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 @value{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.
4137 @item backtrace full
4138 Print the values of the local variables also.
4144 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4145 are additional aliases for @code{backtrace}.
4147 Each line in the backtrace shows the frame number and the function name.
4148 The program counter value is also shown---unless you use @code{set
4149 print address off}. The backtrace also shows the source file name and
4150 line number, as well as the arguments to the function. The program
4151 counter value is omitted if it is at the beginning of the code for that
4154 Here is an example of a backtrace. It was made with the command
4155 @samp{bt 3}, so it shows the innermost three frames.
4159 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4161 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4162 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4164 (More stack frames follow...)
4169 The display for frame zero does not begin with a program counter
4170 value, indicating that your program has stopped at the beginning of the
4171 code for line @code{993} of @code{builtin.c}.
4173 @cindex value optimized out, in backtrace
4174 @cindex function call arguments, optimized out
4175 If your program was compiled with optimizations, some compilers will
4176 optimize away arguments passed to functions if those arguments are
4177 never used after the call. Such optimizations generate code that
4178 passes arguments through registers, but doesn't store those arguments
4179 in the stack frame. @value{GDBN} has no way of displaying such
4180 arguments in stack frames other than the innermost one. Here's what
4181 such a backtrace might look like:
4185 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4187 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4188 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4190 (More stack frames follow...)
4195 The values of arguments that were not saved in their stack frames are
4196 shown as @samp{<value optimized out>}.
4198 If you need to display the values of such optimized-out arguments,
4199 either deduce that from other variables whose values depend on the one
4200 you are interested in, or recompile without optimizations.
4202 @cindex backtrace beyond @code{main} function
4203 @cindex program entry point
4204 @cindex startup code, and backtrace
4205 Most programs have a standard user entry point---a place where system
4206 libraries and startup code transition into user code. For C this is
4207 @code{main}. When @value{GDBN} finds the entry function in a backtrace
4208 it will terminate the backtrace, to avoid tracing into highly
4209 system-specific (and generally uninteresting) code.
4211 If you need to examine the startup code, or limit the number of levels
4212 in a backtrace, you can change this behavior:
4215 @item set backtrace past-main
4216 @itemx set backtrace past-main on
4217 @kindex set backtrace
4218 Backtraces will continue past the user entry point.
4220 @item set backtrace past-main off
4221 Backtraces will stop when they encounter the user entry point. This is the
4224 @item show backtrace past-main
4225 @kindex show backtrace
4226 Display the current user entry point backtrace policy.
4228 @item set backtrace past-entry
4229 @itemx set backtrace past-entry on
4230 Backtraces will continue past the internal entry point of an application.
4231 This entry point is encoded by the linker when the application is built,
4232 and is likely before the user entry point @code{main} (or equivalent) is called.
4234 @item set backtrace past-entry off
4235 Backtraces will stop when they encouter the internal entry point of an
4236 application. This is the default.
4238 @item show backtrace past-entry
4239 Display the current internal entry point backtrace policy.
4241 @item set backtrace limit @var{n}
4242 @itemx set backtrace limit 0
4243 @cindex backtrace limit
4244 Limit the backtrace to @var{n} levels. A value of zero means
4247 @item show backtrace limit
4248 Display the current limit on backtrace levels.
4252 @section Selecting a frame
4254 Most commands for examining the stack and other data in your program work on
4255 whichever stack frame is selected at the moment. Here are the commands for
4256 selecting a stack frame; all of them finish by printing a brief description
4257 of the stack frame just selected.
4260 @kindex frame@r{, selecting}
4261 @kindex f @r{(@code{frame})}
4264 Select frame number @var{n}. Recall that frame zero is the innermost
4265 (currently executing) frame, frame one is the frame that called the
4266 innermost one, and so on. The highest-numbered frame is the one for
4269 @item frame @var{addr}
4271 Select the frame at address @var{addr}. This is useful mainly if the
4272 chaining of stack frames has been damaged by a bug, making it
4273 impossible for @value{GDBN} to assign numbers properly to all frames. In
4274 addition, this can be useful when your program has multiple stacks and
4275 switches between them.
4277 On the SPARC architecture, @code{frame} needs two addresses to
4278 select an arbitrary frame: a frame pointer and a stack pointer.
4280 On the MIPS and Alpha architecture, it needs two addresses: a stack
4281 pointer and a program counter.
4283 On the 29k architecture, it needs three addresses: a register stack
4284 pointer, a program counter, and a memory stack pointer.
4285 @c note to future updaters: this is conditioned on a flag
4286 @c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date
4287 @c as of 27 Jan 1994.
4291 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4292 advances toward the outermost frame, to higher frame numbers, to frames
4293 that have existed longer. @var{n} defaults to one.
4296 @kindex do @r{(@code{down})}
4298 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4299 advances toward the innermost frame, to lower frame numbers, to frames
4300 that were created more recently. @var{n} defaults to one. You may
4301 abbreviate @code{down} as @code{do}.
4304 All of these commands end by printing two lines of output describing the
4305 frame. The first line shows the frame number, the function name, the
4306 arguments, and the source file and line number of execution in that
4307 frame. The second line shows the text of that source line.
4315 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4317 10 read_input_file (argv[i]);
4321 After such a printout, the @code{list} command with no arguments
4322 prints ten lines centered on the point of execution in the frame.
4323 You can also edit the program at the point of execution with your favorite
4324 editing program by typing @code{edit}.
4325 @xref{List, ,Printing source lines},
4329 @kindex down-silently
4331 @item up-silently @var{n}
4332 @itemx down-silently @var{n}
4333 These two commands are variants of @code{up} and @code{down},
4334 respectively; they differ in that they do their work silently, without
4335 causing display of the new frame. They are intended primarily for use
4336 in @value{GDBN} command scripts, where the output might be unnecessary and
4341 @section Information about a frame
4343 There are several other commands to print information about the selected
4349 When used without any argument, this command does not change which
4350 frame is selected, but prints a brief description of the currently
4351 selected stack frame. It can be abbreviated @code{f}. With an
4352 argument, this command is used to select a stack frame.
4353 @xref{Selection, ,Selecting a frame}.
4356 @kindex info f @r{(@code{info frame})}
4359 This command prints a verbose description of the selected stack frame,
4364 the address of the frame
4366 the address of the next frame down (called by this frame)
4368 the address of the next frame up (caller of this frame)
4370 the language in which the source code corresponding to this frame is written
4372 the address of the frame's arguments
4374 the address of the frame's local variables
4376 the program counter saved in it (the address of execution in the caller frame)
4378 which registers were saved in the frame
4381 @noindent The verbose description is useful when
4382 something has gone wrong that has made the stack format fail to fit
4383 the usual conventions.
4385 @item info frame @var{addr}
4386 @itemx info f @var{addr}
4387 Print a verbose description of the frame at address @var{addr}, without
4388 selecting that frame. The selected frame remains unchanged by this
4389 command. This requires the same kind of address (more than one for some
4390 architectures) that you specify in the @code{frame} command.
4391 @xref{Selection, ,Selecting a frame}.
4395 Print the arguments of the selected frame, each on a separate line.
4399 Print the local variables of the selected frame, each on a separate
4400 line. These are all variables (declared either static or automatic)
4401 accessible at the point of execution of the selected frame.
4404 @cindex catch exceptions, list active handlers
4405 @cindex exception handlers, how to list
4407 Print a list of all the exception handlers that are active in the
4408 current stack frame at the current point of execution. To see other
4409 exception handlers, visit the associated frame (using the @code{up},
4410 @code{down}, or @code{frame} commands); then type @code{info catch}.
4411 @xref{Set Catchpoints, , Setting catchpoints}.
4417 @chapter Examining Source Files
4419 @value{GDBN} can print parts of your program's source, since the debugging
4420 information recorded in the program tells @value{GDBN} what source files were
4421 used to build it. When your program stops, @value{GDBN} spontaneously prints
4422 the line where it stopped. Likewise, when you select a stack frame
4423 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4424 execution in that frame has stopped. You can print other portions of
4425 source files by explicit command.
4427 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4428 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4429 @value{GDBN} under @sc{gnu} Emacs}.
4432 * List:: Printing source lines
4433 * Edit:: Editing source files
4434 * Search:: Searching source files
4435 * Source Path:: Specifying source directories
4436 * Machine Code:: Source and machine code
4440 @section Printing source lines
4443 @kindex l @r{(@code{list})}
4444 To print lines from a source file, use the @code{list} command
4445 (abbreviated @code{l}). By default, ten lines are printed.
4446 There are several ways to specify what part of the file you want to print.
4448 Here are the forms of the @code{list} command most commonly used:
4451 @item list @var{linenum}
4452 Print lines centered around line number @var{linenum} in the
4453 current source file.
4455 @item list @var{function}
4456 Print lines centered around the beginning of function
4460 Print more lines. If the last lines printed were printed with a
4461 @code{list} command, this prints lines following the last lines
4462 printed; however, if the last line printed was a solitary line printed
4463 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4464 Stack}), this prints lines centered around that line.
4467 Print lines just before the lines last printed.
4470 @cindex @code{list}, how many lines to display
4471 By default, @value{GDBN} prints ten source lines with any of these forms of
4472 the @code{list} command. You can change this using @code{set listsize}:
4475 @kindex set listsize
4476 @item set listsize @var{count}
4477 Make the @code{list} command display @var{count} source lines (unless
4478 the @code{list} argument explicitly specifies some other number).
4480 @kindex show listsize
4482 Display the number of lines that @code{list} prints.
4485 Repeating a @code{list} command with @key{RET} discards the argument,
4486 so it is equivalent to typing just @code{list}. This is more useful
4487 than listing the same lines again. An exception is made for an
4488 argument of @samp{-}; that argument is preserved in repetition so that
4489 each repetition moves up in the source file.
4492 In general, the @code{list} command expects you to supply zero, one or two
4493 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4494 of writing them, but the effect is always to specify some source line.
4495 Here is a complete description of the possible arguments for @code{list}:
4498 @item list @var{linespec}
4499 Print lines centered around the line specified by @var{linespec}.
4501 @item list @var{first},@var{last}
4502 Print lines from @var{first} to @var{last}. Both arguments are
4505 @item list ,@var{last}
4506 Print lines ending with @var{last}.
4508 @item list @var{first},
4509 Print lines starting with @var{first}.
4512 Print lines just after the lines last printed.
4515 Print lines just before the lines last printed.
4518 As described in the preceding table.
4521 Here are the ways of specifying a single source line---all the
4526 Specifies line @var{number} of the current source file.
4527 When a @code{list} command has two linespecs, this refers to
4528 the same source file as the first linespec.
4531 Specifies the line @var{offset} lines after the last line printed.
4532 When used as the second linespec in a @code{list} command that has
4533 two, this specifies the line @var{offset} lines down from the
4537 Specifies the line @var{offset} lines before the last line printed.
4539 @item @var{filename}:@var{number}
4540 Specifies line @var{number} in the source file @var{filename}.
4542 @item @var{function}
4543 Specifies the line that begins the body of the function @var{function}.
4544 For example: in C, this is the line with the open brace.
4546 @item @var{filename}:@var{function}
4547 Specifies the line of the open-brace that begins the body of the
4548 function @var{function} in the file @var{filename}. You only need the
4549 file name with a function name to avoid ambiguity when there are
4550 identically named functions in different source files.
4552 @item *@var{address}
4553 Specifies the line containing the program address @var{address}.
4554 @var{address} may be any expression.
4558 @section Editing source files
4559 @cindex editing source files
4562 @kindex e @r{(@code{edit})}
4563 To edit the lines in a source file, use the @code{edit} command.
4564 The editing program of your choice
4565 is invoked with the current line set to
4566 the active line in the program.
4567 Alternatively, there are several ways to specify what part of the file you
4568 want to print if you want to see other parts of the program.
4570 Here are the forms of the @code{edit} command most commonly used:
4574 Edit the current source file at the active line number in the program.
4576 @item edit @var{number}
4577 Edit the current source file with @var{number} as the active line number.
4579 @item edit @var{function}
4580 Edit the file containing @var{function} at the beginning of its definition.
4582 @item edit @var{filename}:@var{number}
4583 Specifies line @var{number} in the source file @var{filename}.
4585 @item edit @var{filename}:@var{function}
4586 Specifies the line that begins the body of the
4587 function @var{function} in the file @var{filename}. You only need the
4588 file name with a function name to avoid ambiguity when there are
4589 identically named functions in different source files.
4591 @item edit *@var{address}
4592 Specifies the line containing the program address @var{address}.
4593 @var{address} may be any expression.
4596 @subsection Choosing your editor
4597 You can customize @value{GDBN} to use any editor you want
4599 The only restriction is that your editor (say @code{ex}), recognizes the
4600 following command-line syntax:
4602 ex +@var{number} file
4604 The optional numeric value +@var{number} specifies the number of the line in
4605 the file where to start editing.}.
4606 By default, it is @file{@value{EDITOR}}, but you can change this
4607 by setting the environment variable @code{EDITOR} before using
4608 @value{GDBN}. For example, to configure @value{GDBN} to use the
4609 @code{vi} editor, you could use these commands with the @code{sh} shell:
4615 or in the @code{csh} shell,
4617 setenv EDITOR /usr/bin/vi
4622 @section Searching source files
4623 @cindex searching source files
4625 There are two commands for searching through the current source file for a
4630 @kindex forward-search
4631 @item forward-search @var{regexp}
4632 @itemx search @var{regexp}
4633 The command @samp{forward-search @var{regexp}} checks each line,
4634 starting with the one following the last line listed, for a match for
4635 @var{regexp}. It lists the line that is found. You can use the
4636 synonym @samp{search @var{regexp}} or abbreviate the command name as
4639 @kindex reverse-search
4640 @item reverse-search @var{regexp}
4641 The command @samp{reverse-search @var{regexp}} checks each line, starting
4642 with the one before the last line listed and going backward, for a match
4643 for @var{regexp}. It lists the line that is found. You can abbreviate
4644 this command as @code{rev}.
4648 @section Specifying source directories
4651 @cindex directories for source files
4652 Executable programs sometimes do not record the directories of the source
4653 files from which they were compiled, just the names. Even when they do,
4654 the directories could be moved between the compilation and your debugging
4655 session. @value{GDBN} has a list of directories to search for source files;
4656 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4657 it tries all the directories in the list, in the order they are present
4658 in the list, until it finds a file with the desired name.
4660 For example, suppose an executable references the file
4661 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
4662 @file{/mnt/cross}. The file is first looked up literally; if this
4663 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
4664 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
4665 message is printed. @value{GDBN} does not look up the parts of the
4666 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
4667 Likewise, the subdirectories of the source path are not searched: if
4668 the source path is @file{/mnt/cross}, and the binary refers to
4669 @file{foo.c}, @value{GDBN} would not find it under
4670 @file{/mnt/cross/usr/src/foo-1.0/lib}.
4672 Plain file names, relative file names with leading directories, file
4673 names containing dots, etc.@: are all treated as described above; for
4674 instance, if the source path is @file{/mnt/cross}, and the source file
4675 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
4676 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
4677 that---@file{/mnt/cross/foo.c}.
4679 Note that the executable search path is @emph{not} used to locate the
4680 source files. Neither is the current working directory, unless it
4681 happens to be in the source path.
4683 Whenever you reset or rearrange the source path, @value{GDBN} clears out
4684 any information it has cached about where source files are found and where
4685 each line is in the file.
4689 When you start @value{GDBN}, its source path includes only @samp{cdir}
4690 and @samp{cwd}, in that order.
4691 To add other directories, use the @code{directory} command.
4694 @item directory @var{dirname} @dots{}
4695 @item dir @var{dirname} @dots{}
4696 Add directory @var{dirname} to the front of the source path. Several
4697 directory names may be given to this command, separated by @samp{:}
4698 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4699 part of absolute file names) or
4700 whitespace. You may specify a directory that is already in the source
4701 path; this moves it forward, so @value{GDBN} searches it sooner.
4705 @vindex $cdir@r{, convenience variable}
4706 @vindex $cwdr@r{, convenience variable}
4707 @cindex compilation directory
4708 @cindex current directory
4709 @cindex working directory
4710 @cindex directory, current
4711 @cindex directory, compilation
4712 You can use the string @samp{$cdir} to refer to the compilation
4713 directory (if one is recorded), and @samp{$cwd} to refer to the current
4714 working directory. @samp{$cwd} is not the same as @samp{.}---the former
4715 tracks the current working directory as it changes during your @value{GDBN}
4716 session, while the latter is immediately expanded to the current
4717 directory at the time you add an entry to the source path.
4720 Reset the source path to empty again. This requires confirmation.
4722 @c RET-repeat for @code{directory} is explicitly disabled, but since
4723 @c repeating it would be a no-op we do not say that. (thanks to RMS)
4725 @item show directories
4726 @kindex show directories
4727 Print the source path: show which directories it contains.
4730 If your source path is cluttered with directories that are no longer of
4731 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4732 versions of source. You can correct the situation as follows:
4736 Use @code{directory} with no argument to reset the source path to empty.
4739 Use @code{directory} with suitable arguments to reinstall the
4740 directories you want in the source path. You can add all the
4741 directories in one command.
4745 @section Source and machine code
4746 @cindex source line and its code address
4748 You can use the command @code{info line} to map source lines to program
4749 addresses (and vice versa), and the command @code{disassemble} to display
4750 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
4751 mode, the @code{info line} command causes the arrow to point to the
4752 line specified. Also, @code{info line} prints addresses in symbolic form as
4757 @item info line @var{linespec}
4758 Print the starting and ending addresses of the compiled code for
4759 source line @var{linespec}. You can specify source lines in any of
4760 the ways understood by the @code{list} command (@pxref{List, ,Printing
4764 For example, we can use @code{info line} to discover the location of
4765 the object code for the first line of function
4766 @code{m4_changequote}:
4768 @c FIXME: I think this example should also show the addresses in
4769 @c symbolic form, as they usually would be displayed.
4771 (@value{GDBP}) info line m4_changequote
4772 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4776 @cindex code address and its source line
4777 We can also inquire (using @code{*@var{addr}} as the form for
4778 @var{linespec}) what source line covers a particular address:
4780 (@value{GDBP}) info line *0x63ff
4781 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4784 @cindex @code{$_} and @code{info line}
4785 @cindex @code{x} command, default address
4786 @kindex x@r{(examine), and} info line
4787 After @code{info line}, the default address for the @code{x} command
4788 is changed to the starting address of the line, so that @samp{x/i} is
4789 sufficient to begin examining the machine code (@pxref{Memory,
4790 ,Examining memory}). Also, this address is saved as the value of the
4791 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4796 @cindex assembly instructions
4797 @cindex instructions, assembly
4798 @cindex machine instructions
4799 @cindex listing machine instructions
4801 This specialized command dumps a range of memory as machine
4802 instructions. The default memory range is the function surrounding the
4803 program counter of the selected frame. A single argument to this
4804 command is a program counter value; @value{GDBN} dumps the function
4805 surrounding this value. Two arguments specify a range of addresses
4806 (first inclusive, second exclusive) to dump.
4809 The following example shows the disassembly of a range of addresses of
4810 HP PA-RISC 2.0 code:
4813 (@value{GDBP}) disas 0x32c4 0x32e4
4814 Dump of assembler code from 0x32c4 to 0x32e4:
4815 0x32c4 <main+204>: addil 0,dp
4816 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
4817 0x32cc <main+212>: ldil 0x3000,r31
4818 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
4819 0x32d4 <main+220>: ldo 0(r31),rp
4820 0x32d8 <main+224>: addil -0x800,dp
4821 0x32dc <main+228>: ldo 0x588(r1),r26
4822 0x32e0 <main+232>: ldil 0x3000,r31
4823 End of assembler dump.
4826 Some architectures have more than one commonly-used set of instruction
4827 mnemonics or other syntax.
4830 @kindex set disassembly-flavor
4831 @cindex Intel disassembly flavor
4832 @cindex AT&T disassembly flavor
4833 @item set disassembly-flavor @var{instruction-set}
4834 Select the instruction set to use when disassembling the
4835 program via the @code{disassemble} or @code{x/i} commands.
4837 Currently this command is only defined for the Intel x86 family. You
4838 can set @var{instruction-set} to either @code{intel} or @code{att}.
4839 The default is @code{att}, the AT&T flavor used by default by Unix
4840 assemblers for x86-based targets.
4842 @kindex show disassembly-flavor
4843 @item show disassembly-flavor
4844 Show the current setting of the disassembly flavor.
4849 @chapter Examining Data
4851 @cindex printing data
4852 @cindex examining data
4855 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
4856 @c document because it is nonstandard... Under Epoch it displays in a
4857 @c different window or something like that.
4858 The usual way to examine data in your program is with the @code{print}
4859 command (abbreviated @code{p}), or its synonym @code{inspect}. It
4860 evaluates and prints the value of an expression of the language your
4861 program is written in (@pxref{Languages, ,Using @value{GDBN} with
4862 Different Languages}).
4865 @item print @var{expr}
4866 @itemx print /@var{f} @var{expr}
4867 @var{expr} is an expression (in the source language). By default the
4868 value of @var{expr} is printed in a format appropriate to its data type;
4869 you can choose a different format by specifying @samp{/@var{f}}, where
4870 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
4874 @itemx print /@var{f}
4875 @cindex reprint the last value
4876 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
4877 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
4878 conveniently inspect the same value in an alternative format.
4881 A more low-level way of examining data is with the @code{x} command.
4882 It examines data in memory at a specified address and prints it in a
4883 specified format. @xref{Memory, ,Examining memory}.
4885 If you are interested in information about types, or about how the
4886 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
4887 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
4891 * Expressions:: Expressions
4892 * Variables:: Program variables
4893 * Arrays:: Artificial arrays
4894 * Output Formats:: Output formats
4895 * Memory:: Examining memory
4896 * Auto Display:: Automatic display
4897 * Print Settings:: Print settings
4898 * Value History:: Value history
4899 * Convenience Vars:: Convenience variables
4900 * Registers:: Registers
4901 * Floating Point Hardware:: Floating point hardware
4902 * Vector Unit:: Vector Unit
4903 * OS Information:: Auxiliary data provided by operating system
4904 * Memory Region Attributes:: Memory region attributes
4905 * Dump/Restore Files:: Copy between memory and a file
4906 * Core File Generation:: Cause a program dump its core
4907 * Character Sets:: Debugging programs that use a different
4908 character set than GDB does
4909 * Caching Remote Data:: Data caching for remote targets
4913 @section Expressions
4916 @code{print} and many other @value{GDBN} commands accept an expression and
4917 compute its value. Any kind of constant, variable or operator defined
4918 by the programming language you are using is valid in an expression in
4919 @value{GDBN}. This includes conditional expressions, function calls,
4920 casts, and string constants. It also includes preprocessor macros, if
4921 you compiled your program to include this information; see
4924 @cindex arrays in expressions
4925 @value{GDBN} supports array constants in expressions input by
4926 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
4927 you can use the command @code{print @{1, 2, 3@}} to build up an array in
4928 memory that is @code{malloc}ed in the target program.
4930 Because C is so widespread, most of the expressions shown in examples in
4931 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
4932 Languages}, for information on how to use expressions in other
4935 In this section, we discuss operators that you can use in @value{GDBN}
4936 expressions regardless of your programming language.
4938 @cindex casts, in expressions
4939 Casts are supported in all languages, not just in C, because it is so
4940 useful to cast a number into a pointer in order to examine a structure
4941 at that address in memory.
4942 @c FIXME: casts supported---Mod2 true?
4944 @value{GDBN} supports these operators, in addition to those common
4945 to programming languages:
4949 @samp{@@} is a binary operator for treating parts of memory as arrays.
4950 @xref{Arrays, ,Artificial arrays}, for more information.
4953 @samp{::} allows you to specify a variable in terms of the file or
4954 function where it is defined. @xref{Variables, ,Program variables}.
4956 @cindex @{@var{type}@}
4957 @cindex type casting memory
4958 @cindex memory, viewing as typed object
4959 @cindex casts, to view memory
4960 @item @{@var{type}@} @var{addr}
4961 Refers to an object of type @var{type} stored at address @var{addr} in
4962 memory. @var{addr} may be any expression whose value is an integer or
4963 pointer (but parentheses are required around binary operators, just as in
4964 a cast). This construct is allowed regardless of what kind of data is
4965 normally supposed to reside at @var{addr}.
4969 @section Program variables
4971 The most common kind of expression to use is the name of a variable
4974 Variables in expressions are understood in the selected stack frame
4975 (@pxref{Selection, ,Selecting a frame}); they must be either:
4979 global (or file-static)
4986 visible according to the scope rules of the
4987 programming language from the point of execution in that frame
4990 @noindent This means that in the function
5005 you can examine and use the variable @code{a} whenever your program is
5006 executing within the function @code{foo}, but you can only use or
5007 examine the variable @code{b} while your program is executing inside
5008 the block where @code{b} is declared.
5010 @cindex variable name conflict
5011 There is an exception: you can refer to a variable or function whose
5012 scope is a single source file even if the current execution point is not
5013 in this file. But it is possible to have more than one such variable or
5014 function with the same name (in different source files). If that
5015 happens, referring to that name has unpredictable effects. If you wish,
5016 you can specify a static variable in a particular function or file,
5017 using the colon-colon (@code{::}) notation:
5019 @cindex colon-colon, context for variables/functions
5021 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5022 @cindex @code{::}, context for variables/functions
5025 @var{file}::@var{variable}
5026 @var{function}::@var{variable}
5030 Here @var{file} or @var{function} is the name of the context for the
5031 static @var{variable}. In the case of file names, you can use quotes to
5032 make sure @value{GDBN} parses the file name as a single word---for example,
5033 to print a global value of @code{x} defined in @file{f2.c}:
5036 (@value{GDBP}) p 'f2.c'::x
5039 @cindex C@t{++} scope resolution
5040 This use of @samp{::} is very rarely in conflict with the very similar
5041 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5042 scope resolution operator in @value{GDBN} expressions.
5043 @c FIXME: Um, so what happens in one of those rare cases where it's in
5046 @cindex wrong values
5047 @cindex variable values, wrong
5048 @cindex function entry/exit, wrong values of variables
5049 @cindex optimized code, wrong values of variables
5051 @emph{Warning:} Occasionally, a local variable may appear to have the
5052 wrong value at certain points in a function---just after entry to a new
5053 scope, and just before exit.
5055 You may see this problem when you are stepping by machine instructions.
5056 This is because, on most machines, it takes more than one instruction to
5057 set up a stack frame (including local variable definitions); if you are
5058 stepping by machine instructions, variables may appear to have the wrong
5059 values until the stack frame is completely built. On exit, it usually
5060 also takes more than one machine instruction to destroy a stack frame;
5061 after you begin stepping through that group of instructions, local
5062 variable definitions may be gone.
5064 This may also happen when the compiler does significant optimizations.
5065 To be sure of always seeing accurate values, turn off all optimization
5068 @cindex ``No symbol "foo" in current context''
5069 Another possible effect of compiler optimizations is to optimize
5070 unused variables out of existence, or assign variables to registers (as
5071 opposed to memory addresses). Depending on the support for such cases
5072 offered by the debug info format used by the compiler, @value{GDBN}
5073 might not be able to display values for such local variables. If that
5074 happens, @value{GDBN} will print a message like this:
5077 No symbol "foo" in current context.
5080 To solve such problems, either recompile without optimizations, or use a
5081 different debug info format, if the compiler supports several such
5082 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5083 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5084 produces debug info in a format that is superior to formats such as
5085 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5086 an effective form for debug info. @xref{Debugging Options,,Options
5087 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
5088 @xref{C, , Debugging C++}, for more info about debug info formats
5089 that are best suited to C@t{++} programs.
5092 @section Artificial arrays
5094 @cindex artificial array
5096 @kindex @@@r{, referencing memory as an array}
5097 It is often useful to print out several successive objects of the
5098 same type in memory; a section of an array, or an array of
5099 dynamically determined size for which only a pointer exists in the
5102 You can do this by referring to a contiguous span of memory as an
5103 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5104 operand of @samp{@@} should be the first element of the desired array
5105 and be an individual object. The right operand should be the desired length
5106 of the array. The result is an array value whose elements are all of
5107 the type of the left argument. The first element is actually the left
5108 argument; the second element comes from bytes of memory immediately
5109 following those that hold the first element, and so on. Here is an
5110 example. If a program says
5113 int *array = (int *) malloc (len * sizeof (int));
5117 you can print the contents of @code{array} with
5123 The left operand of @samp{@@} must reside in memory. Array values made
5124 with @samp{@@} in this way behave just like other arrays in terms of
5125 subscripting, and are coerced to pointers when used in expressions.
5126 Artificial arrays most often appear in expressions via the value history
5127 (@pxref{Value History, ,Value history}), after printing one out.
5129 Another way to create an artificial array is to use a cast.
5130 This re-interprets a value as if it were an array.
5131 The value need not be in memory:
5133 (@value{GDBP}) p/x (short[2])0x12345678
5134 $1 = @{0x1234, 0x5678@}
5137 As a convenience, if you leave the array length out (as in
5138 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5139 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5141 (@value{GDBP}) p/x (short[])0x12345678
5142 $2 = @{0x1234, 0x5678@}
5145 Sometimes the artificial array mechanism is not quite enough; in
5146 moderately complex data structures, the elements of interest may not
5147 actually be adjacent---for example, if you are interested in the values
5148 of pointers in an array. One useful work-around in this situation is
5149 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5150 variables}) as a counter in an expression that prints the first
5151 interesting value, and then repeat that expression via @key{RET}. For
5152 instance, suppose you have an array @code{dtab} of pointers to
5153 structures, and you are interested in the values of a field @code{fv}
5154 in each structure. Here is an example of what you might type:
5164 @node Output Formats
5165 @section Output formats
5167 @cindex formatted output
5168 @cindex output formats
5169 By default, @value{GDBN} prints a value according to its data type. Sometimes
5170 this is not what you want. For example, you might want to print a number
5171 in hex, or a pointer in decimal. Or you might want to view data in memory
5172 at a certain address as a character string or as an instruction. To do
5173 these things, specify an @dfn{output format} when you print a value.
5175 The simplest use of output formats is to say how to print a value
5176 already computed. This is done by starting the arguments of the
5177 @code{print} command with a slash and a format letter. The format
5178 letters supported are:
5182 Regard the bits of the value as an integer, and print the integer in
5186 Print as integer in signed decimal.
5189 Print as integer in unsigned decimal.
5192 Print as integer in octal.
5195 Print as integer in binary. The letter @samp{t} stands for ``two''.
5196 @footnote{@samp{b} cannot be used because these format letters are also
5197 used with the @code{x} command, where @samp{b} stands for ``byte'';
5198 see @ref{Memory,,Examining memory}.}
5201 @cindex unknown address, locating
5202 @cindex locate address
5203 Print as an address, both absolute in hexadecimal and as an offset from
5204 the nearest preceding symbol. You can use this format used to discover
5205 where (in what function) an unknown address is located:
5208 (@value{GDBP}) p/a 0x54320
5209 $3 = 0x54320 <_initialize_vx+396>
5213 The command @code{info symbol 0x54320} yields similar results.
5214 @xref{Symbols, info symbol}.
5217 Regard as an integer and print it as a character constant.
5220 Regard the bits of the value as a floating point number and print
5221 using typical floating point syntax.
5224 For example, to print the program counter in hex (@pxref{Registers}), type
5231 Note that no space is required before the slash; this is because command
5232 names in @value{GDBN} cannot contain a slash.
5234 To reprint the last value in the value history with a different format,
5235 you can use the @code{print} command with just a format and no
5236 expression. For example, @samp{p/x} reprints the last value in hex.
5239 @section Examining memory
5241 You can use the command @code{x} (for ``examine'') to examine memory in
5242 any of several formats, independently of your program's data types.
5244 @cindex examining memory
5246 @kindex x @r{(examine memory)}
5247 @item x/@var{nfu} @var{addr}
5250 Use the @code{x} command to examine memory.
5253 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5254 much memory to display and how to format it; @var{addr} is an
5255 expression giving the address where you want to start displaying memory.
5256 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5257 Several commands set convenient defaults for @var{addr}.
5260 @item @var{n}, the repeat count
5261 The repeat count is a decimal integer; the default is 1. It specifies
5262 how much memory (counting by units @var{u}) to display.
5263 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5266 @item @var{f}, the display format
5267 The display format is one of the formats used by @code{print},
5268 @samp{s} (null-terminated string), or @samp{i} (machine instruction).
5269 The default is @samp{x} (hexadecimal) initially.
5270 The default changes each time you use either @code{x} or @code{print}.
5272 @item @var{u}, the unit size
5273 The unit size is any of
5279 Halfwords (two bytes).
5281 Words (four bytes). This is the initial default.
5283 Giant words (eight bytes).
5286 Each time you specify a unit size with @code{x}, that size becomes the
5287 default unit the next time you use @code{x}. (For the @samp{s} and
5288 @samp{i} formats, the unit size is ignored and is normally not written.)
5290 @item @var{addr}, starting display address
5291 @var{addr} is the address where you want @value{GDBN} to begin displaying
5292 memory. The expression need not have a pointer value (though it may);
5293 it is always interpreted as an integer address of a byte of memory.
5294 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5295 @var{addr} is usually just after the last address examined---but several
5296 other commands also set the default address: @code{info breakpoints} (to
5297 the address of the last breakpoint listed), @code{info line} (to the
5298 starting address of a line), and @code{print} (if you use it to display
5299 a value from memory).
5302 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5303 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5304 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5305 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5306 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5308 Since the letters indicating unit sizes are all distinct from the
5309 letters specifying output formats, you do not have to remember whether
5310 unit size or format comes first; either order works. The output
5311 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5312 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5314 Even though the unit size @var{u} is ignored for the formats @samp{s}
5315 and @samp{i}, you might still want to use a count @var{n}; for example,
5316 @samp{3i} specifies that you want to see three machine instructions,
5317 including any operands. The command @code{disassemble} gives an
5318 alternative way of inspecting machine instructions; see @ref{Machine
5319 Code,,Source and machine code}.
5321 All the defaults for the arguments to @code{x} are designed to make it
5322 easy to continue scanning memory with minimal specifications each time
5323 you use @code{x}. For example, after you have inspected three machine
5324 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5325 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5326 the repeat count @var{n} is used again; the other arguments default as
5327 for successive uses of @code{x}.
5329 @cindex @code{$_}, @code{$__}, and value history
5330 The addresses and contents printed by the @code{x} command are not saved
5331 in the value history because there is often too much of them and they
5332 would get in the way. Instead, @value{GDBN} makes these values available for
5333 subsequent use in expressions as values of the convenience variables
5334 @code{$_} and @code{$__}. After an @code{x} command, the last address
5335 examined is available for use in expressions in the convenience variable
5336 @code{$_}. The contents of that address, as examined, are available in
5337 the convenience variable @code{$__}.
5339 If the @code{x} command has a repeat count, the address and contents saved
5340 are from the last memory unit printed; this is not the same as the last
5341 address printed if several units were printed on the last line of output.
5343 @cindex remote memory comparison
5344 @cindex verify remote memory image
5345 When you are debugging a program running on a remote target machine
5346 (@pxref{Remote}), you may wish to verify the program's image in the
5347 remote machine's memory against the executable file you downloaded to
5348 the target. The @code{compare-sections} command is provided for such
5352 @kindex compare-sections
5353 @item compare-sections @r{[}@var{section-name}@r{]}
5354 Compare the data of a loadable section @var{section-name} in the
5355 executable file of the program being debugged with the same section in
5356 the remote machine's memory, and report any mismatches. With no
5357 arguments, compares all loadable sections. This command's
5358 availability depends on the target's support for the @code{"qCRC"}
5363 @section Automatic display
5364 @cindex automatic display
5365 @cindex display of expressions
5367 If you find that you want to print the value of an expression frequently
5368 (to see how it changes), you might want to add it to the @dfn{automatic
5369 display list} so that @value{GDBN} prints its value each time your program stops.
5370 Each expression added to the list is given a number to identify it;
5371 to remove an expression from the list, you specify that number.
5372 The automatic display looks like this:
5376 3: bar[5] = (struct hack *) 0x3804
5380 This display shows item numbers, expressions and their current values. As with
5381 displays you request manually using @code{x} or @code{print}, you can
5382 specify the output format you prefer; in fact, @code{display} decides
5383 whether to use @code{print} or @code{x} depending on how elaborate your
5384 format specification is---it uses @code{x} if you specify a unit size,
5385 or one of the two formats (@samp{i} and @samp{s}) that are only
5386 supported by @code{x}; otherwise it uses @code{print}.
5390 @item display @var{expr}
5391 Add the expression @var{expr} to the list of expressions to display
5392 each time your program stops. @xref{Expressions, ,Expressions}.
5394 @code{display} does not repeat if you press @key{RET} again after using it.
5396 @item display/@var{fmt} @var{expr}
5397 For @var{fmt} specifying only a display format and not a size or
5398 count, add the expression @var{expr} to the auto-display list but
5399 arrange to display it each time in the specified format @var{fmt}.
5400 @xref{Output Formats,,Output formats}.
5402 @item display/@var{fmt} @var{addr}
5403 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5404 number of units, add the expression @var{addr} as a memory address to
5405 be examined each time your program stops. Examining means in effect
5406 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5409 For example, @samp{display/i $pc} can be helpful, to see the machine
5410 instruction about to be executed each time execution stops (@samp{$pc}
5411 is a common name for the program counter; @pxref{Registers, ,Registers}).
5414 @kindex delete display
5416 @item undisplay @var{dnums}@dots{}
5417 @itemx delete display @var{dnums}@dots{}
5418 Remove item numbers @var{dnums} from the list of expressions to display.
5420 @code{undisplay} does not repeat if you press @key{RET} after using it.
5421 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5423 @kindex disable display
5424 @item disable display @var{dnums}@dots{}
5425 Disable the display of item numbers @var{dnums}. A disabled display
5426 item is not printed automatically, but is not forgotten. It may be
5427 enabled again later.
5429 @kindex enable display
5430 @item enable display @var{dnums}@dots{}
5431 Enable display of item numbers @var{dnums}. It becomes effective once
5432 again in auto display of its expression, until you specify otherwise.
5435 Display the current values of the expressions on the list, just as is
5436 done when your program stops.
5438 @kindex info display
5440 Print the list of expressions previously set up to display
5441 automatically, each one with its item number, but without showing the
5442 values. This includes disabled expressions, which are marked as such.
5443 It also includes expressions which would not be displayed right now
5444 because they refer to automatic variables not currently available.
5447 @cindex display disabled out of scope
5448 If a display expression refers to local variables, then it does not make
5449 sense outside the lexical context for which it was set up. Such an
5450 expression is disabled when execution enters a context where one of its
5451 variables is not defined. For example, if you give the command
5452 @code{display last_char} while inside a function with an argument
5453 @code{last_char}, @value{GDBN} displays this argument while your program
5454 continues to stop inside that function. When it stops elsewhere---where
5455 there is no variable @code{last_char}---the display is disabled
5456 automatically. The next time your program stops where @code{last_char}
5457 is meaningful, you can enable the display expression once again.
5459 @node Print Settings
5460 @section Print settings
5462 @cindex format options
5463 @cindex print settings
5464 @value{GDBN} provides the following ways to control how arrays, structures,
5465 and symbols are printed.
5468 These settings are useful for debugging programs in any language:
5472 @item set print address
5473 @itemx set print address on
5474 @cindex print/don't print memory addresses
5475 @value{GDBN} prints memory addresses showing the location of stack
5476 traces, structure values, pointer values, breakpoints, and so forth,
5477 even when it also displays the contents of those addresses. The default
5478 is @code{on}. For example, this is what a stack frame display looks like with
5479 @code{set print address on}:
5484 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5486 530 if (lquote != def_lquote)
5490 @item set print address off
5491 Do not print addresses when displaying their contents. For example,
5492 this is the same stack frame displayed with @code{set print address off}:
5496 (@value{GDBP}) set print addr off
5498 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5499 530 if (lquote != def_lquote)
5503 You can use @samp{set print address off} to eliminate all machine
5504 dependent displays from the @value{GDBN} interface. For example, with
5505 @code{print address off}, you should get the same text for backtraces on
5506 all machines---whether or not they involve pointer arguments.
5509 @item show print address
5510 Show whether or not addresses are to be printed.
5513 When @value{GDBN} prints a symbolic address, it normally prints the
5514 closest earlier symbol plus an offset. If that symbol does not uniquely
5515 identify the address (for example, it is a name whose scope is a single
5516 source file), you may need to clarify. One way to do this is with
5517 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5518 you can set @value{GDBN} to print the source file and line number when
5519 it prints a symbolic address:
5522 @item set print symbol-filename on
5523 @cindex source file and line of a symbol
5524 @cindex symbol, source file and line
5525 Tell @value{GDBN} to print the source file name and line number of a
5526 symbol in the symbolic form of an address.
5528 @item set print symbol-filename off
5529 Do not print source file name and line number of a symbol. This is the
5532 @item show print symbol-filename
5533 Show whether or not @value{GDBN} will print the source file name and
5534 line number of a symbol in the symbolic form of an address.
5537 Another situation where it is helpful to show symbol filenames and line
5538 numbers is when disassembling code; @value{GDBN} shows you the line
5539 number and source file that corresponds to each instruction.
5541 Also, you may wish to see the symbolic form only if the address being
5542 printed is reasonably close to the closest earlier symbol:
5545 @item set print max-symbolic-offset @var{max-offset}
5546 @cindex maximum value for offset of closest symbol
5547 Tell @value{GDBN} to only display the symbolic form of an address if the
5548 offset between the closest earlier symbol and the address is less than
5549 @var{max-offset}. The default is 0, which tells @value{GDBN}
5550 to always print the symbolic form of an address if any symbol precedes it.
5552 @item show print max-symbolic-offset
5553 Ask how large the maximum offset is that @value{GDBN} prints in a
5557 @cindex wild pointer, interpreting
5558 @cindex pointer, finding referent
5559 If you have a pointer and you are not sure where it points, try
5560 @samp{set print symbol-filename on}. Then you can determine the name
5561 and source file location of the variable where it points, using
5562 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5563 For example, here @value{GDBN} shows that a variable @code{ptt} points
5564 at another variable @code{t}, defined in @file{hi2.c}:
5567 (@value{GDBP}) set print symbol-filename on
5568 (@value{GDBP}) p/a ptt
5569 $4 = 0xe008 <t in hi2.c>
5573 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5574 does not show the symbol name and filename of the referent, even with
5575 the appropriate @code{set print} options turned on.
5578 Other settings control how different kinds of objects are printed:
5581 @item set print array
5582 @itemx set print array on
5583 @cindex pretty print arrays
5584 Pretty print arrays. This format is more convenient to read,
5585 but uses more space. The default is off.
5587 @item set print array off
5588 Return to compressed format for arrays.
5590 @item show print array
5591 Show whether compressed or pretty format is selected for displaying
5594 @item set print elements @var{number-of-elements}
5595 @cindex number of array elements to print
5596 @cindex limit on number of printed array elements
5597 Set a limit on how many elements of an array @value{GDBN} will print.
5598 If @value{GDBN} is printing a large array, it stops printing after it has
5599 printed the number of elements set by the @code{set print elements} command.
5600 This limit also applies to the display of strings.
5601 When @value{GDBN} starts, this limit is set to 200.
5602 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5604 @item show print elements
5605 Display the number of elements of a large array that @value{GDBN} will print.
5606 If the number is 0, then the printing is unlimited.
5608 @item set print repeats
5609 @cindex repeated array elements
5610 Set the threshold for suppressing display of repeated array
5611 elelments. When the number of consecutive identical elements of an
5612 array exceeds the threshold, @value{GDBN} prints the string
5613 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
5614 identical repetitions, instead of displaying the identical elements
5615 themselves. Setting the threshold to zero will cause all elements to
5616 be individually printed. The default threshold is 10.
5618 @item show print repeats
5619 Display the current threshold for printing repeated identical
5622 @item set print null-stop
5623 @cindex @sc{null} elements in arrays
5624 Cause @value{GDBN} to stop printing the characters of an array when the first
5625 @sc{null} is encountered. This is useful when large arrays actually
5626 contain only short strings.
5629 @item show print null-stop
5630 Show whether @value{GDBN} stops printing an array on the first
5631 @sc{null} character.
5633 @item set print pretty on
5634 @cindex print structures in indented form
5635 @cindex indentation in structure display
5636 Cause @value{GDBN} to print structures in an indented format with one member
5637 per line, like this:
5652 @item set print pretty off
5653 Cause @value{GDBN} to print structures in a compact format, like this:
5657 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5658 meat = 0x54 "Pork"@}
5663 This is the default format.
5665 @item show print pretty
5666 Show which format @value{GDBN} is using to print structures.
5668 @item set print sevenbit-strings on
5669 @cindex eight-bit characters in strings
5670 @cindex octal escapes in strings
5671 Print using only seven-bit characters; if this option is set,
5672 @value{GDBN} displays any eight-bit characters (in strings or
5673 character values) using the notation @code{\}@var{nnn}. This setting is
5674 best if you are working in English (@sc{ascii}) and you use the
5675 high-order bit of characters as a marker or ``meta'' bit.
5677 @item set print sevenbit-strings off
5678 Print full eight-bit characters. This allows the use of more
5679 international character sets, and is the default.
5681 @item show print sevenbit-strings
5682 Show whether or not @value{GDBN} is printing only seven-bit characters.
5684 @item set print union on
5685 @cindex unions in structures, printing
5686 Tell @value{GDBN} to print unions which are contained in structures
5687 and other unions. This is the default setting.
5689 @item set print union off
5690 Tell @value{GDBN} not to print unions which are contained in
5691 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
5694 @item show print union
5695 Ask @value{GDBN} whether or not it will print unions which are contained in
5696 structures and other unions.
5698 For example, given the declarations
5701 typedef enum @{Tree, Bug@} Species;
5702 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5703 typedef enum @{Caterpillar, Cocoon, Butterfly@}
5714 struct thing foo = @{Tree, @{Acorn@}@};
5718 with @code{set print union on} in effect @samp{p foo} would print
5721 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5725 and with @code{set print union off} in effect it would print
5728 $1 = @{it = Tree, form = @{...@}@}
5732 @code{set print union} affects programs written in C-like languages
5738 These settings are of interest when debugging C@t{++} programs:
5741 @cindex demangling C@t{++} names
5742 @item set print demangle
5743 @itemx set print demangle on
5744 Print C@t{++} names in their source form rather than in the encoded
5745 (``mangled'') form passed to the assembler and linker for type-safe
5746 linkage. The default is on.
5748 @item show print demangle
5749 Show whether C@t{++} names are printed in mangled or demangled form.
5751 @item set print asm-demangle
5752 @itemx set print asm-demangle on
5753 Print C@t{++} names in their source form rather than their mangled form, even
5754 in assembler code printouts such as instruction disassemblies.
5757 @item show print asm-demangle
5758 Show whether C@t{++} names in assembly listings are printed in mangled
5761 @cindex C@t{++} symbol decoding style
5762 @cindex symbol decoding style, C@t{++}
5763 @kindex set demangle-style
5764 @item set demangle-style @var{style}
5765 Choose among several encoding schemes used by different compilers to
5766 represent C@t{++} names. The choices for @var{style} are currently:
5770 Allow @value{GDBN} to choose a decoding style by inspecting your program.
5773 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
5774 This is the default.
5777 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
5780 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
5783 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
5784 @strong{Warning:} this setting alone is not sufficient to allow
5785 debugging @code{cfront}-generated executables. @value{GDBN} would
5786 require further enhancement to permit that.
5789 If you omit @var{style}, you will see a list of possible formats.
5791 @item show demangle-style
5792 Display the encoding style currently in use for decoding C@t{++} symbols.
5794 @item set print object
5795 @itemx set print object on
5796 @cindex derived type of an object, printing
5797 @cindex display derived types
5798 When displaying a pointer to an object, identify the @emph{actual}
5799 (derived) type of the object rather than the @emph{declared} type, using
5800 the virtual function table.
5802 @item set print object off
5803 Display only the declared type of objects, without reference to the
5804 virtual function table. This is the default setting.
5806 @item show print object
5807 Show whether actual, or declared, object types are displayed.
5809 @item set print static-members
5810 @itemx set print static-members on
5811 @cindex static members of C@t{++} objects
5812 Print static members when displaying a C@t{++} object. The default is on.
5814 @item set print static-members off
5815 Do not print static members when displaying a C@t{++} object.
5817 @item show print static-members
5818 Show whether C@t{++} static members are printed or not.
5820 @item set print pascal_static-members
5821 @itemx set print pascal_static-members on
5822 @cindex static members of Pacal objects
5823 @cindex Pacal objects, static members display
5824 Print static members when displaying a Pascal object. The default is on.
5826 @item set print pascal_static-members off
5827 Do not print static members when displaying a Pascal object.
5829 @item show print pascal_static-members
5830 Show whether Pascal static members are printed or not.
5832 @c These don't work with HP ANSI C++ yet.
5833 @item set print vtbl
5834 @itemx set print vtbl on
5835 @cindex pretty print C@t{++} virtual function tables
5836 @cindex virtual functions (C@t{++}) display
5837 @cindex VTBL display
5838 Pretty print C@t{++} virtual function tables. The default is off.
5839 (The @code{vtbl} commands do not work on programs compiled with the HP
5840 ANSI C@t{++} compiler (@code{aCC}).)
5842 @item set print vtbl off
5843 Do not pretty print C@t{++} virtual function tables.
5845 @item show print vtbl
5846 Show whether C@t{++} virtual function tables are pretty printed, or not.
5850 @section Value history
5852 @cindex value history
5853 @cindex history of values printed by @value{GDBN}
5854 Values printed by the @code{print} command are saved in the @value{GDBN}
5855 @dfn{value history}. This allows you to refer to them in other expressions.
5856 Values are kept until the symbol table is re-read or discarded
5857 (for example with the @code{file} or @code{symbol-file} commands).
5858 When the symbol table changes, the value history is discarded,
5859 since the values may contain pointers back to the types defined in the
5864 @cindex history number
5865 The values printed are given @dfn{history numbers} by which you can
5866 refer to them. These are successive integers starting with one.
5867 @code{print} shows you the history number assigned to a value by
5868 printing @samp{$@var{num} = } before the value; here @var{num} is the
5871 To refer to any previous value, use @samp{$} followed by the value's
5872 history number. The way @code{print} labels its output is designed to
5873 remind you of this. Just @code{$} refers to the most recent value in
5874 the history, and @code{$$} refers to the value before that.
5875 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
5876 is the value just prior to @code{$$}, @code{$$1} is equivalent to
5877 @code{$$}, and @code{$$0} is equivalent to @code{$}.
5879 For example, suppose you have just printed a pointer to a structure and
5880 want to see the contents of the structure. It suffices to type
5886 If you have a chain of structures where the component @code{next} points
5887 to the next one, you can print the contents of the next one with this:
5894 You can print successive links in the chain by repeating this
5895 command---which you can do by just typing @key{RET}.
5897 Note that the history records values, not expressions. If the value of
5898 @code{x} is 4 and you type these commands:
5906 then the value recorded in the value history by the @code{print} command
5907 remains 4 even though the value of @code{x} has changed.
5912 Print the last ten values in the value history, with their item numbers.
5913 This is like @samp{p@ $$9} repeated ten times, except that @code{show
5914 values} does not change the history.
5916 @item show values @var{n}
5917 Print ten history values centered on history item number @var{n}.
5920 Print ten history values just after the values last printed. If no more
5921 values are available, @code{show values +} produces no display.
5924 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
5925 same effect as @samp{show values +}.
5927 @node Convenience Vars
5928 @section Convenience variables
5930 @cindex convenience variables
5931 @cindex user-defined variables
5932 @value{GDBN} provides @dfn{convenience variables} that you can use within
5933 @value{GDBN} to hold on to a value and refer to it later. These variables
5934 exist entirely within @value{GDBN}; they are not part of your program, and
5935 setting a convenience variable has no direct effect on further execution
5936 of your program. That is why you can use them freely.
5938 Convenience variables are prefixed with @samp{$}. Any name preceded by
5939 @samp{$} can be used for a convenience variable, unless it is one of
5940 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
5941 (Value history references, in contrast, are @emph{numbers} preceded
5942 by @samp{$}. @xref{Value History, ,Value history}.)
5944 You can save a value in a convenience variable with an assignment
5945 expression, just as you would set a variable in your program.
5949 set $foo = *object_ptr
5953 would save in @code{$foo} the value contained in the object pointed to by
5956 Using a convenience variable for the first time creates it, but its
5957 value is @code{void} until you assign a new value. You can alter the
5958 value with another assignment at any time.
5960 Convenience variables have no fixed types. You can assign a convenience
5961 variable any type of value, including structures and arrays, even if
5962 that variable already has a value of a different type. The convenience
5963 variable, when used as an expression, has the type of its current value.
5966 @kindex show convenience
5967 @cindex show all user variables
5968 @item show convenience
5969 Print a list of convenience variables used so far, and their values.
5970 Abbreviated @code{show conv}.
5973 One of the ways to use a convenience variable is as a counter to be
5974 incremented or a pointer to be advanced. For example, to print
5975 a field from successive elements of an array of structures:
5979 print bar[$i++]->contents
5983 Repeat that command by typing @key{RET}.
5985 Some convenience variables are created automatically by @value{GDBN} and given
5986 values likely to be useful.
5989 @vindex $_@r{, convenience variable}
5991 The variable @code{$_} is automatically set by the @code{x} command to
5992 the last address examined (@pxref{Memory, ,Examining memory}). Other
5993 commands which provide a default address for @code{x} to examine also
5994 set @code{$_} to that address; these commands include @code{info line}
5995 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
5996 except when set by the @code{x} command, in which case it is a pointer
5997 to the type of @code{$__}.
5999 @vindex $__@r{, convenience variable}
6001 The variable @code{$__} is automatically set by the @code{x} command
6002 to the value found in the last address examined. Its type is chosen
6003 to match the format in which the data was printed.
6006 @vindex $_exitcode@r{, convenience variable}
6007 The variable @code{$_exitcode} is automatically set to the exit code when
6008 the program being debugged terminates.
6011 On HP-UX systems, if you refer to a function or variable name that
6012 begins with a dollar sign, @value{GDBN} searches for a user or system
6013 name first, before it searches for a convenience variable.
6019 You can refer to machine register contents, in expressions, as variables
6020 with names starting with @samp{$}. The names of registers are different
6021 for each machine; use @code{info registers} to see the names used on
6025 @kindex info registers
6026 @item info registers
6027 Print the names and values of all registers except floating-point
6028 and vector registers (in the selected stack frame).
6030 @kindex info all-registers
6031 @cindex floating point registers
6032 @item info all-registers
6033 Print the names and values of all registers, including floating-point
6034 and vector registers (in the selected stack frame).
6036 @item info registers @var{regname} @dots{}
6037 Print the @dfn{relativized} value of each specified register @var{regname}.
6038 As discussed in detail below, register values are normally relative to
6039 the selected stack frame. @var{regname} may be any register name valid on
6040 the machine you are using, with or without the initial @samp{$}.
6043 @value{GDBN} has four ``standard'' register names that are available (in
6044 expressions) on most machines---whenever they do not conflict with an
6045 architecture's canonical mnemonics for registers. The register names
6046 @code{$pc} and @code{$sp} are used for the program counter register and
6047 the stack pointer. @code{$fp} is used for a register that contains a
6048 pointer to the current stack frame, and @code{$ps} is used for a
6049 register that contains the processor status. For example,
6050 you could print the program counter in hex with
6057 or print the instruction to be executed next with
6064 or add four to the stack pointer@footnote{This is a way of removing
6065 one word from the stack, on machines where stacks grow downward in
6066 memory (most machines, nowadays). This assumes that the innermost
6067 stack frame is selected; setting @code{$sp} is not allowed when other
6068 stack frames are selected. To pop entire frames off the stack,
6069 regardless of machine architecture, use @code{return};
6070 see @ref{Returning, ,Returning from a function}.} with
6076 Whenever possible, these four standard register names are available on
6077 your machine even though the machine has different canonical mnemonics,
6078 so long as there is no conflict. The @code{info registers} command
6079 shows the canonical names. For example, on the SPARC, @code{info
6080 registers} displays the processor status register as @code{$psr} but you
6081 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6082 is an alias for the @sc{eflags} register.
6084 @value{GDBN} always considers the contents of an ordinary register as an
6085 integer when the register is examined in this way. Some machines have
6086 special registers which can hold nothing but floating point; these
6087 registers are considered to have floating point values. There is no way
6088 to refer to the contents of an ordinary register as floating point value
6089 (although you can @emph{print} it as a floating point value with
6090 @samp{print/f $@var{regname}}).
6092 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6093 means that the data format in which the register contents are saved by
6094 the operating system is not the same one that your program normally
6095 sees. For example, the registers of the 68881 floating point
6096 coprocessor are always saved in ``extended'' (raw) format, but all C
6097 programs expect to work with ``double'' (virtual) format. In such
6098 cases, @value{GDBN} normally works with the virtual format only (the format
6099 that makes sense for your program), but the @code{info registers} command
6100 prints the data in both formats.
6102 Normally, register values are relative to the selected stack frame
6103 (@pxref{Selection, ,Selecting a frame}). This means that you get the
6104 value that the register would contain if all stack frames farther in
6105 were exited and their saved registers restored. In order to see the
6106 true contents of hardware registers, you must select the innermost
6107 frame (with @samp{frame 0}).
6109 However, @value{GDBN} must deduce where registers are saved, from the machine
6110 code generated by your compiler. If some registers are not saved, or if
6111 @value{GDBN} is unable to locate the saved registers, the selected stack
6112 frame makes no difference.
6114 @node Floating Point Hardware
6115 @section Floating point hardware
6116 @cindex floating point
6118 Depending on the configuration, @value{GDBN} may be able to give
6119 you more information about the status of the floating point hardware.
6124 Display hardware-dependent information about the floating
6125 point unit. The exact contents and layout vary depending on the
6126 floating point chip. Currently, @samp{info float} is supported on
6127 the ARM and x86 machines.
6131 @section Vector Unit
6134 Depending on the configuration, @value{GDBN} may be able to give you
6135 more information about the status of the vector unit.
6140 Display information about the vector unit. The exact contents and
6141 layout vary depending on the hardware.
6144 @node OS Information
6145 @section Operating system auxiliary information
6146 @cindex OS information
6148 @value{GDBN} provides interfaces to useful OS facilities that can help
6149 you debug your program.
6151 @cindex @code{ptrace} system call
6152 @cindex @code{struct user} contents
6153 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
6154 machines), it interfaces with the inferior via the @code{ptrace}
6155 system call. The operating system creates a special sata structure,
6156 called @code{struct user}, for this interface. You can use the
6157 command @code{info udot} to display the contents of this data
6163 Display the contents of the @code{struct user} maintained by the OS
6164 kernel for the program being debugged. @value{GDBN} displays the
6165 contents of @code{struct user} as a list of hex numbers, similar to
6166 the @code{examine} command.
6169 @cindex auxiliary vector
6170 @cindex vector, auxiliary
6171 Some operating systems supply an @dfn{auxiliary vector} to programs at
6172 startup. This is akin to the arguments and environment that you
6173 specify for a program, but contains a system-dependent variety of
6174 binary values that tell system libraries important details about the
6175 hardware, operating system, and process. Each value's purpose is
6176 identified by an integer tag; the meanings are well-known but system-specific.
6177 Depending on the configuration and operating system facilities,
6178 @value{GDBN} may be able to show you this information. For remote
6179 targets, this functionality may further depend on the remote stub's
6180 support of the @samp{qPart:auxv:read} packet, see @ref{Remote
6181 configuration, auxiliary vector}.
6186 Display the auxiliary vector of the inferior, which can be either a
6187 live process or a core dump file. @value{GDBN} prints each tag value
6188 numerically, and also shows names and text descriptions for recognized
6189 tags. Some values in the vector are numbers, some bit masks, and some
6190 pointers to strings or other data. @value{GDBN} displays each value in the
6191 most appropriate form for a recognized tag, and in hexadecimal for
6192 an unrecognized tag.
6196 @node Memory Region Attributes
6197 @section Memory region attributes
6198 @cindex memory region attributes
6200 @dfn{Memory region attributes} allow you to describe special handling
6201 required by regions of your target's memory. @value{GDBN} uses attributes
6202 to determine whether to allow certain types of memory accesses; whether to
6203 use specific width accesses; and whether to cache target memory.
6205 Defined memory regions can be individually enabled and disabled. When a
6206 memory region is disabled, @value{GDBN} uses the default attributes when
6207 accessing memory in that region. Similarly, if no memory regions have
6208 been defined, @value{GDBN} uses the default attributes when accessing
6211 When a memory region is defined, it is given a number to identify it;
6212 to enable, disable, or remove a memory region, you specify that number.
6216 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6217 Define a memory region bounded by @var{lower} and @var{upper} with
6218 attributes @var{attributes}@dots{}, and add it to the list of regions
6219 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
6220 case: it is treated as the the target's maximum memory address.
6221 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6224 @item delete mem @var{nums}@dots{}
6225 Remove memory regions @var{nums}@dots{} from the list of regions
6226 monitored by @value{GDBN}.
6229 @item disable mem @var{nums}@dots{}
6230 Disable monitoring of memory regions @var{nums}@dots{}.
6231 A disabled memory region is not forgotten.
6232 It may be enabled again later.
6235 @item enable mem @var{nums}@dots{}
6236 Enable monitoring of memory regions @var{nums}@dots{}.
6240 Print a table of all defined memory regions, with the following columns
6244 @item Memory Region Number
6245 @item Enabled or Disabled.
6246 Enabled memory regions are marked with @samp{y}.
6247 Disabled memory regions are marked with @samp{n}.
6250 The address defining the inclusive lower bound of the memory region.
6253 The address defining the exclusive upper bound of the memory region.
6256 The list of attributes set for this memory region.
6261 @subsection Attributes
6263 @subsubsection Memory Access Mode
6264 The access mode attributes set whether @value{GDBN} may make read or
6265 write accesses to a memory region.
6267 While these attributes prevent @value{GDBN} from performing invalid
6268 memory accesses, they do nothing to prevent the target system, I/O DMA,
6269 etc. from accessing memory.
6273 Memory is read only.
6275 Memory is write only.
6277 Memory is read/write. This is the default.
6280 @subsubsection Memory Access Size
6281 The acccess size attributes tells @value{GDBN} to use specific sized
6282 accesses in the memory region. Often memory mapped device registers
6283 require specific sized accesses. If no access size attribute is
6284 specified, @value{GDBN} may use accesses of any size.
6288 Use 8 bit memory accesses.
6290 Use 16 bit memory accesses.
6292 Use 32 bit memory accesses.
6294 Use 64 bit memory accesses.
6297 @c @subsubsection Hardware/Software Breakpoints
6298 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6299 @c will use hardware or software breakpoints for the internal breakpoints
6300 @c used by the step, next, finish, until, etc. commands.
6304 @c Always use hardware breakpoints
6305 @c @item swbreak (default)
6308 @subsubsection Data Cache
6309 The data cache attributes set whether @value{GDBN} will cache target
6310 memory. While this generally improves performance by reducing debug
6311 protocol overhead, it can lead to incorrect results because @value{GDBN}
6312 does not know about volatile variables or memory mapped device
6317 Enable @value{GDBN} to cache target memory.
6319 Disable @value{GDBN} from caching target memory. This is the default.
6322 @c @subsubsection Memory Write Verification
6323 @c The memory write verification attributes set whether @value{GDBN}
6324 @c will re-reads data after each write to verify the write was successful.
6328 @c @item noverify (default)
6331 @node Dump/Restore Files
6332 @section Copy between memory and a file
6333 @cindex dump/restore files
6334 @cindex append data to a file
6335 @cindex dump data to a file
6336 @cindex restore data from a file
6338 You can use the commands @code{dump}, @code{append}, and
6339 @code{restore} to copy data between target memory and a file. The
6340 @code{dump} and @code{append} commands write data to a file, and the
6341 @code{restore} command reads data from a file back into the inferior's
6342 memory. Files may be in binary, Motorola S-record, Intel hex, or
6343 Tektronix Hex format; however, @value{GDBN} can only append to binary
6349 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6350 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6351 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6352 or the value of @var{expr}, to @var{filename} in the given format.
6354 The @var{format} parameter may be any one of:
6361 Motorola S-record format.
6363 Tektronix Hex format.
6366 @value{GDBN} uses the same definitions of these formats as the
6367 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
6368 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
6372 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6373 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
6374 Append the contents of memory from @var{start_addr} to @var{end_addr},
6375 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
6376 (@value{GDBN} can only append data to files in raw binary form.)
6379 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
6380 Restore the contents of file @var{filename} into memory. The
6381 @code{restore} command can automatically recognize any known @sc{bfd}
6382 file format, except for raw binary. To restore a raw binary file you
6383 must specify the optional keyword @code{binary} after the filename.
6385 If @var{bias} is non-zero, its value will be added to the addresses
6386 contained in the file. Binary files always start at address zero, so
6387 they will be restored at address @var{bias}. Other bfd files have
6388 a built-in location; they will be restored at offset @var{bias}
6391 If @var{start} and/or @var{end} are non-zero, then only data between
6392 file offset @var{start} and file offset @var{end} will be restored.
6393 These offsets are relative to the addresses in the file, before
6394 the @var{bias} argument is applied.
6398 @node Core File Generation
6399 @section How to Produce a Core File from Your Program
6400 @cindex dump core from inferior
6402 A @dfn{core file} or @dfn{core dump} is a file that records the memory
6403 image of a running process and its process status (register values
6404 etc.). Its primary use is post-mortem debugging of a program that
6405 crashed while it ran outside a debugger. A program that crashes
6406 automatically produces a core file, unless this feature is disabled by
6407 the user. @xref{Files}, for information on invoking @value{GDBN} in
6408 the post-mortem debugging mode.
6410 Occasionally, you may wish to produce a core file of the program you
6411 are debugging in order to preserve a snapshot of its state.
6412 @value{GDBN} has a special command for that.
6416 @kindex generate-core-file
6417 @item generate-core-file [@var{file}]
6418 @itemx gcore [@var{file}]
6419 Produce a core dump of the inferior process. The optional argument
6420 @var{file} specifies the file name where to put the core dump. If not
6421 specified, the file name defaults to @file{core.@var{pid}}, where
6422 @var{pid} is the inferior process ID.
6424 Note that this command is implemented only for some systems (as of
6425 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
6428 @node Character Sets
6429 @section Character Sets
6430 @cindex character sets
6432 @cindex translating between character sets
6433 @cindex host character set
6434 @cindex target character set
6436 If the program you are debugging uses a different character set to
6437 represent characters and strings than the one @value{GDBN} uses itself,
6438 @value{GDBN} can automatically translate between the character sets for
6439 you. The character set @value{GDBN} uses we call the @dfn{host
6440 character set}; the one the inferior program uses we call the
6441 @dfn{target character set}.
