to function @var{function} found in file
2543 @var{filename}. Specifying a file name as well as a function name is
2544 superfluous except when multiple files contain similarly named
2547 @item break *@var{address}
2548 Set a breakpoint at address @var{address}. You can use this to set
2549 breakpoints in parts of your program which do not have debugging
2550 information or source files.
2553 When called without any arguments, @code{break} sets a breakpoint at
2554 the next instruction to be executed in the selected stack frame
2555 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2556 innermost, this makes your program stop as soon as control
2557 returns to that frame. This is similar to the effect of a
2558 @code{finish} command in the frame inside the selected frame---except
2559 that @code{finish} does not leave an active breakpoint. If you use
2560 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2561 the next time it reaches the current location; this may be useful
2564 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2565 least one instruction has been executed. If it did not do this, you
2566 would be unable to proceed past a breakpoint without first disabling the
2567 breakpoint. This rule applies whether or not the breakpoint already
2568 existed when your program stopped.
2570 @item break @dots{} if @var{cond}
2571 Set a breakpoint with condition @var{cond}; evaluate the expression
2572 @var{cond} each time the breakpoint is reached, and stop only if the
2573 value is nonzero---that is, if @var{cond} evaluates as true.
2574 @samp{@dots{}} stands for one of the possible arguments described
2575 above (or no argument) specifying where to break. @xref{Conditions,
2576 ,Break conditions}, for more information on breakpoint conditions.
2579 @item tbreak @var{args}
2580 Set a breakpoint enabled only for one stop. @var{args} are the
2581 same as for the @code{break} command, and the breakpoint is set in the same
2582 way, but the breakpoint is automatically deleted after the first time your
2583 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2586 @cindex hardware breakpoints
2587 @item hbreak @var{args}
2588 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2589 @code{break} command and the breakpoint is set in the same way, but the
2590 breakpoint requires hardware support and some target hardware may not
2591 have this support. The main purpose of this is EPROM/ROM code
2592 debugging, so you can set a breakpoint at an instruction without
2593 changing the instruction. This can be used with the new trap-generation
2594 provided by SPARClite DSU and most x86-based targets. These targets
2595 will generate traps when a program accesses some data or instruction
2596 address that is assigned to the debug registers. However the hardware
2597 breakpoint registers can take a limited number of breakpoints. For
2598 example, on the DSU, only two data breakpoints can be set at a time, and
2599 @value{GDBN} will reject this command if more than two are used. Delete
2600 or disable unused hardware breakpoints before setting new ones
2601 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2602 For remote targets, you can restrict the number of hardware
2603 breakpoints @value{GDBN} will use, see @ref{set remote
2604 hardware-breakpoint-limit}.
2608 @item thbreak @var{args}
2609 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2610 are the same as for the @code{hbreak} command and the breakpoint is set in
2611 the same way. However, like the @code{tbreak} command,
2612 the breakpoint is automatically deleted after the
2613 first time your program stops there. Also, like the @code{hbreak}
2614 command, the breakpoint requires hardware support and some target hardware
2615 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2616 See also @ref{Conditions, ,Break conditions}.
2619 @cindex regular expression
2620 @cindex breakpoints in functions matching a regexp
2621 @cindex set breakpoints in many functions
2622 @item rbreak @var{regex}
2623 Set breakpoints on all functions matching the regular expression
2624 @var{regex}. This command sets an unconditional breakpoint on all
2625 matches, printing a list of all breakpoints it set. Once these
2626 breakpoints are set, they are treated just like the breakpoints set with
2627 the @code{break} command. You can delete them, disable them, or make
2628 them conditional the same way as any other breakpoint.
2630 The syntax of the regular expression is the standard one used with tools
2631 like @file{grep}. Note that this is different from the syntax used by
2632 shells, so for instance @code{foo*} matches all functions that include
2633 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2634 @code{.*} leading and trailing the regular expression you supply, so to
2635 match only functions that begin with @code{foo}, use @code{^foo}.
2637 @cindex non-member C@t{++} functions, set breakpoint in
2638 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2639 breakpoints on overloaded functions that are not members of any special
2642 @cindex set breakpoints on all functions
2643 The @code{rbreak} command can be used to set breakpoints in
2644 @strong{all} the functions in a program, like this:
2647 (@value{GDBP}) rbreak .
2650 @kindex info breakpoints
2651 @cindex @code{$_} and @code{info breakpoints}
2652 @item info breakpoints @r{[}@var{n}@r{]}
2653 @itemx info break @r{[}@var{n}@r{]}
2654 @itemx info watchpoints @r{[}@var{n}@r{]}
2655 Print a table of all breakpoints, watchpoints, and catchpoints set and
2656 not deleted, with the following columns for each breakpoint:
2659 @item Breakpoint Numbers
2661 Breakpoint, watchpoint, or catchpoint.
2663 Whether the breakpoint is marked to be disabled or deleted when hit.
2664 @item Enabled or Disabled
2665 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2666 that are not enabled.
2668 Where the breakpoint is in your program, as a memory address. If the
2669 breakpoint is pending (see below for details) on a future load of a shared library, the address
2670 will be listed as @samp{<PENDING>}.
2672 Where the breakpoint is in the source for your program, as a file and
2673 line number. For a pending breakpoint, the original string passed to
2674 the breakpoint command will be listed as it cannot be resolved until
2675 the appropriate shared library is loaded in the future.
2679 If a breakpoint is conditional, @code{info break} shows the condition on
2680 the line following the affected breakpoint; breakpoint commands, if any,
2681 are listed after that. A pending breakpoint is allowed to have a condition
2682 specified for it. The condition is not parsed for validity until a shared
2683 library is loaded that allows the pending breakpoint to resolve to a
2687 @code{info break} with a breakpoint
2688 number @var{n} as argument lists only that breakpoint. The
2689 convenience variable @code{$_} and the default examining-address for
2690 the @code{x} command are set to the address of the last breakpoint
2691 listed (@pxref{Memory, ,Examining memory}).
2694 @code{info break} displays a count of the number of times the breakpoint
2695 has been hit. This is especially useful in conjunction with the
2696 @code{ignore} command. You can ignore a large number of breakpoint
2697 hits, look at the breakpoint info to see how many times the breakpoint
2698 was hit, and then run again, ignoring one less than that number. This
2699 will get you quickly to the last hit of that breakpoint.
2702 @value{GDBN} allows you to set any number of breakpoints at the same place in
2703 your program. There is nothing silly or meaningless about this. When
2704 the breakpoints are conditional, this is even useful
2705 (@pxref{Conditions, ,Break conditions}).
2707 @cindex pending breakpoints
2708 If a specified breakpoint location cannot be found, it may be due to the fact
2709 that the location is in a shared library that is yet to be loaded. In such
2710 a case, you may want @value{GDBN} to create a special breakpoint (known as
2711 a @dfn{pending breakpoint}) that
2712 attempts to resolve itself in the future when an appropriate shared library
2715 Pending breakpoints are useful to set at the start of your
2716 @value{GDBN} session for locations that you know will be dynamically loaded
2717 later by the program being debugged. When shared libraries are loaded,
2718 a check is made to see if the load resolves any pending breakpoint locations.
2719 If a pending breakpoint location gets resolved,
2720 a regular breakpoint is created and the original pending breakpoint is removed.
2722 @value{GDBN} provides some additional commands for controlling pending
2725 @kindex set breakpoint pending
2726 @kindex show breakpoint pending
2728 @item set breakpoint pending auto
2729 This is the default behavior. When @value{GDBN} cannot find the breakpoint
2730 location, it queries you whether a pending breakpoint should be created.
2732 @item set breakpoint pending on
2733 This indicates that an unrecognized breakpoint location should automatically
2734 result in a pending breakpoint being created.
2736 @item set breakpoint pending off
2737 This indicates that pending breakpoints are not to be created. Any
2738 unrecognized breakpoint location results in an error. This setting does
2739 not affect any pending breakpoints previously created.
2741 @item show breakpoint pending
2742 Show the current behavior setting for creating pending breakpoints.
2745 @cindex operations allowed on pending breakpoints
2746 Normal breakpoint operations apply to pending breakpoints as well. You may
2747 specify a condition for a pending breakpoint and/or commands to run when the
2748 breakpoint is reached. You can also enable or disable
2749 the pending breakpoint. When you specify a condition for a pending breakpoint,
2750 the parsing of the condition will be deferred until the point where the
2751 pending breakpoint location is resolved. Disabling a pending breakpoint
2752 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
2753 shared library load. When a pending breakpoint is re-enabled,
2754 @value{GDBN} checks to see if the location is already resolved.
2755 This is done because any number of shared library loads could have
2756 occurred since the time the breakpoint was disabled and one or more
2757 of these loads could resolve the location.
2759 @cindex negative breakpoint numbers
2760 @cindex internal @value{GDBN} breakpoints
2761 @value{GDBN} itself sometimes sets breakpoints in your program for
2762 special purposes, such as proper handling of @code{longjmp} (in C
2763 programs). These internal breakpoints are assigned negative numbers,
2764 starting with @code{-1}; @samp{info breakpoints} does not display them.
2765 You can see these breakpoints with the @value{GDBN} maintenance command
2766 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
2769 @node Set Watchpoints
2770 @subsection Setting watchpoints
2772 @cindex setting watchpoints
2773 You can use a watchpoint to stop execution whenever the value of an
2774 expression changes, without having to predict a particular place where
2777 @cindex software watchpoints
2778 @cindex hardware watchpoints
2779 Depending on your system, watchpoints may be implemented in software or
2780 hardware. @value{GDBN} does software watchpointing by single-stepping your
2781 program and testing the variable's value each time, which is hundreds of
2782 times slower than normal execution. (But this may still be worth it, to
2783 catch errors where you have no clue what part of your program is the
2786 On some systems, such as HP-UX, @sc{gnu}/Linux and most other
2787 x86-based targets, @value{GDBN} includes support for hardware
2788 watchpoints, which do not slow down the running of your program.
2792 @item watch @var{expr}
2793 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
2794 is written into by the program and its value changes.
2797 @item rwatch @var{expr}
2798 Set a watchpoint that will break when the value of @var{expr} is read
2802 @item awatch @var{expr}
2803 Set a watchpoint that will break when @var{expr} is either read from
2804 or written into by the program.
2806 @kindex info watchpoints
2807 @item info watchpoints
2808 This command prints a list of watchpoints, breakpoints, and catchpoints;
2809 it is the same as @code{info break} (@pxref{Set Breaks}).
2812 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
2813 watchpoints execute very quickly, and the debugger reports a change in
2814 value at the exact instruction where the change occurs. If @value{GDBN}
2815 cannot set a hardware watchpoint, it sets a software watchpoint, which
2816 executes more slowly and reports the change in value at the next
2817 @emph{statement}, not the instruction, after the change occurs.
2819 @vindex can-use-hw-watchpoints
2820 @cindex use only software watchpoints
2821 You can force @value{GDBN} to use only software watchpoints with the
2822 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
2823 zero, @value{GDBN} will never try to use hardware watchpoints, even if
2824 the underlying system supports them. (Note that hardware-assisted
2825 watchpoints that were set @emph{before} setting
2826 @code{can-use-hw-watchpoints} to zero will still use the hardware
2827 mechanism of watching expressiion values.)
2830 @item set can-use-hw-watchpoints
2831 @kindex set can-use-hw-watchpoints
2832 Set whether or not to use hardware watchpoints.
2834 @item show can-use-hw-watchpoints
2835 @kindex show can-use-hw-watchpoints
2836 Show the current mode of using hardware watchpoints.
2839 For remote targets, you can restrict the number of hardware
2840 watchpoints @value{GDBN} will use, see @ref{set remote
2841 hardware-breakpoint-limit}.
2843 When you issue the @code{watch} command, @value{GDBN} reports
2846 Hardware watchpoint @var{num}: @var{expr}
2850 if it was able to set a hardware watchpoint.
2852 Currently, the @code{awatch} and @code{rwatch} commands can only set
2853 hardware watchpoints, because accesses to data that don't change the
2854 value of the watched expression cannot be detected without examining
2855 every instruction as it is being executed, and @value{GDBN} does not do
2856 that currently. If @value{GDBN} finds that it is unable to set a
2857 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
2858 will print a message like this:
2861 Expression cannot be implemented with read/access watchpoint.
2864 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
2865 data type of the watched expression is wider than what a hardware
2866 watchpoint on the target machine can handle. For example, some systems
2867 can only watch regions that are up to 4 bytes wide; on such systems you
2868 cannot set hardware watchpoints for an expression that yields a
2869 double-precision floating-point number (which is typically 8 bytes
2870 wide). As a work-around, it might be possible to break the large region
2871 into a series of smaller ones and watch them with separate watchpoints.
2873 If you set too many hardware watchpoints, @value{GDBN} might be unable
2874 to insert all of them when you resume the execution of your program.
2875 Since the precise number of active watchpoints is unknown until such
2876 time as the program is about to be resumed, @value{GDBN} might not be
2877 able to warn you about this when you set the watchpoints, and the
2878 warning will be printed only when the program is resumed:
2881 Hardware watchpoint @var{num}: Could not insert watchpoint
2885 If this happens, delete or disable some of the watchpoints.
2887 The SPARClite DSU will generate traps when a program accesses some data
2888 or instruction address that is assigned to the debug registers. For the
2889 data addresses, DSU facilitates the @code{watch} command. However the
2890 hardware breakpoint registers can only take two data watchpoints, and
2891 both watchpoints must be the same kind. For example, you can set two
2892 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
2893 @strong{or} two with @code{awatch} commands, but you cannot set one
2894 watchpoint with one command and the other with a different command.
2895 @value{GDBN} will reject the command if you try to mix watchpoints.
2896 Delete or disable unused watchpoint commands before setting new ones.
2898 If you call a function interactively using @code{print} or @code{call},
2899 any watchpoints you have set will be inactive until @value{GDBN} reaches another
2900 kind of breakpoint or the call completes.
2902 @value{GDBN} automatically deletes watchpoints that watch local
2903 (automatic) variables, or expressions that involve such variables, when
2904 they go out of scope, that is, when the execution leaves the block in
2905 which these variables were defined. In particular, when the program
2906 being debugged terminates, @emph{all} local variables go out of scope,
2907 and so only watchpoints that watch global variables remain set. If you
2908 rerun the program, you will need to set all such watchpoints again. One
2909 way of doing that would be to set a code breakpoint at the entry to the
2910 @code{main} function and when it breaks, set all the watchpoints.
2913 @cindex watchpoints and threads
2914 @cindex threads and watchpoints
2915 @emph{Warning:} In multi-thread programs, watchpoints have only limited
2916 usefulness. With the current watchpoint implementation, @value{GDBN}
2917 can only watch the value of an expression @emph{in a single thread}. If
2918 you are confident that the expression can only change due to the current
2919 thread's activity (and if you are also confident that no other thread
2920 can become current), then you can use watchpoints as usual. However,
2921 @value{GDBN} may not notice when a non-current thread's activity changes
2924 @c FIXME: this is almost identical to the previous paragraph.
2925 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
2926 have only limited usefulness. If @value{GDBN} creates a software
2927 watchpoint, it can only watch the value of an expression @emph{in a
2928 single thread}. If you are confident that the expression can only
2929 change due to the current thread's activity (and if you are also
2930 confident that no other thread can become current), then you can use
2931 software watchpoints as usual. However, @value{GDBN} may not notice
2932 when a non-current thread's activity changes the expression. (Hardware
2933 watchpoints, in contrast, watch an expression in all threads.)
2936 @xref{set remote hardware-watchpoint-limit}.
2938 @node Set Catchpoints
2939 @subsection Setting catchpoints
2940 @cindex catchpoints, setting
2941 @cindex exception handlers
2942 @cindex event handling
2944 You can use @dfn{catchpoints} to cause the debugger to stop for certain
2945 kinds of program events, such as C@t{++} exceptions or the loading of a
2946 shared library. Use the @code{catch} command to set a catchpoint.
2950 @item catch @var{event}
2951 Stop when @var{event} occurs. @var{event} can be any of the following:
2954 @cindex stop on C@t{++} exceptions
2955 The throwing of a C@t{++} exception.
2958 The catching of a C@t{++} exception.
2961 @cindex break on fork/exec
2962 A call to @code{exec}. This is currently only available for HP-UX.
2965 A call to @code{fork}. This is currently only available for HP-UX.
2968 A call to @code{vfork}. This is currently only available for HP-UX.
2971 @itemx load @var{libname}
2972 @cindex break on load/unload of shared library
2973 The dynamic loading of any shared library, or the loading of the library
2974 @var{libname}. This is currently only available for HP-UX.
2977 @itemx unload @var{libname}
2978 The unloading of any dynamically loaded shared library, or the unloading
2979 of the library @var{libname}. This is currently only available for HP-UX.
2982 @item tcatch @var{event}
2983 Set a catchpoint that is enabled only for one stop. The catchpoint is
2984 automatically deleted after the first time the event is caught.
2988 Use the @code{info break} command to list the current catchpoints.
2990 There are currently some limitations to C@t{++} exception handling
2991 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
2995 If you call a function interactively, @value{GDBN} normally returns
2996 control to you when the function has finished executing. If the call
2997 raises an exception, however, the call may bypass the mechanism that
2998 returns control to you and cause your program either to abort or to
2999 simply continue running until it hits a breakpoint, catches a signal
3000 that @value{GDBN} is listening for, or exits. This is the case even if
3001 you set a catchpoint for the exception; catchpoints on exceptions are
3002 disabled within interactive calls.
3005 You cannot raise an exception interactively.
3008 You cannot install an exception handler interactively.
3011 @cindex raise exceptions
3012 Sometimes @code{catch} is not the best way to debug exception handling:
3013 if you need to know exactly where an exception is raised, it is better to
3014 stop @emph{before} the exception handler is called, since that way you
3015 can see the stack before any unwinding takes place. If you set a
3016 breakpoint in an exception handler instead, it may not be easy to find
3017 out where the exception was raised.
3019 To stop just before an exception handler is called, you need some
3020 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3021 raised by calling a library function named @code{__raise_exception}
3022 which has the following ANSI C interface:
3025 /* @var{addr} is where the exception identifier is stored.
3026 @var{id} is the exception identifier. */
3027 void __raise_exception (void **addr, void *id);
3031 To make the debugger catch all exceptions before any stack
3032 unwinding takes place, set a breakpoint on @code{__raise_exception}
3033 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
3035 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
3036 that depends on the value of @var{id}, you can stop your program when
3037 a specific exception is raised. You can use multiple conditional
3038 breakpoints to stop your program when any of a number of exceptions are
3043 @subsection Deleting breakpoints
3045 @cindex clearing breakpoints, watchpoints, catchpoints
3046 @cindex deleting breakpoints, watchpoints, catchpoints
3047 It is often necessary to eliminate a breakpoint, watchpoint, or
3048 catchpoint once it has done its job and you no longer want your program
3049 to stop there. This is called @dfn{deleting} the breakpoint. A
3050 breakpoint that has been deleted no longer exists; it is forgotten.
3052 With the @code{clear} command you can delete breakpoints according to
3053 where they are in your program. With the @code{delete} command you can
3054 delete individual breakpoints, watchpoints, or catchpoints by specifying
3055 their breakpoint numbers.
3057 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3058 automatically ignores breakpoints on the first instruction to be executed
3059 when you continue execution without changing the execution address.
3064 Delete any breakpoints at the next instruction to be executed in the
3065 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
3066 the innermost frame is selected, this is a good way to delete a
3067 breakpoint where your program just stopped.
3069 @item clear @var{function}
3070 @itemx clear @var{filename}:@var{function}
3071 Delete any breakpoints set at entry to the named @var{function}.
3073 @item clear @var{linenum}
3074 @itemx clear @var{filename}:@var{linenum}
3075 Delete any breakpoints set at or within the code of the specified
3076 @var{linenum} of the specified @var{filename}.
3078 @cindex delete breakpoints
3080 @kindex d @r{(@code{delete})}
3081 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3082 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3083 ranges specified as arguments. If no argument is specified, delete all
3084 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3085 confirm off}). You can abbreviate this command as @code{d}.
3089 @subsection Disabling breakpoints
3091 @cindex enable/disable a breakpoint
3092 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3093 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3094 it had been deleted, but remembers the information on the breakpoint so
3095 that you can @dfn{enable} it again later.
3097 You disable and enable breakpoints, watchpoints, and catchpoints with
3098 the @code{enable} and @code{disable} commands, optionally specifying one
3099 or more breakpoint numbers as arguments. Use @code{info break} or
3100 @code{info watch} to print a list of breakpoints, watchpoints, and
3101 catchpoints if you do not know which numbers to use.
3103 A breakpoint, watchpoint, or catchpoint can have any of four different
3104 states of enablement:
3108 Enabled. The breakpoint stops your program. A breakpoint set
3109 with the @code{break} command starts out in this state.
3111 Disabled. The breakpoint has no effect on your program.
3113 Enabled once. The breakpoint stops your program, but then becomes
3116 Enabled for deletion. The breakpoint stops your program, but
3117 immediately after it does so it is deleted permanently. A breakpoint
3118 set with the @code{tbreak} command starts out in this state.
3121 You can use the following commands to enable or disable breakpoints,
3122 watchpoints, and catchpoints:
3126 @kindex dis @r{(@code{disable})}
3127 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3128 Disable the specified breakpoints---or all breakpoints, if none are
3129 listed. A disabled breakpoint has no effect but is not forgotten. All
3130 options such as ignore-counts, conditions and commands are remembered in
3131 case the breakpoint is enabled again later. You may abbreviate
3132 @code{disable} as @code{dis}.
3135 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3136 Enable the specified breakpoints (or all defined breakpoints). They
3137 become effective once again in stopping your program.
3139 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3140 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3141 of these breakpoints immediately after stopping your program.
3143 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3144 Enable the specified breakpoints to work once, then die. @value{GDBN}
3145 deletes any of these breakpoints as soon as your program stops there.
3146 Breakpoints set by the @code{tbreak} command start out in this state.
3149 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3150 @c confusing: tbreak is also initially enabled.
3151 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3152 ,Setting breakpoints}), breakpoints that you set are initially enabled;
3153 subsequently, they become disabled or enabled only when you use one of
3154 the commands above. (The command @code{until} can set and delete a
3155 breakpoint of its own, but it does not change the state of your other
3156 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3160 @subsection Break conditions
3161 @cindex conditional breakpoints
3162 @cindex breakpoint conditions
3164 @c FIXME what is scope of break condition expr? Context where wanted?
3165 @c in particular for a watchpoint?
3166 The simplest sort of breakpoint breaks every time your program reaches a
3167 specified place. You can also specify a @dfn{condition} for a
3168 breakpoint. A condition is just a Boolean expression in your
3169 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3170 a condition evaluates the expression each time your program reaches it,
3171 and your program stops only if the condition is @emph{true}.
3173 This is the converse of using assertions for program validation; in that
3174 situation, you want to stop when the assertion is violated---that is,
3175 when the condition is false. In C, if you want to test an assertion expressed
3176 by the condition @var{assert}, you should set the condition
3177 @samp{! @var{assert}} on the appropriate breakpoint.
3179 Conditions are also accepted for watchpoints; you may not need them,
3180 since a watchpoint is inspecting the value of an expression anyhow---but
3181 it might be simpler, say, to just set a watchpoint on a variable name,
3182 and specify a condition that tests whether the new value is an interesting
3185 Break conditions can have side effects, and may even call functions in
3186 your program. This can be useful, for example, to activate functions
3187 that log program progress, or to use your own print functions to
3188 format special data structures. The effects are completely predictable
3189 unless there is another enabled breakpoint at the same address. (In
3190 that case, @value{GDBN} might see the other breakpoint first and stop your
3191 program without checking the condition of this one.) Note that
3192 breakpoint commands are usually more convenient and flexible than break
3194 purpose of performing side effects when a breakpoint is reached
3195 (@pxref{Break Commands, ,Breakpoint command lists}).
3197 Break conditions can be specified when a breakpoint is set, by using
3198 @samp{if} in the arguments to the @code{break} command. @xref{Set
3199 Breaks, ,Setting breakpoints}. They can also be changed at any time
3200 with the @code{condition} command.
3202 You can also use the @code{if} keyword with the @code{watch} command.
3203 The @code{catch} command does not recognize the @code{if} keyword;
3204 @code{condition} is the only way to impose a further condition on a
3209 @item condition @var{bnum} @var{expression}
3210 Specify @var{expression} as the break condition for breakpoint,
3211 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3212 breakpoint @var{bnum} stops your program only if the value of
3213 @var{expression} is true (nonzero, in C). When you use
3214 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3215 syntactic correctness, and to determine whether symbols in it have
3216 referents in the context of your breakpoint. If @var{expression} uses
3217 symbols not referenced in the context of the breakpoint, @value{GDBN}
3218 prints an error message:
3221 No symbol "foo" in current context.
3226 not actually evaluate @var{expression} at the time the @code{condition}
3227 command (or a command that sets a breakpoint with a condition, like
3228 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3230 @item condition @var{bnum}
3231 Remove the condition from breakpoint number @var{bnum}. It becomes
3232 an ordinary unconditional breakpoint.
3235 @cindex ignore count (of breakpoint)
3236 A special case of a breakpoint condition is to stop only when the
3237 breakpoint has been reached a certain number of times. This is so
3238 useful that there is a special way to do it, using the @dfn{ignore
3239 count} of the breakpoint. Every breakpoint has an ignore count, which
3240 is an integer. Most of the time, the ignore count is zero, and
3241 therefore has no effect. But if your program reaches a breakpoint whose
3242 ignore count is positive, then instead of stopping, it just decrements
3243 the ignore count by one and continues. As a result, if the ignore count
3244 value is @var{n}, the breakpoint does not stop the next @var{n} times
3245 your program reaches it.
3249 @item ignore @var{bnum} @var{count}
3250 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3251 The next @var{count} times the breakpoint is reached, your program's
3252 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3255 To make the breakpoint stop the next time it is reached, specify
3258 When you use @code{continue} to resume execution of your program from a
3259 breakpoint, you can specify an ignore count directly as an argument to
3260 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3261 Stepping,,Continuing and stepping}.
3263 If a breakpoint has a positive ignore count and a condition, the
3264 condition is not checked. Once the ignore count reaches zero,
3265 @value{GDBN} resumes checking the condition.
3267 You could achieve the effect of the ignore count with a condition such
3268 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3269 is decremented each time. @xref{Convenience Vars, ,Convenience
3273 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3276 @node Break Commands
3277 @subsection Breakpoint command lists
3279 @cindex breakpoint commands
3280 You can give any breakpoint (or watchpoint or catchpoint) a series of
3281 commands to execute when your program stops due to that breakpoint. For
3282 example, you might want to print the values of certain expressions, or
3283 enable other breakpoints.
3288 @item commands @r{[}@var{bnum}@r{]}
3289 @itemx @dots{} @var{command-list} @dots{}
3291 Specify a list of commands for breakpoint number @var{bnum}. The commands
3292 themselves appear on the following lines. Type a line containing just
3293 @code{end} to terminate the commands.
3295 To remove all commands from a breakpoint, type @code{commands} and
3296 follow it immediately with @code{end}; that is, give no commands.
3298 With no @var{bnum} argument, @code{commands} refers to the last
3299 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3300 recently encountered).
3303 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3304 disabled within a @var{command-list}.
3306 You can use breakpoint commands to start your program up again. Simply
3307 use the @code{continue} command, or @code{step}, or any other command
3308 that resumes execution.
3310 Any other commands in the command list, after a command that resumes
3311 execution, are ignored. This is because any time you resume execution
3312 (even with a simple @code{next} or @code{step}), you may encounter
3313 another breakpoint---which could have its own command list, leading to
3314 ambiguities about which list to execute.
3317 If the first command you specify in a command list is @code{silent}, the
3318 usual message about stopping at a breakpoint is not printed. This may
3319 be desirable for breakpoints that are to print a specific message and
3320 then continue. If none of the remaining commands print anything, you
3321 see no sign that the breakpoint was reached. @code{silent} is
3322 meaningful only at the beginning of a breakpoint command list.
3324 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3325 print precisely controlled output, and are often useful in silent
3326 breakpoints. @xref{Output, ,Commands for controlled output}.
3328 For example, here is how you could use breakpoint commands to print the
3329 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3335 printf "x is %d\n",x
3340 One application for breakpoint commands is to compensate for one bug so
3341 you can test for another. Put a breakpoint just after the erroneous line
3342 of code, give it a condition to detect the case in which something
3343 erroneous has been done, and give it commands to assign correct values
3344 to any variables that need them. End with the @code{continue} command
3345 so that your program does not stop, and start with the @code{silent}
3346 command so that no output is produced. Here is an example:
3357 @node Breakpoint Menus
3358 @subsection Breakpoint menus
3360 @cindex symbol overloading
3362 Some programming languages (notably C@t{++} and Objective-C) permit a
3363 single function name
3364 to be defined several times, for application in different contexts.
3365 This is called @dfn{overloading}. When a function name is overloaded,
3366 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3367 a breakpoint. If you realize this is a problem, you can use
3368 something like @samp{break @var{function}(@var{types})} to specify which
3369 particular version of the function you want. Otherwise, @value{GDBN} offers
3370 you a menu of numbered choices for different possible breakpoints, and
3371 waits for your selection with the prompt @samp{>}. The first two
3372 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3373 sets a breakpoint at each definition of @var{function}, and typing
3374 @kbd{0} aborts the @code{break} command without setting any new
3377 For example, the following session excerpt shows an attempt to set a
3378 breakpoint at the overloaded symbol @code{String::after}.
3379 We choose three particular definitions of that function name:
3381 @c FIXME! This is likely to change to show arg type lists, at least
3384 (@value{GDBP}) b String::after
3387 [2] file:String.cc; line number:867
3388 [3] file:String.cc; line number:860
3389 [4] file:String.cc; line number:875
3390 [5] file:String.cc; line number:853
3391 [6] file:String.cc; line number:846
3392 [7] file:String.cc; line number:735
3394 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3395 Breakpoint 2 at 0xb344: file String.cc, line 875.
3396 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3397 Multiple breakpoints were set.
3398 Use the "delete" command to delete unwanted
3404 @c @ifclear BARETARGET
3405 @node Error in Breakpoints
3406 @subsection ``Cannot insert breakpoints''
3408 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3410 Under some operating systems, breakpoints cannot be used in a program if
3411 any other process is running that program. In this situation,
3412 attempting to run or continue a program with a breakpoint causes
3413 @value{GDBN} to print an error message:
3416 Cannot insert breakpoints.
3417 The same program may be running in another process.
3420 When this happens, you have three ways to proceed:
3424 Remove or disable the breakpoints, then continue.
3427 Suspend @value{GDBN}, and copy the file containing your program to a new
3428 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3429 that @value{GDBN} should run your program under that name.
3430 Then start your program again.
3433 Relink your program so that the text segment is nonsharable, using the
3434 linker option @samp{-N}. The operating system limitation may not apply
3435 to nonsharable executables.
3439 A similar message can be printed if you request too many active
3440 hardware-assisted breakpoints and watchpoints:
3442 @c FIXME: the precise wording of this message may change; the relevant
3443 @c source change is not committed yet (Sep 3, 1999).
3445 Stopped; cannot insert breakpoints.
3446 You may have requested too many hardware breakpoints and watchpoints.
3450 This message is printed when you attempt to resume the program, since
3451 only then @value{GDBN} knows exactly how many hardware breakpoints and
3452 watchpoints it needs to insert.
3454 When this message is printed, you need to disable or remove some of the
3455 hardware-assisted breakpoints and watchpoints, and then continue.
3457 @node Breakpoint related warnings
3458 @subsection ``Breakpoint address adjusted...''
3459 @cindex breakpoint address adjusted
3461 Some processor architectures place constraints on the addresses at
3462 which breakpoints may be placed. For architectures thus constrained,
3463 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3464 with the constraints dictated by the architecture.
3466 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3467 a VLIW architecture in which a number of RISC-like instructions may be
3468 bundled together for parallel execution. The FR-V architecture
3469 constrains the location of a breakpoint instruction within such a
3470 bundle to the instruction with the lowest address. @value{GDBN}
3471 honors this constraint by adjusting a breakpoint's address to the
3472 first in the bundle.
3474 It is not uncommon for optimized code to have bundles which contain
3475 instructions from different source statements, thus it may happen that
3476 a breakpoint's address will be adjusted from one source statement to
3477 another. Since this adjustment may significantly alter @value{GDBN}'s
3478 breakpoint related behavior from what the user expects, a warning is
3479 printed when the breakpoint is first set and also when the breakpoint
3482 A warning like the one below is printed when setting a breakpoint
3483 that's been subject to address adjustment:
3486 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3489 Such warnings are printed both for user settable and @value{GDBN}'s
3490 internal breakpoints. If you see one of these warnings, you should
3491 verify that a breakpoint set at the adjusted address will have the
3492 desired affect. If not, the breakpoint in question may be removed and
3493 other breakpoints may be set which will have the desired behavior.
3494 E.g., it may be sufficient to place the breakpoint at a later
3495 instruction. A conditional breakpoint may also be useful in some
3496 cases to prevent the breakpoint from triggering too often.
3498 @value{GDBN} will also issue a warning when stopping at one of these
3499 adjusted breakpoints:
3502 warning: Breakpoint 1 address previously adjusted from 0x00010414
3506 When this warning is encountered, it may be too late to take remedial
3507 action except in cases where the breakpoint is hit earlier or more
3508 frequently than expected.
3510 @node Continuing and Stepping
3511 @section Continuing and stepping
3515 @cindex resuming execution
3516 @dfn{Continuing} means resuming program execution until your program
3517 completes normally. In contrast, @dfn{stepping} means executing just
3518 one more ``step'' of your program, where ``step'' may mean either one
3519 line of source code, or one machine instruction (depending on what
3520 particular command you use). Either when continuing or when stepping,
3521 your program may stop even sooner, due to a breakpoint or a signal. (If
3522 it stops due to a signal, you may want to use @code{handle}, or use
3523 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3527 @kindex c @r{(@code{continue})}
3528 @kindex fg @r{(resume foreground execution)}
3529 @item continue @r{[}@var{ignore-count}@r{]}
3530 @itemx c @r{[}@var{ignore-count}@r{]}
3531 @itemx fg @r{[}@var{ignore-count}@r{]}
3532 Resume program execution, at the address where your program last stopped;
3533 any breakpoints set at that address are bypassed. The optional argument
3534 @var{ignore-count} allows you to specify a further number of times to
3535 ignore a breakpoint at this location; its effect is like that of
3536 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3538 The argument @var{ignore-count} is meaningful only when your program
3539 stopped due to a breakpoint. At other times, the argument to
3540 @code{continue} is ignored.
3542 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3543 debugged program is deemed to be the foreground program) are provided
3544 purely for convenience, and have exactly the same behavior as
3548 To resume execution at a different place, you can use @code{return}
3549 (@pxref{Returning, ,Returning from a function}) to go back to the
3550 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3551 different address}) to go to an arbitrary location in your program.
3553 A typical technique for using stepping is to set a breakpoint
3554 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3555 beginning of the function or the section of your program where a problem
3556 is believed to lie, run your program until it stops at that breakpoint,
3557 and then step through the suspect area, examining the variables that are
3558 interesting, until you see the problem happen.
3562 @kindex s @r{(@code{step})}
3564 Continue running your program until control reaches a different source
3565 line, then stop it and return control to @value{GDBN}. This command is
3566 abbreviated @code{s}.
3569 @c "without debugging information" is imprecise; actually "without line
3570 @c numbers in the debugging information". (gcc -g1 has debugging info but
3571 @c not line numbers). But it seems complex to try to make that
3572 @c distinction here.
3573 @emph{Warning:} If you use the @code{step} command while control is
3574 within a function that was compiled without debugging information,
3575 execution proceeds until control reaches a function that does have
3576 debugging information. Likewise, it will not step into a function which
3577 is compiled without debugging information. To step through functions
3578 without debugging information, use the @code{stepi} command, described
3582 The @code{step} command only stops at the first instruction of a source
3583 line. This prevents the multiple stops that could otherwise occur in
3584 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3585 to stop if a function that has debugging information is called within
3586 the line. In other words, @code{step} @emph{steps inside} any functions
3587 called within the line.
3589 Also, the @code{step} command only enters a function if there is line
3590 number information for the function. Otherwise it acts like the
3591 @code{next} command. This avoids problems when using @code{cc -gl}
3592 on MIPS machines. Previously, @code{step} entered subroutines if there
3593 was any debugging information about the routine.
3595 @item step @var{count}
3596 Continue running as in @code{step}, but do so @var{count} times. If a
3597 breakpoint is reached, or a signal not related to stepping occurs before
3598 @var{count} steps, stepping stops right away.
3601 @kindex n @r{(@code{next})}
3602 @item next @r{[}@var{count}@r{]}
3603 Continue to the next source line in the current (innermost) stack frame.
3604 This is similar to @code{step}, but function calls that appear within
3605 the line of code are executed without stopping. Execution stops when
3606 control reaches a different line of code at the original stack level
3607 that was executing when you gave the @code{next} command. This command
3608 is abbreviated @code{n}.
3610 An argument @var{count} is a repeat count, as for @code{step}.
3613 @c FIX ME!! Do we delete this, or is there a way it fits in with
3614 @c the following paragraph? --- Vctoria
3616 @c @code{next} within a function that lacks debugging information acts like
3617 @c @code{step}, but any function calls appearing within the code of the
3618 @c function are executed without stopping.
3620 The @code{next} command only stops at the first instruction of a
3621 source line. This prevents multiple stops that could otherwise occur in
3622 @code{switch} statements, @code{for} loops, etc.
3624 @kindex set step-mode
3626 @cindex functions without line info, and stepping
3627 @cindex stepping into functions with no line info
3628 @itemx set step-mode on
3629 The @code{set step-mode on} command causes the @code{step} command to
3630 stop at the first instruction of a function which contains no debug line
3631 information rather than stepping over it.
3633 This is useful in cases where you may be interested in inspecting the
3634 machine instructions of a function which has no symbolic info and do not
3635 want @value{GDBN} to automatically skip over this function.
3637 @item set step-mode off
3638 Causes the @code{step} command to step over any functions which contains no
3639 debug information. This is the default.
3641 @item show step-mode
3642 Show whether @value{GDBN} will stop in or step over functions without
3643 source line debug information.
3647 Continue running until just after function in the selected stack frame
3648 returns. Print the returned value (if any).
3650 Contrast this with the @code{return} command (@pxref{Returning,
3651 ,Returning from a function}).
3654 @kindex u @r{(@code{until})}
3655 @cindex run until specified location
3658 Continue running until a source line past the current line, in the
3659 current stack frame, is reached. This command is used to avoid single
3660 stepping through a loop more than once. It is like the @code{next}
3661 command, except that when @code{until} encounters a jump, it
3662 automatically continues execution until the program counter is greater
3663 than the address of the jump.
3665 This means that when you reach the end of a loop after single stepping
3666 though it, @code{until} makes your program continue execution until it
3667 exits the loop. In contrast, a @code{next} command at the end of a loop
3668 simply steps back to the beginning of the loop, which forces you to step
3669 through the next iteration.
3671 @code{until} always stops your program if it attempts to exit the current
3674 @code{until} may produce somewhat counterintuitive results if the order
3675 of machine code does not match the order of the source lines. For
3676 example, in the following excerpt from a debugging session, the @code{f}
3677 (@code{frame}) command shows that execution is stopped at line
3678 @code{206}; yet when we use @code{until}, we get to line @code{195}:
3682 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
3684 (@value{GDBP}) until
3685 195 for ( ; argc > 0; NEXTARG) @{
3688 This happened because, for execution efficiency, the compiler had
3689 generated code for the loop closure test at the end, rather than the
3690 start, of the loop---even though the test in a C @code{for}-loop is
3691 written before the body of the loop. The @code{until} command appeared
3692 to step back to the beginning of the loop when it advanced to this
3693 expression; however, it has not really gone to an earlier
3694 statement---not in terms of the actual machine code.
3696 @code{until} with no argument works by means of single
3697 instruction stepping, and hence is slower than @code{until} with an
3700 @item until @var{location}
3701 @itemx u @var{location}
3702 Continue running your program until either the specified location is
3703 reached, or the current stack frame returns. @var{location} is any of
3704 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
3705 ,Setting breakpoints}). This form of the command uses breakpoints, and
3706 hence is quicker than @code{until} without an argument. The specified
3707 location is actually reached only if it is in the current frame. This
3708 implies that @code{until} can be used to skip over recursive function
3709 invocations. For instance in the code below, if the current location is
3710 line @code{96}, issuing @code{until 99} will execute the program up to
3711 line @code{99} in the same invocation of factorial, i.e. after the inner
3712 invocations have returned.
3715 94 int factorial (int value)
3717 96 if (value > 1) @{
3718 97 value *= factorial (value - 1);
3725 @kindex advance @var{location}
3726 @itemx advance @var{location}
3727 Continue running the program up to the given @var{location}. An argument is
3728 required, which should be of the same form as arguments for the @code{break}
3729 command. Execution will also stop upon exit from the current stack
3730 frame. This command is similar to @code{until}, but @code{advance} will
3731 not skip over recursive function calls, and the target location doesn't
3732 have to be in the same frame as the current one.
3736 @kindex si @r{(@code{stepi})}
3738 @itemx stepi @var{arg}
3740 Execute one machine instruction, then stop and return to the debugger.
3742 It is often useful to do @samp{display/i $pc} when stepping by machine
3743 instructions. This makes @value{GDBN} automatically display the next
3744 instruction to be executed, each time your program stops. @xref{Auto
3745 Display,, Automatic display}.
3747 An argument is a repeat count, as in @code{step}.
3751 @kindex ni @r{(@code{nexti})}
3753 @itemx nexti @var{arg}
3755 Execute one machine instruction, but if it is a function call,
3756 proceed until the function returns.
3758 An argument is a repeat count, as in @code{next}.
3765 A signal is an asynchronous event that can happen in a program. The
3766 operating system defines the possible kinds of signals, and gives each
3767 kind a name and a number. For example, in Unix @code{SIGINT} is the
3768 signal a program gets when you type an interrupt character (often @kbd{C-c});
3769 @code{SIGSEGV} is the signal a program gets from referencing a place in
3770 memory far away from all the areas in use; @code{SIGALRM} occurs when
3771 the alarm clock timer goes off (which happens only if your program has
3772 requested an alarm).
3774 @cindex fatal signals
3775 Some signals, including @code{SIGALRM}, are a normal part of the
3776 functioning of your program. Others, such as @code{SIGSEGV}, indicate
3777 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
3778 program has not specified in advance some other way to handle the signal.
3779 @code{SIGINT} does not indicate an error in your program, but it is normally
3780 fatal so it can carry out the purpose of the interrupt: to kill the program.
3782 @value{GDBN} has the ability to detect any occurrence of a signal in your
3783 program. You can tell @value{GDBN} in advance what to do for each kind of
3786 @cindex handling signals
3787 Normally, @value{GDBN} is set up to let the non-erroneous signals like
3788 @code{SIGALRM} be silently passed to your program
3789 (so as not to interfere with their role in the program's functioning)
3790 but to stop your program immediately whenever an error signal happens.
3791 You can change these settings with the @code{handle} command.
3794 @kindex info signals
3798 Print a table of all the kinds of signals and how @value{GDBN} has been told to
3799 handle each one. You can use this to see the signal numbers of all
3800 the defined types of signals.
3802 @code{info handle} is an alias for @code{info signals}.
3805 @item handle @var{signal} @var{keywords}@dots{}
3806 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
3807 can be the number of a signal or its name (with or without the
3808 @samp{SIG} at the beginning); a list of signal numbers of the form
3809 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
3810 known signals. The @var{keywords} say what change to make.
3814 The keywords allowed by the @code{handle} command can be abbreviated.
3815 Their full names are:
3819 @value{GDBN} should not stop your program when this signal happens. It may
3820 still print a message telling you that the signal has come in.
3823 @value{GDBN} should stop your program when this signal happens. This implies
3824 the @code{print} keyword as well.
3827 @value{GDBN} should print a message when this signal happens.
3830 @value{GDBN} should not mention the occurrence of the signal at all. This
3831 implies the @code{nostop} keyword as well.
3835 @value{GDBN} should allow your program to see this signal; your program
3836 can handle the signal, or else it may terminate if the signal is fatal
3837 and not handled. @code{pass} and @code{noignore} are synonyms.
3841 @value{GDBN} should not allow your program to see this signal.
3842 @code{nopass} and @code{ignore} are synonyms.
3846 When a signal stops your program, the signal is not visible to the
3848 continue. Your program sees the signal then, if @code{pass} is in
3849 effect for the signal in question @emph{at that time}. In other words,
3850 after @value{GDBN} reports a signal, you can use the @code{handle}
3851 command with @code{pass} or @code{nopass} to control whether your
3852 program sees that signal when you continue.
3854 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
3855 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
3856 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
3859 You can also use the @code{signal} command to prevent your program from
3860 seeing a signal, or cause it to see a signal it normally would not see,
3861 or to give it any signal at any time. For example, if your program stopped
3862 due to some sort of memory reference error, you might store correct
3863 values into the erroneous variables and continue, hoping to see more
3864 execution; but your program would probably terminate immediately as
3865 a result of the fatal signal once it saw the signal. To prevent this,
3866 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
3870 @section Stopping and starting multi-thread programs
3872 When your program has multiple threads (@pxref{Threads,, Debugging
3873 programs with multiple threads}), you can choose whether to set
3874 breakpoints on all threads, or on a particular thread.
3877 @cindex breakpoints and threads
3878 @cindex thread breakpoints
3879 @kindex break @dots{} thread @var{threadno}
3880 @item break @var{linespec} thread @var{threadno}
3881 @itemx break @var{linespec} thread @var{threadno} if @dots{}
3882 @var{linespec} specifies source lines; there are several ways of
3883 writing them, but the effect is always to specify some source line.
3885 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
3886 to specify that you only want @value{GDBN} to stop the program when a
3887 particular thread reaches this breakpoint. @var{threadno} is one of the
3888 numeric thread identifiers assigned by @value{GDBN}, shown in the first
3889 column of the @samp{info threads} display.
3891 If you do not specify @samp{thread @var{threadno}} when you set a
3892 breakpoint, the breakpoint applies to @emph{all} threads of your
3895 You can use the @code{thread} qualifier on conditional breakpoints as
3896 well; in this case, place @samp{thread @var{threadno}} before the
3897 breakpoint condition, like this:
3900 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
3905 @cindex stopped threads
3906 @cindex threads, stopped
3907 Whenever your program stops under @value{GDBN} for any reason,
3908 @emph{all} threads of execution stop, not just the current thread. This
3909 allows you to examine the overall state of the program, including
3910 switching between threads, without worrying that things may change
3913 @cindex thread breakpoints and system calls
3914 @cindex system calls and thread breakpoints
3915 @cindex premature return from system calls
3916 There is an unfortunate side effect. If one thread stops for a
3917 breakpoint, or for some other reason, and another thread is blocked in a
3918 system call, then the system call may return prematurely. This is a
3919 consequence of the interaction between multiple threads and the signals
3920 that @value{GDBN} uses to implement breakpoints and other events that
3923 To handle this problem, your program should check the return value of
3924 each system call and react appropriately. This is good programming
3927 For example, do not write code like this:
3933 The call to @code{sleep} will return early if a different thread stops
3934 at a breakpoint or for some other reason.
3936 Instead, write this:
3941 unslept = sleep (unslept);
3944 A system call is allowed to return early, so the system is still
3945 conforming to its specification. But @value{GDBN} does cause your
3946 multi-threaded program to behave differently than it would without
3949 Also, @value{GDBN} uses internal breakpoints in the thread library to
3950 monitor certain events such as thread creation and thread destruction.
3951 When such an event happens, a system call in another thread may return
3952 prematurely, even though your program does not appear to stop.
3954 @cindex continuing threads
3955 @cindex threads, continuing
3956 Conversely, whenever you restart the program, @emph{all} threads start
3957 executing. @emph{This is true even when single-stepping} with commands
3958 like @code{step} or @code{next}.
3960 In particular, @value{GDBN} cannot single-step all threads in lockstep.
3961 Since thread scheduling is up to your debugging target's operating
3962 system (not controlled by @value{GDBN}), other threads may
3963 execute more than one statement while the current thread completes a
3964 single step. Moreover, in general other threads stop in the middle of a
3965 statement, rather than at a clean statement boundary, when the program
3968 You might even find your program stopped in another thread after
3969 continuing or even single-stepping. This happens whenever some other
3970 thread runs into a breakpoint, a signal, or an exception before the
3971 first thread completes whatever you requested.
3973 On some OSes, you can lock the OS scheduler and thus allow only a single
3977 @item set scheduler-locking @var{mode}
3978 @cindex scheduler locking mode
3979 @cindex lock scheduler
3980 Set the scheduler locking mode. If it is @code{off}, then there is no
3981 locking and any thread may run at any time. If @code{on}, then only the
3982 current thread may run when the inferior is resumed. The @code{step}
3983 mode optimizes for single-stepping. It stops other threads from
3984 ``seizing the prompt'' by preempting the current thread while you are
3985 stepping. Other threads will only rarely (or never) get a chance to run
3986 when you step. They are more likely to run when you @samp{next} over a
3987 function call, and they are completely free to run when you use commands
3988 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
3989 thread hits a breakpoint during its timeslice, they will never steal the
3990 @value{GDBN} prompt away from the thread that you are debugging.
3992 @item show scheduler-locking
3993 Display the current scheduler locking mode.
3998 @chapter Examining the Stack
4000 When your program has stopped, the first thing you need to know is where it
4001 stopped and how it got there.
4004 Each time your program performs a function call, information about the call
4006 That information includes the location of the call in your program,
4007 the arguments of the call,
4008 and the local variables of the function being called.
4009 The information is saved in a block of data called a @dfn{stack frame}.
4010 The stack frames are allocated in a region of memory called the @dfn{call
4013 When your program stops, the @value{GDBN} commands for examining the
4014 stack allow you to see all of this information.
4016 @cindex selected frame
4017 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4018 @value{GDBN} commands refer implicitly to the selected frame. In
4019 particular, whenever you ask @value{GDBN} for the value of a variable in
4020 your program, the value is found in the selected frame. There are
4021 special @value{GDBN} commands to select whichever frame you are
4022 interested in. @xref{Selection, ,Selecting a frame}.
4024 When your program stops, @value{GDBN} automatically selects the
4025 currently executing frame and describes it briefly, similar to the
4026 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
4029 * Frames:: Stack frames
4030 * Backtrace:: Backtraces
4031 * Selection:: Selecting a frame
4032 * Frame Info:: Information on a frame
4037 @section Stack frames
4039 @cindex frame, definition
4041 The call stack is divided up into contiguous pieces called @dfn{stack
4042 frames}, or @dfn{frames} for short; each frame is the data associated
4043 with one call to one function. The frame contains the arguments given
4044 to the function, the function's local variables, and the address at
4045 which the function is executing.
4047 @cindex initial frame
4048 @cindex outermost frame
4049 @cindex innermost frame
4050 When your program is started, the stack has only one frame, that of the
4051 function @code{main}. This is called the @dfn{initial} frame or the
4052 @dfn{outermost} frame. Each time a function is called, a new frame is
4053 made. Each time a function returns, the frame for that function invocation
4054 is eliminated. If a function is recursive, there can be many frames for
4055 the same function. The frame for the function in which execution is
4056 actually occurring is called the @dfn{innermost} frame. This is the most
4057 recently created of all the stack frames that still exist.
4059 @cindex frame pointer
4060 Inside your program, stack frames are identified by their addresses. A
4061 stack frame consists of many bytes, each of which has its own address; each
4062 kind of computer has a convention for choosing one byte whose
4063 address serves as the address of the frame. Usually this address is kept
4064 in a register called the @dfn{frame pointer register} while execution is
4065 going on in that frame.
4067 @cindex frame number
4068 @value{GDBN} assigns numbers to all existing stack frames, starting with
4069 zero for the innermost frame, one for the frame that called it,
4070 and so on upward. These numbers do not really exist in your program;
4071 they are assigned by @value{GDBN} to give you a way of designating stack
4072 frames in @value{GDBN} commands.
4074 @c The -fomit-frame-pointer below perennially causes hbox overflow
4075 @c underflow problems.
4076 @cindex frameless execution
4077 Some compilers provide a way to compile functions so that they operate
4078 without stack frames. (For example, the @value{GCC} option
4080 @samp{-fomit-frame-pointer}
4082 generates functions without a frame.)
4083 This is occasionally done with heavily used library functions to save
4084 the frame setup time. @value{GDBN} has limited facilities for dealing
4085 with these function invocations. If the innermost function invocation
4086 has no stack frame, @value{GDBN} nevertheless regards it as though
4087 it had a separate frame, which is numbered zero as usual, allowing
4088 correct tracing of the function call chain. However, @value{GDBN} has
4089 no provision for frameless functions elsewhere in the stack.
4092 @kindex frame@r{, command}
4093 @cindex current stack frame
4094 @item frame @var{args}
4095 The @code{frame} command allows you to move from one stack frame to another,
4096 and to print the stack frame you select. @var{args} may be either the
4097 address of the frame or the stack frame number. Without an argument,
4098 @code{frame} prints the current stack frame.
4100 @kindex select-frame
4101 @cindex selecting frame silently
4103 The @code{select-frame} command allows you to move from one stack frame
4104 to another without printing the frame. This is the silent version of
4112 @cindex call stack traces
4113 A backtrace is a summary of how your program got where it is. It shows one
4114 line per frame, for many frames, starting with the currently executing
4115 frame (frame zero), followed by its caller (frame one), and on up the
4120 @kindex bt @r{(@code{backtrace})}
4123 Print a backtrace of the entire stack: one line per frame for all
4124 frames in the stack.
4126 You can stop the backtrace at any time by typing the system interrupt
4127 character, normally @kbd{C-c}.
4129 @item backtrace @var{n}
4131 Similar, but print only the innermost @var{n} frames.
4133 @item backtrace -@var{n}
4135 Similar, but print only the outermost @var{n} frames.
4140 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4141 are additional aliases for @code{backtrace}.
4143 Each line in the backtrace shows the frame number and the function name.
4144 The program counter value is also shown---unless you use @code{set
4145 print address off}. The backtrace also shows the source file name and
4146 line number, as well as the arguments to the function. The program
4147 counter value is omitted if it is at the beginning of the code for that
4150 Here is an example of a backtrace. It was made with the command
4151 @samp{bt 3}, so it shows the innermost three frames.
4155 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4157 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4158 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4160 (More stack frames follow...)
4165 The display for frame zero does not begin with a program counter
4166 value, indicating that your program has stopped at the beginning of the
4167 code for line @code{993} of @code{builtin.c}.
4169 @cindex backtrace beyond @code{main} function
4170 @cindex program entry point
4171 @cindex startup code, and backtrace
4172 Most programs have a standard user entry point---a place where system
4173 libraries and startup code transition into user code. For C this is
4174 @code{main}. When @value{GDBN} finds the entry function in a backtrace
4175 it will terminate the backtrace, to avoid tracing into highly
4176 system-specific (and generally uninteresting) code.
4178 If you need to examine the startup code, or limit the number of levels
4179 in a backtrace, you can change this behavior:
4182 @item set backtrace past-main
4183 @itemx set backtrace past-main on
4184 @kindex set backtrace
4185 Backtraces will continue past the user entry point.
4187 @item set backtrace past-main off
4188 Backtraces will stop when they encounter the user entry point. This is the
4191 @item show backtrace past-main
4192 @kindex show backtrace
4193 Display the current user entry point backtrace policy.
4195 @item set backtrace past-entry
4196 @itemx set backtrace past-entry on
4197 Backtraces will continue past the internal entry point of an application.
4198 This entry point is encoded by the linker when the application is built,
4199 and is likely before the user entry point @code{main} (or equivalent) is called.
4201 @item set backtrace past-entry off
4202 Backtraces will stop when they encouter the internal entry point of an
4203 application. This is the default.
4205 @item show backtrace past-entry
4206 Display the current internal entry point backtrace policy.
4208 @item set backtrace limit @var{n}
4209 @itemx set backtrace limit 0
4210 @cindex backtrace limit
4211 Limit the backtrace to @var{n} levels. A value of zero means
4214 @item show backtrace limit
4215 Display the current limit on backtrace levels.
4219 @section Selecting a frame
4221 Most commands for examining the stack and other data in your program work on
4222 whichever stack frame is selected at the moment. Here are the commands for
4223 selecting a stack frame; all of them finish by printing a brief description
4224 of the stack frame just selected.
4227 @kindex frame@r{, selecting}
4228 @kindex f @r{(@code{frame})}
4231 Select frame number @var{n}. Recall that frame zero is the innermost
4232 (currently executing) frame, frame one is the frame that called the
4233 innermost one, and so on. The highest-numbered frame is the one for
4236 @item frame @var{addr}
4238 Select the frame at address @var{addr}. This is useful mainly if the
4239 chaining of stack frames has been damaged by a bug, making it
4240 impossible for @value{GDBN} to assign numbers properly to all frames. In
4241 addition, this can be useful when your program has multiple stacks and
4242 switches between them.
4244 On the SPARC architecture, @code{frame} needs two addresses to
4245 select an arbitrary frame: a frame pointer and a stack pointer.
4247 On the MIPS and Alpha architecture, it needs two addresses: a stack
4248 pointer and a program counter.
4250 On the 29k architecture, it needs three addresses: a register stack
4251 pointer, a program counter, and a memory stack pointer.
4252 @c note to future updaters: this is conditioned on a flag
4253 @c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date
4254 @c as of 27 Jan 1994.
4258 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4259 advances toward the outermost frame, to higher frame numbers, to frames
4260 that have existed longer. @var{n} defaults to one.
4263 @kindex do @r{(@code{down})}
4265 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4266 advances toward the innermost frame, to lower frame numbers, to frames
4267 that were created more recently. @var{n} defaults to one. You may
4268 abbreviate @code{down} as @code{do}.
4271 All of these commands end by printing two lines of output describing the
4272 frame. The first line shows the frame number, the function name, the
4273 arguments, and the source file and line number of execution in that
4274 frame. The second line shows the text of that source line.
4282 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4284 10 read_input_file (argv[i]);
4288 After such a printout, the @code{list} command with no arguments
4289 prints ten lines centered on the point of execution in the frame.
4290 You can also edit the program at the point of execution with your favorite
4291 editing program by typing @code{edit}.
4292 @xref{List, ,Printing source lines},
4296 @kindex down-silently
4298 @item up-silently @var{n}
4299 @itemx down-silently @var{n}
4300 These two commands are variants of @code{up} and @code{down},
4301 respectively; they differ in that they do their work silently, without
4302 causing display of the new frame. They are intended primarily for use
4303 in @value{GDBN} command scripts, where the output might be unnecessary and
4308 @section Information about a frame
4310 There are several other commands to print information about the selected
4316 When used without any argument, this command does not change which
4317 frame is selected, but prints a brief description of the currently
4318 selected stack frame. It can be abbreviated @code{f}. With an
4319 argument, this command is used to select a stack frame.
4320 @xref{Selection, ,Selecting a frame}.
4323 @kindex info f @r{(@code{info frame})}
4326 This command prints a verbose description of the selected stack frame,
4331 the address of the frame
4333 the address of the next frame down (called by this frame)
4335 the address of the next frame up (caller of this frame)
4337 the language in which the source code corresponding to this frame is written
4339 the address of the frame's arguments
4341 the address of the frame's local variables
4343 the program counter saved in it (the address of execution in the caller frame)
4345 which registers were saved in the frame
4348 @noindent The verbose description is useful when
4349 something has gone wrong that has made the stack format fail to fit
4350 the usual conventions.
4352 @item info frame @var{addr}
4353 @itemx info f @var{addr}
4354 Print a verbose description of the frame at address @var{addr}, without
4355 selecting that frame. The selected frame remains unchanged by this
4356 command. This requires the same kind of address (more than one for some
4357 architectures) that you specify in the @code{frame} command.
4358 @xref{Selection, ,Selecting a frame}.
4362 Print the arguments of the selected frame, each on a separate line.
4366 Print the local variables of the selected frame, each on a separate
4367 line. These are all variables (declared either static or automatic)
4368 accessible at the point of execution of the selected frame.
4371 @cindex catch exceptions, list active handlers
4372 @cindex exception handlers, how to list
4374 Print a list of all the exception handlers that are active in the
4375 current stack frame at the current point of execution. To see other
4376 exception handlers, visit the associated frame (using the @code{up},
4377 @code{down}, or @code{frame} commands); then type @code{info catch}.
4378 @xref{Set Catchpoints, , Setting catchpoints}.
4384 @chapter Examining Source Files
4386 @value{GDBN} can print parts of your program's source, since the debugging
4387 information recorded in the program tells @value{GDBN} what source files were
4388 used to build it. When your program stops, @value{GDBN} spontaneously prints
4389 the line where it stopped. Likewise, when you select a stack frame
4390 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4391 execution in that frame has stopped. You can print other portions of
4392 source files by explicit command.
4394 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4395 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4396 @value{GDBN} under @sc{gnu} Emacs}.
4399 * List:: Printing source lines
4400 * Edit:: Editing source files
4401 * Search:: Searching source files
4402 * Source Path:: Specifying source directories
4403 * Machine Code:: Source and machine code
4407 @section Printing source lines
4410 @kindex l @r{(@code{list})}
4411 To print lines from a source file, use the @code{list} command
4412 (abbreviated @code{l}). By default, ten lines are printed.
4413 There are several ways to specify what part of the file you want to print.
4415 Here are the forms of the @code{list} command most commonly used:
4418 @item list @var{linenum}
4419 Print lines centered around line number @var{linenum} in the
4420 current source file.
4422 @item list @var{function}
4423 Print lines centered around the beginning of function
4427 Print more lines. If the last lines printed were printed with a
4428 @code{list} command, this prints lines following the last lines
4429 printed; however, if the last line printed was a solitary line printed
4430 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4431 Stack}), this prints lines centered around that line.
4434 Print lines just before the lines last printed.
4437 @cindex @code{list}, how many lines to display
4438 By default, @value{GDBN} prints ten source lines with any of these forms of
4439 the @code{list} command. You can change this using @code{set listsize}:
4442 @kindex set listsize
4443 @item set listsize @var{count}
4444 Make the @code{list} command display @var{count} source lines (unless
4445 the @code{list} argument explicitly specifies some other number).
4447 @kindex show listsize
4449 Display the number of lines that @code{list} prints.
4452 Repeating a @code{list} command with @key{RET} discards the argument,
4453 so it is equivalent to typing just @code{list}. This is more useful
4454 than listing the same lines again. An exception is made for an
4455 argument of @samp{-}; that argument is preserved in repetition so that
4456 each repetition moves up in the source file.
4459 In general, the @code{list} command expects you to supply zero, one or two
4460 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4461 of writing them, but the effect is always to specify some source line.
4462 Here is a complete description of the possible arguments for @code{list}:
4465 @item list @var{linespec}
4466 Print lines centered around the line specified by @var{linespec}.
4468 @item list @var{first},@var{last}
4469 Print lines from @var{first} to @var{last}. Both arguments are
4472 @item list ,@var{last}
4473 Print lines ending with @var{last}.
4475 @item list @var{first},
4476 Print lines starting with @var{first}.
4479 Print lines just after the lines last printed.
4482 Print lines just before the lines last printed.
4485 As described in the preceding table.
4488 Here are the ways of specifying a single source line---all the
4493 Specifies line @var{number} of the current source file.
4494 When a @code{list} command has two linespecs, this refers to
4495 the same source file as the first linespec.
4498 Specifies the line @var{offset} lines after the last line printed.
4499 When used as the second linespec in a @code{list} command that has
4500 two, this specifies the line @var{offset} lines down from the
4504 Specifies the line @var{offset} lines before the last line printed.
4506 @item @var{filename}:@var{number}
4507 Specifies line @var{number} in the source file @var{filename}.
4509 @item @var{function}
4510 Specifies the line that begins the body of the function @var{function}.
4511 For example: in C, this is the line with the open brace.
4513 @item @var{filename}:@var{function}
4514 Specifies the line of the open-brace that begins the body of the
4515 function @var{function} in the file @var{filename}. You only need the
4516 file name with a function name to avoid ambiguity when there are
4517 identically named functions in different source files.
4519 @item *@var{address}
4520 Specifies the line containing the program address @var{address}.
4521 @var{address} may be any expression.
4525 @section Editing source files
4526 @cindex editing source files
4529 @kindex e @r{(@code{edit})}
4530 To edit the lines in a source file, use the @code{edit} command.
4531 The editing program of your choice
4532 is invoked with the current line set to
4533 the active line in the program.
4534 Alternatively, there are several ways to specify what part of the file you
4535 want to print if you want to see other parts of the program.
4537 Here are the forms of the @code{edit} command most commonly used:
4541 Edit the current source file at the active line number in the program.
4543 @item edit @var{number}
4544 Edit the current source file with @var{number} as the active line number.
4546 @item edit @var{function}
4547 Edit the file containing @var{function} at the beginning of its definition.
4549 @item edit @var{filename}:@var{number}
4550 Specifies line @var{number} in the source file @var{filename}.
4552 @item edit @var{filename}:@var{function}
4553 Specifies the line that begins the body of the
4554 function @var{function} in the file @var{filename}. You only need the
4555 file name with a function name to avoid ambiguity when there are
4556 identically named functions in different source files.
4558 @item edit *@var{address}
4559 Specifies the line containing the program address @var{address}.
4560 @var{address} may be any expression.
4563 @subsection Choosing your editor
4564 You can customize @value{GDBN} to use any editor you want
4566 The only restriction is that your editor (say @code{ex}), recognizes the
4567 following command-line syntax:
4569 ex +@var{number} file
4571 The optional numeric value +@var{number} specifies the number of the line in
4572 the file where to start editing.}.
4573 By default, it is @file{@value{EDITOR}}, but you can change this
4574 by setting the environment variable @code{EDITOR} before using
4575 @value{GDBN}. For example, to configure @value{GDBN} to use the
4576 @code{vi} editor, you could use these commands with the @code{sh} shell:
4582 or in the @code{csh} shell,
4584 setenv EDITOR /usr/bin/vi
4589 @section Searching source files
4590 @cindex searching source files
4592 There are two commands for searching through the current source file for a
4597 @kindex forward-search
4598 @item forward-search @var{regexp}
4599 @itemx search @var{regexp}
4600 The command @samp{forward-search @var{regexp}} checks each line,
4601 starting with the one following the last line listed, for a match for
4602 @var{regexp}. It lists the line that is found. You can use the
4603 synonym @samp{search @var{regexp}} or abbreviate the command name as
4606 @kindex reverse-search
4607 @item reverse-search @var{regexp}
4608 The command @samp{reverse-search @var{regexp}} checks each line, starting
4609 with the one before the last line listed and going backward, for a match
4610 for @var{regexp}. It lists the line that is found. You can abbreviate
4611 this command as @code{rev}.
4615 @section Specifying source directories
4618 @cindex directories for source files
4619 Executable programs sometimes do not record the directories of the source
4620 files from which they were compiled, just the names. Even when they do,
4621 the directories could be moved between the compilation and your debugging
4622 session. @value{GDBN} has a list of directories to search for source files;
4623 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4624 it tries all the directories in the list, in the order they are present
4625 in the list, until it finds a file with the desired name.
4627 For example, suppose an executable references the file
4628 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
4629 @file{/mnt/cross}. The file is first looked up literally; if this
4630 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
4631 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
4632 message is printed. @value{GDBN} does not look up the parts of the
4633 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
4634 Likewise, the subdirectories of the source path are not searched: if
4635 the source path is @file{/mnt/cross}, and the binary refers to
4636 @file{foo.c}, @value{GDBN} would not find it under
4637 @file{/mnt/cross/usr/src/foo-1.0/lib}.
4639 Plain file names, relative file names with leading directories, file
4640 names containing dots, etc.@: are all treated as described above; for
4641 instance, if the source path is @file{/mnt/cross}, and the source file
4642 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
4643 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
4644 that---@file{/mnt/cross/foo.c}.
4646 Note that the executable search path is @emph{not} used to locate the
4647 source files. Neither is the current working directory, unless it
4648 happens to be in the source path.
4650 Whenever you reset or rearrange the source path, @value{GDBN} clears out
4651 any information it has cached about where source files are found and where
4652 each line is in the file.
4656 When you start @value{GDBN}, its source path includes only @samp{cdir}
4657 and @samp{cwd}, in that order.
4658 To add other directories, use the @code{directory} command.
4661 @item directory @var{dirname} @dots{}
4662 @item dir @var{dirname} @dots{}
4663 Add directory @var{dirname} to the front of the source path. Several
4664 directory names may be given to this command, separated by @samp{:}
4665 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4666 part of absolute file names) or
4667 whitespace. You may specify a directory that is already in the source
4668 path; this moves it forward, so @value{GDBN} searches it sooner.
4672 @vindex $cdir@r{, convenience variable}
4673 @vindex $cwdr@r{, convenience variable}
4674 @cindex compilation directory
4675 @cindex current directory
4676 @cindex working directory
4677 @cindex directory, current
4678 @cindex directory, compilation
4679 You can use the string @samp{$cdir} to refer to the compilation
4680 directory (if one is recorded), and @samp{$cwd} to refer to the current
4681 working directory. @samp{$cwd} is not the same as @samp{.}---the former
4682 tracks the current working directory as it changes during your @value{GDBN}
4683 session, while the latter is immediately expanded to the current
4684 directory at the time you add an entry to the source path.
4687 Reset the source path to empty again. This requires confirmation.
4689 @c RET-repeat for @code{directory} is explicitly disabled, but since
4690 @c repeating it would be a no-op we do not say that. (thanks to RMS)
4692 @item show directories
4693 @kindex show directories
4694 Print the source path: show which directories it contains.
4697 If your source path is cluttered with directories that are no longer of
4698 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4699 versions of source. You can correct the situation as follows:
4703 Use @code{directory} with no argument to reset the source path to empty.
4706 Use @code{directory} with suitable arguments to reinstall the
4707 directories you want in the source path. You can add all the
4708 directories in one command.
4712 @section Source and machine code
4713 @cindex source line and its code address
4715 You can use the command @code{info line} to map source lines to program
4716 addresses (and vice versa), and the command @code{disassemble} to display
4717 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
4718 mode, the @code{info line} command causes the arrow to point to the
4719 line specified. Also, @code{info line} prints addresses in symbolic form as
4724 @item info line @var{linespec}
4725 Print the starting and ending addresses of the compiled code for
4726 source line @var{linespec}. You can specify source lines in any of
4727 the ways understood by the @code{list} command (@pxref{List, ,Printing
4731 For example, we can use @code{info line} to discover the location of
4732 the object code for the first line of function
4733 @code{m4_changequote}:
4735 @c FIXME: I think this example should also show the addresses in
4736 @c symbolic form, as they usually would be displayed.
4738 (@value{GDBP}) info line m4_changequote
4739 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4743 @cindex code address and its source line
4744 We can also inquire (using @code{*@var{addr}} as the form for
4745 @var{linespec}) what source line covers a particular address:
4747 (@value{GDBP}) info line *0x63ff
4748 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4751 @cindex @code{$_} and @code{info line}
4752 @cindex @code{x} command, default address
4753 @kindex x@r{(examine), and} info line
4754 After @code{info line}, the default address for the @code{x} command
4755 is changed to the starting address of the line, so that @samp{x/i} is
4756 sufficient to begin examining the machine code (@pxref{Memory,
4757 ,Examining memory}). Also, this address is saved as the value of the
4758 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4763 @cindex assembly instructions
4764 @cindex instructions, assembly
4765 @cindex machine instructions
4766 @cindex listing machine instructions
4768 This specialized command dumps a range of memory as machine
4769 instructions. The default memory range is the function surrounding the
4770 program counter of the selected frame. A single argument to this
4771 command is a program counter value; @value{GDBN} dumps the function
4772 surrounding this value. Two arguments specify a range of addresses
4773 (first inclusive, second exclusive) to dump.
4776 The following example shows the disassembly of a range of addresses of
4777 HP PA-RISC 2.0 code:
4780 (@value{GDBP}) disas 0x32c4 0x32e4
4781 Dump of assembler code from 0x32c4 to 0x32e4:
4782 0x32c4 <main+204>: addil 0,dp
4783 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
4784 0x32cc <main+212>: ldil 0x3000,r31
4785 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
4786 0x32d4 <main+220>: ldo 0(r31),rp
4787 0x32d8 <main+224>: addil -0x800,dp
4788 0x32dc <main+228>: ldo 0x588(r1),r26
4789 0x32e0 <main+232>: ldil 0x3000,r31
4790 End of assembler dump.
4793 Some architectures have more than one commonly-used set of instruction
4794 mnemonics or other syntax.
4797 @kindex set disassembly-flavor
4798 @cindex Intel disassembly flavor
4799 @cindex AT&T disassembly flavor
4800 @item set disassembly-flavor @var{instruction-set}
4801 Select the instruction set to use when disassembling the
4802 program via the @code{disassemble} or @code{x/i} commands.
4804 Currently this command is only defined for the Intel x86 family. You
4805 can set @var{instruction-set} to either @code{intel} or @code{att}.
4806 The default is @code{att}, the AT&T flavor used by default by Unix
4807 assemblers for x86-based targets.
4809 @kindex show disassembly-flavor
4810 @item show disassembly-flavor
4811 Show the current setting of the disassembly flavor.
4816 @chapter Examining Data
4818 @cindex printing data
4819 @cindex examining data
4822 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
4823 @c document because it is nonstandard... Under Epoch it displays in a
4824 @c different window or something like that.
