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 Programs that are to be shipped to your customers are compiled with
1647 optimizations, using the @samp{-O} compiler option. However, many
1648 compilers are unable to handle the @samp{-g} and @samp{-O} options
1649 together. Using those compilers, you cannot generate optimized
1650 executables containing debugging information.
1652 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1653 without @samp{-O}, making it possible to debug optimized code. We
1654 recommend that you @emph{always} use @samp{-g} whenever you compile a
1655 program. You may think your program is correct, but there is no sense
1656 in pushing your luck.
1658 @cindex optimized code, debugging
1659 @cindex debugging optimized code
1660 When you debug a program compiled with @samp{-g -O}, remember that the
1661 optimizer is rearranging your code; the debugger shows you what is
1662 really there. Do not be too surprised when the execution path does not
1663 exactly match your source file! An extreme example: if you define a
1664 variable, but never use it, @value{GDBN} never sees that
1665 variable---because the compiler optimizes it out of existence.
1667 Some things do not work as well with @samp{-g -O} as with just
1668 @samp{-g}, particularly on machines with instruction scheduling. If in
1669 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1670 please report it to us as a bug (including a test case!).
1671 @xref{Variables}, for more information about debugging optimized code.
1673 Older versions of the @sc{gnu} C compiler permitted a variant option
1674 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1675 format; if your @sc{gnu} C compiler has this option, do not use it.
1677 @value{GDBN} knows about preprocessor macros and can show you their
1678 expansion (@pxref{Macros}). Most compilers do not include information
1679 about preprocessor macros in the debugging information if you specify
1680 the @option{-g} flag alone, because this information is rather large.
1681 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1682 provides macro information if you specify the options
1683 @option{-gdwarf-2} and @option{-g3}; the former option requests
1684 debugging information in the Dwarf 2 format, and the latter requests
1685 ``extra information''. In the future, we hope to find more compact
1686 ways to represent macro information, so that it can be included with
1691 @section Starting your program
1697 @kindex r @r{(@code{run})}
1700 Use the @code{run} command to start your program under @value{GDBN}.
1701 You must first specify the program name (except on VxWorks) with an
1702 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1703 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1704 (@pxref{Files, ,Commands to specify files}).
1708 If you are running your program in an execution environment that
1709 supports processes, @code{run} creates an inferior process and makes
1710 that process run your program. (In environments without processes,
1711 @code{run} jumps to the start of your program.)
1713 The execution of a program is affected by certain information it
1714 receives from its superior. @value{GDBN} provides ways to specify this
1715 information, which you must do @emph{before} starting your program. (You
1716 can change it after starting your program, but such changes only affect
1717 your program the next time you start it.) This information may be
1718 divided into four categories:
1721 @item The @emph{arguments.}
1722 Specify the arguments to give your program as the arguments of the
1723 @code{run} command. If a shell is available on your target, the shell
1724 is used to pass the arguments, so that you may use normal conventions
1725 (such as wildcard expansion or variable substitution) in describing
1727 In Unix systems, you can control which shell is used with the
1728 @code{SHELL} environment variable.
1729 @xref{Arguments, ,Your program's arguments}.
1731 @item The @emph{environment.}
1732 Your program normally inherits its environment from @value{GDBN}, but you can
1733 use the @value{GDBN} commands @code{set environment} and @code{unset
1734 environment} to change parts of the environment that affect
1735 your program. @xref{Environment, ,Your program's environment}.
1737 @item The @emph{working directory.}
1738 Your program inherits its working directory from @value{GDBN}. You can set
1739 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1740 @xref{Working Directory, ,Your program's working directory}.
1742 @item The @emph{standard input and output.}
1743 Your program normally uses the same device for standard input and
1744 standard output as @value{GDBN} is using. You can redirect input and output
1745 in the @code{run} command line, or you can use the @code{tty} command to
1746 set a different device for your program.
1747 @xref{Input/Output, ,Your program's input and output}.
1750 @emph{Warning:} While input and output redirection work, you cannot use
1751 pipes to pass the output of the program you are debugging to another
1752 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1756 When you issue the @code{run} command, your program begins to execute
1757 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1758 of how to arrange for your program to stop. Once your program has
1759 stopped, you may call functions in your program, using the @code{print}
1760 or @code{call} commands. @xref{Data, ,Examining Data}.
1762 If the modification time of your symbol file has changed since the last
1763 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1764 table, and reads it again. When it does this, @value{GDBN} tries to retain
1765 your current breakpoints.
1770 @cindex run to main procedure
1771 The name of the main procedure can vary from language to language.
1772 With C or C@t{++}, the main procedure name is always @code{main}, but
1773 other languages such as Ada do not require a specific name for their
1774 main procedure. The debugger provides a convenient way to start the
1775 execution of the program and to stop at the beginning of the main
1776 procedure, depending on the language used.
1778 The @samp{start} command does the equivalent of setting a temporary
1779 breakpoint at the beginning of the main procedure and then invoking
1780 the @samp{run} command.
1782 @cindex elaboration phase
1783 Some programs contain an @dfn{elaboration} phase where some startup code is
1784 executed before the main procedure is called. This depends on the
1785 languages used to write your program. In C@t{++}, for instance,
1786 constructors for static and global objects are executed before
1787 @code{main} is called. It is therefore possible that the debugger stops
1788 before reaching the main procedure. However, the temporary breakpoint
1789 will remain to halt execution.
1791 Specify the arguments to give to your program as arguments to the
1792 @samp{start} command. These arguments will be given verbatim to the
1793 underlying @samp{run} command. Note that the same arguments will be
1794 reused if no argument is provided during subsequent calls to
1795 @samp{start} or @samp{run}.
1797 It is sometimes necessary to debug the program during elaboration. In
1798 these cases, using the @code{start} command would stop the execution of
1799 your program too late, as the program would have already completed the
1800 elaboration phase. Under these circumstances, insert breakpoints in your
1801 elaboration code before running your program.
1805 @section Your program's arguments
1807 @cindex arguments (to your program)
1808 The arguments to your program can be specified by the arguments of the
1810 They are passed to a shell, which expands wildcard characters and
1811 performs redirection of I/O, and thence to your program. Your
1812 @code{SHELL} environment variable (if it exists) specifies what shell
1813 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1814 the default shell (@file{/bin/sh} on Unix).
1816 On non-Unix systems, the program is usually invoked directly by
1817 @value{GDBN}, which emulates I/O redirection via the appropriate system
1818 calls, and the wildcard characters are expanded by the startup code of
1819 the program, not by the shell.
1821 @code{run} with no arguments uses the same arguments used by the previous
1822 @code{run}, or those set by the @code{set args} command.
1827 Specify the arguments to be used the next time your program is run. If
1828 @code{set args} has no arguments, @code{run} executes your program
1829 with no arguments. Once you have run your program with arguments,
1830 using @code{set args} before the next @code{run} is the only way to run
1831 it again without arguments.
1835 Show the arguments to give your program when it is started.
1839 @section Your program's environment
1841 @cindex environment (of your program)
1842 The @dfn{environment} consists of a set of environment variables and
1843 their values. Environment variables conventionally record such things as
1844 your user name, your home directory, your terminal type, and your search
1845 path for programs to run. Usually you set up environment variables with
1846 the shell and they are inherited by all the other programs you run. When
1847 debugging, it can be useful to try running your program with a modified
1848 environment without having to start @value{GDBN} over again.
1852 @item path @var{directory}
1853 Add @var{directory} to the front of the @code{PATH} environment variable
1854 (the search path for executables) that will be passed to your program.
1855 The value of @code{PATH} used by @value{GDBN} does not change.
1856 You may specify several directory names, separated by whitespace or by a
1857 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1858 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1859 is moved to the front, so it is searched sooner.
1861 You can use the string @samp{$cwd} to refer to whatever is the current
1862 working directory at the time @value{GDBN} searches the path. If you
1863 use @samp{.} instead, it refers to the directory where you executed the
1864 @code{path} command. @value{GDBN} replaces @samp{.} in the
1865 @var{directory} argument (with the current path) before adding
1866 @var{directory} to the search path.
1867 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1868 @c document that, since repeating it would be a no-op.
1872 Display the list of search paths for executables (the @code{PATH}
1873 environment variable).
1875 @kindex show environment
1876 @item show environment @r{[}@var{varname}@r{]}
1877 Print the value of environment variable @var{varname} to be given to
1878 your program when it starts. If you do not supply @var{varname},
1879 print the names and values of all environment variables to be given to
1880 your program. You can abbreviate @code{environment} as @code{env}.
1882 @kindex set environment
1883 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1884 Set environment variable @var{varname} to @var{value}. The value
1885 changes for your program only, not for @value{GDBN} itself. @var{value} may
1886 be any string; the values of environment variables are just strings, and
1887 any interpretation is supplied by your program itself. The @var{value}
1888 parameter is optional; if it is eliminated, the variable is set to a
1890 @c "any string" here does not include leading, trailing
1891 @c blanks. Gnu asks: does anyone care?
1893 For example, this command:
1900 tells the debugged program, when subsequently run, that its user is named
1901 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
1902 are not actually required.)
1904 @kindex unset environment
1905 @item unset environment @var{varname}
1906 Remove variable @var{varname} from the environment to be passed to your
1907 program. This is different from @samp{set env @var{varname} =};
1908 @code{unset environment} removes the variable from the environment,
1909 rather than assigning it an empty value.
1912 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
1914 by your @code{SHELL} environment variable if it exists (or
1915 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
1916 that runs an initialization file---such as @file{.cshrc} for C-shell, or
1917 @file{.bashrc} for BASH---any variables you set in that file affect
1918 your program. You may wish to move setting of environment variables to
1919 files that are only run when you sign on, such as @file{.login} or
1922 @node Working Directory
1923 @section Your program's working directory
1925 @cindex working directory (of your program)
1926 Each time you start your program with @code{run}, it inherits its
1927 working directory from the current working directory of @value{GDBN}.
1928 The @value{GDBN} working directory is initially whatever it inherited
1929 from its parent process (typically the shell), but you can specify a new
1930 working directory in @value{GDBN} with the @code{cd} command.
1932 The @value{GDBN} working directory also serves as a default for the commands
1933 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
1938 @cindex change working directory
1939 @item cd @var{directory}
1940 Set the @value{GDBN} working directory to @var{directory}.
1944 Print the @value{GDBN} working directory.
1947 It is generally impossible to find the current working directory of
1948 the process being debugged (since a program can change its directory
1949 during its run). If you work on a system where @value{GDBN} is
1950 configured with the @file{/proc} support, you can use the @code{info
1951 proc} command (@pxref{SVR4 Process Information}) to find out the
1952 current working directory of the debuggee.
1955 @section Your program's input and output
1960 By default, the program you run under @value{GDBN} does input and output to
1961 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
1962 to its own terminal modes to interact with you, but it records the terminal
1963 modes your program was using and switches back to them when you continue
1964 running your program.
1967 @kindex info terminal
1969 Displays information recorded by @value{GDBN} about the terminal modes your
1973 You can redirect your program's input and/or output using shell
1974 redirection with the @code{run} command. For example,
1981 starts your program, diverting its output to the file @file{outfile}.
1984 @cindex controlling terminal
1985 Another way to specify where your program should do input and output is
1986 with the @code{tty} command. This command accepts a file name as
1987 argument, and causes this file to be the default for future @code{run}
1988 commands. It also resets the controlling terminal for the child
1989 process, for future @code{run} commands. For example,
1996 directs that processes started with subsequent @code{run} commands
1997 default to do input and output on the terminal @file{/dev/ttyb} and have
1998 that as their controlling terminal.
2000 An explicit redirection in @code{run} overrides the @code{tty} command's
2001 effect on the input/output device, but not its effect on the controlling
2004 When you use the @code{tty} command or redirect input in the @code{run}
2005 command, only the input @emph{for your program} is affected. The input
2006 for @value{GDBN} still comes from your terminal.
2009 @section Debugging an already-running process
2014 @item attach @var{process-id}
2015 This command attaches to a running process---one that was started
2016 outside @value{GDBN}. (@code{info files} shows your active
2017 targets.) The command takes as argument a process ID. The usual way to
2018 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2019 or with the @samp{jobs -l} shell command.
2021 @code{attach} does not repeat if you press @key{RET} a second time after
2022 executing the command.
2025 To use @code{attach}, your program must be running in an environment
2026 which supports processes; for example, @code{attach} does not work for
2027 programs on bare-board targets that lack an operating system. You must
2028 also have permission to send the process a signal.
2030 When you use @code{attach}, the debugger finds the program running in
2031 the process first by looking in the current working directory, then (if
2032 the program is not found) by using the source file search path
2033 (@pxref{Source Path, ,Specifying source directories}). You can also use
2034 the @code{file} command to load the program. @xref{Files, ,Commands to
2037 The first thing @value{GDBN} does after arranging to debug the specified
2038 process is to stop it. You can examine and modify an attached process
2039 with all the @value{GDBN} commands that are ordinarily available when
2040 you start processes with @code{run}. You can insert breakpoints; you
2041 can step and continue; you can modify storage. If you would rather the
2042 process continue running, you may use the @code{continue} command after
2043 attaching @value{GDBN} to the process.
2048 When you have finished debugging the attached process, you can use the
2049 @code{detach} command to release it from @value{GDBN} control. Detaching
2050 the process continues its execution. After the @code{detach} command,
2051 that process and @value{GDBN} become completely independent once more, and you
2052 are ready to @code{attach} another process or start one with @code{run}.
2053 @code{detach} does not repeat if you press @key{RET} again after
2054 executing the command.
2057 If you exit @value{GDBN} or use the @code{run} command while you have an
2058 attached process, you kill that process. By default, @value{GDBN} asks
2059 for confirmation if you try to do either of these things; you can
2060 control whether or not you need to confirm by using the @code{set
2061 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
2065 @section Killing the child process
2070 Kill the child process in which your program is running under @value{GDBN}.
2073 This command is useful if you wish to debug a core dump instead of a
2074 running process. @value{GDBN} ignores any core dump file while your program
2077 On some operating systems, a program cannot be executed outside @value{GDBN}
2078 while you have breakpoints set on it inside @value{GDBN}. You can use the
2079 @code{kill} command in this situation to permit running your program
2080 outside the debugger.
2082 The @code{kill} command is also useful if you wish to recompile and
2083 relink your program, since on many systems it is impossible to modify an
2084 executable file while it is running in a process. In this case, when you
2085 next type @code{run}, @value{GDBN} notices that the file has changed, and
2086 reads the symbol table again (while trying to preserve your current
2087 breakpoint settings).
2090 @section Debugging programs with multiple threads
2092 @cindex threads of execution
2093 @cindex multiple threads
2094 @cindex switching threads
2095 In some operating systems, such as HP-UX and Solaris, a single program
2096 may have more than one @dfn{thread} of execution. The precise semantics
2097 of threads differ from one operating system to another, but in general
2098 the threads of a single program are akin to multiple processes---except
2099 that they share one address space (that is, they can all examine and
2100 modify the same variables). On the other hand, each thread has its own
2101 registers and execution stack, and perhaps private memory.
2103 @value{GDBN} provides these facilities for debugging multi-thread
2107 @item automatic notification of new threads
2108 @item @samp{thread @var{threadno}}, a command to switch among threads
2109 @item @samp{info threads}, a command to inquire about existing threads
2110 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2111 a command to apply a command to a list of threads
2112 @item thread-specific breakpoints
2116 @emph{Warning:} These facilities are not yet available on every
2117 @value{GDBN} configuration where the operating system supports threads.
2118 If your @value{GDBN} does not support threads, these commands have no
2119 effect. For example, a system without thread support shows no output
2120 from @samp{info threads}, and always rejects the @code{thread} command,
2124 (@value{GDBP}) info threads
2125 (@value{GDBP}) thread 1
2126 Thread ID 1 not known. Use the "info threads" command to
2127 see the IDs of currently known threads.
2129 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2130 @c doesn't support threads"?
2133 @cindex focus of debugging
2134 @cindex current thread
2135 The @value{GDBN} thread debugging facility allows you to observe all
2136 threads while your program runs---but whenever @value{GDBN} takes
2137 control, one thread in particular is always the focus of debugging.
2138 This thread is called the @dfn{current thread}. Debugging commands show
2139 program information from the perspective of the current thread.
2141 @cindex @code{New} @var{systag} message
2142 @cindex thread identifier (system)
2143 @c FIXME-implementors!! It would be more helpful if the [New...] message
2144 @c included GDB's numeric thread handle, so you could just go to that
2145 @c thread without first checking `info threads'.
2146 Whenever @value{GDBN} detects a new thread in your program, it displays
2147 the target system's identification for the thread with a message in the
2148 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2149 whose form varies depending on the particular system. For example, on
2150 LynxOS, you might see
2153 [New process 35 thread 27]
2157 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2158 the @var{systag} is simply something like @samp{process 368}, with no
2161 @c FIXME!! (1) Does the [New...] message appear even for the very first
2162 @c thread of a program, or does it only appear for the
2163 @c second---i.e.@: when it becomes obvious we have a multithread
2165 @c (2) *Is* there necessarily a first thread always? Or do some
2166 @c multithread systems permit starting a program with multiple
2167 @c threads ab initio?
2169 @cindex thread number
2170 @cindex thread identifier (GDB)
2171 For debugging purposes, @value{GDBN} associates its own thread
2172 number---always a single integer---with each thread in your program.
2175 @kindex info threads
2177 Display a summary of all threads currently in your
2178 program. @value{GDBN} displays for each thread (in this order):
2182 the thread number assigned by @value{GDBN}
2185 the target system's thread identifier (@var{systag})
2188 the current stack frame summary for that thread
2192 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2193 indicates the current thread.
2197 @c end table here to get a little more width for example
2200 (@value{GDBP}) info threads
2201 3 process 35 thread 27 0x34e5 in sigpause ()
2202 2 process 35 thread 23 0x34e5 in sigpause ()
2203 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2209 @cindex debugging multithreaded programs (on HP-UX)
2210 @cindex thread identifier (GDB), on HP-UX
2211 For debugging purposes, @value{GDBN} associates its own thread
2212 number---a small integer assigned in thread-creation order---with each
2213 thread in your program.
2215 @cindex @code{New} @var{systag} message, on HP-UX
2216 @cindex thread identifier (system), on HP-UX
2217 @c FIXME-implementors!! It would be more helpful if the [New...] message
2218 @c included GDB's numeric thread handle, so you could just go to that
2219 @c thread without first checking `info threads'.
2220 Whenever @value{GDBN} detects a new thread in your program, it displays
2221 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2222 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2223 whose form varies depending on the particular system. For example, on
2227 [New thread 2 (system thread 26594)]
2231 when @value{GDBN} notices a new thread.
2234 @kindex info threads (HP-UX)
2236 Display a summary of all threads currently in your
2237 program. @value{GDBN} displays for each thread (in this order):
2240 @item the thread number assigned by @value{GDBN}
2242 @item the target system's thread identifier (@var{systag})
2244 @item the current stack frame summary for that thread
2248 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2249 indicates the current thread.
2253 @c end table here to get a little more width for example
2256 (@value{GDBP}) info threads
2257 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2259 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2260 from /usr/lib/libc.2
2261 1 system thread 27905 0x7b003498 in _brk () \@*
2262 from /usr/lib/libc.2
2265 On Solaris, you can display more information about user threads with a
2266 Solaris-specific command:
2269 @item maint info sol-threads
2270 @kindex maint info sol-threads
2271 @cindex thread info (Solaris)
2272 Display info on Solaris user threads.
2276 @kindex thread @var{threadno}
2277 @item thread @var{threadno}
2278 Make thread number @var{threadno} the current thread. The command
2279 argument @var{threadno} is the internal @value{GDBN} thread number, as
2280 shown in the first field of the @samp{info threads} display.
2281 @value{GDBN} responds by displaying the system identifier of the thread
2282 you selected, and its current stack frame summary:
2285 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2286 (@value{GDBP}) thread 2
2287 [Switching to process 35 thread 23]
2288 0x34e5 in sigpause ()
2292 As with the @samp{[New @dots{}]} message, the form of the text after
2293 @samp{Switching to} depends on your system's conventions for identifying
2296 @kindex thread apply
2297 @item thread apply [@var{threadno}] [@var{all}] @var{args}
2298 The @code{thread apply} command allows you to apply a command to one or
2299 more threads. Specify the numbers of the threads that you want affected
2300 with the command argument @var{threadno}. @var{threadno} is the internal
2301 @value{GDBN} thread number, as shown in the first field of the @samp{info
2302 threads} display. To apply a command to all threads, use
2303 @code{thread apply all} @var{args}.
2306 @cindex automatic thread selection
2307 @cindex switching threads automatically
2308 @cindex threads, automatic switching
2309 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2310 signal, it automatically selects the thread where that breakpoint or
2311 signal happened. @value{GDBN} alerts you to the context switch with a
2312 message of the form @samp{[Switching to @var{systag}]} to identify the
2315 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2316 more information about how @value{GDBN} behaves when you stop and start
2317 programs with multiple threads.
2319 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2320 watchpoints in programs with multiple threads.
2323 @section Debugging programs with multiple processes
2325 @cindex fork, debugging programs which call
2326 @cindex multiple processes
2327 @cindex processes, multiple
2328 On most systems, @value{GDBN} has no special support for debugging
2329 programs which create additional processes using the @code{fork}
2330 function. When a program forks, @value{GDBN} will continue to debug the
2331 parent process and the child process will run unimpeded. If you have
2332 set a breakpoint in any code which the child then executes, the child
2333 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2334 will cause it to terminate.
2336 However, if you want to debug the child process there is a workaround
2337 which isn't too painful. Put a call to @code{sleep} in the code which
2338 the child process executes after the fork. It may be useful to sleep
2339 only if a certain environment variable is set, or a certain file exists,
2340 so that the delay need not occur when you don't want to run @value{GDBN}
2341 on the child. While the child is sleeping, use the @code{ps} program to
2342 get its process ID. Then tell @value{GDBN} (a new invocation of
2343 @value{GDBN} if you are also debugging the parent process) to attach to
2344 the child process (@pxref{Attach}). From that point on you can debug
2345 the child process just like any other process which you attached to.
2347 On some systems, @value{GDBN} provides support for debugging programs that
2348 create additional processes using the @code{fork} or @code{vfork} functions.
2349 Currently, the only platforms with this feature are HP-UX (11.x and later
2350 only?) and GNU/Linux (kernel version 2.5.60 and later).
2352 By default, when a program forks, @value{GDBN} will continue to debug
2353 the parent process and the child process will run unimpeded.
2355 If you want to follow the child process instead of the parent process,
2356 use the command @w{@code{set follow-fork-mode}}.
2359 @kindex set follow-fork-mode
2360 @item set follow-fork-mode @var{mode}
2361 Set the debugger response to a program call of @code{fork} or
2362 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2363 process. The @var{mode} argument can be:
2367 The original process is debugged after a fork. The child process runs
2368 unimpeded. This is the default.
2371 The new process is debugged after a fork. The parent process runs
2376 @kindex show follow-fork-mode
2377 @item show follow-fork-mode
2378 Display the current debugger response to a @code{fork} or @code{vfork} call.
2381 If you ask to debug a child process and a @code{vfork} is followed by an
2382 @code{exec}, @value{GDBN} executes the new target up to the first
2383 breakpoint in the new target. If you have a breakpoint set on
2384 @code{main} in your original program, the breakpoint will also be set on
2385 the child process's @code{main}.
2387 When a child process is spawned by @code{vfork}, you cannot debug the
2388 child or parent until an @code{exec} call completes.
2390 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2391 call executes, the new target restarts. To restart the parent process,
2392 use the @code{file} command with the parent executable name as its
2395 You can use the @code{catch} command to make @value{GDBN} stop whenever
2396 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2397 Catchpoints, ,Setting catchpoints}.
2400 @chapter Stopping and Continuing
2402 The principal purposes of using a debugger are so that you can stop your
2403 program before it terminates; or so that, if your program runs into
2404 trouble, you can investigate and find out why.
2406 Inside @value{GDBN}, your program may stop for any of several reasons,
2407 such as a signal, a breakpoint, or reaching a new line after a
2408 @value{GDBN} command such as @code{step}. You may then examine and
2409 change variables, set new breakpoints or remove old ones, and then
2410 continue execution. Usually, the messages shown by @value{GDBN} provide
2411 ample explanation of the status of your program---but you can also
2412 explicitly request this information at any time.
2415 @kindex info program
2417 Display information about the status of your program: whether it is
2418 running or not, what process it is, and why it stopped.
2422 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2423 * Continuing and Stepping:: Resuming execution
2425 * Thread Stops:: Stopping and starting multi-thread programs
2429 @section Breakpoints, watchpoints, and catchpoints
2432 A @dfn{breakpoint} makes your program stop whenever a certain point in
2433 the program is reached. For each breakpoint, you can add conditions to
2434 control in finer detail whether your program stops. You can set
2435 breakpoints with the @code{break} command and its variants (@pxref{Set
2436 Breaks, ,Setting breakpoints}), to specify the place where your program
2437 should stop by line number, function name or exact address in the
2440 On some systems, you can set breakpoints in shared libraries before
2441 the executable is run. There is a minor limitation on HP-UX systems:
2442 you must wait until the executable is run in order to set breakpoints
2443 in shared library routines that are not called directly by the program
2444 (for example, routines that are arguments in a @code{pthread_create}
2448 @cindex memory tracing
2449 @cindex breakpoint on memory address
2450 @cindex breakpoint on variable modification
2451 A @dfn{watchpoint} is a special breakpoint that stops your program
2452 when the value of an expression changes. You must use a different
2453 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2454 watchpoints}), but aside from that, you can manage a watchpoint like
2455 any other breakpoint: you enable, disable, and delete both breakpoints
2456 and watchpoints using the same commands.
2458 You can arrange to have values from your program displayed automatically
2459 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2463 @cindex breakpoint on events
2464 A @dfn{catchpoint} is another special breakpoint that stops your program
2465 when a certain kind of event occurs, such as the throwing of a C@t{++}
2466 exception or the loading of a library. As with watchpoints, you use a
2467 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2468 catchpoints}), but aside from that, you can manage a catchpoint like any
2469 other breakpoint. (To stop when your program receives a signal, use the
2470 @code{handle} command; see @ref{Signals, ,Signals}.)
2472 @cindex breakpoint numbers
2473 @cindex numbers for breakpoints
2474 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2475 catchpoint when you create it; these numbers are successive integers
2476 starting with one. In many of the commands for controlling various
2477 features of breakpoints you use the breakpoint number to say which
2478 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2479 @dfn{disabled}; if disabled, it has no effect on your program until you
2482 @cindex breakpoint ranges
2483 @cindex ranges of breakpoints
2484 Some @value{GDBN} commands accept a range of breakpoints on which to
2485 operate. A breakpoint range is either a single breakpoint number, like
2486 @samp{5}, or two such numbers, in increasing order, separated by a
2487 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2488 all breakpoint in that range are operated on.
2491 * Set Breaks:: Setting breakpoints
2492 * Set Watchpoints:: Setting watchpoints
2493 * Set Catchpoints:: Setting catchpoints
2494 * Delete Breaks:: Deleting breakpoints
2495 * Disabling:: Disabling breakpoints
2496 * Conditions:: Break conditions
2497 * Break Commands:: Breakpoint command lists
2498 * Breakpoint Menus:: Breakpoint menus
2499 * Error in Breakpoints:: ``Cannot insert breakpoints''
2500 * Breakpoint related warnings:: ``Breakpoint address adjusted...''
2504 @subsection Setting breakpoints
2506 @c FIXME LMB what does GDB do if no code on line of breakpt?
2507 @c consider in particular declaration with/without initialization.
2509 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2512 @kindex b @r{(@code{break})}
2513 @vindex $bpnum@r{, convenience variable}
2514 @cindex latest breakpoint
2515 Breakpoints are set with the @code{break} command (abbreviated
2516 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2517 number of the breakpoint you've set most recently; see @ref{Convenience
2518 Vars,, Convenience variables}, for a discussion of what you can do with
2519 convenience variables.
2521 You have several ways to say where the breakpoint should go.
2524 @item break @var{function}
2525 Set a breakpoint at entry to function @var{function}.
2526 When using source languages that permit overloading of symbols, such as
2527 C@t{++}, @var{function} may refer to more than one possible place to break.
2528 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2530 @item break +@var{offset}
2531 @itemx break -@var{offset}
2532 Set a breakpoint some number of lines forward or back from the position
2533 at which execution stopped in the currently selected @dfn{stack frame}.
2534 (@xref{Frames, ,Frames}, for a description of stack frames.)
2536 @item break @var{linenum}
2537 Set a breakpoint at line @var{linenum} in the current source file.
2538 The current source file is the last file whose source text was printed.
2539 The breakpoint will stop your program just before it executes any of the
2542 @item break @var{filename}:@var{linenum}
2543 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2545 @item break @var{filename}:@var{function}
2546 Set a breakpoint at entry to function @var{function} found in file
2547 @var{filename}. Specifying a file name as well as a function name is
2548 superfluous except when multiple files contain similarly named
2551 @item break *@var{address}
2552 Set a breakpoint at address @var{address}. You can use this to set
2553 breakpoints in parts of your program which do not have debugging
2554 information or source files.
2557 When called without any arguments, @code{break} sets a breakpoint at
2558 the next instruction to be executed in the selected stack frame
2559 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2560 innermost, this makes your program stop as soon as control
2561 returns to that frame. This is similar to the effect of a
2562 @code{finish} command in the frame inside the selected frame---except
2563 that @code{finish} does not leave an active breakpoint. If you use
2564 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2565 the next time it reaches the current location; this may be useful
2568 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2569 least one instruction has been executed. If it did not do this, you
2570 would be unable to proceed past a breakpoint without first disabling the
2571 breakpoint. This rule applies whether or not the breakpoint already
2572 existed when your program stopped.
2574 @item break @dots{} if @var{cond}
2575 Set a breakpoint with condition @var{cond}; evaluate the expression
2576 @var{cond} each time the breakpoint is reached, and stop only if the
2577 value is nonzero---that is, if @var{cond} evaluates as true.
2578 @samp{@dots{}} stands for one of the possible arguments described
2579 above (or no argument) specifying where to break. @xref{Conditions,
2580 ,Break conditions}, for more information on breakpoint conditions.
2583 @item tbreak @var{args}
2584 Set a breakpoint enabled only for one stop. @var{args} are the
2585 same as for the @code{break} command, and the breakpoint is set in the same
2586 way, but the breakpoint is automatically deleted after the first time your
2587 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2590 @cindex hardware breakpoints
2591 @item hbreak @var{args}
2592 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2593 @code{break} command and the breakpoint is set in the same way, but the
2594 breakpoint requires hardware support and some target hardware may not
2595 have this support. The main purpose of this is EPROM/ROM code
2596 debugging, so you can set a breakpoint at an instruction without
2597 changing the instruction. This can be used with the new trap-generation
2598 provided by SPARClite DSU and most x86-based targets. These targets
2599 will generate traps when a program accesses some data or instruction
2600 address that is assigned to the debug registers. However the hardware
2601 breakpoint registers can take a limited number of breakpoints. For
2602 example, on the DSU, only two data breakpoints can be set at a time, and
2603 @value{GDBN} will reject this command if more than two are used. Delete
2604 or disable unused hardware breakpoints before setting new ones
2605 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2606 For remote targets, you can restrict the number of hardware
2607 breakpoints @value{GDBN} will use, see @ref{set remote
2608 hardware-breakpoint-limit}.
2612 @item thbreak @var{args}
2613 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2614 are the same as for the @code{hbreak} command and the breakpoint is set in
2615 the same way. However, like the @code{tbreak} command,
2616 the breakpoint is automatically deleted after the
2617 first time your program stops there. Also, like the @code{hbreak}
2618 command, the breakpoint requires hardware support and some target hardware
2619 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2620 See also @ref{Conditions, ,Break conditions}.
2623 @cindex regular expression
2624 @cindex breakpoints in functions matching a regexp
2625 @cindex set breakpoints in many functions
2626 @item rbreak @var{regex}
2627 Set breakpoints on all functions matching the regular expression
2628 @var{regex}. This command sets an unconditional breakpoint on all
2629 matches, printing a list of all breakpoints it set. Once these
2630 breakpoints are set, they are treated just like the breakpoints set with
2631 the @code{break} command. You can delete them, disable them, or make
2632 them conditional the same way as any other breakpoint.
2634 The syntax of the regular expression is the standard one used with tools
2635 like @file{grep}. Note that this is different from the syntax used by
2636 shells, so for instance @code{foo*} matches all functions that include
2637 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2638 @code{.*} leading and trailing the regular expression you supply, so to
2639 match only functions that begin with @code{foo}, use @code{^foo}.
2641 @cindex non-member C@t{++} functions, set breakpoint in
2642 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2643 breakpoints on overloaded functions that are not members of any special
2646 @cindex set breakpoints on all functions
2647 The @code{rbreak} command can be used to set breakpoints in
2648 @strong{all} the functions in a program, like this:
2651 (@value{GDBP}) rbreak .
2654 @kindex info breakpoints
2655 @cindex @code{$_} and @code{info breakpoints}
2656 @item info breakpoints @r{[}@var{n}@r{]}
2657 @itemx info break @r{[}@var{n}@r{]}
2658 @itemx info watchpoints @r{[}@var{n}@r{]}
2659 Print a table of all breakpoints, watchpoints, and catchpoints set and
2660 not deleted, with the following columns for each breakpoint:
2663 @item Breakpoint Numbers
2665 Breakpoint, watchpoint, or catchpoint.
2667 Whether the breakpoint is marked to be disabled or deleted when hit.
2668 @item Enabled or Disabled
2669 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2670 that are not enabled.
2672 Where the breakpoint is in your program, as a memory address. If the
2673 breakpoint is pending (see below for details) on a future load of a shared library, the address
2674 will be listed as @samp{<PENDING>}.
2676 Where the breakpoint is in the source for your program, as a file and
2677 line number. For a pending breakpoint, the original string passed to
2678 the breakpoint command will be listed as it cannot be resolved until
2679 the appropriate shared library is loaded in the future.
2683 If a breakpoint is conditional, @code{info break} shows the condition on
2684 the line following the affected breakpoint; breakpoint commands, if any,
2685 are listed after that. A pending breakpoint is allowed to have a condition
2686 specified for it. The condition is not parsed for validity until a shared
2687 library is loaded that allows the pending breakpoint to resolve to a
2691 @code{info break} with a breakpoint
2692 number @var{n} as argument lists only that breakpoint. The
2693 convenience variable @code{$_} and the default examining-address for
2694 the @code{x} command are set to the address of the last breakpoint
2695 listed (@pxref{Memory, ,Examining memory}).
2698 @code{info break} displays a count of the number of times the breakpoint
2699 has been hit. This is especially useful in conjunction with the
2700 @code{ignore} command. You can ignore a large number of breakpoint
2701 hits, look at the breakpoint info to see how many times the breakpoint
2702 was hit, and then run again, ignoring one less than that number. This
2703 will get you quickly to the last hit of that breakpoint.
2706 @value{GDBN} allows you to set any number of breakpoints at the same place in
2707 your program. There is nothing silly or meaningless about this. When
2708 the breakpoints are conditional, this is even useful
2709 (@pxref{Conditions, ,Break conditions}).
2711 @cindex pending breakpoints
2712 If a specified breakpoint location cannot be found, it may be due to the fact
2713 that the location is in a shared library that is yet to be loaded. In such
2714 a case, you may want @value{GDBN} to create a special breakpoint (known as
2715 a @dfn{pending breakpoint}) that
2716 attempts to resolve itself in the future when an appropriate shared library
2719 Pending breakpoints are useful to set at the start of your
2720 @value{GDBN} session for locations that you know will be dynamically loaded
2721 later by the program being debugged. When shared libraries are loaded,
2722 a check is made to see if the load resolves any pending breakpoint locations.
2723 If a pending breakpoint location gets resolved,
2724 a regular breakpoint is created and the original pending breakpoint is removed.
2726 @value{GDBN} provides some additional commands for controlling pending
2729 @kindex set breakpoint pending
2730 @kindex show breakpoint pending
2732 @item set breakpoint pending auto
2733 This is the default behavior. When @value{GDBN} cannot find the breakpoint
2734 location, it queries you whether a pending breakpoint should be created.
2736 @item set breakpoint pending on
2737 This indicates that an unrecognized breakpoint location should automatically
2738 result in a pending breakpoint being created.
2740 @item set breakpoint pending off
2741 This indicates that pending breakpoints are not to be created. Any
2742 unrecognized breakpoint location results in an error. This setting does
2743 not affect any pending breakpoints previously created.
2745 @item show breakpoint pending
2746 Show the current behavior setting for creating pending breakpoints.
2749 @cindex operations allowed on pending breakpoints
2750 Normal breakpoint operations apply to pending breakpoints as well. You may
2751 specify a condition for a pending breakpoint and/or commands to run when the
2752 breakpoint is reached. You can also enable or disable
2753 the pending breakpoint. When you specify a condition for a pending breakpoint,
2754 the parsing of the condition will be deferred until the point where the
2755 pending breakpoint location is resolved. Disabling a pending breakpoint
2756 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
2757 shared library load. When a pending breakpoint is re-enabled,
2758 @value{GDBN} checks to see if the location is already resolved.
2759 This is done because any number of shared library loads could have
2760 occurred since the time the breakpoint was disabled and one or more
2761 of these loads could resolve the location.
2763 @cindex negative breakpoint numbers
2764 @cindex internal @value{GDBN} breakpoints
2765 @value{GDBN} itself sometimes sets breakpoints in your program for
2766 special purposes, such as proper handling of @code{longjmp} (in C
2767 programs). These internal breakpoints are assigned negative numbers,
2768 starting with @code{-1}; @samp{info breakpoints} does not display them.
2769 You can see these breakpoints with the @value{GDBN} maintenance command
2770 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
2773 @node Set Watchpoints
2774 @subsection Setting watchpoints
2776 @cindex setting watchpoints
2777 You can use a watchpoint to stop execution whenever the value of an
2778 expression changes, without having to predict a particular place where
2781 @cindex software watchpoints
2782 @cindex hardware watchpoints
2783 Depending on your system, watchpoints may be implemented in software or
2784 hardware. @value{GDBN} does software watchpointing by single-stepping your
2785 program and testing the variable's value each time, which is hundreds of
2786 times slower than normal execution. (But this may still be worth it, to
2787 catch errors where you have no clue what part of your program is the
2790 On some systems, such as HP-UX, @sc{gnu}/Linux and most other
2791 x86-based targets, @value{GDBN} includes support for hardware
2792 watchpoints, which do not slow down the running of your program.
2796 @item watch @var{expr}
2797 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
2798 is written into by the program and its value changes.
2801 @item rwatch @var{expr}
2802 Set a watchpoint that will break when the value of @var{expr} is read
2806 @item awatch @var{expr}
2807 Set a watchpoint that will break when @var{expr} is either read from
2808 or written into by the program.
2810 @kindex info watchpoints
2811 @item info watchpoints
2812 This command prints a list of watchpoints, breakpoints, and catchpoints;
2813 it is the same as @code{info break} (@pxref{Set Breaks}).
2816 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
2817 watchpoints execute very quickly, and the debugger reports a change in
2818 value at the exact instruction where the change occurs. If @value{GDBN}
2819 cannot set a hardware watchpoint, it sets a software watchpoint, which
2820 executes more slowly and reports the change in value at the next
2821 @emph{statement}, not the instruction, after the change occurs.
2823 @vindex can-use-hw-watchpoints
2824 @cindex use only software watchpoints
2825 You can force @value{GDBN} to use only software watchpoints with the
2826 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
2827 zero, @value{GDBN} will never try to use hardware watchpoints, even if
2828 the underlying system supports them. (Note that hardware-assisted
2829 watchpoints that were set @emph{before} setting
2830 @code{can-use-hw-watchpoints} to zero will still use the hardware
2831 mechanism of watching expressiion values.)