6443 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
6444 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
6445 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
6446 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
6447 then the host character set is Latin-1, and the target character set is
6448 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
6449 target-charset EBCDIC-US}, then @value{GDBN} translates between
6450 @sc{ebcdic} and Latin 1 as you print character or string values, or use
6451 character and string literals in expressions.
6453 @value{GDBN} has no way to automatically recognize which character set
6454 the inferior program uses; you must tell it, using the @code{set
6455 target-charset} command, described below.
6457 Here are the commands for controlling @value{GDBN}'s character set
6461 @item set target-charset @var{charset}
6462 @kindex set target-charset
6463 Set the current target character set to @var{charset}. We list the
6464 character set names @value{GDBN} recognizes below, but if you type
6465 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6466 list the target character sets it supports.
6470 @item set host-charset @var{charset}
6471 @kindex set host-charset
6472 Set the current host character set to @var{charset}.
6474 By default, @value{GDBN} uses a host character set appropriate to the
6475 system it is running on; you can override that default using the
6476 @code{set host-charset} command.
6478 @value{GDBN} can only use certain character sets as its host character
6479 set. We list the character set names @value{GDBN} recognizes below, and
6480 indicate which can be host character sets, but if you type
6481 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6482 list the host character sets it supports.
6484 @item set charset @var{charset}
6486 Set the current host and target character sets to @var{charset}. As
6487 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
6488 @value{GDBN} will list the name of the character sets that can be used
6489 for both host and target.
6493 @kindex show charset
6494 Show the names of the current host and target charsets.
6496 @itemx show host-charset
6497 @kindex show host-charset
6498 Show the name of the current host charset.
6500 @itemx show target-charset
6501 @kindex show target-charset
6502 Show the name of the current target charset.
6506 @value{GDBN} currently includes support for the following character
6512 @cindex ASCII character set
6513 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6517 @cindex ISO 8859-1 character set
6518 @cindex ISO Latin 1 character set
6519 The ISO Latin 1 character set. This extends @sc{ascii} with accented
6520 characters needed for French, German, and Spanish. @value{GDBN} can use
6521 this as its host character set.
6525 @cindex EBCDIC character set
6526 @cindex IBM1047 character set
6527 Variants of the @sc{ebcdic} character set, used on some of IBM's
6528 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6529 @value{GDBN} cannot use these as its host character set.
6533 Note that these are all single-byte character sets. More work inside
6534 GDB is needed to support multi-byte or variable-width character
6535 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6537 Here is an example of @value{GDBN}'s character set support in action.
6538 Assume that the following source code has been placed in the file
6539 @file{charset-test.c}:
6545 = @{72, 101, 108, 108, 111, 44, 32, 119,
6546 111, 114, 108, 100, 33, 10, 0@};
6547 char ibm1047_hello[]
6548 = @{200, 133, 147, 147, 150, 107, 64, 166,
6549 150, 153, 147, 132, 90, 37, 0@};
6553 printf ("Hello, world!\n");
6557 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6558 containing the string @samp{Hello, world!} followed by a newline,
6559 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6561 We compile the program, and invoke the debugger on it:
6564 $ gcc -g charset-test.c -o charset-test
6565 $ gdb -nw charset-test
6566 GNU gdb 2001-12-19-cvs
6567 Copyright 2001 Free Software Foundation, Inc.
6572 We can use the @code{show charset} command to see what character sets
6573 @value{GDBN} is currently using to interpret and display characters and
6577 (@value{GDBP}) show charset
6578 The current host and target character set is `ISO-8859-1'.
6582 For the sake of printing this manual, let's use @sc{ascii} as our
6583 initial character set:
6585 (@value{GDBP}) set charset ASCII
6586 (@value{GDBP}) show charset
6587 The current host and target character set is `ASCII'.
6591 Let's assume that @sc{ascii} is indeed the correct character set for our
6592 host system --- in other words, let's assume that if @value{GDBN} prints
6593 characters using the @sc{ascii} character set, our terminal will display
6594 them properly. Since our current target character set is also
6595 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
6598 (@value{GDBP}) print ascii_hello
6599 $1 = 0x401698 "Hello, world!\n"
6600 (@value{GDBP}) print ascii_hello[0]
6605 @value{GDBN} uses the target character set for character and string
6606 literals you use in expressions:
6609 (@value{GDBP}) print '+'
6614 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
6617 @value{GDBN} relies on the user to tell it which character set the
6618 target program uses. If we print @code{ibm1047_hello} while our target
6619 character set is still @sc{ascii}, we get jibberish:
6622 (@value{GDBP}) print ibm1047_hello
6623 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
6624 (@value{GDBP}) print ibm1047_hello[0]
6629 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
6630 @value{GDBN} tells us the character sets it supports:
6633 (@value{GDBP}) set target-charset
6634 ASCII EBCDIC-US IBM1047 ISO-8859-1
6635 (@value{GDBP}) set target-charset
6638 We can select @sc{ibm1047} as our target character set, and examine the
6639 program's strings again. Now the @sc{ascii} string is wrong, but
6640 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
6641 target character set, @sc{ibm1047}, to the host character set,
6642 @sc{ascii}, and they display correctly:
6645 (@value{GDBP}) set target-charset IBM1047
6646 (@value{GDBP}) show charset
6647 The current host character set is `ASCII'.
6648 The current target character set is `IBM1047'.
6649 (@value{GDBP}) print ascii_hello
6650 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
6651 (@value{GDBP}) print ascii_hello[0]
6653 (@value{GDBP}) print ibm1047_hello
6654 $8 = 0x4016a8 "Hello, world!\n"
6655 (@value{GDBP}) print ibm1047_hello[0]
6660 As above, @value{GDBN} uses the target character set for character and
6661 string literals you use in expressions:
6664 (@value{GDBP}) print '+'
6669 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
6672 @node Caching Remote Data
6673 @section Caching Data of Remote Targets
6674 @cindex caching data of remote targets
6676 @value{GDBN} can cache data exchanged between the debugger and a
6677 remote target (@pxref{Remote}). Such caching generally improves
6678 performance, because it reduces the overhead of the remote protocol by
6679 bundling memory reads and writes into large chunks. Unfortunately,
6680 @value{GDBN} does not currently know anything about volatile
6681 registers, and thus data caching will produce incorrect results when
6682 volatile registers are in use.
6685 @kindex set remotecache
6686 @item set remotecache on
6687 @itemx set remotecache off
6688 Set caching state for remote targets. When @code{ON}, use data
6689 caching. By default, this option is @code{OFF}.
6691 @kindex show remotecache
6692 @item show remotecache
6693 Show the current state of data caching for remote targets.
6697 Print the information about the data cache performance. The
6698 information displayed includes: the dcache width and depth; and for
6699 each cache line, how many times it was referenced, and its data and
6700 state (dirty, bad, ok, etc.). This command is useful for debugging
6701 the data cache operation.
6706 @chapter C Preprocessor Macros
6708 Some languages, such as C and C@t{++}, provide a way to define and invoke
6709 ``preprocessor macros'' which expand into strings of tokens.
6710 @value{GDBN} can evaluate expressions containing macro invocations, show
6711 the result of macro expansion, and show a macro's definition, including
6712 where it was defined.
6714 You may need to compile your program specially to provide @value{GDBN}
6715 with information about preprocessor macros. Most compilers do not
6716 include macros in their debugging information, even when you compile
6717 with the @option{-g} flag. @xref{Compilation}.
6719 A program may define a macro at one point, remove that definition later,
6720 and then provide a different definition after that. Thus, at different
6721 points in the program, a macro may have different definitions, or have
6722 no definition at all. If there is a current stack frame, @value{GDBN}
6723 uses the macros in scope at that frame's source code line. Otherwise,
6724 @value{GDBN} uses the macros in scope at the current listing location;
6727 At the moment, @value{GDBN} does not support the @code{##}
6728 token-splicing operator, the @code{#} stringification operator, or
6729 variable-arity macros.
6731 Whenever @value{GDBN} evaluates an expression, it always expands any
6732 macro invocations present in the expression. @value{GDBN} also provides
6733 the following commands for working with macros explicitly.
6737 @kindex macro expand
6738 @cindex macro expansion, showing the results of preprocessor
6739 @cindex preprocessor macro expansion, showing the results of
6740 @cindex expanding preprocessor macros
6741 @item macro expand @var{expression}
6742 @itemx macro exp @var{expression}
6743 Show the results of expanding all preprocessor macro invocations in
6744 @var{expression}. Since @value{GDBN} simply expands macros, but does
6745 not parse the result, @var{expression} need not be a valid expression;
6746 it can be any string of tokens.
6749 @item macro expand-once @var{expression}
6750 @itemx macro exp1 @var{expression}
6751 @cindex expand macro once
6752 @i{(This command is not yet implemented.)} Show the results of
6753 expanding those preprocessor macro invocations that appear explicitly in
6754 @var{expression}. Macro invocations appearing in that expansion are
6755 left unchanged. This command allows you to see the effect of a
6756 particular macro more clearly, without being confused by further
6757 expansions. Since @value{GDBN} simply expands macros, but does not
6758 parse the result, @var{expression} need not be a valid expression; it
6759 can be any string of tokens.
6762 @cindex macro definition, showing
6763 @cindex definition, showing a macro's
6764 @item info macro @var{macro}
6765 Show the definition of the macro named @var{macro}, and describe the
6766 source location where that definition was established.
6768 @kindex macro define
6769 @cindex user-defined macros
6770 @cindex defining macros interactively
6771 @cindex macros, user-defined
6772 @item macro define @var{macro} @var{replacement-list}
6773 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
6774 @i{(This command is not yet implemented.)} Introduce a definition for a
6775 preprocessor macro named @var{macro}, invocations of which are replaced
6776 by the tokens given in @var{replacement-list}. The first form of this
6777 command defines an ``object-like'' macro, which takes no arguments; the
6778 second form defines a ``function-like'' macro, which takes the arguments
6779 given in @var{arglist}.
6781 A definition introduced by this command is in scope in every expression
6782 evaluated in @value{GDBN}, until it is removed with the @command{macro
6783 undef} command, described below. The definition overrides all
6784 definitions for @var{macro} present in the program being debugged, as
6785 well as any previous user-supplied definition.
6788 @item macro undef @var{macro}
6789 @i{(This command is not yet implemented.)} Remove any user-supplied
6790 definition for the macro named @var{macro}. This command only affects
6791 definitions provided with the @command{macro define} command, described
6792 above; it cannot remove definitions present in the program being
6797 @i{(This command is not yet implemented.)} List all the macros
6798 defined using the @code{macro define} command.
6801 @cindex macros, example of debugging with
6802 Here is a transcript showing the above commands in action. First, we
6803 show our source files:
6811 #define ADD(x) (M + x)
6816 printf ("Hello, world!\n");
6818 printf ("We're so creative.\n");
6820 printf ("Goodbye, world!\n");
6827 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
6828 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
6829 compiler includes information about preprocessor macros in the debugging
6833 $ gcc -gdwarf-2 -g3 sample.c -o sample
6837 Now, we start @value{GDBN} on our sample program:
6841 GNU gdb 2002-05-06-cvs
6842 Copyright 2002 Free Software Foundation, Inc.
6843 GDB is free software, @dots{}
6847 We can expand macros and examine their definitions, even when the
6848 program is not running. @value{GDBN} uses the current listing position
6849 to decide which macro definitions are in scope:
6852 (@value{GDBP}) list main
6855 5 #define ADD(x) (M + x)
6860 10 printf ("Hello, world!\n");
6862 12 printf ("We're so creative.\n");
6863 (@value{GDBP}) info macro ADD
6864 Defined at /home/jimb/gdb/macros/play/sample.c:5
6865 #define ADD(x) (M + x)
6866 (@value{GDBP}) info macro Q
6867 Defined at /home/jimb/gdb/macros/play/sample.h:1
6868 included at /home/jimb/gdb/macros/play/sample.c:2
6870 (@value{GDBP}) macro expand ADD(1)
6871 expands to: (42 + 1)
6872 (@value{GDBP}) macro expand-once ADD(1)
6873 expands to: once (M + 1)
6877 In the example above, note that @command{macro expand-once} expands only
6878 the macro invocation explicit in the original text --- the invocation of
6879 @code{ADD} --- but does not expand the invocation of the macro @code{M},
6880 which was introduced by @code{ADD}.
6882 Once the program is running, GDB uses the macro definitions in force at
6883 the source line of the current stack frame:
6886 (@value{GDBP}) break main
6887 Breakpoint 1 at 0x8048370: file sample.c, line 10.
6889 Starting program: /home/jimb/gdb/macros/play/sample
6891 Breakpoint 1, main () at sample.c:10
6892 10 printf ("Hello, world!\n");
6896 At line 10, the definition of the macro @code{N} at line 9 is in force:
6899 (@value{GDBP}) info macro N
6900 Defined at /home/jimb/gdb/macros/play/sample.c:9
6902 (@value{GDBP}) macro expand N Q M
6904 (@value{GDBP}) print N Q M
6909 As we step over directives that remove @code{N}'s definition, and then
6910 give it a new definition, @value{GDBN} finds the definition (or lack
6911 thereof) in force at each point:
6916 12 printf ("We're so creative.\n");
6917 (@value{GDBP}) info macro N
6918 The symbol `N' has no definition as a C/C++ preprocessor macro
6919 at /home/jimb/gdb/macros/play/sample.c:12
6922 14 printf ("Goodbye, world!\n");
6923 (@value{GDBP}) info macro N
6924 Defined at /home/jimb/gdb/macros/play/sample.c:13
6926 (@value{GDBP}) macro expand N Q M
6927 expands to: 1729 < 42
6928 (@value{GDBP}) print N Q M
6935 @chapter Tracepoints
6936 @c This chapter is based on the documentation written by Michael
6937 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
6940 In some applications, it is not feasible for the debugger to interrupt
6941 the program's execution long enough for the developer to learn
6942 anything helpful about its behavior. If the program's correctness
6943 depends on its real-time behavior, delays introduced by a debugger
6944 might cause the program to change its behavior drastically, or perhaps
6945 fail, even when the code itself is correct. It is useful to be able
6946 to observe the program's behavior without interrupting it.
6948 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
6949 specify locations in the program, called @dfn{tracepoints}, and
6950 arbitrary expressions to evaluate when those tracepoints are reached.
6951 Later, using the @code{tfind} command, you can examine the values
6952 those expressions had when the program hit the tracepoints. The
6953 expressions may also denote objects in memory---structures or arrays,
6954 for example---whose values @value{GDBN} should record; while visiting
6955 a particular tracepoint, you may inspect those objects as if they were
6956 in memory at that moment. However, because @value{GDBN} records these
6957 values without interacting with you, it can do so quickly and
6958 unobtrusively, hopefully not disturbing the program's behavior.
6960 The tracepoint facility is currently available only for remote
6961 targets. @xref{Targets}. In addition, your remote target must know how
6962 to collect trace data. This functionality is implemented in the remote
6963 stub; however, none of the stubs distributed with @value{GDBN} support
6964 tracepoints as of this writing.
6966 This chapter describes the tracepoint commands and features.
6970 * Analyze Collected Data::
6971 * Tracepoint Variables::
6974 @node Set Tracepoints
6975 @section Commands to Set Tracepoints
6977 Before running such a @dfn{trace experiment}, an arbitrary number of
6978 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
6979 tracepoint has a number assigned to it by @value{GDBN}. Like with
6980 breakpoints, tracepoint numbers are successive integers starting from
6981 one. Many of the commands associated with tracepoints take the
6982 tracepoint number as their argument, to identify which tracepoint to
6985 For each tracepoint, you can specify, in advance, some arbitrary set
6986 of data that you want the target to collect in the trace buffer when
6987 it hits that tracepoint. The collected data can include registers,
6988 local variables, or global data. Later, you can use @value{GDBN}
6989 commands to examine the values these data had at the time the
6992 This section describes commands to set tracepoints and associated
6993 conditions and actions.
6996 * Create and Delete Tracepoints::
6997 * Enable and Disable Tracepoints::
6998 * Tracepoint Passcounts::
6999 * Tracepoint Actions::
7000 * Listing Tracepoints::
7001 * Starting and Stopping Trace Experiment::
7004 @node Create and Delete Tracepoints
7005 @subsection Create and Delete Tracepoints
7008 @cindex set tracepoint
7011 The @code{trace} command is very similar to the @code{break} command.
7012 Its argument can be a source line, a function name, or an address in
7013 the target program. @xref{Set Breaks}. The @code{trace} command
7014 defines a tracepoint, which is a point in the target program where the
7015 debugger will briefly stop, collect some data, and then allow the
7016 program to continue. Setting a tracepoint or changing its commands
7017 doesn't take effect until the next @code{tstart} command; thus, you
7018 cannot change the tracepoint attributes once a trace experiment is
7021 Here are some examples of using the @code{trace} command:
7024 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
7026 (@value{GDBP}) @b{trace +2} // 2 lines forward
7028 (@value{GDBP}) @b{trace my_function} // first source line of function
7030 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
7032 (@value{GDBP}) @b{trace *0x2117c4} // an address
7036 You can abbreviate @code{trace} as @code{tr}.
7039 @cindex last tracepoint number
7040 @cindex recent tracepoint number
7041 @cindex tracepoint number
7042 The convenience variable @code{$tpnum} records the tracepoint number
7043 of the most recently set tracepoint.
7045 @kindex delete tracepoint
7046 @cindex tracepoint deletion
7047 @item delete tracepoint @r{[}@var{num}@r{]}
7048 Permanently delete one or more tracepoints. With no argument, the
7049 default is to delete all tracepoints.
7054 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
7056 (@value{GDBP}) @b{delete trace} // remove all tracepoints
7060 You can abbreviate this command as @code{del tr}.
7063 @node Enable and Disable Tracepoints
7064 @subsection Enable and Disable Tracepoints
7067 @kindex disable tracepoint
7068 @item disable tracepoint @r{[}@var{num}@r{]}
7069 Disable tracepoint @var{num}, or all tracepoints if no argument
7070 @var{num} is given. A disabled tracepoint will have no effect during
7071 the next trace experiment, but it is not forgotten. You can re-enable
7072 a disabled tracepoint using the @code{enable tracepoint} command.
7074 @kindex enable tracepoint
7075 @item enable tracepoint @r{[}@var{num}@r{]}
7076 Enable tracepoint @var{num}, or all tracepoints. The enabled
7077 tracepoints will become effective the next time a trace experiment is
7081 @node Tracepoint Passcounts
7082 @subsection Tracepoint Passcounts
7086 @cindex tracepoint pass count
7087 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
7088 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
7089 automatically stop a trace experiment. If a tracepoint's passcount is
7090 @var{n}, then the trace experiment will be automatically stopped on
7091 the @var{n}'th time that tracepoint is hit. If the tracepoint number
7092 @var{num} is not specified, the @code{passcount} command sets the
7093 passcount of the most recently defined tracepoint. If no passcount is
7094 given, the trace experiment will run until stopped explicitly by the
7100 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
7101 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
7103 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
7104 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
7105 (@value{GDBP}) @b{trace foo}
7106 (@value{GDBP}) @b{pass 3}
7107 (@value{GDBP}) @b{trace bar}
7108 (@value{GDBP}) @b{pass 2}
7109 (@value{GDBP}) @b{trace baz}
7110 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
7111 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
7112 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
7113 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
7117 @node Tracepoint Actions
7118 @subsection Tracepoint Action Lists
7122 @cindex tracepoint actions
7123 @item actions @r{[}@var{num}@r{]}
7124 This command will prompt for a list of actions to be taken when the
7125 tracepoint is hit. If the tracepoint number @var{num} is not
7126 specified, this command sets the actions for the one that was most
7127 recently defined (so that you can define a tracepoint and then say
7128 @code{actions} without bothering about its number). You specify the
7129 actions themselves on the following lines, one action at a time, and
7130 terminate the actions list with a line containing just @code{end}. So
7131 far, the only defined actions are @code{collect} and
7132 @code{while-stepping}.
7134 @cindex remove actions from a tracepoint
7135 To remove all actions from a tracepoint, type @samp{actions @var{num}}
7136 and follow it immediately with @samp{end}.
7139 (@value{GDBP}) @b{collect @var{data}} // collect some data
7141 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
7143 (@value{GDBP}) @b{end} // signals the end of actions.
7146 In the following example, the action list begins with @code{collect}
7147 commands indicating the things to be collected when the tracepoint is
7148 hit. Then, in order to single-step and collect additional data
7149 following the tracepoint, a @code{while-stepping} command is used,
7150 followed by the list of things to be collected while stepping. The
7151 @code{while-stepping} command is terminated by its own separate
7152 @code{end} command. Lastly, the action list is terminated by an
7156 (@value{GDBP}) @b{trace foo}
7157 (@value{GDBP}) @b{actions}
7158 Enter actions for tracepoint 1, one per line:
7167 @kindex collect @r{(tracepoints)}
7168 @item collect @var{expr1}, @var{expr2}, @dots{}
7169 Collect values of the given expressions when the tracepoint is hit.
7170 This command accepts a comma-separated list of any valid expressions.
7171 In addition to global, static, or local variables, the following
7172 special arguments are supported:
7176 collect all registers
7179 collect all function arguments
7182 collect all local variables.
7185 You can give several consecutive @code{collect} commands, each one
7186 with a single argument, or one @code{collect} command with several
7187 arguments separated by commas: the effect is the same.
7189 The command @code{info scope} (@pxref{Symbols, info scope}) is
7190 particularly useful for figuring out what data to collect.
7192 @kindex while-stepping @r{(tracepoints)}
7193 @item while-stepping @var{n}
7194 Perform @var{n} single-step traces after the tracepoint, collecting
7195 new data at each step. The @code{while-stepping} command is
7196 followed by the list of what to collect while stepping (followed by
7197 its own @code{end} command):
7201 > collect $regs, myglobal
7207 You may abbreviate @code{while-stepping} as @code{ws} or
7211 @node Listing Tracepoints
7212 @subsection Listing Tracepoints
7215 @kindex info tracepoints
7217 @cindex information about tracepoints
7218 @item info tracepoints @r{[}@var{num}@r{]}
7219 Display information about the tracepoint @var{num}. If you don't specify
7220 a tracepoint number, displays information about all the tracepoints
7221 defined so far. For each tracepoint, the following information is
7228 whether it is enabled or disabled
7232 its passcount as given by the @code{passcount @var{n}} command
7234 its step count as given by the @code{while-stepping @var{n}} command
7236 where in the source files is the tracepoint set
7238 its action list as given by the @code{actions} command
7242 (@value{GDBP}) @b{info trace}
7243 Num Enb Address PassC StepC What
7244 1 y 0x002117c4 0 0 <gdb_asm>
7245 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
7246 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
7251 This command can be abbreviated @code{info tp}.
7254 @node Starting and Stopping Trace Experiment
7255 @subsection Starting and Stopping Trace Experiment
7259 @cindex start a new trace experiment
7260 @cindex collected data discarded
7262 This command takes no arguments. It starts the trace experiment, and
7263 begins collecting data. This has the side effect of discarding all
7264 the data collected in the trace buffer during the previous trace
7268 @cindex stop a running trace experiment
7270 This command takes no arguments. It ends the trace experiment, and
7271 stops collecting data.
7273 @strong{Note}: a trace experiment and data collection may stop
7274 automatically if any tracepoint's passcount is reached
7275 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
7278 @cindex status of trace data collection
7279 @cindex trace experiment, status of
7281 This command displays the status of the current trace data
7285 Here is an example of the commands we described so far:
7288 (@value{GDBP}) @b{trace gdb_c_test}
7289 (@value{GDBP}) @b{actions}
7290 Enter actions for tracepoint #1, one per line.
7291 > collect $regs,$locals,$args
7296 (@value{GDBP}) @b{tstart}
7297 [time passes @dots{}]
7298 (@value{GDBP}) @b{tstop}
7302 @node Analyze Collected Data
7303 @section Using the collected data
7305 After the tracepoint experiment ends, you use @value{GDBN} commands
7306 for examining the trace data. The basic idea is that each tracepoint
7307 collects a trace @dfn{snapshot} every time it is hit and another
7308 snapshot every time it single-steps. All these snapshots are
7309 consecutively numbered from zero and go into a buffer, and you can
7310 examine them later. The way you examine them is to @dfn{focus} on a
7311 specific trace snapshot. When the remote stub is focused on a trace
7312 snapshot, it will respond to all @value{GDBN} requests for memory and
7313 registers by reading from the buffer which belongs to that snapshot,
7314 rather than from @emph{real} memory or registers of the program being
7315 debugged. This means that @strong{all} @value{GDBN} commands
7316 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
7317 behave as if we were currently debugging the program state as it was
7318 when the tracepoint occurred. Any requests for data that are not in
7319 the buffer will fail.
7322 * tfind:: How to select a trace snapshot
7323 * tdump:: How to display all data for a snapshot
7324 * save-tracepoints:: How to save tracepoints for a future run
7328 @subsection @code{tfind @var{n}}
7331 @cindex select trace snapshot
7332 @cindex find trace snapshot
7333 The basic command for selecting a trace snapshot from the buffer is
7334 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
7335 counting from zero. If no argument @var{n} is given, the next
7336 snapshot is selected.
7338 Here are the various forms of using the @code{tfind} command.
7342 Find the first snapshot in the buffer. This is a synonym for
7343 @code{tfind 0} (since 0 is the number of the first snapshot).
7346 Stop debugging trace snapshots, resume @emph{live} debugging.
7349 Same as @samp{tfind none}.
7352 No argument means find the next trace snapshot.
7355 Find the previous trace snapshot before the current one. This permits
7356 retracing earlier steps.
7358 @item tfind tracepoint @var{num}
7359 Find the next snapshot associated with tracepoint @var{num}. Search
7360 proceeds forward from the last examined trace snapshot. If no
7361 argument @var{num} is given, it means find the next snapshot collected
7362 for the same tracepoint as the current snapshot.
7364 @item tfind pc @var{addr}
7365 Find the next snapshot associated with the value @var{addr} of the
7366 program counter. Search proceeds forward from the last examined trace
7367 snapshot. If no argument @var{addr} is given, it means find the next
7368 snapshot with the same value of PC as the current snapshot.
7370 @item tfind outside @var{addr1}, @var{addr2}
7371 Find the next snapshot whose PC is outside the given range of
7374 @item tfind range @var{addr1}, @var{addr2}
7375 Find the next snapshot whose PC is between @var{addr1} and
7376 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
7378 @item tfind line @r{[}@var{file}:@r{]}@var{n}
7379 Find the next snapshot associated with the source line @var{n}. If
7380 the optional argument @var{file} is given, refer to line @var{n} in
7381 that source file. Search proceeds forward from the last examined
7382 trace snapshot. If no argument @var{n} is given, it means find the
7383 next line other than the one currently being examined; thus saying
7384 @code{tfind line} repeatedly can appear to have the same effect as
7385 stepping from line to line in a @emph{live} debugging session.
7388 The default arguments for the @code{tfind} commands are specifically
7389 designed to make it easy to scan through the trace buffer. For
7390 instance, @code{tfind} with no argument selects the next trace
7391 snapshot, and @code{tfind -} with no argument selects the previous
7392 trace snapshot. So, by giving one @code{tfind} command, and then
7393 simply hitting @key{RET} repeatedly you can examine all the trace
7394 snapshots in order. Or, by saying @code{tfind -} and then hitting
7395 @key{RET} repeatedly you can examine the snapshots in reverse order.
7396 The @code{tfind line} command with no argument selects the snapshot
7397 for the next source line executed. The @code{tfind pc} command with
7398 no argument selects the next snapshot with the same program counter
7399 (PC) as the current frame. The @code{tfind tracepoint} command with
7400 no argument selects the next trace snapshot collected by the same
7401 tracepoint as the current one.
7403 In addition to letting you scan through the trace buffer manually,
7404 these commands make it easy to construct @value{GDBN} scripts that
7405 scan through the trace buffer and print out whatever collected data
7406 you are interested in. Thus, if we want to examine the PC, FP, and SP
7407 registers from each trace frame in the buffer, we can say this:
7410 (@value{GDBP}) @b{tfind start}
7411 (@value{GDBP}) @b{while ($trace_frame != -1)}
7412 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
7413 $trace_frame, $pc, $sp, $fp
7417 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
7418 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
7419 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
7420 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
7421 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
7422 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
7423 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
7424 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
7425 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
7426 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
7427 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
7430 Or, if we want to examine the variable @code{X} at each source line in
7434 (@value{GDBP}) @b{tfind start}
7435 (@value{GDBP}) @b{while ($trace_frame != -1)}
7436 > printf "Frame %d, X == %d\n", $trace_frame, X
7446 @subsection @code{tdump}
7448 @cindex dump all data collected at tracepoint
7449 @cindex tracepoint data, display
7451 This command takes no arguments. It prints all the data collected at
7452 the current trace snapshot.
7455 (@value{GDBP}) @b{trace 444}
7456 (@value{GDBP}) @b{actions}
7457 Enter actions for tracepoint #2, one per line:
7458 > collect $regs, $locals, $args, gdb_long_test
7461 (@value{GDBP}) @b{tstart}
7463 (@value{GDBP}) @b{tfind line 444}
7464 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
7466 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
7468 (@value{GDBP}) @b{tdump}
7469 Data collected at tracepoint 2, trace frame 1:
7470 d0 0xc4aa0085 -995491707
7474 d4 0x71aea3d 119204413
7479 a1 0x3000668 50333288
7482 a4 0x3000698 50333336
7484 fp 0x30bf3c 0x30bf3c
7485 sp 0x30bf34 0x30bf34
7487 pc 0x20b2c8 0x20b2c8
7491 p = 0x20e5b4 "gdb-test"
7498 gdb_long_test = 17 '\021'
7503 @node save-tracepoints
7504 @subsection @code{save-tracepoints @var{filename}}
7505 @kindex save-tracepoints
7506 @cindex save tracepoints for future sessions
7508 This command saves all current tracepoint definitions together with
7509 their actions and passcounts, into a file @file{@var{filename}}
7510 suitable for use in a later debugging session. To read the saved
7511 tracepoint definitions, use the @code{source} command (@pxref{Command
7514 @node Tracepoint Variables
7515 @section Convenience Variables for Tracepoints
7516 @cindex tracepoint variables
7517 @cindex convenience variables for tracepoints
7520 @vindex $trace_frame
7521 @item (int) $trace_frame
7522 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
7523 snapshot is selected.
7526 @item (int) $tracepoint
7527 The tracepoint for the current trace snapshot.
7530 @item (int) $trace_line
7531 The line number for the current trace snapshot.
7534 @item (char []) $trace_file
7535 The source file for the current trace snapshot.
7538 @item (char []) $trace_func
7539 The name of the function containing @code{$tracepoint}.
7542 Note: @code{$trace_file} is not suitable for use in @code{printf},
7543 use @code{output} instead.
7545 Here's a simple example of using these convenience variables for
7546 stepping through all the trace snapshots and printing some of their
7550 (@value{GDBP}) @b{tfind start}
7552 (@value{GDBP}) @b{while $trace_frame != -1}
7553 > output $trace_file
7554 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7560 @chapter Debugging Programs That Use Overlays
7563 If your program is too large to fit completely in your target system's
7564 memory, you can sometimes use @dfn{overlays} to work around this
7565 problem. @value{GDBN} provides some support for debugging programs that
7569 * How Overlays Work:: A general explanation of overlays.
7570 * Overlay Commands:: Managing overlays in @value{GDBN}.
7571 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7572 mapped by asking the inferior.
7573 * Overlay Sample Program:: A sample program using overlays.
7576 @node How Overlays Work
7577 @section How Overlays Work
7578 @cindex mapped overlays
7579 @cindex unmapped overlays
7580 @cindex load address, overlay's
7581 @cindex mapped address
7582 @cindex overlay area
7584 Suppose you have a computer whose instruction address space is only 64
7585 kilobytes long, but which has much more memory which can be accessed by
7586 other means: special instructions, segment registers, or memory
7587 management hardware, for example. Suppose further that you want to
7588 adapt a program which is larger than 64 kilobytes to run on this system.
7590 One solution is to identify modules of your program which are relatively
7591 independent, and need not call each other directly; call these modules
7592 @dfn{overlays}. Separate the overlays from the main program, and place
7593 their machine code in the larger memory. Place your main program in
7594 instruction memory, but leave at least enough space there to hold the
7595 largest overlay as well.
7597 Now, to call a function located in an overlay, you must first copy that
7598 overlay's machine code from the large memory into the space set aside
7599 for it in the instruction memory, and then jump to its entry point
7602 @c NB: In the below the mapped area's size is greater or equal to the
7603 @c size of all overlays. This is intentional to remind the developer
7604 @c that overlays don't necessarily need to be the same size.
7608 Data Instruction Larger
7609 Address Space Address Space Address Space
7610 +-----------+ +-----------+ +-----------+
7612 +-----------+ +-----------+ +-----------+<-- overlay 1
7613 | program | | main | .----| overlay 1 | load address
7614 | variables | | program | | +-----------+
7615 | and heap | | | | | |
7616 +-----------+ | | | +-----------+<-- overlay 2
7617 | | +-----------+ | | | load address
7618 +-----------+ | | | .-| overlay 2 |
7620 mapped --->+-----------+ | | +-----------+
7622 | overlay | <-' | | |
7623 | area | <---' +-----------+<-- overlay 3
7624 | | <---. | | load address
7625 +-----------+ `--| overlay 3 |
7632 @anchor{A code overlay}A code overlay
7636 The diagram (@pxref{A code overlay}) shows a system with separate data
7637 and instruction address spaces. To map an overlay, the program copies
7638 its code from the larger address space to the instruction address space.
7639 Since the overlays shown here all use the same mapped address, only one
7640 may be mapped at a time. For a system with a single address space for
7641 data and instructions, the diagram would be similar, except that the
7642 program variables and heap would share an address space with the main
7643 program and the overlay area.
7645 An overlay loaded into instruction memory and ready for use is called a
7646 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
7647 instruction memory. An overlay not present (or only partially present)
7648 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
7649 is its address in the larger memory. The mapped address is also called
7650 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
7651 called the @dfn{load memory address}, or @dfn{LMA}.
7653 Unfortunately, overlays are not a completely transparent way to adapt a
7654 program to limited instruction memory. They introduce a new set of
7655 global constraints you must keep in mind as you design your program:
7660 Before calling or returning to a function in an overlay, your program
7661 must make sure that overlay is actually mapped. Otherwise, the call or
7662 return will transfer control to the right address, but in the wrong
7663 overlay, and your program will probably crash.
7666 If the process of mapping an overlay is expensive on your system, you
7667 will need to choose your overlays carefully to minimize their effect on
7668 your program's performance.
7671 The executable file you load onto your system must contain each
7672 overlay's instructions, appearing at the overlay's load address, not its
7673 mapped address. However, each overlay's instructions must be relocated
7674 and its symbols defined as if the overlay were at its mapped address.
7675 You can use GNU linker scripts to specify different load and relocation
7676 addresses for pieces of your program; see @ref{Overlay Description,,,
7677 ld.info, Using ld: the GNU linker}.
7680 The procedure for loading executable files onto your system must be able
7681 to load their contents into the larger address space as well as the
7682 instruction and data spaces.
7686 The overlay system described above is rather simple, and could be
7687 improved in many ways:
7692 If your system has suitable bank switch registers or memory management
7693 hardware, you could use those facilities to make an overlay's load area
7694 contents simply appear at their mapped address in instruction space.
7695 This would probably be faster than copying the overlay to its mapped
7696 area in the usual way.
7699 If your overlays are small enough, you could set aside more than one
7700 overlay area, and have more than one overlay mapped at a time.
7703 You can use overlays to manage data, as well as instructions. In
7704 general, data overlays are even less transparent to your design than
7705 code overlays: whereas code overlays only require care when you call or
7706 return to functions, data overlays require care every time you access
7707 the data. Also, if you change the contents of a data overlay, you
7708 must copy its contents back out to its load address before you can copy a
7709 different data overlay into the same mapped area.
7714 @node Overlay Commands
7715 @section Overlay Commands
7717 To use @value{GDBN}'s overlay support, each overlay in your program must
7718 correspond to a separate section of the executable file. The section's
7719 virtual memory address and load memory address must be the overlay's
7720 mapped and load addresses. Identifying overlays with sections allows
7721 @value{GDBN} to determine the appropriate address of a function or
7722 variable, depending on whether the overlay is mapped or not.
7724 @value{GDBN}'s overlay commands all start with the word @code{overlay};
7725 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
7730 Disable @value{GDBN}'s overlay support. When overlay support is
7731 disabled, @value{GDBN} assumes that all functions and variables are
7732 always present at their mapped addresses. By default, @value{GDBN}'s
7733 overlay support is disabled.
7735 @item overlay manual
7736 @cindex manual overlay debugging
7737 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
7738 relies on you to tell it which overlays are mapped, and which are not,
7739 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
7740 commands described below.
7742 @item overlay map-overlay @var{overlay}
7743 @itemx overlay map @var{overlay}
7744 @cindex map an overlay
7745 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
7746 be the name of the object file section containing the overlay. When an
7747 overlay is mapped, @value{GDBN} assumes it can find the overlay's
7748 functions and variables at their mapped addresses. @value{GDBN} assumes
7749 that any other overlays whose mapped ranges overlap that of
7750 @var{overlay} are now unmapped.
7752 @item overlay unmap-overlay @var{overlay}
7753 @itemx overlay unmap @var{overlay}
7754 @cindex unmap an overlay
7755 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
7756 must be the name of the object file section containing the overlay.
7757 When an overlay is unmapped, @value{GDBN} assumes it can find the
7758 overlay's functions and variables at their load addresses.
7761 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
7762 consults a data structure the overlay manager maintains in the inferior
7763 to see which overlays are mapped. For details, see @ref{Automatic
7766 @item overlay load-target
7768 @cindex reloading the overlay table
7769 Re-read the overlay table from the inferior. Normally, @value{GDBN}
7770 re-reads the table @value{GDBN} automatically each time the inferior
7771 stops, so this command should only be necessary if you have changed the
7772 overlay mapping yourself using @value{GDBN}. This command is only
7773 useful when using automatic overlay debugging.
7775 @item overlay list-overlays
7777 @cindex listing mapped overlays
7778 Display a list of the overlays currently mapped, along with their mapped
7779 addresses, load addresses, and sizes.
7783 Normally, when @value{GDBN} prints a code address, it includes the name
7784 of the function the address falls in:
7787 (@value{GDBP}) print main
7788 $3 = @{int ()@} 0x11a0 <main>
7791 When overlay debugging is enabled, @value{GDBN} recognizes code in
7792 unmapped overlays, and prints the names of unmapped functions with
7793 asterisks around them. For example, if @code{foo} is a function in an
7794 unmapped overlay, @value{GDBN} prints it this way:
7797 (@value{GDBP}) overlay list
7798 No sections are mapped.
7799 (@value{GDBP}) print foo
7800 $5 = @{int (int)@} 0x100000 <*foo*>
7803 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
7807 (@value{GDBP}) overlay list
7808 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
7809 mapped at 0x1016 - 0x104a
7810 (@value{GDBP}) print foo
7811 $6 = @{int (int)@} 0x1016 <foo>
7814 When overlay debugging is enabled, @value{GDBN} can find the correct
7815 address for functions and variables in an overlay, whether or not the
7816 overlay is mapped. This allows most @value{GDBN} commands, like
7817 @code{break} and @code{disassemble}, to work normally, even on unmapped
7818 code. However, @value{GDBN}'s breakpoint support has some limitations:
7822 @cindex breakpoints in overlays
7823 @cindex overlays, setting breakpoints in
7824 You can set breakpoints in functions in unmapped overlays, as long as
7825 @value{GDBN} can write to the overlay at its load address.
7827 @value{GDBN} can not set hardware or simulator-based breakpoints in
7828 unmapped overlays. However, if you set a breakpoint at the end of your
7829 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
7830 you are using manual overlay management), @value{GDBN} will re-set its
7831 breakpoints properly.
7835 @node Automatic Overlay Debugging
7836 @section Automatic Overlay Debugging
7837 @cindex automatic overlay debugging
7839 @value{GDBN} can automatically track which overlays are mapped and which
7840 are not, given some simple co-operation from the overlay manager in the
7841 inferior. If you enable automatic overlay debugging with the
7842 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
7843 looks in the inferior's memory for certain variables describing the
7844 current state of the overlays.
7846 Here are the variables your overlay manager must define to support
7847 @value{GDBN}'s automatic overlay debugging:
7851 @item @code{_ovly_table}:
7852 This variable must be an array of the following structures:
7857 /* The overlay's mapped address. */
7860 /* The size of the overlay, in bytes. */
7863 /* The overlay's load address. */
7866 /* Non-zero if the overlay is currently mapped;
7868 unsigned long mapped;
7872 @item @code{_novlys}:
7873 This variable must be a four-byte signed integer, holding the total
7874 number of elements in @code{_ovly_table}.
7878 To decide whether a particular overlay is mapped or not, @value{GDBN}
7879 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
7880 @code{lma} members equal the VMA and LMA of the overlay's section in the
7881 executable file. When @value{GDBN} finds a matching entry, it consults
7882 the entry's @code{mapped} member to determine whether the overlay is
7885 In addition, your overlay manager may define a function called
7886 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
7887 will silently set a breakpoint there. If the overlay manager then
7888 calls this function whenever it has changed the overlay table, this
7889 will enable @value{GDBN} to accurately keep track of which overlays
7890 are in program memory, and update any breakpoints that may be set
7891 in overlays. This will allow breakpoints to work even if the
7892 overlays are kept in ROM or other non-writable memory while they
7893 are not being executed.
7895 @node Overlay Sample Program
7896 @section Overlay Sample Program
7897 @cindex overlay example program
7899 When linking a program which uses overlays, you must place the overlays
7900 at their load addresses, while relocating them to run at their mapped
7901 addresses. To do this, you must write a linker script (@pxref{Overlay
7902 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
7903 since linker scripts are specific to a particular host system, target
7904 architecture, and target memory layout, this manual cannot provide
7905 portable sample code demonstrating @value{GDBN}'s overlay support.
7907 However, the @value{GDBN} source distribution does contain an overlaid
7908 program, with linker scripts for a few systems, as part of its test
7909 suite. The program consists of the following files from
7910 @file{gdb/testsuite/gdb.base}:
7914 The main program file.
7916 A simple overlay manager, used by @file{overlays.c}.
7921 Overlay modules, loaded and used by @file{overlays.c}.
7924 Linker scripts for linking the test program on the @code{d10v-elf}
7925 and @code{m32r-elf} targets.
7928 You can build the test program using the @code{d10v-elf} GCC
7929 cross-compiler like this:
7932 $ d10v-elf-gcc -g -c overlays.c
7933 $ d10v-elf-gcc -g -c ovlymgr.c
7934 $ d10v-elf-gcc -g -c foo.c
7935 $ d10v-elf-gcc -g -c bar.c
7936 $ d10v-elf-gcc -g -c baz.c
7937 $ d10v-elf-gcc -g -c grbx.c
7938 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
7939 baz.o grbx.o -Wl,-Td10v.ld -o overlays
7942 The build process is identical for any other architecture, except that
7943 you must substitute the appropriate compiler and linker script for the
7944 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
7948 @chapter Using @value{GDBN} with Different Languages
7951 Although programming languages generally have common aspects, they are
7952 rarely expressed in the same manner. For instance, in ANSI C,
7953 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
7954 Modula-2, it is accomplished by @code{p^}. Values can also be
7955 represented (and displayed) differently. Hex numbers in C appear as
7956 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
7958 @cindex working language
7959 Language-specific information is built into @value{GDBN} for some languages,
7960 allowing you to express operations like the above in your program's
7961 native language, and allowing @value{GDBN} to output values in a manner
7962 consistent with the syntax of your program's native language. The
7963 language you use to build expressions is called the @dfn{working
7967 * Setting:: Switching between source languages
7968 * Show:: Displaying the language
7969 * Checks:: Type and range checks
7970 * Supported languages:: Supported languages
7971 * Unsupported languages:: Unsupported languages
7975 @section Switching between source languages
7977 There are two ways to control the working language---either have @value{GDBN}
7978 set it automatically, or select it manually yourself. You can use the
7979 @code{set language} command for either purpose. On startup, @value{GDBN}
7980 defaults to setting the language automatically. The working language is
7981 used to determine how expressions you type are interpreted, how values
7984 In addition to the working language, every source file that
7985 @value{GDBN} knows about has its own working language. For some object
7986 file formats, the compiler might indicate which language a particular
7987 source file is in. However, most of the time @value{GDBN} infers the
7988 language from the name of the file. The language of a source file
7989 controls whether C@t{++} names are demangled---this way @code{backtrace} can
7990 show each frame appropriately for its own language. There is no way to
7991 set the language of a source file from within @value{GDBN}, but you can
7992 set the language associated with a filename extension. @xref{Show, ,
7993 Displaying the language}.
7995 This is most commonly a problem when you use a program, such
7996 as @code{cfront} or @code{f2c}, that generates C but is written in
7997 another language. In that case, make the
7998 program use @code{#line} directives in its C output; that way
7999 @value{GDBN} will know the correct language of the source code of the original
8000 program, and will display that source code, not the generated C code.
8003 * Filenames:: Filename extensions and languages.
8004 * Manually:: Setting the working language manually
8005 * Automatically:: Having @value{GDBN} infer the source language
8009 @subsection List of filename extensions and languages
8011 If a source file name ends in one of the following extensions, then
8012 @value{GDBN} infers that its language is the one indicated.
8033 Objective-C source file
8040 Modula-2 source file
8044 Assembler source file. This actually behaves almost like C, but
8045 @value{GDBN} does not skip over function prologues when stepping.
8048 In addition, you may set the language associated with a filename
8049 extension. @xref{Show, , Displaying the language}.
8052 @subsection Setting the working language
8054 If you allow @value{GDBN} to set the language automatically,
8055 expressions are interpreted the same way in your debugging session and
8058 @kindex set language
8059 If you wish, you may set the language manually. To do this, issue the
8060 command @samp{set language @var{lang}}, where @var{lang} is the name of
8062 @code{c} or @code{modula-2}.
8063 For a list of the supported languages, type @samp{set language}.
8065 Setting the language manually prevents @value{GDBN} from updating the working
8066 language automatically. This can lead to confusion if you try
8067 to debug a program when the working language is not the same as the
8068 source language, when an expression is acceptable to both
8069 languages---but means different things. For instance, if the current
8070 source file were written in C, and @value{GDBN} was parsing Modula-2, a
8078 might not have the effect you intended. In C, this means to add
8079 @code{b} and @code{c} and place the result in @code{a}. The result
8080 printed would be the value of @code{a}. In Modula-2, this means to compare
8081 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
8084 @subsection Having @value{GDBN} infer the source language
8086 To have @value{GDBN} set the working language automatically, use
8087 @samp{set language local} or @samp{set language auto}. @value{GDBN}
8088 then infers the working language. That is, when your program stops in a
8089 frame (usually by encountering a breakpoint), @value{GDBN} sets the
8090 working language to the language recorded for the function in that
8091 frame. If the language for a frame is unknown (that is, if the function
8092 or block corresponding to the frame was defined in a source file that
8093 does not have a recognized extension), the current working language is
8094 not changed, and @value{GDBN} issues a warning.
8096 This may not seem necessary for most programs, which are written
8097 entirely in one source language. However, program modules and libraries
8098 written in one source language can be used by a main program written in
8099 a different source language. Using @samp{set language auto} in this
8100 case frees you from having to set the working language manually.
8103 @section Displaying the language
8105 The following commands help you find out which language is the
8106 working language, and also what language source files were written in.
8110 @kindex show language
8111 Display the current working language. This is the
8112 language you can use with commands such as @code{print} to
8113 build and compute expressions that may involve variables in your program.
8116 @kindex info frame@r{, show the source language}
8117 Display the source language for this frame. This language becomes the
8118 working language if you use an identifier from this frame.
8119 @xref{Frame Info, ,Information about a frame}, to identify the other
8120 information listed here.
8123 @kindex info source@r{, show the source language}
8124 Display the source language of this source file.
8125 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
8126 information listed here.
8129 In unusual circumstances, you may have source files with extensions
8130 not in the standard list. You can then set the extension associated
8131 with a language explicitly:
8134 @item set extension-language @var{ext} @var{language}
8135 @kindex set extension-language
8136 Tell @value{GDBN} that source files with extension @var{ext} are to be
8137 assumed as written in the source language @var{language}.
8139 @item info extensions
8140 @kindex info extensions
8141 List all the filename extensions and the associated languages.
8145 @section Type and range checking
8148 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
8149 checking are included, but they do not yet have any effect. This
8150 section documents the intended facilities.
8152 @c FIXME remove warning when type/range code added
8154 Some languages are designed to guard you against making seemingly common
8155 errors through a series of compile- and run-time checks. These include
8156 checking the type of arguments to functions and operators, and making
8157 sure mathematical overflows are caught at run time. Checks such as
8158 these help to ensure a program's correctness once it has been compiled
8159 by eliminating type mismatches, and providing active checks for range
8160 errors when your program is running.
8162 @value{GDBN} can check for conditions like the above if you wish.
8163 Although @value{GDBN} does not check the statements in your program,
8164 it can check expressions entered directly into @value{GDBN} for
8165 evaluation via the @code{print} command, for example. As with the
8166 working language, @value{GDBN} can also decide whether or not to check
8167 automatically based on your program's source language.
8168 @xref{Supported languages, ,Supported languages}, for the default
8169 settings of supported languages.
8172 * Type Checking:: An overview of type checking
8173 * Range Checking:: An overview of range checking
8176 @cindex type checking
8177 @cindex checks, type
8179 @subsection An overview of type checking
8181 Some languages, such as Modula-2, are strongly typed, meaning that the
8182 arguments to operators and functions have to be of the correct type,
8183 otherwise an error occurs. These checks prevent type mismatch
8184 errors from ever causing any run-time problems. For example,
8192 The second example fails because the @code{CARDINAL} 1 is not
8193 type-compatible with the @code{REAL} 2.3.
8195 For the expressions you use in @value{GDBN} commands, you can tell the
8196 @value{GDBN} type checker to skip checking;
8197 to treat any mismatches as errors and abandon the expression;
8198 or to only issue warnings when type mismatches occur,
8199 but evaluate the expression anyway. When you choose the last of
8200 these, @value{GDBN} evaluates expressions like the second example above, but
8201 also issues a warning.
8203 Even if you turn type checking off, there may be other reasons
8204 related to type that prevent @value{GDBN} from evaluating an expression.
8205 For instance, @value{GDBN} does not know how to add an @code{int} and
8206 a @code{struct foo}. These particular type errors have nothing to do
8207 with the language in use, and usually arise from expressions, such as
8208 the one described above, which make little sense to evaluate anyway.
8210 Each language defines to what degree it is strict about type. For
8211 instance, both Modula-2 and C require the arguments to arithmetical
8212 operators to be numbers. In C, enumerated types and pointers can be
8213 represented as numbers, so that they are valid arguments to mathematical
8214 operators. @xref{Supported languages, ,Supported languages}, for further
8215 details on specific languages.
8217 @value{GDBN} provides some additional commands for controlling the type checker:
8219 @kindex set check type
8220 @kindex show check type
8222 @item set check type auto
8223 Set type checking on or off based on the current working language.
8224 @xref{Supported languages, ,Supported languages}, for the default settings for
8227 @item set check type on
8228 @itemx set check type off
8229 Set type checking on or off, overriding the default setting for the
8230 current working language. Issue a warning if the setting does not
8231 match the language default. If any type mismatches occur in
8232 evaluating an expression while type checking is on, @value{GDBN} prints a
8233 message and aborts evaluation of the expression.
8235 @item set check type warn
8236 Cause the type checker to issue warnings, but to always attempt to
8237 evaluate the expression. Evaluating the expression may still
8238 be impossible for other reasons. For example, @value{GDBN} cannot add
8239 numbers and structures.
8242 Show the current setting of the type checker, and whether or not @value{GDBN}
8243 is setting it automatically.
8246 @cindex range checking
8247 @cindex checks, range
8248 @node Range Checking
8249 @subsection An overview of range checking
8251 In some languages (such as Modula-2), it is an error to exceed the
8252 bounds of a type; this is enforced with run-time checks. Such range
8253 checking is meant to ensure program correctness by making sure
8254 computations do not overflow, or indices on an array element access do
8255 not exceed the bounds of the array.
8257 For expressions you use in @value{GDBN} commands, you can tell
8258 @value{GDBN} to treat range errors in one of three ways: ignore them,
8259 always treat them as errors and abandon the expression, or issue
8260 warnings but evaluate the expression anyway.
8262 A range error can result from numerical overflow, from exceeding an
8263 array index bound, or when you type a constant that is not a member
8264 of any type. Some languages, however, do not treat overflows as an
8265 error. In many implementations of C, mathematical overflow causes the
8266 result to ``wrap around'' to lower values---for example, if @var{m} is
8267 the largest integer value, and @var{s} is the smallest, then
8270 @var{m} + 1 @result{} @var{s}
8273 This, too, is specific to individual languages, and in some cases
8274 specific to individual compilers or machines. @xref{Supported languages, ,
8275 Supported languages}, for further details on specific languages.
8277 @value{GDBN} provides some additional commands for controlling the range checker:
8279 @kindex set check range
8280 @kindex show check range
8282 @item set check range auto
8283 Set range checking on or off based on the current working language.
8284 @xref{Supported languages, ,Supported languages}, for the default settings for
8287 @item set check range on
8288 @itemx set check range off
8289 Set range checking on or off, overriding the default setting for the
8290 current working language. A warning is issued if the setting does not
8291 match the language default. If a range error occurs and range checking is on,
8292 then a message is printed and evaluation of the expression is aborted.
8294 @item set check range warn
8295 Output messages when the @value{GDBN} range checker detects a range error,
8296 but attempt to evaluate the expression anyway. Evaluating the
8297 expression may still be impossible for other reasons, such as accessing
8298 memory that the process does not own (a typical example from many Unix
8302 Show the current setting of the range checker, and whether or not it is
8303 being set automatically by @value{GDBN}.
8306 @node Supported languages
8307 @section Supported languages
8309 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
8310 assembly, Modula-2, and Ada.
8311 @c This is false ...
8312 Some @value{GDBN} features may be used in expressions regardless of the
8313 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
8314 and the @samp{@{type@}addr} construct (@pxref{Expressions,
8315 ,Expressions}) can be used with the constructs of any supported
8318 The following sections detail to what degree each source language is
8319 supported by @value{GDBN}. These sections are not meant to be language
8320 tutorials or references, but serve only as a reference guide to what the
8321 @value{GDBN} expression parser accepts, and what input and output
8322 formats should look like for different languages. There are many good
8323 books written on each of these languages; please look to these for a
8324 language reference or tutorial.
8328 * Objective-C:: Objective-C
8331 * Modula-2:: Modula-2
8336 @subsection C and C@t{++}
8338 @cindex C and C@t{++}
8339 @cindex expressions in C or C@t{++}
8341 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
8342 to both languages. Whenever this is the case, we discuss those languages
8346 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
8347 @cindex @sc{gnu} C@t{++}
8348 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
8349 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
8350 effectively, you must compile your C@t{++} programs with a supported
8351 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
8352 compiler (@code{aCC}).
8354 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
8355 format; if it doesn't work on your system, try the stabs+ debugging
8356 format. You can select those formats explicitly with the @code{g++}
8357 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
8358 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
8359 CC, gcc.info, Using @sc{gnu} CC}.
8362 * C Operators:: C and C@t{++} operators
8363 * C Constants:: C and C@t{++} constants
8364 * C plus plus expressions:: C@t{++} expressions
8365 * C Defaults:: Default settings for C and C@t{++}
8366 * C Checks:: C and C@t{++} type and range checks
8367 * Debugging C:: @value{GDBN} and C
8368 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
8372 @subsubsection C and C@t{++} operators
8374 @cindex C and C@t{++} operators
8376 Operators must be defined on values of specific types. For instance,
8377 @code{+} is defined on numbers, but not on structures. Operators are
8378 often defined on groups of types.
8380 For the purposes of C and C@t{++}, the following definitions hold:
8385 @emph{Integral types} include @code{int} with any of its storage-class
8386 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
8389 @emph{Floating-point types} include @code{float}, @code{double}, and
8390 @code{long double} (if supported by the target platform).
8393 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
8396 @emph{Scalar types} include all of the above.
8401 The following operators are supported. They are listed here
8402 in order of increasing precedence:
8406 The comma or sequencing operator. Expressions in a comma-separated list
8407 are evaluated from left to right, with the result of the entire
8408 expression being the last expression evaluated.
8411 Assignment. The value of an assignment expression is the value
8412 assigned. Defined on scalar types.
8415 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
8416 and translated to @w{@code{@var{a} = @var{a op b}}}.
8417 @w{@code{@var{op}=}} and @code{=} have the same precedence.
8418 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
8419 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
8422 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
8423 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
8427 Logical @sc{or}. Defined on integral types.
8430 Logical @sc{and}. Defined on integral types.
8433 Bitwise @sc{or}. Defined on integral types.
8436 Bitwise exclusive-@sc{or}. Defined on integral types.
8439 Bitwise @sc{and}. Defined on integral types.
8442 Equality and inequality. Defined on scalar types. The value of these
8443 expressions is 0 for false and non-zero for true.
8445 @item <@r{, }>@r{, }<=@r{, }>=
8446 Less than, greater than, less than or equal, greater than or equal.
8447 Defined on scalar types. The value of these expressions is 0 for false
8448 and non-zero for true.
8451 left shift, and right shift. Defined on integral types.
8454 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8457 Addition and subtraction. Defined on integral types, floating-point types and
8460 @item *@r{, }/@r{, }%
8461 Multiplication, division, and modulus. Multiplication and division are
8462 defined on integral and floating-point types. Modulus is defined on
8466 Increment and decrement. When appearing before a variable, the
8467 operation is performed before the variable is used in an expression;
8468 when appearing after it, the variable's value is used before the
8469 operation takes place.
8472 Pointer dereferencing. Defined on pointer types. Same precedence as
8476 Address operator. Defined on variables. Same precedence as @code{++}.
8478 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
8479 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
8480 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
8481 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
8485 Negative. Defined on integral and floating-point types. Same
8486 precedence as @code{++}.
8489 Logical negation. Defined on integral types. Same precedence as
8493 Bitwise complement operator. Defined on integral types. Same precedence as
8498 Structure member, and pointer-to-structure member. For convenience,
8499 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
8500 pointer based on the stored type information.
8501 Defined on @code{struct} and @code{union} data.
8504 Dereferences of pointers to members.
8507 Array indexing. @code{@var{a}[@var{i}]} is defined as
8508 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
8511 Function parameter list. Same precedence as @code{->}.
8514 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
8515 and @code{class} types.
8518 Doubled colons also represent the @value{GDBN} scope operator
8519 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
8523 If an operator is redefined in the user code, @value{GDBN} usually
8524 attempts to invoke the redefined version instead of using the operator's
8532 @subsubsection C and C@t{++} constants
8534 @cindex C and C@t{++} constants
8536 @value{GDBN} allows you to express the constants of C and C@t{++} in the
8541 Integer constants are a sequence of digits. Octal constants are
8542 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
8543 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
8544 @samp{l}, specifying that the constant should be treated as a
8548 Floating point constants are a sequence of digits, followed by a decimal
8549 point, followed by a sequence of digits, and optionally followed by an
8550 exponent. An exponent is of the form:
8551 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8552 sequence of digits. The @samp{+} is optional for positive exponents.
8553 A floating-point constant may also end with a letter @samp{f} or
8554 @samp{F}, specifying that the constant should be treated as being of
8555 the @code{float} (as opposed to the default @code{double}) type; or with
8556 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8560 Enumerated constants consist of enumerated identifiers, or their
8561 integral equivalents.
8564 Character constants are a single character surrounded by single quotes
8565 (@code{'}), or a number---the ordinal value of the corresponding character
8566 (usually its @sc{ascii} value). Within quotes, the single character may
8567 be represented by a letter or by @dfn{escape sequences}, which are of
8568 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8569 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8570 @samp{@var{x}} is a predefined special character---for example,
8571 @samp{\n} for newline.
8574 String constants are a sequence of character constants surrounded by
8575 double quotes (@code{"}). Any valid character constant (as described
8576 above) may appear. Double quotes within the string must be preceded by
8577 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8581 Pointer constants are an integral value. You can also write pointers
8582 to constants using the C operator @samp{&}.
8585 Array constants are comma-separated lists surrounded by braces @samp{@{}
8586 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8587 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8588 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8592 * C plus plus expressions::
8599 @node C plus plus expressions
8600 @subsubsection C@t{++} expressions
8602 @cindex expressions in C@t{++}
8603 @value{GDBN} expression handling can interpret most C@t{++} expressions.
8605 @cindex debugging C@t{++} programs
8606 @cindex C@t{++} compilers
8607 @cindex debug formats and C@t{++}
8608 @cindex @value{NGCC} and C@t{++}
8610 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
8611 proper compiler and the proper debug format. Currently, @value{GDBN}
8612 works best when debugging C@t{++} code that is compiled with
8613 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
8614 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
8615 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
8616 stabs+ as their default debug format, so you usually don't need to
8617 specify a debug format explicitly. Other compilers and/or debug formats
8618 are likely to work badly or not at all when using @value{GDBN} to debug
8624 @cindex member functions
8626 Member function calls are allowed; you can use expressions like
8629 count = aml->GetOriginal(x, y)
8632 @vindex this@r{, inside C@t{++} member functions}
8633 @cindex namespace in C@t{++}
8635 While a member function is active (in the selected stack frame), your
8636 expressions have the same namespace available as the member function;
8637 that is, @value{GDBN} allows implicit references to the class instance
8638 pointer @code{this} following the same rules as C@t{++}.
8640 @cindex call overloaded functions
8641 @cindex overloaded functions, calling
8642 @cindex type conversions in C@t{++}
8644 You can call overloaded functions; @value{GDBN} resolves the function
8645 call to the right definition, with some restrictions. @value{GDBN} does not
8646 perform overload resolution involving user-defined type conversions,
8647 calls to constructors, or instantiations of templates that do not exist
8648 in the program. It also cannot handle ellipsis argument lists or
8651 It does perform integral conversions and promotions, floating-point
8652 promotions, arithmetic conversions, pointer conversions, conversions of
8653 class objects to base classes, and standard conversions such as those of
8654 functions or arrays to pointers; it requires an exact match on the
8655 number of function arguments.
8657 Overload resolution is always performed, unless you have specified
8658 @code{set overload-resolution off}. @xref{Debugging C plus plus,
8659 ,@value{GDBN} features for C@t{++}}.
8661 You must specify @code{set overload-resolution off} in order to use an
8662 explicit function signature to call an overloaded function, as in
8664 p 'foo(char,int)'('x', 13)
8667 The @value{GDBN} command-completion facility can simplify this;
8668 see @ref{Completion, ,Command completion}.
8670 @cindex reference declarations
8672 @value{GDBN} understands variables declared as C@t{++} references; you can use
8673 them in expressions just as you do in C@t{++} source---they are automatically
8676 In the parameter list shown when @value{GDBN} displays a frame, the values of
8677 reference variables are not displayed (unlike other variables); this
8678 avoids clutter, since references are often used for large structures.
8679 The @emph{address} of a reference variable is always shown, unless
8680 you have specified @samp{set print address off}.
8683 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
8684 expressions can use it just as expressions in your program do. Since
8685 one scope may be defined in another, you can use @code{::} repeatedly if
8686 necessary, for example in an expression like
8687 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
8688 resolving name scope by reference to source files, in both C and C@t{++}
8689 debugging (@pxref{Variables, ,Program variables}).
8692 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
8693 calling virtual functions correctly, printing out virtual bases of
8694 objects, calling functions in a base subobject, casting objects, and
8695 invoking user-defined operators.
8698 @subsubsection C and C@t{++} defaults
8700 @cindex C and C@t{++} defaults
8702 If you allow @value{GDBN} to set type and range checking automatically, they
8703 both default to @code{off} whenever the working language changes to
8704 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
8705 selects the working language.
8707 If you allow @value{GDBN} to set the language automatically, it
8708 recognizes source files whose names end with @file{.c}, @file{.C}, or
8709 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
8710 these files, it sets the working language to C or C@t{++}.
8711 @xref{Automatically, ,Having @value{GDBN} infer the source language},
8712 for further details.
8714 @c Type checking is (a) primarily motivated by Modula-2, and (b)
8715 @c unimplemented. If (b) changes, it might make sense to let this node
8716 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
8719 @subsubsection C and C@t{++} type and range checks
8721 @cindex C and C@t{++} checks
8723 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
8724 is not used. However, if you turn type checking on, @value{GDBN}
8725 considers two variables type equivalent if:
8729 The two variables are structured and have the same structure, union, or
8733 The two variables have the same type name, or types that have been
8734 declared equivalent through @code{typedef}.
8737 @c leaving this out because neither J Gilmore nor R Pesch understand it.
8740 The two @code{struct}, @code{union}, or @code{enum} variables are
8741 declared in the same declaration. (Note: this may not be true for all C
8746 Range checking, if turned on, is done on mathematical operations. Array
8747 indices are not checked, since they are often used to index a pointer
8748 that is not itself an array.
8751 @subsubsection @value{GDBN} and C
8753 The @code{set print union} and @code{show print union} commands apply to
8754 the @code{union} type. When set to @samp{on}, any @code{union} that is
8755 inside a @code{struct} or @code{class} is also printed. Otherwise, it
8756 appears as @samp{@{...@}}.
8758 The @code{@@} operator aids in the debugging of dynamic arrays, formed
8759 with pointers and a memory allocation function. @xref{Expressions,
8763 * Debugging C plus plus::
8766 @node Debugging C plus plus
8767 @subsubsection @value{GDBN} features for C@t{++}
8769 @cindex commands for C@t{++}
8771 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
8772 designed specifically for use with C@t{++}. Here is a summary:
8775 @cindex break in overloaded functions
8776 @item @r{breakpoint menus}
8777 When you want a breakpoint in a function whose name is overloaded,
8778 @value{GDBN} breakpoint menus help you specify which function definition
8779 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
8781 @cindex overloading in C@t{++}
8782 @item rbreak @var{regex}
8783 Setting breakpoints using regular expressions is helpful for setting
8784 breakpoints on overloaded functions that are not members of any special
8786 @xref{Set Breaks, ,Setting breakpoints}.
8788 @cindex C@t{++} exception handling
8791 Debug C@t{++} exception handling using these commands. @xref{Set
8792 Catchpoints, , Setting catchpoints}.
8795 @item ptype @var{typename}
8796 Print inheritance relationships as well as other information for type
8798 @xref{Symbols, ,Examining the Symbol Table}.
8800 @cindex C@t{++} symbol display
8801 @item set print demangle
8802 @itemx show print demangle
8803 @itemx set print asm-demangle
8804 @itemx show print asm-demangle
8805 Control whether C@t{++} symbols display in their source form, both when
8806 displaying code as C@t{++} source and when displaying disassemblies.
8807 @xref{Print Settings, ,Print settings}.