4825 The usual way to examine data in your program is with the @code{print}
4826 command (abbreviated @code{p}), or its synonym @code{inspect}. It
4827 evaluates and prints the value of an expression of the language your
4828 program is written in (@pxref{Languages, ,Using @value{GDBN} with
4829 Different Languages}).
4832 @item print @var{expr}
4833 @itemx print /@var{f} @var{expr}
4834 @var{expr} is an expression (in the source language). By default the
4835 value of @var{expr} is printed in a format appropriate to its data type;
4836 you can choose a different format by specifying @samp{/@var{f}}, where
4837 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
4841 @itemx print /@var{f}
4842 @cindex reprint the last value
4843 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
4844 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
4845 conveniently inspect the same value in an alternative format.
4848 A more low-level way of examining data is with the @code{x} command.
4849 It examines data in memory at a specified address and prints it in a
4850 specified format. @xref{Memory, ,Examining memory}.
4852 If you are interested in information about types, or about how the
4853 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
4854 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
4858 * Expressions:: Expressions
4859 * Variables:: Program variables
4860 * Arrays:: Artificial arrays
4861 * Output Formats:: Output formats
4862 * Memory:: Examining memory
4863 * Auto Display:: Automatic display
4864 * Print Settings:: Print settings
4865 * Value History:: Value history
4866 * Convenience Vars:: Convenience variables
4867 * Registers:: Registers
4868 * Floating Point Hardware:: Floating point hardware
4869 * Vector Unit:: Vector Unit
4870 * OS Information:: Auxiliary data provided by operating system
4871 * Memory Region Attributes:: Memory region attributes
4872 * Dump/Restore Files:: Copy between memory and a file
4873 * Core File Generation:: Cause a program dump its core
4874 * Character Sets:: Debugging programs that use a different
4875 character set than GDB does
4876 * Caching Remote Data:: Data caching for remote targets
4880 @section Expressions
4883 @code{print} and many other @value{GDBN} commands accept an expression and
4884 compute its value. Any kind of constant, variable or operator defined
4885 by the programming language you are using is valid in an expression in
4886 @value{GDBN}. This includes conditional expressions, function calls,
4887 casts, and string constants. It also includes preprocessor macros, if
4888 you compiled your program to include this information; see
4891 @cindex arrays in expressions
4892 @value{GDBN} supports array constants in expressions input by
4893 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
4894 you can use the command @code{print @{1, 2, 3@}} to build up an array in
4895 memory that is @code{malloc}ed in the target program.
4897 Because C is so widespread, most of the expressions shown in examples in
4898 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
4899 Languages}, for information on how to use expressions in other
4902 In this section, we discuss operators that you can use in @value{GDBN}
4903 expressions regardless of your programming language.
4905 @cindex casts, in expressions
4906 Casts are supported in all languages, not just in C, because it is so
4907 useful to cast a number into a pointer in order to examine a structure
4908 at that address in memory.
4909 @c FIXME: casts supported---Mod2 true?
4911 @value{GDBN} supports these operators, in addition to those common
4912 to programming languages:
4916 @samp{@@} is a binary operator for treating parts of memory as arrays.
4917 @xref{Arrays, ,Artificial arrays}, for more information.
4920 @samp{::} allows you to specify a variable in terms of the file or
4921 function where it is defined. @xref{Variables, ,Program variables}.
4923 @cindex @{@var{type}@}
4924 @cindex type casting memory
4925 @cindex memory, viewing as typed object
4926 @cindex casts, to view memory
4927 @item @{@var{type}@} @var{addr}
4928 Refers to an object of type @var{type} stored at address @var{addr} in
4929 memory. @var{addr} may be any expression whose value is an integer or
4930 pointer (but parentheses are required around binary operators, just as in
4931 a cast). This construct is allowed regardless of what kind of data is
4932 normally supposed to reside at @var{addr}.
4936 @section Program variables
4938 The most common kind of expression to use is the name of a variable
4941 Variables in expressions are understood in the selected stack frame
4942 (@pxref{Selection, ,Selecting a frame}); they must be either:
4946 global (or file-static)
4953 visible according to the scope rules of the
4954 programming language from the point of execution in that frame
4957 @noindent This means that in the function
4972 you can examine and use the variable @code{a} whenever your program is
4973 executing within the function @code{foo}, but you can only use or
4974 examine the variable @code{b} while your program is executing inside
4975 the block where @code{b} is declared.
4977 @cindex variable name conflict
4978 There is an exception: you can refer to a variable or function whose
4979 scope is a single source file even if the current execution point is not
4980 in this file. But it is possible to have more than one such variable or
4981 function with the same name (in different source files). If that
4982 happens, referring to that name has unpredictable effects. If you wish,
4983 you can specify a static variable in a particular function or file,
4984 using the colon-colon (@code{::}) notation:
4986 @cindex colon-colon, context for variables/functions
4988 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
4989 @cindex @code{::}, context for variables/functions
4992 @var{file}::@var{variable}
4993 @var{function}::@var{variable}
4997 Here @var{file} or @var{function} is the name of the context for the
4998 static @var{variable}. In the case of file names, you can use quotes to
4999 make sure @value{GDBN} parses the file name as a single word---for example,
5000 to print a global value of @code{x} defined in @file{f2.c}:
5003 (@value{GDBP}) p 'f2.c'::x
5006 @cindex C@t{++} scope resolution
5007 This use of @samp{::} is very rarely in conflict with the very similar
5008 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5009 scope resolution operator in @value{GDBN} expressions.
5010 @c FIXME: Um, so what happens in one of those rare cases where it's in
5013 @cindex wrong values
5014 @cindex variable values, wrong
5015 @cindex function entry/exit, wrong values of variables
5016 @cindex optimized code, wrong values of variables
5018 @emph{Warning:} Occasionally, a local variable may appear to have the
5019 wrong value at certain points in a function---just after entry to a new
5020 scope, and just before exit.
5022 You may see this problem when you are stepping by machine instructions.
5023 This is because, on most machines, it takes more than one instruction to
5024 set up a stack frame (including local variable definitions); if you are
5025 stepping by machine instructions, variables may appear to have the wrong
5026 values until the stack frame is completely built. On exit, it usually
5027 also takes more than one machine instruction to destroy a stack frame;
5028 after you begin stepping through that group of instructions, local
5029 variable definitions may be gone.
5031 This may also happen when the compiler does significant optimizations.
5032 To be sure of always seeing accurate values, turn off all optimization
5035 @cindex ``No symbol "foo" in current context''
5036 Another possible effect of compiler optimizations is to optimize
5037 unused variables out of existence, or assign variables to registers (as
5038 opposed to memory addresses). Depending on the support for such cases
5039 offered by the debug info format used by the compiler, @value{GDBN}
5040 might not be able to display values for such local variables. If that
5041 happens, @value{GDBN} will print a message like this:
5044 No symbol "foo" in current context.
5047 To solve such problems, either recompile without optimizations, or use a
5048 different debug info format, if the compiler supports several such
5049 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5050 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5051 produces debug info in a format that is superior to formats such as
5052 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5053 an effective form for debug info. @xref{Debugging Options,,Options
5054 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
5055 @xref{C, , Debugging C++}, for more info about debug info formats
5056 that are best suited to C@t{++} programs.
5059 @section Artificial arrays
5061 @cindex artificial array
5063 @kindex @@@r{, referencing memory as an array}
5064 It is often useful to print out several successive objects of the
5065 same type in memory; a section of an array, or an array of
5066 dynamically determined size for which only a pointer exists in the
5069 You can do this by referring to a contiguous span of memory as an
5070 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5071 operand of @samp{@@} should be the first element of the desired array
5072 and be an individual object. The right operand should be the desired length
5073 of the array. The result is an array value whose elements are all of
5074 the type of the left argument. The first element is actually the left
5075 argument; the second element comes from bytes of memory immediately
5076 following those that hold the first element, and so on. Here is an
5077 example. If a program says
5080 int *array = (int *) malloc (len * sizeof (int));
5084 you can print the contents of @code{array} with
5090 The left operand of @samp{@@} must reside in memory. Array values made
5091 with @samp{@@} in this way behave just like other arrays in terms of
5092 subscripting, and are coerced to pointers when used in expressions.
5093 Artificial arrays most often appear in expressions via the value history
5094 (@pxref{Value History, ,Value history}), after printing one out.
5096 Another way to create an artificial array is to use a cast.
5097 This re-interprets a value as if it were an array.
5098 The value need not be in memory:
5100 (@value{GDBP}) p/x (short[2])0x12345678
5101 $1 = @{0x1234, 0x5678@}
5104 As a convenience, if you leave the array length out (as in
5105 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5106 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5108 (@value{GDBP}) p/x (short[])0x12345678
5109 $2 = @{0x1234, 0x5678@}
5112 Sometimes the artificial array mechanism is not quite enough; in
5113 moderately complex data structures, the elements of interest may not
5114 actually be adjacent---for example, if you are interested in the values
5115 of pointers in an array. One useful work-around in this situation is
5116 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5117 variables}) as a counter in an expression that prints the first
5118 interesting value, and then repeat that expression via @key{RET}. For
5119 instance, suppose you have an array @code{dtab} of pointers to
5120 structures, and you are interested in the values of a field @code{fv}
5121 in each structure. Here is an example of what you might type:
5131 @node Output Formats
5132 @section Output formats
5134 @cindex formatted output
5135 @cindex output formats
5136 By default, @value{GDBN} prints a value according to its data type. Sometimes
5137 this is not what you want. For example, you might want to print a number
5138 in hex, or a pointer in decimal. Or you might want to view data in memory
5139 at a certain address as a character string or as an instruction. To do
5140 these things, specify an @dfn{output format} when you print a value.
5142 The simplest use of output formats is to say how to print a value
5143 already computed. This is done by starting the arguments of the
5144 @code{print} command with a slash and a format letter. The format
5145 letters supported are:
5149 Regard the bits of the value as an integer, and print the integer in
5153 Print as integer in signed decimal.
5156 Print as integer in unsigned decimal.
5159 Print as integer in octal.
5162 Print as integer in binary. The letter @samp{t} stands for ``two''.
5163 @footnote{@samp{b} cannot be used because these format letters are also
5164 used with the @code{x} command, where @samp{b} stands for ``byte'';
5165 see @ref{Memory,,Examining memory}.}
5168 @cindex unknown address, locating
5169 @cindex locate address
5170 Print as an address, both absolute in hexadecimal and as an offset from
5171 the nearest preceding symbol. You can use this format used to discover
5172 where (in what function) an unknown address is located:
5175 (@value{GDBP}) p/a 0x54320
5176 $3 = 0x54320 <_initialize_vx+396>
5180 The command @code{info symbol 0x54320} yields similar results.
5181 @xref{Symbols, info symbol}.
5184 Regard as an integer and print it as a character constant.
5187 Regard the bits of the value as a floating point number and print
5188 using typical floating point syntax.
5191 For example, to print the program counter in hex (@pxref{Registers}), type
5198 Note that no space is required before the slash; this is because command
5199 names in @value{GDBN} cannot contain a slash.
5201 To reprint the last value in the value history with a different format,
5202 you can use the @code{print} command with just a format and no
5203 expression. For example, @samp{p/x} reprints the last value in hex.
5206 @section Examining memory
5208 You can use the command @code{x} (for ``examine'') to examine memory in
5209 any of several formats, independently of your program's data types.
5211 @cindex examining memory
5213 @kindex x @r{(examine memory)}
5214 @item x/@var{nfu} @var{addr}
5217 Use the @code{x} command to examine memory.
5220 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5221 much memory to display and how to format it; @var{addr} is an
5222 expression giving the address where you want to start displaying memory.
5223 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5224 Several commands set convenient defaults for @var{addr}.
5227 @item @var{n}, the repeat count
5228 The repeat count is a decimal integer; the default is 1. It specifies
5229 how much memory (counting by units @var{u}) to display.
5230 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5233 @item @var{f}, the display format
5234 The display format is one of the formats used by @code{print},
5235 @samp{s} (null-terminated string), or @samp{i} (machine instruction).
5236 The default is @samp{x} (hexadecimal) initially.
5237 The default changes each time you use either @code{x} or @code{print}.
5239 @item @var{u}, the unit size
5240 The unit size is any of
5246 Halfwords (two bytes).
5248 Words (four bytes). This is the initial default.
5250 Giant words (eight bytes).
5253 Each time you specify a unit size with @code{x}, that size becomes the
5254 default unit the next time you use @code{x}. (For the @samp{s} and
5255 @samp{i} formats, the unit size is ignored and is normally not written.)
5257 @item @var{addr}, starting display address
5258 @var{addr} is the address where you want @value{GDBN} to begin displaying
5259 memory. The expression need not have a pointer value (though it may);
5260 it is always interpreted as an integer address of a byte of memory.
5261 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5262 @var{addr} is usually just after the last address examined---but several
5263 other commands also set the default address: @code{info breakpoints} (to
5264 the address of the last breakpoint listed), @code{info line} (to the
5265 starting address of a line), and @code{print} (if you use it to display
5266 a value from memory).
5269 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5270 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5271 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5272 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5273 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5275 Since the letters indicating unit sizes are all distinct from the
5276 letters specifying output formats, you do not have to remember whether
5277 unit size or format comes first; either order works. The output
5278 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5279 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5281 Even though the unit size @var{u} is ignored for the formats @samp{s}
5282 and @samp{i}, you might still want to use a count @var{n}; for example,
5283 @samp{3i} specifies that you want to see three machine instructions,
5284 including any operands. The command @code{disassemble} gives an
5285 alternative way of inspecting machine instructions; see @ref{Machine
5286 Code,,Source and machine code}.
5288 All the defaults for the arguments to @code{x} are designed to make it
5289 easy to continue scanning memory with minimal specifications each time
5290 you use @code{x}. For example, after you have inspected three machine
5291 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5292 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5293 the repeat count @var{n} is used again; the other arguments default as
5294 for successive uses of @code{x}.
5296 @cindex @code{$_}, @code{$__}, and value history
5297 The addresses and contents printed by the @code{x} command are not saved
5298 in the value history because there is often too much of them and they
5299 would get in the way. Instead, @value{GDBN} makes these values available for
5300 subsequent use in expressions as values of the convenience variables
5301 @code{$_} and @code{$__}. After an @code{x} command, the last address
5302 examined is available for use in expressions in the convenience variable
5303 @code{$_}. The contents of that address, as examined, are available in
5304 the convenience variable @code{$__}.
5306 If the @code{x} command has a repeat count, the address and contents saved
5307 are from the last memory unit printed; this is not the same as the last
5308 address printed if several units were printed on the last line of output.
5310 @cindex remote memory comparison
5311 @cindex verify remote memory image
5312 When you are debugging a program running on a remote target machine
5313 (@pxref{Remote}), you may wish to verify the program's image in the
5314 remote machine's memory against the executable file you downloaded to
5315 the target. The @code{compare-sections} command is provided for such
5319 @kindex compare-sections
5320 @item compare-sections @r{[}@var{section-name}@r{]}
5321 Compare the data of a loadable section @var{section-name} in the
5322 executable file of the program being debugged with the same section in
5323 the remote machine's memory, and report any mismatches. With no
5324 arguments, compares all loadable sections. This command's
5325 availability depends on the target's support for the @code{"qCRC"}
5330 @section Automatic display
5331 @cindex automatic display
5332 @cindex display of expressions
5334 If you find that you want to print the value of an expression frequently
5335 (to see how it changes), you might want to add it to the @dfn{automatic
5336 display list} so that @value{GDBN} prints its value each time your program stops.
5337 Each expression added to the list is given a number to identify it;
5338 to remove an expression from the list, you specify that number.
5339 The automatic display looks like this:
5343 3: bar[5] = (struct hack *) 0x3804
5347 This display shows item numbers, expressions and their current values. As with
5348 displays you request manually using @code{x} or @code{print}, you can
5349 specify the output format you prefer; in fact, @code{display} decides
5350 whether to use @code{print} or @code{x} depending on how elaborate your
5351 format specification is---it uses @code{x} if you specify a unit size,
5352 or one of the two formats (@samp{i} and @samp{s}) that are only
5353 supported by @code{x}; otherwise it uses @code{print}.
5357 @item display @var{expr}
5358 Add the expression @var{expr} to the list of expressions to display
5359 each time your program stops. @xref{Expressions, ,Expressions}.
5361 @code{display} does not repeat if you press @key{RET} again after using it.
5363 @item display/@var{fmt} @var{expr}
5364 For @var{fmt} specifying only a display format and not a size or
5365 count, add the expression @var{expr} to the auto-display list but
5366 arrange to display it each time in the specified format @var{fmt}.
5367 @xref{Output Formats,,Output formats}.
5369 @item display/@var{fmt} @var{addr}
5370 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5371 number of units, add the expression @var{addr} as a memory address to
5372 be examined each time your program stops. Examining means in effect
5373 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5376 For example, @samp{display/i $pc} can be helpful, to see the machine
5377 instruction about to be executed each time execution stops (@samp{$pc}
5378 is a common name for the program counter; @pxref{Registers, ,Registers}).
5381 @kindex delete display
5383 @item undisplay @var{dnums}@dots{}
5384 @itemx delete display @var{dnums}@dots{}
5385 Remove item numbers @var{dnums} from the list of expressions to display.
5387 @code{undisplay} does not repeat if you press @key{RET} after using it.
5388 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5390 @kindex disable display
5391 @item disable display @var{dnums}@dots{}
5392 Disable the display of item numbers @var{dnums}. A disabled display
5393 item is not printed automatically, but is not forgotten. It may be
5394 enabled again later.
5396 @kindex enable display
5397 @item enable display @var{dnums}@dots{}
5398 Enable display of item numbers @var{dnums}. It becomes effective once
5399 again in auto display of its expression, until you specify otherwise.
5402 Display the current values of the expressions on the list, just as is
5403 done when your program stops.
5405 @kindex info display
5407 Print the list of expressions previously set up to display
5408 automatically, each one with its item number, but without showing the
5409 values. This includes disabled expressions, which are marked as such.
5410 It also includes expressions which would not be displayed right now
5411 because they refer to automatic variables not currently available.
5414 @cindex display disabled out of scope
5415 If a display expression refers to local variables, then it does not make
5416 sense outside the lexical context for which it was set up. Such an
5417 expression is disabled when execution enters a context where one of its
5418 variables is not defined. For example, if you give the command
5419 @code{display last_char} while inside a function with an argument
5420 @code{last_char}, @value{GDBN} displays this argument while your program
5421 continues to stop inside that function. When it stops elsewhere---where
5422 there is no variable @code{last_char}---the display is disabled
5423 automatically. The next time your program stops where @code{last_char}
5424 is meaningful, you can enable the display expression once again.
5426 @node Print Settings
5427 @section Print settings
5429 @cindex format options
5430 @cindex print settings
5431 @value{GDBN} provides the following ways to control how arrays, structures,
5432 and symbols are printed.
5435 These settings are useful for debugging programs in any language:
5439 @item set print address
5440 @itemx set print address on
5441 @cindex print/don't print memory addresses
5442 @value{GDBN} prints memory addresses showing the location of stack
5443 traces, structure values, pointer values, breakpoints, and so forth,
5444 even when it also displays the contents of those addresses. The default
5445 is @code{on}. For example, this is what a stack frame display looks like with
5446 @code{set print address on}:
5451 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5453 530 if (lquote != def_lquote)
5457 @item set print address off
5458 Do not print addresses when displaying their contents. For example,
5459 this is the same stack frame displayed with @code{set print address off}:
5463 (@value{GDBP}) set print addr off
5465 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5466 530 if (lquote != def_lquote)
5470 You can use @samp{set print address off} to eliminate all machine
5471 dependent displays from the @value{GDBN} interface. For example, with
5472 @code{print address off}, you should get the same text for backtraces on
5473 all machines---whether or not they involve pointer arguments.
5476 @item show print address
5477 Show whether or not addresses are to be printed.
5480 When @value{GDBN} prints a symbolic address, it normally prints the
5481 closest earlier symbol plus an offset. If that symbol does not uniquely
5482 identify the address (for example, it is a name whose scope is a single
5483 source file), you may need to clarify. One way to do this is with
5484 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5485 you can set @value{GDBN} to print the source file and line number when
5486 it prints a symbolic address:
5489 @item set print symbol-filename on
5490 @cindex source file and line of a symbol
5491 @cindex symbol, source file and line
5492 Tell @value{GDBN} to print the source file name and line number of a
5493 symbol in the symbolic form of an address.
5495 @item set print symbol-filename off
5496 Do not print source file name and line number of a symbol. This is the
5499 @item show print symbol-filename
5500 Show whether or not @value{GDBN} will print the source file name and
5501 line number of a symbol in the symbolic form of an address.
5504 Another situation where it is helpful to show symbol filenames and line
5505 numbers is when disassembling code; @value{GDBN} shows you the line
5506 number and source file that corresponds to each instruction.
5508 Also, you may wish to see the symbolic form only if the address being
5509 printed is reasonably close to the closest earlier symbol:
5512 @item set print max-symbolic-offset @var{max-offset}
5513 @cindex maximum value for offset of closest symbol
5514 Tell @value{GDBN} to only display the symbolic form of an address if the
5515 offset between the closest earlier symbol and the address is less than
5516 @var{max-offset}. The default is 0, which tells @value{GDBN}
5517 to always print the symbolic form of an address if any symbol precedes it.
5519 @item show print max-symbolic-offset
5520 Ask how large the maximum offset is that @value{GDBN} prints in a
5524 @cindex wild pointer, interpreting
5525 @cindex pointer, finding referent
5526 If you have a pointer and you are not sure where it points, try
5527 @samp{set print symbol-filename on}. Then you can determine the name
5528 and source file location of the variable where it points, using
5529 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5530 For example, here @value{GDBN} shows that a variable @code{ptt} points
5531 at another variable @code{t}, defined in @file{hi2.c}:
5534 (@value{GDBP}) set print symbol-filename on
5535 (@value{GDBP}) p/a ptt
5536 $4 = 0xe008 <t in hi2.c>
5540 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5541 does not show the symbol name and filename of the referent, even with
5542 the appropriate @code{set print} options turned on.
5545 Other settings control how different kinds of objects are printed:
5548 @item set print array
5549 @itemx set print array on
5550 @cindex pretty print arrays
5551 Pretty print arrays. This format is more convenient to read,
5552 but uses more space. The default is off.
5554 @item set print array off
5555 Return to compressed format for arrays.
5557 @item show print array
5558 Show whether compressed or pretty format is selected for displaying
5561 @item set print elements @var{number-of-elements}
5562 @cindex number of array elements to print
5563 @cindex limit on number of printed array elements
5564 Set a limit on how many elements of an array @value{GDBN} will print.
5565 If @value{GDBN} is printing a large array, it stops printing after it has
5566 printed the number of elements set by the @code{set print elements} command.
5567 This limit also applies to the display of strings.
5568 When @value{GDBN} starts, this limit is set to 200.
5569 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5571 @item show print elements
5572 Display the number of elements of a large array that @value{GDBN} will print.
5573 If the number is 0, then the printing is unlimited.
5575 @item set print repeats
5576 @cindex repeated array elements
5577 Set the threshold for suppressing display of repeated array
5578 elelments. When the number of consecutive identical elements of an
5579 array exceeds the threshold, @value{GDBN} prints the string
5580 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
5581 identical repetitions, instead of displaying the identical elements
5582 themselves. Setting the threshold to zero will cause all elements to
5583 be individually printed. The default threshold is 10.
5585 @item show print repeats
5586 Display the current threshold for printing repeated identical
5589 @item set print null-stop
5590 @cindex @sc{null} elements in arrays
5591 Cause @value{GDBN} to stop printing the characters of an array when the first
5592 @sc{null} is encountered. This is useful when large arrays actually
5593 contain only short strings.
5596 @item show print null-stop
5597 Show whether @value{GDBN} stops printing an array on the first
5598 @sc{null} character.
5600 @item set print pretty on
5601 @cindex print structures in indented form
5602 @cindex indentation in structure display
5603 Cause @value{GDBN} to print structures in an indented format with one member
5604 per line, like this:
5619 @item set print pretty off
5620 Cause @value{GDBN} to print structures in a compact format, like this:
5624 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5625 meat = 0x54 "Pork"@}
5630 This is the default format.
5632 @item show print pretty
5633 Show which format @value{GDBN} is using to print structures.
5635 @item set print sevenbit-strings on
5636 @cindex eight-bit characters in strings
5637 @cindex octal escapes in strings
5638 Print using only seven-bit characters; if this option is set,
5639 @value{GDBN} displays any eight-bit characters (in strings or
5640 character values) using the notation @code{\}@var{nnn}. This setting is
5641 best if you are working in English (@sc{ascii}) and you use the
5642 high-order bit of characters as a marker or ``meta'' bit.
5644 @item set print sevenbit-strings off
5645 Print full eight-bit characters. This allows the use of more
5646 international character sets, and is the default.
5648 @item show print sevenbit-strings
5649 Show whether or not @value{GDBN} is printing only seven-bit characters.
5651 @item set print union on
5652 @cindex unions in structures, printing
5653 Tell @value{GDBN} to print unions which are contained in structures
5654 and other unions. This is the default setting.
5656 @item set print union off
5657 Tell @value{GDBN} not to print unions which are contained in
5658 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
5661 @item show print union
5662 Ask @value{GDBN} whether or not it will print unions which are contained in
5663 structures and other unions.
5665 For example, given the declarations
5668 typedef enum @{Tree, Bug@} Species;
5669 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5670 typedef enum @{Caterpillar, Cocoon, Butterfly@}
5681 struct thing foo = @{Tree, @{Acorn@}@};
5685 with @code{set print union on} in effect @samp{p foo} would print
5688 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5692 and with @code{set print union off} in effect it would print
5695 $1 = @{it = Tree, form = @{...@}@}
5699 @code{set print union} affects programs written in C-like languages
5705 These settings are of interest when debugging C@t{++} programs:
5708 @cindex demangling C@t{++} names
5709 @item set print demangle
5710 @itemx set print demangle on
5711 Print C@t{++} names in their source form rather than in the encoded
5712 (``mangled'') form passed to the assembler and linker for type-safe
5713 linkage. The default is on.
5715 @item show print demangle
5716 Show whether C@t{++} names are printed in mangled or demangled form.
5718 @item set print asm-demangle
5719 @itemx set print asm-demangle on
5720 Print C@t{++} names in their source form rather than their mangled form, even
5721 in assembler code printouts such as instruction disassemblies.
5724 @item show print asm-demangle
5725 Show whether C@t{++} names in assembly listings are printed in mangled
5728 @cindex C@t{++} symbol decoding style
5729 @cindex symbol decoding style, C@t{++}
5730 @kindex set demangle-style
5731 @item set demangle-style @var{style}
5732 Choose among several encoding schemes used by different compilers to
5733 represent C@t{++} names. The choices for @var{style} are currently:
5737 Allow @value{GDBN} to choose a decoding style by inspecting your program.
5740 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
5741 This is the default.
5744 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
5747 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
5750 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
5751 @strong{Warning:} this setting alone is not sufficient to allow
5752 debugging @code{cfront}-generated executables. @value{GDBN} would
5753 require further enhancement to permit that.
5756 If you omit @var{style}, you will see a list of possible formats.
5758 @item show demangle-style
5759 Display the encoding style currently in use for decoding C@t{++} symbols.
5761 @item set print object
5762 @itemx set print object on
5763 @cindex derived type of an object, printing
5764 @cindex display derived types
5765 When displaying a pointer to an object, identify the @emph{actual}
5766 (derived) type of the object rather than the @emph{declared} type, using
5767 the virtual function table.
5769 @item set print object off
5770 Display only the declared type of objects, without reference to the
5771 virtual function table. This is the default setting.
5773 @item show print object
5774 Show whether actual, or declared, object types are displayed.
5776 @item set print static-members
5777 @itemx set print static-members on
5778 @cindex static members of C@t{++} objects
5779 Print static members when displaying a C@t{++} object. The default is on.
5781 @item set print static-members off
5782 Do not print static members when displaying a C@t{++} object.
5784 @item show print static-members
5785 Show whether C@t{++} static members are printed or not.
5787 @item set print pascal_static-members
5788 @itemx set print pascal_static-members on
5789 @cindex static members of Pacal objects
5790 @cindex Pacal objects, static members display
5791 Print static members when displaying a Pascal object. The default is on.
5793 @item set print pascal_static-members off
5794 Do not print static members when displaying a Pascal object.
5796 @item show print pascal_static-members
5797 Show whether Pascal static members are printed or not.
5799 @c These don't work with HP ANSI C++ yet.
5800 @item set print vtbl
5801 @itemx set print vtbl on
5802 @cindex pretty print C@t{++} virtual function tables
5803 @cindex virtual functions (C@t{++}) display
5804 @cindex VTBL display
5805 Pretty print C@t{++} virtual function tables. The default is off.
5806 (The @code{vtbl} commands do not work on programs compiled with the HP
5807 ANSI C@t{++} compiler (@code{aCC}).)
5809 @item set print vtbl off
5810 Do not pretty print C@t{++} virtual function tables.
5812 @item show print vtbl
5813 Show whether C@t{++} virtual function tables are pretty printed, or not.
5817 @section Value history
5819 @cindex value history
5820 @cindex history of values printed by @value{GDBN}
5821 Values printed by the @code{print} command are saved in the @value{GDBN}
5822 @dfn{value history}. This allows you to refer to them in other expressions.
5823 Values are kept until the symbol table is re-read or discarded
5824 (for example with the @code{file} or @code{symbol-file} commands).
5825 When the symbol table changes, the value history is discarded,
5826 since the values may contain pointers back to the types defined in the
5831 @cindex history number
5832 The values printed are given @dfn{history numbers} by which you can
5833 refer to them. These are successive integers starting with one.
5834 @code{print} shows you the history number assigned to a value by
5835 printing @samp{$@var{num} = } before the value; here @var{num} is the
5838 To refer to any previous value, use @samp{$} followed by the value's
5839 history number. The way @code{print} labels its output is designed to
5840 remind you of this. Just @code{$} refers to the most recent value in
5841 the history, and @code{$$} refers to the value before that.
5842 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
5843 is the value just prior to @code{$$}, @code{$$1} is equivalent to
5844 @code{$$}, and @code{$$0} is equivalent to @code{$}.
5846 For example, suppose you have just printed a pointer to a structure and
5847 want to see the contents of the structure. It suffices to type
5853 If you have a chain of structures where the component @code{next} points
5854 to the next one, you can print the contents of the next one with this:
5861 You can print successive links in the chain by repeating this
5862 command---which you can do by just typing @key{RET}.
5864 Note that the history records values, not expressions. If the value of
5865 @code{x} is 4 and you type these commands:
5873 then the value recorded in the value history by the @code{print} command
5874 remains 4 even though the value of @code{x} has changed.
5879 Print the last ten values in the value history, with their item numbers.
5880 This is like @samp{p@ $$9} repeated ten times, except that @code{show
5881 values} does not change the history.
5883 @item show values @var{n}
5884 Print ten history values centered on history item number @var{n}.
5887 Print ten history values just after the values last printed. If no more
5888 values are available, @code{show values +} produces no display.
5891 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
5892 same effect as @samp{show values +}.
5894 @node Convenience Vars
5895 @section Convenience variables
5897 @cindex convenience variables
5898 @cindex user-defined variables
5899 @value{GDBN} provides @dfn{convenience variables} that you can use within
5900 @value{GDBN} to hold on to a value and refer to it later. These variables
5901 exist entirely within @value{GDBN}; they are not part of your program, and
5902 setting a convenience variable has no direct effect on further execution
5903 of your program. That is why you can use them freely.
5905 Convenience variables are prefixed with @samp{$}. Any name preceded by
5906 @samp{$} can be used for a convenience variable, unless it is one of
5907 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
5908 (Value history references, in contrast, are @emph{numbers} preceded
5909 by @samp{$}. @xref{Value History, ,Value history}.)
5911 You can save a value in a convenience variable with an assignment
5912 expression, just as you would set a variable in your program.
5916 set $foo = *object_ptr
5920 would save in @code{$foo} the value contained in the object pointed to by
5923 Using a convenience variable for the first time creates it, but its
5924 value is @code{void} until you assign a new value. You can alter the
5925 value with another assignment at any time.
5927 Convenience variables have no fixed types. You can assign a convenience
5928 variable any type of value, including structures and arrays, even if
5929 that variable already has a value of a different type. The convenience
5930 variable, when used as an expression, has the type of its current value.
5933 @kindex show convenience
5934 @cindex show all user variables
5935 @item show convenience
5936 Print a list of convenience variables used so far, and their values.
5937 Abbreviated @code{show conv}.
5940 One of the ways to use a convenience variable is as a counter to be
5941 incremented or a pointer to be advanced. For example, to print
5942 a field from successive elements of an array of structures:
5946 print bar[$i++]->contents
5950 Repeat that command by typing @key{RET}.
5952 Some convenience variables are created automatically by @value{GDBN} and given
5953 values likely to be useful.
5956 @vindex $_@r{, convenience variable}
5958 The variable @code{$_} is automatically set by the @code{x} command to
5959 the last address examined (@pxref{Memory, ,Examining memory}). Other
5960 commands which provide a default address for @code{x} to examine also
5961 set @code{$_} to that address; these commands include @code{info line}
5962 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
5963 except when set by the @code{x} command, in which case it is a pointer
5964 to the type of @code{$__}.
5966 @vindex $__@r{, convenience variable}
5968 The variable @code{$__} is automatically set by the @code{x} command
5969 to the value found in the last address examined. Its type is chosen
5970 to match the format in which the data was printed.
5973 @vindex $_exitcode@r{, convenience variable}
5974 The variable @code{$_exitcode} is automatically set to the exit code when
5975 the program being debugged terminates.
5978 On HP-UX systems, if you refer to a function or variable name that
5979 begins with a dollar sign, @value{GDBN} searches for a user or system
5980 name first, before it searches for a convenience variable.
5986 You can refer to machine register contents, in expressions, as variables
5987 with names starting with @samp{$}. The names of registers are different
5988 for each machine; use @code{info registers} to see the names used on
5992 @kindex info registers
5993 @item info registers
5994 Print the names and values of all registers except floating-point
5995 and vector registers (in the selected stack frame).
5997 @kindex info all-registers
5998 @cindex floating point registers
5999 @item info all-registers
6000 Print the names and values of all registers, including floating-point
6001 and vector registers (in the selected stack frame).
6003 @item info registers @var{regname} @dots{}
6004 Print the @dfn{relativized} value of each specified register @var{regname}.
6005 As discussed in detail below, register values are normally relative to
6006 the selected stack frame. @var{regname} may be any register name valid on
6007 the machine you are using, with or without the initial @samp{$}.
6010 @value{GDBN} has four ``standard'' register names that are available (in
6011 expressions) on most machines---whenever they do not conflict with an
6012 architecture's canonical mnemonics for registers. The register names
6013 @code{$pc} and @code{$sp} are used for the program counter register and
6014 the stack pointer. @code{$fp} is used for a register that contains a
6015 pointer to the current stack frame, and @code{$ps} is used for a
6016 register that contains the processor status. For example,
6017 you could print the program counter in hex with
6024 or print the instruction to be executed next with
6031 or add four to the stack pointer@footnote{This is a way of removing
6032 one word from the stack, on machines where stacks grow downward in
6033 memory (most machines, nowadays). This assumes that the innermost
6034 stack frame is selected; setting @code{$sp} is not allowed when other
6035 stack frames are selected. To pop entire frames off the stack,
6036 regardless of machine architecture, use @code{return};
6037 see @ref{Returning, ,Returning from a function}.} with
6043 Whenever possible, these four standard register names are available on
6044 your machine even though the machine has different canonical mnemonics,
6045 so long as there is no conflict. The @code{info registers} command
6046 shows the canonical names. For example, on the SPARC, @code{info
6047 registers} displays the processor status register as @code{$psr} but you
6048 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6049 is an alias for the @sc{eflags} register.
6051 @value{GDBN} always considers the contents of an ordinary register as an
6052 integer when the register is examined in this way. Some machines have
6053 special registers which can hold nothing but floating point; these
6054 registers are considered to have floating point values. There is no way
6055 to refer to the contents of an ordinary register as floating point value
6056 (although you can @emph{print} it as a floating point value with
6057 @samp{print/f $@var{regname}}).
6059 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6060 means that the data format in which the register contents are saved by
6061 the operating system is not the same one that your program normally
6062 sees. For example, the registers of the 68881 floating point
6063 coprocessor are always saved in ``extended'' (raw) format, but all C
6064 programs expect to work with ``double'' (virtual) format. In such
6065 cases, @value{GDBN} normally works with the virtual format only (the format
6066 that makes sense for your program), but the @code{info registers} command
6067 prints the data in both formats.
6069 Normally, register values are relative to the selected stack frame
6070 (@pxref{Selection, ,Selecting a frame}). This means that you get the
6071 value that the register would contain if all stack frames farther in
6072 were exited and their saved registers restored. In order to see the
6073 true contents of hardware registers, you must select the innermost
6074 frame (with @samp{frame 0}).
6076 However, @value{GDBN} must deduce where registers are saved, from the machine
6077 code generated by your compiler. If some registers are not saved, or if
6078 @value{GDBN} is unable to locate the saved registers, the selected stack
6079 frame makes no difference.
6081 @node Floating Point Hardware
6082 @section Floating point hardware
6083 @cindex floating point
6085 Depending on the configuration, @value{GDBN} may be able to give
6086 you more information about the status of the floating point hardware.
6091 Display hardware-dependent information about the floating
6092 point unit. The exact contents and layout vary depending on the
6093 floating point chip. Currently, @samp{info float} is supported on
6094 the ARM and x86 machines.
6098 @section Vector Unit
6101 Depending on the configuration, @value{GDBN} may be able to give you
6102 more information about the status of the vector unit.
6107 Display information about the vector unit. The exact contents and
6108 layout vary depending on the hardware.
6111 @node OS Information
6112 @section Operating system auxiliary information
6113 @cindex OS information
6115 @value{GDBN} provides interfaces to useful OS facilities that can help
6116 you debug your program.
6118 @cindex @code{ptrace} system call
6119 @cindex @code{struct user} contents
6120 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
6121 machines), it interfaces with the inferior via the @code{ptrace}
6122 system call. The operating system creates a special sata structure,
6123 called @code{struct user}, for this interface. You can use the
6124 command @code{info udot} to display the contents of this data
6130 Display the contents of the @code{struct user} maintained by the OS
6131 kernel for the program being debugged. @value{GDBN} displays the
6132 contents of @code{struct user} as a list of hex numbers, similar to
6133 the @code{examine} command.
6136 @cindex auxiliary vector
6137 @cindex vector, auxiliary
6138 Some operating systems supply an @dfn{auxiliary vector} to programs at
6139 startup. This is akin to the arguments and environment that you
6140 specify for a program, but contains a system-dependent variety of
6141 binary values that tell system libraries important details about the
6142 hardware, operating system, and process. Each value's purpose is
6143 identified by an integer tag; the meanings are well-known but system-specific.
6144 Depending on the configuration and operating system facilities,
6145 @value{GDBN} may be able to show you this information. For remote
6146 targets, this functionality may further depend on the remote stub's
6147 support of the @samp{qPart:auxv:read} packet, see @ref{Remote
6148 configuration, auxiliary vector}.
6153 Display the auxiliary vector of the inferior, which can be either a
6154 live process or a core dump file. @value{GDBN} prints each tag value
6155 numerically, and also shows names and text descriptions for recognized
6156 tags. Some values in the vector are numbers, some bit masks, and some
6157 pointers to strings or other data. @value{GDBN} displays each value in the
6158 most appropriate form for a recognized tag, and in hexadecimal for
6159 an unrecognized tag.
6163 @node Memory Region Attributes
6164 @section Memory region attributes
6165 @cindex memory region attributes
6167 @dfn{Memory region attributes} allow you to describe special handling
6168 required by regions of your target's memory. @value{GDBN} uses attributes
6169 to determine whether to allow certain types of memory accesses; whether to
6170 use specific width accesses; and whether to cache target memory.
6172 Defined memory regions can be individually enabled and disabled. When a
6173 memory region is disabled, @value{GDBN} uses the default attributes when
6174 accessing memory in that region. Similarly, if no memory regions have
6175 been defined, @value{GDBN} uses the default attributes when accessing
6178 When a memory region is defined, it is given a number to identify it;
6179 to enable, disable, or remove a memory region, you specify that number.
6183 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6184 Define a memory region bounded by @var{lower} and @var{upper} with
6185 attributes @var{attributes}@dots{}, and add it to the list of regions
6186 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
6187 case: it is treated as the the target's maximum memory address.
6188 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6191 @item delete mem @var{nums}@dots{}
6192 Remove memory regions @var{nums}@dots{} from the list of regions
6193 monitored by @value{GDBN}.
6196 @item disable mem @var{nums}@dots{}
6197 Disable monitoring of memory regions @var{nums}@dots{}.
6198 A disabled memory region is not forgotten.
6199 It may be enabled again later.
6202 @item enable mem @var{nums}@dots{}
6203 Enable monitoring of memory regions @var{nums}@dots{}.
6207 Print a table of all defined memory regions, with the following columns
6211 @item Memory Region Number
6212 @item Enabled or Disabled.
6213 Enabled memory regions are marked with @samp{y}.
6214 Disabled memory regions are marked with @samp{n}.
6217 The address defining the inclusive lower bound of the memory region.
6220 The address defining the exclusive upper bound of the memory region.
6223 The list of attributes set for this memory region.
6228 @subsection Attributes
6230 @subsubsection Memory Access Mode
6231 The access mode attributes set whether @value{GDBN} may make read or
6232 write accesses to a memory region.
6234 While these attributes prevent @value{GDBN} from performing invalid
6235 memory accesses, they do nothing to prevent the target system, I/O DMA,
6236 etc. from accessing memory.
6240 Memory is read only.
6242 Memory is write only.
6244 Memory is read/write. This is the default.
6247 @subsubsection Memory Access Size
6248 The acccess size attributes tells @value{GDBN} to use specific sized
6249 accesses in the memory region. Often memory mapped device registers
6250 require specific sized accesses. If no access size attribute is
6251 specified, @value{GDBN} may use accesses of any size.
6255 Use 8 bit memory accesses.
6257 Use 16 bit memory accesses.
6259 Use 32 bit memory accesses.
6261 Use 64 bit memory accesses.
6264 @c @subsubsection Hardware/Software Breakpoints
6265 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6266 @c will use hardware or software breakpoints for the internal breakpoints
6267 @c used by the step, next, finish, until, etc. commands.
6271 @c Always use hardware breakpoints
6272 @c @item swbreak (default)
6275 @subsubsection Data Cache
6276 The data cache attributes set whether @value{GDBN} will cache target
6277 memory. While this generally improves performance by reducing debug
6278 protocol overhead, it can lead to incorrect results because @value{GDBN}
6279 does not know about volatile variables or memory mapped device
6284 Enable @value{GDBN} to cache target memory.
6286 Disable @value{GDBN} from caching target memory. This is the default.
6289 @c @subsubsection Memory Write Verification
6290 @c The memory write verification attributes set whether @value{GDBN}
6291 @c will re-reads data after each write to verify the write was successful.
6295 @c @item noverify (default)
6298 @node Dump/Restore Files
6299 @section Copy between memory and a file
6300 @cindex dump/restore files
6301 @cindex append data to a file
6302 @cindex dump data to a file
6303 @cindex restore data from a file
6305 You can use the commands @code{dump}, @code{append}, and
6306 @code{restore} to copy data between target memory and a file. The
6307 @code{dump} and @code{append} commands write data to a file, and the
6308 @code{restore} command reads data from a file back into the inferior's
6309 memory. Files may be in binary, Motorola S-record, Intel hex, or
6310 Tektronix Hex format; however, @value{GDBN} can only append to binary
6316 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6317 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6318 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6319 or the value of @var{expr}, to @var{filename} in the given format.
6321 The @var{format} parameter may be any one of:
6328 Motorola S-record format.
6330 Tektronix Hex format.
6333 @value{GDBN} uses the same definitions of these formats as the
6334 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
6335 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
6339 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6340 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
6341 Append the contents of memory from @var{start_addr} to @var{end_addr},
6342 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
6343 (@value{GDBN} can only append data to files in raw binary form.)
6346 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
6347 Restore the contents of file @var{filename} into memory. The
6348 @code{restore} command can automatically recognize any known @sc{bfd}
6349 file format, except for raw binary. To restore a raw binary file you
6350 must specify the optional keyword @code{binary} after the filename.
6352 If @var{bias} is non-zero, its value will be added to the addresses
6353 contained in the file. Binary files always start at address zero, so
6354 they will be restored at address @var{bias}. Other bfd files have
6355 a built-in location; they will be restored at offset @var{bias}
6358 If @var{start} and/or @var{end} are non-zero, then only data between
6359 file offset @var{start} and file offset @var{end} will be restored.
6360 These offsets are relative to the addresses in the file, before
6361 the @var{bias} argument is applied.
6365 @node Core File Generation
6366 @section How to Produce a Core File from Your Program
6367 @cindex dump core from inferior
6369 A @dfn{core file} or @dfn{core dump} is a file that records the memory
6370 image of a running process and its process status (register values
6371 etc.). Its primary use is post-mortem debugging of a program that
6372 crashed while it ran outside a debugger. A program that crashes
6373 automatically produces a core file, unless this feature is disabled by
6374 the user. @xref{Files}, for information on invoking @value{GDBN} in
6375 the post-mortem debugging mode.
6377 Occasionally, you may wish to produce a core file of the program you
6378 are debugging in order to preserve a snapshot of its state.
6379 @value{GDBN} has a special command for that.
6383 @kindex generate-core-file
6384 @item generate-core-file [@var{file}]
6385 @itemx gcore [@var{file}]
6386 Produce a core dump of the inferior process. The optional argument
6387 @var{file} specifies the file name where to put the core dump. If not
6388 specified, the file name defaults to @file{core.@var{pid}}, where
6389 @var{pid} is the inferior process ID.
6391 Note that this command is implemented only for some systems (as of
6392 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
6395 @node Character Sets
6396 @section Character Sets
6397 @cindex character sets
6399 @cindex translating between character sets
6400 @cindex host character set
6401 @cindex target character set
6403 If the program you are debugging uses a different character set to
6404 represent characters and strings than the one @value{GDBN} uses itself,
6405 @value{GDBN} can automatically translate between the character sets for
6406 you. The character set @value{GDBN} uses we call the @dfn{host
6407 character set}; the one the inferior program uses we call the
6408 @dfn{target character set}.
6410 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
6411 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
6412 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
6413 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
6414 then the host character set is Latin-1, and the target character set is
6415 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
6416 target-charset EBCDIC-US}, then @value{GDBN} translates between
6417 @sc{ebcdic} and Latin 1 as you print character or string values, or use
6418 character and string literals in expressions.
6420 @value{GDBN} has no way to automatically recognize which character set
6421 the inferior program uses; you must tell it, using the @code{set
6422 target-charset} command, described below.
6424 Here are the commands for controlling @value{GDBN}'s character set
6428 @item set target-charset @var{charset}
6429 @kindex set target-charset
6430 Set the current target character set to @var{charset}. We list the
6431 character set names @value{GDBN} recognizes below, but if you type
6432 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6433 list the target character sets it supports.
6437 @item set host-charset @var{charset}
6438 @kindex set host-charset
6439 Set the current host character set to @var{charset}.
6441 By default, @value{GDBN} uses a host character set appropriate to the
6442 system it is running on; you can override that default using the
6443 @code{set host-charset} command.
6445 @value{GDBN} can only use certain character sets as its host character
6446 set. We list the character set names @value{GDBN} recognizes below, and
6447 indicate which can be host character sets, but if you type
6448 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6449 list the host character sets it supports.
6451 @item set charset @var{charset}
6453 Set the current host and target character sets to @var{charset}. As
6454 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
6455 @value{GDBN} will list the name of the character sets that can be used
6456 for both host and target.
6460 @kindex show charset
6461 Show the names of the current host and target charsets.
6463 @itemx show host-charset
6464 @kindex show host-charset
6465 Show the name of the current host charset.
6467 @itemx show target-charset
6468 @kindex show target-charset
6469 Show the name of the current target charset.
6473 @value{GDBN} currently includes support for the following character
6479 @cindex ASCII character set
6480 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6484 @cindex ISO 8859-1 character set
6485 @cindex ISO Latin 1 character set
6486 The ISO Latin 1 character set. This extends @sc{ascii} with accented
6487 characters needed for French, German, and Spanish. @value{GDBN} can use
6488 this as its host character set.
6492 @cindex EBCDIC character set
6493 @cindex IBM1047 character set
6494 Variants of the @sc{ebcdic} character set, used on some of IBM's
6495 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6496 @value{GDBN} cannot use these as its host character set.
6500 Note that these are all single-byte character sets. More work inside
6501 GDB is needed to support multi-byte or variable-width character
6502 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6504 Here is an example of @value{GDBN}'s character set support in action.
6505 Assume that the following source code has been placed in the file
6506 @file{charset-test.c}:
6512 = @{72, 101, 108, 108, 111, 44, 32, 119,
6513 111, 114, 108, 100, 33, 10, 0@};
6514 char ibm1047_hello[]
6515 = @{200, 133, 147, 147, 150, 107, 64, 166,
6516 150, 153, 147, 132, 90, 37, 0@};
6520 printf ("Hello, world!\n");
6524 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6525 containing the string @samp{Hello, world!} followed by a newline,
6526 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6528 We compile the program, and invoke the debugger on it:
6531 $ gcc -g charset-test.c -o charset-test
6532 $ gdb -nw charset-test
6533 GNU gdb 2001-12-19-cvs
6534 Copyright 2001 Free Software Foundation, Inc.
6539 We can use the @code{show charset} command to see what character sets
6540 @value{GDBN} is currently using to interpret and display characters and
6544 (@value{GDBP}) show charset
6545 The current host and target character set is `ISO-8859-1'.
6549 For the sake of printing this manual, let's use @sc{ascii} as our
6550 initial character set:
6552 (@value{GDBP}) set charset ASCII
6553 (@value{GDBP}) show charset
6554 The current host and target character set is `ASCII'.
6558 Let's assume that @sc{ascii} is indeed the correct character set for our
6559 host system --- in other words, let's assume that if @value{GDBN} prints
6560 characters using the @sc{ascii} character set, our terminal will display
6561 them properly. Since our current target character set is also
6562 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
6565 (@value{GDBP}) print ascii_hello
6566 $1 = 0x401698 "Hello, world!\n"
6567 (@value{GDBP}) print ascii_hello[0]
6572 @value{GDBN} uses the target character set for character and string
6573 literals you use in expressions:
6576 (@value{GDBP}) print '+'
6581 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
6584 @value{GDBN} relies on the user to tell it which character set the
6585 target program uses. If we print @code{ibm1047_hello} while our target
6586 character set is still @sc{ascii}, we get jibberish:
6589 (@value{GDBP}) print ibm1047_hello
6590 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
6591 (@value{GDBP}) print ibm1047_hello[0]
6596 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
6597 @value{GDBN} tells us the character sets it supports:
6600 (@value{GDBP}) set target-charset
6601 ASCII EBCDIC-US IBM1047 ISO-8859-1
6602 (@value{GDBP}) set target-charset
6605 We can select @sc{ibm1047} as our target character set, and examine the
6606 program's strings again. Now the @sc{ascii} string is wrong, but
6607 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
6608 target character set, @sc{ibm1047}, to the host character set,
6609 @sc{ascii}, and they display correctly:
6612 (@value{GDBP}) set target-charset IBM1047
6613 (@value{GDBP}) show charset
6614 The current host character set is `ASCII'.
6615 The current target character set is `IBM1047'.
6616 (@value{GDBP}) print ascii_hello
6617 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
6618 (@value{GDBP}) print ascii_hello[0]
6620 (@value{GDBP}) print ibm1047_hello
6621 $8 = 0x4016a8 "Hello, world!\n"
6622 (@value{GDBP}) print ibm1047_hello[0]
6627 As above, @value{GDBN} uses the target character set for character and
6628 string literals you use in expressions:
6631 (@value{GDBP}) print '+'
6636 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
6639 @node Caching Remote Data
6640 @section Caching Data of Remote Targets
6641 @cindex caching data of remote targets
6643 @value{GDBN} can cache data exchanged between the debugger and a
6644 remote target (@pxref{Remote}). Such caching generally improves
6645 performance, because it reduces the overhead of the remote protocol by
6646 bundling memory reads and writes into large chunks. Unfortunately,
6647 @value{GDBN} does not currently know anything about volatile
6648 registers, and thus data caching will produce incorrect results when
6649 volatile registers are in use.
6652 @kindex set remotecache
6653 @item set remotecache on
6654 @itemx set remotecache off
6655 Set caching state for remote targets. When @code{ON}, use data
6656 caching. By default, this option is @code{OFF}.
6658 @kindex show remotecache
6659 @item show remotecache
6660 Show the current state of data caching for remote targets.
6664 Print the information about the data cache performance. The
6665 information displayed includes: the dcache width and depth; and for
6666 each cache line, how many times it was referenced, and its data and
6667 state (dirty, bad, ok, etc.). This command is useful for debugging
6668 the data cache operation.
6673 @chapter C Preprocessor Macros
6675 Some languages, such as C and C@t{++}, provide a way to define and invoke
6676 ``preprocessor macros'' which expand into strings of tokens.
6677 @value{GDBN} can evaluate expressions containing macro invocations, show
6678 the result of macro expansion, and show a macro's definition, including
6679 where it was defined.
6681 You may need to compile your program specially to provide @value{GDBN}
6682 with information about preprocessor macros. Most compilers do not
6683 include macros in their debugging information, even when you compile
6684 with the @option{-g} flag. @xref{Compilation}.
6686 A program may define a macro at one point, remove that definition later,
6687 and then provide a different definition after that. Thus, at different
6688 points in the program, a macro may have different definitions, or have
6689 no definition at all. If there is a current stack frame, @value{GDBN}
6690 uses the macros in scope at that frame's source code line. Otherwise,
6691 @value{GDBN} uses the macros in scope at the current listing location;
6694 At the moment, @value{GDBN} does not support the @code{##}
6695 token-splicing operator, the @code{#} stringification operator, or
6696 variable-arity macros.
6698 Whenever @value{GDBN} evaluates an expression, it always expands any
6699 macro invocations present in the expression. @value{GDBN} also provides
6700 the following commands for working with macros explicitly.
6704 @kindex macro expand
6705 @cindex macro expansion, showing the results of preprocessor
6706 @cindex preprocessor macro expansion, showing the results of
6707 @cindex expanding preprocessor macros
6708 @item macro expand @var{expression}
6709 @itemx macro exp @var{expression}
6710 Show the results of expanding all preprocessor macro invocations in
6711 @var{expression}. Since @value{GDBN} simply expands macros, but does
6712 not parse the result, @var{expression} need not be a valid expression;
6713 it can be any string of tokens.
6716 @item macro expand-once @var{expression}
6717 @itemx macro exp1 @var{expression}
6718 @cindex expand macro once
6719 @i{(This command is not yet implemented.)} Show the results of
6720 expanding those preprocessor macro invocations that appear explicitly in
6721 @var{expression}. Macro invocations appearing in that expansion are
6722 left unchanged. This command allows you to see the effect of a
6723 particular macro more clearly, without being confused by further
6724 expansions. Since @value{GDBN} simply expands macros, but does not
6725 parse the result, @var{expression} need not be a valid expression; it
6726 can be any string of tokens.
6729 @cindex macro definition, showing
6730 @cindex definition, showing a macro's
6731 @item info macro @var{macro}
6732 Show the definition of the macro named @var{macro}, and describe the
6733 source location where that definition was established.
6735 @kindex macro define
6736 @cindex user-defined macros
6737 @cindex defining macros interactively
6738 @cindex macros, user-defined
6739 @item macro define @var{macro} @var{replacement-list}
6740 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
6741 @i{(This command is not yet implemented.)} Introduce a definition for a
6742 preprocessor macro named @var{macro}, invocations of which are replaced
6743 by the tokens given in @var{replacement-list}. The first form of this
6744 command defines an ``object-like'' macro, which takes no arguments; the
6745 second form defines a ``function-like'' macro, which takes the arguments
6746 given in @var{arglist}.
6748 A definition introduced by this command is in scope in every expression
6749 evaluated in @value{GDBN}, until it is removed with the @command{macro
6750 undef} command, described below. The definition overrides all
6751 definitions for @var{macro} present in the program being debugged, as
6752 well as any previous user-supplied definition.
6755 @item macro undef @var{macro}
6756 @i{(This command is not yet implemented.)} Remove any user-supplied
6757 definition for the macro named @var{macro}. This command only affects
6758 definitions provided with the @command{macro define} command, described
6759 above; it cannot remove definitions present in the program being
6764 @i{(This command is not yet implemented.)} List all the macros
6765 defined using the @code{macro define} command.
6768 @cindex macros, example of debugging with
6769 Here is a transcript showing the above commands in action. First, we
6770 show our source files:
6778 #define ADD(x) (M + x)
6783 printf ("Hello, world!\n");
6785 printf ("We're so creative.\n");
6787 printf ("Goodbye, world!\n");
6794 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
6795 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
6796 compiler includes information about preprocessor macros in the debugging
6800 $ gcc -gdwarf-2 -g3 sample.c -o sample
6804 Now, we start @value{GDBN} on our sample program:
6808 GNU gdb 2002-05-06-cvs
6809 Copyright 2002 Free Software Foundation, Inc.
6810 GDB is free software, @dots{}
6814 We can expand macros and examine their definitions, even when the
6815 program is not running. @value{GDBN} uses the current listing position
6816 to decide which macro definitions are in scope:
6819 (@value{GDBP}) list main
6822 5 #define ADD(x) (M + x)
6827 10 printf ("Hello, world!\n");
6829 12 printf ("We're so creative.\n");
6830 (@value{GDBP}) info macro ADD
6831 Defined at /home/jimb/gdb/macros/play/sample.c:5
6832 #define ADD(x) (M + x)
6833 (@value{GDBP}) info macro Q
6834 Defined at /home/jimb/gdb/macros/play/sample.h:1
6835 included at /home/jimb/gdb/macros/play/sample.c:2
6837 (@value{GDBP}) macro expand ADD(1)
6838 expands to: (42 + 1)
6839 (@value{GDBP}) macro expand-once ADD(1)
6840 expands to: once (M + 1)
6844 In the example above, note that @command{macro expand-once} expands only
6845 the macro invocation explicit in the original text --- the invocation of
6846 @code{ADD} --- but does not expand the invocation of the macro @code{M},
6847 which was introduced by @code{ADD}.
6849 Once the program is running, GDB uses the macro definitions in force at
6850 the source line of the current stack frame:
6853 (@value{GDBP}) break main
6854 Breakpoint 1 at 0x8048370: file sample.c, line 10.
6856 Starting program: /home/jimb/gdb/macros/play/sample
6858 Breakpoint 1, main () at sample.c:10
6859 10 printf ("Hello, world!\n");
6863 At line 10, the definition of the macro @code{N} at line 9 is in force:
6866 (@value{GDBP}) info macro N
6867 Defined at /home/jimb/gdb/macros/play/sample.c:9
6869 (@value{GDBP}) macro expand N Q M
6871 (@value{GDBP}) print N Q M
6876 As we step over directives that remove @code{N}'s definition, and then
6877 give it a new definition, @value{GDBN} finds the definition (or lack
6878 thereof) in force at each point:
6883 12 printf ("We're so creative.\n");
6884 (@value{GDBP}) info macro N
6885 The symbol `N' has no definition as a C/C++ preprocessor macro
6886 at /home/jimb/gdb/macros/play/sample.c:12
6889 14 printf ("Goodbye, world!\n");
6890 (@value{GDBP}) info macro N
6891 Defined at /home/jimb/gdb/macros/play/sample.c:13
6893 (@value{GDBP}) macro expand N Q M
6894 expands to: 1729 < 42
6895 (@value{GDBP}) print N Q M
6902 @chapter Tracepoints
6903 @c This chapter is based on the documentation written by Michael
6904 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
6907 In some applications, it is not feasible for the debugger to interrupt
6908 the program's execution long enough for the developer to learn
6909 anything helpful about its behavior. If the program's correctness
6910 depends on its real-time behavior, delays introduced by a debugger
6911 might cause the program to change its behavior drastically, or perhaps
6912 fail, even when the code itself is correct. It is useful to be able
6913 to observe the program's behavior without interrupting it.
6915 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
6916 specify locations in the program, called @dfn{tracepoints}, and
6917 arbitrary expressions to evaluate when those tracepoints are reached.
6918 Later, using the @code{tfind} command, you can examine the values
6919 those expressions had when the program hit the tracepoints. The
6920 expressions may also denote objects in memory---structures or arrays,
6921 for example---whose values @value{GDBN} should record; while visiting
6922 a particular tracepoint, you may inspect those objects as if they were
6923 in memory at that moment. However, because @value{GDBN} records these
6924 values without interacting with you, it can do so quickly and
6925 unobtrusively, hopefully not disturbing the program's behavior.
6927 The tracepoint facility is currently available only for remote
6928 targets. @xref{Targets}. In addition, your remote target must know how
6929 to collect trace data. This functionality is implemented in the remote
6930 stub; however, none of the stubs distributed with @value{GDBN} support
6931 tracepoints as of this writing.
6933 This chapter describes the tracepoint commands and features.
6937 * Analyze Collected Data::
6938 * Tracepoint Variables::
6941 @node Set Tracepoints
6942 @section Commands to Set Tracepoints
6944 Before running such a @dfn{trace experiment}, an arbitrary number of
6945 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
6946 tracepoint has a number assigned to it by @value{GDBN}. Like with
6947 breakpoints, tracepoint numbers are successive integers starting from
6948 one. Many of the commands associated with tracepoints take the
6949 tracepoint number as their argument, to identify which tracepoint to
6952 For each tracepoint, you can specify, in advance, some arbitrary set
6953 of data that you want the target to collect in the trace buffer when
6954 it hits that tracepoint. The collected data can include registers,
6955 local variables, or global data. Later, you can use @value{GDBN}
6956 commands to examine the values these data had at the time the
6959 This section describes commands to set tracepoints and associated
6960 conditions and actions.
6963 * Create and Delete Tracepoints::
6964 * Enable and Disable Tracepoints::
6965 * Tracepoint Passcounts::
6966 * Tracepoint Actions::
6967 * Listing Tracepoints::
6968 * Starting and Stopping Trace Experiment::
6971 @node Create and Delete Tracepoints
6972 @subsection Create and Delete Tracepoints
6975 @cindex set tracepoint
6978 The @code{trace} command is very similar to the @code{break} command.
6979 Its argument can be a source line, a function name, or an address in
6980 the target program. @xref{Set Breaks}. The @code{trace} command
6981 defines a tracepoint, which is a point in the target program where the
6982 debugger will briefly stop, collect some data, and then allow the
6983 program to continue. Setting a tracepoint or changing its commands
6984 doesn't take effect until the next @code{tstart} command; thus, you
6985 cannot change the tracepoint attributes once a trace experiment is
6988 Here are some examples of using the @code{trace} command:
6991 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
6993 (@value{GDBP}) @b{trace +2} // 2 lines forward
6995 (@value{GDBP}) @b{trace my_function} // first source line of function
6997 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
6999 (@value{GDBP}) @b{trace *0x2117c4} // an address
7003 You can abbreviate @code{trace} as @code{tr}.
7006 @cindex last tracepoint number
7007 @cindex recent tracepoint number
7008 @cindex tracepoint number
7009 The convenience variable @code{$tpnum} records the tracepoint number
7010 of the most recently set tracepoint.
7012 @kindex delete tracepoint
7013 @cindex tracepoint deletion
7014 @item delete tracepoint @r{[}@var{num}@r{]}
7015 Permanently delete one or more tracepoints. With no argument, the
7016 default is to delete all tracepoints.
7021 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
7023 (@value{GDBP}) @b{delete trace} // remove all tracepoints
7027 You can abbreviate this command as @code{del tr}.
7030 @node Enable and Disable Tracepoints
7031 @subsection Enable and Disable Tracepoints
7034 @kindex disable tracepoint
7035 @item disable tracepoint @r{[}@var{num}@r{]}
7036 Disable tracepoint @var{num}, or all tracepoints if no argument
7037 @var{num} is given. A disabled tracepoint will have no effect during
7038 the next trace experiment, but it is not forgotten. You can re-enable
7039 a disabled tracepoint using the @code{enable tracepoint} command.
7041 @kindex enable tracepoint
7042 @item enable tracepoint @r{[}@var{num}@r{]}
7043 Enable tracepoint @var{num}, or all tracepoints. The enabled
7044 tracepoints will become effective the next time a trace experiment is
7048 @node Tracepoint Passcounts
7049 @subsection Tracepoint Passcounts
7053 @cindex tracepoint pass count
7054 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
7055 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
7056 automatically stop a trace experiment. If a tracepoint's passcount is
7057 @var{n}, then the trace experiment will be automatically stopped on
7058 the @var{n}'th time that tracepoint is hit. If the tracepoint number
7059 @var{num} is not specified, the @code{passcount} command sets the
7060 passcount of the most recently defined tracepoint. If no passcount is
7061 given, the trace experiment will run until stopped explicitly by the
7067 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
7068 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
7070 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
7071 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
7072 (@value{GDBP}) @b{trace foo}
7073 (@value{GDBP}) @b{pass 3}
7074 (@value{GDBP}) @b{trace bar}
7075 (@value{GDBP}) @b{pass 2}
7076 (@value{GDBP}) @b{trace baz}
7077 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
7078 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
7079 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
7080 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
7084 @node Tracepoint Actions
7085 @subsection Tracepoint Action Lists
7089 @cindex tracepoint actions
7090 @item actions @r{[}@var{num}@r{]}
7091 This command will prompt for a list of actions to be taken when the
7092 tracepoint is hit. If the tracepoint number @var{num} is not
7093 specified, this command sets the actions for the one that was most
7094 recently defined (so that you can define a tracepoint and then say
7095 @code{actions} without bothering about its number). You specify the
7096 actions themselves on the following lines, one action at a time, and
7097 terminate the actions list with a line containing just @code{end}. So
7098 far, the only defined actions are @code{collect} and
7099 @code{while-stepping}.
7101 @cindex remove actions from a tracepoint
7102 To remove all actions from a tracepoint, type @samp{actions @var{num}}
7103 and follow it immediately with @samp{end}.
7106 (@value{GDBP}) @b{collect @var{data}} // collect some data
7108 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
7110 (@value{GDBP}) @b{end} // signals the end of actions.
7113 In the following example, the action list begins with @code{collect}
7114 commands indicating the things to be collected when the tracepoint is
7115 hit. Then, in order to single-step and collect additional data
7116 following the tracepoint, a @code{while-stepping} command is used,
7117 followed by the list of things to be collected while stepping. The
7118 @code{while-stepping} command is terminated by its own separate
7119 @code{end} command. Lastly, the action list is terminated by an
7123 (@value{GDBP}) @b{trace foo}
7124 (@value{GDBP}) @b{actions}
7125 Enter actions for tracepoint 1, one per line:
7134 @kindex collect @r{(tracepoints)}
7135 @item collect @var{expr1}, @var{expr2}, @dots{}
7136 Collect values of the given expressions when the tracepoint is hit.
7137 This command accepts a comma-separated list of any valid expressions.
7138 In addition to global, static, or local variables, the following
7139 special arguments are supported:
7143 collect all registers
7146 collect all function arguments
7149 collect all local variables.
7152 You can give several consecutive @code{collect} commands, each one
7153 with a single argument, or one @code{collect} command with several
7154 arguments separated by commas: the effect is the same.
7156 The command @code{info scope} (@pxref{Symbols, info scope}) is
7157 particularly useful for figuring out what data to collect.
7159 @kindex while-stepping @r{(tracepoints)}
7160 @item while-stepping @var{n}
7161 Perform @var{n} single-step traces after the tracepoint, collecting
7162 new data at each step. The @code{while-stepping} command is
7163 followed by the list of what to collect while stepping (followed by
7164 its own @code{end} command):
7168 > collect $regs, myglobal
7174 You may abbreviate @code{while-stepping} as @code{ws} or
7178 @node Listing Tracepoints
7179 @subsection Listing Tracepoints
7182 @kindex info tracepoints
7184 @cindex information about tracepoints
7185 @item info tracepoints @r{[}@var{num}@r{]}
7186 Display information about the tracepoint @var{num}. If you don't specify
7187 a tracepoint number, displays information about all the tracepoints
7188 defined so far. For each tracepoint, the following information is
7195 whether it is enabled or disabled
7199 its passcount as given by the @code{passcount @var{n}} command
7201 its step count as given by the @code{while-stepping @var{n}} command
7203 where in the source files is the tracepoint set
7205 its action list as given by the @code{actions} command
7209 (@value{GDBP}) @b{info trace}
7210 Num Enb Address PassC StepC What
7211 1 y 0x002117c4 0 0 <gdb_asm>
7212 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
7213 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
7218 This command can be abbreviated @code{info tp}.
7221 @node Starting and Stopping Trace Experiment
7222 @subsection Starting and Stopping Trace Experiment
7226 @cindex start a new trace experiment
7227 @cindex collected data discarded
7229 This command takes no arguments. It starts the trace experiment, and
7230 begins collecting data. This has the side effect of discarding all
7231 the data collected in the trace buffer during the previous trace
7235 @cindex stop a running trace experiment
7237 This command takes no arguments. It ends the trace experiment, and
7238 stops collecting data.
7240 @strong{Note}: a trace experiment and data collection may stop
7241 automatically if any tracepoint's passcount is reached
7242 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
7245 @cindex status of trace data collection
7246 @cindex trace experiment, status of
7248 This command displays the status of the current trace data
7252 Here is an example of the commands we described so far:
7255 (@value{GDBP}) @b{trace gdb_c_test}
7256 (@value{GDBP}) @b{actions}
7257 Enter actions for tracepoint #1, one per line.
7258 > collect $regs,$locals,$args
7263 (@value{GDBP}) @b{tstart}
7264 [time passes @dots{}]
7265 (@value{GDBP}) @b{tstop}
7269 @node Analyze Collected Data
7270 @section Using the collected data
7272 After the tracepoint experiment ends, you use @value{GDBN} commands
7273 for examining the trace data. The basic idea is that each tracepoint
7274 collects a trace @dfn{snapshot} every time it is hit and another
7275 snapshot every time it single-steps. All these snapshots are
7276 consecutively numbered from zero and go into a buffer, and you can
7277 examine them later. The way you examine them is to @dfn{focus} on a
7278 specific trace snapshot. When the remote stub is focused on a trace
7279 snapshot, it will respond to all @value{GDBN} requests for memory and
7280 registers by reading from the buffer which belongs to that snapshot,
7281 rather than from @emph{real} memory or registers of the program being
7282 debugged. This means that @strong{all} @value{GDBN} commands
7283 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
7284 behave as if we were currently debugging the program state as it was
7285 when the tracepoint occurred. Any requests for data that are not in
7286 the buffer will fail.
7289 * tfind:: How to select a trace snapshot
7290 * tdump:: How to display all data for a snapshot
7291 * save-tracepoints:: How to save tracepoints for a future run
7295 @subsection @code{tfind @var{n}}
7298 @cindex select trace snapshot
7299 @cindex find trace snapshot
7300 The basic command for selecting a trace snapshot from the buffer is
7301 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
7302 counting from zero. If no argument @var{n} is given, the next
7303 snapshot is selected.
7305 Here are the various forms of using the @code{tfind} command.
7309 Find the first snapshot in the buffer. This is a synonym for
7310 @code{tfind 0} (since 0 is the number of the first snapshot).
7313 Stop debugging trace snapshots, resume @emph{live} debugging.
7316 Same as @samp{tfind none}.
7319 No argument means find the next trace snapshot.
7322 Find the previous trace snapshot before the current one. This permits
7323 retracing earlier steps.
7325 @item tfind tracepoint @var{num}
7326 Find the next snapshot associated with tracepoint @var{num}. Search
7327 proceeds forward from the last examined trace snapshot. If no
7328 argument @var{num} is given, it means find the next snapshot collected
7329 for the same tracepoint as the current snapshot.
7331 @item tfind pc @var{addr}
7332 Find the next snapshot associated with the value @var{addr} of the
7333 program counter. Search proceeds forward from the last examined trace
7334 snapshot. If no argument @var{addr} is given, it means find the next
7335 snapshot with the same value of PC as the current snapshot.
7337 @item tfind outside @var{addr1}, @var{addr2}
7338 Find the next snapshot whose PC is outside the given range of
7341 @item tfind range @var{addr1}, @var{addr2}
7342 Find the next snapshot whose PC is between @var{addr1} and
7343 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
7345 @item tfind line @r{[}@var{file}:@r{]}@var{n}
7346 Find the next snapshot associated with the source line @var{n}. If
7347 the optional argument @var{file} is given, refer to line @var{n} in
7348 that source file. Search proceeds forward from the last examined
7349 trace snapshot. If no argument @var{n} is given, it means find the
7350 next line other than the one currently being examined; thus saying
7351 @code{tfind line} repeatedly can appear to have the same effect as
7352 stepping from line to line in a @emph{live} debugging session.
7355 The default arguments for the @code{tfind} commands are specifically
7356 designed to make it easy to scan through the trace buffer. For
7357 instance, @code{tfind} with no argument selects the next trace
7358 snapshot, and @code{tfind -} with no argument selects the previous
7359 trace snapshot. So, by giving one @code{tfind} command, and then
7360 simply hitting @key{RET} repeatedly you can examine all the trace
7361 snapshots in order. Or, by saying @code{tfind -} and then hitting
7362 @key{RET} repeatedly you can examine the snapshots in reverse order.