2834 @item set can-use-hw-watchpoints
2835 @kindex set can-use-hw-watchpoints
2836 Set whether or not to use hardware watchpoints.
2838 @item show can-use-hw-watchpoints
2839 @kindex show can-use-hw-watchpoints
2840 Show the current mode of using hardware watchpoints.
2843 For remote targets, you can restrict the number of hardware
2844 watchpoints @value{GDBN} will use, see @ref{set remote
2845 hardware-breakpoint-limit}.
2847 When you issue the @code{watch} command, @value{GDBN} reports
2850 Hardware watchpoint @var{num}: @var{expr}
2854 if it was able to set a hardware watchpoint.
2856 Currently, the @code{awatch} and @code{rwatch} commands can only set
2857 hardware watchpoints, because accesses to data that don't change the
2858 value of the watched expression cannot be detected without examining
2859 every instruction as it is being executed, and @value{GDBN} does not do
2860 that currently. If @value{GDBN} finds that it is unable to set a
2861 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
2862 will print a message like this:
2865 Expression cannot be implemented with read/access watchpoint.
2868 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
2869 data type of the watched expression is wider than what a hardware
2870 watchpoint on the target machine can handle. For example, some systems
2871 can only watch regions that are up to 4 bytes wide; on such systems you
2872 cannot set hardware watchpoints for an expression that yields a
2873 double-precision floating-point number (which is typically 8 bytes
2874 wide). As a work-around, it might be possible to break the large region
2875 into a series of smaller ones and watch them with separate watchpoints.
2877 If you set too many hardware watchpoints, @value{GDBN} might be unable
2878 to insert all of them when you resume the execution of your program.
2879 Since the precise number of active watchpoints is unknown until such
2880 time as the program is about to be resumed, @value{GDBN} might not be
2881 able to warn you about this when you set the watchpoints, and the
2882 warning will be printed only when the program is resumed:
2885 Hardware watchpoint @var{num}: Could not insert watchpoint
2889 If this happens, delete or disable some of the watchpoints.
2891 The SPARClite DSU will generate traps when a program accesses some data
2892 or instruction address that is assigned to the debug registers. For the
2893 data addresses, DSU facilitates the @code{watch} command. However the
2894 hardware breakpoint registers can only take two data watchpoints, and
2895 both watchpoints must be the same kind. For example, you can set two
2896 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
2897 @strong{or} two with @code{awatch} commands, but you cannot set one
2898 watchpoint with one command and the other with a different command.
2899 @value{GDBN} will reject the command if you try to mix watchpoints.
2900 Delete or disable unused watchpoint commands before setting new ones.
2902 If you call a function interactively using @code{print} or @code{call},
2903 any watchpoints you have set will be inactive until @value{GDBN} reaches another
2904 kind of breakpoint or the call completes.
2906 @value{GDBN} automatically deletes watchpoints that watch local
2907 (automatic) variables, or expressions that involve such variables, when
2908 they go out of scope, that is, when the execution leaves the block in
2909 which these variables were defined. In particular, when the program
2910 being debugged terminates, @emph{all} local variables go out of scope,
2911 and so only watchpoints that watch global variables remain set. If you
2912 rerun the program, you will need to set all such watchpoints again. One
2913 way of doing that would be to set a code breakpoint at the entry to the
2914 @code{main} function and when it breaks, set all the watchpoints.
2917 @cindex watchpoints and threads
2918 @cindex threads and watchpoints
2919 @emph{Warning:} In multi-thread programs, watchpoints have only limited
2920 usefulness. With the current watchpoint implementation, @value{GDBN}
2921 can only watch the value of an expression @emph{in a single thread}. If
2922 you are confident that the expression can only change due to the current
2923 thread's activity (and if you are also confident that no other thread
2924 can become current), then you can use watchpoints as usual. However,
2925 @value{GDBN} may not notice when a non-current thread's activity changes
2928 @c FIXME: this is almost identical to the previous paragraph.
2929 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
2930 have only limited usefulness. If @value{GDBN} creates a software
2931 watchpoint, it can only watch the value of an expression @emph{in a
2932 single thread}. If you are confident that the expression can only
2933 change due to the current thread's activity (and if you are also
2934 confident that no other thread can become current), then you can use
2935 software watchpoints as usual. However, @value{GDBN} may not notice
2936 when a non-current thread's activity changes the expression. (Hardware
2937 watchpoints, in contrast, watch an expression in all threads.)
2940 @xref{set remote hardware-watchpoint-limit}.
2942 @node Set Catchpoints
2943 @subsection Setting catchpoints
2944 @cindex catchpoints, setting
2945 @cindex exception handlers
2946 @cindex event handling
2948 You can use @dfn{catchpoints} to cause the debugger to stop for certain
2949 kinds of program events, such as C@t{++} exceptions or the loading of a
2950 shared library. Use the @code{catch} command to set a catchpoint.
2954 @item catch @var{event}
2955 Stop when @var{event} occurs. @var{event} can be any of the following:
2958 @cindex stop on C@t{++} exceptions
2959 The throwing of a C@t{++} exception.
2962 The catching of a C@t{++} exception.
2965 @cindex break on fork/exec
2966 A call to @code{exec}. This is currently only available for HP-UX.
2969 A call to @code{fork}. This is currently only available for HP-UX.
2972 A call to @code{vfork}. This is currently only available for HP-UX.
2975 @itemx load @var{libname}
2976 @cindex break on load/unload of shared library
2977 The dynamic loading of any shared library, or the loading of the library
2978 @var{libname}. This is currently only available for HP-UX.
2981 @itemx unload @var{libname}
2982 The unloading of any dynamically loaded shared library, or the unloading
2983 of the library @var{libname}. This is currently only available for HP-UX.
2986 @item tcatch @var{event}
2987 Set a catchpoint that is enabled only for one stop. The catchpoint is
2988 automatically deleted after the first time the event is caught.
2992 Use the @code{info break} command to list the current catchpoints.
2994 There are currently some limitations to C@t{++} exception handling
2995 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
2999 If you call a function interactively, @value{GDBN} normally returns
3000 control to you when the function has finished executing. If the call
3001 raises an exception, however, the call may bypass the mechanism that
3002 returns control to you and cause your program either to abort or to
3003 simply continue running until it hits a breakpoint, catches a signal
3004 that @value{GDBN} is listening for, or exits. This is the case even if
3005 you set a catchpoint for the exception; catchpoints on exceptions are
3006 disabled within interactive calls.
3009 You cannot raise an exception interactively.
3012 You cannot install an exception handler interactively.
3015 @cindex raise exceptions
3016 Sometimes @code{catch} is not the best way to debug exception handling:
3017 if you need to know exactly where an exception is raised, it is better to
3018 stop @emph{before} the exception handler is called, since that way you
3019 can see the stack before any unwinding takes place. If you set a
3020 breakpoint in an exception handler instead, it may not be easy to find
3021 out where the exception was raised.
3023 To stop just before an exception handler is called, you need some
3024 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3025 raised by calling a library function named @code{__raise_exception}
3026 which has the following ANSI C interface:
3029 /* @var{addr} is where the exception identifier is stored.
3030 @var{id} is the exception identifier. */
3031 void __raise_exception (void **addr, void *id);
3035 To make the debugger catch all exceptions before any stack
3036 unwinding takes place, set a breakpoint on @code{__raise_exception}
3037 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
3039 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
3040 that depends on the value of @var{id}, you can stop your program when
3041 a specific exception is raised. You can use multiple conditional
3042 breakpoints to stop your program when any of a number of exceptions are
3047 @subsection Deleting breakpoints
3049 @cindex clearing breakpoints, watchpoints, catchpoints
3050 @cindex deleting breakpoints, watchpoints, catchpoints
3051 It is often necessary to eliminate a breakpoint, watchpoint, or
3052 catchpoint once it has done its job and you no longer want your program
3053 to stop there. This is called @dfn{deleting} the breakpoint. A
3054 breakpoint that has been deleted no longer exists; it is forgotten.
3056 With the @code{clear} command you can delete breakpoints according to
3057 where they are in your program. With the @code{delete} command you can
3058 delete individual breakpoints, watchpoints, or catchpoints by specifying
3059 their breakpoint numbers.
3061 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3062 automatically ignores breakpoints on the first instruction to be executed
3063 when you continue execution without changing the execution address.
3068 Delete any breakpoints at the next instruction to be executed in the
3069 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
3070 the innermost frame is selected, this is a good way to delete a
3071 breakpoint where your program just stopped.
3073 @item clear @var{function}
3074 @itemx clear @var{filename}:@var{function}
3075 Delete any breakpoints set at entry to the named @var{function}.
3077 @item clear @var{linenum}
3078 @itemx clear @var{filename}:@var{linenum}
3079 Delete any breakpoints set at or within the code of the specified
3080 @var{linenum} of the specified @var{filename}.
3082 @cindex delete breakpoints
3084 @kindex d @r{(@code{delete})}
3085 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3086 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3087 ranges specified as arguments. If no argument is specified, delete all
3088 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3089 confirm off}). You can abbreviate this command as @code{d}.
3093 @subsection Disabling breakpoints
3095 @cindex enable/disable a breakpoint
3096 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3097 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3098 it had been deleted, but remembers the information on the breakpoint so
3099 that you can @dfn{enable} it again later.
3101 You disable and enable breakpoints, watchpoints, and catchpoints with
3102 the @code{enable} and @code{disable} commands, optionally specifying one
3103 or more breakpoint numbers as arguments. Use @code{info break} or
3104 @code{info watch} to print a list of breakpoints, watchpoints, and
3105 catchpoints if you do not know which numbers to use.
3107 A breakpoint, watchpoint, or catchpoint can have any of four different
3108 states of enablement:
3112 Enabled. The breakpoint stops your program. A breakpoint set
3113 with the @code{break} command starts out in this state.
3115 Disabled. The breakpoint has no effect on your program.
3117 Enabled once. The breakpoint stops your program, but then becomes
3120 Enabled for deletion. The breakpoint stops your program, but
3121 immediately after it does so it is deleted permanently. A breakpoint
3122 set with the @code{tbreak} command starts out in this state.
3125 You can use the following commands to enable or disable breakpoints,
3126 watchpoints, and catchpoints:
3130 @kindex dis @r{(@code{disable})}
3131 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3132 Disable the specified breakpoints---or all breakpoints, if none are
3133 listed. A disabled breakpoint has no effect but is not forgotten. All
3134 options such as ignore-counts, conditions and commands are remembered in
3135 case the breakpoint is enabled again later. You may abbreviate
3136 @code{disable} as @code{dis}.
3139 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3140 Enable the specified breakpoints (or all defined breakpoints). They
3141 become effective once again in stopping your program.
3143 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3144 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3145 of these breakpoints immediately after stopping your program.
3147 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3148 Enable the specified breakpoints to work once, then die. @value{GDBN}
3149 deletes any of these breakpoints as soon as your program stops there.
3150 Breakpoints set by the @code{tbreak} command start out in this state.
3153 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3154 @c confusing: tbreak is also initially enabled.
3155 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3156 ,Setting breakpoints}), breakpoints that you set are initially enabled;
3157 subsequently, they become disabled or enabled only when you use one of
3158 the commands above. (The command @code{until} can set and delete a
3159 breakpoint of its own, but it does not change the state of your other
3160 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3164 @subsection Break conditions
3165 @cindex conditional breakpoints
3166 @cindex breakpoint conditions
3168 @c FIXME what is scope of break condition expr? Context where wanted?
3169 @c in particular for a watchpoint?
3170 The simplest sort of breakpoint breaks every time your program reaches a
3171 specified place. You can also specify a @dfn{condition} for a
3172 breakpoint. A condition is just a Boolean expression in your
3173 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3174 a condition evaluates the expression each time your program reaches it,
3175 and your program stops only if the condition is @emph{true}.
3177 This is the converse of using assertions for program validation; in that
3178 situation, you want to stop when the assertion is violated---that is,
3179 when the condition is false. In C, if you want to test an assertion expressed
3180 by the condition @var{assert}, you should set the condition
3181 @samp{! @var{assert}} on the appropriate breakpoint.
3183 Conditions are also accepted for watchpoints; you may not need them,
3184 since a watchpoint is inspecting the value of an expression anyhow---but
3185 it might be simpler, say, to just set a watchpoint on a variable name,
3186 and specify a condition that tests whether the new value is an interesting
3189 Break conditions can have side effects, and may even call functions in
3190 your program. This can be useful, for example, to activate functions
3191 that log program progress, or to use your own print functions to
3192 format special data structures. The effects are completely predictable
3193 unless there is another enabled breakpoint at the same address. (In
3194 that case, @value{GDBN} might see the other breakpoint first and stop your
3195 program without checking the condition of this one.) Note that
3196 breakpoint commands are usually more convenient and flexible than break
3198 purpose of performing side effects when a breakpoint is reached
3199 (@pxref{Break Commands, ,Breakpoint command lists}).
3201 Break conditions can be specified when a breakpoint is set, by using
3202 @samp{if} in the arguments to the @code{break} command. @xref{Set
3203 Breaks, ,Setting breakpoints}. They can also be changed at any time
3204 with the @code{condition} command.
3206 You can also use the @code{if} keyword with the @code{watch} command.
3207 The @code{catch} command does not recognize the @code{if} keyword;
3208 @code{condition} is the only way to impose a further condition on a
3213 @item condition @var{bnum} @var{expression}
3214 Specify @var{expression} as the break condition for breakpoint,
3215 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3216 breakpoint @var{bnum} stops your program only if the value of
3217 @var{expression} is true (nonzero, in C). When you use
3218 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3219 syntactic correctness, and to determine whether symbols in it have
3220 referents in the context of your breakpoint. If @var{expression} uses
3221 symbols not referenced in the context of the breakpoint, @value{GDBN}
3222 prints an error message:
3225 No symbol "foo" in current context.
3230 not actually evaluate @var{expression} at the time the @code{condition}
3231 command (or a command that sets a breakpoint with a condition, like
3232 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3234 @item condition @var{bnum}
3235 Remove the condition from breakpoint number @var{bnum}. It becomes
3236 an ordinary unconditional breakpoint.
3239 @cindex ignore count (of breakpoint)
3240 A special case of a breakpoint condition is to stop only when the
3241 breakpoint has been reached a certain number of times. This is so
3242 useful that there is a special way to do it, using the @dfn{ignore
3243 count} of the breakpoint. Every breakpoint has an ignore count, which
3244 is an integer. Most of the time, the ignore count is zero, and
3245 therefore has no effect. But if your program reaches a breakpoint whose
3246 ignore count is positive, then instead of stopping, it just decrements
3247 the ignore count by one and continues. As a result, if the ignore count
3248 value is @var{n}, the breakpoint does not stop the next @var{n} times
3249 your program reaches it.
3253 @item ignore @var{bnum} @var{count}
3254 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3255 The next @var{count} times the breakpoint is reached, your program's
3256 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3259 To make the breakpoint stop the next time it is reached, specify
3262 When you use @code{continue} to resume execution of your program from a
3263 breakpoint, you can specify an ignore count directly as an argument to
3264 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3265 Stepping,,Continuing and stepping}.
3267 If a breakpoint has a positive ignore count and a condition, the
3268 condition is not checked. Once the ignore count reaches zero,
3269 @value{GDBN} resumes checking the condition.
3271 You could achieve the effect of the ignore count with a condition such
3272 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3273 is decremented each time. @xref{Convenience Vars, ,Convenience
3277 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3280 @node Break Commands
3281 @subsection Breakpoint command lists
3283 @cindex breakpoint commands
3284 You can give any breakpoint (or watchpoint or catchpoint) a series of
3285 commands to execute when your program stops due to that breakpoint. For
3286 example, you might want to print the values of certain expressions, or
3287 enable other breakpoints.
3292 @item commands @r{[}@var{bnum}@r{]}
3293 @itemx @dots{} @var{command-list} @dots{}
3295 Specify a list of commands for breakpoint number @var{bnum}. The commands
3296 themselves appear on the following lines. Type a line containing just
3297 @code{end} to terminate the commands.
3299 To remove all commands from a breakpoint, type @code{commands} and
3300 follow it immediately with @code{end}; that is, give no commands.
3302 With no @var{bnum} argument, @code{commands} refers to the last
3303 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3304 recently encountered).
3307 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3308 disabled within a @var{command-list}.
3310 You can use breakpoint commands to start your program up again. Simply
3311 use the @code{continue} command, or @code{step}, or any other command
3312 that resumes execution.
3314 Any other commands in the command list, after a command that resumes
3315 execution, are ignored. This is because any time you resume execution
3316 (even with a simple @code{next} or @code{step}), you may encounter
3317 another breakpoint---which could have its own command list, leading to
3318 ambiguities about which list to execute.
3321 If the first command you specify in a command list is @code{silent}, the
3322 usual message about stopping at a breakpoint is not printed. This may
3323 be desirable for breakpoints that are to print a specific message and
3324 then continue. If none of the remaining commands print anything, you
3325 see no sign that the breakpoint was reached. @code{silent} is
3326 meaningful only at the beginning of a breakpoint command list.
3328 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3329 print precisely controlled output, and are often useful in silent
3330 breakpoints. @xref{Output, ,Commands for controlled output}.
3332 For example, here is how you could use breakpoint commands to print the
3333 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3339 printf "x is %d\n",x
3344 One application for breakpoint commands is to compensate for one bug so
3345 you can test for another. Put a breakpoint just after the erroneous line
3346 of code, give it a condition to detect the case in which something
3347 erroneous has been done, and give it commands to assign correct values
3348 to any variables that need them. End with the @code{continue} command
3349 so that your program does not stop, and start with the @code{silent}
3350 command so that no output is produced. Here is an example:
3361 @node Breakpoint Menus
3362 @subsection Breakpoint menus
3364 @cindex symbol overloading
3366 Some programming languages (notably C@t{++} and Objective-C) permit a
3367 single function name
3368 to be defined several times, for application in different contexts.
3369 This is called @dfn{overloading}. When a function name is overloaded,
3370 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3371 a breakpoint. If you realize this is a problem, you can use
3372 something like @samp{break @var{function}(@var{types})} to specify which
3373 particular version of the function you want. Otherwise, @value{GDBN} offers
3374 you a menu of numbered choices for different possible breakpoints, and
3375 waits for your selection with the prompt @samp{>}. The first two
3376 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3377 sets a breakpoint at each definition of @var{function}, and typing
3378 @kbd{0} aborts the @code{break} command without setting any new
3381 For example, the following session excerpt shows an attempt to set a
3382 breakpoint at the overloaded symbol @code{String::after}.
3383 We choose three particular definitions of that function name:
3385 @c FIXME! This is likely to change to show arg type lists, at least
3388 (@value{GDBP}) b String::after
3391 [2] file:String.cc; line number:867
3392 [3] file:String.cc; line number:860
3393 [4] file:String.cc; line number:875
3394 [5] file:String.cc; line number:853
3395 [6] file:String.cc; line number:846
3396 [7] file:String.cc; line number:735
3398 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3399 Breakpoint 2 at 0xb344: file String.cc, line 875.
3400 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3401 Multiple breakpoints were set.
3402 Use the "delete" command to delete unwanted
3408 @c @ifclear BARETARGET
3409 @node Error in Breakpoints
3410 @subsection ``Cannot insert breakpoints''
3412 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3414 Under some operating systems, breakpoints cannot be used in a program if
3415 any other process is running that program. In this situation,
3416 attempting to run or continue a program with a breakpoint causes
3417 @value{GDBN} to print an error message:
3420 Cannot insert breakpoints.
3421 The same program may be running in another process.
3424 When this happens, you have three ways to proceed:
3428 Remove or disable the breakpoints, then continue.
3431 Suspend @value{GDBN}, and copy the file containing your program to a new
3432 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3433 that @value{GDBN} should run your program under that name.
3434 Then start your program again.
3437 Relink your program so that the text segment is nonsharable, using the
3438 linker option @samp{-N}. The operating system limitation may not apply
3439 to nonsharable executables.
3443 A similar message can be printed if you request too many active
3444 hardware-assisted breakpoints and watchpoints:
3446 @c FIXME: the precise wording of this message may change; the relevant
3447 @c source change is not committed yet (Sep 3, 1999).
3449 Stopped; cannot insert breakpoints.
3450 You may have requested too many hardware breakpoints and watchpoints.
3454 This message is printed when you attempt to resume the program, since
3455 only then @value{GDBN} knows exactly how many hardware breakpoints and
3456 watchpoints it needs to insert.
3458 When this message is printed, you need to disable or remove some of the
3459 hardware-assisted breakpoints and watchpoints, and then continue.
3461 @node Breakpoint related warnings
3462 @subsection ``Breakpoint address adjusted...''
3463 @cindex breakpoint address adjusted
3465 Some processor architectures place constraints on the addresses at
3466 which breakpoints may be placed. For architectures thus constrained,
3467 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3468 with the constraints dictated by the architecture.
3470 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3471 a VLIW architecture in which a number of RISC-like instructions may be
3472 bundled together for parallel execution. The FR-V architecture
3473 constrains the location of a breakpoint instruction within such a
3474 bundle to the instruction with the lowest address. @value{GDBN}
3475 honors this constraint by adjusting a breakpoint's address to the
3476 first in the bundle.
3478 It is not uncommon for optimized code to have bundles which contain
3479 instructions from different source statements, thus it may happen that
3480 a breakpoint's address will be adjusted from one source statement to
3481 another. Since this adjustment may significantly alter @value{GDBN}'s
3482 breakpoint related behavior from what the user expects, a warning is
3483 printed when the breakpoint is first set and also when the breakpoint
3486 A warning like the one below is printed when setting a breakpoint
3487 that's been subject to address adjustment:
3490 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3493 Such warnings are printed both for user settable and @value{GDBN}'s
3494 internal breakpoints. If you see one of these warnings, you should
3495 verify that a breakpoint set at the adjusted address will have the
3496 desired affect. If not, the breakpoint in question may be removed and
3497 other breakpoints may be set which will have the desired behavior.
3498 E.g., it may be sufficient to place the breakpoint at a later
3499 instruction. A conditional breakpoint may also be useful in some
3500 cases to prevent the breakpoint from triggering too often.
3502 @value{GDBN} will also issue a warning when stopping at one of these
3503 adjusted breakpoints:
3506 warning: Breakpoint 1 address previously adjusted from 0x00010414
3510 When this warning is encountered, it may be too late to take remedial
3511 action except in cases where the breakpoint is hit earlier or more
3512 frequently than expected.
3514 @node Continuing and Stepping
3515 @section Continuing and stepping
3519 @cindex resuming execution
3520 @dfn{Continuing} means resuming program execution until your program
3521 completes normally. In contrast, @dfn{stepping} means executing just
3522 one more ``step'' of your program, where ``step'' may mean either one
3523 line of source code, or one machine instruction (depending on what
3524 particular command you use). Either when continuing or when stepping,
3525 your program may stop even sooner, due to a breakpoint or a signal. (If
3526 it stops due to a signal, you may want to use @code{handle}, or use
3527 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3531 @kindex c @r{(@code{continue})}
3532 @kindex fg @r{(resume foreground execution)}
3533 @item continue @r{[}@var{ignore-count}@r{]}
3534 @itemx c @r{[}@var{ignore-count}@r{]}
3535 @itemx fg @r{[}@var{ignore-count}@r{]}
3536 Resume program execution, at the address where your program last stopped;
3537 any breakpoints set at that address are bypassed. The optional argument
3538 @var{ignore-count} allows you to specify a further number of times to
3539 ignore a breakpoint at this location; its effect is like that of
3540 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3542 The argument @var{ignore-count} is meaningful only when your program
3543 stopped due to a breakpoint. At other times, the argument to
3544 @code{continue} is ignored.
3546 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3547 debugged program is deemed to be the foreground program) are provided
3548 purely for convenience, and have exactly the same behavior as
3552 To resume execution at a different place, you can use @code{return}
3553 (@pxref{Returning, ,Returning from a function}) to go back to the
3554 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3555 different address}) to go to an arbitrary location in your program.
3557 A typical technique for using stepping is to set a breakpoint
3558 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3559 beginning of the function or the section of your program where a problem
3560 is believed to lie, run your program until it stops at that breakpoint,
3561 and then step through the suspect area, examining the variables that are
3562 interesting, until you see the problem happen.
3566 @kindex s @r{(@code{step})}
3568 Continue running your program until control reaches a different source
3569 line, then stop it and return control to @value{GDBN}. This command is
3570 abbreviated @code{s}.
3573 @c "without debugging information" is imprecise; actually "without line
3574 @c numbers in the debugging information". (gcc -g1 has debugging info but
3575 @c not line numbers). But it seems complex to try to make that
3576 @c distinction here.
3577 @emph{Warning:} If you use the @code{step} command while control is
3578 within a function that was compiled without debugging information,
3579 execution proceeds until control reaches a function that does have
3580 debugging information. Likewise, it will not step into a function which
3581 is compiled without debugging information. To step through functions
3582 without debugging information, use the @code{stepi} command, described
3586 The @code{step} command only stops at the first instruction of a source
3587 line. This prevents the multiple stops that could otherwise occur in
3588 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3589 to stop if a function that has debugging information is called within
3590 the line. In other words, @code{step} @emph{steps inside} any functions
3591 called within the line.
3593 Also, the @code{step} command only enters a function if there is line
3594 number information for the function. Otherwise it acts like the
3595 @code{next} command. This avoids problems when using @code{cc -gl}
3596 on MIPS machines. Previously, @code{step} entered subroutines if there
3597 was any debugging information about the routine.
3599 @item step @var{count}
3600 Continue running as in @code{step}, but do so @var{count} times. If a
3601 breakpoint is reached, or a signal not related to stepping occurs before
3602 @var{count} steps, stepping stops right away.
3605 @kindex n @r{(@code{next})}
3606 @item next @r{[}@var{count}@r{]}
3607 Continue to the next source line in the current (innermost) stack frame.
3608 This is similar to @code{step}, but function calls that appear within
3609 the line of code are executed without stopping. Execution stops when
3610 control reaches a different line of code at the original stack level
3611 that was executing when you gave the @code{next} command. This command
3612 is abbreviated @code{n}.
3614 An argument @var{count} is a repeat count, as for @code{step}.
3617 @c FIX ME!! Do we delete this, or is there a way it fits in with
3618 @c the following paragraph? --- Vctoria
3620 @c @code{next} within a function that lacks debugging information acts like
3621 @c @code{step}, but any function calls appearing within the code of the
3622 @c function are executed without stopping.
3624 The @code{next} command only stops at the first instruction of a
3625 source line. This prevents multiple stops that could otherwise occur in
3626 @code{switch} statements, @code{for} loops, etc.
3628 @kindex set step-mode
3630 @cindex functions without line info, and stepping
3631 @cindex stepping into functions with no line info
3632 @itemx set step-mode on
3633 The @code{set step-mode on} command causes the @code{step} command to
3634 stop at the first instruction of a function which contains no debug line
3635 information rather than stepping over it.
3637 This is useful in cases where you may be interested in inspecting the
3638 machine instructions of a function which has no symbolic info and do not
3639 want @value{GDBN} to automatically skip over this function.
3641 @item set step-mode off
3642 Causes the @code{step} command to step over any functions which contains no
3643 debug information. This is the default.
3645 @item show step-mode
3646 Show whether @value{GDBN} will stop in or step over functions without
3647 source line debug information.
3651 Continue running until just after function in the selected stack frame
3652 returns. Print the returned value (if any).
3654 Contrast this with the @code{return} command (@pxref{Returning,
3655 ,Returning from a function}).
3658 @kindex u @r{(@code{until})}
3659 @cindex run until specified location
3662 Continue running until a source line past the current line, in the
3663 current stack frame, is reached. This command is used to avoid single
3664 stepping through a loop more than once. It is like the @code{next}
3665 command, except that when @code{until} encounters a jump, it
3666 automatically continues execution until the program counter is greater
3667 than the address of the jump.
3669 This means that when you reach the end of a loop after single stepping
3670 though it, @code{until} makes your program continue execution until it
3671 exits the loop. In contrast, a @code{next} command at the end of a loop
3672 simply steps back to the beginning of the loop, which forces you to step
3673 through the next iteration.
3675 @code{until} always stops your program if it attempts to exit the current
3678 @code{until} may produce somewhat counterintuitive results if the order
3679 of machine code does not match the order of the source lines. For
3680 example, in the following excerpt from a debugging session, the @code{f}
3681 (@code{frame}) command shows that execution is stopped at line
3682 @code{206}; yet when we use @code{until}, we get to line @code{195}:
3686 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
3688 (@value{GDBP}) until
3689 195 for ( ; argc > 0; NEXTARG) @{
3692 This happened because, for execution efficiency, the compiler had
3693 generated code for the loop closure test at the end, rather than the
3694 start, of the loop---even though the test in a C @code{for}-loop is
3695 written before the body of the loop. The @code{until} command appeared
3696 to step back to the beginning of the loop when it advanced to this
3697 expression; however, it has not really gone to an earlier
3698 statement---not in terms of the actual machine code.
3700 @code{until} with no argument works by means of single
3701 instruction stepping, and hence is slower than @code{until} with an
3704 @item until @var{location}
3705 @itemx u @var{location}
3706 Continue running your program until either the specified location is
3707 reached, or the current stack frame returns. @var{location} is any of
3708 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
3709 ,Setting breakpoints}). This form of the command uses breakpoints, and
3710 hence is quicker than @code{until} without an argument. The specified
3711 location is actually reached only if it is in the current frame. This
3712 implies that @code{until} can be used to skip over recursive function
3713 invocations. For instance in the code below, if the current location is
3714 line @code{96}, issuing @code{until 99} will execute the program up to
3715 line @code{99} in the same invocation of factorial, i.e. after the inner
3716 invocations have returned.
3719 94 int factorial (int value)
3721 96 if (value > 1) @{
3722 97 value *= factorial (value - 1);
3729 @kindex advance @var{location}
3730 @itemx advance @var{location}
3731 Continue running the program up to the given @var{location}. An argument is
3732 required, which should be of the same form as arguments for the @code{break}
3733 command. Execution will also stop upon exit from the current stack
3734 frame. This command is similar to @code{until}, but @code{advance} will
3735 not skip over recursive function calls, and the target location doesn't
3736 have to be in the same frame as the current one.
3740 @kindex si @r{(@code{stepi})}
3742 @itemx stepi @var{arg}
3744 Execute one machine instruction, then stop and return to the debugger.
3746 It is often useful to do @samp{display/i $pc} when stepping by machine
3747 instructions. This makes @value{GDBN} automatically display the next
3748 instruction to be executed, each time your program stops. @xref{Auto
3749 Display,, Automatic display}.
3751 An argument is a repeat count, as in @code{step}.
3755 @kindex ni @r{(@code{nexti})}
3757 @itemx nexti @var{arg}
3759 Execute one machine instruction, but if it is a function call,
3760 proceed until the function returns.
3762 An argument is a repeat count, as in @code{next}.
3769 A signal is an asynchronous event that can happen in a program. The
3770 operating system defines the possible kinds of signals, and gives each
3771 kind a name and a number. For example, in Unix @code{SIGINT} is the
3772 signal a program gets when you type an interrupt character (often @kbd{C-c});
3773 @code{SIGSEGV} is the signal a program gets from referencing a place in
3774 memory far away from all the areas in use; @code{SIGALRM} occurs when
3775 the alarm clock timer goes off (which happens only if your program has
3776 requested an alarm).
3778 @cindex fatal signals
3779 Some signals, including @code{SIGALRM}, are a normal part of the
3780 functioning of your program. Others, such as @code{SIGSEGV}, indicate
3781 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
3782 program has not specified in advance some other way to handle the signal.
3783 @code{SIGINT} does not indicate an error in your program, but it is normally
3784 fatal so it can carry out the purpose of the interrupt: to kill the program.
3786 @value{GDBN} has the ability to detect any occurrence of a signal in your
3787 program. You can tell @value{GDBN} in advance what to do for each kind of
3790 @cindex handling signals
3791 Normally, @value{GDBN} is set up to let the non-erroneous signals like
3792 @code{SIGALRM} be silently passed to your program
3793 (so as not to interfere with their role in the program's functioning)
3794 but to stop your program immediately whenever an error signal happens.
3795 You can change these settings with the @code{handle} command.
3798 @kindex info signals
3802 Print a table of all the kinds of signals and how @value{GDBN} has been told to
3803 handle each one. You can use this to see the signal numbers of all
3804 the defined types of signals.
3806 @code{info handle} is an alias for @code{info signals}.
3809 @item handle @var{signal} @var{keywords}@dots{}
3810 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
3811 can be the number of a signal or its name (with or without the
3812 @samp{SIG} at the beginning); a list of signal numbers of the form
3813 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
3814 known signals. The @var{keywords} say what change to make.
3818 The keywords allowed by the @code{handle} command can be abbreviated.
3819 Their full names are:
3823 @value{GDBN} should not stop your program when this signal happens. It may
3824 still print a message telling you that the signal has come in.
3827 @value{GDBN} should stop your program when this signal happens. This implies
3828 the @code{print} keyword as well.
3831 @value{GDBN} should print a message when this signal happens.
3834 @value{GDBN} should not mention the occurrence of the signal at all. This
3835 implies the @code{nostop} keyword as well.
3839 @value{GDBN} should allow your program to see this signal; your program
3840 can handle the signal, or else it may terminate if the signal is fatal
3841 and not handled. @code{pass} and @code{noignore} are synonyms.
3845 @value{GDBN} should not allow your program to see this signal.
3846 @code{nopass} and @code{ignore} are synonyms.
3850 When a signal stops your program, the signal is not visible to the
3852 continue. Your program sees the signal then, if @code{pass} is in
3853 effect for the signal in question @emph{at that time}. In other words,
3854 after @value{GDBN} reports a signal, you can use the @code{handle}
3855 command with @code{pass} or @code{nopass} to control whether your
3856 program sees that signal when you continue.
3858 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
3859 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
3860 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
3863 You can also use the @code{signal} command to prevent your program from
3864 seeing a signal, or cause it to see a signal it normally would not see,
3865 or to give it any signal at any time. For example, if your program stopped
3866 due to some sort of memory reference error, you might store correct
3867 values into the erroneous variables and continue, hoping to see more
3868 execution; but your program would probably terminate immediately as
3869 a result of the fatal signal once it saw the signal. To prevent this,
3870 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
3874 @section Stopping and starting multi-thread programs
3876 When your program has multiple threads (@pxref{Threads,, Debugging
3877 programs with multiple threads}), you can choose whether to set
3878 breakpoints on all threads, or on a particular thread.
3881 @cindex breakpoints and threads
3882 @cindex thread breakpoints
3883 @kindex break @dots{} thread @var{threadno}
3884 @item break @var{linespec} thread @var{threadno}
3885 @itemx break @var{linespec} thread @var{threadno} if @dots{}
3886 @var{linespec} specifies source lines; there are several ways of
3887 writing them, but the effect is always to specify some source line.
3889 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
3890 to specify that you only want @value{GDBN} to stop the program when a
3891 particular thread reaches this breakpoint. @var{threadno} is one of the
3892 numeric thread identifiers assigned by @value{GDBN}, shown in the first
3893 column of the @samp{info threads} display.
3895 If you do not specify @samp{thread @var{threadno}} when you set a
3896 breakpoint, the breakpoint applies to @emph{all} threads of your
3899 You can use the @code{thread} qualifier on conditional breakpoints as
3900 well; in this case, place @samp{thread @var{threadno}} before the
3901 breakpoint condition, like this:
3904 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
3909 @cindex stopped threads
3910 @cindex threads, stopped
3911 Whenever your program stops under @value{GDBN} for any reason,
3912 @emph{all} threads of execution stop, not just the current thread. This
3913 allows you to examine the overall state of the program, including
3914 switching between threads, without worrying that things may change
3917 @cindex thread breakpoints and system calls
3918 @cindex system calls and thread breakpoints
3919 @cindex premature return from system calls
3920 There is an unfortunate side effect. If one thread stops for a
3921 breakpoint, or for some other reason, and another thread is blocked in a
3922 system call, then the system call may return prematurely. This is a
3923 consequence of the interaction between multiple threads and the signals
3924 that @value{GDBN} uses to implement breakpoints and other events that
3927 To handle this problem, your program should check the return value of
3928 each system call and react appropriately. This is good programming
3931 For example, do not write code like this:
3937 The call to @code{sleep} will return early if a different thread stops
3938 at a breakpoint or for some other reason.
3940 Instead, write this:
3945 unslept = sleep (unslept);
3948 A system call is allowed to return early, so the system is still
3949 conforming to its specification. But @value{GDBN} does cause your
3950 multi-threaded program to behave differently than it would without
3953 Also, @value{GDBN} uses internal breakpoints in the thread library to
3954 monitor certain events such as thread creation and thread destruction.
3955 When such an event happens, a system call in another thread may return
3956 prematurely, even though your program does not appear to stop.
3958 @cindex continuing threads
3959 @cindex threads, continuing
3960 Conversely, whenever you restart the program, @emph{all} threads start
3961 executing. @emph{This is true even when single-stepping} with commands
3962 like @code{step} or @code{next}.
3964 In particular, @value{GDBN} cannot single-step all threads in lockstep.
3965 Since thread scheduling is up to your debugging target's operating
3966 system (not controlled by @value{GDBN}), other threads may
3967 execute more than one statement while the current thread completes a
3968 single step. Moreover, in general other threads stop in the middle of a
3969 statement, rather than at a clean statement boundary, when the program
3972 You might even find your program stopped in another thread after
3973 continuing or even single-stepping. This happens whenever some other
3974 thread runs into a breakpoint, a signal, or an exception before the
3975 first thread completes whatever you requested.
3977 On some OSes, you can lock the OS scheduler and thus allow only a single
3981 @item set scheduler-locking @var{mode}
3982 @cindex scheduler locking mode
3983 @cindex lock scheduler
3984 Set the scheduler locking mode. If it is @code{off}, then there is no
3985 locking and any thread may run at any time. If @code{on}, then only the
3986 current thread may run when the inferior is resumed. The @code{step}
3987 mode optimizes for single-stepping. It stops other threads from
3988 ``seizing the prompt'' by preempting the current thread while you are
3989 stepping. Other threads will only rarely (or never) get a chance to run
3990 when you step. They are more likely to run when you @samp{next} over a
3991 function call, and they are completely free to run when you use commands
3992 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
3993 thread hits a breakpoint during its timeslice, they will never steal the
3994 @value{GDBN} prompt away from the thread that you are debugging.
3996 @item show scheduler-locking
3997 Display the current scheduler locking mode.
4002 @chapter Examining the Stack
4004 When your program has stopped, the first thing you need to know is where it
4005 stopped and how it got there.
4008 Each time your program performs a function call, information about the call
4010 That information includes the location of the call in your program,
4011 the arguments of the call,
4012 and the local variables of the function being called.
4013 The information is saved in a block of data called a @dfn{stack frame}.
4014 The stack frames are allocated in a region of memory called the @dfn{call
4017 When your program stops, the @value{GDBN} commands for examining the
4018 stack allow you to see all of this information.
4020 @cindex selected frame
4021 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4022 @value{GDBN} commands refer implicitly to the selected frame. In
4023 particular, whenever you ask @value{GDBN} for the value of a variable in
4024 your program, the value is found in the selected frame. There are
4025 special @value{GDBN} commands to select whichever frame you are
4026 interested in. @xref{Selection, ,Selecting a frame}.
4028 When your program stops, @value{GDBN} automatically selects the
4029 currently executing frame and describes it briefly, similar to the
4030 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
4033 * Frames:: Stack frames
4034 * Backtrace:: Backtraces
4035 * Selection:: Selecting a frame
4036 * Frame Info:: Information on a frame
4041 @section Stack frames
4043 @cindex frame, definition
4045 The call stack is divided up into contiguous pieces called @dfn{stack
4046 frames}, or @dfn{frames} for short; each frame is the data associated
4047 with one call to one function. The frame contains the arguments given
4048 to the function, the function's local variables, and the address at
4049 which the function is executing.
4051 @cindex initial frame
4052 @cindex outermost frame
4053 @cindex innermost frame
4054 When your program is started, the stack has only one frame, that of the
4055 function @code{main}. This is called the @dfn{initial} frame or the
4056 @dfn{outermost} frame. Each time a function is called, a new frame is
4057 made. Each time a function returns, the frame for that function invocation
4058 is eliminated. If a function is recursive, there can be many frames for
4059 the same function. The frame for the function in which execution is
4060 actually occurring is called the @dfn{innermost} frame. This is the most
4061 recently created of all the stack frames that still exist.