8809 @item set print object
8810 @itemx show print object
8811 Choose whether to print derived (actual) or declared types of objects.
8812 @xref{Print Settings, ,Print settings}.
8814 @item set print vtbl
8815 @itemx show print vtbl
8816 Control the format for printing virtual function tables.
8817 @xref{Print Settings, ,Print settings}.
8818 (The @code{vtbl} commands do not work on programs compiled with the HP
8819 ANSI C@t{++} compiler (@code{aCC}).)
8821 @kindex set overload-resolution
8822 @cindex overloaded functions, overload resolution
8823 @item set overload-resolution on
8824 Enable overload resolution for C@t{++} expression evaluation. The default
8825 is on. For overloaded functions, @value{GDBN} evaluates the arguments
8826 and searches for a function whose signature matches the argument types,
8827 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
8828 expressions}, for details). If it cannot find a match, it emits a
8831 @item set overload-resolution off
8832 Disable overload resolution for C@t{++} expression evaluation. For
8833 overloaded functions that are not class member functions, @value{GDBN}
8834 chooses the first function of the specified name that it finds in the
8835 symbol table, whether or not its arguments are of the correct type. For
8836 overloaded functions that are class member functions, @value{GDBN}
8837 searches for a function whose signature @emph{exactly} matches the
8840 @kindex show overload-resolution
8841 @item show overload-resolution
8842 Show the current setting of overload resolution.
8844 @item @r{Overloaded symbol names}
8845 You can specify a particular definition of an overloaded symbol, using
8846 the same notation that is used to declare such symbols in C@t{++}: type
8847 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
8848 also use the @value{GDBN} command-line word completion facilities to list the
8849 available choices, or to finish the type list for you.
8850 @xref{Completion,, Command completion}, for details on how to do this.
8854 @subsection Objective-C
8857 This section provides information about some commands and command
8858 options that are useful for debugging Objective-C code. See also
8859 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
8860 few more commands specific to Objective-C support.
8863 * Method Names in Commands::
8864 * The Print Command with Objective-C::
8867 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
8868 @subsubsection Method Names in Commands
8870 The following commands have been extended to accept Objective-C method
8871 names as line specifications:
8873 @kindex clear@r{, and Objective-C}
8874 @kindex break@r{, and Objective-C}
8875 @kindex info line@r{, and Objective-C}
8876 @kindex jump@r{, and Objective-C}
8877 @kindex list@r{, and Objective-C}
8881 @item @code{info line}
8886 A fully qualified Objective-C method name is specified as
8889 -[@var{Class} @var{methodName}]
8892 where the minus sign is used to indicate an instance method and a
8893 plus sign (not shown) is used to indicate a class method. The class
8894 name @var{Class} and method name @var{methodName} are enclosed in
8895 brackets, similar to the way messages are specified in Objective-C
8896 source code. For example, to set a breakpoint at the @code{create}
8897 instance method of class @code{Fruit} in the program currently being
8901 break -[Fruit create]
8904 To list ten program lines around the @code{initialize} class method,
8908 list +[NSText initialize]
8911 In the current version of @value{GDBN}, the plus or minus sign is
8912 required. In future versions of @value{GDBN}, the plus or minus
8913 sign will be optional, but you can use it to narrow the search. It
8914 is also possible to specify just a method name:
8920 You must specify the complete method name, including any colons. If
8921 your program's source files contain more than one @code{create} method,
8922 you'll be presented with a numbered list of classes that implement that
8923 method. Indicate your choice by number, or type @samp{0} to exit if
8926 As another example, to clear a breakpoint established at the
8927 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
8930 clear -[NSWindow makeKeyAndOrderFront:]
8933 @node The Print Command with Objective-C
8934 @subsubsection The Print Command With Objective-C
8935 @cindex Objective-C, print objects
8936 @kindex print-object
8937 @kindex po @r{(@code{print-object})}
8939 The print command has also been extended to accept methods. For example:
8942 print -[@var{object} hash]
8945 @cindex print an Objective-C object description
8946 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
8948 will tell @value{GDBN} to send the @code{hash} message to @var{object}
8949 and print the result. Also, an additional command has been added,
8950 @code{print-object} or @code{po} for short, which is meant to print
8951 the description of an object. However, this command may only work
8952 with certain Objective-C libraries that have a particular hook
8953 function, @code{_NSPrintForDebugger}, defined.
8957 @cindex Fortran-specific support in @value{GDBN}
8960 @cindex @code{COMMON} blocks, Fortran
8962 @item info common @r{[}@var{common-name}@r{]}
8963 This command prints the values contained in the Fortran @code{COMMON}
8964 block whose name is @var{common-name}. With no argument, the names of
8965 all @code{COMMON} blocks visible at current program location are
8969 Fortran symbols are usually case-insensitive, so @value{GDBN} by
8970 default uses case-insensitive matches for Fortran symbols. You can
8971 change that with the @samp{set case-insensitive} command, see
8972 @ref{Symbols}, for the details.
8977 @cindex Pascal support in @value{GDBN}, limitations
8978 Debugging Pascal programs which use sets, subranges, file variables, or
8979 nested functions does not currently work. @value{GDBN} does not support
8980 entering expressions, printing values, or similar features using Pascal
8983 The Pascal-specific command @code{set print pascal_static-members}
8984 controls whether static members of Pascal objects are displayed.
8985 @xref{Print Settings, pascal_static-members}.
8988 @subsection Modula-2
8990 @cindex Modula-2, @value{GDBN} support
8992 The extensions made to @value{GDBN} to support Modula-2 only support
8993 output from the @sc{gnu} Modula-2 compiler (which is currently being
8994 developed). Other Modula-2 compilers are not currently supported, and
8995 attempting to debug executables produced by them is most likely
8996 to give an error as @value{GDBN} reads in the executable's symbol
8999 @cindex expressions in Modula-2
9001 * M2 Operators:: Built-in operators
9002 * Built-In Func/Proc:: Built-in functions and procedures
9003 * M2 Constants:: Modula-2 constants
9004 * M2 Defaults:: Default settings for Modula-2
9005 * Deviations:: Deviations from standard Modula-2
9006 * M2 Checks:: Modula-2 type and range checks
9007 * M2 Scope:: The scope operators @code{::} and @code{.}
9008 * GDB/M2:: @value{GDBN} and Modula-2
9012 @subsubsection Operators
9013 @cindex Modula-2 operators
9015 Operators must be defined on values of specific types. For instance,
9016 @code{+} is defined on numbers, but not on structures. Operators are
9017 often defined on groups of types. For the purposes of Modula-2, the
9018 following definitions hold:
9023 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
9027 @emph{Character types} consist of @code{CHAR} and its subranges.
9030 @emph{Floating-point types} consist of @code{REAL}.
9033 @emph{Pointer types} consist of anything declared as @code{POINTER TO
9037 @emph{Scalar types} consist of all of the above.
9040 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
9043 @emph{Boolean types} consist of @code{BOOLEAN}.
9047 The following operators are supported, and appear in order of
9048 increasing precedence:
9052 Function argument or array index separator.
9055 Assignment. The value of @var{var} @code{:=} @var{value} is
9059 Less than, greater than on integral, floating-point, or enumerated
9063 Less than or equal to, greater than or equal to
9064 on integral, floating-point and enumerated types, or set inclusion on
9065 set types. Same precedence as @code{<}.
9067 @item =@r{, }<>@r{, }#
9068 Equality and two ways of expressing inequality, valid on scalar types.
9069 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
9070 available for inequality, since @code{#} conflicts with the script
9074 Set membership. Defined on set types and the types of their members.
9075 Same precedence as @code{<}.
9078 Boolean disjunction. Defined on boolean types.
9081 Boolean conjunction. Defined on boolean types.
9084 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9087 Addition and subtraction on integral and floating-point types, or union
9088 and difference on set types.
9091 Multiplication on integral and floating-point types, or set intersection
9095 Division on floating-point types, or symmetric set difference on set
9096 types. Same precedence as @code{*}.
9099 Integer division and remainder. Defined on integral types. Same
9100 precedence as @code{*}.
9103 Negative. Defined on @code{INTEGER} and @code{REAL} data.
9106 Pointer dereferencing. Defined on pointer types.
9109 Boolean negation. Defined on boolean types. Same precedence as
9113 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
9114 precedence as @code{^}.
9117 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
9120 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
9124 @value{GDBN} and Modula-2 scope operators.
9128 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
9129 treats the use of the operator @code{IN}, or the use of operators
9130 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
9131 @code{<=}, and @code{>=} on sets as an error.
9135 @node Built-In Func/Proc
9136 @subsubsection Built-in functions and procedures
9137 @cindex Modula-2 built-ins
9139 Modula-2 also makes available several built-in procedures and functions.
9140 In describing these, the following metavariables are used:
9145 represents an @code{ARRAY} variable.
9148 represents a @code{CHAR} constant or variable.
9151 represents a variable or constant of integral type.
9154 represents an identifier that belongs to a set. Generally used in the
9155 same function with the metavariable @var{s}. The type of @var{s} should
9156 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
9159 represents a variable or constant of integral or floating-point type.
9162 represents a variable or constant of floating-point type.
9168 represents a variable.
9171 represents a variable or constant of one of many types. See the
9172 explanation of the function for details.
9175 All Modula-2 built-in procedures also return a result, described below.
9179 Returns the absolute value of @var{n}.
9182 If @var{c} is a lower case letter, it returns its upper case
9183 equivalent, otherwise it returns its argument.
9186 Returns the character whose ordinal value is @var{i}.
9189 Decrements the value in the variable @var{v} by one. Returns the new value.
9191 @item DEC(@var{v},@var{i})
9192 Decrements the value in the variable @var{v} by @var{i}. Returns the
9195 @item EXCL(@var{m},@var{s})
9196 Removes the element @var{m} from the set @var{s}. Returns the new
9199 @item FLOAT(@var{i})
9200 Returns the floating point equivalent of the integer @var{i}.
9203 Returns the index of the last member of @var{a}.
9206 Increments the value in the variable @var{v} by one. Returns the new value.
9208 @item INC(@var{v},@var{i})
9209 Increments the value in the variable @var{v} by @var{i}. Returns the
9212 @item INCL(@var{m},@var{s})
9213 Adds the element @var{m} to the set @var{s} if it is not already
9214 there. Returns the new set.
9217 Returns the maximum value of the type @var{t}.
9220 Returns the minimum value of the type @var{t}.
9223 Returns boolean TRUE if @var{i} is an odd number.
9226 Returns the ordinal value of its argument. For example, the ordinal
9227 value of a character is its @sc{ascii} value (on machines supporting the
9228 @sc{ascii} character set). @var{x} must be of an ordered type, which include
9229 integral, character and enumerated types.
9232 Returns the size of its argument. @var{x} can be a variable or a type.
9234 @item TRUNC(@var{r})
9235 Returns the integral part of @var{r}.
9237 @item VAL(@var{t},@var{i})
9238 Returns the member of the type @var{t} whose ordinal value is @var{i}.
9242 @emph{Warning:} Sets and their operations are not yet supported, so
9243 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
9247 @cindex Modula-2 constants
9249 @subsubsection Constants
9251 @value{GDBN} allows you to express the constants of Modula-2 in the following
9257 Integer constants are simply a sequence of digits. When used in an
9258 expression, a constant is interpreted to be type-compatible with the
9259 rest of the expression. Hexadecimal integers are specified by a
9260 trailing @samp{H}, and octal integers by a trailing @samp{B}.
9263 Floating point constants appear as a sequence of digits, followed by a
9264 decimal point and another sequence of digits. An optional exponent can
9265 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
9266 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
9267 digits of the floating point constant must be valid decimal (base 10)
9271 Character constants consist of a single character enclosed by a pair of
9272 like quotes, either single (@code{'}) or double (@code{"}). They may
9273 also be expressed by their ordinal value (their @sc{ascii} value, usually)
9274 followed by a @samp{C}.
9277 String constants consist of a sequence of characters enclosed by a
9278 pair of like quotes, either single (@code{'}) or double (@code{"}).
9279 Escape sequences in the style of C are also allowed. @xref{C
9280 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
9284 Enumerated constants consist of an enumerated identifier.
9287 Boolean constants consist of the identifiers @code{TRUE} and
9291 Pointer constants consist of integral values only.
9294 Set constants are not yet supported.
9298 @subsubsection Modula-2 defaults
9299 @cindex Modula-2 defaults
9301 If type and range checking are set automatically by @value{GDBN}, they
9302 both default to @code{on} whenever the working language changes to
9303 Modula-2. This happens regardless of whether you or @value{GDBN}
9304 selected the working language.
9306 If you allow @value{GDBN} to set the language automatically, then entering
9307 code compiled from a file whose name ends with @file{.mod} sets the
9308 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
9309 the language automatically}, for further details.
9312 @subsubsection Deviations from standard Modula-2
9313 @cindex Modula-2, deviations from
9315 A few changes have been made to make Modula-2 programs easier to debug.
9316 This is done primarily via loosening its type strictness:
9320 Unlike in standard Modula-2, pointer constants can be formed by
9321 integers. This allows you to modify pointer variables during
9322 debugging. (In standard Modula-2, the actual address contained in a
9323 pointer variable is hidden from you; it can only be modified
9324 through direct assignment to another pointer variable or expression that
9325 returned a pointer.)
9328 C escape sequences can be used in strings and characters to represent
9329 non-printable characters. @value{GDBN} prints out strings with these
9330 escape sequences embedded. Single non-printable characters are
9331 printed using the @samp{CHR(@var{nnn})} format.
9334 The assignment operator (@code{:=}) returns the value of its right-hand
9338 All built-in procedures both modify @emph{and} return their argument.
9342 @subsubsection Modula-2 type and range checks
9343 @cindex Modula-2 checks
9346 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
9349 @c FIXME remove warning when type/range checks added
9351 @value{GDBN} considers two Modula-2 variables type equivalent if:
9355 They are of types that have been declared equivalent via a @code{TYPE
9356 @var{t1} = @var{t2}} statement
9359 They have been declared on the same line. (Note: This is true of the
9360 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
9363 As long as type checking is enabled, any attempt to combine variables
9364 whose types are not equivalent is an error.
9366 Range checking is done on all mathematical operations, assignment, array
9367 index bounds, and all built-in functions and procedures.
9370 @subsubsection The scope operators @code{::} and @code{.}
9372 @cindex @code{.}, Modula-2 scope operator
9373 @cindex colon, doubled as scope operator
9375 @vindex colon-colon@r{, in Modula-2}
9376 @c Info cannot handle :: but TeX can.
9379 @vindex ::@r{, in Modula-2}
9382 There are a few subtle differences between the Modula-2 scope operator
9383 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
9388 @var{module} . @var{id}
9389 @var{scope} :: @var{id}
9393 where @var{scope} is the name of a module or a procedure,
9394 @var{module} the name of a module, and @var{id} is any declared
9395 identifier within your program, except another module.
9397 Using the @code{::} operator makes @value{GDBN} search the scope
9398 specified by @var{scope} for the identifier @var{id}. If it is not
9399 found in the specified scope, then @value{GDBN} searches all scopes
9400 enclosing the one specified by @var{scope}.
9402 Using the @code{.} operator makes @value{GDBN} search the current scope for
9403 the identifier specified by @var{id} that was imported from the
9404 definition module specified by @var{module}. With this operator, it is
9405 an error if the identifier @var{id} was not imported from definition
9406 module @var{module}, or if @var{id} is not an identifier in
9410 @subsubsection @value{GDBN} and Modula-2
9412 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
9413 Five subcommands of @code{set print} and @code{show print} apply
9414 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
9415 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
9416 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
9417 analogue in Modula-2.
9419 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
9420 with any language, is not useful with Modula-2. Its
9421 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
9422 created in Modula-2 as they can in C or C@t{++}. However, because an
9423 address can be specified by an integral constant, the construct
9424 @samp{@{@var{type}@}@var{adrexp}} is still useful.
9426 @cindex @code{#} in Modula-2
9427 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
9428 interpreted as the beginning of a comment. Use @code{<>} instead.
9434 The extensions made to @value{GDBN} for Ada only support
9435 output from the @sc{gnu} Ada (GNAT) compiler.
9436 Other Ada compilers are not currently supported, and
9437 attempting to debug executables produced by them is most likely
9441 @cindex expressions in Ada
9443 * Ada Mode Intro:: General remarks on the Ada syntax
9444 and semantics supported by Ada mode
9446 * Omissions from Ada:: Restrictions on the Ada expression syntax.
9447 * Additions to Ada:: Extensions of the Ada expression syntax.
9448 * Stopping Before Main Program:: Debugging the program during elaboration.
9449 * Ada Glitches:: Known peculiarities of Ada mode.
9452 @node Ada Mode Intro
9453 @subsubsection Introduction
9454 @cindex Ada mode, general
9456 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
9457 syntax, with some extensions.
9458 The philosophy behind the design of this subset is
9462 That @value{GDBN} should provide basic literals and access to operations for
9463 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
9464 leaving more sophisticated computations to subprograms written into the
9465 program (which therefore may be called from @value{GDBN}).
9468 That type safety and strict adherence to Ada language restrictions
9469 are not particularly important to the @value{GDBN} user.
9472 That brevity is important to the @value{GDBN} user.
9475 Thus, for brevity, the debugger acts as if there were
9476 implicit @code{with} and @code{use} clauses in effect for all user-written
9477 packages, making it unnecessary to fully qualify most names with
9478 their packages, regardless of context. Where this causes ambiguity,
9479 @value{GDBN} asks the user's intent.
9481 The debugger will start in Ada mode if it detects an Ada main program.
9482 As for other languages, it will enter Ada mode when stopped in a program that
9483 was translated from an Ada source file.
9485 While in Ada mode, you may use `@t{--}' for comments. This is useful
9486 mostly for documenting command files. The standard @value{GDBN} comment
9487 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
9488 middle (to allow based literals).
9490 The debugger supports limited overloading. Given a subprogram call in which
9491 the function symbol has multiple definitions, it will use the number of
9492 actual parameters and some information about their types to attempt to narrow
9493 the set of definitions. It also makes very limited use of context, preferring
9494 procedures to functions in the context of the @code{call} command, and
9495 functions to procedures elsewhere.
9497 @node Omissions from Ada
9498 @subsubsection Omissions from Ada
9499 @cindex Ada, omissions from
9501 Here are the notable omissions from the subset:
9505 Only a subset of the attributes are supported:
9509 @t{'First}, @t{'Last}, and @t{'Length}
9510 on array objects (not on types and subtypes).
9513 @t{'Min} and @t{'Max}.
9516 @t{'Pos} and @t{'Val}.
9522 @t{'Range} on array objects (not subtypes), but only as the right
9523 operand of the membership (@code{in}) operator.
9526 @t{'Access}, @t{'Unchecked_Access}, and
9527 @t{'Unrestricted_Access} (a GNAT extension).
9535 @code{Characters.Latin_1} are not available and
9536 concatenation is not implemented. Thus, escape characters in strings are
9537 not currently available.
9540 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
9541 equality of representations. They will generally work correctly
9542 for strings and arrays whose elements have integer or enumeration types.
9543 They may not work correctly for arrays whose element
9544 types have user-defined equality, for arrays of real values
9545 (in particular, IEEE-conformant floating point, because of negative
9546 zeroes and NaNs), and for arrays whose elements contain unused bits with
9547 indeterminate values.
9550 The other component-by-component array operations (@code{and}, @code{or},
9551 @code{xor}, @code{not}, and relational tests other than equality)
9552 are not implemented.
9555 There are no record or array aggregates.
9558 Calls to dispatching subprograms are not implemented.
9561 The overloading algorithm is much more limited (i.e., less selective)
9562 than that of real Ada. It makes only limited use of the context in which a subexpression
9563 appears to resolve its meaning, and it is much looser in its rules for allowing
9564 type matches. As a result, some function calls will be ambiguous, and the user
9565 will be asked to choose the proper resolution.
9568 The @code{new} operator is not implemented.
9571 Entry calls are not implemented.
9574 Aside from printing, arithmetic operations on the native VAX floating-point
9575 formats are not supported.
9578 It is not possible to slice a packed array.
9581 @node Additions to Ada
9582 @subsubsection Additions to Ada
9583 @cindex Ada, deviations from
9585 As it does for other languages, @value{GDBN} makes certain generic
9586 extensions to Ada (@pxref{Expressions}):
9590 If the expression @var{E} is a variable residing in memory
9591 (typically a local variable or array element) and @var{N} is
9592 a positive integer, then @code{@var{E}@@@var{N}} displays the values of
9593 @var{E} and the @var{N}-1 adjacent variables following it in memory as an array.
9594 In Ada, this operator is generally not necessary, since its prime use
9595 is in displaying parts of an array, and slicing will usually do this in Ada.
9596 However, there are occasional uses when debugging programs
9597 in which certain debugging information has been optimized away.
9600 @code{@var{B}::@var{var}} means ``the variable named @var{var} that appears
9601 in function or file @var{B}.'' When @var{B} is a file name, you must typically
9602 surround it in single quotes.
9605 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
9606 @var{type} that appears at address @var{addr}.''
9609 A name starting with @samp{$} is a convenience variable
9610 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
9613 In addition, @value{GDBN} provides a few other shortcuts and outright additions specific
9618 The assignment statement is allowed as an expression, returning
9619 its right-hand operand as its value. Thus, you may enter
9623 print A(tmp := y + 1)
9627 The semicolon is allowed as an ``operator,'' returning as its value
9628 the value of its right-hand operand.
9629 This allows, for example,
9630 complex conditional breaks:
9634 condition 1 (report(i); k += 1; A(k) > 100)
9638 Rather than use catenation and symbolic character names to introduce special
9639 characters into strings, one may instead use a special bracket notation,
9640 which is also used to print strings. A sequence of characters of the form
9641 @samp{["@var{XX}"]} within a string or character literal denotes the
9642 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
9643 sequence of characters @samp{["""]} also denotes a single quotation mark
9644 in strings. For example,
9646 "One line.["0a"]Next line.["0a"]"
9649 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF}) after each
9653 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
9654 @t{'Max} is optional (and is ignored in any case). For example, it is valid
9662 When printing arrays, @value{GDBN} uses positional notation when the
9663 array has a lower bound of 1, and uses a modified named notation otherwise.
9664 For example, a one-dimensional array of three integers with a lower bound of 3 might print as
9671 That is, in contrast to valid Ada, only the first component has a @code{=>}
9675 You may abbreviate attributes in expressions with any unique,
9676 multi-character subsequence of
9677 their names (an exact match gets preference).
9678 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
9679 in place of @t{a'length}.
9682 @cindex quoting Ada internal identifiers
9683 Since Ada is case-insensitive, the debugger normally maps identifiers you type
9684 to lower case. The GNAT compiler uses upper-case characters for
9685 some of its internal identifiers, which are normally of no interest to users.
9686 For the rare occasions when you actually have to look at them,
9687 enclose them in angle brackets to avoid the lower-case mapping.
9690 @value{GDBP} print <JMPBUF_SAVE>[0]
9694 Printing an object of class-wide type or dereferencing an
9695 access-to-class-wide value will display all the components of the object's
9696 specific type (as indicated by its run-time tag). Likewise, component
9697 selection on such a value will operate on the specific type of the
9702 @node Stopping Before Main Program
9703 @subsubsection Stopping at the Very Beginning
9705 @cindex breakpointing Ada elaboration code
9706 It is sometimes necessary to debug the program during elaboration, and
9707 before reaching the main procedure.
9708 As defined in the Ada Reference
9709 Manual, the elaboration code is invoked from a procedure called
9710 @code{adainit}. To run your program up to the beginning of
9711 elaboration, simply use the following two commands:
9712 @code{tbreak adainit} and @code{run}.
9715 @subsubsection Known Peculiarities of Ada Mode
9716 @cindex Ada, problems
9718 Besides the omissions listed previously (@pxref{Omissions from Ada}),
9719 we know of several problems with and limitations of Ada mode in
9721 some of which will be fixed with planned future releases of the debugger
9722 and the GNU Ada compiler.
9726 Currently, the debugger
9727 has insufficient information to determine whether certain pointers represent
9728 pointers to objects or the objects themselves.
9729 Thus, the user may have to tack an extra @code{.all} after an expression
9730 to get it printed properly.
9733 Static constants that the compiler chooses not to materialize as objects in
9734 storage are invisible to the debugger.
9737 Named parameter associations in function argument lists are ignored (the
9738 argument lists are treated as positional).
9741 Many useful library packages are currently invisible to the debugger.
9744 Fixed-point arithmetic, conversions, input, and output is carried out using
9745 floating-point arithmetic, and may give results that only approximate those on
9749 The type of the @t{'Address} attribute may not be @code{System.Address}.
9752 The GNAT compiler never generates the prefix @code{Standard} for any of
9753 the standard symbols defined by the Ada language. @value{GDBN} knows about
9754 this: it will strip the prefix from names when you use it, and will never
9755 look for a name you have so qualified among local symbols, nor match against
9756 symbols in other packages or subprograms. If you have
9757 defined entities anywhere in your program other than parameters and
9758 local variables whose simple names match names in @code{Standard},
9759 GNAT's lack of qualification here can cause confusion. When this happens,
9760 you can usually resolve the confusion
9761 by qualifying the problematic names with package
9762 @code{Standard} explicitly.
9765 @node Unsupported languages
9766 @section Unsupported languages
9768 @cindex unsupported languages
9769 @cindex minimal language
9770 In addition to the other fully-supported programming languages,
9771 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
9772 It does not represent a real programming language, but provides a set
9773 of capabilities close to what the C or assembly languages provide.
9774 This should allow most simple operations to be performed while debugging
9775 an application that uses a language currently not supported by @value{GDBN}.
9777 If the language is set to @code{auto}, @value{GDBN} will automatically
9778 select this language if the current frame corresponds to an unsupported
9782 @chapter Examining the Symbol Table
9784 The commands described in this chapter allow you to inquire about the
9785 symbols (names of variables, functions and types) defined in your
9786 program. This information is inherent in the text of your program and
9787 does not change as your program executes. @value{GDBN} finds it in your
9788 program's symbol table, in the file indicated when you started @value{GDBN}
9789 (@pxref{File Options, ,Choosing files}), or by one of the
9790 file-management commands (@pxref{Files, ,Commands to specify files}).
9792 @cindex symbol names
9793 @cindex names of symbols
9794 @cindex quoting names
9795 Occasionally, you may need to refer to symbols that contain unusual
9796 characters, which @value{GDBN} ordinarily treats as word delimiters. The
9797 most frequent case is in referring to static variables in other
9798 source files (@pxref{Variables,,Program variables}). File names
9799 are recorded in object files as debugging symbols, but @value{GDBN} would
9800 ordinarily parse a typical file name, like @file{foo.c}, as the three words
9801 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
9802 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
9809 looks up the value of @code{x} in the scope of the file @file{foo.c}.
9812 @cindex case-insensitive symbol names
9813 @cindex case sensitivity in symbol names
9814 @kindex set case-sensitive
9815 @item set case-sensitive on
9816 @itemx set case-sensitive off
9817 @itemx set case-sensitive auto
9818 Normally, when @value{GDBN} looks up symbols, it matches their names
9819 with case sensitivity determined by the current source language.
9820 Occasionally, you may wish to control that. The command @code{set
9821 case-sensitive} lets you do that by specifying @code{on} for
9822 case-sensitive matches or @code{off} for case-insensitive ones. If
9823 you specify @code{auto}, case sensitivity is reset to the default
9824 suitable for the source language. The default is case-sensitive
9825 matches for all languages except for Fortran, for which the default is
9826 case-insensitive matches.
9828 @kindex show case-sensitive
9829 @item show case-sensitive
9830 This command shows the current setting of case sensitivity for symbols
9833 @kindex info address
9834 @cindex address of a symbol
9835 @item info address @var{symbol}
9836 Describe where the data for @var{symbol} is stored. For a register
9837 variable, this says which register it is kept in. For a non-register
9838 local variable, this prints the stack-frame offset at which the variable
9841 Note the contrast with @samp{print &@var{symbol}}, which does not work
9842 at all for a register variable, and for a stack local variable prints
9843 the exact address of the current instantiation of the variable.
9846 @cindex symbol from address
9847 @cindex closest symbol and offset for an address
9848 @item info symbol @var{addr}
9849 Print the name of a symbol which is stored at the address @var{addr}.
9850 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
9851 nearest symbol and an offset from it:
9854 (@value{GDBP}) info symbol 0x54320
9855 _initialize_vx + 396 in section .text
9859 This is the opposite of the @code{info address} command. You can use
9860 it to find out the name of a variable or a function given its address.
9863 @item whatis @var{expr}
9864 Print the data type of expression @var{expr}. @var{expr} is not
9865 actually evaluated, and any side-effecting operations (such as
9866 assignments or function calls) inside it do not take place.
9867 @xref{Expressions, ,Expressions}.
9870 Print the data type of @code{$}, the last value in the value history.
9873 @item ptype @var{typename}
9874 Print a description of data type @var{typename}. @var{typename} may be
9875 the name of a type, or for C code it may have the form @samp{class
9876 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
9877 @var{union-tag}} or @samp{enum @var{enum-tag}}.
9879 @item ptype @var{expr}
9881 Print a description of the type of expression @var{expr}. @code{ptype}
9882 differs from @code{whatis} by printing a detailed description, instead
9883 of just the name of the type.
9885 For example, for this variable declaration:
9888 struct complex @{double real; double imag;@} v;
9892 the two commands give this output:
9896 (@value{GDBP}) whatis v
9897 type = struct complex
9898 (@value{GDBP}) ptype v
9899 type = struct complex @{
9907 As with @code{whatis}, using @code{ptype} without an argument refers to
9908 the type of @code{$}, the last value in the value history.
9911 @item info types @var{regexp}
9913 Print a brief description of all types whose names match the regular
9914 expression @var{regexp} (or all types in your program, if you supply
9915 no argument). Each complete typename is matched as though it were a
9916 complete line; thus, @samp{i type value} gives information on all
9917 types in your program whose names include the string @code{value}, but
9918 @samp{i type ^value$} gives information only on types whose complete
9919 name is @code{value}.
9921 This command differs from @code{ptype} in two ways: first, like
9922 @code{whatis}, it does not print a detailed description; second, it
9923 lists all source files where a type is defined.
9926 @cindex local variables
9927 @item info scope @var{location}
9928 List all the variables local to a particular scope. This command
9929 accepts a @var{location} argument---a function name, a source line, or
9930 an address preceded by a @samp{*}, and prints all the variables local
9931 to the scope defined by that location. For example:
9934 (@value{GDBP}) @b{info scope command_line_handler}
9935 Scope for command_line_handler:
9936 Symbol rl is an argument at stack/frame offset 8, length 4.
9937 Symbol linebuffer is in static storage at address 0x150a18, length 4.
9938 Symbol linelength is in static storage at address 0x150a1c, length 4.
9939 Symbol p is a local variable in register $esi, length 4.
9940 Symbol p1 is a local variable in register $ebx, length 4.
9941 Symbol nline is a local variable in register $edx, length 4.
9942 Symbol repeat is a local variable at frame offset -8, length 4.
9946 This command is especially useful for determining what data to collect
9947 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
9952 Show information about the current source file---that is, the source file for
9953 the function containing the current point of execution:
9956 the name of the source file, and the directory containing it,
9958 the directory it was compiled in,
9960 its length, in lines,
9962 which programming language it is written in,
9964 whether the executable includes debugging information for that file, and
9965 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
9967 whether the debugging information includes information about
9968 preprocessor macros.
9972 @kindex info sources
9974 Print the names of all source files in your program for which there is
9975 debugging information, organized into two lists: files whose symbols
9976 have already been read, and files whose symbols will be read when needed.
9978 @kindex info functions
9979 @item info functions
9980 Print the names and data types of all defined functions.
9982 @item info functions @var{regexp}
9983 Print the names and data types of all defined functions
9984 whose names contain a match for regular expression @var{regexp}.
9985 Thus, @samp{info fun step} finds all functions whose names
9986 include @code{step}; @samp{info fun ^step} finds those whose names
9987 start with @code{step}. If a function name contains characters
9988 that conflict with the regular expression language (eg.
9989 @samp{operator*()}), they may be quoted with a backslash.
9991 @kindex info variables
9992 @item info variables
9993 Print the names and data types of all variables that are declared
9994 outside of functions (i.e.@: excluding local variables).
9996 @item info variables @var{regexp}
9997 Print the names and data types of all variables (except for local
9998 variables) whose names contain a match for regular expression
10001 @kindex info classes
10002 @cindex Objective-C, classes and selectors
10004 @itemx info classes @var{regexp}
10005 Display all Objective-C classes in your program, or
10006 (with the @var{regexp} argument) all those matching a particular regular
10009 @kindex info selectors
10010 @item info selectors
10011 @itemx info selectors @var{regexp}
10012 Display all Objective-C selectors in your program, or
10013 (with the @var{regexp} argument) all those matching a particular regular
10017 This was never implemented.
10018 @kindex info methods
10020 @itemx info methods @var{regexp}
10021 The @code{info methods} command permits the user to examine all defined
10022 methods within C@t{++} program, or (with the @var{regexp} argument) a
10023 specific set of methods found in the various C@t{++} classes. Many
10024 C@t{++} classes provide a large number of methods. Thus, the output
10025 from the @code{ptype} command can be overwhelming and hard to use. The
10026 @code{info-methods} command filters the methods, printing only those
10027 which match the regular-expression @var{regexp}.
10030 @cindex reloading symbols
10031 Some systems allow individual object files that make up your program to
10032 be replaced without stopping and restarting your program. For example,
10033 in VxWorks you can simply recompile a defective object file and keep on
10034 running. If you are running on one of these systems, you can allow
10035 @value{GDBN} to reload the symbols for automatically relinked modules:
10038 @kindex set symbol-reloading
10039 @item set symbol-reloading on
10040 Replace symbol definitions for the corresponding source file when an
10041 object file with a particular name is seen again.
10043 @item set symbol-reloading off
10044 Do not replace symbol definitions when encountering object files of the
10045 same name more than once. This is the default state; if you are not
10046 running on a system that permits automatic relinking of modules, you
10047 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
10048 may discard symbols when linking large programs, that may contain
10049 several modules (from different directories or libraries) with the same
10052 @kindex show symbol-reloading
10053 @item show symbol-reloading
10054 Show the current @code{on} or @code{off} setting.
10057 @cindex opaque data types
10058 @kindex set opaque-type-resolution
10059 @item set opaque-type-resolution on
10060 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
10061 declared as a pointer to a @code{struct}, @code{class}, or
10062 @code{union}---for example, @code{struct MyType *}---that is used in one
10063 source file although the full declaration of @code{struct MyType} is in
10064 another source file. The default is on.
10066 A change in the setting of this subcommand will not take effect until
10067 the next time symbols for a file are loaded.
10069 @item set opaque-type-resolution off
10070 Tell @value{GDBN} not to resolve opaque types. In this case, the type
10071 is printed as follows:
10073 @{<no data fields>@}
10076 @kindex show opaque-type-resolution
10077 @item show opaque-type-resolution
10078 Show whether opaque types are resolved or not.
10080 @kindex maint print symbols
10081 @cindex symbol dump
10082 @kindex maint print psymbols
10083 @cindex partial symbol dump
10084 @item maint print symbols @var{filename}
10085 @itemx maint print psymbols @var{filename}
10086 @itemx maint print msymbols @var{filename}
10087 Write a dump of debugging symbol data into the file @var{filename}.
10088 These commands are used to debug the @value{GDBN} symbol-reading code. Only
10089 symbols with debugging data are included. If you use @samp{maint print
10090 symbols}, @value{GDBN} includes all the symbols for which it has already
10091 collected full details: that is, @var{filename} reflects symbols for
10092 only those files whose symbols @value{GDBN} has read. You can use the
10093 command @code{info sources} to find out which files these are. If you
10094 use @samp{maint print psymbols} instead, the dump shows information about
10095 symbols that @value{GDBN} only knows partially---that is, symbols defined in
10096 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
10097 @samp{maint print msymbols} dumps just the minimal symbol information
10098 required for each object file from which @value{GDBN} has read some symbols.
10099 @xref{Files, ,Commands to specify files}, for a discussion of how
10100 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
10102 @kindex maint info symtabs
10103 @kindex maint info psymtabs
10104 @cindex listing @value{GDBN}'s internal symbol tables
10105 @cindex symbol tables, listing @value{GDBN}'s internal
10106 @cindex full symbol tables, listing @value{GDBN}'s internal
10107 @cindex partial symbol tables, listing @value{GDBN}'s internal
10108 @item maint info symtabs @r{[} @var{regexp} @r{]}
10109 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
10111 List the @code{struct symtab} or @code{struct partial_symtab}
10112 structures whose names match @var{regexp}. If @var{regexp} is not
10113 given, list them all. The output includes expressions which you can
10114 copy into a @value{GDBN} debugging this one to examine a particular
10115 structure in more detail. For example:
10118 (@value{GDBP}) maint info psymtabs dwarf2read
10119 @{ objfile /home/gnu/build/gdb/gdb
10120 ((struct objfile *) 0x82e69d0)
10121 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
10122 ((struct partial_symtab *) 0x8474b10)
10125 text addresses 0x814d3c8 -- 0x8158074
10126 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
10127 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
10128 dependencies (none)
10131 (@value{GDBP}) maint info symtabs
10135 We see that there is one partial symbol table whose filename contains
10136 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
10137 and we see that @value{GDBN} has not read in any symtabs yet at all.
10138 If we set a breakpoint on a function, that will cause @value{GDBN} to
10139 read the symtab for the compilation unit containing that function:
10142 (@value{GDBP}) break dwarf2_psymtab_to_symtab
10143 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
10145 (@value{GDBP}) maint info symtabs
10146 @{ objfile /home/gnu/build/gdb/gdb
10147 ((struct objfile *) 0x82e69d0)
10148 @{ symtab /home/gnu/src/gdb/dwarf2read.c
10149 ((struct symtab *) 0x86c1f38)
10152 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
10153 debugformat DWARF 2
10162 @chapter Altering Execution
10164 Once you think you have found an error in your program, you might want to
10165 find out for certain whether correcting the apparent error would lead to
10166 correct results in the rest of the run. You can find the answer by
10167 experiment, using the @value{GDBN} features for altering execution of the
10170 For example, you can store new values into variables or memory
10171 locations, give your program a signal, restart it at a different
10172 address, or even return prematurely from a function.
10175 * Assignment:: Assignment to variables
10176 * Jumping:: Continuing at a different address
10177 * Signaling:: Giving your program a signal
10178 * Returning:: Returning from a function
10179 * Calling:: Calling your program's functions
10180 * Patching:: Patching your program
10184 @section Assignment to variables
10187 @cindex setting variables
10188 To alter the value of a variable, evaluate an assignment expression.
10189 @xref{Expressions, ,Expressions}. For example,
10196 stores the value 4 into the variable @code{x}, and then prints the
10197 value of the assignment expression (which is 4).
10198 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
10199 information on operators in supported languages.
10201 @kindex set variable
10202 @cindex variables, setting
10203 If you are not interested in seeing the value of the assignment, use the
10204 @code{set} command instead of the @code{print} command. @code{set} is
10205 really the same as @code{print} except that the expression's value is
10206 not printed and is not put in the value history (@pxref{Value History,
10207 ,Value history}). The expression is evaluated only for its effects.
10209 If the beginning of the argument string of the @code{set} command
10210 appears identical to a @code{set} subcommand, use the @code{set
10211 variable} command instead of just @code{set}. This command is identical
10212 to @code{set} except for its lack of subcommands. For example, if your
10213 program has a variable @code{width}, you get an error if you try to set
10214 a new value with just @samp{set width=13}, because @value{GDBN} has the
10215 command @code{set width}:
10218 (@value{GDBP}) whatis width
10220 (@value{GDBP}) p width
10222 (@value{GDBP}) set width=47
10223 Invalid syntax in expression.
10227 The invalid expression, of course, is @samp{=47}. In
10228 order to actually set the program's variable @code{width}, use
10231 (@value{GDBP}) set var width=47
10234 Because the @code{set} command has many subcommands that can conflict
10235 with the names of program variables, it is a good idea to use the
10236 @code{set variable} command instead of just @code{set}. For example, if
10237 your program has a variable @code{g}, you run into problems if you try
10238 to set a new value with just @samp{set g=4}, because @value{GDBN} has
10239 the command @code{set gnutarget}, abbreviated @code{set g}:
10243 (@value{GDBP}) whatis g
10247 (@value{GDBP}) set g=4
10251 The program being debugged has been started already.
10252 Start it from the beginning? (y or n) y
10253 Starting program: /home/smith/cc_progs/a.out
10254 "/home/smith/cc_progs/a.out": can't open to read symbols:
10255 Invalid bfd target.
10256 (@value{GDBP}) show g
10257 The current BFD target is "=4".
10262 The program variable @code{g} did not change, and you silently set the
10263 @code{gnutarget} to an invalid value. In order to set the variable
10267 (@value{GDBP}) set var g=4
10270 @value{GDBN} allows more implicit conversions in assignments than C; you can
10271 freely store an integer value into a pointer variable or vice versa,
10272 and you can convert any structure to any other structure that is the
10273 same length or shorter.
10274 @comment FIXME: how do structs align/pad in these conversions?
10275 @comment /doc@cygnus.com 18dec1990
10277 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
10278 construct to generate a value of specified type at a specified address
10279 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
10280 to memory location @code{0x83040} as an integer (which implies a certain size
10281 and representation in memory), and
10284 set @{int@}0x83040 = 4
10288 stores the value 4 into that memory location.
10291 @section Continuing at a different address
10293 Ordinarily, when you continue your program, you do so at the place where
10294 it stopped, with the @code{continue} command. You can instead continue at
10295 an address of your own choosing, with the following commands:
10299 @item jump @var{linespec}
10300 Resume execution at line @var{linespec}. Execution stops again
10301 immediately if there is a breakpoint there. @xref{List, ,Printing
10302 source lines}, for a description of the different forms of
10303 @var{linespec}. It is common practice to use the @code{tbreak} command
10304 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
10307 The @code{jump} command does not change the current stack frame, or
10308 the stack pointer, or the contents of any memory location or any
10309 register other than the program counter. If line @var{linespec} is in
10310 a different function from the one currently executing, the results may
10311 be bizarre if the two functions expect different patterns of arguments or
10312 of local variables. For this reason, the @code{jump} command requests
10313 confirmation if the specified line is not in the function currently
10314 executing. However, even bizarre results are predictable if you are
10315 well acquainted with the machine-language code of your program.
10317 @item jump *@var{address}
10318 Resume execution at the instruction at address @var{address}.
10321 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
10322 On many systems, you can get much the same effect as the @code{jump}
10323 command by storing a new value into the register @code{$pc}. The
10324 difference is that this does not start your program running; it only
10325 changes the address of where it @emph{will} run when you continue. For
10333 makes the next @code{continue} command or stepping command execute at
10334 address @code{0x485}, rather than at the address where your program stopped.
10335 @xref{Continuing and Stepping, ,Continuing and stepping}.
10337 The most common occasion to use the @code{jump} command is to back
10338 up---perhaps with more breakpoints set---over a portion of a program
10339 that has already executed, in order to examine its execution in more
10344 @section Giving your program a signal
10345 @cindex deliver a signal to a program
10349 @item signal @var{signal}
10350 Resume execution where your program stopped, but immediately give it the
10351 signal @var{signal}. @var{signal} can be the name or the number of a
10352 signal. For example, on many systems @code{signal 2} and @code{signal
10353 SIGINT} are both ways of sending an interrupt signal.
10355 Alternatively, if @var{signal} is zero, continue execution without
10356 giving a signal. This is useful when your program stopped on account of
10357 a signal and would ordinary see the signal when resumed with the
10358 @code{continue} command; @samp{signal 0} causes it to resume without a
10361 @code{signal} does not repeat when you press @key{RET} a second time
10362 after executing the command.
10366 Invoking the @code{signal} command is not the same as invoking the
10367 @code{kill} utility from the shell. Sending a signal with @code{kill}
10368 causes @value{GDBN} to decide what to do with the signal depending on
10369 the signal handling tables (@pxref{Signals}). The @code{signal} command
10370 passes the signal directly to your program.
10374 @section Returning from a function
10377 @cindex returning from a function
10380 @itemx return @var{expression}
10381 You can cancel execution of a function call with the @code{return}
10382 command. If you give an
10383 @var{expression} argument, its value is used as the function's return
10387 When you use @code{return}, @value{GDBN} discards the selected stack frame
10388 (and all frames within it). You can think of this as making the
10389 discarded frame return prematurely. If you wish to specify a value to
10390 be returned, give that value as the argument to @code{return}.
10392 This pops the selected stack frame (@pxref{Selection, ,Selecting a
10393 frame}), and any other frames inside of it, leaving its caller as the
10394 innermost remaining frame. That frame becomes selected. The
10395 specified value is stored in the registers used for returning values
10398 The @code{return} command does not resume execution; it leaves the
10399 program stopped in the state that would exist if the function had just
10400 returned. In contrast, the @code{finish} command (@pxref{Continuing
10401 and Stepping, ,Continuing and stepping}) resumes execution until the
10402 selected stack frame returns naturally.
10405 @section Calling program functions
10408 @cindex calling functions
10409 @cindex inferior functions, calling
10410 @item print @var{expr}
10411 Evaluate the expression @var{expr} and display the resuling value.
10412 @var{expr} may include calls to functions in the program being
10416 @item call @var{expr}
10417 Evaluate the expression @var{expr} without displaying @code{void}
10420 You can use this variant of the @code{print} command if you want to
10421 execute a function from your program that does not return anything
10422 (a.k.a.@: @dfn{a void function}), but without cluttering the output
10423 with @code{void} returned values that @value{GDBN} will otherwise
10424 print. If the result is not void, it is printed and saved in the
10428 It is possible for the function you call via the @code{print} or
10429 @code{call} command to generate a signal (e.g., if there's a bug in
10430 the function, or if you passed it incorrect arguments). What happens
10431 in that case is controlled by the @code{set unwindonsignal} command.
10434 @item set unwindonsignal
10435 @kindex set unwindonsignal
10436 @cindex unwind stack in called functions
10437 @cindex call dummy stack unwinding
10438 Set unwinding of the stack if a signal is received while in a function
10439 that @value{GDBN} called in the program being debugged. If set to on,
10440 @value{GDBN} unwinds the stack it created for the call and restores
10441 the context to what it was before the call. If set to off (the
10442 default), @value{GDBN} stops in the frame where the signal was
10445 @item show unwindonsignal
10446 @kindex show unwindonsignal
10447 Show the current setting of stack unwinding in the functions called by
10451 @cindex weak alias functions
10452 Sometimes, a function you wish to call is actually a @dfn{weak alias}
10453 for another function. In such case, @value{GDBN} might not pick up
10454 the type information, including the types of the function arguments,
10455 which causes @value{GDBN} to call the inferior function incorrectly.
10456 As a result, the called function will function erroneously and may
10457 even crash. A solution to that is to use the name of the aliased
10461 @section Patching programs
10463 @cindex patching binaries
10464 @cindex writing into executables
10465 @cindex writing into corefiles
10467 By default, @value{GDBN} opens the file containing your program's
10468 executable code (or the corefile) read-only. This prevents accidental
10469 alterations to machine code; but it also prevents you from intentionally
10470 patching your program's binary.
10472 If you'd like to be able to patch the binary, you can specify that
10473 explicitly with the @code{set write} command. For example, you might
10474 want to turn on internal debugging flags, or even to make emergency
10480 @itemx set write off
10481 If you specify @samp{set write on}, @value{GDBN} opens executable and
10482 core files for both reading and writing; if you specify @samp{set write
10483 off} (the default), @value{GDBN} opens them read-only.
10485 If you have already loaded a file, you must load it again (using the
10486 @code{exec-file} or @code{core-file} command) after changing @code{set
10487 write}, for your new setting to take effect.
10491 Display whether executable files and core files are opened for writing
10492 as well as reading.
10496 @chapter @value{GDBN} Files
10498 @value{GDBN} needs to know the file name of the program to be debugged,
10499 both in order to read its symbol table and in order to start your
10500 program. To debug a core dump of a previous run, you must also tell
10501 @value{GDBN} the name of the core dump file.
10504 * Files:: Commands to specify files
10505 * Separate Debug Files:: Debugging information in separate files
10506 * Symbol Errors:: Errors reading symbol files
10510 @section Commands to specify files
10512 @cindex symbol table
10513 @cindex core dump file
10515 You may want to specify executable and core dump file names. The usual
10516 way to do this is at start-up time, using the arguments to
10517 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
10518 Out of @value{GDBN}}).
10520 Occasionally it is necessary to change to a different file during a
10521 @value{GDBN} session. Or you may run @value{GDBN} and forget to specify
10522 a file you want to use. In these situations the @value{GDBN} commands
10523 to specify new files are useful.
10526 @cindex executable file
10528 @item file @var{filename}
10529 Use @var{filename} as the program to be debugged. It is read for its
10530 symbols and for the contents of pure memory. It is also the program
10531 executed when you use the @code{run} command. If you do not specify a
10532 directory and the file is not found in the @value{GDBN} working directory,
10533 @value{GDBN} uses the environment variable @code{PATH} as a list of
10534 directories to search, just as the shell does when looking for a program
10535 to run. You can change the value of this variable, for both @value{GDBN}
10536 and your program, using the @code{path} command.
10538 On systems with memory-mapped files, an auxiliary file named
10539 @file{@var{filename}.syms} may hold symbol table information for
10540 @var{filename}. If so, @value{GDBN} maps in the symbol table from
10541 @file{@var{filename}.syms}, starting up more quickly. See the
10542 descriptions of the file options @samp{-mapped} and @samp{-readnow}
10543 (available on the command line, see @ref{File Options, , -readnow},
10544 and with the commands @code{file}, @code{symbol-file}, or
10545 @code{add-symbol-file}, described below), for more information.
10548 @code{file} with no argument makes @value{GDBN} discard any information it
10549 has on both executable file and the symbol table.
10552 @item exec-file @r{[} @var{filename} @r{]}
10553 Specify that the program to be run (but not the symbol table) is found
10554 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
10555 if necessary to locate your program. Omitting @var{filename} means to
10556 discard information on the executable file.
10558 @kindex symbol-file
10559 @item symbol-file @r{[} @var{filename} @r{]}
10560 Read symbol table information from file @var{filename}. @code{PATH} is
10561 searched when necessary. Use the @code{file} command to get both symbol
10562 table and program to run from the same file.
10564 @code{symbol-file} with no argument clears out @value{GDBN} information on your
10565 program's symbol table.
10567 The @code{symbol-file} command causes @value{GDBN} to forget the contents
10568 of its convenience variables, the value history, and all breakpoints and
10569 auto-display expressions. This is because they may contain pointers to
10570 the internal data recording symbols and data types, which are part of
10571 the old symbol table data being discarded inside @value{GDBN}.
10573 @code{symbol-file} does not repeat if you press @key{RET} again after
10576 When @value{GDBN} is configured for a particular environment, it
10577 understands debugging information in whatever format is the standard
10578 generated for that environment; you may use either a @sc{gnu} compiler, or
10579 other compilers that adhere to the local conventions.
10580 Best results are usually obtained from @sc{gnu} compilers; for example,
10581 using @code{@value{GCC}} you can generate debugging information for
10584 For most kinds of object files, with the exception of old SVR3 systems
10585 using COFF, the @code{symbol-file} command does not normally read the
10586 symbol table in full right away. Instead, it scans the symbol table
10587 quickly to find which source files and which symbols are present. The
10588 details are read later, one source file at a time, as they are needed.
10590 The purpose of this two-stage reading strategy is to make @value{GDBN}
10591 start up faster. For the most part, it is invisible except for
10592 occasional pauses while the symbol table details for a particular source
10593 file are being read. (The @code{set verbose} command can turn these
10594 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
10595 warnings and messages}.)
10597 We have not implemented the two-stage strategy for COFF yet. When the
10598 symbol table is stored in COFF format, @code{symbol-file} reads the
10599 symbol table data in full right away. Note that ``stabs-in-COFF''
10600 still does the two-stage strategy, since the debug info is actually
10604 @cindex reading symbols immediately
10605 @cindex symbols, reading immediately
10607 @cindex memory-mapped symbol file
10608 @cindex saving symbol table
10609 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10610 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10611 You can override the @value{GDBN} two-stage strategy for reading symbol
10612 tables by using the @samp{-readnow} option with any of the commands that
10613 load symbol table information, if you want to be sure @value{GDBN} has the
10614 entire symbol table available.
10616 If memory-mapped files are available on your system through the
10617 @code{mmap} system call, you can use another option, @samp{-mapped}, to
10618 cause @value{GDBN} to write the symbols for your program into a reusable
10619 file. Future @value{GDBN} debugging sessions map in symbol information
10620 from this auxiliary symbol file (if the program has not changed), rather
10621 than spending time reading the symbol table from the executable
10622 program. Using the @samp{-mapped} option has the same effect as
10623 starting @value{GDBN} with the @samp{-mapped} command-line option.
10625 You can use both options together, to make sure the auxiliary symbol
10626 file has all the symbol information for your program.
10628 The auxiliary symbol file for a program called @var{myprog} is called
10629 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
10630 than the corresponding executable), @value{GDBN} always attempts to use
10631 it when you debug @var{myprog}; no special options or commands are
10634 The @file{.syms} file is specific to the host machine where you run
10635 @value{GDBN}. It holds an exact image of the internal @value{GDBN}
10636 symbol table. It cannot be shared across multiple host platforms.
10638 @c FIXME: for now no mention of directories, since this seems to be in
10639 @c flux. 13mar1992 status is that in theory GDB would look either in
10640 @c current dir or in same dir as myprog; but issues like competing
10641 @c GDB's, or clutter in system dirs, mean that in practice right now
10642 @c only current dir is used. FFish says maybe a special GDB hierarchy
10643 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
10647 @item core-file @r{[}@var{filename}@r{]}
10649 Specify the whereabouts of a core dump file to be used as the ``contents
10650 of memory''. Traditionally, core files contain only some parts of the
10651 address space of the process that generated them; @value{GDBN} can access the
10652 executable file itself for other parts.
10654 @code{core-file} with no argument specifies that no core file is
10657 Note that the core file is ignored when your program is actually running
10658 under @value{GDBN}. So, if you have been running your program and you
10659 wish to debug a core file instead, you must kill the subprocess in which
10660 the program is running. To do this, use the @code{kill} command
10661 (@pxref{Kill Process, ,Killing the child process}).
10663 @kindex add-symbol-file
10664 @cindex dynamic linking
10665 @item add-symbol-file @var{filename} @var{address}
10666 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10667 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
10668 The @code{add-symbol-file} command reads additional symbol table
10669 information from the file @var{filename}. You would use this command
10670 when @var{filename} has been dynamically loaded (by some other means)
10671 into the program that is running. @var{address} should be the memory
10672 address at which the file has been loaded; @value{GDBN} cannot figure
10673 this out for itself. You can additionally specify an arbitrary number
10674 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
10675 section name and base address for that section. You can specify any
10676 @var{address} as an expression.
10678 The symbol table of the file @var{filename} is added to the symbol table
10679 originally read with the @code{symbol-file} command. You can use the
10680 @code{add-symbol-file} command any number of times; the new symbol data
10681 thus read keeps adding to the old. To discard all old symbol data
10682 instead, use the @code{symbol-file} command without any arguments.
10684 @cindex relocatable object files, reading symbols from
10685 @cindex object files, relocatable, reading symbols from
10686 @cindex reading symbols from relocatable object files
10687 @cindex symbols, reading from relocatable object files
10688 @cindex @file{.o} files, reading symbols from
10689 Although @var{filename} is typically a shared library file, an
10690 executable file, or some other object file which has been fully
10691 relocated for loading into a process, you can also load symbolic
10692 information from relocatable @file{.o} files, as long as:
10696 the file's symbolic information refers only to linker symbols defined in
10697 that file, not to symbols defined by other object files,
10699 every section the file's symbolic information refers to has actually
10700 been loaded into the inferior, as it appears in the file, and
10702 you can determine the address at which every section was loaded, and
10703 provide these to the @code{add-symbol-file} command.
10707 Some embedded operating systems, like Sun Chorus and VxWorks, can load
10708 relocatable files into an already running program; such systems
10709 typically make the requirements above easy to meet. However, it's
10710 important to recognize that many native systems use complex link
10711 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
10712 assembly, for example) that make the requirements difficult to meet. In
10713 general, one cannot assume that using @code{add-symbol-file} to read a
10714 relocatable object file's symbolic information will have the same effect
10715 as linking the relocatable object file into the program in the normal
10718 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
10720 You can use the @samp{-mapped} and @samp{-readnow} options just as with
10721 the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
10722 table information for @var{filename}.
10724 @kindex add-symbol-file-from-memory
10725 @cindex @code{syscall DSO}
10726 @cindex load symbols from memory
10727 @item add-symbol-file-from-memory @var{address}
10728 Load symbols from the given @var{address} in a dynamically loaded
10729 object file whose image is mapped directly into the inferior's memory.
10730 For example, the Linux kernel maps a @code{syscall DSO} into each
10731 process's address space; this DSO provides kernel-specific code for
10732 some system calls. The argument can be any expression whose
10733 evaluation yields the address of the file's shared object file header.
10734 For this command to work, you must have used @code{symbol-file} or
10735 @code{exec-file} commands in advance.
10737 @kindex add-shared-symbol-files
10739 @item add-shared-symbol-files @var{library-file}
10740 @itemx assf @var{library-file}
10741 The @code{add-shared-symbol-files} command can currently be used only
10742 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
10743 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
10744 @value{GDBN} automatically looks for shared libraries, however if
10745 @value{GDBN} does not find yours, you can invoke
10746 @code{add-shared-symbol-files}. It takes one argument: the shared
10747 library's file name. @code{assf} is a shorthand alias for
10748 @code{add-shared-symbol-files}.
10751 @item section @var{section} @var{addr}
10752 The @code{section} command changes the base address of the named
10753 @var{section} of the exec file to @var{addr}. This can be used if the
10754 exec file does not contain section addresses, (such as in the
10755 @code{a.out} format), or when the addresses specified in the file
10756 itself are wrong. Each section must be changed separately. The
10757 @code{info files} command, described below, lists all the sections and
10761 @kindex info target
10764 @code{info files} and @code{info target} are synonymous; both print the
10765 current target (@pxref{Targets, ,Specifying a Debugging Target}),
10766 including the names of the executable and core dump files currently in
10767 use by @value{GDBN}, and the files from which symbols were loaded. The
10768 command @code{help target} lists all possible targets rather than
10771 @kindex maint info sections
10772 @item maint info sections
10773 Another command that can give you extra information about program sections
10774 is @code{maint info sections}. In addition to the section information
10775 displayed by @code{info files}, this command displays the flags and file
10776 offset of each section in the executable and core dump files. In addition,
10777 @code{maint info sections} provides the following command options (which
10778 may be arbitrarily combined):
10782 Display sections for all loaded object files, including shared libraries.
10783 @item @var{sections}
10784 Display info only for named @var{sections}.
10785 @item @var{section-flags}
10786 Display info only for sections for which @var{section-flags} are true.
10787 The section flags that @value{GDBN} currently knows about are:
10790 Section will have space allocated in the process when loaded.
10791 Set for all sections except those containing debug information.
10793 Section will be loaded from the file into the child process memory.
10794 Set for pre-initialized code and data, clear for @code{.bss} sections.
10796 Section needs to be relocated before loading.
10798 Section cannot be modified by the child process.
10800 Section contains executable code only.
10802 Section contains data only (no executable code).
10804 Section will reside in ROM.
10806 Section contains data for constructor/destructor lists.
10808 Section is not empty.
10810 An instruction to the linker to not output the section.
10811 @item COFF_SHARED_LIBRARY
10812 A notification to the linker that the section contains
10813 COFF shared library information.
10815 Section contains common symbols.
10818 @kindex set trust-readonly-sections
10819 @cindex read-only sections
10820 @item set trust-readonly-sections on
10821 Tell @value{GDBN} that readonly sections in your object file
10822 really are read-only (i.e.@: that their contents will not change).
10823 In that case, @value{GDBN} can fetch values from these sections
10824 out of the object file, rather than from the target program.
10825 For some targets (notably embedded ones), this can be a significant
10826 enhancement to debugging performance.
10828 The default is off.
10830 @item set trust-readonly-sections off
10831 Tell @value{GDBN} not to trust readonly sections. This means that
10832 the contents of the section might change while the program is running,
10833 and must therefore be fetched from the target when needed.
10835 @item show trust-readonly-sections
10836 Show the current setting of trusting readonly sections.
10839 All file-specifying commands allow both absolute and relative file names
10840 as arguments. @value{GDBN} always converts the file name to an absolute file
10841 name and remembers it that way.
10843 @cindex shared libraries
10844 @value{GDBN} supports GNU/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
10845 and IBM RS/6000 AIX shared libraries.
10847 @value{GDBN} automatically loads symbol definitions from shared libraries
10848 when you use the @code{run} command, or when you examine a core file.
10849 (Before you issue the @code{run} command, @value{GDBN} does not understand
10850 references to a function in a shared library, however---unless you are
10851 debugging a core file).
10853 On HP-UX, if the program loads a library explicitly, @value{GDBN}
10854 automatically loads the symbols at the time of the @code{shl_load} call.
10856 @c FIXME: some @value{GDBN} release may permit some refs to undef
10857 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
10858 @c FIXME...lib; check this from time to time when updating manual
10860 There are times, however, when you may wish to not automatically load
10861 symbol definitions from shared libraries, such as when they are
10862 particularly large or there are many of them.
10864 To control the automatic loading of shared library symbols, use the
10868 @kindex set auto-solib-add
10869 @item set auto-solib-add @var{mode}
10870 If @var{mode} is @code{on}, symbols from all shared object libraries
10871 will be loaded automatically when the inferior begins execution, you
10872 attach to an independently started inferior, or when the dynamic linker
10873 informs @value{GDBN} that a new library has been loaded. If @var{mode}
10874 is @code{off}, symbols must be loaded manually, using the
10875 @code{sharedlibrary} command. The default value is @code{on}.
10877 @cindex memory used for symbol tables
10878 If your program uses lots of shared libraries with debug info that
10879 takes large amounts of memory, you can decrease the @value{GDBN}
10880 memory footprint by preventing it from automatically loading the
10881 symbols from shared libraries. To that end, type @kbd{set
10882 auto-solib-add off} before running the inferior, then load each
10883 library whose debug symbols you do need with @kbd{sharedlibrary
10884 @var{regexp}}, where @var{regexp} is a regular expresion that matches
10885 the libraries whose symbols you want to be loaded.
10887 @kindex show auto-solib-add
10888 @item show auto-solib-add
10889 Display the current autoloading mode.
10892 @cindex load shared library
10893 To explicitly load shared library symbols, use the @code{sharedlibrary}
10897 @kindex info sharedlibrary
10900 @itemx info sharedlibrary
10901 Print the names of the shared libraries which are currently loaded.
10903 @kindex sharedlibrary
10905 @item sharedlibrary @var{regex}
10906 @itemx share @var{regex}
10907 Load shared object library symbols for files matching a
10908 Unix regular expression.
10909 As with files loaded automatically, it only loads shared libraries
10910 required by your program for a core file or after typing @code{run}. If
10911 @var{regex} is omitted all shared libraries required by your program are
10914 @item nosharedlibrary
10915 @kindex nosharedlibrary
10916 @cindex unload symbols from shared libraries
10917 Unload all shared object library symbols. This discards all symbols
10918 that have been loaded from all shared libraries. Symbols from shared
10919 libraries that were loaded by explicit user requests are not
10923 On some systems, such as HP-UX systems, @value{GDBN} supports
10924 autoloading shared library symbols until a limiting threshold size is
10925 reached. This provides the benefit of allowing autoloading to remain on
10926 by default, but avoids autoloading excessively large shared libraries,
10927 up to a threshold that is initially set, but which you can modify if you
10930 Beyond that threshold, symbols from shared libraries must be explicitly
10931 loaded. To load these symbols, use the command @code{sharedlibrary
10932 @var{filename}}. The base address of the shared library is determined
10933 automatically by @value{GDBN} and need not be specified.
10935 To display or set the threshold, use the commands:
10938 @kindex set auto-solib-limit
10939 @item set auto-solib-limit @var{threshold}
10940 Set the autoloading size threshold, in an integral number of megabytes.
10941 If @var{threshold} is nonzero and shared library autoloading is enabled,
10942 symbols from all shared object libraries will be loaded until the total
10943 size of the loaded shared library symbols exceeds this threshold.
10944 Otherwise, symbols must be loaded manually, using the
10945 @code{sharedlibrary} command. The default threshold is 100 (i.e.@: 100
10948 @kindex show auto-solib-limit
10949 @item show auto-solib-limit
10950 Display the current autoloading size threshold, in megabytes.
10953 Sometimes you may wish that @value{GDBN} stops and gives you control
10954 when any of shared library events happen. Use the @code{set
10955 stop-on-solib-events} command for this:
10958 @item set stop-on-solib-events
10959 @kindex set stop-on-solib-events
10960 This command controls whether @value{GDBN} should give you control
10961 when the dynamic linker notifies it about some shared library event.
10962 The most common event of interest is loading or unloading of a new
10965 @item show stop-on-solib-events
10966 @kindex show stop-on-solib-events
10967 Show whether @value{GDBN} stops and gives you control when shared
10968 library events happen.
10971 Shared libraries are also supported in many cross or remote debugging
10972 configurations. A copy of the target's libraries need to be present on the
10973 host system; they need to be the same as the target libraries, although the
10974 copies on the target can be stripped as long as the copies on the host are
10977 You need to tell @value{GDBN} where the target libraries are, so that it can
10978 load the correct copies---otherwise, it may try to load the host's libraries.
10979 @value{GDBN} has two variables to specify the search directories for target
10983 @kindex set solib-absolute-prefix
10984 @item set solib-absolute-prefix @var{path}
10985 If this variable is set, @var{path} will be used as a prefix for any
10986 absolute shared library paths; many runtime loaders store the absolute
10987 paths to the shared library in the target program's memory. If you use
10988 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
10989 out in the same way that they are on the target, with e.g.@: a
10990 @file{/usr/lib} hierarchy under @var{path}.
10992 You can set the default value of @samp{solib-absolute-prefix} by using the
10993 configure-time @samp{--with-sysroot} option.
10995 @kindex show solib-absolute-prefix
10996 @item show solib-absolute-prefix
10997 Display the current shared library prefix.
10999 @kindex set solib-search-path
11000 @item set solib-search-path @var{path}
11001 If this variable is set, @var{path} is a colon-separated list of directories
11002 to search for shared libraries. @samp{solib-search-path} is used after
11003 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
11004 the library is relative instead of absolute. If you want to use
11005 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
11006 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
11007 @value{GDBN} from finding your host's libraries.