7363 The @code{tfind line} command with no argument selects the snapshot
7364 for the next source line executed. The @code{tfind pc} command with
7365 no argument selects the next snapshot with the same program counter
7366 (PC) as the current frame. The @code{tfind tracepoint} command with
7367 no argument selects the next trace snapshot collected by the same
7368 tracepoint as the current one.
7370 In addition to letting you scan through the trace buffer manually,
7371 these commands make it easy to construct @value{GDBN} scripts that
7372 scan through the trace buffer and print out whatever collected data
7373 you are interested in. Thus, if we want to examine the PC, FP, and SP
7374 registers from each trace frame in the buffer, we can say this:
7377 (@value{GDBP}) @b{tfind start}
7378 (@value{GDBP}) @b{while ($trace_frame != -1)}
7379 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
7380 $trace_frame, $pc, $sp, $fp
7384 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
7385 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
7386 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
7387 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
7388 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
7389 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
7390 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
7391 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
7392 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
7393 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
7394 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
7397 Or, if we want to examine the variable @code{X} at each source line in
7401 (@value{GDBP}) @b{tfind start}
7402 (@value{GDBP}) @b{while ($trace_frame != -1)}
7403 > printf "Frame %d, X == %d\n", $trace_frame, X
7413 @subsection @code{tdump}
7415 @cindex dump all data collected at tracepoint
7416 @cindex tracepoint data, display
7418 This command takes no arguments. It prints all the data collected at
7419 the current trace snapshot.
7422 (@value{GDBP}) @b{trace 444}
7423 (@value{GDBP}) @b{actions}
7424 Enter actions for tracepoint #2, one per line:
7425 > collect $regs, $locals, $args, gdb_long_test
7428 (@value{GDBP}) @b{tstart}
7430 (@value{GDBP}) @b{tfind line 444}
7431 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
7433 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
7435 (@value{GDBP}) @b{tdump}
7436 Data collected at tracepoint 2, trace frame 1:
7437 d0 0xc4aa0085 -995491707
7441 d4 0x71aea3d 119204413
7446 a1 0x3000668 50333288
7449 a4 0x3000698 50333336
7451 fp 0x30bf3c 0x30bf3c
7452 sp 0x30bf34 0x30bf34
7454 pc 0x20b2c8 0x20b2c8
7458 p = 0x20e5b4 "gdb-test"
7465 gdb_long_test = 17 '\021'
7470 @node save-tracepoints
7471 @subsection @code{save-tracepoints @var{filename}}
7472 @kindex save-tracepoints
7473 @cindex save tracepoints for future sessions
7475 This command saves all current tracepoint definitions together with
7476 their actions and passcounts, into a file @file{@var{filename}}
7477 suitable for use in a later debugging session. To read the saved
7478 tracepoint definitions, use the @code{source} command (@pxref{Command
7481 @node Tracepoint Variables
7482 @section Convenience Variables for Tracepoints
7483 @cindex tracepoint variables
7484 @cindex convenience variables for tracepoints
7487 @vindex $trace_frame
7488 @item (int) $trace_frame
7489 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
7490 snapshot is selected.
7493 @item (int) $tracepoint
7494 The tracepoint for the current trace snapshot.
7497 @item (int) $trace_line
7498 The line number for the current trace snapshot.
7501 @item (char []) $trace_file
7502 The source file for the current trace snapshot.
7505 @item (char []) $trace_func
7506 The name of the function containing @code{$tracepoint}.
7509 Note: @code{$trace_file} is not suitable for use in @code{printf},
7510 use @code{output} instead.
7512 Here's a simple example of using these convenience variables for
7513 stepping through all the trace snapshots and printing some of their
7517 (@value{GDBP}) @b{tfind start}
7519 (@value{GDBP}) @b{while $trace_frame != -1}
7520 > output $trace_file
7521 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7527 @chapter Debugging Programs That Use Overlays
7530 If your program is too large to fit completely in your target system's
7531 memory, you can sometimes use @dfn{overlays} to work around this
7532 problem. @value{GDBN} provides some support for debugging programs that
7536 * How Overlays Work:: A general explanation of overlays.
7537 * Overlay Commands:: Managing overlays in @value{GDBN}.
7538 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7539 mapped by asking the inferior.
7540 * Overlay Sample Program:: A sample program using overlays.
7543 @node How Overlays Work
7544 @section How Overlays Work
7545 @cindex mapped overlays
7546 @cindex unmapped overlays
7547 @cindex load address, overlay's
7548 @cindex mapped address
7549 @cindex overlay area
7551 Suppose you have a computer whose instruction address space is only 64
7552 kilobytes long, but which has much more memory which can be accessed by
7553 other means: special instructions, segment registers, or memory
7554 management hardware, for example. Suppose further that you want to
7555 adapt a program which is larger than 64 kilobytes to run on this system.
7557 One solution is to identify modules of your program which are relatively
7558 independent, and need not call each other directly; call these modules
7559 @dfn{overlays}. Separate the overlays from the main program, and place
7560 their machine code in the larger memory. Place your main program in
7561 instruction memory, but leave at least enough space there to hold the
7562 largest overlay as well.
7564 Now, to call a function located in an overlay, you must first copy that
7565 overlay's machine code from the large memory into the space set aside
7566 for it in the instruction memory, and then jump to its entry point
7569 @c NB: In the below the mapped area's size is greater or equal to the
7570 @c size of all overlays. This is intentional to remind the developer
7571 @c that overlays don't necessarily need to be the same size.
7575 Data Instruction Larger
7576 Address Space Address Space Address Space
7577 +-----------+ +-----------+ +-----------+
7579 +-----------+ +-----------+ +-----------+<-- overlay 1
7580 | program | | main | .----| overlay 1 | load address
7581 | variables | | program | | +-----------+
7582 | and heap | | | | | |
7583 +-----------+ | | | +-----------+<-- overlay 2
7584 | | +-----------+ | | | load address
7585 +-----------+ | | | .-| overlay 2 |
7587 mapped --->+-----------+ | | +-----------+
7589 | overlay | <-' | | |
7590 | area | <---' +-----------+<-- overlay 3
7591 | | <---. | | load address
7592 +-----------+ `--| overlay 3 |
7599 @anchor{A code overlay}A code overlay
7603 The diagram (@pxref{A code overlay}) shows a system with separate data
7604 and instruction address spaces. To map an overlay, the program copies
7605 its code from the larger address space to the instruction address space.
7606 Since the overlays shown here all use the same mapped address, only one
7607 may be mapped at a time. For a system with a single address space for
7608 data and instructions, the diagram would be similar, except that the
7609 program variables and heap would share an address space with the main
7610 program and the overlay area.
7612 An overlay loaded into instruction memory and ready for use is called a
7613 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
7614 instruction memory. An overlay not present (or only partially present)
7615 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
7616 is its address in the larger memory. The mapped address is also called
7617 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
7618 called the @dfn{load memory address}, or @dfn{LMA}.
7620 Unfortunately, overlays are not a completely transparent way to adapt a
7621 program to limited instruction memory. They introduce a new set of
7622 global constraints you must keep in mind as you design your program:
7627 Before calling or returning to a function in an overlay, your program
7628 must make sure that overlay is actually mapped. Otherwise, the call or
7629 return will transfer control to the right address, but in the wrong
7630 overlay, and your program will probably crash.
7633 If the process of mapping an overlay is expensive on your system, you
7634 will need to choose your overlays carefully to minimize their effect on
7635 your program's performance.
7638 The executable file you load onto your system must contain each
7639 overlay's instructions, appearing at the overlay's load address, not its
7640 mapped address. However, each overlay's instructions must be relocated
7641 and its symbols defined as if the overlay were at its mapped address.
7642 You can use GNU linker scripts to specify different load and relocation
7643 addresses for pieces of your program; see @ref{Overlay Description,,,
7644 ld.info, Using ld: the GNU linker}.
7647 The procedure for loading executable files onto your system must be able
7648 to load their contents into the larger address space as well as the
7649 instruction and data spaces.
7653 The overlay system described above is rather simple, and could be
7654 improved in many ways:
7659 If your system has suitable bank switch registers or memory management
7660 hardware, you could use those facilities to make an overlay's load area
7661 contents simply appear at their mapped address in instruction space.
7662 This would probably be faster than copying the overlay to its mapped
7663 area in the usual way.
7666 If your overlays are small enough, you could set aside more than one
7667 overlay area, and have more than one overlay mapped at a time.
7670 You can use overlays to manage data, as well as instructions. In
7671 general, data overlays are even less transparent to your design than
7672 code overlays: whereas code overlays only require care when you call or
7673 return to functions, data overlays require care every time you access
7674 the data. Also, if you change the contents of a data overlay, you
7675 must copy its contents back out to its load address before you can copy a
7676 different data overlay into the same mapped area.
7681 @node Overlay Commands
7682 @section Overlay Commands
7684 To use @value{GDBN}'s overlay support, each overlay in your program must
7685 correspond to a separate section of the executable file. The section's
7686 virtual memory address and load memory address must be the overlay's
7687 mapped and load addresses. Identifying overlays with sections allows
7688 @value{GDBN} to determine the appropriate address of a function or
7689 variable, depending on whether the overlay is mapped or not.
7691 @value{GDBN}'s overlay commands all start with the word @code{overlay};
7692 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
7697 Disable @value{GDBN}'s overlay support. When overlay support is
7698 disabled, @value{GDBN} assumes that all functions and variables are
7699 always present at their mapped addresses. By default, @value{GDBN}'s
7700 overlay support is disabled.
7702 @item overlay manual
7703 @cindex manual overlay debugging
7704 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
7705 relies on you to tell it which overlays are mapped, and which are not,
7706 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
7707 commands described below.
7709 @item overlay map-overlay @var{overlay}
7710 @itemx overlay map @var{overlay}
7711 @cindex map an overlay
7712 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
7713 be the name of the object file section containing the overlay. When an
7714 overlay is mapped, @value{GDBN} assumes it can find the overlay's
7715 functions and variables at their mapped addresses. @value{GDBN} assumes
7716 that any other overlays whose mapped ranges overlap that of
7717 @var{overlay} are now unmapped.
7719 @item overlay unmap-overlay @var{overlay}
7720 @itemx overlay unmap @var{overlay}
7721 @cindex unmap an overlay
7722 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
7723 must be the name of the object file section containing the overlay.
7724 When an overlay is unmapped, @value{GDBN} assumes it can find the
7725 overlay's functions and variables at their load addresses.
7728 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
7729 consults a data structure the overlay manager maintains in the inferior
7730 to see which overlays are mapped. For details, see @ref{Automatic
7733 @item overlay load-target
7735 @cindex reloading the overlay table
7736 Re-read the overlay table from the inferior. Normally, @value{GDBN}
7737 re-reads the table @value{GDBN} automatically each time the inferior
7738 stops, so this command should only be necessary if you have changed the
7739 overlay mapping yourself using @value{GDBN}. This command is only
7740 useful when using automatic overlay debugging.
7742 @item overlay list-overlays
7744 @cindex listing mapped overlays
7745 Display a list of the overlays currently mapped, along with their mapped
7746 addresses, load addresses, and sizes.
7750 Normally, when @value{GDBN} prints a code address, it includes the name
7751 of the function the address falls in:
7754 (@value{GDBP}) print main
7755 $3 = @{int ()@} 0x11a0 <main>
7758 When overlay debugging is enabled, @value{GDBN} recognizes code in
7759 unmapped overlays, and prints the names of unmapped functions with
7760 asterisks around them. For example, if @code{foo} is a function in an
7761 unmapped overlay, @value{GDBN} prints it this way:
7764 (@value{GDBP}) overlay list
7765 No sections are mapped.
7766 (@value{GDBP}) print foo
7767 $5 = @{int (int)@} 0x100000 <*foo*>
7770 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
7774 (@value{GDBP}) overlay list
7775 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
7776 mapped at 0x1016 - 0x104a
7777 (@value{GDBP}) print foo
7778 $6 = @{int (int)@} 0x1016 <foo>
7781 When overlay debugging is enabled, @value{GDBN} can find the correct
7782 address for functions and variables in an overlay, whether or not the
7783 overlay is mapped. This allows most @value{GDBN} commands, like
7784 @code{break} and @code{disassemble}, to work normally, even on unmapped
7785 code. However, @value{GDBN}'s breakpoint support has some limitations:
7789 @cindex breakpoints in overlays
7790 @cindex overlays, setting breakpoints in
7791 You can set breakpoints in functions in unmapped overlays, as long as
7792 @value{GDBN} can write to the overlay at its load address.
7794 @value{GDBN} can not set hardware or simulator-based breakpoints in
7795 unmapped overlays. However, if you set a breakpoint at the end of your
7796 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
7797 you are using manual overlay management), @value{GDBN} will re-set its
7798 breakpoints properly.
7802 @node Automatic Overlay Debugging
7803 @section Automatic Overlay Debugging
7804 @cindex automatic overlay debugging
7806 @value{GDBN} can automatically track which overlays are mapped and which
7807 are not, given some simple co-operation from the overlay manager in the
7808 inferior. If you enable automatic overlay debugging with the
7809 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
7810 looks in the inferior's memory for certain variables describing the
7811 current state of the overlays.
7813 Here are the variables your overlay manager must define to support
7814 @value{GDBN}'s automatic overlay debugging:
7818 @item @code{_ovly_table}:
7819 This variable must be an array of the following structures:
7824 /* The overlay's mapped address. */
7827 /* The size of the overlay, in bytes. */
7830 /* The overlay's load address. */
7833 /* Non-zero if the overlay is currently mapped;
7835 unsigned long mapped;
7839 @item @code{_novlys}:
7840 This variable must be a four-byte signed integer, holding the total
7841 number of elements in @code{_ovly_table}.
7845 To decide whether a particular overlay is mapped or not, @value{GDBN}
7846 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
7847 @code{lma} members equal the VMA and LMA of the overlay's section in the
7848 executable file. When @value{GDBN} finds a matching entry, it consults
7849 the entry's @code{mapped} member to determine whether the overlay is
7852 In addition, your overlay manager may define a function called
7853 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
7854 will silently set a breakpoint there. If the overlay manager then
7855 calls this function whenever it has changed the overlay table, this
7856 will enable @value{GDBN} to accurately keep track of which overlays
7857 are in program memory, and update any breakpoints that may be set
7858 in overlays. This will allow breakpoints to work even if the
7859 overlays are kept in ROM or other non-writable memory while they
7860 are not being executed.
7862 @node Overlay Sample Program
7863 @section Overlay Sample Program
7864 @cindex overlay example program
7866 When linking a program which uses overlays, you must place the overlays
7867 at their load addresses, while relocating them to run at their mapped
7868 addresses. To do this, you must write a linker script (@pxref{Overlay
7869 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
7870 since linker scripts are specific to a particular host system, target
7871 architecture, and target memory layout, this manual cannot provide
7872 portable sample code demonstrating @value{GDBN}'s overlay support.
7874 However, the @value{GDBN} source distribution does contain an overlaid
7875 program, with linker scripts for a few systems, as part of its test
7876 suite. The program consists of the following files from
7877 @file{gdb/testsuite/gdb.base}:
7881 The main program file.
7883 A simple overlay manager, used by @file{overlays.c}.
7888 Overlay modules, loaded and used by @file{overlays.c}.
7891 Linker scripts for linking the test program on the @code{d10v-elf}
7892 and @code{m32r-elf} targets.
7895 You can build the test program using the @code{d10v-elf} GCC
7896 cross-compiler like this:
7899 $ d10v-elf-gcc -g -c overlays.c
7900 $ d10v-elf-gcc -g -c ovlymgr.c
7901 $ d10v-elf-gcc -g -c foo.c
7902 $ d10v-elf-gcc -g -c bar.c
7903 $ d10v-elf-gcc -g -c baz.c
7904 $ d10v-elf-gcc -g -c grbx.c
7905 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
7906 baz.o grbx.o -Wl,-Td10v.ld -o overlays
7909 The build process is identical for any other architecture, except that
7910 you must substitute the appropriate compiler and linker script for the
7911 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
7915 @chapter Using @value{GDBN} with Different Languages
7918 Although programming languages generally have common aspects, they are
7919 rarely expressed in the same manner. For instance, in ANSI C,
7920 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
7921 Modula-2, it is accomplished by @code{p^}. Values can also be
7922 represented (and displayed) differently. Hex numbers in C appear as
7923 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
7925 @cindex working language
7926 Language-specific information is built into @value{GDBN} for some languages,
7927 allowing you to express operations like the above in your program's
7928 native language, and allowing @value{GDBN} to output values in a manner
7929 consistent with the syntax of your program's native language. The
7930 language you use to build expressions is called the @dfn{working
7934 * Setting:: Switching between source languages
7935 * Show:: Displaying the language
7936 * Checks:: Type and range checks
7937 * Supported languages:: Supported languages
7938 * Unsupported languages:: Unsupported languages
7942 @section Switching between source languages
7944 There are two ways to control the working language---either have @value{GDBN}
7945 set it automatically, or select it manually yourself. You can use the
7946 @code{set language} command for either purpose. On startup, @value{GDBN}
7947 defaults to setting the language automatically. The working language is
7948 used to determine how expressions you type are interpreted, how values
7951 In addition to the working language, every source file that
7952 @value{GDBN} knows about has its own working language. For some object
7953 file formats, the compiler might indicate which language a particular
7954 source file is in. However, most of the time @value{GDBN} infers the
7955 language from the name of the file. The language of a source file
7956 controls whether C@t{++} names are demangled---this way @code{backtrace} can
7957 show each frame appropriately for its own language. There is no way to
7958 set the language of a source file from within @value{GDBN}, but you can
7959 set the language associated with a filename extension. @xref{Show, ,
7960 Displaying the language}.
7962 This is most commonly a problem when you use a program, such
7963 as @code{cfront} or @code{f2c}, that generates C but is written in
7964 another language. In that case, make the
7965 program use @code{#line} directives in its C output; that way
7966 @value{GDBN} will know the correct language of the source code of the original
7967 program, and will display that source code, not the generated C code.
7970 * Filenames:: Filename extensions and languages.
7971 * Manually:: Setting the working language manually
7972 * Automatically:: Having @value{GDBN} infer the source language
7976 @subsection List of filename extensions and languages
7978 If a source file name ends in one of the following extensions, then
7979 @value{GDBN} infers that its language is the one indicated.
8000 Objective-C source file
8007 Modula-2 source file
8011 Assembler source file. This actually behaves almost like C, but
8012 @value{GDBN} does not skip over function prologues when stepping.
8015 In addition, you may set the language associated with a filename
8016 extension. @xref{Show, , Displaying the language}.
8019 @subsection Setting the working language
8021 If you allow @value{GDBN} to set the language automatically,
8022 expressions are interpreted the same way in your debugging session and
8025 @kindex set language
8026 If you wish, you may set the language manually. To do this, issue the
8027 command @samp{set language @var{lang}}, where @var{lang} is the name of
8029 @code{c} or @code{modula-2}.
8030 For a list of the supported languages, type @samp{set language}.
8032 Setting the language manually prevents @value{GDBN} from updating the working
8033 language automatically. This can lead to confusion if you try
8034 to debug a program when the working language is not the same as the
8035 source language, when an expression is acceptable to both
8036 languages---but means different things. For instance, if the current
8037 source file were written in C, and @value{GDBN} was parsing Modula-2, a
8045 might not have the effect you intended. In C, this means to add
8046 @code{b} and @code{c} and place the result in @code{a}. The result
8047 printed would be the value of @code{a}. In Modula-2, this means to compare
8048 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
8051 @subsection Having @value{GDBN} infer the source language
8053 To have @value{GDBN} set the working language automatically, use
8054 @samp{set language local} or @samp{set language auto}. @value{GDBN}
8055 then infers the working language. That is, when your program stops in a
8056 frame (usually by encountering a breakpoint), @value{GDBN} sets the
8057 working language to the language recorded for the function in that
8058 frame. If the language for a frame is unknown (that is, if the function
8059 or block corresponding to the frame was defined in a source file that
8060 does not have a recognized extension), the current working language is
8061 not changed, and @value{GDBN} issues a warning.
8063 This may not seem necessary for most programs, which are written
8064 entirely in one source language. However, program modules and libraries
8065 written in one source language can be used by a main program written in
8066 a different source language. Using @samp{set language auto} in this
8067 case frees you from having to set the working language manually.
8070 @section Displaying the language
8072 The following commands help you find out which language is the
8073 working language, and also what language source files were written in.
8077 @kindex show language
8078 Display the current working language. This is the
8079 language you can use with commands such as @code{print} to
8080 build and compute expressions that may involve variables in your program.
8083 @kindex info frame@r{, show the source language}
8084 Display the source language for this frame. This language becomes the
8085 working language if you use an identifier from this frame.
8086 @xref{Frame Info, ,Information about a frame}, to identify the other
8087 information listed here.
8090 @kindex info source@r{, show the source language}
8091 Display the source language of this source file.
8092 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
8093 information listed here.
8096 In unusual circumstances, you may have source files with extensions
8097 not in the standard list. You can then set the extension associated
8098 with a language explicitly:
8101 @item set extension-language @var{ext} @var{language}
8102 @kindex set extension-language
8103 Tell @value{GDBN} that source files with extension @var{ext} are to be
8104 assumed as written in the source language @var{language}.
8106 @item info extensions
8107 @kindex info extensions
8108 List all the filename extensions and the associated languages.
8112 @section Type and range checking
8115 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
8116 checking are included, but they do not yet have any effect. This
8117 section documents the intended facilities.
8119 @c FIXME remove warning when type/range code added
8121 Some languages are designed to guard you against making seemingly common
8122 errors through a series of compile- and run-time checks. These include
8123 checking the type of arguments to functions and operators, and making
8124 sure mathematical overflows are caught at run time. Checks such as
8125 these help to ensure a program's correctness once it has been compiled
8126 by eliminating type mismatches, and providing active checks for range
8127 errors when your program is running.
8129 @value{GDBN} can check for conditions like the above if you wish.
8130 Although @value{GDBN} does not check the statements in your program,
8131 it can check expressions entered directly into @value{GDBN} for
8132 evaluation via the @code{print} command, for example. As with the
8133 working language, @value{GDBN} can also decide whether or not to check
8134 automatically based on your program's source language.
8135 @xref{Supported languages, ,Supported languages}, for the default
8136 settings of supported languages.
8139 * Type Checking:: An overview of type checking
8140 * Range Checking:: An overview of range checking
8143 @cindex type checking
8144 @cindex checks, type
8146 @subsection An overview of type checking
8148 Some languages, such as Modula-2, are strongly typed, meaning that the
8149 arguments to operators and functions have to be of the correct type,
8150 otherwise an error occurs. These checks prevent type mismatch
8151 errors from ever causing any run-time problems. For example,
8159 The second example fails because the @code{CARDINAL} 1 is not
8160 type-compatible with the @code{REAL} 2.3.
8162 For the expressions you use in @value{GDBN} commands, you can tell the
8163 @value{GDBN} type checker to skip checking;
8164 to treat any mismatches as errors and abandon the expression;
8165 or to only issue warnings when type mismatches occur,
8166 but evaluate the expression anyway. When you choose the last of
8167 these, @value{GDBN} evaluates expressions like the second example above, but
8168 also issues a warning.
8170 Even if you turn type checking off, there may be other reasons
8171 related to type that prevent @value{GDBN} from evaluating an expression.
8172 For instance, @value{GDBN} does not know how to add an @code{int} and
8173 a @code{struct foo}. These particular type errors have nothing to do
8174 with the language in use, and usually arise from expressions, such as
8175 the one described above, which make little sense to evaluate anyway.
8177 Each language defines to what degree it is strict about type. For
8178 instance, both Modula-2 and C require the arguments to arithmetical
8179 operators to be numbers. In C, enumerated types and pointers can be
8180 represented as numbers, so that they are valid arguments to mathematical
8181 operators. @xref{Supported languages, ,Supported languages}, for further
8182 details on specific languages.
8184 @value{GDBN} provides some additional commands for controlling the type checker:
8186 @kindex set check type
8187 @kindex show check type
8189 @item set check type auto
8190 Set type checking on or off based on the current working language.
8191 @xref{Supported languages, ,Supported languages}, for the default settings for
8194 @item set check type on
8195 @itemx set check type off
8196 Set type checking on or off, overriding the default setting for the
8197 current working language. Issue a warning if the setting does not
8198 match the language default. If any type mismatches occur in
8199 evaluating an expression while type checking is on, @value{GDBN} prints a
8200 message and aborts evaluation of the expression.
8202 @item set check type warn
8203 Cause the type checker to issue warnings, but to always attempt to
8204 evaluate the expression. Evaluating the expression may still
8205 be impossible for other reasons. For example, @value{GDBN} cannot add
8206 numbers and structures.
8209 Show the current setting of the type checker, and whether or not @value{GDBN}
8210 is setting it automatically.
8213 @cindex range checking
8214 @cindex checks, range
8215 @node Range Checking
8216 @subsection An overview of range checking
8218 In some languages (such as Modula-2), it is an error to exceed the
8219 bounds of a type; this is enforced with run-time checks. Such range
8220 checking is meant to ensure program correctness by making sure
8221 computations do not overflow, or indices on an array element access do
8222 not exceed the bounds of the array.
8224 For expressions you use in @value{GDBN} commands, you can tell
8225 @value{GDBN} to treat range errors in one of three ways: ignore them,
8226 always treat them as errors and abandon the expression, or issue
8227 warnings but evaluate the expression anyway.
8229 A range error can result from numerical overflow, from exceeding an
8230 array index bound, or when you type a constant that is not a member
8231 of any type. Some languages, however, do not treat overflows as an
8232 error. In many implementations of C, mathematical overflow causes the
8233 result to ``wrap around'' to lower values---for example, if @var{m} is
8234 the largest integer value, and @var{s} is the smallest, then
8237 @var{m} + 1 @result{} @var{s}
8240 This, too, is specific to individual languages, and in some cases
8241 specific to individual compilers or machines. @xref{Supported languages, ,
8242 Supported languages}, for further details on specific languages.
8244 @value{GDBN} provides some additional commands for controlling the range checker:
8246 @kindex set check range
8247 @kindex show check range
8249 @item set check range auto
8250 Set range checking on or off based on the current working language.
8251 @xref{Supported languages, ,Supported languages}, for the default settings for
8254 @item set check range on
8255 @itemx set check range off
8256 Set range checking on or off, overriding the default setting for the
8257 current working language. A warning is issued if the setting does not
8258 match the language default. If a range error occurs and range checking is on,
8259 then a message is printed and evaluation of the expression is aborted.
8261 @item set check range warn
8262 Output messages when the @value{GDBN} range checker detects a range error,
8263 but attempt to evaluate the expression anyway. Evaluating the
8264 expression may still be impossible for other reasons, such as accessing
8265 memory that the process does not own (a typical example from many Unix
8269 Show the current setting of the range checker, and whether or not it is
8270 being set automatically by @value{GDBN}.
8273 @node Supported languages
8274 @section Supported languages
8276 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
8277 assembly, Modula-2, and Ada.
8278 @c This is false ...
8279 Some @value{GDBN} features may be used in expressions regardless of the
8280 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
8281 and the @samp{@{type@}addr} construct (@pxref{Expressions,
8282 ,Expressions}) can be used with the constructs of any supported
8285 The following sections detail to what degree each source language is
8286 supported by @value{GDBN}. These sections are not meant to be language
8287 tutorials or references, but serve only as a reference guide to what the
8288 @value{GDBN} expression parser accepts, and what input and output
8289 formats should look like for different languages. There are many good
8290 books written on each of these languages; please look to these for a
8291 language reference or tutorial.
8295 * Objective-C:: Objective-C
8298 * Modula-2:: Modula-2
8303 @subsection C and C@t{++}
8305 @cindex C and C@t{++}
8306 @cindex expressions in C or C@t{++}
8308 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
8309 to both languages. Whenever this is the case, we discuss those languages
8313 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
8314 @cindex @sc{gnu} C@t{++}
8315 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
8316 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
8317 effectively, you must compile your C@t{++} programs with a supported
8318 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
8319 compiler (@code{aCC}).
8321 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
8322 format; if it doesn't work on your system, try the stabs+ debugging
8323 format. You can select those formats explicitly with the @code{g++}
8324 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
8325 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
8326 CC, gcc.info, Using @sc{gnu} CC}.
8329 * C Operators:: C and C@t{++} operators
8330 * C Constants:: C and C@t{++} constants
8331 * C plus plus expressions:: C@t{++} expressions
8332 * C Defaults:: Default settings for C and C@t{++}
8333 * C Checks:: C and C@t{++} type and range checks
8334 * Debugging C:: @value{GDBN} and C
8335 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
8339 @subsubsection C and C@t{++} operators
8341 @cindex C and C@t{++} operators
8343 Operators must be defined on values of specific types. For instance,
8344 @code{+} is defined on numbers, but not on structures. Operators are
8345 often defined on groups of types.
8347 For the purposes of C and C@t{++}, the following definitions hold:
8352 @emph{Integral types} include @code{int} with any of its storage-class
8353 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
8356 @emph{Floating-point types} include @code{float}, @code{double}, and
8357 @code{long double} (if supported by the target platform).
8360 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
8363 @emph{Scalar types} include all of the above.
8368 The following operators are supported. They are listed here
8369 in order of increasing precedence:
8373 The comma or sequencing operator. Expressions in a comma-separated list
8374 are evaluated from left to right, with the result of the entire
8375 expression being the last expression evaluated.
8378 Assignment. The value of an assignment expression is the value
8379 assigned. Defined on scalar types.
8382 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
8383 and translated to @w{@code{@var{a} = @var{a op b}}}.
8384 @w{@code{@var{op}=}} and @code{=} have the same precedence.
8385 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
8386 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
8389 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
8390 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
8394 Logical @sc{or}. Defined on integral types.
8397 Logical @sc{and}. Defined on integral types.
8400 Bitwise @sc{or}. Defined on integral types.
8403 Bitwise exclusive-@sc{or}. Defined on integral types.
8406 Bitwise @sc{and}. Defined on integral types.
8409 Equality and inequality. Defined on scalar types. The value of these
8410 expressions is 0 for false and non-zero for true.
8412 @item <@r{, }>@r{, }<=@r{, }>=
8413 Less than, greater than, less than or equal, greater than or equal.
8414 Defined on scalar types. The value of these expressions is 0 for false
8415 and non-zero for true.
8418 left shift, and right shift. Defined on integral types.
8421 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8424 Addition and subtraction. Defined on integral types, floating-point types and
8427 @item *@r{, }/@r{, }%
8428 Multiplication, division, and modulus. Multiplication and division are
8429 defined on integral and floating-point types. Modulus is defined on
8433 Increment and decrement. When appearing before a variable, the
8434 operation is performed before the variable is used in an expression;
8435 when appearing after it, the variable's value is used before the
8436 operation takes place.
8439 Pointer dereferencing. Defined on pointer types. Same precedence as
8443 Address operator. Defined on variables. Same precedence as @code{++}.
8445 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
8446 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
8447 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
8448 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
8452 Negative. Defined on integral and floating-point types. Same
8453 precedence as @code{++}.
8456 Logical negation. Defined on integral types. Same precedence as
8460 Bitwise complement operator. Defined on integral types. Same precedence as
8465 Structure member, and pointer-to-structure member. For convenience,
8466 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
8467 pointer based on the stored type information.
8468 Defined on @code{struct} and @code{union} data.
8471 Dereferences of pointers to members.
8474 Array indexing. @code{@var{a}[@var{i}]} is defined as
8475 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
8478 Function parameter list. Same precedence as @code{->}.
8481 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
8482 and @code{class} types.
8485 Doubled colons also represent the @value{GDBN} scope operator
8486 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
8490 If an operator is redefined in the user code, @value{GDBN} usually
8491 attempts to invoke the redefined version instead of using the operator's
8499 @subsubsection C and C@t{++} constants
8501 @cindex C and C@t{++} constants
8503 @value{GDBN} allows you to express the constants of C and C@t{++} in the
8508 Integer constants are a sequence of digits. Octal constants are
8509 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
8510 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
8511 @samp{l}, specifying that the constant should be treated as a
8515 Floating point constants are a sequence of digits, followed by a decimal
8516 point, followed by a sequence of digits, and optionally followed by an
8517 exponent. An exponent is of the form:
8518 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8519 sequence of digits. The @samp{+} is optional for positive exponents.
8520 A floating-point constant may also end with a letter @samp{f} or
8521 @samp{F}, specifying that the constant should be treated as being of
8522 the @code{float} (as opposed to the default @code{double}) type; or with
8523 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8527 Enumerated constants consist of enumerated identifiers, or their
8528 integral equivalents.
8531 Character constants are a single character surrounded by single quotes
8532 (@code{'}), or a number---the ordinal value of the corresponding character
8533 (usually its @sc{ascii} value). Within quotes, the single character may
8534 be represented by a letter or by @dfn{escape sequences}, which are of
8535 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8536 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8537 @samp{@var{x}} is a predefined special character---for example,
8538 @samp{\n} for newline.
8541 String constants are a sequence of character constants surrounded by
8542 double quotes (@code{"}). Any valid character constant (as described
8543 above) may appear. Double quotes within the string must be preceded by
8544 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8548 Pointer constants are an integral value. You can also write pointers
8549 to constants using the C operator @samp{&}.
8552 Array constants are comma-separated lists surrounded by braces @samp{@{}
8553 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8554 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8555 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8559 * C plus plus expressions::
8566 @node C plus plus expressions
8567 @subsubsection C@t{++} expressions
8569 @cindex expressions in C@t{++}
8570 @value{GDBN} expression handling can interpret most C@t{++} expressions.
8572 @cindex debugging C@t{++} programs
8573 @cindex C@t{++} compilers
8574 @cindex debug formats and C@t{++}
8575 @cindex @value{NGCC} and C@t{++}
8577 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
8578 proper compiler and the proper debug format. Currently, @value{GDBN}
8579 works best when debugging C@t{++} code that is compiled with
8580 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
8581 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
8582 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
8583 stabs+ as their default debug format, so you usually don't need to
8584 specify a debug format explicitly. Other compilers and/or debug formats
8585 are likely to work badly or not at all when using @value{GDBN} to debug
8591 @cindex member functions
8593 Member function calls are allowed; you can use expressions like
8596 count = aml->GetOriginal(x, y)
8599 @vindex this@r{, inside C@t{++} member functions}
8600 @cindex namespace in C@t{++}
8602 While a member function is active (in the selected stack frame), your
8603 expressions have the same namespace available as the member function;
8604 that is, @value{GDBN} allows implicit references to the class instance
8605 pointer @code{this} following the same rules as C@t{++}.
8607 @cindex call overloaded functions
8608 @cindex overloaded functions, calling
8609 @cindex type conversions in C@t{++}
8611 You can call overloaded functions; @value{GDBN} resolves the function
8612 call to the right definition, with some restrictions. @value{GDBN} does not
8613 perform overload resolution involving user-defined type conversions,
8614 calls to constructors, or instantiations of templates that do not exist
8615 in the program. It also cannot handle ellipsis argument lists or
8618 It does perform integral conversions and promotions, floating-point
8619 promotions, arithmetic conversions, pointer conversions, conversions of
8620 class objects to base classes, and standard conversions such as those of
8621 functions or arrays to pointers; it requires an exact match on the
8622 number of function arguments.
8624 Overload resolution is always performed, unless you have specified
8625 @code{set overload-resolution off}. @xref{Debugging C plus plus,
8626 ,@value{GDBN} features for C@t{++}}.
8628 You must specify @code{set overload-resolution off} in order to use an
8629 explicit function signature to call an overloaded function, as in
8631 p 'foo(char,int)'('x', 13)
8634 The @value{GDBN} command-completion facility can simplify this;
8635 see @ref{Completion, ,Command completion}.
8637 @cindex reference declarations
8639 @value{GDBN} understands variables declared as C@t{++} references; you can use
8640 them in expressions just as you do in C@t{++} source---they are automatically
8643 In the parameter list shown when @value{GDBN} displays a frame, the values of
8644 reference variables are not displayed (unlike other variables); this
8645 avoids clutter, since references are often used for large structures.
8646 The @emph{address} of a reference variable is always shown, unless
8647 you have specified @samp{set print address off}.
8650 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
8651 expressions can use it just as expressions in your program do. Since
8652 one scope may be defined in another, you can use @code{::} repeatedly if
8653 necessary, for example in an expression like
8654 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
8655 resolving name scope by reference to source files, in both C and C@t{++}
8656 debugging (@pxref{Variables, ,Program variables}).
8659 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
8660 calling virtual functions correctly, printing out virtual bases of
8661 objects, calling functions in a base subobject, casting objects, and
8662 invoking user-defined operators.
8665 @subsubsection C and C@t{++} defaults
8667 @cindex C and C@t{++} defaults
8669 If you allow @value{GDBN} to set type and range checking automatically, they
8670 both default to @code{off} whenever the working language changes to
8671 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
8672 selects the working language.
8674 If you allow @value{GDBN} to set the language automatically, it
8675 recognizes source files whose names end with @file{.c}, @file{.C}, or
8676 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
8677 these files, it sets the working language to C or C@t{++}.
8678 @xref{Automatically, ,Having @value{GDBN} infer the source language},
8679 for further details.
8681 @c Type checking is (a) primarily motivated by Modula-2, and (b)
8682 @c unimplemented. If (b) changes, it might make sense to let this node
8683 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
8686 @subsubsection C and C@t{++} type and range checks
8688 @cindex C and C@t{++} checks
8690 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
8691 is not used. However, if you turn type checking on, @value{GDBN}
8692 considers two variables type equivalent if:
8696 The two variables are structured and have the same structure, union, or
8700 The two variables have the same type name, or types that have been
8701 declared equivalent through @code{typedef}.
8704 @c leaving this out because neither J Gilmore nor R Pesch understand it.
8707 The two @code{struct}, @code{union}, or @code{enum} variables are
8708 declared in the same declaration. (Note: this may not be true for all C
8713 Range checking, if turned on, is done on mathematical operations. Array
8714 indices are not checked, since they are often used to index a pointer
8715 that is not itself an array.
8718 @subsubsection @value{GDBN} and C
8720 The @code{set print union} and @code{show print union} commands apply to
8721 the @code{union} type. When set to @samp{on}, any @code{union} that is
8722 inside a @code{struct} or @code{class} is also printed. Otherwise, it
8723 appears as @samp{@{...@}}.
8725 The @code{@@} operator aids in the debugging of dynamic arrays, formed
8726 with pointers and a memory allocation function. @xref{Expressions,
8730 * Debugging C plus plus::
8733 @node Debugging C plus plus
8734 @subsubsection @value{GDBN} features for C@t{++}
8736 @cindex commands for C@t{++}
8738 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
8739 designed specifically for use with C@t{++}. Here is a summary:
8742 @cindex break in overloaded functions
8743 @item @r{breakpoint menus}
8744 When you want a breakpoint in a function whose name is overloaded,
8745 @value{GDBN} breakpoint menus help you specify which function definition
8746 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
8748 @cindex overloading in C@t{++}
8749 @item rbreak @var{regex}
8750 Setting breakpoints using regular expressions is helpful for setting
8751 breakpoints on overloaded functions that are not members of any special
8753 @xref{Set Breaks, ,Setting breakpoints}.
8755 @cindex C@t{++} exception handling
8758 Debug C@t{++} exception handling using these commands. @xref{Set
8759 Catchpoints, , Setting catchpoints}.
8762 @item ptype @var{typename}
8763 Print inheritance relationships as well as other information for type
8765 @xref{Symbols, ,Examining the Symbol Table}.
8767 @cindex C@t{++} symbol display
8768 @item set print demangle
8769 @itemx show print demangle
8770 @itemx set print asm-demangle
8771 @itemx show print asm-demangle
8772 Control whether C@t{++} symbols display in their source form, both when
8773 displaying code as C@t{++} source and when displaying disassemblies.
8774 @xref{Print Settings, ,Print settings}.
8776 @item set print object
8777 @itemx show print object
8778 Choose whether to print derived (actual) or declared types of objects.
8779 @xref{Print Settings, ,Print settings}.
8781 @item set print vtbl
8782 @itemx show print vtbl
8783 Control the format for printing virtual function tables.
8784 @xref{Print Settings, ,Print settings}.
8785 (The @code{vtbl} commands do not work on programs compiled with the HP
8786 ANSI C@t{++} compiler (@code{aCC}).)
8788 @kindex set overload-resolution
8789 @cindex overloaded functions, overload resolution
8790 @item set overload-resolution on
8791 Enable overload resolution for C@t{++} expression evaluation. The default
8792 is on. For overloaded functions, @value{GDBN} evaluates the arguments
8793 and searches for a function whose signature matches the argument types,
8794 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
8795 expressions}, for details). If it cannot find a match, it emits a
8798 @item set overload-resolution off
8799 Disable overload resolution for C@t{++} expression evaluation. For
8800 overloaded functions that are not class member functions, @value{GDBN}
8801 chooses the first function of the specified name that it finds in the
8802 symbol table, whether or not its arguments are of the correct type. For
8803 overloaded functions that are class member functions, @value{GDBN}
8804 searches for a function whose signature @emph{exactly} matches the
8807 @kindex show overload-resolution
8808 @item show overload-resolution
8809 Show the current setting of overload resolution.
8811 @item @r{Overloaded symbol names}
8812 You can specify a particular definition of an overloaded symbol, using
8813 the same notation that is used to declare such symbols in C@t{++}: type
8814 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
8815 also use the @value{GDBN} command-line word completion facilities to list the
8816 available choices, or to finish the type list for you.
8817 @xref{Completion,, Command completion}, for details on how to do this.
8821 @subsection Objective-C
8824 This section provides information about some commands and command
8825 options that are useful for debugging Objective-C code. See also
8826 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
8827 few more commands specific to Objective-C support.
8830 * Method Names in Commands::
8831 * The Print Command with Objective-C::
8834 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
8835 @subsubsection Method Names in Commands
8837 The following commands have been extended to accept Objective-C method
8838 names as line specifications:
8840 @kindex clear@r{, and Objective-C}
8841 @kindex break@r{, and Objective-C}
8842 @kindex info line@r{, and Objective-C}
8843 @kindex jump@r{, and Objective-C}
8844 @kindex list@r{, and Objective-C}
8848 @item @code{info line}
8853 A fully qualified Objective-C method name is specified as
8856 -[@var{Class} @var{methodName}]
8859 where the minus sign is used to indicate an instance method and a
8860 plus sign (not shown) is used to indicate a class method. The class
8861 name @var{Class} and method name @var{methodName} are enclosed in
8862 brackets, similar to the way messages are specified in Objective-C
8863 source code. For example, to set a breakpoint at the @code{create}
8864 instance method of class @code{Fruit} in the program currently being
8868 break -[Fruit create]
8871 To list ten program lines around the @code{initialize} class method,
8875 list +[NSText initialize]
8878 In the current version of @value{GDBN}, the plus or minus sign is
8879 required. In future versions of @value{GDBN}, the plus or minus
8880 sign will be optional, but you can use it to narrow the search. It
8881 is also possible to specify just a method name:
8887 You must specify the complete method name, including any colons. If
8888 your program's source files contain more than one @code{create} method,
8889 you'll be presented with a numbered list of classes that implement that
8890 method. Indicate your choice by number, or type @samp{0} to exit if
8893 As another example, to clear a breakpoint established at the
8894 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
8897 clear -[NSWindow makeKeyAndOrderFront:]
8900 @node The Print Command with Objective-C
8901 @subsubsection The Print Command With Objective-C
8902 @cindex Objective-C, print objects
8903 @kindex print-object
8904 @kindex po @r{(@code{print-object})}
8906 The print command has also been extended to accept methods. For example:
8909 print -[@var{object} hash]
8912 @cindex print an Objective-C object description
8913 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
8915 will tell @value{GDBN} to send the @code{hash} message to @var{object}
8916 and print the result. Also, an additional command has been added,
8917 @code{print-object} or @code{po} for short, which is meant to print
8918 the description of an object. However, this command may only work
8919 with certain Objective-C libraries that have a particular hook
8920 function, @code{_NSPrintForDebugger}, defined.
8924 @cindex Fortran-specific support in @value{GDBN}
8927 @cindex @code{COMMON} blocks, Fortran
8929 @item info common @r{[}@var{common-name}@r{]}
8930 This command prints the values contained in the Fortran @code{COMMON}
8931 block whose name is @var{common-name}. With no argument, the names of
8932 all @code{COMMON} blocks visible at current program location are
8936 Fortran symbols are usually case-insensitive, so @value{GDBN} by
8937 default uses case-insensitive matches for Fortran symbols. You can
8938 change that with the @samp{set case-insensitive} command, see
8939 @ref{Symbols}, for the details.
8944 @cindex Pascal support in @value{GDBN}, limitations
8945 Debugging Pascal programs which use sets, subranges, file variables, or
8946 nested functions does not currently work. @value{GDBN} does not support
8947 entering expressions, printing values, or similar features using Pascal
8950 The Pascal-specific command @code{set print pascal_static-members}
8951 controls whether static members of Pascal objects are displayed.
8952 @xref{Print Settings, pascal_static-members}.
8955 @subsection Modula-2
8957 @cindex Modula-2, @value{GDBN} support
8959 The extensions made to @value{GDBN} to support Modula-2 only support
8960 output from the @sc{gnu} Modula-2 compiler (which is currently being
8961 developed). Other Modula-2 compilers are not currently supported, and
8962 attempting to debug executables produced by them is most likely
8963 to give an error as @value{GDBN} reads in the executable's symbol
8966 @cindex expressions in Modula-2
8968 * M2 Operators:: Built-in operators
8969 * Built-In Func/Proc:: Built-in functions and procedures
8970 * M2 Constants:: Modula-2 constants
8971 * M2 Defaults:: Default settings for Modula-2
8972 * Deviations:: Deviations from standard Modula-2
8973 * M2 Checks:: Modula-2 type and range checks
8974 * M2 Scope:: The scope operators @code{::} and @code{.}
8975 * GDB/M2:: @value{GDBN} and Modula-2
8979 @subsubsection Operators
8980 @cindex Modula-2 operators
8982 Operators must be defined on values of specific types. For instance,
8983 @code{+} is defined on numbers, but not on structures. Operators are
8984 often defined on groups of types. For the purposes of Modula-2, the
8985 following definitions hold:
8990 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
8994 @emph{Character types} consist of @code{CHAR} and its subranges.
8997 @emph{Floating-point types} consist of @code{REAL}.
9000 @emph{Pointer types} consist of anything declared as @code{POINTER TO
9004 @emph{Scalar types} consist of all of the above.
9007 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
9010 @emph{Boolean types} consist of @code{BOOLEAN}.
9014 The following operators are supported, and appear in order of
9015 increasing precedence:
9019 Function argument or array index separator.
9022 Assignment. The value of @var{var} @code{:=} @var{value} is
9026 Less than, greater than on integral, floating-point, or enumerated
9030 Less than or equal to, greater than or equal to
9031 on integral, floating-point and enumerated types, or set inclusion on
9032 set types. Same precedence as @code{<}.
9034 @item =@r{, }<>@r{, }#
9035 Equality and two ways of expressing inequality, valid on scalar types.
9036 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
9037 available for inequality, since @code{#} conflicts with the script
9041 Set membership. Defined on set types and the types of their members.
9042 Same precedence as @code{<}.
9045 Boolean disjunction. Defined on boolean types.
9048 Boolean conjunction. Defined on boolean types.
9051 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9054 Addition and subtraction on integral and floating-point types, or union
9055 and difference on set types.
9058 Multiplication on integral and floating-point types, or set intersection
9062 Division on floating-point types, or symmetric set difference on set
9063 types. Same precedence as @code{*}.
9066 Integer division and remainder. Defined on integral types. Same
9067 precedence as @code{*}.
9070 Negative. Defined on @code{INTEGER} and @code{REAL} data.
9073 Pointer dereferencing. Defined on pointer types.
9076 Boolean negation. Defined on boolean types. Same precedence as
9080 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
9081 precedence as @code{^}.
9084 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
9087 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
9091 @value{GDBN} and Modula-2 scope operators.
9095 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
9096 treats the use of the operator @code{IN}, or the use of operators
9097 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
9098 @code{<=}, and @code{>=} on sets as an error.
9102 @node Built-In Func/Proc
9103 @subsubsection Built-in functions and procedures
9104 @cindex Modula-2 built-ins
9106 Modula-2 also makes available several built-in procedures and functions.
9107 In describing these, the following metavariables are used:
9112 represents an @code{ARRAY} variable.
9115 represents a @code{CHAR} constant or variable.
9118 represents a variable or constant of integral type.
9121 represents an identifier that belongs to a set. Generally used in the
9122 same function with the metavariable @var{s}. The type of @var{s} should
9123 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
9126 represents a variable or constant of integral or floating-point type.
9129 represents a variable or constant of floating-point type.
9135 represents a variable.
9138 represents a variable or constant of one of many types. See the
9139 explanation of the function for details.
9142 All Modula-2 built-in procedures also return a result, described below.
9146 Returns the absolute value of @var{n}.
9149 If @var{c} is a lower case letter, it returns its upper case
9150 equivalent, otherwise it returns its argument.
9153 Returns the character whose ordinal value is @var{i}.
9156 Decrements the value in the variable @var{v} by one. Returns the new value.
9158 @item DEC(@var{v},@var{i})
9159 Decrements the value in the variable @var{v} by @var{i}. Returns the
9162 @item EXCL(@var{m},@var{s})
9163 Removes the element @var{m} from the set @var{s}. Returns the new
9166 @item FLOAT(@var{i})
9167 Returns the floating point equivalent of the integer @var{i}.
9170 Returns the index of the last member of @var{a}.
9173 Increments the value in the variable @var{v} by one. Returns the new value.
9175 @item INC(@var{v},@var{i})
9176 Increments the value in the variable @var{v} by @var{i}. Returns the
9179 @item INCL(@var{m},@var{s})
9180 Adds the element @var{m} to the set @var{s} if it is not already
9181 there. Returns the new set.
9184 Returns the maximum value of the type @var{t}.
9187 Returns the minimum value of the type @var{t}.
9190 Returns boolean TRUE if @var{i} is an odd number.
9193 Returns the ordinal value of its argument. For example, the ordinal
9194 value of a character is its @sc{ascii} value (on machines supporting the
9195 @sc{ascii} character set). @var{x} must be of an ordered type, which include
9196 integral, character and enumerated types.
9199 Returns the size of its argument. @var{x} can be a variable or a type.
9201 @item TRUNC(@var{r})
9202 Returns the integral part of @var{r}.
9204 @item VAL(@var{t},@var{i})
9205 Returns the member of the type @var{t} whose ordinal value is @var{i}.
9209 @emph{Warning:} Sets and their operations are not yet supported, so
9210 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
9214 @cindex Modula-2 constants
9216 @subsubsection Constants
9218 @value{GDBN} allows you to express the constants of Modula-2 in the following
9224 Integer constants are simply a sequence of digits. When used in an
9225 expression, a constant is interpreted to be type-compatible with the
9226 rest of the expression. Hexadecimal integers are specified by a
9227 trailing @samp{H}, and octal integers by a trailing @samp{B}.
9230 Floating point constants appear as a sequence of digits, followed by a
9231 decimal point and another sequence of digits. An optional exponent can
9232 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
9233 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
9234 digits of the floating point constant must be valid decimal (base 10)
9238 Character constants consist of a single character enclosed by a pair of
9239 like quotes, either single (@code{'}) or double (@code{"}). They may
9240 also be expressed by their ordinal value (their @sc{ascii} value, usually)
9241 followed by a @samp{C}.
9244 String constants consist of a sequence of characters enclosed by a
9245 pair of like quotes, either single (@code{'}) or double (@code{"}).
9246 Escape sequences in the style of C are also allowed. @xref{C
9247 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
9251 Enumerated constants consist of an enumerated identifier.
9254 Boolean constants consist of the identifiers @code{TRUE} and
9258 Pointer constants consist of integral values only.
9261 Set constants are not yet supported.
9265 @subsubsection Modula-2 defaults
9266 @cindex Modula-2 defaults
9268 If type and range checking are set automatically by @value{GDBN}, they
9269 both default to @code{on} whenever the working language changes to
9270 Modula-2. This happens regardless of whether you or @value{GDBN}
9271 selected the working language.
9273 If you allow @value{GDBN} to set the language automatically, then entering
9274 code compiled from a file whose name ends with @file{.mod} sets the
9275 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
9276 the language automatically}, for further details.
9279 @subsubsection Deviations from standard Modula-2
9280 @cindex Modula-2, deviations from
9282 A few changes have been made to make Modula-2 programs easier to debug.
9283 This is done primarily via loosening its type strictness:
9287 Unlike in standard Modula-2, pointer constants can be formed by
9288 integers. This allows you to modify pointer variables during
9289 debugging. (In standard Modula-2, the actual address contained in a
9290 pointer variable is hidden from you; it can only be modified
9291 through direct assignment to another pointer variable or expression that
9292 returned a pointer.)
9295 C escape sequences can be used in strings and characters to represent
9296 non-printable characters. @value{GDBN} prints out strings with these
9297 escape sequences embedded. Single non-printable characters are
9298 printed using the @samp{CHR(@var{nnn})} format.
9301 The assignment operator (@code{:=}) returns the value of its right-hand
9305 All built-in procedures both modify @emph{and} return their argument.
9309 @subsubsection Modula-2 type and range checks
9310 @cindex Modula-2 checks
9313 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
9316 @c FIXME remove warning when type/range checks added
9318 @value{GDBN} considers two Modula-2 variables type equivalent if:
9322 They are of types that have been declared equivalent via a @code{TYPE
9323 @var{t1} = @var{t2}} statement
9326 They have been declared on the same line. (Note: This is true of the
9327 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
9330 As long as type checking is enabled, any attempt to combine variables
9331 whose types are not equivalent is an error.
9333 Range checking is done on all mathematical operations, assignment, array
9334 index bounds, and all built-in functions and procedures.
9337 @subsubsection The scope operators @code{::} and @code{.}
9339 @cindex @code{.}, Modula-2 scope operator
9340 @cindex colon, doubled as scope operator
9342 @vindex colon-colon@r{, in Modula-2}
9343 @c Info cannot handle :: but TeX can.
9346 @vindex ::@r{, in Modula-2}
9349 There are a few subtle differences between the Modula-2 scope operator
9350 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
9355 @var{module} . @var{id}
9356 @var{scope} :: @var{id}
9360 where @var{scope} is the name of a module or a procedure,
9361 @var{module} the name of a module, and @var{id} is any declared
9362 identifier within your program, except another module.
9364 Using the @code{::} operator makes @value{GDBN} search the scope
9365 specified by @var{scope} for the identifier @var{id}. If it is not
9366 found in the specified scope, then @value{GDBN} searches all scopes
9367 enclosing the one specified by @var{scope}.
9369 Using the @code{.} operator makes @value{GDBN} search the current scope for
9370 the identifier specified by @var{id} that was imported from the
9371 definition module specified by @var{module}. With this operator, it is
9372 an error if the identifier @var{id} was not imported from definition
9373 module @var{module}, or if @var{id} is not an identifier in
9377 @subsubsection @value{GDBN} and Modula-2
9379 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
9380 Five subcommands of @code{set print} and @code{show print} apply
9381 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
9382 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
9383 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
9384 analogue in Modula-2.
9386 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
9387 with any language, is not useful with Modula-2. Its
9388 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
9389 created in Modula-2 as they can in C or C@t{++}. However, because an
9390 address can be specified by an integral constant, the construct
9391 @samp{@{@var{type}@}@var{adrexp}} is still useful.
9393 @cindex @code{#} in Modula-2
9394 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
9395 interpreted as the beginning of a comment. Use @code{<>} instead.
9401 The extensions made to @value{GDBN} for Ada only support
9402 output from the @sc{gnu} Ada (GNAT) compiler.
9403 Other Ada compilers are not currently supported, and
9404 attempting to debug executables produced by them is most likely
9408 @cindex expressions in Ada
9410 * Ada Mode Intro:: General remarks on the Ada syntax
9411 and semantics supported by Ada mode
9413 * Omissions from Ada:: Restrictions on the Ada expression syntax.
9414 * Additions to Ada:: Extensions of the Ada expression syntax.
9415 * Stopping Before Main Program:: Debugging the program during elaboration.
9416 * Ada Glitches:: Known peculiarities of Ada mode.
9419 @node Ada Mode Intro
9420 @subsubsection Introduction
9421 @cindex Ada mode, general
9423 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
9424 syntax, with some extensions.
9425 The philosophy behind the design of this subset is
9429 That @value{GDBN} should provide basic literals and access to operations for
9430 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
9431 leaving more sophisticated computations to subprograms written into the
9432 program (which therefore may be called from @value{GDBN}).
9435 That type safety and strict adherence to Ada language restrictions
9436 are not particularly important to the @value{GDBN} user.
9439 That brevity is important to the @value{GDBN} user.
9442 Thus, for brevity, the debugger acts as if there were
9443 implicit @code{with} and @code{use} clauses in effect for all user-written
9444 packages, making it unnecessary to fully qualify most names with
9445 their packages, regardless of context. Where this causes ambiguity,
9446 @value{GDBN} asks the user's intent.
9448 The debugger will start in Ada mode if it detects an Ada main program.
9449 As for other languages, it will enter Ada mode when stopped in a program that
9450 was translated from an Ada source file.
9452 While in Ada mode, you may use `@t{--}' for comments. This is useful
9453 mostly for documenting command files. The standard @value{GDBN} comment
9454 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
9455 middle (to allow based literals).
9457 The debugger supports limited overloading. Given a subprogram call in which
9458 the function symbol has multiple definitions, it will use the number of
9459 actual parameters and some information about their types to attempt to narrow
9460 the set of definitions. It also makes very limited use of context, preferring
9461 procedures to functions in the context of the @code{call} command, and
9462 functions to procedures elsewhere.
9464 @node Omissions from Ada
9465 @subsubsection Omissions from Ada
9466 @cindex Ada, omissions from
9468 Here are the notable omissions from the subset:
9472 Only a subset of the attributes are supported:
9476 @t{'First}, @t{'Last}, and @t{'Length}
9477 on array objects (not on types and subtypes).
9480 @t{'Min} and @t{'Max}.
9483 @t{'Pos} and @t{'Val}.
9489 @t{'Range} on array objects (not subtypes), but only as the right
9490 operand of the membership (@code{in}) operator.
9493 @t{'Access}, @t{'Unchecked_Access}, and
9494 @t{'Unrestricted_Access} (a GNAT extension).
9502 @code{Characters.Latin_1} are not available and
9503 concatenation is not implemented. Thus, escape characters in strings are
9504 not currently available.
9507 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
9508 equality of representations. They will generally work correctly
9509 for strings and arrays whose elements have integer or enumeration types.
9510 They may not work correctly for arrays whose element
9511 types have user-defined equality, for arrays of real values
9512 (in particular, IEEE-conformant floating point, because of negative
9513 zeroes and NaNs), and for arrays whose elements contain unused bits with
9514 indeterminate values.
9517 The other component-by-component array operations (@code{and}, @code{or},
9518 @code{xor}, @code{not}, and relational tests other than equality)
9519 are not implemented.
9522 There are no record or array aggregates.
9525 Calls to dispatching subprograms are not implemented.
9528 The overloading algorithm is much more limited (i.e., less selective)
9529 than that of real Ada. It makes only limited use of the context in which a subexpression
9530 appears to resolve its meaning, and it is much looser in its rules for allowing
9531 type matches. As a result, some function calls will be ambiguous, and the user
9532 will be asked to choose the proper resolution.
9535 The @code{new} operator is not implemented.
9538 Entry calls are not implemented.
9541 Aside from printing, arithmetic operations on the native VAX floating-point
9542 formats are not supported.
9545 It is not possible to slice a packed array.
9548 @node Additions to Ada
9549 @subsubsection Additions to Ada
9550 @cindex Ada, deviations from
9552 As it does for other languages, @value{GDBN} makes certain generic
9553 extensions to Ada (@pxref{Expressions}):
9557 If the expression @var{E} is a variable residing in memory
9558 (typically a local variable or array element) and @var{N} is
9559 a positive integer, then @code{@var{E}@@@var{N}} displays the values of
9560 @var{E} and the @var{N}-1 adjacent variables following it in memory as an array.
9561 In Ada, this operator is generally not necessary, since its prime use
9562 is in displaying parts of an array, and slicing will usually do this in Ada.
9563 However, there are occasional uses when debugging programs
9564 in which certain debugging information has been optimized away.
9567 @code{@var{B}::@var{var}} means ``the variable named @var{var} that appears
9568 in function or file @var{B}.'' When @var{B} is a file name, you must typically
9569 surround it in single quotes.
9572 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
9573 @var{type} that appears at address @var{addr}.''
9576 A name starting with @samp{$} is a convenience variable
9577 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
9580 In addition, @value{GDBN} provides a few other shortcuts and outright additions specific
9585 The assignment statement is allowed as an expression, returning
9586 its right-hand operand as its value. Thus, you may enter
9590 print A(tmp := y + 1)
9594 The semicolon is allowed as an ``operator,'' returning as its value
9595 the value of its right-hand operand.
9596 This allows, for example,
9597 complex conditional breaks:
9601 condition 1 (report(i); k += 1; A(k) > 100)
9605 Rather than use catenation and symbolic character names to introduce special
9606 characters into strings, one may instead use a special bracket notation,
9607 which is also used to print strings. A sequence of characters of the form
9608 @samp{["@var{XX}"]} within a string or character literal denotes the
9609 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
9610 sequence of characters @samp{["""]} also denotes a single quotation mark
9611 in strings. For example,
9613 "One line.["0a"]Next line.["0a"]"
9616 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF}) after each
9620 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
9621 @t{'Max} is optional (and is ignored in any case). For example, it is valid
9629 When printing arrays, @value{GDBN} uses positional notation when the
9630 array has a lower bound of 1, and uses a modified named notation otherwise.
9631 For example, a one-dimensional array of three integers with a lower bound of 3 might print as
9638 That is, in contrast to valid Ada, only the first component has a @code{=>}
9642 You may abbreviate attributes in expressions with any unique,
9643 multi-character subsequence of
9644 their names (an exact match gets preference).
9645 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
9646 in place of @t{a'length}.
9649 @cindex quoting Ada internal identifiers
9650 Since Ada is case-insensitive, the debugger normally maps identifiers you type
9651 to lower case. The GNAT compiler uses upper-case characters for
9652 some of its internal identifiers, which are normally of no interest to users.
9653 For the rare occasions when you actually have to look at them,
9654 enclose them in angle brackets to avoid the lower-case mapping.
9657 @value{GDBP} print <JMPBUF_SAVE>[0]
9661 Printing an object of class-wide type or dereferencing an
9662 access-to-class-wide value will display all the components of the object's
9663 specific type (as indicated by its run-time tag). Likewise, component
9664 selection on such a value will operate on the specific type of the
9669 @node Stopping Before Main Program
9670 @subsubsection Stopping at the Very Beginning
9672 @cindex breakpointing Ada elaboration code
9673 It is sometimes necessary to debug the program during elaboration, and
9674 before reaching the main procedure.
9675 As defined in the Ada Reference
9676 Manual, the elaboration code is invoked from a procedure called
9677 @code{adainit}. To run your program up to the beginning of
9678 elaboration, simply use the following two commands:
9679 @code{tbreak adainit} and @code{run}.
9682 @subsubsection Known Peculiarities of Ada Mode
9683 @cindex Ada, problems
9685 Besides the omissions listed previously (@pxref{Omissions from Ada}),
9686 we know of several problems with and limitations of Ada mode in
9688 some of which will be fixed with planned future releases of the debugger
9689 and the GNU Ada compiler.
9693 Currently, the debugger
9694 has insufficient information to determine whether certain pointers represent
9695 pointers to objects or the objects themselves.
9696 Thus, the user may have to tack an extra @code{.all} after an expression
9697 to get it printed properly.
9700 Static constants that the compiler chooses not to materialize as objects in
9701 storage are invisible to the debugger.
9704 Named parameter associations in function argument lists are ignored (the
9705 argument lists are treated as positional).
9708 Many useful library packages are currently invisible to the debugger.
9711 Fixed-point arithmetic, conversions, input, and output is carried out using
9712 floating-point arithmetic, and may give results that only approximate those on
9716 The type of the @t{'Address} attribute may not be @code{System.Address}.
9719 The GNAT compiler never generates the prefix @code{Standard} for any of
9720 the standard symbols defined by the Ada language. @value{GDBN} knows about
9721 this: it will strip the prefix from names when you use it, and will never
9722 look for a name you have so qualified among local symbols, nor match against
9723 symbols in other packages or subprograms. If you have
9724 defined entities anywhere in your program other than parameters and
9725 local variables whose simple names match names in @code{Standard},
9726 GNAT's lack of qualification here can cause confusion. When this happens,
9727 you can usually resolve the confusion
9728 by qualifying the problematic names with package
9729 @code{Standard} explicitly.
9732 @node Unsupported languages
9733 @section Unsupported languages
9735 @cindex unsupported languages
9736 @cindex minimal language
9737 In addition to the other fully-supported programming languages,
9738 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
9739 It does not represent a real programming language, but provides a set
9740 of capabilities close to what the C or assembly languages provide.
9741 This should allow most simple operations to be performed while debugging
9742 an application that uses a language currently not supported by @value{GDBN}.
9744 If the language is set to @code{auto}, @value{GDBN} will automatically
9745 select this language if the current frame corresponds to an unsupported
9749 @chapter Examining the Symbol Table
9751 The commands described in this chapter allow you to inquire about the
9752 symbols (names of variables, functions and types) defined in your
9753 program. This information is inherent in the text of your program and
9754 does not change as your program executes. @value{GDBN} finds it in your
9755 program's symbol table, in the file indicated when you started @value{GDBN}
9756 (@pxref{File Options, ,Choosing files}), or by one of the
9757 file-management commands (@pxref{Files, ,Commands to specify files}).
9759 @cindex symbol names
9760 @cindex names of symbols
9761 @cindex quoting names
9762 Occasionally, you may need to refer to symbols that contain unusual
9763 characters, which @value{GDBN} ordinarily treats as word delimiters. The
9764 most frequent case is in referring to static variables in other
9765 source files (@pxref{Variables,,Program variables}). File names
9766 are recorded in object files as debugging symbols, but @value{GDBN} would
9767 ordinarily parse a typical file name, like @file{foo.c}, as the three words
9768 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
9769 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
9776 looks up the value of @code{x} in the scope of the file @file{foo.c}.
9779 @cindex case-insensitive symbol names
9780 @cindex case sensitivity in symbol names
9781 @kindex set case-sensitive
9782 @item set case-sensitive on
9783 @itemx set case-sensitive off
9784 @itemx set case-sensitive auto
9785 Normally, when @value{GDBN} looks up symbols, it matches their names
9786 with case sensitivity determined by the current source language.
9787 Occasionally, you may wish to control that. The command @code{set
9788 case-sensitive} lets you do that by specifying @code{on} for
9789 case-sensitive matches or @code{off} for case-insensitive ones. If
9790 you specify @code{auto}, case sensitivity is reset to the default
9791 suitable for the source language. The default is case-sensitive
9792 matches for all languages except for Fortran, for which the default is
9793 case-insensitive matches.
9795 @kindex show case-sensitive
9796 @item show case-sensitive
9797 This command shows the current setting of case sensitivity for symbols
9800 @kindex info address
9801 @cindex address of a symbol
9802 @item info address @var{symbol}
9803 Describe where the data for @var{symbol} is stored. For a register
9804 variable, this says which register it is kept in. For a non-register
9805 local variable, this prints the stack-frame offset at which the variable
9808 Note the contrast with @samp{print &@var{symbol}}, which does not work
9809 at all for a register variable, and for a stack local variable prints
9810 the exact address of the current instantiation of the variable.
9813 @cindex symbol from address
9814 @cindex closest symbol and offset for an address
9815 @item info symbol @var{addr}
9816 Print the name of a symbol which is stored at the address @var{addr}.
9817 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
9818 nearest symbol and an offset from it:
9821 (@value{GDBP}) info symbol 0x54320
9822 _initialize_vx + 396 in section .text
9826 This is the opposite of the @code{info address} command. You can use
9827 it to find out the name of a variable or a function given its address.
9830 @item whatis @var{expr}
9831 Print the data type of expression @var{expr}. @var{expr} is not
9832 actually evaluated, and any side-effecting operations (such as
9833 assignments or function calls) inside it do not take place.
9834 @xref{Expressions, ,Expressions}.
9837 Print the data type of @code{$}, the last value in the value history.
9840 @item ptype @var{typename}
9841 Print a description of data type @var{typename}. @var{typename} may be
9842 the name of a type, or for C code it may have the form @samp{class
9843 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
9844 @var{union-tag}} or @samp{enum @var{enum-tag}}.
9846 @item ptype @var{expr}
9848 Print a description of the type of expression @var{expr}. @code{ptype}
9849 differs from @code{whatis} by printing a detailed description, instead
9850 of just the name of the type.
9852 For example, for this variable declaration:
9855 struct complex @{double real; double imag;@} v;
9859 the two commands give this output:
9863 (@value{GDBP}) whatis v
9864 type = struct complex
9865 (@value{GDBP}) ptype v
9866 type = struct complex @{
9874 As with @code{whatis}, using @code{ptype} without an argument refers to
9875 the type of @code{$}, the last value in the value history.
9878 @item info types @var{regexp}
9880 Print a brief description of all types whose names match the regular
9881 expression @var{regexp} (or all types in your program, if you supply
9882 no argument). Each complete typename is matched as though it were a
9883 complete line; thus, @samp{i type value} gives information on all
9884 types in your program whose names include the string @code{value}, but
9885 @samp{i type ^value$} gives information only on types whose complete
9886 name is @code{value}.
9888 This command differs from @code{ptype} in two ways: first, like
9889 @code{whatis}, it does not print a detailed description; second, it
9890 lists all source files where a type is defined.
9893 @cindex local variables
9894 @item info scope @var{location}
9895 List all the variables local to a particular scope. This command
9896 accepts a @var{location} argument---a function name, a source line, or
9897 an address preceded by a @samp{*}, and prints all the variables local
9898 to the scope defined by that location. For example:
9901 (@value{GDBP}) @b{info scope command_line_handler}
9902 Scope for command_line_handler:
9903 Symbol rl is an argument at stack/frame offset 8, length 4.
9904 Symbol linebuffer is in static storage at address 0x150a18, length 4.
9905 Symbol linelength is in static storage at address 0x150a1c, length 4.
9906 Symbol p is a local variable in register $esi, length 4.
9907 Symbol p1 is a local variable in register $ebx, length 4.
9908 Symbol nline is a local variable in register $edx, length 4.
9909 Symbol repeat is a local variable at frame offset -8, length 4.
9913 This command is especially useful for determining what data to collect
9914 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
9919 Show information about the current source file---that is, the source file for
9920 the function containing the current point of execution:
9923 the name of the source file, and the directory containing it,
9925 the directory it was compiled in,
9927 its length, in lines,
9929 which programming language it is written in,
9931 whether the executable includes debugging information for that file, and
9932 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
9934 whether the debugging information includes information about
9935 preprocessor macros.
9939 @kindex info sources
9941 Print the names of all source files in your program for which there is
9942 debugging information, organized into two lists: files whose symbols
9943 have already been read, and files whose symbols will be read when needed.
9945 @kindex info functions
9946 @item info functions
9947 Print the names and data types of all defined functions.
9949 @item info functions @var{regexp}
9950 Print the names and data types of all defined functions
9951 whose names contain a match for regular expression @var{regexp}.
9952 Thus, @samp{info fun step} finds all functions whose names
9953 include @code{step}; @samp{info fun ^step} finds those whose names
9954 start with @code{step}. If a function name contains characters
9955 that conflict with the regular expression language (eg.
9956 @samp{operator*()}), they may be quoted with a backslash.
9958 @kindex info variables
9959 @item info variables
9960 Print the names and data types of all variables that are declared
9961 outside of functions (i.e.@: excluding local variables).
9963 @item info variables @var{regexp}
9964 Print the names and data types of all variables (except for local
9965 variables) whose names contain a match for regular expression
9968 @kindex info classes
9969 @cindex Objective-C, classes and selectors
9971 @itemx info classes @var{regexp}
9972 Display all Objective-C classes in your program, or
9973 (with the @var{regexp} argument) all those matching a particular regular
9976 @kindex info selectors
9977 @item info selectors
9978 @itemx info selectors @var{regexp}
9979 Display all Objective-C selectors in your program, or
9980 (with the @var{regexp} argument) all those matching a particular regular
9984 This was never implemented.
9985 @kindex info methods
9987 @itemx info methods @var{regexp}
9988 The @code{info methods} command permits the user to examine all defined
9989 methods within C@t{++} program, or (with the @var{regexp} argument) a
9990 specific set of methods found in the various C@t{++} classes. Many
9991 C@t{++} classes provide a large number of methods. Thus, the output
9992 from the @code{ptype} command can be overwhelming and hard to use. The
9993 @code{info-methods} command filters the methods, printing only those
9994 which match the regular-expression @var{regexp}.
9997 @cindex reloading symbols
9998 Some systems allow individual object files that make up your program to
9999 be replaced without stopping and restarting your program. For example,
10000 in VxWorks you can simply recompile a defective object file and keep on
10001 running. If you are running on one of these systems, you can allow
10002 @value{GDBN} to reload the symbols for automatically relinked modules:
10005 @kindex set symbol-reloading
10006 @item set symbol-reloading on
10007 Replace symbol definitions for the corresponding source file when an
10008 object file with a particular name is seen again.