4063 @cindex frame pointer
4064 Inside your program, stack frames are identified by their addresses. A
4065 stack frame consists of many bytes, each of which has its own address; each
4066 kind of computer has a convention for choosing one byte whose
4067 address serves as the address of the frame. Usually this address is kept
4068 in a register called the @dfn{frame pointer register} while execution is
4069 going on in that frame.
4071 @cindex frame number
4072 @value{GDBN} assigns numbers to all existing stack frames, starting with
4073 zero for the innermost frame, one for the frame that called it,
4074 and so on upward. These numbers do not really exist in your program;
4075 they are assigned by @value{GDBN} to give you a way of designating stack
4076 frames in @value{GDBN} commands.
4078 @c The -fomit-frame-pointer below perennially causes hbox overflow
4079 @c underflow problems.
4080 @cindex frameless execution
4081 Some compilers provide a way to compile functions so that they operate
4082 without stack frames. (For example, the @value{GCC} option
4084 @samp{-fomit-frame-pointer}
4086 generates functions without a frame.)
4087 This is occasionally done with heavily used library functions to save
4088 the frame setup time. @value{GDBN} has limited facilities for dealing
4089 with these function invocations. If the innermost function invocation
4090 has no stack frame, @value{GDBN} nevertheless regards it as though
4091 it had a separate frame, which is numbered zero as usual, allowing
4092 correct tracing of the function call chain. However, @value{GDBN} has
4093 no provision for frameless functions elsewhere in the stack.
4096 @kindex frame@r{, command}
4097 @cindex current stack frame
4098 @item frame @var{args}
4099 The @code{frame} command allows you to move from one stack frame to another,
4100 and to print the stack frame you select. @var{args} may be either the
4101 address of the frame or the stack frame number. Without an argument,
4102 @code{frame} prints the current stack frame.
4104 @kindex select-frame
4105 @cindex selecting frame silently
4107 The @code{select-frame} command allows you to move from one stack frame
4108 to another without printing the frame. This is the silent version of
4116 @cindex call stack traces
4117 A backtrace is a summary of how your program got where it is. It shows one
4118 line per frame, for many frames, starting with the currently executing
4119 frame (frame zero), followed by its caller (frame one), and on up the
4124 @kindex bt @r{(@code{backtrace})}
4127 Print a backtrace of the entire stack: one line per frame for all
4128 frames in the stack.
4130 You can stop the backtrace at any time by typing the system interrupt
4131 character, normally @kbd{C-c}.
4133 @item backtrace @var{n}
4135 Similar, but print only the innermost @var{n} frames.
4137 @item backtrace -@var{n}
4139 Similar, but print only the outermost @var{n} frames.
4141 @item backtrace full
4142 Print the values of the local variables also.
4148 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4149 are additional aliases for @code{backtrace}.
4151 Each line in the backtrace shows the frame number and the function name.
4152 The program counter value is also shown---unless you use @code{set
4153 print address off}. The backtrace also shows the source file name and
4154 line number, as well as the arguments to the function. The program
4155 counter value is omitted if it is at the beginning of the code for that
4158 Here is an example of a backtrace. It was made with the command
4159 @samp{bt 3}, so it shows the innermost three frames.
4163 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4165 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4166 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4168 (More stack frames follow...)
4173 The display for frame zero does not begin with a program counter
4174 value, indicating that your program has stopped at the beginning of the
4175 code for line @code{993} of @code{builtin.c}.
4177 @cindex value optimized out, in backtrace
4178 @cindex function call arguments, optimized out
4179 If your program was compiled with optimizations, some compilers will
4180 optimize away arguments passed to functions if those arguments are
4181 never used after the call. Such optimizations generate code that
4182 passes arguments through registers, but doesn't store those arguments
4183 in the stack frame. @value{GDBN} has no way of displaying such
4184 arguments in stack frames other than the innermost one. Here's what
4185 such a backtrace might look like:
4189 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4191 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4192 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4194 (More stack frames follow...)
4199 The values of arguments that were not saved in their stack frames are
4200 shown as @samp{<value optimized out>}.
4202 If you need to display the values of such optimized-out arguments,
4203 either deduce that from other variables whose values depend on the one
4204 you are interested in, or recompile without optimizations.
4206 @cindex backtrace beyond @code{main} function
4207 @cindex program entry point
4208 @cindex startup code, and backtrace
4209 Most programs have a standard user entry point---a place where system
4210 libraries and startup code transition into user code. For C this is
4211 @code{main}. When @value{GDBN} finds the entry function in a backtrace
4212 it will terminate the backtrace, to avoid tracing into highly
4213 system-specific (and generally uninteresting) code.
4215 If you need to examine the startup code, or limit the number of levels
4216 in a backtrace, you can change this behavior:
4219 @item set backtrace past-main
4220 @itemx set backtrace past-main on
4221 @kindex set backtrace
4222 Backtraces will continue past the user entry point.
4224 @item set backtrace past-main off
4225 Backtraces will stop when they encounter the user entry point. This is the
4228 @item show backtrace past-main
4229 @kindex show backtrace
4230 Display the current user entry point backtrace policy.
4232 @item set backtrace past-entry
4233 @itemx set backtrace past-entry on
4234 Backtraces will continue past the internal entry point of an application.
4235 This entry point is encoded by the linker when the application is built,
4236 and is likely before the user entry point @code{main} (or equivalent) is called.
4238 @item set backtrace past-entry off
4239 Backtraces will stop when they encouter the internal entry point of an
4240 application. This is the default.
4242 @item show backtrace past-entry
4243 Display the current internal entry point backtrace policy.
4245 @item set backtrace limit @var{n}
4246 @itemx set backtrace limit 0
4247 @cindex backtrace limit
4248 Limit the backtrace to @var{n} levels. A value of zero means
4251 @item show backtrace limit
4252 Display the current limit on backtrace levels.
4256 @section Selecting a frame
4258 Most commands for examining the stack and other data in your program work on
4259 whichever stack frame is selected at the moment. Here are the commands for
4260 selecting a stack frame; all of them finish by printing a brief description
4261 of the stack frame just selected.
4264 @kindex frame@r{, selecting}
4265 @kindex f @r{(@code{frame})}
4268 Select frame number @var{n}. Recall that frame zero is the innermost
4269 (currently executing) frame, frame one is the frame that called the
4270 innermost one, and so on. The highest-numbered frame is the one for
4273 @item frame @var{addr}
4275 Select the frame at address @var{addr}. This is useful mainly if the
4276 chaining of stack frames has been damaged by a bug, making it
4277 impossible for @value{GDBN} to assign numbers properly to all frames. In
4278 addition, this can be useful when your program has multiple stacks and
4279 switches between them.
4281 On the SPARC architecture, @code{frame} needs two addresses to
4282 select an arbitrary frame: a frame pointer and a stack pointer.
4284 On the MIPS and Alpha architecture, it needs two addresses: a stack
4285 pointer and a program counter.
4287 On the 29k architecture, it needs three addresses: a register stack
4288 pointer, a program counter, and a memory stack pointer.
4289 @c note to future updaters: this is conditioned on a flag
4290 @c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date
4291 @c as of 27 Jan 1994.
4295 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4296 advances toward the outermost frame, to higher frame numbers, to frames
4297 that have existed longer. @var{n} defaults to one.
4300 @kindex do @r{(@code{down})}
4302 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4303 advances toward the innermost frame, to lower frame numbers, to frames
4304 that were created more recently. @var{n} defaults to one. You may
4305 abbreviate @code{down} as @code{do}.
4308 All of these commands end by printing two lines of output describing the
4309 frame. The first line shows the frame number, the function name, the
4310 arguments, and the source file and line number of execution in that
4311 frame. The second line shows the text of that source line.
4319 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4321 10 read_input_file (argv[i]);
4325 After such a printout, the @code{list} command with no arguments
4326 prints ten lines centered on the point of execution in the frame.
4327 You can also edit the program at the point of execution with your favorite
4328 editing program by typing @code{edit}.
4329 @xref{List, ,Printing source lines},
4333 @kindex down-silently
4335 @item up-silently @var{n}
4336 @itemx down-silently @var{n}
4337 These two commands are variants of @code{up} and @code{down},
4338 respectively; they differ in that they do their work silently, without
4339 causing display of the new frame. They are intended primarily for use
4340 in @value{GDBN} command scripts, where the output might be unnecessary and
4345 @section Information about a frame
4347 There are several other commands to print information about the selected
4353 When used without any argument, this command does not change which
4354 frame is selected, but prints a brief description of the currently
4355 selected stack frame. It can be abbreviated @code{f}. With an
4356 argument, this command is used to select a stack frame.
4357 @xref{Selection, ,Selecting a frame}.
4360 @kindex info f @r{(@code{info frame})}
4363 This command prints a verbose description of the selected stack frame,
4368 the address of the frame
4370 the address of the next frame down (called by this frame)
4372 the address of the next frame up (caller of this frame)
4374 the language in which the source code corresponding to this frame is written
4376 the address of the frame's arguments
4378 the address of the frame's local variables
4380 the program counter saved in it (the address of execution in the caller frame)
4382 which registers were saved in the frame
4385 @noindent The verbose description is useful when
4386 something has gone wrong that has made the stack format fail to fit
4387 the usual conventions.
4389 @item info frame @var{addr}
4390 @itemx info f @var{addr}
4391 Print a verbose description of the frame at address @var{addr}, without
4392 selecting that frame. The selected frame remains unchanged by this
4393 command. This requires the same kind of address (more than one for some
4394 architectures) that you specify in the @code{frame} command.
4395 @xref{Selection, ,Selecting a frame}.
4399 Print the arguments of the selected frame, each on a separate line.
4403 Print the local variables of the selected frame, each on a separate
4404 line. These are all variables (declared either static or automatic)
4405 accessible at the point of execution of the selected frame.
4408 @cindex catch exceptions, list active handlers
4409 @cindex exception handlers, how to list
4411 Print a list of all the exception handlers that are active in the
4412 current stack frame at the current point of execution. To see other
4413 exception handlers, visit the associated frame (using the @code{up},
4414 @code{down}, or @code{frame} commands); then type @code{info catch}.
4415 @xref{Set Catchpoints, , Setting catchpoints}.
4421 @chapter Examining Source Files
4423 @value{GDBN} can print parts of your program's source, since the debugging
4424 information recorded in the program tells @value{GDBN} what source files were
4425 used to build it. When your program stops, @value{GDBN} spontaneously prints
4426 the line where it stopped. Likewise, when you select a stack frame
4427 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4428 execution in that frame has stopped. You can print other portions of
4429 source files by explicit command.
4431 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4432 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4433 @value{GDBN} under @sc{gnu} Emacs}.
4436 * List:: Printing source lines
4437 * Edit:: Editing source files
4438 * Search:: Searching source files
4439 * Source Path:: Specifying source directories
4440 * Machine Code:: Source and machine code
4444 @section Printing source lines
4447 @kindex l @r{(@code{list})}
4448 To print lines from a source file, use the @code{list} command
4449 (abbreviated @code{l}). By default, ten lines are printed.
4450 There are several ways to specify what part of the file you want to print.
4452 Here are the forms of the @code{list} command most commonly used:
4455 @item list @var{linenum}
4456 Print lines centered around line number @var{linenum} in the
4457 current source file.
4459 @item list @var{function}
4460 Print lines centered around the beginning of function
4464 Print more lines. If the last lines printed were printed with a
4465 @code{list} command, this prints lines following the last lines
4466 printed; however, if the last line printed was a solitary line printed
4467 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4468 Stack}), this prints lines centered around that line.
4471 Print lines just before the lines last printed.
4474 @cindex @code{list}, how many lines to display
4475 By default, @value{GDBN} prints ten source lines with any of these forms of
4476 the @code{list} command. You can change this using @code{set listsize}:
4479 @kindex set listsize
4480 @item set listsize @var{count}
4481 Make the @code{list} command display @var{count} source lines (unless
4482 the @code{list} argument explicitly specifies some other number).
4484 @kindex show listsize
4486 Display the number of lines that @code{list} prints.
4489 Repeating a @code{list} command with @key{RET} discards the argument,
4490 so it is equivalent to typing just @code{list}. This is more useful
4491 than listing the same lines again. An exception is made for an
4492 argument of @samp{-}; that argument is preserved in repetition so that
4493 each repetition moves up in the source file.
4496 In general, the @code{list} command expects you to supply zero, one or two
4497 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4498 of writing them, but the effect is always to specify some source line.
4499 Here is a complete description of the possible arguments for @code{list}:
4502 @item list @var{linespec}
4503 Print lines centered around the line specified by @var{linespec}.
4505 @item list @var{first},@var{last}
4506 Print lines from @var{first} to @var{last}. Both arguments are
4509 @item list ,@var{last}
4510 Print lines ending with @var{last}.
4512 @item list @var{first},
4513 Print lines starting with @var{first}.
4516 Print lines just after the lines last printed.
4519 Print lines just before the lines last printed.
4522 As described in the preceding table.
4525 Here are the ways of specifying a single source line---all the
4530 Specifies line @var{number} of the current source file.
4531 When a @code{list} command has two linespecs, this refers to
4532 the same source file as the first linespec.
4535 Specifies the line @var{offset} lines after the last line printed.
4536 When used as the second linespec in a @code{list} command that has
4537 two, this specifies the line @var{offset} lines down from the
4541 Specifies the line @var{offset} lines before the last line printed.
4543 @item @var{filename}:@var{number}
4544 Specifies line @var{number} in the source file @var{filename}.
4546 @item @var{function}
4547 Specifies the line that begins the body of the function @var{function}.
4548 For example: in C, this is the line with the open brace.
4550 @item @var{filename}:@var{function}
4551 Specifies the line of the open-brace that begins the body of the
4552 function @var{function} in the file @var{filename}. You only need the
4553 file name with a function name to avoid ambiguity when there are
4554 identically named functions in different source files.
4556 @item *@var{address}
4557 Specifies the line containing the program address @var{address}.
4558 @var{address} may be any expression.
4562 @section Editing source files
4563 @cindex editing source files
4566 @kindex e @r{(@code{edit})}
4567 To edit the lines in a source file, use the @code{edit} command.
4568 The editing program of your choice
4569 is invoked with the current line set to
4570 the active line in the program.
4571 Alternatively, there are several ways to specify what part of the file you
4572 want to print if you want to see other parts of the program.
4574 Here are the forms of the @code{edit} command most commonly used:
4578 Edit the current source file at the active line number in the program.
4580 @item edit @var{number}
4581 Edit the current source file with @var{number} as the active line number.
4583 @item edit @var{function}
4584 Edit the file containing @var{function} at the beginning of its definition.
4586 @item edit @var{filename}:@var{number}
4587 Specifies line @var{number} in the source file @var{filename}.
4589 @item edit @var{filename}:@var{function}
4590 Specifies the line that begins the body of the
4591 function @var{function} in the file @var{filename}. You only need the
4592 file name with a function name to avoid ambiguity when there are
4593 identically named functions in different source files.
4595 @item edit *@var{address}
4596 Specifies the line containing the program address @var{address}.
4597 @var{address} may be any expression.
4600 @subsection Choosing your editor
4601 You can customize @value{GDBN} to use any editor you want
4603 The only restriction is that your editor (say @code{ex}), recognizes the
4604 following command-line syntax:
4606 ex +@var{number} file
4608 The optional numeric value +@var{number} specifies the number of the line in
4609 the file where to start editing.}.
4610 By default, it is @file{@value{EDITOR}}, but you can change this
4611 by setting the environment variable @code{EDITOR} before using
4612 @value{GDBN}. For example, to configure @value{GDBN} to use the
4613 @code{vi} editor, you could use these commands with the @code{sh} shell:
4619 or in the @code{csh} shell,
4621 setenv EDITOR /usr/bin/vi
4626 @section Searching source files
4627 @cindex searching source files
4629 There are two commands for searching through the current source file for a
4634 @kindex forward-search
4635 @item forward-search @var{regexp}
4636 @itemx search @var{regexp}
4637 The command @samp{forward-search @var{regexp}} checks each line,
4638 starting with the one following the last line listed, for a match for
4639 @var{regexp}. It lists the line that is found. You can use the
4640 synonym @samp{search @var{regexp}} or abbreviate the command name as
4643 @kindex reverse-search
4644 @item reverse-search @var{regexp}
4645 The command @samp{reverse-search @var{regexp}} checks each line, starting
4646 with the one before the last line listed and going backward, for a match
4647 for @var{regexp}. It lists the line that is found. You can abbreviate
4648 this command as @code{rev}.
4652 @section Specifying source directories
4655 @cindex directories for source files
4656 Executable programs sometimes do not record the directories of the source
4657 files from which they were compiled, just the names. Even when they do,
4658 the directories could be moved between the compilation and your debugging
4659 session. @value{GDBN} has a list of directories to search for source files;
4660 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4661 it tries all the directories in the list, in the order they are present
4662 in the list, until it finds a file with the desired name.
4664 For example, suppose an executable references the file
4665 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
4666 @file{/mnt/cross}. The file is first looked up literally; if this
4667 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
4668 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
4669 message is printed. @value{GDBN} does not look up the parts of the
4670 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
4671 Likewise, the subdirectories of the source path are not searched: if
4672 the source path is @file{/mnt/cross}, and the binary refers to
4673 @file{foo.c}, @value{GDBN} would not find it under
4674 @file{/mnt/cross/usr/src/foo-1.0/lib}.
4676 Plain file names, relative file names with leading directories, file
4677 names containing dots, etc.@: are all treated as described above; for
4678 instance, if the source path is @file{/mnt/cross}, and the source file
4679 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
4680 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
4681 that---@file{/mnt/cross/foo.c}.
4683 Note that the executable search path is @emph{not} used to locate the
4684 source files. Neither is the current working directory, unless it
4685 happens to be in the source path.
4687 Whenever you reset or rearrange the source path, @value{GDBN} clears out
4688 any information it has cached about where source files are found and where
4689 each line is in the file.
4693 When you start @value{GDBN}, its source path includes only @samp{cdir}
4694 and @samp{cwd}, in that order.
4695 To add other directories, use the @code{directory} command.
4698 @item directory @var{dirname} @dots{}
4699 @item dir @var{dirname} @dots{}
4700 Add directory @var{dirname} to the front of the source path. Several
4701 directory names may be given to this command, separated by @samp{:}
4702 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4703 part of absolute file names) or
4704 whitespace. You may specify a directory that is already in the source
4705 path; this moves it forward, so @value{GDBN} searches it sooner.
4709 @vindex $cdir@r{, convenience variable}
4710 @vindex $cwdr@r{, convenience variable}
4711 @cindex compilation directory
4712 @cindex current directory
4713 @cindex working directory
4714 @cindex directory, current
4715 @cindex directory, compilation
4716 You can use the string @samp{$cdir} to refer to the compilation
4717 directory (if one is recorded), and @samp{$cwd} to refer to the current
4718 working directory. @samp{$cwd} is not the same as @samp{.}---the former
4719 tracks the current working directory as it changes during your @value{GDBN}
4720 session, while the latter is immediately expanded to the current
4721 directory at the time you add an entry to the source path.
4724 Reset the source path to empty again. This requires confirmation.
4726 @c RET-repeat for @code{directory} is explicitly disabled, but since
4727 @c repeating it would be a no-op we do not say that. (thanks to RMS)
4729 @item show directories
4730 @kindex show directories
4731 Print the source path: show which directories it contains.
4734 If your source path is cluttered with directories that are no longer of
4735 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4736 versions of source. You can correct the situation as follows:
4740 Use @code{directory} with no argument to reset the source path to empty.
4743 Use @code{directory} with suitable arguments to reinstall the
4744 directories you want in the source path. You can add all the
4745 directories in one command.
4749 @section Source and machine code
4750 @cindex source line and its code address
4752 You can use the command @code{info line} to map source lines to program
4753 addresses (and vice versa), and the command @code{disassemble} to display
4754 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
4755 mode, the @code{info line} command causes the arrow to point to the
4756 line specified. Also, @code{info line} prints addresses in symbolic form as
4761 @item info line @var{linespec}
4762 Print the starting and ending addresses of the compiled code for
4763 source line @var{linespec}. You can specify source lines in any of
4764 the ways understood by the @code{list} command (@pxref{List, ,Printing
4768 For example, we can use @code{info line} to discover the location of
4769 the object code for the first line of function
4770 @code{m4_changequote}:
4772 @c FIXME: I think this example should also show the addresses in
4773 @c symbolic form, as they usually would be displayed.
4775 (@value{GDBP}) info line m4_changequote
4776 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4780 @cindex code address and its source line
4781 We can also inquire (using @code{*@var{addr}} as the form for
4782 @var{linespec}) what source line covers a particular address:
4784 (@value{GDBP}) info line *0x63ff
4785 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4788 @cindex @code{$_} and @code{info line}
4789 @cindex @code{x} command, default address
4790 @kindex x@r{(examine), and} info line
4791 After @code{info line}, the default address for the @code{x} command
4792 is changed to the starting address of the line, so that @samp{x/i} is
4793 sufficient to begin examining the machine code (@pxref{Memory,
4794 ,Examining memory}). Also, this address is saved as the value of the
4795 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4800 @cindex assembly instructions
4801 @cindex instructions, assembly
4802 @cindex machine instructions
4803 @cindex listing machine instructions
4805 This specialized command dumps a range of memory as machine
4806 instructions. The default memory range is the function surrounding the
4807 program counter of the selected frame. A single argument to this
4808 command is a program counter value; @value{GDBN} dumps the function
4809 surrounding this value. Two arguments specify a range of addresses
4810 (first inclusive, second exclusive) to dump.
4813 The following example shows the disassembly of a range of addresses of
4814 HP PA-RISC 2.0 code:
4817 (@value{GDBP}) disas 0x32c4 0x32e4
4818 Dump of assembler code from 0x32c4 to 0x32e4:
4819 0x32c4 <main+204>: addil 0,dp
4820 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
4821 0x32cc <main+212>: ldil 0x3000,r31
4822 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
4823 0x32d4 <main+220>: ldo 0(r31),rp
4824 0x32d8 <main+224>: addil -0x800,dp
4825 0x32dc <main+228>: ldo 0x588(r1),r26
4826 0x32e0 <main+232>: ldil 0x3000,r31
4827 End of assembler dump.
4830 Some architectures have more than one commonly-used set of instruction
4831 mnemonics or other syntax.
4834 @kindex set disassembly-flavor
4835 @cindex Intel disassembly flavor
4836 @cindex AT&T disassembly flavor
4837 @item set disassembly-flavor @var{instruction-set}
4838 Select the instruction set to use when disassembling the
4839 program via the @code{disassemble} or @code{x/i} commands.
4841 Currently this command is only defined for the Intel x86 family. You
4842 can set @var{instruction-set} to either @code{intel} or @code{att}.
4843 The default is @code{att}, the AT&T flavor used by default by Unix
4844 assemblers for x86-based targets.
4846 @kindex show disassembly-flavor
4847 @item show disassembly-flavor
4848 Show the current setting of the disassembly flavor.
4853 @chapter Examining Data
4855 @cindex printing data
4856 @cindex examining data
4859 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
4860 @c document because it is nonstandard... Under Epoch it displays in a
4861 @c different window or something like that.
4862 The usual way to examine data in your program is with the @code{print}
4863 command (abbreviated @code{p}), or its synonym @code{inspect}. It
4864 evaluates and prints the value of an expression of the language your
4865 program is written in (@pxref{Languages, ,Using @value{GDBN} with
4866 Different Languages}).
4869 @item print @var{expr}
4870 @itemx print /@var{f} @var{expr}
4871 @var{expr} is an expression (in the source language). By default the
4872 value of @var{expr} is printed in a format appropriate to its data type;
4873 you can choose a different format by specifying @samp{/@var{f}}, where
4874 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
4878 @itemx print /@var{f}
4879 @cindex reprint the last value
4880 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
4881 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
4882 conveniently inspect the same value in an alternative format.
4885 A more low-level way of examining data is with the @code{x} command.
4886 It examines data in memory at a specified address and prints it in a
4887 specified format. @xref{Memory, ,Examining memory}.
4889 If you are interested in information about types, or about how the
4890 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
4891 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
4895 * Expressions:: Expressions
4896 * Variables:: Program variables
4897 * Arrays:: Artificial arrays
4898 * Output Formats:: Output formats
4899 * Memory:: Examining memory
4900 * Auto Display:: Automatic display
4901 * Print Settings:: Print settings
4902 * Value History:: Value history
4903 * Convenience Vars:: Convenience variables
4904 * Registers:: Registers
4905 * Floating Point Hardware:: Floating point hardware
4906 * Vector Unit:: Vector Unit
4907 * OS Information:: Auxiliary data provided by operating system
4908 * Memory Region Attributes:: Memory region attributes
4909 * Dump/Restore Files:: Copy between memory and a file
4910 * Core File Generation:: Cause a program dump its core
4911 * Character Sets:: Debugging programs that use a different
4912 character set than GDB does
4913 * Caching Remote Data:: Data caching for remote targets
4917 @section Expressions
4920 @code{print} and many other @value{GDBN} commands accept an expression and
4921 compute its value. Any kind of constant, variable or operator defined
4922 by the programming language you are using is valid in an expression in
4923 @value{GDBN}. This includes conditional expressions, function calls,
4924 casts, and string constants. It also includes preprocessor macros, if
4925 you compiled your program to include this information; see
4928 @cindex arrays in expressions
4929 @value{GDBN} supports array constants in expressions input by
4930 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
4931 you can use the command @code{print @{1, 2, 3@}} to build up an array in
4932 memory that is @code{malloc}ed in the target program.
4934 Because C is so widespread, most of the expressions shown in examples in
4935 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
4936 Languages}, for information on how to use expressions in other
4939 In this section, we discuss operators that you can use in @value{GDBN}
4940 expressions regardless of your programming language.
4942 @cindex casts, in expressions
4943 Casts are supported in all languages, not just in C, because it is so
4944 useful to cast a number into a pointer in order to examine a structure
4945 at that address in memory.
4946 @c FIXME: casts supported---Mod2 true?
4948 @value{GDBN} supports these operators, in addition to those common
4949 to programming languages:
4953 @samp{@@} is a binary operator for treating parts of memory as arrays.
4954 @xref{Arrays, ,Artificial arrays}, for more information.
4957 @samp{::} allows you to specify a variable in terms of the file or
4958 function where it is defined. @xref{Variables, ,Program variables}.
4960 @cindex @{@var{type}@}
4961 @cindex type casting memory
4962 @cindex memory, viewing as typed object
4963 @cindex casts, to view memory
4964 @item @{@var{type}@} @var{addr}
4965 Refers to an object of type @var{type} stored at address @var{addr} in
4966 memory. @var{addr} may be any expression whose value is an integer or
4967 pointer (but parentheses are required around binary operators, just as in
4968 a cast). This construct is allowed regardless of what kind of data is
4969 normally supposed to reside at @var{addr}.
4973 @section Program variables
4975 The most common kind of expression to use is the name of a variable
4978 Variables in expressions are understood in the selected stack frame
4979 (@pxref{Selection, ,Selecting a frame}); they must be either:
4983 global (or file-static)
4990 visible according to the scope rules of the
4991 programming language from the point of execution in that frame
4994 @noindent This means that in the function
5009 you can examine and use the variable @code{a} whenever your program is
5010 executing within the function @code{foo}, but you can only use or
5011 examine the variable @code{b} while your program is executing inside
5012 the block where @code{b} is declared.
5014 @cindex variable name conflict
5015 There is an exception: you can refer to a variable or function whose
5016 scope is a single source file even if the current execution point is not
5017 in this file. But it is possible to have more than one such variable or
5018 function with the same name (in different source files). If that
5019 happens, referring to that name has unpredictable effects. If you wish,
5020 you can specify a static variable in a particular function or file,
5021 using the colon-colon (@code{::}) notation:
5023 @cindex colon-colon, context for variables/functions
5025 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5026 @cindex @code{::}, context for variables/functions
5029 @var{file}::@var{variable}
5030 @var{function}::@var{variable}
5034 Here @var{file} or @var{function} is the name of the context for the
5035 static @var{variable}. In the case of file names, you can use quotes to
5036 make sure @value{GDBN} parses the file name as a single word---for example,
5037 to print a global value of @code{x} defined in @file{f2.c}:
5040 (@value{GDBP}) p 'f2.c'::x
5043 @cindex C@t{++} scope resolution
5044 This use of @samp{::} is very rarely in conflict with the very similar
5045 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5046 scope resolution operator in @value{GDBN} expressions.
5047 @c FIXME: Um, so what happens in one of those rare cases where it's in
5050 @cindex wrong values
5051 @cindex variable values, wrong
5052 @cindex function entry/exit, wrong values of variables
5053 @cindex optimized code, wrong values of variables
5055 @emph{Warning:} Occasionally, a local variable may appear to have the
5056 wrong value at certain points in a function---just after entry to a new
5057 scope, and just before exit.
5059 You may see this problem when you are stepping by machine instructions.
5060 This is because, on most machines, it takes more than one instruction to
5061 set up a stack frame (including local variable definitions); if you are
5062 stepping by machine instructions, variables may appear to have the wrong
5063 values until the stack frame is completely built. On exit, it usually
5064 also takes more than one machine instruction to destroy a stack frame;
5065 after you begin stepping through that group of instructions, local
5066 variable definitions may be gone.
5068 This may also happen when the compiler does significant optimizations.
5069 To be sure of always seeing accurate values, turn off all optimization
5072 @cindex ``No symbol "foo" in current context''
5073 Another possible effect of compiler optimizations is to optimize
5074 unused variables out of existence, or assign variables to registers (as
5075 opposed to memory addresses). Depending on the support for such cases
5076 offered by the debug info format used by the compiler, @value{GDBN}
5077 might not be able to display values for such local variables. If that
5078 happens, @value{GDBN} will print a message like this:
5081 No symbol "foo" in current context.
5084 To solve such problems, either recompile without optimizations, or use a
5085 different debug info format, if the compiler supports several such
5086 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5087 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5088 produces debug info in a format that is superior to formats such as
5089 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5090 an effective form for debug info. @xref{Debugging Options,,Options
5091 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
5092 @xref{C, , Debugging C++}, for more info about debug info formats
5093 that are best suited to C@t{++} programs.
5096 @section Artificial arrays
5098 @cindex artificial array
5100 @kindex @@@r{, referencing memory as an array}
5101 It is often useful to print out several successive objects of the
5102 same type in memory; a section of an array, or an array of
5103 dynamically determined size for which only a pointer exists in the
5106 You can do this by referring to a contiguous span of memory as an
5107 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5108 operand of @samp{@@} should be the first element of the desired array
5109 and be an individual object. The right operand should be the desired length
5110 of the array. The result is an array value whose elements are all of
5111 the type of the left argument. The first element is actually the left
5112 argument; the second element comes from bytes of memory immediately
5113 following those that hold the first element, and so on. Here is an
5114 example. If a program says
5117 int *array = (int *) malloc (len * sizeof (int));
5121 you can print the contents of @code{array} with
5127 The left operand of @samp{@@} must reside in memory. Array values made
5128 with @samp{@@} in this way behave just like other arrays in terms of
5129 subscripting, and are coerced to pointers when used in expressions.
5130 Artificial arrays most often appear in expressions via the value history
5131 (@pxref{Value History, ,Value history}), after printing one out.
5133 Another way to create an artificial array is to use a cast.
5134 This re-interprets a value as if it were an array.
5135 The value need not be in memory:
5137 (@value{GDBP}) p/x (short[2])0x12345678
5138 $1 = @{0x1234, 0x5678@}
5141 As a convenience, if you leave the array length out (as in
5142 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5143 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5145 (@value{GDBP}) p/x (short[])0x12345678
5146 $2 = @{0x1234, 0x5678@}
5149 Sometimes the artificial array mechanism is not quite enough; in
5150 moderately complex data structures, the elements of interest may not
5151 actually be adjacent---for example, if you are interested in the values
5152 of pointers in an array. One useful work-around in this situation is
5153 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5154 variables}) as a counter in an expression that prints the first
5155 interesting value, and then repeat that expression via @key{RET}. For
5156 instance, suppose you have an array @code{dtab} of pointers to
5157 structures, and you are interested in the values of a field @code{fv}
5158 in each structure. Here is an example of what you might type:
5168 @node Output Formats
5169 @section Output formats
5171 @cindex formatted output
5172 @cindex output formats
5173 By default, @value{GDBN} prints a value according to its data type. Sometimes
5174 this is not what you want. For example, you might want to print a number
5175 in hex, or a pointer in decimal. Or you might want to view data in memory
5176 at a certain address as a character string or as an instruction. To do
5177 these things, specify an @dfn{output format} when you print a value.
5179 The simplest use of output formats is to say how to print a value
5180 already computed. This is done by starting the arguments of the
5181 @code{print} command with a slash and a format letter. The format
5182 letters supported are:
5186 Regard the bits of the value as an integer, and print the integer in
5190 Print as integer in signed decimal.
5193 Print as integer in unsigned decimal.
5196 Print as integer in octal.
5199 Print as integer in binary. The letter @samp{t} stands for ``two''.
5200 @footnote{@samp{b} cannot be used because these format letters are also
5201 used with the @code{x} command, where @samp{b} stands for ``byte'';
5202 see @ref{Memory,,Examining memory}.}
5205 @cindex unknown address, locating
5206 @cindex locate address
5207 Print as an address, both absolute in hexadecimal and as an offset from
5208 the nearest preceding symbol. You can use this format used to discover
5209 where (in what function) an unknown address is located:
5212 (@value{GDBP}) p/a 0x54320
5213 $3 = 0x54320 <_initialize_vx+396>
5217 The command @code{info symbol 0x54320} yields similar results.
5218 @xref{Symbols, info symbol}.
5221 Regard as an integer and print it as a character constant.
5224 Regard the bits of the value as a floating point number and print
5225 using typical floating point syntax.
5228 For example, to print the program counter in hex (@pxref{Registers}), type
5235 Note that no space is required before the slash; this is because command
5236 names in @value{GDBN} cannot contain a slash.
5238 To reprint the last value in the value history with a different format,
5239 you can use the @code{print} command with just a format and no
5240 expression. For example, @samp{p/x} reprints the last value in hex.
5243 @section Examining memory
5245 You can use the command @code{x} (for ``examine'') to examine memory in
5246 any of several formats, independently of your program's data types.
5248 @cindex examining memory
5250 @kindex x @r{(examine memory)}
5251 @item x/@var{nfu} @var{addr}
5254 Use the @code{x} command to examine memory.
5257 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5258 much memory to display and how to format it; @var{addr} is an
5259 expression giving the address where you want to start displaying memory.
5260 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5261 Several commands set convenient defaults for @var{addr}.
5264 @item @var{n}, the repeat count
5265 The repeat count is a decimal integer; the default is 1. It specifies
5266 how much memory (counting by units @var{u}) to display.
5267 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5270 @item @var{f}, the display format
5271 The display format is one of the formats used by @code{print},
5272 @samp{s} (null-terminated string), or @samp{i} (machine instruction).
5273 The default is @samp{x} (hexadecimal) initially.
5274 The default changes each time you use either @code{x} or @code{print}.
5276 @item @var{u}, the unit size
5277 The unit size is any of
5283 Halfwords (two bytes).
5285 Words (four bytes). This is the initial default.
5287 Giant words (eight bytes).
5290 Each time you specify a unit size with @code{x}, that size becomes the
5291 default unit the next time you use @code{x}. (For the @samp{s} and
5292 @samp{i} formats, the unit size is ignored and is normally not written.)
5294 @item @var{addr}, starting display address
5295 @var{addr} is the address where you want @value{GDBN} to begin displaying
5296 memory. The expression need not have a pointer value (though it may);
5297 it is always interpreted as an integer address of a byte of memory.
5298 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5299 @var{addr} is usually just after the last address examined---but several
5300 other commands also set the default address: @code{info breakpoints} (to
5301 the address of the last breakpoint listed), @code{info line} (to the
5302 starting address of a line), and @code{print} (if you use it to display
5303 a value from memory).
5306 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5307 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5308 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5309 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5310 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5312 Since the letters indicating unit sizes are all distinct from the
5313 letters specifying output formats, you do not have to remember whether
5314 unit size or format comes first; either order works. The output
5315 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5316 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5318 Even though the unit size @var{u} is ignored for the formats @samp{s}
5319 and @samp{i}, you might still want to use a count @var{n}; for example,
5320 @samp{3i} specifies that you want to see three machine instructions,
5321 including any operands. The command @code{disassemble} gives an
5322 alternative way of inspecting machine instructions; see @ref{Machine
5323 Code,,Source and machine code}.
5325 All the defaults for the arguments to @code{x} are designed to make it
5326 easy to continue scanning memory with minimal specifications each time
5327 you use @code{x}. For example, after you have inspected three machine
5328 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5329 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5330 the repeat count @var{n} is used again; the other arguments default as
5331 for successive uses of @code{x}.
5333 @cindex @code{$_}, @code{$__}, and value history
5334 The addresses and contents printed by the @code{x} command are not saved
5335 in the value history because there is often too much of them and they
5336 would get in the way. Instead, @value{GDBN} makes these values available for
5337 subsequent use in expressions as values of the convenience variables
5338 @code{$_} and @code{$__}. After an @code{x} command, the last address
5339 examined is available for use in expressions in the convenience variable
5340 @code{$_}. The contents of that address, as examined, are available in
5341 the convenience variable @code{$__}.
5343 If the @code{x} command has a repeat count, the address and contents saved
5344 are from the last memory unit printed; this is not the same as the last
5345 address printed if several units were printed on the last line of output.
5347 @cindex remote memory comparison
5348 @cindex verify remote memory image
5349 When you are debugging a program running on a remote target machine
5350 (@pxref{Remote}), you may wish to verify the program's image in the
5351 remote machine's memory against the executable file you downloaded to
5352 the target. The @code{compare-sections} command is provided for such
5356 @kindex compare-sections
5357 @item compare-sections @r{[}@var{section-name}@r{]}
5358 Compare the data of a loadable section @var{section-name} in the
5359 executable file of the program being debugged with the same section in
5360 the remote machine's memory, and report any mismatches. With no
5361 arguments, compares all loadable sections. This command's
5362 availability depends on the target's support for the @code{"qCRC"}
5367 @section Automatic display
5368 @cindex automatic display
5369 @cindex display of expressions
5371 If you find that you want to print the value of an expression frequently
5372 (to see how it changes), you might want to add it to the @dfn{automatic
5373 display list} so that @value{GDBN} prints its value each time your program stops.
5374 Each expression added to the list is given a number to identify it;
5375 to remove an expression from the list, you specify that number.
5376 The automatic display looks like this:
5380 3: bar[5] = (struct hack *) 0x3804
5384 This display shows item numbers, expressions and their current values. As with
5385 displays you request manually using @code{x} or @code{print}, you can
5386 specify the output format you prefer; in fact, @code{display} decides
5387 whether to use @code{print} or @code{x} depending on how elaborate your
5388 format specification is---it uses @code{x} if you specify a unit size,
5389 or one of the two formats (@samp{i} and @samp{s}) that are only
5390 supported by @code{x}; otherwise it uses @code{print}.
5394 @item display @var{expr}
5395 Add the expression @var{expr} to the list of expressions to display
5396 each time your program stops. @xref{Expressions, ,Expressions}.
5398 @code{display} does not repeat if you press @key{RET} again after using it.
5400 @item display/@var{fmt} @var{expr}
5401 For @var{fmt} specifying only a display format and not a size or
5402 count, add the expression @var{expr} to the auto-display list but
5403 arrange to display it each time in the specified format @var{fmt}.
5404 @xref{Output Formats,,Output formats}.
5406 @item display/@var{fmt} @var{addr}
5407 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5408 number of units, add the expression @var{addr} as a memory address to
5409 be examined each time your program stops. Examining means in effect
5410 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5413 For example, @samp{display/i $pc} can be helpful, to see the machine
5414 instruction about to be executed each time execution stops (@samp{$pc}
5415 is a common name for the program counter; @pxref{Registers, ,Registers}).