11009 @kindex show solib-search-path
11010 @item show solib-search-path
11011 Display the current shared library search path.
11015 @node Separate Debug Files
11016 @section Debugging Information in Separate Files
11017 @cindex separate debugging information files
11018 @cindex debugging information in separate files
11019 @cindex @file{.debug} subdirectories
11020 @cindex debugging information directory, global
11021 @cindex global debugging information directory
11023 @value{GDBN} allows you to put a program's debugging information in a
11024 file separate from the executable itself, in a way that allows
11025 @value{GDBN} to find and load the debugging information automatically.
11026 Since debugging information can be very large --- sometimes larger
11027 than the executable code itself --- some systems distribute debugging
11028 information for their executables in separate files, which users can
11029 install only when they need to debug a problem.
11031 If an executable's debugging information has been extracted to a
11032 separate file, the executable should contain a @dfn{debug link} giving
11033 the name of the debugging information file (with no directory
11034 components), and a checksum of its contents. (The exact form of a
11035 debug link is described below.) If the full name of the directory
11036 containing the executable is @var{execdir}, and the executable has a
11037 debug link that specifies the name @var{debugfile}, then @value{GDBN}
11038 will automatically search for the debugging information file in three
11043 the directory containing the executable file (that is, it will look
11044 for a file named @file{@var{execdir}/@var{debugfile}},
11046 a subdirectory of that directory named @file{.debug} (that is, the
11047 file @file{@var{execdir}/.debug/@var{debugfile}}, and
11049 a subdirectory of the global debug file directory that includes the
11050 executable's full path, and the name from the link (that is, the file
11051 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
11052 @var{globaldebugdir} is the global debug file directory, and
11053 @var{execdir} has been turned into a relative path).
11056 @value{GDBN} checks under each of these names for a debugging
11057 information file whose checksum matches that given in the link, and
11058 reads the debugging information from the first one it finds.
11060 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
11061 which has a link containing the name @file{ls.debug}, and the global
11062 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
11063 for debug information in @file{/usr/bin/ls.debug},
11064 @file{/usr/bin/.debug/ls.debug}, and
11065 @file{/usr/lib/debug/usr/bin/ls.debug}.
11067 You can set the global debugging info directory's name, and view the
11068 name @value{GDBN} is currently using.
11072 @kindex set debug-file-directory
11073 @item set debug-file-directory @var{directory}
11074 Set the directory which @value{GDBN} searches for separate debugging
11075 information files to @var{directory}.
11077 @kindex show debug-file-directory
11078 @item show debug-file-directory
11079 Show the directory @value{GDBN} searches for separate debugging
11084 @cindex @code{.gnu_debuglink} sections
11085 @cindex debug links
11086 A debug link is a special section of the executable file named
11087 @code{.gnu_debuglink}. The section must contain:
11091 A filename, with any leading directory components removed, followed by
11094 zero to three bytes of padding, as needed to reach the next four-byte
11095 boundary within the section, and
11097 a four-byte CRC checksum, stored in the same endianness used for the
11098 executable file itself. The checksum is computed on the debugging
11099 information file's full contents by the function given below, passing
11100 zero as the @var{crc} argument.
11103 Any executable file format can carry a debug link, as long as it can
11104 contain a section named @code{.gnu_debuglink} with the contents
11107 The debugging information file itself should be an ordinary
11108 executable, containing a full set of linker symbols, sections, and
11109 debugging information. The sections of the debugging information file
11110 should have the same names, addresses and sizes as the original file,
11111 but they need not contain any data --- much like a @code{.bss} section
11112 in an ordinary executable.
11114 As of December 2002, there is no standard GNU utility to produce
11115 separated executable / debugging information file pairs. Ulrich
11116 Drepper's @file{elfutils} package, starting with version 0.53,
11117 contains a version of the @code{strip} command such that the command
11118 @kbd{strip foo -f foo.debug} removes the debugging information from
11119 the executable file @file{foo}, places it in the file
11120 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
11122 Since there are many different ways to compute CRC's (different
11123 polynomials, reversals, byte ordering, etc.), the simplest way to
11124 describe the CRC used in @code{.gnu_debuglink} sections is to give the
11125 complete code for a function that computes it:
11127 @kindex gnu_debuglink_crc32
11130 gnu_debuglink_crc32 (unsigned long crc,
11131 unsigned char *buf, size_t len)
11133 static const unsigned long crc32_table[256] =
11135 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
11136 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
11137 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
11138 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
11139 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
11140 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
11141 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
11142 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
11143 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
11144 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
11145 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
11146 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
11147 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
11148 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
11149 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
11150 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
11151 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
11152 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
11153 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
11154 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
11155 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
11156 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
11157 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
11158 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
11159 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
11160 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
11161 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
11162 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
11163 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
11164 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
11165 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
11166 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
11167 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
11168 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
11169 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
11170 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
11171 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
11172 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
11173 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
11174 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
11175 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
11176 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
11177 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
11178 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
11179 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
11180 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
11181 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
11182 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
11183 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
11184 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
11185 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
11188 unsigned char *end;
11190 crc = ~crc & 0xffffffff;
11191 for (end = buf + len; buf < end; ++buf)
11192 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
11193 return ~crc & 0xffffffff;
11198 @node Symbol Errors
11199 @section Errors reading symbol files
11201 While reading a symbol file, @value{GDBN} occasionally encounters problems,
11202 such as symbol types it does not recognize, or known bugs in compiler
11203 output. By default, @value{GDBN} does not notify you of such problems, since
11204 they are relatively common and primarily of interest to people
11205 debugging compilers. If you are interested in seeing information
11206 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
11207 only one message about each such type of problem, no matter how many
11208 times the problem occurs; or you can ask @value{GDBN} to print more messages,
11209 to see how many times the problems occur, with the @code{set
11210 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
11213 The messages currently printed, and their meanings, include:
11216 @item inner block not inside outer block in @var{symbol}
11218 The symbol information shows where symbol scopes begin and end
11219 (such as at the start of a function or a block of statements). This
11220 error indicates that an inner scope block is not fully contained
11221 in its outer scope blocks.
11223 @value{GDBN} circumvents the problem by treating the inner block as if it had
11224 the same scope as the outer block. In the error message, @var{symbol}
11225 may be shown as ``@code{(don't know)}'' if the outer block is not a
11228 @item block at @var{address} out of order
11230 The symbol information for symbol scope blocks should occur in
11231 order of increasing addresses. This error indicates that it does not
11234 @value{GDBN} does not circumvent this problem, and has trouble
11235 locating symbols in the source file whose symbols it is reading. (You
11236 can often determine what source file is affected by specifying
11237 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
11240 @item bad block start address patched
11242 The symbol information for a symbol scope block has a start address
11243 smaller than the address of the preceding source line. This is known
11244 to occur in the SunOS 4.1.1 (and earlier) C compiler.
11246 @value{GDBN} circumvents the problem by treating the symbol scope block as
11247 starting on the previous source line.
11249 @item bad string table offset in symbol @var{n}
11252 Symbol number @var{n} contains a pointer into the string table which is
11253 larger than the size of the string table.
11255 @value{GDBN} circumvents the problem by considering the symbol to have the
11256 name @code{foo}, which may cause other problems if many symbols end up
11259 @item unknown symbol type @code{0x@var{nn}}
11261 The symbol information contains new data types that @value{GDBN} does
11262 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
11263 uncomprehended information, in hexadecimal.
11265 @value{GDBN} circumvents the error by ignoring this symbol information.
11266 This usually allows you to debug your program, though certain symbols
11267 are not accessible. If you encounter such a problem and feel like
11268 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
11269 on @code{complain}, then go up to the function @code{read_dbx_symtab}
11270 and examine @code{*bufp} to see the symbol.
11272 @item stub type has NULL name
11274 @value{GDBN} could not find the full definition for a struct or class.
11276 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
11277 The symbol information for a C@t{++} member function is missing some
11278 information that recent versions of the compiler should have output for
11281 @item info mismatch between compiler and debugger
11283 @value{GDBN} could not parse a type specification output by the compiler.
11288 @chapter Specifying a Debugging Target
11290 @cindex debugging target
11291 A @dfn{target} is the execution environment occupied by your program.
11293 Often, @value{GDBN} runs in the same host environment as your program;
11294 in that case, the debugging target is specified as a side effect when
11295 you use the @code{file} or @code{core} commands. When you need more
11296 flexibility---for example, running @value{GDBN} on a physically separate
11297 host, or controlling a standalone system over a serial port or a
11298 realtime system over a TCP/IP connection---you can use the @code{target}
11299 command to specify one of the target types configured for @value{GDBN}
11300 (@pxref{Target Commands, ,Commands for managing targets}).
11302 @cindex target architecture
11303 It is possible to build @value{GDBN} for several different @dfn{target
11304 architectures}. When @value{GDBN} is built like that, you can choose
11305 one of the available architectures with the @kbd{set architecture}
11309 @kindex set architecture
11310 @kindex show architecture
11311 @item set architecture @var{arch}
11312 This command sets the current target architecture to @var{arch}. The
11313 value of @var{arch} can be @code{"auto"}, in addition to one of the
11314 supported architectures.
11316 @item show architecture
11317 Show the current target architecture.
11319 @item set processor
11321 @kindex set processor
11322 @kindex show processor
11323 These are alias commands for, respectively, @code{set architecture}
11324 and @code{show architecture}.
11328 * Active Targets:: Active targets
11329 * Target Commands:: Commands for managing targets
11330 * Byte Order:: Choosing target byte order
11331 * Remote:: Remote debugging
11332 * KOD:: Kernel Object Display
11336 @node Active Targets
11337 @section Active targets
11339 @cindex stacking targets
11340 @cindex active targets
11341 @cindex multiple targets
11343 There are three classes of targets: processes, core files, and
11344 executable files. @value{GDBN} can work concurrently on up to three
11345 active targets, one in each class. This allows you to (for example)
11346 start a process and inspect its activity without abandoning your work on
11349 For example, if you execute @samp{gdb a.out}, then the executable file
11350 @code{a.out} is the only active target. If you designate a core file as
11351 well---presumably from a prior run that crashed and coredumped---then
11352 @value{GDBN} has two active targets and uses them in tandem, looking
11353 first in the corefile target, then in the executable file, to satisfy
11354 requests for memory addresses. (Typically, these two classes of target
11355 are complementary, since core files contain only a program's
11356 read-write memory---variables and so on---plus machine status, while
11357 executable files contain only the program text and initialized data.)
11359 When you type @code{run}, your executable file becomes an active process
11360 target as well. When a process target is active, all @value{GDBN}
11361 commands requesting memory addresses refer to that target; addresses in
11362 an active core file or executable file target are obscured while the
11363 process target is active.
11365 Use the @code{core-file} and @code{exec-file} commands to select a new
11366 core file or executable target (@pxref{Files, ,Commands to specify
11367 files}). To specify as a target a process that is already running, use
11368 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
11371 @node Target Commands
11372 @section Commands for managing targets
11375 @item target @var{type} @var{parameters}
11376 Connects the @value{GDBN} host environment to a target machine or
11377 process. A target is typically a protocol for talking to debugging
11378 facilities. You use the argument @var{type} to specify the type or
11379 protocol of the target machine.
11381 Further @var{parameters} are interpreted by the target protocol, but
11382 typically include things like device names or host names to connect
11383 with, process numbers, and baud rates.
11385 The @code{target} command does not repeat if you press @key{RET} again
11386 after executing the command.
11388 @kindex help target
11390 Displays the names of all targets available. To display targets
11391 currently selected, use either @code{info target} or @code{info files}
11392 (@pxref{Files, ,Commands to specify files}).
11394 @item help target @var{name}
11395 Describe a particular target, including any parameters necessary to
11398 @kindex set gnutarget
11399 @item set gnutarget @var{args}
11400 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
11401 knows whether it is reading an @dfn{executable},
11402 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
11403 with the @code{set gnutarget} command. Unlike most @code{target} commands,
11404 with @code{gnutarget} the @code{target} refers to a program, not a machine.
11407 @emph{Warning:} To specify a file format with @code{set gnutarget},
11408 you must know the actual BFD name.
11412 @xref{Files, , Commands to specify files}.
11414 @kindex show gnutarget
11415 @item show gnutarget
11416 Use the @code{show gnutarget} command to display what file format
11417 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
11418 @value{GDBN} will determine the file format for each file automatically,
11419 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
11422 @cindex common targets
11423 Here are some common targets (available, or not, depending on the GDB
11428 @item target exec @var{program}
11429 @cindex executable file target
11430 An executable file. @samp{target exec @var{program}} is the same as
11431 @samp{exec-file @var{program}}.
11433 @item target core @var{filename}
11434 @cindex core dump file target
11435 A core dump file. @samp{target core @var{filename}} is the same as
11436 @samp{core-file @var{filename}}.
11438 @item target remote @var{dev}
11439 @cindex remote target
11440 Remote serial target in GDB-specific protocol. The argument @var{dev}
11441 specifies what serial device to use for the connection (e.g.
11442 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
11443 supports the @code{load} command. This is only useful if you have
11444 some other way of getting the stub to the target system, and you can put
11445 it somewhere in memory where it won't get clobbered by the download.
11448 @cindex built-in simulator target
11449 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
11457 works; however, you cannot assume that a specific memory map, device
11458 drivers, or even basic I/O is available, although some simulators do
11459 provide these. For info about any processor-specific simulator details,
11460 see the appropriate section in @ref{Embedded Processors, ,Embedded
11465 Some configurations may include these targets as well:
11469 @item target nrom @var{dev}
11470 @cindex NetROM ROM emulator target
11471 NetROM ROM emulator. This target only supports downloading.
11475 Different targets are available on different configurations of @value{GDBN};
11476 your configuration may have more or fewer targets.
11478 Many remote targets require you to download the executable's code once
11479 you've successfully established a connection. You may wish to control
11480 various aspects of this process, such as the size of the data chunks
11481 used by @value{GDBN} to download program parts to the remote target.
11484 @kindex set download-write-size
11485 @item set download-write-size @var{size}
11486 Set the write size used when downloading a program. Only used when
11487 downloading a program onto a remote target. Specify zero or a
11488 negative value to disable blocked writes. The actual size of each
11489 transfer is also limited by the size of the target packet and the
11492 @kindex show download-write-size
11493 @item show download-write-size
11494 @kindex show download-write-size
11495 Show the current value of the write size.
11498 @kindex set hash@r{, for remote monitors}
11499 @cindex hash mark while downloading
11500 This command controls whether a hash mark @samp{#} is displayed while
11501 downloading a file to the remote monitor. If on, a hash mark is
11502 displayed after each S-record is successfully downloaded to the
11506 @kindex show hash@r{, for remote monitors}
11507 Show the current status of displaying the hash mark.
11509 @item set debug monitor
11510 @kindex set debug monitor
11511 @cindex display remote monitor communications
11512 Enable or disable display of communications messages between
11513 @value{GDBN} and the remote monitor.
11515 @item show debug monitor
11516 @kindex show debug monitor
11517 Show the current status of displaying communications between
11518 @value{GDBN} and the remote monitor.
11523 @kindex load @var{filename}
11524 @item load @var{filename}
11525 Depending on what remote debugging facilities are configured into
11526 @value{GDBN}, the @code{load} command may be available. Where it exists, it
11527 is meant to make @var{filename} (an executable) available for debugging
11528 on the remote system---by downloading, or dynamic linking, for example.
11529 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
11530 the @code{add-symbol-file} command.
11532 If your @value{GDBN} does not have a @code{load} command, attempting to
11533 execute it gets the error message ``@code{You can't do that when your
11534 target is @dots{}}''
11536 The file is loaded at whatever address is specified in the executable.
11537 For some object file formats, you can specify the load address when you
11538 link the program; for other formats, like a.out, the object file format
11539 specifies a fixed address.
11540 @c FIXME! This would be a good place for an xref to the GNU linker doc.
11542 @code{load} does not repeat if you press @key{RET} again after using it.
11546 @section Choosing target byte order
11548 @cindex choosing target byte order
11549 @cindex target byte order
11551 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
11552 offer the ability to run either big-endian or little-endian byte
11553 orders. Usually the executable or symbol will include a bit to
11554 designate the endian-ness, and you will not need to worry about
11555 which to use. However, you may still find it useful to adjust
11556 @value{GDBN}'s idea of processor endian-ness manually.
11560 @item set endian big
11561 Instruct @value{GDBN} to assume the target is big-endian.
11563 @item set endian little
11564 Instruct @value{GDBN} to assume the target is little-endian.
11566 @item set endian auto
11567 Instruct @value{GDBN} to use the byte order associated with the
11571 Display @value{GDBN}'s current idea of the target byte order.
11575 Note that these commands merely adjust interpretation of symbolic
11576 data on the host, and that they have absolutely no effect on the
11580 @section Remote debugging
11581 @cindex remote debugging
11583 If you are trying to debug a program running on a machine that cannot run
11584 @value{GDBN} in the usual way, it is often useful to use remote debugging.
11585 For example, you might use remote debugging on an operating system kernel,
11586 or on a small system which does not have a general purpose operating system
11587 powerful enough to run a full-featured debugger.
11589 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
11590 to make this work with particular debugging targets. In addition,
11591 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
11592 but not specific to any particular target system) which you can use if you
11593 write the remote stubs---the code that runs on the remote system to
11594 communicate with @value{GDBN}.
11596 Other remote targets may be available in your
11597 configuration of @value{GDBN}; use @code{help target} to list them.
11599 Once you've connected to the remote target, @value{GDBN} allows you to
11600 send arbitrary commands to the remote monitor:
11603 @item remote @var{command}
11604 @kindex remote@r{, a command}
11605 @cindex send command to remote monitor
11606 Send an arbitrary @var{command} string to the remote monitor.
11611 @section Kernel Object Display
11612 @cindex kernel object display
11615 Some targets support kernel object display. Using this facility,
11616 @value{GDBN} communicates specially with the underlying operating system
11617 and can display information about operating system-level objects such as
11618 mutexes and other synchronization objects. Exactly which objects can be
11619 displayed is determined on a per-OS basis.
11622 Use the @code{set os} command to set the operating system. This tells
11623 @value{GDBN} which kernel object display module to initialize:
11626 (@value{GDBP}) set os cisco
11630 The associated command @code{show os} displays the operating system
11631 set with the @code{set os} command; if no operating system has been
11632 set, @code{show os} will display an empty string @samp{""}.
11634 If @code{set os} succeeds, @value{GDBN} will display some information
11635 about the operating system, and will create a new @code{info} command
11636 which can be used to query the target. The @code{info} command is named
11637 after the operating system:
11641 (@value{GDBP}) info cisco
11642 List of Cisco Kernel Objects
11644 any Any and all objects
11647 Further subcommands can be used to query about particular objects known
11650 There is currently no way to determine whether a given operating
11651 system is supported other than to try setting it with @kbd{set os
11652 @var{name}}, where @var{name} is the name of the operating system you
11656 @node Remote Debugging
11657 @chapter Debugging remote programs
11660 * Connecting:: Connecting to a remote target
11661 * Server:: Using the gdbserver program
11662 * NetWare:: Using the gdbserve.nlm program
11663 * Remote configuration:: Remote configuration
11664 * remote stub:: Implementing a remote stub
11668 @section Connecting to a remote target
11670 On the @value{GDBN} host machine, you will need an unstripped copy of
11671 your program, since @value{GDBN} needs symobl and debugging information.
11672 Start up @value{GDBN} as usual, using the name of the local copy of your
11673 program as the first argument.
11675 @cindex serial line, @code{target remote}
11676 If you're using a serial line, you may want to give @value{GDBN} the
11677 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
11678 (@pxref{Remote configuration, set remotebaud}) before the
11679 @code{target} command.
11681 After that, use @code{target remote} to establish communications with
11682 the target machine. Its argument specifies how to communicate---either
11683 via a devicename attached to a direct serial line, or a TCP or UDP port
11684 (possibly to a terminal server which in turn has a serial line to the
11685 target). For example, to use a serial line connected to the device
11686 named @file{/dev/ttyb}:
11689 target remote /dev/ttyb
11692 @cindex TCP port, @code{target remote}
11693 To use a TCP connection, use an argument of the form
11694 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
11695 For example, to connect to port 2828 on a
11696 terminal server named @code{manyfarms}:
11699 target remote manyfarms:2828
11702 If your remote target is actually running on the same machine as
11703 your debugger session (e.g.@: a simulator of your target running on
11704 the same host), you can omit the hostname. For example, to connect
11705 to port 1234 on your local machine:
11708 target remote :1234
11712 Note that the colon is still required here.
11714 @cindex UDP port, @code{target remote}
11715 To use a UDP connection, use an argument of the form
11716 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
11717 on a terminal server named @code{manyfarms}:
11720 target remote udp:manyfarms:2828
11723 When using a UDP connection for remote debugging, you should keep in mind
11724 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
11725 busy or unreliable networks, which will cause havoc with your debugging
11728 Now you can use all the usual commands to examine and change data and to
11729 step and continue the remote program.
11731 @cindex interrupting remote programs
11732 @cindex remote programs, interrupting
11733 Whenever @value{GDBN} is waiting for the remote program, if you type the
11734 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
11735 program. This may or may not succeed, depending in part on the hardware
11736 and the serial drivers the remote system uses. If you type the
11737 interrupt character once again, @value{GDBN} displays this prompt:
11740 Interrupted while waiting for the program.
11741 Give up (and stop debugging it)? (y or n)
11744 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
11745 (If you decide you want to try again later, you can use @samp{target
11746 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
11747 goes back to waiting.
11750 @kindex detach (remote)
11752 When you have finished debugging the remote program, you can use the
11753 @code{detach} command to release it from @value{GDBN} control.
11754 Detaching from the target normally resumes its execution, but the results
11755 will depend on your particular remote stub. After the @code{detach}
11756 command, @value{GDBN} is free to connect to another target.
11760 The @code{disconnect} command behaves like @code{detach}, except that
11761 the target is generally not resumed. It will wait for @value{GDBN}
11762 (this instance or another one) to connect and continue debugging. After
11763 the @code{disconnect} command, @value{GDBN} is again free to connect to
11766 @cindex send command to remote monitor
11768 @item monitor @var{cmd}
11769 This command allows you to send commands directly to the remote
11774 @section Using the @code{gdbserver} program
11777 @cindex remote connection without stubs
11778 @code{gdbserver} is a control program for Unix-like systems, which
11779 allows you to connect your program with a remote @value{GDBN} via
11780 @code{target remote}---but without linking in the usual debugging stub.
11782 @code{gdbserver} is not a complete replacement for the debugging stubs,
11783 because it requires essentially the same operating-system facilities
11784 that @value{GDBN} itself does. In fact, a system that can run
11785 @code{gdbserver} to connect to a remote @value{GDBN} could also run
11786 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
11787 because it is a much smaller program than @value{GDBN} itself. It is
11788 also easier to port than all of @value{GDBN}, so you may be able to get
11789 started more quickly on a new system by using @code{gdbserver}.
11790 Finally, if you develop code for real-time systems, you may find that
11791 the tradeoffs involved in real-time operation make it more convenient to
11792 do as much development work as possible on another system, for example
11793 by cross-compiling. You can use @code{gdbserver} to make a similar
11794 choice for debugging.
11796 @value{GDBN} and @code{gdbserver} communicate via either a serial line
11797 or a TCP connection, using the standard @value{GDBN} remote serial
11801 @item On the target machine,
11802 you need to have a copy of the program you want to debug.
11803 @code{gdbserver} does not need your program's symbol table, so you can
11804 strip the program if necessary to save space. @value{GDBN} on the host
11805 system does all the symbol handling.
11807 To use the server, you must tell it how to communicate with @value{GDBN};
11808 the name of your program; and the arguments for your program. The usual
11812 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
11815 @var{comm} is either a device name (to use a serial line) or a TCP
11816 hostname and portnumber. For example, to debug Emacs with the argument
11817 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
11821 target> gdbserver /dev/com1 emacs foo.txt
11824 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
11827 To use a TCP connection instead of a serial line:
11830 target> gdbserver host:2345 emacs foo.txt
11833 The only difference from the previous example is the first argument,
11834 specifying that you are communicating with the host @value{GDBN} via
11835 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
11836 expect a TCP connection from machine @samp{host} to local TCP port 2345.
11837 (Currently, the @samp{host} part is ignored.) You can choose any number
11838 you want for the port number as long as it does not conflict with any
11839 TCP ports already in use on the target system (for example, @code{23} is
11840 reserved for @code{telnet}).@footnote{If you choose a port number that
11841 conflicts with another service, @code{gdbserver} prints an error message
11842 and exits.} You must use the same port number with the host @value{GDBN}
11843 @code{target remote} command.
11845 On some targets, @code{gdbserver} can also attach to running programs.
11846 This is accomplished via the @code{--attach} argument. The syntax is:
11849 target> gdbserver @var{comm} --attach @var{pid}
11852 @var{pid} is the process ID of a currently running process. It isn't necessary
11853 to point @code{gdbserver} at a binary for the running process.
11856 @cindex attach to a program by name
11857 You can debug processes by name instead of process ID if your target has the
11858 @code{pidof} utility:
11861 target> gdbserver @var{comm} --attach `pidof @var{PROGRAM}`
11864 In case more than one copy of @var{PROGRAM} is running, or @var{PROGRAM}
11865 has multiple threads, most versions of @code{pidof} support the
11866 @code{-s} option to only return the first process ID.
11868 @item On the host machine,
11869 connect to your target (@pxref{Connecting,,Connecting to a remote target}).
11870 For TCP connections, you must start up @code{gdbserver} prior to using
11871 the @code{target remote} command. Otherwise you may get an error whose
11872 text depends on the host system, but which usually looks something like
11873 @samp{Connection refused}. You don't need to use the @code{load}
11874 command in @value{GDBN} when using gdbserver, since the program is
11875 already on the target.
11880 @section Using the @code{gdbserve.nlm} program
11882 @kindex gdbserve.nlm
11883 @code{gdbserve.nlm} is a control program for NetWare systems, which
11884 allows you to connect your program with a remote @value{GDBN} via
11885 @code{target remote}.
11887 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
11888 using the standard @value{GDBN} remote serial protocol.
11891 @item On the target machine,
11892 you need to have a copy of the program you want to debug.
11893 @code{gdbserve.nlm} does not need your program's symbol table, so you
11894 can strip the program if necessary to save space. @value{GDBN} on the
11895 host system does all the symbol handling.
11897 To use the server, you must tell it how to communicate with
11898 @value{GDBN}; the name of your program; and the arguments for your
11899 program. The syntax is:
11902 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
11903 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
11906 @var{board} and @var{port} specify the serial line; @var{baud} specifies
11907 the baud rate used by the connection. @var{port} and @var{node} default
11908 to 0, @var{baud} defaults to 9600@dmn{bps}.
11910 For example, to debug Emacs with the argument @samp{foo.txt}and
11911 communicate with @value{GDBN} over serial port number 2 or board 1
11912 using a 19200@dmn{bps} connection:
11915 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
11919 On the @value{GDBN} host machine, connect to your target (@pxref{Connecting,,
11920 Connecting to a remote target}).
11924 @node Remote configuration
11925 @section Remote configuration
11928 @kindex show remote
11929 This section documents the configuration options available when
11930 debugging remote programs. For the options related to the File I/O
11931 extensions of the remote protocol, see @ref{The system call,
11932 system-call-allowed}.
11935 @item set remoteaddresssize @var{bits}
11936 @cindex adress size for remote targets
11937 @cindex bits in remote address
11938 Set the maximum size of address in a memory packet to the specified
11939 number of bits. @value{GDBN} will mask off the address bits above
11940 that number, when it passes addresses to the remote target. The
11941 default value is the number of bits in the target's address.
11943 @item show remoteaddresssize
11944 Show the current value of remote address size in bits.
11946 @item set remotebaud @var{n}
11947 @cindex baud rate for remote targets
11948 Set the baud rate for the remote serial I/O to @var{n} baud. The
11949 value is used to set the speed of the serial port used for debugging
11952 @item show remotebaud
11953 Show the current speed of the remote connection.
11955 @item set remotebreak
11956 @cindex interrupt remote programs
11957 @cindex BREAK signal instead of Ctrl-C
11958 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
11959 when you press the @key{Ctrl-C} key to interrupt the program running
11960 on the remote. If set to off, @value{GDBN} sends the @samp{Strl-C}
11961 character instead. The default is off, since most remote systems
11962 expect to see @samp{Ctrl-C} as the interrupt signal.
11964 @item show remotebreak
11965 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
11966 interrupt the remote program.
11968 @item set remotedebug
11969 @cindex debug remote protocol
11970 @cindex remote protocol debugging
11971 @cindex display remote packets
11972 Control the debugging of the remote protocol. When enabled, each
11973 packet sent to or received from the remote target is displayed. The
11976 @item show remotedebug
11977 Show the current setting of the remote protocol debugging.
11979 @item set remotedevice @var{device}
11980 @cindex serial port name
11981 Set the name of the serial port through which to communicate to the
11982 remote target to @var{device}. This is the device used by
11983 @value{GDBN} to open the serial communications line to the remote
11984 target. There's no default, so you must set a valid port name for the
11985 remote serial communications to work. (Some varieties of the
11986 @code{target} command accept the port name as part of their
11989 @item show remotedevice
11990 Show the current name of the serial port.
11992 @item set remotelogbase @var{base}
11993 Set the base (a.k.a.@: radix) of logging serial protocol
11994 communications to @var{base}. Supported values of @var{base} are:
11995 @code{ascii}, @code{octal}, and @code{hex}. The default is
11998 @item show remotelogbase
11999 Show the current setting of the radix for logging remote serial
12002 @item set remotelogfile @var{file}
12003 @cindex record serial communications on file
12004 Record remote serial communications on the named @var{file}. The
12005 default is not to record at all.
12007 @item show remotelogfile.
12008 Show the current setting of the file name on which to record the
12009 serial communications.
12011 @item set remotetimeout @var{num}
12012 @cindex timeout for serial communications
12013 @cindex remote timeout
12014 Set the timeout limit to wait for the remote target to respond to
12015 @var{num} seconds. The default is 2 seconds.
12017 @item show remotetimeout
12018 Show the current number of seconds to wait for the remote target
12021 @cindex limit hardware breakpoints and watchpoints
12022 @cindex remote target, limit break- and watchpoints
12023 @anchor{set remote hardware-watchpoint-limit}
12024 @anchor{set remote hardware-breakpoint-limit}
12025 @item set remote hardware-watchpoint-limit @var{limit}
12026 @itemx set remote hardware-breakpoint-limit @var{limit}
12027 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
12028 watchpoints. A limit of -1, the default, is treated as unlimited.
12030 @item set remote fetch-register-packet
12031 @itemx set remote set-register-packet
12032 @itemx set remote P-packet
12033 @itemx set remote p-packet
12035 @cindex fetch registers from remote targets
12036 @cindex set registers in remote targets
12037 Determine whether @value{GDBN} can set and fetch registers from the
12038 remote target using the @samp{P} packets. The default depends on the
12039 remote stub's support of the @samp{P} packets (@value{GDBN} queries
12040 the stub when this packet is first required).
12042 @item show remote fetch-register-packet
12043 @itemx show remote set-register-packet
12044 @itemx show remote P-packet
12045 @itemx show remote p-packet
12046 Show the current setting of using the @samp{P} packets for setting and
12047 fetching registers from the remote target.
12049 @cindex binary downloads
12051 @item set remote binary-download-packet
12052 @itemx set remote X-packet
12053 Determine whether @value{GDBN} sends downloads in binary mode using
12054 the @samp{X} packets. The default is on.
12056 @item show remote binary-download-packet
12057 @itemx show remote X-packet
12058 Show the current setting of using the @samp{X} packets for binary
12061 @item set remote read-aux-vector-packet
12062 @cindex auxiliary vector of remote target
12063 @cindex @code{auxv}, and remote targets
12064 Set the use of the remote protocol's @samp{qPart:auxv:read} (target
12065 auxiliary vector read) request. This request is used to fetch the
12066 remote target's @dfn{auxiliary vector}, see @ref{OS Information,
12067 Auxiliary Vector}. The default setting depends on the remote stub's
12068 support of this request (@value{GDBN} queries the stub when this
12069 request is first required). @xref{General Query Packets, qPart}, for
12070 more information about this request.
12072 @item show remote read-aux-vector-packet
12073 Show the current setting of use of the @samp{qPart:auxv:read} request.
12075 @item set remote symbol-lookup-packet
12076 @cindex remote symbol lookup request
12077 Set the use of the remote protocol's @samp{qSymbol} (target symbol
12078 lookup) request. This request is used to communicate symbol
12079 information to the remote target, e.g., whenever a new shared library
12080 is loaded by the remote (@pxref{Files, shared libraries}). The
12081 default setting depends on the remote stub's support of this request
12082 (@value{GDBN} queries the stub when this request is first required).
12083 @xref{General Query Packets, qSymbol}, for more information about this
12086 @item show remote symbol-lookup-packet
12087 Show the current setting of use of the @samp{qSymbol} request.
12089 @item set remote verbose-resume-packet
12090 @cindex resume remote target
12091 @cindex signal thread, and remote targets
12092 @cindex single-step thread, and remote targets
12093 @cindex thread-specific operations on remote targets
12094 Set the use of the remote protocol's @samp{vCont} (descriptive resume)
12095 request. This request is used to resume specific threads in the
12096 remote target, and to single-step or signal them. The default setting
12097 depends on the remote stub's support of this request (@value{GDBN}
12098 queries the stub when this request is first required). This setting
12099 affects debugging of multithreaded programs: if @samp{vCont} cannot be
12100 used, @value{GDBN} might be unable to single-step a specific thread,
12101 especially under @code{set scheduler-locking off}; it is also
12102 impossible to pause a specific thread. @xref{Packets, vCont}, for
12105 @item show remote verbose-resume-packet
12106 Show the current setting of use of the @samp{vCont} request
12108 @item set remote software-breakpoint-packet
12109 @itemx set remote hardware-breakpoint-packet
12110 @itemx set remote write-watchpoint-packet
12111 @itemx set remote read-watchpoint-packet
12112 @itemx set remote access-watchpoint-packet
12113 @itemx set remote Z-packet
12115 @cindex remote hardware breakpoints and watchpoints
12116 These commands enable or disable the use of @samp{Z} packets for
12117 setting breakpoints and watchpoints in the remote target. The default
12118 depends on the remote stub's support of the @samp{Z} packets
12119 (@value{GDBN} queries the stub when each packet is first required).
12120 The command @code{set remote Z-packet}, kept for back-compatibility,
12121 turns on or off all the features that require the use of @samp{Z}
12124 @item show remote software-breakpoint-packet
12125 @itemx show remote hardware-breakpoint-packet
12126 @itemx show remote write-watchpoint-packet
12127 @itemx show remote read-watchpoint-packet
12128 @itemx show remote access-watchpoint-packet
12129 @itemx show remote Z-packet
12130 Show the current setting of @samp{Z} packets usage.
12132 @item set remote get-thread-local-storage-address
12133 @kindex set remote get-thread-local-storage-address
12134 @cindex thread local storage of remote targets
12135 This command enables or disables the use of the @samp{qGetTLSAddr}
12136 (Get Thread Local Storage Address) request packet. The default
12137 depends on whether the remote stub supports this request.
12138 @xref{General Query Packets, qGetTLSAddr}, for more details about this
12141 @item show remote get-thread-local-storage-address
12142 @kindex show remote get-thread-local-storage-address
12143 Show the current setting of @samp{qGetTLSAddr} packet usage.
12147 @section Implementing a remote stub
12149 @cindex debugging stub, example
12150 @cindex remote stub, example
12151 @cindex stub example, remote debugging
12152 The stub files provided with @value{GDBN} implement the target side of the
12153 communication protocol, and the @value{GDBN} side is implemented in the
12154 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
12155 these subroutines to communicate, and ignore the details. (If you're
12156 implementing your own stub file, you can still ignore the details: start
12157 with one of the existing stub files. @file{sparc-stub.c} is the best
12158 organized, and therefore the easiest to read.)
12160 @cindex remote serial debugging, overview
12161 To debug a program running on another machine (the debugging
12162 @dfn{target} machine), you must first arrange for all the usual
12163 prerequisites for the program to run by itself. For example, for a C
12168 A startup routine to set up the C runtime environment; these usually
12169 have a name like @file{crt0}. The startup routine may be supplied by
12170 your hardware supplier, or you may have to write your own.
12173 A C subroutine library to support your program's
12174 subroutine calls, notably managing input and output.
12177 A way of getting your program to the other machine---for example, a
12178 download program. These are often supplied by the hardware
12179 manufacturer, but you may have to write your own from hardware
12183 The next step is to arrange for your program to use a serial port to
12184 communicate with the machine where @value{GDBN} is running (the @dfn{host}
12185 machine). In general terms, the scheme looks like this:
12189 @value{GDBN} already understands how to use this protocol; when everything
12190 else is set up, you can simply use the @samp{target remote} command
12191 (@pxref{Targets,,Specifying a Debugging Target}).
12193 @item On the target,
12194 you must link with your program a few special-purpose subroutines that
12195 implement the @value{GDBN} remote serial protocol. The file containing these
12196 subroutines is called a @dfn{debugging stub}.
12198 On certain remote targets, you can use an auxiliary program
12199 @code{gdbserver} instead of linking a stub into your program.
12200 @xref{Server,,Using the @code{gdbserver} program}, for details.
12203 The debugging stub is specific to the architecture of the remote
12204 machine; for example, use @file{sparc-stub.c} to debug programs on
12207 @cindex remote serial stub list
12208 These working remote stubs are distributed with @value{GDBN}:
12213 @cindex @file{i386-stub.c}
12216 For Intel 386 and compatible architectures.
12219 @cindex @file{m68k-stub.c}
12220 @cindex Motorola 680x0
12222 For Motorola 680x0 architectures.
12225 @cindex @file{sh-stub.c}
12228 For Renesas SH architectures.
12231 @cindex @file{sparc-stub.c}
12233 For @sc{sparc} architectures.
12235 @item sparcl-stub.c
12236 @cindex @file{sparcl-stub.c}
12239 For Fujitsu @sc{sparclite} architectures.
12243 The @file{README} file in the @value{GDBN} distribution may list other
12244 recently added stubs.
12247 * Stub Contents:: What the stub can do for you
12248 * Bootstrapping:: What you must do for the stub
12249 * Debug Session:: Putting it all together
12252 @node Stub Contents
12253 @subsection What the stub can do for you
12255 @cindex remote serial stub
12256 The debugging stub for your architecture supplies these three
12260 @item set_debug_traps
12261 @findex set_debug_traps
12262 @cindex remote serial stub, initialization
12263 This routine arranges for @code{handle_exception} to run when your
12264 program stops. You must call this subroutine explicitly near the
12265 beginning of your program.
12267 @item handle_exception
12268 @findex handle_exception
12269 @cindex remote serial stub, main routine
12270 This is the central workhorse, but your program never calls it
12271 explicitly---the setup code arranges for @code{handle_exception} to
12272 run when a trap is triggered.
12274 @code{handle_exception} takes control when your program stops during
12275 execution (for example, on a breakpoint), and mediates communications
12276 with @value{GDBN} on the host machine. This is where the communications
12277 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
12278 representative on the target machine. It begins by sending summary
12279 information on the state of your program, then continues to execute,
12280 retrieving and transmitting any information @value{GDBN} needs, until you
12281 execute a @value{GDBN} command that makes your program resume; at that point,
12282 @code{handle_exception} returns control to your own code on the target
12286 @cindex @code{breakpoint} subroutine, remote
12287 Use this auxiliary subroutine to make your program contain a
12288 breakpoint. Depending on the particular situation, this may be the only
12289 way for @value{GDBN} to get control. For instance, if your target
12290 machine has some sort of interrupt button, you won't need to call this;
12291 pressing the interrupt button transfers control to
12292 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
12293 simply receiving characters on the serial port may also trigger a trap;
12294 again, in that situation, you don't need to call @code{breakpoint} from
12295 your own program---simply running @samp{target remote} from the host
12296 @value{GDBN} session gets control.
12298 Call @code{breakpoint} if none of these is true, or if you simply want
12299 to make certain your program stops at a predetermined point for the
12300 start of your debugging session.
12303 @node Bootstrapping
12304 @subsection What you must do for the stub
12306 @cindex remote stub, support routines
12307 The debugging stubs that come with @value{GDBN} are set up for a particular
12308 chip architecture, but they have no information about the rest of your
12309 debugging target machine.
12311 First of all you need to tell the stub how to communicate with the
12315 @item int getDebugChar()
12316 @findex getDebugChar
12317 Write this subroutine to read a single character from the serial port.
12318 It may be identical to @code{getchar} for your target system; a
12319 different name is used to allow you to distinguish the two if you wish.
12321 @item void putDebugChar(int)
12322 @findex putDebugChar
12323 Write this subroutine to write a single character to the serial port.
12324 It may be identical to @code{putchar} for your target system; a
12325 different name is used to allow you to distinguish the two if you wish.
12328 @cindex control C, and remote debugging
12329 @cindex interrupting remote targets
12330 If you want @value{GDBN} to be able to stop your program while it is
12331 running, you need to use an interrupt-driven serial driver, and arrange
12332 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
12333 character). That is the character which @value{GDBN} uses to tell the
12334 remote system to stop.
12336 Getting the debugging target to return the proper status to @value{GDBN}
12337 probably requires changes to the standard stub; one quick and dirty way
12338 is to just execute a breakpoint instruction (the ``dirty'' part is that
12339 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
12341 Other routines you need to supply are:
12344 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
12345 @findex exceptionHandler
12346 Write this function to install @var{exception_address} in the exception
12347 handling tables. You need to do this because the stub does not have any
12348 way of knowing what the exception handling tables on your target system
12349 are like (for example, the processor's table might be in @sc{rom},
12350 containing entries which point to a table in @sc{ram}).
12351 @var{exception_number} is the exception number which should be changed;
12352 its meaning is architecture-dependent (for example, different numbers
12353 might represent divide by zero, misaligned access, etc). When this
12354 exception occurs, control should be transferred directly to
12355 @var{exception_address}, and the processor state (stack, registers,
12356 and so on) should be just as it is when a processor exception occurs. So if
12357 you want to use a jump instruction to reach @var{exception_address}, it
12358 should be a simple jump, not a jump to subroutine.
12360 For the 386, @var{exception_address} should be installed as an interrupt
12361 gate so that interrupts are masked while the handler runs. The gate
12362 should be at privilege level 0 (the most privileged level). The
12363 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
12364 help from @code{exceptionHandler}.
12366 @item void flush_i_cache()
12367 @findex flush_i_cache
12368 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
12369 instruction cache, if any, on your target machine. If there is no
12370 instruction cache, this subroutine may be a no-op.
12372 On target machines that have instruction caches, @value{GDBN} requires this
12373 function to make certain that the state of your program is stable.
12377 You must also make sure this library routine is available:
12380 @item void *memset(void *, int, int)
12382 This is the standard library function @code{memset} that sets an area of
12383 memory to a known value. If you have one of the free versions of
12384 @code{libc.a}, @code{memset} can be found there; otherwise, you must
12385 either obtain it from your hardware manufacturer, or write your own.
12388 If you do not use the GNU C compiler, you may need other standard
12389 library subroutines as well; this varies from one stub to another,
12390 but in general the stubs are likely to use any of the common library
12391 subroutines which @code{@value{GCC}} generates as inline code.
12394 @node Debug Session
12395 @subsection Putting it all together
12397 @cindex remote serial debugging summary
12398 In summary, when your program is ready to debug, you must follow these
12403 Make sure you have defined the supporting low-level routines
12404 (@pxref{Bootstrapping,,What you must do for the stub}):
12406 @code{getDebugChar}, @code{putDebugChar},
12407 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
12411 Insert these lines near the top of your program:
12419 For the 680x0 stub only, you need to provide a variable called
12420 @code{exceptionHook}. Normally you just use:
12423 void (*exceptionHook)() = 0;
12427 but if before calling @code{set_debug_traps}, you set it to point to a
12428 function in your program, that function is called when
12429 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
12430 error). The function indicated by @code{exceptionHook} is called with
12431 one parameter: an @code{int} which is the exception number.
12434 Compile and link together: your program, the @value{GDBN} debugging stub for
12435 your target architecture, and the supporting subroutines.
12438 Make sure you have a serial connection between your target machine and
12439 the @value{GDBN} host, and identify the serial port on the host.
12442 @c The "remote" target now provides a `load' command, so we should
12443 @c document that. FIXME.
12444 Download your program to your target machine (or get it there by
12445 whatever means the manufacturer provides), and start it.
12448 Start @value{GDBN} on the host, and connect to the target
12449 (@pxref{Connecting,,Connecting to a remote target}).
12453 @node Configurations
12454 @chapter Configuration-Specific Information
12456 While nearly all @value{GDBN} commands are available for all native and
12457 cross versions of the debugger, there are some exceptions. This chapter
12458 describes things that are only available in certain configurations.
12460 There are three major categories of configurations: native
12461 configurations, where the host and target are the same, embedded
12462 operating system configurations, which are usually the same for several
12463 different processor architectures, and bare embedded processors, which
12464 are quite different from each other.
12469 * Embedded Processors::
12476 This section describes details specific to particular native
12481 * BSD libkvm Interface:: Debugging BSD kernel memory images
12482 * SVR4 Process Information:: SVR4 process information
12483 * DJGPP Native:: Features specific to the DJGPP port
12484 * Cygwin Native:: Features specific to the Cygwin port
12485 * Hurd Native:: Features specific to @sc{gnu} Hurd
12486 * Neutrino:: Features specific to QNX Neutrino
12492 On HP-UX systems, if you refer to a function or variable name that
12493 begins with a dollar sign, @value{GDBN} searches for a user or system
12494 name first, before it searches for a convenience variable.
12497 @node BSD libkvm Interface
12498 @subsection BSD libkvm Interface
12501 @cindex kernel memory image
12502 @cindex kernel crash dump
12504 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
12505 interface that provides a uniform interface for accessing kernel virtual
12506 memory images, including live systems and crash dumps. @value{GDBN}
12507 uses this interface to allow you to debug live kernels and kernel crash
12508 dumps on many native BSD configurations. This is implemented as a
12509 special @code{kvm} debugging target. For debugging a live system, load
12510 the currently running kernel into @value{GDBN} and connect to the
12514 (@value{GDBP}) @b{target kvm}
12517 For debugging crash dumps, provide the file name of the crash dump as an
12521 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
12524 Once connected to the @code{kvm} target, the following commands are
12530 Set current context from the @dfn{Process Control Block} (PCB) address.
12533 Set current context from proc address. This command isn't available on
12534 modern FreeBSD systems.
12537 @node SVR4 Process Information
12538 @subsection SVR4 process information
12540 @cindex examine process image
12541 @cindex process info via @file{/proc}
12543 Many versions of SVR4 and compatible systems provide a facility called
12544 @samp{/proc} that can be used to examine the image of a running
12545 process using file-system subroutines. If @value{GDBN} is configured
12546 for an operating system with this facility, the command @code{info
12547 proc} is available to report information about the process running
12548 your program, or about any process running on your system. @code{info
12549 proc} works only on SVR4 systems that include the @code{procfs} code.
12550 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
12551 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
12557 @itemx info proc @var{process-id}
12558 Summarize available information about any running process. If a
12559 process ID is specified by @var{process-id}, display information about
12560 that process; otherwise display information about the program being
12561 debugged. The summary includes the debugged process ID, the command
12562 line used to invoke it, its current working directory, and its
12563 executable file's absolute file name.
12565 On some systems, @var{process-id} can be of the form
12566 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
12567 within a process. If the optional @var{pid} part is missing, it means
12568 a thread from the process being debugged (the leading @samp{/} still
12569 needs to be present, or else @value{GDBN} will interpret the number as
12570 a process ID rather than a thread ID).
12572 @item info proc mappings
12573 @cindex memory address space mappings
12574 Report the memory address space ranges accessible in the program, with
12575 information on whether the process has read, write, or execute access
12576 rights to each range. On @sc{gnu}/Linux systems, each memory range
12577 includes the object file which is mapped to that range, instead of the
12578 memory access rights to that range.
12580 @item info proc stat
12581 @itemx info proc status
12582 @cindex process detailed status information
12583 These subcommands are specific to @sc{gnu}/Linux systems. They show
12584 the process-related information, including the user ID and group ID;
12585 how many threads are there in the process; its virtual memory usage;
12586 the signals that are pending, blocked, and ignored; its TTY; its
12587 consumption of system and user time; its stack size; its @samp{nice}
12588 value; etc. For more information, see the @samp{proc(5)} man page
12589 (type @kbd{man 5 proc} from your shell prompt).
12591 @item info proc all
12592 Show all the information about the process described under all of the
12593 above @code{info proc} subcommands.
12596 @comment These sub-options of 'info proc' were not included when
12597 @comment procfs.c was re-written. Keep their descriptions around
12598 @comment against the day when someone finds the time to put them back in.
12599 @kindex info proc times
12600 @item info proc times
12601 Starting time, user CPU time, and system CPU time for your program and
12604 @kindex info proc id
12606 Report on the process IDs related to your program: its own process ID,
12607 the ID of its parent, the process group ID, and the session ID.
12610 @item set procfs-trace
12611 @kindex set procfs-trace
12612 @cindex @code{procfs} API calls
12613 This command enables and disables tracing of @code{procfs} API calls.
12615 @item show procfs-trace
12616 @kindex show procfs-trace
12617 Show the current state of @code{procfs} API call tracing.
12619 @item set procfs-file @var{file}
12620 @kindex set procfs-file
12621 Tell @value{GDBN} to write @code{procfs} API trace to the named
12622 @var{file}. @value{GDBN} appends the trace info to the previous
12623 contents of the file. The default is to display the trace on the
12626 @item show procfs-file
12627 @kindex show procfs-file
12628 Show the file to which @code{procfs} API trace is written.
12630 @item proc-trace-entry
12631 @itemx proc-trace-exit
12632 @itemx proc-untrace-entry
12633 @itemx proc-untrace-exit
12634 @kindex proc-trace-entry
12635 @kindex proc-trace-exit
12636 @kindex proc-untrace-entry
12637 @kindex proc-untrace-exit
12638 These commands enable and disable tracing of entries into and exits
12639 from the @code{syscall} interface.
12642 @kindex info pidlist
12643 @cindex process list, QNX Neutrino
12644 For QNX Neutrino only, this command displays the list of all the
12645 processes and all the threads within each process.
12648 @kindex info meminfo
12649 @cindex mapinfo list, QNX Neutrino
12650 For QNX Neutrino only, this command displays the list of all mapinfos.
12654 @subsection Features for Debugging @sc{djgpp} Programs
12655 @cindex @sc{djgpp} debugging
12656 @cindex native @sc{djgpp} debugging
12657 @cindex MS-DOS-specific commands
12659 @sc{djgpp} is the port of @sc{gnu} development tools to MS-DOS and
12660 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
12661 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
12662 top of real-mode DOS systems and their emulations.
12664 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
12665 defines a few commands specific to the @sc{djgpp} port. This
12666 subsection describes those commands.
12671 This is a prefix of @sc{djgpp}-specific commands which print
12672 information about the target system and important OS structures.
12675 @cindex MS-DOS system info
12676 @cindex free memory information (MS-DOS)
12677 @item info dos sysinfo
12678 This command displays assorted information about the underlying
12679 platform: the CPU type and features, the OS version and flavor, the
12680 DPMI version, and the available conventional and DPMI memory.
12685 @cindex segment descriptor tables
12686 @cindex descriptor tables display
12688 @itemx info dos ldt
12689 @itemx info dos idt
12690 These 3 commands display entries from, respectively, Global, Local,
12691 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
12692 tables are data structures which store a descriptor for each segment
12693 that is currently in use. The segment's selector is an index into a
12694 descriptor table; the table entry for that index holds the
12695 descriptor's base address and limit, and its attributes and access
12698 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
12699 segment (used for both data and the stack), and a DOS segment (which
12700 allows access to DOS/BIOS data structures and absolute addresses in
12701 conventional memory). However, the DPMI host will usually define
12702 additional segments in order to support the DPMI environment.
12704 @cindex garbled pointers
12705 These commands allow to display entries from the descriptor tables.
12706 Without an argument, all entries from the specified table are
12707 displayed. An argument, which should be an integer expression, means
12708 display a single entry whose index is given by the argument. For
12709 example, here's a convenient way to display information about the
12710 debugged program's data segment:
12713 @exdent @code{(@value{GDBP}) info dos ldt $ds}
12714 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
12718 This comes in handy when you want to see whether a pointer is outside
12719 the data segment's limit (i.e.@: @dfn{garbled}).
12721 @cindex page tables display (MS-DOS)
12723 @itemx info dos pte
12724 These two commands display entries from, respectively, the Page
12725 Directory and the Page Tables. Page Directories and Page Tables are
12726 data structures which control how virtual memory addresses are mapped
12727 into physical addresses. A Page Table includes an entry for every
12728 page of memory that is mapped into the program's address space; there
12729 may be several Page Tables, each one holding up to 4096 entries. A
12730 Page Directory has up to 4096 entries, one each for every Page Table
12731 that is currently in use.
12733 Without an argument, @kbd{info dos pde} displays the entire Page
12734 Directory, and @kbd{info dos pte} displays all the entries in all of
12735 the Page Tables. An argument, an integer expression, given to the
12736 @kbd{info dos pde} command means display only that entry from the Page
12737 Directory table. An argument given to the @kbd{info dos pte} command
12738 means display entries from a single Page Table, the one pointed to by
12739 the specified entry in the Page Directory.
12741 @cindex direct memory access (DMA) on MS-DOS
12742 These commands are useful when your program uses @dfn{DMA} (Direct
12743 Memory Access), which needs physical addresses to program the DMA
12746 These commands are supported only with some DPMI servers.
12748 @cindex physical address from linear address
12749 @item info dos address-pte @var{addr}
12750 This command displays the Page Table entry for a specified linear
12751 address. The argument linear address @var{addr} should already have the
12752 appropriate segment's base address added to it, because this command
12753 accepts addresses which may belong to @emph{any} segment. For
12754 example, here's how to display the Page Table entry for the page where
12755 the variable @code{i} is stored:
12758 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
12759 @exdent @code{Page Table entry for address 0x11a00d30:}
12760 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
12764 This says that @code{i} is stored at offset @code{0xd30} from the page
12765 whose physical base address is @code{0x02698000}, and prints all the
12766 attributes of that page.
12768 Note that you must cast the addresses of variables to a @code{char *},
12769 since otherwise the value of @code{__djgpp_base_address}, the base
12770 address of all variables and functions in a @sc{djgpp} program, will
12771 be added using the rules of C pointer arithmetics: if @code{i} is
12772 declared an @code{int}, @value{GDBN} will add 4 times the value of
12773 @code{__djgpp_base_address} to the address of @code{i}.
12775 Here's another example, it displays the Page Table entry for the
12779 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
12780 @exdent @code{Page Table entry for address 0x29110:}
12781 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
12785 (The @code{+ 3} offset is because the transfer buffer's address is the
12786 3rd member of the @code{_go32_info_block} structure.) The output of
12787 this command clearly shows that addresses in conventional memory are
12788 mapped 1:1, i.e.@: the physical and linear addresses are identical.
12790 This command is supported only with some DPMI servers.
12793 @cindex DOS serial data link, remote debugging
12794 In addition to native debugging, the DJGPP port supports remote
12795 debugging via a serial data link. The following commands are specific
12796 to remote serial debugging in the DJGPP port of @value{GDBN}.
12799 @kindex set com1base
12800 @kindex set com1irq
12801 @kindex set com2base
12802 @kindex set com2irq
12803 @kindex set com3base
12804 @kindex set com3irq
12805 @kindex set com4base
12806 @kindex set com4irq
12807 @item set com1base @var{addr}
12808 This command sets the base I/O port address of the @file{COM1} serial
12811 @item set com1irq @var{irq}
12812 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
12813 for the @file{COM1} serial port.
12815 There are similar commands @samp{set com2base}, @samp{set com3irq},
12816 etc.@: for setting the port address and the @code{IRQ} lines for the
12819 @kindex show com1base
12820 @kindex show com1irq
12821 @kindex show com2base
12822 @kindex show com2irq
12823 @kindex show com3base
12824 @kindex show com3irq
12825 @kindex show com4base
12826 @kindex show com4irq
12827 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
12828 display the current settings of the base address and the @code{IRQ}
12829 lines used by the COM ports.
12832 @kindex info serial
12833 @cindex DOS serial port status
12834 This command prints the status of the 4 DOS serial ports. For each
12835 port, it prints whether it's active or not, its I/O base address and
12836 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
12837 counts of various errors encountered so far.
12841 @node Cygwin Native
12842 @subsection Features for Debugging MS Windows PE executables
12843 @cindex MS Windows debugging
12844 @cindex native Cygwin debugging
12845 @cindex Cygwin-specific commands
12847 @value{GDBN} supports native debugging of MS Windows programs, including
12848 DLLs with and without symbolic debugging information. There are various
12849 additional Cygwin-specific commands, described in this subsection. The
12850 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
12851 that have no debugging symbols.
12857 This is a prefix of MS Windows specific commands which print
12858 information about the target system and important OS structures.
12860 @item info w32 selector
12861 This command displays information returned by
12862 the Win32 API @code{GetThreadSelectorEntry} function.
12863 It takes an optional argument that is evaluated to
12864 a long value to give the information about this given selector.
12865 Without argument, this command displays information
12866 about the the six segment registers.
12870 This is a Cygwin specific alias of info shared.
12872 @kindex dll-symbols
12874 This command loads symbols from a dll similarly to
12875 add-sym command but without the need to specify a base address.
12877 @kindex set new-console
12878 @item set new-console @var{mode}
12879 If @var{mode} is @code{on} the debuggee will
12880 be started in a new console on next start.
12881 If @var{mode} is @code{off}i, the debuggee will
12882 be started in the same console as the debugger.
12884 @kindex show new-console
12885 @item show new-console
12886 Displays whether a new console is used
12887 when the debuggee is started.
12889 @kindex set new-group
12890 @item set new-group @var{mode}
12891 This boolean value controls whether the debuggee should
12892 start a new group or stay in the same group as the debugger.
12893 This affects the way the Windows OS handles
12896 @kindex show new-group
12897 @item show new-group
12898 Displays current value of new-group boolean.
12900 @kindex set debugevents
12901 @item set debugevents
12902 This boolean value adds debug output concerning events seen by the debugger.
12904 @kindex set debugexec
12905 @item set debugexec
12906 This boolean value adds debug output concerning execute events
12907 seen by the debugger.
12909 @kindex set debugexceptions
12910 @item set debugexceptions
12911 This boolean value adds debug ouptut concerning exception events
12912 seen by the debugger.
12914 @kindex set debugmemory
12915 @item set debugmemory
12916 This boolean value adds debug ouptut concerning memory events
12917 seen by the debugger.
12921 This boolean values specifies whether the debuggee is called
12922 via a shell or directly (default value is on).
12926 Displays if the debuggee will be started with a shell.
12931 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
12934 @node Non-debug DLL symbols
12935 @subsubsection Support for DLLs without debugging symbols
12936 @cindex DLLs with no debugging symbols
12937 @cindex Minimal symbols and DLLs
12939 Very often on windows, some of the DLLs that your program relies on do
12940 not include symbolic debugging information (for example,
12941 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
12942 symbols in a DLL, it relies on the minimal amount of symbolic
12943 information contained in the DLL's export table. This subsubsection
12944 describes working with such symbols, known internally to @value{GDBN} as
12945 ``minimal symbols''.
12947 Note that before the debugged program has started execution, no DLLs
12948 will have been loaded. The easiest way around this problem is simply to
12949 start the program --- either by setting a breakpoint or letting the
12950 program run once to completion. It is also possible to force
12951 @value{GDBN} to load a particular DLL before starting the executable ---
12952 see the shared library information in @pxref{Files} or the
12953 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
12954 explicitly loading symbols from a DLL with no debugging information will
12955 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
12956 which may adversely affect symbol lookup performance.
12958 @subsubsection DLL name prefixes
12960 In keeping with the naming conventions used by the Microsoft debugging
12961 tools, DLL export symbols are made available with a prefix based on the
12962 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
12963 also entered into the symbol table, so @code{CreateFileA} is often
12964 sufficient. In some cases there will be name clashes within a program
12965 (particularly if the executable itself includes full debugging symbols)
12966 necessitating the use of the fully qualified name when referring to the
12967 contents of the DLL. Use single-quotes around the name to avoid the
12968 exclamation mark (``!'') being interpreted as a language operator.
12970 Note that the internal name of the DLL may be all upper-case, even
12971 though the file name of the DLL is lower-case, or vice-versa. Since
12972 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
12973 some confusion. If in doubt, try the @code{info functions} and
12974 @code{info variables} commands or even @code{maint print msymbols} (see
12975 @pxref{Symbols}). Here's an example:
12978 (@value{GDBP}) info function CreateFileA
12979 All functions matching regular expression "CreateFileA":
12981 Non-debugging symbols:
12982 0x77e885f4 CreateFileA
12983 0x77e885f4 KERNEL32!CreateFileA
12987 (@value{GDBP}) info function !
12988 All functions matching regular expression "!":
12990 Non-debugging symbols:
12991 0x6100114c cygwin1!__assert
12992 0x61004034 cygwin1!_dll_crt0@@0
12993 0x61004240 cygwin1!dll_crt0(per_process *)
12997 @subsubsection Working with minimal symbols
12999 Symbols extracted from a DLL's export table do not contain very much
13000 type information. All that @value{GDBN} can do is guess whether a symbol
13001 refers to a function or variable depending on the linker section that
13002 contains the symbol. Also note that the actual contents of the memory
13003 contained in a DLL are not available unless the program is running. This
13004 means that you cannot examine the contents of a variable or disassemble
13005 a function within a DLL without a running program.
13007 Variables are generally treated as pointers and dereferenced
13008 automatically. For this reason, it is often necessary to prefix a
13009 variable name with the address-of operator (``&'') and provide explicit
13010 type information in the command. Here's an example of the type of
13014 (@value{GDBP}) print 'cygwin1!__argv'
13019 (@value{GDBP}) x 'cygwin1!__argv'
13020 0x10021610: "\230y\""
13023 And two possible solutions:
13026 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
13027 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
13031 (@value{GDBP}) x/2x &'cygwin1!__argv'
13032 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
13033 (@value{GDBP}) x/x 0x10021608
13034 0x10021608: 0x0022fd98
13035 (@value{GDBP}) x/s 0x0022fd98
13036 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
13039 Setting a break point within a DLL is possible even before the program
13040 starts execution. However, under these circumstances, @value{GDBN} can't
13041 examine the initial instructions of the function in order to skip the
13042 function's frame set-up code. You can work around this by using ``*&''
13043 to set the breakpoint at a raw memory address:
13046 (@value{GDBP}) break *&'python22!PyOS_Readline'
13047 Breakpoint 1 at 0x1e04eff0
13050 The author of these extensions is not entirely convinced that setting a
13051 break point within a shared DLL like @file{kernel32.dll} is completely
13055 @subsection Commands specific to @sc{gnu} Hurd systems
13056 @cindex @sc{gnu} Hurd debugging
13058 This subsection describes @value{GDBN} commands specific to the
13059 @sc{gnu} Hurd native debugging.
13064 @kindex set signals@r{, Hurd command}
13065 @kindex set sigs@r{, Hurd command}
13066 This command toggles the state of inferior signal interception by
13067 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
13068 affected by this command. @code{sigs} is a shorthand alias for
13073 @kindex show signals@r{, Hurd command}
13074 @kindex show sigs@r{, Hurd command}
13075 Show the current state of intercepting inferior's signals.
13077 @item set signal-thread
13078 @itemx set sigthread
13079 @kindex set signal-thread
13080 @kindex set sigthread
13081 This command tells @value{GDBN} which thread is the @code{libc} signal
13082 thread. That thread is run when a signal is delivered to a running
13083 process. @code{set sigthread} is the shorthand alias of @code{set
13086 @item show signal-thread
13087 @itemx show sigthread
13088 @kindex show signal-thread
13089 @kindex show sigthread
13090 These two commands show which thread will run when the inferior is
13091 delivered a signal.
13094 @kindex set stopped@r{, Hurd command}
13095 This commands tells @value{GDBN} that the inferior process is stopped,
13096 as with the @code{SIGSTOP} signal. The stopped process can be
13097 continued by delivering a signal to it.
13100 @kindex show stopped@r{, Hurd command}
13101 This command shows whether @value{GDBN} thinks the debuggee is
13104 @item set exceptions
13105 @kindex set exceptions@r{, Hurd command}
13106 Use this command to turn off trapping of exceptions in the inferior.
13107 When exception trapping is off, neither breakpoints nor
13108 single-stepping will work. To restore the default, set exception
13111 @item show exceptions
13112 @kindex show exceptions@r{, Hurd command}
13113 Show the current state of trapping exceptions in the inferior.
13115 @item set task pause
13116 @kindex set task@r{, Hurd commands}
13117 @cindex task attributes (@sc{gnu} Hurd)
13118 @cindex pause current task (@sc{gnu} Hurd)
13119 This command toggles task suspension when @value{GDBN} has control.
13120 Setting it to on takes effect immediately, and the task is suspended
13121 whenever @value{GDBN} gets control. Setting it to off will take
13122 effect the next time the inferior is continued. If this option is set
13123 to off, you can use @code{set thread default pause on} or @code{set
13124 thread pause on} (see below) to pause individual threads.
13126 @item show task pause
13127 @kindex show task@r{, Hurd commands}
13128 Show the current state of task suspension.
13130 @item set task detach-suspend-count
13131 @cindex task suspend count
13132 @cindex detach from task, @sc{gnu} Hurd
13133 This command sets the suspend count the task will be left with when
13134 @value{GDBN} detaches from it.
13136 @item show task detach-suspend-count
13137 Show the suspend count the task will be left with when detaching.
13139 @item set task exception-port
13140 @itemx set task excp
13141 @cindex task exception port, @sc{gnu} Hurd
13142 This command sets the task exception port to which @value{GDBN} will
13143 forward exceptions. The argument should be the value of the @dfn{send
13144 rights} of the task. @code{set task excp} is a shorthand alias.
13146 @item set noninvasive
13147 @cindex noninvasive task options
13148 This command switches @value{GDBN} to a mode that is the least
13149 invasive as far as interfering with the inferior is concerned. This
13150 is the same as using @code{set task pause}, @code{set exceptions}, and
13151 @code{set signals} to values opposite to the defaults.
13153 @item info send-rights
13154 @itemx info receive-rights
13155 @itemx info port-rights
13156 @itemx info port-sets
13157 @itemx info dead-names
13160 @cindex send rights, @sc{gnu} Hurd
13161 @cindex receive rights, @sc{gnu} Hurd
13162 @cindex port rights, @sc{gnu} Hurd
13163 @cindex port sets, @sc{gnu} Hurd
13164 @cindex dead names, @sc{gnu} Hurd
13165 These commands display information about, respectively, send rights,
13166 receive rights, port rights, port sets, and dead names of a task.
13167 There are also shorthand aliases: @code{info ports} for @code{info
13168 port-rights} and @code{info psets} for @code{info port-sets}.