10010 @item set symbol-reloading off
10011 Do not replace symbol definitions when encountering object files of the
10012 same name more than once. This is the default state; if you are not
10013 running on a system that permits automatic relinking of modules, you
10014 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
10015 may discard symbols when linking large programs, that may contain
10016 several modules (from different directories or libraries) with the same
10019 @kindex show symbol-reloading
10020 @item show symbol-reloading
10021 Show the current @code{on} or @code{off} setting.
10024 @cindex opaque data types
10025 @kindex set opaque-type-resolution
10026 @item set opaque-type-resolution on
10027 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
10028 declared as a pointer to a @code{struct}, @code{class}, or
10029 @code{union}---for example, @code{struct MyType *}---that is used in one
10030 source file although the full declaration of @code{struct MyType} is in
10031 another source file. The default is on.
10033 A change in the setting of this subcommand will not take effect until
10034 the next time symbols for a file are loaded.
10036 @item set opaque-type-resolution off
10037 Tell @value{GDBN} not to resolve opaque types. In this case, the type
10038 is printed as follows:
10040 @{<no data fields>@}
10043 @kindex show opaque-type-resolution
10044 @item show opaque-type-resolution
10045 Show whether opaque types are resolved or not.
10047 @kindex maint print symbols
10048 @cindex symbol dump
10049 @kindex maint print psymbols
10050 @cindex partial symbol dump
10051 @item maint print symbols @var{filename}
10052 @itemx maint print psymbols @var{filename}
10053 @itemx maint print msymbols @var{filename}
10054 Write a dump of debugging symbol data into the file @var{filename}.
10055 These commands are used to debug the @value{GDBN} symbol-reading code. Only
10056 symbols with debugging data are included. If you use @samp{maint print
10057 symbols}, @value{GDBN} includes all the symbols for which it has already
10058 collected full details: that is, @var{filename} reflects symbols for
10059 only those files whose symbols @value{GDBN} has read. You can use the
10060 command @code{info sources} to find out which files these are. If you
10061 use @samp{maint print psymbols} instead, the dump shows information about
10062 symbols that @value{GDBN} only knows partially---that is, symbols defined in
10063 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
10064 @samp{maint print msymbols} dumps just the minimal symbol information
10065 required for each object file from which @value{GDBN} has read some symbols.
10066 @xref{Files, ,Commands to specify files}, for a discussion of how
10067 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
10069 @kindex maint info symtabs
10070 @kindex maint info psymtabs
10071 @cindex listing @value{GDBN}'s internal symbol tables
10072 @cindex symbol tables, listing @value{GDBN}'s internal
10073 @cindex full symbol tables, listing @value{GDBN}'s internal
10074 @cindex partial symbol tables, listing @value{GDBN}'s internal
10075 @item maint info symtabs @r{[} @var{regexp} @r{]}
10076 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
10078 List the @code{struct symtab} or @code{struct partial_symtab}
10079 structures whose names match @var{regexp}. If @var{regexp} is not
10080 given, list them all. The output includes expressions which you can
10081 copy into a @value{GDBN} debugging this one to examine a particular
10082 structure in more detail. For example:
10085 (@value{GDBP}) maint info psymtabs dwarf2read
10086 @{ objfile /home/gnu/build/gdb/gdb
10087 ((struct objfile *) 0x82e69d0)
10088 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
10089 ((struct partial_symtab *) 0x8474b10)
10092 text addresses 0x814d3c8 -- 0x8158074
10093 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
10094 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
10095 dependencies (none)
10098 (@value{GDBP}) maint info symtabs
10102 We see that there is one partial symbol table whose filename contains
10103 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
10104 and we see that @value{GDBN} has not read in any symtabs yet at all.
10105 If we set a breakpoint on a function, that will cause @value{GDBN} to
10106 read the symtab for the compilation unit containing that function:
10109 (@value{GDBP}) break dwarf2_psymtab_to_symtab
10110 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
10112 (@value{GDBP}) maint info symtabs
10113 @{ objfile /home/gnu/build/gdb/gdb
10114 ((struct objfile *) 0x82e69d0)
10115 @{ symtab /home/gnu/src/gdb/dwarf2read.c
10116 ((struct symtab *) 0x86c1f38)
10119 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
10120 debugformat DWARF 2
10129 @chapter Altering Execution
10131 Once you think you have found an error in your program, you might want to
10132 find out for certain whether correcting the apparent error would lead to
10133 correct results in the rest of the run. You can find the answer by
10134 experiment, using the @value{GDBN} features for altering execution of the
10137 For example, you can store new values into variables or memory
10138 locations, give your program a signal, restart it at a different
10139 address, or even return prematurely from a function.
10142 * Assignment:: Assignment to variables
10143 * Jumping:: Continuing at a different address
10144 * Signaling:: Giving your program a signal
10145 * Returning:: Returning from a function
10146 * Calling:: Calling your program's functions
10147 * Patching:: Patching your program
10151 @section Assignment to variables
10154 @cindex setting variables
10155 To alter the value of a variable, evaluate an assignment expression.
10156 @xref{Expressions, ,Expressions}. For example,
10163 stores the value 4 into the variable @code{x}, and then prints the
10164 value of the assignment expression (which is 4).
10165 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
10166 information on operators in supported languages.
10168 @kindex set variable
10169 @cindex variables, setting
10170 If you are not interested in seeing the value of the assignment, use the
10171 @code{set} command instead of the @code{print} command. @code{set} is
10172 really the same as @code{print} except that the expression's value is
10173 not printed and is not put in the value history (@pxref{Value History,
10174 ,Value history}). The expression is evaluated only for its effects.
10176 If the beginning of the argument string of the @code{set} command
10177 appears identical to a @code{set} subcommand, use the @code{set
10178 variable} command instead of just @code{set}. This command is identical
10179 to @code{set} except for its lack of subcommands. For example, if your
10180 program has a variable @code{width}, you get an error if you try to set
10181 a new value with just @samp{set width=13}, because @value{GDBN} has the
10182 command @code{set width}:
10185 (@value{GDBP}) whatis width
10187 (@value{GDBP}) p width
10189 (@value{GDBP}) set width=47
10190 Invalid syntax in expression.
10194 The invalid expression, of course, is @samp{=47}. In
10195 order to actually set the program's variable @code{width}, use
10198 (@value{GDBP}) set var width=47
10201 Because the @code{set} command has many subcommands that can conflict
10202 with the names of program variables, it is a good idea to use the
10203 @code{set variable} command instead of just @code{set}. For example, if
10204 your program has a variable @code{g}, you run into problems if you try
10205 to set a new value with just @samp{set g=4}, because @value{GDBN} has
10206 the command @code{set gnutarget}, abbreviated @code{set g}:
10210 (@value{GDBP}) whatis g
10214 (@value{GDBP}) set g=4
10218 The program being debugged has been started already.
10219 Start it from the beginning? (y or n) y
10220 Starting program: /home/smith/cc_progs/a.out
10221 "/home/smith/cc_progs/a.out": can't open to read symbols:
10222 Invalid bfd target.
10223 (@value{GDBP}) show g
10224 The current BFD target is "=4".
10229 The program variable @code{g} did not change, and you silently set the
10230 @code{gnutarget} to an invalid value. In order to set the variable
10234 (@value{GDBP}) set var g=4
10237 @value{GDBN} allows more implicit conversions in assignments than C; you can
10238 freely store an integer value into a pointer variable or vice versa,
10239 and you can convert any structure to any other structure that is the
10240 same length or shorter.
10241 @comment FIXME: how do structs align/pad in these conversions?
10242 @comment /doc@cygnus.com 18dec1990
10244 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
10245 construct to generate a value of specified type at a specified address
10246 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
10247 to memory location @code{0x83040} as an integer (which implies a certain size
10248 and representation in memory), and
10251 set @{int@}0x83040 = 4
10255 stores the value 4 into that memory location.
10258 @section Continuing at a different address
10260 Ordinarily, when you continue your program, you do so at the place where
10261 it stopped, with the @code{continue} command. You can instead continue at
10262 an address of your own choosing, with the following commands:
10266 @item jump @var{linespec}
10267 Resume execution at line @var{linespec}. Execution stops again
10268 immediately if there is a breakpoint there. @xref{List, ,Printing
10269 source lines}, for a description of the different forms of
10270 @var{linespec}. It is common practice to use the @code{tbreak} command
10271 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
10274 The @code{jump} command does not change the current stack frame, or
10275 the stack pointer, or the contents of any memory location or any
10276 register other than the program counter. If line @var{linespec} is in
10277 a different function from the one currently executing, the results may
10278 be bizarre if the two functions expect different patterns of arguments or
10279 of local variables. For this reason, the @code{jump} command requests
10280 confirmation if the specified line is not in the function currently
10281 executing. However, even bizarre results are predictable if you are
10282 well acquainted with the machine-language code of your program.
10284 @item jump *@var{address}
10285 Resume execution at the instruction at address @var{address}.
10288 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
10289 On many systems, you can get much the same effect as the @code{jump}
10290 command by storing a new value into the register @code{$pc}. The
10291 difference is that this does not start your program running; it only
10292 changes the address of where it @emph{will} run when you continue. For
10300 makes the next @code{continue} command or stepping command execute at
10301 address @code{0x485}, rather than at the address where your program stopped.
10302 @xref{Continuing and Stepping, ,Continuing and stepping}.
10304 The most common occasion to use the @code{jump} command is to back
10305 up---perhaps with more breakpoints set---over a portion of a program
10306 that has already executed, in order to examine its execution in more
10311 @section Giving your program a signal
10312 @cindex deliver a signal to a program
10316 @item signal @var{signal}
10317 Resume execution where your program stopped, but immediately give it the
10318 signal @var{signal}. @var{signal} can be the name or the number of a
10319 signal. For example, on many systems @code{signal 2} and @code{signal
10320 SIGINT} are both ways of sending an interrupt signal.
10322 Alternatively, if @var{signal} is zero, continue execution without
10323 giving a signal. This is useful when your program stopped on account of
10324 a signal and would ordinary see the signal when resumed with the
10325 @code{continue} command; @samp{signal 0} causes it to resume without a
10328 @code{signal} does not repeat when you press @key{RET} a second time
10329 after executing the command.
10333 Invoking the @code{signal} command is not the same as invoking the
10334 @code{kill} utility from the shell. Sending a signal with @code{kill}
10335 causes @value{GDBN} to decide what to do with the signal depending on
10336 the signal handling tables (@pxref{Signals}). The @code{signal} command
10337 passes the signal directly to your program.
10341 @section Returning from a function
10344 @cindex returning from a function
10347 @itemx return @var{expression}
10348 You can cancel execution of a function call with the @code{return}
10349 command. If you give an
10350 @var{expression} argument, its value is used as the function's return
10354 When you use @code{return}, @value{GDBN} discards the selected stack frame
10355 (and all frames within it). You can think of this as making the
10356 discarded frame return prematurely. If you wish to specify a value to
10357 be returned, give that value as the argument to @code{return}.
10359 This pops the selected stack frame (@pxref{Selection, ,Selecting a
10360 frame}), and any other frames inside of it, leaving its caller as the
10361 innermost remaining frame. That frame becomes selected. The
10362 specified value is stored in the registers used for returning values
10365 The @code{return} command does not resume execution; it leaves the
10366 program stopped in the state that would exist if the function had just
10367 returned. In contrast, the @code{finish} command (@pxref{Continuing
10368 and Stepping, ,Continuing and stepping}) resumes execution until the
10369 selected stack frame returns naturally.
10372 @section Calling program functions
10375 @cindex calling functions
10376 @cindex inferior functions, calling
10377 @item print @var{expr}
10378 Evaluate the expression @var{expr} and display the resuling value.
10379 @var{expr} may include calls to functions in the program being
10383 @item call @var{expr}
10384 Evaluate the expression @var{expr} without displaying @code{void}
10387 You can use this variant of the @code{print} command if you want to
10388 execute a function from your program that does not return anything
10389 (a.k.a.@: @dfn{a void function}), but without cluttering the output
10390 with @code{void} returned values that @value{GDBN} will otherwise
10391 print. If the result is not void, it is printed and saved in the
10395 It is possible for the function you call via the @code{print} or
10396 @code{call} command to generate a signal (e.g., if there's a bug in
10397 the function, or if you passed it incorrect arguments). What happens
10398 in that case is controlled by the @code{set unwindonsignal} command.
10401 @item set unwindonsignal
10402 @kindex set unwindonsignal
10403 @cindex unwind stack in called functions
10404 @cindex call dummy stack unwinding
10405 Set unwinding of the stack if a signal is received while in a function
10406 that @value{GDBN} called in the program being debugged. If set to on,
10407 @value{GDBN} unwinds the stack it created for the call and restores
10408 the context to what it was before the call. If set to off (the
10409 default), @value{GDBN} stops in the frame where the signal was
10412 @item show unwindonsignal
10413 @kindex show unwindonsignal
10414 Show the current setting of stack unwinding in the functions called by
10418 @cindex weak alias functions
10419 Sometimes, a function you wish to call is actually a @dfn{weak alias}
10420 for another function. In such case, @value{GDBN} might not pick up
10421 the type information, including the types of the function arguments,
10422 which causes @value{GDBN} to call the inferior function incorrectly.
10423 As a result, the called function will function erroneously and may
10424 even crash. A solution to that is to use the name of the aliased
10428 @section Patching programs
10430 @cindex patching binaries
10431 @cindex writing into executables
10432 @cindex writing into corefiles
10434 By default, @value{GDBN} opens the file containing your program's
10435 executable code (or the corefile) read-only. This prevents accidental
10436 alterations to machine code; but it also prevents you from intentionally
10437 patching your program's binary.
10439 If you'd like to be able to patch the binary, you can specify that
10440 explicitly with the @code{set write} command. For example, you might
10441 want to turn on internal debugging flags, or even to make emergency
10447 @itemx set write off
10448 If you specify @samp{set write on}, @value{GDBN} opens executable and
10449 core files for both reading and writing; if you specify @samp{set write
10450 off} (the default), @value{GDBN} opens them read-only.
10452 If you have already loaded a file, you must load it again (using the
10453 @code{exec-file} or @code{core-file} command) after changing @code{set
10454 write}, for your new setting to take effect.
10458 Display whether executable files and core files are opened for writing
10459 as well as reading.
10463 @chapter @value{GDBN} Files
10465 @value{GDBN} needs to know the file name of the program to be debugged,
10466 both in order to read its symbol table and in order to start your
10467 program. To debug a core dump of a previous run, you must also tell
10468 @value{GDBN} the name of the core dump file.
10471 * Files:: Commands to specify files
10472 * Separate Debug Files:: Debugging information in separate files
10473 * Symbol Errors:: Errors reading symbol files
10477 @section Commands to specify files
10479 @cindex symbol table
10480 @cindex core dump file
10482 You may want to specify executable and core dump file names. The usual
10483 way to do this is at start-up time, using the arguments to
10484 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
10485 Out of @value{GDBN}}).
10487 Occasionally it is necessary to change to a different file during a
10488 @value{GDBN} session. Or you may run @value{GDBN} and forget to specify
10489 a file you want to use. In these situations the @value{GDBN} commands
10490 to specify new files are useful.
10493 @cindex executable file
10495 @item file @var{filename}
10496 Use @var{filename} as the program to be debugged. It is read for its
10497 symbols and for the contents of pure memory. It is also the program
10498 executed when you use the @code{run} command. If you do not specify a
10499 directory and the file is not found in the @value{GDBN} working directory,
10500 @value{GDBN} uses the environment variable @code{PATH} as a list of
10501 directories to search, just as the shell does when looking for a program
10502 to run. You can change the value of this variable, for both @value{GDBN}
10503 and your program, using the @code{path} command.
10505 On systems with memory-mapped files, an auxiliary file named
10506 @file{@var{filename}.syms} may hold symbol table information for
10507 @var{filename}. If so, @value{GDBN} maps in the symbol table from
10508 @file{@var{filename}.syms}, starting up more quickly. See the
10509 descriptions of the file options @samp{-mapped} and @samp{-readnow}
10510 (available on the command line, see @ref{File Options, , -readnow},
10511 and with the commands @code{file}, @code{symbol-file}, or
10512 @code{add-symbol-file}, described below), for more information.
10515 @code{file} with no argument makes @value{GDBN} discard any information it
10516 has on both executable file and the symbol table.
10519 @item exec-file @r{[} @var{filename} @r{]}
10520 Specify that the program to be run (but not the symbol table) is found
10521 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
10522 if necessary to locate your program. Omitting @var{filename} means to
10523 discard information on the executable file.
10525 @kindex symbol-file
10526 @item symbol-file @r{[} @var{filename} @r{]}
10527 Read symbol table information from file @var{filename}. @code{PATH} is
10528 searched when necessary. Use the @code{file} command to get both symbol
10529 table and program to run from the same file.
10531 @code{symbol-file} with no argument clears out @value{GDBN} information on your
10532 program's symbol table.
10534 The @code{symbol-file} command causes @value{GDBN} to forget the contents
10535 of its convenience variables, the value history, and all breakpoints and
10536 auto-display expressions. This is because they may contain pointers to
10537 the internal data recording symbols and data types, which are part of
10538 the old symbol table data being discarded inside @value{GDBN}.
10540 @code{symbol-file} does not repeat if you press @key{RET} again after
10543 When @value{GDBN} is configured for a particular environment, it
10544 understands debugging information in whatever format is the standard
10545 generated for that environment; you may use either a @sc{gnu} compiler, or
10546 other compilers that adhere to the local conventions.
10547 Best results are usually obtained from @sc{gnu} compilers; for example,
10548 using @code{@value{GCC}} you can generate debugging information for
10551 For most kinds of object files, with the exception of old SVR3 systems
10552 using COFF, the @code{symbol-file} command does not normally read the
10553 symbol table in full right away. Instead, it scans the symbol table
10554 quickly to find which source files and which symbols are present. The
10555 details are read later, one source file at a time, as they are needed.
10557 The purpose of this two-stage reading strategy is to make @value{GDBN}
10558 start up faster. For the most part, it is invisible except for
10559 occasional pauses while the symbol table details for a particular source
10560 file are being read. (The @code{set verbose} command can turn these
10561 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
10562 warnings and messages}.)
10564 We have not implemented the two-stage strategy for COFF yet. When the
10565 symbol table is stored in COFF format, @code{symbol-file} reads the
10566 symbol table data in full right away. Note that ``stabs-in-COFF''
10567 still does the two-stage strategy, since the debug info is actually
10571 @cindex reading symbols immediately
10572 @cindex symbols, reading immediately
10574 @cindex memory-mapped symbol file
10575 @cindex saving symbol table
10576 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10577 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10578 You can override the @value{GDBN} two-stage strategy for reading symbol
10579 tables by using the @samp{-readnow} option with any of the commands that
10580 load symbol table information, if you want to be sure @value{GDBN} has the
10581 entire symbol table available.
10583 If memory-mapped files are available on your system through the
10584 @code{mmap} system call, you can use another option, @samp{-mapped}, to
10585 cause @value{GDBN} to write the symbols for your program into a reusable
10586 file. Future @value{GDBN} debugging sessions map in symbol information
10587 from this auxiliary symbol file (if the program has not changed), rather
10588 than spending time reading the symbol table from the executable
10589 program. Using the @samp{-mapped} option has the same effect as
10590 starting @value{GDBN} with the @samp{-mapped} command-line option.
10592 You can use both options together, to make sure the auxiliary symbol
10593 file has all the symbol information for your program.
10595 The auxiliary symbol file for a program called @var{myprog} is called
10596 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
10597 than the corresponding executable), @value{GDBN} always attempts to use
10598 it when you debug @var{myprog}; no special options or commands are
10601 The @file{.syms} file is specific to the host machine where you run
10602 @value{GDBN}. It holds an exact image of the internal @value{GDBN}
10603 symbol table. It cannot be shared across multiple host platforms.
10605 @c FIXME: for now no mention of directories, since this seems to be in
10606 @c flux. 13mar1992 status is that in theory GDB would look either in
10607 @c current dir or in same dir as myprog; but issues like competing
10608 @c GDB's, or clutter in system dirs, mean that in practice right now
10609 @c only current dir is used. FFish says maybe a special GDB hierarchy
10610 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
10614 @item core-file @r{[}@var{filename}@r{]}
10616 Specify the whereabouts of a core dump file to be used as the ``contents
10617 of memory''. Traditionally, core files contain only some parts of the
10618 address space of the process that generated them; @value{GDBN} can access the
10619 executable file itself for other parts.
10621 @code{core-file} with no argument specifies that no core file is
10624 Note that the core file is ignored when your program is actually running
10625 under @value{GDBN}. So, if you have been running your program and you
10626 wish to debug a core file instead, you must kill the subprocess in which
10627 the program is running. To do this, use the @code{kill} command
10628 (@pxref{Kill Process, ,Killing the child process}).
10630 @kindex add-symbol-file
10631 @cindex dynamic linking
10632 @item add-symbol-file @var{filename} @var{address}
10633 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10634 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
10635 The @code{add-symbol-file} command reads additional symbol table
10636 information from the file @var{filename}. You would use this command
10637 when @var{filename} has been dynamically loaded (by some other means)
10638 into the program that is running. @var{address} should be the memory
10639 address at which the file has been loaded; @value{GDBN} cannot figure
10640 this out for itself. You can additionally specify an arbitrary number
10641 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
10642 section name and base address for that section. You can specify any
10643 @var{address} as an expression.
10645 The symbol table of the file @var{filename} is added to the symbol table
10646 originally read with the @code{symbol-file} command. You can use the
10647 @code{add-symbol-file} command any number of times; the new symbol data
10648 thus read keeps adding to the old. To discard all old symbol data
10649 instead, use the @code{symbol-file} command without any arguments.
10651 @cindex relocatable object files, reading symbols from
10652 @cindex object files, relocatable, reading symbols from
10653 @cindex reading symbols from relocatable object files
10654 @cindex symbols, reading from relocatable object files
10655 @cindex @file{.o} files, reading symbols from
10656 Although @var{filename} is typically a shared library file, an
10657 executable file, or some other object file which has been fully
10658 relocated for loading into a process, you can also load symbolic
10659 information from relocatable @file{.o} files, as long as:
10663 the file's symbolic information refers only to linker symbols defined in
10664 that file, not to symbols defined by other object files,
10666 every section the file's symbolic information refers to has actually
10667 been loaded into the inferior, as it appears in the file, and
10669 you can determine the address at which every section was loaded, and
10670 provide these to the @code{add-symbol-file} command.
10674 Some embedded operating systems, like Sun Chorus and VxWorks, can load
10675 relocatable files into an already running program; such systems
10676 typically make the requirements above easy to meet. However, it's
10677 important to recognize that many native systems use complex link
10678 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
10679 assembly, for example) that make the requirements difficult to meet. In
10680 general, one cannot assume that using @code{add-symbol-file} to read a
10681 relocatable object file's symbolic information will have the same effect
10682 as linking the relocatable object file into the program in the normal
10685 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
10687 You can use the @samp{-mapped} and @samp{-readnow} options just as with
10688 the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
10689 table information for @var{filename}.
10691 @kindex add-symbol-file-from-memory
10692 @cindex @code{syscall DSO}
10693 @cindex load symbols from memory
10694 @item add-symbol-file-from-memory @var{address}
10695 Load symbols from the given @var{address} in a dynamically loaded
10696 object file whose image is mapped directly into the inferior's memory.
10697 For example, the Linux kernel maps a @code{syscall DSO} into each
10698 process's address space; this DSO provides kernel-specific code for
10699 some system calls. The argument can be any expression whose
10700 evaluation yields the address of the file's shared object file header.
10701 For this command to work, you must have used @code{symbol-file} or
10702 @code{exec-file} commands in advance.
10704 @kindex add-shared-symbol-files
10706 @item add-shared-symbol-files @var{library-file}
10707 @itemx assf @var{library-file}
10708 The @code{add-shared-symbol-files} command can currently be used only
10709 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
10710 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
10711 @value{GDBN} automatically looks for shared libraries, however if
10712 @value{GDBN} does not find yours, you can invoke
10713 @code{add-shared-symbol-files}. It takes one argument: the shared
10714 library's file name. @code{assf} is a shorthand alias for
10715 @code{add-shared-symbol-files}.
10718 @item section @var{section} @var{addr}
10719 The @code{section} command changes the base address of the named
10720 @var{section} of the exec file to @var{addr}. This can be used if the
10721 exec file does not contain section addresses, (such as in the
10722 @code{a.out} format), or when the addresses specified in the file
10723 itself are wrong. Each section must be changed separately. The
10724 @code{info files} command, described below, lists all the sections and
10728 @kindex info target
10731 @code{info files} and @code{info target} are synonymous; both print the
10732 current target (@pxref{Targets, ,Specifying a Debugging Target}),
10733 including the names of the executable and core dump files currently in
10734 use by @value{GDBN}, and the files from which symbols were loaded. The
10735 command @code{help target} lists all possible targets rather than
10738 @kindex maint info sections
10739 @item maint info sections
10740 Another command that can give you extra information about program sections
10741 is @code{maint info sections}. In addition to the section information
10742 displayed by @code{info files}, this command displays the flags and file
10743 offset of each section in the executable and core dump files. In addition,
10744 @code{maint info sections} provides the following command options (which
10745 may be arbitrarily combined):
10749 Display sections for all loaded object files, including shared libraries.
10750 @item @var{sections}
10751 Display info only for named @var{sections}.
10752 @item @var{section-flags}
10753 Display info only for sections for which @var{section-flags} are true.
10754 The section flags that @value{GDBN} currently knows about are:
10757 Section will have space allocated in the process when loaded.
10758 Set for all sections except those containing debug information.
10760 Section will be loaded from the file into the child process memory.
10761 Set for pre-initialized code and data, clear for @code{.bss} sections.
10763 Section needs to be relocated before loading.
10765 Section cannot be modified by the child process.
10767 Section contains executable code only.
10769 Section contains data only (no executable code).
10771 Section will reside in ROM.
10773 Section contains data for constructor/destructor lists.
10775 Section is not empty.
10777 An instruction to the linker to not output the section.
10778 @item COFF_SHARED_LIBRARY
10779 A notification to the linker that the section contains
10780 COFF shared library information.
10782 Section contains common symbols.
10785 @kindex set trust-readonly-sections
10786 @cindex read-only sections
10787 @item set trust-readonly-sections on
10788 Tell @value{GDBN} that readonly sections in your object file
10789 really are read-only (i.e.@: that their contents will not change).
10790 In that case, @value{GDBN} can fetch values from these sections
10791 out of the object file, rather than from the target program.
10792 For some targets (notably embedded ones), this can be a significant
10793 enhancement to debugging performance.
10795 The default is off.
10797 @item set trust-readonly-sections off
10798 Tell @value{GDBN} not to trust readonly sections. This means that
10799 the contents of the section might change while the program is running,
10800 and must therefore be fetched from the target when needed.
10802 @item show trust-readonly-sections
10803 Show the current setting of trusting readonly sections.
10806 All file-specifying commands allow both absolute and relative file names
10807 as arguments. @value{GDBN} always converts the file name to an absolute file
10808 name and remembers it that way.
10810 @cindex shared libraries
10811 @value{GDBN} supports GNU/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
10812 and IBM RS/6000 AIX shared libraries.
10814 @value{GDBN} automatically loads symbol definitions from shared libraries
10815 when you use the @code{run} command, or when you examine a core file.
10816 (Before you issue the @code{run} command, @value{GDBN} does not understand
10817 references to a function in a shared library, however---unless you are
10818 debugging a core file).
10820 On HP-UX, if the program loads a library explicitly, @value{GDBN}
10821 automatically loads the symbols at the time of the @code{shl_load} call.
10823 @c FIXME: some @value{GDBN} release may permit some refs to undef
10824 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
10825 @c FIXME...lib; check this from time to time when updating manual
10827 There are times, however, when you may wish to not automatically load
10828 symbol definitions from shared libraries, such as when they are
10829 particularly large or there are many of them.
10831 To control the automatic loading of shared library symbols, use the
10835 @kindex set auto-solib-add
10836 @item set auto-solib-add @var{mode}
10837 If @var{mode} is @code{on}, symbols from all shared object libraries
10838 will be loaded automatically when the inferior begins execution, you
10839 attach to an independently started inferior, or when the dynamic linker
10840 informs @value{GDBN} that a new library has been loaded. If @var{mode}
10841 is @code{off}, symbols must be loaded manually, using the
10842 @code{sharedlibrary} command. The default value is @code{on}.
10844 @cindex memory used for symbol tables
10845 If your program uses lots of shared libraries with debug info that
10846 takes large amounts of memory, you can decrease the @value{GDBN}
10847 memory footprint by preventing it from automatically loading the
10848 symbols from shared libraries. To that end, type @kbd{set
10849 auto-solib-add off} before running the inferior, then load each
10850 library whose debug symbols you do need with @kbd{sharedlibrary
10851 @var{regexp}}, where @var{regexp} is a regular expresion that matches
10852 the libraries whose symbols you want to be loaded.
10854 @kindex show auto-solib-add
10855 @item show auto-solib-add
10856 Display the current autoloading mode.
10859 @cindex load shared library
10860 To explicitly load shared library symbols, use the @code{sharedlibrary}
10864 @kindex info sharedlibrary
10867 @itemx info sharedlibrary
10868 Print the names of the shared libraries which are currently loaded.
10870 @kindex sharedlibrary
10872 @item sharedlibrary @var{regex}
10873 @itemx share @var{regex}
10874 Load shared object library symbols for files matching a
10875 Unix regular expression.
10876 As with files loaded automatically, it only loads shared libraries
10877 required by your program for a core file or after typing @code{run}. If
10878 @var{regex} is omitted all shared libraries required by your program are
10881 @item nosharedlibrary
10882 @kindex nosharedlibrary
10883 @cindex unload symbols from shared libraries
10884 Unload all shared object library symbols. This discards all symbols
10885 that have been loaded from all shared libraries. Symbols from shared
10886 libraries that were loaded by explicit user requests are not
10890 On some systems, such as HP-UX systems, @value{GDBN} supports
10891 autoloading shared library symbols until a limiting threshold size is
10892 reached. This provides the benefit of allowing autoloading to remain on
10893 by default, but avoids autoloading excessively large shared libraries,
10894 up to a threshold that is initially set, but which you can modify if you
10897 Beyond that threshold, symbols from shared libraries must be explicitly
10898 loaded. To load these symbols, use the command @code{sharedlibrary
10899 @var{filename}}. The base address of the shared library is determined
10900 automatically by @value{GDBN} and need not be specified.
10902 To display or set the threshold, use the commands:
10905 @kindex set auto-solib-limit
10906 @item set auto-solib-limit @var{threshold}
10907 Set the autoloading size threshold, in an integral number of megabytes.
10908 If @var{threshold} is nonzero and shared library autoloading is enabled,
10909 symbols from all shared object libraries will be loaded until the total
10910 size of the loaded shared library symbols exceeds this threshold.
10911 Otherwise, symbols must be loaded manually, using the
10912 @code{sharedlibrary} command. The default threshold is 100 (i.e.@: 100
10915 @kindex show auto-solib-limit
10916 @item show auto-solib-limit
10917 Display the current autoloading size threshold, in megabytes.
10920 Sometimes you may wish that @value{GDBN} stops and gives you control
10921 when any of shared library events happen. Use the @code{set
10922 stop-on-solib-events} command for this:
10925 @item set stop-on-solib-events
10926 @kindex set stop-on-solib-events
10927 This command controls whether @value{GDBN} should give you control
10928 when the dynamic linker notifies it about some shared library event.
10929 The most common event of interest is loading or unloading of a new
10932 @item show stop-on-solib-events
10933 @kindex show stop-on-solib-events
10934 Show whether @value{GDBN} stops and gives you control when shared
10935 library events happen.
10938 Shared libraries are also supported in many cross or remote debugging
10939 configurations. A copy of the target's libraries need to be present on the
10940 host system; they need to be the same as the target libraries, although the
10941 copies on the target can be stripped as long as the copies on the host are
10944 You need to tell @value{GDBN} where the target libraries are, so that it can
10945 load the correct copies---otherwise, it may try to load the host's libraries.
10946 @value{GDBN} has two variables to specify the search directories for target
10950 @kindex set solib-absolute-prefix
10951 @item set solib-absolute-prefix @var{path}
10952 If this variable is set, @var{path} will be used as a prefix for any
10953 absolute shared library paths; many runtime loaders store the absolute
10954 paths to the shared library in the target program's memory. If you use
10955 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
10956 out in the same way that they are on the target, with e.g.@: a
10957 @file{/usr/lib} hierarchy under @var{path}.
10959 You can set the default value of @samp{solib-absolute-prefix} by using the
10960 configure-time @samp{--with-sysroot} option.
10962 @kindex show solib-absolute-prefix
10963 @item show solib-absolute-prefix
10964 Display the current shared library prefix.
10966 @kindex set solib-search-path
10967 @item set solib-search-path @var{path}
10968 If this variable is set, @var{path} is a colon-separated list of directories
10969 to search for shared libraries. @samp{solib-search-path} is used after
10970 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
10971 the library is relative instead of absolute. If you want to use
10972 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
10973 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
10974 @value{GDBN} from finding your host's libraries.
10976 @kindex show solib-search-path
10977 @item show solib-search-path
10978 Display the current shared library search path.
10982 @node Separate Debug Files
10983 @section Debugging Information in Separate Files
10984 @cindex separate debugging information files
10985 @cindex debugging information in separate files
10986 @cindex @file{.debug} subdirectories
10987 @cindex debugging information directory, global
10988 @cindex global debugging information directory
10990 @value{GDBN} allows you to put a program's debugging information in a
10991 file separate from the executable itself, in a way that allows
10992 @value{GDBN} to find and load the debugging information automatically.
10993 Since debugging information can be very large --- sometimes larger
10994 than the executable code itself --- some systems distribute debugging
10995 information for their executables in separate files, which users can
10996 install only when they need to debug a problem.
10998 If an executable's debugging information has been extracted to a
10999 separate file, the executable should contain a @dfn{debug link} giving
11000 the name of the debugging information file (with no directory
11001 components), and a checksum of its contents. (The exact form of a
11002 debug link is described below.) If the full name of the directory
11003 containing the executable is @var{execdir}, and the executable has a
11004 debug link that specifies the name @var{debugfile}, then @value{GDBN}
11005 will automatically search for the debugging information file in three
11010 the directory containing the executable file (that is, it will look
11011 for a file named @file{@var{execdir}/@var{debugfile}},
11013 a subdirectory of that directory named @file{.debug} (that is, the
11014 file @file{@var{execdir}/.debug/@var{debugfile}}, and
11016 a subdirectory of the global debug file directory that includes the
11017 executable's full path, and the name from the link (that is, the file
11018 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
11019 @var{globaldebugdir} is the global debug file directory, and
11020 @var{execdir} has been turned into a relative path).
11023 @value{GDBN} checks under each of these names for a debugging
11024 information file whose checksum matches that given in the link, and
11025 reads the debugging information from the first one it finds.
11027 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
11028 which has a link containing the name @file{ls.debug}, and the global
11029 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
11030 for debug information in @file{/usr/bin/ls.debug},
11031 @file{/usr/bin/.debug/ls.debug}, and
11032 @file{/usr/lib/debug/usr/bin/ls.debug}.
11034 You can set the global debugging info directory's name, and view the
11035 name @value{GDBN} is currently using.
11039 @kindex set debug-file-directory
11040 @item set debug-file-directory @var{directory}
11041 Set the directory which @value{GDBN} searches for separate debugging
11042 information files to @var{directory}.
11044 @kindex show debug-file-directory
11045 @item show debug-file-directory
11046 Show the directory @value{GDBN} searches for separate debugging
11051 @cindex @code{.gnu_debuglink} sections
11052 @cindex debug links
11053 A debug link is a special section of the executable file named
11054 @code{.gnu_debuglink}. The section must contain:
11058 A filename, with any leading directory components removed, followed by
11061 zero to three bytes of padding, as needed to reach the next four-byte
11062 boundary within the section, and
11064 a four-byte CRC checksum, stored in the same endianness used for the
11065 executable file itself. The checksum is computed on the debugging
11066 information file's full contents by the function given below, passing
11067 zero as the @var{crc} argument.
11070 Any executable file format can carry a debug link, as long as it can
11071 contain a section named @code{.gnu_debuglink} with the contents
11074 The debugging information file itself should be an ordinary
11075 executable, containing a full set of linker symbols, sections, and
11076 debugging information. The sections of the debugging information file
11077 should have the same names, addresses and sizes as the original file,
11078 but they need not contain any data --- much like a @code{.bss} section
11079 in an ordinary executable.
11081 As of December 2002, there is no standard GNU utility to produce
11082 separated executable / debugging information file pairs. Ulrich
11083 Drepper's @file{elfutils} package, starting with version 0.53,
11084 contains a version of the @code{strip} command such that the command
11085 @kbd{strip foo -f foo.debug} removes the debugging information from
11086 the executable file @file{foo}, places it in the file
11087 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
11089 Since there are many different ways to compute CRC's (different
11090 polynomials, reversals, byte ordering, etc.), the simplest way to
11091 describe the CRC used in @code{.gnu_debuglink} sections is to give the
11092 complete code for a function that computes it:
11094 @kindex gnu_debuglink_crc32
11097 gnu_debuglink_crc32 (unsigned long crc,
11098 unsigned char *buf, size_t len)
11100 static const unsigned long crc32_table[256] =
11102 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
11103 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
11104 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
11105 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
11106 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
11107 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
11108 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
11109 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
11110 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
11111 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
11112 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
11113 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
11114 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
11115 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
11116 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
11117 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
11118 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
11119 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
11120 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
11121 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
11122 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
11123 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
11124 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
11125 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
11126 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
11127 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
11128 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
11129 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
11130 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
11131 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
11132 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
11133 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
11134 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
11135 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
11136 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
11137 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
11138 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
11139 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
11140 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
11141 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
11142 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
11143 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
11144 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
11145 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
11146 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
11147 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
11148 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
11149 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
11150 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
11151 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
11152 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
11155 unsigned char *end;
11157 crc = ~crc & 0xffffffff;
11158 for (end = buf + len; buf < end; ++buf)
11159 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
11160 return ~crc & 0xffffffff;
11165 @node Symbol Errors
11166 @section Errors reading symbol files
11168 While reading a symbol file, @value{GDBN} occasionally encounters problems,
11169 such as symbol types it does not recognize, or known bugs in compiler
11170 output. By default, @value{GDBN} does not notify you of such problems, since
11171 they are relatively common and primarily of interest to people
11172 debugging compilers. If you are interested in seeing information
11173 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
11174 only one message about each such type of problem, no matter how many
11175 times the problem occurs; or you can ask @value{GDBN} to print more messages,
11176 to see how many times the problems occur, with the @code{set
11177 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
11180 The messages currently printed, and their meanings, include:
11183 @item inner block not inside outer block in @var{symbol}
11185 The symbol information shows where symbol scopes begin and end
11186 (such as at the start of a function or a block of statements). This
11187 error indicates that an inner scope block is not fully contained
11188 in its outer scope blocks.
11190 @value{GDBN} circumvents the problem by treating the inner block as if it had
11191 the same scope as the outer block. In the error message, @var{symbol}
11192 may be shown as ``@code{(don't know)}'' if the outer block is not a
11195 @item block at @var{address} out of order
11197 The symbol information for symbol scope blocks should occur in
11198 order of increasing addresses. This error indicates that it does not
11201 @value{GDBN} does not circumvent this problem, and has trouble
11202 locating symbols in the source file whose symbols it is reading. (You
11203 can often determine what source file is affected by specifying
11204 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
11207 @item bad block start address patched
11209 The symbol information for a symbol scope block has a start address
11210 smaller than the address of the preceding source line. This is known
11211 to occur in the SunOS 4.1.1 (and earlier) C compiler.
11213 @value{GDBN} circumvents the problem by treating the symbol scope block as
11214 starting on the previous source line.
11216 @item bad string table offset in symbol @var{n}
11219 Symbol number @var{n} contains a pointer into the string table which is
11220 larger than the size of the string table.
11222 @value{GDBN} circumvents the problem by considering the symbol to have the
11223 name @code{foo}, which may cause other problems if many symbols end up
11226 @item unknown symbol type @code{0x@var{nn}}
11228 The symbol information contains new data types that @value{GDBN} does
11229 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
11230 uncomprehended information, in hexadecimal.
11232 @value{GDBN} circumvents the error by ignoring this symbol information.
11233 This usually allows you to debug your program, though certain symbols
11234 are not accessible. If you encounter such a problem and feel like
11235 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
11236 on @code{complain}, then go up to the function @code{read_dbx_symtab}
11237 and examine @code{*bufp} to see the symbol.
11239 @item stub type has NULL name
11241 @value{GDBN} could not find the full definition for a struct or class.
11243 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
11244 The symbol information for a C@t{++} member function is missing some
11245 information that recent versions of the compiler should have output for
11248 @item info mismatch between compiler and debugger
11250 @value{GDBN} could not parse a type specification output by the compiler.
11255 @chapter Specifying a Debugging Target
11257 @cindex debugging target
11258 A @dfn{target} is the execution environment occupied by your program.
11260 Often, @value{GDBN} runs in the same host environment as your program;
11261 in that case, the debugging target is specified as a side effect when
11262 you use the @code{file} or @code{core} commands. When you need more
11263 flexibility---for example, running @value{GDBN} on a physically separate
11264 host, or controlling a standalone system over a serial port or a
11265 realtime system over a TCP/IP connection---you can use the @code{target}
11266 command to specify one of the target types configured for @value{GDBN}
11267 (@pxref{Target Commands, ,Commands for managing targets}).
11269 @cindex target architecture
11270 It is possible to build @value{GDBN} for several different @dfn{target
11271 architectures}. When @value{GDBN} is built like that, you can choose
11272 one of the available architectures with the @kbd{set architecture}
11276 @kindex set architecture
11277 @kindex show architecture
11278 @item set architecture @var{arch}
11279 This command sets the current target architecture to @var{arch}. The
11280 value of @var{arch} can be @code{"auto"}, in addition to one of the
11281 supported architectures.
11283 @item show architecture
11284 Show the current target architecture.
11286 @item set processor
11288 @kindex set processor
11289 @kindex show processor
11290 These are alias commands for, respectively, @code{set architecture}
11291 and @code{show architecture}.
11295 * Active Targets:: Active targets
11296 * Target Commands:: Commands for managing targets
11297 * Byte Order:: Choosing target byte order
11298 * Remote:: Remote debugging
11299 * KOD:: Kernel Object Display
11303 @node Active Targets
11304 @section Active targets
11306 @cindex stacking targets
11307 @cindex active targets
11308 @cindex multiple targets
11310 There are three classes of targets: processes, core files, and
11311 executable files. @value{GDBN} can work concurrently on up to three
11312 active targets, one in each class. This allows you to (for example)
11313 start a process and inspect its activity without abandoning your work on
11316 For example, if you execute @samp{gdb a.out}, then the executable file
11317 @code{a.out} is the only active target. If you designate a core file as
11318 well---presumably from a prior run that crashed and coredumped---then
11319 @value{GDBN} has two active targets and uses them in tandem, looking
11320 first in the corefile target, then in the executable file, to satisfy
11321 requests for memory addresses. (Typically, these two classes of target
11322 are complementary, since core files contain only a program's
11323 read-write memory---variables and so on---plus machine status, while
11324 executable files contain only the program text and initialized data.)
11326 When you type @code{run}, your executable file becomes an active process
11327 target as well. When a process target is active, all @value{GDBN}
11328 commands requesting memory addresses refer to that target; addresses in
11329 an active core file or executable file target are obscured while the
11330 process target is active.
11332 Use the @code{core-file} and @code{exec-file} commands to select a new
11333 core file or executable target (@pxref{Files, ,Commands to specify
11334 files}). To specify as a target a process that is already running, use
11335 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
11338 @node Target Commands
11339 @section Commands for managing targets
11342 @item target @var{type} @var{parameters}
11343 Connects the @value{GDBN} host environment to a target machine or
11344 process. A target is typically a protocol for talking to debugging
11345 facilities. You use the argument @var{type} to specify the type or
11346 protocol of the target machine.
11348 Further @var{parameters} are interpreted by the target protocol, but
11349 typically include things like device names or host names to connect
11350 with, process numbers, and baud rates.
11352 The @code{target} command does not repeat if you press @key{RET} again
11353 after executing the command.
11355 @kindex help target
11357 Displays the names of all targets available. To display targets
11358 currently selected, use either @code{info target} or @code{info files}
11359 (@pxref{Files, ,Commands to specify files}).
11361 @item help target @var{name}
11362 Describe a particular target, including any parameters necessary to
11365 @kindex set gnutarget
11366 @item set gnutarget @var{args}
11367 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
11368 knows whether it is reading an @dfn{executable},
11369 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
11370 with the @code{set gnutarget} command. Unlike most @code{target} commands,
11371 with @code{gnutarget} the @code{target} refers to a program, not a machine.
11374 @emph{Warning:} To specify a file format with @code{set gnutarget},
11375 you must know the actual BFD name.
11379 @xref{Files, , Commands to specify files}.
11381 @kindex show gnutarget
11382 @item show gnutarget
11383 Use the @code{show gnutarget} command to display what file format
11384 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
11385 @value{GDBN} will determine the file format for each file automatically,
11386 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
11389 @cindex common targets
11390 Here are some common targets (available, or not, depending on the GDB
11395 @item target exec @var{program}
11396 @cindex executable file target
11397 An executable file. @samp{target exec @var{program}} is the same as
11398 @samp{exec-file @var{program}}.
11400 @item target core @var{filename}
11401 @cindex core dump file target
11402 A core dump file. @samp{target core @var{filename}} is the same as
11403 @samp{core-file @var{filename}}.
11405 @item target remote @var{dev}
11406 @cindex remote target
11407 Remote serial target in GDB-specific protocol. The argument @var{dev}
11408 specifies what serial device to use for the connection (e.g.
11409 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
11410 supports the @code{load} command. This is only useful if you have
11411 some other way of getting the stub to the target system, and you can put
11412 it somewhere in memory where it won't get clobbered by the download.
11415 @cindex built-in simulator target
11416 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
11424 works; however, you cannot assume that a specific memory map, device
11425 drivers, or even basic I/O is available, although some simulators do
11426 provide these. For info about any processor-specific simulator details,
11427 see the appropriate section in @ref{Embedded Processors, ,Embedded
11432 Some configurations may include these targets as well:
11436 @item target nrom @var{dev}
11437 @cindex NetROM ROM emulator target
11438 NetROM ROM emulator. This target only supports downloading.
11442 Different targets are available on different configurations of @value{GDBN};
11443 your configuration may have more or fewer targets.
11445 Many remote targets require you to download the executable's code once
11446 you've successfully established a connection. You may wish to control
11447 various aspects of this process, such as the size of the data chunks
11448 used by @value{GDBN} to download program parts to the remote target.
11451 @kindex set download-write-size
11452 @item set download-write-size @var{size}
11453 Set the write size used when downloading a program. Only used when
11454 downloading a program onto a remote target. Specify zero or a
11455 negative value to disable blocked writes. The actual size of each
11456 transfer is also limited by the size of the target packet and the
11459 @kindex show download-write-size
11460 @item show download-write-size
11461 @kindex show download-write-size
11462 Show the current value of the write size.
11465 @kindex set hash@r{, for remote monitors}
11466 @cindex hash mark while downloading
11467 This command controls whether a hash mark @samp{#} is displayed while
11468 downloading a file to the remote monitor. If on, a hash mark is
11469 displayed after each S-record is successfully downloaded to the
11473 @kindex show hash@r{, for remote monitors}
11474 Show the current status of displaying the hash mark.
11476 @item set debug monitor
11477 @kindex set debug monitor
11478 @cindex display remote monitor communications
11479 Enable or disable display of communications messages between
11480 @value{GDBN} and the remote monitor.
11482 @item show debug monitor
11483 @kindex show debug monitor
11484 Show the current status of displaying communications between
11485 @value{GDBN} and the remote monitor.
11490 @kindex load @var{filename}
11491 @item load @var{filename}
11492 Depending on what remote debugging facilities are configured into
11493 @value{GDBN}, the @code{load} command may be available. Where it exists, it
11494 is meant to make @var{filename} (an executable) available for debugging
11495 on the remote system---by downloading, or dynamic linking, for example.
11496 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
11497 the @code{add-symbol-file} command.
11499 If your @value{GDBN} does not have a @code{load} command, attempting to
11500 execute it gets the error message ``@code{You can't do that when your
11501 target is @dots{}}''
11503 The file is loaded at whatever address is specified in the executable.
11504 For some object file formats, you can specify the load address when you
11505 link the program; for other formats, like a.out, the object file format
11506 specifies a fixed address.
11507 @c FIXME! This would be a good place for an xref to the GNU linker doc.
11509 @code{load} does not repeat if you press @key{RET} again after using it.
11513 @section Choosing target byte order
11515 @cindex choosing target byte order
11516 @cindex target byte order
11518 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
11519 offer the ability to run either big-endian or little-endian byte
11520 orders. Usually the executable or symbol will include a bit to
11521 designate the endian-ness, and you will not need to worry about
11522 which to use. However, you may still find it useful to adjust
11523 @value{GDBN}'s idea of processor endian-ness manually.
11527 @item set endian big
11528 Instruct @value{GDBN} to assume the target is big-endian.
11530 @item set endian little
11531 Instruct @value{GDBN} to assume the target is little-endian.
11533 @item set endian auto
11534 Instruct @value{GDBN} to use the byte order associated with the
11538 Display @value{GDBN}'s current idea of the target byte order.
11542 Note that these commands merely adjust interpretation of symbolic
11543 data on the host, and that they have absolutely no effect on the
11547 @section Remote debugging
11548 @cindex remote debugging
11550 If you are trying to debug a program running on a machine that cannot run
11551 @value{GDBN} in the usual way, it is often useful to use remote debugging.
11552 For example, you might use remote debugging on an operating system kernel,
11553 or on a small system which does not have a general purpose operating system
11554 powerful enough to run a full-featured debugger.
11556 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
11557 to make this work with particular debugging targets. In addition,
11558 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
11559 but not specific to any particular target system) which you can use if you
11560 write the remote stubs---the code that runs on the remote system to
11561 communicate with @value{GDBN}.
11563 Other remote targets may be available in your
11564 configuration of @value{GDBN}; use @code{help target} to list them.
11566 Once you've connected to the remote target, @value{GDBN} allows you to
11567 send arbitrary commands to the remote monitor:
11570 @item remote @var{command}
11571 @kindex remote@r{, a command}
11572 @cindex send command to remote monitor
11573 Send an arbitrary @var{command} string to the remote monitor.
11578 @section Kernel Object Display
11579 @cindex kernel object display
11582 Some targets support kernel object display. Using this facility,
11583 @value{GDBN} communicates specially with the underlying operating system
11584 and can display information about operating system-level objects such as
11585 mutexes and other synchronization objects. Exactly which objects can be
11586 displayed is determined on a per-OS basis.
11589 Use the @code{set os} command to set the operating system. This tells
11590 @value{GDBN} which kernel object display module to initialize:
11593 (@value{GDBP}) set os cisco
11597 The associated command @code{show os} displays the operating system
11598 set with the @code{set os} command; if no operating system has been
11599 set, @code{show os} will display an empty string @samp{""}.
11601 If @code{set os} succeeds, @value{GDBN} will display some information
11602 about the operating system, and will create a new @code{info} command
11603 which can be used to query the target. The @code{info} command is named
11604 after the operating system:
11608 (@value{GDBP}) info cisco
11609 List of Cisco Kernel Objects
11611 any Any and all objects
11614 Further subcommands can be used to query about particular objects known
11617 There is currently no way to determine whether a given operating
11618 system is supported other than to try setting it with @kbd{set os
11619 @var{name}}, where @var{name} is the name of the operating system you
11623 @node Remote Debugging
11624 @chapter Debugging remote programs
11627 * Connecting:: Connecting to a remote target
11628 * Server:: Using the gdbserver program
11629 * NetWare:: Using the gdbserve.nlm program
11630 * Remote configuration:: Remote configuration
11631 * remote stub:: Implementing a remote stub
11635 @section Connecting to a remote target
11637 On the @value{GDBN} host machine, you will need an unstripped copy of
11638 your program, since @value{GDBN} needs symobl and debugging information.
11639 Start up @value{GDBN} as usual, using the name of the local copy of your
11640 program as the first argument.
11642 @cindex serial line, @code{target remote}
11643 If you're using a serial line, you may want to give @value{GDBN} the
11644 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
11645 (@pxref{Remote configuration, set remotebaud}) before the
11646 @code{target} command.
11648 After that, use @code{target remote} to establish communications with
11649 the target machine. Its argument specifies how to communicate---either
11650 via a devicename attached to a direct serial line, or a TCP or UDP port
11651 (possibly to a terminal server which in turn has a serial line to the
11652 target). For example, to use a serial line connected to the device
11653 named @file{/dev/ttyb}:
11656 target remote /dev/ttyb
11659 @cindex TCP port, @code{target remote}
11660 To use a TCP connection, use an argument of the form
11661 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
11662 For example, to connect to port 2828 on a
11663 terminal server named @code{manyfarms}:
11666 target remote manyfarms:2828
11669 If your remote target is actually running on the same machine as
11670 your debugger session (e.g.@: a simulator of your target running on
11671 the same host), you can omit the hostname. For example, to connect
11672 to port 1234 on your local machine:
11675 target remote :1234
11679 Note that the colon is still required here.
11681 @cindex UDP port, @code{target remote}
11682 To use a UDP connection, use an argument of the form
11683 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
11684 on a terminal server named @code{manyfarms}:
11687 target remote udp:manyfarms:2828
11690 When using a UDP connection for remote debugging, you should keep in mind
11691 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
11692 busy or unreliable networks, which will cause havoc with your debugging
11695 Now you can use all the usual commands to examine and change data and to
11696 step and continue the remote program.
11698 @cindex interrupting remote programs
11699 @cindex remote programs, interrupting
11700 Whenever @value{GDBN} is waiting for the remote program, if you type the
11701 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
11702 program. This may or may not succeed, depending in part on the hardware
11703 and the serial drivers the remote system uses. If you type the
11704 interrupt character once again, @value{GDBN} displays this prompt:
11707 Interrupted while waiting for the program.
11708 Give up (and stop debugging it)? (y or n)
11711 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
11712 (If you decide you want to try again later, you can use @samp{target
11713 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
11714 goes back to waiting.
11717 @kindex detach (remote)
11719 When you have finished debugging the remote program, you can use the
11720 @code{detach} command to release it from @value{GDBN} control.
11721 Detaching from the target normally resumes its execution, but the results
11722 will depend on your particular remote stub. After the @code{detach}
11723 command, @value{GDBN} is free to connect to another target.
11727 The @code{disconnect} command behaves like @code{detach}, except that
11728 the target is generally not resumed. It will wait for @value{GDBN}
11729 (this instance or another one) to connect and continue debugging. After
11730 the @code{disconnect} command, @value{GDBN} is again free to connect to
11733 @cindex send command to remote monitor
11735 @item monitor @var{cmd}
11736 This command allows you to send commands directly to the remote
11741 @section Using the @code{gdbserver} program
11744 @cindex remote connection without stubs
11745 @code{gdbserver} is a control program for Unix-like systems, which
11746 allows you to connect your program with a remote @value{GDBN} via
11747 @code{target remote}---but without linking in the usual debugging stub.
11749 @code{gdbserver} is not a complete replacement for the debugging stubs,
11750 because it requires essentially the same operating-system facilities
11751 that @value{GDBN} itself does. In fact, a system that can run
11752 @code{gdbserver} to connect to a remote @value{GDBN} could also run
11753 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
11754 because it is a much smaller program than @value{GDBN} itself. It is
11755 also easier to port than all of @value{GDBN}, so you may be able to get
11756 started more quickly on a new system by using @code{gdbserver}.
11757 Finally, if you develop code for real-time systems, you may find that
11758 the tradeoffs involved in real-time operation make it more convenient to
11759 do as much development work as possible on another system, for example
11760 by cross-compiling. You can use @code{gdbserver} to make a similar
11761 choice for debugging.
11763 @value{GDBN} and @code{gdbserver} communicate via either a serial line
11764 or a TCP connection, using the standard @value{GDBN} remote serial
11768 @item On the target machine,
11769 you need to have a copy of the program you want to debug.
11770 @code{gdbserver} does not need your program's symbol table, so you can
11771 strip the program if necessary to save space. @value{GDBN} on the host
11772 system does all the symbol handling.
11774 To use the server, you must tell it how to communicate with @value{GDBN};
11775 the name of your program; and the arguments for your program. The usual
11779 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
11782 @var{comm} is either a device name (to use a serial line) or a TCP
11783 hostname and portnumber. For example, to debug Emacs with the argument
11784 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
11788 target> gdbserver /dev/com1 emacs foo.txt
11791 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
11794 To use a TCP connection instead of a serial line:
11797 target> gdbserver host:2345 emacs foo.txt
11800 The only difference from the previous example is the first argument,
11801 specifying that you are communicating with the host @value{GDBN} via
11802 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
11803 expect a TCP connection from machine @samp{host} to local TCP port 2345.
11804 (Currently, the @samp{host} part is ignored.) You can choose any number
11805 you want for the port number as long as it does not conflict with any
11806 TCP ports already in use on the target system (for example, @code{23} is
11807 reserved for @code{telnet}).@footnote{If you choose a port number that
11808 conflicts with another service, @code{gdbserver} prints an error message
11809 and exits.} You must use the same port number with the host @value{GDBN}
11810 @code{target remote} command.
11812 On some targets, @code{gdbserver} can also attach to running programs.
11813 This is accomplished via the @code{--attach} argument. The syntax is:
11816 target> gdbserver @var{comm} --attach @var{pid}
11819 @var{pid} is the process ID of a currently running process. It isn't necessary
11820 to point @code{gdbserver} at a binary for the running process.
11823 @cindex attach to a program by name
11824 You can debug processes by name instead of process ID if your target has the
11825 @code{pidof} utility:
11828 target> gdbserver @var{comm} --attach `pidof @var{PROGRAM}`
11831 In case more than one copy of @var{PROGRAM} is running, or @var{PROGRAM}
11832 has multiple threads, most versions of @code{pidof} support the
11833 @code{-s} option to only return the first process ID.
11835 @item On the host machine,
11836 connect to your target (@pxref{Connecting,,Connecting to a remote target}).
11837 For TCP connections, you must start up @code{gdbserver} prior to using
11838 the @code{target remote} command. Otherwise you may get an error whose
11839 text depends on the host system, but which usually looks something like
11840 @samp{Connection refused}. You don't need to use the @code{load}
11841 command in @value{GDBN} when using gdbserver, since the program is
11842 already on the target.
11847 @section Using the @code{gdbserve.nlm} program
11849 @kindex gdbserve.nlm
11850 @code{gdbserve.nlm} is a control program for NetWare systems, which
11851 allows you to connect your program with a remote @value{GDBN} via
11852 @code{target remote}.
11854 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
11855 using the standard @value{GDBN} remote serial protocol.
11858 @item On the target machine,
11859 you need to have a copy of the program you want to debug.
11860 @code{gdbserve.nlm} does not need your program's symbol table, so you
11861 can strip the program if necessary to save space. @value{GDBN} on the
11862 host system does all the symbol handling.
11864 To use the server, you must tell it how to communicate with
11865 @value{GDBN}; the name of your program; and the arguments for your
11866 program. The syntax is:
11869 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
11870 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
11873 @var{board} and @var{port} specify the serial line; @var{baud} specifies
11874 the baud rate used by the connection. @var{port} and @var{node} default
11875 to 0, @var{baud} defaults to 9600@dmn{bps}.
11877 For example, to debug Emacs with the argument @samp{foo.txt}and
11878 communicate with @value{GDBN} over serial port number 2 or board 1
11879 using a 19200@dmn{bps} connection:
11882 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
11886 On the @value{GDBN} host machine, connect to your target (@pxref{Connecting,,
11887 Connecting to a remote target}).
11891 @node Remote configuration
11892 @section Remote configuration
11895 @kindex show remote
11896 This section documents the configuration options available when
11897 debugging remote programs. For the options related to the File I/O
11898 extensions of the remote protocol, see @ref{The system call,
11899 system-call-allowed}.
11902 @item set remoteaddresssize @var{bits}
11903 @cindex adress size for remote targets
11904 @cindex bits in remote address
11905 Set the maximum size of address in a memory packet to the specified
11906 number of bits. @value{GDBN} will mask off the address bits above
11907 that number, when it passes addresses to the remote target. The
11908 default value is the number of bits in the target's address.
11910 @item show remoteaddresssize
11911 Show the current value of remote address size in bits.
11913 @item set remotebaud @var{n}
11914 @cindex baud rate for remote targets
11915 Set the baud rate for the remote serial I/O to @var{n} baud. The
11916 value is used to set the speed of the serial port used for debugging
11919 @item show remotebaud
11920 Show the current speed of the remote connection.
11922 @item set remotebreak
11923 @cindex interrupt remote programs
11924 @cindex BREAK signal instead of Ctrl-C
11925 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
11926 when you press the @key{Ctrl-C} key to interrupt the program running
11927 on the remote. If set to off, @value{GDBN} sends the @samp{Strl-C}
11928 character instead. The default is off, since most remote systems
11929 expect to see @samp{Ctrl-C} as the interrupt signal.
11931 @item show remotebreak
11932 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
11933 interrupt the remote program.
11935 @item set remotedebug
11936 @cindex debug remote protocol
11937 @cindex remote protocol debugging
11938 @cindex display remote packets
11939 Control the debugging of the remote protocol. When enabled, each
11940 packet sent to or received from the remote target is displayed. The
11943 @item show remotedebug
11944 Show the current setting of the remote protocol debugging.
11946 @item set remotedevice @var{device}
11947 @cindex serial port name
11948 Set the name of the serial port through which to communicate to the
11949 remote target to @var{device}. This is the device used by
11950 @value{GDBN} to open the serial communications line to the remote
11951 target. There's no default, so you must set a valid port name for the
11952 remote serial communications to work. (Some varieties of the
11953 @code{target} command accept the port name as part of their
11956 @item show remotedevice
11957 Show the current name of the serial port.
11959 @item set remotelogbase @var{base}
11960 Set the base (a.k.a.@: radix) of logging serial protocol
11961 communications to @var{base}. Supported values of @var{base} are:
11962 @code{ascii}, @code{octal}, and @code{hex}. The default is
11965 @item show remotelogbase
11966 Show the current setting of the radix for logging remote serial
11969 @item set remotelogfile @var{file}
11970 @cindex record serial communications on file
11971 Record remote serial communications on the named @var{file}. The
11972 default is not to record at all.
11974 @item show remotelogfile.
11975 Show the current setting of the file name on which to record the
11976 serial communications.
11978 @item set remotetimeout @var{num}
11979 @cindex timeout for serial communications
11980 @cindex remote timeout
11981 Set the timeout limit to wait for the remote target to respond to
11982 @var{num} seconds. The default is 2 seconds.
11984 @item show remotetimeout
11985 Show the current number of seconds to wait for the remote target
11988 @cindex limit hardware breakpoints and watchpoints
11989 @cindex remote target, limit break- and watchpoints
11990 @anchor{set remote hardware-watchpoint-limit}
11991 @anchor{set remote hardware-breakpoint-limit}
11992 @item set remote hardware-watchpoint-limit @var{limit}
11993 @itemx set remote hardware-breakpoint-limit @var{limit}
11994 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
11995 watchpoints. A limit of -1, the default, is treated as unlimited.
11997 @item set remote fetch-register-packet
11998 @itemx set remote set-register-packet
11999 @itemx set remote P-packet
12000 @itemx set remote p-packet
12002 @cindex fetch registers from remote targets
12003 @cindex set registers in remote targets
12004 Determine whether @value{GDBN} can set and fetch registers from the
12005 remote target using the @samp{P} packets. The default depends on the
12006 remote stub's support of the @samp{P} packets (@value{GDBN} queries
12007 the stub when this packet is first required).
12009 @item show remote fetch-register-packet
12010 @itemx show remote set-register-packet
12011 @itemx show remote P-packet
12012 @itemx show remote p-packet
12013 Show the current setting of using the @samp{P} packets for setting and
12014 fetching registers from the remote target.
12016 @cindex binary downloads
12018 @item set remote binary-download-packet
12019 @itemx set remote X-packet
12020 Determine whether @value{GDBN} sends downloads in binary mode using
12021 the @samp{X} packets. The default is on.
12023 @item show remote binary-download-packet
12024 @itemx show remote X-packet
12025 Show the current setting of using the @samp{X} packets for binary
12028 @item set remote read-aux-vector-packet
12029 @cindex auxiliary vector of remote target
12030 @cindex @code{auxv}, and remote targets
12031 Set the use of the remote protocol's @samp{qPart:auxv:read} (target
12032 auxiliary vector read) request. This request is used to fetch the
12033 remote target's @dfn{auxiliary vector}, see @ref{OS Information,
12034 Auxiliary Vector}. The default setting depends on the remote stub's
12035 support of this request (@value{GDBN} queries the stub when this
12036 request is first required). @xref{General Query Packets, qPart}, for
12037 more information about this request.
12039 @item show remote read-aux-vector-packet
12040 Show the current setting of use of the @samp{qPart:auxv:read} request.
12042 @item set remote symbol-lookup-packet
12043 @cindex remote symbol lookup request
12044 Set the use of the remote protocol's @samp{qSymbol} (target symbol
12045 lookup) request. This request is used to communicate symbol
12046 information to the remote target, e.g., whenever a new shared library
12047 is loaded by the remote (@pxref{Files, shared libraries}). The
12048 default setting depends on the remote stub's support of this request
12049 (@value{GDBN} queries the stub when this request is first required).
12050 @xref{General Query Packets, qSymbol}, for more information about this
12053 @item show remote symbol-lookup-packet
12054 Show the current setting of use of the @samp{qSymbol} request.
12056 @item set remote verbose-resume-packet
12057 @cindex resume remote target
12058 @cindex signal thread, and remote targets
12059 @cindex single-step thread, and remote targets
12060 @cindex thread-specific operations on remote targets
12061 Set the use of the remote protocol's @samp{vCont} (descriptive resume)
12062 request. This request is used to resume specific threads in the
12063 remote target, and to single-step or signal them. The default setting
12064 depends on the remote stub's support of this request (@value{GDBN}
12065 queries the stub when this request is first required). This setting
12066 affects debugging of multithreaded programs: if @samp{vCont} cannot be
12067 used, @value{GDBN} might be unable to single-step a specific thread,
12068 especially under @code{set scheduler-locking off}; it is also
12069 impossible to pause a specific thread. @xref{Packets, vCont}, for
12072 @item show remote verbose-resume-packet
12073 Show the current setting of use of the @samp{vCont} request
12075 @item set remote software-breakpoint-packet
12076 @itemx set remote hardware-breakpoint-packet
12077 @itemx set remote write-watchpoint-packet
12078 @itemx set remote read-watchpoint-packet
12079 @itemx set remote access-watchpoint-packet
12080 @itemx set remote Z-packet
12082 @cindex remote hardware breakpoints and watchpoints
12083 These commands enable or disable the use of @samp{Z} packets for
12084 setting breakpoints and watchpoints in the remote target. The default
12085 depends on the remote stub's support of the @samp{Z} packets
12086 (@value{GDBN} queries the stub when each packet is first required).
12087 The command @code{set remote Z-packet}, kept for back-compatibility,
12088 turns on or off all the features that require the use of @samp{Z}
12091 @item show remote software-breakpoint-packet
12092 @itemx show remote hardware-breakpoint-packet
12093 @itemx show remote write-watchpoint-packet
12094 @itemx show remote read-watchpoint-packet
12095 @itemx show remote access-watchpoint-packet
12096 @itemx show remote Z-packet
12097 Show the current setting of @samp{Z} packets usage.
12101 @section Implementing a remote stub
12103 @cindex debugging stub, example
12104 @cindex remote stub, example
12105 @cindex stub example, remote debugging
12106 The stub files provided with @value{GDBN} implement the target side of the
12107 communication protocol, and the @value{GDBN} side is implemented in the
12108 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
12109 these subroutines to communicate, and ignore the details. (If you're
12110 implementing your own stub file, you can still ignore the details: start
12111 with one of the existing stub files. @file{sparc-stub.c} is the best
12112 organized, and therefore the easiest to read.)
12114 @cindex remote serial debugging, overview
12115 To debug a program running on another machine (the debugging
12116 @dfn{target} machine), you must first arrange for all the usual
12117 prerequisites for the program to run by itself. For example, for a C
12122 A startup routine to set up the C runtime environment; these usually
12123 have a name like @file{crt0}. The startup routine may be supplied by
12124 your hardware supplier, or you may have to write your own.
12127 A C subroutine library to support your program's
12128 subroutine calls, notably managing input and output.
12131 A way of getting your program to the other machine---for example, a
12132 download program. These are often supplied by the hardware
12133 manufacturer, but you may have to write your own from hardware
12137 The next step is to arrange for your program to use a serial port to
12138 communicate with the machine where @value{GDBN} is running (the @dfn{host}
12139 machine). In general terms, the scheme looks like this:
12143 @value{GDBN} already understands how to use this protocol; when everything
12144 else is set up, you can simply use the @samp{target remote} command
12145 (@pxref{Targets,,Specifying a Debugging Target}).
12147 @item On the target,
12148 you must link with your program a few special-purpose subroutines that
12149 implement the @value{GDBN} remote serial protocol. The file containing these
12150 subroutines is called a @dfn{debugging stub}.
12152 On certain remote targets, you can use an auxiliary program
12153 @code{gdbserver} instead of linking a stub into your program.
12154 @xref{Server,,Using the @code{gdbserver} program}, for details.
12157 The debugging stub is specific to the architecture of the remote
12158 machine; for example, use @file{sparc-stub.c} to debug programs on
12161 @cindex remote serial stub list
12162 These working remote stubs are distributed with @value{GDBN}:
12167 @cindex @file{i386-stub.c}
12170 For Intel 386 and compatible architectures.
12173 @cindex @file{m68k-stub.c}
12174 @cindex Motorola 680x0
12176 For Motorola 680x0 architectures.
12179 @cindex @file{sh-stub.c}
12182 For Renesas SH architectures.
12185 @cindex @file{sparc-stub.c}
12187 For @sc{sparc} architectures.
12189 @item sparcl-stub.c
12190 @cindex @file{sparcl-stub.c}
12193 For Fujitsu @sc{sparclite} architectures.
12197 The @file{README} file in the @value{GDBN} distribution may list other
12198 recently added stubs.
12201 * Stub Contents:: What the stub can do for you
12202 * Bootstrapping:: What you must do for the stub
12203 * Debug Session:: Putting it all together
12206 @node Stub Contents
12207 @subsection What the stub can do for you
12209 @cindex remote serial stub
12210 The debugging stub for your architecture supplies these three
12214 @item set_debug_traps
12215 @findex set_debug_traps
12216 @cindex remote serial stub, initialization
12217 This routine arranges for @code{handle_exception} to run when your
12218 program stops. You must call this subroutine explicitly near the
12219 beginning of your program.
12221 @item handle_exception
12222 @findex handle_exception
12223 @cindex remote serial stub, main routine
12224 This is the central workhorse, but your program never calls it
12225 explicitly---the setup code arranges for @code{handle_exception} to
12226 run when a trap is triggered.
12228 @code{handle_exception} takes control when your program stops during
12229 execution (for example, on a breakpoint), and mediates communications
12230 with @value{GDBN} on the host machine. This is where the communications
12231 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
12232 representative on the target machine. It begins by sending summary
12233 information on the state of your program, then continues to execute,
12234 retrieving and transmitting any information @value{GDBN} needs, until you
12235 execute a @value{GDBN} command that makes your program resume; at that point,
12236 @code{handle_exception} returns control to your own code on the target
12240 @cindex @code{breakpoint} subroutine, remote
12241 Use this auxiliary subroutine to make your program contain a
12242 breakpoint. Depending on the particular situation, this may be the only
12243 way for @value{GDBN} to get control. For instance, if your target
12244 machine has some sort of interrupt button, you won't need to call this;
12245 pressing the interrupt button transfers control to
12246 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
12247 simply receiving characters on the serial port may also trigger a trap;
12248 again, in that situation, you don't need to call @code{breakpoint} from
12249 your own program---simply running @samp{target remote} from the host
12250 @value{GDBN} session gets control.
12252 Call @code{breakpoint} if none of these is true, or if you simply want
12253 to make certain your program stops at a predetermined point for the
12254 start of your debugging session.
12257 @node Bootstrapping
12258 @subsection What you must do for the stub
12260 @cindex remote stub, support routines
12261 The debugging stubs that come with @value{GDBN} are set up for a particular
12262 chip architecture, but they have no information about the rest of your
12263 debugging target machine.
12265 First of all you need to tell the stub how to communicate with the
12269 @item int getDebugChar()
12270 @findex getDebugChar
12271 Write this subroutine to read a single character from the serial port.
12272 It may be identical to @code{getchar} for your target system; a
12273 different name is used to allow you to distinguish the two if you wish.
12275 @item void putDebugChar(int)
12276 @findex putDebugChar
12277 Write this subroutine to write a single character to the serial port.
12278 It may be identical to @code{putchar} for your target system; a
12279 different name is used to allow you to distinguish the two if you wish.