5418 @kindex delete display
5420 @item undisplay @var{dnums}@dots{}
5421 @itemx delete display @var{dnums}@dots{}
5422 Remove item numbers @var{dnums} from the list of expressions to display.
5424 @code{undisplay} does not repeat if you press @key{RET} after using it.
5425 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5427 @kindex disable display
5428 @item disable display @var{dnums}@dots{}
5429 Disable the display of item numbers @var{dnums}. A disabled display
5430 item is not printed automatically, but is not forgotten. It may be
5431 enabled again later.
5433 @kindex enable display
5434 @item enable display @var{dnums}@dots{}
5435 Enable display of item numbers @var{dnums}. It becomes effective once
5436 again in auto display of its expression, until you specify otherwise.
5439 Display the current values of the expressions on the list, just as is
5440 done when your program stops.
5442 @kindex info display
5444 Print the list of expressions previously set up to display
5445 automatically, each one with its item number, but without showing the
5446 values. This includes disabled expressions, which are marked as such.
5447 It also includes expressions which would not be displayed right now
5448 because they refer to automatic variables not currently available.
5451 @cindex display disabled out of scope
5452 If a display expression refers to local variables, then it does not make
5453 sense outside the lexical context for which it was set up. Such an
5454 expression is disabled when execution enters a context where one of its
5455 variables is not defined. For example, if you give the command
5456 @code{display last_char} while inside a function with an argument
5457 @code{last_char}, @value{GDBN} displays this argument while your program
5458 continues to stop inside that function. When it stops elsewhere---where
5459 there is no variable @code{last_char}---the display is disabled
5460 automatically. The next time your program stops where @code{last_char}
5461 is meaningful, you can enable the display expression once again.
5463 @node Print Settings
5464 @section Print settings
5466 @cindex format options
5467 @cindex print settings
5468 @value{GDBN} provides the following ways to control how arrays, structures,
5469 and symbols are printed.
5472 These settings are useful for debugging programs in any language:
5476 @item set print address
5477 @itemx set print address on
5478 @cindex print/don't print memory addresses
5479 @value{GDBN} prints memory addresses showing the location of stack
5480 traces, structure values, pointer values, breakpoints, and so forth,
5481 even when it also displays the contents of those addresses. The default
5482 is @code{on}. For example, this is what a stack frame display looks like with
5483 @code{set print address on}:
5488 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5490 530 if (lquote != def_lquote)
5494 @item set print address off
5495 Do not print addresses when displaying their contents. For example,
5496 this is the same stack frame displayed with @code{set print address off}:
5500 (@value{GDBP}) set print addr off
5502 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5503 530 if (lquote != def_lquote)
5507 You can use @samp{set print address off} to eliminate all machine
5508 dependent displays from the @value{GDBN} interface. For example, with
5509 @code{print address off}, you should get the same text for backtraces on
5510 all machines---whether or not they involve pointer arguments.
5513 @item show print address
5514 Show whether or not addresses are to be printed.
5517 When @value{GDBN} prints a symbolic address, it normally prints the
5518 closest earlier symbol plus an offset. If that symbol does not uniquely
5519 identify the address (for example, it is a name whose scope is a single
5520 source file), you may need to clarify. One way to do this is with
5521 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5522 you can set @value{GDBN} to print the source file and line number when
5523 it prints a symbolic address:
5526 @item set print symbol-filename on
5527 @cindex source file and line of a symbol
5528 @cindex symbol, source file and line
5529 Tell @value{GDBN} to print the source file name and line number of a
5530 symbol in the symbolic form of an address.
5532 @item set print symbol-filename off
5533 Do not print source file name and line number of a symbol. This is the
5536 @item show print symbol-filename
5537 Show whether or not @value{GDBN} will print the source file name and
5538 line number of a symbol in the symbolic form of an address.
5541 Another situation where it is helpful to show symbol filenames and line
5542 numbers is when disassembling code; @value{GDBN} shows you the line
5543 number and source file that corresponds to each instruction.
5545 Also, you may wish to see the symbolic form only if the address being
5546 printed is reasonably close to the closest earlier symbol:
5549 @item set print max-symbolic-offset @var{max-offset}
5550 @cindex maximum value for offset of closest symbol
5551 Tell @value{GDBN} to only display the symbolic form of an address if the
5552 offset between the closest earlier symbol and the address is less than
5553 @var{max-offset}. The default is 0, which tells @value{GDBN}
5554 to always print the symbolic form of an address if any symbol precedes it.
5556 @item show print max-symbolic-offset
5557 Ask how large the maximum offset is that @value{GDBN} prints in a
5561 @cindex wild pointer, interpreting
5562 @cindex pointer, finding referent
5563 If you have a pointer and you are not sure where it points, try
5564 @samp{set print symbol-filename on}. Then you can determine the name
5565 and source file location of the variable where it points, using
5566 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5567 For example, here @value{GDBN} shows that a variable @code{ptt} points
5568 at another variable @code{t}, defined in @file{hi2.c}:
5571 (@value{GDBP}) set print symbol-filename on
5572 (@value{GDBP}) p/a ptt
5573 $4 = 0xe008 <t in hi2.c>
5577 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5578 does not show the symbol name and filename of the referent, even with
5579 the appropriate @code{set print} options turned on.
5582 Other settings control how different kinds of objects are printed:
5585 @item set print array
5586 @itemx set print array on
5587 @cindex pretty print arrays
5588 Pretty print arrays. This format is more convenient to read,
5589 but uses more space. The default is off.
5591 @item set print array off
5592 Return to compressed format for arrays.
5594 @item show print array
5595 Show whether compressed or pretty format is selected for displaying
5598 @item set print elements @var{number-of-elements}
5599 @cindex number of array elements to print
5600 @cindex limit on number of printed array elements
5601 Set a limit on how many elements of an array @value{GDBN} will print.
5602 If @value{GDBN} is printing a large array, it stops printing after it has
5603 printed the number of elements set by the @code{set print elements} command.
5604 This limit also applies to the display of strings.
5605 When @value{GDBN} starts, this limit is set to 200.
5606 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5608 @item show print elements
5609 Display the number of elements of a large array that @value{GDBN} will print.
5610 If the number is 0, then the printing is unlimited.
5612 @item set print repeats
5613 @cindex repeated array elements
5614 Set the threshold for suppressing display of repeated array
5615 elelments. When the number of consecutive identical elements of an
5616 array exceeds the threshold, @value{GDBN} prints the string
5617 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
5618 identical repetitions, instead of displaying the identical elements
5619 themselves. Setting the threshold to zero will cause all elements to
5620 be individually printed. The default threshold is 10.
5622 @item show print repeats
5623 Display the current threshold for printing repeated identical
5626 @item set print null-stop
5627 @cindex @sc{null} elements in arrays
5628 Cause @value{GDBN} to stop printing the characters of an array when the first
5629 @sc{null} is encountered. This is useful when large arrays actually
5630 contain only short strings.
5633 @item show print null-stop
5634 Show whether @value{GDBN} stops printing an array on the first
5635 @sc{null} character.
5637 @item set print pretty on
5638 @cindex print structures in indented form
5639 @cindex indentation in structure display
5640 Cause @value{GDBN} to print structures in an indented format with one member
5641 per line, like this:
5656 @item set print pretty off
5657 Cause @value{GDBN} to print structures in a compact format, like this:
5661 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5662 meat = 0x54 "Pork"@}
5667 This is the default format.
5669 @item show print pretty
5670 Show which format @value{GDBN} is using to print structures.
5672 @item set print sevenbit-strings on
5673 @cindex eight-bit characters in strings
5674 @cindex octal escapes in strings
5675 Print using only seven-bit characters; if this option is set,
5676 @value{GDBN} displays any eight-bit characters (in strings or
5677 character values) using the notation @code{\}@var{nnn}. This setting is
5678 best if you are working in English (@sc{ascii}) and you use the
5679 high-order bit of characters as a marker or ``meta'' bit.
5681 @item set print sevenbit-strings off
5682 Print full eight-bit characters. This allows the use of more
5683 international character sets, and is the default.
5685 @item show print sevenbit-strings
5686 Show whether or not @value{GDBN} is printing only seven-bit characters.
5688 @item set print union on
5689 @cindex unions in structures, printing
5690 Tell @value{GDBN} to print unions which are contained in structures
5691 and other unions. This is the default setting.
5693 @item set print union off
5694 Tell @value{GDBN} not to print unions which are contained in
5695 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
5698 @item show print union
5699 Ask @value{GDBN} whether or not it will print unions which are contained in
5700 structures and other unions.
5702 For example, given the declarations
5705 typedef enum @{Tree, Bug@} Species;
5706 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5707 typedef enum @{Caterpillar, Cocoon, Butterfly@}
5718 struct thing foo = @{Tree, @{Acorn@}@};
5722 with @code{set print union on} in effect @samp{p foo} would print
5725 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5729 and with @code{set print union off} in effect it would print
5732 $1 = @{it = Tree, form = @{...@}@}
5736 @code{set print union} affects programs written in C-like languages
5742 These settings are of interest when debugging C@t{++} programs:
5745 @cindex demangling C@t{++} names
5746 @item set print demangle
5747 @itemx set print demangle on
5748 Print C@t{++} names in their source form rather than in the encoded
5749 (``mangled'') form passed to the assembler and linker for type-safe
5750 linkage. The default is on.
5752 @item show print demangle
5753 Show whether C@t{++} names are printed in mangled or demangled form.
5755 @item set print asm-demangle
5756 @itemx set print asm-demangle on
5757 Print C@t{++} names in their source form rather than their mangled form, even
5758 in assembler code printouts such as instruction disassemblies.
5761 @item show print asm-demangle
5762 Show whether C@t{++} names in assembly listings are printed in mangled
5765 @cindex C@t{++} symbol decoding style
5766 @cindex symbol decoding style, C@t{++}
5767 @kindex set demangle-style
5768 @item set demangle-style @var{style}
5769 Choose among several encoding schemes used by different compilers to
5770 represent C@t{++} names. The choices for @var{style} are currently:
5774 Allow @value{GDBN} to choose a decoding style by inspecting your program.
5777 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
5778 This is the default.
5781 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
5784 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
5787 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
5788 @strong{Warning:} this setting alone is not sufficient to allow
5789 debugging @code{cfront}-generated executables. @value{GDBN} would
5790 require further enhancement to permit that.
5793 If you omit @var{style}, you will see a list of possible formats.
5795 @item show demangle-style
5796 Display the encoding style currently in use for decoding C@t{++} symbols.
5798 @item set print object
5799 @itemx set print object on
5800 @cindex derived type of an object, printing
5801 @cindex display derived types
5802 When displaying a pointer to an object, identify the @emph{actual}
5803 (derived) type of the object rather than the @emph{declared} type, using
5804 the virtual function table.
5806 @item set print object off
5807 Display only the declared type of objects, without reference to the
5808 virtual function table. This is the default setting.
5810 @item show print object
5811 Show whether actual, or declared, object types are displayed.
5813 @item set print static-members
5814 @itemx set print static-members on
5815 @cindex static members of C@t{++} objects
5816 Print static members when displaying a C@t{++} object. The default is on.
5818 @item set print static-members off
5819 Do not print static members when displaying a C@t{++} object.
5821 @item show print static-members
5822 Show whether C@t{++} static members are printed or not.
5824 @item set print pascal_static-members
5825 @itemx set print pascal_static-members on
5826 @cindex static members of Pacal objects
5827 @cindex Pacal objects, static members display
5828 Print static members when displaying a Pascal object. The default is on.
5830 @item set print pascal_static-members off
5831 Do not print static members when displaying a Pascal object.
5833 @item show print pascal_static-members
5834 Show whether Pascal static members are printed or not.
5836 @c These don't work with HP ANSI C++ yet.
5837 @item set print vtbl
5838 @itemx set print vtbl on
5839 @cindex pretty print C@t{++} virtual function tables
5840 @cindex virtual functions (C@t{++}) display
5841 @cindex VTBL display
5842 Pretty print C@t{++} virtual function tables. The default is off.
5843 (The @code{vtbl} commands do not work on programs compiled with the HP
5844 ANSI C@t{++} compiler (@code{aCC}).)
5846 @item set print vtbl off
5847 Do not pretty print C@t{++} virtual function tables.
5849 @item show print vtbl
5850 Show whether C@t{++} virtual function tables are pretty printed, or not.
5854 @section Value history
5856 @cindex value history
5857 @cindex history of values printed by @value{GDBN}
5858 Values printed by the @code{print} command are saved in the @value{GDBN}
5859 @dfn{value history}. This allows you to refer to them in other expressions.
5860 Values are kept until the symbol table is re-read or discarded
5861 (for example with the @code{file} or @code{symbol-file} commands).
5862 When the symbol table changes, the value history is discarded,
5863 since the values may contain pointers back to the types defined in the
5868 @cindex history number
5869 The values printed are given @dfn{history numbers} by which you can
5870 refer to them. These are successive integers starting with one.
5871 @code{print} shows you the history number assigned to a value by
5872 printing @samp{$@var{num} = } before the value; here @var{num} is the
5875 To refer to any previous value, use @samp{$} followed by the value's
5876 history number. The way @code{print} labels its output is designed to
5877 remind you of this. Just @code{$} refers to the most recent value in
5878 the history, and @code{$$} refers to the value before that.
5879 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
5880 is the value just prior to @code{$$}, @code{$$1} is equivalent to
5881 @code{$$}, and @code{$$0} is equivalent to @code{$}.
5883 For example, suppose you have just printed a pointer to a structure and
5884 want to see the contents of the structure. It suffices to type
5890 If you have a chain of structures where the component @code{next} points
5891 to the next one, you can print the contents of the next one with this:
5898 You can print successive links in the chain by repeating this
5899 command---which you can do by just typing @key{RET}.
5901 Note that the history records values, not expressions. If the value of
5902 @code{x} is 4 and you type these commands:
5910 then the value recorded in the value history by the @code{print} command
5911 remains 4 even though the value of @code{x} has changed.
5916 Print the last ten values in the value history, with their item numbers.
5917 This is like @samp{p@ $$9} repeated ten times, except that @code{show
5918 values} does not change the history.
5920 @item show values @var{n}
5921 Print ten history values centered on history item number @var{n}.
5924 Print ten history values just after the values last printed. If no more
5925 values are available, @code{show values +} produces no display.
5928 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
5929 same effect as @samp{show values +}.
5931 @node Convenience Vars
5932 @section Convenience variables
5934 @cindex convenience variables
5935 @cindex user-defined variables
5936 @value{GDBN} provides @dfn{convenience variables} that you can use within
5937 @value{GDBN} to hold on to a value and refer to it later. These variables
5938 exist entirely within @value{GDBN}; they are not part of your program, and
5939 setting a convenience variable has no direct effect on further execution
5940 of your program. That is why you can use them freely.
5942 Convenience variables are prefixed with @samp{$}. Any name preceded by
5943 @samp{$} can be used for a convenience variable, unless it is one of
5944 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
5945 (Value history references, in contrast, are @emph{numbers} preceded
5946 by @samp{$}. @xref{Value History, ,Value history}.)
5948 You can save a value in a convenience variable with an assignment
5949 expression, just as you would set a variable in your program.
5953 set $foo = *object_ptr
5957 would save in @code{$foo} the value contained in the object pointed to by
5960 Using a convenience variable for the first time creates it, but its
5961 value is @code{void} until you assign a new value. You can alter the
5962 value with another assignment at any time.
5964 Convenience variables have no fixed types. You can assign a convenience
5965 variable any type of value, including structures and arrays, even if
5966 that variable already has a value of a different type. The convenience
5967 variable, when used as an expression, has the type of its current value.
5970 @kindex show convenience
5971 @cindex show all user variables
5972 @item show convenience
5973 Print a list of convenience variables used so far, and their values.
5974 Abbreviated @code{show conv}.
5977 One of the ways to use a convenience variable is as a counter to be
5978 incremented or a pointer to be advanced. For example, to print
5979 a field from successive elements of an array of structures:
5983 print bar[$i++]->contents
5987 Repeat that command by typing @key{RET}.
5989 Some convenience variables are created automatically by @value{GDBN} and given
5990 values likely to be useful.
5993 @vindex $_@r{, convenience variable}
5995 The variable @code{$_} is automatically set by the @code{x} command to
5996 the last address examined (@pxref{Memory, ,Examining memory}). Other
5997 commands which provide a default address for @code{x} to examine also
5998 set @code{$_} to that address; these commands include @code{info line}
5999 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
6000 except when set by the @code{x} command, in which case it is a pointer
6001 to the type of @code{$__}.
6003 @vindex $__@r{, convenience variable}
6005 The variable @code{$__} is automatically set by the @code{x} command
6006 to the value found in the last address examined. Its type is chosen
6007 to match the format in which the data was printed.
6010 @vindex $_exitcode@r{, convenience variable}
6011 The variable @code{$_exitcode} is automatically set to the exit code when
6012 the program being debugged terminates.
6015 On HP-UX systems, if you refer to a function or variable name that
6016 begins with a dollar sign, @value{GDBN} searches for a user or system
6017 name first, before it searches for a convenience variable.
6023 You can refer to machine register contents, in expressions, as variables
6024 with names starting with @samp{$}. The names of registers are different
6025 for each machine; use @code{info registers} to see the names used on
6029 @kindex info registers
6030 @item info registers
6031 Print the names and values of all registers except floating-point
6032 and vector registers (in the selected stack frame).
6034 @kindex info all-registers
6035 @cindex floating point registers
6036 @item info all-registers
6037 Print the names and values of all registers, including floating-point
6038 and vector registers (in the selected stack frame).
6040 @item info registers @var{regname} @dots{}
6041 Print the @dfn{relativized} value of each specified register @var{regname}.
6042 As discussed in detail below, register values are normally relative to
6043 the selected stack frame. @var{regname} may be any register name valid on
6044 the machine you are using, with or without the initial @samp{$}.
6047 @value{GDBN} has four ``standard'' register names that are available (in
6048 expressions) on most machines---whenever they do not conflict with an
6049 architecture's canonical mnemonics for registers. The register names
6050 @code{$pc} and @code{$sp} are used for the program counter register and
6051 the stack pointer. @code{$fp} is used for a register that contains a
6052 pointer to the current stack frame, and @code{$ps} is used for a
6053 register that contains the processor status. For example,
6054 you could print the program counter in hex with
6061 or print the instruction to be executed next with
6068 or add four to the stack pointer@footnote{This is a way of removing
6069 one word from the stack, on machines where stacks grow downward in
6070 memory (most machines, nowadays). This assumes that the innermost
6071 stack frame is selected; setting @code{$sp} is not allowed when other
6072 stack frames are selected. To pop entire frames off the stack,
6073 regardless of machine architecture, use @code{return};
6074 see @ref{Returning, ,Returning from a function}.} with
6080 Whenever possible, these four standard register names are available on
6081 your machine even though the machine has different canonical mnemonics,
6082 so long as there is no conflict. The @code{info registers} command
6083 shows the canonical names. For example, on the SPARC, @code{info
6084 registers} displays the processor status register as @code{$psr} but you
6085 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6086 is an alias for the @sc{eflags} register.
6088 @value{GDBN} always considers the contents of an ordinary register as an
6089 integer when the register is examined in this way. Some machines have
6090 special registers which can hold nothing but floating point; these
6091 registers are considered to have floating point values. There is no way
6092 to refer to the contents of an ordinary register as floating point value
6093 (although you can @emph{print} it as a floating point value with
6094 @samp{print/f $@var{regname}}).
6096 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6097 means that the data format in which the register contents are saved by
6098 the operating system is not the same one that your program normally
6099 sees. For example, the registers of the 68881 floating point
6100 coprocessor are always saved in ``extended'' (raw) format, but all C
6101 programs expect to work with ``double'' (virtual) format. In such
6102 cases, @value{GDBN} normally works with the virtual format only (the format
6103 that makes sense for your program), but the @code{info registers} command
6104 prints the data in both formats.
6106 Normally, register values are relative to the selected stack frame
6107 (@pxref{Selection, ,Selecting a frame}). This means that you get the
6108 value that the register would contain if all stack frames farther in
6109 were exited and their saved registers restored. In order to see the
6110 true contents of hardware registers, you must select the innermost
6111 frame (with @samp{frame 0}).
6113 However, @value{GDBN} must deduce where registers are saved, from the machine
6114 code generated by your compiler. If some registers are not saved, or if
6115 @value{GDBN} is unable to locate the saved registers, the selected stack
6116 frame makes no difference.
6118 @node Floating Point Hardware
6119 @section Floating point hardware
6120 @cindex floating point
6122 Depending on the configuration, @value{GDBN} may be able to give
6123 you more information about the status of the floating point hardware.
6128 Display hardware-dependent information about the floating
6129 point unit. The exact contents and layout vary depending on the
6130 floating point chip. Currently, @samp{info float} is supported on
6131 the ARM and x86 machines.
6135 @section Vector Unit
6138 Depending on the configuration, @value{GDBN} may be able to give you
6139 more information about the status of the vector unit.
6144 Display information about the vector unit. The exact contents and
6145 layout vary depending on the hardware.
6148 @node OS Information
6149 @section Operating system auxiliary information
6150 @cindex OS information
6152 @value{GDBN} provides interfaces to useful OS facilities that can help
6153 you debug your program.
6155 @cindex @code{ptrace} system call
6156 @cindex @code{struct user} contents
6157 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
6158 machines), it interfaces with the inferior via the @code{ptrace}
6159 system call. The operating system creates a special sata structure,
6160 called @code{struct user}, for this interface. You can use the
6161 command @code{info udot} to display the contents of this data
6167 Display the contents of the @code{struct user} maintained by the OS
6168 kernel for the program being debugged. @value{GDBN} displays the
6169 contents of @code{struct user} as a list of hex numbers, similar to
6170 the @code{examine} command.
6173 @cindex auxiliary vector
6174 @cindex vector, auxiliary
6175 Some operating systems supply an @dfn{auxiliary vector} to programs at
6176 startup. This is akin to the arguments and environment that you
6177 specify for a program, but contains a system-dependent variety of
6178 binary values that tell system libraries important details about the
6179 hardware, operating system, and process. Each value's purpose is
6180 identified by an integer tag; the meanings are well-known but system-specific.
6181 Depending on the configuration and operating system facilities,
6182 @value{GDBN} may be able to show you this information. For remote
6183 targets, this functionality may further depend on the remote stub's
6184 support of the @samp{qPart:auxv:read} packet, see @ref{Remote
6185 configuration, auxiliary vector}.
6190 Display the auxiliary vector of the inferior, which can be either a
6191 live process or a core dump file. @value{GDBN} prints each tag value
6192 numerically, and also shows names and text descriptions for recognized
6193 tags. Some values in the vector are numbers, some bit masks, and some
6194 pointers to strings or other data. @value{GDBN} displays each value in the
6195 most appropriate form for a recognized tag, and in hexadecimal for
6196 an unrecognized tag.
6200 @node Memory Region Attributes
6201 @section Memory region attributes
6202 @cindex memory region attributes
6204 @dfn{Memory region attributes} allow you to describe special handling
6205 required by regions of your target's memory. @value{GDBN} uses attributes
6206 to determine whether to allow certain types of memory accesses; whether to
6207 use specific width accesses; and whether to cache target memory.
6209 Defined memory regions can be individually enabled and disabled. When a
6210 memory region is disabled, @value{GDBN} uses the default attributes when
6211 accessing memory in that region. Similarly, if no memory regions have
6212 been defined, @value{GDBN} uses the default attributes when accessing
6215 When a memory region is defined, it is given a number to identify it;
6216 to enable, disable, or remove a memory region, you specify that number.
6220 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6221 Define a memory region bounded by @var{lower} and @var{upper} with
6222 attributes @var{attributes}@dots{}, and add it to the list of regions
6223 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
6224 case: it is treated as the the target's maximum memory address.
6225 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6228 @item delete mem @var{nums}@dots{}
6229 Remove memory regions @var{nums}@dots{} from the list of regions
6230 monitored by @value{GDBN}.
6233 @item disable mem @var{nums}@dots{}
6234 Disable monitoring of memory regions @var{nums}@dots{}.
6235 A disabled memory region is not forgotten.
6236 It may be enabled again later.
6239 @item enable mem @var{nums}@dots{}
6240 Enable monitoring of memory regions @var{nums}@dots{}.
6244 Print a table of all defined memory regions, with the following columns
6248 @item Memory Region Number
6249 @item Enabled or Disabled.
6250 Enabled memory regions are marked with @samp{y}.
6251 Disabled memory regions are marked with @samp{n}.
6254 The address defining the inclusive lower bound of the memory region.
6257 The address defining the exclusive upper bound of the memory region.
6260 The list of attributes set for this memory region.
6265 @subsection Attributes
6267 @subsubsection Memory Access Mode
6268 The access mode attributes set whether @value{GDBN} may make read or
6269 write accesses to a memory region.
6271 While these attributes prevent @value{GDBN} from performing invalid
6272 memory accesses, they do nothing to prevent the target system, I/O DMA,
6273 etc. from accessing memory.
6277 Memory is read only.
6279 Memory is write only.
6281 Memory is read/write. This is the default.
6284 @subsubsection Memory Access Size
6285 The acccess size attributes tells @value{GDBN} to use specific sized
6286 accesses in the memory region. Often memory mapped device registers
6287 require specific sized accesses. If no access size attribute is
6288 specified, @value{GDBN} may use accesses of any size.
6292 Use 8 bit memory accesses.
6294 Use 16 bit memory accesses.
6296 Use 32 bit memory accesses.
6298 Use 64 bit memory accesses.
6301 @c @subsubsection Hardware/Software Breakpoints
6302 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6303 @c will use hardware or software breakpoints for the internal breakpoints
6304 @c used by the step, next, finish, until, etc. commands.
6308 @c Always use hardware breakpoints
6309 @c @item swbreak (default)
6312 @subsubsection Data Cache
6313 The data cache attributes set whether @value{GDBN} will cache target
6314 memory. While this generally improves performance by reducing debug
6315 protocol overhead, it can lead to incorrect results because @value{GDBN}
6316 does not know about volatile variables or memory mapped device
6321 Enable @value{GDBN} to cache target memory.
6323 Disable @value{GDBN} from caching target memory. This is the default.
6326 @c @subsubsection Memory Write Verification
6327 @c The memory write verification attributes set whether @value{GDBN}
6328 @c will re-reads data after each write to verify the write was successful.
6332 @c @item noverify (default)
6335 @node Dump/Restore Files
6336 @section Copy between memory and a file
6337 @cindex dump/restore files
6338 @cindex append data to a file
6339 @cindex dump data to a file
6340 @cindex restore data from a file
6342 You can use the commands @code{dump}, @code{append}, and
6343 @code{restore} to copy data between target memory and a file. The
6344 @code{dump} and @code{append} commands write data to a file, and the
6345 @code{restore} command reads data from a file back into the inferior's
6346 memory. Files may be in binary, Motorola S-record, Intel hex, or
6347 Tektronix Hex format; however, @value{GDBN} can only append to binary
6353 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6354 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6355 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6356 or the value of @var{expr}, to @var{filename} in the given format.
6358 The @var{format} parameter may be any one of:
6365 Motorola S-record format.
6367 Tektronix Hex format.
6370 @value{GDBN} uses the same definitions of these formats as the
6371 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
6372 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
6376 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6377 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
6378 Append the contents of memory from @var{start_addr} to @var{end_addr},
6379 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
6380 (@value{GDBN} can only append data to files in raw binary form.)
6383 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
6384 Restore the contents of file @var{filename} into memory. The
6385 @code{restore} command can automatically recognize any known @sc{bfd}
6386 file format, except for raw binary. To restore a raw binary file you
6387 must specify the optional keyword @code{binary} after the filename.
6389 If @var{bias} is non-zero, its value will be added to the addresses
6390 contained in the file. Binary files always start at address zero, so
6391 they will be restored at address @var{bias}. Other bfd files have
6392 a built-in location; they will be restored at offset @var{bias}
6395 If @var{start} and/or @var{end} are non-zero, then only data between
6396 file offset @var{start} and file offset @var{end} will be restored.
6397 These offsets are relative to the addresses in the file, before
6398 the @var{bias} argument is applied.
6402 @node Core File Generation
6403 @section How to Produce a Core File from Your Program
6404 @cindex dump core from inferior
6406 A @dfn{core file} or @dfn{core dump} is a file that records the memory
6407 image of a running process and its process status (register values
6408 etc.). Its primary use is post-mortem debugging of a program that
6409 crashed while it ran outside a debugger. A program that crashes
6410 automatically produces a core file, unless this feature is disabled by
6411 the user. @xref{Files}, for information on invoking @value{GDBN} in
6412 the post-mortem debugging mode.
6414 Occasionally, you may wish to produce a core file of the program you
6415 are debugging in order to preserve a snapshot of its state.
6416 @value{GDBN} has a special command for that.
6420 @kindex generate-core-file
6421 @item generate-core-file [@var{file}]
6422 @itemx gcore [@var{file}]
6423 Produce a core dump of the inferior process. The optional argument
6424 @var{file} specifies the file name where to put the core dump. If not
6425 specified, the file name defaults to @file{core.@var{pid}}, where
6426 @var{pid} is the inferior process ID.
6428 Note that this command is implemented only for some systems (as of
6429 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
6432 @node Character Sets
6433 @section Character Sets
6434 @cindex character sets
6436 @cindex translating between character sets
6437 @cindex host character set
6438 @cindex target character set
6440 If the program you are debugging uses a different character set to
6441 represent characters and strings than the one @value{GDBN} uses itself,
6442 @value{GDBN} can automatically translate between the character sets for
6443 you. The character set @value{GDBN} uses we call the @dfn{host
6444 character set}; the one the inferior program uses we call the
6445 @dfn{target character set}.
6447 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
6448 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
6449 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
6450 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
6451 then the host character set is Latin-1, and the target character set is
6452 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
6453 target-charset EBCDIC-US}, then @value{GDBN} translates between
6454 @sc{ebcdic} and Latin 1 as you print character or string values, or use
6455 character and string literals in expressions.
6457 @value{GDBN} has no way to automatically recognize which character set
6458 the inferior program uses; you must tell it, using the @code{set
6459 target-charset} command, described below.
6461 Here are the commands for controlling @value{GDBN}'s character set
6465 @item set target-charset @var{charset}
6466 @kindex set target-charset
6467 Set the current target character set to @var{charset}. We list the
6468 character set names @value{GDBN} recognizes below, but if you type
6469 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6470 list the target character sets it supports.
6474 @item set host-charset @var{charset}
6475 @kindex set host-charset
6476 Set the current host character set to @var{charset}.
6478 By default, @value{GDBN} uses a host character set appropriate to the
6479 system it is running on; you can override that default using the
6480 @code{set host-charset} command.
6482 @value{GDBN} can only use certain character sets as its host character
6483 set. We list the character set names @value{GDBN} recognizes below, and
6484 indicate which can be host character sets, but if you type
6485 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6486 list the host character sets it supports.
6488 @item set charset @var{charset}
6490 Set the current host and target character sets to @var{charset}. As
6491 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
6492 @value{GDBN} will list the name of the character sets that can be used
6493 for both host and target.
6497 @kindex show charset
6498 Show the names of the current host and target charsets.
6500 @itemx show host-charset
6501 @kindex show host-charset
6502 Show the name of the current host charset.
6504 @itemx show target-charset
6505 @kindex show target-charset
6506 Show the name of the current target charset.
6510 @value{GDBN} currently includes support for the following character
6516 @cindex ASCII character set
6517 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6521 @cindex ISO 8859-1 character set
6522 @cindex ISO Latin 1 character set
6523 The ISO Latin 1 character set. This extends @sc{ascii} with accented
6524 characters needed for French, German, and Spanish. @value{GDBN} can use
6525 this as its host character set.
6529 @cindex EBCDIC character set
6530 @cindex IBM1047 character set
6531 Variants of the @sc{ebcdic} character set, used on some of IBM's
6532 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6533 @value{GDBN} cannot use these as its host character set.
6537 Note that these are all single-byte character sets. More work inside
6538 GDB is needed to support multi-byte or variable-width character
6539 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6541 Here is an example of @value{GDBN}'s character set support in action.
6542 Assume that the following source code has been placed in the file
6543 @file{charset-test.c}:
6549 = @{72, 101, 108, 108, 111, 44, 32, 119,
6550 111, 114, 108, 100, 33, 10, 0@};
6551 char ibm1047_hello[]
6552 = @{200, 133, 147, 147, 150, 107, 64, 166,
6553 150, 153, 147, 132, 90, 37, 0@};
6557 printf ("Hello, world!\n");
6561 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6562 containing the string @samp{Hello, world!} followed by a newline,
6563 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6565 We compile the program, and invoke the debugger on it:
6568 $ gcc -g charset-test.c -o charset-test
6569 $ gdb -nw charset-test
6570 GNU gdb 2001-12-19-cvs
6571 Copyright 2001 Free Software Foundation, Inc.
6576 We can use the @code{show charset} command to see what character sets
6577 @value{GDBN} is currently using to interpret and display characters and
6581 (@value{GDBP}) show charset
6582 The current host and target character set is `ISO-8859-1'.
6586 For the sake of printing this manual, let's use @sc{ascii} as our
6587 initial character set:
6589 (@value{GDBP}) set charset ASCII
6590 (@value{GDBP}) show charset
6591 The current host and target character set is `ASCII'.
6595 Let's assume that @sc{ascii} is indeed the correct character set for our
6596 host system --- in other words, let's assume that if @value{GDBN} prints
6597 characters using the @sc{ascii} character set, our terminal will display
6598 them properly. Since our current target character set is also
6599 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
6602 (@value{GDBP}) print ascii_hello
6603 $1 = 0x401698 "Hello, world!\n"
6604 (@value{GDBP}) print ascii_hello[0]
6609 @value{GDBN} uses the target character set for character and string
6610 literals you use in expressions:
6613 (@value{GDBP}) print '+'
6618 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
6621 @value{GDBN} relies on the user to tell it which character set the
6622 target program uses. If we print @code{ibm1047_hello} while our target
6623 character set is still @sc{ascii}, we get jibberish:
6626 (@value{GDBP}) print ibm1047_hello
6627 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
6628 (@value{GDBP}) print ibm1047_hello[0]
6633 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
6634 @value{GDBN} tells us the character sets it supports:
6637 (@value{GDBP}) set target-charset
6638 ASCII EBCDIC-US IBM1047 ISO-8859-1
6639 (@value{GDBP}) set target-charset
6642 We can select @sc{ibm1047} as our target character set, and examine the
6643 program's strings again. Now the @sc{ascii} string is wrong, but
6644 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
6645 target character set, @sc{ibm1047}, to the host character set,
6646 @sc{ascii}, and they display correctly:
6649 (@value{GDBP}) set target-charset IBM1047
6650 (@value{GDBP}) show charset
6651 The current host character set is `ASCII'.
6652 The current target character set is `IBM1047'.
6653 (@value{GDBP}) print ascii_hello
6654 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
6655 (@value{GDBP}) print ascii_hello[0]
6657 (@value{GDBP}) print ibm1047_hello
6658 $8 = 0x4016a8 "Hello, world!\n"
6659 (@value{GDBP}) print ibm1047_hello[0]
6664 As above, @value{GDBN} uses the target character set for character and
6665 string literals you use in expressions:
6668 (@value{GDBP}) print '+'
6673 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
6676 @node Caching Remote Data
6677 @section Caching Data of Remote Targets
6678 @cindex caching data of remote targets
6680 @value{GDBN} can cache data exchanged between the debugger and a
6681 remote target (@pxref{Remote}). Such caching generally improves
6682 performance, because it reduces the overhead of the remote protocol by
6683 bundling memory reads and writes into large chunks. Unfortunately,
6684 @value{GDBN} does not currently know anything about volatile
6685 registers, and thus data caching will produce incorrect results when
6686 volatile registers are in use.
6689 @kindex set remotecache
6690 @item set remotecache on
6691 @itemx set remotecache off
6692 Set caching state for remote targets. When @code{ON}, use data
6693 caching. By default, this option is @code{OFF}.
6695 @kindex show remotecache
6696 @item show remotecache
6697 Show the current state of data caching for remote targets.
6701 Print the information about the data cache performance. The
6702 information displayed includes: the dcache width and depth; and for
6703 each cache line, how many times it was referenced, and its data and
6704 state (dirty, bad, ok, etc.). This command is useful for debugging
6705 the data cache operation.
6710 @chapter C Preprocessor Macros
6712 Some languages, such as C and C@t{++}, provide a way to define and invoke
6713 ``preprocessor macros'' which expand into strings of tokens.
6714 @value{GDBN} can evaluate expressions containing macro invocations, show
6715 the result of macro expansion, and show a macro's definition, including
6716 where it was defined.
6718 You may need to compile your program specially to provide @value{GDBN}
6719 with information about preprocessor macros. Most compilers do not
6720 include macros in their debugging information, even when you compile
6721 with the @option{-g} flag. @xref{Compilation}.
6723 A program may define a macro at one point, remove that definition later,
6724 and then provide a different definition after that. Thus, at different
6725 points in the program, a macro may have different definitions, or have
6726 no definition at all. If there is a current stack frame, @value{GDBN}
6727 uses the macros in scope at that frame's source code line. Otherwise,
6728 @value{GDBN} uses the macros in scope at the current listing location;
6731 At the moment, @value{GDBN} does not support the @code{##}
6732 token-splicing operator, the @code{#} stringification operator, or
6733 variable-arity macros.
6735 Whenever @value{GDBN} evaluates an expression, it always expands any
6736 macro invocations present in the expression. @value{GDBN} also provides
6737 the following commands for working with macros explicitly.
6741 @kindex macro expand
6742 @cindex macro expansion, showing the results of preprocessor
6743 @cindex preprocessor macro expansion, showing the results of
6744 @cindex expanding preprocessor macros
6745 @item macro expand @var{expression}
6746 @itemx macro exp @var{expression}
6747 Show the results of expanding all preprocessor macro invocations in
6748 @var{expression}. Since @value{GDBN} simply expands macros, but does
6749 not parse the result, @var{expression} need not be a valid expression;
6750 it can be any string of tokens.
6753 @item macro expand-once @var{expression}
6754 @itemx macro exp1 @var{expression}
6755 @cindex expand macro once
6756 @i{(This command is not yet implemented.)} Show the results of
6757 expanding those preprocessor macro invocations that appear explicitly in
6758 @var{expression}. Macro invocations appearing in that expansion are
6759 left unchanged. This command allows you to see the effect of a
6760 particular macro more clearly, without being confused by further
6761 expansions. Since @value{GDBN} simply expands macros, but does not
6762 parse the result, @var{expression} need not be a valid expression; it
6763 can be any string of tokens.
6766 @cindex macro definition, showing
6767 @cindex definition, showing a macro's
6768 @item info macro @var{macro}
6769 Show the definition of the macro named @var{macro}, and describe the
6770 source location where that definition was established.
6772 @kindex macro define
6773 @cindex user-defined macros
6774 @cindex defining macros interactively
6775 @cindex macros, user-defined
6776 @item macro define @var{macro} @var{replacement-list}
6777 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
6778 @i{(This command is not yet implemented.)} Introduce a definition for a
6779 preprocessor macro named @var{macro}, invocations of which are replaced
6780 by the tokens given in @var{replacement-list}. The first form of this
6781 command defines an ``object-like'' macro, which takes no arguments; the
6782 second form defines a ``function-like'' macro, which takes the arguments
6783 given in @var{arglist}.
6785 A definition introduced by this command is in scope in every expression
6786 evaluated in @value{GDBN}, until it is removed with the @command{macro
6787 undef} command, described below. The definition overrides all
6788 definitions for @var{macro} present in the program being debugged, as
6789 well as any previous user-supplied definition.
6792 @item macro undef @var{macro}
6793 @i{(This command is not yet implemented.)} Remove any user-supplied
6794 definition for the macro named @var{macro}. This command only affects
6795 definitions provided with the @command{macro define} command, described
6796 above; it cannot remove definitions present in the program being
6801 @i{(This command is not yet implemented.)} List all the macros
6802 defined using the @code{macro define} command.