13170 @item set thread pause
13171 @kindex set thread@r{, Hurd command}
13172 @cindex thread properties, @sc{gnu} Hurd
13173 @cindex pause current thread (@sc{gnu} Hurd)
13174 This command toggles current thread suspension when @value{GDBN} has
13175 control. Setting it to on takes effect immediately, and the current
13176 thread is suspended whenever @value{GDBN} gets control. Setting it to
13177 off will take effect the next time the inferior is continued.
13178 Normally, this command has no effect, since when @value{GDBN} has
13179 control, the whole task is suspended. However, if you used @code{set
13180 task pause off} (see above), this command comes in handy to suspend
13181 only the current thread.
13183 @item show thread pause
13184 @kindex show thread@r{, Hurd command}
13185 This command shows the state of current thread suspension.
13187 @item set thread run
13188 This comamnd sets whether the current thread is allowed to run.
13190 @item show thread run
13191 Show whether the current thread is allowed to run.
13193 @item set thread detach-suspend-count
13194 @cindex thread suspend count, @sc{gnu} Hurd
13195 @cindex detach from thread, @sc{gnu} Hurd
13196 This command sets the suspend count @value{GDBN} will leave on a
13197 thread when detaching. This number is relative to the suspend count
13198 found by @value{GDBN} when it notices the thread; use @code{set thread
13199 takeover-suspend-count} to force it to an absolute value.
13201 @item show thread detach-suspend-count
13202 Show the suspend count @value{GDBN} will leave on the thread when
13205 @item set thread exception-port
13206 @itemx set thread excp
13207 Set the thread exception port to which to forward exceptions. This
13208 overrides the port set by @code{set task exception-port} (see above).
13209 @code{set thread excp} is the shorthand alias.
13211 @item set thread takeover-suspend-count
13212 Normally, @value{GDBN}'s thread suspend counts are relative to the
13213 value @value{GDBN} finds when it notices each thread. This command
13214 changes the suspend counts to be absolute instead.
13216 @item set thread default
13217 @itemx show thread default
13218 @cindex thread default settings, @sc{gnu} Hurd
13219 Each of the above @code{set thread} commands has a @code{set thread
13220 default} counterpart (e.g., @code{set thread default pause}, @code{set
13221 thread default exception-port}, etc.). The @code{thread default}
13222 variety of commands sets the default thread properties for all
13223 threads; you can then change the properties of individual threads with
13224 the non-default commands.
13229 @subsection QNX Neutrino
13230 @cindex QNX Neutrino
13232 @value{GDBN} provides the following commands specific to the QNX
13236 @item set debug nto-debug
13237 @kindex set debug nto-debug
13238 When set to on, enables debugging messages specific to the QNX
13241 @item show debug nto-debug
13242 @kindex show debug nto-debug
13243 Show the current state of QNX Neutrino messages.
13248 @section Embedded Operating Systems
13250 This section describes configurations involving the debugging of
13251 embedded operating systems that are available for several different
13255 * VxWorks:: Using @value{GDBN} with VxWorks
13258 @value{GDBN} includes the ability to debug programs running on
13259 various real-time operating systems.
13262 @subsection Using @value{GDBN} with VxWorks
13268 @kindex target vxworks
13269 @item target vxworks @var{machinename}
13270 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
13271 is the target system's machine name or IP address.
13275 On VxWorks, @code{load} links @var{filename} dynamically on the
13276 current target system as well as adding its symbols in @value{GDBN}.
13278 @value{GDBN} enables developers to spawn and debug tasks running on networked
13279 VxWorks targets from a Unix host. Already-running tasks spawned from
13280 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
13281 both the Unix host and on the VxWorks target. The program
13282 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
13283 installed with the name @code{vxgdb}, to distinguish it from a
13284 @value{GDBN} for debugging programs on the host itself.)
13287 @item VxWorks-timeout @var{args}
13288 @kindex vxworks-timeout
13289 All VxWorks-based targets now support the option @code{vxworks-timeout}.
13290 This option is set by the user, and @var{args} represents the number of
13291 seconds @value{GDBN} waits for responses to rpc's. You might use this if
13292 your VxWorks target is a slow software simulator or is on the far side
13293 of a thin network line.
13296 The following information on connecting to VxWorks was current when
13297 this manual was produced; newer releases of VxWorks may use revised
13300 @findex INCLUDE_RDB
13301 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
13302 to include the remote debugging interface routines in the VxWorks
13303 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
13304 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
13305 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
13306 source debugging task @code{tRdbTask} when VxWorks is booted. For more
13307 information on configuring and remaking VxWorks, see the manufacturer's
13309 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
13311 Once you have included @file{rdb.a} in your VxWorks system image and set
13312 your Unix execution search path to find @value{GDBN}, you are ready to
13313 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
13314 @code{vxgdb}, depending on your installation).
13316 @value{GDBN} comes up showing the prompt:
13323 * VxWorks Connection:: Connecting to VxWorks
13324 * VxWorks Download:: VxWorks download
13325 * VxWorks Attach:: Running tasks
13328 @node VxWorks Connection
13329 @subsubsection Connecting to VxWorks
13331 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
13332 network. To connect to a target whose host name is ``@code{tt}'', type:
13335 (vxgdb) target vxworks tt
13339 @value{GDBN} displays messages like these:
13342 Attaching remote machine across net...
13347 @value{GDBN} then attempts to read the symbol tables of any object modules
13348 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
13349 these files by searching the directories listed in the command search
13350 path (@pxref{Environment, ,Your program's environment}); if it fails
13351 to find an object file, it displays a message such as:
13354 prog.o: No such file or directory.
13357 When this happens, add the appropriate directory to the search path with
13358 the @value{GDBN} command @code{path}, and execute the @code{target}
13361 @node VxWorks Download
13362 @subsubsection VxWorks download
13364 @cindex download to VxWorks
13365 If you have connected to the VxWorks target and you want to debug an
13366 object that has not yet been loaded, you can use the @value{GDBN}
13367 @code{load} command to download a file from Unix to VxWorks
13368 incrementally. The object file given as an argument to the @code{load}
13369 command is actually opened twice: first by the VxWorks target in order
13370 to download the code, then by @value{GDBN} in order to read the symbol
13371 table. This can lead to problems if the current working directories on
13372 the two systems differ. If both systems have NFS mounted the same
13373 filesystems, you can avoid these problems by using absolute paths.
13374 Otherwise, it is simplest to set the working directory on both systems
13375 to the directory in which the object file resides, and then to reference
13376 the file by its name, without any path. For instance, a program
13377 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
13378 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
13379 program, type this on VxWorks:
13382 -> cd "@var{vxpath}/vw/demo/rdb"
13386 Then, in @value{GDBN}, type:
13389 (vxgdb) cd @var{hostpath}/vw/demo/rdb
13390 (vxgdb) load prog.o
13393 @value{GDBN} displays a response similar to this:
13396 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
13399 You can also use the @code{load} command to reload an object module
13400 after editing and recompiling the corresponding source file. Note that
13401 this makes @value{GDBN} delete all currently-defined breakpoints,
13402 auto-displays, and convenience variables, and to clear the value
13403 history. (This is necessary in order to preserve the integrity of
13404 debugger's data structures that reference the target system's symbol
13407 @node VxWorks Attach
13408 @subsubsection Running tasks
13410 @cindex running VxWorks tasks
13411 You can also attach to an existing task using the @code{attach} command as
13415 (vxgdb) attach @var{task}
13419 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
13420 or suspended when you attach to it. Running tasks are suspended at
13421 the time of attachment.
13423 @node Embedded Processors
13424 @section Embedded Processors
13426 This section goes into details specific to particular embedded
13429 @cindex send command to simulator
13430 Whenever a specific embedded processor has a simulator, @value{GDBN}
13431 allows to send an arbitrary command to the simulator.
13434 @item sim @var{command}
13435 @kindex sim@r{, a command}
13436 Send an arbitrary @var{command} string to the simulator. Consult the
13437 documentation for the specific simulator in use for information about
13438 acceptable commands.
13444 * H8/300:: Renesas H8/300
13445 * H8/500:: Renesas H8/500
13446 * M32R/D:: Renesas M32R/D
13447 * M68K:: Motorola M68K
13448 * MIPS Embedded:: MIPS Embedded
13449 * OpenRISC 1000:: OpenRisc 1000
13450 * PA:: HP PA Embedded
13453 * Sparclet:: Tsqware Sparclet
13454 * Sparclite:: Fujitsu Sparclite
13455 * ST2000:: Tandem ST2000
13456 * Z8000:: Zilog Z8000
13459 * Super-H:: Renesas Super-H
13460 * WinCE:: Windows CE child processes
13469 @item target rdi @var{dev}
13470 ARM Angel monitor, via RDI library interface to ADP protocol. You may
13471 use this target to communicate with both boards running the Angel
13472 monitor, or with the EmbeddedICE JTAG debug device.
13475 @item target rdp @var{dev}
13480 @value{GDBN} provides the following ARM-specific commands:
13483 @item set arm disassembler
13485 This commands selects from a list of disassembly styles. The
13486 @code{"std"} style is the standard style.
13488 @item show arm disassembler
13490 Show the current disassembly style.
13492 @item set arm apcs32
13493 @cindex ARM 32-bit mode
13494 This command toggles ARM operation mode between 32-bit and 26-bit.
13496 @item show arm apcs32
13497 Display the current usage of the ARM 32-bit mode.
13499 @item set arm fpu @var{fputype}
13500 This command sets the ARM floating-point unit (FPU) type. The
13501 argument @var{fputype} can be one of these:
13505 Determine the FPU type by querying the OS ABI.
13507 Software FPU, with mixed-endian doubles on little-endian ARM
13510 GCC-compiled FPA co-processor.
13512 Software FPU with pure-endian doubles.
13518 Show the current type of the FPU.
13521 This command forces @value{GDBN} to use the specified ABI.
13524 Show the currently used ABI.
13526 @item set debug arm
13527 Toggle whether to display ARM-specific debugging messages from the ARM
13528 target support subsystem.
13530 @item show debug arm
13531 Show whether ARM-specific debugging messages are enabled.
13534 The following commands are available when an ARM target is debugged
13535 using the RDI interface:
13538 @item rdilogfile @r{[}@var{file}@r{]}
13540 @cindex ADP (Angel Debugger Protocol) logging
13541 Set the filename for the ADP (Angel Debugger Protocol) packet log.
13542 With an argument, sets the log file to the specified @var{file}. With
13543 no argument, show the current log file name. The default log file is
13546 @item rdilogenable @r{[}@var{arg}@r{]}
13547 @kindex rdilogenable
13548 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
13549 enables logging, with an argument 0 or @code{"no"} disables it. With
13550 no arguments displays the current setting. When logging is enabled,
13551 ADP packets exchanged between @value{GDBN} and the RDI target device
13552 are logged to a file.
13554 @item set rdiromatzero
13555 @kindex set rdiromatzero
13556 @cindex ROM at zero address, RDI
13557 Tell @value{GDBN} whether the target has ROM at address 0. If on,
13558 vector catching is disabled, so that zero address can be used. If off
13559 (the default), vector catching is enabled. For this command to take
13560 effect, it needs to be invoked prior to the @code{target rdi} command.
13562 @item show rdiromatzero
13563 @kindex show rdiromatzero
13564 Show the current setting of ROM at zero address.
13566 @item set rdiheartbeat
13567 @kindex set rdiheartbeat
13568 @cindex RDI heartbeat
13569 Enable or disable RDI heartbeat packets. It is not recommended to
13570 turn on this option, since it confuses ARM and EPI JTAG interface, as
13571 well as the Angel monitor.
13573 @item show rdiheartbeat
13574 @kindex show rdiheartbeat
13575 Show the setting of RDI heartbeat packets.
13580 @subsection Renesas H8/300
13584 @kindex target hms@r{, with H8/300}
13585 @item target hms @var{dev}
13586 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
13587 Use special commands @code{device} and @code{speed} to control the serial
13588 line and the communications speed used.
13590 @kindex target e7000@r{, with H8/300}
13591 @item target e7000 @var{dev}
13592 E7000 emulator for Renesas H8 and SH.
13594 @kindex target sh3@r{, with H8/300}
13595 @kindex target sh3e@r{, with H8/300}
13596 @item target sh3 @var{dev}
13597 @itemx target sh3e @var{dev}
13598 Renesas SH-3 and SH-3E target systems.
13602 @cindex download to H8/300 or H8/500
13603 @cindex H8/300 or H8/500 download
13604 @cindex download to Renesas SH
13605 @cindex Renesas SH download
13606 When you select remote debugging to a Renesas SH, H8/300, or H8/500
13607 board, the @code{load} command downloads your program to the Renesas
13608 board and also opens it as the current executable target for
13609 @value{GDBN} on your host (like the @code{file} command).
13611 @value{GDBN} needs to know these things to talk to your
13612 Renesas SH, H8/300, or H8/500:
13616 that you want to use @samp{target hms}, the remote debugging interface
13617 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
13618 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
13619 the default when @value{GDBN} is configured specifically for the Renesas SH,
13620 H8/300, or H8/500.)
13623 what serial device connects your host to your Renesas board (the first
13624 serial device available on your host is the default).
13627 what speed to use over the serial device.
13631 * Renesas Boards:: Connecting to Renesas boards.
13632 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
13633 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
13636 @node Renesas Boards
13637 @subsubsection Connecting to Renesas boards
13639 @c only for Unix hosts
13641 @cindex serial device, Renesas micros
13642 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
13643 need to explicitly set the serial device. The default @var{port} is the
13644 first available port on your host. This is only necessary on Unix
13645 hosts, where it is typically something like @file{/dev/ttya}.
13648 @cindex serial line speed, Renesas micros
13649 @code{@value{GDBN}} has another special command to set the communications
13650 speed: @samp{speed @var{bps}}. This command also is only used from Unix
13651 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
13652 the DOS @code{mode} command (for instance,
13653 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
13655 The @samp{device} and @samp{speed} commands are available only when you
13656 use a Unix host to debug your Renesas microprocessor programs. If you
13658 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
13659 called @code{asynctsr} to communicate with the development board
13660 through a PC serial port. You must also use the DOS @code{mode} command
13661 to set up the serial port on the DOS side.
13663 The following sample session illustrates the steps needed to start a
13664 program under @value{GDBN} control on an H8/300. The example uses a
13665 sample H8/300 program called @file{t.x}. The procedure is the same for
13666 the Renesas SH and the H8/500.
13668 First hook up your development board. In this example, we use a
13669 board attached to serial port @code{COM2}; if you use a different serial
13670 port, substitute its name in the argument of the @code{mode} command.
13671 When you call @code{asynctsr}, the auxiliary comms program used by the
13672 debugger, you give it just the numeric part of the serial port's name;
13673 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
13677 C:\H8300\TEST> asynctsr 2
13678 C:\H8300\TEST> mode com2:9600,n,8,1,p
13680 Resident portion of MODE loaded
13682 COM2: 9600, n, 8, 1, p
13687 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
13688 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
13689 disable it, or even boot without it, to use @code{asynctsr} to control
13690 your development board.
13693 @kindex target hms@r{, and serial protocol}
13694 Now that serial communications are set up, and the development board is
13695 connected, you can start up @value{GDBN}. Call @code{@value{GDBN}} with
13696 the name of your program as the argument. @code{@value{GDBN}} prompts
13697 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
13698 commands to begin your debugging session: @samp{target hms} to specify
13699 cross-debugging to the Renesas board, and the @code{load} command to
13700 download your program to the board. @code{load} displays the names of
13701 the program's sections, and a @samp{*} for each 2K of data downloaded.
13702 (If you want to refresh @value{GDBN} data on symbols or on the
13703 executable file without downloading, use the @value{GDBN} commands
13704 @code{file} or @code{symbol-file}. These commands, and @code{load}
13705 itself, are described in @ref{Files,,Commands to specify files}.)
13708 (eg-C:\H8300\TEST) @value{GDBP} t.x
13709 @value{GDBN} is free software and you are welcome to distribute copies
13710 of it under certain conditions; type "show copying" to see
13712 There is absolutely no warranty for @value{GDBN}; type "show warranty"
13714 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
13715 (@value{GDBP}) target hms
13716 Connected to remote H8/300 HMS system.
13717 (@value{GDBP}) load t.x
13718 .text : 0x8000 .. 0xabde ***********
13719 .data : 0xabde .. 0xad30 *
13720 .stack : 0xf000 .. 0xf014 *
13723 At this point, you're ready to run or debug your program. From here on,
13724 you can use all the usual @value{GDBN} commands. The @code{break} command
13725 sets breakpoints; the @code{run} command starts your program;
13726 @code{print} or @code{x} display data; the @code{continue} command
13727 resumes execution after stopping at a breakpoint. You can use the
13728 @code{help} command at any time to find out more about @value{GDBN} commands.
13730 Remember, however, that @emph{operating system} facilities aren't
13731 available on your development board; for example, if your program hangs,
13732 you can't send an interrupt---but you can press the @sc{reset} switch!
13734 Use the @sc{reset} button on the development board
13737 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
13738 no way to pass an interrupt signal to the development board); and
13741 to return to the @value{GDBN} command prompt after your program finishes
13742 normally. The communications protocol provides no other way for @value{GDBN}
13743 to detect program completion.
13746 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
13747 development board as a ``normal exit'' of your program.
13750 @subsubsection Using the E7000 in-circuit emulator
13752 @kindex target e7000@r{, with Renesas ICE}
13753 You can use the E7000 in-circuit emulator to develop code for either the
13754 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
13755 e7000} command to connect @value{GDBN} to your E7000:
13758 @item target e7000 @var{port} @var{speed}
13759 Use this form if your E7000 is connected to a serial port. The
13760 @var{port} argument identifies what serial port to use (for example,
13761 @samp{com2}). The third argument is the line speed in bits per second
13762 (for example, @samp{9600}).
13764 @item target e7000 @var{hostname}
13765 If your E7000 is installed as a host on a TCP/IP network, you can just
13766 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
13769 The following special commands are available when debugging with the
13773 @item e7000 @var{command}
13775 @cindex send command to E7000 monitor
13776 This sends the specified @var{command} to the E7000 monitor.
13778 @item ftplogin @var{machine} @var{username} @var{password} @var{dir}
13779 @kindex ftplogin@r{, E7000}
13780 This command records information for subsequent interface with the
13781 E7000 monitor via the FTP protocol: @value{GDBN} will log into the
13782 named @var{machine} using specified @var{username} and @var{password},
13783 and then chdir to the named directory @var{dir}.
13785 @item ftpload @var{file}
13786 @kindex ftpload@r{, E7000}
13787 This command uses credentials recorded by @code{ftplogin} to fetch and
13788 load the named @var{file} from the E7000 monitor.
13791 @kindex drain@r{, E7000}
13792 This command drains any pending text buffers stored on the E7000.
13794 @item set usehardbreakpoints
13795 @itemx show usehardbreakpoints
13796 @kindex set usehardbreakpoints@r{, E7000}
13797 @kindex show usehardbreakpoints@r{, E7000}
13798 @cindex hardware breakpoints, and E7000
13799 These commands set and show the use of hardware breakpoints for all
13800 breakpoints. @xref{Set Breaks, hardware-assisted breakpoint}, for
13801 more information about using hardware breakpoints selectively.
13804 @node Renesas Special
13805 @subsubsection Special @value{GDBN} commands for Renesas micros
13807 Some @value{GDBN} commands are available only for the H8/300:
13811 @kindex set machine
13812 @kindex show machine
13813 @item set machine h8300
13814 @itemx set machine h8300h
13815 Condition @value{GDBN} for one of the two variants of the H8/300
13816 architecture with @samp{set machine}. You can use @samp{show machine}
13817 to check which variant is currently in effect.
13826 @kindex set memory @var{mod}
13827 @cindex memory models, H8/500
13828 @item set memory @var{mod}
13830 Specify which H8/500 memory model (@var{mod}) you are using with
13831 @samp{set memory}; check which memory model is in effect with @samp{show
13832 memory}. The accepted values for @var{mod} are @code{small},
13833 @code{big}, @code{medium}, and @code{compact}.
13838 @subsection Renesas M32R/D and M32R/SDI
13841 @kindex target m32r
13842 @item target m32r @var{dev}
13843 Renesas M32R/D ROM monitor.
13845 @kindex target m32rsdi
13846 @item target m32rsdi @var{dev}
13847 Renesas M32R SDI server, connected via parallel port to the board.
13850 The following @value{GDBN} commands are specific to the M32R monitor:
13853 @item set download-path @var{path}
13854 @kindex set download-path
13855 @cindex find downloadable @sc{srec} files (M32R)
13856 Set the default path for finding donwloadable @sc{srec} files.
13858 @item show download-path
13859 @kindex show download-path
13860 Show the default path for downloadable @sc{srec} files.
13862 @item set board-address @var{addr}
13863 @kindex set board-address
13864 @cindex M32-EVA target board address
13865 Set the IP address for the M32R-EVA target board.
13867 @item show board-address
13868 @kindex show board-address
13869 Show the current IP address of the target board.
13871 @item set server-address @var{addr}
13872 @kindex set server-address
13873 @cindex download server address (M32R)
13874 Set the IP address for the download server, which is the @value{GDBN}'s
13877 @item show server-address
13878 @kindex show server-address
13879 Display the IP address of the download server.
13881 @item upload @r{[}@var{file}@r{]}
13882 @kindex upload@r{, M32R}
13883 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
13884 upload capability. If no @var{file} argument is given, the current
13885 executable file is uploaded.
13887 @item tload @r{[}@var{file}@r{]}
13888 @kindex tload@r{, M32R}
13889 Test the @code{upload} command.
13892 The following commands are available for M32R/SDI:
13897 @cindex reset SDI connection, M32R
13898 This command resets the SDI connection.
13902 This command shows the SDI connection status.
13905 @kindex debug_chaos
13906 @cindex M32R/Chaos debugging
13907 Instructs the remote that M32R/Chaos debugging is to be used.
13909 @item use_debug_dma
13910 @kindex use_debug_dma
13911 Instructs the remote to use the DEBUG_DMA method of accessing memory.
13914 @kindex use_mon_code
13915 Instructs the remote to use the MON_CODE method of accessing memory.
13918 @kindex use_ib_break
13919 Instructs the remote to set breakpoints by IB break.
13921 @item use_dbt_break
13922 @kindex use_dbt_break
13923 Instructs the remote to set breakpoints by DBT.
13929 The Motorola m68k configuration includes ColdFire support, and
13930 target command for the following ROM monitors.
13934 @kindex target abug
13935 @item target abug @var{dev}
13936 ABug ROM monitor for M68K.
13938 @kindex target cpu32bug
13939 @item target cpu32bug @var{dev}
13940 CPU32BUG monitor, running on a CPU32 (M68K) board.
13942 @kindex target dbug
13943 @item target dbug @var{dev}
13944 dBUG ROM monitor for Motorola ColdFire.
13947 @item target est @var{dev}
13948 EST-300 ICE monitor, running on a CPU32 (M68K) board.
13950 @kindex target rom68k
13951 @item target rom68k @var{dev}
13952 ROM 68K monitor, running on an M68K IDP board.
13958 @kindex target rombug
13959 @item target rombug @var{dev}
13960 ROMBUG ROM monitor for OS/9000.
13964 @node MIPS Embedded
13965 @subsection MIPS Embedded
13967 @cindex MIPS boards
13968 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
13969 MIPS board attached to a serial line. This is available when
13970 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
13973 Use these @value{GDBN} commands to specify the connection to your target board:
13976 @item target mips @var{port}
13977 @kindex target mips @var{port}
13978 To run a program on the board, start up @code{@value{GDBP}} with the
13979 name of your program as the argument. To connect to the board, use the
13980 command @samp{target mips @var{port}}, where @var{port} is the name of
13981 the serial port connected to the board. If the program has not already
13982 been downloaded to the board, you may use the @code{load} command to
13983 download it. You can then use all the usual @value{GDBN} commands.
13985 For example, this sequence connects to the target board through a serial
13986 port, and loads and runs a program called @var{prog} through the
13990 host$ @value{GDBP} @var{prog}
13991 @value{GDBN} is free software and @dots{}
13992 (@value{GDBP}) target mips /dev/ttyb
13993 (@value{GDBP}) load @var{prog}
13997 @item target mips @var{hostname}:@var{portnumber}
13998 On some @value{GDBN} host configurations, you can specify a TCP
13999 connection (for instance, to a serial line managed by a terminal
14000 concentrator) instead of a serial port, using the syntax
14001 @samp{@var{hostname}:@var{portnumber}}.
14003 @item target pmon @var{port}
14004 @kindex target pmon @var{port}
14007 @item target ddb @var{port}
14008 @kindex target ddb @var{port}
14009 NEC's DDB variant of PMON for Vr4300.
14011 @item target lsi @var{port}
14012 @kindex target lsi @var{port}
14013 LSI variant of PMON.
14015 @kindex target r3900
14016 @item target r3900 @var{dev}
14017 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
14019 @kindex target array
14020 @item target array @var{dev}
14021 Array Tech LSI33K RAID controller board.
14027 @value{GDBN} also supports these special commands for MIPS targets:
14030 @item set mipsfpu double
14031 @itemx set mipsfpu single
14032 @itemx set mipsfpu none
14033 @itemx set mipsfpu auto
14034 @itemx show mipsfpu
14035 @kindex set mipsfpu
14036 @kindex show mipsfpu
14037 @cindex MIPS remote floating point
14038 @cindex floating point, MIPS remote
14039 If your target board does not support the MIPS floating point
14040 coprocessor, you should use the command @samp{set mipsfpu none} (if you
14041 need this, you may wish to put the command in your @value{GDBN} init
14042 file). This tells @value{GDBN} how to find the return value of
14043 functions which return floating point values. It also allows
14044 @value{GDBN} to avoid saving the floating point registers when calling
14045 functions on the board. If you are using a floating point coprocessor
14046 with only single precision floating point support, as on the @sc{r4650}
14047 processor, use the command @samp{set mipsfpu single}. The default
14048 double precision floating point coprocessor may be selected using
14049 @samp{set mipsfpu double}.
14051 In previous versions the only choices were double precision or no
14052 floating point, so @samp{set mipsfpu on} will select double precision
14053 and @samp{set mipsfpu off} will select no floating point.
14055 As usual, you can inquire about the @code{mipsfpu} variable with
14056 @samp{show mipsfpu}.
14058 @item set timeout @var{seconds}
14059 @itemx set retransmit-timeout @var{seconds}
14060 @itemx show timeout
14061 @itemx show retransmit-timeout
14062 @cindex @code{timeout}, MIPS protocol
14063 @cindex @code{retransmit-timeout}, MIPS protocol
14064 @kindex set timeout
14065 @kindex show timeout
14066 @kindex set retransmit-timeout
14067 @kindex show retransmit-timeout
14068 You can control the timeout used while waiting for a packet, in the MIPS
14069 remote protocol, with the @code{set timeout @var{seconds}} command. The
14070 default is 5 seconds. Similarly, you can control the timeout used while
14071 waiting for an acknowledgement of a packet with the @code{set
14072 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
14073 You can inspect both values with @code{show timeout} and @code{show
14074 retransmit-timeout}. (These commands are @emph{only} available when
14075 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
14077 The timeout set by @code{set timeout} does not apply when @value{GDBN}
14078 is waiting for your program to stop. In that case, @value{GDBN} waits
14079 forever because it has no way of knowing how long the program is going
14080 to run before stopping.
14082 @item set syn-garbage-limit @var{num}
14083 @kindex set syn-garbage-limit@r{, MIPS remote}
14084 @cindex synchronize with remote MIPS target
14085 Limit the maximum number of characters @value{GDBN} should ignore when
14086 it tries to synchronize with the remote target. The default is 10
14087 characters. Setting the limit to -1 means there's no limit.
14089 @item show syn-garbage-limit
14090 @kindex show syn-garbage-limit@r{, MIPS remote}
14091 Show the current limit on the number of characters to ignore when
14092 trying to synchronize with the remote system.
14094 @item set monitor-prompt @var{prompt}
14095 @kindex set monitor-prompt@r{, MIPS remote}
14096 @cindex remote monitor prompt
14097 Tell @value{GDBN} to expect the specified @var{prompt} string from the
14098 remote monitor. The default depends on the target:
14108 @item show monitor-prompt
14109 @kindex show monitor-prompt@r{, MIPS remote}
14110 Show the current strings @value{GDBN} expects as the prompt from the
14113 @item set monitor-warnings
14114 @kindex set monitor-warnings@r{, MIPS remote}
14115 Enable or disable monitor warnings about hardware breakpoints. This
14116 has effect only for the @code{lsi} target. When on, @value{GDBN} will
14117 display warning messages whose codes are returned by the @code{lsi}
14118 PMON monitor for breakpoint commands.
14120 @item show monitor-warnings
14121 @kindex show monitor-warnings@r{, MIPS remote}
14122 Show the current setting of printing monitor warnings.
14124 @item pmon @var{command}
14125 @kindex pmon@r{, MIPS remote}
14126 @cindex send PMON command
14127 This command allows sending an arbitrary @var{command} string to the
14128 monitor. The monitor must be in debug mode for this to work.
14131 @node OpenRISC 1000
14132 @subsection OpenRISC 1000
14133 @cindex OpenRISC 1000
14135 @cindex or1k boards
14136 See OR1k Architecture document (@uref{www.opencores.org}) for more information
14137 about platform and commands.
14141 @kindex target jtag
14142 @item target jtag jtag://@var{host}:@var{port}
14144 Connects to remote JTAG server.
14145 JTAG remote server can be either an or1ksim or JTAG server,
14146 connected via parallel port to the board.
14148 Example: @code{target jtag jtag://localhost:9999}
14151 @item or1ksim @var{command}
14152 If connected to @code{or1ksim} OpenRISC 1000 Architectural
14153 Simulator, proprietary commands can be executed.
14155 @kindex info or1k spr
14156 @item info or1k spr
14157 Displays spr groups.
14159 @item info or1k spr @var{group}
14160 @itemx info or1k spr @var{groupno}
14161 Displays register names in selected group.
14163 @item info or1k spr @var{group} @var{register}
14164 @itemx info or1k spr @var{register}
14165 @itemx info or1k spr @var{groupno} @var{registerno}
14166 @itemx info or1k spr @var{registerno}
14167 Shows information about specified spr register.
14170 @item spr @var{group} @var{register} @var{value}
14171 @itemx spr @var{register @var{value}}
14172 @itemx spr @var{groupno} @var{registerno @var{value}}
14173 @itemx spr @var{registerno @var{value}}
14174 Writes @var{value} to specified spr register.
14177 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
14178 It is very similar to @value{GDBN} trace, except it does not interfere with normal
14179 program execution and is thus much faster. Hardware breakpoints/watchpoint
14180 triggers can be set using:
14183 Load effective address/data
14185 Store effective address/data
14187 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
14192 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
14193 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
14195 @code{htrace} commands:
14196 @cindex OpenRISC 1000 htrace
14199 @item hwatch @var{conditional}
14200 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
14201 or Data. For example:
14203 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14205 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14209 Display information about current HW trace configuration.
14211 @item htrace trigger @var{conditional}
14212 Set starting criteria for HW trace.
14214 @item htrace qualifier @var{conditional}
14215 Set acquisition qualifier for HW trace.
14217 @item htrace stop @var{conditional}
14218 Set HW trace stopping criteria.
14220 @item htrace record [@var{data}]*
14221 Selects the data to be recorded, when qualifier is met and HW trace was
14224 @item htrace enable
14225 @itemx htrace disable
14226 Enables/disables the HW trace.
14228 @item htrace rewind [@var{filename}]
14229 Clears currently recorded trace data.
14231 If filename is specified, new trace file is made and any newly collected data
14232 will be written there.
14234 @item htrace print [@var{start} [@var{len}]]
14235 Prints trace buffer, using current record configuration.
14237 @item htrace mode continuous
14238 Set continuous trace mode.
14240 @item htrace mode suspend
14241 Set suspend trace mode.
14246 @subsection PowerPC
14249 @kindex target dink32
14250 @item target dink32 @var{dev}
14251 DINK32 ROM monitor.
14253 @kindex target ppcbug
14254 @item target ppcbug @var{dev}
14255 @kindex target ppcbug1
14256 @item target ppcbug1 @var{dev}
14257 PPCBUG ROM monitor for PowerPC.
14260 @item target sds @var{dev}
14261 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
14264 @cindex SDS protocol
14265 The following commands specifi to the SDS protocol are supported
14269 @item set sdstimeout @var{nsec}
14270 @kindex set sdstimeout
14271 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
14272 default is 2 seconds.
14274 @item show sdstimeout
14275 @kindex show sdstimeout
14276 Show the current value of the SDS timeout.
14278 @item sds @var{command}
14279 @kindex sds@r{, a command}
14280 Send the specified @var{command} string to the SDS monitor.
14285 @subsection HP PA Embedded
14289 @kindex target op50n
14290 @item target op50n @var{dev}
14291 OP50N monitor, running on an OKI HPPA board.
14293 @kindex target w89k
14294 @item target w89k @var{dev}
14295 W89K monitor, running on a Winbond HPPA board.
14300 @subsection Renesas SH
14304 @kindex target hms@r{, with Renesas SH}
14305 @item target hms @var{dev}
14306 A Renesas SH board attached via serial line to your host. Use special
14307 commands @code{device} and @code{speed} to control the serial line and
14308 the communications speed used.
14310 @kindex target e7000@r{, with Renesas SH}
14311 @item target e7000 @var{dev}
14312 E7000 emulator for Renesas SH.
14314 @kindex target sh3@r{, with SH}
14315 @kindex target sh3e@r{, with SH}
14316 @item target sh3 @var{dev}
14317 @item target sh3e @var{dev}
14318 Renesas SH-3 and SH-3E target systems.
14323 @subsection Tsqware Sparclet
14327 @value{GDBN} enables developers to debug tasks running on
14328 Sparclet targets from a Unix host.
14329 @value{GDBN} uses code that runs on
14330 both the Unix host and on the Sparclet target. The program
14331 @code{@value{GDBP}} is installed and executed on the Unix host.
14334 @item remotetimeout @var{args}
14335 @kindex remotetimeout
14336 @value{GDBN} supports the option @code{remotetimeout}.
14337 This option is set by the user, and @var{args} represents the number of
14338 seconds @value{GDBN} waits for responses.
14341 @cindex compiling, on Sparclet
14342 When compiling for debugging, include the options @samp{-g} to get debug
14343 information and @samp{-Ttext} to relocate the program to where you wish to
14344 load it on the target. You may also want to add the options @samp{-n} or
14345 @samp{-N} in order to reduce the size of the sections. Example:
14348 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
14351 You can use @code{objdump} to verify that the addresses are what you intended:
14354 sparclet-aout-objdump --headers --syms prog
14357 @cindex running, on Sparclet
14359 your Unix execution search path to find @value{GDBN}, you are ready to
14360 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
14361 (or @code{sparclet-aout-gdb}, depending on your installation).
14363 @value{GDBN} comes up showing the prompt:
14370 * Sparclet File:: Setting the file to debug
14371 * Sparclet Connection:: Connecting to Sparclet
14372 * Sparclet Download:: Sparclet download
14373 * Sparclet Execution:: Running and debugging
14376 @node Sparclet File
14377 @subsubsection Setting file to debug
14379 The @value{GDBN} command @code{file} lets you choose with program to debug.
14382 (gdbslet) file prog
14386 @value{GDBN} then attempts to read the symbol table of @file{prog}.
14387 @value{GDBN} locates
14388 the file by searching the directories listed in the command search
14390 If the file was compiled with debug information (option "-g"), source
14391 files will be searched as well.
14392 @value{GDBN} locates
14393 the source files by searching the directories listed in the directory search
14394 path (@pxref{Environment, ,Your program's environment}).
14396 to find a file, it displays a message such as:
14399 prog: No such file or directory.
14402 When this happens, add the appropriate directories to the search paths with
14403 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
14404 @code{target} command again.
14406 @node Sparclet Connection
14407 @subsubsection Connecting to Sparclet
14409 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
14410 To connect to a target on serial port ``@code{ttya}'', type:
14413 (gdbslet) target sparclet /dev/ttya
14414 Remote target sparclet connected to /dev/ttya
14415 main () at ../prog.c:3
14419 @value{GDBN} displays messages like these:
14425 @node Sparclet Download
14426 @subsubsection Sparclet download
14428 @cindex download to Sparclet
14429 Once connected to the Sparclet target,
14430 you can use the @value{GDBN}
14431 @code{load} command to download the file from the host to the target.
14432 The file name and load offset should be given as arguments to the @code{load}
14434 Since the file format is aout, the program must be loaded to the starting
14435 address. You can use @code{objdump} to find out what this value is. The load
14436 offset is an offset which is added to the VMA (virtual memory address)
14437 of each of the file's sections.
14438 For instance, if the program
14439 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
14440 and bss at 0x12010170, in @value{GDBN}, type:
14443 (gdbslet) load prog 0x12010000
14444 Loading section .text, size 0xdb0 vma 0x12010000
14447 If the code is loaded at a different address then what the program was linked
14448 to, you may need to use the @code{section} and @code{add-symbol-file} commands
14449 to tell @value{GDBN} where to map the symbol table.
14451 @node Sparclet Execution
14452 @subsubsection Running and debugging
14454 @cindex running and debugging Sparclet programs
14455 You can now begin debugging the task using @value{GDBN}'s execution control
14456 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
14457 manual for the list of commands.
14461 Breakpoint 1 at 0x12010000: file prog.c, line 3.
14463 Starting program: prog
14464 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
14465 3 char *symarg = 0;
14467 4 char *execarg = "hello!";
14472 @subsection Fujitsu Sparclite
14476 @kindex target sparclite
14477 @item target sparclite @var{dev}
14478 Fujitsu sparclite boards, used only for the purpose of loading.
14479 You must use an additional command to debug the program.
14480 For example: target remote @var{dev} using @value{GDBN} standard
14486 @subsection Tandem ST2000
14488 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
14491 To connect your ST2000 to the host system, see the manufacturer's
14492 manual. Once the ST2000 is physically attached, you can run:
14495 target st2000 @var{dev} @var{speed}
14499 to establish it as your debugging environment. @var{dev} is normally
14500 the name of a serial device, such as @file{/dev/ttya}, connected to the
14501 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
14502 connection (for example, to a serial line attached via a terminal
14503 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
14505 The @code{load} and @code{attach} commands are @emph{not} defined for
14506 this target; you must load your program into the ST2000 as you normally
14507 would for standalone operation. @value{GDBN} reads debugging information
14508 (such as symbols) from a separate, debugging version of the program
14509 available on your host computer.
14510 @c FIXME!! This is terribly vague; what little content is here is
14511 @c basically hearsay.
14513 @cindex ST2000 auxiliary commands
14514 These auxiliary @value{GDBN} commands are available to help you with the ST2000
14518 @item st2000 @var{command}
14519 @kindex st2000 @var{cmd}
14520 @cindex STDBUG commands (ST2000)
14521 @cindex commands to STDBUG (ST2000)
14522 Send a @var{command} to the STDBUG monitor. See the manufacturer's
14523 manual for available commands.
14526 @cindex connect (to STDBUG)
14527 Connect the controlling terminal to the STDBUG command monitor. When
14528 you are done interacting with STDBUG, typing either of two character
14529 sequences gets you back to the @value{GDBN} command prompt:
14530 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
14531 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
14535 @subsection Zilog Z8000
14538 @cindex simulator, Z8000
14539 @cindex Zilog Z8000 simulator
14541 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
14544 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
14545 unsegmented variant of the Z8000 architecture) or the Z8001 (the
14546 segmented variant). The simulator recognizes which architecture is
14547 appropriate by inspecting the object code.
14550 @item target sim @var{args}
14552 @kindex target sim@r{, with Z8000}
14553 Debug programs on a simulated CPU. If the simulator supports setup
14554 options, specify them via @var{args}.
14558 After specifying this target, you can debug programs for the simulated
14559 CPU in the same style as programs for your host computer; use the
14560 @code{file} command to load a new program image, the @code{run} command
14561 to run your program, and so on.
14563 As well as making available all the usual machine registers
14564 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
14565 additional items of information as specially named registers:
14570 Counts clock-ticks in the simulator.
14573 Counts instructions run in the simulator.
14576 Execution time in 60ths of a second.
14580 You can refer to these values in @value{GDBN} expressions with the usual
14581 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
14582 conditional breakpoint that suspends only after at least 5000
14583 simulated clock ticks.
14586 @subsection Atmel AVR
14589 When configured for debugging the Atmel AVR, @value{GDBN} supports the
14590 following AVR-specific commands:
14593 @item info io_registers
14594 @kindex info io_registers@r{, AVR}
14595 @cindex I/O registers (Atmel AVR)
14596 This command displays information about the AVR I/O registers. For
14597 each register, @value{GDBN} prints its number and value.
14604 When configured for debugging CRIS, @value{GDBN} provides the
14605 following CRIS-specific commands:
14608 @item set cris-version @var{ver}
14609 @cindex CRIS version
14610 Set the current CRIS version to @var{ver}. The CRIS version affects
14611 register names and sizes. This command is useful in case
14612 autodetection of the CRIS version fails.
14614 @item show cris-version
14615 Show the current CRIS version.
14617 @item set cris-dwarf2-cfi
14618 @cindex DWARF-2 CFI and CRIS
14619 Set the usage of DWARF-2 CFI for CRIS debugging. The default is off
14620 if using @code{gcc-cris} whose version is below @code{R59}, otherwise
14623 @item show cris-dwarf2-cfi
14624 Show the current state of using DWARF-2 CFI.
14628 @subsection Renesas Super-H
14631 For the Renesas Super-H processor, @value{GDBN} provides these
14636 @kindex regs@r{, Super-H}
14637 Show the values of all Super-H registers.
14641 @subsection Windows CE
14644 The following commands are available for Windows CE:
14647 @item set remotedirectory @var{dir}
14648 @kindex set remotedirectory
14649 Tell @value{GDBN} to upload files from the named directory @var{dir}.
14650 The default is @file{/gdb}, i.e.@: the root directory on the current
14653 @item show remotedirectory
14654 @kindex show remotedirectory
14655 Show the current value of the upload directory.
14657 @item set remoteupload @var{method}
14658 @kindex set remoteupload
14659 Set the method used to upload files to remote device. Valid values
14660 for @var{method} are @samp{always}, @samp{newer}, and @samp{never}.
14661 The default is @samp{newer}.
14663 @item show remoteupload
14664 @kindex show remoteupload
14665 Show the current setting of the upload method.
14667 @item set remoteaddhost
14668 @kindex set remoteaddhost
14669 Tell @value{GDBN} whether to add this host to the remote stub's
14670 arguments when you debug over a network.
14672 @item show remoteaddhost
14673 @kindex show remoteaddhost
14674 Show whether to add this host to remote stub's arguments when
14675 debugging over a network.
14679 @node Architectures
14680 @section Architectures
14682 This section describes characteristics of architectures that affect
14683 all uses of @value{GDBN} with the architecture, both native and cross.
14690 * HPPA:: HP PA architecture
14694 @subsection x86 Architecture-specific issues.
14697 @item set struct-convention @var{mode}
14698 @kindex set struct-convention
14699 @cindex struct return convention
14700 @cindex struct/union returned in registers
14701 Set the convention used by the inferior to return @code{struct}s and
14702 @code{union}s from functions to @var{mode}. Possible values of
14703 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
14704 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
14705 are returned on the stack, while @code{"reg"} means that a
14706 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
14707 be returned in a register.
14709 @item show struct-convention
14710 @kindex show struct-convention
14711 Show the current setting of the convention to return @code{struct}s
14720 @kindex set rstack_high_address
14721 @cindex AMD 29K register stack
14722 @cindex register stack, AMD29K
14723 @item set rstack_high_address @var{address}
14724 On AMD 29000 family processors, registers are saved in a separate
14725 @dfn{register stack}. There is no way for @value{GDBN} to determine the
14726 extent of this stack. Normally, @value{GDBN} just assumes that the
14727 stack is ``large enough''. This may result in @value{GDBN} referencing
14728 memory locations that do not exist. If necessary, you can get around
14729 this problem by specifying the ending address of the register stack with
14730 the @code{set rstack_high_address} command. The argument should be an
14731 address, which you probably want to precede with @samp{0x} to specify in
14734 @kindex show rstack_high_address
14735 @item show rstack_high_address
14736 Display the current limit of the register stack, on AMD 29000 family
14744 See the following section.
14749 @cindex stack on Alpha
14750 @cindex stack on MIPS
14751 @cindex Alpha stack
14753 Alpha- and MIPS-based computers use an unusual stack frame, which
14754 sometimes requires @value{GDBN} to search backward in the object code to
14755 find the beginning of a function.
14757 @cindex response time, MIPS debugging
14758 To improve response time (especially for embedded applications, where
14759 @value{GDBN} may be restricted to a slow serial line for this search)
14760 you may want to limit the size of this search, using one of these
14764 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
14765 @item set heuristic-fence-post @var{limit}
14766 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
14767 search for the beginning of a function. A value of @var{0} (the
14768 default) means there is no limit. However, except for @var{0}, the
14769 larger the limit the more bytes @code{heuristic-fence-post} must search
14770 and therefore the longer it takes to run. You should only need to use
14771 this command when debugging a stripped executable.
14773 @item show heuristic-fence-post
14774 Display the current limit.
14778 These commands are available @emph{only} when @value{GDBN} is configured
14779 for debugging programs on Alpha or MIPS processors.
14781 Several MIPS-specific commands are available when debugging MIPS
14785 @item set mips saved-gpreg-size @var{size}
14786 @kindex set mips saved-gpreg-size
14787 @cindex MIPS GP register size on stack
14788 Set the size of MIPS general-purpose registers saved on the stack.
14789 The argument @var{size} can be one of the following:
14793 32-bit GP registers
14795 64-bit GP registers
14797 Use the target's default setting or autodetect the saved size from the
14798 information contained in the executable. This is the default
14801 @item show mips saved-gpreg-size
14802 @kindex show mips saved-gpreg-size
14803 Show the current size of MIPS GP registers on the stack.
14805 @item set mips stack-arg-size @var{size}
14806 @kindex set mips stack-arg-size
14807 @cindex MIPS stack space for arguments
14808 Set the amount of stack space reserved for arguments to functions.
14809 The argument can be one of @code{"32"}, @code{"64"} or @code{"auto"}
14812 @item set mips abi @var{arg}
14813 @kindex set mips abi
14814 @cindex set ABI for MIPS
14815 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
14816 values of @var{arg} are:
14820 The default ABI associated with the current binary (this is the
14831 @item show mips abi
14832 @kindex show mips abi
14833 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
14836 @itemx show mipsfpu
14837 @xref{MIPS Embedded, set mipsfpu}.
14839 @item set mips mask-address @var{arg}
14840 @kindex set mips mask-address
14841 @cindex MIPS addresses, masking
14842 This command determines whether the most-significant 32 bits of 64-bit
14843 MIPS addresses are masked off. The argument @var{arg} can be
14844 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
14845 setting, which lets @value{GDBN} determine the correct value.
14847 @item show mips mask-address
14848 @kindex show mips mask-address
14849 Show whether the upper 32 bits of MIPS addresses are masked off or
14852 @item set remote-mips64-transfers-32bit-regs
14853 @kindex set remote-mips64-transfers-32bit-regs
14854 This command controls compatibility with 64-bit MIPS targets that
14855 transfer data in 32-bit quantities. If you have an old MIPS 64 target
14856 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
14857 and 64 bits for other registers, set this option to @samp{on}.
14859 @item show remote-mips64-transfers-32bit-regs
14860 @kindex show remote-mips64-transfers-32bit-regs
14861 Show the current setting of compatibility with older MIPS 64 targets.
14863 @item set debug mips
14864 @kindex set debug mips
14865 This command turns on and off debugging messages for the MIPS-specific
14866 target code in @value{GDBN}.
14868 @item show debug mips
14869 @kindex show debug mips
14870 Show the current setting of MIPS debugging messages.
14876 @cindex HPPA support
14878 When @value{GDBN} is debugging te HP PA architecture, it provides the
14879 following special commands:
14882 @item set debug hppa
14883 @kindex set debug hppa
14884 THis command determines whether HPPA architecture specific debugging
14885 messages are to be displayed.
14887 @item show debug hppa
14888 Show whether HPPA debugging messages are displayed.
14890 @item maint print unwind @var{address}
14891 @kindex maint print unwind@r{, HPPA}
14892 This command displays the contents of the unwind table entry at the
14893 given @var{address}.
14898 @node Controlling GDB
14899 @chapter Controlling @value{GDBN}
14901 You can alter the way @value{GDBN} interacts with you by using the
14902 @code{set} command. For commands controlling how @value{GDBN} displays
14903 data, see @ref{Print Settings, ,Print settings}. Other settings are
14908 * Editing:: Command editing
14909 * History:: Command history
14910 * Screen Size:: Screen size
14911 * Numbers:: Numbers
14912 * ABI:: Configuring the current ABI
14913 * Messages/Warnings:: Optional warnings and messages
14914 * Debugging Output:: Optional messages about internal happenings
14922 @value{GDBN} indicates its readiness to read a command by printing a string
14923 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
14924 can change the prompt string with the @code{set prompt} command. For
14925 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
14926 the prompt in one of the @value{GDBN} sessions so that you can always tell
14927 which one you are talking to.
14929 @emph{Note:} @code{set prompt} does not add a space for you after the
14930 prompt you set. This allows you to set a prompt which ends in a space
14931 or a prompt that does not.
14935 @item set prompt @var{newprompt}
14936 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
14938 @kindex show prompt
14940 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
14944 @section Command editing
14946 @cindex command line editing
14948 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
14949 @sc{gnu} library provides consistent behavior for programs which provide a
14950 command line interface to the user. Advantages are @sc{gnu} Emacs-style
14951 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
14952 substitution, and a storage and recall of command history across
14953 debugging sessions.
14955 You may control the behavior of command line editing in @value{GDBN} with the
14956 command @code{set}.
14959 @kindex set editing
14962 @itemx set editing on
14963 Enable command line editing (enabled by default).
14965 @item set editing off
14966 Disable command line editing.
14968 @kindex show editing
14970 Show whether command line editing is enabled.
14973 @xref{Command Line Editing}, for more details about the Readline
14974 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
14975 encouraged to read that chapter.
14978 @section Command history
14979 @cindex command history
14981 @value{GDBN} can keep track of the commands you type during your
14982 debugging sessions, so that you can be certain of precisely what
14983 happened. Use these commands to manage the @value{GDBN} command
14986 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
14987 package, to provide the history facility. @xref{Using History
14988 Interactively}, for the detailed description of the History library.
14990 Here is the description of @value{GDBN} commands related to command
14994 @cindex history substitution
14995 @cindex history file
14996 @kindex set history filename
14997 @cindex @env{GDBHISTFILE}, environment variable
14998 @item set history filename @var{fname}
14999 Set the name of the @value{GDBN} command history file to @var{fname}.
15000 This is the file where @value{GDBN} reads an initial command history
15001 list, and where it writes the command history from this session when it
15002 exits. You can access this list through history expansion or through
15003 the history command editing characters listed below. This file defaults
15004 to the value of the environment variable @code{GDBHISTFILE}, or to
15005 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
15008 @cindex save command history
15009 @kindex set history save
15010 @item set history save
15011 @itemx set history save on
15012 Record command history in a file, whose name may be specified with the
15013 @code{set history filename} command. By default, this option is disabled.
15015 @item set history save off
15016 Stop recording command history in a file.
15018 @cindex history size
15019 @kindex set history size
15020 @item set history size @var{size}
15021 Set the number of commands which @value{GDBN} keeps in its history list.
15022 This defaults to the value of the environment variable
15023 @code{HISTSIZE}, or to 256 if this variable is not set.
15026 History expansion assigns special meaning to the character @kbd{!}.
15027 @xref{Event Designators}, for more details.
15029 @cindex history expansion, turn on/off
15030 Since @kbd{!} is also the logical not operator in C, history expansion
15031 is off by default. If you decide to enable history expansion with the
15032 @code{set history expansion on} command, you may sometimes need to
15033 follow @kbd{!} (when it is used as logical not, in an expression) with
15034 a space or a tab to prevent it from being expanded. The readline
15035 history facilities do not attempt substitution on the strings
15036 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
15038 The commands to control history expansion are:
15041 @item set history expansion on
15042 @itemx set history expansion
15043 @kindex set history expansion
15044 Enable history expansion. History expansion is off by default.
15046 @item set history expansion off
15047 Disable history expansion.
15050 @kindex show history
15052 @itemx show history filename
15053 @itemx show history save
15054 @itemx show history size
15055 @itemx show history expansion
15056 These commands display the state of the @value{GDBN} history parameters.
15057 @code{show history} by itself displays all four states.
15062 @kindex show commands
15063 @cindex show last commands
15064 @cindex display command history
15065 @item show commands
15066 Display the last ten commands in the command history.
15068 @item show commands @var{n}
15069 Print ten commands centered on command number @var{n}.
15071 @item show commands +
15072 Print ten commands just after the commands last printed.
15076 @section Screen size
15077 @cindex size of screen
15078 @cindex pauses in output
15080 Certain commands to @value{GDBN} may produce large amounts of
15081 information output to the screen. To help you read all of it,
15082 @value{GDBN} pauses and asks you for input at the end of each page of
15083 output. Type @key{RET} when you want to continue the output, or @kbd{q}
15084 to discard the remaining output. Also, the screen width setting
15085 determines when to wrap lines of output. Depending on what is being
15086 printed, @value{GDBN} tries to break the line at a readable place,
15087 rather than simply letting it overflow onto the following line.
15089 Normally @value{GDBN} knows the size of the screen from the terminal
15090 driver software. For example, on Unix @value{GDBN} uses the termcap data base
15091 together with the value of the @code{TERM} environment variable and the
15092 @code{stty rows} and @code{stty cols} settings. If this is not correct,
15093 you can override it with the @code{set height} and @code{set
15100 @kindex show height
15101 @item set height @var{lpp}
15103 @itemx set width @var{cpl}
15105 These @code{set} commands specify a screen height of @var{lpp} lines and
15106 a screen width of @var{cpl} characters. The associated @code{show}
15107 commands display the current settings.
15109 If you specify a height of zero lines, @value{GDBN} does not pause during
15110 output no matter how long the output is. This is useful if output is to a
15111 file or to an editor buffer.
15113 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
15114 from wrapping its output.
15116 @item set pagination on
15117 @itemx set pagination off
15118 @kindex set pagination
15119 Turn the output pagination on or off; the default is on. Turning
15120 pagination off is the alternative to @code{set height 0}.
15122 @item show pagination
15123 @kindex show pagination
15124 Show the current pagination mode.
15129 @cindex number representation
15130 @cindex entering numbers
15132 You can always enter numbers in octal, decimal, or hexadecimal in
15133 @value{GDBN} by the usual conventions: octal numbers begin with
15134 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
15135 begin with @samp{0x}. Numbers that begin with none of these are, by
15136 default, entered in base 10; likewise, the default display for
15137 numbers---when no particular format is specified---is base 10. You can
15138 change the default base for both input and output with the @code{set
15142 @kindex set input-radix
15143 @item set input-radix @var{base}
15144 Set the default base for numeric input. Supported choices
15145 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15146 specified either unambiguously or using the current default radix; for
15150 set input-radix 012
15151 set input-radix 10.
15152 set input-radix 0xa
15156 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
15157 leaves the input radix unchanged, no matter what it was.
15159 @kindex set output-radix
15160 @item set output-radix @var{base}
15161 Set the default base for numeric display. Supported choices
15162 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15163 specified either unambiguously or using the current default radix.
15165 @kindex show input-radix
15166 @item show input-radix
15167 Display the current default base for numeric input.
15169 @kindex show output-radix
15170 @item show output-radix
15171 Display the current default base for numeric display.
15173 @item set radix @r{[}@var{base}@r{]}
15177 These commands set and show the default base for both input and output
15178 of numbers. @code{set radix} sets the radix of input and output to
15179 the same base; without an argument, it resets the radix back to its
15180 default value of 10.
15185 @section Configuring the current ABI
15187 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
15188 application automatically. However, sometimes you need to override its
15189 conclusions. Use these commands to manage @value{GDBN}'s view of the
15196 One @value{GDBN} configuration can debug binaries for multiple operating
15197 system targets, either via remote debugging or native emulation.
15198 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
15199 but you can override its conclusion using the @code{set osabi} command.
15200 One example where this is useful is in debugging of binaries which use
15201 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
15202 not have the same identifying marks that the standard C library for your
15207 Show the OS ABI currently in use.
15210 With no argument, show the list of registered available OS ABI's.
15212 @item set osabi @var{abi}
15213 Set the current OS ABI to @var{abi}.
15216 @cindex float promotion
15218 Generally, the way that an argument of type @code{float} is passed to a
15219 function depends on whether the function is prototyped. For a prototyped
15220 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
15221 according to the architecture's convention for @code{float}. For unprototyped
15222 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
15223 @code{double} and then passed.
15225 Unfortunately, some forms of debug information do not reliably indicate whether
15226 a function is prototyped. If @value{GDBN} calls a function that is not marked
15227 as prototyped, it consults @kbd{set coerce-float-to-double}.
15230 @kindex set coerce-float-to-double
15231 @item set coerce-float-to-double
15232 @itemx set coerce-float-to-double on
15233 Arguments of type @code{float} will be promoted to @code{double} when passed
15234 to an unprototyped function. This is the default setting.
15236 @item set coerce-float-to-double off
15237 Arguments of type @code{float} will be passed directly to unprototyped
15240 @kindex show coerce-float-to-double
15241 @item show coerce-float-to-double
15242 Show the current setting of promoting @code{float} to @code{double}.
15246 @kindex show cp-abi
15247 @value{GDBN} needs to know the ABI used for your program's C@t{++}
15248 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
15249 used to build your application. @value{GDBN} only fully supports
15250 programs with a single C@t{++} ABI; if your program contains code using
15251 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
15252 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
15253 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
15254 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
15255 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
15256 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
15261 Show the C@t{++} ABI currently in use.
15264 With no argument, show the list of supported C@t{++} ABI's.
15266 @item set cp-abi @var{abi}
15267 @itemx set cp-abi auto
15268 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
15271 @node Messages/Warnings
15272 @section Optional warnings and messages
15274 @cindex verbose operation
15275 @cindex optional warnings
15276 By default, @value{GDBN} is silent about its inner workings. If you are
15277 running on a slow machine, you may want to use the @code{set verbose}
15278 command. This makes @value{GDBN} tell you when it does a lengthy
15279 internal operation, so you will not think it has crashed.
15281 Currently, the messages controlled by @code{set verbose} are those
15282 which announce that the symbol table for a source file is being read;
15283 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
15286 @kindex set verbose
15287 @item set verbose on
15288 Enables @value{GDBN} output of certain informational messages.
15290 @item set verbose off
15291 Disables @value{GDBN} output of certain informational messages.
15293 @kindex show verbose
15295 Displays whether @code{set verbose} is on or off.
15298 By default, if @value{GDBN} encounters bugs in the symbol table of an
15299 object file, it is silent; but if you are debugging a compiler, you may
15300 find this information useful (@pxref{Symbol Errors, ,Errors reading
15305 @kindex set complaints
15306 @item set complaints @var{limit}
15307 Permits @value{GDBN} to output @var{limit} complaints about each type of
15308 unusual symbols before becoming silent about the problem. Set
15309 @var{limit} to zero to suppress all complaints; set it to a large number
15310 to prevent complaints from being suppressed.
15312 @kindex show complaints
15313 @item show complaints
15314 Displays how many symbol complaints @value{GDBN} is permitted to produce.
15318 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
15319 lot of stupid questions to confirm certain commands. For example, if
15320 you try to run a program which is already running:
15324 The program being debugged has been started already.
15325 Start it from the beginning? (y or n)
15328 If you are willing to unflinchingly face the consequences of your own
15329 commands, you can disable this ``feature'':
15333 @kindex set confirm
15335 @cindex confirmation
15336 @cindex stupid questions
15337 @item set confirm off
15338 Disables confirmation requests.
15340 @item set confirm on
15341 Enables confirmation requests (the default).
15343 @kindex show confirm
15345 Displays state of confirmation requests.
15349 @node Debugging Output
15350 @section Optional messages about internal happenings
15351 @cindex optional debugging messages
15353 @value{GDBN} has commands that enable optional debugging messages from
15354 various @value{GDBN} subsystems; normally these commands are of
15355 interest to @value{GDBN} maintainers, or when reporting a bug. This
15356 section documents those commands.
15359 @kindex set exec-done-display
15360 @item set exec-done-display
15361 Turns on or off the notification of asynchronous commands'
15362 completion. When on, @value{GDBN} will print a message when an
15363 asynchronous command finishes its execution. The default is off.
15364 @kindex show exec-done-display
15365 @item show exec-done-display
15366 Displays the current setting of asynchronous command completion
15369 @cindex gdbarch debugging info
15370 @cindex architecture debugging info
15371 @item set debug arch
15372 Turns on or off display of gdbarch debugging info. The default is off
15374 @item show debug arch
15375 Displays the current state of displaying gdbarch debugging info.
15376 @item set debug aix-thread
15377 @cindex AIX threads
15378 Display debugging messages about inner workings of the AIX thread
15380 @item show debug aix-thread
15381 Show the current state of AIX thread debugging info display.
15382 @item set debug event
15383 @cindex event debugging info
15384 Turns on or off display of @value{GDBN} event debugging info. The
15386 @item show debug event
15387 Displays the current state of displaying @value{GDBN} event debugging
15389 @item set debug expression
15390 @cindex expression debugging info
15391 Turns on or off display of debugging info about @value{GDBN}
15392 expression parsing. The default is off.
15393 @item show debug expression
15394 Displays the current state of displaying debugging info about
15395 @value{GDBN} expression parsing.
15396 @item set debug frame
15397 @cindex frame debugging info
15398 Turns on or off display of @value{GDBN} frame debugging info. The
15400 @item show debug frame
15401 Displays the current state of displaying @value{GDBN} frame debugging
15403 @item set debug infrun
15404 @cindex inferior debugging info
15405 Turns on or off display of @value{GDBN} debugging info for running the inferior.
15406 The default is off. @file{infrun.c} contains GDB's runtime state machine used
15407 for implementing operations such as single-stepping the inferior.
15408 @item show debug infrun
15409 Displays the current state of @value{GDBN} inferior debugging.
15410 @item set debug lin-lwp
15411 @cindex @sc{gnu}/Linux LWP debug messages
15412 @cindex Linux lightweight processes
15413 Turns on or off debugging messages from the Linux LWP debug support.
15414 @item show debug lin-lwp
15415 Show the current state of Linux LWP debugging messages.
15416 @item set debug observer
15417 @cindex observer debugging info
15418 Turns on or off display of @value{GDBN} observer debugging. This
15419 includes info such as the notification of observable events.
15420 @item show debug observer
15421 Displays the current state of observer debugging.
15422 @item set debug overload
15423 @cindex C@t{++} overload debugging info
15424 Turns on or off display of @value{GDBN} C@t{++} overload debugging
15425 info. This includes info such as ranking of functions, etc. The default
15427 @item show debug overload
15428 Displays the current state of displaying @value{GDBN} C@t{++} overload
15430 @cindex packets, reporting on stdout
15431 @cindex serial connections, debugging
15432 @item set debug remote
15433 Turns on or off display of reports on all packets sent back and forth across
15434 the serial line to the remote machine. The info is printed on the
15435 @value{GDBN} standard output stream. The default is off.
15436 @item show debug remote
15437 Displays the state of display of remote packets.
15438 @item set debug serial
15439 Turns on or off display of @value{GDBN} serial debugging info. The
15441 @item show debug serial
15442 Displays the current state of displaying @value{GDBN} serial debugging
15444 @item set debug solib-frv
15445 @cindex FR-V shared-library debugging
15446 Turns on or off debugging messages for FR-V shared-library code.
15447 @item show debug solib-frv
15448 Display the current state of FR-V shared-library code debugging
15450 @item set debug target
15451 @cindex target debugging info
15452 Turns on or off display of @value{GDBN} target debugging info. This info
15453 includes what is going on at the target level of GDB, as it happens. The
15454 default is 0. Set it to 1 to track events, and to 2 to also track the
15455 value of large memory transfers. Changes to this flag do not take effect
15456 until the next time you connect to a target or use the @code{run} command.
15457 @item show debug target
15458 Displays the current state of displaying @value{GDBN} target debugging
15460 @item set debugvarobj
15461 @cindex variable object debugging info
15462 Turns on or off display of @value{GDBN} variable object debugging
15463 info. The default is off.
15464 @item show debugvarobj
15465 Displays the current state of displaying @value{GDBN} variable object
15470 @chapter Canned Sequences of Commands
15472 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
15473 command lists}), @value{GDBN} provides two ways to store sequences of
15474 commands for execution as a unit: user-defined commands and command
15478 * Define:: User-defined commands
15479 * Hooks:: User-defined command hooks
15480 * Command Files:: Command files
15481 * Output:: Commands for controlled output
15485 @section User-defined commands
15487 @cindex user-defined command
15488 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
15489 which you assign a new name as a command. This is done with the
15490 @code{define} command. User commands may accept up to 10 arguments
15491 separated by whitespace. Arguments are accessed within the user command
15492 via @var{$arg0@dots{}$arg9}. A trivial example:
15496 print $arg0 + $arg1 + $arg2
15500 To execute the command use:
15507 This defines the command @code{adder}, which prints the sum of
15508 its three arguments. Note the arguments are text substitutions, so they may
15509 reference variables, use complex expressions, or even perform inferior
15515 @item define @var{commandname}
15516 Define a command named @var{commandname}. If there is already a command
15517 by that name, you are asked to confirm that you want to redefine it.
15519 The definition of the command is made up of other @value{GDBN} command lines,
15520 which are given following the @code{define} command. The end of these
15521 commands is marked by a line containing @code{end}.
15527 Takes a single argument, which is an expression to evaluate.
15528 It is followed by a series of commands that are executed
15529 only if the expression is true (nonzero).
15530 There can then optionally be a line @code{else}, followed
15531 by a series of commands that are only executed if the expression
15532 was false. The end of the list is marked by a line containing @code{end}.
15536 The syntax is similar to @code{if}: the command takes a single argument,
15537 which is an expression to evaluate, and must be followed by the commands to
15538 execute, one per line, terminated by an @code{end}.
15539 The commands are executed repeatedly as long as the expression
15543 @item document @var{commandname}
15544 Document the user-defined command @var{commandname}, so that it can be
15545 accessed by @code{help}. The command @var{commandname} must already be
15546 defined. This command reads lines of documentation just as @code{define}
15547 reads the lines of the command definition, ending with @code{end}.
15548 After the @code{document} command is finished, @code{help} on command
15549 @var{commandname} displays the documentation you have written.
15551 You may use the @code{document} command again to change the
15552 documentation of a command. Redefining the command with @code{define}
15553 does not change the documentation.