12282 @cindex control C, and remote debugging
12283 @cindex interrupting remote targets
12284 If you want @value{GDBN} to be able to stop your program while it is
12285 running, you need to use an interrupt-driven serial driver, and arrange
12286 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
12287 character). That is the character which @value{GDBN} uses to tell the
12288 remote system to stop.
12290 Getting the debugging target to return the proper status to @value{GDBN}
12291 probably requires changes to the standard stub; one quick and dirty way
12292 is to just execute a breakpoint instruction (the ``dirty'' part is that
12293 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
12295 Other routines you need to supply are:
12298 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
12299 @findex exceptionHandler
12300 Write this function to install @var{exception_address} in the exception
12301 handling tables. You need to do this because the stub does not have any
12302 way of knowing what the exception handling tables on your target system
12303 are like (for example, the processor's table might be in @sc{rom},
12304 containing entries which point to a table in @sc{ram}).
12305 @var{exception_number} is the exception number which should be changed;
12306 its meaning is architecture-dependent (for example, different numbers
12307 might represent divide by zero, misaligned access, etc). When this
12308 exception occurs, control should be transferred directly to
12309 @var{exception_address}, and the processor state (stack, registers,
12310 and so on) should be just as it is when a processor exception occurs. So if
12311 you want to use a jump instruction to reach @var{exception_address}, it
12312 should be a simple jump, not a jump to subroutine.
12314 For the 386, @var{exception_address} should be installed as an interrupt
12315 gate so that interrupts are masked while the handler runs. The gate
12316 should be at privilege level 0 (the most privileged level). The
12317 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
12318 help from @code{exceptionHandler}.
12320 @item void flush_i_cache()
12321 @findex flush_i_cache
12322 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
12323 instruction cache, if any, on your target machine. If there is no
12324 instruction cache, this subroutine may be a no-op.
12326 On target machines that have instruction caches, @value{GDBN} requires this
12327 function to make certain that the state of your program is stable.
12331 You must also make sure this library routine is available:
12334 @item void *memset(void *, int, int)
12336 This is the standard library function @code{memset} that sets an area of
12337 memory to a known value. If you have one of the free versions of
12338 @code{libc.a}, @code{memset} can be found there; otherwise, you must
12339 either obtain it from your hardware manufacturer, or write your own.
12342 If you do not use the GNU C compiler, you may need other standard
12343 library subroutines as well; this varies from one stub to another,
12344 but in general the stubs are likely to use any of the common library
12345 subroutines which @code{@value{GCC}} generates as inline code.
12348 @node Debug Session
12349 @subsection Putting it all together
12351 @cindex remote serial debugging summary
12352 In summary, when your program is ready to debug, you must follow these
12357 Make sure you have defined the supporting low-level routines
12358 (@pxref{Bootstrapping,,What you must do for the stub}):
12360 @code{getDebugChar}, @code{putDebugChar},
12361 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
12365 Insert these lines near the top of your program:
12373 For the 680x0 stub only, you need to provide a variable called
12374 @code{exceptionHook}. Normally you just use:
12377 void (*exceptionHook)() = 0;
12381 but if before calling @code{set_debug_traps}, you set it to point to a
12382 function in your program, that function is called when
12383 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
12384 error). The function indicated by @code{exceptionHook} is called with
12385 one parameter: an @code{int} which is the exception number.
12388 Compile and link together: your program, the @value{GDBN} debugging stub for
12389 your target architecture, and the supporting subroutines.
12392 Make sure you have a serial connection between your target machine and
12393 the @value{GDBN} host, and identify the serial port on the host.
12396 @c The "remote" target now provides a `load' command, so we should
12397 @c document that. FIXME.
12398 Download your program to your target machine (or get it there by
12399 whatever means the manufacturer provides), and start it.
12402 Start @value{GDBN} on the host, and connect to the target
12403 (@pxref{Connecting,,Connecting to a remote target}).
12407 @node Configurations
12408 @chapter Configuration-Specific Information
12410 While nearly all @value{GDBN} commands are available for all native and
12411 cross versions of the debugger, there are some exceptions. This chapter
12412 describes things that are only available in certain configurations.
12414 There are three major categories of configurations: native
12415 configurations, where the host and target are the same, embedded
12416 operating system configurations, which are usually the same for several
12417 different processor architectures, and bare embedded processors, which
12418 are quite different from each other.
12423 * Embedded Processors::
12430 This section describes details specific to particular native
12435 * BSD libkvm Interface:: Debugging BSD kernel memory images
12436 * SVR4 Process Information:: SVR4 process information
12437 * DJGPP Native:: Features specific to the DJGPP port
12438 * Cygwin Native:: Features specific to the Cygwin port
12439 * Hurd Native:: Features specific to @sc{gnu} Hurd
12440 * Neutrino:: Features specific to QNX Neutrino
12446 On HP-UX systems, if you refer to a function or variable name that
12447 begins with a dollar sign, @value{GDBN} searches for a user or system
12448 name first, before it searches for a convenience variable.
12451 @node BSD libkvm Interface
12452 @subsection BSD libkvm Interface
12455 @cindex kernel memory image
12456 @cindex kernel crash dump
12458 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
12459 interface that provides a uniform interface for accessing kernel virtual
12460 memory images, including live systems and crash dumps. @value{GDBN}
12461 uses this interface to allow you to debug live kernels and kernel crash
12462 dumps on many native BSD configurations. This is implemented as a
12463 special @code{kvm} debugging target. For debugging a live system, load
12464 the currently running kernel into @value{GDBN} and connect to the
12468 (@value{GDBP}) @b{target kvm}
12471 For debugging crash dumps, provide the file name of the crash dump as an
12475 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
12478 Once connected to the @code{kvm} target, the following commands are
12484 Set current context from the @dfn{Process Control Block} (PCB) address.
12487 Set current context from proc address. This command isn't available on
12488 modern FreeBSD systems.
12491 @node SVR4 Process Information
12492 @subsection SVR4 process information
12494 @cindex examine process image
12495 @cindex process info via @file{/proc}
12497 Many versions of SVR4 and compatible systems provide a facility called
12498 @samp{/proc} that can be used to examine the image of a running
12499 process using file-system subroutines. If @value{GDBN} is configured
12500 for an operating system with this facility, the command @code{info
12501 proc} is available to report information about the process running
12502 your program, or about any process running on your system. @code{info
12503 proc} works only on SVR4 systems that include the @code{procfs} code.
12504 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
12505 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
12511 @itemx info proc @var{process-id}
12512 Summarize available information about any running process. If a
12513 process ID is specified by @var{process-id}, display information about
12514 that process; otherwise display information about the program being
12515 debugged. The summary includes the debugged process ID, the command
12516 line used to invoke it, its current working directory, and its
12517 executable file's absolute file name.
12519 On some systems, @var{process-id} can be of the form
12520 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
12521 within a process. If the optional @var{pid} part is missing, it means
12522 a thread from the process being debugged (the leading @samp{/} still
12523 needs to be present, or else @value{GDBN} will interpret the number as
12524 a process ID rather than a thread ID).
12526 @item info proc mappings
12527 @cindex memory address space mappings
12528 Report the memory address space ranges accessible in the program, with
12529 information on whether the process has read, write, or execute access
12530 rights to each range. On @sc{gnu}/Linux systems, each memory range
12531 includes the object file which is mapped to that range, instead of the
12532 memory access rights to that range.
12534 @item info proc stat
12535 @itemx info proc status
12536 @cindex process detailed status information
12537 These subcommands are specific to @sc{gnu}/Linux systems. They show
12538 the process-related information, including the user ID and group ID;
12539 how many threads are there in the process; its virtual memory usage;
12540 the signals that are pending, blocked, and ignored; its TTY; its
12541 consumption of system and user time; its stack size; its @samp{nice}
12542 value; etc. For more information, see the @samp{proc(5)} man page
12543 (type @kbd{man 5 proc} from your shell prompt).
12545 @item info proc all
12546 Show all the information about the process described under all of the
12547 above @code{info proc} subcommands.
12550 @comment These sub-options of 'info proc' were not included when
12551 @comment procfs.c was re-written. Keep their descriptions around
12552 @comment against the day when someone finds the time to put them back in.
12553 @kindex info proc times
12554 @item info proc times
12555 Starting time, user CPU time, and system CPU time for your program and
12558 @kindex info proc id
12560 Report on the process IDs related to your program: its own process ID,
12561 the ID of its parent, the process group ID, and the session ID.
12564 @item set procfs-trace
12565 @kindex set procfs-trace
12566 @cindex @code{procfs} API calls
12567 This command enables and disables tracing of @code{procfs} API calls.
12569 @item show procfs-trace
12570 @kindex show procfs-trace
12571 Show the current state of @code{procfs} API call tracing.
12573 @item set procfs-file @var{file}
12574 @kindex set procfs-file
12575 Tell @value{GDBN} to write @code{procfs} API trace to the named
12576 @var{file}. @value{GDBN} appends the trace info to the previous
12577 contents of the file. The default is to display the trace on the
12580 @item show procfs-file
12581 @kindex show procfs-file
12582 Show the file to which @code{procfs} API trace is written.
12584 @item proc-trace-entry
12585 @itemx proc-trace-exit
12586 @itemx proc-untrace-entry
12587 @itemx proc-untrace-exit
12588 @kindex proc-trace-entry
12589 @kindex proc-trace-exit
12590 @kindex proc-untrace-entry
12591 @kindex proc-untrace-exit
12592 These commands enable and disable tracing of entries into and exits
12593 from the @code{syscall} interface.
12596 @kindex info pidlist
12597 @cindex process list, QNX Neutrino
12598 For QNX Neutrino only, this command displays the list of all the
12599 processes and all the threads within each process.
12602 @kindex info meminfo
12603 @cindex mapinfo list, QNX Neutrino
12604 For QNX Neutrino only, this command displays the list of all mapinfos.
12608 @subsection Features for Debugging @sc{djgpp} Programs
12609 @cindex @sc{djgpp} debugging
12610 @cindex native @sc{djgpp} debugging
12611 @cindex MS-DOS-specific commands
12613 @sc{djgpp} is the port of @sc{gnu} development tools to MS-DOS and
12614 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
12615 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
12616 top of real-mode DOS systems and their emulations.
12618 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
12619 defines a few commands specific to the @sc{djgpp} port. This
12620 subsection describes those commands.
12625 This is a prefix of @sc{djgpp}-specific commands which print
12626 information about the target system and important OS structures.
12629 @cindex MS-DOS system info
12630 @cindex free memory information (MS-DOS)
12631 @item info dos sysinfo
12632 This command displays assorted information about the underlying
12633 platform: the CPU type and features, the OS version and flavor, the
12634 DPMI version, and the available conventional and DPMI memory.
12639 @cindex segment descriptor tables
12640 @cindex descriptor tables display
12642 @itemx info dos ldt
12643 @itemx info dos idt
12644 These 3 commands display entries from, respectively, Global, Local,
12645 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
12646 tables are data structures which store a descriptor for each segment
12647 that is currently in use. The segment's selector is an index into a
12648 descriptor table; the table entry for that index holds the
12649 descriptor's base address and limit, and its attributes and access
12652 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
12653 segment (used for both data and the stack), and a DOS segment (which
12654 allows access to DOS/BIOS data structures and absolute addresses in
12655 conventional memory). However, the DPMI host will usually define
12656 additional segments in order to support the DPMI environment.
12658 @cindex garbled pointers
12659 These commands allow to display entries from the descriptor tables.
12660 Without an argument, all entries from the specified table are
12661 displayed. An argument, which should be an integer expression, means
12662 display a single entry whose index is given by the argument. For
12663 example, here's a convenient way to display information about the
12664 debugged program's data segment:
12667 @exdent @code{(@value{GDBP}) info dos ldt $ds}
12668 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
12672 This comes in handy when you want to see whether a pointer is outside
12673 the data segment's limit (i.e.@: @dfn{garbled}).
12675 @cindex page tables display (MS-DOS)
12677 @itemx info dos pte
12678 These two commands display entries from, respectively, the Page
12679 Directory and the Page Tables. Page Directories and Page Tables are
12680 data structures which control how virtual memory addresses are mapped
12681 into physical addresses. A Page Table includes an entry for every
12682 page of memory that is mapped into the program's address space; there
12683 may be several Page Tables, each one holding up to 4096 entries. A
12684 Page Directory has up to 4096 entries, one each for every Page Table
12685 that is currently in use.
12687 Without an argument, @kbd{info dos pde} displays the entire Page
12688 Directory, and @kbd{info dos pte} displays all the entries in all of
12689 the Page Tables. An argument, an integer expression, given to the
12690 @kbd{info dos pde} command means display only that entry from the Page
12691 Directory table. An argument given to the @kbd{info dos pte} command
12692 means display entries from a single Page Table, the one pointed to by
12693 the specified entry in the Page Directory.
12695 @cindex direct memory access (DMA) on MS-DOS
12696 These commands are useful when your program uses @dfn{DMA} (Direct
12697 Memory Access), which needs physical addresses to program the DMA
12700 These commands are supported only with some DPMI servers.
12702 @cindex physical address from linear address
12703 @item info dos address-pte @var{addr}
12704 This command displays the Page Table entry for a specified linear
12705 address. The argument linear address @var{addr} should already have the
12706 appropriate segment's base address added to it, because this command
12707 accepts addresses which may belong to @emph{any} segment. For
12708 example, here's how to display the Page Table entry for the page where
12709 the variable @code{i} is stored:
12712 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
12713 @exdent @code{Page Table entry for address 0x11a00d30:}
12714 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
12718 This says that @code{i} is stored at offset @code{0xd30} from the page
12719 whose physical base address is @code{0x02698000}, and prints all the
12720 attributes of that page.
12722 Note that you must cast the addresses of variables to a @code{char *},
12723 since otherwise the value of @code{__djgpp_base_address}, the base
12724 address of all variables and functions in a @sc{djgpp} program, will
12725 be added using the rules of C pointer arithmetics: if @code{i} is
12726 declared an @code{int}, @value{GDBN} will add 4 times the value of
12727 @code{__djgpp_base_address} to the address of @code{i}.
12729 Here's another example, it displays the Page Table entry for the
12733 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
12734 @exdent @code{Page Table entry for address 0x29110:}
12735 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
12739 (The @code{+ 3} offset is because the transfer buffer's address is the
12740 3rd member of the @code{_go32_info_block} structure.) The output of
12741 this command clearly shows that addresses in conventional memory are
12742 mapped 1:1, i.e.@: the physical and linear addresses are identical.
12744 This command is supported only with some DPMI servers.
12747 @cindex DOS serial data link, remote debugging
12748 In addition to native debugging, the DJGPP port supports remote
12749 debugging via a serial data link. The following commands are specific
12750 to remote serial debugging in the DJGPP port of @value{GDBN}.
12753 @kindex set com1base
12754 @kindex set com1irq
12755 @kindex set com2base
12756 @kindex set com2irq
12757 @kindex set com3base
12758 @kindex set com3irq
12759 @kindex set com4base
12760 @kindex set com4irq
12761 @item set com1base @var{addr}
12762 This command sets the base I/O port address of the @file{COM1} serial
12765 @item set com1irq @var{irq}
12766 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
12767 for the @file{COM1} serial port.
12769 There are similar commands @samp{set com2base}, @samp{set com3irq},
12770 etc.@: for setting the port address and the @code{IRQ} lines for the
12773 @kindex show com1base
12774 @kindex show com1irq
12775 @kindex show com2base
12776 @kindex show com2irq
12777 @kindex show com3base
12778 @kindex show com3irq
12779 @kindex show com4base
12780 @kindex show com4irq
12781 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
12782 display the current settings of the base address and the @code{IRQ}
12783 lines used by the COM ports.
12786 @kindex info serial
12787 @cindex DOS serial port status
12788 This command prints the status of the 4 DOS serial ports. For each
12789 port, it prints whether it's active or not, its I/O base address and
12790 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
12791 counts of various errors encountered so far.
12795 @node Cygwin Native
12796 @subsection Features for Debugging MS Windows PE executables
12797 @cindex MS Windows debugging
12798 @cindex native Cygwin debugging
12799 @cindex Cygwin-specific commands
12801 @value{GDBN} supports native debugging of MS Windows programs, including
12802 DLLs with and without symbolic debugging information. There are various
12803 additional Cygwin-specific commands, described in this subsection. The
12804 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
12805 that have no debugging symbols.
12811 This is a prefix of MS Windows specific commands which print
12812 information about the target system and important OS structures.
12814 @item info w32 selector
12815 This command displays information returned by
12816 the Win32 API @code{GetThreadSelectorEntry} function.
12817 It takes an optional argument that is evaluated to
12818 a long value to give the information about this given selector.
12819 Without argument, this command displays information
12820 about the the six segment registers.
12824 This is a Cygwin specific alias of info shared.
12826 @kindex dll-symbols
12828 This command loads symbols from a dll similarly to
12829 add-sym command but without the need to specify a base address.
12831 @kindex set new-console
12832 @item set new-console @var{mode}
12833 If @var{mode} is @code{on} the debuggee will
12834 be started in a new console on next start.
12835 If @var{mode} is @code{off}i, the debuggee will
12836 be started in the same console as the debugger.
12838 @kindex show new-console
12839 @item show new-console
12840 Displays whether a new console is used
12841 when the debuggee is started.
12843 @kindex set new-group
12844 @item set new-group @var{mode}
12845 This boolean value controls whether the debuggee should
12846 start a new group or stay in the same group as the debugger.
12847 This affects the way the Windows OS handles
12850 @kindex show new-group
12851 @item show new-group
12852 Displays current value of new-group boolean.
12854 @kindex set debugevents
12855 @item set debugevents
12856 This boolean value adds debug output concerning events seen by the debugger.
12858 @kindex set debugexec
12859 @item set debugexec
12860 This boolean value adds debug output concerning execute events
12861 seen by the debugger.
12863 @kindex set debugexceptions
12864 @item set debugexceptions
12865 This boolean value adds debug ouptut concerning exception events
12866 seen by the debugger.
12868 @kindex set debugmemory
12869 @item set debugmemory
12870 This boolean value adds debug ouptut concerning memory events
12871 seen by the debugger.
12875 This boolean values specifies whether the debuggee is called
12876 via a shell or directly (default value is on).
12880 Displays if the debuggee will be started with a shell.
12885 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
12888 @node Non-debug DLL symbols
12889 @subsubsection Support for DLLs without debugging symbols
12890 @cindex DLLs with no debugging symbols
12891 @cindex Minimal symbols and DLLs
12893 Very often on windows, some of the DLLs that your program relies on do
12894 not include symbolic debugging information (for example,
12895 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
12896 symbols in a DLL, it relies on the minimal amount of symbolic
12897 information contained in the DLL's export table. This subsubsection
12898 describes working with such symbols, known internally to @value{GDBN} as
12899 ``minimal symbols''.
12901 Note that before the debugged program has started execution, no DLLs
12902 will have been loaded. The easiest way around this problem is simply to
12903 start the program --- either by setting a breakpoint or letting the
12904 program run once to completion. It is also possible to force
12905 @value{GDBN} to load a particular DLL before starting the executable ---
12906 see the shared library information in @pxref{Files} or the
12907 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
12908 explicitly loading symbols from a DLL with no debugging information will
12909 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
12910 which may adversely affect symbol lookup performance.
12912 @subsubsection DLL name prefixes
12914 In keeping with the naming conventions used by the Microsoft debugging
12915 tools, DLL export symbols are made available with a prefix based on the
12916 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
12917 also entered into the symbol table, so @code{CreateFileA} is often
12918 sufficient. In some cases there will be name clashes within a program
12919 (particularly if the executable itself includes full debugging symbols)
12920 necessitating the use of the fully qualified name when referring to the
12921 contents of the DLL. Use single-quotes around the name to avoid the
12922 exclamation mark (``!'') being interpreted as a language operator.
12924 Note that the internal name of the DLL may be all upper-case, even
12925 though the file name of the DLL is lower-case, or vice-versa. Since
12926 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
12927 some confusion. If in doubt, try the @code{info functions} and
12928 @code{info variables} commands or even @code{maint print msymbols} (see
12929 @pxref{Symbols}). Here's an example:
12932 (@value{GDBP}) info function CreateFileA
12933 All functions matching regular expression "CreateFileA":
12935 Non-debugging symbols:
12936 0x77e885f4 CreateFileA
12937 0x77e885f4 KERNEL32!CreateFileA
12941 (@value{GDBP}) info function !
12942 All functions matching regular expression "!":
12944 Non-debugging symbols:
12945 0x6100114c cygwin1!__assert
12946 0x61004034 cygwin1!_dll_crt0@@0
12947 0x61004240 cygwin1!dll_crt0(per_process *)
12951 @subsubsection Working with minimal symbols
12953 Symbols extracted from a DLL's export table do not contain very much
12954 type information. All that @value{GDBN} can do is guess whether a symbol
12955 refers to a function or variable depending on the linker section that
12956 contains the symbol. Also note that the actual contents of the memory
12957 contained in a DLL are not available unless the program is running. This
12958 means that you cannot examine the contents of a variable or disassemble
12959 a function within a DLL without a running program.
12961 Variables are generally treated as pointers and dereferenced
12962 automatically. For this reason, it is often necessary to prefix a
12963 variable name with the address-of operator (``&'') and provide explicit
12964 type information in the command. Here's an example of the type of
12968 (@value{GDBP}) print 'cygwin1!__argv'
12973 (@value{GDBP}) x 'cygwin1!__argv'
12974 0x10021610: "\230y\""
12977 And two possible solutions:
12980 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
12981 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
12985 (@value{GDBP}) x/2x &'cygwin1!__argv'
12986 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
12987 (@value{GDBP}) x/x 0x10021608
12988 0x10021608: 0x0022fd98
12989 (@value{GDBP}) x/s 0x0022fd98
12990 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
12993 Setting a break point within a DLL is possible even before the program
12994 starts execution. However, under these circumstances, @value{GDBN} can't
12995 examine the initial instructions of the function in order to skip the
12996 function's frame set-up code. You can work around this by using ``*&''
12997 to set the breakpoint at a raw memory address:
13000 (@value{GDBP}) break *&'python22!PyOS_Readline'
13001 Breakpoint 1 at 0x1e04eff0
13004 The author of these extensions is not entirely convinced that setting a
13005 break point within a shared DLL like @file{kernel32.dll} is completely
13009 @subsection Commands specific to @sc{gnu} Hurd systems
13010 @cindex @sc{gnu} Hurd debugging
13012 This subsection describes @value{GDBN} commands specific to the
13013 @sc{gnu} Hurd native debugging.
13018 @kindex set signals@r{, Hurd command}
13019 @kindex set sigs@r{, Hurd command}
13020 This command toggles the state of inferior signal interception by
13021 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
13022 affected by this command. @code{sigs} is a shorthand alias for
13027 @kindex show signals@r{, Hurd command}
13028 @kindex show sigs@r{, Hurd command}
13029 Show the current state of intercepting inferior's signals.
13031 @item set signal-thread
13032 @itemx set sigthread
13033 @kindex set signal-thread
13034 @kindex set sigthread
13035 This command tells @value{GDBN} which thread is the @code{libc} signal
13036 thread. That thread is run when a signal is delivered to a running
13037 process. @code{set sigthread} is the shorthand alias of @code{set
13040 @item show signal-thread
13041 @itemx show sigthread
13042 @kindex show signal-thread
13043 @kindex show sigthread
13044 These two commands show which thread will run when the inferior is
13045 delivered a signal.
13048 @kindex set stopped@r{, Hurd command}
13049 This commands tells @value{GDBN} that the inferior process is stopped,
13050 as with the @code{SIGSTOP} signal. The stopped process can be
13051 continued by delivering a signal to it.
13054 @kindex show stopped@r{, Hurd command}
13055 This command shows whether @value{GDBN} thinks the debuggee is
13058 @item set exceptions
13059 @kindex set exceptions@r{, Hurd command}
13060 Use this command to turn off trapping of exceptions in the inferior.
13061 When exception trapping is off, neither breakpoints nor
13062 single-stepping will work. To restore the default, set exception
13065 @item show exceptions
13066 @kindex show exceptions@r{, Hurd command}
13067 Show the current state of trapping exceptions in the inferior.
13069 @item set task pause
13070 @kindex set task@r{, Hurd commands}
13071 @cindex task attributes (@sc{gnu} Hurd)
13072 @cindex pause current task (@sc{gnu} Hurd)
13073 This command toggles task suspension when @value{GDBN} has control.
13074 Setting it to on takes effect immediately, and the task is suspended
13075 whenever @value{GDBN} gets control. Setting it to off will take
13076 effect the next time the inferior is continued. If this option is set
13077 to off, you can use @code{set thread default pause on} or @code{set
13078 thread pause on} (see below) to pause individual threads.
13080 @item show task pause
13081 @kindex show task@r{, Hurd commands}
13082 Show the current state of task suspension.
13084 @item set task detach-suspend-count
13085 @cindex task suspend count
13086 @cindex detach from task, @sc{gnu} Hurd
13087 This command sets the suspend count the task will be left with when
13088 @value{GDBN} detaches from it.
13090 @item show task detach-suspend-count
13091 Show the suspend count the task will be left with when detaching.
13093 @item set task exception-port
13094 @itemx set task excp
13095 @cindex task exception port, @sc{gnu} Hurd
13096 This command sets the task exception port to which @value{GDBN} will
13097 forward exceptions. The argument should be the value of the @dfn{send
13098 rights} of the task. @code{set task excp} is a shorthand alias.
13100 @item set noninvasive
13101 @cindex noninvasive task options
13102 This command switches @value{GDBN} to a mode that is the least
13103 invasive as far as interfering with the inferior is concerned. This
13104 is the same as using @code{set task pause}, @code{set exceptions}, and
13105 @code{set signals} to values opposite to the defaults.
13107 @item info send-rights
13108 @itemx info receive-rights
13109 @itemx info port-rights
13110 @itemx info port-sets
13111 @itemx info dead-names
13114 @cindex send rights, @sc{gnu} Hurd
13115 @cindex receive rights, @sc{gnu} Hurd
13116 @cindex port rights, @sc{gnu} Hurd
13117 @cindex port sets, @sc{gnu} Hurd
13118 @cindex dead names, @sc{gnu} Hurd
13119 These commands display information about, respectively, send rights,
13120 receive rights, port rights, port sets, and dead names of a task.
13121 There are also shorthand aliases: @code{info ports} for @code{info
13122 port-rights} and @code{info psets} for @code{info port-sets}.
13124 @item set thread pause
13125 @kindex set thread@r{, Hurd command}
13126 @cindex thread properties, @sc{gnu} Hurd
13127 @cindex pause current thread (@sc{gnu} Hurd)
13128 This command toggles current thread suspension when @value{GDBN} has
13129 control. Setting it to on takes effect immediately, and the current
13130 thread is suspended whenever @value{GDBN} gets control. Setting it to
13131 off will take effect the next time the inferior is continued.
13132 Normally, this command has no effect, since when @value{GDBN} has
13133 control, the whole task is suspended. However, if you used @code{set
13134 task pause off} (see above), this command comes in handy to suspend
13135 only the current thread.
13137 @item show thread pause
13138 @kindex show thread@r{, Hurd command}
13139 This command shows the state of current thread suspension.
13141 @item set thread run
13142 This comamnd sets whether the current thread is allowed to run.
13144 @item show thread run
13145 Show whether the current thread is allowed to run.
13147 @item set thread detach-suspend-count
13148 @cindex thread suspend count, @sc{gnu} Hurd
13149 @cindex detach from thread, @sc{gnu} Hurd
13150 This command sets the suspend count @value{GDBN} will leave on a
13151 thread when detaching. This number is relative to the suspend count
13152 found by @value{GDBN} when it notices the thread; use @code{set thread
13153 takeover-suspend-count} to force it to an absolute value.
13155 @item show thread detach-suspend-count
13156 Show the suspend count @value{GDBN} will leave on the thread when
13159 @item set thread exception-port
13160 @itemx set thread excp
13161 Set the thread exception port to which to forward exceptions. This
13162 overrides the port set by @code{set task exception-port} (see above).
13163 @code{set thread excp} is the shorthand alias.
13165 @item set thread takeover-suspend-count
13166 Normally, @value{GDBN}'s thread suspend counts are relative to the
13167 value @value{GDBN} finds when it notices each thread. This command
13168 changes the suspend counts to be absolute instead.
13170 @item set thread default
13171 @itemx show thread default
13172 @cindex thread default settings, @sc{gnu} Hurd
13173 Each of the above @code{set thread} commands has a @code{set thread
13174 default} counterpart (e.g., @code{set thread default pause}, @code{set
13175 thread default exception-port}, etc.). The @code{thread default}
13176 variety of commands sets the default thread properties for all
13177 threads; you can then change the properties of individual threads with
13178 the non-default commands.
13183 @subsection QNX Neutrino
13184 @cindex QNX Neutrino
13186 @value{GDBN} provides the following commands specific to the QNX
13190 @item set debug nto-debug
13191 @kindex set debug nto-debug
13192 When set to on, enables debugging messages specific to the QNX
13195 @item show debug nto-debug
13196 @kindex show debug nto-debug
13197 Show the current state of QNX Neutrino messages.
13202 @section Embedded Operating Systems
13204 This section describes configurations involving the debugging of
13205 embedded operating systems that are available for several different
13209 * VxWorks:: Using @value{GDBN} with VxWorks
13212 @value{GDBN} includes the ability to debug programs running on
13213 various real-time operating systems.
13216 @subsection Using @value{GDBN} with VxWorks
13222 @kindex target vxworks
13223 @item target vxworks @var{machinename}
13224 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
13225 is the target system's machine name or IP address.
13229 On VxWorks, @code{load} links @var{filename} dynamically on the
13230 current target system as well as adding its symbols in @value{GDBN}.
13232 @value{GDBN} enables developers to spawn and debug tasks running on networked
13233 VxWorks targets from a Unix host. Already-running tasks spawned from
13234 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
13235 both the Unix host and on the VxWorks target. The program
13236 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
13237 installed with the name @code{vxgdb}, to distinguish it from a
13238 @value{GDBN} for debugging programs on the host itself.)
13241 @item VxWorks-timeout @var{args}
13242 @kindex vxworks-timeout
13243 All VxWorks-based targets now support the option @code{vxworks-timeout}.
13244 This option is set by the user, and @var{args} represents the number of
13245 seconds @value{GDBN} waits for responses to rpc's. You might use this if
13246 your VxWorks target is a slow software simulator or is on the far side
13247 of a thin network line.
13250 The following information on connecting to VxWorks was current when
13251 this manual was produced; newer releases of VxWorks may use revised
13254 @findex INCLUDE_RDB
13255 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
13256 to include the remote debugging interface routines in the VxWorks
13257 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
13258 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
13259 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
13260 source debugging task @code{tRdbTask} when VxWorks is booted. For more
13261 information on configuring and remaking VxWorks, see the manufacturer's
13263 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
13265 Once you have included @file{rdb.a} in your VxWorks system image and set
13266 your Unix execution search path to find @value{GDBN}, you are ready to
13267 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
13268 @code{vxgdb}, depending on your installation).
13270 @value{GDBN} comes up showing the prompt:
13277 * VxWorks Connection:: Connecting to VxWorks
13278 * VxWorks Download:: VxWorks download
13279 * VxWorks Attach:: Running tasks
13282 @node VxWorks Connection
13283 @subsubsection Connecting to VxWorks
13285 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
13286 network. To connect to a target whose host name is ``@code{tt}'', type:
13289 (vxgdb) target vxworks tt
13293 @value{GDBN} displays messages like these:
13296 Attaching remote machine across net...
13301 @value{GDBN} then attempts to read the symbol tables of any object modules
13302 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
13303 these files by searching the directories listed in the command search
13304 path (@pxref{Environment, ,Your program's environment}); if it fails
13305 to find an object file, it displays a message such as:
13308 prog.o: No such file or directory.
13311 When this happens, add the appropriate directory to the search path with
13312 the @value{GDBN} command @code{path}, and execute the @code{target}
13315 @node VxWorks Download
13316 @subsubsection VxWorks download
13318 @cindex download to VxWorks
13319 If you have connected to the VxWorks target and you want to debug an
13320 object that has not yet been loaded, you can use the @value{GDBN}
13321 @code{load} command to download a file from Unix to VxWorks
13322 incrementally. The object file given as an argument to the @code{load}
13323 command is actually opened twice: first by the VxWorks target in order
13324 to download the code, then by @value{GDBN} in order to read the symbol
13325 table. This can lead to problems if the current working directories on
13326 the two systems differ. If both systems have NFS mounted the same
13327 filesystems, you can avoid these problems by using absolute paths.
13328 Otherwise, it is simplest to set the working directory on both systems
13329 to the directory in which the object file resides, and then to reference
13330 the file by its name, without any path. For instance, a program
13331 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
13332 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
13333 program, type this on VxWorks:
13336 -> cd "@var{vxpath}/vw/demo/rdb"
13340 Then, in @value{GDBN}, type:
13343 (vxgdb) cd @var{hostpath}/vw/demo/rdb
13344 (vxgdb) load prog.o
13347 @value{GDBN} displays a response similar to this:
13350 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
13353 You can also use the @code{load} command to reload an object module
13354 after editing and recompiling the corresponding source file. Note that
13355 this makes @value{GDBN} delete all currently-defined breakpoints,
13356 auto-displays, and convenience variables, and to clear the value
13357 history. (This is necessary in order to preserve the integrity of
13358 debugger's data structures that reference the target system's symbol
13361 @node VxWorks Attach
13362 @subsubsection Running tasks
13364 @cindex running VxWorks tasks
13365 You can also attach to an existing task using the @code{attach} command as
13369 (vxgdb) attach @var{task}
13373 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
13374 or suspended when you attach to it. Running tasks are suspended at
13375 the time of attachment.
13377 @node Embedded Processors
13378 @section Embedded Processors
13380 This section goes into details specific to particular embedded
13383 @cindex send command to simulator
13384 Whenever a specific embedded processor has a simulator, @value{GDBN}
13385 allows to send an arbitrary command to the simulator.
13388 @item sim @var{command}
13389 @kindex sim@r{, a command}
13390 Send an arbitrary @var{command} string to the simulator. Consult the
13391 documentation for the specific simulator in use for information about
13392 acceptable commands.
13398 * H8/300:: Renesas H8/300
13399 * H8/500:: Renesas H8/500
13400 * M32R/D:: Renesas M32R/D
13401 * M68K:: Motorola M68K
13402 * MIPS Embedded:: MIPS Embedded
13403 * OpenRISC 1000:: OpenRisc 1000
13404 * PA:: HP PA Embedded
13407 * Sparclet:: Tsqware Sparclet
13408 * Sparclite:: Fujitsu Sparclite
13409 * ST2000:: Tandem ST2000
13410 * Z8000:: Zilog Z8000
13413 * Super-H:: Renesas Super-H
13414 * WinCE:: Windows CE child processes
13423 @item target rdi @var{dev}
13424 ARM Angel monitor, via RDI library interface to ADP protocol. You may
13425 use this target to communicate with both boards running the Angel
13426 monitor, or with the EmbeddedICE JTAG debug device.
13429 @item target rdp @var{dev}
13434 @value{GDBN} provides the following ARM-specific commands:
13437 @item set arm disassembler
13439 This commands selects from a list of disassembly styles. The
13440 @code{"std"} style is the standard style.
13442 @item show arm disassembler
13444 Show the current disassembly style.
13446 @item set arm apcs32
13447 @cindex ARM 32-bit mode
13448 This command toggles ARM operation mode between 32-bit and 26-bit.
13450 @item show arm apcs32
13451 Display the current usage of the ARM 32-bit mode.
13453 @item set arm fpu @var{fputype}
13454 This command sets the ARM floating-point unit (FPU) type. The
13455 argument @var{fputype} can be one of these:
13459 Determine the FPU type by querying the OS ABI.
13461 Software FPU, with mixed-endian doubles on little-endian ARM
13464 GCC-compiled FPA co-processor.
13466 Software FPU with pure-endian doubles.
13472 Show the current type of the FPU.
13475 This command forces @value{GDBN} to use the specified ABI.
13478 Show the currently used ABI.
13480 @item set debug arm
13481 Toggle whether to display ARM-specific debugging messages from the ARM
13482 target support subsystem.
13484 @item show debug arm
13485 Show whether ARM-specific debugging messages are enabled.
13488 The following commands are available when an ARM target is debugged
13489 using the RDI interface:
13492 @item rdilogfile @r{[}@var{file}@r{]}
13494 @cindex ADP (Angel Debugger Protocol) logging
13495 Set the filename for the ADP (Angel Debugger Protocol) packet log.
13496 With an argument, sets the log file to the specified @var{file}. With
13497 no argument, show the current log file name. The default log file is
13500 @item rdilogenable @r{[}@var{arg}@r{]}
13501 @kindex rdilogenable
13502 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
13503 enables logging, with an argument 0 or @code{"no"} disables it. With
13504 no arguments displays the current setting. When logging is enabled,
13505 ADP packets exchanged between @value{GDBN} and the RDI target device
13506 are logged to a file.
13508 @item set rdiromatzero
13509 @kindex set rdiromatzero
13510 @cindex ROM at zero address, RDI
13511 Tell @value{GDBN} whether the target has ROM at address 0. If on,
13512 vector catching is disabled, so that zero address can be used. If off
13513 (the default), vector catching is enabled. For this command to take
13514 effect, it needs to be invoked prior to the @code{target rdi} command.
13516 @item show rdiromatzero
13517 @kindex show rdiromatzero
13518 Show the current setting of ROM at zero address.
13520 @item set rdiheartbeat
13521 @kindex set rdiheartbeat
13522 @cindex RDI heartbeat
13523 Enable or disable RDI heartbeat packets. It is not recommended to
13524 turn on this option, since it confuses ARM and EPI JTAG interface, as
13525 well as the Angel monitor.
13527 @item show rdiheartbeat
13528 @kindex show rdiheartbeat
13529 Show the setting of RDI heartbeat packets.
13534 @subsection Renesas H8/300
13538 @kindex target hms@r{, with H8/300}
13539 @item target hms @var{dev}
13540 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
13541 Use special commands @code{device} and @code{speed} to control the serial
13542 line and the communications speed used.
13544 @kindex target e7000@r{, with H8/300}
13545 @item target e7000 @var{dev}
13546 E7000 emulator for Renesas H8 and SH.
13548 @kindex target sh3@r{, with H8/300}
13549 @kindex target sh3e@r{, with H8/300}
13550 @item target sh3 @var{dev}
13551 @itemx target sh3e @var{dev}
13552 Renesas SH-3 and SH-3E target systems.
13556 @cindex download to H8/300 or H8/500
13557 @cindex H8/300 or H8/500 download
13558 @cindex download to Renesas SH
13559 @cindex Renesas SH download
13560 When you select remote debugging to a Renesas SH, H8/300, or H8/500
13561 board, the @code{load} command downloads your program to the Renesas
13562 board and also opens it as the current executable target for
13563 @value{GDBN} on your host (like the @code{file} command).
13565 @value{GDBN} needs to know these things to talk to your
13566 Renesas SH, H8/300, or H8/500:
13570 that you want to use @samp{target hms}, the remote debugging interface
13571 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
13572 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
13573 the default when @value{GDBN} is configured specifically for the Renesas SH,
13574 H8/300, or H8/500.)
13577 what serial device connects your host to your Renesas board (the first
13578 serial device available on your host is the default).
13581 what speed to use over the serial device.
13585 * Renesas Boards:: Connecting to Renesas boards.
13586 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
13587 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
13590 @node Renesas Boards
13591 @subsubsection Connecting to Renesas boards
13593 @c only for Unix hosts
13595 @cindex serial device, Renesas micros
13596 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
13597 need to explicitly set the serial device. The default @var{port} is the
13598 first available port on your host. This is only necessary on Unix
13599 hosts, where it is typically something like @file{/dev/ttya}.
13602 @cindex serial line speed, Renesas micros
13603 @code{@value{GDBN}} has another special command to set the communications
13604 speed: @samp{speed @var{bps}}. This command also is only used from Unix
13605 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
13606 the DOS @code{mode} command (for instance,
13607 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
13609 The @samp{device} and @samp{speed} commands are available only when you
13610 use a Unix host to debug your Renesas microprocessor programs. If you
13612 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
13613 called @code{asynctsr} to communicate with the development board
13614 through a PC serial port. You must also use the DOS @code{mode} command
13615 to set up the serial port on the DOS side.
13617 The following sample session illustrates the steps needed to start a
13618 program under @value{GDBN} control on an H8/300. The example uses a
13619 sample H8/300 program called @file{t.x}. The procedure is the same for
13620 the Renesas SH and the H8/500.
13622 First hook up your development board. In this example, we use a
13623 board attached to serial port @code{COM2}; if you use a different serial
13624 port, substitute its name in the argument of the @code{mode} command.
13625 When you call @code{asynctsr}, the auxiliary comms program used by the
13626 debugger, you give it just the numeric part of the serial port's name;
13627 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
13631 C:\H8300\TEST> asynctsr 2
13632 C:\H8300\TEST> mode com2:9600,n,8,1,p
13634 Resident portion of MODE loaded
13636 COM2: 9600, n, 8, 1, p
13641 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
13642 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
13643 disable it, or even boot without it, to use @code{asynctsr} to control
13644 your development board.
13647 @kindex target hms@r{, and serial protocol}
13648 Now that serial communications are set up, and the development board is
13649 connected, you can start up @value{GDBN}. Call @code{@value{GDBN}} with
13650 the name of your program as the argument. @code{@value{GDBN}} prompts
13651 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
13652 commands to begin your debugging session: @samp{target hms} to specify
13653 cross-debugging to the Renesas board, and the @code{load} command to
13654 download your program to the board. @code{load} displays the names of
13655 the program's sections, and a @samp{*} for each 2K of data downloaded.
13656 (If you want to refresh @value{GDBN} data on symbols or on the
13657 executable file without downloading, use the @value{GDBN} commands
13658 @code{file} or @code{symbol-file}. These commands, and @code{load}
13659 itself, are described in @ref{Files,,Commands to specify files}.)
13662 (eg-C:\H8300\TEST) @value{GDBP} t.x
13663 @value{GDBN} is free software and you are welcome to distribute copies
13664 of it under certain conditions; type "show copying" to see
13666 There is absolutely no warranty for @value{GDBN}; type "show warranty"
13668 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
13669 (@value{GDBP}) target hms
13670 Connected to remote H8/300 HMS system.
13671 (@value{GDBP}) load t.x
13672 .text : 0x8000 .. 0xabde ***********
13673 .data : 0xabde .. 0xad30 *
13674 .stack : 0xf000 .. 0xf014 *
13677 At this point, you're ready to run or debug your program. From here on,
13678 you can use all the usual @value{GDBN} commands. The @code{break} command
13679 sets breakpoints; the @code{run} command starts your program;
13680 @code{print} or @code{x} display data; the @code{continue} command
13681 resumes execution after stopping at a breakpoint. You can use the
13682 @code{help} command at any time to find out more about @value{GDBN} commands.
13684 Remember, however, that @emph{operating system} facilities aren't
13685 available on your development board; for example, if your program hangs,
13686 you can't send an interrupt---but you can press the @sc{reset} switch!
13688 Use the @sc{reset} button on the development board
13691 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
13692 no way to pass an interrupt signal to the development board); and
13695 to return to the @value{GDBN} command prompt after your program finishes
13696 normally. The communications protocol provides no other way for @value{GDBN}
13697 to detect program completion.
13700 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
13701 development board as a ``normal exit'' of your program.
13704 @subsubsection Using the E7000 in-circuit emulator
13706 @kindex target e7000@r{, with Renesas ICE}
13707 You can use the E7000 in-circuit emulator to develop code for either the
13708 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
13709 e7000} command to connect @value{GDBN} to your E7000:
13712 @item target e7000 @var{port} @var{speed}
13713 Use this form if your E7000 is connected to a serial port. The
13714 @var{port} argument identifies what serial port to use (for example,
13715 @samp{com2}). The third argument is the line speed in bits per second
13716 (for example, @samp{9600}).
13718 @item target e7000 @var{hostname}
13719 If your E7000 is installed as a host on a TCP/IP network, you can just
13720 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
13723 The following special commands are available when debugging with the
13727 @item e7000 @var{command}
13729 @cindex send command to E7000 monitor
13730 This sends the specified @var{command} to the E7000 monitor.
13732 @item ftplogin @var{machine} @var{username} @var{password} @var{dir}
13733 @kindex ftplogin@r{, E7000}
13734 This command records information for subsequent interface with the
13735 E7000 monitor via the FTP protocol: @value{GDBN} will log into the
13736 named @var{machine} using specified @var{username} and @var{password},
13737 and then chdir to the named directory @var{dir}.
13739 @item ftpload @var{file}
13740 @kindex ftpload@r{, E7000}
13741 This command uses credentials recorded by @code{ftplogin} to fetch and
13742 load the named @var{file} from the E7000 monitor.
13745 @kindex drain@r{, E7000}
13746 This command drains any pending text buffers stored on the E7000.
13748 @item set usehardbreakpoints
13749 @itemx show usehardbreakpoints
13750 @kindex set usehardbreakpoints@r{, E7000}
13751 @kindex show usehardbreakpoints@r{, E7000}
13752 @cindex hardware breakpoints, and E7000
13753 These commands set and show the use of hardware breakpoints for all
13754 breakpoints. @xref{Set Breaks, hardware-assisted breakpoint}, for
13755 more information about using hardware breakpoints selectively.
13758 @node Renesas Special
13759 @subsubsection Special @value{GDBN} commands for Renesas micros
13761 Some @value{GDBN} commands are available only for the H8/300:
13765 @kindex set machine
13766 @kindex show machine
13767 @item set machine h8300
13768 @itemx set machine h8300h
13769 Condition @value{GDBN} for one of the two variants of the H8/300
13770 architecture with @samp{set machine}. You can use @samp{show machine}
13771 to check which variant is currently in effect.
13780 @kindex set memory @var{mod}
13781 @cindex memory models, H8/500
13782 @item set memory @var{mod}
13784 Specify which H8/500 memory model (@var{mod}) you are using with
13785 @samp{set memory}; check which memory model is in effect with @samp{show
13786 memory}. The accepted values for @var{mod} are @code{small},
13787 @code{big}, @code{medium}, and @code{compact}.
13792 @subsection Renesas M32R/D and M32R/SDI
13795 @kindex target m32r
13796 @item target m32r @var{dev}
13797 Renesas M32R/D ROM monitor.
13799 @kindex target m32rsdi
13800 @item target m32rsdi @var{dev}
13801 Renesas M32R SDI server, connected via parallel port to the board.
13804 The following @value{GDBN} commands are specific to the M32R monitor:
13807 @item set download-path @var{path}
13808 @kindex set download-path
13809 @cindex find downloadable @sc{srec} files (M32R)
13810 Set the default path for finding donwloadable @sc{srec} files.
13812 @item show download-path
13813 @kindex show download-path
13814 Show the default path for downloadable @sc{srec} files.
13816 @item set board-address @var{addr}
13817 @kindex set board-address
13818 @cindex M32-EVA target board address
13819 Set the IP address for the M32R-EVA target board.
13821 @item show board-address
13822 @kindex show board-address
13823 Show the current IP address of the target board.
13825 @item set server-address @var{addr}
13826 @kindex set server-address
13827 @cindex download server address (M32R)
13828 Set the IP address for the download server, which is the @value{GDBN}'s
13831 @item show server-address
13832 @kindex show server-address
13833 Display the IP address of the download server.
13835 @item upload @r{[}@var{file}@r{]}
13836 @kindex upload@r{, M32R}
13837 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
13838 upload capability. If no @var{file} argument is given, the current
13839 executable file is uploaded.
13841 @item tload @r{[}@var{file}@r{]}
13842 @kindex tload@r{, M32R}
13843 Test the @code{upload} command.
13846 The following commands are available for M32R/SDI:
13851 @cindex reset SDI connection, M32R
13852 This command resets the SDI connection.
13856 This command shows the SDI connection status.
13859 @kindex debug_chaos
13860 @cindex M32R/Chaos debugging
13861 Instructs the remote that M32R/Chaos debugging is to be used.
13863 @item use_debug_dma
13864 @kindex use_debug_dma
13865 Instructs the remote to use the DEBUG_DMA method of accessing memory.
13868 @kindex use_mon_code
13869 Instructs the remote to use the MON_CODE method of accessing memory.
13872 @kindex use_ib_break
13873 Instructs the remote to set breakpoints by IB break.
13875 @item use_dbt_break
13876 @kindex use_dbt_break
13877 Instructs the remote to set breakpoints by DBT.
13883 The Motorola m68k configuration includes ColdFire support, and
13884 target command for the following ROM monitors.
13888 @kindex target abug
13889 @item target abug @var{dev}
13890 ABug ROM monitor for M68K.
13892 @kindex target cpu32bug
13893 @item target cpu32bug @var{dev}
13894 CPU32BUG monitor, running on a CPU32 (M68K) board.
13896 @kindex target dbug
13897 @item target dbug @var{dev}
13898 dBUG ROM monitor for Motorola ColdFire.
13901 @item target est @var{dev}
13902 EST-300 ICE monitor, running on a CPU32 (M68K) board.
13904 @kindex target rom68k
13905 @item target rom68k @var{dev}
13906 ROM 68K monitor, running on an M68K IDP board.
13912 @kindex target rombug
13913 @item target rombug @var{dev}
13914 ROMBUG ROM monitor for OS/9000.
13918 @node MIPS Embedded
13919 @subsection MIPS Embedded
13921 @cindex MIPS boards
13922 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
13923 MIPS board attached to a serial line. This is available when
13924 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
13927 Use these @value{GDBN} commands to specify the connection to your target board:
13930 @item target mips @var{port}
13931 @kindex target mips @var{port}
13932 To run a program on the board, start up @code{@value{GDBP}} with the
13933 name of your program as the argument. To connect to the board, use the
13934 command @samp{target mips @var{port}}, where @var{port} is the name of
13935 the serial port connected to the board. If the program has not already
13936 been downloaded to the board, you may use the @code{load} command to
13937 download it. You can then use all the usual @value{GDBN} commands.
13939 For example, this sequence connects to the target board through a serial
13940 port, and loads and runs a program called @var{prog} through the
13944 host$ @value{GDBP} @var{prog}
13945 @value{GDBN} is free software and @dots{}
13946 (@value{GDBP}) target mips /dev/ttyb
13947 (@value{GDBP}) load @var{prog}
13951 @item target mips @var{hostname}:@var{portnumber}
13952 On some @value{GDBN} host configurations, you can specify a TCP
13953 connection (for instance, to a serial line managed by a terminal
13954 concentrator) instead of a serial port, using the syntax
13955 @samp{@var{hostname}:@var{portnumber}}.
13957 @item target pmon @var{port}
13958 @kindex target pmon @var{port}
13961 @item target ddb @var{port}
13962 @kindex target ddb @var{port}
13963 NEC's DDB variant of PMON for Vr4300.
13965 @item target lsi @var{port}
13966 @kindex target lsi @var{port}
13967 LSI variant of PMON.
13969 @kindex target r3900
13970 @item target r3900 @var{dev}
13971 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
13973 @kindex target array
13974 @item target array @var{dev}
13975 Array Tech LSI33K RAID controller board.
13981 @value{GDBN} also supports these special commands for MIPS targets:
13984 @item set mipsfpu double
13985 @itemx set mipsfpu single
13986 @itemx set mipsfpu none
13987 @itemx set mipsfpu auto
13988 @itemx show mipsfpu
13989 @kindex set mipsfpu
13990 @kindex show mipsfpu
13991 @cindex MIPS remote floating point
13992 @cindex floating point, MIPS remote
13993 If your target board does not support the MIPS floating point
13994 coprocessor, you should use the command @samp{set mipsfpu none} (if you
13995 need this, you may wish to put the command in your @value{GDBN} init
13996 file). This tells @value{GDBN} how to find the return value of
13997 functions which return floating point values. It also allows
13998 @value{GDBN} to avoid saving the floating point registers when calling
13999 functions on the board. If you are using a floating point coprocessor
14000 with only single precision floating point support, as on the @sc{r4650}
14001 processor, use the command @samp{set mipsfpu single}. The default
14002 double precision floating point coprocessor may be selected using
14003 @samp{set mipsfpu double}.
14005 In previous versions the only choices were double precision or no
14006 floating point, so @samp{set mipsfpu on} will select double precision
14007 and @samp{set mipsfpu off} will select no floating point.
14009 As usual, you can inquire about the @code{mipsfpu} variable with
14010 @samp{show mipsfpu}.
14012 @item set timeout @var{seconds}
14013 @itemx set retransmit-timeout @var{seconds}
14014 @itemx show timeout
14015 @itemx show retransmit-timeout
14016 @cindex @code{timeout}, MIPS protocol
14017 @cindex @code{retransmit-timeout}, MIPS protocol
14018 @kindex set timeout
14019 @kindex show timeout
14020 @kindex set retransmit-timeout
14021 @kindex show retransmit-timeout
14022 You can control the timeout used while waiting for a packet, in the MIPS
14023 remote protocol, with the @code{set timeout @var{seconds}} command. The
14024 default is 5 seconds. Similarly, you can control the timeout used while
14025 waiting for an acknowledgement of a packet with the @code{set
14026 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
14027 You can inspect both values with @code{show timeout} and @code{show
14028 retransmit-timeout}. (These commands are @emph{only} available when
14029 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
14031 The timeout set by @code{set timeout} does not apply when @value{GDBN}
14032 is waiting for your program to stop. In that case, @value{GDBN} waits
14033 forever because it has no way of knowing how long the program is going
14034 to run before stopping.
14036 @item set syn-garbage-limit @var{num}
14037 @kindex set syn-garbage-limit@r{, MIPS remote}
14038 @cindex synchronize with remote MIPS target
14039 Limit the maximum number of characters @value{GDBN} should ignore when
14040 it tries to synchronize with the remote target. The default is 10
14041 characters. Setting the limit to -1 means there's no limit.
14043 @item show syn-garbage-limit
14044 @kindex show syn-garbage-limit@r{, MIPS remote}
14045 Show the current limit on the number of characters to ignore when
14046 trying to synchronize with the remote system.
14048 @item set monitor-prompt @var{prompt}
14049 @kindex set monitor-prompt@r{, MIPS remote}
14050 @cindex remote monitor prompt
14051 Tell @value{GDBN} to expect the specified @var{prompt} string from the
14052 remote monitor. The default depends on the target:
14062 @item show monitor-prompt
14063 @kindex show monitor-prompt@r{, MIPS remote}
14064 Show the current strings @value{GDBN} expects as the prompt from the
14067 @item set monitor-warnings
14068 @kindex set monitor-warnings@r{, MIPS remote}
14069 Enable or disable monitor warnings about hardware breakpoints. This
14070 has effect only for the @code{lsi} target. When on, @value{GDBN} will
14071 display warning messages whose codes are returned by the @code{lsi}
14072 PMON monitor for breakpoint commands.
14074 @item show monitor-warnings
14075 @kindex show monitor-warnings@r{, MIPS remote}
14076 Show the current setting of printing monitor warnings.
14078 @item pmon @var{command}
14079 @kindex pmon@r{, MIPS remote}
14080 @cindex send PMON command
14081 This command allows sending an arbitrary @var{command} string to the
14082 monitor. The monitor must be in debug mode for this to work.
14085 @node OpenRISC 1000
14086 @subsection OpenRISC 1000
14087 @cindex OpenRISC 1000
14089 @cindex or1k boards
14090 See OR1k Architecture document (@uref{www.opencores.org}) for more information
14091 about platform and commands.
14095 @kindex target jtag
14096 @item target jtag jtag://@var{host}:@var{port}
14098 Connects to remote JTAG server.
14099 JTAG remote server can be either an or1ksim or JTAG server,
14100 connected via parallel port to the board.
14102 Example: @code{target jtag jtag://localhost:9999}
14105 @item or1ksim @var{command}
14106 If connected to @code{or1ksim} OpenRISC 1000 Architectural
14107 Simulator, proprietary commands can be executed.
14109 @kindex info or1k spr
14110 @item info or1k spr
14111 Displays spr groups.
14113 @item info or1k spr @var{group}
14114 @itemx info or1k spr @var{groupno}
14115 Displays register names in selected group.
14117 @item info or1k spr @var{group} @var{register}
14118 @itemx info or1k spr @var{register}
14119 @itemx info or1k spr @var{groupno} @var{registerno}
14120 @itemx info or1k spr @var{registerno}
14121 Shows information about specified spr register.
14124 @item spr @var{group} @var{register} @var{value}
14125 @itemx spr @var{register @var{value}}
14126 @itemx spr @var{groupno} @var{registerno @var{value}}
14127 @itemx spr @var{registerno @var{value}}
14128 Writes @var{value} to specified spr register.
14131 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
14132 It is very similar to @value{GDBN} trace, except it does not interfere with normal
14133 program execution and is thus much faster. Hardware breakpoints/watchpoint
14134 triggers can be set using:
14137 Load effective address/data
14139 Store effective address/data
14141 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
14146 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
14147 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
14149 @code{htrace} commands:
14150 @cindex OpenRISC 1000 htrace
14153 @item hwatch @var{conditional}
14154 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
14155 or Data. For example:
14157 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14159 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14163 Display information about current HW trace configuration.
14165 @item htrace trigger @var{conditional}
14166 Set starting criteria for HW trace.
14168 @item htrace qualifier @var{conditional}
14169 Set acquisition qualifier for HW trace.
14171 @item htrace stop @var{conditional}
14172 Set HW trace stopping criteria.
14174 @item htrace record [@var{data}]*
14175 Selects the data to be recorded, when qualifier is met and HW trace was
14178 @item htrace enable
14179 @itemx htrace disable
14180 Enables/disables the HW trace.
14182 @item htrace rewind [@var{filename}]
14183 Clears currently recorded trace data.
14185 If filename is specified, new trace file is made and any newly collected data
14186 will be written there.
14188 @item htrace print [@var{start} [@var{len}]]
14189 Prints trace buffer, using current record configuration.
14191 @item htrace mode continuous
14192 Set continuous trace mode.
14194 @item htrace mode suspend
14195 Set suspend trace mode.
14200 @subsection PowerPC
14203 @kindex target dink32
14204 @item target dink32 @var{dev}
14205 DINK32 ROM monitor.
14207 @kindex target ppcbug
14208 @item target ppcbug @var{dev}
14209 @kindex target ppcbug1
14210 @item target ppcbug1 @var{dev}
14211 PPCBUG ROM monitor for PowerPC.
14214 @item target sds @var{dev}
14215 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
14218 @cindex SDS protocol
14219 The following commands specifi to the SDS protocol are supported
14223 @item set sdstimeout @var{nsec}
14224 @kindex set sdstimeout
14225 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
14226 default is 2 seconds.
14228 @item show sdstimeout
14229 @kindex show sdstimeout
14230 Show the current value of the SDS timeout.
14232 @item sds @var{command}
14233 @kindex sds@r{, a command}
14234 Send the specified @var{command} string to the SDS monitor.
14239 @subsection HP PA Embedded
14243 @kindex target op50n
14244 @item target op50n @var{dev}
14245 OP50N monitor, running on an OKI HPPA board.
14247 @kindex target w89k
14248 @item target w89k @var{dev}
14249 W89K monitor, running on a Winbond HPPA board.
14254 @subsection Renesas SH
14258 @kindex target hms@r{, with Renesas SH}
14259 @item target hms @var{dev}
14260 A Renesas SH board attached via serial line to your host. Use special
14261 commands @code{device} and @code{speed} to control the serial line and
14262 the communications speed used.
14264 @kindex target e7000@r{, with Renesas SH}
14265 @item target e7000 @var{dev}
14266 E7000 emulator for Renesas SH.
14268 @kindex target sh3@r{, with SH}
14269 @kindex target sh3e@r{, with SH}
14270 @item target sh3 @var{dev}
14271 @item target sh3e @var{dev}
14272 Renesas SH-3 and SH-3E target systems.
14277 @subsection Tsqware Sparclet
14281 @value{GDBN} enables developers to debug tasks running on
14282 Sparclet targets from a Unix host.
14283 @value{GDBN} uses code that runs on
14284 both the Unix host and on the Sparclet target. The program
14285 @code{@value{GDBP}} is installed and executed on the Unix host.
14288 @item remotetimeout @var{args}
14289 @kindex remotetimeout
14290 @value{GDBN} supports the option @code{remotetimeout}.
14291 This option is set by the user, and @var{args} represents the number of
14292 seconds @value{GDBN} waits for responses.
14295 @cindex compiling, on Sparclet
14296 When compiling for debugging, include the options @samp{-g} to get debug
14297 information and @samp{-Ttext} to relocate the program to where you wish to
14298 load it on the target. You may also want to add the options @samp{-n} or
14299 @samp{-N} in order to reduce the size of the sections. Example:
14302 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
14305 You can use @code{objdump} to verify that the addresses are what you intended:
14308 sparclet-aout-objdump --headers --syms prog
14311 @cindex running, on Sparclet
14313 your Unix execution search path to find @value{GDBN}, you are ready to
14314 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
14315 (or @code{sparclet-aout-gdb}, depending on your installation).
14317 @value{GDBN} comes up showing the prompt:
14324 * Sparclet File:: Setting the file to debug
14325 * Sparclet Connection:: Connecting to Sparclet
14326 * Sparclet Download:: Sparclet download
14327 * Sparclet Execution:: Running and debugging
14330 @node Sparclet File
14331 @subsubsection Setting file to debug
14333 The @value{GDBN} command @code{file} lets you choose with program to debug.
14336 (gdbslet) file prog
14340 @value{GDBN} then attempts to read the symbol table of @file{prog}.
14341 @value{GDBN} locates
14342 the file by searching the directories listed in the command search
14344 If the file was compiled with debug information (option "-g"), source
14345 files will be searched as well.
14346 @value{GDBN} locates
14347 the source files by searching the directories listed in the directory search
14348 path (@pxref{Environment, ,Your program's environment}).
14350 to find a file, it displays a message such as:
14353 prog: No such file or directory.
14356 When this happens, add the appropriate directories to the search paths with
14357 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
14358 @code{target} command again.
14360 @node Sparclet Connection
14361 @subsubsection Connecting to Sparclet
14363 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
14364 To connect to a target on serial port ``@code{ttya}'', type:
14367 (gdbslet) target sparclet /dev/ttya
14368 Remote target sparclet connected to /dev/ttya
14369 main () at ../prog.c:3
14373 @value{GDBN} displays messages like these:
14379 @node Sparclet Download
14380 @subsubsection Sparclet download
14382 @cindex download to Sparclet
14383 Once connected to the Sparclet target,
14384 you can use the @value{GDBN}
14385 @code{load} command to download the file from the host to the target.
14386 The file name and load offset should be given as arguments to the @code{load}
14388 Since the file format is aout, the program must be loaded to the starting
14389 address. You can use @code{objdump} to find out what this value is. The load
14390 offset is an offset which is added to the VMA (virtual memory address)
14391 of each of the file's sections.
14392 For instance, if the program
14393 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
14394 and bss at 0x12010170, in @value{GDBN}, type:
14397 (gdbslet) load prog 0x12010000
14398 Loading section .text, size 0xdb0 vma 0x12010000
14401 If the code is loaded at a different address then what the program was linked
14402 to, you may need to use the @code{section} and @code{add-symbol-file} commands
14403 to tell @value{GDBN} where to map the symbol table.
14405 @node Sparclet Execution
14406 @subsubsection Running and debugging
14408 @cindex running and debugging Sparclet programs
14409 You can now begin debugging the task using @value{GDBN}'s execution control
14410 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
14411 manual for the list of commands.
14415 Breakpoint 1 at 0x12010000: file prog.c, line 3.
14417 Starting program: prog
14418 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
14419 3 char *symarg = 0;
14421 4 char *execarg = "hello!";
14426 @subsection Fujitsu Sparclite
14430 @kindex target sparclite
14431 @item target sparclite @var{dev}
14432 Fujitsu sparclite boards, used only for the purpose of loading.
14433 You must use an additional command to debug the program.
14434 For example: target remote @var{dev} using @value{GDBN} standard
14440 @subsection Tandem ST2000
14442 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
14445 To connect your ST2000 to the host system, see the manufacturer's
14446 manual. Once the ST2000 is physically attached, you can run:
14449 target st2000 @var{dev} @var{speed}
14453 to establish it as your debugging environment. @var{dev} is normally
14454 the name of a serial device, such as @file{/dev/ttya}, connected to the
14455 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
14456 connection (for example, to a serial line attached via a terminal
14457 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
14459 The @code{load} and @code{attach} commands are @emph{not} defined for
14460 this target; you must load your program into the ST2000 as you normally
14461 would for standalone operation. @value{GDBN} reads debugging information
14462 (such as symbols) from a separate, debugging version of the program
14463 available on your host computer.
14464 @c FIXME!! This is terribly vague; what little content is here is
14465 @c basically hearsay.
14467 @cindex ST2000 auxiliary commands
14468 These auxiliary @value{GDBN} commands are available to help you with the ST2000
14472 @item st2000 @var{command}
14473 @kindex st2000 @var{cmd}
14474 @cindex STDBUG commands (ST2000)
14475 @cindex commands to STDBUG (ST2000)
14476 Send a @var{command} to the STDBUG monitor. See the manufacturer's
14477 manual for available commands.
14480 @cindex connect (to STDBUG)
14481 Connect the controlling terminal to the STDBUG command monitor. When
14482 you are done interacting with STDBUG, typing either of two character
14483 sequences gets you back to the @value{GDBN} command prompt:
14484 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
14485 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
14489 @subsection Zilog Z8000
14492 @cindex simulator, Z8000
14493 @cindex Zilog Z8000 simulator
14495 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
14498 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
14499 unsegmented variant of the Z8000 architecture) or the Z8001 (the
14500 segmented variant). The simulator recognizes which architecture is
14501 appropriate by inspecting the object code.
14504 @item target sim @var{args}
14506 @kindex target sim@r{, with Z8000}
14507 Debug programs on a simulated CPU. If the simulator supports setup
14508 options, specify them via @var{args}.
14512 After specifying this target, you can debug programs for the simulated
14513 CPU in the same style as programs for your host computer; use the
14514 @code{file} command to load a new program image, the @code{run} command
14515 to run your program, and so on.
14517 As well as making available all the usual machine registers
14518 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
14519 additional items of information as specially named registers:
14524 Counts clock-ticks in the simulator.
14527 Counts instructions run in the simulator.
14530 Execution time in 60ths of a second.
14534 You can refer to these values in @value{GDBN} expressions with the usual
14535 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
14536 conditional breakpoint that suspends only after at least 5000
14537 simulated clock ticks.
14540 @subsection Atmel AVR
14543 When configured for debugging the Atmel AVR, @value{GDBN} supports the
14544 following AVR-specific commands:
14547 @item info io_registers
14548 @kindex info io_registers@r{, AVR}
14549 @cindex I/O registers (Atmel AVR)
14550 This command displays information about the AVR I/O registers. For
14551 each register, @value{GDBN} prints its number and value.
14558 When configured for debugging CRIS, @value{GDBN} provides the
14559 following CRIS-specific commands:
14562 @item set cris-version @var{ver}
14563 @cindex CRIS version
14564 Set the current CRIS version to @var{ver}. The CRIS version affects
14565 register names and sizes. This command is useful in case
14566 autodetection of the CRIS version fails.
14568 @item show cris-version
14569 Show the current CRIS version.
14571 @item set cris-dwarf2-cfi
14572 @cindex DWARF-2 CFI and CRIS
14573 Set the usage of DWARF-2 CFI for CRIS debugging. The default is off
14574 if using @code{gcc-cris} whose version is below @code{R59}, otherwise
14577 @item show cris-dwarf2-cfi
14578 Show the current state of using DWARF-2 CFI.
14582 @subsection Renesas Super-H
14585 For the Renesas Super-H processor, @value{GDBN} provides these
14590 @kindex regs@r{, Super-H}
14591 Show the values of all Super-H registers.
14595 @subsection Windows CE
14598 The following commands are available for Windows CE:
14601 @item set remotedirectory @var{dir}
14602 @kindex set remotedirectory
14603 Tell @value{GDBN} to upload files from the named directory @var{dir}.
14604 The default is @file{/gdb}, i.e.@: the root directory on the current
14607 @item show remotedirectory
14608 @kindex show remotedirectory
14609 Show the current value of the upload directory.
14611 @item set remoteupload @var{method}
14612 @kindex set remoteupload
14613 Set the method used to upload files to remote device. Valid values
14614 for @var{method} are @samp{always}, @samp{newer}, and @samp{never}.
14615 The default is @samp{newer}.
14617 @item show remoteupload
14618 @kindex show remoteupload
14619 Show the current setting of the upload method.
14621 @item set remoteaddhost
14622 @kindex set remoteaddhost
14623 Tell @value{GDBN} whether to add this host to the remote stub's
14624 arguments when you debug over a network.
14626 @item show remoteaddhost
14627 @kindex show remoteaddhost
14628 Show whether to add this host to remote stub's arguments when
14629 debugging over a network.
14633 @node Architectures
14634 @section Architectures
14636 This section describes characteristics of architectures that affect
14637 all uses of @value{GDBN} with the architecture, both native and cross.
14644 * HPPA:: HP PA architecture
14648 @subsection x86 Architecture-specific issues.
14651 @item set struct-convention @var{mode}
14652 @kindex set struct-convention
14653 @cindex struct return convention
14654 @cindex struct/union returned in registers
14655 Set the convention used by the inferior to return @code{struct}s and
14656 @code{union}s from functions to @var{mode}. Possible values of
14657 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
14658 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
14659 are returned on the stack, while @code{"reg"} means that a
14660 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
14661 be returned in a register.
14663 @item show struct-convention
14664 @kindex show struct-convention
14665 Show the current setting of the convention to return @code{struct}s
14674 @kindex set rstack_high_address
14675 @cindex AMD 29K register stack
14676 @cindex register stack, AMD29K
14677 @item set rstack_high_address @var{address}
14678 On AMD 29000 family processors, registers are saved in a separate
14679 @dfn{register stack}. There is no way for @value{GDBN} to determine the
14680 extent of this stack. Normally, @value{GDBN} just assumes that the
14681 stack is ``large enough''. This may result in @value{GDBN} referencing
14682 memory locations that do not exist. If necessary, you can get around
14683 this problem by specifying the ending address of the register stack with
14684 the @code{set rstack_high_address} command. The argument should be an
14685 address, which you probably want to precede with @samp{0x} to specify in
14688 @kindex show rstack_high_address
14689 @item show rstack_high_address
14690 Display the current limit of the register stack, on AMD 29000 family
14698 See the following section.
14703 @cindex stack on Alpha
14704 @cindex stack on MIPS
14705 @cindex Alpha stack
14707 Alpha- and MIPS-based computers use an unusual stack frame, which
14708 sometimes requires @value{GDBN} to search backward in the object code to
14709 find the beginning of a function.
14711 @cindex response time, MIPS debugging
14712 To improve response time (especially for embedded applications, where
14713 @value{GDBN} may be restricted to a slow serial line for this search)
14714 you may want to limit the size of this search, using one of these
14718 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
14719 @item set heuristic-fence-post @var{limit}
14720 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
14721 search for the beginning of a function. A value of @var{0} (the
14722 default) means there is no limit. However, except for @var{0}, the
14723 larger the limit the more bytes @code{heuristic-fence-post} must search
14724 and therefore the longer it takes to run. You should only need to use
14725 this command when debugging a stripped executable.
14727 @item show heuristic-fence-post
14728 Display the current limit.
14732 These commands are available @emph{only} when @value{GDBN} is configured
14733 for debugging programs on Alpha or MIPS processors.
14735 Several MIPS-specific commands are available when debugging MIPS
14739 @item set mips saved-gpreg-size @var{size}
14740 @kindex set mips saved-gpreg-size
14741 @cindex MIPS GP register size on stack
14742 Set the size of MIPS general-purpose registers saved on the stack.
14743 The argument @var{size} can be one of the following:
14747 32-bit GP registers
14749 64-bit GP registers
14751 Use the target's default setting or autodetect the saved size from the
14752 information contained in the executable. This is the default
14755 @item show mips saved-gpreg-size
14756 @kindex show mips saved-gpreg-size
14757 Show the current size of MIPS GP registers on the stack.
14759 @item set mips stack-arg-size @var{size}
14760 @kindex set mips stack-arg-size
14761 @cindex MIPS stack space for arguments
14762 Set the amount of stack space reserved for arguments to functions.
14763 The argument can be one of @code{"32"}, @code{"64"} or @code{"auto"}
14766 @item set mips abi @var{arg}
14767 @kindex set mips abi
14768 @cindex set ABI for MIPS
14769 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
14770 values of @var{arg} are:
14774 The default ABI associated with the current binary (this is the
14785 @item show mips abi
14786 @kindex show mips abi
14787 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
14790 @itemx show mipsfpu
14791 @xref{MIPS Embedded, set mipsfpu}.
14793 @item set mips mask-address @var{arg}
14794 @kindex set mips mask-address
14795 @cindex MIPS addresses, masking
14796 This command determines whether the most-significant 32 bits of 64-bit
14797 MIPS addresses are masked off. The argument @var{arg} can be
14798 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
14799 setting, which lets @value{GDBN} determine the correct value.
14801 @item show mips mask-address
14802 @kindex show mips mask-address
14803 Show whether the upper 32 bits of MIPS addresses are masked off or
14806 @item set remote-mips64-transfers-32bit-regs
14807 @kindex set remote-mips64-transfers-32bit-regs
14808 This command controls compatibility with 64-bit MIPS targets that
14809 transfer data in 32-bit quantities. If you have an old MIPS 64 target
14810 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
14811 and 64 bits for other registers, set this option to @samp{on}.