6805 @cindex macros, example of debugging with
6806 Here is a transcript showing the above commands in action. First, we
6807 show our source files:
6815 #define ADD(x) (M + x)
6820 printf ("Hello, world!\n");
6822 printf ("We're so creative.\n");
6824 printf ("Goodbye, world!\n");
6831 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
6832 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
6833 compiler includes information about preprocessor macros in the debugging
6837 $ gcc -gdwarf-2 -g3 sample.c -o sample
6841 Now, we start @value{GDBN} on our sample program:
6845 GNU gdb 2002-05-06-cvs
6846 Copyright 2002 Free Software Foundation, Inc.
6847 GDB is free software, @dots{}
6851 We can expand macros and examine their definitions, even when the
6852 program is not running. @value{GDBN} uses the current listing position
6853 to decide which macro definitions are in scope:
6856 (@value{GDBP}) list main
6859 5 #define ADD(x) (M + x)
6864 10 printf ("Hello, world!\n");
6866 12 printf ("We're so creative.\n");
6867 (@value{GDBP}) info macro ADD
6868 Defined at /home/jimb/gdb/macros/play/sample.c:5
6869 #define ADD(x) (M + x)
6870 (@value{GDBP}) info macro Q
6871 Defined at /home/jimb/gdb/macros/play/sample.h:1
6872 included at /home/jimb/gdb/macros/play/sample.c:2
6874 (@value{GDBP}) macro expand ADD(1)
6875 expands to: (42 + 1)
6876 (@value{GDBP}) macro expand-once ADD(1)
6877 expands to: once (M + 1)
6881 In the example above, note that @command{macro expand-once} expands only
6882 the macro invocation explicit in the original text --- the invocation of
6883 @code{ADD} --- but does not expand the invocation of the macro @code{M},
6884 which was introduced by @code{ADD}.
6886 Once the program is running, GDB uses the macro definitions in force at
6887 the source line of the current stack frame:
6890 (@value{GDBP}) break main
6891 Breakpoint 1 at 0x8048370: file sample.c, line 10.
6893 Starting program: /home/jimb/gdb/macros/play/sample
6895 Breakpoint 1, main () at sample.c:10
6896 10 printf ("Hello, world!\n");
6900 At line 10, the definition of the macro @code{N} at line 9 is in force:
6903 (@value{GDBP}) info macro N
6904 Defined at /home/jimb/gdb/macros/play/sample.c:9
6906 (@value{GDBP}) macro expand N Q M
6908 (@value{GDBP}) print N Q M
6913 As we step over directives that remove @code{N}'s definition, and then
6914 give it a new definition, @value{GDBN} finds the definition (or lack
6915 thereof) in force at each point:
6920 12 printf ("We're so creative.\n");
6921 (@value{GDBP}) info macro N
6922 The symbol `N' has no definition as a C/C++ preprocessor macro
6923 at /home/jimb/gdb/macros/play/sample.c:12
6926 14 printf ("Goodbye, world!\n");
6927 (@value{GDBP}) info macro N
6928 Defined at /home/jimb/gdb/macros/play/sample.c:13
6930 (@value{GDBP}) macro expand N Q M
6931 expands to: 1729 < 42
6932 (@value{GDBP}) print N Q M
6939 @chapter Tracepoints
6940 @c This chapter is based on the documentation written by Michael
6941 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
6944 In some applications, it is not feasible for the debugger to interrupt
6945 the program's execution long enough for the developer to learn
6946 anything helpful about its behavior. If the program's correctness
6947 depends on its real-time behavior, delays introduced by a debugger
6948 might cause the program to change its behavior drastically, or perhaps
6949 fail, even when the code itself is correct. It is useful to be able
6950 to observe the program's behavior without interrupting it.
6952 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
6953 specify locations in the program, called @dfn{tracepoints}, and
6954 arbitrary expressions to evaluate when those tracepoints are reached.
6955 Later, using the @code{tfind} command, you can examine the values
6956 those expressions had when the program hit the tracepoints. The
6957 expressions may also denote objects in memory---structures or arrays,
6958 for example---whose values @value{GDBN} should record; while visiting
6959 a particular tracepoint, you may inspect those objects as if they were
6960 in memory at that moment. However, because @value{GDBN} records these
6961 values without interacting with you, it can do so quickly and
6962 unobtrusively, hopefully not disturbing the program's behavior.
6964 The tracepoint facility is currently available only for remote
6965 targets. @xref{Targets}. In addition, your remote target must know how
6966 to collect trace data. This functionality is implemented in the remote
6967 stub; however, none of the stubs distributed with @value{GDBN} support
6968 tracepoints as of this writing.
6970 This chapter describes the tracepoint commands and features.
6974 * Analyze Collected Data::
6975 * Tracepoint Variables::
6978 @node Set Tracepoints
6979 @section Commands to Set Tracepoints
6981 Before running such a @dfn{trace experiment}, an arbitrary number of
6982 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
6983 tracepoint has a number assigned to it by @value{GDBN}. Like with
6984 breakpoints, tracepoint numbers are successive integers starting from
6985 one. Many of the commands associated with tracepoints take the
6986 tracepoint number as their argument, to identify which tracepoint to
6989 For each tracepoint, you can specify, in advance, some arbitrary set
6990 of data that you want the target to collect in the trace buffer when
6991 it hits that tracepoint. The collected data can include registers,
6992 local variables, or global data. Later, you can use @value{GDBN}
6993 commands to examine the values these data had at the time the
6996 This section describes commands to set tracepoints and associated
6997 conditions and actions.
7000 * Create and Delete Tracepoints::
7001 * Enable and Disable Tracepoints::
7002 * Tracepoint Passcounts::
7003 * Tracepoint Actions::
7004 * Listing Tracepoints::
7005 * Starting and Stopping Trace Experiment::
7008 @node Create and Delete Tracepoints
7009 @subsection Create and Delete Tracepoints
7012 @cindex set tracepoint
7015 The @code{trace} command is very similar to the @code{break} command.
7016 Its argument can be a source line, a function name, or an address in
7017 the target program. @xref{Set Breaks}. The @code{trace} command
7018 defines a tracepoint, which is a point in the target program where the
7019 debugger will briefly stop, collect some data, and then allow the
7020 program to continue. Setting a tracepoint or changing its commands
7021 doesn't take effect until the next @code{tstart} command; thus, you
7022 cannot change the tracepoint attributes once a trace experiment is
7025 Here are some examples of using the @code{trace} command:
7028 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
7030 (@value{GDBP}) @b{trace +2} // 2 lines forward
7032 (@value{GDBP}) @b{trace my_function} // first source line of function
7034 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
7036 (@value{GDBP}) @b{trace *0x2117c4} // an address
7040 You can abbreviate @code{trace} as @code{tr}.
7043 @cindex last tracepoint number
7044 @cindex recent tracepoint number
7045 @cindex tracepoint number
7046 The convenience variable @code{$tpnum} records the tracepoint number
7047 of the most recently set tracepoint.
7049 @kindex delete tracepoint
7050 @cindex tracepoint deletion
7051 @item delete tracepoint @r{[}@var{num}@r{]}
7052 Permanently delete one or more tracepoints. With no argument, the
7053 default is to delete all tracepoints.
7058 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
7060 (@value{GDBP}) @b{delete trace} // remove all tracepoints
7064 You can abbreviate this command as @code{del tr}.
7067 @node Enable and Disable Tracepoints
7068 @subsection Enable and Disable Tracepoints
7071 @kindex disable tracepoint
7072 @item disable tracepoint @r{[}@var{num}@r{]}
7073 Disable tracepoint @var{num}, or all tracepoints if no argument
7074 @var{num} is given. A disabled tracepoint will have no effect during
7075 the next trace experiment, but it is not forgotten. You can re-enable
7076 a disabled tracepoint using the @code{enable tracepoint} command.
7078 @kindex enable tracepoint
7079 @item enable tracepoint @r{[}@var{num}@r{]}
7080 Enable tracepoint @var{num}, or all tracepoints. The enabled
7081 tracepoints will become effective the next time a trace experiment is
7085 @node Tracepoint Passcounts
7086 @subsection Tracepoint Passcounts
7090 @cindex tracepoint pass count
7091 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
7092 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
7093 automatically stop a trace experiment. If a tracepoint's passcount is
7094 @var{n}, then the trace experiment will be automatically stopped on
7095 the @var{n}'th time that tracepoint is hit. If the tracepoint number
7096 @var{num} is not specified, the @code{passcount} command sets the
7097 passcount of the most recently defined tracepoint. If no passcount is
7098 given, the trace experiment will run until stopped explicitly by the
7104 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
7105 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
7107 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
7108 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
7109 (@value{GDBP}) @b{trace foo}
7110 (@value{GDBP}) @b{pass 3}
7111 (@value{GDBP}) @b{trace bar}
7112 (@value{GDBP}) @b{pass 2}
7113 (@value{GDBP}) @b{trace baz}
7114 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
7115 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
7116 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
7117 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
7121 @node Tracepoint Actions
7122 @subsection Tracepoint Action Lists
7126 @cindex tracepoint actions
7127 @item actions @r{[}@var{num}@r{]}
7128 This command will prompt for a list of actions to be taken when the
7129 tracepoint is hit. If the tracepoint number @var{num} is not
7130 specified, this command sets the actions for the one that was most
7131 recently defined (so that you can define a tracepoint and then say
7132 @code{actions} without bothering about its number). You specify the
7133 actions themselves on the following lines, one action at a time, and
7134 terminate the actions list with a line containing just @code{end}. So
7135 far, the only defined actions are @code{collect} and
7136 @code{while-stepping}.
7138 @cindex remove actions from a tracepoint
7139 To remove all actions from a tracepoint, type @samp{actions @var{num}}
7140 and follow it immediately with @samp{end}.
7143 (@value{GDBP}) @b{collect @var{data}} // collect some data
7145 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
7147 (@value{GDBP}) @b{end} // signals the end of actions.
7150 In the following example, the action list begins with @code{collect}
7151 commands indicating the things to be collected when the tracepoint is
7152 hit. Then, in order to single-step and collect additional data
7153 following the tracepoint, a @code{while-stepping} command is used,
7154 followed by the list of things to be collected while stepping. The
7155 @code{while-stepping} command is terminated by its own separate
7156 @code{end} command. Lastly, the action list is terminated by an
7160 (@value{GDBP}) @b{trace foo}
7161 (@value{GDBP}) @b{actions}
7162 Enter actions for tracepoint 1, one per line:
7171 @kindex collect @r{(tracepoints)}
7172 @item collect @var{expr1}, @var{expr2}, @dots{}
7173 Collect values of the given expressions when the tracepoint is hit.
7174 This command accepts a comma-separated list of any valid expressions.
7175 In addition to global, static, or local variables, the following
7176 special arguments are supported:
7180 collect all registers
7183 collect all function arguments
7186 collect all local variables.
7189 You can give several consecutive @code{collect} commands, each one
7190 with a single argument, or one @code{collect} command with several
7191 arguments separated by commas: the effect is the same.
7193 The command @code{info scope} (@pxref{Symbols, info scope}) is
7194 particularly useful for figuring out what data to collect.
7196 @kindex while-stepping @r{(tracepoints)}
7197 @item while-stepping @var{n}
7198 Perform @var{n} single-step traces after the tracepoint, collecting
7199 new data at each step. The @code{while-stepping} command is
7200 followed by the list of what to collect while stepping (followed by
7201 its own @code{end} command):
7205 > collect $regs, myglobal
7211 You may abbreviate @code{while-stepping} as @code{ws} or
7215 @node Listing Tracepoints
7216 @subsection Listing Tracepoints
7219 @kindex info tracepoints
7221 @cindex information about tracepoints
7222 @item info tracepoints @r{[}@var{num}@r{]}
7223 Display information about the tracepoint @var{num}. If you don't specify
7224 a tracepoint number, displays information about all the tracepoints
7225 defined so far. For each tracepoint, the following information is
7232 whether it is enabled or disabled
7236 its passcount as given by the @code{passcount @var{n}} command
7238 its step count as given by the @code{while-stepping @var{n}} command
7240 where in the source files is the tracepoint set
7242 its action list as given by the @code{actions} command
7246 (@value{GDBP}) @b{info trace}
7247 Num Enb Address PassC StepC What
7248 1 y 0x002117c4 0 0 <gdb_asm>
7249 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
7250 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
7255 This command can be abbreviated @code{info tp}.
7258 @node Starting and Stopping Trace Experiment
7259 @subsection Starting and Stopping Trace Experiment
7263 @cindex start a new trace experiment
7264 @cindex collected data discarded
7266 This command takes no arguments. It starts the trace experiment, and
7267 begins collecting data. This has the side effect of discarding all
7268 the data collected in the trace buffer during the previous trace
7272 @cindex stop a running trace experiment
7274 This command takes no arguments. It ends the trace experiment, and
7275 stops collecting data.
7277 @strong{Note}: a trace experiment and data collection may stop
7278 automatically if any tracepoint's passcount is reached
7279 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
7282 @cindex status of trace data collection
7283 @cindex trace experiment, status of
7285 This command displays the status of the current trace data
7289 Here is an example of the commands we described so far:
7292 (@value{GDBP}) @b{trace gdb_c_test}
7293 (@value{GDBP}) @b{actions}
7294 Enter actions for tracepoint #1, one per line.
7295 > collect $regs,$locals,$args
7300 (@value{GDBP}) @b{tstart}
7301 [time passes @dots{}]
7302 (@value{GDBP}) @b{tstop}
7306 @node Analyze Collected Data
7307 @section Using the collected data
7309 After the tracepoint experiment ends, you use @value{GDBN} commands
7310 for examining the trace data. The basic idea is that each tracepoint
7311 collects a trace @dfn{snapshot} every time it is hit and another
7312 snapshot every time it single-steps. All these snapshots are
7313 consecutively numbered from zero and go into a buffer, and you can
7314 examine them later. The way you examine them is to @dfn{focus} on a
7315 specific trace snapshot. When the remote stub is focused on a trace
7316 snapshot, it will respond to all @value{GDBN} requests for memory and
7317 registers by reading from the buffer which belongs to that snapshot,
7318 rather than from @emph{real} memory or registers of the program being
7319 debugged. This means that @strong{all} @value{GDBN} commands
7320 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
7321 behave as if we were currently debugging the program state as it was
7322 when the tracepoint occurred. Any requests for data that are not in
7323 the buffer will fail.
7326 * tfind:: How to select a trace snapshot
7327 * tdump:: How to display all data for a snapshot
7328 * save-tracepoints:: How to save tracepoints for a future run
7332 @subsection @code{tfind @var{n}}
7335 @cindex select trace snapshot
7336 @cindex find trace snapshot
7337 The basic command for selecting a trace snapshot from the buffer is
7338 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
7339 counting from zero. If no argument @var{n} is given, the next
7340 snapshot is selected.
7342 Here are the various forms of using the @code{tfind} command.
7346 Find the first snapshot in the buffer. This is a synonym for
7347 @code{tfind 0} (since 0 is the number of the first snapshot).
7350 Stop debugging trace snapshots, resume @emph{live} debugging.
7353 Same as @samp{tfind none}.
7356 No argument means find the next trace snapshot.
7359 Find the previous trace snapshot before the current one. This permits
7360 retracing earlier steps.
7362 @item tfind tracepoint @var{num}
7363 Find the next snapshot associated with tracepoint @var{num}. Search
7364 proceeds forward from the last examined trace snapshot. If no
7365 argument @var{num} is given, it means find the next snapshot collected
7366 for the same tracepoint as the current snapshot.
7368 @item tfind pc @var{addr}
7369 Find the next snapshot associated with the value @var{addr} of the
7370 program counter. Search proceeds forward from the last examined trace
7371 snapshot. If no argument @var{addr} is given, it means find the next
7372 snapshot with the same value of PC as the current snapshot.
7374 @item tfind outside @var{addr1}, @var{addr2}
7375 Find the next snapshot whose PC is outside the given range of
7378 @item tfind range @var{addr1}, @var{addr2}
7379 Find the next snapshot whose PC is between @var{addr1} and
7380 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
7382 @item tfind line @r{[}@var{file}:@r{]}@var{n}
7383 Find the next snapshot associated with the source line @var{n}. If
7384 the optional argument @var{file} is given, refer to line @var{n} in
7385 that source file. Search proceeds forward from the last examined
7386 trace snapshot. If no argument @var{n} is given, it means find the
7387 next line other than the one currently being examined; thus saying
7388 @code{tfind line} repeatedly can appear to have the same effect as
7389 stepping from line to line in a @emph{live} debugging session.
7392 The default arguments for the @code{tfind} commands are specifically
7393 designed to make it easy to scan through the trace buffer. For
7394 instance, @code{tfind} with no argument selects the next trace
7395 snapshot, and @code{tfind -} with no argument selects the previous
7396 trace snapshot. So, by giving one @code{tfind} command, and then
7397 simply hitting @key{RET} repeatedly you can examine all the trace
7398 snapshots in order. Or, by saying @code{tfind -} and then hitting
7399 @key{RET} repeatedly you can examine the snapshots in reverse order.
7400 The @code{tfind line} command with no argument selects the snapshot
7401 for the next source line executed. The @code{tfind pc} command with
7402 no argument selects the next snapshot with the same program counter
7403 (PC) as the current frame. The @code{tfind tracepoint} command with
7404 no argument selects the next trace snapshot collected by the same
7405 tracepoint as the current one.
7407 In addition to letting you scan through the trace buffer manually,
7408 these commands make it easy to construct @value{GDBN} scripts that
7409 scan through the trace buffer and print out whatever collected data
7410 you are interested in. Thus, if we want to examine the PC, FP, and SP
7411 registers from each trace frame in the buffer, we can say this:
7414 (@value{GDBP}) @b{tfind start}
7415 (@value{GDBP}) @b{while ($trace_frame != -1)}
7416 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
7417 $trace_frame, $pc, $sp, $fp
7421 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
7422 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
7423 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
7424 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
7425 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
7426 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
7427 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
7428 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
7429 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
7430 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
7431 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
7434 Or, if we want to examine the variable @code{X} at each source line in
7438 (@value{GDBP}) @b{tfind start}
7439 (@value{GDBP}) @b{while ($trace_frame != -1)}
7440 > printf "Frame %d, X == %d\n", $trace_frame, X
7450 @subsection @code{tdump}
7452 @cindex dump all data collected at tracepoint
7453 @cindex tracepoint data, display
7455 This command takes no arguments. It prints all the data collected at
7456 the current trace snapshot.
7459 (@value{GDBP}) @b{trace 444}
7460 (@value{GDBP}) @b{actions}
7461 Enter actions for tracepoint #2, one per line:
7462 > collect $regs, $locals, $args, gdb_long_test
7465 (@value{GDBP}) @b{tstart}
7467 (@value{GDBP}) @b{tfind line 444}
7468 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
7470 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
7472 (@value{GDBP}) @b{tdump}
7473 Data collected at tracepoint 2, trace frame 1:
7474 d0 0xc4aa0085 -995491707
7478 d4 0x71aea3d 119204413
7483 a1 0x3000668 50333288
7486 a4 0x3000698 50333336
7488 fp 0x30bf3c 0x30bf3c
7489 sp 0x30bf34 0x30bf34
7491 pc 0x20b2c8 0x20b2c8
7495 p = 0x20e5b4 "gdb-test"
7502 gdb_long_test = 17 '\021'
7507 @node save-tracepoints
7508 @subsection @code{save-tracepoints @var{filename}}
7509 @kindex save-tracepoints
7510 @cindex save tracepoints for future sessions
7512 This command saves all current tracepoint definitions together with
7513 their actions and passcounts, into a file @file{@var{filename}}
7514 suitable for use in a later debugging session. To read the saved
7515 tracepoint definitions, use the @code{source} command (@pxref{Command
7518 @node Tracepoint Variables
7519 @section Convenience Variables for Tracepoints
7520 @cindex tracepoint variables
7521 @cindex convenience variables for tracepoints
7524 @vindex $trace_frame
7525 @item (int) $trace_frame
7526 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
7527 snapshot is selected.
7530 @item (int) $tracepoint
7531 The tracepoint for the current trace snapshot.
7534 @item (int) $trace_line
7535 The line number for the current trace snapshot.
7538 @item (char []) $trace_file
7539 The source file for the current trace snapshot.
7542 @item (char []) $trace_func
7543 The name of the function containing @code{$tracepoint}.
7546 Note: @code{$trace_file} is not suitable for use in @code{printf},
7547 use @code{output} instead.
7549 Here's a simple example of using these convenience variables for
7550 stepping through all the trace snapshots and printing some of their
7554 (@value{GDBP}) @b{tfind start}
7556 (@value{GDBP}) @b{while $trace_frame != -1}
7557 > output $trace_file
7558 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7564 @chapter Debugging Programs That Use Overlays
7567 If your program is too large to fit completely in your target system's
7568 memory, you can sometimes use @dfn{overlays} to work around this
7569 problem. @value{GDBN} provides some support for debugging programs that
7573 * How Overlays Work:: A general explanation of overlays.
7574 * Overlay Commands:: Managing overlays in @value{GDBN}.
7575 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7576 mapped by asking the inferior.
7577 * Overlay Sample Program:: A sample program using overlays.
7580 @node How Overlays Work
7581 @section How Overlays Work
7582 @cindex mapped overlays
7583 @cindex unmapped overlays
7584 @cindex load address, overlay's
7585 @cindex mapped address
7586 @cindex overlay area
7588 Suppose you have a computer whose instruction address space is only 64
7589 kilobytes long, but which has much more memory which can be accessed by
7590 other means: special instructions, segment registers, or memory
7591 management hardware, for example. Suppose further that you want to
7592 adapt a program which is larger than 64 kilobytes to run on this system.
7594 One solution is to identify modules of your program which are relatively
7595 independent, and need not call each other directly; call these modules
7596 @dfn{overlays}. Separate the overlays from the main program, and place
7597 their machine code in the larger memory. Place your main program in
7598 instruction memory, but leave at least enough space there to hold the
7599 largest overlay as well.
7601 Now, to call a function located in an overlay, you must first copy that
7602 overlay's machine code from the large memory into the space set aside
7603 for it in the instruction memory, and then jump to its entry point
7606 @c NB: In the below the mapped area's size is greater or equal to the
7607 @c size of all overlays. This is intentional to remind the developer
7608 @c that overlays don't necessarily need to be the same size.
7612 Data Instruction Larger
7613 Address Space Address Space Address Space
7614 +-----------+ +-----------+ +-----------+
7616 +-----------+ +-----------+ +-----------+<-- overlay 1
7617 | program | | main | .----| overlay 1 | load address
7618 | variables | | program | | +-----------+
7619 | and heap | | | | | |
7620 +-----------+ | | | +-----------+<-- overlay 2
7621 | | +-----------+ | | | load address
7622 +-----------+ | | | .-| overlay 2 |
7624 mapped --->+-----------+ | | +-----------+
7626 | overlay | <-' | | |
7627 | area | <---' +-----------+<-- overlay 3
7628 | | <---. | | load address
7629 +-----------+ `--| overlay 3 |
7636 @anchor{A code overlay}A code overlay
7640 The diagram (@pxref{A code overlay}) shows a system with separate data
7641 and instruction address spaces. To map an overlay, the program copies
7642 its code from the larger address space to the instruction address space.
7643 Since the overlays shown here all use the same mapped address, only one
7644 may be mapped at a time. For a system with a single address space for
7645 data and instructions, the diagram would be similar, except that the
7646 program variables and heap would share an address space with the main
7647 program and the overlay area.
7649 An overlay loaded into instruction memory and ready for use is called a
7650 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
7651 instruction memory. An overlay not present (or only partially present)
7652 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
7653 is its address in the larger memory. The mapped address is also called
7654 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
7655 called the @dfn{load memory address}, or @dfn{LMA}.
7657 Unfortunately, overlays are not a completely transparent way to adapt a
7658 program to limited instruction memory. They introduce a new set of
7659 global constraints you must keep in mind as you design your program:
7664 Before calling or returning to a function in an overlay, your program
7665 must make sure that overlay is actually mapped. Otherwise, the call or
7666 return will transfer control to the right address, but in the wrong
7667 overlay, and your program will probably crash.
7670 If the process of mapping an overlay is expensive on your system, you
7671 will need to choose your overlays carefully to minimize their effect on
7672 your program's performance.
7675 The executable file you load onto your system must contain each
7676 overlay's instructions, appearing at the overlay's load address, not its
7677 mapped address. However, each overlay's instructions must be relocated
7678 and its symbols defined as if the overlay were at its mapped address.
7679 You can use GNU linker scripts to specify different load and relocation
7680 addresses for pieces of your program; see @ref{Overlay Description,,,
7681 ld.info, Using ld: the GNU linker}.
7684 The procedure for loading executable files onto your system must be able
7685 to load their contents into the larger address space as well as the
7686 instruction and data spaces.
7690 The overlay system described above is rather simple, and could be
7691 improved in many ways:
7696 If your system has suitable bank switch registers or memory management
7697 hardware, you could use those facilities to make an overlay's load area
7698 contents simply appear at their mapped address in instruction space.
7699 This would probably be faster than copying the overlay to its mapped
7700 area in the usual way.
7703 If your overlays are small enough, you could set aside more than one
7704 overlay area, and have more than one overlay mapped at a time.
7707 You can use overlays to manage data, as well as instructions. In
7708 general, data overlays are even less transparent to your design than
7709 code overlays: whereas code overlays only require care when you call or
7710 return to functions, data overlays require care every time you access
7711 the data. Also, if you change the contents of a data overlay, you
7712 must copy its contents back out to its load address before you can copy a
7713 different data overlay into the same mapped area.
7718 @node Overlay Commands
7719 @section Overlay Commands
7721 To use @value{GDBN}'s overlay support, each overlay in your program must
7722 correspond to a separate section of the executable file. The section's
7723 virtual memory address and load memory address must be the overlay's
7724 mapped and load addresses. Identifying overlays with sections allows
7725 @value{GDBN} to determine the appropriate address of a function or
7726 variable, depending on whether the overlay is mapped or not.
7728 @value{GDBN}'s overlay commands all start with the word @code{overlay};
7729 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
7734 Disable @value{GDBN}'s overlay support. When overlay support is
7735 disabled, @value{GDBN} assumes that all functions and variables are
7736 always present at their mapped addresses. By default, @value{GDBN}'s
7737 overlay support is disabled.
7739 @item overlay manual
7740 @cindex manual overlay debugging
7741 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
7742 relies on you to tell it which overlays are mapped, and which are not,
7743 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
7744 commands described below.
7746 @item overlay map-overlay @var{overlay}
7747 @itemx overlay map @var{overlay}
7748 @cindex map an overlay
7749 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
7750 be the name of the object file section containing the overlay. When an
7751 overlay is mapped, @value{GDBN} assumes it can find the overlay's
7752 functions and variables at their mapped addresses. @value{GDBN} assumes
7753 that any other overlays whose mapped ranges overlap that of
7754 @var{overlay} are now unmapped.
7756 @item overlay unmap-overlay @var{overlay}
7757 @itemx overlay unmap @var{overlay}
7758 @cindex unmap an overlay
7759 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
7760 must be the name of the object file section containing the overlay.
7761 When an overlay is unmapped, @value{GDBN} assumes it can find the
7762 overlay's functions and variables at their load addresses.
7765 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
7766 consults a data structure the overlay manager maintains in the inferior
7767 to see which overlays are mapped. For details, see @ref{Automatic
7770 @item overlay load-target
7772 @cindex reloading the overlay table
7773 Re-read the overlay table from the inferior. Normally, @value{GDBN}
7774 re-reads the table @value{GDBN} automatically each time the inferior
7775 stops, so this command should only be necessary if you have changed the
7776 overlay mapping yourself using @value{GDBN}. This command is only
7777 useful when using automatic overlay debugging.
7779 @item overlay list-overlays
7781 @cindex listing mapped overlays
7782 Display a list of the overlays currently mapped, along with their mapped
7783 addresses, load addresses, and sizes.
7787 Normally, when @value{GDBN} prints a code address, it includes the name
7788 of the function the address falls in:
7791 (@value{GDBP}) print main
7792 $3 = @{int ()@} 0x11a0 <main>
7795 When overlay debugging is enabled, @value{GDBN} recognizes code in
7796 unmapped overlays, and prints the names of unmapped functions with
7797 asterisks around them. For example, if @code{foo} is a function in an
7798 unmapped overlay, @value{GDBN} prints it this way:
7801 (@value{GDBP}) overlay list
7802 No sections are mapped.
7803 (@value{GDBP}) print foo
7804 $5 = @{int (int)@} 0x100000 <*foo*>
7807 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
7811 (@value{GDBP}) overlay list
7812 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
7813 mapped at 0x1016 - 0x104a
7814 (@value{GDBP}) print foo
7815 $6 = @{int (int)@} 0x1016 <foo>
7818 When overlay debugging is enabled, @value{GDBN} can find the correct
7819 address for functions and variables in an overlay, whether or not the
7820 overlay is mapped. This allows most @value{GDBN} commands, like
7821 @code{break} and @code{disassemble}, to work normally, even on unmapped
7822 code. However, @value{GDBN}'s breakpoint support has some limitations:
7826 @cindex breakpoints in overlays
7827 @cindex overlays, setting breakpoints in
7828 You can set breakpoints in functions in unmapped overlays, as long as
7829 @value{GDBN} can write to the overlay at its load address.
7831 @value{GDBN} can not set hardware or simulator-based breakpoints in
7832 unmapped overlays. However, if you set a breakpoint at the end of your
7833 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
7834 you are using manual overlay management), @value{GDBN} will re-set its
7835 breakpoints properly.
7839 @node Automatic Overlay Debugging
7840 @section Automatic Overlay Debugging
7841 @cindex automatic overlay debugging
7843 @value{GDBN} can automatically track which overlays are mapped and which
7844 are not, given some simple co-operation from the overlay manager in the
7845 inferior. If you enable automatic overlay debugging with the
7846 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
7847 looks in the inferior's memory for certain variables describing the
7848 current state of the overlays.
7850 Here are the variables your overlay manager must define to support
7851 @value{GDBN}'s automatic overlay debugging:
7855 @item @code{_ovly_table}:
7856 This variable must be an array of the following structures:
7861 /* The overlay's mapped address. */
7864 /* The size of the overlay, in bytes. */
7867 /* The overlay's load address. */
7870 /* Non-zero if the overlay is currently mapped;
7872 unsigned long mapped;
7876 @item @code{_novlys}:
7877 This variable must be a four-byte signed integer, holding the total
7878 number of elements in @code{_ovly_table}.
7882 To decide whether a particular overlay is mapped or not, @value{GDBN}
7883 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
7884 @code{lma} members equal the VMA and LMA of the overlay's section in the
7885 executable file. When @value{GDBN} finds a matching entry, it consults
7886 the entry's @code{mapped} member to determine whether the overlay is
7889 In addition, your overlay manager may define a function called
7890 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
7891 will silently set a breakpoint there. If the overlay manager then
7892 calls this function whenever it has changed the overlay table, this
7893 will enable @value{GDBN} to accurately keep track of which overlays
7894 are in program memory, and update any breakpoints that may be set
7895 in overlays. This will allow breakpoints to work even if the
7896 overlays are kept in ROM or other non-writable memory while they
7897 are not being executed.
7899 @node Overlay Sample Program
7900 @section Overlay Sample Program
7901 @cindex overlay example program
7903 When linking a program which uses overlays, you must place the overlays
7904 at their load addresses, while relocating them to run at their mapped
7905 addresses. To do this, you must write a linker script (@pxref{Overlay
7906 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
7907 since linker scripts are specific to a particular host system, target
7908 architecture, and target memory layout, this manual cannot provide
7909 portable sample code demonstrating @value{GDBN}'s overlay support.
7911 However, the @value{GDBN} source distribution does contain an overlaid
7912 program, with linker scripts for a few systems, as part of its test
7913 suite. The program consists of the following files from
7914 @file{gdb/testsuite/gdb.base}:
7918 The main program file.
7920 A simple overlay manager, used by @file{overlays.c}.
7925 Overlay modules, loaded and used by @file{overlays.c}.
7928 Linker scripts for linking the test program on the @code{d10v-elf}
7929 and @code{m32r-elf} targets.
7932 You can build the test program using the @code{d10v-elf} GCC
7933 cross-compiler like this:
7936 $ d10v-elf-gcc -g -c overlays.c
7937 $ d10v-elf-gcc -g -c ovlymgr.c
7938 $ d10v-elf-gcc -g -c foo.c
7939 $ d10v-elf-gcc -g -c bar.c
7940 $ d10v-elf-gcc -g -c baz.c
7941 $ d10v-elf-gcc -g -c grbx.c
7942 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
7943 baz.o grbx.o -Wl,-Td10v.ld -o overlays
7946 The build process is identical for any other architecture, except that
7947 you must substitute the appropriate compiler and linker script for the
7948 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
7952 @chapter Using @value{GDBN} with Different Languages
7955 Although programming languages generally have common aspects, they are
7956 rarely expressed in the same manner. For instance, in ANSI C,
7957 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
7958 Modula-2, it is accomplished by @code{p^}. Values can also be
7959 represented (and displayed) differently. Hex numbers in C appear as
7960 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
7962 @cindex working language
7963 Language-specific information is built into @value{GDBN} for some languages,
7964 allowing you to express operations like the above in your program's
7965 native language, and allowing @value{GDBN} to output values in a manner
7966 consistent with the syntax of your program's native language. The
7967 language you use to build expressions is called the @dfn{working
7971 * Setting:: Switching between source languages
7972 * Show:: Displaying the language
7973 * Checks:: Type and range checks
7974 * Supported languages:: Supported languages
7975 * Unsupported languages:: Unsupported languages
7979 @section Switching between source languages
7981 There are two ways to control the working language---either have @value{GDBN}
7982 set it automatically, or select it manually yourself. You can use the
7983 @code{set language} command for either purpose. On startup, @value{GDBN}
7984 defaults to setting the language automatically. The working language is
7985 used to determine how expressions you type are interpreted, how values
7988 In addition to the working language, every source file that
7989 @value{GDBN} knows about has its own working language. For some object
7990 file formats, the compiler might indicate which language a particular
7991 source file is in. However, most of the time @value{GDBN} infers the
7992 language from the name of the file. The language of a source file
7993 controls whether C@t{++} names are demangled---this way @code{backtrace} can
7994 show each frame appropriately for its own language. There is no way to
7995 set the language of a source file from within @value{GDBN}, but you can
7996 set the language associated with a filename extension. @xref{Show, ,
7997 Displaying the language}.
7999 This is most commonly a problem when you use a program, such
8000 as @code{cfront} or @code{f2c}, that generates C but is written in
8001 another language. In that case, make the
8002 program use @code{#line} directives in its C output; that way
8003 @value{GDBN} will know the correct language of the source code of the original
8004 program, and will display that source code, not the generated C code.
8007 * Filenames:: Filename extensions and languages.
8008 * Manually:: Setting the working language manually
8009 * Automatically:: Having @value{GDBN} infer the source language
8013 @subsection List of filename extensions and languages
8015 If a source file name ends in one of the following extensions, then
8016 @value{GDBN} infers that its language is the one indicated.
8037 Objective-C source file
8044 Modula-2 source file
8048 Assembler source file. This actually behaves almost like C, but
8049 @value{GDBN} does not skip over function prologues when stepping.
8052 In addition, you may set the language associated with a filename
8053 extension. @xref{Show, , Displaying the language}.
8056 @subsection Setting the working language
8058 If you allow @value{GDBN} to set the language automatically,
8059 expressions are interpreted the same way in your debugging session and
8062 @kindex set language
8063 If you wish, you may set the language manually. To do this, issue the
8064 command @samp{set language @var{lang}}, where @var{lang} is the name of
8066 @code{c} or @code{modula-2}.
8067 For a list of the supported languages, type @samp{set language}.
8069 Setting the language manually prevents @value{GDBN} from updating the working
8070 language automatically. This can lead to confusion if you try
8071 to debug a program when the working language is not the same as the
8072 source language, when an expression is acceptable to both
8073 languages---but means different things. For instance, if the current
8074 source file were written in C, and @value{GDBN} was parsing Modula-2, a
8082 might not have the effect you intended. In C, this means to add
8083 @code{b} and @code{c} and place the result in @code{a}. The result
8084 printed would be the value of @code{a}. In Modula-2, this means to compare
8085 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
8088 @subsection Having @value{GDBN} infer the source language
8090 To have @value{GDBN} set the working language automatically, use
8091 @samp{set language local} or @samp{set language auto}. @value{GDBN}
8092 then infers the working language. That is, when your program stops in a
8093 frame (usually by encountering a breakpoint), @value{GDBN} sets the
8094 working language to the language recorded for the function in that
8095 frame. If the language for a frame is unknown (that is, if the function
8096 or block corresponding to the frame was defined in a source file that
8097 does not have a recognized extension), the current working language is
8098 not changed, and @value{GDBN} issues a warning.
8100 This may not seem necessary for most programs, which are written
8101 entirely in one source language. However, program modules and libraries
8102 written in one source language can be used by a main program written in
8103 a different source language. Using @samp{set language auto} in this
8104 case frees you from having to set the working language manually.
8107 @section Displaying the language
8109 The following commands help you find out which language is the
8110 working language, and also what language source files were written in.
8114 @kindex show language
8115 Display the current working language. This is the
8116 language you can use with commands such as @code{print} to
8117 build and compute expressions that may involve variables in your program.
8120 @kindex info frame@r{, show the source language}
8121 Display the source language for this frame. This language becomes the
8122 working language if you use an identifier from this frame.
8123 @xref{Frame Info, ,Information about a frame}, to identify the other
8124 information listed here.
8127 @kindex info source@r{, show the source language}
8128 Display the source language of this source file.
8129 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
8130 information listed here.
8133 In unusual circumstances, you may have source files with extensions
8134 not in the standard list. You can then set the extension associated
8135 with a language explicitly:
8138 @item set extension-language @var{ext} @var{language}
8139 @kindex set extension-language
8140 Tell @value{GDBN} that source files with extension @var{ext} are to be
8141 assumed as written in the source language @var{language}.
8143 @item info extensions
8144 @kindex info extensions
8145 List all the filename extensions and the associated languages.
8149 @section Type and range checking
8152 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
8153 checking are included, but they do not yet have any effect. This
8154 section documents the intended facilities.
8156 @c FIXME remove warning when type/range code added
8158 Some languages are designed to guard you against making seemingly common
8159 errors through a series of compile- and run-time checks. These include
8160 checking the type of arguments to functions and operators, and making
8161 sure mathematical overflows are caught at run time. Checks such as
8162 these help to ensure a program's correctness once it has been compiled
8163 by eliminating type mismatches, and providing active checks for range
8164 errors when your program is running.
8166 @value{GDBN} can check for conditions like the above if you wish.
8167 Although @value{GDBN} does not check the statements in your program,
8168 it can check expressions entered directly into @value{GDBN} for
8169 evaluation via the @code{print} command, for example. As with the
8170 working language, @value{GDBN} can also decide whether or not to check
8171 automatically based on your program's source language.
8172 @xref{Supported languages, ,Supported languages}, for the default
8173 settings of supported languages.
8176 * Type Checking:: An overview of type checking
8177 * Range Checking:: An overview of range checking
8180 @cindex type checking
8181 @cindex checks, type
8183 @subsection An overview of type checking
8185 Some languages, such as Modula-2, are strongly typed, meaning that the
8186 arguments to operators and functions have to be of the correct type,
8187 otherwise an error occurs. These checks prevent type mismatch
8188 errors from ever causing any run-time problems. For example,
8196 The second example fails because the @code{CARDINAL} 1 is not
8197 type-compatible with the @code{REAL} 2.3.
8199 For the expressions you use in @value{GDBN} commands, you can tell the
8200 @value{GDBN} type checker to skip checking;
8201 to treat any mismatches as errors and abandon the expression;
8202 or to only issue warnings when type mismatches occur,
8203 but evaluate the expression anyway. When you choose the last of
8204 these, @value{GDBN} evaluates expressions like the second example above, but
8205 also issues a warning.
8207 Even if you turn type checking off, there may be other reasons
8208 related to type that prevent @value{GDBN} from evaluating an expression.