15555 @kindex dont-repeat
15556 @cindex don't repeat command
15558 Used inside a user-defined command, this tells @value{GDBN} that this
15559 command should not be repeated when the user hits @key{RET}
15560 (@pxref{Command Syntax, repeat last command}).
15562 @kindex help user-defined
15563 @item help user-defined
15564 List all user-defined commands, with the first line of the documentation
15569 @itemx show user @var{commandname}
15570 Display the @value{GDBN} commands used to define @var{commandname} (but
15571 not its documentation). If no @var{commandname} is given, display the
15572 definitions for all user-defined commands.
15574 @cindex infinite recusrion in user-defined commands
15575 @kindex show max-user-call-depth
15576 @kindex set max-user-call-depth
15577 @item show max-user-call-depth
15578 @itemx set max-user-call-depth
15579 The value of @code{max-user-call-depth} controls how many recursion
15580 levels are allowed in user-defined commands before GDB suspects an
15581 infinite recursion and aborts the command.
15585 When user-defined commands are executed, the
15586 commands of the definition are not printed. An error in any command
15587 stops execution of the user-defined command.
15589 If used interactively, commands that would ask for confirmation proceed
15590 without asking when used inside a user-defined command. Many @value{GDBN}
15591 commands that normally print messages to say what they are doing omit the
15592 messages when used in a user-defined command.
15595 @section User-defined command hooks
15596 @cindex command hooks
15597 @cindex hooks, for commands
15598 @cindex hooks, pre-command
15601 You may define @dfn{hooks}, which are a special kind of user-defined
15602 command. Whenever you run the command @samp{foo}, if the user-defined
15603 command @samp{hook-foo} exists, it is executed (with no arguments)
15604 before that command.
15606 @cindex hooks, post-command
15608 A hook may also be defined which is run after the command you executed.
15609 Whenever you run the command @samp{foo}, if the user-defined command
15610 @samp{hookpost-foo} exists, it is executed (with no arguments) after
15611 that command. Post-execution hooks may exist simultaneously with
15612 pre-execution hooks, for the same command.
15614 It is valid for a hook to call the command which it hooks. If this
15615 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
15617 @c It would be nice if hookpost could be passed a parameter indicating
15618 @c if the command it hooks executed properly or not. FIXME!
15620 @kindex stop@r{, a pseudo-command}
15621 In addition, a pseudo-command, @samp{stop} exists. Defining
15622 (@samp{hook-stop}) makes the associated commands execute every time
15623 execution stops in your program: before breakpoint commands are run,
15624 displays are printed, or the stack frame is printed.
15626 For example, to ignore @code{SIGALRM} signals while
15627 single-stepping, but treat them normally during normal execution,
15632 handle SIGALRM nopass
15636 handle SIGALRM pass
15639 define hook-continue
15640 handle SIGLARM pass
15644 As a further example, to hook at the begining and end of the @code{echo}
15645 command, and to add extra text to the beginning and end of the message,
15653 define hookpost-echo
15657 (@value{GDBP}) echo Hello World
15658 <<<---Hello World--->>>
15663 You can define a hook for any single-word command in @value{GDBN}, but
15664 not for command aliases; you should define a hook for the basic command
15665 name, e.g. @code{backtrace} rather than @code{bt}.
15666 @c FIXME! So how does Joe User discover whether a command is an alias
15668 If an error occurs during the execution of your hook, execution of
15669 @value{GDBN} commands stops and @value{GDBN} issues a prompt
15670 (before the command that you actually typed had a chance to run).
15672 If you try to define a hook which does not match any known command, you
15673 get a warning from the @code{define} command.
15675 @node Command Files
15676 @section Command files
15678 @cindex command files
15679 A command file for @value{GDBN} is a file of lines that are @value{GDBN}
15680 commands. Comments (lines starting with @kbd{#}) may also be included.
15681 An empty line in a command file does nothing; it does not mean to repeat
15682 the last command, as it would from the terminal.
15685 @cindex @file{.gdbinit}
15686 @cindex @file{gdb.ini}
15687 When you start @value{GDBN}, it automatically executes commands from its
15688 @dfn{init files}, normally called @file{.gdbinit}@footnote{The DJGPP
15689 port of @value{GDBN} uses the name @file{gdb.ini} instead, due to the
15690 limitations of file names imposed by DOS filesystems.}.
15691 During startup, @value{GDBN} does the following:
15695 Reads the init file (if any) in your home directory@footnote{On
15696 DOS/Windows systems, the home directory is the one pointed to by the
15697 @code{HOME} environment variable.}.
15700 Processes command line options and operands.
15703 Reads the init file (if any) in the current working directory.
15706 Reads command files specified by the @samp{-x} option.
15709 The init file in your home directory can set options (such as @samp{set
15710 complaints}) that affect subsequent processing of command line options
15711 and operands. Init files are not executed if you use the @samp{-nx}
15712 option (@pxref{Mode Options, ,Choosing modes}).
15714 @cindex init file name
15715 On some configurations of @value{GDBN}, the init file is known by a
15716 different name (these are typically environments where a specialized
15717 form of @value{GDBN} may need to coexist with other forms, hence a
15718 different name for the specialized version's init file). These are the
15719 environments with special init file names:
15721 @cindex @file{.vxgdbinit}
15724 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
15726 @cindex @file{.os68gdbinit}
15728 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
15730 @cindex @file{.esgdbinit}
15732 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
15735 You can also request the execution of a command file with the
15736 @code{source} command:
15740 @item source @var{filename}
15741 Execute the command file @var{filename}.
15744 The lines in a command file are executed sequentially. They are not
15745 printed as they are executed. An error in any command terminates
15746 execution of the command file and control is returned to the console.
15748 Commands that would ask for confirmation if used interactively proceed
15749 without asking when used in a command file. Many @value{GDBN} commands that
15750 normally print messages to say what they are doing omit the messages
15751 when called from command files.
15753 @value{GDBN} also accepts command input from standard input. In this
15754 mode, normal output goes to standard output and error output goes to
15755 standard error. Errors in a command file supplied on standard input do
15756 not terminate execution of the command file --- execution continues with
15760 gdb < cmds > log 2>&1
15763 (The syntax above will vary depending on the shell used.) This example
15764 will execute commands from the file @file{cmds}. All output and errors
15765 would be directed to @file{log}.
15768 @section Commands for controlled output
15770 During the execution of a command file or a user-defined command, normal
15771 @value{GDBN} output is suppressed; the only output that appears is what is
15772 explicitly printed by the commands in the definition. This section
15773 describes three commands useful for generating exactly the output you
15778 @item echo @var{text}
15779 @c I do not consider backslash-space a standard C escape sequence
15780 @c because it is not in ANSI.
15781 Print @var{text}. Nonprinting characters can be included in
15782 @var{text} using C escape sequences, such as @samp{\n} to print a
15783 newline. @strong{No newline is printed unless you specify one.}
15784 In addition to the standard C escape sequences, a backslash followed
15785 by a space stands for a space. This is useful for displaying a
15786 string with spaces at the beginning or the end, since leading and
15787 trailing spaces are otherwise trimmed from all arguments.
15788 To print @samp{@w{ }and foo =@w{ }}, use the command
15789 @samp{echo \@w{ }and foo = \@w{ }}.
15791 A backslash at the end of @var{text} can be used, as in C, to continue
15792 the command onto subsequent lines. For example,
15795 echo This is some text\n\
15796 which is continued\n\
15797 onto several lines.\n
15800 produces the same output as
15803 echo This is some text\n
15804 echo which is continued\n
15805 echo onto several lines.\n
15809 @item output @var{expression}
15810 Print the value of @var{expression} and nothing but that value: no
15811 newlines, no @samp{$@var{nn} = }. The value is not entered in the
15812 value history either. @xref{Expressions, ,Expressions}, for more information
15815 @item output/@var{fmt} @var{expression}
15816 Print the value of @var{expression} in format @var{fmt}. You can use
15817 the same formats as for @code{print}. @xref{Output Formats,,Output
15818 formats}, for more information.
15821 @item printf @var{string}, @var{expressions}@dots{}
15822 Print the values of the @var{expressions} under the control of
15823 @var{string}. The @var{expressions} are separated by commas and may be
15824 either numbers or pointers. Their values are printed as specified by
15825 @var{string}, exactly as if your program were to execute the C
15827 @c FIXME: the above implies that at least all ANSI C formats are
15828 @c supported, but it isn't true: %E and %G don't work (or so it seems).
15829 @c Either this is a bug, or the manual should document what formats are
15833 printf (@var{string}, @var{expressions}@dots{});
15836 For example, you can print two values in hex like this:
15839 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
15842 The only backslash-escape sequences that you can use in the format
15843 string are the simple ones that consist of backslash followed by a
15848 @chapter Command Interpreters
15849 @cindex command interpreters
15851 @value{GDBN} supports multiple command interpreters, and some command
15852 infrastructure to allow users or user interface writers to switch
15853 between interpreters or run commands in other interpreters.
15855 @value{GDBN} currently supports two command interpreters, the console
15856 interpreter (sometimes called the command-line interpreter or @sc{cli})
15857 and the machine interface interpreter (or @sc{gdb/mi}). This manual
15858 describes both of these interfaces in great detail.
15860 By default, @value{GDBN} will start with the console interpreter.
15861 However, the user may choose to start @value{GDBN} with another
15862 interpreter by specifying the @option{-i} or @option{--interpreter}
15863 startup options. Defined interpreters include:
15867 @cindex console interpreter
15868 The traditional console or command-line interpreter. This is the most often
15869 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
15870 @value{GDBN} will use this interpreter.
15873 @cindex mi interpreter
15874 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
15875 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
15876 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
15880 @cindex mi2 interpreter
15881 The current @sc{gdb/mi} interface.
15884 @cindex mi1 interpreter
15885 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
15889 @cindex invoke another interpreter
15890 The interpreter being used by @value{GDBN} may not be dynamically
15891 switched at runtime. Although possible, this could lead to a very
15892 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
15893 enters the command "interpreter-set console" in a console view,
15894 @value{GDBN} would switch to using the console interpreter, rendering
15895 the IDE inoperable!
15897 @kindex interpreter-exec
15898 Although you may only choose a single interpreter at startup, you may execute
15899 commands in any interpreter from the current interpreter using the appropriate
15900 command. If you are running the console interpreter, simply use the
15901 @code{interpreter-exec} command:
15904 interpreter-exec mi "-data-list-register-names"
15907 @sc{gdb/mi} has a similar command, although it is only available in versions of
15908 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
15911 @chapter @value{GDBN} Text User Interface
15913 @cindex Text User Interface
15916 * TUI Overview:: TUI overview
15917 * TUI Keys:: TUI key bindings
15918 * TUI Single Key Mode:: TUI single key mode
15919 * TUI Commands:: TUI specific commands
15920 * TUI Configuration:: TUI configuration variables
15923 The @value{GDBN} Text User Interface, TUI in short, is a terminal
15924 interface which uses the @code{curses} library to show the source
15925 file, the assembly output, the program registers and @value{GDBN}
15926 commands in separate text windows.
15928 The TUI is enabled by invoking @value{GDBN} using either
15930 @samp{gdbtui} or @samp{gdb -tui}.
15933 @section TUI overview
15935 The TUI has two display modes that can be switched while
15940 A curses (or TUI) mode in which it displays several text
15941 windows on the terminal.
15944 A standard mode which corresponds to the @value{GDBN} configured without
15948 In the TUI mode, @value{GDBN} can display several text window
15953 This window is the @value{GDBN} command window with the @value{GDBN}
15954 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
15955 managed using readline but through the TUI. The @emph{command}
15956 window is always visible.
15959 The source window shows the source file of the program. The current
15960 line as well as active breakpoints are displayed in this window.
15963 The assembly window shows the disassembly output of the program.
15966 This window shows the processor registers. It detects when
15967 a register is changed and when this is the case, registers that have
15968 changed are highlighted.
15972 The source and assembly windows show the current program position
15973 by highlighting the current line and marking them with the @samp{>} marker.
15974 Breakpoints are also indicated with two markers. A first one
15975 indicates the breakpoint type:
15979 Breakpoint which was hit at least once.
15982 Breakpoint which was never hit.
15985 Hardware breakpoint which was hit at least once.
15988 Hardware breakpoint which was never hit.
15992 The second marker indicates whether the breakpoint is enabled or not:
15996 Breakpoint is enabled.
15999 Breakpoint is disabled.
16003 The source, assembly and register windows are attached to the thread
16004 and the frame position. They are updated when the current thread
16005 changes, when the frame changes or when the program counter changes.
16006 These three windows are arranged by the TUI according to several
16007 layouts. The layout defines which of these three windows are visible.
16008 The following layouts are available:
16018 source and assembly
16021 source and registers
16024 assembly and registers
16028 On top of the command window a status line gives various information
16029 concerning the current process begin debugged. The status line is
16030 updated when the information it shows changes. The following fields
16035 Indicates the current gdb target
16036 (@pxref{Targets, ,Specifying a Debugging Target}).
16039 Gives information about the current process or thread number.
16040 When no process is being debugged, this field is set to @code{No process}.
16043 Gives the current function name for the selected frame.
16044 The name is demangled if demangling is turned on (@pxref{Print Settings}).
16045 When there is no symbol corresponding to the current program counter
16046 the string @code{??} is displayed.
16049 Indicates the current line number for the selected frame.
16050 When the current line number is not known the string @code{??} is displayed.
16053 Indicates the current program counter address.
16058 @section TUI Key Bindings
16059 @cindex TUI key bindings
16061 The TUI installs several key bindings in the readline keymaps
16062 (@pxref{Command Line Editing}).
16063 They allow to leave or enter in the TUI mode or they operate
16064 directly on the TUI layout and windows. The TUI also provides
16065 a @emph{SingleKey} keymap which binds several keys directly to
16066 @value{GDBN} commands. The following key bindings
16067 are installed for both TUI mode and the @value{GDBN} standard mode.
16076 Enter or leave the TUI mode. When the TUI mode is left,
16077 the curses window management is left and @value{GDBN} operates using
16078 its standard mode writing on the terminal directly. When the TUI
16079 mode is entered, the control is given back to the curses windows.
16080 The screen is then refreshed.
16084 Use a TUI layout with only one window. The layout will
16085 either be @samp{source} or @samp{assembly}. When the TUI mode
16086 is not active, it will switch to the TUI mode.
16088 Think of this key binding as the Emacs @kbd{C-x 1} binding.
16092 Use a TUI layout with at least two windows. When the current
16093 layout shows already two windows, a next layout with two windows is used.
16094 When a new layout is chosen, one window will always be common to the
16095 previous layout and the new one.
16097 Think of it as the Emacs @kbd{C-x 2} binding.
16101 Change the active window. The TUI associates several key bindings
16102 (like scrolling and arrow keys) to the active window. This command
16103 gives the focus to the next TUI window.
16105 Think of it as the Emacs @kbd{C-x o} binding.
16109 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
16110 (@pxref{TUI Single Key Mode}).
16114 The following key bindings are handled only by the TUI mode:
16119 Scroll the active window one page up.
16123 Scroll the active window one page down.
16127 Scroll the active window one line up.
16131 Scroll the active window one line down.
16135 Scroll the active window one column left.
16139 Scroll the active window one column right.
16143 Refresh the screen.
16147 In the TUI mode, the arrow keys are used by the active window
16148 for scrolling. This means they are available for readline when the
16149 active window is the command window. When the command window
16150 does not have the focus, it is necessary to use other readline
16151 key bindings such as @key{C-p}, @key{C-n}, @key{C-b} and @key{C-f}.
16153 @node TUI Single Key Mode
16154 @section TUI Single Key Mode
16155 @cindex TUI single key mode
16157 The TUI provides a @emph{SingleKey} mode in which it installs a particular
16158 key binding in the readline keymaps to connect single keys to
16162 @kindex c @r{(SingleKey TUI key)}
16166 @kindex d @r{(SingleKey TUI key)}
16170 @kindex f @r{(SingleKey TUI key)}
16174 @kindex n @r{(SingleKey TUI key)}
16178 @kindex q @r{(SingleKey TUI key)}
16180 exit the @emph{SingleKey} mode.
16182 @kindex r @r{(SingleKey TUI key)}
16186 @kindex s @r{(SingleKey TUI key)}
16190 @kindex u @r{(SingleKey TUI key)}
16194 @kindex v @r{(SingleKey TUI key)}
16198 @kindex w @r{(SingleKey TUI key)}
16204 Other keys temporarily switch to the @value{GDBN} command prompt.
16205 The key that was pressed is inserted in the editing buffer so that
16206 it is possible to type most @value{GDBN} commands without interaction
16207 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
16208 @emph{SingleKey} mode is restored. The only way to permanently leave
16209 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
16213 @section TUI specific commands
16214 @cindex TUI commands
16216 The TUI has specific commands to control the text windows.
16217 These commands are always available, that is they do not depend on
16218 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
16219 is in the standard mode, using these commands will automatically switch
16225 List and give the size of all displayed windows.
16229 Display the next layout.
16232 Display the previous layout.
16235 Display the source window only.
16238 Display the assembly window only.
16241 Display the source and assembly window.
16244 Display the register window together with the source or assembly window.
16246 @item focus next | prev | src | asm | regs | split
16248 Set the focus to the named window.
16249 This command allows to change the active window so that scrolling keys
16250 can be affected to another window.
16254 Refresh the screen. This is similar to using @key{C-L} key.
16256 @item tui reg float
16258 Show the floating point registers in the register window.
16260 @item tui reg general
16261 Show the general registers in the register window.
16264 Show the next register group. The list of register groups as well as
16265 their order is target specific. The predefined register groups are the
16266 following: @code{general}, @code{float}, @code{system}, @code{vector},
16267 @code{all}, @code{save}, @code{restore}.
16269 @item tui reg system
16270 Show the system registers in the register window.
16274 Update the source window and the current execution point.
16276 @item winheight @var{name} +@var{count}
16277 @itemx winheight @var{name} -@var{count}
16279 Change the height of the window @var{name} by @var{count}
16280 lines. Positive counts increase the height, while negative counts
16284 @kindex tabset @var{nchars}
16285 Set the width of tab stops to be @var{nchars} characters.
16289 @node TUI Configuration
16290 @section TUI configuration variables
16291 @cindex TUI configuration variables
16293 The TUI has several configuration variables that control the
16294 appearance of windows on the terminal.
16297 @item set tui border-kind @var{kind}
16298 @kindex set tui border-kind
16299 Select the border appearance for the source, assembly and register windows.
16300 The possible values are the following:
16303 Use a space character to draw the border.
16306 Use ascii characters + - and | to draw the border.
16309 Use the Alternate Character Set to draw the border. The border is
16310 drawn using character line graphics if the terminal supports them.
16314 @item set tui active-border-mode @var{mode}
16315 @kindex set tui active-border-mode
16316 Select the attributes to display the border of the active window.
16317 The possible values are @code{normal}, @code{standout}, @code{reverse},
16318 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
16320 @item set tui border-mode @var{mode}
16321 @kindex set tui border-mode
16322 Select the attributes to display the border of other windows.
16323 The @var{mode} can be one of the following:
16326 Use normal attributes to display the border.
16332 Use reverse video mode.
16335 Use half bright mode.
16337 @item half-standout
16338 Use half bright and standout mode.
16341 Use extra bright or bold mode.
16343 @item bold-standout
16344 Use extra bright or bold and standout mode.
16351 @chapter Using @value{GDBN} under @sc{gnu} Emacs
16354 @cindex @sc{gnu} Emacs
16355 A special interface allows you to use @sc{gnu} Emacs to view (and
16356 edit) the source files for the program you are debugging with
16359 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
16360 executable file you want to debug as an argument. This command starts
16361 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
16362 created Emacs buffer.
16363 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
16365 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
16370 All ``terminal'' input and output goes through the Emacs buffer.
16373 This applies both to @value{GDBN} commands and their output, and to the input
16374 and output done by the program you are debugging.
16376 This is useful because it means that you can copy the text of previous
16377 commands and input them again; you can even use parts of the output
16380 All the facilities of Emacs' Shell mode are available for interacting
16381 with your program. In particular, you can send signals the usual
16382 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
16387 @value{GDBN} displays source code through Emacs.
16390 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
16391 source file for that frame and puts an arrow (@samp{=>}) at the
16392 left margin of the current line. Emacs uses a separate buffer for
16393 source display, and splits the screen to show both your @value{GDBN} session
16396 Explicit @value{GDBN} @code{list} or search commands still produce output as
16397 usual, but you probably have no reason to use them from Emacs.
16399 If you specify an absolute file name when prompted for the @kbd{M-x
16400 gdb} argument, then Emacs sets your current working directory to where
16401 your program resides. If you only specify the file name, then Emacs
16402 sets your current working directory to to the directory associated
16403 with the previous buffer. In this case, @value{GDBN} may find your
16404 program by searching your environment's @code{PATH} variable, but on
16405 some operating systems it might not find the source. So, although the
16406 @value{GDBN} input and output session proceeds normally, the auxiliary
16407 buffer does not display the current source and line of execution.
16409 The initial working directory of @value{GDBN} is printed on the top
16410 line of the @value{GDBN} I/O buffer and this serves as a default for
16411 the commands that specify files for @value{GDBN} to operate
16412 on. @xref{Files, ,Commands to specify files}.
16414 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
16415 need to call @value{GDBN} by a different name (for example, if you
16416 keep several configurations around, with different names) you can
16417 customize the Emacs variable @code{gud-gdb-command-name} to run the
16420 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
16421 addition to the standard Shell mode commands:
16425 Describe the features of Emacs' @value{GDBN} Mode.
16428 Execute to another source line, like the @value{GDBN} @code{step} command; also
16429 update the display window to show the current file and location.
16432 Execute to next source line in this function, skipping all function
16433 calls, like the @value{GDBN} @code{next} command. Then update the display window
16434 to show the current file and location.
16437 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
16438 display window accordingly.
16441 Execute until exit from the selected stack frame, like the @value{GDBN}
16442 @code{finish} command.
16445 Continue execution of your program, like the @value{GDBN} @code{continue}
16449 Go up the number of frames indicated by the numeric argument
16450 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
16451 like the @value{GDBN} @code{up} command.
16454 Go down the number of frames indicated by the numeric argument, like the
16455 @value{GDBN} @code{down} command.
16458 In any source file, the Emacs command @kbd{C-x SPC} (@code{gud-break})
16459 tells @value{GDBN} to set a breakpoint on the source line point is on.
16461 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
16462 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
16463 point to any frame in the stack and type @key{RET} to make it become the
16464 current frame and display the associated source in the source buffer.
16465 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
16468 If you accidentally delete the source-display buffer, an easy way to get
16469 it back is to type the command @code{f} in the @value{GDBN} buffer, to
16470 request a frame display; when you run under Emacs, this recreates
16471 the source buffer if necessary to show you the context of the current
16474 The source files displayed in Emacs are in ordinary Emacs buffers
16475 which are visiting the source files in the usual way. You can edit
16476 the files with these buffers if you wish; but keep in mind that @value{GDBN}
16477 communicates with Emacs in terms of line numbers. If you add or
16478 delete lines from the text, the line numbers that @value{GDBN} knows cease
16479 to correspond properly with the code.
16481 The description given here is for GNU Emacs version 21.3 and a more
16482 detailed description of its interaction with @value{GDBN} is given in
16483 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
16485 @c The following dropped because Epoch is nonstandard. Reactivate
16486 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
16488 @kindex Emacs Epoch environment
16492 Version 18 of @sc{gnu} Emacs has a built-in window system
16493 called the @code{epoch}
16494 environment. Users of this environment can use a new command,
16495 @code{inspect} which performs identically to @code{print} except that
16496 each value is printed in its own window.
16501 @chapter The @sc{gdb/mi} Interface
16503 @unnumberedsec Function and Purpose
16505 @cindex @sc{gdb/mi}, its purpose
16506 @sc{gdb/mi} is a line based machine oriented text interface to
16507 @value{GDBN} and is activated by specifying using the
16508 @option{--interpreter} command line option (@pxref{Mode Options}). It
16509 is specifically intended to support the development of systems which
16510 use the debugger as just one small component of a larger system.
16512 This chapter is a specification of the @sc{gdb/mi} interface. It is written
16513 in the form of a reference manual.
16515 Note that @sc{gdb/mi} is still under construction, so some of the
16516 features described below are incomplete and subject to change.
16518 @unnumberedsec Notation and Terminology
16520 @cindex notational conventions, for @sc{gdb/mi}
16521 This chapter uses the following notation:
16525 @code{|} separates two alternatives.
16528 @code{[ @var{something} ]} indicates that @var{something} is optional:
16529 it may or may not be given.
16532 @code{( @var{group} )*} means that @var{group} inside the parentheses
16533 may repeat zero or more times.
16536 @code{( @var{group} )+} means that @var{group} inside the parentheses
16537 may repeat one or more times.
16540 @code{"@var{string}"} means a literal @var{string}.
16544 @heading Dependencies
16547 @heading Acknowledgments
16549 In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
16553 * GDB/MI Command Syntax::
16554 * GDB/MI Compatibility with CLI::
16555 * GDB/MI Output Records::
16556 * GDB/MI Command Description Format::
16557 * GDB/MI Breakpoint Table Commands::
16558 * GDB/MI Data Manipulation::
16559 * GDB/MI Program Control::
16560 * GDB/MI Miscellaneous Commands::
16562 * GDB/MI Kod Commands::
16563 * GDB/MI Memory Overlay Commands::
16564 * GDB/MI Signal Handling Commands::
16566 * GDB/MI Stack Manipulation::
16567 * GDB/MI Symbol Query::
16568 * GDB/MI Target Manipulation::
16569 * GDB/MI Thread Commands::
16570 * GDB/MI Tracepoint Commands::
16571 * GDB/MI Variable Objects::
16574 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16575 @node GDB/MI Command Syntax
16576 @section @sc{gdb/mi} Command Syntax
16579 * GDB/MI Input Syntax::
16580 * GDB/MI Output Syntax::
16581 * GDB/MI Simple Examples::
16584 @node GDB/MI Input Syntax
16585 @subsection @sc{gdb/mi} Input Syntax
16587 @cindex input syntax for @sc{gdb/mi}
16588 @cindex @sc{gdb/mi}, input syntax
16590 @item @var{command} @expansion{}
16591 @code{@var{cli-command} | @var{mi-command}}
16593 @item @var{cli-command} @expansion{}
16594 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
16595 @var{cli-command} is any existing @value{GDBN} CLI command.
16597 @item @var{mi-command} @expansion{}
16598 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
16599 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
16601 @item @var{token} @expansion{}
16602 "any sequence of digits"
16604 @item @var{option} @expansion{}
16605 @code{"-" @var{parameter} [ " " @var{parameter} ]}
16607 @item @var{parameter} @expansion{}
16608 @code{@var{non-blank-sequence} | @var{c-string}}
16610 @item @var{operation} @expansion{}
16611 @emph{any of the operations described in this chapter}
16613 @item @var{non-blank-sequence} @expansion{}
16614 @emph{anything, provided it doesn't contain special characters such as
16615 "-", @var{nl}, """ and of course " "}
16617 @item @var{c-string} @expansion{}
16618 @code{""" @var{seven-bit-iso-c-string-content} """}
16620 @item @var{nl} @expansion{}
16629 The CLI commands are still handled by the @sc{mi} interpreter; their
16630 output is described below.
16633 The @code{@var{token}}, when present, is passed back when the command
16637 Some @sc{mi} commands accept optional arguments as part of the parameter
16638 list. Each option is identified by a leading @samp{-} (dash) and may be
16639 followed by an optional argument parameter. Options occur first in the
16640 parameter list and can be delimited from normal parameters using
16641 @samp{--} (this is useful when some parameters begin with a dash).
16648 We want easy access to the existing CLI syntax (for debugging).
16651 We want it to be easy to spot a @sc{mi} operation.
16654 @node GDB/MI Output Syntax
16655 @subsection @sc{gdb/mi} Output Syntax
16657 @cindex output syntax of @sc{gdb/mi}
16658 @cindex @sc{gdb/mi}, output syntax
16659 The output from @sc{gdb/mi} consists of zero or more out-of-band records
16660 followed, optionally, by a single result record. This result record
16661 is for the most recent command. The sequence of output records is
16662 terminated by @samp{(@value{GDBP})}.
16664 If an input command was prefixed with a @code{@var{token}} then the
16665 corresponding output for that command will also be prefixed by that same
16669 @item @var{output} @expansion{}
16670 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(@value{GDBP})" @var{nl}}
16672 @item @var{result-record} @expansion{}
16673 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
16675 @item @var{out-of-band-record} @expansion{}
16676 @code{@var{async-record} | @var{stream-record}}
16678 @item @var{async-record} @expansion{}
16679 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
16681 @item @var{exec-async-output} @expansion{}
16682 @code{[ @var{token} ] "*" @var{async-output}}
16684 @item @var{status-async-output} @expansion{}
16685 @code{[ @var{token} ] "+" @var{async-output}}
16687 @item @var{notify-async-output} @expansion{}
16688 @code{[ @var{token} ] "=" @var{async-output}}
16690 @item @var{async-output} @expansion{}
16691 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
16693 @item @var{result-class} @expansion{}
16694 @code{"done" | "running" | "connected" | "error" | "exit"}
16696 @item @var{async-class} @expansion{}
16697 @code{"stopped" | @var{others}} (where @var{others} will be added
16698 depending on the needs---this is still in development).
16700 @item @var{result} @expansion{}
16701 @code{ @var{variable} "=" @var{value}}
16703 @item @var{variable} @expansion{}
16704 @code{ @var{string} }
16706 @item @var{value} @expansion{}
16707 @code{ @var{const} | @var{tuple} | @var{list} }
16709 @item @var{const} @expansion{}
16710 @code{@var{c-string}}
16712 @item @var{tuple} @expansion{}
16713 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
16715 @item @var{list} @expansion{}
16716 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
16717 @var{result} ( "," @var{result} )* "]" }
16719 @item @var{stream-record} @expansion{}
16720 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
16722 @item @var{console-stream-output} @expansion{}
16723 @code{"~" @var{c-string}}
16725 @item @var{target-stream-output} @expansion{}
16726 @code{"@@" @var{c-string}}
16728 @item @var{log-stream-output} @expansion{}
16729 @code{"&" @var{c-string}}
16731 @item @var{nl} @expansion{}
16734 @item @var{token} @expansion{}
16735 @emph{any sequence of digits}.
16743 All output sequences end in a single line containing a period.
16746 The @code{@var{token}} is from the corresponding request. If an execution
16747 command is interrupted by the @samp{-exec-interrupt} command, the
16748 @var{token} associated with the @samp{*stopped} message is the one of the
16749 original execution command, not the one of the interrupt command.
16752 @cindex status output in @sc{gdb/mi}
16753 @var{status-async-output} contains on-going status information about the
16754 progress of a slow operation. It can be discarded. All status output is
16755 prefixed by @samp{+}.
16758 @cindex async output in @sc{gdb/mi}
16759 @var{exec-async-output} contains asynchronous state change on the target
16760 (stopped, started, disappeared). All async output is prefixed by
16764 @cindex notify output in @sc{gdb/mi}
16765 @var{notify-async-output} contains supplementary information that the
16766 client should handle (e.g., a new breakpoint information). All notify
16767 output is prefixed by @samp{=}.
16770 @cindex console output in @sc{gdb/mi}
16771 @var{console-stream-output} is output that should be displayed as is in the
16772 console. It is the textual response to a CLI command. All the console
16773 output is prefixed by @samp{~}.
16776 @cindex target output in @sc{gdb/mi}
16777 @var{target-stream-output} is the output produced by the target program.
16778 All the target output is prefixed by @samp{@@}.
16781 @cindex log output in @sc{gdb/mi}
16782 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
16783 instance messages that should be displayed as part of an error log. All
16784 the log output is prefixed by @samp{&}.
16787 @cindex list output in @sc{gdb/mi}
16788 New @sc{gdb/mi} commands should only output @var{lists} containing
16794 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
16795 details about the various output records.
16797 @node GDB/MI Simple Examples
16798 @subsection Simple Examples of @sc{gdb/mi} Interaction
16799 @cindex @sc{gdb/mi}, simple examples
16801 This subsection presents several simple examples of interaction using
16802 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
16803 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
16804 the output received from @sc{gdb/mi}.
16806 @subsubheading Target Stop
16807 @c Ummm... There is no "-stop" command. This assumes async, no?
16808 Here's an example of stopping the inferior process:
16819 <- *stop,reason="stop",address="0x123",source="a.c:123"
16823 @subsubheading Simple CLI Command
16825 Here's an example of a simple CLI command being passed through
16826 @sc{gdb/mi} and on to the CLI.
16836 @subsubheading Command With Side Effects
16839 -> -symbol-file xyz.exe
16840 <- *breakpoint,nr="3",address="0x123",source="a.c:123"
16844 @subsubheading A Bad Command
16846 Here's what happens if you pass a non-existent command:
16850 <- ^error,msg="Undefined MI command: rubbish"
16854 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16855 @node GDB/MI Compatibility with CLI
16856 @section @sc{gdb/mi} Compatibility with CLI
16858 @cindex compatibility, @sc{gdb/mi} and CLI
16859 @cindex @sc{gdb/mi}, compatibility with CLI
16860 To help users familiar with @value{GDBN}'s existing CLI interface, @sc{gdb/mi}
16861 accepts existing CLI commands. As specified by the syntax, such
16862 commands can be directly entered into the @sc{gdb/mi} interface and @value{GDBN} will
16865 This mechanism is provided as an aid to developers of @sc{gdb/mi}
16866 clients and not as a reliable interface into the CLI. Since the command
16867 is being interpreteted in an environment that assumes @sc{gdb/mi}
16868 behaviour, the exact output of such commands is likely to end up being
16869 an un-supported hybrid of @sc{gdb/mi} and CLI output.
16871 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16872 @node GDB/MI Output Records
16873 @section @sc{gdb/mi} Output Records
16876 * GDB/MI Result Records::
16877 * GDB/MI Stream Records::
16878 * GDB/MI Out-of-band Records::
16881 @node GDB/MI Result Records
16882 @subsection @sc{gdb/mi} Result Records
16884 @cindex result records in @sc{gdb/mi}
16885 @cindex @sc{gdb/mi}, result records
16886 In addition to a number of out-of-band notifications, the response to a
16887 @sc{gdb/mi} command includes one of the following result indications:
16891 @item "^done" [ "," @var{results} ]
16892 The synchronous operation was successful, @code{@var{results}} are the return
16897 @c Is this one correct? Should it be an out-of-band notification?
16898 The asynchronous operation was successfully started. The target is
16901 @item "^error" "," @var{c-string}
16903 The operation failed. The @code{@var{c-string}} contains the corresponding
16907 @node GDB/MI Stream Records
16908 @subsection @sc{gdb/mi} Stream Records
16910 @cindex @sc{gdb/mi}, stream records
16911 @cindex stream records in @sc{gdb/mi}
16912 @value{GDBN} internally maintains a number of output streams: the console, the
16913 target, and the log. The output intended for each of these streams is
16914 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
16916 Each stream record begins with a unique @dfn{prefix character} which
16917 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
16918 Syntax}). In addition to the prefix, each stream record contains a
16919 @code{@var{string-output}}. This is either raw text (with an implicit new
16920 line) or a quoted C string (which does not contain an implicit newline).
16923 @item "~" @var{string-output}
16924 The console output stream contains text that should be displayed in the
16925 CLI console window. It contains the textual responses to CLI commands.
16927 @item "@@" @var{string-output}
16928 The target output stream contains any textual output from the running
16931 @item "&" @var{string-output}
16932 The log stream contains debugging messages being produced by @value{GDBN}'s
16936 @node GDB/MI Out-of-band Records
16937 @subsection @sc{gdb/mi} Out-of-band Records
16939 @cindex out-of-band records in @sc{gdb/mi}
16940 @cindex @sc{gdb/mi}, out-of-band records
16941 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
16942 additional changes that have occurred. Those changes can either be a
16943 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
16944 target activity (e.g., target stopped).
16946 The following is a preliminary list of possible out-of-band records.
16953 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16954 @node GDB/MI Command Description Format
16955 @section @sc{gdb/mi} Command Description Format
16957 The remaining sections describe blocks of commands. Each block of
16958 commands is laid out in a fashion similar to this section.
16960 Note the the line breaks shown in the examples are here only for
16961 readability. They don't appear in the real output.
16962 Also note that the commands with a non-available example (N.A.@:) are
16963 not yet implemented.
16965 @subheading Motivation
16967 The motivation for this collection of commands.
16969 @subheading Introduction
16971 A brief introduction to this collection of commands as a whole.
16973 @subheading Commands
16975 For each command in the block, the following is described:
16977 @subsubheading Synopsis
16980 -command @var{args}@dots{}
16983 @subsubheading @value{GDBN} Command
16985 The corresponding @value{GDBN} CLI command.
16987 @subsubheading Result
16989 @subsubheading Out-of-band
16991 @subsubheading Notes
16993 @subsubheading Example
16996 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16997 @node GDB/MI Breakpoint Table Commands
16998 @section @sc{gdb/mi} Breakpoint table commands
17000 @cindex breakpoint commands for @sc{gdb/mi}
17001 @cindex @sc{gdb/mi}, breakpoint commands
17002 This section documents @sc{gdb/mi} commands for manipulating
17005 @subheading The @code{-break-after} Command
17006 @findex -break-after
17008 @subsubheading Synopsis
17011 -break-after @var{number} @var{count}
17014 The breakpoint number @var{number} is not in effect until it has been
17015 hit @var{count} times. To see how this is reflected in the output of
17016 the @samp{-break-list} command, see the description of the
17017 @samp{-break-list} command below.
17019 @subsubheading @value{GDBN} Command
17021 The corresponding @value{GDBN} command is @samp{ignore}.
17023 @subsubheading Example
17028 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",line="5"@}
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",times="0",
17049 @subheading The @code{-break-catch} Command
17050 @findex -break-catch
17052 @subheading The @code{-break-commands} Command
17053 @findex -break-commands
17057 @subheading The @code{-break-condition} Command
17058 @findex -break-condition
17060 @subsubheading Synopsis
17063 -break-condition @var{number} @var{expr}
17066 Breakpoint @var{number} will stop the program only if the condition in
17067 @var{expr} is true. The condition becomes part of the
17068 @samp{-break-list} output (see the description of the @samp{-break-list}
17071 @subsubheading @value{GDBN} Command
17073 The corresponding @value{GDBN} command is @samp{condition}.
17075 @subsubheading Example
17079 -break-condition 1 1
17083 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17084 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17085 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17086 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17087 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17088 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17089 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17090 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17091 addr="0x000100d0",func="main",file="hello.c",line="5",cond="1",
17092 times="0",ignore="3"@}]@}
17096 @subheading The @code{-break-delete} Command
17097 @findex -break-delete
17099 @subsubheading Synopsis
17102 -break-delete ( @var{breakpoint} )+
17105 Delete the breakpoint(s) whose number(s) are specified in the argument
17106 list. This is obviously reflected in the breakpoint list.
17108 @subsubheading @value{GDBN} command
17110 The corresponding @value{GDBN} command is @samp{delete}.
17112 @subsubheading Example
17120 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17121 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17122 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17123 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17124 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17125 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17126 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17131 @subheading The @code{-break-disable} Command
17132 @findex -break-disable
17134 @subsubheading Synopsis
17137 -break-disable ( @var{breakpoint} )+
17140 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
17141 break list is now set to @samp{n} for the named @var{breakpoint}(s).
17143 @subsubheading @value{GDBN} Command
17145 The corresponding @value{GDBN} command is @samp{disable}.
17147 @subsubheading Example
17155 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17156 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17157 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17158 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17159 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17160 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17161 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17162 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
17163 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
17167 @subheading The @code{-break-enable} Command
17168 @findex -break-enable
17170 @subsubheading Synopsis
17173 -break-enable ( @var{breakpoint} )+
17176 Enable (previously disabled) @var{breakpoint}(s).
17178 @subsubheading @value{GDBN} Command
17180 The corresponding @value{GDBN} command is @samp{enable}.
17182 @subsubheading Example
17190 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17191 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17192 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17193 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17194 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17195 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17196 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17197 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17198 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
17202 @subheading The @code{-break-info} Command
17203 @findex -break-info
17205 @subsubheading Synopsis
17208 -break-info @var{breakpoint}
17212 Get information about a single breakpoint.
17214 @subsubheading @value{GDBN} command
17216 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
17218 @subsubheading Example
17221 @subheading The @code{-break-insert} Command
17222 @findex -break-insert
17224 @subsubheading Synopsis
17227 -break-insert [ -t ] [ -h ] [ -r ]
17228 [ -c @var{condition} ] [ -i @var{ignore-count} ]
17229 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
17233 If specified, @var{line}, can be one of:
17240 @item filename:linenum
17241 @item filename:function
17245 The possible optional parameters of this command are:
17249 Insert a tempoary breakpoint.
17251 Insert a hardware breakpoint.
17252 @item -c @var{condition}
17253 Make the breakpoint conditional on @var{condition}.
17254 @item -i @var{ignore-count}
17255 Initialize the @var{ignore-count}.
17257 Insert a regular breakpoint in all the functions whose names match the
17258 given regular expression. Other flags are not applicable to regular
17262 @subsubheading Result
17264 The result is in the form:
17267 ^done,bkptno="@var{number}",func="@var{funcname}",
17268 file="@var{filename}",line="@var{lineno}"
17272 where @var{number} is the @value{GDBN} number for this breakpoint, @var{funcname}
17273 is the name of the function where the breakpoint was inserted,
17274 @var{filename} is the name of the source file which contains this
17275 function, and @var{lineno} is the source line number within that file.
17277 Note: this format is open to change.
17278 @c An out-of-band breakpoint instead of part of the result?
17280 @subsubheading @value{GDBN} Command
17282 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
17283 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
17285 @subsubheading Example
17290 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
17292 -break-insert -t foo
17293 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",line="11"@}
17296 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17297 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17298 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17299 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17300 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17301 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17302 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17303 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17304 addr="0x0001072c", func="main",file="recursive2.c",line="4",times="0"@},
17305 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
17306 addr="0x00010774",func="foo",file="recursive2.c",line="11",times="0"@}]@}
17308 -break-insert -r foo.*
17309 ~int foo(int, int);
17310 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c",line="11"@}
17314 @subheading The @code{-break-list} Command
17315 @findex -break-list
17317 @subsubheading Synopsis
17323 Displays the list of inserted breakpoints, showing the following fields:
17327 number of the breakpoint
17329 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
17331 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
17334 is the breakpoint enabled or no: @samp{y} or @samp{n}
17336 memory location at which the breakpoint is set
17338 logical location of the breakpoint, expressed by function name, file
17341 number of times the breakpoint has been hit
17344 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
17345 @code{body} field is an empty list.
17347 @subsubheading @value{GDBN} Command
17349 The corresponding @value{GDBN} command is @samp{info break}.
17351 @subsubheading Example
17356 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17357 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17358 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17359 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17360 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17361 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17362 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17363 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17364 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
17365 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17366 addr="0x00010114",func="foo",file="hello.c",line="13",times="0"@}]@}
17370 Here's an example of the result when there are no breakpoints:
17375 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17376 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17377 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17378 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17379 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17380 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17381 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17386 @subheading The @code{-break-watch} Command
17387 @findex -break-watch
17389 @subsubheading Synopsis
17392 -break-watch [ -a | -r ]
17395 Create a watchpoint. With the @samp{-a} option it will create an
17396 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
17397 read from or on a write to the memory location. With the @samp{-r}
17398 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
17399 trigger only when the memory location is accessed for reading. Without
17400 either of the options, the watchpoint created is a regular watchpoint,
17401 i.e. it will trigger when the memory location is accessed for writing.
17402 @xref{Set Watchpoints, , Setting watchpoints}.
17404 Note that @samp{-break-list} will report a single list of watchpoints and
17405 breakpoints inserted.
17407 @subsubheading @value{GDBN} Command
17409 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
17412 @subsubheading Example
17414 Setting a watchpoint on a variable in the @code{main} function:
17419 ^done,wpt=@{number="2",exp="x"@}
17423 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
17424 value=@{old="-268439212",new="55"@},
17425 frame=@{func="main",args=[],file="recursive2.c",line="5"@}
17429 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
17430 the program execution twice: first for the variable changing value, then
17431 for the watchpoint going out of scope.
17436 ^done,wpt=@{number="5",exp="C"@}
17440 ^done,reason="watchpoint-trigger",
17441 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
17442 frame=@{func="callee4",args=[],
17443 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
17447 ^done,reason="watchpoint-scope",wpnum="5",
17448 frame=@{func="callee3",args=[@{name="strarg",
17449 value="0x11940 \"A string argument.\""@}],
17450 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
17454 Listing breakpoints and watchpoints, at different points in the program
17455 execution. Note that once the watchpoint goes out of scope, it is
17461 ^done,wpt=@{number="2",exp="C"@}
17464 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17465 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17466 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17467 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17468 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17469 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17470 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17471 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17472 addr="0x00010734",func="callee4",
17473 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
17474 bkpt=@{number="2",type="watchpoint",disp="keep",
17475 enabled="y",addr="",what="C",times="0"@}]@}
17479 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
17480 value=@{old="-276895068",new="3"@},
17481 frame=@{func="callee4",args=[],
17482 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
17485 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17486 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17487 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17488 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17489 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17490 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17491 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17492 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17493 addr="0x00010734",func="callee4",
17494 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
17495 bkpt=@{number="2",type="watchpoint",disp="keep",
17496 enabled="y",addr="",what="C",times="-5"@}]@}
17500 ^done,reason="watchpoint-scope",wpnum="2",
17501 frame=@{func="callee3",args=[@{name="strarg",
17502 value="0x11940 \"A string argument.\""@}],
17503 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
17506 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17507 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17508 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17509 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17510 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17511 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17512 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17513 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17514 addr="0x00010734",func="callee4",
17515 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@}]@}
17519 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17520 @node GDB/MI Data Manipulation
17521 @section @sc{gdb/mi} Data Manipulation
17523 @cindex data manipulation, in @sc{gdb/mi}
17524 @cindex @sc{gdb/mi}, data manipulation
17525 This section describes the @sc{gdb/mi} commands that manipulate data:
17526 examine memory and registers, evaluate expressions, etc.
17528 @c REMOVED FROM THE INTERFACE.
17529 @c @subheading -data-assign
17530 @c Change the value of a program variable. Plenty of side effects.
17531 @c @subsubheading GDB command
17533 @c @subsubheading Example
17536 @subheading The @code{-data-disassemble} Command
17537 @findex -data-disassemble
17539 @subsubheading Synopsis
17543 [ -s @var{start-addr} -e @var{end-addr} ]
17544 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
17552 @item @var{start-addr}
17553 is the beginning address (or @code{$pc})
17554 @item @var{end-addr}
17556 @item @var{filename}
17557 is the name of the file to disassemble
17558 @item @var{linenum}
17559 is the line number to disassemble around
17561 is the the number of disassembly lines to be produced. If it is -1,
17562 the whole function will be disassembled, in case no @var{end-addr} is
17563 specified. If @var{end-addr} is specified as a non-zero value, and
17564 @var{lines} is lower than the number of disassembly lines between
17565 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
17566 displayed; if @var{lines} is higher than the number of lines between
17567 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
17570 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
17574 @subsubheading Result
17576 The output for each instruction is composed of four fields:
17585 Note that whatever included in the instruction field, is not manipulated
17586 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
17588 @subsubheading @value{GDBN} Command
17590 There's no direct mapping from this command to the CLI.
17592 @subsubheading Example
17594 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
17598 -data-disassemble -s $pc -e "$pc + 20" -- 0
17601 @{address="0x000107c0",func-name="main",offset="4",
17602 inst="mov 2, %o0"@},
17603 @{address="0x000107c4",func-name="main",offset="8",
17604 inst="sethi %hi(0x11800), %o2"@},
17605 @{address="0x000107c8",func-name="main",offset="12",
17606 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
17607 @{address="0x000107cc",func-name="main",offset="16",
17608 inst="sethi %hi(0x11800), %o2"@},
17609 @{address="0x000107d0",func-name="main",offset="20",
17610 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
17614 Disassemble the whole @code{main} function. Line 32 is part of
17618 -data-disassemble -f basics.c -l 32 -- 0
17620 @{address="0x000107bc",func-name="main",offset="0",
17621 inst="save %sp, -112, %sp"@},
17622 @{address="0x000107c0",func-name="main",offset="4",
17623 inst="mov 2, %o0"@},
17624 @{address="0x000107c4",func-name="main",offset="8",
17625 inst="sethi %hi(0x11800), %o2"@},
17627 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
17628 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
17632 Disassemble 3 instructions from the start of @code{main}:
17636 -data-disassemble -f basics.c -l 32 -n 3 -- 0
17638 @{address="0x000107bc",func-name="main",offset="0",
17639 inst="save %sp, -112, %sp"@},
17640 @{address="0x000107c0",func-name="main",offset="4",
17641 inst="mov 2, %o0"@},
17642 @{address="0x000107c4",func-name="main",offset="8",
17643 inst="sethi %hi(0x11800), %o2"@}]
17647 Disassemble 3 instructions from the start of @code{main} in mixed mode:
17651 -data-disassemble -f basics.c -l 32 -n 3 -- 1
17653 src_and_asm_line=@{line="31",
17654 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
17655 testsuite/gdb.mi/basics.c",line_asm_insn=[
17656 @{address="0x000107bc",func-name="main",offset="0",
17657 inst="save %sp, -112, %sp"@}]@},
17658 src_and_asm_line=@{line="32",
17659 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
17660 testsuite/gdb.mi/basics.c",line_asm_insn=[
17661 @{address="0x000107c0",func-name="main",offset="4",
17662 inst="mov 2, %o0"@},
17663 @{address="0x000107c4",func-name="main",offset="8",
17664 inst="sethi %hi(0x11800), %o2"@}]@}]
17669 @subheading The @code{-data-evaluate-expression} Command
17670 @findex -data-evaluate-expression
17672 @subsubheading Synopsis
17675 -data-evaluate-expression @var{expr}
17678 Evaluate @var{expr} as an expression. The expression could contain an
17679 inferior function call. The function call will execute synchronously.
17680 If the expression contains spaces, it must be enclosed in double quotes.
17682 @subsubheading @value{GDBN} Command
17684 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
17685 @samp{call}. In @code{gdbtk} only, there's a corresponding
17686 @samp{gdb_eval} command.
17688 @subsubheading Example
17690 In the following example, the numbers that precede the commands are the
17691 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
17692 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
17696 211-data-evaluate-expression A
17699 311-data-evaluate-expression &A
17700 311^done,value="0xefffeb7c"
17702 411-data-evaluate-expression A+3
17705 511-data-evaluate-expression "A + 3"
17711 @subheading The @code{-data-list-changed-registers} Command
17712 @findex -data-list-changed-registers
17714 @subsubheading Synopsis
17717 -data-list-changed-registers
17720 Display a list of the registers that have changed.
17722 @subsubheading @value{GDBN} Command
17724 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
17725 has the corresponding command @samp{gdb_changed_register_list}.
17727 @subsubheading Example
17729 On a PPC MBX board:
17737 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
17738 args=[],file="try.c",line="5"@}
17740 -data-list-changed-registers
17741 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
17742 "10","11","13","14","15","16","17","18","19","20","21","22","23",
17743 "24","25","26","27","28","30","31","64","65","66","67","69"]
17748 @subheading The @code{-data-list-register-names} Command
17749 @findex -data-list-register-names
17751 @subsubheading Synopsis
17754 -data-list-register-names [ ( @var{regno} )+ ]
17757 Show a list of register names for the current target. If no arguments
17758 are given, it shows a list of the names of all the registers. If
17759 integer numbers are given as arguments, it will print a list of the
17760 names of the registers corresponding to the arguments. To ensure
17761 consistency between a register name and its number, the output list may
17762 include empty register names.
17764 @subsubheading @value{GDBN} Command
17766 @value{GDBN} does not have a command which corresponds to
17767 @samp{-data-list-register-names}. In @code{gdbtk} there is a
17768 corresponding command @samp{gdb_regnames}.
17770 @subsubheading Example
17772 For the PPC MBX board:
17775 -data-list-register-names
17776 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
17777 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
17778 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
17779 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
17780 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
17781 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
17782 "", "pc","ps","cr","lr","ctr","xer"]
17784 -data-list-register-names 1 2 3
17785 ^done,register-names=["r1","r2","r3"]
17789 @subheading The @code{-data-list-register-values} Command
17790 @findex -data-list-register-values
17792 @subsubheading Synopsis
17795 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
17798 Display the registers' contents. @var{fmt} is the format according to
17799 which the registers' contents are to be returned, followed by an optional
17800 list of numbers specifying the registers to display. A missing list of
17801 numbers indicates that the contents of all the registers must be returned.
17803 Allowed formats for @var{fmt} are:
17820 @subsubheading @value{GDBN} Command
17822 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
17823 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
17825 @subsubheading Example
17827 For a PPC MBX board (note: line breaks are for readability only, they
17828 don't appear in the actual output):
17832 -data-list-register-values r 64 65
17833 ^done,register-values=[@{number="64",value="0xfe00a300"@},
17834 @{number="65",value="0x00029002"@}]
17836 -data-list-register-values x
17837 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
17838 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
17839 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
17840 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
17841 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
17842 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
17843 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
17844 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
17845 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
17846 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
17847 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
17848 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
17849 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
17850 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
17851 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
17852 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
17853 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
17854 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
17855 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
17856 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
17857 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
17858 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
17859 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
17860 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
17861 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
17862 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
17863 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
17864 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
17865 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
17866 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
17867 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
17868 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
17869 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
17870 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
17871 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
17872 @{number="69",value="0x20002b03"@}]
17877 @subheading The @code{-data-read-memory} Command
17878 @findex -data-read-memory
17880 @subsubheading Synopsis
17883 -data-read-memory [ -o @var{byte-offset} ]
17884 @var{address} @var{word-format} @var{word-size}
17885 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
17892 @item @var{address}
17893 An expression specifying the address of the first memory word to be
17894 read. Complex expressions containing embedded white space should be
17895 quoted using the C convention.
17897 @item @var{word-format}
17898 The format to be used to print the memory words. The notation is the
17899 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
17902 @item @var{word-size}
17903 The size of each memory word in bytes.
17905 @item @var{nr-rows}
17906 The number of rows in the output table.
17908 @item @var{nr-cols}
17909 The number of columns in the output table.
17912 If present, indicates that each row should include an @sc{ascii} dump. The
17913 value of @var{aschar} is used as a padding character when a byte is not a
17914 member of the printable @sc{ascii} character set (printable @sc{ascii}
17915 characters are those whose code is between 32 and 126, inclusively).
17917 @item @var{byte-offset}
17918 An offset to add to the @var{address} before fetching memory.
17921 This command displays memory contents as a table of @var{nr-rows} by
17922 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
17923 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
17924 (returned as @samp{total-bytes}). Should less than the requested number
17925 of bytes be returned by the target, the missing words are identified
17926 using @samp{N/A}. The number of bytes read from the target is returned
17927 in @samp{nr-bytes} and the starting address used to read memory in
17930 The address of the next/previous row or page is available in
17931 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
17934 @subsubheading @value{GDBN} Command
17936 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
17937 @samp{gdb_get_mem} memory read command.
17939 @subsubheading Example
17941 Read six bytes of memory starting at @code{bytes+6} but then offset by
17942 @code{-6} bytes. Format as three rows of two columns. One byte per
17943 word. Display each word in hex.
17947 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
17948 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
17949 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
17950 prev-page="0x0000138a",memory=[
17951 @{addr="0x00001390",data=["0x00","0x01"]@},
17952 @{addr="0x00001392",data=["0x02","0x03"]@},
17953 @{addr="0x00001394",data=["0x04","0x05"]@}]
17957 Read two bytes of memory starting at address @code{shorts + 64} and
17958 display as a single word formatted in decimal.
17962 5-data-read-memory shorts+64 d 2 1 1
17963 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
17964 next-row="0x00001512",prev-row="0x0000150e",
17965 next-page="0x00001512",prev-page="0x0000150e",memory=[
17966 @{addr="0x00001510",data=["128"]@}]
17970 Read thirty two bytes of memory starting at @code{bytes+16} and format
17971 as eight rows of four columns. Include a string encoding with @samp{x}
17972 used as the non-printable character.
17976 4-data-read-memory bytes+16 x 1 8 4 x
17977 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
17978 next-row="0x000013c0",prev-row="0x0000139c",
17979 next-page="0x000013c0",prev-page="0x00001380",memory=[
17980 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
17981 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
17982 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
17983 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
17984 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
17985 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
17986 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
17987 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
17991 @subheading The @code{-display-delete} Command
17992 @findex -display-delete
17994 @subsubheading Synopsis
17997 -display-delete @var{number}
18000 Delete the display @var{number}.
18002 @subsubheading @value{GDBN} Command
18004 The corresponding @value{GDBN} command is @samp{delete display}.
18006 @subsubheading Example
18010 @subheading The @code{-display-disable} Command
18011 @findex -display-disable
18013 @subsubheading Synopsis
18016 -display-disable @var{number}
18019 Disable display @var{number}.
18021 @subsubheading @value{GDBN} Command
18023 The corresponding @value{GDBN} command is @samp{disable display}.
18025 @subsubheading Example
18029 @subheading The @code{-display-enable} Command
18030 @findex -display-enable
18032 @subsubheading Synopsis
18035 -display-enable @var{number}
18038 Enable display @var{number}.
18040 @subsubheading @value{GDBN} Command
18042 The corresponding @value{GDBN} command is @samp{enable display}.
18044 @subsubheading Example
18048 @subheading The @code{-display-insert} Command
18049 @findex -display-insert
18051 @subsubheading Synopsis
18054 -display-insert @var{expression}
18057 Display @var{expression} every time the program stops.
18059 @subsubheading @value{GDBN} Command
18061 The corresponding @value{GDBN} command is @samp{display}.
18063 @subsubheading Example
18067 @subheading The @code{-display-list} Command
18068 @findex -display-list
18070 @subsubheading Synopsis
18076 List the displays. Do not show the current values.
18078 @subsubheading @value{GDBN} Command
18080 The corresponding @value{GDBN} command is @samp{info display}.
18082 @subsubheading Example
18086 @subheading The @code{-environment-cd} Command
18087 @findex -environment-cd
18089 @subsubheading Synopsis
18092 -environment-cd @var{pathdir}
18095 Set @value{GDBN}'s working directory.
18097 @subsubheading @value{GDBN} Command
18099 The corresponding @value{GDBN} command is @samp{cd}.
18101 @subsubheading Example
18105 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18111 @subheading The @code{-environment-directory} Command
18112 @findex -environment-directory
18114 @subsubheading Synopsis
18117 -environment-directory [ -r ] [ @var{pathdir} ]+
18120 Add directories @var{pathdir} to beginning of search path for source files.
18121 If the @samp{-r} option is used, the search path is reset to the default
18122 search path. If directories @var{pathdir} are supplied in addition to the
18123 @samp{-r} option, the search path is first reset and then addition
18125 Multiple directories may be specified, separated by blanks. Specifying
18126 multiple directories in a single command
18127 results in the directories added to the beginning of the
18128 search path in the same order they were presented in the command.
18129 If blanks are needed as
18130 part of a directory name, double-quotes should be used around
18131 the name. In the command output, the path will show up separated
18132 by the system directory-separator character. The directory-seperator
18133 character must not be used
18134 in any directory name.
18135 If no directories are specified, the current search path is displayed.
18137 @subsubheading @value{GDBN} Command
18139 The corresponding @value{GDBN} command is @samp{dir}.
18141 @subsubheading Example
18145 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18146 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18148 -environment-directory ""
18149 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18151 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
18152 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
18154 -environment-directory -r
18155 ^done,source-path="$cdir:$cwd"
18160 @subheading The @code{-environment-path} Command
18161 @findex -environment-path
18163 @subsubheading Synopsis
18166 -environment-path [ -r ] [ @var{pathdir} ]+
18169 Add directories @var{pathdir} to beginning of search path for object files.
18170 If the @samp{-r} option is used, the search path is reset to the original
18171 search path that existed at gdb start-up. If directories @var{pathdir} are
18172 supplied in addition to the
18173 @samp{-r} option, the search path is first reset and then addition
18175 Multiple directories may be specified, separated by blanks. Specifying
18176 multiple directories in a single command
18177 results in the directories added to the beginning of the
18178 search path in the same order they were presented in the command.
18179 If blanks are needed as
18180 part of a directory name, double-quotes should be used around
18181 the name. In the command output, the path will show up separated
18182 by the system directory-separator character. The directory-seperator
18183 character must not be used
18184 in any directory name.
18185 If no directories are specified, the current path is displayed.
18188 @subsubheading @value{GDBN} Command
18190 The corresponding @value{GDBN} command is @samp{path}.
18192 @subsubheading Example
18197 ^done,path="/usr/bin"
18199 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
18200 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
18202 -environment-path -r /usr/local/bin
18203 ^done,path="/usr/local/bin:/usr/bin"
18208 @subheading The @code{-environment-pwd} Command
18209 @findex -environment-pwd
18211 @subsubheading Synopsis
18217 Show the current working directory.
18219 @subsubheading @value{GDBN} command
18221 The corresponding @value{GDBN} command is @samp{pwd}.
18223 @subsubheading Example
18228 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
18232 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18233 @node GDB/MI Program Control
18234 @section @sc{gdb/mi} Program control
18236 @subsubheading Program termination
18238 As a result of execution, the inferior program can run to completion, if
18239 it doesn't encounter any breakpoints. In this case the output will
18240 include an exit code, if the program has exited exceptionally.
18242 @subsubheading Examples
18245 Program exited normally:
18253 *stopped,reason="exited-normally"
18258 Program exited exceptionally:
18266 *stopped,reason="exited",exit-code="01"
18270 Another way the program can terminate is if it receives a signal such as
18271 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
18275 *stopped,reason="exited-signalled",signal-name="SIGINT",
18276 signal-meaning="Interrupt"
18280 @subheading The @code{-exec-abort} Command
18281 @findex -exec-abort
18283 @subsubheading Synopsis
18289 Kill the inferior running program.
18291 @subsubheading @value{GDBN} Command
18293 The corresponding @value{GDBN} command is @samp{kill}.
18295 @subsubheading Example
18299 @subheading The @code{-exec-arguments} Command
18300 @findex -exec-arguments
18302 @subsubheading Synopsis
18305 -exec-arguments @var{args}
18308 Set the inferior program arguments, to be used in the next
18311 @subsubheading @value{GDBN} Command
18313 The corresponding @value{GDBN} command is @samp{set args}.
18315 @subsubheading Example
18318 Don't have one around.
18321 @subheading The @code{-exec-continue} Command
18322 @findex -exec-continue
18324 @subsubheading Synopsis
18330 Asynchronous command. Resumes the execution of the inferior program
18331 until a breakpoint is encountered, or until the inferior exits.
18333 @subsubheading @value{GDBN} Command
18335 The corresponding @value{GDBN} corresponding is @samp{continue}.
18337 @subsubheading Example
18344 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
18345 file="hello.c",line="13"@}
18350 @subheading The @code{-exec-finish} Command
18351 @findex -exec-finish
18353 @subsubheading Synopsis
18359 Asynchronous command. Resumes the execution of the inferior program
18360 until the current function is exited. Displays the results returned by
18363 @subsubheading @value{GDBN} Command
18365 The corresponding @value{GDBN} command is @samp{finish}.
18367 @subsubheading Example
18369 Function returning @code{void}.
18376 *stopped,reason="function-finished",frame=@{func="main",args=[],
18377 file="hello.c",line="7"@}
18381 Function returning other than @code{void}. The name of the internal
18382 @value{GDBN} variable storing the result is printed, together with the
18389 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
18390 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
18391 file="recursive2.c",line="14"@},
18392 gdb-result-var="$1",return-value="0"
18397 @subheading The @code{-exec-interrupt} Command
18398 @findex -exec-interrupt
18400 @subsubheading Synopsis
18406 Asynchronous command. Interrupts the background execution of the target.
18407 Note how the token associated with the stop message is the one for the
18408 execution command that has been interrupted. The token for the interrupt
18409 itself only appears in the @samp{^done} output. If the user is trying to
18410 interrupt a non-running program, an error message will be printed.
18412 @subsubheading @value{GDBN} Command
18414 The corresponding @value{GDBN} command is @samp{interrupt}.
18416 @subsubheading Example
18427 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
18428 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",line="13"@}
18433 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
18438 @subheading The @code{-exec-next} Command
18441 @subsubheading Synopsis
18447 Asynchronous command. Resumes execution of the inferior program, stopping
18448 when the beginning of the next source line is reached.
18450 @subsubheading @value{GDBN} Command
18452 The corresponding @value{GDBN} command is @samp{next}.
18454 @subsubheading Example
18460 *stopped,reason="end-stepping-range",line="8",file="hello.c"
18465 @subheading The @code{-exec-next-instruction} Command
18466 @findex -exec-next-instruction
18468 @subsubheading Synopsis
18471 -exec-next-instruction
18474 Asynchronous command. Executes one machine instruction. If the
18475 instruction is a function call continues until the function returns. If
18476 the program stops at an instruction in the middle of a source line, the
18477 address will be printed as well.
18479 @subsubheading @value{GDBN} Command
18481 The corresponding @value{GDBN} command is @samp{nexti}.
18483 @subsubheading Example
18487 -exec-next-instruction
18491 *stopped,reason="end-stepping-range",
18492 addr="0x000100d4",line="5",file="hello.c"
18497 @subheading The @code{-exec-return} Command
18498 @findex -exec-return
18500 @subsubheading Synopsis
18506 Makes current function return immediately. Doesn't execute the inferior.
18507 Displays the new current frame.
18509 @subsubheading @value{GDBN} Command
18511 The corresponding @value{GDBN} command is @samp{return}.
18513 @subsubheading Example
18517 200-break-insert callee4
18518 200^done,bkpt=@{number="1",addr="0x00010734",
18519 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18524 000*stopped,reason="breakpoint-hit",bkptno="1",
18525 frame=@{func="callee4",args=[],
18526 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18532 111^done,frame=@{level="0",func="callee3",
18533 args=[@{name="strarg",
18534 value="0x11940 \"A string argument.\""@}],
18535 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18540 @subheading The @code{-exec-run} Command
18543 @subsubheading Synopsis
18549 Asynchronous command. Starts execution of the inferior from the
18550 beginning. The inferior executes until either a breakpoint is
18551 encountered or the program exits.
18553 @subsubheading @value{GDBN} Command
18555 The corresponding @value{GDBN} command is @samp{run}.
18557 @subsubheading Example
18562 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
18567 *stopped,reason="breakpoint-hit",bkptno="1",
18568 frame=@{func="main",args=[],file="recursive2.c",line="4"@}
18573 @subheading The @code{-exec-show-arguments} Command
18574 @findex -exec-show-arguments
18576 @subsubheading Synopsis
18579 -exec-show-arguments
18582 Print the arguments of the program.
18584 @subsubheading @value{GDBN} Command
18586 The corresponding @value{GDBN} command is @samp{show args}.
18588 @subsubheading Example
18591 @c @subheading -exec-signal
18593 @subheading The @code{-exec-step} Command
18596 @subsubheading Synopsis
18602 Asynchronous command. Resumes execution of the inferior program, stopping
18603 when the beginning of the next source line is reached, if the next
18604 source line is not a function call. If it is, stop at the first
18605 instruction of the called function.