14813 @item show remote-mips64-transfers-32bit-regs
14814 @kindex show remote-mips64-transfers-32bit-regs
14815 Show the current setting of compatibility with older MIPS 64 targets.
14817 @item set debug mips
14818 @kindex set debug mips
14819 This command turns on and off debugging messages for the MIPS-specific
14820 target code in @value{GDBN}.
14822 @item show debug mips
14823 @kindex show debug mips
14824 Show the current setting of MIPS debugging messages.
14830 @cindex HPPA support
14832 When @value{GDBN} is debugging te HP PA architecture, it provides the
14833 following special commands:
14836 @item set debug hppa
14837 @kindex set debug hppa
14838 THis command determines whether HPPA architecture specific debugging
14839 messages are to be displayed.
14841 @item show debug hppa
14842 Show whether HPPA debugging messages are displayed.
14844 @item maint print unwind @var{address}
14845 @kindex maint print unwind@r{, HPPA}
14846 This command displays the contents of the unwind table entry at the
14847 given @var{address}.
14852 @node Controlling GDB
14853 @chapter Controlling @value{GDBN}
14855 You can alter the way @value{GDBN} interacts with you by using the
14856 @code{set} command. For commands controlling how @value{GDBN} displays
14857 data, see @ref{Print Settings, ,Print settings}. Other settings are
14862 * Editing:: Command editing
14863 * History:: Command history
14864 * Screen Size:: Screen size
14865 * Numbers:: Numbers
14866 * ABI:: Configuring the current ABI
14867 * Messages/Warnings:: Optional warnings and messages
14868 * Debugging Output:: Optional messages about internal happenings
14876 @value{GDBN} indicates its readiness to read a command by printing a string
14877 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
14878 can change the prompt string with the @code{set prompt} command. For
14879 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
14880 the prompt in one of the @value{GDBN} sessions so that you can always tell
14881 which one you are talking to.
14883 @emph{Note:} @code{set prompt} does not add a space for you after the
14884 prompt you set. This allows you to set a prompt which ends in a space
14885 or a prompt that does not.
14889 @item set prompt @var{newprompt}
14890 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
14892 @kindex show prompt
14894 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
14898 @section Command editing
14900 @cindex command line editing
14902 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
14903 @sc{gnu} library provides consistent behavior for programs which provide a
14904 command line interface to the user. Advantages are @sc{gnu} Emacs-style
14905 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
14906 substitution, and a storage and recall of command history across
14907 debugging sessions.
14909 You may control the behavior of command line editing in @value{GDBN} with the
14910 command @code{set}.
14913 @kindex set editing
14916 @itemx set editing on
14917 Enable command line editing (enabled by default).
14919 @item set editing off
14920 Disable command line editing.
14922 @kindex show editing
14924 Show whether command line editing is enabled.
14927 @xref{Command Line Editing}, for more details about the Readline
14928 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
14929 encouraged to read that chapter.
14932 @section Command history
14933 @cindex command history
14935 @value{GDBN} can keep track of the commands you type during your
14936 debugging sessions, so that you can be certain of precisely what
14937 happened. Use these commands to manage the @value{GDBN} command
14940 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
14941 package, to provide the history facility. @xref{Using History
14942 Interactively}, for the detailed description of the History library.
14944 Here is the description of @value{GDBN} commands related to command
14948 @cindex history substitution
14949 @cindex history file
14950 @kindex set history filename
14951 @cindex @env{GDBHISTFILE}, environment variable
14952 @item set history filename @var{fname}
14953 Set the name of the @value{GDBN} command history file to @var{fname}.
14954 This is the file where @value{GDBN} reads an initial command history
14955 list, and where it writes the command history from this session when it
14956 exits. You can access this list through history expansion or through
14957 the history command editing characters listed below. This file defaults
14958 to the value of the environment variable @code{GDBHISTFILE}, or to
14959 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
14962 @cindex save command history
14963 @kindex set history save
14964 @item set history save
14965 @itemx set history save on
14966 Record command history in a file, whose name may be specified with the
14967 @code{set history filename} command. By default, this option is disabled.
14969 @item set history save off
14970 Stop recording command history in a file.
14972 @cindex history size
14973 @kindex set history size
14974 @item set history size @var{size}
14975 Set the number of commands which @value{GDBN} keeps in its history list.
14976 This defaults to the value of the environment variable
14977 @code{HISTSIZE}, or to 256 if this variable is not set.
14980 History expansion assigns special meaning to the character @kbd{!}.
14981 @xref{Event Designators}, for more details.
14983 @cindex history expansion, turn on/off
14984 Since @kbd{!} is also the logical not operator in C, history expansion
14985 is off by default. If you decide to enable history expansion with the
14986 @code{set history expansion on} command, you may sometimes need to
14987 follow @kbd{!} (when it is used as logical not, in an expression) with
14988 a space or a tab to prevent it from being expanded. The readline
14989 history facilities do not attempt substitution on the strings
14990 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
14992 The commands to control history expansion are:
14995 @item set history expansion on
14996 @itemx set history expansion
14997 @kindex set history expansion
14998 Enable history expansion. History expansion is off by default.
15000 @item set history expansion off
15001 Disable history expansion.
15004 @kindex show history
15006 @itemx show history filename
15007 @itemx show history save
15008 @itemx show history size
15009 @itemx show history expansion
15010 These commands display the state of the @value{GDBN} history parameters.
15011 @code{show history} by itself displays all four states.
15016 @kindex show commands
15017 @cindex show last commands
15018 @cindex display command history
15019 @item show commands
15020 Display the last ten commands in the command history.
15022 @item show commands @var{n}
15023 Print ten commands centered on command number @var{n}.
15025 @item show commands +
15026 Print ten commands just after the commands last printed.
15030 @section Screen size
15031 @cindex size of screen
15032 @cindex pauses in output
15034 Certain commands to @value{GDBN} may produce large amounts of
15035 information output to the screen. To help you read all of it,
15036 @value{GDBN} pauses and asks you for input at the end of each page of
15037 output. Type @key{RET} when you want to continue the output, or @kbd{q}
15038 to discard the remaining output. Also, the screen width setting
15039 determines when to wrap lines of output. Depending on what is being
15040 printed, @value{GDBN} tries to break the line at a readable place,
15041 rather than simply letting it overflow onto the following line.
15043 Normally @value{GDBN} knows the size of the screen from the terminal
15044 driver software. For example, on Unix @value{GDBN} uses the termcap data base
15045 together with the value of the @code{TERM} environment variable and the
15046 @code{stty rows} and @code{stty cols} settings. If this is not correct,
15047 you can override it with the @code{set height} and @code{set
15054 @kindex show height
15055 @item set height @var{lpp}
15057 @itemx set width @var{cpl}
15059 These @code{set} commands specify a screen height of @var{lpp} lines and
15060 a screen width of @var{cpl} characters. The associated @code{show}
15061 commands display the current settings.
15063 If you specify a height of zero lines, @value{GDBN} does not pause during
15064 output no matter how long the output is. This is useful if output is to a
15065 file or to an editor buffer.
15067 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
15068 from wrapping its output.
15070 @item set pagination on
15071 @itemx set pagination off
15072 @kindex set pagination
15073 Turn the output pagination on or off; the default is on. Turning
15074 pagination off is the alternative to @code{set height 0}.
15076 @item show pagination
15077 @kindex show pagination
15078 Show the current pagination mode.
15083 @cindex number representation
15084 @cindex entering numbers
15086 You can always enter numbers in octal, decimal, or hexadecimal in
15087 @value{GDBN} by the usual conventions: octal numbers begin with
15088 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
15089 begin with @samp{0x}. Numbers that begin with none of these are, by
15090 default, entered in base 10; likewise, the default display for
15091 numbers---when no particular format is specified---is base 10. You can
15092 change the default base for both input and output with the @code{set
15096 @kindex set input-radix
15097 @item set input-radix @var{base}
15098 Set the default base for numeric input. Supported choices
15099 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15100 specified either unambiguously or using the current default radix; for
15104 set input-radix 012
15105 set input-radix 10.
15106 set input-radix 0xa
15110 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
15111 leaves the input radix unchanged, no matter what it was.
15113 @kindex set output-radix
15114 @item set output-radix @var{base}
15115 Set the default base for numeric display. Supported choices
15116 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15117 specified either unambiguously or using the current default radix.
15119 @kindex show input-radix
15120 @item show input-radix
15121 Display the current default base for numeric input.
15123 @kindex show output-radix
15124 @item show output-radix
15125 Display the current default base for numeric display.
15127 @item set radix @r{[}@var{base}@r{]}
15131 These commands set and show the default base for both input and output
15132 of numbers. @code{set radix} sets the radix of input and output to
15133 the same base; without an argument, it resets the radix back to its
15134 default value of 10.
15139 @section Configuring the current ABI
15141 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
15142 application automatically. However, sometimes you need to override its
15143 conclusions. Use these commands to manage @value{GDBN}'s view of the
15150 One @value{GDBN} configuration can debug binaries for multiple operating
15151 system targets, either via remote debugging or native emulation.
15152 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
15153 but you can override its conclusion using the @code{set osabi} command.
15154 One example where this is useful is in debugging of binaries which use
15155 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
15156 not have the same identifying marks that the standard C library for your
15161 Show the OS ABI currently in use.
15164 With no argument, show the list of registered available OS ABI's.
15166 @item set osabi @var{abi}
15167 Set the current OS ABI to @var{abi}.
15170 @cindex float promotion
15172 Generally, the way that an argument of type @code{float} is passed to a
15173 function depends on whether the function is prototyped. For a prototyped
15174 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
15175 according to the architecture's convention for @code{float}. For unprototyped
15176 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
15177 @code{double} and then passed.
15179 Unfortunately, some forms of debug information do not reliably indicate whether
15180 a function is prototyped. If @value{GDBN} calls a function that is not marked
15181 as prototyped, it consults @kbd{set coerce-float-to-double}.
15184 @kindex set coerce-float-to-double
15185 @item set coerce-float-to-double
15186 @itemx set coerce-float-to-double on
15187 Arguments of type @code{float} will be promoted to @code{double} when passed
15188 to an unprototyped function. This is the default setting.
15190 @item set coerce-float-to-double off
15191 Arguments of type @code{float} will be passed directly to unprototyped
15194 @kindex show coerce-float-to-double
15195 @item show coerce-float-to-double
15196 Show the current setting of promoting @code{float} to @code{double}.
15200 @kindex show cp-abi
15201 @value{GDBN} needs to know the ABI used for your program's C@t{++}
15202 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
15203 used to build your application. @value{GDBN} only fully supports
15204 programs with a single C@t{++} ABI; if your program contains code using
15205 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
15206 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
15207 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
15208 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
15209 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
15210 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
15215 Show the C@t{++} ABI currently in use.
15218 With no argument, show the list of supported C@t{++} ABI's.
15220 @item set cp-abi @var{abi}
15221 @itemx set cp-abi auto
15222 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
15225 @node Messages/Warnings
15226 @section Optional warnings and messages
15228 @cindex verbose operation
15229 @cindex optional warnings
15230 By default, @value{GDBN} is silent about its inner workings. If you are
15231 running on a slow machine, you may want to use the @code{set verbose}
15232 command. This makes @value{GDBN} tell you when it does a lengthy
15233 internal operation, so you will not think it has crashed.
15235 Currently, the messages controlled by @code{set verbose} are those
15236 which announce that the symbol table for a source file is being read;
15237 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
15240 @kindex set verbose
15241 @item set verbose on
15242 Enables @value{GDBN} output of certain informational messages.
15244 @item set verbose off
15245 Disables @value{GDBN} output of certain informational messages.
15247 @kindex show verbose
15249 Displays whether @code{set verbose} is on or off.
15252 By default, if @value{GDBN} encounters bugs in the symbol table of an
15253 object file, it is silent; but if you are debugging a compiler, you may
15254 find this information useful (@pxref{Symbol Errors, ,Errors reading
15259 @kindex set complaints
15260 @item set complaints @var{limit}
15261 Permits @value{GDBN} to output @var{limit} complaints about each type of
15262 unusual symbols before becoming silent about the problem. Set
15263 @var{limit} to zero to suppress all complaints; set it to a large number
15264 to prevent complaints from being suppressed.
15266 @kindex show complaints
15267 @item show complaints
15268 Displays how many symbol complaints @value{GDBN} is permitted to produce.
15272 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
15273 lot of stupid questions to confirm certain commands. For example, if
15274 you try to run a program which is already running:
15278 The program being debugged has been started already.
15279 Start it from the beginning? (y or n)
15282 If you are willing to unflinchingly face the consequences of your own
15283 commands, you can disable this ``feature'':
15287 @kindex set confirm
15289 @cindex confirmation
15290 @cindex stupid questions
15291 @item set confirm off
15292 Disables confirmation requests.
15294 @item set confirm on
15295 Enables confirmation requests (the default).
15297 @kindex show confirm
15299 Displays state of confirmation requests.
15303 @node Debugging Output
15304 @section Optional messages about internal happenings
15305 @cindex optional debugging messages
15307 @value{GDBN} has commands that enable optional debugging messages from
15308 various @value{GDBN} subsystems; normally these commands are of
15309 interest to @value{GDBN} maintainers, or when reporting a bug. This
15310 section documents those commands.
15313 @kindex set exec-done-display
15314 @item set exec-done-display
15315 Turns on or off the notification of asynchronous commands'
15316 completion. When on, @value{GDBN} will print a message when an
15317 asynchronous command finishes its execution. The default is off.
15318 @kindex show exec-done-display
15319 @item show exec-done-display
15320 Displays the current setting of asynchronous command completion
15323 @cindex gdbarch debugging info
15324 @cindex architecture debugging info
15325 @item set debug arch
15326 Turns on or off display of gdbarch debugging info. The default is off
15328 @item show debug arch
15329 Displays the current state of displaying gdbarch debugging info.
15330 @item set debug aix-thread
15331 @cindex AIX threads
15332 Display debugging messages about inner workings of the AIX thread
15334 @item show debug aix-thread
15335 Show the current state of AIX thread debugging info display.
15336 @item set debug event
15337 @cindex event debugging info
15338 Turns on or off display of @value{GDBN} event debugging info. The
15340 @item show debug event
15341 Displays the current state of displaying @value{GDBN} event debugging
15343 @item set debug expression
15344 @cindex expression debugging info
15345 Turns on or off display of debugging info about @value{GDBN}
15346 expression parsing. The default is off.
15347 @item show debug expression
15348 Displays the current state of displaying debugging info about
15349 @value{GDBN} expression parsing.
15350 @item set debug frame
15351 @cindex frame debugging info
15352 Turns on or off display of @value{GDBN} frame debugging info. The
15354 @item show debug frame
15355 Displays the current state of displaying @value{GDBN} frame debugging
15357 @item set debug infrun
15358 @cindex inferior debugging info
15359 Turns on or off display of @value{GDBN} debugging info for running the inferior.
15360 The default is off. @file{infrun.c} contains GDB's runtime state machine used
15361 for implementing operations such as single-stepping the inferior.
15362 @item show debug infrun
15363 Displays the current state of @value{GDBN} inferior debugging.
15364 @item set debug lin-lwp
15365 @cindex @sc{gnu}/Linux LWP debug messages
15366 @cindex Linux lightweight processes
15367 Turns on or off debugging messages from the Linux LWP debug support.
15368 @item show debug lin-lwp
15369 Show the current state of Linux LWP debugging messages.
15370 @item set debug observer
15371 @cindex observer debugging info
15372 Turns on or off display of @value{GDBN} observer debugging. This
15373 includes info such as the notification of observable events.
15374 @item show debug observer
15375 Displays the current state of observer debugging.
15376 @item set debug overload
15377 @cindex C@t{++} overload debugging info
15378 Turns on or off display of @value{GDBN} C@t{++} overload debugging
15379 info. This includes info such as ranking of functions, etc. The default
15381 @item show debug overload
15382 Displays the current state of displaying @value{GDBN} C@t{++} overload
15384 @cindex packets, reporting on stdout
15385 @cindex serial connections, debugging
15386 @item set debug remote
15387 Turns on or off display of reports on all packets sent back and forth across
15388 the serial line to the remote machine. The info is printed on the
15389 @value{GDBN} standard output stream. The default is off.
15390 @item show debug remote
15391 Displays the state of display of remote packets.
15392 @item set debug serial
15393 Turns on or off display of @value{GDBN} serial debugging info. The
15395 @item show debug serial
15396 Displays the current state of displaying @value{GDBN} serial debugging
15398 @item set debug solib-frv
15399 @cindex FR-V shared-library debugging
15400 Turns on or off debugging messages for FR-V shared-library code.
15401 @item show debug solib-frv
15402 Display the current state of FR-V shared-library code debugging
15404 @item set debug target
15405 @cindex target debugging info
15406 Turns on or off display of @value{GDBN} target debugging info. This info
15407 includes what is going on at the target level of GDB, as it happens. The
15408 default is 0. Set it to 1 to track events, and to 2 to also track the
15409 value of large memory transfers. Changes to this flag do not take effect
15410 until the next time you connect to a target or use the @code{run} command.
15411 @item show debug target
15412 Displays the current state of displaying @value{GDBN} target debugging
15414 @item set debugvarobj
15415 @cindex variable object debugging info
15416 Turns on or off display of @value{GDBN} variable object debugging
15417 info. The default is off.
15418 @item show debugvarobj
15419 Displays the current state of displaying @value{GDBN} variable object
15424 @chapter Canned Sequences of Commands
15426 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
15427 command lists}), @value{GDBN} provides two ways to store sequences of
15428 commands for execution as a unit: user-defined commands and command
15432 * Define:: User-defined commands
15433 * Hooks:: User-defined command hooks
15434 * Command Files:: Command files
15435 * Output:: Commands for controlled output
15439 @section User-defined commands
15441 @cindex user-defined command
15442 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
15443 which you assign a new name as a command. This is done with the
15444 @code{define} command. User commands may accept up to 10 arguments
15445 separated by whitespace. Arguments are accessed within the user command
15446 via @var{$arg0@dots{}$arg9}. A trivial example:
15450 print $arg0 + $arg1 + $arg2
15454 To execute the command use:
15461 This defines the command @code{adder}, which prints the sum of
15462 its three arguments. Note the arguments are text substitutions, so they may
15463 reference variables, use complex expressions, or even perform inferior
15469 @item define @var{commandname}
15470 Define a command named @var{commandname}. If there is already a command
15471 by that name, you are asked to confirm that you want to redefine it.
15473 The definition of the command is made up of other @value{GDBN} command lines,
15474 which are given following the @code{define} command. The end of these
15475 commands is marked by a line containing @code{end}.
15481 Takes a single argument, which is an expression to evaluate.
15482 It is followed by a series of commands that are executed
15483 only if the expression is true (nonzero).
15484 There can then optionally be a line @code{else}, followed
15485 by a series of commands that are only executed if the expression
15486 was false. The end of the list is marked by a line containing @code{end}.
15490 The syntax is similar to @code{if}: the command takes a single argument,
15491 which is an expression to evaluate, and must be followed by the commands to
15492 execute, one per line, terminated by an @code{end}.
15493 The commands are executed repeatedly as long as the expression
15497 @item document @var{commandname}
15498 Document the user-defined command @var{commandname}, so that it can be
15499 accessed by @code{help}. The command @var{commandname} must already be
15500 defined. This command reads lines of documentation just as @code{define}
15501 reads the lines of the command definition, ending with @code{end}.
15502 After the @code{document} command is finished, @code{help} on command
15503 @var{commandname} displays the documentation you have written.
15505 You may use the @code{document} command again to change the
15506 documentation of a command. Redefining the command with @code{define}
15507 does not change the documentation.
15509 @kindex dont-repeat
15510 @cindex don't repeat command
15512 Used inside a user-defined command, this tells @value{GDBN} that this
15513 command should not be repeated when the user hits @key{RET}
15514 (@pxref{Command Syntax, repeat last command}).
15516 @kindex help user-defined
15517 @item help user-defined
15518 List all user-defined commands, with the first line of the documentation
15523 @itemx show user @var{commandname}
15524 Display the @value{GDBN} commands used to define @var{commandname} (but
15525 not its documentation). If no @var{commandname} is given, display the
15526 definitions for all user-defined commands.
15528 @cindex infinite recusrion in user-defined commands
15529 @kindex show max-user-call-depth
15530 @kindex set max-user-call-depth
15531 @item show max-user-call-depth
15532 @itemx set max-user-call-depth
15533 The value of @code{max-user-call-depth} controls how many recursion
15534 levels are allowed in user-defined commands before GDB suspects an
15535 infinite recursion and aborts the command.
15539 When user-defined commands are executed, the
15540 commands of the definition are not printed. An error in any command
15541 stops execution of the user-defined command.
15543 If used interactively, commands that would ask for confirmation proceed
15544 without asking when used inside a user-defined command. Many @value{GDBN}
15545 commands that normally print messages to say what they are doing omit the
15546 messages when used in a user-defined command.
15549 @section User-defined command hooks
15550 @cindex command hooks
15551 @cindex hooks, for commands
15552 @cindex hooks, pre-command
15555 You may define @dfn{hooks}, which are a special kind of user-defined
15556 command. Whenever you run the command @samp{foo}, if the user-defined
15557 command @samp{hook-foo} exists, it is executed (with no arguments)
15558 before that command.
15560 @cindex hooks, post-command
15562 A hook may also be defined which is run after the command you executed.
15563 Whenever you run the command @samp{foo}, if the user-defined command
15564 @samp{hookpost-foo} exists, it is executed (with no arguments) after
15565 that command. Post-execution hooks may exist simultaneously with
15566 pre-execution hooks, for the same command.
15568 It is valid for a hook to call the command which it hooks. If this
15569 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
15571 @c It would be nice if hookpost could be passed a parameter indicating
15572 @c if the command it hooks executed properly or not. FIXME!
15574 @kindex stop@r{, a pseudo-command}
15575 In addition, a pseudo-command, @samp{stop} exists. Defining
15576 (@samp{hook-stop}) makes the associated commands execute every time
15577 execution stops in your program: before breakpoint commands are run,
15578 displays are printed, or the stack frame is printed.
15580 For example, to ignore @code{SIGALRM} signals while
15581 single-stepping, but treat them normally during normal execution,
15586 handle SIGALRM nopass
15590 handle SIGALRM pass
15593 define hook-continue
15594 handle SIGLARM pass
15598 As a further example, to hook at the begining and end of the @code{echo}
15599 command, and to add extra text to the beginning and end of the message,
15607 define hookpost-echo
15611 (@value{GDBP}) echo Hello World
15612 <<<---Hello World--->>>
15617 You can define a hook for any single-word command in @value{GDBN}, but
15618 not for command aliases; you should define a hook for the basic command
15619 name, e.g. @code{backtrace} rather than @code{bt}.
15620 @c FIXME! So how does Joe User discover whether a command is an alias
15622 If an error occurs during the execution of your hook, execution of
15623 @value{GDBN} commands stops and @value{GDBN} issues a prompt
15624 (before the command that you actually typed had a chance to run).
15626 If you try to define a hook which does not match any known command, you
15627 get a warning from the @code{define} command.
15629 @node Command Files
15630 @section Command files
15632 @cindex command files
15633 A command file for @value{GDBN} is a file of lines that are @value{GDBN}
15634 commands. Comments (lines starting with @kbd{#}) may also be included.
15635 An empty line in a command file does nothing; it does not mean to repeat
15636 the last command, as it would from the terminal.
15639 @cindex @file{.gdbinit}
15640 @cindex @file{gdb.ini}
15641 When you start @value{GDBN}, it automatically executes commands from its
15642 @dfn{init files}, normally called @file{.gdbinit}@footnote{The DJGPP
15643 port of @value{GDBN} uses the name @file{gdb.ini} instead, due to the
15644 limitations of file names imposed by DOS filesystems.}.
15645 During startup, @value{GDBN} does the following:
15649 Reads the init file (if any) in your home directory@footnote{On
15650 DOS/Windows systems, the home directory is the one pointed to by the
15651 @code{HOME} environment variable.}.
15654 Processes command line options and operands.
15657 Reads the init file (if any) in the current working directory.
15660 Reads command files specified by the @samp{-x} option.
15663 The init file in your home directory can set options (such as @samp{set
15664 complaints}) that affect subsequent processing of command line options
15665 and operands. Init files are not executed if you use the @samp{-nx}
15666 option (@pxref{Mode Options, ,Choosing modes}).
15668 @cindex init file name
15669 On some configurations of @value{GDBN}, the init file is known by a
15670 different name (these are typically environments where a specialized
15671 form of @value{GDBN} may need to coexist with other forms, hence a
15672 different name for the specialized version's init file). These are the
15673 environments with special init file names:
15675 @cindex @file{.vxgdbinit}
15678 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
15680 @cindex @file{.os68gdbinit}
15682 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
15684 @cindex @file{.esgdbinit}
15686 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
15689 You can also request the execution of a command file with the
15690 @code{source} command:
15694 @item source @var{filename}
15695 Execute the command file @var{filename}.
15698 The lines in a command file are executed sequentially. They are not
15699 printed as they are executed. An error in any command terminates
15700 execution of the command file and control is returned to the console.
15702 Commands that would ask for confirmation if used interactively proceed
15703 without asking when used in a command file. Many @value{GDBN} commands that
15704 normally print messages to say what they are doing omit the messages
15705 when called from command files.
15707 @value{GDBN} also accepts command input from standard input. In this
15708 mode, normal output goes to standard output and error output goes to
15709 standard error. Errors in a command file supplied on standard input do
15710 not terminate execution of the command file --- execution continues with
15714 gdb < cmds > log 2>&1
15717 (The syntax above will vary depending on the shell used.) This example
15718 will execute commands from the file @file{cmds}. All output and errors
15719 would be directed to @file{log}.
15722 @section Commands for controlled output
15724 During the execution of a command file or a user-defined command, normal
15725 @value{GDBN} output is suppressed; the only output that appears is what is
15726 explicitly printed by the commands in the definition. This section
15727 describes three commands useful for generating exactly the output you
15732 @item echo @var{text}
15733 @c I do not consider backslash-space a standard C escape sequence
15734 @c because it is not in ANSI.
15735 Print @var{text}. Nonprinting characters can be included in
15736 @var{text} using C escape sequences, such as @samp{\n} to print a
15737 newline. @strong{No newline is printed unless you specify one.}
15738 In addition to the standard C escape sequences, a backslash followed
15739 by a space stands for a space. This is useful for displaying a
15740 string with spaces at the beginning or the end, since leading and
15741 trailing spaces are otherwise trimmed from all arguments.
15742 To print @samp{@w{ }and foo =@w{ }}, use the command
15743 @samp{echo \@w{ }and foo = \@w{ }}.
15745 A backslash at the end of @var{text} can be used, as in C, to continue
15746 the command onto subsequent lines. For example,
15749 echo This is some text\n\
15750 which is continued\n\
15751 onto several lines.\n
15754 produces the same output as
15757 echo This is some text\n
15758 echo which is continued\n
15759 echo onto several lines.\n
15763 @item output @var{expression}
15764 Print the value of @var{expression} and nothing but that value: no
15765 newlines, no @samp{$@var{nn} = }. The value is not entered in the
15766 value history either. @xref{Expressions, ,Expressions}, for more information
15769 @item output/@var{fmt} @var{expression}
15770 Print the value of @var{expression} in format @var{fmt}. You can use
15771 the same formats as for @code{print}. @xref{Output Formats,,Output
15772 formats}, for more information.
15775 @item printf @var{string}, @var{expressions}@dots{}
15776 Print the values of the @var{expressions} under the control of
15777 @var{string}. The @var{expressions} are separated by commas and may be
15778 either numbers or pointers. Their values are printed as specified by
15779 @var{string}, exactly as if your program were to execute the C
15781 @c FIXME: the above implies that at least all ANSI C formats are
15782 @c supported, but it isn't true: %E and %G don't work (or so it seems).
15783 @c Either this is a bug, or the manual should document what formats are
15787 printf (@var{string}, @var{expressions}@dots{});
15790 For example, you can print two values in hex like this:
15793 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
15796 The only backslash-escape sequences that you can use in the format
15797 string are the simple ones that consist of backslash followed by a
15802 @chapter Command Interpreters
15803 @cindex command interpreters
15805 @value{GDBN} supports multiple command interpreters, and some command
15806 infrastructure to allow users or user interface writers to switch
15807 between interpreters or run commands in other interpreters.
15809 @value{GDBN} currently supports two command interpreters, the console
15810 interpreter (sometimes called the command-line interpreter or @sc{cli})
15811 and the machine interface interpreter (or @sc{gdb/mi}). This manual
15812 describes both of these interfaces in great detail.
15814 By default, @value{GDBN} will start with the console interpreter.
15815 However, the user may choose to start @value{GDBN} with another
15816 interpreter by specifying the @option{-i} or @option{--interpreter}
15817 startup options. Defined interpreters include:
15821 @cindex console interpreter
15822 The traditional console or command-line interpreter. This is the most often
15823 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
15824 @value{GDBN} will use this interpreter.
15827 @cindex mi interpreter
15828 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
15829 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
15830 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
15834 @cindex mi2 interpreter
15835 The current @sc{gdb/mi} interface.
15838 @cindex mi1 interpreter
15839 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
15843 @cindex invoke another interpreter
15844 The interpreter being used by @value{GDBN} may not be dynamically
15845 switched at runtime. Although possible, this could lead to a very
15846 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
15847 enters the command "interpreter-set console" in a console view,
15848 @value{GDBN} would switch to using the console interpreter, rendering
15849 the IDE inoperable!
15851 @kindex interpreter-exec
15852 Although you may only choose a single interpreter at startup, you may execute
15853 commands in any interpreter from the current interpreter using the appropriate
15854 command. If you are running the console interpreter, simply use the
15855 @code{interpreter-exec} command:
15858 interpreter-exec mi "-data-list-register-names"
15861 @sc{gdb/mi} has a similar command, although it is only available in versions of
15862 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
15865 @chapter @value{GDBN} Text User Interface
15867 @cindex Text User Interface
15870 * TUI Overview:: TUI overview
15871 * TUI Keys:: TUI key bindings
15872 * TUI Single Key Mode:: TUI single key mode
15873 * TUI Commands:: TUI specific commands
15874 * TUI Configuration:: TUI configuration variables
15877 The @value{GDBN} Text User Interface, TUI in short, is a terminal
15878 interface which uses the @code{curses} library to show the source
15879 file, the assembly output, the program registers and @value{GDBN}
15880 commands in separate text windows.
15882 The TUI is enabled by invoking @value{GDBN} using either
15884 @samp{gdbtui} or @samp{gdb -tui}.
15887 @section TUI overview
15889 The TUI has two display modes that can be switched while
15894 A curses (or TUI) mode in which it displays several text
15895 windows on the terminal.
15898 A standard mode which corresponds to the @value{GDBN} configured without
15902 In the TUI mode, @value{GDBN} can display several text window
15907 This window is the @value{GDBN} command window with the @value{GDBN}
15908 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
15909 managed using readline but through the TUI. The @emph{command}
15910 window is always visible.
15913 The source window shows the source file of the program. The current
15914 line as well as active breakpoints are displayed in this window.
15917 The assembly window shows the disassembly output of the program.
15920 This window shows the processor registers. It detects when
15921 a register is changed and when this is the case, registers that have
15922 changed are highlighted.
15926 The source and assembly windows show the current program position
15927 by highlighting the current line and marking them with the @samp{>} marker.
15928 Breakpoints are also indicated with two markers. A first one
15929 indicates the breakpoint type:
15933 Breakpoint which was hit at least once.
15936 Breakpoint which was never hit.
15939 Hardware breakpoint which was hit at least once.
15942 Hardware breakpoint which was never hit.
15946 The second marker indicates whether the breakpoint is enabled or not:
15950 Breakpoint is enabled.
15953 Breakpoint is disabled.
15957 The source, assembly and register windows are attached to the thread
15958 and the frame position. They are updated when the current thread
15959 changes, when the frame changes or when the program counter changes.
15960 These three windows are arranged by the TUI according to several
15961 layouts. The layout defines which of these three windows are visible.
15962 The following layouts are available:
15972 source and assembly
15975 source and registers
15978 assembly and registers
15982 On top of the command window a status line gives various information
15983 concerning the current process begin debugged. The status line is
15984 updated when the information it shows changes. The following fields
15989 Indicates the current gdb target
15990 (@pxref{Targets, ,Specifying a Debugging Target}).
15993 Gives information about the current process or thread number.
15994 When no process is being debugged, this field is set to @code{No process}.
15997 Gives the current function name for the selected frame.
15998 The name is demangled if demangling is turned on (@pxref{Print Settings}).
15999 When there is no symbol corresponding to the current program counter
16000 the string @code{??} is displayed.
16003 Indicates the current line number for the selected frame.
16004 When the current line number is not known the string @code{??} is displayed.
16007 Indicates the current program counter address.
16012 @section TUI Key Bindings
16013 @cindex TUI key bindings
16015 The TUI installs several key bindings in the readline keymaps
16016 (@pxref{Command Line Editing}).
16017 They allow to leave or enter in the TUI mode or they operate
16018 directly on the TUI layout and windows. The TUI also provides
16019 a @emph{SingleKey} keymap which binds several keys directly to
16020 @value{GDBN} commands. The following key bindings
16021 are installed for both TUI mode and the @value{GDBN} standard mode.
16030 Enter or leave the TUI mode. When the TUI mode is left,
16031 the curses window management is left and @value{GDBN} operates using
16032 its standard mode writing on the terminal directly. When the TUI
16033 mode is entered, the control is given back to the curses windows.
16034 The screen is then refreshed.
16038 Use a TUI layout with only one window. The layout will
16039 either be @samp{source} or @samp{assembly}. When the TUI mode
16040 is not active, it will switch to the TUI mode.
16042 Think of this key binding as the Emacs @kbd{C-x 1} binding.
16046 Use a TUI layout with at least two windows. When the current
16047 layout shows already two windows, a next layout with two windows is used.
16048 When a new layout is chosen, one window will always be common to the
16049 previous layout and the new one.
16051 Think of it as the Emacs @kbd{C-x 2} binding.
16055 Change the active window. The TUI associates several key bindings
16056 (like scrolling and arrow keys) to the active window. This command
16057 gives the focus to the next TUI window.
16059 Think of it as the Emacs @kbd{C-x o} binding.
16063 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
16064 (@pxref{TUI Single Key Mode}).
16068 The following key bindings are handled only by the TUI mode:
16073 Scroll the active window one page up.
16077 Scroll the active window one page down.
16081 Scroll the active window one line up.
16085 Scroll the active window one line down.
16089 Scroll the active window one column left.
16093 Scroll the active window one column right.
16097 Refresh the screen.
16101 In the TUI mode, the arrow keys are used by the active window
16102 for scrolling. This means they are available for readline when the
16103 active window is the command window. When the command window
16104 does not have the focus, it is necessary to use other readline
16105 key bindings such as @key{C-p}, @key{C-n}, @key{C-b} and @key{C-f}.
16107 @node TUI Single Key Mode
16108 @section TUI Single Key Mode
16109 @cindex TUI single key mode
16111 The TUI provides a @emph{SingleKey} mode in which it installs a particular
16112 key binding in the readline keymaps to connect single keys to
16116 @kindex c @r{(SingleKey TUI key)}
16120 @kindex d @r{(SingleKey TUI key)}
16124 @kindex f @r{(SingleKey TUI key)}
16128 @kindex n @r{(SingleKey TUI key)}
16132 @kindex q @r{(SingleKey TUI key)}
16134 exit the @emph{SingleKey} mode.
16136 @kindex r @r{(SingleKey TUI key)}
16140 @kindex s @r{(SingleKey TUI key)}
16144 @kindex u @r{(SingleKey TUI key)}
16148 @kindex v @r{(SingleKey TUI key)}
16152 @kindex w @r{(SingleKey TUI key)}
16158 Other keys temporarily switch to the @value{GDBN} command prompt.
16159 The key that was pressed is inserted in the editing buffer so that
16160 it is possible to type most @value{GDBN} commands without interaction
16161 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
16162 @emph{SingleKey} mode is restored. The only way to permanently leave
16163 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
16167 @section TUI specific commands
16168 @cindex TUI commands
16170 The TUI has specific commands to control the text windows.
16171 These commands are always available, that is they do not depend on
16172 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
16173 is in the standard mode, using these commands will automatically switch
16179 List and give the size of all displayed windows.
16183 Display the next layout.
16186 Display the previous layout.
16189 Display the source window only.
16192 Display the assembly window only.
16195 Display the source and assembly window.
16198 Display the register window together with the source or assembly window.
16200 @item focus next | prev | src | asm | regs | split
16202 Set the focus to the named window.
16203 This command allows to change the active window so that scrolling keys
16204 can be affected to another window.
16208 Refresh the screen. This is similar to using @key{C-L} key.
16210 @item tui reg float
16212 Show the floating point registers in the register window.
16214 @item tui reg general
16215 Show the general registers in the register window.
16218 Show the next register group. The list of register groups as well as
16219 their order is target specific. The predefined register groups are the
16220 following: @code{general}, @code{float}, @code{system}, @code{vector},
16221 @code{all}, @code{save}, @code{restore}.
16223 @item tui reg system
16224 Show the system registers in the register window.
16228 Update the source window and the current execution point.
16230 @item winheight @var{name} +@var{count}
16231 @itemx winheight @var{name} -@var{count}
16233 Change the height of the window @var{name} by @var{count}
16234 lines. Positive counts increase the height, while negative counts
16238 @kindex tabset @var{nchars}
16239 Set the width of tab stops to be @var{nchars} characters.
16243 @node TUI Configuration
16244 @section TUI configuration variables
16245 @cindex TUI configuration variables
16247 The TUI has several configuration variables that control the
16248 appearance of windows on the terminal.
16251 @item set tui border-kind @var{kind}
16252 @kindex set tui border-kind
16253 Select the border appearance for the source, assembly and register windows.
16254 The possible values are the following:
16257 Use a space character to draw the border.
16260 Use ascii characters + - and | to draw the border.
16263 Use the Alternate Character Set to draw the border. The border is
16264 drawn using character line graphics if the terminal supports them.
16268 @item set tui active-border-mode @var{mode}
16269 @kindex set tui active-border-mode
16270 Select the attributes to display the border of the active window.
16271 The possible values are @code{normal}, @code{standout}, @code{reverse},
16272 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
16274 @item set tui border-mode @var{mode}
16275 @kindex set tui border-mode
16276 Select the attributes to display the border of other windows.
16277 The @var{mode} can be one of the following:
16280 Use normal attributes to display the border.
16286 Use reverse video mode.
16289 Use half bright mode.
16291 @item half-standout
16292 Use half bright and standout mode.
16295 Use extra bright or bold mode.
16297 @item bold-standout
16298 Use extra bright or bold and standout mode.
16305 @chapter Using @value{GDBN} under @sc{gnu} Emacs
16308 @cindex @sc{gnu} Emacs
16309 A special interface allows you to use @sc{gnu} Emacs to view (and
16310 edit) the source files for the program you are debugging with
16313 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
16314 executable file you want to debug as an argument. This command starts
16315 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
16316 created Emacs buffer.
16317 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
16319 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
16324 All ``terminal'' input and output goes through the Emacs buffer.
16327 This applies both to @value{GDBN} commands and their output, and to the input
16328 and output done by the program you are debugging.
16330 This is useful because it means that you can copy the text of previous
16331 commands and input them again; you can even use parts of the output
16334 All the facilities of Emacs' Shell mode are available for interacting
16335 with your program. In particular, you can send signals the usual
16336 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
16341 @value{GDBN} displays source code through Emacs.
16344 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
16345 source file for that frame and puts an arrow (@samp{=>}) at the
16346 left margin of the current line. Emacs uses a separate buffer for
16347 source display, and splits the screen to show both your @value{GDBN} session
16350 Explicit @value{GDBN} @code{list} or search commands still produce output as
16351 usual, but you probably have no reason to use them from Emacs.
16353 If you specify an absolute file name when prompted for the @kbd{M-x
16354 gdb} argument, then Emacs sets your current working directory to where
16355 your program resides. If you only specify the file name, then Emacs
16356 sets your current working directory to to the directory associated
16357 with the previous buffer. In this case, @value{GDBN} may find your
16358 program by searching your environment's @code{PATH} variable, but on
16359 some operating systems it might not find the source. So, although the
16360 @value{GDBN} input and output session proceeds normally, the auxiliary
16361 buffer does not display the current source and line of execution.
16363 The initial working directory of @value{GDBN} is printed on the top
16364 line of the @value{GDBN} I/O buffer and this serves as a default for
16365 the commands that specify files for @value{GDBN} to operate
16366 on. @xref{Files, ,Commands to specify files}.
16368 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
16369 need to call @value{GDBN} by a different name (for example, if you
16370 keep several configurations around, with different names) you can
16371 customize the Emacs variable @code{gud-gdb-command-name} to run the
16374 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
16375 addition to the standard Shell mode commands:
16379 Describe the features of Emacs' @value{GDBN} Mode.
16382 Execute to another source line, like the @value{GDBN} @code{step} command; also
16383 update the display window to show the current file and location.
16386 Execute to next source line in this function, skipping all function
16387 calls, like the @value{GDBN} @code{next} command. Then update the display window
16388 to show the current file and location.
16391 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
16392 display window accordingly.
16395 Execute until exit from the selected stack frame, like the @value{GDBN}
16396 @code{finish} command.
16399 Continue execution of your program, like the @value{GDBN} @code{continue}
16403 Go up the number of frames indicated by the numeric argument
16404 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
16405 like the @value{GDBN} @code{up} command.
16408 Go down the number of frames indicated by the numeric argument, like the
16409 @value{GDBN} @code{down} command.
16412 In any source file, the Emacs command @kbd{C-x SPC} (@code{gud-break})
16413 tells @value{GDBN} to set a breakpoint on the source line point is on.
16415 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
16416 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
16417 point to any frame in the stack and type @key{RET} to make it become the
16418 current frame and display the associated source in the source buffer.
16419 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
16422 If you accidentally delete the source-display buffer, an easy way to get
16423 it back is to type the command @code{f} in the @value{GDBN} buffer, to
16424 request a frame display; when you run under Emacs, this recreates
16425 the source buffer if necessary to show you the context of the current
16428 The source files displayed in Emacs are in ordinary Emacs buffers
16429 which are visiting the source files in the usual way. You can edit
16430 the files with these buffers if you wish; but keep in mind that @value{GDBN}
16431 communicates with Emacs in terms of line numbers. If you add or
16432 delete lines from the text, the line numbers that @value{GDBN} knows cease
16433 to correspond properly with the code.
16435 The description given here is for GNU Emacs version 21.3 and a more
16436 detailed description of its interaction with @value{GDBN} is given in
16437 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
16439 @c The following dropped because Epoch is nonstandard. Reactivate
16440 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
16442 @kindex Emacs Epoch environment
16446 Version 18 of @sc{gnu} Emacs has a built-in window system
16447 called the @code{epoch}
16448 environment. Users of this environment can use a new command,
16449 @code{inspect} which performs identically to @code{print} except that
16450 each value is printed in its own window.
16455 @chapter The @sc{gdb/mi} Interface
16457 @unnumberedsec Function and Purpose
16459 @cindex @sc{gdb/mi}, its purpose
16460 @sc{gdb/mi} is a line based machine oriented text interface to @value{GDBN}. It is
16461 specifically intended to support the development of systems which use
16462 the debugger as just one small component of a larger system.
16464 This chapter is a specification of the @sc{gdb/mi} interface. It is written
16465 in the form of a reference manual.
16467 Note that @sc{gdb/mi} is still under construction, so some of the
16468 features described below are incomplete and subject to change.
16470 @unnumberedsec Notation and Terminology
16472 @cindex notational conventions, for @sc{gdb/mi}
16473 This chapter uses the following notation:
16477 @code{|} separates two alternatives.
16480 @code{[ @var{something} ]} indicates that @var{something} is optional:
16481 it may or may not be given.
16484 @code{( @var{group} )*} means that @var{group} inside the parentheses
16485 may repeat zero or more times.
16488 @code{( @var{group} )+} means that @var{group} inside the parentheses
16489 may repeat one or more times.
16492 @code{"@var{string}"} means a literal @var{string}.
16496 @heading Dependencies
16499 @heading Acknowledgments
16501 In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
16505 * GDB/MI Command Syntax::
16506 * GDB/MI Compatibility with CLI::
16507 * GDB/MI Output Records::
16508 * GDB/MI Command Description Format::
16509 * GDB/MI Breakpoint Table Commands::
16510 * GDB/MI Data Manipulation::
16511 * GDB/MI Program Control::
16512 * GDB/MI Miscellaneous Commands::
16514 * GDB/MI Kod Commands::
16515 * GDB/MI Memory Overlay Commands::
16516 * GDB/MI Signal Handling Commands::
16518 * GDB/MI Stack Manipulation::
16519 * GDB/MI Symbol Query::
16520 * GDB/MI Target Manipulation::
16521 * GDB/MI Thread Commands::
16522 * GDB/MI Tracepoint Commands::
16523 * GDB/MI Variable Objects::
16526 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16527 @node GDB/MI Command Syntax
16528 @section @sc{gdb/mi} Command Syntax
16531 * GDB/MI Input Syntax::
16532 * GDB/MI Output Syntax::
16533 * GDB/MI Simple Examples::
16536 @node GDB/MI Input Syntax
16537 @subsection @sc{gdb/mi} Input Syntax
16539 @cindex input syntax for @sc{gdb/mi}
16540 @cindex @sc{gdb/mi}, input syntax
16542 @item @var{command} @expansion{}
16543 @code{@var{cli-command} | @var{mi-command}}
16545 @item @var{cli-command} @expansion{}
16546 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
16547 @var{cli-command} is any existing @value{GDBN} CLI command.
16549 @item @var{mi-command} @expansion{}
16550 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
16551 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
16553 @item @var{token} @expansion{}
16554 "any sequence of digits"
16556 @item @var{option} @expansion{}
16557 @code{"-" @var{parameter} [ " " @var{parameter} ]}
16559 @item @var{parameter} @expansion{}
16560 @code{@var{non-blank-sequence} | @var{c-string}}
16562 @item @var{operation} @expansion{}
16563 @emph{any of the operations described in this chapter}
16565 @item @var{non-blank-sequence} @expansion{}
16566 @emph{anything, provided it doesn't contain special characters such as
16567 "-", @var{nl}, """ and of course " "}
16569 @item @var{c-string} @expansion{}
16570 @code{""" @var{seven-bit-iso-c-string-content} """}
16572 @item @var{nl} @expansion{}
16581 The CLI commands are still handled by the @sc{mi} interpreter; their
16582 output is described below.
16585 The @code{@var{token}}, when present, is passed back when the command
16589 Some @sc{mi} commands accept optional arguments as part of the parameter
16590 list. Each option is identified by a leading @samp{-} (dash) and may be
16591 followed by an optional argument parameter. Options occur first in the
16592 parameter list and can be delimited from normal parameters using
16593 @samp{--} (this is useful when some parameters begin with a dash).
16600 We want easy access to the existing CLI syntax (for debugging).
16603 We want it to be easy to spot a @sc{mi} operation.
16606 @node GDB/MI Output Syntax
16607 @subsection @sc{gdb/mi} Output Syntax
16609 @cindex output syntax of @sc{gdb/mi}
16610 @cindex @sc{gdb/mi}, output syntax
16611 The output from @sc{gdb/mi} consists of zero or more out-of-band records
16612 followed, optionally, by a single result record. This result record
16613 is for the most recent command. The sequence of output records is
16614 terminated by @samp{(@value{GDBP})}.
16616 If an input command was prefixed with a @code{@var{token}} then the
16617 corresponding output for that command will also be prefixed by that same
16621 @item @var{output} @expansion{}
16622 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(@value{GDBP})" @var{nl}}
16624 @item @var{result-record} @expansion{}
16625 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
16627 @item @var{out-of-band-record} @expansion{}
16628 @code{@var{async-record} | @var{stream-record}}
16630 @item @var{async-record} @expansion{}
16631 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
16633 @item @var{exec-async-output} @expansion{}
16634 @code{[ @var{token} ] "*" @var{async-output}}
16636 @item @var{status-async-output} @expansion{}
16637 @code{[ @var{token} ] "+" @var{async-output}}
16639 @item @var{notify-async-output} @expansion{}
16640 @code{[ @var{token} ] "=" @var{async-output}}
16642 @item @var{async-output} @expansion{}
16643 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
16645 @item @var{result-class} @expansion{}
16646 @code{"done" | "running" | "connected" | "error" | "exit"}
16648 @item @var{async-class} @expansion{}
16649 @code{"stopped" | @var{others}} (where @var{others} will be added
16650 depending on the needs---this is still in development).
16652 @item @var{result} @expansion{}
16653 @code{ @var{variable} "=" @var{value}}
16655 @item @var{variable} @expansion{}
16656 @code{ @var{string} }
16658 @item @var{value} @expansion{}
16659 @code{ @var{const} | @var{tuple} | @var{list} }
16661 @item @var{const} @expansion{}
16662 @code{@var{c-string}}
16664 @item @var{tuple} @expansion{}
16665 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
16667 @item @var{list} @expansion{}
16668 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
16669 @var{result} ( "," @var{result} )* "]" }
16671 @item @var{stream-record} @expansion{}
16672 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
16674 @item @var{console-stream-output} @expansion{}
16675 @code{"~" @var{c-string}}
16677 @item @var{target-stream-output} @expansion{}
16678 @code{"@@" @var{c-string}}
16680 @item @var{log-stream-output} @expansion{}
16681 @code{"&" @var{c-string}}
16683 @item @var{nl} @expansion{}
16686 @item @var{token} @expansion{}
16687 @emph{any sequence of digits}.
16695 All output sequences end in a single line containing a period.
16698 The @code{@var{token}} is from the corresponding request. If an execution
16699 command is interrupted by the @samp{-exec-interrupt} command, the
16700 @var{token} associated with the @samp{*stopped} message is the one of the
16701 original execution command, not the one of the interrupt command.
16704 @cindex status output in @sc{gdb/mi}
16705 @var{status-async-output} contains on-going status information about the
16706 progress of a slow operation. It can be discarded. All status output is
16707 prefixed by @samp{+}.
16710 @cindex async output in @sc{gdb/mi}
16711 @var{exec-async-output} contains asynchronous state change on the target
16712 (stopped, started, disappeared). All async output is prefixed by
16716 @cindex notify output in @sc{gdb/mi}
16717 @var{notify-async-output} contains supplementary information that the
16718 client should handle (e.g., a new breakpoint information). All notify
16719 output is prefixed by @samp{=}.
16722 @cindex console output in @sc{gdb/mi}
16723 @var{console-stream-output} is output that should be displayed as is in the
16724 console. It is the textual response to a CLI command. All the console
16725 output is prefixed by @samp{~}.
16728 @cindex target output in @sc{gdb/mi}
16729 @var{target-stream-output} is the output produced by the target program.
16730 All the target output is prefixed by @samp{@@}.
16733 @cindex log output in @sc{gdb/mi}
16734 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
16735 instance messages that should be displayed as part of an error log. All
16736 the log output is prefixed by @samp{&}.
16739 @cindex list output in @sc{gdb/mi}
16740 New @sc{gdb/mi} commands should only output @var{lists} containing
16746 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
16747 details about the various output records.
16749 @node GDB/MI Simple Examples
16750 @subsection Simple Examples of @sc{gdb/mi} Interaction
16751 @cindex @sc{gdb/mi}, simple examples
16753 This subsection presents several simple examples of interaction using
16754 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
16755 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
16756 the output received from @sc{gdb/mi}.
16758 @subsubheading Target Stop
16759 @c Ummm... There is no "-stop" command. This assumes async, no?
16760 Here's an example of stopping the inferior process:
16771 <- *stop,reason="stop",address="0x123",source="a.c:123"
16775 @subsubheading Simple CLI Command
16777 Here's an example of a simple CLI command being passed through
16778 @sc{gdb/mi} and on to the CLI.
16788 @subsubheading Command With Side Effects
16791 -> -symbol-file xyz.exe
16792 <- *breakpoint,nr="3",address="0x123",source="a.c:123"
16796 @subsubheading A Bad Command
16798 Here's what happens if you pass a non-existent command:
16802 <- ^error,msg="Undefined MI command: rubbish"
16806 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16807 @node GDB/MI Compatibility with CLI
16808 @section @sc{gdb/mi} Compatibility with CLI
16810 @cindex compatibility, @sc{gdb/mi} and CLI
16811 @cindex @sc{gdb/mi}, compatibility with CLI
16812 To help users familiar with @value{GDBN}'s existing CLI interface, @sc{gdb/mi}
16813 accepts existing CLI commands. As specified by the syntax, such
16814 commands can be directly entered into the @sc{gdb/mi} interface and @value{GDBN} will
16817 This mechanism is provided as an aid to developers of @sc{gdb/mi}
16818 clients and not as a reliable interface into the CLI. Since the command
16819 is being interpreteted in an environment that assumes @sc{gdb/mi}
16820 behaviour, the exact output of such commands is likely to end up being
16821 an un-supported hybrid of @sc{gdb/mi} and CLI output.
16823 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16824 @node GDB/MI Output Records
16825 @section @sc{gdb/mi} Output Records
16828 * GDB/MI Result Records::
16829 * GDB/MI Stream Records::
16830 * GDB/MI Out-of-band Records::
16833 @node GDB/MI Result Records
16834 @subsection @sc{gdb/mi} Result Records
16836 @cindex result records in @sc{gdb/mi}
16837 @cindex @sc{gdb/mi}, result records
16838 In addition to a number of out-of-band notifications, the response to a
16839 @sc{gdb/mi} command includes one of the following result indications:
16843 @item "^done" [ "," @var{results} ]
16844 The synchronous operation was successful, @code{@var{results}} are the return
16849 @c Is this one correct? Should it be an out-of-band notification?
16850 The asynchronous operation was successfully started. The target is
16853 @item "^error" "," @var{c-string}
16855 The operation failed. The @code{@var{c-string}} contains the corresponding
16859 @node GDB/MI Stream Records
16860 @subsection @sc{gdb/mi} Stream Records
16862 @cindex @sc{gdb/mi}, stream records
16863 @cindex stream records in @sc{gdb/mi}
16864 @value{GDBN} internally maintains a number of output streams: the console, the
16865 target, and the log. The output intended for each of these streams is
16866 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
16868 Each stream record begins with a unique @dfn{prefix character} which
16869 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
16870 Syntax}). In addition to the prefix, each stream record contains a
16871 @code{@var{string-output}}. This is either raw text (with an implicit new
16872 line) or a quoted C string (which does not contain an implicit newline).
16875 @item "~" @var{string-output}
16876 The console output stream contains text that should be displayed in the
16877 CLI console window. It contains the textual responses to CLI commands.
16879 @item "@@" @var{string-output}
16880 The target output stream contains any textual output from the running
16883 @item "&" @var{string-output}
16884 The log stream contains debugging messages being produced by @value{GDBN}'s
16888 @node GDB/MI Out-of-band Records
16889 @subsection @sc{gdb/mi} Out-of-band Records
16891 @cindex out-of-band records in @sc{gdb/mi}
16892 @cindex @sc{gdb/mi}, out-of-band records
16893 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
16894 additional changes that have occurred. Those changes can either be a
16895 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
16896 target activity (e.g., target stopped).
16898 The following is a preliminary list of possible out-of-band records.
16905 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16906 @node GDB/MI Command Description Format
16907 @section @sc{gdb/mi} Command Description Format
16909 The remaining sections describe blocks of commands. Each block of
16910 commands is laid out in a fashion similar to this section.
16912 Note the the line breaks shown in the examples are here only for
16913 readability. They don't appear in the real output.
16914 Also note that the commands with a non-available example (N.A.@:) are
16915 not yet implemented.
16917 @subheading Motivation
16919 The motivation for this collection of commands.
16921 @subheading Introduction
16923 A brief introduction to this collection of commands as a whole.
16925 @subheading Commands
16927 For each command in the block, the following is described:
16929 @subsubheading Synopsis
16932 -command @var{args}@dots{}
16935 @subsubheading @value{GDBN} Command
16937 The corresponding @value{GDBN} CLI command.
16939 @subsubheading Result
16941 @subsubheading Out-of-band
16943 @subsubheading Notes
16945 @subsubheading Example
16948 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16949 @node GDB/MI Breakpoint Table Commands
16950 @section @sc{gdb/mi} Breakpoint table commands
16952 @cindex breakpoint commands for @sc{gdb/mi}
16953 @cindex @sc{gdb/mi}, breakpoint commands
16954 This section documents @sc{gdb/mi} commands for manipulating
16957 @subheading The @code{-break-after} Command
16958 @findex -break-after
16960 @subsubheading Synopsis
16963 -break-after @var{number} @var{count}
16966 The breakpoint number @var{number} is not in effect until it has been
16967 hit @var{count} times. To see how this is reflected in the output of
16968 the @samp{-break-list} command, see the description of the
16969 @samp{-break-list} command below.
16971 @subsubheading @value{GDBN} Command
16973 The corresponding @value{GDBN} command is @samp{ignore}.
16975 @subsubheading Example
16980 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",line="5"@}
16987 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
16988 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
16989 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
16990 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
16991 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
16992 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
16993 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
16994 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
16995 addr="0x000100d0",func="main",file="hello.c",line="5",times="0",
17001 @subheading The @code{-break-catch} Command
17002 @findex -break-catch
17004 @subheading The @code{-break-commands} Command
17005 @findex -break-commands
17009 @subheading The @code{-break-condition} Command
17010 @findex -break-condition
17012 @subsubheading Synopsis
17015 -break-condition @var{number} @var{expr}
17018 Breakpoint @var{number} will stop the program only if the condition in
17019 @var{expr} is true. The condition becomes part of the
17020 @samp{-break-list} output (see the description of the @samp{-break-list}
17023 @subsubheading @value{GDBN} Command
17025 The corresponding @value{GDBN} command is @samp{condition}.
17027 @subsubheading Example
17031 -break-condition 1 1
17035 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17036 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17037 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17038 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17039 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17040 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17041 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17042 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17043 addr="0x000100d0",func="main",file="hello.c",line="5",cond="1",
17044 times="0",ignore="3"@}]@}
17048 @subheading The @code{-break-delete} Command
17049 @findex -break-delete
17051 @subsubheading Synopsis
17054 -break-delete ( @var{breakpoint} )+
17057 Delete the breakpoint(s) whose number(s) are specified in the argument
17058 list. This is obviously reflected in the breakpoint list.
17060 @subsubheading @value{GDBN} command
17062 The corresponding @value{GDBN} command is @samp{delete}.
17064 @subsubheading Example
17072 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17073 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17074 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17075 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17076 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17077 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17078 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17083 @subheading The @code{-break-disable} Command
17084 @findex -break-disable
17086 @subsubheading Synopsis
17089 -break-disable ( @var{breakpoint} )+
17092 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
17093 break list is now set to @samp{n} for the named @var{breakpoint}(s).
17095 @subsubheading @value{GDBN} Command
17097 The corresponding @value{GDBN} command is @samp{disable}.
17099 @subsubheading Example
17107 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17108 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17109 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17110 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17111 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17112 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17113 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17114 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
17115 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
17119 @subheading The @code{-break-enable} Command
17120 @findex -break-enable
17122 @subsubheading Synopsis
17125 -break-enable ( @var{breakpoint} )+
17128 Enable (previously disabled) @var{breakpoint}(s).
17130 @subsubheading @value{GDBN} Command
17132 The corresponding @value{GDBN} command is @samp{enable}.
17134 @subsubheading Example
17142 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17143 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17144 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17145 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17146 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17147 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17148 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17149 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17150 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
17154 @subheading The @code{-break-info} Command
17155 @findex -break-info
17157 @subsubheading Synopsis
17160 -break-info @var{breakpoint}
17164 Get information about a single breakpoint.
17166 @subsubheading @value{GDBN} command
17168 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
17170 @subsubheading Example
17173 @subheading The @code{-break-insert} Command
17174 @findex -break-insert
17176 @subsubheading Synopsis
17179 -break-insert [ -t ] [ -h ] [ -r ]
17180 [ -c @var{condition} ] [ -i @var{ignore-count} ]
17181 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
17185 If specified, @var{line}, can be one of:
17192 @item filename:linenum
17193 @item filename:function
17197 The possible optional parameters of this command are:
17201 Insert a tempoary breakpoint.
17203 Insert a hardware breakpoint.
17204 @item -c @var{condition}
17205 Make the breakpoint conditional on @var{condition}.
17206 @item -i @var{ignore-count}
17207 Initialize the @var{ignore-count}.
17209 Insert a regular breakpoint in all the functions whose names match the
17210 given regular expression. Other flags are not applicable to regular
17214 @subsubheading Result
17216 The result is in the form:
17219 ^done,bkptno="@var{number}",func="@var{funcname}",
17220 file="@var{filename}",line="@var{lineno}"
17224 where @var{number} is the @value{GDBN} number for this breakpoint, @var{funcname}
17225 is the name of the function where the breakpoint was inserted,
17226 @var{filename} is the name of the source file which contains this
17227 function, and @var{lineno} is the source line number within that file.
17229 Note: this format is open to change.
17230 @c An out-of-band breakpoint instead of part of the result?
17232 @subsubheading @value{GDBN} Command
17234 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
17235 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
17237 @subsubheading Example
17242 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
17244 -break-insert -t foo
17245 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",line="11"@}
17248 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17249 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17250 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17251 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17252 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17253 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17254 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17255 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17256 addr="0x0001072c", func="main",file="recursive2.c",line="4",times="0"@},
17257 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
17258 addr="0x00010774",func="foo",file="recursive2.c",line="11",times="0"@}]@}
17260 -break-insert -r foo.*
17261 ~int foo(int, int);
17262 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c",line="11"@}
17266 @subheading The @code{-break-list} Command
17267 @findex -break-list
17269 @subsubheading Synopsis
17275 Displays the list of inserted breakpoints, showing the following fields:
17279 number of the breakpoint
17281 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
17283 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
17286 is the breakpoint enabled or no: @samp{y} or @samp{n}
17288 memory location at which the breakpoint is set
17290 logical location of the breakpoint, expressed by function name, file
17293 number of times the breakpoint has been hit
17296 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
17297 @code{body} field is an empty list.
17299 @subsubheading @value{GDBN} Command
17301 The corresponding @value{GDBN} command is @samp{info break}.
17303 @subsubheading Example
17308 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17309 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17310 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17311 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17312 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17313 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17314 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17315 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17316 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
17317 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17318 addr="0x00010114",func="foo",file="hello.c",line="13",times="0"@}]@}
17322 Here's an example of the result when there are no breakpoints:
17327 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17328 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17329 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17330 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17331 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17332 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17333 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17338 @subheading The @code{-break-watch} Command
17339 @findex -break-watch
17341 @subsubheading Synopsis
17344 -break-watch [ -a | -r ]
17347 Create a watchpoint. With the @samp{-a} option it will create an
17348 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
17349 read from or on a write to the memory location. With the @samp{-r}
17350 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
17351 trigger only when the memory location is accessed for reading. Without
17352 either of the options, the watchpoint created is a regular watchpoint,
17353 i.e. it will trigger when the memory location is accessed for writing.
17354 @xref{Set Watchpoints, , Setting watchpoints}.
17356 Note that @samp{-break-list} will report a single list of watchpoints and
17357 breakpoints inserted.
17359 @subsubheading @value{GDBN} Command
17361 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
17364 @subsubheading Example
17366 Setting a watchpoint on a variable in the @code{main} function:
17371 ^done,wpt=@{number="2",exp="x"@}
17375 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
17376 value=@{old="-268439212",new="55"@},
17377 frame=@{func="main",args=[],file="recursive2.c",line="5"@}
17381 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
17382 the program execution twice: first for the variable changing value, then
17383 for the watchpoint going out of scope.
17388 ^done,wpt=@{number="5",exp="C"@}
17392 ^done,reason="watchpoint-trigger",
17393 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
17394 frame=@{func="callee4",args=[],
17395 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
17399 ^done,reason="watchpoint-scope",wpnum="5",
17400 frame=@{func="callee3",args=[@{name="strarg",
17401 value="0x11940 \"A string argument.\""@}],
17402 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
17406 Listing breakpoints and watchpoints, at different points in the program
17407 execution. Note that once the watchpoint goes out of scope, it is
17413 ^done,wpt=@{number="2",exp="C"@}
17416 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17417 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17418 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17419 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17420 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17421 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17422 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17423 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17424 addr="0x00010734",func="callee4",
17425 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
17426 bkpt=@{number="2",type="watchpoint",disp="keep",
17427 enabled="y",addr="",what="C",times="0"@}]@}
17431 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
17432 value=@{old="-276895068",new="3"@},
17433 frame=@{func="callee4",args=[],
17434 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
17437 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17438 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17439 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17440 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17441 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17442 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17443 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17444 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17445 addr="0x00010734",func="callee4",
17446 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
17447 bkpt=@{number="2",type="watchpoint",disp="keep",
17448 enabled="y",addr="",what="C",times="-5"@}]@}
17452 ^done,reason="watchpoint-scope",wpnum="2",
17453 frame=@{func="callee3",args=[@{name="strarg",
17454 value="0x11940 \"A string argument.\""@}],
17455 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
17458 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17459 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17460 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17461 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17462 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17463 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17464 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17465 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17466 addr="0x00010734",func="callee4",
17467 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@}]@}
17471 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17472 @node GDB/MI Data Manipulation
17473 @section @sc{gdb/mi} Data Manipulation
17475 @cindex data manipulation, in @sc{gdb/mi}
17476 @cindex @sc{gdb/mi}, data manipulation
17477 This section describes the @sc{gdb/mi} commands that manipulate data:
17478 examine memory and registers, evaluate expressions, etc.
17480 @c REMOVED FROM THE INTERFACE.
17481 @c @subheading -data-assign
17482 @c Change the value of a program variable. Plenty of side effects.
17483 @c @subsubheading GDB command
17485 @c @subsubheading Example
17488 @subheading The @code{-data-disassemble} Command
17489 @findex -data-disassemble
17491 @subsubheading Synopsis
17495 [ -s @var{start-addr} -e @var{end-addr} ]
17496 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
17504 @item @var{start-addr}
17505 is the beginning address (or @code{$pc})
17506 @item @var{end-addr}
17508 @item @var{filename}
17509 is the name of the file to disassemble
17510 @item @var{linenum}
17511 is the line number to disassemble around
17513 is the the number of disassembly lines to be produced. If it is -1,
17514 the whole function will be disassembled, in case no @var{end-addr} is
17515 specified. If @var{end-addr} is specified as a non-zero value, and
17516 @var{lines} is lower than the number of disassembly lines between
17517 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
17518 displayed; if @var{lines} is higher than the number of lines between
17519 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
17522 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
17526 @subsubheading Result
17528 The output for each instruction is composed of four fields:
17537 Note that whatever included in the instruction field, is not manipulated
17538 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
17540 @subsubheading @value{GDBN} Command
17542 There's no direct mapping from this command to the CLI.
17544 @subsubheading Example
17546 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
17550 -data-disassemble -s $pc -e "$pc + 20" -- 0
17553 @{address="0x000107c0",func-name="main",offset="4",
17554 inst="mov 2, %o0"@},
17555 @{address="0x000107c4",func-name="main",offset="8",
17556 inst="sethi %hi(0x11800), %o2"@},
17557 @{address="0x000107c8",func-name="main",offset="12",
17558 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
17559 @{address="0x000107cc",func-name="main",offset="16",
17560 inst="sethi %hi(0x11800), %o2"@},
17561 @{address="0x000107d0",func-name="main",offset="20",
17562 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
17566 Disassemble the whole @code{main} function. Line 32 is part of
17570 -data-disassemble -f basics.c -l 32 -- 0
17572 @{address="0x000107bc",func-name="main",offset="0",
17573 inst="save %sp, -112, %sp"@},
17574 @{address="0x000107c0",func-name="main",offset="4",
17575 inst="mov 2, %o0"@},
17576 @{address="0x000107c4",func-name="main",offset="8",
17577 inst="sethi %hi(0x11800), %o2"@},
17579 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
17580 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
17584 Disassemble 3 instructions from the start of @code{main}:
17588 -data-disassemble -f basics.c -l 32 -n 3 -- 0
17590 @{address="0x000107bc",func-name="main",offset="0",
17591 inst="save %sp, -112, %sp"@},
17592 @{address="0x000107c0",func-name="main",offset="4",
17593 inst="mov 2, %o0"@},
17594 @{address="0x000107c4",func-name="main",offset="8",
17595 inst="sethi %hi(0x11800), %o2"@}]
17599 Disassemble 3 instructions from the start of @code{main} in mixed mode:
17603 -data-disassemble -f basics.c -l 32 -n 3 -- 1
17605 src_and_asm_line=@{line="31",
17606 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
17607 testsuite/gdb.mi/basics.c",line_asm_insn=[
17608 @{address="0x000107bc",func-name="main",offset="0",
17609 inst="save %sp, -112, %sp"@}]@},
17610 src_and_asm_line=@{line="32",
17611 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
17612 testsuite/gdb.mi/basics.c",line_asm_insn=[
17613 @{address="0x000107c0",func-name="main",offset="4",
17614 inst="mov 2, %o0"@},
17615 @{address="0x000107c4",func-name="main",offset="8",
17616 inst="sethi %hi(0x11800), %o2"@}]@}]
17621 @subheading The @code{-data-evaluate-expression} Command
17622 @findex -data-evaluate-expression
17624 @subsubheading Synopsis
17627 -data-evaluate-expression @var{expr}
17630 Evaluate @var{expr} as an expression. The expression could contain an
17631 inferior function call. The function call will execute synchronously.
17632 If the expression contains spaces, it must be enclosed in double quotes.
17634 @subsubheading @value{GDBN} Command
17636 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
17637 @samp{call}. In @code{gdbtk} only, there's a corresponding
17638 @samp{gdb_eval} command.
17640 @subsubheading Example
17642 In the following example, the numbers that precede the commands are the
17643 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
17644 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
17648 211-data-evaluate-expression A
17651 311-data-evaluate-expression &A
17652 311^done,value="0xefffeb7c"
17654 411-data-evaluate-expression A+3
17657 511-data-evaluate-expression "A + 3"
17663 @subheading The @code{-data-list-changed-registers} Command
17664 @findex -data-list-changed-registers
17666 @subsubheading Synopsis
17669 -data-list-changed-registers
17672 Display a list of the registers that have changed.
17674 @subsubheading @value{GDBN} Command
17676 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
17677 has the corresponding command @samp{gdb_changed_register_list}.
17679 @subsubheading Example
17681 On a PPC MBX board:
17689 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
17690 args=[],file="try.c",line="5"@}
17692 -data-list-changed-registers
17693 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
17694 "10","11","13","14","15","16","17","18","19","20","21","22","23",
17695 "24","25","26","27","28","30","31","64","65","66","67","69"]
17700 @subheading The @code{-data-list-register-names} Command
17701 @findex -data-list-register-names
17703 @subsubheading Synopsis
17706 -data-list-register-names [ ( @var{regno} )+ ]
17709 Show a list of register names for the current target. If no arguments
17710 are given, it shows a list of the names of all the registers. If
17711 integer numbers are given as arguments, it will print a list of the
17712 names of the registers corresponding to the arguments. To ensure
17713 consistency between a register name and its number, the output list may
17714 include empty register names.
17716 @subsubheading @value{GDBN} Command
17718 @value{GDBN} does not have a command which corresponds to
17719 @samp{-data-list-register-names}. In @code{gdbtk} there is a
17720 corresponding command @samp{gdb_regnames}.
17722 @subsubheading Example
17724 For the PPC MBX board:
17727 -data-list-register-names
17728 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
17729 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
17730 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
17731 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
17732 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
17733 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
17734 "", "pc","ps","cr","lr","ctr","xer"]
17736 -data-list-register-names 1 2 3
17737 ^done,register-names=["r1","r2","r3"]
17741 @subheading The @code{-data-list-register-values} Command
17742 @findex -data-list-register-values
17744 @subsubheading Synopsis
17747 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
17750 Display the registers' contents. @var{fmt} is the format according to
17751 which the registers' contents are to be returned, followed by an optional
17752 list of numbers specifying the registers to display. A missing list of
17753 numbers indicates that the contents of all the registers must be returned.
17755 Allowed formats for @var{fmt} are:
17772 @subsubheading @value{GDBN} Command
17774 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
17775 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
17777 @subsubheading Example
17779 For a PPC MBX board (note: line breaks are for readability only, they
17780 don't appear in the actual output):
17784 -data-list-register-values r 64 65
17785 ^done,register-values=[@{number="64",value="0xfe00a300"@},
17786 @{number="65",value="0x00029002"@}]
17788 -data-list-register-values x
17789 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
17790 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
17791 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
17792 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
17793 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
17794 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
17795 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
17796 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
17797 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
17798 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
17799 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
17800 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
17801 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
17802 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
17803 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
17804 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
17805 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
17806 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
17807 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
17808 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
17809 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
17810 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
17811 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
17812 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
17813 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
17814 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
17815 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
17816 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
17817 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
17818 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
17819 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
17820 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
17821 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
17822 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
17823 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
17824 @{number="69",value="0x20002b03"@}]
17829 @subheading The @code{-data-read-memory} Command
17830 @findex -data-read-memory
17832 @subsubheading Synopsis
17835 -data-read-memory [ -o @var{byte-offset} ]
17836 @var{address} @var{word-format} @var{word-size}
17837 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
17844 @item @var{address}
17845 An expression specifying the address of the first memory word to be
17846 read. Complex expressions containing embedded white space should be
17847 quoted using the C convention.