8209 For instance, @value{GDBN} does not know how to add an @code{int} and
8210 a @code{struct foo}. These particular type errors have nothing to do
8211 with the language in use, and usually arise from expressions, such as
8212 the one described above, which make little sense to evaluate anyway.
8214 Each language defines to what degree it is strict about type. For
8215 instance, both Modula-2 and C require the arguments to arithmetical
8216 operators to be numbers. In C, enumerated types and pointers can be
8217 represented as numbers, so that they are valid arguments to mathematical
8218 operators. @xref{Supported languages, ,Supported languages}, for further
8219 details on specific languages.
8221 @value{GDBN} provides some additional commands for controlling the type checker:
8223 @kindex set check type
8224 @kindex show check type
8226 @item set check type auto
8227 Set type checking on or off based on the current working language.
8228 @xref{Supported languages, ,Supported languages}, for the default settings for
8231 @item set check type on
8232 @itemx set check type off
8233 Set type checking on or off, overriding the default setting for the
8234 current working language. Issue a warning if the setting does not
8235 match the language default. If any type mismatches occur in
8236 evaluating an expression while type checking is on, @value{GDBN} prints a
8237 message and aborts evaluation of the expression.
8239 @item set check type warn
8240 Cause the type checker to issue warnings, but to always attempt to
8241 evaluate the expression. Evaluating the expression may still
8242 be impossible for other reasons. For example, @value{GDBN} cannot add
8243 numbers and structures.
8246 Show the current setting of the type checker, and whether or not @value{GDBN}
8247 is setting it automatically.
8250 @cindex range checking
8251 @cindex checks, range
8252 @node Range Checking
8253 @subsection An overview of range checking
8255 In some languages (such as Modula-2), it is an error to exceed the
8256 bounds of a type; this is enforced with run-time checks. Such range
8257 checking is meant to ensure program correctness by making sure
8258 computations do not overflow, or indices on an array element access do
8259 not exceed the bounds of the array.
8261 For expressions you use in @value{GDBN} commands, you can tell
8262 @value{GDBN} to treat range errors in one of three ways: ignore them,
8263 always treat them as errors and abandon the expression, or issue
8264 warnings but evaluate the expression anyway.
8266 A range error can result from numerical overflow, from exceeding an
8267 array index bound, or when you type a constant that is not a member
8268 of any type. Some languages, however, do not treat overflows as an
8269 error. In many implementations of C, mathematical overflow causes the
8270 result to ``wrap around'' to lower values---for example, if @var{m} is
8271 the largest integer value, and @var{s} is the smallest, then
8274 @var{m} + 1 @result{} @var{s}
8277 This, too, is specific to individual languages, and in some cases
8278 specific to individual compilers or machines. @xref{Supported languages, ,
8279 Supported languages}, for further details on specific languages.
8281 @value{GDBN} provides some additional commands for controlling the range checker:
8283 @kindex set check range
8284 @kindex show check range
8286 @item set check range auto
8287 Set range checking on or off based on the current working language.
8288 @xref{Supported languages, ,Supported languages}, for the default settings for
8291 @item set check range on
8292 @itemx set check range off
8293 Set range checking on or off, overriding the default setting for the
8294 current working language. A warning is issued if the setting does not
8295 match the language default. If a range error occurs and range checking is on,
8296 then a message is printed and evaluation of the expression is aborted.
8298 @item set check range warn
8299 Output messages when the @value{GDBN} range checker detects a range error,
8300 but attempt to evaluate the expression anyway. Evaluating the
8301 expression may still be impossible for other reasons, such as accessing
8302 memory that the process does not own (a typical example from many Unix
8306 Show the current setting of the range checker, and whether or not it is
8307 being set automatically by @value{GDBN}.
8310 @node Supported languages
8311 @section Supported languages
8313 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
8314 assembly, Modula-2, and Ada.
8315 @c This is false ...
8316 Some @value{GDBN} features may be used in expressions regardless of the
8317 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
8318 and the @samp{@{type@}addr} construct (@pxref{Expressions,
8319 ,Expressions}) can be used with the constructs of any supported
8322 The following sections detail to what degree each source language is
8323 supported by @value{GDBN}. These sections are not meant to be language
8324 tutorials or references, but serve only as a reference guide to what the
8325 @value{GDBN} expression parser accepts, and what input and output
8326 formats should look like for different languages. There are many good
8327 books written on each of these languages; please look to these for a
8328 language reference or tutorial.
8332 * Objective-C:: Objective-C
8335 * Modula-2:: Modula-2
8340 @subsection C and C@t{++}
8342 @cindex C and C@t{++}
8343 @cindex expressions in C or C@t{++}
8345 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
8346 to both languages. Whenever this is the case, we discuss those languages
8350 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
8351 @cindex @sc{gnu} C@t{++}
8352 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
8353 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
8354 effectively, you must compile your C@t{++} programs with a supported
8355 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
8356 compiler (@code{aCC}).
8358 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
8359 format; if it doesn't work on your system, try the stabs+ debugging
8360 format. You can select those formats explicitly with the @code{g++}
8361 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
8362 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
8363 CC, gcc.info, Using @sc{gnu} CC}.
8366 * C Operators:: C and C@t{++} operators
8367 * C Constants:: C and C@t{++} constants
8368 * C plus plus expressions:: C@t{++} expressions
8369 * C Defaults:: Default settings for C and C@t{++}
8370 * C Checks:: C and C@t{++} type and range checks
8371 * Debugging C:: @value{GDBN} and C
8372 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
8376 @subsubsection C and C@t{++} operators
8378 @cindex C and C@t{++} operators
8380 Operators must be defined on values of specific types. For instance,
8381 @code{+} is defined on numbers, but not on structures. Operators are
8382 often defined on groups of types.
8384 For the purposes of C and C@t{++}, the following definitions hold:
8389 @emph{Integral types} include @code{int} with any of its storage-class
8390 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
8393 @emph{Floating-point types} include @code{float}, @code{double}, and
8394 @code{long double} (if supported by the target platform).
8397 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
8400 @emph{Scalar types} include all of the above.
8405 The following operators are supported. They are listed here
8406 in order of increasing precedence:
8410 The comma or sequencing operator. Expressions in a comma-separated list
8411 are evaluated from left to right, with the result of the entire
8412 expression being the last expression evaluated.
8415 Assignment. The value of an assignment expression is the value
8416 assigned. Defined on scalar types.
8419 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
8420 and translated to @w{@code{@var{a} = @var{a op b}}}.
8421 @w{@code{@var{op}=}} and @code{=} have the same precedence.
8422 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
8423 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
8426 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
8427 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
8431 Logical @sc{or}. Defined on integral types.
8434 Logical @sc{and}. Defined on integral types.
8437 Bitwise @sc{or}. Defined on integral types.
8440 Bitwise exclusive-@sc{or}. Defined on integral types.
8443 Bitwise @sc{and}. Defined on integral types.
8446 Equality and inequality. Defined on scalar types. The value of these
8447 expressions is 0 for false and non-zero for true.
8449 @item <@r{, }>@r{, }<=@r{, }>=
8450 Less than, greater than, less than or equal, greater than or equal.
8451 Defined on scalar types. The value of these expressions is 0 for false
8452 and non-zero for true.
8455 left shift, and right shift. Defined on integral types.
8458 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8461 Addition and subtraction. Defined on integral types, floating-point types and
8464 @item *@r{, }/@r{, }%
8465 Multiplication, division, and modulus. Multiplication and division are
8466 defined on integral and floating-point types. Modulus is defined on
8470 Increment and decrement. When appearing before a variable, the
8471 operation is performed before the variable is used in an expression;
8472 when appearing after it, the variable's value is used before the
8473 operation takes place.
8476 Pointer dereferencing. Defined on pointer types. Same precedence as
8480 Address operator. Defined on variables. Same precedence as @code{++}.
8482 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
8483 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
8484 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
8485 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
8489 Negative. Defined on integral and floating-point types. Same
8490 precedence as @code{++}.
8493 Logical negation. Defined on integral types. Same precedence as
8497 Bitwise complement operator. Defined on integral types. Same precedence as
8502 Structure member, and pointer-to-structure member. For convenience,
8503 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
8504 pointer based on the stored type information.
8505 Defined on @code{struct} and @code{union} data.
8508 Dereferences of pointers to members.
8511 Array indexing. @code{@var{a}[@var{i}]} is defined as
8512 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
8515 Function parameter list. Same precedence as @code{->}.
8518 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
8519 and @code{class} types.
8522 Doubled colons also represent the @value{GDBN} scope operator
8523 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
8527 If an operator is redefined in the user code, @value{GDBN} usually
8528 attempts to invoke the redefined version instead of using the operator's
8536 @subsubsection C and C@t{++} constants
8538 @cindex C and C@t{++} constants
8540 @value{GDBN} allows you to express the constants of C and C@t{++} in the
8545 Integer constants are a sequence of digits. Octal constants are
8546 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
8547 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
8548 @samp{l}, specifying that the constant should be treated as a
8552 Floating point constants are a sequence of digits, followed by a decimal
8553 point, followed by a sequence of digits, and optionally followed by an
8554 exponent. An exponent is of the form:
8555 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8556 sequence of digits. The @samp{+} is optional for positive exponents.
8557 A floating-point constant may also end with a letter @samp{f} or
8558 @samp{F}, specifying that the constant should be treated as being of
8559 the @code{float} (as opposed to the default @code{double}) type; or with
8560 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8564 Enumerated constants consist of enumerated identifiers, or their
8565 integral equivalents.
8568 Character constants are a single character surrounded by single quotes
8569 (@code{'}), or a number---the ordinal value of the corresponding character
8570 (usually its @sc{ascii} value). Within quotes, the single character may
8571 be represented by a letter or by @dfn{escape sequences}, which are of
8572 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8573 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8574 @samp{@var{x}} is a predefined special character---for example,
8575 @samp{\n} for newline.
8578 String constants are a sequence of character constants surrounded by
8579 double quotes (@code{"}). Any valid character constant (as described
8580 above) may appear. Double quotes within the string must be preceded by
8581 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8585 Pointer constants are an integral value. You can also write pointers
8586 to constants using the C operator @samp{&}.
8589 Array constants are comma-separated lists surrounded by braces @samp{@{}
8590 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8591 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8592 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8596 * C plus plus expressions::
8603 @node C plus plus expressions
8604 @subsubsection C@t{++} expressions
8606 @cindex expressions in C@t{++}
8607 @value{GDBN} expression handling can interpret most C@t{++} expressions.
8609 @cindex debugging C@t{++} programs
8610 @cindex C@t{++} compilers
8611 @cindex debug formats and C@t{++}
8612 @cindex @value{NGCC} and C@t{++}
8614 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
8615 proper compiler and the proper debug format. Currently, @value{GDBN}
8616 works best when debugging C@t{++} code that is compiled with
8617 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
8618 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
8619 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
8620 stabs+ as their default debug format, so you usually don't need to
8621 specify a debug format explicitly. Other compilers and/or debug formats
8622 are likely to work badly or not at all when using @value{GDBN} to debug
8628 @cindex member functions
8630 Member function calls are allowed; you can use expressions like
8633 count = aml->GetOriginal(x, y)
8636 @vindex this@r{, inside C@t{++} member functions}
8637 @cindex namespace in C@t{++}
8639 While a member function is active (in the selected stack frame), your
8640 expressions have the same namespace available as the member function;
8641 that is, @value{GDBN} allows implicit references to the class instance
8642 pointer @code{this} following the same rules as C@t{++}.
8644 @cindex call overloaded functions
8645 @cindex overloaded functions, calling
8646 @cindex type conversions in C@t{++}
8648 You can call overloaded functions; @value{GDBN} resolves the function
8649 call to the right definition, with some restrictions. @value{GDBN} does not
8650 perform overload resolution involving user-defined type conversions,
8651 calls to constructors, or instantiations of templates that do not exist
8652 in the program. It also cannot handle ellipsis argument lists or
8655 It does perform integral conversions and promotions, floating-point
8656 promotions, arithmetic conversions, pointer conversions, conversions of
8657 class objects to base classes, and standard conversions such as those of
8658 functions or arrays to pointers; it requires an exact match on the
8659 number of function arguments.
8661 Overload resolution is always performed, unless you have specified
8662 @code{set overload-resolution off}. @xref{Debugging C plus plus,
8663 ,@value{GDBN} features for C@t{++}}.
8665 You must specify @code{set overload-resolution off} in order to use an
8666 explicit function signature to call an overloaded function, as in
8668 p 'foo(char,int)'('x', 13)
8671 The @value{GDBN} command-completion facility can simplify this;
8672 see @ref{Completion, ,Command completion}.
8674 @cindex reference declarations
8676 @value{GDBN} understands variables declared as C@t{++} references; you can use
8677 them in expressions just as you do in C@t{++} source---they are automatically
8680 In the parameter list shown when @value{GDBN} displays a frame, the values of
8681 reference variables are not displayed (unlike other variables); this
8682 avoids clutter, since references are often used for large structures.
8683 The @emph{address} of a reference variable is always shown, unless
8684 you have specified @samp{set print address off}.
8687 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
8688 expressions can use it just as expressions in your program do. Since
8689 one scope may be defined in another, you can use @code{::} repeatedly if
8690 necessary, for example in an expression like
8691 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
8692 resolving name scope by reference to source files, in both C and C@t{++}
8693 debugging (@pxref{Variables, ,Program variables}).
8696 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
8697 calling virtual functions correctly, printing out virtual bases of
8698 objects, calling functions in a base subobject, casting objects, and
8699 invoking user-defined operators.
8702 @subsubsection C and C@t{++} defaults
8704 @cindex C and C@t{++} defaults
8706 If you allow @value{GDBN} to set type and range checking automatically, they
8707 both default to @code{off} whenever the working language changes to
8708 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
8709 selects the working language.
8711 If you allow @value{GDBN} to set the language automatically, it
8712 recognizes source files whose names end with @file{.c}, @file{.C}, or
8713 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
8714 these files, it sets the working language to C or C@t{++}.
8715 @xref{Automatically, ,Having @value{GDBN} infer the source language},
8716 for further details.
8718 @c Type checking is (a) primarily motivated by Modula-2, and (b)
8719 @c unimplemented. If (b) changes, it might make sense to let this node
8720 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
8723 @subsubsection C and C@t{++} type and range checks
8725 @cindex C and C@t{++} checks
8727 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
8728 is not used. However, if you turn type checking on, @value{GDBN}
8729 considers two variables type equivalent if:
8733 The two variables are structured and have the same structure, union, or
8737 The two variables have the same type name, or types that have been
8738 declared equivalent through @code{typedef}.
8741 @c leaving this out because neither J Gilmore nor R Pesch understand it.
8744 The two @code{struct}, @code{union}, or @code{enum} variables are
8745 declared in the same declaration. (Note: this may not be true for all C
8750 Range checking, if turned on, is done on mathematical operations. Array
8751 indices are not checked, since they are often used to index a pointer
8752 that is not itself an array.
8755 @subsubsection @value{GDBN} and C
8757 The @code{set print union} and @code{show print union} commands apply to
8758 the @code{union} type. When set to @samp{on}, any @code{union} that is
8759 inside a @code{struct} or @code{class} is also printed. Otherwise, it
8760 appears as @samp{@{...@}}.
8762 The @code{@@} operator aids in the debugging of dynamic arrays, formed
8763 with pointers and a memory allocation function. @xref{Expressions,
8767 * Debugging C plus plus::
8770 @node Debugging C plus plus
8771 @subsubsection @value{GDBN} features for C@t{++}
8773 @cindex commands for C@t{++}
8775 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
8776 designed specifically for use with C@t{++}. Here is a summary:
8779 @cindex break in overloaded functions
8780 @item @r{breakpoint menus}
8781 When you want a breakpoint in a function whose name is overloaded,
8782 @value{GDBN} breakpoint menus help you specify which function definition
8783 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
8785 @cindex overloading in C@t{++}
8786 @item rbreak @var{regex}
8787 Setting breakpoints using regular expressions is helpful for setting
8788 breakpoints on overloaded functions that are not members of any special
8790 @xref{Set Breaks, ,Setting breakpoints}.
8792 @cindex C@t{++} exception handling
8795 Debug C@t{++} exception handling using these commands. @xref{Set
8796 Catchpoints, , Setting catchpoints}.
8799 @item ptype @var{typename}
8800 Print inheritance relationships as well as other information for type
8802 @xref{Symbols, ,Examining the Symbol Table}.
8804 @cindex C@t{++} symbol display
8805 @item set print demangle
8806 @itemx show print demangle
8807 @itemx set print asm-demangle
8808 @itemx show print asm-demangle
8809 Control whether C@t{++} symbols display in their source form, both when
8810 displaying code as C@t{++} source and when displaying disassemblies.
8811 @xref{Print Settings, ,Print settings}.
8813 @item set print object
8814 @itemx show print object
8815 Choose whether to print derived (actual) or declared types of objects.
8816 @xref{Print Settings, ,Print settings}.
8818 @item set print vtbl
8819 @itemx show print vtbl
8820 Control the format for printing virtual function tables.
8821 @xref{Print Settings, ,Print settings}.
8822 (The @code{vtbl} commands do not work on programs compiled with the HP
8823 ANSI C@t{++} compiler (@code{aCC}).)
8825 @kindex set overload-resolution
8826 @cindex overloaded functions, overload resolution
8827 @item set overload-resolution on
8828 Enable overload resolution for C@t{++} expression evaluation. The default
8829 is on. For overloaded functions, @value{GDBN} evaluates the arguments
8830 and searches for a function whose signature matches the argument types,
8831 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
8832 expressions}, for details). If it cannot find a match, it emits a
8835 @item set overload-resolution off
8836 Disable overload resolution for C@t{++} expression evaluation. For
8837 overloaded functions that are not class member functions, @value{GDBN}
8838 chooses the first function of the specified name that it finds in the
8839 symbol table, whether or not its arguments are of the correct type. For
8840 overloaded functions that are class member functions, @value{GDBN}
8841 searches for a function whose signature @emph{exactly} matches the
8844 @kindex show overload-resolution
8845 @item show overload-resolution
8846 Show the current setting of overload resolution.
8848 @item @r{Overloaded symbol names}
8849 You can specify a particular definition of an overloaded symbol, using
8850 the same notation that is used to declare such symbols in C@t{++}: type
8851 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
8852 also use the @value{GDBN} command-line word completion facilities to list the
8853 available choices, or to finish the type list for you.
8854 @xref{Completion,, Command completion}, for details on how to do this.
8858 @subsection Objective-C
8861 This section provides information about some commands and command
8862 options that are useful for debugging Objective-C code. See also
8863 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
8864 few more commands specific to Objective-C support.
8867 * Method Names in Commands::
8868 * The Print Command with Objective-C::
8871 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
8872 @subsubsection Method Names in Commands
8874 The following commands have been extended to accept Objective-C method
8875 names as line specifications:
8877 @kindex clear@r{, and Objective-C}
8878 @kindex break@r{, and Objective-C}
8879 @kindex info line@r{, and Objective-C}
8880 @kindex jump@r{, and Objective-C}
8881 @kindex list@r{, and Objective-C}
8885 @item @code{info line}
8890 A fully qualified Objective-C method name is specified as
8893 -[@var{Class} @var{methodName}]
8896 where the minus sign is used to indicate an instance method and a
8897 plus sign (not shown) is used to indicate a class method. The class
8898 name @var{Class} and method name @var{methodName} are enclosed in
8899 brackets, similar to the way messages are specified in Objective-C
8900 source code. For example, to set a breakpoint at the @code{create}
8901 instance method of class @code{Fruit} in the program currently being
8905 break -[Fruit create]
8908 To list ten program lines around the @code{initialize} class method,
8912 list +[NSText initialize]
8915 In the current version of @value{GDBN}, the plus or minus sign is
8916 required. In future versions of @value{GDBN}, the plus or minus
8917 sign will be optional, but you can use it to narrow the search. It
8918 is also possible to specify just a method name:
8924 You must specify the complete method name, including any colons. If
8925 your program's source files contain more than one @code{create} method,
8926 you'll be presented with a numbered list of classes that implement that
8927 method. Indicate your choice by number, or type @samp{0} to exit if
8930 As another example, to clear a breakpoint established at the
8931 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
8934 clear -[NSWindow makeKeyAndOrderFront:]
8937 @node The Print Command with Objective-C
8938 @subsubsection The Print Command With Objective-C
8939 @cindex Objective-C, print objects
8940 @kindex print-object
8941 @kindex po @r{(@code{print-object})}
8943 The print command has also been extended to accept methods. For example:
8946 print -[@var{object} hash]
8949 @cindex print an Objective-C object description
8950 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
8952 will tell @value{GDBN} to send the @code{hash} message to @var{object}
8953 and print the result. Also, an additional command has been added,
8954 @code{print-object} or @code{po} for short, which is meant to print
8955 the description of an object. However, this command may only work
8956 with certain Objective-C libraries that have a particular hook
8957 function, @code{_NSPrintForDebugger}, defined.
8961 @cindex Fortran-specific support in @value{GDBN}
8964 @cindex @code{COMMON} blocks, Fortran
8966 @item info common @r{[}@var{common-name}@r{]}
8967 This command prints the values contained in the Fortran @code{COMMON}
8968 block whose name is @var{common-name}. With no argument, the names of
8969 all @code{COMMON} blocks visible at current program location are
8973 Fortran symbols are usually case-insensitive, so @value{GDBN} by
8974 default uses case-insensitive matches for Fortran symbols. You can
8975 change that with the @samp{set case-insensitive} command, see
8976 @ref{Symbols}, for the details.
8981 @cindex Pascal support in @value{GDBN}, limitations
8982 Debugging Pascal programs which use sets, subranges, file variables, or
8983 nested functions does not currently work. @value{GDBN} does not support
8984 entering expressions, printing values, or similar features using Pascal
8987 The Pascal-specific command @code{set print pascal_static-members}
8988 controls whether static members of Pascal objects are displayed.
8989 @xref{Print Settings, pascal_static-members}.
8992 @subsection Modula-2
8994 @cindex Modula-2, @value{GDBN} support
8996 The extensions made to @value{GDBN} to support Modula-2 only support
8997 output from the @sc{gnu} Modula-2 compiler (which is currently being
8998 developed). Other Modula-2 compilers are not currently supported, and
8999 attempting to debug executables produced by them is most likely
9000 to give an error as @value{GDBN} reads in the executable's symbol
9003 @cindex expressions in Modula-2
9005 * M2 Operators:: Built-in operators
9006 * Built-In Func/Proc:: Built-in functions and procedures
9007 * M2 Constants:: Modula-2 constants
9008 * M2 Defaults:: Default settings for Modula-2
9009 * Deviations:: Deviations from standard Modula-2
9010 * M2 Checks:: Modula-2 type and range checks
9011 * M2 Scope:: The scope operators @code{::} and @code{.}
9012 * GDB/M2:: @value{GDBN} and Modula-2
9016 @subsubsection Operators
9017 @cindex Modula-2 operators
9019 Operators must be defined on values of specific types. For instance,
9020 @code{+} is defined on numbers, but not on structures. Operators are
9021 often defined on groups of types. For the purposes of Modula-2, the
9022 following definitions hold:
9027 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
9031 @emph{Character types} consist of @code{CHAR} and its subranges.
9034 @emph{Floating-point types} consist of @code{REAL}.
9037 @emph{Pointer types} consist of anything declared as @code{POINTER TO
9041 @emph{Scalar types} consist of all of the above.
9044 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
9047 @emph{Boolean types} consist of @code{BOOLEAN}.
9051 The following operators are supported, and appear in order of
9052 increasing precedence:
9056 Function argument or array index separator.
9059 Assignment. The value of @var{var} @code{:=} @var{value} is
9063 Less than, greater than on integral, floating-point, or enumerated
9067 Less than or equal to, greater than or equal to
9068 on integral, floating-point and enumerated types, or set inclusion on
9069 set types. Same precedence as @code{<}.
9071 @item =@r{, }<>@r{, }#
9072 Equality and two ways of expressing inequality, valid on scalar types.
9073 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
9074 available for inequality, since @code{#} conflicts with the script
9078 Set membership. Defined on set types and the types of their members.
9079 Same precedence as @code{<}.
9082 Boolean disjunction. Defined on boolean types.
9085 Boolean conjunction. Defined on boolean types.
9088 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9091 Addition and subtraction on integral and floating-point types, or union
9092 and difference on set types.
9095 Multiplication on integral and floating-point types, or set intersection
9099 Division on floating-point types, or symmetric set difference on set
9100 types. Same precedence as @code{*}.
9103 Integer division and remainder. Defined on integral types. Same
9104 precedence as @code{*}.
9107 Negative. Defined on @code{INTEGER} and @code{REAL} data.
9110 Pointer dereferencing. Defined on pointer types.
9113 Boolean negation. Defined on boolean types. Same precedence as
9117 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
9118 precedence as @code{^}.
9121 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
9124 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
9128 @value{GDBN} and Modula-2 scope operators.
9132 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
9133 treats the use of the operator @code{IN}, or the use of operators
9134 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
9135 @code{<=}, and @code{>=} on sets as an error.
9139 @node Built-In Func/Proc
9140 @subsubsection Built-in functions and procedures
9141 @cindex Modula-2 built-ins
9143 Modula-2 also makes available several built-in procedures and functions.
9144 In describing these, the following metavariables are used:
9149 represents an @code{ARRAY} variable.
9152 represents a @code{CHAR} constant or variable.
9155 represents a variable or constant of integral type.
9158 represents an identifier that belongs to a set. Generally used in the
9159 same function with the metavariable @var{s}. The type of @var{s} should
9160 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
9163 represents a variable or constant of integral or floating-point type.
9166 represents a variable or constant of floating-point type.
9172 represents a variable.
9175 represents a variable or constant of one of many types. See the
9176 explanation of the function for details.
9179 All Modula-2 built-in procedures also return a result, described below.
9183 Returns the absolute value of @var{n}.
9186 If @var{c} is a lower case letter, it returns its upper case
9187 equivalent, otherwise it returns its argument.
9190 Returns the character whose ordinal value is @var{i}.
9193 Decrements the value in the variable @var{v} by one. Returns the new value.
9195 @item DEC(@var{v},@var{i})
9196 Decrements the value in the variable @var{v} by @var{i}. Returns the
9199 @item EXCL(@var{m},@var{s})
9200 Removes the element @var{m} from the set @var{s}. Returns the new
9203 @item FLOAT(@var{i})
9204 Returns the floating point equivalent of the integer @var{i}.
9207 Returns the index of the last member of @var{a}.
9210 Increments the value in the variable @var{v} by one. Returns the new value.
9212 @item INC(@var{v},@var{i})
9213 Increments the value in the variable @var{v} by @var{i}. Returns the
9216 @item INCL(@var{m},@var{s})
9217 Adds the element @var{m} to the set @var{s} if it is not already
9218 there. Returns the new set.
9221 Returns the maximum value of the type @var{t}.
9224 Returns the minimum value of the type @var{t}.
9227 Returns boolean TRUE if @var{i} is an odd number.
9230 Returns the ordinal value of its argument. For example, the ordinal
9231 value of a character is its @sc{ascii} value (on machines supporting the
9232 @sc{ascii} character set). @var{x} must be of an ordered type, which include
9233 integral, character and enumerated types.
9236 Returns the size of its argument. @var{x} can be a variable or a type.
9238 @item TRUNC(@var{r})
9239 Returns the integral part of @var{r}.
9241 @item VAL(@var{t},@var{i})
9242 Returns the member of the type @var{t} whose ordinal value is @var{i}.
9246 @emph{Warning:} Sets and their operations are not yet supported, so
9247 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
9251 @cindex Modula-2 constants
9253 @subsubsection Constants
9255 @value{GDBN} allows you to express the constants of Modula-2 in the following
9261 Integer constants are simply a sequence of digits. When used in an
9262 expression, a constant is interpreted to be type-compatible with the
9263 rest of the expression. Hexadecimal integers are specified by a
9264 trailing @samp{H}, and octal integers by a trailing @samp{B}.
9267 Floating point constants appear as a sequence of digits, followed by a
9268 decimal point and another sequence of digits. An optional exponent can
9269 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
9270 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
9271 digits of the floating point constant must be valid decimal (base 10)
9275 Character constants consist of a single character enclosed by a pair of
9276 like quotes, either single (@code{'}) or double (@code{"}). They may
9277 also be expressed by their ordinal value (their @sc{ascii} value, usually)
9278 followed by a @samp{C}.
9281 String constants consist of a sequence of characters enclosed by a
9282 pair of like quotes, either single (@code{'}) or double (@code{"}).
9283 Escape sequences in the style of C are also allowed. @xref{C
9284 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
9288 Enumerated constants consist of an enumerated identifier.
9291 Boolean constants consist of the identifiers @code{TRUE} and
9295 Pointer constants consist of integral values only.
9298 Set constants are not yet supported.
9302 @subsubsection Modula-2 defaults
9303 @cindex Modula-2 defaults
9305 If type and range checking are set automatically by @value{GDBN}, they
9306 both default to @code{on} whenever the working language changes to
9307 Modula-2. This happens regardless of whether you or @value{GDBN}
9308 selected the working language.
9310 If you allow @value{GDBN} to set the language automatically, then entering
9311 code compiled from a file whose name ends with @file{.mod} sets the
9312 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
9313 the language automatically}, for further details.
9316 @subsubsection Deviations from standard Modula-2
9317 @cindex Modula-2, deviations from
9319 A few changes have been made to make Modula-2 programs easier to debug.
9320 This is done primarily via loosening its type strictness:
9324 Unlike in standard Modula-2, pointer constants can be formed by
9325 integers. This allows you to modify pointer variables during
9326 debugging. (In standard Modula-2, the actual address contained in a
9327 pointer variable is hidden from you; it can only be modified
9328 through direct assignment to another pointer variable or expression that
9329 returned a pointer.)
9332 C escape sequences can be used in strings and characters to represent
9333 non-printable characters. @value{GDBN} prints out strings with these
9334 escape sequences embedded. Single non-printable characters are
9335 printed using the @samp{CHR(@var{nnn})} format.
9338 The assignment operator (@code{:=}) returns the value of its right-hand
9342 All built-in procedures both modify @emph{and} return their argument.
9346 @subsubsection Modula-2 type and range checks
9347 @cindex Modula-2 checks
9350 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
9353 @c FIXME remove warning when type/range checks added
9355 @value{GDBN} considers two Modula-2 variables type equivalent if:
9359 They are of types that have been declared equivalent via a @code{TYPE
9360 @var{t1} = @var{t2}} statement
9363 They have been declared on the same line. (Note: This is true of the
9364 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
9367 As long as type checking is enabled, any attempt to combine variables
9368 whose types are not equivalent is an error.
9370 Range checking is done on all mathematical operations, assignment, array
9371 index bounds, and all built-in functions and procedures.
9374 @subsubsection The scope operators @code{::} and @code{.}
9376 @cindex @code{.}, Modula-2 scope operator
9377 @cindex colon, doubled as scope operator
9379 @vindex colon-colon@r{, in Modula-2}
9380 @c Info cannot handle :: but TeX can.
9383 @vindex ::@r{, in Modula-2}
9386 There are a few subtle differences between the Modula-2 scope operator
9387 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
9392 @var{module} . @var{id}
9393 @var{scope} :: @var{id}
9397 where @var{scope} is the name of a module or a procedure,
9398 @var{module} the name of a module, and @var{id} is any declared
9399 identifier within your program, except another module.
9401 Using the @code{::} operator makes @value{GDBN} search the scope
9402 specified by @var{scope} for the identifier @var{id}. If it is not
9403 found in the specified scope, then @value{GDBN} searches all scopes
9404 enclosing the one specified by @var{scope}.
9406 Using the @code{.} operator makes @value{GDBN} search the current scope for
9407 the identifier specified by @var{id} that was imported from the
9408 definition module specified by @var{module}. With this operator, it is
9409 an error if the identifier @var{id} was not imported from definition
9410 module @var{module}, or if @var{id} is not an identifier in
9414 @subsubsection @value{GDBN} and Modula-2
9416 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
9417 Five subcommands of @code{set print} and @code{show print} apply
9418 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
9419 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
9420 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
9421 analogue in Modula-2.
9423 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
9424 with any language, is not useful with Modula-2. Its
9425 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
9426 created in Modula-2 as they can in C or C@t{++}. However, because an
9427 address can be specified by an integral constant, the construct
9428 @samp{@{@var{type}@}@var{adrexp}} is still useful.
9430 @cindex @code{#} in Modula-2
9431 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
9432 interpreted as the beginning of a comment. Use @code{<>} instead.
9438 The extensions made to @value{GDBN} for Ada only support
9439 output from the @sc{gnu} Ada (GNAT) compiler.
9440 Other Ada compilers are not currently supported, and
9441 attempting to debug executables produced by them is most likely
9445 @cindex expressions in Ada
9447 * Ada Mode Intro:: General remarks on the Ada syntax
9448 and semantics supported by Ada mode
9450 * Omissions from Ada:: Restrictions on the Ada expression syntax.
9451 * Additions to Ada:: Extensions of the Ada expression syntax.
9452 * Stopping Before Main Program:: Debugging the program during elaboration.
9453 * Ada Glitches:: Known peculiarities of Ada mode.
9456 @node Ada Mode Intro
9457 @subsubsection Introduction
9458 @cindex Ada mode, general
9460 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
9461 syntax, with some extensions.
9462 The philosophy behind the design of this subset is
9466 That @value{GDBN} should provide basic literals and access to operations for
9467 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
9468 leaving more sophisticated computations to subprograms written into the
9469 program (which therefore may be called from @value{GDBN}).
9472 That type safety and strict adherence to Ada language restrictions
9473 are not particularly important to the @value{GDBN} user.
9476 That brevity is important to the @value{GDBN} user.
9479 Thus, for brevity, the debugger acts as if there were
9480 implicit @code{with} and @code{use} clauses in effect for all user-written
9481 packages, making it unnecessary to fully qualify most names with
9482 their packages, regardless of context. Where this causes ambiguity,
9483 @value{GDBN} asks the user's intent.
9485 The debugger will start in Ada mode if it detects an Ada main program.
9486 As for other languages, it will enter Ada mode when stopped in a program that
9487 was translated from an Ada source file.
9489 While in Ada mode, you may use `@t{--}' for comments. This is useful
9490 mostly for documenting command files. The standard @value{GDBN} comment
9491 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
9492 middle (to allow based literals).
9494 The debugger supports limited overloading. Given a subprogram call in which
9495 the function symbol has multiple definitions, it will use the number of
9496 actual parameters and some information about their types to attempt to narrow
9497 the set of definitions. It also makes very limited use of context, preferring
9498 procedures to functions in the context of the @code{call} command, and
9499 functions to procedures elsewhere.
9501 @node Omissions from Ada
9502 @subsubsection Omissions from Ada
9503 @cindex Ada, omissions from
9505 Here are the notable omissions from the subset:
9509 Only a subset of the attributes are supported:
9513 @t{'First}, @t{'Last}, and @t{'Length}
9514 on array objects (not on types and subtypes).
9517 @t{'Min} and @t{'Max}.
9520 @t{'Pos} and @t{'Val}.
9526 @t{'Range} on array objects (not subtypes), but only as the right
9527 operand of the membership (@code{in}) operator.
9530 @t{'Access}, @t{'Unchecked_Access}, and
9531 @t{'Unrestricted_Access} (a GNAT extension).
9539 @code{Characters.Latin_1} are not available and
9540 concatenation is not implemented. Thus, escape characters in strings are
9541 not currently available.
9544 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
9545 equality of representations. They will generally work correctly
9546 for strings and arrays whose elements have integer or enumeration types.
9547 They may not work correctly for arrays whose element
9548 types have user-defined equality, for arrays of real values
9549 (in particular, IEEE-conformant floating point, because of negative
9550 zeroes and NaNs), and for arrays whose elements contain unused bits with
9551 indeterminate values.
9554 The other component-by-component array operations (@code{and}, @code{or},
9555 @code{xor}, @code{not}, and relational tests other than equality)
9556 are not implemented.
9559 There are no record or array aggregates.
9562 Calls to dispatching subprograms are not implemented.
9565 The overloading algorithm is much more limited (i.e., less selective)
9566 than that of real Ada. It makes only limited use of the context in which a subexpression
9567 appears to resolve its meaning, and it is much looser in its rules for allowing
9568 type matches. As a result, some function calls will be ambiguous, and the user
9569 will be asked to choose the proper resolution.
9572 The @code{new} operator is not implemented.
9575 Entry calls are not implemented.
9578 Aside from printing, arithmetic operations on the native VAX floating-point
9579 formats are not supported.
9582 It is not possible to slice a packed array.
9585 @node Additions to Ada
9586 @subsubsection Additions to Ada
9587 @cindex Ada, deviations from
9589 As it does for other languages, @value{GDBN} makes certain generic
9590 extensions to Ada (@pxref{Expressions}):
9594 If the expression @var{E} is a variable residing in memory
9595 (typically a local variable or array element) and @var{N} is
9596 a positive integer, then @code{@var{E}@@@var{N}} displays the values of
9597 @var{E} and the @var{N}-1 adjacent variables following it in memory as an array.
9598 In Ada, this operator is generally not necessary, since its prime use
9599 is in displaying parts of an array, and slicing will usually do this in Ada.
9600 However, there are occasional uses when debugging programs
9601 in which certain debugging information has been optimized away.
9604 @code{@var{B}::@var{var}} means ``the variable named @var{var} that appears
9605 in function or file @var{B}.'' When @var{B} is a file name, you must typically
9606 surround it in single quotes.
9609 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
9610 @var{type} that appears at address @var{addr}.''
9613 A name starting with @samp{$} is a convenience variable
9614 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
9617 In addition, @value{GDBN} provides a few other shortcuts and outright additions specific
9622 The assignment statement is allowed as an expression, returning
9623 its right-hand operand as its value. Thus, you may enter
9627 print A(tmp := y + 1)
9631 The semicolon is allowed as an ``operator,'' returning as its value
9632 the value of its right-hand operand.
9633 This allows, for example,
9634 complex conditional breaks:
9638 condition 1 (report(i); k += 1; A(k) > 100)
9642 Rather than use catenation and symbolic character names to introduce special
9643 characters into strings, one may instead use a special bracket notation,
9644 which is also used to print strings. A sequence of characters of the form
9645 @samp{["@var{XX}"]} within a string or character literal denotes the
9646 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
9647 sequence of characters @samp{["""]} also denotes a single quotation mark
9648 in strings. For example,
9650 "One line.["0a"]Next line.["0a"]"
9653 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF}) after each
9657 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
9658 @t{'Max} is optional (and is ignored in any case). For example, it is valid
9666 When printing arrays, @value{GDBN} uses positional notation when the
9667 array has a lower bound of 1, and uses a modified named notation otherwise.
9668 For example, a one-dimensional array of three integers with a lower bound of 3 might print as
9675 That is, in contrast to valid Ada, only the first component has a @code{=>}
9679 You may abbreviate attributes in expressions with any unique,
9680 multi-character subsequence of
9681 their names (an exact match gets preference).
9682 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
9683 in place of @t{a'length}.
9686 @cindex quoting Ada internal identifiers
9687 Since Ada is case-insensitive, the debugger normally maps identifiers you type
9688 to lower case. The GNAT compiler uses upper-case characters for
9689 some of its internal identifiers, which are normally of no interest to users.
9690 For the rare occasions when you actually have to look at them,
9691 enclose them in angle brackets to avoid the lower-case mapping.
9694 @value{GDBP} print <JMPBUF_SAVE>[0]
9698 Printing an object of class-wide type or dereferencing an
9699 access-to-class-wide value will display all the components of the object's
9700 specific type (as indicated by its run-time tag). Likewise, component
9701 selection on such a value will operate on the specific type of the
9706 @node Stopping Before Main Program
9707 @subsubsection Stopping at the Very Beginning
9709 @cindex breakpointing Ada elaboration code
9710 It is sometimes necessary to debug the program during elaboration, and
9711 before reaching the main procedure.