18607 @subsubheading @value{GDBN} Command
18609 The corresponding @value{GDBN} command is @samp{step}.
18611 @subsubheading Example
18613 Stepping into a function:
18619 *stopped,reason="end-stepping-range",
18620 frame=@{func="foo",args=[@{name="a",value="10"@},
18621 @{name="b",value="0"@}],file="recursive2.c",line="11"@}
18631 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
18636 @subheading The @code{-exec-step-instruction} Command
18637 @findex -exec-step-instruction
18639 @subsubheading Synopsis
18642 -exec-step-instruction
18645 Asynchronous command. Resumes the inferior which executes one machine
18646 instruction. The output, once @value{GDBN} has stopped, will vary depending on
18647 whether we have stopped in the middle of a source line or not. In the
18648 former case, the address at which the program stopped will be printed as
18651 @subsubheading @value{GDBN} Command
18653 The corresponding @value{GDBN} command is @samp{stepi}.
18655 @subsubheading Example
18659 -exec-step-instruction
18663 *stopped,reason="end-stepping-range",
18664 frame=@{func="foo",args=[],file="try.c",line="10"@}
18666 -exec-step-instruction
18670 *stopped,reason="end-stepping-range",
18671 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",line="10"@}
18676 @subheading The @code{-exec-until} Command
18677 @findex -exec-until
18679 @subsubheading Synopsis
18682 -exec-until [ @var{location} ]
18685 Asynchronous command. Executes the inferior until the @var{location}
18686 specified in the argument is reached. If there is no argument, the inferior
18687 executes until a source line greater than the current one is reached.
18688 The reason for stopping in this case will be @samp{location-reached}.
18690 @subsubheading @value{GDBN} Command
18692 The corresponding @value{GDBN} command is @samp{until}.
18694 @subsubheading Example
18698 -exec-until recursive2.c:6
18702 *stopped,reason="location-reached",frame=@{func="main",args=[],
18703 file="recursive2.c",line="6"@}
18708 @subheading -file-clear
18709 Is this going away????
18713 @subheading The @code{-file-exec-and-symbols} Command
18714 @findex -file-exec-and-symbols
18716 @subsubheading Synopsis
18719 -file-exec-and-symbols @var{file}
18722 Specify the executable file to be debugged. This file is the one from
18723 which the symbol table is also read. If no file is specified, the
18724 command clears the executable and symbol information. If breakpoints
18725 are set when using this command with no arguments, @value{GDBN} will produce
18726 error messages. Otherwise, no output is produced, except a completion
18729 @subsubheading @value{GDBN} Command
18731 The corresponding @value{GDBN} command is @samp{file}.
18733 @subsubheading Example
18737 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18743 @subheading The @code{-file-exec-file} Command
18744 @findex -file-exec-file
18746 @subsubheading Synopsis
18749 -file-exec-file @var{file}
18752 Specify the executable file to be debugged. Unlike
18753 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
18754 from this file. If used without argument, @value{GDBN} clears the information
18755 about the executable file. No output is produced, except a completion
18758 @subsubheading @value{GDBN} Command
18760 The corresponding @value{GDBN} command is @samp{exec-file}.
18762 @subsubheading Example
18766 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18772 @subheading The @code{-file-list-exec-sections} Command
18773 @findex -file-list-exec-sections
18775 @subsubheading Synopsis
18778 -file-list-exec-sections
18781 List the sections of the current executable file.
18783 @subsubheading @value{GDBN} Command
18785 The @value{GDBN} command @samp{info file} shows, among the rest, the same
18786 information as this command. @code{gdbtk} has a corresponding command
18787 @samp{gdb_load_info}.
18789 @subsubheading Example
18793 @subheading The @code{-file-list-exec-source-file} Command
18794 @findex -file-list-exec-source-file
18796 @subsubheading Synopsis
18799 -file-list-exec-source-file
18802 List the line number, the current source file, and the absolute path
18803 to the current source file for the current executable.
18805 @subsubheading @value{GDBN} Command
18807 There's no @value{GDBN} command which directly corresponds to this one.
18809 @subsubheading Example
18813 123-file-list-exec-source-file
18814 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
18819 @subheading The @code{-file-list-exec-source-files} Command
18820 @findex -file-list-exec-source-files
18822 @subsubheading Synopsis
18825 -file-list-exec-source-files
18828 List the source files for the current executable.
18830 It will always output the filename, but only when GDB can find the absolute
18831 file name of a source file, will it output the fullname.
18833 @subsubheading @value{GDBN} Command
18835 There's no @value{GDBN} command which directly corresponds to this one.
18836 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
18838 @subsubheading Example
18841 -file-list-exec-source-files
18843 @{file=foo.c,fullname=/home/foo.c@},
18844 @{file=/home/bar.c,fullname=/home/bar.c@},
18845 @{file=gdb_could_not_find_fullpath.c@}]
18849 @subheading The @code{-file-list-shared-libraries} Command
18850 @findex -file-list-shared-libraries
18852 @subsubheading Synopsis
18855 -file-list-shared-libraries
18858 List the shared libraries in the program.
18860 @subsubheading @value{GDBN} Command
18862 The corresponding @value{GDBN} command is @samp{info shared}.
18864 @subsubheading Example
18868 @subheading The @code{-file-list-symbol-files} Command
18869 @findex -file-list-symbol-files
18871 @subsubheading Synopsis
18874 -file-list-symbol-files
18879 @subsubheading @value{GDBN} Command
18881 The corresponding @value{GDBN} command is @samp{info file} (part of it).
18883 @subsubheading Example
18887 @subheading The @code{-file-symbol-file} Command
18888 @findex -file-symbol-file
18890 @subsubheading Synopsis
18893 -file-symbol-file @var{file}
18896 Read symbol table info from the specified @var{file} argument. When
18897 used without arguments, clears @value{GDBN}'s symbol table info. No output is
18898 produced, except for a completion notification.
18900 @subsubheading @value{GDBN} Command
18902 The corresponding @value{GDBN} command is @samp{symbol-file}.
18904 @subsubheading Example
18908 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18913 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18914 @node GDB/MI Miscellaneous Commands
18915 @section Miscellaneous @value{GDBN} commands in @sc{gdb/mi}
18917 @c @subheading -gdb-complete
18919 @subheading The @code{-gdb-exit} Command
18922 @subsubheading Synopsis
18928 Exit @value{GDBN} immediately.
18930 @subsubheading @value{GDBN} Command
18932 Approximately corresponds to @samp{quit}.
18934 @subsubheading Example
18941 @subheading The @code{-gdb-set} Command
18944 @subsubheading Synopsis
18950 Set an internal @value{GDBN} variable.
18951 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
18953 @subsubheading @value{GDBN} Command
18955 The corresponding @value{GDBN} command is @samp{set}.
18957 @subsubheading Example
18967 @subheading The @code{-gdb-show} Command
18970 @subsubheading Synopsis
18976 Show the current value of a @value{GDBN} variable.
18978 @subsubheading @value{GDBN} command
18980 The corresponding @value{GDBN} command is @samp{show}.
18982 @subsubheading Example
18991 @c @subheading -gdb-source
18994 @subheading The @code{-gdb-version} Command
18995 @findex -gdb-version
18997 @subsubheading Synopsis
19003 Show version information for @value{GDBN}. Used mostly in testing.
19005 @subsubheading @value{GDBN} Command
19007 There's no equivalent @value{GDBN} command. @value{GDBN} by default shows this
19008 information when you start an interactive session.
19010 @subsubheading Example
19012 @c This example modifies the actual output from GDB to avoid overfull
19018 ~Copyright 2000 Free Software Foundation, Inc.
19019 ~GDB is free software, covered by the GNU General Public License, and
19020 ~you are welcome to change it and/or distribute copies of it under
19021 ~ certain conditions.
19022 ~Type "show copying" to see the conditions.
19023 ~There is absolutely no warranty for GDB. Type "show warranty" for
19025 ~This GDB was configured as
19026 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
19031 @subheading The @code{-interpreter-exec} Command
19032 @findex -interpreter-exec
19034 @subheading Synopsis
19037 -interpreter-exec @var{interpreter} @var{command}
19040 Execute the specified @var{command} in the given @var{interpreter}.
19042 @subheading @value{GDBN} Command
19044 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
19046 @subheading Example
19050 -interpreter-exec console "break main"
19051 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
19052 &"During symbol reading, bad structure-type format.\n"
19053 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
19059 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19060 @node GDB/MI Kod Commands
19061 @section @sc{gdb/mi} Kod Commands
19063 The Kod commands are not implemented.
19065 @c @subheading -kod-info
19067 @c @subheading -kod-list
19069 @c @subheading -kod-list-object-types
19071 @c @subheading -kod-show
19073 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19074 @node GDB/MI Memory Overlay Commands
19075 @section @sc{gdb/mi} Memory Overlay Commands
19077 The memory overlay commands are not implemented.
19079 @c @subheading -overlay-auto
19081 @c @subheading -overlay-list-mapping-state
19083 @c @subheading -overlay-list-overlays
19085 @c @subheading -overlay-map
19087 @c @subheading -overlay-off
19089 @c @subheading -overlay-on
19091 @c @subheading -overlay-unmap
19093 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19094 @node GDB/MI Signal Handling Commands
19095 @section @sc{gdb/mi} Signal Handling Commands
19097 Signal handling commands are not implemented.
19099 @c @subheading -signal-handle
19101 @c @subheading -signal-list-handle-actions
19103 @c @subheading -signal-list-signal-types
19107 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19108 @node GDB/MI Stack Manipulation
19109 @section @sc{gdb/mi} Stack Manipulation Commands
19112 @subheading The @code{-stack-info-frame} Command
19113 @findex -stack-info-frame
19115 @subsubheading Synopsis
19121 Get info on the current frame.
19123 @subsubheading @value{GDBN} Command
19125 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
19126 (without arguments).
19128 @subsubheading Example
19131 @subheading The @code{-stack-info-depth} Command
19132 @findex -stack-info-depth
19134 @subsubheading Synopsis
19137 -stack-info-depth [ @var{max-depth} ]
19140 Return the depth of the stack. If the integer argument @var{max-depth}
19141 is specified, do not count beyond @var{max-depth} frames.
19143 @subsubheading @value{GDBN} Command
19145 There's no equivalent @value{GDBN} command.
19147 @subsubheading Example
19149 For a stack with frame levels 0 through 11:
19156 -stack-info-depth 4
19159 -stack-info-depth 12
19162 -stack-info-depth 11
19165 -stack-info-depth 13
19170 @subheading The @code{-stack-list-arguments} Command
19171 @findex -stack-list-arguments
19173 @subsubheading Synopsis
19176 -stack-list-arguments @var{show-values}
19177 [ @var{low-frame} @var{high-frame} ]
19180 Display a list of the arguments for the frames between @var{low-frame}
19181 and @var{high-frame} (inclusive). If @var{low-frame} and
19182 @var{high-frame} are not provided, list the arguments for the whole call
19185 The @var{show-values} argument must have a value of 0 or 1. A value of
19186 0 means that only the names of the arguments are listed, a value of 1
19187 means that both names and values of the arguments are printed.
19189 @subsubheading @value{GDBN} Command
19191 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19192 @samp{gdb_get_args} command which partially overlaps with the
19193 functionality of @samp{-stack-list-arguments}.
19195 @subsubheading Example
19202 frame=@{level="0",addr="0x00010734",func="callee4",
19203 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19204 frame=@{level="1",addr="0x0001076c",func="callee3",
19205 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19206 frame=@{level="2",addr="0x0001078c",func="callee2",
19207 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19208 frame=@{level="3",addr="0x000107b4",func="callee1",
19209 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19210 frame=@{level="4",addr="0x000107e0",func="main",
19211 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19213 -stack-list-arguments 0
19216 frame=@{level="0",args=[]@},
19217 frame=@{level="1",args=[name="strarg"]@},
19218 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19219 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19220 frame=@{level="4",args=[]@}]
19222 -stack-list-arguments 1
19225 frame=@{level="0",args=[]@},
19227 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19228 frame=@{level="2",args=[
19229 @{name="intarg",value="2"@},
19230 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19231 @{frame=@{level="3",args=[
19232 @{name="intarg",value="2"@},
19233 @{name="strarg",value="0x11940 \"A string argument.\""@},
19234 @{name="fltarg",value="3.5"@}]@},
19235 frame=@{level="4",args=[]@}]
19237 -stack-list-arguments 0 2 2
19238 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19240 -stack-list-arguments 1 2 2
19241 ^done,stack-args=[frame=@{level="2",
19242 args=[@{name="intarg",value="2"@},
19243 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19247 @c @subheading -stack-list-exception-handlers
19250 @subheading The @code{-stack-list-frames} Command
19251 @findex -stack-list-frames
19253 @subsubheading Synopsis
19256 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19259 List the frames currently on the stack. For each frame it displays the
19264 The frame number, 0 being the topmost frame, i.e. the innermost function.
19266 The @code{$pc} value for that frame.
19270 File name of the source file where the function lives.
19272 Line number corresponding to the @code{$pc}.
19275 If invoked without arguments, this command prints a backtrace for the
19276 whole stack. If given two integer arguments, it shows the frames whose
19277 levels are between the two arguments (inclusive). If the two arguments
19278 are equal, it shows the single frame at the corresponding level.
19280 @subsubheading @value{GDBN} Command
19282 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19284 @subsubheading Example
19286 Full stack backtrace:
19292 [frame=@{level="0",addr="0x0001076c",func="foo",
19293 file="recursive2.c",line="11"@},
19294 frame=@{level="1",addr="0x000107a4",func="foo",
19295 file="recursive2.c",line="14"@},
19296 frame=@{level="2",addr="0x000107a4",func="foo",
19297 file="recursive2.c",line="14"@},
19298 frame=@{level="3",addr="0x000107a4",func="foo",
19299 file="recursive2.c",line="14"@},
19300 frame=@{level="4",addr="0x000107a4",func="foo",
19301 file="recursive2.c",line="14"@},
19302 frame=@{level="5",addr="0x000107a4",func="foo",
19303 file="recursive2.c",line="14"@},
19304 frame=@{level="6",addr="0x000107a4",func="foo",
19305 file="recursive2.c",line="14"@},
19306 frame=@{level="7",addr="0x000107a4",func="foo",
19307 file="recursive2.c",line="14"@},
19308 frame=@{level="8",addr="0x000107a4",func="foo",
19309 file="recursive2.c",line="14"@},
19310 frame=@{level="9",addr="0x000107a4",func="foo",
19311 file="recursive2.c",line="14"@},
19312 frame=@{level="10",addr="0x000107a4",func="foo",
19313 file="recursive2.c",line="14"@},
19314 frame=@{level="11",addr="0x00010738",func="main",
19315 file="recursive2.c",line="4"@}]
19319 Show frames between @var{low_frame} and @var{high_frame}:
19323 -stack-list-frames 3 5
19325 [frame=@{level="3",addr="0x000107a4",func="foo",
19326 file="recursive2.c",line="14"@},
19327 frame=@{level="4",addr="0x000107a4",func="foo",
19328 file="recursive2.c",line="14"@},
19329 frame=@{level="5",addr="0x000107a4",func="foo",
19330 file="recursive2.c",line="14"@}]
19334 Show a single frame:
19338 -stack-list-frames 3 3
19340 [frame=@{level="3",addr="0x000107a4",func="foo",
19341 file="recursive2.c",line="14"@}]
19346 @subheading The @code{-stack-list-locals} Command
19347 @findex -stack-list-locals
19349 @subsubheading Synopsis
19352 -stack-list-locals @var{print-values}
19355 Display the local variable names for the current frame. With an
19356 argument of 0 or @code{--no-values}, prints only the names of the variables.
19357 With argument of 1 or @code{--all-values}, prints also their values. With
19358 argument of 2 or @code{--simple-values}, prints the name, type and value for
19359 simple data types and the name and type for arrays, structures and
19360 unions. In this last case, the idea is that the user can see the
19361 value of simple data types immediately and he can create variable
19362 objects for other data types if he wishes to explore their values in
19365 @subsubheading @value{GDBN} Command
19367 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
19369 @subsubheading Example
19373 -stack-list-locals 0
19374 ^done,locals=[name="A",name="B",name="C"]
19376 -stack-list-locals --all-values
19377 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
19378 @{name="C",value="@{1, 2, 3@}"@}]
19379 -stack-list-locals --simple-values
19380 ^done,locals=[@{name="A",type="int",value="1"@},
19381 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
19386 @subheading The @code{-stack-select-frame} Command
19387 @findex -stack-select-frame
19389 @subsubheading Synopsis
19392 -stack-select-frame @var{framenum}
19395 Change the current frame. Select a different frame @var{framenum} on
19398 @subsubheading @value{GDBN} Command
19400 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
19401 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
19403 @subsubheading Example
19407 -stack-select-frame 2
19412 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19413 @node GDB/MI Symbol Query
19414 @section @sc{gdb/mi} Symbol Query Commands
19417 @subheading The @code{-symbol-info-address} Command
19418 @findex -symbol-info-address
19420 @subsubheading Synopsis
19423 -symbol-info-address @var{symbol}
19426 Describe where @var{symbol} is stored.
19428 @subsubheading @value{GDBN} Command
19430 The corresponding @value{GDBN} command is @samp{info address}.
19432 @subsubheading Example
19436 @subheading The @code{-symbol-info-file} Command
19437 @findex -symbol-info-file
19439 @subsubheading Synopsis
19445 Show the file for the symbol.
19447 @subsubheading @value{GDBN} Command
19449 There's no equivalent @value{GDBN} command. @code{gdbtk} has
19450 @samp{gdb_find_file}.
19452 @subsubheading Example
19456 @subheading The @code{-symbol-info-function} Command
19457 @findex -symbol-info-function
19459 @subsubheading Synopsis
19462 -symbol-info-function
19465 Show which function the symbol lives in.
19467 @subsubheading @value{GDBN} Command
19469 @samp{gdb_get_function} in @code{gdbtk}.
19471 @subsubheading Example
19475 @subheading The @code{-symbol-info-line} Command
19476 @findex -symbol-info-line
19478 @subsubheading Synopsis
19484 Show the core addresses of the code for a source line.
19486 @subsubheading @value{GDBN} Command
19488 The corresponding @value{GDBN} command is @samp{info line}.
19489 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
19491 @subsubheading Example
19495 @subheading The @code{-symbol-info-symbol} Command
19496 @findex -symbol-info-symbol
19498 @subsubheading Synopsis
19501 -symbol-info-symbol @var{addr}
19504 Describe what symbol is at location @var{addr}.
19506 @subsubheading @value{GDBN} Command
19508 The corresponding @value{GDBN} command is @samp{info symbol}.
19510 @subsubheading Example
19514 @subheading The @code{-symbol-list-functions} Command
19515 @findex -symbol-list-functions
19517 @subsubheading Synopsis
19520 -symbol-list-functions
19523 List the functions in the executable.
19525 @subsubheading @value{GDBN} Command
19527 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
19528 @samp{gdb_search} in @code{gdbtk}.
19530 @subsubheading Example
19534 @subheading The @code{-symbol-list-lines} Command
19535 @findex -symbol-list-lines
19537 @subsubheading Synopsis
19540 -symbol-list-lines @var{filename}
19543 Print the list of lines that contain code and their associated program
19544 addresses for the given source filename. The entries are sorted in
19545 ascending PC order.
19547 @subsubheading @value{GDBN} Command
19549 There is no corresponding @value{GDBN} command.
19551 @subsubheading Example
19554 -symbol-list-lines basics.c
19555 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
19560 @subheading The @code{-symbol-list-types} Command
19561 @findex -symbol-list-types
19563 @subsubheading Synopsis
19569 List all the type names.
19571 @subsubheading @value{GDBN} Command
19573 The corresponding commands are @samp{info types} in @value{GDBN},
19574 @samp{gdb_search} in @code{gdbtk}.
19576 @subsubheading Example
19580 @subheading The @code{-symbol-list-variables} Command
19581 @findex -symbol-list-variables
19583 @subsubheading Synopsis
19586 -symbol-list-variables
19589 List all the global and static variable names.
19591 @subsubheading @value{GDBN} Command
19593 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
19595 @subsubheading Example
19599 @subheading The @code{-symbol-locate} Command
19600 @findex -symbol-locate
19602 @subsubheading Synopsis
19608 @subsubheading @value{GDBN} Command
19610 @samp{gdb_loc} in @code{gdbtk}.
19612 @subsubheading Example
19616 @subheading The @code{-symbol-type} Command
19617 @findex -symbol-type
19619 @subsubheading Synopsis
19622 -symbol-type @var{variable}
19625 Show type of @var{variable}.
19627 @subsubheading @value{GDBN} Command
19629 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
19630 @samp{gdb_obj_variable}.
19632 @subsubheading Example
19636 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19637 @node GDB/MI Target Manipulation
19638 @section @sc{gdb/mi} Target Manipulation Commands
19641 @subheading The @code{-target-attach} Command
19642 @findex -target-attach
19644 @subsubheading Synopsis
19647 -target-attach @var{pid} | @var{file}
19650 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
19652 @subsubheading @value{GDBN} command
19654 The corresponding @value{GDBN} command is @samp{attach}.
19656 @subsubheading Example
19660 @subheading The @code{-target-compare-sections} Command
19661 @findex -target-compare-sections
19663 @subsubheading Synopsis
19666 -target-compare-sections [ @var{section} ]
19669 Compare data of section @var{section} on target to the exec file.
19670 Without the argument, all sections are compared.
19672 @subsubheading @value{GDBN} Command
19674 The @value{GDBN} equivalent is @samp{compare-sections}.
19676 @subsubheading Example
19680 @subheading The @code{-target-detach} Command
19681 @findex -target-detach
19683 @subsubheading Synopsis
19689 Disconnect from the remote target. There's no output.
19691 @subsubheading @value{GDBN} command
19693 The corresponding @value{GDBN} command is @samp{detach}.
19695 @subsubheading Example
19705 @subheading The @code{-target-disconnect} Command
19706 @findex -target-disconnect
19708 @subsubheading Synopsis
19714 Disconnect from the remote target. There's no output.
19716 @subsubheading @value{GDBN} command
19718 The corresponding @value{GDBN} command is @samp{disconnect}.
19720 @subsubheading Example
19730 @subheading The @code{-target-download} Command
19731 @findex -target-download
19733 @subsubheading Synopsis
19739 Loads the executable onto the remote target.
19740 It prints out an update message every half second, which includes the fields:
19744 The name of the section.
19746 The size of what has been sent so far for that section.
19748 The size of the section.
19750 The total size of what was sent so far (the current and the previous sections).
19752 The size of the overall executable to download.
19756 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
19757 @sc{gdb/mi} Output Syntax}).
19759 In addition, it prints the name and size of the sections, as they are
19760 downloaded. These messages include the following fields:
19764 The name of the section.
19766 The size of the section.
19768 The size of the overall executable to download.
19772 At the end, a summary is printed.
19774 @subsubheading @value{GDBN} Command
19776 The corresponding @value{GDBN} command is @samp{load}.
19778 @subsubheading Example
19780 Note: each status message appears on a single line. Here the messages
19781 have been broken down so that they can fit onto a page.
19786 +download,@{section=".text",section-size="6668",total-size="9880"@}
19787 +download,@{section=".text",section-sent="512",section-size="6668",
19788 total-sent="512",total-size="9880"@}
19789 +download,@{section=".text",section-sent="1024",section-size="6668",
19790 total-sent="1024",total-size="9880"@}
19791 +download,@{section=".text",section-sent="1536",section-size="6668",
19792 total-sent="1536",total-size="9880"@}
19793 +download,@{section=".text",section-sent="2048",section-size="6668",
19794 total-sent="2048",total-size="9880"@}
19795 +download,@{section=".text",section-sent="2560",section-size="6668",
19796 total-sent="2560",total-size="9880"@}
19797 +download,@{section=".text",section-sent="3072",section-size="6668",
19798 total-sent="3072",total-size="9880"@}
19799 +download,@{section=".text",section-sent="3584",section-size="6668",
19800 total-sent="3584",total-size="9880"@}
19801 +download,@{section=".text",section-sent="4096",section-size="6668",
19802 total-sent="4096",total-size="9880"@}
19803 +download,@{section=".text",section-sent="4608",section-size="6668",
19804 total-sent="4608",total-size="9880"@}
19805 +download,@{section=".text",section-sent="5120",section-size="6668",
19806 total-sent="5120",total-size="9880"@}
19807 +download,@{section=".text",section-sent="5632",section-size="6668",
19808 total-sent="5632",total-size="9880"@}
19809 +download,@{section=".text",section-sent="6144",section-size="6668",
19810 total-sent="6144",total-size="9880"@}
19811 +download,@{section=".text",section-sent="6656",section-size="6668",
19812 total-sent="6656",total-size="9880"@}
19813 +download,@{section=".init",section-size="28",total-size="9880"@}
19814 +download,@{section=".fini",section-size="28",total-size="9880"@}
19815 +download,@{section=".data",section-size="3156",total-size="9880"@}
19816 +download,@{section=".data",section-sent="512",section-size="3156",
19817 total-sent="7236",total-size="9880"@}
19818 +download,@{section=".data",section-sent="1024",section-size="3156",
19819 total-sent="7748",total-size="9880"@}
19820 +download,@{section=".data",section-sent="1536",section-size="3156",
19821 total-sent="8260",total-size="9880"@}
19822 +download,@{section=".data",section-sent="2048",section-size="3156",
19823 total-sent="8772",total-size="9880"@}
19824 +download,@{section=".data",section-sent="2560",section-size="3156",
19825 total-sent="9284",total-size="9880"@}
19826 +download,@{section=".data",section-sent="3072",section-size="3156",
19827 total-sent="9796",total-size="9880"@}
19828 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
19834 @subheading The @code{-target-exec-status} Command
19835 @findex -target-exec-status
19837 @subsubheading Synopsis
19840 -target-exec-status
19843 Provide information on the state of the target (whether it is running or
19844 not, for instance).
19846 @subsubheading @value{GDBN} Command
19848 There's no equivalent @value{GDBN} command.
19850 @subsubheading Example
19854 @subheading The @code{-target-list-available-targets} Command
19855 @findex -target-list-available-targets
19857 @subsubheading Synopsis
19860 -target-list-available-targets
19863 List the possible targets to connect to.
19865 @subsubheading @value{GDBN} Command
19867 The corresponding @value{GDBN} command is @samp{help target}.
19869 @subsubheading Example
19873 @subheading The @code{-target-list-current-targets} Command
19874 @findex -target-list-current-targets
19876 @subsubheading Synopsis
19879 -target-list-current-targets
19882 Describe the current target.
19884 @subsubheading @value{GDBN} Command
19886 The corresponding information is printed by @samp{info file} (among
19889 @subsubheading Example
19893 @subheading The @code{-target-list-parameters} Command
19894 @findex -target-list-parameters
19896 @subsubheading Synopsis
19899 -target-list-parameters
19904 @subsubheading @value{GDBN} Command
19908 @subsubheading Example
19912 @subheading The @code{-target-select} Command
19913 @findex -target-select
19915 @subsubheading Synopsis
19918 -target-select @var{type} @var{parameters @dots{}}
19921 Connect @value{GDBN} to the remote target. This command takes two args:
19925 The type of target, for instance @samp{async}, @samp{remote}, etc.
19926 @item @var{parameters}
19927 Device names, host names and the like. @xref{Target Commands, ,
19928 Commands for managing targets}, for more details.
19931 The output is a connection notification, followed by the address at
19932 which the target program is, in the following form:
19935 ^connected,addr="@var{address}",func="@var{function name}",
19936 args=[@var{arg list}]
19939 @subsubheading @value{GDBN} Command
19941 The corresponding @value{GDBN} command is @samp{target}.
19943 @subsubheading Example
19947 -target-select async /dev/ttya
19948 ^connected,addr="0xfe00a300",func="??",args=[]
19952 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19953 @node GDB/MI Thread Commands
19954 @section @sc{gdb/mi} Thread Commands
19957 @subheading The @code{-thread-info} Command
19958 @findex -thread-info
19960 @subsubheading Synopsis
19966 @subsubheading @value{GDBN} command
19970 @subsubheading Example
19974 @subheading The @code{-thread-list-all-threads} Command
19975 @findex -thread-list-all-threads
19977 @subsubheading Synopsis
19980 -thread-list-all-threads
19983 @subsubheading @value{GDBN} Command
19985 The equivalent @value{GDBN} command is @samp{info threads}.
19987 @subsubheading Example
19991 @subheading The @code{-thread-list-ids} Command
19992 @findex -thread-list-ids
19994 @subsubheading Synopsis
20000 Produces a list of the currently known @value{GDBN} thread ids. At the
20001 end of the list it also prints the total number of such threads.
20003 @subsubheading @value{GDBN} Command
20005 Part of @samp{info threads} supplies the same information.
20007 @subsubheading Example
20009 No threads present, besides the main process:
20014 ^done,thread-ids=@{@},number-of-threads="0"
20024 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20025 number-of-threads="3"
20030 @subheading The @code{-thread-select} Command
20031 @findex -thread-select
20033 @subsubheading Synopsis
20036 -thread-select @var{threadnum}
20039 Make @var{threadnum} the current thread. It prints the number of the new
20040 current thread, and the topmost frame for that thread.
20042 @subsubheading @value{GDBN} Command
20044 The corresponding @value{GDBN} command is @samp{thread}.
20046 @subsubheading Example
20053 *stopped,reason="end-stepping-range",thread-id="2",line="187",
20054 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
20058 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20059 number-of-threads="3"
20062 ^done,new-thread-id="3",
20063 frame=@{level="0",func="vprintf",
20064 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
20065 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
20069 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20070 @node GDB/MI Tracepoint Commands
20071 @section @sc{gdb/mi} Tracepoint Commands
20073 The tracepoint commands are not yet implemented.
20075 @c @subheading -trace-actions
20077 @c @subheading -trace-delete
20079 @c @subheading -trace-disable
20081 @c @subheading -trace-dump
20083 @c @subheading -trace-enable
20085 @c @subheading -trace-exists
20087 @c @subheading -trace-find
20089 @c @subheading -trace-frame-number
20091 @c @subheading -trace-info
20093 @c @subheading -trace-insert
20095 @c @subheading -trace-list
20097 @c @subheading -trace-pass-count
20099 @c @subheading -trace-save
20101 @c @subheading -trace-start
20103 @c @subheading -trace-stop
20106 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20107 @node GDB/MI Variable Objects
20108 @section @sc{gdb/mi} Variable Objects
20111 @subheading Motivation for Variable Objects in @sc{gdb/mi}
20113 For the implementation of a variable debugger window (locals, watched
20114 expressions, etc.), we are proposing the adaptation of the existing code
20115 used by @code{Insight}.
20117 The two main reasons for that are:
20121 It has been proven in practice (it is already on its second generation).
20124 It will shorten development time (needless to say how important it is
20128 The original interface was designed to be used by Tcl code, so it was
20129 slightly changed so it could be used through @sc{gdb/mi}. This section
20130 describes the @sc{gdb/mi} operations that will be available and gives some
20131 hints about their use.
20133 @emph{Note}: In addition to the set of operations described here, we
20134 expect the @sc{gui} implementation of a variable window to require, at
20135 least, the following operations:
20138 @item @code{-gdb-show} @code{output-radix}
20139 @item @code{-stack-list-arguments}
20140 @item @code{-stack-list-locals}
20141 @item @code{-stack-select-frame}
20144 @subheading Introduction to Variable Objects in @sc{gdb/mi}
20146 @cindex variable objects in @sc{gdb/mi}
20147 The basic idea behind variable objects is the creation of a named object
20148 to represent a variable, an expression, a memory location or even a CPU
20149 register. For each object created, a set of operations is available for
20150 examining or changing its properties.
20152 Furthermore, complex data types, such as C structures, are represented
20153 in a tree format. For instance, the @code{struct} type variable is the
20154 root and the children will represent the struct members. If a child
20155 is itself of a complex type, it will also have children of its own.
20156 Appropriate language differences are handled for C, C@t{++} and Java.
20158 When returning the actual values of the objects, this facility allows
20159 for the individual selection of the display format used in the result
20160 creation. It can be chosen among: binary, decimal, hexadecimal, octal
20161 and natural. Natural refers to a default format automatically
20162 chosen based on the variable type (like decimal for an @code{int}, hex
20163 for pointers, etc.).
20165 The following is the complete set of @sc{gdb/mi} operations defined to
20166 access this functionality:
20168 @multitable @columnfractions .4 .6
20169 @item @strong{Operation}
20170 @tab @strong{Description}
20172 @item @code{-var-create}
20173 @tab create a variable object
20174 @item @code{-var-delete}
20175 @tab delete the variable object and its children
20176 @item @code{-var-set-format}
20177 @tab set the display format of this variable
20178 @item @code{-var-show-format}
20179 @tab show the display format of this variable
20180 @item @code{-var-info-num-children}
20181 @tab tells how many children this object has
20182 @item @code{-var-list-children}
20183 @tab return a list of the object's children
20184 @item @code{-var-info-type}
20185 @tab show the type of this variable object
20186 @item @code{-var-info-expression}
20187 @tab print what this variable object represents
20188 @item @code{-var-show-attributes}
20189 @tab is this variable editable? does it exist here?
20190 @item @code{-var-evaluate-expression}
20191 @tab get the value of this variable
20192 @item @code{-var-assign}
20193 @tab set the value of this variable
20194 @item @code{-var-update}
20195 @tab update the variable and its children
20198 In the next subsection we describe each operation in detail and suggest
20199 how it can be used.
20201 @subheading Description And Use of Operations on Variable Objects
20203 @subheading The @code{-var-create} Command
20204 @findex -var-create
20206 @subsubheading Synopsis
20209 -var-create @{@var{name} | "-"@}
20210 @{@var{frame-addr} | "*"@} @var{expression}
20213 This operation creates a variable object, which allows the monitoring of
20214 a variable, the result of an expression, a memory cell or a CPU
20217 The @var{name} parameter is the string by which the object can be
20218 referenced. It must be unique. If @samp{-} is specified, the varobj
20219 system will generate a string ``varNNNNNN'' automatically. It will be
20220 unique provided that one does not specify @var{name} on that format.
20221 The command fails if a duplicate name is found.
20223 The frame under which the expression should be evaluated can be
20224 specified by @var{frame-addr}. A @samp{*} indicates that the current
20225 frame should be used.
20227 @var{expression} is any expression valid on the current language set (must not
20228 begin with a @samp{*}), or one of the following:
20232 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
20235 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
20238 @samp{$@var{regname}} --- a CPU register name
20241 @subsubheading Result
20243 This operation returns the name, number of children and the type of the
20244 object created. Type is returned as a string as the ones generated by
20245 the @value{GDBN} CLI:
20248 name="@var{name}",numchild="N",type="@var{type}"
20252 @subheading The @code{-var-delete} Command
20253 @findex -var-delete
20255 @subsubheading Synopsis
20258 -var-delete @var{name}
20261 Deletes a previously created variable object and all of its children.
20263 Returns an error if the object @var{name} is not found.
20266 @subheading The @code{-var-set-format} Command
20267 @findex -var-set-format
20269 @subsubheading Synopsis
20272 -var-set-format @var{name} @var{format-spec}
20275 Sets the output format for the value of the object @var{name} to be
20278 The syntax for the @var{format-spec} is as follows:
20281 @var{format-spec} @expansion{}
20282 @{binary | decimal | hexadecimal | octal | natural@}
20286 @subheading The @code{-var-show-format} Command
20287 @findex -var-show-format
20289 @subsubheading Synopsis
20292 -var-show-format @var{name}
20295 Returns the format used to display the value of the object @var{name}.
20298 @var{format} @expansion{}
20303 @subheading The @code{-var-info-num-children} Command
20304 @findex -var-info-num-children
20306 @subsubheading Synopsis
20309 -var-info-num-children @var{name}
20312 Returns the number of children of a variable object @var{name}:
20319 @subheading The @code{-var-list-children} Command
20320 @findex -var-list-children
20322 @subsubheading Synopsis
20325 -var-list-children [@var{print-values}] @var{name}
20328 Returns a list of the children of the specified variable object. With
20329 just the variable object name as an argument or with an optional
20330 preceding argument of 0 or @code{--no-values}, prints only the names of the
20331 variables. With an optional preceding argument of 1 or @code{--all-values},
20332 also prints their values.
20334 @subsubheading Example
20338 -var-list-children n
20339 numchild=@var{n},children=[@{name=@var{name},
20340 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
20342 -var-list-children --all-values n
20343 numchild=@var{n},children=[@{name=@var{name},
20344 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
20348 @subheading The @code{-var-info-type} Command
20349 @findex -var-info-type
20351 @subsubheading Synopsis
20354 -var-info-type @var{name}
20357 Returns the type of the specified variable @var{name}. The type is
20358 returned as a string in the same format as it is output by the
20362 type=@var{typename}
20366 @subheading The @code{-var-info-expression} Command
20367 @findex -var-info-expression
20369 @subsubheading Synopsis
20372 -var-info-expression @var{name}
20375 Returns what is represented by the variable object @var{name}:
20378 lang=@var{lang-spec},exp=@var{expression}
20382 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
20384 @subheading The @code{-var-show-attributes} Command
20385 @findex -var-show-attributes
20387 @subsubheading Synopsis
20390 -var-show-attributes @var{name}
20393 List attributes of the specified variable object @var{name}:
20396 status=@var{attr} [ ( ,@var{attr} )* ]
20400 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
20402 @subheading The @code{-var-evaluate-expression} Command
20403 @findex -var-evaluate-expression
20405 @subsubheading Synopsis
20408 -var-evaluate-expression @var{name}
20411 Evaluates the expression that is represented by the specified variable
20412 object and returns its value as a string in the current format specified
20419 Note that one must invoke @code{-var-list-children} for a variable
20420 before the value of a child variable can be evaluated.
20422 @subheading The @code{-var-assign} Command
20423 @findex -var-assign
20425 @subsubheading Synopsis
20428 -var-assign @var{name} @var{expression}
20431 Assigns the value of @var{expression} to the variable object specified
20432 by @var{name}. The object must be @samp{editable}. If the variable's
20433 value is altered by the assign, the variable will show up in any
20434 subsequent @code{-var-update} list.
20436 @subsubheading Example
20444 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
20448 @subheading The @code{-var-update} Command
20449 @findex -var-update
20451 @subsubheading Synopsis
20454 -var-update @{@var{name} | "*"@}
20457 Update the value of the variable object @var{name} by evaluating its
20458 expression after fetching all the new values from memory or registers.
20459 A @samp{*} causes all existing variable objects to be updated.
20463 @chapter @value{GDBN} Annotations
20465 This chapter describes annotations in @value{GDBN}. Annotations were
20466 designed to interface @value{GDBN} to graphical user interfaces or other
20467 similar programs which want to interact with @value{GDBN} at a
20468 relatively high level.
20470 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
20474 This is Edition @value{EDITION}, @value{DATE}.
20478 * Annotations Overview:: What annotations are; the general syntax.
20479 * Server Prefix:: Issuing a command without affecting user state.
20480 * Prompting:: Annotations marking @value{GDBN}'s need for input.
20481 * Errors:: Annotations for error messages.
20482 * Invalidation:: Some annotations describe things now invalid.
20483 * Annotations for Running::
20484 Whether the program is running, how it stopped, etc.
20485 * Source Annotations:: Annotations describing source code.
20488 @node Annotations Overview
20489 @section What is an Annotation?
20490 @cindex annotations
20492 Annotations start with a newline character, two @samp{control-z}
20493 characters, and the name of the annotation. If there is no additional
20494 information associated with this annotation, the name of the annotation
20495 is followed immediately by a newline. If there is additional
20496 information, the name of the annotation is followed by a space, the
20497 additional information, and a newline. The additional information
20498 cannot contain newline characters.
20500 Any output not beginning with a newline and two @samp{control-z}
20501 characters denotes literal output from @value{GDBN}. Currently there is
20502 no need for @value{GDBN} to output a newline followed by two
20503 @samp{control-z} characters, but if there was such a need, the
20504 annotations could be extended with an @samp{escape} annotation which
20505 means those three characters as output.
20507 The annotation @var{level}, which is specified using the
20508 @option{--annotate} command line option (@pxref{Mode Options}), controls
20509 how much information @value{GDBN} prints together with its prompt,
20510 values of expressions, source lines, and other types of output. Level 0
20511 is for no anntations, level 1 is for use when @value{GDBN} is run as a
20512 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
20513 for programs that control @value{GDBN}, and level 2 annotations have
20514 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
20515 Interface, annotate, GDB's Obsolete Annotations}).
20518 @kindex set annotate
20519 @item set annotate @var{level}
20520 The @value{GDB} command @code{set annotate} sets the level of
20521 annotations to the specified @var{level}.
20523 @item show annotate
20524 @kindex show annotate
20525 Show the current annotation level.
20528 This chapter describes level 3 annotations.
20530 A simple example of starting up @value{GDBN} with annotations is:
20533 $ @kbd{gdb --annotate=3}
20535 Copyright 2003 Free Software Foundation, Inc.
20536 GDB is free software, covered by the GNU General Public License,
20537 and you are welcome to change it and/or distribute copies of it
20538 under certain conditions.
20539 Type "show copying" to see the conditions.
20540 There is absolutely no warranty for GDB. Type "show warranty"
20542 This GDB was configured as "i386-pc-linux-gnu"
20553 Here @samp{quit} is input to @value{GDBN}; the rest is output from
20554 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
20555 denotes a @samp{control-z} character) are annotations; the rest is
20556 output from @value{GDBN}.
20558 @node Server Prefix
20559 @section The Server Prefix
20560 @cindex server prefix for annotations
20562 To issue a command to @value{GDBN} without affecting certain aspects of
20563 the state which is seen by users, prefix it with @samp{server }. This
20564 means that this command will not affect the command history, nor will it
20565 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
20566 pressed on a line by itself.
20568 The server prefix does not affect the recording of values into the value
20569 history; to print a value without recording it into the value history,
20570 use the @code{output} command instead of the @code{print} command.
20573 @section Annotation for @value{GDBN} Input
20575 @cindex annotations for prompts
20576 When @value{GDBN} prompts for input, it annotates this fact so it is possible
20577 to know when to send output, when the output from a given command is
20580 Different kinds of input each have a different @dfn{input type}. Each
20581 input type has three annotations: a @code{pre-} annotation, which
20582 denotes the beginning of any prompt which is being output, a plain
20583 annotation, which denotes the end of the prompt, and then a @code{post-}
20584 annotation which denotes the end of any echo which may (or may not) be
20585 associated with the input. For example, the @code{prompt} input type
20586 features the following annotations:
20594 The input types are
20599 @findex post-prompt
20601 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
20603 @findex pre-commands
20605 @findex post-commands
20607 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
20608 command. The annotations are repeated for each command which is input.
20610 @findex pre-overload-choice
20611 @findex overload-choice
20612 @findex post-overload-choice
20613 @item overload-choice
20614 When @value{GDBN} wants the user to select between various overloaded functions.
20620 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
20622 @findex pre-prompt-for-continue
20623 @findex prompt-for-continue
20624 @findex post-prompt-for-continue
20625 @item prompt-for-continue
20626 When @value{GDBN} is asking the user to press return to continue. Note: Don't
20627 expect this to work well; instead use @code{set height 0} to disable
20628 prompting. This is because the counting of lines is buggy in the
20629 presence of annotations.
20634 @cindex annotations for errors, warnings and interrupts
20641 This annotation occurs right before @value{GDBN} responds to an interrupt.
20648 This annotation occurs right before @value{GDBN} responds to an error.
20650 Quit and error annotations indicate that any annotations which @value{GDBN} was
20651 in the middle of may end abruptly. For example, if a
20652 @code{value-history-begin} annotation is followed by a @code{error}, one
20653 cannot expect to receive the matching @code{value-history-end}. One
20654 cannot expect not to receive it either, however; an error annotation
20655 does not necessarily mean that @value{GDBN} is immediately returning all the way
20658 @findex error-begin
20659 A quit or error annotation may be preceded by
20665 Any output between that and the quit or error annotation is the error
20668 Warning messages are not yet annotated.
20669 @c If we want to change that, need to fix warning(), type_error(),
20670 @c range_error(), and possibly other places.
20673 @section Invalidation Notices
20675 @cindex annotations for invalidation messages
20676 The following annotations say that certain pieces of state may have
20680 @findex frames-invalid
20681 @item ^Z^Zframes-invalid
20683 The frames (for example, output from the @code{backtrace} command) may
20686 @findex breakpoints-invalid
20687 @item ^Z^Zbreakpoints-invalid
20689 The breakpoints may have changed. For example, the user just added or
20690 deleted a breakpoint.
20693 @node Annotations for Running
20694 @section Running the Program
20695 @cindex annotations for running programs
20699 When the program starts executing due to a @value{GDBN} command such as
20700 @code{step} or @code{continue},
20706 is output. When the program stops,
20712 is output. Before the @code{stopped} annotation, a variety of
20713 annotations describe how the program stopped.
20717 @item ^Z^Zexited @var{exit-status}
20718 The program exited, and @var{exit-status} is the exit status (zero for
20719 successful exit, otherwise nonzero).
20722 @findex signal-name
20723 @findex signal-name-end
20724 @findex signal-string
20725 @findex signal-string-end
20726 @item ^Z^Zsignalled
20727 The program exited with a signal. After the @code{^Z^Zsignalled}, the
20728 annotation continues:
20734 ^Z^Zsignal-name-end
20738 ^Z^Zsignal-string-end
20743 where @var{name} is the name of the signal, such as @code{SIGILL} or
20744 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
20745 as @code{Illegal Instruction} or @code{Segmentation fault}.
20746 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
20747 user's benefit and have no particular format.
20751 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
20752 just saying that the program received the signal, not that it was
20753 terminated with it.
20756 @item ^Z^Zbreakpoint @var{number}
20757 The program hit breakpoint number @var{number}.
20760 @item ^Z^Zwatchpoint @var{number}
20761 The program hit watchpoint number @var{number}.
20764 @node Source Annotations
20765 @section Displaying Source
20766 @cindex annotations for source display
20769 The following annotation is used instead of displaying source code:
20772 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
20775 where @var{filename} is an absolute file name indicating which source
20776 file, @var{line} is the line number within that file (where 1 is the
20777 first line in the file), @var{character} is the character position
20778 within the file (where 0 is the first character in the file) (for most
20779 debug formats this will necessarily point to the beginning of a line),
20780 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
20781 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
20782 @var{addr} is the address in the target program associated with the
20783 source which is being displayed. @var{addr} is in the form @samp{0x}
20784 followed by one or more lowercase hex digits (note that this does not
20785 depend on the language).
20788 @chapter Reporting Bugs in @value{GDBN}
20789 @cindex bugs in @value{GDBN}
20790 @cindex reporting bugs in @value{GDBN}
20792 Your bug reports play an essential role in making @value{GDBN} reliable.
20794 Reporting a bug may help you by bringing a solution to your problem, or it
20795 may not. But in any case the principal function of a bug report is to help
20796 the entire community by making the next version of @value{GDBN} work better. Bug
20797 reports are your contribution to the maintenance of @value{GDBN}.
20799 In order for a bug report to serve its purpose, you must include the
20800 information that enables us to fix the bug.
20803 * Bug Criteria:: Have you found a bug?
20804 * Bug Reporting:: How to report bugs
20808 @section Have you found a bug?
20809 @cindex bug criteria
20811 If you are not sure whether you have found a bug, here are some guidelines:
20814 @cindex fatal signal
20815 @cindex debugger crash
20816 @cindex crash of debugger
20818 If the debugger gets a fatal signal, for any input whatever, that is a
20819 @value{GDBN} bug. Reliable debuggers never crash.
20821 @cindex error on valid input
20823 If @value{GDBN} produces an error message for valid input, that is a
20824 bug. (Note that if you're cross debugging, the problem may also be
20825 somewhere in the connection to the target.)
20827 @cindex invalid input
20829 If @value{GDBN} does not produce an error message for invalid input,
20830 that is a bug. However, you should note that your idea of
20831 ``invalid input'' might be our idea of ``an extension'' or ``support
20832 for traditional practice''.
20835 If you are an experienced user of debugging tools, your suggestions
20836 for improvement of @value{GDBN} are welcome in any case.
20839 @node Bug Reporting
20840 @section How to report bugs
20841 @cindex bug reports
20842 @cindex @value{GDBN} bugs, reporting
20844 A number of companies and individuals offer support for @sc{gnu} products.
20845 If you obtained @value{GDBN} from a support organization, we recommend you
20846 contact that organization first.
20848 You can find contact information for many support companies and
20849 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
20851 @c should add a web page ref...
20853 In any event, we also recommend that you submit bug reports for
20854 @value{GDBN}. The prefered method is to submit them directly using
20855 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
20856 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
20859 @strong{Do not send bug reports to @samp{info-gdb}, or to
20860 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
20861 not want to receive bug reports. Those that do have arranged to receive
20864 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
20865 serves as a repeater. The mailing list and the newsgroup carry exactly
20866 the same messages. Often people think of posting bug reports to the
20867 newsgroup instead of mailing them. This appears to work, but it has one
20868 problem which can be crucial: a newsgroup posting often lacks a mail
20869 path back to the sender. Thus, if we need to ask for more information,
20870 we may be unable to reach you. For this reason, it is better to send
20871 bug reports to the mailing list.
20873 The fundamental principle of reporting bugs usefully is this:
20874 @strong{report all the facts}. If you are not sure whether to state a
20875 fact or leave it out, state it!
20877 Often people omit facts because they think they know what causes the
20878 problem and assume that some details do not matter. Thus, you might
20879 assume that the name of the variable you use in an example does not matter.
20880 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
20881 stray memory reference which happens to fetch from the location where that
20882 name is stored in memory; perhaps, if the name were different, the contents
20883 of that location would fool the debugger into doing the right thing despite
20884 the bug. Play it safe and give a specific, complete example. That is the
20885 easiest thing for you to do, and the most helpful.
20887 Keep in mind that the purpose of a bug report is to enable us to fix the
20888 bug. It may be that the bug has been reported previously, but neither
20889 you nor we can know that unless your bug report is complete and
20892 Sometimes people give a few sketchy facts and ask, ``Does this ring a
20893 bell?'' Those bug reports are useless, and we urge everyone to
20894 @emph{refuse to respond to them} except to chide the sender to report
20897 To enable us to fix the bug, you should include all these things:
20901 The version of @value{GDBN}. @value{GDBN} announces it if you start
20902 with no arguments; you can also print it at any time using @code{show
20905 Without this, we will not know whether there is any point in looking for
20906 the bug in the current version of @value{GDBN}.
20909 The type of machine you are using, and the operating system name and
20913 What compiler (and its version) was used to compile @value{GDBN}---e.g.
20914 ``@value{GCC}--2.8.1''.
20917 What compiler (and its version) was used to compile the program you are
20918 debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
20919 C Compiler''. For GCC, you can say @code{gcc --version} to get this
20920 information; for other compilers, see the documentation for those
20924 The command arguments you gave the compiler to compile your example and
20925 observe the bug. For example, did you use @samp{-O}? To guarantee
20926 you will not omit something important, list them all. A copy of the
20927 Makefile (or the output from make) is sufficient.
20929 If we were to try to guess the arguments, we would probably guess wrong
20930 and then we might not encounter the bug.
20933 A complete input script, and all necessary source files, that will
20937 A description of what behavior you observe that you believe is
20938 incorrect. For example, ``It gets a fatal signal.''
20940 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
20941 will certainly notice it. But if the bug is incorrect output, we might
20942 not notice unless it is glaringly wrong. You might as well not give us
20943 a chance to make a mistake.
20945 Even if the problem you experience is a fatal signal, you should still
20946 say so explicitly. Suppose something strange is going on, such as, your
20947 copy of @value{GDBN} is out of synch, or you have encountered a bug in
20948 the C library on your system. (This has happened!) Your copy might
20949 crash and ours would not. If you told us to expect a crash, then when
20950 ours fails to crash, we would know that the bug was not happening for
20951 us. If you had not told us to expect a crash, then we would not be able
20952 to draw any conclusion from our observations.
20955 @cindex recording a session script
20956 To collect all this information, you can use a session recording program
20957 such as @command{script}, which is available on many Unix systems.
20958 Just run your @value{GDBN} session inside @command{script} and then
20959 include the @file{typescript} file with your bug report.
20961 Another way to record a @value{GDBN} session is to run @value{GDBN}
20962 inside Emacs and then save the entire buffer to a file.
20965 If you wish to suggest changes to the @value{GDBN} source, send us context
20966 diffs. If you even discuss something in the @value{GDBN} source, refer to
20967 it by context, not by line number.
20969 The line numbers in our development sources will not match those in your
20970 sources. Your line numbers would convey no useful information to us.
20974 Here are some things that are not necessary:
20978 A description of the envelope of the bug.
20980 Often people who encounter a bug spend a lot of time investigating
20981 which changes to the input file will make the bug go away and which
20982 changes will not affect it.
20984 This is often time consuming and not very useful, because the way we
20985 will find the bug is by running a single example under the debugger
20986 with breakpoints, not by pure deduction from a series of examples.
20987 We recommend that you save your time for something else.
20989 Of course, if you can find a simpler example to report @emph{instead}
20990 of the original one, that is a convenience for us. Errors in the
20991 output will be easier to spot, running under the debugger will take
20992 less time, and so on.
20994 However, simplification is not vital; if you do not want to do this,
20995 report the bug anyway and send us the entire test case you used.
20998 A patch for the bug.
21000 A patch for the bug does help us if it is a good one. But do not omit
21001 the necessary information, such as the test case, on the assumption that
21002 a patch is all we need. We might see problems with your patch and decide
21003 to fix the problem another way, or we might not understand it at all.
21005 Sometimes with a program as complicated as @value{GDBN} it is very hard to
21006 construct an example that will make the program follow a certain path
21007 through the code. If you do not send us the example, we will not be able
21008 to construct one, so we will not be able to verify that the bug is fixed.
21010 And if we cannot understand what bug you are trying to fix, or why your
21011 patch should be an improvement, we will not install it. A test case will
21012 help us to understand.
21015 A guess about what the bug is or what it depends on.
21017 Such guesses are usually wrong. Even we cannot guess right about such
21018 things without first using the debugger to find the facts.
21021 @c The readline documentation is distributed with the readline code
21022 @c and consists of the two following files:
21024 @c inc-hist.texinfo
21025 @c Use -I with makeinfo to point to the appropriate directory,
21026 @c environment var TEXINPUTS with TeX.
21027 @include rluser.texinfo
21028 @include inc-hist.texinfo
21031 @node Formatting Documentation
21032 @appendix Formatting Documentation
21034 @cindex @value{GDBN} reference card
21035 @cindex reference card
21036 The @value{GDBN} 4 release includes an already-formatted reference card, ready
21037 for printing with PostScript or Ghostscript, in the @file{gdb}
21038 subdirectory of the main source directory@footnote{In
21039 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
21040 release.}. If you can use PostScript or Ghostscript with your printer,
21041 you can print the reference card immediately with @file{refcard.ps}.
21043 The release also includes the source for the reference card. You
21044 can format it, using @TeX{}, by typing:
21050 The @value{GDBN} reference card is designed to print in @dfn{landscape}
21051 mode on US ``letter'' size paper;
21052 that is, on a sheet 11 inches wide by 8.5 inches
21053 high. You will need to specify this form of printing as an option to
21054 your @sc{dvi} output program.
21056 @cindex documentation
21058 All the documentation for @value{GDBN} comes as part of the machine-readable
21059 distribution. The documentation is written in Texinfo format, which is
21060 a documentation system that uses a single source file to produce both
21061 on-line information and a printed manual. You can use one of the Info
21062 formatting commands to create the on-line version of the documentation
21063 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
21065 @value{GDBN} includes an already formatted copy of the on-line Info
21066 version of this manual in the @file{gdb} subdirectory. The main Info
21067 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
21068 subordinate files matching @samp{gdb.info*} in the same directory. If
21069 necessary, you can print out these files, or read them with any editor;
21070 but they are easier to read using the @code{info} subsystem in @sc{gnu}
21071 Emacs or the standalone @code{info} program, available as part of the
21072 @sc{gnu} Texinfo distribution.
21074 If you want to format these Info files yourself, you need one of the
21075 Info formatting programs, such as @code{texinfo-format-buffer} or
21078 If you have @code{makeinfo} installed, and are in the top level
21079 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
21080 version @value{GDBVN}), you can make the Info file by typing:
21087 If you want to typeset and print copies of this manual, you need @TeX{},
21088 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
21089 Texinfo definitions file.
21091 @TeX{} is a typesetting program; it does not print files directly, but
21092 produces output files called @sc{dvi} files. To print a typeset
21093 document, you need a program to print @sc{dvi} files. If your system
21094 has @TeX{} installed, chances are it has such a program. The precise
21095 command to use depends on your system; @kbd{lpr -d} is common; another
21096 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
21097 require a file name without any extension or a @samp{.dvi} extension.
21099 @TeX{} also requires a macro definitions file called
21100 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
21101 written in Texinfo format. On its own, @TeX{} cannot either read or
21102 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
21103 and is located in the @file{gdb-@var{version-number}/texinfo}
21106 If you have @TeX{} and a @sc{dvi} printer program installed, you can
21107 typeset and print this manual. First switch to the the @file{gdb}
21108 subdirectory of the main source directory (for example, to
21109 @file{gdb-@value{GDBVN}/gdb}) and type:
21115 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
21117 @node Installing GDB
21118 @appendix Installing @value{GDBN}
21119 @cindex configuring @value{GDBN}
21120 @cindex installation
21121 @cindex configuring @value{GDBN}, and source tree subdirectories
21123 @value{GDBN} comes with a @code{configure} script that automates the process
21124 of preparing @value{GDBN} for installation; you can then use @code{make} to
21125 build the @code{gdb} program.
21127 @c irrelevant in info file; it's as current as the code it lives with.
21128 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
21129 look at the @file{README} file in the sources; we may have improved the
21130 installation procedures since publishing this manual.}
21133 The @value{GDBN} distribution includes all the source code you need for
21134 @value{GDBN} in a single directory, whose name is usually composed by
21135 appending the version number to @samp{gdb}.
21137 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
21138 @file{gdb-@value{GDBVN}} directory. That directory contains:
21141 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
21142 script for configuring @value{GDBN} and all its supporting libraries
21144 @item gdb-@value{GDBVN}/gdb
21145 the source specific to @value{GDBN} itself
21147 @item gdb-@value{GDBVN}/bfd
21148 source for the Binary File Descriptor library
21150 @item gdb-@value{GDBVN}/include
21151 @sc{gnu} include files
21153 @item gdb-@value{GDBVN}/libiberty
21154 source for the @samp{-liberty} free software library
21156 @item gdb-@value{GDBVN}/opcodes
21157 source for the library of opcode tables and disassemblers
21159 @item gdb-@value{GDBVN}/readline
21160 source for the @sc{gnu} command-line interface
21162 @item gdb-@value{GDBVN}/glob
21163 source for the @sc{gnu} filename pattern-matching subroutine
21165 @item gdb-@value{GDBVN}/mmalloc
21166 source for the @sc{gnu} memory-mapped malloc package
21169 The simplest way to configure and build @value{GDBN} is to run @code{configure}
21170 from the @file{gdb-@var{version-number}} source directory, which in
21171 this example is the @file{gdb-@value{GDBVN}} directory.
21173 First switch to the @file{gdb-@var{version-number}} source directory
21174 if you are not already in it; then run @code{configure}. Pass the
21175 identifier for the platform on which @value{GDBN} will run as an
21181 cd gdb-@value{GDBVN}
21182 ./configure @var{host}
21187 where @var{host} is an identifier such as @samp{sun4} or
21188 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
21189 (You can often leave off @var{host}; @code{configure} tries to guess the
21190 correct value by examining your system.)
21192 Running @samp{configure @var{host}} and then running @code{make} builds the
21193 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
21194 libraries, then @code{gdb} itself. The configured source files, and the
21195 binaries, are left in the corresponding source directories.
21198 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
21199 system does not recognize this automatically when you run a different
21200 shell, you may need to run @code{sh} on it explicitly:
21203 sh configure @var{host}
21206 If you run @code{configure} from a directory that contains source
21207 directories for multiple libraries or programs, such as the
21208 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
21209 creates configuration files for every directory level underneath (unless
21210 you tell it not to, with the @samp{--norecursion} option).
21212 You should run the @code{configure} script from the top directory in the
21213 source tree, the @file{gdb-@var{version-number}} directory. If you run
21214 @code{configure} from one of the subdirectories, you will configure only
21215 that subdirectory. That is usually not what you want. In particular,
21216 if you run the first @code{configure} from the @file{gdb} subdirectory
21217 of the @file{gdb-@var{version-number}} directory, you will omit the
21218 configuration of @file{bfd}, @file{readline}, and other sibling
21219 directories of the @file{gdb} subdirectory. This leads to build errors
21220 about missing include files such as @file{bfd/bfd.h}.
21222 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
21223 However, you should make sure that the shell on your path (named by
21224 the @samp{SHELL} environment variable) is publicly readable. Remember
21225 that @value{GDBN} uses the shell to start your program---some systems refuse to
21226 let @value{GDBN} debug child processes whose programs are not readable.
21229 * Separate Objdir:: Compiling @value{GDBN} in another directory
21230 * Config Names:: Specifying names for hosts and targets
21231 * Configure Options:: Summary of options for configure
21234 @node Separate Objdir
21235 @section Compiling @value{GDBN} in another directory
21237 If you want to run @value{GDBN} versions for several host or target machines,
21238 you need a different @code{gdb} compiled for each combination of
21239 host and target. @code{configure} is designed to make this easy by
21240 allowing you to generate each configuration in a separate subdirectory,
21241 rather than in the source directory. If your @code{make} program
21242 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
21243 @code{make} in each of these directories builds the @code{gdb}
21244 program specified there.
21246 To build @code{gdb} in a separate directory, run @code{configure}
21247 with the @samp{--srcdir} option to specify where to find the source.
21248 (You also need to specify a path to find @code{configure}
21249 itself from your working directory. If the path to @code{configure}
21250 would be the same as the argument to @samp{--srcdir}, you can leave out
21251 the @samp{--srcdir} option; it is assumed.)
21253 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
21254 separate directory for a Sun 4 like this:
21258 cd gdb-@value{GDBVN}
21261 ../gdb-@value{GDBVN}/configure sun4
21266 When @code{configure} builds a configuration using a remote source
21267 directory, it creates a tree for the binaries with the same structure
21268 (and using the same names) as the tree under the source directory. In
21269 the example, you'd find the Sun 4 library @file{libiberty.a} in the
21270 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
21271 @file{gdb-sun4/gdb}.
21273 Make sure that your path to the @file{configure} script has just one
21274 instance of @file{gdb} in it. If your path to @file{configure} looks
21275 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
21276 one subdirectory of @value{GDBN}, not the whole package. This leads to
21277 build errors about missing include files such as @file{bfd/bfd.h}.
21279 One popular reason to build several @value{GDBN} configurations in separate
21280 directories is to configure @value{GDBN} for cross-compiling (where
21281 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
21282 programs that run on another machine---the @dfn{target}).
21283 You specify a cross-debugging target by
21284 giving the @samp{--target=@var{target}} option to @code{configure}.
21286 When you run @code{make} to build a program or library, you must run
21287 it in a configured directory---whatever directory you were in when you
21288 called @code{configure} (or one of its subdirectories).
21290 The @code{Makefile} that @code{configure} generates in each source
21291 directory also runs recursively. If you type @code{make} in a source
21292 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
21293 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
21294 will build all the required libraries, and then build GDB.
21296 When you have multiple hosts or targets configured in separate
21297 directories, you can run @code{make} on them in parallel (for example,
21298 if they are NFS-mounted on each of the hosts); they will not interfere
21302 @section Specifying names for hosts and targets
21304 The specifications used for hosts and targets in the @code{configure}
21305 script are based on a three-part naming scheme, but some short predefined
21306 aliases are also supported. The full naming scheme encodes three pieces
21307 of information in the following pattern:
21310 @var{architecture}-@var{vendor}-@var{os}
21313 For example, you can use the alias @code{sun4} as a @var{host} argument,
21314 or as the value for @var{target} in a @code{--target=@var{target}}
21315 option. The equivalent full name is @samp{sparc-sun-sunos4}.
21317 The @code{configure} script accompanying @value{GDBN} does not provide
21318 any query facility to list all supported host and target names or
21319 aliases. @code{configure} calls the Bourne shell script
21320 @code{config.sub} to map abbreviations to full names; you can read the
21321 script, if you wish, or you can use it to test your guesses on
21322 abbreviations---for example:
21325 % sh config.sub i386-linux
21327 % sh config.sub alpha-linux
21328 alpha-unknown-linux-gnu
21329 % sh config.sub hp9k700
21331 % sh config.sub sun4
21332 sparc-sun-sunos4.1.1
21333 % sh config.sub sun3
21334 m68k-sun-sunos4.1.1
21335 % sh config.sub i986v
21336 Invalid configuration `i986v': machine `i986v' not recognized
21340 @code{config.sub} is also distributed in the @value{GDBN} source
21341 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
21343 @node Configure Options
21344 @section @code{configure} options
21346 Here is a summary of the @code{configure} options and arguments that
21347 are most often useful for building @value{GDBN}. @code{configure} also has
21348 several other options not listed here. @inforef{What Configure
21349 Does,,configure.info}, for a full explanation of @code{configure}.
21352 configure @r{[}--help@r{]}
21353 @r{[}--prefix=@var{dir}@r{]}
21354 @r{[}--exec-prefix=@var{dir}@r{]}
21355 @r{[}--srcdir=@var{dirname}@r{]}
21356 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
21357 @r{[}--target=@var{target}@r{]}
21362 You may introduce options with a single @samp{-} rather than
21363 @samp{--} if you prefer; but you may abbreviate option names if you use
21368 Display a quick summary of how to invoke @code{configure}.
21370 @item --prefix=@var{dir}
21371 Configure the source to install programs and files under directory
21374 @item --exec-prefix=@var{dir}
21375 Configure the source to install programs under directory
21378 @c avoid splitting the warning from the explanation:
21380 @item --srcdir=@var{dirname}
21381 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
21382 @code{make} that implements the @code{VPATH} feature.}@*
21383 Use this option to make configurations in directories separate from the
21384 @value{GDBN} source directories. Among other things, you can use this to
21385 build (or maintain) several configurations simultaneously, in separate
21386 directories. @code{configure} writes configuration specific files in
21387 the current directory, but arranges for them to use the source in the
21388 directory @var{dirname}. @code{configure} creates directories under
21389 the working directory in parallel to the source directories below
21392 @item --norecursion
21393 Configure only the directory level where @code{configure} is executed; do not
21394 propagate configuration to subdirectories.