17849 @item @var{word-format}
17850 The format to be used to print the memory words. The notation is the
17851 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
17854 @item @var{word-size}
17855 The size of each memory word in bytes.
17857 @item @var{nr-rows}
17858 The number of rows in the output table.
17860 @item @var{nr-cols}
17861 The number of columns in the output table.
17864 If present, indicates that each row should include an @sc{ascii} dump. The
17865 value of @var{aschar} is used as a padding character when a byte is not a
17866 member of the printable @sc{ascii} character set (printable @sc{ascii}
17867 characters are those whose code is between 32 and 126, inclusively).
17869 @item @var{byte-offset}
17870 An offset to add to the @var{address} before fetching memory.
17873 This command displays memory contents as a table of @var{nr-rows} by
17874 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
17875 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
17876 (returned as @samp{total-bytes}). Should less than the requested number
17877 of bytes be returned by the target, the missing words are identified
17878 using @samp{N/A}. The number of bytes read from the target is returned
17879 in @samp{nr-bytes} and the starting address used to read memory in
17882 The address of the next/previous row or page is available in
17883 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
17886 @subsubheading @value{GDBN} Command
17888 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
17889 @samp{gdb_get_mem} memory read command.
17891 @subsubheading Example
17893 Read six bytes of memory starting at @code{bytes+6} but then offset by
17894 @code{-6} bytes. Format as three rows of two columns. One byte per
17895 word. Display each word in hex.
17899 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
17900 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
17901 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
17902 prev-page="0x0000138a",memory=[
17903 @{addr="0x00001390",data=["0x00","0x01"]@},
17904 @{addr="0x00001392",data=["0x02","0x03"]@},
17905 @{addr="0x00001394",data=["0x04","0x05"]@}]
17909 Read two bytes of memory starting at address @code{shorts + 64} and
17910 display as a single word formatted in decimal.
17914 5-data-read-memory shorts+64 d 2 1 1
17915 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
17916 next-row="0x00001512",prev-row="0x0000150e",
17917 next-page="0x00001512",prev-page="0x0000150e",memory=[
17918 @{addr="0x00001510",data=["128"]@}]
17922 Read thirty two bytes of memory starting at @code{bytes+16} and format
17923 as eight rows of four columns. Include a string encoding with @samp{x}
17924 used as the non-printable character.
17928 4-data-read-memory bytes+16 x 1 8 4 x
17929 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
17930 next-row="0x000013c0",prev-row="0x0000139c",
17931 next-page="0x000013c0",prev-page="0x00001380",memory=[
17932 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
17933 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
17934 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
17935 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
17936 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
17937 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
17938 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
17939 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
17943 @subheading The @code{-display-delete} Command
17944 @findex -display-delete
17946 @subsubheading Synopsis
17949 -display-delete @var{number}
17952 Delete the display @var{number}.
17954 @subsubheading @value{GDBN} Command
17956 The corresponding @value{GDBN} command is @samp{delete display}.
17958 @subsubheading Example
17962 @subheading The @code{-display-disable} Command
17963 @findex -display-disable
17965 @subsubheading Synopsis
17968 -display-disable @var{number}
17971 Disable display @var{number}.
17973 @subsubheading @value{GDBN} Command
17975 The corresponding @value{GDBN} command is @samp{disable display}.
17977 @subsubheading Example
17981 @subheading The @code{-display-enable} Command
17982 @findex -display-enable
17984 @subsubheading Synopsis
17987 -display-enable @var{number}
17990 Enable display @var{number}.
17992 @subsubheading @value{GDBN} Command
17994 The corresponding @value{GDBN} command is @samp{enable display}.
17996 @subsubheading Example
18000 @subheading The @code{-display-insert} Command
18001 @findex -display-insert
18003 @subsubheading Synopsis
18006 -display-insert @var{expression}
18009 Display @var{expression} every time the program stops.
18011 @subsubheading @value{GDBN} Command
18013 The corresponding @value{GDBN} command is @samp{display}.
18015 @subsubheading Example
18019 @subheading The @code{-display-list} Command
18020 @findex -display-list
18022 @subsubheading Synopsis
18028 List the displays. Do not show the current values.
18030 @subsubheading @value{GDBN} Command
18032 The corresponding @value{GDBN} command is @samp{info display}.
18034 @subsubheading Example
18038 @subheading The @code{-environment-cd} Command
18039 @findex -environment-cd
18041 @subsubheading Synopsis
18044 -environment-cd @var{pathdir}
18047 Set @value{GDBN}'s working directory.
18049 @subsubheading @value{GDBN} Command
18051 The corresponding @value{GDBN} command is @samp{cd}.
18053 @subsubheading Example
18057 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18063 @subheading The @code{-environment-directory} Command
18064 @findex -environment-directory
18066 @subsubheading Synopsis
18069 -environment-directory [ -r ] [ @var{pathdir} ]+
18072 Add directories @var{pathdir} to beginning of search path for source files.
18073 If the @samp{-r} option is used, the search path is reset to the default
18074 search path. If directories @var{pathdir} are supplied in addition to the
18075 @samp{-r} option, the search path is first reset and then addition
18077 Multiple directories may be specified, separated by blanks. Specifying
18078 multiple directories in a single command
18079 results in the directories added to the beginning of the
18080 search path in the same order they were presented in the command.
18081 If blanks are needed as
18082 part of a directory name, double-quotes should be used around
18083 the name. In the command output, the path will show up separated
18084 by the system directory-separator character. The directory-seperator
18085 character must not be used
18086 in any directory name.
18087 If no directories are specified, the current search path is displayed.
18089 @subsubheading @value{GDBN} Command
18091 The corresponding @value{GDBN} command is @samp{dir}.
18093 @subsubheading Example
18097 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18098 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18100 -environment-directory ""
18101 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18103 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
18104 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
18106 -environment-directory -r
18107 ^done,source-path="$cdir:$cwd"
18112 @subheading The @code{-environment-path} Command
18113 @findex -environment-path
18115 @subsubheading Synopsis
18118 -environment-path [ -r ] [ @var{pathdir} ]+
18121 Add directories @var{pathdir} to beginning of search path for object files.
18122 If the @samp{-r} option is used, the search path is reset to the original
18123 search path that existed at gdb start-up. If directories @var{pathdir} are
18124 supplied in addition to the
18125 @samp{-r} option, the search path is first reset and then addition
18127 Multiple directories may be specified, separated by blanks. Specifying
18128 multiple directories in a single command
18129 results in the directories added to the beginning of the
18130 search path in the same order they were presented in the command.
18131 If blanks are needed as
18132 part of a directory name, double-quotes should be used around
18133 the name. In the command output, the path will show up separated
18134 by the system directory-separator character. The directory-seperator
18135 character must not be used
18136 in any directory name.
18137 If no directories are specified, the current path is displayed.
18140 @subsubheading @value{GDBN} Command
18142 The corresponding @value{GDBN} command is @samp{path}.
18144 @subsubheading Example
18149 ^done,path="/usr/bin"
18151 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
18152 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
18154 -environment-path -r /usr/local/bin
18155 ^done,path="/usr/local/bin:/usr/bin"
18160 @subheading The @code{-environment-pwd} Command
18161 @findex -environment-pwd
18163 @subsubheading Synopsis
18169 Show the current working directory.
18171 @subsubheading @value{GDBN} command
18173 The corresponding @value{GDBN} command is @samp{pwd}.
18175 @subsubheading Example
18180 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
18184 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18185 @node GDB/MI Program Control
18186 @section @sc{gdb/mi} Program control
18188 @subsubheading Program termination
18190 As a result of execution, the inferior program can run to completion, if
18191 it doesn't encounter any breakpoints. In this case the output will
18192 include an exit code, if the program has exited exceptionally.
18194 @subsubheading Examples
18197 Program exited normally:
18205 *stopped,reason="exited-normally"
18210 Program exited exceptionally:
18218 *stopped,reason="exited",exit-code="01"
18222 Another way the program can terminate is if it receives a signal such as
18223 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
18227 *stopped,reason="exited-signalled",signal-name="SIGINT",
18228 signal-meaning="Interrupt"
18232 @subheading The @code{-exec-abort} Command
18233 @findex -exec-abort
18235 @subsubheading Synopsis
18241 Kill the inferior running program.
18243 @subsubheading @value{GDBN} Command
18245 The corresponding @value{GDBN} command is @samp{kill}.
18247 @subsubheading Example
18251 @subheading The @code{-exec-arguments} Command
18252 @findex -exec-arguments
18254 @subsubheading Synopsis
18257 -exec-arguments @var{args}
18260 Set the inferior program arguments, to be used in the next
18263 @subsubheading @value{GDBN} Command
18265 The corresponding @value{GDBN} command is @samp{set args}.
18267 @subsubheading Example
18270 Don't have one around.
18273 @subheading The @code{-exec-continue} Command
18274 @findex -exec-continue
18276 @subsubheading Synopsis
18282 Asynchronous command. Resumes the execution of the inferior program
18283 until a breakpoint is encountered, or until the inferior exits.
18285 @subsubheading @value{GDBN} Command
18287 The corresponding @value{GDBN} corresponding is @samp{continue}.
18289 @subsubheading Example
18296 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
18297 file="hello.c",line="13"@}
18302 @subheading The @code{-exec-finish} Command
18303 @findex -exec-finish
18305 @subsubheading Synopsis
18311 Asynchronous command. Resumes the execution of the inferior program
18312 until the current function is exited. Displays the results returned by
18315 @subsubheading @value{GDBN} Command
18317 The corresponding @value{GDBN} command is @samp{finish}.
18319 @subsubheading Example
18321 Function returning @code{void}.
18328 *stopped,reason="function-finished",frame=@{func="main",args=[],
18329 file="hello.c",line="7"@}
18333 Function returning other than @code{void}. The name of the internal
18334 @value{GDBN} variable storing the result is printed, together with the
18341 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
18342 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
18343 file="recursive2.c",line="14"@},
18344 gdb-result-var="$1",return-value="0"
18349 @subheading The @code{-exec-interrupt} Command
18350 @findex -exec-interrupt
18352 @subsubheading Synopsis
18358 Asynchronous command. Interrupts the background execution of the target.
18359 Note how the token associated with the stop message is the one for the
18360 execution command that has been interrupted. The token for the interrupt
18361 itself only appears in the @samp{^done} output. If the user is trying to
18362 interrupt a non-running program, an error message will be printed.
18364 @subsubheading @value{GDBN} Command
18366 The corresponding @value{GDBN} command is @samp{interrupt}.
18368 @subsubheading Example
18379 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
18380 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",line="13"@}
18385 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
18390 @subheading The @code{-exec-next} Command
18393 @subsubheading Synopsis
18399 Asynchronous command. Resumes execution of the inferior program, stopping
18400 when the beginning of the next source line is reached.
18402 @subsubheading @value{GDBN} Command
18404 The corresponding @value{GDBN} command is @samp{next}.
18406 @subsubheading Example
18412 *stopped,reason="end-stepping-range",line="8",file="hello.c"
18417 @subheading The @code{-exec-next-instruction} Command
18418 @findex -exec-next-instruction
18420 @subsubheading Synopsis
18423 -exec-next-instruction
18426 Asynchronous command. Executes one machine instruction. If the
18427 instruction is a function call continues until the function returns. If
18428 the program stops at an instruction in the middle of a source line, the
18429 address will be printed as well.
18431 @subsubheading @value{GDBN} Command
18433 The corresponding @value{GDBN} command is @samp{nexti}.
18435 @subsubheading Example
18439 -exec-next-instruction
18443 *stopped,reason="end-stepping-range",
18444 addr="0x000100d4",line="5",file="hello.c"
18449 @subheading The @code{-exec-return} Command
18450 @findex -exec-return
18452 @subsubheading Synopsis
18458 Makes current function return immediately. Doesn't execute the inferior.
18459 Displays the new current frame.
18461 @subsubheading @value{GDBN} Command
18463 The corresponding @value{GDBN} command is @samp{return}.
18465 @subsubheading Example
18469 200-break-insert callee4
18470 200^done,bkpt=@{number="1",addr="0x00010734",
18471 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18476 000*stopped,reason="breakpoint-hit",bkptno="1",
18477 frame=@{func="callee4",args=[],
18478 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18484 111^done,frame=@{level="0",func="callee3",
18485 args=[@{name="strarg",
18486 value="0x11940 \"A string argument.\""@}],
18487 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18492 @subheading The @code{-exec-run} Command
18495 @subsubheading Synopsis
18501 Asynchronous command. Starts execution of the inferior from the
18502 beginning. The inferior executes until either a breakpoint is
18503 encountered or the program exits.
18505 @subsubheading @value{GDBN} Command
18507 The corresponding @value{GDBN} command is @samp{run}.
18509 @subsubheading Example
18514 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
18519 *stopped,reason="breakpoint-hit",bkptno="1",
18520 frame=@{func="main",args=[],file="recursive2.c",line="4"@}
18525 @subheading The @code{-exec-show-arguments} Command
18526 @findex -exec-show-arguments
18528 @subsubheading Synopsis
18531 -exec-show-arguments
18534 Print the arguments of the program.
18536 @subsubheading @value{GDBN} Command
18538 The corresponding @value{GDBN} command is @samp{show args}.
18540 @subsubheading Example
18543 @c @subheading -exec-signal
18545 @subheading The @code{-exec-step} Command
18548 @subsubheading Synopsis
18554 Asynchronous command. Resumes execution of the inferior program, stopping
18555 when the beginning of the next source line is reached, if the next
18556 source line is not a function call. If it is, stop at the first
18557 instruction of the called function.
18559 @subsubheading @value{GDBN} Command
18561 The corresponding @value{GDBN} command is @samp{step}.
18563 @subsubheading Example
18565 Stepping into a function:
18571 *stopped,reason="end-stepping-range",
18572 frame=@{func="foo",args=[@{name="a",value="10"@},
18573 @{name="b",value="0"@}],file="recursive2.c",line="11"@}
18583 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
18588 @subheading The @code{-exec-step-instruction} Command
18589 @findex -exec-step-instruction
18591 @subsubheading Synopsis
18594 -exec-step-instruction
18597 Asynchronous command. Resumes the inferior which executes one machine
18598 instruction. The output, once @value{GDBN} has stopped, will vary depending on
18599 whether we have stopped in the middle of a source line or not. In the
18600 former case, the address at which the program stopped will be printed as
18603 @subsubheading @value{GDBN} Command
18605 The corresponding @value{GDBN} command is @samp{stepi}.
18607 @subsubheading Example
18611 -exec-step-instruction
18615 *stopped,reason="end-stepping-range",
18616 frame=@{func="foo",args=[],file="try.c",line="10"@}
18618 -exec-step-instruction
18622 *stopped,reason="end-stepping-range",
18623 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",line="10"@}
18628 @subheading The @code{-exec-until} Command
18629 @findex -exec-until
18631 @subsubheading Synopsis
18634 -exec-until [ @var{location} ]
18637 Asynchronous command. Executes the inferior until the @var{location}
18638 specified in the argument is reached. If there is no argument, the inferior
18639 executes until a source line greater than the current one is reached.
18640 The reason for stopping in this case will be @samp{location-reached}.
18642 @subsubheading @value{GDBN} Command
18644 The corresponding @value{GDBN} command is @samp{until}.
18646 @subsubheading Example
18650 -exec-until recursive2.c:6
18654 *stopped,reason="location-reached",frame=@{func="main",args=[],
18655 file="recursive2.c",line="6"@}
18660 @subheading -file-clear
18661 Is this going away????
18665 @subheading The @code{-file-exec-and-symbols} Command
18666 @findex -file-exec-and-symbols
18668 @subsubheading Synopsis
18671 -file-exec-and-symbols @var{file}
18674 Specify the executable file to be debugged. This file is the one from
18675 which the symbol table is also read. If no file is specified, the
18676 command clears the executable and symbol information. If breakpoints
18677 are set when using this command with no arguments, @value{GDBN} will produce
18678 error messages. Otherwise, no output is produced, except a completion
18681 @subsubheading @value{GDBN} Command
18683 The corresponding @value{GDBN} command is @samp{file}.
18685 @subsubheading Example
18689 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18695 @subheading The @code{-file-exec-file} Command
18696 @findex -file-exec-file
18698 @subsubheading Synopsis
18701 -file-exec-file @var{file}
18704 Specify the executable file to be debugged. Unlike
18705 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
18706 from this file. If used without argument, @value{GDBN} clears the information
18707 about the executable file. No output is produced, except a completion
18710 @subsubheading @value{GDBN} Command
18712 The corresponding @value{GDBN} command is @samp{exec-file}.
18714 @subsubheading Example
18718 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18724 @subheading The @code{-file-list-exec-sections} Command
18725 @findex -file-list-exec-sections
18727 @subsubheading Synopsis
18730 -file-list-exec-sections
18733 List the sections of the current executable file.
18735 @subsubheading @value{GDBN} Command
18737 The @value{GDBN} command @samp{info file} shows, among the rest, the same
18738 information as this command. @code{gdbtk} has a corresponding command
18739 @samp{gdb_load_info}.
18741 @subsubheading Example
18745 @subheading The @code{-file-list-exec-source-file} Command
18746 @findex -file-list-exec-source-file
18748 @subsubheading Synopsis
18751 -file-list-exec-source-file
18754 List the line number, the current source file, and the absolute path
18755 to the current source file for the current executable.
18757 @subsubheading @value{GDBN} Command
18759 There's no @value{GDBN} command which directly corresponds to this one.
18761 @subsubheading Example
18765 123-file-list-exec-source-file
18766 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
18771 @subheading The @code{-file-list-exec-source-files} Command
18772 @findex -file-list-exec-source-files
18774 @subsubheading Synopsis
18777 -file-list-exec-source-files
18780 List the source files for the current executable.
18782 It will always output the filename, but only when GDB can find the absolute
18783 file name of a source file, will it output the fullname.
18785 @subsubheading @value{GDBN} Command
18787 There's no @value{GDBN} command which directly corresponds to this one.
18788 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
18790 @subsubheading Example
18793 -file-list-exec-source-files
18795 @{file=foo.c,fullname=/home/foo.c@},
18796 @{file=/home/bar.c,fullname=/home/bar.c@},
18797 @{file=gdb_could_not_find_fullpath.c@}]
18801 @subheading The @code{-file-list-shared-libraries} Command
18802 @findex -file-list-shared-libraries
18804 @subsubheading Synopsis
18807 -file-list-shared-libraries
18810 List the shared libraries in the program.
18812 @subsubheading @value{GDBN} Command
18814 The corresponding @value{GDBN} command is @samp{info shared}.
18816 @subsubheading Example
18820 @subheading The @code{-file-list-symbol-files} Command
18821 @findex -file-list-symbol-files
18823 @subsubheading Synopsis
18826 -file-list-symbol-files
18831 @subsubheading @value{GDBN} Command
18833 The corresponding @value{GDBN} command is @samp{info file} (part of it).
18835 @subsubheading Example
18839 @subheading The @code{-file-symbol-file} Command
18840 @findex -file-symbol-file
18842 @subsubheading Synopsis
18845 -file-symbol-file @var{file}
18848 Read symbol table info from the specified @var{file} argument. When
18849 used without arguments, clears @value{GDBN}'s symbol table info. No output is
18850 produced, except for a completion notification.
18852 @subsubheading @value{GDBN} Command
18854 The corresponding @value{GDBN} command is @samp{symbol-file}.
18856 @subsubheading Example
18860 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18865 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18866 @node GDB/MI Miscellaneous Commands
18867 @section Miscellaneous @value{GDBN} commands in @sc{gdb/mi}
18869 @c @subheading -gdb-complete
18871 @subheading The @code{-gdb-exit} Command
18874 @subsubheading Synopsis
18880 Exit @value{GDBN} immediately.
18882 @subsubheading @value{GDBN} Command
18884 Approximately corresponds to @samp{quit}.
18886 @subsubheading Example
18893 @subheading The @code{-gdb-set} Command
18896 @subsubheading Synopsis
18902 Set an internal @value{GDBN} variable.
18903 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
18905 @subsubheading @value{GDBN} Command
18907 The corresponding @value{GDBN} command is @samp{set}.
18909 @subsubheading Example
18919 @subheading The @code{-gdb-show} Command
18922 @subsubheading Synopsis
18928 Show the current value of a @value{GDBN} variable.
18930 @subsubheading @value{GDBN} command
18932 The corresponding @value{GDBN} command is @samp{show}.
18934 @subsubheading Example
18943 @c @subheading -gdb-source
18946 @subheading The @code{-gdb-version} Command
18947 @findex -gdb-version
18949 @subsubheading Synopsis
18955 Show version information for @value{GDBN}. Used mostly in testing.
18957 @subsubheading @value{GDBN} Command
18959 There's no equivalent @value{GDBN} command. @value{GDBN} by default shows this
18960 information when you start an interactive session.
18962 @subsubheading Example
18964 @c This example modifies the actual output from GDB to avoid overfull
18970 ~Copyright 2000 Free Software Foundation, Inc.
18971 ~GDB is free software, covered by the GNU General Public License, and
18972 ~you are welcome to change it and/or distribute copies of it under
18973 ~ certain conditions.
18974 ~Type "show copying" to see the conditions.
18975 ~There is absolutely no warranty for GDB. Type "show warranty" for
18977 ~This GDB was configured as
18978 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
18983 @subheading The @code{-interpreter-exec} Command
18984 @findex -interpreter-exec
18986 @subheading Synopsis
18989 -interpreter-exec @var{interpreter} @var{command}
18992 Execute the specified @var{command} in the given @var{interpreter}.
18994 @subheading @value{GDBN} Command
18996 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
18998 @subheading Example
19002 -interpreter-exec console "break main"
19003 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
19004 &"During symbol reading, bad structure-type format.\n"
19005 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
19011 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19012 @node GDB/MI Kod Commands
19013 @section @sc{gdb/mi} Kod Commands
19015 The Kod commands are not implemented.
19017 @c @subheading -kod-info
19019 @c @subheading -kod-list
19021 @c @subheading -kod-list-object-types
19023 @c @subheading -kod-show
19025 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19026 @node GDB/MI Memory Overlay Commands
19027 @section @sc{gdb/mi} Memory Overlay Commands
19029 The memory overlay commands are not implemented.
19031 @c @subheading -overlay-auto
19033 @c @subheading -overlay-list-mapping-state
19035 @c @subheading -overlay-list-overlays
19037 @c @subheading -overlay-map
19039 @c @subheading -overlay-off
19041 @c @subheading -overlay-on
19043 @c @subheading -overlay-unmap
19045 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19046 @node GDB/MI Signal Handling Commands
19047 @section @sc{gdb/mi} Signal Handling Commands
19049 Signal handling commands are not implemented.
19051 @c @subheading -signal-handle
19053 @c @subheading -signal-list-handle-actions
19055 @c @subheading -signal-list-signal-types
19059 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19060 @node GDB/MI Stack Manipulation
19061 @section @sc{gdb/mi} Stack Manipulation Commands
19064 @subheading The @code{-stack-info-frame} Command
19065 @findex -stack-info-frame
19067 @subsubheading Synopsis
19073 Get info on the current frame.
19075 @subsubheading @value{GDBN} Command
19077 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
19078 (without arguments).
19080 @subsubheading Example
19083 @subheading The @code{-stack-info-depth} Command
19084 @findex -stack-info-depth
19086 @subsubheading Synopsis
19089 -stack-info-depth [ @var{max-depth} ]
19092 Return the depth of the stack. If the integer argument @var{max-depth}
19093 is specified, do not count beyond @var{max-depth} frames.
19095 @subsubheading @value{GDBN} Command
19097 There's no equivalent @value{GDBN} command.
19099 @subsubheading Example
19101 For a stack with frame levels 0 through 11:
19108 -stack-info-depth 4
19111 -stack-info-depth 12
19114 -stack-info-depth 11
19117 -stack-info-depth 13
19122 @subheading The @code{-stack-list-arguments} Command
19123 @findex -stack-list-arguments
19125 @subsubheading Synopsis
19128 -stack-list-arguments @var{show-values}
19129 [ @var{low-frame} @var{high-frame} ]
19132 Display a list of the arguments for the frames between @var{low-frame}
19133 and @var{high-frame} (inclusive). If @var{low-frame} and
19134 @var{high-frame} are not provided, list the arguments for the whole call
19137 The @var{show-values} argument must have a value of 0 or 1. A value of
19138 0 means that only the names of the arguments are listed, a value of 1
19139 means that both names and values of the arguments are printed.
19141 @subsubheading @value{GDBN} Command
19143 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19144 @samp{gdb_get_args} command which partially overlaps with the
19145 functionality of @samp{-stack-list-arguments}.
19147 @subsubheading Example
19154 frame=@{level="0",addr="0x00010734",func="callee4",
19155 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19156 frame=@{level="1",addr="0x0001076c",func="callee3",
19157 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19158 frame=@{level="2",addr="0x0001078c",func="callee2",
19159 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19160 frame=@{level="3",addr="0x000107b4",func="callee1",
19161 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19162 frame=@{level="4",addr="0x000107e0",func="main",
19163 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19165 -stack-list-arguments 0
19168 frame=@{level="0",args=[]@},
19169 frame=@{level="1",args=[name="strarg"]@},
19170 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19171 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19172 frame=@{level="4",args=[]@}]
19174 -stack-list-arguments 1
19177 frame=@{level="0",args=[]@},
19179 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19180 frame=@{level="2",args=[
19181 @{name="intarg",value="2"@},
19182 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19183 @{frame=@{level="3",args=[
19184 @{name="intarg",value="2"@},
19185 @{name="strarg",value="0x11940 \"A string argument.\""@},
19186 @{name="fltarg",value="3.5"@}]@},
19187 frame=@{level="4",args=[]@}]
19189 -stack-list-arguments 0 2 2
19190 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19192 -stack-list-arguments 1 2 2
19193 ^done,stack-args=[frame=@{level="2",
19194 args=[@{name="intarg",value="2"@},
19195 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19199 @c @subheading -stack-list-exception-handlers
19202 @subheading The @code{-stack-list-frames} Command
19203 @findex -stack-list-frames
19205 @subsubheading Synopsis
19208 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19211 List the frames currently on the stack. For each frame it displays the
19216 The frame number, 0 being the topmost frame, i.e. the innermost function.
19218 The @code{$pc} value for that frame.
19222 File name of the source file where the function lives.
19224 Line number corresponding to the @code{$pc}.
19227 If invoked without arguments, this command prints a backtrace for the
19228 whole stack. If given two integer arguments, it shows the frames whose
19229 levels are between the two arguments (inclusive). If the two arguments
19230 are equal, it shows the single frame at the corresponding level.
19232 @subsubheading @value{GDBN} Command
19234 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19236 @subsubheading Example
19238 Full stack backtrace:
19244 [frame=@{level="0",addr="0x0001076c",func="foo",
19245 file="recursive2.c",line="11"@},
19246 frame=@{level="1",addr="0x000107a4",func="foo",
19247 file="recursive2.c",line="14"@},
19248 frame=@{level="2",addr="0x000107a4",func="foo",
19249 file="recursive2.c",line="14"@},
19250 frame=@{level="3",addr="0x000107a4",func="foo",
19251 file="recursive2.c",line="14"@},
19252 frame=@{level="4",addr="0x000107a4",func="foo",
19253 file="recursive2.c",line="14"@},
19254 frame=@{level="5",addr="0x000107a4",func="foo",
19255 file="recursive2.c",line="14"@},
19256 frame=@{level="6",addr="0x000107a4",func="foo",
19257 file="recursive2.c",line="14"@},
19258 frame=@{level="7",addr="0x000107a4",func="foo",
19259 file="recursive2.c",line="14"@},
19260 frame=@{level="8",addr="0x000107a4",func="foo",
19261 file="recursive2.c",line="14"@},
19262 frame=@{level="9",addr="0x000107a4",func="foo",
19263 file="recursive2.c",line="14"@},
19264 frame=@{level="10",addr="0x000107a4",func="foo",
19265 file="recursive2.c",line="14"@},
19266 frame=@{level="11",addr="0x00010738",func="main",
19267 file="recursive2.c",line="4"@}]
19271 Show frames between @var{low_frame} and @var{high_frame}:
19275 -stack-list-frames 3 5
19277 [frame=@{level="3",addr="0x000107a4",func="foo",
19278 file="recursive2.c",line="14"@},
19279 frame=@{level="4",addr="0x000107a4",func="foo",
19280 file="recursive2.c",line="14"@},
19281 frame=@{level="5",addr="0x000107a4",func="foo",
19282 file="recursive2.c",line="14"@}]
19286 Show a single frame:
19290 -stack-list-frames 3 3
19292 [frame=@{level="3",addr="0x000107a4",func="foo",
19293 file="recursive2.c",line="14"@}]
19298 @subheading The @code{-stack-list-locals} Command
19299 @findex -stack-list-locals
19301 @subsubheading Synopsis
19304 -stack-list-locals @var{print-values}
19307 Display the local variable names for the current frame. With an
19308 argument of 0 or @code{--no-values}, prints only the names of the variables.
19309 With argument of 1 or @code{--all-values}, prints also their values. With
19310 argument of 2 or @code{--simple-values}, prints the name, type and value for
19311 simple data types and the name and type for arrays, structures and
19312 unions. In this last case, the idea is that the user can see the
19313 value of simple data types immediately and he can create variable
19314 objects for other data types if he wishes to explore their values in
19317 @subsubheading @value{GDBN} Command
19319 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
19321 @subsubheading Example
19325 -stack-list-locals 0
19326 ^done,locals=[name="A",name="B",name="C"]
19328 -stack-list-locals --all-values
19329 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
19330 @{name="C",value="@{1, 2, 3@}"@}]
19331 -stack-list-locals --simple-values
19332 ^done,locals=[@{name="A",type="int",value="1"@},
19333 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
19338 @subheading The @code{-stack-select-frame} Command
19339 @findex -stack-select-frame
19341 @subsubheading Synopsis
19344 -stack-select-frame @var{framenum}
19347 Change the current frame. Select a different frame @var{framenum} on
19350 @subsubheading @value{GDBN} Command
19352 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
19353 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
19355 @subsubheading Example
19359 -stack-select-frame 2
19364 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19365 @node GDB/MI Symbol Query
19366 @section @sc{gdb/mi} Symbol Query Commands
19369 @subheading The @code{-symbol-info-address} Command
19370 @findex -symbol-info-address
19372 @subsubheading Synopsis
19375 -symbol-info-address @var{symbol}
19378 Describe where @var{symbol} is stored.
19380 @subsubheading @value{GDBN} Command
19382 The corresponding @value{GDBN} command is @samp{info address}.
19384 @subsubheading Example
19388 @subheading The @code{-symbol-info-file} Command
19389 @findex -symbol-info-file
19391 @subsubheading Synopsis
19397 Show the file for the symbol.
19399 @subsubheading @value{GDBN} Command
19401 There's no equivalent @value{GDBN} command. @code{gdbtk} has
19402 @samp{gdb_find_file}.
19404 @subsubheading Example
19408 @subheading The @code{-symbol-info-function} Command
19409 @findex -symbol-info-function
19411 @subsubheading Synopsis
19414 -symbol-info-function
19417 Show which function the symbol lives in.
19419 @subsubheading @value{GDBN} Command
19421 @samp{gdb_get_function} in @code{gdbtk}.
19423 @subsubheading Example
19427 @subheading The @code{-symbol-info-line} Command
19428 @findex -symbol-info-line
19430 @subsubheading Synopsis
19436 Show the core addresses of the code for a source line.
19438 @subsubheading @value{GDBN} Command
19440 The corresponding @value{GDBN} command is @samp{info line}.
19441 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
19443 @subsubheading Example
19447 @subheading The @code{-symbol-info-symbol} Command
19448 @findex -symbol-info-symbol
19450 @subsubheading Synopsis
19453 -symbol-info-symbol @var{addr}
19456 Describe what symbol is at location @var{addr}.
19458 @subsubheading @value{GDBN} Command
19460 The corresponding @value{GDBN} command is @samp{info symbol}.
19462 @subsubheading Example
19466 @subheading The @code{-symbol-list-functions} Command
19467 @findex -symbol-list-functions
19469 @subsubheading Synopsis
19472 -symbol-list-functions
19475 List the functions in the executable.
19477 @subsubheading @value{GDBN} Command
19479 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
19480 @samp{gdb_search} in @code{gdbtk}.
19482 @subsubheading Example
19486 @subheading The @code{-symbol-list-lines} Command
19487 @findex -symbol-list-lines
19489 @subsubheading Synopsis
19492 -symbol-list-lines @var{filename}
19495 Print the list of lines that contain code and their associated program
19496 addresses for the given source filename. The entries are sorted in
19497 ascending PC order.
19499 @subsubheading @value{GDBN} Command
19501 There is no corresponding @value{GDBN} command.
19503 @subsubheading Example
19506 -symbol-list-lines basics.c
19507 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
19512 @subheading The @code{-symbol-list-types} Command
19513 @findex -symbol-list-types
19515 @subsubheading Synopsis
19521 List all the type names.
19523 @subsubheading @value{GDBN} Command
19525 The corresponding commands are @samp{info types} in @value{GDBN},
19526 @samp{gdb_search} in @code{gdbtk}.
19528 @subsubheading Example
19532 @subheading The @code{-symbol-list-variables} Command
19533 @findex -symbol-list-variables
19535 @subsubheading Synopsis
19538 -symbol-list-variables
19541 List all the global and static variable names.
19543 @subsubheading @value{GDBN} Command
19545 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
19547 @subsubheading Example
19551 @subheading The @code{-symbol-locate} Command
19552 @findex -symbol-locate
19554 @subsubheading Synopsis
19560 @subsubheading @value{GDBN} Command
19562 @samp{gdb_loc} in @code{gdbtk}.
19564 @subsubheading Example
19568 @subheading The @code{-symbol-type} Command
19569 @findex -symbol-type
19571 @subsubheading Synopsis
19574 -symbol-type @var{variable}
19577 Show type of @var{variable}.
19579 @subsubheading @value{GDBN} Command
19581 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
19582 @samp{gdb_obj_variable}.
19584 @subsubheading Example
19588 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19589 @node GDB/MI Target Manipulation
19590 @section @sc{gdb/mi} Target Manipulation Commands
19593 @subheading The @code{-target-attach} Command
19594 @findex -target-attach
19596 @subsubheading Synopsis
19599 -target-attach @var{pid} | @var{file}
19602 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
19604 @subsubheading @value{GDBN} command
19606 The corresponding @value{GDBN} command is @samp{attach}.
19608 @subsubheading Example
19612 @subheading The @code{-target-compare-sections} Command
19613 @findex -target-compare-sections
19615 @subsubheading Synopsis
19618 -target-compare-sections [ @var{section} ]
19621 Compare data of section @var{section} on target to the exec file.
19622 Without the argument, all sections are compared.
19624 @subsubheading @value{GDBN} Command
19626 The @value{GDBN} equivalent is @samp{compare-sections}.
19628 @subsubheading Example
19632 @subheading The @code{-target-detach} Command
19633 @findex -target-detach
19635 @subsubheading Synopsis
19641 Disconnect from the remote target. There's no output.
19643 @subsubheading @value{GDBN} command
19645 The corresponding @value{GDBN} command is @samp{detach}.
19647 @subsubheading Example
19657 @subheading The @code{-target-disconnect} Command
19658 @findex -target-disconnect
19660 @subsubheading Synopsis
19666 Disconnect from the remote target. There's no output.
19668 @subsubheading @value{GDBN} command
19670 The corresponding @value{GDBN} command is @samp{disconnect}.
19672 @subsubheading Example
19682 @subheading The @code{-target-download} Command
19683 @findex -target-download
19685 @subsubheading Synopsis
19691 Loads the executable onto the remote target.
19692 It prints out an update message every half second, which includes the fields:
19696 The name of the section.
19698 The size of what has been sent so far for that section.
19700 The size of the section.
19702 The total size of what was sent so far (the current and the previous sections).
19704 The size of the overall executable to download.
19708 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
19709 @sc{gdb/mi} Output Syntax}).
19711 In addition, it prints the name and size of the sections, as they are
19712 downloaded. These messages include the following fields:
19716 The name of the section.
19718 The size of the section.
19720 The size of the overall executable to download.
19724 At the end, a summary is printed.
19726 @subsubheading @value{GDBN} Command
19728 The corresponding @value{GDBN} command is @samp{load}.
19730 @subsubheading Example
19732 Note: each status message appears on a single line. Here the messages
19733 have been broken down so that they can fit onto a page.
19738 +download,@{section=".text",section-size="6668",total-size="9880"@}
19739 +download,@{section=".text",section-sent="512",section-size="6668",
19740 total-sent="512",total-size="9880"@}
19741 +download,@{section=".text",section-sent="1024",section-size="6668",
19742 total-sent="1024",total-size="9880"@}
19743 +download,@{section=".text",section-sent="1536",section-size="6668",
19744 total-sent="1536",total-size="9880"@}
19745 +download,@{section=".text",section-sent="2048",section-size="6668",
19746 total-sent="2048",total-size="9880"@}
19747 +download,@{section=".text",section-sent="2560",section-size="6668",
19748 total-sent="2560",total-size="9880"@}
19749 +download,@{section=".text",section-sent="3072",section-size="6668",
19750 total-sent="3072",total-size="9880"@}
19751 +download,@{section=".text",section-sent="3584",section-size="6668",
19752 total-sent="3584",total-size="9880"@}
19753 +download,@{section=".text",section-sent="4096",section-size="6668",
19754 total-sent="4096",total-size="9880"@}
19755 +download,@{section=".text",section-sent="4608",section-size="6668",
19756 total-sent="4608",total-size="9880"@}
19757 +download,@{section=".text",section-sent="5120",section-size="6668",
19758 total-sent="5120",total-size="9880"@}
19759 +download,@{section=".text",section-sent="5632",section-size="6668",
19760 total-sent="5632",total-size="9880"@}
19761 +download,@{section=".text",section-sent="6144",section-size="6668",
19762 total-sent="6144",total-size="9880"@}
19763 +download,@{section=".text",section-sent="6656",section-size="6668",
19764 total-sent="6656",total-size="9880"@}
19765 +download,@{section=".init",section-size="28",total-size="9880"@}
19766 +download,@{section=".fini",section-size="28",total-size="9880"@}
19767 +download,@{section=".data",section-size="3156",total-size="9880"@}
19768 +download,@{section=".data",section-sent="512",section-size="3156",
19769 total-sent="7236",total-size="9880"@}
19770 +download,@{section=".data",section-sent="1024",section-size="3156",
19771 total-sent="7748",total-size="9880"@}
19772 +download,@{section=".data",section-sent="1536",section-size="3156",
19773 total-sent="8260",total-size="9880"@}
19774 +download,@{section=".data",section-sent="2048",section-size="3156",
19775 total-sent="8772",total-size="9880"@}
19776 +download,@{section=".data",section-sent="2560",section-size="3156",
19777 total-sent="9284",total-size="9880"@}
19778 +download,@{section=".data",section-sent="3072",section-size="3156",
19779 total-sent="9796",total-size="9880"@}
19780 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
19786 @subheading The @code{-target-exec-status} Command
19787 @findex -target-exec-status
19789 @subsubheading Synopsis
19792 -target-exec-status
19795 Provide information on the state of the target (whether it is running or
19796 not, for instance).
19798 @subsubheading @value{GDBN} Command
19800 There's no equivalent @value{GDBN} command.
19802 @subsubheading Example
19806 @subheading The @code{-target-list-available-targets} Command
19807 @findex -target-list-available-targets
19809 @subsubheading Synopsis
19812 -target-list-available-targets
19815 List the possible targets to connect to.
19817 @subsubheading @value{GDBN} Command
19819 The corresponding @value{GDBN} command is @samp{help target}.
19821 @subsubheading Example
19825 @subheading The @code{-target-list-current-targets} Command
19826 @findex -target-list-current-targets
19828 @subsubheading Synopsis
19831 -target-list-current-targets
19834 Describe the current target.
19836 @subsubheading @value{GDBN} Command
19838 The corresponding information is printed by @samp{info file} (among
19841 @subsubheading Example
19845 @subheading The @code{-target-list-parameters} Command
19846 @findex -target-list-parameters
19848 @subsubheading Synopsis
19851 -target-list-parameters
19856 @subsubheading @value{GDBN} Command
19860 @subsubheading Example
19864 @subheading The @code{-target-select} Command
19865 @findex -target-select
19867 @subsubheading Synopsis
19870 -target-select @var{type} @var{parameters @dots{}}
19873 Connect @value{GDBN} to the remote target. This command takes two args:
19877 The type of target, for instance @samp{async}, @samp{remote}, etc.
19878 @item @var{parameters}
19879 Device names, host names and the like. @xref{Target Commands, ,
19880 Commands for managing targets}, for more details.
19883 The output is a connection notification, followed by the address at
19884 which the target program is, in the following form:
19887 ^connected,addr="@var{address}",func="@var{function name}",
19888 args=[@var{arg list}]
19891 @subsubheading @value{GDBN} Command
19893 The corresponding @value{GDBN} command is @samp{target}.
19895 @subsubheading Example
19899 -target-select async /dev/ttya
19900 ^connected,addr="0xfe00a300",func="??",args=[]
19904 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19905 @node GDB/MI Thread Commands
19906 @section @sc{gdb/mi} Thread Commands
19909 @subheading The @code{-thread-info} Command
19910 @findex -thread-info
19912 @subsubheading Synopsis
19918 @subsubheading @value{GDBN} command
19922 @subsubheading Example
19926 @subheading The @code{-thread-list-all-threads} Command
19927 @findex -thread-list-all-threads
19929 @subsubheading Synopsis
19932 -thread-list-all-threads
19935 @subsubheading @value{GDBN} Command
19937 The equivalent @value{GDBN} command is @samp{info threads}.
19939 @subsubheading Example
19943 @subheading The @code{-thread-list-ids} Command
19944 @findex -thread-list-ids
19946 @subsubheading Synopsis
19952 Produces a list of the currently known @value{GDBN} thread ids. At the
19953 end of the list it also prints the total number of such threads.
19955 @subsubheading @value{GDBN} Command
19957 Part of @samp{info threads} supplies the same information.
19959 @subsubheading Example
19961 No threads present, besides the main process:
19966 ^done,thread-ids=@{@},number-of-threads="0"
19976 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
19977 number-of-threads="3"
19982 @subheading The @code{-thread-select} Command
19983 @findex -thread-select
19985 @subsubheading Synopsis
19988 -thread-select @var{threadnum}
19991 Make @var{threadnum} the current thread. It prints the number of the new
19992 current thread, and the topmost frame for that thread.
19994 @subsubheading @value{GDBN} Command
19996 The corresponding @value{GDBN} command is @samp{thread}.
19998 @subsubheading Example
20005 *stopped,reason="end-stepping-range",thread-id="2",line="187",
20006 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
20010 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20011 number-of-threads="3"
20014 ^done,new-thread-id="3",
20015 frame=@{level="0",func="vprintf",
20016 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
20017 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
20021 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20022 @node GDB/MI Tracepoint Commands
20023 @section @sc{gdb/mi} Tracepoint Commands
20025 The tracepoint commands are not yet implemented.
20027 @c @subheading -trace-actions
20029 @c @subheading -trace-delete
20031 @c @subheading -trace-disable
20033 @c @subheading -trace-dump
20035 @c @subheading -trace-enable
20037 @c @subheading -trace-exists
20039 @c @subheading -trace-find
20041 @c @subheading -trace-frame-number
20043 @c @subheading -trace-info
20045 @c @subheading -trace-insert
20047 @c @subheading -trace-list
20049 @c @subheading -trace-pass-count
20051 @c @subheading -trace-save
20053 @c @subheading -trace-start
20055 @c @subheading -trace-stop
20058 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20059 @node GDB/MI Variable Objects
20060 @section @sc{gdb/mi} Variable Objects
20063 @subheading Motivation for Variable Objects in @sc{gdb/mi}
20065 For the implementation of a variable debugger window (locals, watched
20066 expressions, etc.), we are proposing the adaptation of the existing code
20067 used by @code{Insight}.
20069 The two main reasons for that are:
20073 It has been proven in practice (it is already on its second generation).
20076 It will shorten development time (needless to say how important it is
20080 The original interface was designed to be used by Tcl code, so it was
20081 slightly changed so it could be used through @sc{gdb/mi}. This section
20082 describes the @sc{gdb/mi} operations that will be available and gives some
20083 hints about their use.
20085 @emph{Note}: In addition to the set of operations described here, we
20086 expect the @sc{gui} implementation of a variable window to require, at
20087 least, the following operations:
20090 @item @code{-gdb-show} @code{output-radix}
20091 @item @code{-stack-list-arguments}
20092 @item @code{-stack-list-locals}
20093 @item @code{-stack-select-frame}
20096 @subheading Introduction to Variable Objects in @sc{gdb/mi}
20098 @cindex variable objects in @sc{gdb/mi}
20099 The basic idea behind variable objects is the creation of a named object
20100 to represent a variable, an expression, a memory location or even a CPU
20101 register. For each object created, a set of operations is available for
20102 examining or changing its properties.
20104 Furthermore, complex data types, such as C structures, are represented
20105 in a tree format. For instance, the @code{struct} type variable is the
20106 root and the children will represent the struct members. If a child
20107 is itself of a complex type, it will also have children of its own.
20108 Appropriate language differences are handled for C, C@t{++} and Java.
20110 When returning the actual values of the objects, this facility allows
20111 for the individual selection of the display format used in the result
20112 creation. It can be chosen among: binary, decimal, hexadecimal, octal
20113 and natural. Natural refers to a default format automatically
20114 chosen based on the variable type (like decimal for an @code{int}, hex
20115 for pointers, etc.).
20117 The following is the complete set of @sc{gdb/mi} operations defined to
20118 access this functionality:
20120 @multitable @columnfractions .4 .6
20121 @item @strong{Operation}
20122 @tab @strong{Description}
20124 @item @code{-var-create}
20125 @tab create a variable object
20126 @item @code{-var-delete}
20127 @tab delete the variable object and its children
20128 @item @code{-var-set-format}
20129 @tab set the display format of this variable
20130 @item @code{-var-show-format}
20131 @tab show the display format of this variable
20132 @item @code{-var-info-num-children}
20133 @tab tells how many children this object has
20134 @item @code{-var-list-children}
20135 @tab return a list of the object's children
20136 @item @code{-var-info-type}
20137 @tab show the type of this variable object
20138 @item @code{-var-info-expression}
20139 @tab print what this variable object represents
20140 @item @code{-var-show-attributes}
20141 @tab is this variable editable? does it exist here?
20142 @item @code{-var-evaluate-expression}
20143 @tab get the value of this variable
20144 @item @code{-var-assign}
20145 @tab set the value of this variable
20146 @item @code{-var-update}
20147 @tab update the variable and its children
20150 In the next subsection we describe each operation in detail and suggest
20151 how it can be used.
20153 @subheading Description And Use of Operations on Variable Objects
20155 @subheading The @code{-var-create} Command
20156 @findex -var-create
20158 @subsubheading Synopsis
20161 -var-create @{@var{name} | "-"@}
20162 @{@var{frame-addr} | "*"@} @var{expression}
20165 This operation creates a variable object, which allows the monitoring of
20166 a variable, the result of an expression, a memory cell or a CPU
20169 The @var{name} parameter is the string by which the object can be
20170 referenced. It must be unique. If @samp{-} is specified, the varobj
20171 system will generate a string ``varNNNNNN'' automatically. It will be
20172 unique provided that one does not specify @var{name} on that format.
20173 The command fails if a duplicate name is found.
20175 The frame under which the expression should be evaluated can be
20176 specified by @var{frame-addr}. A @samp{*} indicates that the current
20177 frame should be used.
20179 @var{expression} is any expression valid on the current language set (must not
20180 begin with a @samp{*}), or one of the following:
20184 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
20187 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
20190 @samp{$@var{regname}} --- a CPU register name
20193 @subsubheading Result
20195 This operation returns the name, number of children and the type of the
20196 object created. Type is returned as a string as the ones generated by
20197 the @value{GDBN} CLI:
20200 name="@var{name}",numchild="N",type="@var{type}"
20204 @subheading The @code{-var-delete} Command
20205 @findex -var-delete
20207 @subsubheading Synopsis
20210 -var-delete @var{name}
20213 Deletes a previously created variable object and all of its children.
20215 Returns an error if the object @var{name} is not found.
20218 @subheading The @code{-var-set-format} Command
20219 @findex -var-set-format
20221 @subsubheading Synopsis
20224 -var-set-format @var{name} @var{format-spec}
20227 Sets the output format for the value of the object @var{name} to be
20230 The syntax for the @var{format-spec} is as follows:
20233 @var{format-spec} @expansion{}
20234 @{binary | decimal | hexadecimal | octal | natural@}
20238 @subheading The @code{-var-show-format} Command
20239 @findex -var-show-format
20241 @subsubheading Synopsis
20244 -var-show-format @var{name}
20247 Returns the format used to display the value of the object @var{name}.
20250 @var{format} @expansion{}
20255 @subheading The @code{-var-info-num-children} Command
20256 @findex -var-info-num-children
20258 @subsubheading Synopsis
20261 -var-info-num-children @var{name}
20264 Returns the number of children of a variable object @var{name}:
20271 @subheading The @code{-var-list-children} Command
20272 @findex -var-list-children
20274 @subsubheading Synopsis
20277 -var-list-children [@var{print-values}] @var{name}
20280 Returns a list of the children of the specified variable object. With
20281 just the variable object name as an argument or with an optional
20282 preceding argument of 0 or @code{--no-values}, prints only the names of the
20283 variables. With an optional preceding argument of 1 or @code{--all-values},
20284 also prints their values.
20286 @subsubheading Example
20290 -var-list-children n
20291 numchild=@var{n},children=[@{name=@var{name},
20292 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
20294 -var-list-children --all-values n
20295 numchild=@var{n},children=[@{name=@var{name},
20296 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
20300 @subheading The @code{-var-info-type} Command
20301 @findex -var-info-type
20303 @subsubheading Synopsis
20306 -var-info-type @var{name}
20309 Returns the type of the specified variable @var{name}. The type is
20310 returned as a string in the same format as it is output by the
20314 type=@var{typename}
20318 @subheading The @code{-var-info-expression} Command
20319 @findex -var-info-expression
20321 @subsubheading Synopsis
20324 -var-info-expression @var{name}
20327 Returns what is represented by the variable object @var{name}:
20330 lang=@var{lang-spec},exp=@var{expression}
20334 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
20336 @subheading The @code{-var-show-attributes} Command
20337 @findex -var-show-attributes
20339 @subsubheading Synopsis
20342 -var-show-attributes @var{name}
20345 List attributes of the specified variable object @var{name}:
20348 status=@var{attr} [ ( ,@var{attr} )* ]
20352 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
20354 @subheading The @code{-var-evaluate-expression} Command
20355 @findex -var-evaluate-expression
20357 @subsubheading Synopsis
20360 -var-evaluate-expression @var{name}
20363 Evaluates the expression that is represented by the specified variable
20364 object and returns its value as a string in the current format specified
20371 Note that one must invoke @code{-var-list-children} for a variable
20372 before the value of a child variable can be evaluated.
20374 @subheading The @code{-var-assign} Command
20375 @findex -var-assign
20377 @subsubheading Synopsis
20380 -var-assign @var{name} @var{expression}
20383 Assigns the value of @var{expression} to the variable object specified
20384 by @var{name}. The object must be @samp{editable}. If the variable's
20385 value is altered by the assign, the variable will show up in any
20386 subsequent @code{-var-update} list.
20388 @subsubheading Example
20396 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
20400 @subheading The @code{-var-update} Command
20401 @findex -var-update
20403 @subsubheading Synopsis
20406 -var-update @{@var{name} | "*"@}
20409 Update the value of the variable object @var{name} by evaluating its
20410 expression after fetching all the new values from memory or registers.
20411 A @samp{*} causes all existing variable objects to be updated.
20415 @chapter @value{GDBN} Annotations
20417 This chapter describes annotations in @value{GDBN}. Annotations were
20418 designed to interface @value{GDBN} to graphical user interfaces or other
20419 similar programs which want to interact with @value{GDBN} at a
20420 relatively high level.
20422 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
20426 This is Edition @value{EDITION}, @value{DATE}.
20430 * Annotations Overview:: What annotations are; the general syntax.
20431 * Server Prefix:: Issuing a command without affecting user state.
20432 * Prompting:: Annotations marking @value{GDBN}'s need for input.
20433 * Errors:: Annotations for error messages.
20434 * Invalidation:: Some annotations describe things now invalid.
20435 * Annotations for Running::
20436 Whether the program is running, how it stopped, etc.
20437 * Source Annotations:: Annotations describing source code.
20440 @node Annotations Overview
20441 @section What is an Annotation?
20442 @cindex annotations
20444 Annotations start with a newline character, two @samp{control-z}
20445 characters, and the name of the annotation. If there is no additional
20446 information associated with this annotation, the name of the annotation
20447 is followed immediately by a newline. If there is additional
20448 information, the name of the annotation is followed by a space, the
20449 additional information, and a newline. The additional information
20450 cannot contain newline characters.
20452 Any output not beginning with a newline and two @samp{control-z}
20453 characters denotes literal output from @value{GDBN}. Currently there is
20454 no need for @value{GDBN} to output a newline followed by two
20455 @samp{control-z} characters, but if there was such a need, the
20456 annotations could be extended with an @samp{escape} annotation which
20457 means those three characters as output.
20459 The annotation @var{level}, which is specified using the
20460 @option{--annotate} command line option (@pxref{Mode Options}), controls
20461 how much information @value{GDBN} prints together with its prompt,
20462 values of expressions, source lines, and other types of output. Level 0
20463 is for no anntations, level 1 is for use when @value{GDBN} is run as a
20464 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
20465 for programs that control @value{GDBN}, and level 2 annotations have
20466 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
20467 Interface, annotate, GDB's Obsolete Annotations}).
20470 @kindex set annotate
20471 @item set annotate @var{level}
20472 The @value{GDB} command @code{set annotate} sets the level of
20473 annotations to the specified @var{level}.
20475 @item show annotate
20476 @kindex show annotate
20477 Show the current annotation level.
20480 This chapter describes level 3 annotations.
20482 A simple example of starting up @value{GDBN} with annotations is:
20485 $ @kbd{gdb --annotate=3}
20487 Copyright 2003 Free Software Foundation, Inc.
20488 GDB is free software, covered by the GNU General Public License,
20489 and you are welcome to change it and/or distribute copies of it
20490 under certain conditions.
20491 Type "show copying" to see the conditions.
20492 There is absolutely no warranty for GDB. Type "show warranty"
20494 This GDB was configured as "i386-pc-linux-gnu"
20505 Here @samp{quit} is input to @value{GDBN}; the rest is output from
20506 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
20507 denotes a @samp{control-z} character) are annotations; the rest is
20508 output from @value{GDBN}.
20510 @node Server Prefix
20511 @section The Server Prefix
20512 @cindex server prefix for annotations
20514 To issue a command to @value{GDBN} without affecting certain aspects of
20515 the state which is seen by users, prefix it with @samp{server }. This
20516 means that this command will not affect the command history, nor will it
20517 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
20518 pressed on a line by itself.
20520 The server prefix does not affect the recording of values into the value
20521 history; to print a value without recording it into the value history,
20522 use the @code{output} command instead of the @code{print} command.
20525 @section Annotation for @value{GDBN} Input
20527 @cindex annotations for prompts
20528 When @value{GDBN} prompts for input, it annotates this fact so it is possible
20529 to know when to send output, when the output from a given command is
20532 Different kinds of input each have a different @dfn{input type}. Each
20533 input type has three annotations: a @code{pre-} annotation, which
20534 denotes the beginning of any prompt which is being output, a plain
20535 annotation, which denotes the end of the prompt, and then a @code{post-}
20536 annotation which denotes the end of any echo which may (or may not) be
20537 associated with the input. For example, the @code{prompt} input type
20538 features the following annotations:
20546 The input types are
20551 @findex post-prompt
20553 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
20555 @findex pre-commands
20557 @findex post-commands
20559 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
20560 command. The annotations are repeated for each command which is input.
20562 @findex pre-overload-choice
20563 @findex overload-choice
20564 @findex post-overload-choice
20565 @item overload-choice
20566 When @value{GDBN} wants the user to select between various overloaded functions.
20572 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
20574 @findex pre-prompt-for-continue
20575 @findex prompt-for-continue
20576 @findex post-prompt-for-continue
20577 @item prompt-for-continue
20578 When @value{GDBN} is asking the user to press return to continue. Note: Don't
20579 expect this to work well; instead use @code{set height 0} to disable
20580 prompting. This is because the counting of lines is buggy in the
20581 presence of annotations.
20586 @cindex annotations for errors, warnings and interrupts
20593 This annotation occurs right before @value{GDBN} responds to an interrupt.
20600 This annotation occurs right before @value{GDBN} responds to an error.
20602 Quit and error annotations indicate that any annotations which @value{GDBN} was
20603 in the middle of may end abruptly. For example, if a
20604 @code{value-history-begin} annotation is followed by a @code{error}, one
20605 cannot expect to receive the matching @code{value-history-end}. One
20606 cannot expect not to receive it either, however; an error annotation
20607 does not necessarily mean that @value{GDBN} is immediately returning all the way
20610 @findex error-begin
20611 A quit or error annotation may be preceded by
20617 Any output between that and the quit or error annotation is the error
20620 Warning messages are not yet annotated.
20621 @c If we want to change that, need to fix warning(), type_error(),
20622 @c range_error(), and possibly other places.
20625 @section Invalidation Notices
20627 @cindex annotations for invalidation messages
20628 The following annotations say that certain pieces of state may have
20632 @findex frames-invalid
20633 @item ^Z^Zframes-invalid
20635 The frames (for example, output from the @code{backtrace} command) may
20638 @findex breakpoints-invalid
20639 @item ^Z^Zbreakpoints-invalid
20641 The breakpoints may have changed. For example, the user just added or
20642 deleted a breakpoint.
20645 @node Annotations for Running
20646 @section Running the Program
20647 @cindex annotations for running programs
20651 When the program starts executing due to a @value{GDBN} command such as
20652 @code{step} or @code{continue},
20658 is output. When the program stops,
20664 is output. Before the @code{stopped} annotation, a variety of
20665 annotations describe how the program stopped.
20669 @item ^Z^Zexited @var{exit-status}
20670 The program exited, and @var{exit-status} is the exit status (zero for
20671 successful exit, otherwise nonzero).
20674 @findex signal-name
20675 @findex signal-name-end
20676 @findex signal-string
20677 @findex signal-string-end
20678 @item ^Z^Zsignalled
20679 The program exited with a signal. After the @code{^Z^Zsignalled}, the
20680 annotation continues:
20686 ^Z^Zsignal-name-end
20690 ^Z^Zsignal-string-end
20695 where @var{name} is the name of the signal, such as @code{SIGILL} or
20696 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
20697 as @code{Illegal Instruction} or @code{Segmentation fault}.
20698 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
20699 user's benefit and have no particular format.
20703 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
20704 just saying that the program received the signal, not that it was
20705 terminated with it.
20708 @item ^Z^Zbreakpoint @var{number}
20709 The program hit breakpoint number @var{number}.
20712 @item ^Z^Zwatchpoint @var{number}
20713 The program hit watchpoint number @var{number}.
20716 @node Source Annotations
20717 @section Displaying Source
20718 @cindex annotations for source display
20721 The following annotation is used instead of displaying source code:
20724 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
20727 where @var{filename} is an absolute file name indicating which source
20728 file, @var{line} is the line number within that file (where 1 is the
20729 first line in the file), @var{character} is the character position
20730 within the file (where 0 is the first character in the file) (for most
20731 debug formats this will necessarily point to the beginning of a line),
20732 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
20733 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
20734 @var{addr} is the address in the target program associated with the
20735 source which is being displayed. @var{addr} is in the form @samp{0x}
20736 followed by one or more lowercase hex digits (note that this does not
20737 depend on the language).
20740 @chapter Reporting Bugs in @value{GDBN}
20741 @cindex bugs in @value{GDBN}
20742 @cindex reporting bugs in @value{GDBN}
20744 Your bug reports play an essential role in making @value{GDBN} reliable.
20746 Reporting a bug may help you by bringing a solution to your problem, or it
20747 may not. But in any case the principal function of a bug report is to help
20748 the entire community by making the next version of @value{GDBN} work better. Bug
20749 reports are your contribution to the maintenance of @value{GDBN}.
20751 In order for a bug report to serve its purpose, you must include the
20752 information that enables us to fix the bug.
20755 * Bug Criteria:: Have you found a bug?
20756 * Bug Reporting:: How to report bugs
20760 @section Have you found a bug?
20761 @cindex bug criteria
20763 If you are not sure whether you have found a bug, here are some guidelines:
20766 @cindex fatal signal
20767 @cindex debugger crash
20768 @cindex crash of debugger
20770 If the debugger gets a fatal signal, for any input whatever, that is a
20771 @value{GDBN} bug. Reliable debuggers never crash.
20773 @cindex error on valid input
20775 If @value{GDBN} produces an error message for valid input, that is a
20776 bug. (Note that if you're cross debugging, the problem may also be
20777 somewhere in the connection to the target.)
20779 @cindex invalid input
20781 If @value{GDBN} does not produce an error message for invalid input,
20782 that is a bug. However, you should note that your idea of
20783 ``invalid input'' might be our idea of ``an extension'' or ``support
20784 for traditional practice''.
20787 If you are an experienced user of debugging tools, your suggestions
20788 for improvement of @value{GDBN} are welcome in any case.
20791 @node Bug Reporting
20792 @section How to report bugs
20793 @cindex bug reports
20794 @cindex @value{GDBN} bugs, reporting
20796 A number of companies and individuals offer support for @sc{gnu} products.
20797 If you obtained @value{GDBN} from a support organization, we recommend you
20798 contact that organization first.
20800 You can find contact information for many support companies and
20801 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
20803 @c should add a web page ref...
20805 In any event, we also recommend that you submit bug reports for
20806 @value{GDBN}. The prefered method is to submit them directly using
20807 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
20808 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
20811 @strong{Do not send bug reports to @samp{info-gdb}, or to
20812 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
20813 not want to receive bug reports. Those that do have arranged to receive
20816 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
20817 serves as a repeater. The mailing list and the newsgroup carry exactly
20818 the same messages. Often people think of posting bug reports to the
20819 newsgroup instead of mailing them. This appears to work, but it has one
20820 problem which can be crucial: a newsgroup posting often lacks a mail
20821 path back to the sender. Thus, if we need to ask for more information,
20822 we may be unable to reach you. For this reason, it is better to send
20823 bug reports to the mailing list.
20825 The fundamental principle of reporting bugs usefully is this:
20826 @strong{report all the facts}. If you are not sure whether to state a
20827 fact or leave it out, state it!
20829 Often people omit facts because they think they know what causes the
20830 problem and assume that some details do not matter. Thus, you might
20831 assume that the name of the variable you use in an example does not matter.
20832 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
20833 stray memory reference which happens to fetch from the location where that
20834 name is stored in memory; perhaps, if the name were different, the contents
20835 of that location would fool the debugger into doing the right thing despite
20836 the bug. Play it safe and give a specific, complete example. That is the
20837 easiest thing for you to do, and the most helpful.
20839 Keep in mind that the purpose of a bug report is to enable us to fix the
20840 bug. It may be that the bug has been reported previously, but neither
20841 you nor we can know that unless your bug report is complete and
20844 Sometimes people give a few sketchy facts and ask, ``Does this ring a
20845 bell?'' Those bug reports are useless, and we urge everyone to
20846 @emph{refuse to respond to them} except to chide the sender to report
20849 To enable us to fix the bug, you should include all these things:
20853 The version of @value{GDBN}. @value{GDBN} announces it if you start
20854 with no arguments; you can also print it at any time using @code{show
20857 Without this, we will not know whether there is any point in looking for
20858 the bug in the current version of @value{GDBN}.
20861 The type of machine you are using, and the operating system name and
20865 What compiler (and its version) was used to compile @value{GDBN}---e.g.
20866 ``@value{GCC}--2.8.1''.
20869 What compiler (and its version) was used to compile the program you are
20870 debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
20871 C Compiler''. For GCC, you can say @code{gcc --version} to get this
20872 information; for other compilers, see the documentation for those
20876 The command arguments you gave the compiler to compile your example and
20877 observe the bug. For example, did you use @samp{-O}? To guarantee
20878 you will not omit something important, list them all. A copy of the
20879 Makefile (or the output from make) is sufficient.
20881 If we were to try to guess the arguments, we would probably guess wrong
20882 and then we might not encounter the bug.
20885 A complete input script, and all necessary source files, that will
20889 A description of what behavior you observe that you believe is
20890 incorrect. For example, ``It gets a fatal signal.''
20892 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
20893 will certainly notice it. But if the bug is incorrect output, we might
20894 not notice unless it is glaringly wrong. You might as well not give us
20895 a chance to make a mistake.
20897 Even if the problem you experience is a fatal signal, you should still
20898 say so explicitly. Suppose something strange is going on, such as, your
20899 copy of @value{GDBN} is out of synch, or you have encountered a bug in
20900 the C library on your system. (This has happened!) Your copy might
20901 crash and ours would not. If you told us to expect a crash, then when
20902 ours fails to crash, we would know that the bug was not happening for
20903 us. If you had not told us to expect a crash, then we would not be able
20904 to draw any conclusion from our observations.
20907 @cindex recording a session script
20908 To collect all this information, you can use a session recording program
20909 such as @command{script}, which is available on many Unix systems.
20910 Just run your @value{GDBN} session inside @command{script} and then
20911 include the @file{typescript} file with your bug report.
20913 Another way to record a @value{GDBN} session is to run @value{GDBN}
20914 inside Emacs and then save the entire buffer to a file.
20917 If you wish to suggest changes to the @value{GDBN} source, send us context
20918 diffs. If you even discuss something in the @value{GDBN} source, refer to
20919 it by context, not by line number.
20921 The line numbers in our development sources will not match those in your
20922 sources. Your line numbers would convey no useful information to us.
20926 Here are some things that are not necessary:
20930 A description of the envelope of the bug.
20932 Often people who encounter a bug spend a lot of time investigating
20933 which changes to the input file will make the bug go away and which
20934 changes will not affect it.
20936 This is often time consuming and not very useful, because the way we
20937 will find the bug is by running a single example under the debugger
20938 with breakpoints, not by pure deduction from a series of examples.
20939 We recommend that you save your time for something else.
20941 Of course, if you can find a simpler example to report @emph{instead}
20942 of the original one, that is a convenience for us. Errors in the
20943 output will be easier to spot, running under the debugger will take
20944 less time, and so on.
20946 However, simplification is not vital; if you do not want to do this,
20947 report the bug anyway and send us the entire test case you used.
20950 A patch for the bug.
20952 A patch for the bug does help us if it is a good one. But do not omit
20953 the necessary information, such as the test case, on the assumption that
20954 a patch is all we need. We might see problems with your patch and decide
20955 to fix the problem another way, or we might not understand it at all.
20957 Sometimes with a program as complicated as @value{GDBN} it is very hard to
20958 construct an example that will make the program follow a certain path
20959 through the code. If you do not send us the example, we will not be able
20960 to construct one, so we will not be able to verify that the bug is fixed.
20962 And if we cannot understand what bug you are trying to fix, or why your
20963 patch should be an improvement, we will not install it. A test case will
20964 help us to understand.
20967 A guess about what the bug is or what it depends on.
20969 Such guesses are usually wrong. Even we cannot guess right about such
20970 things without first using the debugger to find the facts.
20973 @c The readline documentation is distributed with the readline code
20974 @c and consists of the two following files:
20976 @c inc-hist.texinfo
20977 @c Use -I with makeinfo to point to the appropriate directory,
20978 @c environment var TEXINPUTS with TeX.
20979 @include rluser.texinfo
20980 @include inc-hist.texinfo
20983 @node Formatting Documentation
20984 @appendix Formatting Documentation
20986 @cindex @value{GDBN} reference card
20987 @cindex reference card
20988 The @value{GDBN} 4 release includes an already-formatted reference card, ready
20989 for printing with PostScript or Ghostscript, in the @file{gdb}
20990 subdirectory of the main source directory@footnote{In
20991 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
20992 release.}. If you can use PostScript or Ghostscript with your printer,
20993 you can print the reference card immediately with @file{refcard.ps}.
20995 The release also includes the source for the reference card. You
20996 can format it, using @TeX{}, by typing:
21002 The @value{GDBN} reference card is designed to print in @dfn{landscape}
21003 mode on US ``letter'' size paper;
21004 that is, on a sheet 11 inches wide by 8.5 inches
21005 high. You will need to specify this form of printing as an option to
21006 your @sc{dvi} output program.
21008 @cindex documentation
21010 All the documentation for @value{GDBN} comes as part of the machine-readable
21011 distribution. The documentation is written in Texinfo format, which is
21012 a documentation system that uses a single source file to produce both
21013 on-line information and a printed manual. You can use one of the Info
21014 formatting commands to create the on-line version of the documentation
21015 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
21017 @value{GDBN} includes an already formatted copy of the on-line Info
21018 version of this manual in the @file{gdb} subdirectory. The main Info
21019 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
21020 subordinate files matching @samp{gdb.info*} in the same directory. If
21021 necessary, you can print out these files, or read them with any editor;
21022 but they are easier to read using the @code{info} subsystem in @sc{gnu}
21023 Emacs or the standalone @code{info} program, available as part of the
21024 @sc{gnu} Texinfo distribution.
21026 If you want to format these Info files yourself, you need one of the
21027 Info formatting programs, such as @code{texinfo-format-buffer} or
21030 If you have @code{makeinfo} installed, and are in the top level
21031 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
21032 version @value{GDBVN}), you can make the Info file by typing:
21039 If you want to typeset and print copies of this manual, you need @TeX{},
21040 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
21041 Texinfo definitions file.
21043 @TeX{} is a typesetting program; it does not print files directly, but
21044 produces output files called @sc{dvi} files. To print a typeset
21045 document, you need a program to print @sc{dvi} files. If your system
21046 has @TeX{} installed, chances are it has such a program. The precise
21047 command to use depends on your system; @kbd{lpr -d} is common; another
21048 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
21049 require a file name without any extension or a @samp{.dvi} extension.
21051 @TeX{} also requires a macro definitions file called
21052 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
21053 written in Texinfo format. On its own, @TeX{} cannot either read or
21054 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
21055 and is located in the @file{gdb-@var{version-number}/texinfo}
21058 If you have @TeX{} and a @sc{dvi} printer program installed, you can
21059 typeset and print this manual. First switch to the the @file{gdb}
21060 subdirectory of the main source directory (for example, to
21061 @file{gdb-@value{GDBVN}/gdb}) and type:
21067 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
21069 @node Installing GDB
21070 @appendix Installing @value{GDBN}
21071 @cindex configuring @value{GDBN}
21072 @cindex installation
21073 @cindex configuring @value{GDBN}, and source tree subdirectories
21075 @value{GDBN} comes with a @code{configure} script that automates the process
21076 of preparing @value{GDBN} for installation; you can then use @code{make} to
21077 build the @code{gdb} program.
21079 @c irrelevant in info file; it's as current as the code it lives with.
21080 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
21081 look at the @file{README} file in the sources; we may have improved the
21082 installation procedures since publishing this manual.}
21085 The @value{GDBN} distribution includes all the source code you need for
21086 @value{GDBN} in a single directory, whose name is usually composed by
21087 appending the version number to @samp{gdb}.
21089 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
21090 @file{gdb-@value{GDBVN}} directory. That directory contains:
21093 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
21094 script for configuring @value{GDBN} and all its supporting libraries
21096 @item gdb-@value{GDBVN}/gdb
21097 the source specific to @value{GDBN} itself
21099 @item gdb-@value{GDBVN}/bfd
21100 source for the Binary File Descriptor library
21102 @item gdb-@value{GDBVN}/include
21103 @sc{gnu} include files
21105 @item gdb-@value{GDBVN}/libiberty
21106 source for the @samp{-liberty} free software library
21108 @item gdb-@value{GDBVN}/opcodes
21109 source for the library of opcode tables and disassemblers
21111 @item gdb-@value{GDBVN}/readline
21112 source for the @sc{gnu} command-line interface
21114 @item gdb-@value{GDBVN}/glob
21115 source for the @sc{gnu} filename pattern-matching subroutine
21117 @item gdb-@value{GDBVN}/mmalloc
21118 source for the @sc{gnu} memory-mapped malloc package
21121 The simplest way to configure and build @value{GDBN} is to run @code{configure}
21122 from the @file{gdb-@var{version-number}} source directory, which in
21123 this example is the @file{gdb-@value{GDBVN}} directory.
21125 First switch to the @file{gdb-@var{version-number}} source directory
21126 if you are not already in it; then run @code{configure}. Pass the
21127 identifier for the platform on which @value{GDBN} will run as an
21133 cd gdb-@value{GDBVN}
21134 ./configure @var{host}
21139 where @var{host} is an identifier such as @samp{sun4} or
21140 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
21141 (You can often leave off @var{host}; @code{configure} tries to guess the
21142 correct value by examining your system.)
21144 Running @samp{configure @var{host}} and then running @code{make} builds the
21145 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
21146 libraries, then @code{gdb} itself. The configured source files, and the
21147 binaries, are left in the corresponding source directories.