9712 As defined in the Ada Reference
9713 Manual, the elaboration code is invoked from a procedure called
9714 @code{adainit}. To run your program up to the beginning of
9715 elaboration, simply use the following two commands:
9716 @code{tbreak adainit} and @code{run}.
9719 @subsubsection Known Peculiarities of Ada Mode
9720 @cindex Ada, problems
9722 Besides the omissions listed previously (@pxref{Omissions from Ada}),
9723 we know of several problems with and limitations of Ada mode in
9725 some of which will be fixed with planned future releases of the debugger
9726 and the GNU Ada compiler.
9730 Currently, the debugger
9731 has insufficient information to determine whether certain pointers represent
9732 pointers to objects or the objects themselves.
9733 Thus, the user may have to tack an extra @code{.all} after an expression
9734 to get it printed properly.
9737 Static constants that the compiler chooses not to materialize as objects in
9738 storage are invisible to the debugger.
9741 Named parameter associations in function argument lists are ignored (the
9742 argument lists are treated as positional).
9745 Many useful library packages are currently invisible to the debugger.
9748 Fixed-point arithmetic, conversions, input, and output is carried out using
9749 floating-point arithmetic, and may give results that only approximate those on
9753 The type of the @t{'Address} attribute may not be @code{System.Address}.
9756 The GNAT compiler never generates the prefix @code{Standard} for any of
9757 the standard symbols defined by the Ada language. @value{GDBN} knows about
9758 this: it will strip the prefix from names when you use it, and will never
9759 look for a name you have so qualified among local symbols, nor match against
9760 symbols in other packages or subprograms. If you have
9761 defined entities anywhere in your program other than parameters and
9762 local variables whose simple names match names in @code{Standard},
9763 GNAT's lack of qualification here can cause confusion. When this happens,
9764 you can usually resolve the confusion
9765 by qualifying the problematic names with package
9766 @code{Standard} explicitly.
9769 @node Unsupported languages
9770 @section Unsupported languages
9772 @cindex unsupported languages
9773 @cindex minimal language
9774 In addition to the other fully-supported programming languages,
9775 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
9776 It does not represent a real programming language, but provides a set
9777 of capabilities close to what the C or assembly languages provide.
9778 This should allow most simple operations to be performed while debugging
9779 an application that uses a language currently not supported by @value{GDBN}.
9781 If the language is set to @code{auto}, @value{GDBN} will automatically
9782 select this language if the current frame corresponds to an unsupported
9786 @chapter Examining the Symbol Table
9788 The commands described in this chapter allow you to inquire about the
9789 symbols (names of variables, functions and types) defined in your
9790 program. This information is inherent in the text of your program and
9791 does not change as your program executes. @value{GDBN} finds it in your
9792 program's symbol table, in the file indicated when you started @value{GDBN}
9793 (@pxref{File Options, ,Choosing files}), or by one of the
9794 file-management commands (@pxref{Files, ,Commands to specify files}).
9796 @cindex symbol names
9797 @cindex names of symbols
9798 @cindex quoting names
9799 Occasionally, you may need to refer to symbols that contain unusual
9800 characters, which @value{GDBN} ordinarily treats as word delimiters. The
9801 most frequent case is in referring to static variables in other
9802 source files (@pxref{Variables,,Program variables}). File names
9803 are recorded in object files as debugging symbols, but @value{GDBN} would
9804 ordinarily parse a typical file name, like @file{foo.c}, as the three words
9805 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
9806 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
9813 looks up the value of @code{x} in the scope of the file @file{foo.c}.
9816 @cindex case-insensitive symbol names
9817 @cindex case sensitivity in symbol names
9818 @kindex set case-sensitive
9819 @item set case-sensitive on
9820 @itemx set case-sensitive off
9821 @itemx set case-sensitive auto
9822 Normally, when @value{GDBN} looks up symbols, it matches their names
9823 with case sensitivity determined by the current source language.
9824 Occasionally, you may wish to control that. The command @code{set
9825 case-sensitive} lets you do that by specifying @code{on} for
9826 case-sensitive matches or @code{off} for case-insensitive ones. If
9827 you specify @code{auto}, case sensitivity is reset to the default
9828 suitable for the source language. The default is case-sensitive
9829 matches for all languages except for Fortran, for which the default is
9830 case-insensitive matches.
9832 @kindex show case-sensitive
9833 @item show case-sensitive
9834 This command shows the current setting of case sensitivity for symbols
9837 @kindex info address
9838 @cindex address of a symbol
9839 @item info address @var{symbol}
9840 Describe where the data for @var{symbol} is stored. For a register
9841 variable, this says which register it is kept in. For a non-register
9842 local variable, this prints the stack-frame offset at which the variable
9845 Note the contrast with @samp{print &@var{symbol}}, which does not work
9846 at all for a register variable, and for a stack local variable prints
9847 the exact address of the current instantiation of the variable.
9850 @cindex symbol from address
9851 @cindex closest symbol and offset for an address
9852 @item info symbol @var{addr}
9853 Print the name of a symbol which is stored at the address @var{addr}.
9854 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
9855 nearest symbol and an offset from it:
9858 (@value{GDBP}) info symbol 0x54320
9859 _initialize_vx + 396 in section .text
9863 This is the opposite of the @code{info address} command. You can use
9864 it to find out the name of a variable or a function given its address.
9867 @item whatis @var{expr}
9868 Print the data type of expression @var{expr}. @var{expr} is not
9869 actually evaluated, and any side-effecting operations (such as
9870 assignments or function calls) inside it do not take place.
9871 @xref{Expressions, ,Expressions}.
9874 Print the data type of @code{$}, the last value in the value history.
9877 @item ptype @var{typename}
9878 Print a description of data type @var{typename}. @var{typename} may be
9879 the name of a type, or for C code it may have the form @samp{class
9880 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
9881 @var{union-tag}} or @samp{enum @var{enum-tag}}.
9883 @item ptype @var{expr}
9885 Print a description of the type of expression @var{expr}. @code{ptype}
9886 differs from @code{whatis} by printing a detailed description, instead
9887 of just the name of the type.
9889 For example, for this variable declaration:
9892 struct complex @{double real; double imag;@} v;
9896 the two commands give this output:
9900 (@value{GDBP}) whatis v
9901 type = struct complex
9902 (@value{GDBP}) ptype v
9903 type = struct complex @{
9911 As with @code{whatis}, using @code{ptype} without an argument refers to
9912 the type of @code{$}, the last value in the value history.
9915 @item info types @var{regexp}
9917 Print a brief description of all types whose names match the regular
9918 expression @var{regexp} (or all types in your program, if you supply
9919 no argument). Each complete typename is matched as though it were a
9920 complete line; thus, @samp{i type value} gives information on all
9921 types in your program whose names include the string @code{value}, but
9922 @samp{i type ^value$} gives information only on types whose complete
9923 name is @code{value}.
9925 This command differs from @code{ptype} in two ways: first, like
9926 @code{whatis}, it does not print a detailed description; second, it
9927 lists all source files where a type is defined.
9930 @cindex local variables
9931 @item info scope @var{location}
9932 List all the variables local to a particular scope. This command
9933 accepts a @var{location} argument---a function name, a source line, or
9934 an address preceded by a @samp{*}, and prints all the variables local
9935 to the scope defined by that location. For example:
9938 (@value{GDBP}) @b{info scope command_line_handler}
9939 Scope for command_line_handler:
9940 Symbol rl is an argument at stack/frame offset 8, length 4.
9941 Symbol linebuffer is in static storage at address 0x150a18, length 4.
9942 Symbol linelength is in static storage at address 0x150a1c, length 4.
9943 Symbol p is a local variable in register $esi, length 4.
9944 Symbol p1 is a local variable in register $ebx, length 4.
9945 Symbol nline is a local variable in register $edx, length 4.
9946 Symbol repeat is a local variable at frame offset -8, length 4.
9950 This command is especially useful for determining what data to collect
9951 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
9956 Show information about the current source file---that is, the source file for
9957 the function containing the current point of execution:
9960 the name of the source file, and the directory containing it,
9962 the directory it was compiled in,
9964 its length, in lines,
9966 which programming language it is written in,
9968 whether the executable includes debugging information for that file, and
9969 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
9971 whether the debugging information includes information about
9972 preprocessor macros.
9976 @kindex info sources
9978 Print the names of all source files in your program for which there is
9979 debugging information, organized into two lists: files whose symbols
9980 have already been read, and files whose symbols will be read when needed.
9982 @kindex info functions
9983 @item info functions
9984 Print the names and data types of all defined functions.
9986 @item info functions @var{regexp}
9987 Print the names and data types of all defined functions
9988 whose names contain a match for regular expression @var{regexp}.
9989 Thus, @samp{info fun step} finds all functions whose names
9990 include @code{step}; @samp{info fun ^step} finds those whose names
9991 start with @code{step}. If a function name contains characters
9992 that conflict with the regular expression language (eg.
9993 @samp{operator*()}), they may be quoted with a backslash.
9995 @kindex info variables
9996 @item info variables
9997 Print the names and data types of all variables that are declared
9998 outside of functions (i.e.@: excluding local variables).
10000 @item info variables @var{regexp}
10001 Print the names and data types of all variables (except for local
10002 variables) whose names contain a match for regular expression
10005 @kindex info classes
10006 @cindex Objective-C, classes and selectors
10008 @itemx info classes @var{regexp}
10009 Display all Objective-C classes in your program, or
10010 (with the @var{regexp} argument) all those matching a particular regular
10013 @kindex info selectors
10014 @item info selectors
10015 @itemx info selectors @var{regexp}
10016 Display all Objective-C selectors in your program, or
10017 (with the @var{regexp} argument) all those matching a particular regular
10021 This was never implemented.
10022 @kindex info methods
10024 @itemx info methods @var{regexp}
10025 The @code{info methods} command permits the user to examine all defined
10026 methods within C@t{++} program, or (with the @var{regexp} argument) a
10027 specific set of methods found in the various C@t{++} classes. Many
10028 C@t{++} classes provide a large number of methods. Thus, the output
10029 from the @code{ptype} command can be overwhelming and hard to use. The
10030 @code{info-methods} command filters the methods, printing only those
10031 which match the regular-expression @var{regexp}.
10034 @cindex reloading symbols
10035 Some systems allow individual object files that make up your program to
10036 be replaced without stopping and restarting your program. For example,
10037 in VxWorks you can simply recompile a defective object file and keep on
10038 running. If you are running on one of these systems, you can allow
10039 @value{GDBN} to reload the symbols for automatically relinked modules:
10042 @kindex set symbol-reloading
10043 @item set symbol-reloading on
10044 Replace symbol definitions for the corresponding source file when an
10045 object file with a particular name is seen again.
10047 @item set symbol-reloading off
10048 Do not replace symbol definitions when encountering object files of the
10049 same name more than once. This is the default state; if you are not
10050 running on a system that permits automatic relinking of modules, you
10051 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
10052 may discard symbols when linking large programs, that may contain
10053 several modules (from different directories or libraries) with the same
10056 @kindex show symbol-reloading
10057 @item show symbol-reloading
10058 Show the current @code{on} or @code{off} setting.
10061 @cindex opaque data types
10062 @kindex set opaque-type-resolution
10063 @item set opaque-type-resolution on
10064 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
10065 declared as a pointer to a @code{struct}, @code{class}, or
10066 @code{union}---for example, @code{struct MyType *}---that is used in one
10067 source file although the full declaration of @code{struct MyType} is in
10068 another source file. The default is on.
10070 A change in the setting of this subcommand will not take effect until
10071 the next time symbols for a file are loaded.
10073 @item set opaque-type-resolution off
10074 Tell @value{GDBN} not to resolve opaque types. In this case, the type
10075 is printed as follows:
10077 @{<no data fields>@}
10080 @kindex show opaque-type-resolution
10081 @item show opaque-type-resolution
10082 Show whether opaque types are resolved or not.
10084 @kindex maint print symbols
10085 @cindex symbol dump
10086 @kindex maint print psymbols
10087 @cindex partial symbol dump
10088 @item maint print symbols @var{filename}
10089 @itemx maint print psymbols @var{filename}
10090 @itemx maint print msymbols @var{filename}
10091 Write a dump of debugging symbol data into the file @var{filename}.
10092 These commands are used to debug the @value{GDBN} symbol-reading code. Only
10093 symbols with debugging data are included. If you use @samp{maint print
10094 symbols}, @value{GDBN} includes all the symbols for which it has already
10095 collected full details: that is, @var{filename} reflects symbols for
10096 only those files whose symbols @value{GDBN} has read. You can use the
10097 command @code{info sources} to find out which files these are. If you
10098 use @samp{maint print psymbols} instead, the dump shows information about
10099 symbols that @value{GDBN} only knows partially---that is, symbols defined in
10100 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
10101 @samp{maint print msymbols} dumps just the minimal symbol information
10102 required for each object file from which @value{GDBN} has read some symbols.
10103 @xref{Files, ,Commands to specify files}, for a discussion of how
10104 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
10106 @kindex maint info symtabs
10107 @kindex maint info psymtabs
10108 @cindex listing @value{GDBN}'s internal symbol tables
10109 @cindex symbol tables, listing @value{GDBN}'s internal
10110 @cindex full symbol tables, listing @value{GDBN}'s internal
10111 @cindex partial symbol tables, listing @value{GDBN}'s internal
10112 @item maint info symtabs @r{[} @var{regexp} @r{]}
10113 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
10115 List the @code{struct symtab} or @code{struct partial_symtab}
10116 structures whose names match @var{regexp}. If @var{regexp} is not
10117 given, list them all. The output includes expressions which you can
10118 copy into a @value{GDBN} debugging this one to examine a particular
10119 structure in more detail. For example:
10122 (@value{GDBP}) maint info psymtabs dwarf2read
10123 @{ objfile /home/gnu/build/gdb/gdb
10124 ((struct objfile *) 0x82e69d0)
10125 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
10126 ((struct partial_symtab *) 0x8474b10)
10129 text addresses 0x814d3c8 -- 0x8158074
10130 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
10131 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
10132 dependencies (none)
10135 (@value{GDBP}) maint info symtabs
10139 We see that there is one partial symbol table whose filename contains
10140 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
10141 and we see that @value{GDBN} has not read in any symtabs yet at all.
10142 If we set a breakpoint on a function, that will cause @value{GDBN} to
10143 read the symtab for the compilation unit containing that function:
10146 (@value{GDBP}) break dwarf2_psymtab_to_symtab
10147 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
10149 (@value{GDBP}) maint info symtabs
10150 @{ objfile /home/gnu/build/gdb/gdb
10151 ((struct objfile *) 0x82e69d0)
10152 @{ symtab /home/gnu/src/gdb/dwarf2read.c
10153 ((struct symtab *) 0x86c1f38)
10156 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
10157 debugformat DWARF 2
10166 @chapter Altering Execution
10168 Once you think you have found an error in your program, you might want to
10169 find out for certain whether correcting the apparent error would lead to
10170 correct results in the rest of the run. You can find the answer by
10171 experiment, using the @value{GDBN} features for altering execution of the
10174 For example, you can store new values into variables or memory
10175 locations, give your program a signal, restart it at a different
10176 address, or even return prematurely from a function.
10179 * Assignment:: Assignment to variables
10180 * Jumping:: Continuing at a different address
10181 * Signaling:: Giving your program a signal
10182 * Returning:: Returning from a function
10183 * Calling:: Calling your program's functions
10184 * Patching:: Patching your program
10188 @section Assignment to variables
10191 @cindex setting variables
10192 To alter the value of a variable, evaluate an assignment expression.
10193 @xref{Expressions, ,Expressions}. For example,
10200 stores the value 4 into the variable @code{x}, and then prints the
10201 value of the assignment expression (which is 4).
10202 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
10203 information on operators in supported languages.
10205 @kindex set variable
10206 @cindex variables, setting
10207 If you are not interested in seeing the value of the assignment, use the
10208 @code{set} command instead of the @code{print} command. @code{set} is
10209 really the same as @code{print} except that the expression's value is
10210 not printed and is not put in the value history (@pxref{Value History,
10211 ,Value history}). The expression is evaluated only for its effects.
10213 If the beginning of the argument string of the @code{set} command
10214 appears identical to a @code{set} subcommand, use the @code{set
10215 variable} command instead of just @code{set}. This command is identical
10216 to @code{set} except for its lack of subcommands. For example, if your
10217 program has a variable @code{width}, you get an error if you try to set
10218 a new value with just @samp{set width=13}, because @value{GDBN} has the
10219 command @code{set width}:
10222 (@value{GDBP}) whatis width
10224 (@value{GDBP}) p width
10226 (@value{GDBP}) set width=47
10227 Invalid syntax in expression.
10231 The invalid expression, of course, is @samp{=47}. In
10232 order to actually set the program's variable @code{width}, use
10235 (@value{GDBP}) set var width=47
10238 Because the @code{set} command has many subcommands that can conflict
10239 with the names of program variables, it is a good idea to use the
10240 @code{set variable} command instead of just @code{set}. For example, if
10241 your program has a variable @code{g}, you run into problems if you try
10242 to set a new value with just @samp{set g=4}, because @value{GDBN} has
10243 the command @code{set gnutarget}, abbreviated @code{set g}:
10247 (@value{GDBP}) whatis g
10251 (@value{GDBP}) set g=4
10255 The program being debugged has been started already.
10256 Start it from the beginning? (y or n) y
10257 Starting program: /home/smith/cc_progs/a.out
10258 "/home/smith/cc_progs/a.out": can't open to read symbols:
10259 Invalid bfd target.
10260 (@value{GDBP}) show g
10261 The current BFD target is "=4".
10266 The program variable @code{g} did not change, and you silently set the
10267 @code{gnutarget} to an invalid value. In order to set the variable
10271 (@value{GDBP}) set var g=4
10274 @value{GDBN} allows more implicit conversions in assignments than C; you can
10275 freely store an integer value into a pointer variable or vice versa,
10276 and you can convert any structure to any other structure that is the
10277 same length or shorter.
10278 @comment FIXME: how do structs align/pad in these conversions?
10279 @comment /doc@cygnus.com 18dec1990
10281 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
10282 construct to generate a value of specified type at a specified address
10283 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
10284 to memory location @code{0x83040} as an integer (which implies a certain size
10285 and representation in memory), and
10288 set @{int@}0x83040 = 4
10292 stores the value 4 into that memory location.
10295 @section Continuing at a different address
10297 Ordinarily, when you continue your program, you do so at the place where
10298 it stopped, with the @code{continue} command. You can instead continue at
10299 an address of your own choosing, with the following commands:
10303 @item jump @var{linespec}
10304 Resume execution at line @var{linespec}. Execution stops again
10305 immediately if there is a breakpoint there. @xref{List, ,Printing
10306 source lines}, for a description of the different forms of
10307 @var{linespec}. It is common practice to use the @code{tbreak} command
10308 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
10311 The @code{jump} command does not change the current stack frame, or
10312 the stack pointer, or the contents of any memory location or any
10313 register other than the program counter. If line @var{linespec} is in
10314 a different function from the one currently executing, the results may
10315 be bizarre if the two functions expect different patterns of arguments or
10316 of local variables. For this reason, the @code{jump} command requests
10317 confirmation if the specified line is not in the function currently
10318 executing. However, even bizarre results are predictable if you are
10319 well acquainted with the machine-language code of your program.
10321 @item jump *@var{address}
10322 Resume execution at the instruction at address @var{address}.
10325 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
10326 On many systems, you can get much the same effect as the @code{jump}
10327 command by storing a new value into the register @code{$pc}. The
10328 difference is that this does not start your program running; it only
10329 changes the address of where it @emph{will} run when you continue. For
10337 makes the next @code{continue} command or stepping command execute at
10338 address @code{0x485}, rather than at the address where your program stopped.
10339 @xref{Continuing and Stepping, ,Continuing and stepping}.
10341 The most common occasion to use the @code{jump} command is to back
10342 up---perhaps with more breakpoints set---over a portion of a program
10343 that has already executed, in order to examine its execution in more
10348 @section Giving your program a signal
10349 @cindex deliver a signal to a program
10353 @item signal @var{signal}
10354 Resume execution where your program stopped, but immediately give it the
10355 signal @var{signal}. @var{signal} can be the name or the number of a
10356 signal. For example, on many systems @code{signal 2} and @code{signal
10357 SIGINT} are both ways of sending an interrupt signal.
10359 Alternatively, if @var{signal} is zero, continue execution without
10360 giving a signal. This is useful when your program stopped on account of
10361 a signal and would ordinary see the signal when resumed with the
10362 @code{continue} command; @samp{signal 0} causes it to resume without a
10365 @code{signal} does not repeat when you press @key{RET} a second time
10366 after executing the command.
10370 Invoking the @code{signal} command is not the same as invoking the
10371 @code{kill} utility from the shell. Sending a signal with @code{kill}
10372 causes @value{GDBN} to decide what to do with the signal depending on
10373 the signal handling tables (@pxref{Signals}). The @code{signal} command
10374 passes the signal directly to your program.
10378 @section Returning from a function
10381 @cindex returning from a function
10384 @itemx return @var{expression}
10385 You can cancel execution of a function call with the @code{return}
10386 command. If you give an
10387 @var{expression} argument, its value is used as the function's return
10391 When you use @code{return}, @value{GDBN} discards the selected stack frame
10392 (and all frames within it). You can think of this as making the
10393 discarded frame return prematurely. If you wish to specify a value to
10394 be returned, give that value as the argument to @code{return}.
10396 This pops the selected stack frame (@pxref{Selection, ,Selecting a
10397 frame}), and any other frames inside of it, leaving its caller as the
10398 innermost remaining frame. That frame becomes selected. The
10399 specified value is stored in the registers used for returning values
10402 The @code{return} command does not resume execution; it leaves the
10403 program stopped in the state that would exist if the function had just
10404 returned. In contrast, the @code{finish} command (@pxref{Continuing
10405 and Stepping, ,Continuing and stepping}) resumes execution until the
10406 selected stack frame returns naturally.
10409 @section Calling program functions
10412 @cindex calling functions
10413 @cindex inferior functions, calling
10414 @item print @var{expr}
10415 Evaluate the expression @var{expr} and display the resuling value.
10416 @var{expr} may include calls to functions in the program being
10420 @item call @var{expr}
10421 Evaluate the expression @var{expr} without displaying @code{void}
10424 You can use this variant of the @code{print} command if you want to
10425 execute a function from your program that does not return anything
10426 (a.k.a.@: @dfn{a void function}), but without cluttering the output
10427 with @code{void} returned values that @value{GDBN} will otherwise
10428 print. If the result is not void, it is printed and saved in the
10432 It is possible for the function you call via the @code{print} or
10433 @code{call} command to generate a signal (e.g., if there's a bug in
10434 the function, or if you passed it incorrect arguments). What happens
10435 in that case is controlled by the @code{set unwindonsignal} command.
10438 @item set unwindonsignal
10439 @kindex set unwindonsignal
10440 @cindex unwind stack in called functions
10441 @cindex call dummy stack unwinding
10442 Set unwinding of the stack if a signal is received while in a function
10443 that @value{GDBN} called in the program being debugged. If set to on,
10444 @value{GDBN} unwinds the stack it created for the call and restores
10445 the context to what it was before the call. If set to off (the
10446 default), @value{GDBN} stops in the frame where the signal was
10449 @item show unwindonsignal
10450 @kindex show unwindonsignal
10451 Show the current setting of stack unwinding in the functions called by
10455 @cindex weak alias functions
10456 Sometimes, a function you wish to call is actually a @dfn{weak alias}
10457 for another function. In such case, @value{GDBN} might not pick up
10458 the type information, including the types of the function arguments,
10459 which causes @value{GDBN} to call the inferior function incorrectly.
10460 As a result, the called function will function erroneously and may
10461 even crash. A solution to that is to use the name of the aliased
10465 @section Patching programs
10467 @cindex patching binaries
10468 @cindex writing into executables
10469 @cindex writing into corefiles
10471 By default, @value{GDBN} opens the file containing your program's
10472 executable code (or the corefile) read-only. This prevents accidental
10473 alterations to machine code; but it also prevents you from intentionally
10474 patching your program's binary.
10476 If you'd like to be able to patch the binary, you can specify that
10477 explicitly with the @code{set write} command. For example, you might
10478 want to turn on internal debugging flags, or even to make emergency
10484 @itemx set write off
10485 If you specify @samp{set write on}, @value{GDBN} opens executable and
10486 core files for both reading and writing; if you specify @samp{set write
10487 off} (the default), @value{GDBN} opens them read-only.
10489 If you have already loaded a file, you must load it again (using the
10490 @code{exec-file} or @code{core-file} command) after changing @code{set
10491 write}, for your new setting to take effect.
10495 Display whether executable files and core files are opened for writing
10496 as well as reading.
10500 @chapter @value{GDBN} Files
10502 @value{GDBN} needs to know the file name of the program to be debugged,
10503 both in order to read its symbol table and in order to start your
10504 program. To debug a core dump of a previous run, you must also tell
10505 @value{GDBN} the name of the core dump file.
10508 * Files:: Commands to specify files
10509 * Separate Debug Files:: Debugging information in separate files
10510 * Symbol Errors:: Errors reading symbol files
10514 @section Commands to specify files
10516 @cindex symbol table
10517 @cindex core dump file
10519 You may want to specify executable and core dump file names. The usual
10520 way to do this is at start-up time, using the arguments to
10521 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
10522 Out of @value{GDBN}}).
10524 Occasionally it is necessary to change to a different file during a
10525 @value{GDBN} session. Or you may run @value{GDBN} and forget to specify
10526 a file you want to use. In these situations the @value{GDBN} commands
10527 to specify new files are useful.
10530 @cindex executable file
10532 @item file @var{filename}
10533 Use @var{filename} as the program to be debugged. It is read for its
10534 symbols and for the contents of pure memory. It is also the program
10535 executed when you use the @code{run} command. If you do not specify a
10536 directory and the file is not found in the @value{GDBN} working directory,
10537 @value{GDBN} uses the environment variable @code{PATH} as a list of
10538 directories to search, just as the shell does when looking for a program
10539 to run. You can change the value of this variable, for both @value{GDBN}
10540 and your program, using the @code{path} command.
10542 On systems with memory-mapped files, an auxiliary file named
10543 @file{@var{filename}.syms} may hold symbol table information for
10544 @var{filename}. If so, @value{GDBN} maps in the symbol table from
10545 @file{@var{filename}.syms}, starting up more quickly. See the
10546 descriptions of the file options @samp{-mapped} and @samp{-readnow}
10547 (available on the command line, see @ref{File Options, , -readnow},
10548 and with the commands @code{file}, @code{symbol-file}, or
10549 @code{add-symbol-file}, described below), for more information.
10552 @code{file} with no argument makes @value{GDBN} discard any information it
10553 has on both executable file and the symbol table.
10556 @item exec-file @r{[} @var{filename} @r{]}
10557 Specify that the program to be run (but not the symbol table) is found
10558 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
10559 if necessary to locate your program. Omitting @var{filename} means to
10560 discard information on the executable file.
10562 @kindex symbol-file
10563 @item symbol-file @r{[} @var{filename} @r{]}
10564 Read symbol table information from file @var{filename}. @code{PATH} is
10565 searched when necessary. Use the @code{file} command to get both symbol
10566 table and program to run from the same file.
10568 @code{symbol-file} with no argument clears out @value{GDBN} information on your
10569 program's symbol table.
10571 The @code{symbol-file} command causes @value{GDBN} to forget the contents
10572 of its convenience variables, the value history, and all breakpoints and
10573 auto-display expressions. This is because they may contain pointers to
10574 the internal data recording symbols and data types, which are part of
10575 the old symbol table data being discarded inside @value{GDBN}.
10577 @code{symbol-file} does not repeat if you press @key{RET} again after
10580 When @value{GDBN} is configured for a particular environment, it
10581 understands debugging information in whatever format is the standard
10582 generated for that environment; you may use either a @sc{gnu} compiler, or
10583 other compilers that adhere to the local conventions.
10584 Best results are usually obtained from @sc{gnu} compilers; for example,
10585 using @code{@value{GCC}} you can generate debugging information for
10588 For most kinds of object files, with the exception of old SVR3 systems
10589 using COFF, the @code{symbol-file} command does not normally read the
10590 symbol table in full right away. Instead, it scans the symbol table
10591 quickly to find which source files and which symbols are present. The
10592 details are read later, one source file at a time, as they are needed.
10594 The purpose of this two-stage reading strategy is to make @value{GDBN}
10595 start up faster. For the most part, it is invisible except for
10596 occasional pauses while the symbol table details for a particular source
10597 file are being read. (The @code{set verbose} command can turn these
10598 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
10599 warnings and messages}.)
10601 We have not implemented the two-stage strategy for COFF yet. When the
10602 symbol table is stored in COFF format, @code{symbol-file} reads the
10603 symbol table data in full right away. Note that ``stabs-in-COFF''
10604 still does the two-stage strategy, since the debug info is actually
10608 @cindex reading symbols immediately
10609 @cindex symbols, reading immediately
10611 @cindex memory-mapped symbol file
10612 @cindex saving symbol table
10613 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10614 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10615 You can override the @value{GDBN} two-stage strategy for reading symbol
10616 tables by using the @samp{-readnow} option with any of the commands that
10617 load symbol table information, if you want to be sure @value{GDBN} has the
10618 entire symbol table available.
10620 If memory-mapped files are available on your system through the
10621 @code{mmap} system call, you can use another option, @samp{-mapped}, to
10622 cause @value{GDBN} to write the symbols for your program into a reusable
10623 file. Future @value{GDBN} debugging sessions map in symbol information
10624 from this auxiliary symbol file (if the program has not changed), rather
10625 than spending time reading the symbol table from the executable
10626 program. Using the @samp{-mapped} option has the same effect as
10627 starting @value{GDBN} with the @samp{-mapped} command-line option.
10629 You can use both options together, to make sure the auxiliary symbol
10630 file has all the symbol information for your program.
10632 The auxiliary symbol file for a program called @var{myprog} is called
10633 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
10634 than the corresponding executable), @value{GDBN} always attempts to use
10635 it when you debug @var{myprog}; no special options or commands are
10638 The @file{.syms} file is specific to the host machine where you run
10639 @value{GDBN}. It holds an exact image of the internal @value{GDBN}
10640 symbol table. It cannot be shared across multiple host platforms.
10642 @c FIXME: for now no mention of directories, since this seems to be in
10643 @c flux. 13mar1992 status is that in theory GDB would look either in
10644 @c current dir or in same dir as myprog; but issues like competing
10645 @c GDB's, or clutter in system dirs, mean that in practice right now
10646 @c only current dir is used. FFish says maybe a special GDB hierarchy
10647 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
10651 @item core-file @r{[}@var{filename}@r{]}
10653 Specify the whereabouts of a core dump file to be used as the ``contents
10654 of memory''. Traditionally, core files contain only some parts of the
10655 address space of the process that generated them; @value{GDBN} can access the
10656 executable file itself for other parts.
10658 @code{core-file} with no argument specifies that no core file is
10661 Note that the core file is ignored when your program is actually running
10662 under @value{GDBN}. So, if you have been running your program and you
10663 wish to debug a core file instead, you must kill the subprocess in which
10664 the program is running. To do this, use the @code{kill} command
10665 (@pxref{Kill Process, ,Killing the child process}).
10667 @kindex add-symbol-file
10668 @cindex dynamic linking
10669 @item add-symbol-file @var{filename} @var{address}
10670 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10671 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
10672 The @code{add-symbol-file} command reads additional symbol table
10673 information from the file @var{filename}. You would use this command
10674 when @var{filename} has been dynamically loaded (by some other means)
10675 into the program that is running. @var{address} should be the memory
10676 address at which the file has been loaded; @value{GDBN} cannot figure
10677 this out for itself. You can additionally specify an arbitrary number
10678 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
10679 section name and base address for that section. You can specify any
10680 @var{address} as an expression.
10682 The symbol table of the file @var{filename} is added to the symbol table
10683 originally read with the @code{symbol-file} command. You can use the
10684 @code{add-symbol-file} command any number of times; the new symbol data
10685 thus read keeps adding to the old. To discard all old symbol data
10686 instead, use the @code{symbol-file} command without any arguments.
10688 @cindex relocatable object files, reading symbols from
10689 @cindex object files, relocatable, reading symbols from
10690 @cindex reading symbols from relocatable object files
10691 @cindex symbols, reading from relocatable object files
10692 @cindex @file{.o} files, reading symbols from
10693 Although @var{filename} is typically a shared library file, an
10694 executable file, or some other object file which has been fully
10695 relocated for loading into a process, you can also load symbolic
10696 information from relocatable @file{.o} files, as long as:
10700 the file's symbolic information refers only to linker symbols defined in
10701 that file, not to symbols defined by other object files,
10703 every section the file's symbolic information refers to has actually
10704 been loaded into the inferior, as it appears in the file, and
10706 you can determine the address at which every section was loaded, and
10707 provide these to the @code{add-symbol-file} command.
10711 Some embedded operating systems, like Sun Chorus and VxWorks, can load
10712 relocatable files into an already running program; such systems
10713 typically make the requirements above easy to meet. However, it's
10714 important to recognize that many native systems use complex link
10715 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
10716 assembly, for example) that make the requirements difficult to meet. In
10717 general, one cannot assume that using @code{add-symbol-file} to read a
10718 relocatable object file's symbolic information will have the same effect
10719 as linking the relocatable object file into the program in the normal
10722 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
10724 You can use the @samp{-mapped} and @samp{-readnow} options just as with
10725 the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
10726 table information for @var{filename}.
10728 @kindex add-symbol-file-from-memory
10729 @cindex @code{syscall DSO}
10730 @cindex load symbols from memory
10731 @item add-symbol-file-from-memory @var{address}
10732 Load symbols from the given @var{address} in a dynamically loaded
10733 object file whose image is mapped directly into the inferior's memory.
10734 For example, the Linux kernel maps a @code{syscall DSO} into each
10735 process's address space; this DSO provides kernel-specific code for
10736 some system calls. The argument can be any expression whose
10737 evaluation yields the address of the file's shared object file header.
10738 For this command to work, you must have used @code{symbol-file} or
10739 @code{exec-file} commands in advance.
10741 @kindex add-shared-symbol-files
10743 @item add-shared-symbol-files @var{library-file}
10744 @itemx assf @var{library-file}
10745 The @code{add-shared-symbol-files} command can currently be used only
10746 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
10747 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
10748 @value{GDBN} automatically looks for shared libraries, however if
10749 @value{GDBN} does not find yours, you can invoke
10750 @code{add-shared-symbol-files}. It takes one argument: the shared
10751 library's file name. @code{assf} is a shorthand alias for
10752 @code{add-shared-symbol-files}.
10755 @item section @var{section} @var{addr}
10756 The @code{section} command changes the base address of the named
10757 @var{section} of the exec file to @var{addr}. This can be used if the
10758 exec file does not contain section addresses, (such as in the
10759 @code{a.out} format), or when the addresses specified in the file
10760 itself are wrong. Each section must be changed separately. The
10761 @code{info files} command, described below, lists all the sections and
10765 @kindex info target
10768 @code{info files} and @code{info target} are synonymous; both print the
10769 current target (@pxref{Targets, ,Specifying a Debugging Target}),
10770 including the names of the executable and core dump files currently in
10771 use by @value{GDBN}, and the files from which symbols were loaded. The
10772 command @code{help target} lists all possible targets rather than
10775 @kindex maint info sections
10776 @item maint info sections
10777 Another command that can give you extra information about program sections
10778 is @code{maint info sections}. In addition to the section information
10779 displayed by @code{info files}, this command displays the flags and file
10780 offset of each section in the executable and core dump files. In addition,
10781 @code{maint info sections} provides the following command options (which
10782 may be arbitrarily combined):
10786 Display sections for all loaded object files, including shared libraries.
10787 @item @var{sections}
10788 Display info only for named @var{sections}.
10789 @item @var{section-flags}
10790 Display info only for sections for which @var{section-flags} are true.
10791 The section flags that @value{GDBN} currently knows about are:
10794 Section will have space allocated in the process when loaded.
10795 Set for all sections except those containing debug information.
10797 Section will be loaded from the file into the child process memory.
10798 Set for pre-initialized code and data, clear for @code{.bss} sections.
10800 Section needs to be relocated before loading.
10802 Section cannot be modified by the child process.
10804 Section contains executable code only.
10806 Section contains data only (no executable code).
10808 Section will reside in ROM.
10810 Section contains data for constructor/destructor lists.
10812 Section is not empty.
10814 An instruction to the linker to not output the section.
10815 @item COFF_SHARED_LIBRARY
10816 A notification to the linker that the section contains
10817 COFF shared library information.
10819 Section contains common symbols.
10822 @kindex set trust-readonly-sections
10823 @cindex read-only sections
10824 @item set trust-readonly-sections on
10825 Tell @value{GDBN} that readonly sections in your object file
10826 really are read-only (i.e.@: that their contents will not change).
10827 In that case, @value{GDBN} can fetch values from these sections
10828 out of the object file, rather than from the target program.
10829 For some targets (notably embedded ones), this can be a significant
10830 enhancement to debugging performance.
10832 The default is off.
10834 @item set trust-readonly-sections off
10835 Tell @value{GDBN} not to trust readonly sections. This means that
10836 the contents of the section might change while the program is running,
10837 and must therefore be fetched from the target when needed.
10839 @item show trust-readonly-sections
10840 Show the current setting of trusting readonly sections.
10843 All file-specifying commands allow both absolute and relative file names
10844 as arguments. @value{GDBN} always converts the file name to an absolute file
10845 name and remembers it that way.
10847 @cindex shared libraries
10848 @value{GDBN} supports GNU/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
10849 and IBM RS/6000 AIX shared libraries.
10851 @value{GDBN} automatically loads symbol definitions from shared libraries
10852 when you use the @code{run} command, or when you examine a core file.
10853 (Before you issue the @code{run} command, @value{GDBN} does not understand
10854 references to a function in a shared library, however---unless you are
10855 debugging a core file).
10857 On HP-UX, if the program loads a library explicitly, @value{GDBN}
10858 automatically loads the symbols at the time of the @code{shl_load} call.
10860 @c FIXME: some @value{GDBN} release may permit some refs to undef
10861 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
10862 @c FIXME...lib; check this from time to time when updating manual
10864 There are times, however, when you may wish to not automatically load
10865 symbol definitions from shared libraries, such as when they are
10866 particularly large or there are many of them.
10868 To control the automatic loading of shared library symbols, use the
10872 @kindex set auto-solib-add
10873 @item set auto-solib-add @var{mode}
10874 If @var{mode} is @code{on}, symbols from all shared object libraries
10875 will be loaded automatically when the inferior begins execution, you
10876 attach to an independently started inferior, or when the dynamic linker
10877 informs @value{GDBN} that a new library has been loaded. If @var{mode}
10878 is @code{off}, symbols must be loaded manually, using the
10879 @code{sharedlibrary} command. The default value is @code{on}.
10881 @cindex memory used for symbol tables
10882 If your program uses lots of shared libraries with debug info that
10883 takes large amounts of memory, you can decrease the @value{GDBN}
10884 memory footprint by preventing it from automatically loading the
10885 symbols from shared libraries. To that end, type @kbd{set
10886 auto-solib-add off} before running the inferior, then load each
10887 library whose debug symbols you do need with @kbd{sharedlibrary
10888 @var{regexp}}, where @var{regexp} is a regular expresion that matches
10889 the libraries whose symbols you want to be loaded.
10891 @kindex show auto-solib-add
10892 @item show auto-solib-add
10893 Display the current autoloading mode.
10896 @cindex load shared library
10897 To explicitly load shared library symbols, use the @code{sharedlibrary}
10901 @kindex info sharedlibrary
10904 @itemx info sharedlibrary
10905 Print the names of the shared libraries which are currently loaded.
10907 @kindex sharedlibrary
10909 @item sharedlibrary @var{regex}
10910 @itemx share @var{regex}
10911 Load shared object library symbols for files matching a
10912 Unix regular expression.
10913 As with files loaded automatically, it only loads shared libraries
10914 required by your program for a core file or after typing @code{run}. If
10915 @var{regex} is omitted all shared libraries required by your program are
10918 @item nosharedlibrary
10919 @kindex nosharedlibrary
10920 @cindex unload symbols from shared libraries
10921 Unload all shared object library symbols. This discards all symbols
10922 that have been loaded from all shared libraries. Symbols from shared
10923 libraries that were loaded by explicit user requests are not
10927 On some systems, such as HP-UX systems, @value{GDBN} supports
10928 autoloading shared library symbols until a limiting threshold size is
10929 reached. This provides the benefit of allowing autoloading to remain on
10930 by default, but avoids autoloading excessively large shared libraries,
10931 up to a threshold that is initially set, but which you can modify if you
10934 Beyond that threshold, symbols from shared libraries must be explicitly
10935 loaded. To load these symbols, use the command @code{sharedlibrary
10936 @var{filename}}. The base address of the shared library is determined
10937 automatically by @value{GDBN} and need not be specified.