21396 @item --target=@var{target}
21397 Configure @value{GDBN} for cross-debugging programs running on the specified
21398 @var{target}. Without this option, @value{GDBN} is configured to debug
21399 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
21401 There is no convenient way to generate a list of all available targets.
21403 @item @var{host} @dots{}
21404 Configure @value{GDBN} to run on the specified @var{host}.
21406 There is no convenient way to generate a list of all available hosts.
21409 There are many other options available as well, but they are generally
21410 needed for special purposes only.
21412 @node Maintenance Commands
21413 @appendix Maintenance Commands
21414 @cindex maintenance commands
21415 @cindex internal commands
21417 In addition to commands intended for @value{GDBN} users, @value{GDBN}
21418 includes a number of commands intended for @value{GDBN} developers,
21419 that are not documented elsewhere in this manual. These commands are
21420 provided here for reference. (For commands that turn on debugging
21421 messages, see @ref{Debugging Output}.)
21424 @kindex maint agent
21425 @item maint agent @var{expression}
21426 Translate the given @var{expression} into remote agent bytecodes.
21427 This command is useful for debugging the Agent Expression mechanism
21428 (@pxref{Agent Expressions}).
21430 @kindex maint info breakpoints
21431 @item @anchor{maint info breakpoints}maint info breakpoints
21432 Using the same format as @samp{info breakpoints}, display both the
21433 breakpoints you've set explicitly, and those @value{GDBN} is using for
21434 internal purposes. Internal breakpoints are shown with negative
21435 breakpoint numbers. The type column identifies what kind of breakpoint
21440 Normal, explicitly set breakpoint.
21443 Normal, explicitly set watchpoint.
21446 Internal breakpoint, used to handle correctly stepping through
21447 @code{longjmp} calls.
21449 @item longjmp resume
21450 Internal breakpoint at the target of a @code{longjmp}.
21453 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
21456 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
21459 Shared library events.
21463 @kindex maint check-symtabs
21464 @item maint check-symtabs
21465 Check the consistency of psymtabs and symtabs.
21467 @kindex maint cplus first_component
21468 @item maint cplus first_component @var{name}
21469 Print the first C@t{++} class/namespace component of @var{name}.
21471 @kindex maint cplus namespace
21472 @item maint cplus namespace
21473 Print the list of possible C@t{++} namespaces.
21475 @kindex maint demangle
21476 @item maint demangle @var{name}
21477 Demangle a C@t{++} or Objective-C manled @var{name}.
21479 @kindex maint deprecate
21480 @kindex maint undeprecate
21481 @cindex deprecated commands
21482 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
21483 @itemx maint undeprecate @var{command}
21484 Deprecate or undeprecate the named @var{command}. Deprecated commands
21485 cause @value{GDBN} to issue a warning when you use them. The optional
21486 argument @var{replacement} says which newer command should be used in
21487 favor of the deprecated one; if it is given, @value{GDBN} will mention
21488 the replacement as part of the warning.
21490 @kindex maint dump-me
21491 @item maint dump-me
21492 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
21493 Cause a fatal signal in the debugger and force it to dump its core.
21494 This is supported only on systems which support aborting a program
21495 with the @code{SIGQUIT} signal.
21497 @kindex maint internal-error
21498 @kindex maint internal-warning
21499 @item maint internal-error @r{[}@var{message-text}@r{]}
21500 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
21501 Cause @value{GDBN} to call the internal function @code{internal_error}
21502 or @code{internal_warning} and hence behave as though an internal error
21503 or internal warning has been detected. In addition to reporting the
21504 internal problem, these functions give the user the opportunity to
21505 either quit @value{GDBN} or create a core file of the current
21506 @value{GDBN} session.
21508 These commands take an optional parameter @var{message-text} that is
21509 used as the text of the error or warning message.
21511 Here's an example of using @code{indernal-error}:
21514 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
21515 @dots{}/maint.c:121: internal-error: testing, 1, 2
21516 A problem internal to GDB has been detected. Further
21517 debugging may prove unreliable.
21518 Quit this debugging session? (y or n) @kbd{n}
21519 Create a core file? (y or n) @kbd{n}
21523 @kindex maint packet
21524 @item maint packet @var{text}
21525 If @value{GDBN} is talking to an inferior via the serial protocol,
21526 then this command sends the string @var{text} to the inferior, and
21527 displays the response packet. @value{GDBN} supplies the initial
21528 @samp{$} character, the terminating @samp{#} character, and the
21531 @kindex maint print architecture
21532 @item maint print architecture @r{[}@var{file}@r{]}
21533 Print the entire architecture configuration. The optional argument
21534 @var{file} names the file where the output goes.
21536 @kindex maint print dummy-frames
21537 @item maint print dummy-frames
21538 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
21541 (@value{GDBP}) @kbd{b add}
21543 (@value{GDBP}) @kbd{print add(2,3)}
21544 Breakpoint 2, add (a=2, b=3) at @dots{}
21546 The program being debugged stopped while in a function called from GDB.
21548 (@value{GDBP}) @kbd{maint print dummy-frames}
21549 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
21550 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
21551 call_lo=0x01014000 call_hi=0x01014001
21555 Takes an optional file parameter.
21557 @kindex maint print registers
21558 @kindex maint print raw-registers
21559 @kindex maint print cooked-registers
21560 @kindex maint print register-groups
21561 @item maint print registers @r{[}@var{file}@r{]}
21562 @itemx maint print raw-registers @r{[}@var{file}@r{]}
21563 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
21564 @itemx maint print register-groups @r{[}@var{file}@r{]}
21565 Print @value{GDBN}'s internal register data structures.
21567 The command @code{maint print raw-registers} includes the contents of
21568 the raw register cache; the command @code{maint print cooked-registers}
21569 includes the (cooked) value of all registers; and the command
21570 @code{maint print register-groups} includes the groups that each
21571 register is a member of. @xref{Registers,, Registers, gdbint,
21572 @value{GDBN} Internals}.
21574 These commands take an optional parameter, a file name to which to
21575 write the information.
21577 @kindex maint print reggroups
21578 @item maint print reggroups @r{[}@var{file}@r{]}
21579 Print @value{GDBN}'s internal register group data structures. The
21580 optional argument @var{file} tells to what file to write the
21583 The register groups info looks like this:
21586 (@value{GDBP}) @kbd{maint print reggroups}
21599 This command forces @value{GDBN} to flush its internal register cache.
21601 @kindex maint print objfiles
21602 @cindex info for known object files
21603 @item maint print objfiles
21604 Print a dump of all known object files. For each object file, this
21605 command prints its name, address in memory, and all of its psymtabs
21608 @kindex maint print statistics
21609 @cindex bcache statistics
21610 @item maint print statistics
21611 This command prints, for each object file in the program, various data
21612 about that object file followed by the byte cache (@dfn{bcache})
21613 statistics for the object file. The objfile data includes the number
21614 of minimal, partical, full, and stabs symbols, the number of types
21615 defined by the objfile, the number of as yet unexpanded psym tables,
21616 the number of line tables and string tables, and the amount of memory
21617 used by the various tables. The bcache statistics include the counts,
21618 sizes, and counts of duplicates of all and unique objects, max,
21619 average, and median entry size, total memory used and its overhead and
21620 savings, and various measures of the hash table size and chain
21623 @kindex maint print type
21624 @cindex type chain of a data type
21625 @item maint print type @var{expr}
21626 Print the type chain for a type specified by @var{expr}. The argument
21627 can be either a type name or a symbol. If it is a symbol, the type of
21628 that symbol is described. The type chain produced by this command is
21629 a recursive definition of the data type as stored in @value{GDBN}'s
21630 data structures, including its flags and contained types.
21632 @kindex maint set dwarf2 max-cache-age
21633 @kindex maint show dwarf2 max-cache-age
21634 @item maint set dwarf2 max-cache-age
21635 @itemx maint show dwarf2 max-cache-age
21636 Control the DWARF 2 compilation unit cache.
21638 @cindex DWARF 2 compilation units cache
21639 In object files with inter-compilation-unit references, such as those
21640 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
21641 reader needs to frequently refer to previously read compilation units.
21642 This setting controls how long a compilation unit will remain in the
21643 cache if it is not referenced. A higher limit means that cached
21644 compilation units will be stored in memory longer, and more total
21645 memory will be used. Setting it to zero disables caching, which will
21646 slow down @value{GDBN} startup, but reduce memory consumption.
21648 @kindex maint set profile
21649 @kindex maint show profile
21650 @cindex profiling GDB
21651 @item maint set profile
21652 @itemx maint show profile
21653 Control profiling of @value{GDBN}.
21655 Profiling will be disabled until you use the @samp{maint set profile}
21656 command to enable it. When you enable profiling, the system will begin
21657 collecting timing and execution count data; when you disable profiling or
21658 exit @value{GDBN}, the results will be written to a log file. Remember that
21659 if you use profiling, @value{GDBN} will overwrite the profiling log file
21660 (often called @file{gmon.out}). If you have a record of important profiling
21661 data in a @file{gmon.out} file, be sure to move it to a safe location.
21663 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
21664 compiled with the @samp{-pg} compiler option.
21666 @kindex maint show-debug-regs
21667 @cindex x86 hardware debug registers
21668 @item maint show-debug-regs
21669 Control whether to show variables that mirror the x86 hardware debug
21670 registers. Use @code{ON} to enable, @code{OFF} to disable. If
21671 enabled, the debug registers values are shown when GDB inserts or
21672 removes a hardware breakpoint or watchpoint, and when the inferior
21673 triggers a hardware-assisted breakpoint or watchpoint.
21675 @kindex maint space
21676 @cindex memory used by commands
21678 Control whether to display memory usage for each command. If set to a
21679 nonzero value, @value{GDBN} will display how much memory each command
21680 took, following the command's own output. This can also be requested
21681 by invoking @value{GDBN} with the @option{--statistics} command-line
21682 switch (@pxref{Mode Options}).
21685 @cindex time of command execution
21687 Control whether to display the execution time for each command. If
21688 set to a nonzero value, @value{GDBN} will display how much time it
21689 took to execute each command, following the command's own output.
21690 This can also be requested by invoking @value{GDBN} with the
21691 @option{--statistics} command-line switch (@pxref{Mode Options}).
21693 @kindex maint translate-address
21694 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
21695 Find the symbol stored at the location specified by the address
21696 @var{addr} and an optional section name @var{section}. If found,
21697 @value{GDBN} prints the name of the closest symbol and an offset from
21698 the symbol's location to the specified address. This is similar to
21699 the @code{info address} command (@pxref{Symbols}), except that this
21700 command also allows to find symbols in other sections.
21704 The following command is useful for non-interactive invocations of
21705 @value{GDBN}, such as in the test suite.
21708 @item set watchdog @var{nsec}
21709 @kindex set watchdog
21710 @cindex watchdog timer
21711 @cindex timeout for commands
21712 Set the maximum number of seconds @value{GDBN} will wait for the
21713 target operation to finish. If this time expires, @value{GDBN}
21714 reports and error and the command is aborted.
21716 @item show watchdog
21717 Show the current setting of the target wait timeout.
21720 @node Remote Protocol
21721 @appendix @value{GDBN} Remote Serial Protocol
21726 * Stop Reply Packets::
21727 * General Query Packets::
21728 * Register Packet Format::
21730 * File-I/O remote protocol extension::
21736 There may be occasions when you need to know something about the
21737 protocol---for example, if there is only one serial port to your target
21738 machine, you might want your program to do something special if it
21739 recognizes a packet meant for @value{GDBN}.
21741 In the examples below, @samp{->} and @samp{<-} are used to indicate
21742 transmitted and received data respectfully.
21744 @cindex protocol, @value{GDBN} remote serial
21745 @cindex serial protocol, @value{GDBN} remote
21746 @cindex remote serial protocol
21747 All @value{GDBN} commands and responses (other than acknowledgments) are
21748 sent as a @var{packet}. A @var{packet} is introduced with the character
21749 @samp{$}, the actual @var{packet-data}, and the terminating character
21750 @samp{#} followed by a two-digit @var{checksum}:
21753 @code{$}@var{packet-data}@code{#}@var{checksum}
21757 @cindex checksum, for @value{GDBN} remote
21759 The two-digit @var{checksum} is computed as the modulo 256 sum of all
21760 characters between the leading @samp{$} and the trailing @samp{#} (an
21761 eight bit unsigned checksum).
21763 Implementors should note that prior to @value{GDBN} 5.0 the protocol
21764 specification also included an optional two-digit @var{sequence-id}:
21767 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
21770 @cindex sequence-id, for @value{GDBN} remote
21772 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
21773 has never output @var{sequence-id}s. Stubs that handle packets added
21774 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
21776 @cindex acknowledgment, for @value{GDBN} remote
21777 When either the host or the target machine receives a packet, the first
21778 response expected is an acknowledgment: either @samp{+} (to indicate
21779 the package was received correctly) or @samp{-} (to request
21783 -> @code{$}@var{packet-data}@code{#}@var{checksum}
21788 The host (@value{GDBN}) sends @var{command}s, and the target (the
21789 debugging stub incorporated in your program) sends a @var{response}. In
21790 the case of step and continue @var{command}s, the response is only sent
21791 when the operation has completed (the target has again stopped).
21793 @var{packet-data} consists of a sequence of characters with the
21794 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
21797 Fields within the packet should be separated using @samp{,} @samp{;} or
21798 @cindex remote protocol, field separator
21799 @samp{:}. Except where otherwise noted all numbers are represented in
21800 @sc{hex} with leading zeros suppressed.
21802 Implementors should note that prior to @value{GDBN} 5.0, the character
21803 @samp{:} could not appear as the third character in a packet (as it
21804 would potentially conflict with the @var{sequence-id}).
21806 Response @var{data} can be run-length encoded to save space. A @samp{*}
21807 means that the next character is an @sc{ascii} encoding giving a repeat count
21808 which stands for that many repetitions of the character preceding the
21809 @samp{*}. The encoding is @code{n+29}, yielding a printable character
21810 where @code{n >=3} (which is where rle starts to win). The printable
21811 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
21812 value greater than 126 should not be used.
21819 means the same as "0000".
21821 The error response returned for some packets includes a two character
21822 error number. That number is not well defined.
21824 For any @var{command} not supported by the stub, an empty response
21825 (@samp{$#00}) should be returned. That way it is possible to extend the
21826 protocol. A newer @value{GDBN} can tell if a packet is supported based
21829 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
21830 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
21836 The following table provides a complete list of all currently defined
21837 @var{command}s and their corresponding response @var{data}.
21838 @xref{File-I/O remote protocol extension}, for details about the File
21839 I/O extension of the remote protocol.
21843 @item @code{!} --- extended mode
21844 @cindex @code{!} packet
21846 Enable extended mode. In extended mode, the remote server is made
21847 persistent. The @samp{R} packet is used to restart the program being
21853 The remote target both supports and has enabled extended mode.
21856 @item @code{?} --- last signal
21857 @cindex @code{?} packet
21859 Indicate the reason the target halted. The reply is the same as for
21863 @xref{Stop Reply Packets}, for the reply specifications.
21865 @item @code{a} --- reserved
21867 Reserved for future use.
21869 @item @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,@dots{}} --- set program arguments @strong{(reserved)}
21870 @cindex @code{A} packet
21872 Initialized @samp{argv[]} array passed into program. @var{arglen}
21873 specifies the number of bytes in the hex encoded byte stream @var{arg}.
21874 See @code{gdbserver} for more details.
21882 @item @code{b}@var{baud} --- set baud @strong{(deprecated)}
21883 @cindex @code{b} packet
21885 Change the serial line speed to @var{baud}.
21887 JTC: @emph{When does the transport layer state change? When it's
21888 received, or after the ACK is transmitted. In either case, there are
21889 problems if the command or the acknowledgment packet is dropped.}
21891 Stan: @emph{If people really wanted to add something like this, and get
21892 it working for the first time, they ought to modify ser-unix.c to send
21893 some kind of out-of-band message to a specially-setup stub and have the
21894 switch happen "in between" packets, so that from remote protocol's point
21895 of view, nothing actually happened.}
21897 @item @code{B}@var{addr},@var{mode} --- set breakpoint @strong{(deprecated)}
21898 @cindex @code{B} packet
21900 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
21901 breakpoint at @var{addr}.
21903 This packet has been replaced by the @samp{Z} and @samp{z} packets
21904 (@pxref{insert breakpoint or watchpoint packet}).
21906 @item @code{c}@var{addr} --- continue
21907 @cindex @code{c} packet
21909 @var{addr} is address to resume. If @var{addr} is omitted, resume at
21913 @xref{Stop Reply Packets}, for the reply specifications.
21915 @item @code{C}@var{sig}@code{;}@var{addr} --- continue with signal
21916 @cindex @code{C} packet
21918 Continue with signal @var{sig} (hex signal number). If
21919 @code{;}@var{addr} is omitted, resume at same address.
21922 @xref{Stop Reply Packets}, for the reply specifications.
21924 @item @code{d} --- toggle debug @strong{(deprecated)}
21925 @cindex @code{d} packet
21929 @item @code{D} --- detach
21930 @cindex @code{D} packet
21932 Detach @value{GDBN} from the remote system. Sent to the remote target
21933 before @value{GDBN} disconnects via the @code{detach} command.
21937 @item @emph{no response}
21938 @value{GDBN} does not check for any response after sending this packet.
21941 @item @code{e} --- reserved
21943 Reserved for future use.
21945 @item @code{E} --- reserved
21947 Reserved for future use.
21949 @item @code{f} --- reserved
21951 Reserved for future use.
21953 @item @code{F}@var{RC}@code{,}@var{EE}@code{,}@var{CF}@code{;}@var{XX} --- Reply to target's F packet.
21954 @cindex @code{F} packet
21956 This packet is send by @value{GDBN} as reply to a @code{F} request packet
21957 sent by the target. This is part of the File-I/O protocol extension.
21958 @xref{File-I/O remote protocol extension}, for the specification.
21960 @item @code{g} --- read registers
21961 @anchor{read registers packet}
21962 @cindex @code{g} packet
21964 Read general registers.
21968 @item @var{XX@dots{}}
21969 Each byte of register data is described by two hex digits. The bytes
21970 with the register are transmitted in target byte order. The size of
21971 each register and their position within the @samp{g} @var{packet} are
21972 determined by the @value{GDBN} internal macros
21973 @var{DEPRECATED_REGISTER_RAW_SIZE} and @var{REGISTER_NAME} macros. The
21974 specification of several standard @code{g} packets is specified below.
21979 @item @code{G}@var{XX@dots{}} --- write regs
21980 @cindex @code{G} packet
21982 @xref{read registers packet}, for a description of the @var{XX@dots{}}
21993 @item @code{h} --- reserved
21995 Reserved for future use.
21997 @item @code{H}@var{c}@var{t@dots{}} --- set thread
21998 @cindex @code{H} packet
22000 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
22001 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
22002 should be @samp{c} for step and continue operations, @samp{g} for other
22003 operations. The thread designator @var{t@dots{}} may be -1, meaning all
22004 the threads, a thread number, or zero which means pick any thread.
22015 @c 'H': How restrictive (or permissive) is the thread model. If a
22016 @c thread is selected and stopped, are other threads allowed
22017 @c to continue to execute? As I mentioned above, I think the
22018 @c semantics of each command when a thread is selected must be
22019 @c described. For example:
22021 @c 'g': If the stub supports threads and a specific thread is
22022 @c selected, returns the register block from that thread;
22023 @c otherwise returns current registers.
22025 @c 'G' If the stub supports threads and a specific thread is
22026 @c selected, sets the registers of the register block of
22027 @c that thread; otherwise sets current registers.
22029 @item @code{i}@var{addr}@code{,}@var{nnn} --- cycle step @strong{(draft)}
22030 @anchor{cycle step packet}
22031 @cindex @code{i} packet
22033 Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
22034 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
22035 step starting at that address.
22037 @item @code{I} --- signal then cycle step @strong{(reserved)}
22038 @cindex @code{I} packet
22040 @xref{step with signal packet}. @xref{cycle step packet}.
22042 @item @code{j} --- reserved
22044 Reserved for future use.
22046 @item @code{J} --- reserved
22048 Reserved for future use.
22050 @item @code{k} --- kill request
22051 @cindex @code{k} packet
22053 FIXME: @emph{There is no description of how to operate when a specific
22054 thread context has been selected (i.e.@: does 'k' kill only that
22057 @item @code{K} --- reserved
22059 Reserved for future use.
22061 @item @code{l} --- reserved
22063 Reserved for future use.
22065 @item @code{L} --- reserved
22067 Reserved for future use.
22069 @item @code{m}@var{addr}@code{,}@var{length} --- read memory
22070 @cindex @code{m} packet
22072 Read @var{length} bytes of memory starting at address @var{addr}.
22073 Neither @value{GDBN} nor the stub assume that sized memory transfers are
22074 assumed using word aligned accesses. FIXME: @emph{A word aligned memory
22075 transfer mechanism is needed.}
22079 @item @var{XX@dots{}}
22080 @var{XX@dots{}} is mem contents. Can be fewer bytes than requested if able
22081 to read only part of the data. Neither @value{GDBN} nor the stub assume
22082 that sized memory transfers are assumed using word aligned
22083 accesses. FIXME: @emph{A word aligned memory transfer mechanism is
22089 @item @code{M}@var{addr},@var{length}@code{:}@var{XX@dots{}} --- write mem
22090 @cindex @code{M} packet
22092 Write @var{length} bytes of memory starting at address @var{addr}.
22093 @var{XX@dots{}} is the data.
22100 for an error (this includes the case where only part of the data was
22104 @item @code{n} --- reserved
22106 Reserved for future use.
22108 @item @code{N} --- reserved
22110 Reserved for future use.
22112 @item @code{o} --- reserved
22114 Reserved for future use.
22116 @item @code{O} --- reserved
22118 @item @code{p}@var{hex number of register} --- read register packet
22119 @cindex @code{p} packet
22121 @xref{read registers packet}, for a description of how the returned
22122 register value is encoded.
22126 @item @var{XX@dots{}}
22127 the register's value
22131 Indicating an unrecognized @var{query}.
22134 @item @code{P}@var{n@dots{}}@code{=}@var{r@dots{}} --- write register
22135 @anchor{write register packet}
22136 @cindex @code{P} packet
22138 Write register @var{n@dots{}} with value @var{r@dots{}}, which contains two hex
22139 digits for each byte in the register (target byte order).
22149 @item @code{q}@var{query} --- general query
22150 @anchor{general query packet}
22151 @cindex @code{q} packet
22153 Request info about @var{query}. In general @value{GDBN} queries have a
22154 leading upper case letter. Custom vendor queries should use a company
22155 prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may optionally
22156 be followed by a @samp{,} or @samp{;} separated list. Stubs must ensure
22157 that they match the full @var{query} name.
22161 @item @var{XX@dots{}}
22162 Hex encoded data from query. The reply can not be empty.
22166 Indicating an unrecognized @var{query}.
22169 @item @code{Q}@var{var}@code{=}@var{val} --- general set
22170 @cindex @code{Q} packet
22172 Set value of @var{var} to @var{val}.
22174 @xref{general query packet}, for a discussion of naming conventions.
22176 @item @code{r} --- reset @strong{(deprecated)}
22177 @cindex @code{r} packet
22179 Reset the entire system.
22181 @item @code{R}@var{XX} --- remote restart
22182 @cindex @code{R} packet
22184 Restart the program being debugged. @var{XX}, while needed, is ignored.
22185 This packet is only available in extended mode.
22189 @item @emph{no reply}
22190 The @samp{R} packet has no reply.
22193 @item @code{s}@var{addr} --- step
22194 @cindex @code{s} packet
22196 @var{addr} is address to resume. If @var{addr} is omitted, resume at
22200 @xref{Stop Reply Packets}, for the reply specifications.
22202 @item @code{S}@var{sig}@code{;}@var{addr} --- step with signal
22203 @anchor{step with signal packet}
22204 @cindex @code{S} packet
22206 Like @samp{C} but step not continue.
22209 @xref{Stop Reply Packets}, for the reply specifications.
22211 @item @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} --- search
22212 @cindex @code{t} packet
22214 Search backwards starting at address @var{addr} for a match with pattern
22215 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
22216 @var{addr} must be at least 3 digits.
22218 @item @code{T}@var{XX} --- thread alive
22219 @cindex @code{T} packet
22221 Find out if the thread XX is alive.
22226 thread is still alive
22231 @item @code{u} --- reserved
22233 Reserved for future use.
22235 @item @code{U} --- reserved
22237 Reserved for future use.
22239 @item @code{v} --- verbose packet prefix
22241 Packets starting with @code{v} are identified by a multi-letter name,
22242 up to the first @code{;} or @code{?} (or the end of the packet).
22244 @item @code{vCont}[;@var{action}[@code{:}@var{tid}]]... --- extended resume
22245 @cindex @code{vCont} packet
22247 Resume the inferior. Different actions may be specified for each thread.
22248 If an action is specified with no @var{tid}, then it is applied to any
22249 threads that don't have a specific action specified; if no default action is
22250 specified then other threads should remain stopped. Specifying multiple
22251 default actions is an error; specifying no actions is also an error.
22252 Thread IDs are specified in hexadecimal. Currently supported actions are:
22258 Continue with signal @var{sig}. @var{sig} should be two hex digits.
22262 Step with signal @var{sig}. @var{sig} should be two hex digits.
22265 The optional @var{addr} argument normally associated with these packets is
22266 not supported in @code{vCont}.
22269 @xref{Stop Reply Packets}, for the reply specifications.
22271 @item @code{vCont?} --- extended resume query
22272 @cindex @code{vCont?} packet
22274 Query support for the @code{vCont} packet.
22278 @item @code{vCont}[;@var{action}]...
22279 The @code{vCont} packet is supported. Each @var{action} is a supported
22280 command in the @code{vCont} packet.
22282 The @code{vCont} packet is not supported.
22285 @item @code{V} --- reserved
22287 Reserved for future use.
22289 @item @code{w} --- reserved
22291 Reserved for future use.
22293 @item @code{W} --- reserved
22295 Reserved for future use.
22297 @item @code{x} --- reserved
22299 Reserved for future use.
22301 @item @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX@dots{}} --- write mem (binary)
22302 @cindex @code{X} packet
22304 @var{addr} is address, @var{length} is number of bytes, @var{XX@dots{}}
22305 is binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
22306 escaped using @code{0x7d}, and then XORed with @code{0x20}.
22307 For example, @code{0x7d} would be transmitted as @code{0x7d 0x5d}.
22317 @item @code{y} --- reserved
22319 Reserved for future use.
22321 @item @code{Y} reserved
22323 Reserved for future use.
22325 @item @code{z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- remove breakpoint or watchpoint @strong{(draft)}
22326 @itemx @code{Z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- insert breakpoint or watchpoint @strong{(draft)}
22327 @anchor{insert breakpoint or watchpoint packet}
22328 @cindex @code{z} packet
22329 @cindex @code{Z} packets
22331 Insert (@code{Z}) or remove (@code{z}) a @var{type} breakpoint or
22332 watchpoint starting at address @var{address} and covering the next
22333 @var{length} bytes.
22335 Each breakpoint and watchpoint packet @var{type} is documented
22338 @emph{Implementation notes: A remote target shall return an empty string
22339 for an unrecognized breakpoint or watchpoint packet @var{type}. A
22340 remote target shall support either both or neither of a given
22341 @code{Z}@var{type}@dots{} and @code{z}@var{type}@dots{} packet pair. To
22342 avoid potential problems with duplicate packets, the operations should
22343 be implemented in an idempotent way.}
22345 @item @code{z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- remove memory breakpoint @strong{(draft)}
22346 @item @code{Z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- insert memory breakpoint @strong{(draft)}
22347 @cindex @code{z0} packet
22348 @cindex @code{Z0} packet
22350 Insert (@code{Z0}) or remove (@code{z0}) a memory breakpoint at address
22351 @code{addr} of size @code{length}.
22353 A memory breakpoint is implemented by replacing the instruction at
22354 @var{addr} with a software breakpoint or trap instruction. The
22355 @code{length} is used by targets that indicates the size of the
22356 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
22357 @sc{mips} can insert either a 2 or 4 byte breakpoint).
22359 @emph{Implementation note: It is possible for a target to copy or move
22360 code that contains memory breakpoints (e.g., when implementing
22361 overlays). The behavior of this packet, in the presence of such a
22362 target, is not defined.}
22374 @item @code{z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- remove hardware breakpoint @strong{(draft)}
22375 @item @code{Z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- insert hardware breakpoint @strong{(draft)}
22376 @cindex @code{z1} packet
22377 @cindex @code{Z1} packet
22379 Insert (@code{Z1}) or remove (@code{z1}) a hardware breakpoint at
22380 address @code{addr} of size @code{length}.
22382 A hardware breakpoint is implemented using a mechanism that is not
22383 dependant on being able to modify the target's memory.
22385 @emph{Implementation note: A hardware breakpoint is not affected by code
22398 @item @code{z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- remove write watchpoint @strong{(draft)}
22399 @item @code{Z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- insert write watchpoint @strong{(draft)}
22400 @cindex @code{z2} packet
22401 @cindex @code{Z2} packet
22403 Insert (@code{Z2}) or remove (@code{z2}) a write watchpoint.
22415 @item @code{z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- remove read watchpoint @strong{(draft)}
22416 @item @code{Z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- insert read watchpoint @strong{(draft)}
22417 @cindex @code{z3} packet
22418 @cindex @code{Z3} packet
22420 Insert (@code{Z3}) or remove (@code{z3}) a read watchpoint.
22432 @item @code{z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- remove access watchpoint @strong{(draft)}
22433 @item @code{Z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- insert access watchpoint @strong{(draft)}
22434 @cindex @code{z4} packet
22435 @cindex @code{Z4} packet
22437 Insert (@code{Z4}) or remove (@code{z4}) an access watchpoint.
22451 @node Stop Reply Packets
22452 @section Stop Reply Packets
22453 @cindex stop reply packets
22455 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
22456 receive any of the below as a reply. In the case of the @samp{C},
22457 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
22458 when the target halts. In the below the exact meaning of @samp{signal
22459 number} is poorly defined. In general one of the UNIX signal numbering
22460 conventions is used.
22465 @var{AA} is the signal number
22467 @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
22468 @cindex @code{T} packet reply
22470 @var{AA} = two hex digit signal number; @var{n...} = register number
22471 (hex), @var{r...} = target byte ordered register contents, size defined
22472 by @code{DEPRECATED_REGISTER_RAW_SIZE}; @var{n...} = @samp{thread},
22473 @var{r...} = thread process ID, this is a hex integer; @var{n...} =
22474 (@samp{watch} | @samp{rwatch} | @samp{awatch}, @var{r...} = data
22475 address, this is a hex integer; @var{n...} = other string not starting
22476 with valid hex digit. @value{GDBN} should ignore this @var{n...},
22477 @var{r...} pair and go on to the next. This way we can extend the
22482 The process exited, and @var{AA} is the exit status. This is only
22483 applicable to certain targets.
22487 The process terminated with signal @var{AA}.
22489 @item O@var{XX@dots{}}
22491 @var{XX@dots{}} is hex encoding of @sc{ascii} data. This can happen at
22492 any time while the program is running and the debugger should continue
22493 to wait for @samp{W}, @samp{T}, etc.
22495 @item F@var{call-id}@code{,}@var{parameter@dots{}}
22497 @var{call-id} is the identifier which says which host system call should
22498 be called. This is just the name of the function. Translation into the
22499 correct system call is only applicable as it's defined in @value{GDBN}.
22500 @xref{File-I/O remote protocol extension}, for a list of implemented
22503 @var{parameter@dots{}} is a list of parameters as defined for this very
22506 The target replies with this packet when it expects @value{GDBN} to call
22507 a host system call on behalf of the target. @value{GDBN} replies with
22508 an appropriate @code{F} packet and keeps up waiting for the next reply
22509 packet from the target. The latest @samp{C}, @samp{c}, @samp{S} or
22510 @samp{s} action is expected to be continued.
22511 @xref{File-I/O remote protocol extension}, for more details.
22515 @node General Query Packets
22516 @section General Query Packets
22517 @cindex remote query requests
22519 The following set and query packets have already been defined.
22523 @item @code{q}@code{C} --- current thread
22524 @cindex current thread, remote request
22525 @cindex @code{qC} packet
22526 Return the current thread id.
22530 @item @code{QC}@var{pid}
22531 Where @var{pid} is an unsigned hexidecimal process id.
22533 Any other reply implies the old pid.
22536 @item @code{q}@code{fThreadInfo} -- all thread ids
22537 @cindex list active threads, remote request
22538 @cindex @code{qfThreadInfo} packet
22539 @code{q}@code{sThreadInfo}
22541 Obtain a list of active thread ids from the target (OS). Since there
22542 may be too many active threads to fit into one reply packet, this query
22543 works iteratively: it may require more than one query/reply sequence to
22544 obtain the entire list of threads. The first query of the sequence will
22545 be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
22546 sequence will be the @code{qs}@code{ThreadInfo} query.
22548 NOTE: replaces the @code{qL} query (see below).
22552 @item @code{m}@var{id}
22554 @item @code{m}@var{id},@var{id}@dots{}
22555 a comma-separated list of thread ids
22557 (lower case 'el') denotes end of list.
22560 In response to each query, the target will reply with a list of one or
22561 more thread ids, in big-endian unsigned hex, separated by commas.
22562 @value{GDBN} will respond to each reply with a request for more thread
22563 ids (using the @code{qs} form of the query), until the target responds
22564 with @code{l} (lower-case el, for @code{'last'}).
22566 @item @code{q}@code{ThreadExtraInfo}@code{,}@var{id} --- extra thread info
22567 @cindex thread attributes info, remote request
22568 @cindex @code{qThreadExtraInfo} packet
22569 Where @var{id} is a thread-id in big-endian hex. Obtain a printable
22570 string description of a thread's attributes from the target OS. This
22571 string may contain anything that the target OS thinks is interesting for
22572 @value{GDBN} to tell the user about the thread. The string is displayed
22573 in @value{GDBN}'s @samp{info threads} display. Some examples of
22574 possible thread extra info strings are ``Runnable'', or ``Blocked on
22579 @item @var{XX@dots{}}
22580 Where @var{XX@dots{}} is a hex encoding of @sc{ascii} data, comprising
22581 the printable string containing the extra information about the thread's
22585 @item @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} --- query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
22587 Obtain thread information from RTOS. Where: @var{startflag} (one hex
22588 digit) is one to indicate the first query and zero to indicate a
22589 subsequent query; @var{threadcount} (two hex digits) is the maximum
22590 number of threads the response packet can contain; and @var{nextthread}
22591 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
22592 returned in the response as @var{argthread}.
22594 NOTE: this query is replaced by the @code{q}@code{fThreadInfo} query
22599 @item @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread@dots{}}
22600 Where: @var{count} (two hex digits) is the number of threads being
22601 returned; @var{done} (one hex digit) is zero to indicate more threads
22602 and one indicates no further threads; @var{argthreadid} (eight hex
22603 digits) is @var{nextthread} from the request packet; @var{thread@dots{}}
22604 is a sequence of thread IDs from the target. @var{threadid} (eight hex
22605 digits). See @code{remote.c:parse_threadlist_response()}.
22608 @item @code{q}@code{CRC:}@var{addr}@code{,}@var{length} --- compute CRC of memory block
22609 @cindex CRC of memory block, remote request
22610 @cindex @code{qCRC} packet
22613 @item @code{E}@var{NN}
22614 An error (such as memory fault)
22615 @item @code{C}@var{CRC32}
22616 A 32 bit cyclic redundancy check of the specified memory region.
22619 @item @code{q}@code{Offsets} --- query sect offs
22620 @cindex section offsets, remote request
22621 @cindex @code{qOffsets} packet
22622 Get section offsets that the target used when re-locating the downloaded
22623 image. @emph{Note: while a @code{Bss} offset is included in the
22624 response, @value{GDBN} ignores this and instead applies the @code{Data}
22625 offset to the @code{Bss} section.}
22629 @item @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
22632 @item @code{q}@code{P}@var{mode}@var{threadid} --- thread info request
22633 @cindex thread information, remote request
22634 @cindex @code{qP} packet
22635 Returns information on @var{threadid}. Where: @var{mode} is a hex
22636 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
22643 See @code{remote.c:remote_unpack_thread_info_response()}.
22645 @item @code{q}@code{Rcmd,}@var{command} --- remote command
22646 @cindex execute remote command, remote request
22647 @cindex @code{qRcmd} packet
22648 @var{command} (hex encoded) is passed to the local interpreter for
22649 execution. Invalid commands should be reported using the output string.
22650 Before the final result packet, the target may also respond with a
22651 number of intermediate @code{O}@var{output} console output packets.
22652 @emph{Implementors should note that providing access to a stubs's
22653 interpreter may have security implications}.
22658 A command response with no output.
22660 A command response with the hex encoded output string @var{OUTPUT}.
22661 @item @code{E}@var{NN}
22662 Indicate a badly formed request.
22664 When @samp{q}@samp{Rcmd} is not recognized.
22667 @item @code{qSymbol::} --- symbol lookup
22668 @cindex symbol lookup, remote request
22669 @cindex @code{qSymbol} packet
22670 Notify the target that @value{GDBN} is prepared to serve symbol lookup
22671 requests. Accept requests from the target for the values of symbols.
22676 The target does not need to look up any (more) symbols.
22677 @item @code{qSymbol:}@var{sym_name}
22678 The target requests the value of symbol @var{sym_name} (hex encoded).
22679 @value{GDBN} may provide the value by using the
22680 @code{qSymbol:}@var{sym_value}:@var{sym_name} message, described below.
22683 @item @code{qSymbol:}@var{sym_value}:@var{sym_name} --- symbol value
22685 Set the value of @var{sym_name} to @var{sym_value}.
22687 @var{sym_name} (hex encoded) is the name of a symbol whose value the
22688 target has previously requested.
22690 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
22691 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
22697 The target does not need to look up any (more) symbols.
22698 @item @code{qSymbol:}@var{sym_name}
22699 The target requests the value of a new symbol @var{sym_name} (hex
22700 encoded). @value{GDBN} will continue to supply the values of symbols
22701 (if available), until the target ceases to request them.
22704 @item @code{qPart}:@var{object}:@code{read}:@var{annex}:@var{offset},@var{length} --- read special data
22705 @cindex read special object, remote request
22706 @cindex @code{qPart} packet
22707 Read uninterpreted bytes from the target's special data area
22708 identified by the keyword @code{object}.
22709 Request @var{length} bytes starting at @var{offset} bytes into the data.
22710 The content and encoding of @var{annex} is specific to the object;
22711 it can supply additional details about what data to access.
22713 Here are the specific requests of this form defined so far.
22714 All @samp{@code{qPart}:@var{object}:@code{read}:@dots{}}
22715 requests use the same reply formats, listed below.
22718 @item @code{qPart}:@code{auxv}:@code{read}::@var{offset},@var{length}
22719 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
22720 auxiliary vector}, and see @ref{Remote configuration,
22721 read-aux-vector-packet}. Note @var{annex} must be empty.
22727 The @var{offset} in the request is at the end of the data.
22728 There is no more data to be read.
22730 @item @var{XX@dots{}}
22731 Hex encoded data bytes read.
22732 This may be fewer bytes than the @var{length} in the request.
22735 The request was malformed, or @var{annex} was invalid.
22737 @item @code{E}@var{nn}
22738 The offset was invalid, or there was an error encountered reading the data.
22739 @var{nn} is a hex-encoded @code{errno} value.
22741 @item @code{""} (empty)
22742 An empty reply indicates the @var{object} or @var{annex} string was not
22743 recognized by the stub.
22746 @item @code{qPart}:@var{object}:@code{write}:@var{annex}:@var{offset}:@var{data@dots{}}
22747 @cindex write data into object, remote request
22748 Write uninterpreted bytes into the target's special data area
22749 identified by the keyword @code{object},
22750 starting at @var{offset} bytes into the data.
22751 @var{data@dots{}} is the hex-encoded data to be written.
22752 The content and encoding of @var{annex} is specific to the object;
22753 it can supply additional details about what data to access.
22755 No requests of this form are presently in use. This specification
22756 serves as a placeholder to document the common format that new
22757 specific request specifications ought to use.
22762 @var{nn} (hex encoded) is the number of bytes written.
22763 This may be fewer bytes than supplied in the request.
22766 The request was malformed, or @var{annex} was invalid.
22768 @item @code{E}@var{nn}
22769 The offset was invalid, or there was an error encountered writing the data.
22770 @var{nn} is a hex-encoded @code{errno} value.
22772 @item @code{""} (empty)
22773 An empty reply indicates the @var{object} or @var{annex} string was not
22774 recognized by the stub, or that the object does not support writing.
22777 @item @code{qPart}:@var{object}:@var{operation}:@dots{}
22778 Requests of this form may be added in the future. When a stub does
22779 not recognize the @var{object} keyword, or its support for
22780 @var{object} does not recognize the @var{operation} keyword,
22781 the stub must respond with an empty packet.
22783 @item @code{qGetTLSAddr}:@var{thread-id},@var{offset},@var{lm} --- get thread local storage address
22784 @cindex get thread-local storage address, remote request
22785 @cindex @code{qGetTLSAddr} packet
22786 Fetch the address associated with thread local storage specified
22787 by @var{thread-id}, @var{offset}, and @var{lm}.
22789 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
22790 thread for which to fetch the TLS address.
22792 @var{offset} is the (big endian, hex encoded) offset associated with the
22793 thread local variable. (This offset is obtained from the debug
22794 information associated with the variable.)
22796 @var{lm} is the (big endian, hex encoded) OS/ABI specific encoding of the
22797 the load module associated with the thread local storage. For example,
22798 a @sc{gnu}/Linux system will pass the link map address of the shared
22799 object associated with the thread local storage under consideration.
22800 Other operating environments may choose to represent the load module
22801 differently, so the precise meaning of this parameter will vary.
22805 @item @var{XX@dots{}}
22806 Hex encoded (big endian) bytes representing the address of the thread
22807 local storage requested.
22809 @item @code{E}@var{nn} (where @var{nn} are hex digits)
22812 @item @code{""} (empty)
22813 An empty reply indicates that @code{qGetTLSAddr} is not supported by the stub.
22816 Use of this request packet is controlled by the @code{set remote
22817 get-thread-local-storage-address} command (@pxref{Remote
22818 configuration, set remote get-thread-local-storage-address}).
22822 @node Register Packet Format
22823 @section Register Packet Format
22825 The following @samp{g}/@samp{G} packets have previously been defined.
22826 In the below, some thirty-two bit registers are transferred as
22827 sixty-four bits. Those registers should be zero/sign extended (which?)
22828 to fill the space allocated. Register bytes are transfered in target
22829 byte order. The two nibbles within a register byte are transfered
22830 most-significant - least-significant.
22836 All registers are transfered as thirty-two bit quantities in the order:
22837 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
22838 registers; fsr; fir; fp.
22842 All registers are transfered as sixty-four bit quantities (including
22843 thirty-two bit registers such as @code{sr}). The ordering is the same
22851 Example sequence of a target being re-started. Notice how the restart
22852 does not get any direct output:
22857 @emph{target restarts}
22860 <- @code{T001:1234123412341234}
22864 Example sequence of a target being stepped by a single instruction:
22867 -> @code{G1445@dots{}}
22872 <- @code{T001:1234123412341234}
22876 <- @code{1455@dots{}}
22880 @node File-I/O remote protocol extension
22881 @section File-I/O remote protocol extension
22882 @cindex File-I/O remote protocol extension
22885 * File-I/O Overview::
22886 * Protocol basics::
22887 * The F request packet::
22888 * The F reply packet::
22889 * Memory transfer::
22890 * The Ctrl-C message::
22892 * The isatty call::
22893 * The system call::
22894 * List of supported calls::
22895 * Protocol specific representation of datatypes::
22897 * File-I/O Examples::
22900 @node File-I/O Overview
22901 @subsection File-I/O Overview
22902 @cindex file-i/o overview
22904 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
22905 target to use the host's file system and console I/O when calling various
22906 system calls. System calls on the target system are translated into a
22907 remote protocol packet to the host system which then performs the needed
22908 actions and returns with an adequate response packet to the target system.
22909 This simulates file system operations even on targets that lack file systems.
22911 The protocol is defined host- and target-system independent. It uses
22912 its own independent representation of datatypes and values. Both,
22913 @value{GDBN} and the target's @value{GDBN} stub are responsible for
22914 translating the system dependent values into the unified protocol values
22915 when data is transmitted.
22917 The communication is synchronous. A system call is possible only
22918 when GDB is waiting for the @samp{C}, @samp{c}, @samp{S} or @samp{s}
22919 packets. While @value{GDBN} handles the request for a system call,
22920 the target is stopped to allow deterministic access to the target's
22921 memory. Therefore File-I/O is not interuptible by target signals. It
22922 is possible to interrupt File-I/O by a user interrupt (Ctrl-C), though.
22924 The target's request to perform a host system call does not finish
22925 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
22926 after finishing the system call, the target returns to continuing the
22927 previous activity (continue, step). No additional continue or step
22928 request from @value{GDBN} is required.
22931 (@value{GDBP}) continue
22932 <- target requests 'system call X'
22933 target is stopped, @value{GDBN} executes system call
22934 -> GDB returns result
22935 ... target continues, GDB returns to wait for the target
22936 <- target hits breakpoint and sends a Txx packet
22939 The protocol is only used for files on the host file system and
22940 for I/O on the console. Character or block special devices, pipes,
22941 named pipes or sockets or any other communication method on the host
22942 system are not supported by this protocol.
22944 @node Protocol basics
22945 @subsection Protocol basics
22946 @cindex protocol basics, file-i/o
22948 The File-I/O protocol uses the @code{F} packet, as request as well
22949 as as reply packet. Since a File-I/O system call can only occur when
22950 @value{GDBN} is waiting for the continuing or stepping target, the
22951 File-I/O request is a reply that @value{GDBN} has to expect as a result
22952 of a former @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
22953 This @code{F} packet contains all information needed to allow @value{GDBN}
22954 to call the appropriate host system call:
22958 A unique identifier for the requested system call.
22961 All parameters to the system call. Pointers are given as addresses
22962 in the target memory address space. Pointers to strings are given as
22963 pointer/length pair. Numerical values are given as they are.
22964 Numerical control values are given in a protocol specific representation.
22968 At that point @value{GDBN} has to perform the following actions.
22972 If parameter pointer values are given, which point to data needed as input
22973 to a system call, @value{GDBN} requests this data from the target with a
22974 standard @code{m} packet request. This additional communication has to be
22975 expected by the target implementation and is handled as any other @code{m}
22979 @value{GDBN} translates all value from protocol representation to host
22980 representation as needed. Datatypes are coerced into the host types.
22983 @value{GDBN} calls the system call
22986 It then coerces datatypes back to protocol representation.
22989 If pointer parameters in the request packet point to buffer space in which
22990 a system call is expected to copy data to, the data is transmitted to the
22991 target using a @code{M} or @code{X} packet. This packet has to be expected
22992 by the target implementation and is handled as any other @code{M} or @code{X}
22997 Eventually @value{GDBN} replies with another @code{F} packet which contains all
22998 necessary information for the target to continue. This at least contains
23005 @code{errno}, if has been changed by the system call.
23012 After having done the needed type and value coercion, the target continues
23013 the latest continue or step action.
23015 @node The F request packet
23016 @subsection The @code{F} request packet
23017 @cindex file-i/o request packet
23018 @cindex @code{F} request packet
23020 The @code{F} request packet has the following format:
23025 @code{F}@var{call-id}@code{,}@var{parameter@dots{}}
23028 @var{call-id} is the identifier to indicate the host system call to be called.
23029 This is just the name of the function.
23031 @var{parameter@dots{}} are the parameters to the system call.
23035 Parameters are hexadecimal integer values, either the real values in case
23036 of scalar datatypes, as pointers to target buffer space in case of compound
23037 datatypes and unspecified memory areas or as pointer/length pairs in case
23038 of string parameters. These are appended to the call-id, each separated
23039 from its predecessor by a comma. All values are transmitted in ASCII
23040 string representation, pointer/length pairs separated by a slash.
23042 @node The F reply packet
23043 @subsection The @code{F} reply packet
23044 @cindex file-i/o reply packet
23045 @cindex @code{F} reply packet
23047 The @code{F} reply packet has the following format:
23052 @code{F}@var{retcode}@code{,}@var{errno}@code{,}@var{Ctrl-C flag}@code{;}@var{call specific attachment}
23055 @var{retcode} is the return code of the system call as hexadecimal value.
23057 @var{errno} is the errno set by the call, in protocol specific representation.
23058 This parameter can be omitted if the call was successful.
23060 @var{Ctrl-C flag} is only send if the user requested a break. In this
23061 case, @var{errno} must be send as well, even if the call was successful.
23062 The @var{Ctrl-C flag} itself consists of the character 'C':
23069 or, if the call was interupted before the host call has been performed:
23076 assuming 4 is the protocol specific representation of @code{EINTR}.
23080 @node Memory transfer
23081 @subsection Memory transfer
23082 @cindex memory transfer, in file-i/o protocol
23084 Structured data which is transferred using a memory read or write as e.g.@:
23085 a @code{struct stat} is expected to be in a protocol specific format with
23086 all scalar multibyte datatypes being big endian. This should be done by
23087 the target before the @code{F} packet is sent resp.@: by @value{GDBN} before
23088 it transfers memory to the target. Transferred pointers to structured
23089 data should point to the already coerced data at any time.
23091 @node The Ctrl-C message
23092 @subsection The Ctrl-C message
23093 @cindex ctrl-c message, in file-i/o protocol
23095 A special case is, if the @var{Ctrl-C flag} is set in the @value{GDBN}
23096 reply packet. In this case the target should behave, as if it had
23097 gotten a break message. The meaning for the target is ``system call
23098 interupted by @code{SIGINT}''. Consequentially, the target should actually stop
23099 (as with a break message) and return to @value{GDBN} with a @code{T02}
23100 packet. In this case, it's important for the target to know, in which
23101 state the system call was interrupted. Since this action is by design
23102 not an atomic operation, we have to differ between two cases:
23106 The system call hasn't been performed on the host yet.
23109 The system call on the host has been finished.
23113 These two states can be distinguished by the target by the value of the
23114 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
23115 call hasn't been performed. This is equivalent to the @code{EINTR} handling
23116 on POSIX systems. In any other case, the target may presume that the
23117 system call has been finished --- successful or not --- and should behave
23118 as if the break message arrived right after the system call.
23120 @value{GDBN} must behave reliable. If the system call has not been called
23121 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
23122 @code{errno} in the packet. If the system call on the host has been finished
23123 before the user requests a break, the full action must be finshed by
23124 @value{GDBN}. This requires sending @code{M} or @code{X} packets as they fit.
23125 The @code{F} packet may only be send when either nothing has happened
23126 or the full action has been completed.
23129 @subsection Console I/O
23130 @cindex console i/o as part of file-i/o
23132 By default and if not explicitely closed by the target system, the file
23133 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
23134 on the @value{GDBN} console is handled as any other file output operation
23135 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
23136 by @value{GDBN} so that after the target read request from file descriptor
23137 0 all following typing is buffered until either one of the following
23142 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, the
23144 system call is treated as finished.
23147 The user presses @kbd{Enter}. This is treated as end of input with a trailing
23151 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
23152 character, especially no Ctrl-D is appended to the input.
23156 If the user has typed more characters as fit in the buffer given to
23157 the read call, the trailing characters are buffered in @value{GDBN} until
23158 either another @code{read(0, @dots{})} is requested by the target or debugging
23159 is stopped on users request.
23161 @node The isatty call
23162 @subsection The isatty(3) call
23163 @cindex isatty call, file-i/o protocol
23165 A special case in this protocol is the library call @code{isatty} which
23166 is implemented as its own call inside of this protocol. It returns
23167 1 to the target if the file descriptor given as parameter is attached
23168 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
23169 would require implementing @code{ioctl} and would be more complex than
23172 @node The system call
23173 @subsection The system(3) call
23174 @cindex system call, file-i/o protocol
23176 The other special case in this protocol is the @code{system} call which
23177 is implemented as its own call, too. @value{GDBN} is taking over the full
23178 task of calling the necessary host calls to perform the @code{system}
23179 call. The return value of @code{system} is simplified before it's returned
23180 to the target. Basically, the only signal transmitted back is @code{EINTR}
23181 in case the user pressed @kbd{Ctrl-C}. Otherwise the return value consists
23182 entirely of the exit status of the called command.
23184 Due to security concerns, the @code{system} call is by default refused
23185 by @value{GDBN}. The user has to allow this call explicitly with the
23186 @kbd{set remote system-call-allowed 1} command.
23189 @item set remote system-call-allowed
23190 @kindex set remote system-call-allowed
23191 Control whether to allow the @code{system} calls in the File I/O
23192 protocol for the remote target. The default is zero (disabled).
23194 @item show remote system-call-allowed
23195 @kindex show remote system-call-allowed
23196 Show the current setting of system calls for the remote File I/O
23200 @node List of supported calls
23201 @subsection List of supported calls
23202 @cindex list of supported file-i/o calls
23219 @unnumberedsubsubsec open
23220 @cindex open, file-i/o system call
23224 int open(const char *pathname, int flags);
23225 int open(const char *pathname, int flags, mode_t mode);
23228 Fopen,pathptr/len,flags,mode
23232 @code{flags} is the bitwise or of the following values:
23236 If the file does not exist it will be created. The host
23237 rules apply as far as file ownership and time stamps
23241 When used with O_CREAT, if the file already exists it is
23242 an error and open() fails.
23245 If the file already exists and the open mode allows
23246 writing (O_RDWR or O_WRONLY is given) it will be
23247 truncated to length 0.
23250 The file is opened in append mode.
23253 The file is opened for reading only.
23256 The file is opened for writing only.
23259 The file is opened for reading and writing.
23262 Each other bit is silently ignored.
23267 @code{mode} is the bitwise or of the following values:
23271 User has read permission.
23274 User has write permission.
23277 Group has read permission.
23280 Group has write permission.
23283 Others have read permission.
23286 Others have write permission.
23289 Each other bit is silently ignored.
23294 @exdent Return value:
23295 open returns the new file descriptor or -1 if an error
23303 pathname already exists and O_CREAT and O_EXCL were used.
23306 pathname refers to a directory.
23309 The requested access is not allowed.
23312 pathname was too long.
23315 A directory component in pathname does not exist.
23318 pathname refers to a device, pipe, named pipe or socket.
23321 pathname refers to a file on a read-only filesystem and
23322 write access was requested.
23325 pathname is an invalid pointer value.
23328 No space on device to create the file.
23331 The process already has the maximum number of files open.
23334 The limit on the total number of files open on the system
23338 The call was interrupted by the user.
23342 @unnumberedsubsubsec close
23343 @cindex close, file-i/o system call
23352 @exdent Return value:
23353 close returns zero on success, or -1 if an error occurred.
23360 fd isn't a valid open file descriptor.
23363 The call was interrupted by the user.
23367 @unnumberedsubsubsec read
23368 @cindex read, file-i/o system call
23372 int read(int fd, void *buf, unsigned int count);
23375 Fread,fd,bufptr,count
23377 @exdent Return value:
23378 On success, the number of bytes read is returned.
23379 Zero indicates end of file. If count is zero, read
23380 returns zero as well. On error, -1 is returned.
23387 fd is not a valid file descriptor or is not open for
23391 buf is an invalid pointer value.
23394 The call was interrupted by the user.
23398 @unnumberedsubsubsec write
23399 @cindex write, file-i/o system call
23403 int write(int fd, const void *buf, unsigned int count);
23406 Fwrite,fd,bufptr,count
23408 @exdent Return value:
23409 On success, the number of bytes written are returned.
23410 Zero indicates nothing was written. On error, -1
23418 fd is not a valid file descriptor or is not open for
23422 buf is an invalid pointer value.
23425 An attempt was made to write a file that exceeds the
23426 host specific maximum file size allowed.
23429 No space on device to write the data.
23432 The call was interrupted by the user.
23436 @unnumberedsubsubsec lseek
23437 @cindex lseek, file-i/o system call
23441 long lseek (int fd, long offset, int flag);
23444 Flseek,fd,offset,flag
23447 @code{flag} is one of:
23451 The offset is set to offset bytes.
23454 The offset is set to its current location plus offset
23458 The offset is set to the size of the file plus offset
23463 @exdent Return value:
23464 On success, the resulting unsigned offset in bytes from
23465 the beginning of the file is returned. Otherwise, a
23466 value of -1 is returned.
23473 fd is not a valid open file descriptor.
23476 fd is associated with the @value{GDBN} console.
23479 flag is not a proper value.
23482 The call was interrupted by the user.
23486 @unnumberedsubsubsec rename
23487 @cindex rename, file-i/o system call
23491 int rename(const char *oldpath, const char *newpath);
23494 Frename,oldpathptr/len,newpathptr/len
23496 @exdent Return value:
23497 On success, zero is returned. On error, -1 is returned.
23504 newpath is an existing directory, but oldpath is not a
23508 newpath is a non-empty directory.
23511 oldpath or newpath is a directory that is in use by some
23515 An attempt was made to make a directory a subdirectory
23519 A component used as a directory in oldpath or new
23520 path is not a directory. Or oldpath is a directory
23521 and newpath exists but is not a directory.
23524 oldpathptr or newpathptr are invalid pointer values.
23527 No access to the file or the path of the file.
23531 oldpath or newpath was too long.
23534 A directory component in oldpath or newpath does not exist.
23537 The file is on a read-only filesystem.
23540 The device containing the file has no room for the new
23544 The call was interrupted by the user.
23548 @unnumberedsubsubsec unlink
23549 @cindex unlink, file-i/o system call
23553 int unlink(const char *pathname);
23556 Funlink,pathnameptr/len
23558 @exdent Return value:
23559 On success, zero is returned. On error, -1 is returned.
23566 No access to the file or the path of the file.
23569 The system does not allow unlinking of directories.
23572 The file pathname cannot be unlinked because it's
23573 being used by another process.
23576 pathnameptr is an invalid pointer value.
23579 pathname was too long.
23582 A directory component in pathname does not exist.
23585 A component of the path is not a directory.
23588 The file is on a read-only filesystem.
23591 The call was interrupted by the user.
23595 @unnumberedsubsubsec stat/fstat
23596 @cindex fstat, file-i/o system call
23597 @cindex stat, file-i/o system call
23601 int stat(const char *pathname, struct stat *buf);
23602 int fstat(int fd, struct stat *buf);
23605 Fstat,pathnameptr/len,bufptr
23608 @exdent Return value:
23609 On success, zero is returned. On error, -1 is returned.
23616 fd is not a valid open file.
23619 A directory component in pathname does not exist or the
23620 path is an empty string.
23623 A component of the path is not a directory.
23626 pathnameptr is an invalid pointer value.
23629 No access to the file or the path of the file.
23632 pathname was too long.
23635 The call was interrupted by the user.
23639 @unnumberedsubsubsec gettimeofday
23640 @cindex gettimeofday, file-i/o system call
23644 int gettimeofday(struct timeval *tv, void *tz);
23647 Fgettimeofday,tvptr,tzptr
23649 @exdent Return value:
23650 On success, 0 is returned, -1 otherwise.
23657 tz is a non-NULL pointer.
23660 tvptr and/or tzptr is an invalid pointer value.
23664 @unnumberedsubsubsec isatty
23665 @cindex isatty, file-i/o system call
23669 int isatty(int fd);
23674 @exdent Return value:
23675 Returns 1 if fd refers to the @value{GDBN} console, 0 otherwise.
23682 The call was interrupted by the user.
23686 @unnumberedsubsubsec system
23687 @cindex system, file-i/o system call
23691 int system(const char *command);
23694 Fsystem,commandptr/len
23696 @exdent Return value:
23697 The value returned is -1 on error and the return status
23698 of the command otherwise. Only the exit status of the
23699 command is returned, which is extracted from the hosts
23700 system return value by calling WEXITSTATUS(retval).
23701 In case /bin/sh could not be executed, 127 is returned.
23708 The call was interrupted by the user.
23711 @node Protocol specific representation of datatypes
23712 @subsection Protocol specific representation of datatypes
23713 @cindex protocol specific representation of datatypes, in file-i/o protocol
23716 * Integral datatypes::
23722 @node Integral datatypes
23723 @unnumberedsubsubsec Integral datatypes
23724 @cindex integral datatypes, in file-i/o protocol
23726 The integral datatypes used in the system calls are
23729 int@r{,} unsigned int@r{,} long@r{,} unsigned long@r{,} mode_t @r{and} time_t
23732 @code{Int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
23733 implemented as 32 bit values in this protocol.
23735 @code{Long} and @code{unsigned long} are implemented as 64 bit types.
23737 @xref{Limits}, for corresponding MIN and MAX values (similar to those
23738 in @file{limits.h}) to allow range checking on host and target.
23740 @code{time_t} datatypes are defined as seconds since the Epoch.
23742 All integral datatypes transferred as part of a memory read or write of a
23743 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
23746 @node Pointer values
23747 @unnumberedsubsubsec Pointer values
23748 @cindex pointer values, in file-i/o protocol
23750 Pointers to target data are transmitted as they are. An exception
23751 is made for pointers to buffers for which the length isn't
23752 transmitted as part of the function call, namely strings. Strings
23753 are transmitted as a pointer/length pair, both as hex values, e.g.@:
23760 which is a pointer to data of length 18 bytes at position 0x1aaf.
23761 The length is defined as the full string length in bytes, including
23762 the trailing null byte. Example:
23765 ``hello, world'' at address 0x123456
23776 @unnumberedsubsubsec struct stat
23777 @cindex struct stat, in file-i/o protocol
23779 The buffer of type struct stat used by the target and @value{GDBN} is defined
23784 unsigned int st_dev; /* device */
23785 unsigned int st_ino; /* inode */
23786 mode_t st_mode; /* protection */
23787 unsigned int st_nlink; /* number of hard links */
23788 unsigned int st_uid; /* user ID of owner */
23789 unsigned int st_gid; /* group ID of owner */
23790 unsigned int st_rdev; /* device type (if inode device) */
23791 unsigned long st_size; /* total size, in bytes */
23792 unsigned long st_blksize; /* blocksize for filesystem I/O */
23793 unsigned long st_blocks; /* number of blocks allocated */
23794 time_t st_atime; /* time of last access */
23795 time_t st_mtime; /* time of last modification */
23796 time_t st_ctime; /* time of last change */
23800 The integral datatypes are conforming to the definitions given in the
23801 approriate section (see @ref{Integral datatypes}, for details) so this
23802 structure is of size 64 bytes.
23804 The values of several fields have a restricted meaning and/or
23811 st_ino: No valid meaning for the target. Transmitted unchanged.
23813 st_mode: Valid mode bits are described in Appendix C. Any other
23814 bits have currently no meaning for the target.
23816 st_uid: No valid meaning for the target. Transmitted unchanged.
23818 st_gid: No valid meaning for the target. Transmitted unchanged.
23820 st_rdev: No valid meaning for the target. Transmitted unchanged.
23822 st_atime, st_mtime, st_ctime:
23823 These values have a host and file system dependent
23824 accuracy. Especially on Windows hosts the file systems
23825 don't support exact timing values.
23828 The target gets a struct stat of the above representation and is
23829 responsible to coerce it to the target representation before
23832 Note that due to size differences between the host and target
23833 representation of stat members, these members could eventually
23834 get truncated on the target.
23836 @node struct timeval
23837 @unnumberedsubsubsec struct timeval
23838 @cindex struct timeval, in file-i/o protocol
23840 The buffer of type struct timeval used by the target and @value{GDBN}
23841 is defined as follows:
23845 time_t tv_sec; /* second */
23846 long tv_usec; /* microsecond */
23850 The integral datatypes are conforming to the definitions given in the
23851 approriate section (see @ref{Integral datatypes}, for details) so this
23852 structure is of size 8 bytes.
23855 @subsection Constants
23856 @cindex constants, in file-i/o protocol
23858 The following values are used for the constants inside of the
23859 protocol. @value{GDBN} and target are resposible to translate these
23860 values before and after the call as needed.
23871 @unnumberedsubsubsec Open flags
23872 @cindex open flags, in file-i/o protocol
23874 All values are given in hexadecimal representation.
23886 @node mode_t values
23887 @unnumberedsubsubsec mode_t values
23888 @cindex mode_t values, in file-i/o protocol
23890 All values are given in octal representation.
23907 @unnumberedsubsubsec Errno values
23908 @cindex errno values, in file-i/o protocol
23910 All values are given in decimal representation.
23935 EUNKNOWN is used as a fallback error value if a host system returns
23936 any error value not in the list of supported error numbers.
23939 @unnumberedsubsubsec Lseek flags
23940 @cindex lseek flags, in file-i/o protocol
23949 @unnumberedsubsubsec Limits
23950 @cindex limits, in file-i/o protocol
23952 All values are given in decimal representation.
23955 INT_MIN -2147483648
23957 UINT_MAX 4294967295
23958 LONG_MIN -9223372036854775808
23959 LONG_MAX 9223372036854775807
23960 ULONG_MAX 18446744073709551615
23963 @node File-I/O Examples
23964 @subsection File-I/O Examples
23965 @cindex file-i/o examples
23967 Example sequence of a write call, file descriptor 3, buffer is at target
23968 address 0x1234, 6 bytes should be written:
23971 <- @code{Fwrite,3,1234,6}
23972 @emph{request memory read from target}
23975 @emph{return "6 bytes written"}
23979 Example sequence of a read call, file descriptor 3, buffer is at target
23980 address 0x1234, 6 bytes should be read:
23983 <- @code{Fread,3,1234,6}
23984 @emph{request memory write to target}
23985 -> @code{X1234,6:XXXXXX}
23986 @emph{return "6 bytes read"}
23990 Example sequence of a read call, call fails on the host due to invalid
23991 file descriptor (EBADF):
23994 <- @code{Fread,3,1234,6}
23998 Example sequence of a read call, user presses Ctrl-C before syscall on
24002 <- @code{Fread,3,1234,6}
24007 Example sequence of a read call, user presses Ctrl-C after syscall on
24011 <- @code{Fread,3,1234,6}
24012 -> @code{X1234,6:XXXXXX}
24016 @include agentexpr.texi
24030 % I think something like @colophon should be in texinfo. In the
24032 \long\def\colophon{\hbox to0pt{}\vfill
24033 \centerline{The body of this manual is set in}
24034 \centerline{\fontname\tenrm,}
24035 \centerline{with headings in {\bf\fontname\tenbf}}
24036 \centerline{and examples in {\tt\fontname\tentt}.}
24037 \centerline{{\it\fontname\tenit\/},}
24038 \centerline{{\bf\fontname\tenbf}, and}
24039 \centerline{{\sl\fontname\tensl\/}}
24040 \centerline{are used for emphasis.}\vfill}
24042 % Blame: doc@cygnus.com, 1991.