21150 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
21151 system does not recognize this automatically when you run a different
21152 shell, you may need to run @code{sh} on it explicitly:
21155 sh configure @var{host}
21158 If you run @code{configure} from a directory that contains source
21159 directories for multiple libraries or programs, such as the
21160 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
21161 creates configuration files for every directory level underneath (unless
21162 you tell it not to, with the @samp{--norecursion} option).
21164 You should run the @code{configure} script from the top directory in the
21165 source tree, the @file{gdb-@var{version-number}} directory. If you run
21166 @code{configure} from one of the subdirectories, you will configure only
21167 that subdirectory. That is usually not what you want. In particular,
21168 if you run the first @code{configure} from the @file{gdb} subdirectory
21169 of the @file{gdb-@var{version-number}} directory, you will omit the
21170 configuration of @file{bfd}, @file{readline}, and other sibling
21171 directories of the @file{gdb} subdirectory. This leads to build errors
21172 about missing include files such as @file{bfd/bfd.h}.
21174 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
21175 However, you should make sure that the shell on your path (named by
21176 the @samp{SHELL} environment variable) is publicly readable. Remember
21177 that @value{GDBN} uses the shell to start your program---some systems refuse to
21178 let @value{GDBN} debug child processes whose programs are not readable.
21181 * Separate Objdir:: Compiling @value{GDBN} in another directory
21182 * Config Names:: Specifying names for hosts and targets
21183 * Configure Options:: Summary of options for configure
21186 @node Separate Objdir
21187 @section Compiling @value{GDBN} in another directory
21189 If you want to run @value{GDBN} versions for several host or target machines,
21190 you need a different @code{gdb} compiled for each combination of
21191 host and target. @code{configure} is designed to make this easy by
21192 allowing you to generate each configuration in a separate subdirectory,
21193 rather than in the source directory. If your @code{make} program
21194 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
21195 @code{make} in each of these directories builds the @code{gdb}
21196 program specified there.
21198 To build @code{gdb} in a separate directory, run @code{configure}
21199 with the @samp{--srcdir} option to specify where to find the source.
21200 (You also need to specify a path to find @code{configure}
21201 itself from your working directory. If the path to @code{configure}
21202 would be the same as the argument to @samp{--srcdir}, you can leave out
21203 the @samp{--srcdir} option; it is assumed.)
21205 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
21206 separate directory for a Sun 4 like this:
21210 cd gdb-@value{GDBVN}
21213 ../gdb-@value{GDBVN}/configure sun4
21218 When @code{configure} builds a configuration using a remote source
21219 directory, it creates a tree for the binaries with the same structure
21220 (and using the same names) as the tree under the source directory. In
21221 the example, you'd find the Sun 4 library @file{libiberty.a} in the
21222 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
21223 @file{gdb-sun4/gdb}.
21225 Make sure that your path to the @file{configure} script has just one
21226 instance of @file{gdb} in it. If your path to @file{configure} looks
21227 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
21228 one subdirectory of @value{GDBN}, not the whole package. This leads to
21229 build errors about missing include files such as @file{bfd/bfd.h}.
21231 One popular reason to build several @value{GDBN} configurations in separate
21232 directories is to configure @value{GDBN} for cross-compiling (where
21233 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
21234 programs that run on another machine---the @dfn{target}).
21235 You specify a cross-debugging target by
21236 giving the @samp{--target=@var{target}} option to @code{configure}.
21238 When you run @code{make} to build a program or library, you must run
21239 it in a configured directory---whatever directory you were in when you
21240 called @code{configure} (or one of its subdirectories).
21242 The @code{Makefile} that @code{configure} generates in each source
21243 directory also runs recursively. If you type @code{make} in a source
21244 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
21245 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
21246 will build all the required libraries, and then build GDB.
21248 When you have multiple hosts or targets configured in separate
21249 directories, you can run @code{make} on them in parallel (for example,
21250 if they are NFS-mounted on each of the hosts); they will not interfere
21254 @section Specifying names for hosts and targets
21256 The specifications used for hosts and targets in the @code{configure}
21257 script are based on a three-part naming scheme, but some short predefined
21258 aliases are also supported. The full naming scheme encodes three pieces
21259 of information in the following pattern:
21262 @var{architecture}-@var{vendor}-@var{os}
21265 For example, you can use the alias @code{sun4} as a @var{host} argument,
21266 or as the value for @var{target} in a @code{--target=@var{target}}
21267 option. The equivalent full name is @samp{sparc-sun-sunos4}.
21269 The @code{configure} script accompanying @value{GDBN} does not provide
21270 any query facility to list all supported host and target names or
21271 aliases. @code{configure} calls the Bourne shell script
21272 @code{config.sub} to map abbreviations to full names; you can read the
21273 script, if you wish, or you can use it to test your guesses on
21274 abbreviations---for example:
21277 % sh config.sub i386-linux
21279 % sh config.sub alpha-linux
21280 alpha-unknown-linux-gnu
21281 % sh config.sub hp9k700
21283 % sh config.sub sun4
21284 sparc-sun-sunos4.1.1
21285 % sh config.sub sun3
21286 m68k-sun-sunos4.1.1
21287 % sh config.sub i986v
21288 Invalid configuration `i986v': machine `i986v' not recognized
21292 @code{config.sub} is also distributed in the @value{GDBN} source
21293 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
21295 @node Configure Options
21296 @section @code{configure} options
21298 Here is a summary of the @code{configure} options and arguments that
21299 are most often useful for building @value{GDBN}. @code{configure} also has
21300 several other options not listed here. @inforef{What Configure
21301 Does,,configure.info}, for a full explanation of @code{configure}.
21304 configure @r{[}--help@r{]}
21305 @r{[}--prefix=@var{dir}@r{]}
21306 @r{[}--exec-prefix=@var{dir}@r{]}
21307 @r{[}--srcdir=@var{dirname}@r{]}
21308 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
21309 @r{[}--target=@var{target}@r{]}
21314 You may introduce options with a single @samp{-} rather than
21315 @samp{--} if you prefer; but you may abbreviate option names if you use
21320 Display a quick summary of how to invoke @code{configure}.
21322 @item --prefix=@var{dir}
21323 Configure the source to install programs and files under directory
21326 @item --exec-prefix=@var{dir}
21327 Configure the source to install programs under directory
21330 @c avoid splitting the warning from the explanation:
21332 @item --srcdir=@var{dirname}
21333 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
21334 @code{make} that implements the @code{VPATH} feature.}@*
21335 Use this option to make configurations in directories separate from the
21336 @value{GDBN} source directories. Among other things, you can use this to
21337 build (or maintain) several configurations simultaneously, in separate
21338 directories. @code{configure} writes configuration specific files in
21339 the current directory, but arranges for them to use the source in the
21340 directory @var{dirname}. @code{configure} creates directories under
21341 the working directory in parallel to the source directories below
21344 @item --norecursion
21345 Configure only the directory level where @code{configure} is executed; do not
21346 propagate configuration to subdirectories.
21348 @item --target=@var{target}
21349 Configure @value{GDBN} for cross-debugging programs running on the specified
21350 @var{target}. Without this option, @value{GDBN} is configured to debug
21351 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
21353 There is no convenient way to generate a list of all available targets.
21355 @item @var{host} @dots{}
21356 Configure @value{GDBN} to run on the specified @var{host}.
21358 There is no convenient way to generate a list of all available hosts.
21361 There are many other options available as well, but they are generally
21362 needed for special purposes only.
21364 @node Maintenance Commands
21365 @appendix Maintenance Commands
21366 @cindex maintenance commands
21367 @cindex internal commands
21369 In addition to commands intended for @value{GDBN} users, @value{GDBN}
21370 includes a number of commands intended for @value{GDBN} developers,
21371 that are not documented elsewhere in this manual. These commands are
21372 provided here for reference. (For commands that turn on debugging
21373 messages, see @ref{Debugging Output}.)
21376 @kindex maint agent
21377 @item maint agent @var{expression}
21378 Translate the given @var{expression} into remote agent bytecodes.
21379 This command is useful for debugging the Agent Expression mechanism
21380 (@pxref{Agent Expressions}).
21382 @kindex maint info breakpoints
21383 @item @anchor{maint info breakpoints}maint info breakpoints
21384 Using the same format as @samp{info breakpoints}, display both the
21385 breakpoints you've set explicitly, and those @value{GDBN} is using for
21386 internal purposes. Internal breakpoints are shown with negative
21387 breakpoint numbers. The type column identifies what kind of breakpoint
21392 Normal, explicitly set breakpoint.
21395 Normal, explicitly set watchpoint.
21398 Internal breakpoint, used to handle correctly stepping through
21399 @code{longjmp} calls.
21401 @item longjmp resume
21402 Internal breakpoint at the target of a @code{longjmp}.
21405 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
21408 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
21411 Shared library events.
21415 @kindex maint check-symtabs
21416 @item maint check-symtabs
21417 Check the consistency of psymtabs and symtabs.
21419 @kindex maint cplus first_component
21420 @item maint cplus first_component @var{name}
21421 Print the first C@t{++} class/namespace component of @var{name}.
21423 @kindex maint cplus namespace
21424 @item maint cplus namespace
21425 Print the list of possible C@t{++} namespaces.
21427 @kindex maint demangle
21428 @item maint demangle @var{name}
21429 Demangle a C@t{++} or Objective-C manled @var{name}.
21431 @kindex maint deprecate
21432 @kindex maint undeprecate
21433 @cindex deprecated commands
21434 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
21435 @itemx maint undeprecate @var{command}
21436 Deprecate or undeprecate the named @var{command}. Deprecated commands
21437 cause @value{GDBN} to issue a warning when you use them. The optional
21438 argument @var{replacement} says which newer command should be used in
21439 favor of the deprecated one; if it is given, @value{GDBN} will mention
21440 the replacement as part of the warning.
21442 @kindex maint dump-me
21443 @item maint dump-me
21444 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
21445 Cause a fatal signal in the debugger and force it to dump its core.
21446 This is supported only on systems which support aborting a program
21447 with the @code{SIGQUIT} signal.
21449 @kindex maint internal-error
21450 @kindex maint internal-warning
21451 @item maint internal-error @r{[}@var{message-text}@r{]}
21452 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
21453 Cause @value{GDBN} to call the internal function @code{internal_error}
21454 or @code{internal_warning} and hence behave as though an internal error
21455 or internal warning has been detected. In addition to reporting the
21456 internal problem, these functions give the user the opportunity to
21457 either quit @value{GDBN} or create a core file of the current
21458 @value{GDBN} session.
21460 These commands take an optional parameter @var{message-text} that is
21461 used as the text of the error or warning message.
21463 Here's an example of using @code{indernal-error}:
21466 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
21467 @dots{}/maint.c:121: internal-error: testing, 1, 2
21468 A problem internal to GDB has been detected. Further
21469 debugging may prove unreliable.
21470 Quit this debugging session? (y or n) @kbd{n}
21471 Create a core file? (y or n) @kbd{n}
21475 @kindex maint packet
21476 @item maint packet @var{text}
21477 If @value{GDBN} is talking to an inferior via the serial protocol,
21478 then this command sends the string @var{text} to the inferior, and
21479 displays the response packet. @value{GDBN} supplies the initial
21480 @samp{$} character, the terminating @samp{#} character, and the
21483 @kindex maint print architecture
21484 @item maint print architecture @r{[}@var{file}@r{]}
21485 Print the entire architecture configuration. The optional argument
21486 @var{file} names the file where the output goes.
21488 @kindex maint print dummy-frames
21489 @item maint print dummy-frames
21490 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
21493 (@value{GDBP}) @kbd{b add}
21495 (@value{GDBP}) @kbd{print add(2,3)}
21496 Breakpoint 2, add (a=2, b=3) at @dots{}
21498 The program being debugged stopped while in a function called from GDB.
21500 (@value{GDBP}) @kbd{maint print dummy-frames}
21501 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
21502 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
21503 call_lo=0x01014000 call_hi=0x01014001
21507 Takes an optional file parameter.
21509 @kindex maint print registers
21510 @kindex maint print raw-registers
21511 @kindex maint print cooked-registers
21512 @kindex maint print register-groups
21513 @item maint print registers @r{[}@var{file}@r{]}
21514 @itemx maint print raw-registers @r{[}@var{file}@r{]}
21515 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
21516 @itemx maint print register-groups @r{[}@var{file}@r{]}
21517 Print @value{GDBN}'s internal register data structures.
21519 The command @code{maint print raw-registers} includes the contents of
21520 the raw register cache; the command @code{maint print cooked-registers}
21521 includes the (cooked) value of all registers; and the command
21522 @code{maint print register-groups} includes the groups that each
21523 register is a member of. @xref{Registers,, Registers, gdbint,
21524 @value{GDBN} Internals}.
21526 These commands take an optional parameter, a file name to which to
21527 write the information.
21529 @kindex maint print reggroups
21530 @item maint print reggroups @r{[}@var{file}@r{]}
21531 Print @value{GDBN}'s internal register group data structures. The
21532 optional argument @var{file} tells to what file to write the
21535 The register groups info looks like this:
21538 (@value{GDBP}) @kbd{maint print reggroups}
21551 This command forces @value{GDBN} to flush its internal register cache.
21553 @kindex maint print objfiles
21554 @cindex info for known object files
21555 @item maint print objfiles
21556 Print a dump of all known object files. For each object file, this
21557 command prints its name, address in memory, and all of its psymtabs
21560 @kindex maint print statistics
21561 @cindex bcache statistics
21562 @item maint print statistics
21563 This command prints, for each object file in the program, various data
21564 about that object file followed by the byte cache (@dfn{bcache})
21565 statistics for the object file. The objfile data includes the number
21566 of minimal, partical, full, and stabs symbols, the number of types
21567 defined by the objfile, the number of as yet unexpanded psym tables,
21568 the number of line tables and string tables, and the amount of memory
21569 used by the various tables. The bcache statistics include the counts,
21570 sizes, and counts of duplicates of all and unique objects, max,
21571 average, and median entry size, total memory used and its overhead and
21572 savings, and various measures of the hash table size and chain
21575 @kindex maint print type
21576 @cindex type chain of a data type
21577 @item maint print type @var{expr}
21578 Print the type chain for a type specified by @var{expr}. The argument
21579 can be either a type name or a symbol. If it is a symbol, the type of
21580 that symbol is described. The type chain produced by this command is
21581 a recursive definition of the data type as stored in @value{GDBN}'s
21582 data structures, including its flags and contained types.
21584 @kindex maint set dwarf2 max-cache-age
21585 @kindex maint show dwarf2 max-cache-age
21586 @item maint set dwarf2 max-cache-age
21587 @itemx maint show dwarf2 max-cache-age
21588 Control the DWARF 2 compilation unit cache.
21590 @cindex DWARF 2 compilation units cache
21591 In object files with inter-compilation-unit references, such as those
21592 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
21593 reader needs to frequently refer to previously read compilation units.
21594 This setting controls how long a compilation unit will remain in the
21595 cache if it is not referenced. A higher limit means that cached
21596 compilation units will be stored in memory longer, and more total
21597 memory will be used. Setting it to zero disables caching, which will
21598 slow down @value{GDBN} startup, but reduce memory consumption.
21600 @kindex maint set profile
21601 @kindex maint show profile
21602 @cindex profiling GDB
21603 @item maint set profile
21604 @itemx maint show profile
21605 Control profiling of @value{GDBN}.
21607 Profiling will be disabled until you use the @samp{maint set profile}
21608 command to enable it. When you enable profiling, the system will begin
21609 collecting timing and execution count data; when you disable profiling or
21610 exit @value{GDBN}, the results will be written to a log file. Remember that
21611 if you use profiling, @value{GDBN} will overwrite the profiling log file
21612 (often called @file{gmon.out}). If you have a record of important profiling
21613 data in a @file{gmon.out} file, be sure to move it to a safe location.
21615 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
21616 compiled with the @samp{-pg} compiler option.
21618 @kindex maint show-debug-regs
21619 @cindex x86 hardware debug registers
21620 @item maint show-debug-regs
21621 Control whether to show variables that mirror the x86 hardware debug
21622 registers. Use @code{ON} to enable, @code{OFF} to disable. If
21623 enabled, the debug registers values are shown when GDB inserts or
21624 removes a hardware breakpoint or watchpoint, and when the inferior
21625 triggers a hardware-assisted breakpoint or watchpoint.
21627 @kindex maint space
21628 @cindex memory used by commands
21630 Control whether to display memory usage for each command. If set to a
21631 nonzero value, @value{GDBN} will display how much memory each command
21632 took, following the command's own output. This can also be requested
21633 by invoking @value{GDBN} with the @option{--statistics} command-line
21634 switch (@pxref{Mode Options}).
21637 @cindex time of command execution
21639 Control whether to display the execution time for each command. If
21640 set to a nonzero value, @value{GDBN} will display how much time it
21641 took to execute each command, following the command's own output.
21642 This can also be requested by invoking @value{GDBN} with the
21643 @option{--statistics} command-line switch (@pxref{Mode Options}).
21645 @kindex maint translate-address
21646 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
21647 Find the symbol stored at the location specified by the address
21648 @var{addr} and an optional section name @var{section}. If found,
21649 @value{GDBN} prints the name of the closest symbol and an offset from
21650 the symbol's location to the specified address. This is similar to
21651 the @code{info address} command (@pxref{Symbols}), except that this
21652 command also allows to find symbols in other sections.
21656 The following command is useful for non-interactive invocations of
21657 @value{GDBN}, such as in the test suite.
21660 @item set watchdog @var{nsec}
21661 @kindex set watchdog
21662 @cindex watchdog timer
21663 @cindex timeout for commands
21664 Set the maximum number of seconds @value{GDBN} will wait for the
21665 target operation to finish. If this time expires, @value{GDBN}
21666 reports and error and the command is aborted.
21668 @item show watchdog
21669 Show the current setting of the target wait timeout.
21672 @node Remote Protocol
21673 @appendix @value{GDBN} Remote Serial Protocol
21678 * Stop Reply Packets::
21679 * General Query Packets::
21680 * Register Packet Format::
21682 * File-I/O remote protocol extension::
21688 There may be occasions when you need to know something about the
21689 protocol---for example, if there is only one serial port to your target
21690 machine, you might want your program to do something special if it
21691 recognizes a packet meant for @value{GDBN}.
21693 In the examples below, @samp{->} and @samp{<-} are used to indicate
21694 transmitted and received data respectfully.
21696 @cindex protocol, @value{GDBN} remote serial
21697 @cindex serial protocol, @value{GDBN} remote
21698 @cindex remote serial protocol
21699 All @value{GDBN} commands and responses (other than acknowledgments) are
21700 sent as a @var{packet}. A @var{packet} is introduced with the character
21701 @samp{$}, the actual @var{packet-data}, and the terminating character
21702 @samp{#} followed by a two-digit @var{checksum}:
21705 @code{$}@var{packet-data}@code{#}@var{checksum}
21709 @cindex checksum, for @value{GDBN} remote
21711 The two-digit @var{checksum} is computed as the modulo 256 sum of all
21712 characters between the leading @samp{$} and the trailing @samp{#} (an
21713 eight bit unsigned checksum).
21715 Implementors should note that prior to @value{GDBN} 5.0 the protocol
21716 specification also included an optional two-digit @var{sequence-id}:
21719 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
21722 @cindex sequence-id, for @value{GDBN} remote
21724 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
21725 has never output @var{sequence-id}s. Stubs that handle packets added
21726 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
21728 @cindex acknowledgment, for @value{GDBN} remote
21729 When either the host or the target machine receives a packet, the first
21730 response expected is an acknowledgment: either @samp{+} (to indicate
21731 the package was received correctly) or @samp{-} (to request
21735 -> @code{$}@var{packet-data}@code{#}@var{checksum}
21740 The host (@value{GDBN}) sends @var{command}s, and the target (the
21741 debugging stub incorporated in your program) sends a @var{response}. In
21742 the case of step and continue @var{command}s, the response is only sent
21743 when the operation has completed (the target has again stopped).
21745 @var{packet-data} consists of a sequence of characters with the
21746 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
21749 Fields within the packet should be separated using @samp{,} @samp{;} or
21750 @cindex remote protocol, field separator
21751 @samp{:}. Except where otherwise noted all numbers are represented in
21752 @sc{hex} with leading zeros suppressed.
21754 Implementors should note that prior to @value{GDBN} 5.0, the character
21755 @samp{:} could not appear as the third character in a packet (as it
21756 would potentially conflict with the @var{sequence-id}).
21758 Response @var{data} can be run-length encoded to save space. A @samp{*}
21759 means that the next character is an @sc{ascii} encoding giving a repeat count
21760 which stands for that many repetitions of the character preceding the
21761 @samp{*}. The encoding is @code{n+29}, yielding a printable character
21762 where @code{n >=3} (which is where rle starts to win). The printable
21763 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
21764 value greater than 126 should not be used.
21771 means the same as "0000".
21773 The error response returned for some packets includes a two character
21774 error number. That number is not well defined.
21776 For any @var{command} not supported by the stub, an empty response
21777 (@samp{$#00}) should be returned. That way it is possible to extend the
21778 protocol. A newer @value{GDBN} can tell if a packet is supported based
21781 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
21782 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
21788 The following table provides a complete list of all currently defined
21789 @var{command}s and their corresponding response @var{data}.
21790 @xref{File-I/O remote protocol extension}, for details about the File
21791 I/O extension of the remote protocol.
21795 @item @code{!} --- extended mode
21796 @cindex @code{!} packet
21798 Enable extended mode. In extended mode, the remote server is made
21799 persistent. The @samp{R} packet is used to restart the program being
21805 The remote target both supports and has enabled extended mode.
21808 @item @code{?} --- last signal
21809 @cindex @code{?} packet
21811 Indicate the reason the target halted. The reply is the same as for
21815 @xref{Stop Reply Packets}, for the reply specifications.
21817 @item @code{a} --- reserved
21819 Reserved for future use.
21821 @item @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,@dots{}} --- set program arguments @strong{(reserved)}
21822 @cindex @code{A} packet
21824 Initialized @samp{argv[]} array passed into program. @var{arglen}
21825 specifies the number of bytes in the hex encoded byte stream @var{arg}.
21826 See @code{gdbserver} for more details.
21834 @item @code{b}@var{baud} --- set baud @strong{(deprecated)}
21835 @cindex @code{b} packet
21837 Change the serial line speed to @var{baud}.
21839 JTC: @emph{When does the transport layer state change? When it's
21840 received, or after the ACK is transmitted. In either case, there are
21841 problems if the command or the acknowledgment packet is dropped.}
21843 Stan: @emph{If people really wanted to add something like this, and get
21844 it working for the first time, they ought to modify ser-unix.c to send
21845 some kind of out-of-band message to a specially-setup stub and have the
21846 switch happen "in between" packets, so that from remote protocol's point
21847 of view, nothing actually happened.}
21849 @item @code{B}@var{addr},@var{mode} --- set breakpoint @strong{(deprecated)}
21850 @cindex @code{B} packet
21852 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
21853 breakpoint at @var{addr}.
21855 This packet has been replaced by the @samp{Z} and @samp{z} packets
21856 (@pxref{insert breakpoint or watchpoint packet}).
21858 @item @code{c}@var{addr} --- continue
21859 @cindex @code{c} packet
21861 @var{addr} is address to resume. If @var{addr} is omitted, resume at
21865 @xref{Stop Reply Packets}, for the reply specifications.
21867 @item @code{C}@var{sig}@code{;}@var{addr} --- continue with signal
21868 @cindex @code{C} packet
21870 Continue with signal @var{sig} (hex signal number). If
21871 @code{;}@var{addr} is omitted, resume at same address.
21874 @xref{Stop Reply Packets}, for the reply specifications.
21876 @item @code{d} --- toggle debug @strong{(deprecated)}
21877 @cindex @code{d} packet
21881 @item @code{D} --- detach
21882 @cindex @code{D} packet
21884 Detach @value{GDBN} from the remote system. Sent to the remote target
21885 before @value{GDBN} disconnects via the @code{detach} command.
21889 @item @emph{no response}
21890 @value{GDBN} does not check for any response after sending this packet.
21893 @item @code{e} --- reserved
21895 Reserved for future use.
21897 @item @code{E} --- reserved
21899 Reserved for future use.
21901 @item @code{f} --- reserved
21903 Reserved for future use.
21905 @item @code{F}@var{RC}@code{,}@var{EE}@code{,}@var{CF}@code{;}@var{XX} --- Reply to target's F packet.
21906 @cindex @code{F} packet
21908 This packet is send by @value{GDBN} as reply to a @code{F} request packet
21909 sent by the target. This is part of the File-I/O protocol extension.
21910 @xref{File-I/O remote protocol extension}, for the specification.
21912 @item @code{g} --- read registers
21913 @anchor{read registers packet}
21914 @cindex @code{g} packet
21916 Read general registers.
21920 @item @var{XX@dots{}}
21921 Each byte of register data is described by two hex digits. The bytes
21922 with the register are transmitted in target byte order. The size of
21923 each register and their position within the @samp{g} @var{packet} are
21924 determined by the @value{GDBN} internal macros
21925 @var{DEPRECATED_REGISTER_RAW_SIZE} and @var{REGISTER_NAME} macros. The
21926 specification of several standard @code{g} packets is specified below.
21931 @item @code{G}@var{XX@dots{}} --- write regs
21932 @cindex @code{G} packet
21934 @xref{read registers packet}, for a description of the @var{XX@dots{}}
21945 @item @code{h} --- reserved
21947 Reserved for future use.
21949 @item @code{H}@var{c}@var{t@dots{}} --- set thread
21950 @cindex @code{H} packet
21952 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
21953 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
21954 should be @samp{c} for step and continue operations, @samp{g} for other
21955 operations. The thread designator @var{t@dots{}} may be -1, meaning all
21956 the threads, a thread number, or zero which means pick any thread.
21967 @c 'H': How restrictive (or permissive) is the thread model. If a
21968 @c thread is selected and stopped, are other threads allowed
21969 @c to continue to execute? As I mentioned above, I think the
21970 @c semantics of each command when a thread is selected must be
21971 @c described. For example:
21973 @c 'g': If the stub supports threads and a specific thread is
21974 @c selected, returns the register block from that thread;
21975 @c otherwise returns current registers.
21977 @c 'G' If the stub supports threads and a specific thread is
21978 @c selected, sets the registers of the register block of
21979 @c that thread; otherwise sets current registers.
21981 @item @code{i}@var{addr}@code{,}@var{nnn} --- cycle step @strong{(draft)}
21982 @anchor{cycle step packet}
21983 @cindex @code{i} packet
21985 Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
21986 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
21987 step starting at that address.
21989 @item @code{I} --- signal then cycle step @strong{(reserved)}
21990 @cindex @code{I} packet
21992 @xref{step with signal packet}. @xref{cycle step packet}.
21994 @item @code{j} --- reserved
21996 Reserved for future use.
21998 @item @code{J} --- reserved
22000 Reserved for future use.
22002 @item @code{k} --- kill request
22003 @cindex @code{k} packet
22005 FIXME: @emph{There is no description of how to operate when a specific
22006 thread context has been selected (i.e.@: does 'k' kill only that
22009 @item @code{K} --- reserved
22011 Reserved for future use.
22013 @item @code{l} --- reserved
22015 Reserved for future use.
22017 @item @code{L} --- reserved
22019 Reserved for future use.
22021 @item @code{m}@var{addr}@code{,}@var{length} --- read memory
22022 @cindex @code{m} packet
22024 Read @var{length} bytes of memory starting at address @var{addr}.
22025 Neither @value{GDBN} nor the stub assume that sized memory transfers are
22026 assumed using word aligned accesses. FIXME: @emph{A word aligned memory
22027 transfer mechanism is needed.}
22031 @item @var{XX@dots{}}
22032 @var{XX@dots{}} is mem contents. Can be fewer bytes than requested if able
22033 to read only part of the data. Neither @value{GDBN} nor the stub assume
22034 that sized memory transfers are assumed using word aligned
22035 accesses. FIXME: @emph{A word aligned memory transfer mechanism is
22041 @item @code{M}@var{addr},@var{length}@code{:}@var{XX@dots{}} --- write mem
22042 @cindex @code{M} packet
22044 Write @var{length} bytes of memory starting at address @var{addr}.
22045 @var{XX@dots{}} is the data.
22052 for an error (this includes the case where only part of the data was
22056 @item @code{n} --- reserved
22058 Reserved for future use.
22060 @item @code{N} --- reserved
22062 Reserved for future use.
22064 @item @code{o} --- reserved
22066 Reserved for future use.
22068 @item @code{O} --- reserved
22070 @item @code{p}@var{hex number of register} --- read register packet
22071 @cindex @code{p} packet
22073 @xref{read registers packet}, for a description of how the returned
22074 register value is encoded.
22078 @item @var{XX@dots{}}
22079 the register's value
22083 Indicating an unrecognized @var{query}.
22086 @item @code{P}@var{n@dots{}}@code{=}@var{r@dots{}} --- write register
22087 @anchor{write register packet}
22088 @cindex @code{P} packet
22090 Write register @var{n@dots{}} with value @var{r@dots{}}, which contains two hex
22091 digits for each byte in the register (target byte order).
22101 @item @code{q}@var{query} --- general query
22102 @anchor{general query packet}
22103 @cindex @code{q} packet
22105 Request info about @var{query}. In general @value{GDBN} queries have a
22106 leading upper case letter. Custom vendor queries should use a company
22107 prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may optionally
22108 be followed by a @samp{,} or @samp{;} separated list. Stubs must ensure
22109 that they match the full @var{query} name.
22113 @item @var{XX@dots{}}
22114 Hex encoded data from query. The reply can not be empty.
22118 Indicating an unrecognized @var{query}.
22121 @item @code{Q}@var{var}@code{=}@var{val} --- general set
22122 @cindex @code{Q} packet
22124 Set value of @var{var} to @var{val}.
22126 @xref{general query packet}, for a discussion of naming conventions.
22128 @item @code{r} --- reset @strong{(deprecated)}
22129 @cindex @code{r} packet
22131 Reset the entire system.
22133 @item @code{R}@var{XX} --- remote restart
22134 @cindex @code{R} packet
22136 Restart the program being debugged. @var{XX}, while needed, is ignored.
22137 This packet is only available in extended mode.
22141 @item @emph{no reply}
22142 The @samp{R} packet has no reply.
22145 @item @code{s}@var{addr} --- step
22146 @cindex @code{s} packet
22148 @var{addr} is address to resume. If @var{addr} is omitted, resume at
22152 @xref{Stop Reply Packets}, for the reply specifications.
22154 @item @code{S}@var{sig}@code{;}@var{addr} --- step with signal
22155 @anchor{step with signal packet}
22156 @cindex @code{S} packet
22158 Like @samp{C} but step not continue.
22161 @xref{Stop Reply Packets}, for the reply specifications.
22163 @item @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} --- search
22164 @cindex @code{t} packet
22166 Search backwards starting at address @var{addr} for a match with pattern
22167 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
22168 @var{addr} must be at least 3 digits.
22170 @item @code{T}@var{XX} --- thread alive
22171 @cindex @code{T} packet
22173 Find out if the thread XX is alive.
22178 thread is still alive
22183 @item @code{u} --- reserved
22185 Reserved for future use.
22187 @item @code{U} --- reserved
22189 Reserved for future use.
22191 @item @code{v} --- verbose packet prefix
22193 Packets starting with @code{v} are identified by a multi-letter name,
22194 up to the first @code{;} or @code{?} (or the end of the packet).
22196 @item @code{vCont}[;@var{action}[@code{:}@var{tid}]]... --- extended resume
22197 @cindex @code{vCont} packet
22199 Resume the inferior. Different actions may be specified for each thread.
22200 If an action is specified with no @var{tid}, then it is applied to any
22201 threads that don't have a specific action specified; if no default action is
22202 specified then other threads should remain stopped. Specifying multiple
22203 default actions is an error; specifying no actions is also an error.
22204 Thread IDs are specified in hexadecimal. Currently supported actions are:
22210 Continue with signal @var{sig}. @var{sig} should be two hex digits.
22214 Step with signal @var{sig}. @var{sig} should be two hex digits.
22217 The optional @var{addr} argument normally associated with these packets is
22218 not supported in @code{vCont}.
22221 @xref{Stop Reply Packets}, for the reply specifications.
22223 @item @code{vCont?} --- extended resume query
22224 @cindex @code{vCont?} packet
22226 Query support for the @code{vCont} packet.
22230 @item @code{vCont}[;@var{action}]...
22231 The @code{vCont} packet is supported. Each @var{action} is a supported
22232 command in the @code{vCont} packet.
22234 The @code{vCont} packet is not supported.
22237 @item @code{V} --- reserved
22239 Reserved for future use.
22241 @item @code{w} --- reserved
22243 Reserved for future use.
22245 @item @code{W} --- reserved
22247 Reserved for future use.
22249 @item @code{x} --- reserved
22251 Reserved for future use.
22253 @item @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX@dots{}} --- write mem (binary)
22254 @cindex @code{X} packet
22256 @var{addr} is address, @var{length} is number of bytes, @var{XX@dots{}}
22257 is binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
22258 escaped using @code{0x7d}, and then XORed with @code{0x20}.
22259 For example, @code{0x7d} would be transmitted as @code{0x7d 0x5d}.
22269 @item @code{y} --- reserved
22271 Reserved for future use.
22273 @item @code{Y} reserved
22275 Reserved for future use.
22277 @item @code{z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- remove breakpoint or watchpoint @strong{(draft)}
22278 @itemx @code{Z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- insert breakpoint or watchpoint @strong{(draft)}
22279 @anchor{insert breakpoint or watchpoint packet}
22280 @cindex @code{z} packet
22281 @cindex @code{Z} packets
22283 Insert (@code{Z}) or remove (@code{z}) a @var{type} breakpoint or
22284 watchpoint starting at address @var{address} and covering the next
22285 @var{length} bytes.
22287 Each breakpoint and watchpoint packet @var{type} is documented
22290 @emph{Implementation notes: A remote target shall return an empty string
22291 for an unrecognized breakpoint or watchpoint packet @var{type}. A
22292 remote target shall support either both or neither of a given
22293 @code{Z}@var{type}@dots{} and @code{z}@var{type}@dots{} packet pair. To
22294 avoid potential problems with duplicate packets, the operations should
22295 be implemented in an idempotent way.}
22297 @item @code{z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- remove memory breakpoint @strong{(draft)}
22298 @item @code{Z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- insert memory breakpoint @strong{(draft)}
22299 @cindex @code{z0} packet
22300 @cindex @code{Z0} packet
22302 Insert (@code{Z0}) or remove (@code{z0}) a memory breakpoint at address
22303 @code{addr} of size @code{length}.
22305 A memory breakpoint is implemented by replacing the instruction at
22306 @var{addr} with a software breakpoint or trap instruction. The
22307 @code{length} is used by targets that indicates the size of the
22308 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
22309 @sc{mips} can insert either a 2 or 4 byte breakpoint).
22311 @emph{Implementation note: It is possible for a target to copy or move
22312 code that contains memory breakpoints (e.g., when implementing
22313 overlays). The behavior of this packet, in the presence of such a
22314 target, is not defined.}
22326 @item @code{z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- remove hardware breakpoint @strong{(draft)}
22327 @item @code{Z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- insert hardware breakpoint @strong{(draft)}
22328 @cindex @code{z1} packet
22329 @cindex @code{Z1} packet
22331 Insert (@code{Z1}) or remove (@code{z1}) a hardware breakpoint at
22332 address @code{addr} of size @code{length}.
22334 A hardware breakpoint is implemented using a mechanism that is not
22335 dependant on being able to modify the target's memory.
22337 @emph{Implementation note: A hardware breakpoint is not affected by code
22350 @item @code{z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- remove write watchpoint @strong{(draft)}
22351 @item @code{Z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- insert write watchpoint @strong{(draft)}
22352 @cindex @code{z2} packet
22353 @cindex @code{Z2} packet
22355 Insert (@code{Z2}) or remove (@code{z2}) a write watchpoint.
22367 @item @code{z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- remove read watchpoint @strong{(draft)}
22368 @item @code{Z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- insert read watchpoint @strong{(draft)}
22369 @cindex @code{z3} packet
22370 @cindex @code{Z3} packet
22372 Insert (@code{Z3}) or remove (@code{z3}) a read watchpoint.
22384 @item @code{z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- remove access watchpoint @strong{(draft)}
22385 @item @code{Z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- insert access watchpoint @strong{(draft)}
22386 @cindex @code{z4} packet
22387 @cindex @code{Z4} packet
22389 Insert (@code{Z4}) or remove (@code{z4}) an access watchpoint.
22403 @node Stop Reply Packets
22404 @section Stop Reply Packets
22405 @cindex stop reply packets
22407 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
22408 receive any of the below as a reply. In the case of the @samp{C},
22409 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
22410 when the target halts. In the below the exact meaning of @samp{signal
22411 number} is poorly defined. In general one of the UNIX signal numbering
22412 conventions is used.
22417 @var{AA} is the signal number
22419 @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
22420 @cindex @code{T} packet reply
22422 @var{AA} = two hex digit signal number; @var{n...} = register number
22423 (hex), @var{r...} = target byte ordered register contents, size defined
22424 by @code{DEPRECATED_REGISTER_RAW_SIZE}; @var{n...} = @samp{thread},
22425 @var{r...} = thread process ID, this is a hex integer; @var{n...} =
22426 (@samp{watch} | @samp{rwatch} | @samp{awatch}, @var{r...} = data
22427 address, this is a hex integer; @var{n...} = other string not starting
22428 with valid hex digit. @value{GDBN} should ignore this @var{n...},
22429 @var{r...} pair and go on to the next. This way we can extend the
22434 The process exited, and @var{AA} is the exit status. This is only
22435 applicable to certain targets.
22439 The process terminated with signal @var{AA}.
22441 @item O@var{XX@dots{}}
22443 @var{XX@dots{}} is hex encoding of @sc{ascii} data. This can happen at
22444 any time while the program is running and the debugger should continue
22445 to wait for @samp{W}, @samp{T}, etc.
22447 @item F@var{call-id}@code{,}@var{parameter@dots{}}
22449 @var{call-id} is the identifier which says which host system call should
22450 be called. This is just the name of the function. Translation into the
22451 correct system call is only applicable as it's defined in @value{GDBN}.
22452 @xref{File-I/O remote protocol extension}, for a list of implemented
22455 @var{parameter@dots{}} is a list of parameters as defined for this very
22458 The target replies with this packet when it expects @value{GDBN} to call
22459 a host system call on behalf of the target. @value{GDBN} replies with
22460 an appropriate @code{F} packet and keeps up waiting for the next reply
22461 packet from the target. The latest @samp{C}, @samp{c}, @samp{S} or
22462 @samp{s} action is expected to be continued.
22463 @xref{File-I/O remote protocol extension}, for more details.
22467 @node General Query Packets
22468 @section General Query Packets
22469 @cindex remote query requests
22471 The following set and query packets have already been defined.
22475 @item @code{q}@code{C} --- current thread
22476 @cindex current thread, remote request
22477 @cindex @code{qC} packet
22478 Return the current thread id.
22482 @item @code{QC}@var{pid}
22483 Where @var{pid} is an unsigned hexidecimal process id.
22485 Any other reply implies the old pid.
22488 @item @code{q}@code{fThreadInfo} -- all thread ids
22489 @cindex list active threads, remote request
22490 @cindex @code{qfThreadInfo} packet
22491 @code{q}@code{sThreadInfo}
22493 Obtain a list of active thread ids from the target (OS). Since there
22494 may be too many active threads to fit into one reply packet, this query
22495 works iteratively: it may require more than one query/reply sequence to
22496 obtain the entire list of threads. The first query of the sequence will
22497 be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
22498 sequence will be the @code{qs}@code{ThreadInfo} query.
22500 NOTE: replaces the @code{qL} query (see below).
22504 @item @code{m}@var{id}
22506 @item @code{m}@var{id},@var{id}@dots{}
22507 a comma-separated list of thread ids
22509 (lower case 'el') denotes end of list.
22512 In response to each query, the target will reply with a list of one or
22513 more thread ids, in big-endian unsigned hex, separated by commas.
22514 @value{GDBN} will respond to each reply with a request for more thread
22515 ids (using the @code{qs} form of the query), until the target responds
22516 with @code{l} (lower-case el, for @code{'last'}).
22518 @item @code{q}@code{ThreadExtraInfo}@code{,}@var{id} --- extra thread info
22519 @cindex thread attributes info, remote request
22520 @cindex @code{qThreadExtraInfo} packet
22521 Where @var{id} is a thread-id in big-endian hex. Obtain a printable
22522 string description of a thread's attributes from the target OS. This
22523 string may contain anything that the target OS thinks is interesting for
22524 @value{GDBN} to tell the user about the thread. The string is displayed
22525 in @value{GDBN}'s @samp{info threads} display. Some examples of
22526 possible thread extra info strings are ``Runnable'', or ``Blocked on
22531 @item @var{XX@dots{}}
22532 Where @var{XX@dots{}} is a hex encoding of @sc{ascii} data, comprising
22533 the printable string containing the extra information about the thread's
22537 @item @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} --- query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
22539 Obtain thread information from RTOS. Where: @var{startflag} (one hex
22540 digit) is one to indicate the first query and zero to indicate a
22541 subsequent query; @var{threadcount} (two hex digits) is the maximum
22542 number of threads the response packet can contain; and @var{nextthread}
22543 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
22544 returned in the response as @var{argthread}.
22546 NOTE: this query is replaced by the @code{q}@code{fThreadInfo} query
22551 @item @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread@dots{}}
22552 Where: @var{count} (two hex digits) is the number of threads being
22553 returned; @var{done} (one hex digit) is zero to indicate more threads
22554 and one indicates no further threads; @var{argthreadid} (eight hex
22555 digits) is @var{nextthread} from the request packet; @var{thread@dots{}}
22556 is a sequence of thread IDs from the target. @var{threadid} (eight hex
22557 digits). See @code{remote.c:parse_threadlist_response()}.
22560 @item @code{q}@code{CRC:}@var{addr}@code{,}@var{length} --- compute CRC of memory block
22561 @cindex CRC of memory block, remote request
22562 @cindex @code{qCRC} packet
22565 @item @code{E}@var{NN}
22566 An error (such as memory fault)
22567 @item @code{C}@var{CRC32}
22568 A 32 bit cyclic redundancy check of the specified memory region.
22571 @item @code{q}@code{Offsets} --- query sect offs
22572 @cindex section offsets, remote request
22573 @cindex @code{qOffsets} packet
22574 Get section offsets that the target used when re-locating the downloaded
22575 image. @emph{Note: while a @code{Bss} offset is included in the
22576 response, @value{GDBN} ignores this and instead applies the @code{Data}
22577 offset to the @code{Bss} section.}
22581 @item @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
22584 @item @code{q}@code{P}@var{mode}@var{threadid} --- thread info request
22585 @cindex thread information, remote request
22586 @cindex @code{qP} packet
22587 Returns information on @var{threadid}. Where: @var{mode} is a hex
22588 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
22595 See @code{remote.c:remote_unpack_thread_info_response()}.
22597 @item @code{q}@code{Rcmd,}@var{command} --- remote command
22598 @cindex execute remote command, remote request
22599 @cindex @code{qRcmd} packet
22600 @var{command} (hex encoded) is passed to the local interpreter for
22601 execution. Invalid commands should be reported using the output string.
22602 Before the final result packet, the target may also respond with a
22603 number of intermediate @code{O}@var{output} console output packets.
22604 @emph{Implementors should note that providing access to a stubs's
22605 interpreter may have security implications}.
22610 A command response with no output.
22612 A command response with the hex encoded output string @var{OUTPUT}.
22613 @item @code{E}@var{NN}
22614 Indicate a badly formed request.
22616 When @samp{q}@samp{Rcmd} is not recognized.
22619 @item @code{qSymbol::} --- symbol lookup
22620 @cindex symbol lookup, remote request
22621 @cindex @code{qSymbol} packet
22622 Notify the target that @value{GDBN} is prepared to serve symbol lookup
22623 requests. Accept requests from the target for the values of symbols.
22628 The target does not need to look up any (more) symbols.
22629 @item @code{qSymbol:}@var{sym_name}
22630 The target requests the value of symbol @var{sym_name} (hex encoded).
22631 @value{GDBN} may provide the value by using the
22632 @code{qSymbol:}@var{sym_value}:@var{sym_name} message, described below.
22635 @item @code{qSymbol:}@var{sym_value}:@var{sym_name} --- symbol value
22637 Set the value of @var{sym_name} to @var{sym_value}.
22639 @var{sym_name} (hex encoded) is the name of a symbol whose value the
22640 target has previously requested.
22642 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
22643 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
22649 The target does not need to look up any (more) symbols.
22650 @item @code{qSymbol:}@var{sym_name}
22651 The target requests the value of a new symbol @var{sym_name} (hex
22652 encoded). @value{GDBN} will continue to supply the values of symbols
22653 (if available), until the target ceases to request them.
22656 @item @code{qPart}:@var{object}:@code{read}:@var{annex}:@var{offset},@var{length} --- read special data
22657 @cindex read special object, remote request
22658 @cindex @code{qPart} packet
22659 Read uninterpreted bytes from the target's special data area
22660 identified by the keyword @code{object}.
22661 Request @var{length} bytes starting at @var{offset} bytes into the data.
22662 The content and encoding of @var{annex} is specific to the object;
22663 it can supply additional details about what data to access.
22665 Here are the specific requests of this form defined so far.
22666 All @samp{@code{qPart}:@var{object}:@code{read}:@dots{}}
22667 requests use the same reply formats, listed below.
22670 @item @code{qPart}:@code{auxv}:@code{read}::@var{offset},@var{length}
22671 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
22672 auxiliary vector}, and see @ref{Remote configuration,
22673 read-aux-vector-packet}. Note @var{annex} must be empty.
22679 The @var{offset} in the request is at the end of the data.
22680 There is no more data to be read.
22682 @item @var{XX@dots{}}
22683 Hex encoded data bytes read.
22684 This may be fewer bytes than the @var{length} in the request.
22687 The request was malformed, or @var{annex} was invalid.
22689 @item @code{E}@var{nn}
22690 The offset was invalid, or there was an error encountered reading the data.
22691 @var{nn} is a hex-encoded @code{errno} value.
22693 @item @code{""} (empty)
22694 An empty reply indicates the @var{object} or @var{annex} string was not
22695 recognized by the stub.
22698 @item @code{qPart}:@var{object}:@code{write}:@var{annex}:@var{offset}:@var{data@dots{}}
22699 @cindex write data into object, remote request
22700 Write uninterpreted bytes into the target's special data area
22701 identified by the keyword @code{object},
22702 starting at @var{offset} bytes into the data.
22703 @var{data@dots{}} is the hex-encoded data to be written.
22704 The content and encoding of @var{annex} is specific to the object;
22705 it can supply additional details about what data to access.
22707 No requests of this form are presently in use. This specification
22708 serves as a placeholder to document the common format that new
22709 specific request specifications ought to use.
22714 @var{nn} (hex encoded) is the number of bytes written.
22715 This may be fewer bytes than supplied in the request.
22718 The request was malformed, or @var{annex} was invalid.
22720 @item @code{E}@var{nn}
22721 The offset was invalid, or there was an error encountered writing the data.
22722 @var{nn} is a hex-encoded @code{errno} value.
22724 @item @code{""} (empty)
22725 An empty reply indicates the @var{object} or @var{annex} string was not
22726 recognized by the stub, or that the object does not support writing.
22729 @item @code{qPart}:@var{object}:@var{operation}:@dots{}
22730 Requests of this form may be added in the future. When a stub does
22731 not recognize the @var{object} keyword, or its support for
22732 @var{object} does not recognize the @var{operation} keyword,
22733 the stub must respond with an empty packet.
22735 @item @code{qGetTLSAddr}:@var{thread-id},@var{offset},@var{lm} --- get thread local storage address
22736 @cindex get thread-local storage address, remote request
22737 @cindex @code{qGetTLSAddr} packet
22738 Fetch the address associated with thread local storage specified
22739 by @var{thread-id}, @var{offset}, and @var{lm}.
22741 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
22742 thread for which to fetch the TLS address.
22744 @var{offset} is the (big endian, hex encoded) offset associated with the
22745 thread local variable. (This offset is obtained from the debug
22746 information associated with the variable.)
22748 @var{lm} is the (big endian, hex encoded) OS/ABI specific encoding of the
22749 the load module associated with the thread local storage. For example,
22750 a @sc{gnu}/Linux system will pass the link map address of the shared
22751 object associated with the thread local storage under consideration.
22752 Other operating environments may choose to represent the load module
22753 differently, so the precise meaning of this parameter will vary.
22757 @item @var{XX@dots{}}
22758 Hex encoded (big endian) bytes representing the address of the thread
22759 local storage requested.
22761 @item @code{E}@var{nn} (where @var{nn} are hex digits)
22764 @item @code{""} (empty)
22765 An empty reply indicates that @code{qGetTLSAddr} is not supported by the stub.
22770 @node Register Packet Format
22771 @section Register Packet Format
22773 The following @samp{g}/@samp{G} packets have previously been defined.
22774 In the below, some thirty-two bit registers are transferred as
22775 sixty-four bits. Those registers should be zero/sign extended (which?)
22776 to fill the space allocated. Register bytes are transfered in target
22777 byte order. The two nibbles within a register byte are transfered
22778 most-significant - least-significant.
22784 All registers are transfered as thirty-two bit quantities in the order:
22785 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
22786 registers; fsr; fir; fp.
22790 All registers are transfered as sixty-four bit quantities (including
22791 thirty-two bit registers such as @code{sr}). The ordering is the same
22799 Example sequence of a target being re-started. Notice how the restart
22800 does not get any direct output:
22805 @emph{target restarts}
22808 <- @code{T001:1234123412341234}
22812 Example sequence of a target being stepped by a single instruction:
22815 -> @code{G1445@dots{}}
22820 <- @code{T001:1234123412341234}
22824 <- @code{1455@dots{}}
22828 @node File-I/O remote protocol extension
22829 @section File-I/O remote protocol extension
22830 @cindex File-I/O remote protocol extension
22833 * File-I/O Overview::
22834 * Protocol basics::
22835 * The F request packet::
22836 * The F reply packet::
22837 * Memory transfer::
22838 * The Ctrl-C message::
22840 * The isatty call::
22841 * The system call::
22842 * List of supported calls::
22843 * Protocol specific representation of datatypes::
22845 * File-I/O Examples::
22848 @node File-I/O Overview
22849 @subsection File-I/O Overview
22850 @cindex file-i/o overview
22852 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
22853 target to use the host's file system and console I/O when calling various
22854 system calls. System calls on the target system are translated into a
22855 remote protocol packet to the host system which then performs the needed
22856 actions and returns with an adequate response packet to the target system.
22857 This simulates file system operations even on targets that lack file systems.
22859 The protocol is defined host- and target-system independent. It uses
22860 its own independent representation of datatypes and values. Both,
22861 @value{GDBN} and the target's @value{GDBN} stub are responsible for
22862 translating the system dependent values into the unified protocol values
22863 when data is transmitted.
22865 The communication is synchronous. A system call is possible only
22866 when GDB is waiting for the @samp{C}, @samp{c}, @samp{S} or @samp{s}
22867 packets. While @value{GDBN} handles the request for a system call,
22868 the target is stopped to allow deterministic access to the target's
22869 memory. Therefore File-I/O is not interuptible by target signals. It
22870 is possible to interrupt File-I/O by a user interrupt (Ctrl-C), though.
22872 The target's request to perform a host system call does not finish
22873 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
22874 after finishing the system call, the target returns to continuing the
22875 previous activity (continue, step). No additional continue or step
22876 request from @value{GDBN} is required.
22879 (@value{GDBP}) continue
22880 <- target requests 'system call X'
22881 target is stopped, @value{GDBN} executes system call
22882 -> GDB returns result
22883 ... target continues, GDB returns to wait for the target
22884 <- target hits breakpoint and sends a Txx packet
22887 The protocol is only used for files on the host file system and
22888 for I/O on the console. Character or block special devices, pipes,
22889 named pipes or sockets or any other communication method on the host
22890 system are not supported by this protocol.
22892 @node Protocol basics
22893 @subsection Protocol basics
22894 @cindex protocol basics, file-i/o
22896 The File-I/O protocol uses the @code{F} packet, as request as well
22897 as as reply packet. Since a File-I/O system call can only occur when
22898 @value{GDBN} is waiting for the continuing or stepping target, the
22899 File-I/O request is a reply that @value{GDBN} has to expect as a result
22900 of a former @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
22901 This @code{F} packet contains all information needed to allow @value{GDBN}
22902 to call the appropriate host system call:
22906 A unique identifier for the requested system call.
22909 All parameters to the system call. Pointers are given as addresses
22910 in the target memory address space. Pointers to strings are given as
22911 pointer/length pair. Numerical values are given as they are.
22912 Numerical control values are given in a protocol specific representation.
22916 At that point @value{GDBN} has to perform the following actions.
22920 If parameter pointer values are given, which point to data needed as input
22921 to a system call, @value{GDBN} requests this data from the target with a
22922 standard @code{m} packet request. This additional communication has to be
22923 expected by the target implementation and is handled as any other @code{m}
22927 @value{GDBN} translates all value from protocol representation to host
22928 representation as needed. Datatypes are coerced into the host types.
22931 @value{GDBN} calls the system call
22934 It then coerces datatypes back to protocol representation.
22937 If pointer parameters in the request packet point to buffer space in which
22938 a system call is expected to copy data to, the data is transmitted to the
22939 target using a @code{M} or @code{X} packet. This packet has to be expected
22940 by the target implementation and is handled as any other @code{M} or @code{X}
22945 Eventually @value{GDBN} replies with another @code{F} packet which contains all
22946 necessary information for the target to continue. This at least contains
22953 @code{errno}, if has been changed by the system call.
22960 After having done the needed type and value coercion, the target continues
22961 the latest continue or step action.
22963 @node The F request packet
22964 @subsection The @code{F} request packet
22965 @cindex file-i/o request packet
22966 @cindex @code{F} request packet
22968 The @code{F} request packet has the following format:
22973 @code{F}@var{call-id}@code{,}@var{parameter@dots{}}
22976 @var{call-id} is the identifier to indicate the host system call to be called.
22977 This is just the name of the function.
22979 @var{parameter@dots{}} are the parameters to the system call.
22983 Parameters are hexadecimal integer values, either the real values in case
22984 of scalar datatypes, as pointers to target buffer space in case of compound
22985 datatypes and unspecified memory areas or as pointer/length pairs in case
22986 of string parameters. These are appended to the call-id, each separated
22987 from its predecessor by a comma. All values are transmitted in ASCII
22988 string representation, pointer/length pairs separated by a slash.
22990 @node The F reply packet
22991 @subsection The @code{F} reply packet
22992 @cindex file-i/o reply packet
22993 @cindex @code{F} reply packet
22995 The @code{F} reply packet has the following format:
23000 @code{F}@var{retcode}@code{,}@var{errno}@code{,}@var{Ctrl-C flag}@code{;}@var{call specific attachment}
23003 @var{retcode} is the return code of the system call as hexadecimal value.
23005 @var{errno} is the errno set by the call, in protocol specific representation.
23006 This parameter can be omitted if the call was successful.
23008 @var{Ctrl-C flag} is only send if the user requested a break. In this
23009 case, @var{errno} must be send as well, even if the call was successful.
23010 The @var{Ctrl-C flag} itself consists of the character 'C':
23017 or, if the call was interupted before the host call has been performed:
23024 assuming 4 is the protocol specific representation of @code{EINTR}.
23028 @node Memory transfer
23029 @subsection Memory transfer
23030 @cindex memory transfer, in file-i/o protocol
23032 Structured data which is transferred using a memory read or write as e.g.@:
23033 a @code{struct stat} is expected to be in a protocol specific format with
23034 all scalar multibyte datatypes being big endian. This should be done by
23035 the target before the @code{F} packet is sent resp.@: by @value{GDBN} before
23036 it transfers memory to the target. Transferred pointers to structured
23037 data should point to the already coerced data at any time.
23039 @node The Ctrl-C message
23040 @subsection The Ctrl-C message
23041 @cindex ctrl-c message, in file-i/o protocol
23043 A special case is, if the @var{Ctrl-C flag} is set in the @value{GDBN}
23044 reply packet. In this case the target should behave, as if it had
23045 gotten a break message. The meaning for the target is ``system call
23046 interupted by @code{SIGINT}''. Consequentially, the target should actually stop
23047 (as with a break message) and return to @value{GDBN} with a @code{T02}
23048 packet. In this case, it's important for the target to know, in which
23049 state the system call was interrupted. Since this action is by design
23050 not an atomic operation, we have to differ between two cases:
23054 The system call hasn't been performed on the host yet.
23057 The system call on the host has been finished.
23061 These two states can be distinguished by the target by the value of the
23062 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
23063 call hasn't been performed. This is equivalent to the @code{EINTR} handling
23064 on POSIX systems. In any other case, the target may presume that the
23065 system call has been finished --- successful or not --- and should behave
23066 as if the break message arrived right after the system call.
23068 @value{GDBN} must behave reliable. If the system call has not been called
23069 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
23070 @code{errno} in the packet. If the system call on the host has been finished
23071 before the user requests a break, the full action must be finshed by
23072 @value{GDBN}. This requires sending @code{M} or @code{X} packets as they fit.
23073 The @code{F} packet may only be send when either nothing has happened
23074 or the full action has been completed.
23077 @subsection Console I/O
23078 @cindex console i/o as part of file-i/o
23080 By default and if not explicitely closed by the target system, the file
23081 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
23082 on the @value{GDBN} console is handled as any other file output operation
23083 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
23084 by @value{GDBN} so that after the target read request from file descriptor
23085 0 all following typing is buffered until either one of the following
23090 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, the
23092 system call is treated as finished.
23095 The user presses @kbd{Enter}. This is treated as end of input with a trailing
23099 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
23100 character, especially no Ctrl-D is appended to the input.
23104 If the user has typed more characters as fit in the buffer given to
23105 the read call, the trailing characters are buffered in @value{GDBN} until
23106 either another @code{read(0, @dots{})} is requested by the target or debugging
23107 is stopped on users request.
23109 @node The isatty call
23110 @subsection The isatty(3) call
23111 @cindex isatty call, file-i/o protocol
23113 A special case in this protocol is the library call @code{isatty} which
23114 is implemented as its own call inside of this protocol. It returns
23115 1 to the target if the file descriptor given as parameter is attached
23116 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
23117 would require implementing @code{ioctl} and would be more complex than
23120 @node The system call
23121 @subsection The system(3) call
23122 @cindex system call, file-i/o protocol
23124 The other special case in this protocol is the @code{system} call which
23125 is implemented as its own call, too. @value{GDBN} is taking over the full
23126 task of calling the necessary host calls to perform the @code{system}
23127 call. The return value of @code{system} is simplified before it's returned
23128 to the target. Basically, the only signal transmitted back is @code{EINTR}
23129 in case the user pressed @kbd{Ctrl-C}. Otherwise the return value consists
23130 entirely of the exit status of the called command.
23132 Due to security concerns, the @code{system} call is by default refused
23133 by @value{GDBN}. The user has to allow this call explicitly with the
23134 @kbd{set remote system-call-allowed 1} command.
23137 @item set remote system-call-allowed
23138 @kindex set remote system-call-allowed
23139 Control whether to allow the @code{system} calls in the File I/O
23140 protocol for the remote target. The default is zero (disabled).
23142 @item show remote system-call-allowed
23143 @kindex show remote system-call-allowed
23144 Show the current setting of system calls for the remote File I/O
23148 @node List of supported calls
23149 @subsection List of supported calls
23150 @cindex list of supported file-i/o calls
23167 @unnumberedsubsubsec open
23168 @cindex open, file-i/o system call
23172 int open(const char *pathname, int flags);
23173 int open(const char *pathname, int flags, mode_t mode);
23176 Fopen,pathptr/len,flags,mode
23180 @code{flags} is the bitwise or of the following values:
23184 If the file does not exist it will be created. The host
23185 rules apply as far as file ownership and time stamps
23189 When used with O_CREAT, if the file already exists it is
23190 an error and open() fails.
23193 If the file already exists and the open mode allows
23194 writing (O_RDWR or O_WRONLY is given) it will be
23195 truncated to length 0.
23198 The file is opened in append mode.
23201 The file is opened for reading only.
23204 The file is opened for writing only.
23207 The file is opened for reading and writing.
23210 Each other bit is silently ignored.
23215 @code{mode} is the bitwise or of the following values:
23219 User has read permission.
23222 User has write permission.
23225 Group has read permission.
23228 Group has write permission.
23231 Others have read permission.
23234 Others have write permission.
23237 Each other bit is silently ignored.
23242 @exdent Return value:
23243 open returns the new file descriptor or -1 if an error
23251 pathname already exists and O_CREAT and O_EXCL were used.
23254 pathname refers to a directory.
23257 The requested access is not allowed.
23260 pathname was too long.
23263 A directory component in pathname does not exist.
23266 pathname refers to a device, pipe, named pipe or socket.
23269 pathname refers to a file on a read-only filesystem and
23270 write access was requested.
23273 pathname is an invalid pointer value.
23276 No space on device to create the file.
23279 The process already has the maximum number of files open.
23282 The limit on the total number of files open on the system
23286 The call was interrupted by the user.
23290 @unnumberedsubsubsec close
23291 @cindex close, file-i/o system call
23300 @exdent Return value:
23301 close returns zero on success, or -1 if an error occurred.
23308 fd isn't a valid open file descriptor.
23311 The call was interrupted by the user.
23315 @unnumberedsubsubsec read
23316 @cindex read, file-i/o system call
23320 int read(int fd, void *buf, unsigned int count);
23323 Fread,fd,bufptr,count
23325 @exdent Return value:
23326 On success, the number of bytes read is returned.
23327 Zero indicates end of file. If count is zero, read
23328 returns zero as well. On error, -1 is returned.
23335 fd is not a valid file descriptor or is not open for
23339 buf is an invalid pointer value.
23342 The call was interrupted by the user.
23346 @unnumberedsubsubsec write
23347 @cindex write, file-i/o system call
23351 int write(int fd, const void *buf, unsigned int count);
23354 Fwrite,fd,bufptr,count
23356 @exdent Return value:
23357 On success, the number of bytes written are returned.
23358 Zero indicates nothing was written. On error, -1
23366 fd is not a valid file descriptor or is not open for
23370 buf is an invalid pointer value.
23373 An attempt was made to write a file that exceeds the
23374 host specific maximum file size allowed.
23377 No space on device to write the data.
23380 The call was interrupted by the user.
23384 @unnumberedsubsubsec lseek
23385 @cindex lseek, file-i/o system call
23389 long lseek (int fd, long offset, int flag);
23392 Flseek,fd,offset,flag
23395 @code{flag} is one of:
23399 The offset is set to offset bytes.
23402 The offset is set to its current location plus offset
23406 The offset is set to the size of the file plus offset
23411 @exdent Return value:
23412 On success, the resulting unsigned offset in bytes from
23413 the beginning of the file is returned. Otherwise, a
23414 value of -1 is returned.
23421 fd is not a valid open file descriptor.
23424 fd is associated with the @value{GDBN} console.
23427 flag is not a proper value.
23430 The call was interrupted by the user.
23434 @unnumberedsubsubsec rename
23435 @cindex rename, file-i/o system call
23439 int rename(const char *oldpath, const char *newpath);
23442 Frename,oldpathptr/len,newpathptr/len
23444 @exdent Return value:
23445 On success, zero is returned. On error, -1 is returned.
23452 newpath is an existing directory, but oldpath is not a
23456 newpath is a non-empty directory.
23459 oldpath or newpath is a directory that is in use by some
23463 An attempt was made to make a directory a subdirectory
23467 A component used as a directory in oldpath or new
23468 path is not a directory. Or oldpath is a directory
23469 and newpath exists but is not a directory.
23472 oldpathptr or newpathptr are invalid pointer values.
23475 No access to the file or the path of the file.
23479 oldpath or newpath was too long.
23482 A directory component in oldpath or newpath does not exist.
23485 The file is on a read-only filesystem.
23488 The device containing the file has no room for the new
23492 The call was interrupted by the user.
23496 @unnumberedsubsubsec unlink
23497 @cindex unlink, file-i/o system call
23501 int unlink(const char *pathname);
23504 Funlink,pathnameptr/len
23506 @exdent Return value:
23507 On success, zero is returned. On error, -1 is returned.
23514 No access to the file or the path of the file.
23517 The system does not allow unlinking of directories.
23520 The file pathname cannot be unlinked because it's
23521 being used by another process.
23524 pathnameptr is an invalid pointer value.
23527 pathname was too long.
23530 A directory component in pathname does not exist.
23533 A component of the path is not a directory.
23536 The file is on a read-only filesystem.
23539 The call was interrupted by the user.
23543 @unnumberedsubsubsec stat/fstat
23544 @cindex fstat, file-i/o system call
23545 @cindex stat, file-i/o system call
23549 int stat(const char *pathname, struct stat *buf);
23550 int fstat(int fd, struct stat *buf);
23553 Fstat,pathnameptr/len,bufptr
23556 @exdent Return value:
23557 On success, zero is returned. On error, -1 is returned.
23564 fd is not a valid open file.
23567 A directory component in pathname does not exist or the
23568 path is an empty string.
23571 A component of the path is not a directory.
23574 pathnameptr is an invalid pointer value.
23577 No access to the file or the path of the file.
23580 pathname was too long.
23583 The call was interrupted by the user.
23587 @unnumberedsubsubsec gettimeofday
23588 @cindex gettimeofday, file-i/o system call
23592 int gettimeofday(struct timeval *tv, void *tz);
23595 Fgettimeofday,tvptr,tzptr
23597 @exdent Return value:
23598 On success, 0 is returned, -1 otherwise.
23605 tz is a non-NULL pointer.
23608 tvptr and/or tzptr is an invalid pointer value.
23612 @unnumberedsubsubsec isatty
23613 @cindex isatty, file-i/o system call
23617 int isatty(int fd);
23622 @exdent Return value:
23623 Returns 1 if fd refers to the @value{GDBN} console, 0 otherwise.
23630 The call was interrupted by the user.
23634 @unnumberedsubsubsec system
23635 @cindex system, file-i/o system call
23639 int system(const char *command);
23642 Fsystem,commandptr/len
23644 @exdent Return value:
23645 The value returned is -1 on error and the return status
23646 of the command otherwise. Only the exit status of the
23647 command is returned, which is extracted from the hosts
23648 system return value by calling WEXITSTATUS(retval).
23649 In case /bin/sh could not be executed, 127 is returned.
23656 The call was interrupted by the user.
23659 @node Protocol specific representation of datatypes
23660 @subsection Protocol specific representation of datatypes
23661 @cindex protocol specific representation of datatypes, in file-i/o protocol
23664 * Integral datatypes::
23670 @node Integral datatypes
23671 @unnumberedsubsubsec Integral datatypes
23672 @cindex integral datatypes, in file-i/o protocol
23674 The integral datatypes used in the system calls are
23677 int@r{,} unsigned int@r{,} long@r{,} unsigned long@r{,} mode_t @r{and} time_t
23680 @code{Int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
23681 implemented as 32 bit values in this protocol.
23683 @code{Long} and @code{unsigned long} are implemented as 64 bit types.
23685 @xref{Limits}, for corresponding MIN and MAX values (similar to those
23686 in @file{limits.h}) to allow range checking on host and target.
23688 @code{time_t} datatypes are defined as seconds since the Epoch.
23690 All integral datatypes transferred as part of a memory read or write of a
23691 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
23694 @node Pointer values
23695 @unnumberedsubsubsec Pointer values
23696 @cindex pointer values, in file-i/o protocol
23698 Pointers to target data are transmitted as they are. An exception
23699 is made for pointers to buffers for which the length isn't
23700 transmitted as part of the function call, namely strings. Strings
23701 are transmitted as a pointer/length pair, both as hex values, e.g.@:
23708 which is a pointer to data of length 18 bytes at position 0x1aaf.
23709 The length is defined as the full string length in bytes, including
23710 the trailing null byte. Example:
23713 ``hello, world'' at address 0x123456
23724 @unnumberedsubsubsec struct stat
23725 @cindex struct stat, in file-i/o protocol
23727 The buffer of type struct stat used by the target and @value{GDBN} is defined
23732 unsigned int st_dev; /* device */
23733 unsigned int st_ino; /* inode */
23734 mode_t st_mode; /* protection */
23735 unsigned int st_nlink; /* number of hard links */
23736 unsigned int st_uid; /* user ID of owner */
23737 unsigned int st_gid; /* group ID of owner */
23738 unsigned int st_rdev; /* device type (if inode device) */
23739 unsigned long st_size; /* total size, in bytes */
23740 unsigned long st_blksize; /* blocksize for filesystem I/O */
23741 unsigned long st_blocks; /* number of blocks allocated */
23742 time_t st_atime; /* time of last access */
23743 time_t st_mtime; /* time of last modification */
23744 time_t st_ctime; /* time of last change */
23748 The integral datatypes are conforming to the definitions given in the
23749 approriate section (see @ref{Integral datatypes}, for details) so this
23750 structure is of size 64 bytes.
23752 The values of several fields have a restricted meaning and/or
23759 st_ino: No valid meaning for the target. Transmitted unchanged.
23761 st_mode: Valid mode bits are described in Appendix C. Any other
23762 bits have currently no meaning for the target.
23764 st_uid: No valid meaning for the target. Transmitted unchanged.
23766 st_gid: No valid meaning for the target. Transmitted unchanged.
23768 st_rdev: No valid meaning for the target. Transmitted unchanged.
23770 st_atime, st_mtime, st_ctime:
23771 These values have a host and file system dependent
23772 accuracy. Especially on Windows hosts the file systems
23773 don't support exact timing values.
23776 The target gets a struct stat of the above representation and is
23777 responsible to coerce it to the target representation before
23780 Note that due to size differences between the host and target
23781 representation of stat members, these members could eventually
23782 get truncated on the target.
23784 @node struct timeval
23785 @unnumberedsubsubsec struct timeval
23786 @cindex struct timeval, in file-i/o protocol
23788 The buffer of type struct timeval used by the target and @value{GDBN}
23789 is defined as follows:
23793 time_t tv_sec; /* second */
23794 long tv_usec; /* microsecond */
23798 The integral datatypes are conforming to the definitions given in the
23799 approriate section (see @ref{Integral datatypes}, for details) so this
23800 structure is of size 8 bytes.
23803 @subsection Constants
23804 @cindex constants, in file-i/o protocol
23806 The following values are used for the constants inside of the
23807 protocol. @value{GDBN} and target are resposible to translate these
23808 values before and after the call as needed.
23819 @unnumberedsubsubsec Open flags
23820 @cindex open flags, in file-i/o protocol
23822 All values are given in hexadecimal representation.
23834 @node mode_t values
23835 @unnumberedsubsubsec mode_t values
23836 @cindex mode_t values, in file-i/o protocol
23838 All values are given in octal representation.
23855 @unnumberedsubsubsec Errno values
23856 @cindex errno values, in file-i/o protocol
23858 All values are given in decimal representation.
23883 EUNKNOWN is used as a fallback error value if a host system returns
23884 any error value not in the list of supported error numbers.
23887 @unnumberedsubsubsec Lseek flags
23888 @cindex lseek flags, in file-i/o protocol
23897 @unnumberedsubsubsec Limits
23898 @cindex limits, in file-i/o protocol
23900 All values are given in decimal representation.
23903 INT_MIN -2147483648
23905 UINT_MAX 4294967295
23906 LONG_MIN -9223372036854775808
23907 LONG_MAX 9223372036854775807
23908 ULONG_MAX 18446744073709551615
23911 @node File-I/O Examples
23912 @subsection File-I/O Examples
23913 @cindex file-i/o examples
23915 Example sequence of a write call, file descriptor 3, buffer is at target
23916 address 0x1234, 6 bytes should be written:
23919 <- @code{Fwrite,3,1234,6}
23920 @emph{request memory read from target}
23923 @emph{return "6 bytes written"}
23927 Example sequence of a read call, file descriptor 3, buffer is at target
23928 address 0x1234, 6 bytes should be read:
23931 <- @code{Fread,3,1234,6}
23932 @emph{request memory write to target}
23933 -> @code{X1234,6:XXXXXX}
23934 @emph{return "6 bytes read"}
23938 Example sequence of a read call, call fails on the host due to invalid
23939 file descriptor (EBADF):
23942 <- @code{Fread,3,1234,6}
23946 Example sequence of a read call, user presses Ctrl-C before syscall on
23950 <- @code{Fread,3,1234,6}
23955 Example sequence of a read call, user presses Ctrl-C after syscall on
23959 <- @code{Fread,3,1234,6}
23960 -> @code{X1234,6:XXXXXX}
23964 @include agentexpr.texi
23978 % I think something like @colophon should be in texinfo. In the
23980 \long\def\colophon{\hbox to0pt{}\vfill
23981 \centerline{The body of this manual is set in}
23982 \centerline{\fontname\tenrm,}
23983 \centerline{with headings in {\bf\fontname\tenbf}}
23984 \centerline{and examples in {\tt\fontname\tentt}.}
23985 \centerline{{\it\fontname\tenit\/},}
23986 \centerline{{\bf\fontname\tenbf}, and}
23987 \centerline{{\sl\fontname\tensl\/}}
23988 \centerline{are used for emphasis.}\vfill}
23990 % Blame: doc@cygnus.com, 1991.