10939 To display or set the threshold, use the commands:
10942 @kindex set auto-solib-limit
10943 @item set auto-solib-limit @var{threshold}
10944 Set the autoloading size threshold, in an integral number of megabytes.
10945 If @var{threshold} is nonzero and shared library autoloading is enabled,
10946 symbols from all shared object libraries will be loaded until the total
10947 size of the loaded shared library symbols exceeds this threshold.
10948 Otherwise, symbols must be loaded manually, using the
10949 @code{sharedlibrary} command. The default threshold is 100 (i.e.@: 100
10952 @kindex show auto-solib-limit
10953 @item show auto-solib-limit
10954 Display the current autoloading size threshold, in megabytes.
10957 Sometimes you may wish that @value{GDBN} stops and gives you control
10958 when any of shared library events happen. Use the @code{set
10959 stop-on-solib-events} command for this:
10962 @item set stop-on-solib-events
10963 @kindex set stop-on-solib-events
10964 This command controls whether @value{GDBN} should give you control
10965 when the dynamic linker notifies it about some shared library event.
10966 The most common event of interest is loading or unloading of a new
10969 @item show stop-on-solib-events
10970 @kindex show stop-on-solib-events
10971 Show whether @value{GDBN} stops and gives you control when shared
10972 library events happen.
10975 Shared libraries are also supported in many cross or remote debugging
10976 configurations. A copy of the target's libraries need to be present on the
10977 host system; they need to be the same as the target libraries, although the
10978 copies on the target can be stripped as long as the copies on the host are
10981 You need to tell @value{GDBN} where the target libraries are, so that it can
10982 load the correct copies---otherwise, it may try to load the host's libraries.
10983 @value{GDBN} has two variables to specify the search directories for target
10987 @kindex set solib-absolute-prefix
10988 @item set solib-absolute-prefix @var{path}
10989 If this variable is set, @var{path} will be used as a prefix for any
10990 absolute shared library paths; many runtime loaders store the absolute
10991 paths to the shared library in the target program's memory. If you use
10992 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
10993 out in the same way that they are on the target, with e.g.@: a
10994 @file{/usr/lib} hierarchy under @var{path}.
10996 You can set the default value of @samp{solib-absolute-prefix} by using the
10997 configure-time @samp{--with-sysroot} option.
10999 @kindex show solib-absolute-prefix
11000 @item show solib-absolute-prefix
11001 Display the current shared library prefix.
11003 @kindex set solib-search-path
11004 @item set solib-search-path @var{path}
11005 If this variable is set, @var{path} is a colon-separated list of directories
11006 to search for shared libraries. @samp{solib-search-path} is used after
11007 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
11008 the library is relative instead of absolute. If you want to use
11009 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
11010 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
11011 @value{GDBN} from finding your host's libraries.
11013 @kindex show solib-search-path
11014 @item show solib-search-path
11015 Display the current shared library search path.
11019 @node Separate Debug Files
11020 @section Debugging Information in Separate Files
11021 @cindex separate debugging information files
11022 @cindex debugging information in separate files
11023 @cindex @file{.debug} subdirectories
11024 @cindex debugging information directory, global
11025 @cindex global debugging information directory
11027 @value{GDBN} allows you to put a program's debugging information in a
11028 file separate from the executable itself, in a way that allows
11029 @value{GDBN} to find and load the debugging information automatically.
11030 Since debugging information can be very large --- sometimes larger
11031 than the executable code itself --- some systems distribute debugging
11032 information for their executables in separate files, which users can
11033 install only when they need to debug a problem.
11035 If an executable's debugging information has been extracted to a
11036 separate file, the executable should contain a @dfn{debug link} giving
11037 the name of the debugging information file (with no directory
11038 components), and a checksum of its contents. (The exact form of a
11039 debug link is described below.) If the full name of the directory
11040 containing the executable is @var{execdir}, and the executable has a
11041 debug link that specifies the name @var{debugfile}, then @value{GDBN}
11042 will automatically search for the debugging information file in three
11047 the directory containing the executable file (that is, it will look
11048 for a file named @file{@var{execdir}/@var{debugfile}},
11050 a subdirectory of that directory named @file{.debug} (that is, the
11051 file @file{@var{execdir}/.debug/@var{debugfile}}, and
11053 a subdirectory of the global debug file directory that includes the
11054 executable's full path, and the name from the link (that is, the file
11055 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
11056 @var{globaldebugdir} is the global debug file directory, and
11057 @var{execdir} has been turned into a relative path).
11060 @value{GDBN} checks under each of these names for a debugging
11061 information file whose checksum matches that given in the link, and
11062 reads the debugging information from the first one it finds.
11064 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
11065 which has a link containing the name @file{ls.debug}, and the global
11066 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
11067 for debug information in @file{/usr/bin/ls.debug},
11068 @file{/usr/bin/.debug/ls.debug}, and
11069 @file{/usr/lib/debug/usr/bin/ls.debug}.
11071 You can set the global debugging info directory's name, and view the
11072 name @value{GDBN} is currently using.
11076 @kindex set debug-file-directory
11077 @item set debug-file-directory @var{directory}
11078 Set the directory which @value{GDBN} searches for separate debugging
11079 information files to @var{directory}.
11081 @kindex show debug-file-directory
11082 @item show debug-file-directory
11083 Show the directory @value{GDBN} searches for separate debugging
11088 @cindex @code{.gnu_debuglink} sections
11089 @cindex debug links
11090 A debug link is a special section of the executable file named
11091 @code{.gnu_debuglink}. The section must contain:
11095 A filename, with any leading directory components removed, followed by
11098 zero to three bytes of padding, as needed to reach the next four-byte
11099 boundary within the section, and
11101 a four-byte CRC checksum, stored in the same endianness used for the
11102 executable file itself. The checksum is computed on the debugging
11103 information file's full contents by the function given below, passing
11104 zero as the @var{crc} argument.
11107 Any executable file format can carry a debug link, as long as it can
11108 contain a section named @code{.gnu_debuglink} with the contents
11111 The debugging information file itself should be an ordinary
11112 executable, containing a full set of linker symbols, sections, and
11113 debugging information. The sections of the debugging information file
11114 should have the same names, addresses and sizes as the original file,
11115 but they need not contain any data --- much like a @code{.bss} section
11116 in an ordinary executable.
11118 As of December 2002, there is no standard GNU utility to produce
11119 separated executable / debugging information file pairs. Ulrich
11120 Drepper's @file{elfutils} package, starting with version 0.53,
11121 contains a version of the @code{strip} command such that the command
11122 @kbd{strip foo -f foo.debug} removes the debugging information from
11123 the executable file @file{foo}, places it in the file
11124 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
11126 Since there are many different ways to compute CRC's (different
11127 polynomials, reversals, byte ordering, etc.), the simplest way to
11128 describe the CRC used in @code{.gnu_debuglink} sections is to give the
11129 complete code for a function that computes it:
11131 @kindex gnu_debuglink_crc32
11134 gnu_debuglink_crc32 (unsigned long crc,
11135 unsigned char *buf, size_t len)
11137 static const unsigned long crc32_table[256] =
11139 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
11140 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
11141 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
11142 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
11143 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
11144 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
11145 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
11146 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
11147 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
11148 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
11149 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
11150 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
11151 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
11152 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
11153 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
11154 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
11155 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
11156 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
11157 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
11158 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
11159 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
11160 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
11161 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
11162 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
11163 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
11164 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
11165 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
11166 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
11167 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
11168 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
11169 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
11170 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
11171 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
11172 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
11173 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
11174 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
11175 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
11176 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
11177 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
11178 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
11179 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
11180 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
11181 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
11182 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
11183 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
11184 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
11185 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
11186 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
11187 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
11188 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
11189 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
11192 unsigned char *end;
11194 crc = ~crc & 0xffffffff;
11195 for (end = buf + len; buf < end; ++buf)
11196 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
11197 return ~crc & 0xffffffff;
11202 @node Symbol Errors
11203 @section Errors reading symbol files
11205 While reading a symbol file, @value{GDBN} occasionally encounters problems,
11206 such as symbol types it does not recognize, or known bugs in compiler
11207 output. By default, @value{GDBN} does not notify you of such problems, since
11208 they are relatively common and primarily of interest to people
11209 debugging compilers. If you are interested in seeing information
11210 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
11211 only one message about each such type of problem, no matter how many
11212 times the problem occurs; or you can ask @value{GDBN} to print more messages,
11213 to see how many times the problems occur, with the @code{set
11214 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
11217 The messages currently printed, and their meanings, include:
11220 @item inner block not inside outer block in @var{symbol}
11222 The symbol information shows where symbol scopes begin and end
11223 (such as at the start of a function or a block of statements). This
11224 error indicates that an inner scope block is not fully contained
11225 in its outer scope blocks.
11227 @value{GDBN} circumvents the problem by treating the inner block as if it had
11228 the same scope as the outer block. In the error message, @var{symbol}
11229 may be shown as ``@code{(don't know)}'' if the outer block is not a
11232 @item block at @var{address} out of order
11234 The symbol information for symbol scope blocks should occur in
11235 order of increasing addresses. This error indicates that it does not
11238 @value{GDBN} does not circumvent this problem, and has trouble
11239 locating symbols in the source file whose symbols it is reading. (You
11240 can often determine what source file is affected by specifying
11241 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
11244 @item bad block start address patched
11246 The symbol information for a symbol scope block has a start address
11247 smaller than the address of the preceding source line. This is known
11248 to occur in the SunOS 4.1.1 (and earlier) C compiler.
11250 @value{GDBN} circumvents the problem by treating the symbol scope block as
11251 starting on the previous source line.
11253 @item bad string table offset in symbol @var{n}
11256 Symbol number @var{n} contains a pointer into the string table which is
11257 larger than the size of the string table.
11259 @value{GDBN} circumvents the problem by considering the symbol to have the
11260 name @code{foo}, which may cause other problems if many symbols end up
11263 @item unknown symbol type @code{0x@var{nn}}
11265 The symbol information contains new data types that @value{GDBN} does
11266 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
11267 uncomprehended information, in hexadecimal.
11269 @value{GDBN} circumvents the error by ignoring this symbol information.
11270 This usually allows you to debug your program, though certain symbols
11271 are not accessible. If you encounter such a problem and feel like
11272 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
11273 on @code{complain}, then go up to the function @code{read_dbx_symtab}
11274 and examine @code{*bufp} to see the symbol.
11276 @item stub type has NULL name
11278 @value{GDBN} could not find the full definition for a struct or class.
11280 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
11281 The symbol information for a C@t{++} member function is missing some
11282 information that recent versions of the compiler should have output for
11285 @item info mismatch between compiler and debugger
11287 @value{GDBN} could not parse a type specification output by the compiler.
11292 @chapter Specifying a Debugging Target
11294 @cindex debugging target
11295 A @dfn{target} is the execution environment occupied by your program.
11297 Often, @value{GDBN} runs in the same host environment as your program;
11298 in that case, the debugging target is specified as a side effect when
11299 you use the @code{file} or @code{core} commands. When you need more
11300 flexibility---for example, running @value{GDBN} on a physically separate
11301 host, or controlling a standalone system over a serial port or a
11302 realtime system over a TCP/IP connection---you can use the @code{target}
11303 command to specify one of the target types configured for @value{GDBN}
11304 (@pxref{Target Commands, ,Commands for managing targets}).
11306 @cindex target architecture
11307 It is possible to build @value{GDBN} for several different @dfn{target
11308 architectures}. When @value{GDBN} is built like that, you can choose
11309 one of the available architectures with the @kbd{set architecture}
11313 @kindex set architecture
11314 @kindex show architecture
11315 @item set architecture @var{arch}
11316 This command sets the current target architecture to @var{arch}. The
11317 value of @var{arch} can be @code{"auto"}, in addition to one of the
11318 supported architectures.
11320 @item show architecture
11321 Show the current target architecture.
11323 @item set processor
11325 @kindex set processor
11326 @kindex show processor
11327 These are alias commands for, respectively, @code{set architecture}
11328 and @code{show architecture}.
11332 * Active Targets:: Active targets
11333 * Target Commands:: Commands for managing targets
11334 * Byte Order:: Choosing target byte order
11335 * Remote:: Remote debugging
11336 * KOD:: Kernel Object Display
11340 @node Active Targets
11341 @section Active targets
11343 @cindex stacking targets
11344 @cindex active targets
11345 @cindex multiple targets
11347 There are three classes of targets: processes, core files, and
11348 executable files. @value{GDBN} can work concurrently on up to three
11349 active targets, one in each class. This allows you to (for example)
11350 start a process and inspect its activity without abandoning your work on
11353 For example, if you execute @samp{gdb a.out}, then the executable file
11354 @code{a.out} is the only active target. If you designate a core file as
11355 well---presumably from a prior run that crashed and coredumped---then
11356 @value{GDBN} has two active targets and uses them in tandem, looking
11357 first in the corefile target, then in the executable file, to satisfy
11358 requests for memory addresses. (Typically, these two classes of target
11359 are complementary, since core files contain only a program's
11360 read-write memory---variables and so on---plus machine status, while
11361 executable files contain only the program text and initialized data.)
11363 When you type @code{run}, your executable file becomes an active process
11364 target as well. When a process target is active, all @value{GDBN}
11365 commands requesting memory addresses refer to that target; addresses in
11366 an active core file or executable file target are obscured while the
11367 process target is active.
11369 Use the @code{core-file} and @code{exec-file} commands to select a new
11370 core file or executable target (@pxref{Files, ,Commands to specify
11371 files}). To specify as a target a process that is already running, use
11372 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
11375 @node Target Commands
11376 @section Commands for managing targets
11379 @item target @var{type} @var{parameters}
11380 Connects the @value{GDBN} host environment to a target machine or
11381 process. A target is typically a protocol for talking to debugging
11382 facilities. You use the argument @var{type} to specify the type or
11383 protocol of the target machine.
11385 Further @var{parameters} are interpreted by the target protocol, but
11386 typically include things like device names or host names to connect
11387 with, process numbers, and baud rates.
11389 The @code{target} command does not repeat if you press @key{RET} again
11390 after executing the command.
11392 @kindex help target
11394 Displays the names of all targets available. To display targets
11395 currently selected, use either @code{info target} or @code{info files}
11396 (@pxref{Files, ,Commands to specify files}).
11398 @item help target @var{name}
11399 Describe a particular target, including any parameters necessary to
11402 @kindex set gnutarget
11403 @item set gnutarget @var{args}
11404 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
11405 knows whether it is reading an @dfn{executable},
11406 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
11407 with the @code{set gnutarget} command. Unlike most @code{target} commands,
11408 with @code{gnutarget} the @code{target} refers to a program, not a machine.
11411 @emph{Warning:} To specify a file format with @code{set gnutarget},
11412 you must know the actual BFD name.
11416 @xref{Files, , Commands to specify files}.
11418 @kindex show gnutarget
11419 @item show gnutarget
11420 Use the @code{show gnutarget} command to display what file format
11421 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
11422 @value{GDBN} will determine the file format for each file automatically,
11423 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
11426 @cindex common targets
11427 Here are some common targets (available, or not, depending on the GDB
11432 @item target exec @var{program}
11433 @cindex executable file target
11434 An executable file. @samp{target exec @var{program}} is the same as
11435 @samp{exec-file @var{program}}.
11437 @item target core @var{filename}
11438 @cindex core dump file target
11439 A core dump file. @samp{target core @var{filename}} is the same as
11440 @samp{core-file @var{filename}}.
11442 @item target remote @var{dev}
11443 @cindex remote target
11444 Remote serial target in GDB-specific protocol. The argument @var{dev}
11445 specifies what serial device to use for the connection (e.g.
11446 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
11447 supports the @code{load} command. This is only useful if you have
11448 some other way of getting the stub to the target system, and you can put
11449 it somewhere in memory where it won't get clobbered by the download.
11452 @cindex built-in simulator target
11453 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
11461 works; however, you cannot assume that a specific memory map, device
11462 drivers, or even basic I/O is available, although some simulators do
11463 provide these. For info about any processor-specific simulator details,
11464 see the appropriate section in @ref{Embedded Processors, ,Embedded
11469 Some configurations may include these targets as well:
11473 @item target nrom @var{dev}
11474 @cindex NetROM ROM emulator target
11475 NetROM ROM emulator. This target only supports downloading.
11479 Different targets are available on different configurations of @value{GDBN};
11480 your configuration may have more or fewer targets.
11482 Many remote targets require you to download the executable's code once
11483 you've successfully established a connection. You may wish to control
11484 various aspects of this process, such as the size of the data chunks
11485 used by @value{GDBN} to download program parts to the remote target.
11488 @kindex set download-write-size
11489 @item set download-write-size @var{size}
11490 Set the write size used when downloading a program. Only used when
11491 downloading a program onto a remote target. Specify zero or a
11492 negative value to disable blocked writes. The actual size of each
11493 transfer is also limited by the size of the target packet and the
11496 @kindex show download-write-size
11497 @item show download-write-size
11498 @kindex show download-write-size
11499 Show the current value of the write size.
11502 @kindex set hash@r{, for remote monitors}
11503 @cindex hash mark while downloading
11504 This command controls whether a hash mark @samp{#} is displayed while
11505 downloading a file to the remote monitor. If on, a hash mark is
11506 displayed after each S-record is successfully downloaded to the
11510 @kindex show hash@r{, for remote monitors}
11511 Show the current status of displaying the hash mark.
11513 @item set debug monitor
11514 @kindex set debug monitor
11515 @cindex display remote monitor communications
11516 Enable or disable display of communications messages between
11517 @value{GDBN} and the remote monitor.
11519 @item show debug monitor
11520 @kindex show debug monitor
11521 Show the current status of displaying communications between
11522 @value{GDBN} and the remote monitor.
11527 @kindex load @var{filename}
11528 @item load @var{filename}
11529 Depending on what remote debugging facilities are configured into
11530 @value{GDBN}, the @code{load} command may be available. Where it exists, it
11531 is meant to make @var{filename} (an executable) available for debugging
11532 on the remote system---by downloading, or dynamic linking, for example.
11533 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
11534 the @code{add-symbol-file} command.
11536 If your @value{GDBN} does not have a @code{load} command, attempting to
11537 execute it gets the error message ``@code{You can't do that when your
11538 target is @dots{}}''
11540 The file is loaded at whatever address is specified in the executable.
11541 For some object file formats, you can specify the load address when you
11542 link the program; for other formats, like a.out, the object file format
11543 specifies a fixed address.
11544 @c FIXME! This would be a good place for an xref to the GNU linker doc.
11546 @code{load} does not repeat if you press @key{RET} again after using it.
11550 @section Choosing target byte order
11552 @cindex choosing target byte order
11553 @cindex target byte order
11555 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
11556 offer the ability to run either big-endian or little-endian byte
11557 orders. Usually the executable or symbol will include a bit to
11558 designate the endian-ness, and you will not need to worry about
11559 which to use. However, you may still find it useful to adjust
11560 @value{GDBN}'s idea of processor endian-ness manually.
11564 @item set endian big
11565 Instruct @value{GDBN} to assume the target is big-endian.
11567 @item set endian little
11568 Instruct @value{GDBN} to assume the target is little-endian.
11570 @item set endian auto
11571 Instruct @value{GDBN} to use the byte order associated with the
11575 Display @value{GDBN}'s current idea of the target byte order.
11579 Note that these commands merely adjust interpretation of symbolic
11580 data on the host, and that they have absolutely no effect on the
11584 @section Remote debugging
11585 @cindex remote debugging
11587 If you are trying to debug a program running on a machine that cannot run
11588 @value{GDBN} in the usual way, it is often useful to use remote debugging.
11589 For example, you might use remote debugging on an operating system kernel,
11590 or on a small system which does not have a general purpose operating system
11591 powerful enough to run a full-featured debugger.
11593 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
11594 to make this work with particular debugging targets. In addition,
11595 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
11596 but not specific to any particular target system) which you can use if you
11597 write the remote stubs---the code that runs on the remote system to
11598 communicate with @value{GDBN}.
11600 Other remote targets may be available in your
11601 configuration of @value{GDBN}; use @code{help target} to list them.
11603 Once you've connected to the remote target, @value{GDBN} allows you to
11604 send arbitrary commands to the remote monitor:
11607 @item remote @var{command}
11608 @kindex remote@r{, a command}
11609 @cindex send command to remote monitor
11610 Send an arbitrary @var{command} string to the remote monitor.
11615 @section Kernel Object Display
11616 @cindex kernel object display
11619 Some targets support kernel object display. Using this facility,
11620 @value{GDBN} communicates specially with the underlying operating system
11621 and can display information about operating system-level objects such as
11622 mutexes and other synchronization objects. Exactly which objects can be
11623 displayed is determined on a per-OS basis.
11626 Use the @code{set os} command to set the operating system. This tells
11627 @value{GDBN} which kernel object display module to initialize:
11630 (@value{GDBP}) set os cisco
11634 The associated command @code{show os} displays the operating system
11635 set with the @code{set os} command; if no operating system has been
11636 set, @code{show os} will display an empty string @samp{""}.
11638 If @code{set os} succeeds, @value{GDBN} will display some information
11639 about the operating system, and will create a new @code{info} command
11640 which can be used to query the target. The @code{info} command is named
11641 after the operating system:
11645 (@value{GDBP}) info cisco
11646 List of Cisco Kernel Objects
11648 any Any and all objects
11651 Further subcommands can be used to query about particular objects known
11654 There is currently no way to determine whether a given operating
11655 system is supported other than to try setting it with @kbd{set os
11656 @var{name}}, where @var{name} is the name of the operating system you
11660 @node Remote Debugging
11661 @chapter Debugging remote programs
11664 * Connecting:: Connecting to a remote target
11665 * Server:: Using the gdbserver program
11666 * NetWare:: Using the gdbserve.nlm program
11667 * Remote configuration:: Remote configuration
11668 * remote stub:: Implementing a remote stub
11672 @section Connecting to a remote target
11674 On the @value{GDBN} host machine, you will need an unstripped copy of
11675 your program, since @value{GDBN} needs symobl and debugging information.
11676 Start up @value{GDBN} as usual, using the name of the local copy of your
11677 program as the first argument.
11679 @cindex serial line, @code{target remote}
11680 If you're using a serial line, you may want to give @value{GDBN} the
11681 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
11682 (@pxref{Remote configuration, set remotebaud}) before the
11683 @code{target} command.
11685 After that, use @code{target remote} to establish communications with
11686 the target machine. Its argument specifies how to communicate---either
11687 via a devicename attached to a direct serial line, or a TCP or UDP port
11688 (possibly to a terminal server which in turn has a serial line to the
11689 target). For example, to use a serial line connected to the device
11690 named @file{/dev/ttyb}:
11693 target remote /dev/ttyb
11696 @cindex TCP port, @code{target remote}
11697 To use a TCP connection, use an argument of the form
11698 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
11699 For example, to connect to port 2828 on a
11700 terminal server named @code{manyfarms}:
11703 target remote manyfarms:2828
11706 If your remote target is actually running on the same machine as
11707 your debugger session (e.g.@: a simulator of your target running on
11708 the same host), you can omit the hostname. For example, to connect
11709 to port 1234 on your local machine:
11712 target remote :1234
11716 Note that the colon is still required here.
11718 @cindex UDP port, @code{target remote}
11719 To use a UDP connection, use an argument of the form
11720 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
11721 on a terminal server named @code{manyfarms}:
11724 target remote udp:manyfarms:2828
11727 When using a UDP connection for remote debugging, you should keep in mind
11728 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
11729 busy or unreliable networks, which will cause havoc with your debugging
11732 Now you can use all the usual commands to examine and change data and to
11733 step and continue the remote program.
11735 @cindex interrupting remote programs
11736 @cindex remote programs, interrupting
11737 Whenever @value{GDBN} is waiting for the remote program, if you type the
11738 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
11739 program. This may or may not succeed, depending in part on the hardware
11740 and the serial drivers the remote system uses. If you type the
11741 interrupt character once again, @value{GDBN} displays this prompt:
11744 Interrupted while waiting for the program.
11745 Give up (and stop debugging it)? (y or n)
11748 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
11749 (If you decide you want to try again later, you can use @samp{target
11750 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
11751 goes back to waiting.
11754 @kindex detach (remote)
11756 When you have finished debugging the remote program, you can use the
11757 @code{detach} command to release it from @value{GDBN} control.
11758 Detaching from the target normally resumes its execution, but the results
11759 will depend on your particular remote stub. After the @code{detach}
11760 command, @value{GDBN} is free to connect to another target.
11764 The @code{disconnect} command behaves like @code{detach}, except that
11765 the target is generally not resumed. It will wait for @value{GDBN}
11766 (this instance or another one) to connect and continue debugging. After
11767 the @code{disconnect} command, @value{GDBN} is again free to connect to
11770 @cindex send command to remote monitor
11772 @item monitor @var{cmd}
11773 This command allows you to send commands directly to the remote
11778 @section Using the @code{gdbserver} program
11781 @cindex remote connection without stubs
11782 @code{gdbserver} is a control program for Unix-like systems, which
11783 allows you to connect your program with a remote @value{GDBN} via
11784 @code{target remote}---but without linking in the usual debugging stub.
11786 @code{gdbserver} is not a complete replacement for the debugging stubs,
11787 because it requires essentially the same operating-system facilities
11788 that @value{GDBN} itself does. In fact, a system that can run
11789 @code{gdbserver} to connect to a remote @value{GDBN} could also run
11790 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
11791 because it is a much smaller program than @value{GDBN} itself. It is
11792 also easier to port than all of @value{GDBN}, so you may be able to get
11793 started more quickly on a new system by using @code{gdbserver}.
11794 Finally, if you develop code for real-time systems, you may find that
11795 the tradeoffs involved in real-time operation make it more convenient to
11796 do as much development work as possible on another system, for example
11797 by cross-compiling. You can use @code{gdbserver} to make a similar
11798 choice for debugging.
11800 @value{GDBN} and @code{gdbserver} communicate via either a serial line
11801 or a TCP connection, using the standard @value{GDBN} remote serial
11805 @item On the target machine,
11806 you need to have a copy of the program you want to debug.
11807 @code{gdbserver} does not need your program's symbol table, so you can
11808 strip the program if necessary to save space. @value{GDBN} on the host
11809 system does all the symbol handling.
11811 To use the server, you must tell it how to communicate with @value{GDBN};
11812 the name of your program; and the arguments for your program. The usual
11816 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
11819 @var{comm} is either a device name (to use a serial line) or a TCP
11820 hostname and portnumber. For example, to debug Emacs with the argument
11821 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
11825 target> gdbserver /dev/com1 emacs foo.txt
11828 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
11831 To use a TCP connection instead of a serial line:
11834 target> gdbserver host:2345 emacs foo.txt
11837 The only difference from the previous example is the first argument,
11838 specifying that you are communicating with the host @value{GDBN} via
11839 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
11840 expect a TCP connection from machine @samp{host} to local TCP port 2345.
11841 (Currently, the @samp{host} part is ignored.) You can choose any number
11842 you want for the port number as long as it does not conflict with any
11843 TCP ports already in use on the target system (for example, @code{23} is
11844 reserved for @code{telnet}).@footnote{If you choose a port number that
11845 conflicts with another service, @code{gdbserver} prints an error message
11846 and exits.} You must use the same port number with the host @value{GDBN}
11847 @code{target remote} command.
11849 On some targets, @code{gdbserver} can also attach to running programs.
11850 This is accomplished via the @code{--attach} argument. The syntax is:
11853 target> gdbserver @var{comm} --attach @var{pid}
11856 @var{pid} is the process ID of a currently running process. It isn't necessary
11857 to point @code{gdbserver} at a binary for the running process.
11860 @cindex attach to a program by name
11861 You can debug processes by name instead of process ID if your target has the
11862 @code{pidof} utility:
11865 target> gdbserver @var{comm} --attach `pidof @var{PROGRAM}`
11868 In case more than one copy of @var{PROGRAM} is running, or @var{PROGRAM}
11869 has multiple threads, most versions of @code{pidof} support the
11870 @code{-s} option to only return the first process ID.
11872 @item On the host machine,
11873 connect to your target (@pxref{Connecting,,Connecting to a remote target}).
11874 For TCP connections, you must start up @code{gdbserver} prior to using
11875 the @code{target remote} command. Otherwise you may get an error whose
11876 text depends on the host system, but which usually looks something like
11877 @samp{Connection refused}. You don't need to use the @code{load}
11878 command in @value{GDBN} when using gdbserver, since the program is
11879 already on the target.
11884 @section Using the @code{gdbserve.nlm} program
11886 @kindex gdbserve.nlm
11887 @code{gdbserve.nlm} is a control program for NetWare systems, which
11888 allows you to connect your program with a remote @value{GDBN} via
11889 @code{target remote}.
11891 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
11892 using the standard @value{GDBN} remote serial protocol.
11895 @item On the target machine,
11896 you need to have a copy of the program you want to debug.
11897 @code{gdbserve.nlm} does not need your program's symbol table, so you
11898 can strip the program if necessary to save space. @value{GDBN} on the
11899 host system does all the symbol handling.
11901 To use the server, you must tell it how to communicate with
11902 @value{GDBN}; the name of your program; and the arguments for your
11903 program. The syntax is:
11906 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
11907 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
11910 @var{board} and @var{port} specify the serial line; @var{baud} specifies
11911 the baud rate used by the connection. @var{port} and @var{node} default
11912 to 0, @var{baud} defaults to 9600@dmn{bps}.
11914 For example, to debug Emacs with the argument @samp{foo.txt}and
11915 communicate with @value{GDBN} over serial port number 2 or board 1
11916 using a 19200@dmn{bps} connection:
11919 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
11923 On the @value{GDBN} host machine, connect to your target (@pxref{Connecting,,
11924 Connecting to a remote target}).
11928 @node Remote configuration
11929 @section Remote configuration
11932 @kindex show remote
11933 This section documents the configuration options available when
11934 debugging remote programs. For the options related to the File I/O
11935 extensions of the remote protocol, see @ref{The system call,
11936 system-call-allowed}.
11939 @item set remoteaddresssize @var{bits}
11940 @cindex adress size for remote targets
11941 @cindex bits in remote address
11942 Set the maximum size of address in a memory packet to the specified
11943 number of bits. @value{GDBN} will mask off the address bits above
11944 that number, when it passes addresses to the remote target. The
11945 default value is the number of bits in the target's address.
11947 @item show remoteaddresssize
11948 Show the current value of remote address size in bits.
11950 @item set remotebaud @var{n}
11951 @cindex baud rate for remote targets
11952 Set the baud rate for the remote serial I/O to @var{n} baud. The
11953 value is used to set the speed of the serial port used for debugging
11956 @item show remotebaud
11957 Show the current speed of the remote connection.
11959 @item set remotebreak
11960 @cindex interrupt remote programs
11961 @cindex BREAK signal instead of Ctrl-C
11962 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
11963 when you press the @key{Ctrl-C} key to interrupt the program running
11964 on the remote. If set to off, @value{GDBN} sends the @samp{Strl-C}
11965 character instead. The default is off, since most remote systems
11966 expect to see @samp{Ctrl-C} as the interrupt signal.
11968 @item show remotebreak
11969 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
11970 interrupt the remote program.
11972 @item set remotedebug
11973 @cindex debug remote protocol
11974 @cindex remote protocol debugging
11975 @cindex display remote packets
11976 Control the debugging of the remote protocol. When enabled, each
11977 packet sent to or received from the remote target is displayed. The
11980 @item show remotedebug
11981 Show the current setting of the remote protocol debugging.
11983 @item set remotedevice @var{device}
11984 @cindex serial port name
11985 Set the name of the serial port through which to communicate to the
11986 remote target to @var{device}. This is the device used by
11987 @value{GDBN} to open the serial communications line to the remote
11988 target. There's no default, so you must set a valid port name for the
11989 remote serial communications to work. (Some varieties of the
11990 @code{target} command accept the port name as part of their
11993 @item show remotedevice
11994 Show the current name of the serial port.
11996 @item set remotelogbase @var{base}
11997 Set the base (a.k.a.@: radix) of logging serial protocol
11998 communications to @var{base}. Supported values of @var{base} are:
11999 @code{ascii}, @code{octal}, and @code{hex}. The default is
12002 @item show remotelogbase
12003 Show the current setting of the radix for logging remote serial
12006 @item set remotelogfile @var{file}
12007 @cindex record serial communications on file
12008 Record remote serial communications on the named @var{file}. The
12009 default is not to record at all.
12011 @item show remotelogfile.
12012 Show the current setting of the file name on which to record the
12013 serial communications.
12015 @item set remotetimeout @var{num}
12016 @cindex timeout for serial communications
12017 @cindex remote timeout
12018 Set the timeout limit to wait for the remote target to respond to
12019 @var{num} seconds. The default is 2 seconds.
12021 @item show remotetimeout
12022 Show the current number of seconds to wait for the remote target
12025 @cindex limit hardware breakpoints and watchpoints
12026 @cindex remote target, limit break- and watchpoints
12027 @anchor{set remote hardware-watchpoint-limit}
12028 @anchor{set remote hardware-breakpoint-limit}
12029 @item set remote hardware-watchpoint-limit @var{limit}
12030 @itemx set remote hardware-breakpoint-limit @var{limit}
12031 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
12032 watchpoints. A limit of -1, the default, is treated as unlimited.
12034 @item set remote fetch-register-packet
12035 @itemx set remote set-register-packet
12036 @itemx set remote P-packet
12037 @itemx set remote p-packet
12039 @cindex fetch registers from remote targets
12040 @cindex set registers in remote targets
12041 Determine whether @value{GDBN} can set and fetch registers from the
12042 remote target using the @samp{P} packets. The default depends on the
12043 remote stub's support of the @samp{P} packets (@value{GDBN} queries
12044 the stub when this packet is first required).
12046 @item show remote fetch-register-packet
12047 @itemx show remote set-register-packet
12048 @itemx show remote P-packet
12049 @itemx show remote p-packet
12050 Show the current setting of using the @samp{P} packets for setting and
12051 fetching registers from the remote target.
12053 @cindex binary downloads
12055 @item set remote binary-download-packet
12056 @itemx set remote X-packet
12057 Determine whether @value{GDBN} sends downloads in binary mode using
12058 the @samp{X} packets. The default is on.
12060 @item show remote binary-download-packet
12061 @itemx show remote X-packet
12062 Show the current setting of using the @samp{X} packets for binary
12065 @item set remote read-aux-vector-packet
12066 @cindex auxiliary vector of remote target
12067 @cindex @code{auxv}, and remote targets
12068 Set the use of the remote protocol's @samp{qPart:auxv:read} (target
12069 auxiliary vector read) request. This request is used to fetch the
12070 remote target's @dfn{auxiliary vector}, see @ref{OS Information,
12071 Auxiliary Vector}. The default setting depends on the remote stub's
12072 support of this request (@value{GDBN} queries the stub when this
12073 request is first required). @xref{General Query Packets, qPart}, for
12074 more information about this request.
12076 @item show remote read-aux-vector-packet
12077 Show the current setting of use of the @samp{qPart:auxv:read} request.
12079 @item set remote symbol-lookup-packet
12080 @cindex remote symbol lookup request
12081 Set the use of the remote protocol's @samp{qSymbol} (target symbol
12082 lookup) request. This request is used to communicate symbol
12083 information to the remote target, e.g., whenever a new shared library
12084 is loaded by the remote (@pxref{Files, shared libraries}). The
12085 default setting depends on the remote stub's support of this request
12086 (@value{GDBN} queries the stub when this request is first required).
12087 @xref{General Query Packets, qSymbol}, for more information about this
12090 @item show remote symbol-lookup-packet
12091 Show the current setting of use of the @samp{qSymbol} request.
12093 @item set remote verbose-resume-packet
12094 @cindex resume remote target
12095 @cindex signal thread, and remote targets
12096 @cindex single-step thread, and remote targets
12097 @cindex thread-specific operations on remote targets
12098 Set the use of the remote protocol's @samp{vCont} (descriptive resume)
12099 request. This request is used to resume specific threads in the
12100 remote target, and to single-step or signal them. The default setting
12101 depends on the remote stub's support of this request (@value{GDBN}
12102 queries the stub when this request is first required). This setting
12103 affects debugging of multithreaded programs: if @samp{vCont} cannot be
12104 used, @value{GDBN} might be unable to single-step a specific thread,
12105 especially under @code{set scheduler-locking off}; it is also
12106 impossible to pause a specific thread. @xref{Packets, vCont}, for
12109 @item show remote verbose-resume-packet
12110 Show the current setting of use of the @samp{vCont} request
12112 @item set remote software-breakpoint-packet
12113 @itemx set remote hardware-breakpoint-packet
12114 @itemx set remote write-watchpoint-packet
12115 @itemx set remote read-watchpoint-packet
12116 @itemx set remote access-watchpoint-packet
12117 @itemx set remote Z-packet
12119 @cindex remote hardware breakpoints and watchpoints
12120 These commands enable or disable the use of @samp{Z} packets for
12121 setting breakpoints and watchpoints in the remote target. The default
12122 depends on the remote stub's support of the @samp{Z} packets
12123 (@value{GDBN} queries the stub when each packet is first required).
12124 The command @code{set remote Z-packet}, kept for back-compatibility,
12125 turns on or off all the features that require the use of @samp{Z}
12128 @item show remote software-breakpoint-packet
12129 @itemx show remote hardware-breakpoint-packet
12130 @itemx show remote write-watchpoint-packet
12131 @itemx show remote read-watchpoint-packet
12132 @itemx show remote access-watchpoint-packet
12133 @itemx show remote Z-packet
12134 Show the current setting of @samp{Z} packets usage.
12136 @item set remote get-thread-local-storage-address
12137 @kindex set remote get-thread-local-storage-address
12138 @cindex thread local storage of remote targets
12139 This command enables or disables the use of the @samp{qGetTLSAddr}
12140 (Get Thread Local Storage Address) request packet. The default
12141 depends on whether the remote stub supports this request.
12142 @xref{General Query Packets, qGetTLSAddr}, for more details about this
12145 @item show remote get-thread-local-storage-address
12146 @kindex show remote get-thread-local-storage-address
12147 Show the current setting of @samp{qGetTLSAddr} packet usage.
12151 @section Implementing a remote stub
12153 @cindex debugging stub, example
12154 @cindex remote stub, example
12155 @cindex stub example, remote debugging
12156 The stub files provided with @value{GDBN} implement the target side of the
12157 communication protocol, and the @value{GDBN} side is implemented in the
12158 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
12159 these subroutines to communicate, and ignore the details. (If you're
12160 implementing your own stub file, you can still ignore the details: start
12161 with one of the existing stub files. @file{sparc-stub.c} is the best
12162 organized, and therefore the easiest to read.)
12164 @cindex remote serial debugging, overview
12165 To debug a program running on another machine (the debugging
12166 @dfn{target} machine), you must first arrange for all the usual
12167 prerequisites for the program to run by itself. For example, for a C
12172 A startup routine to set up the C runtime environment; these usually
12173 have a name like @file{crt0}. The startup routine may be supplied by
12174 your hardware supplier, or you may have to write your own.
12177 A C subroutine library to support your program's
12178 subroutine calls, notably managing input and output.
12181 A way of getting your program to the other machine---for example, a
12182 download program. These are often supplied by the hardware
12183 manufacturer, but you may have to write your own from hardware
12187 The next step is to arrange for your program to use a serial port to
12188 communicate with the machine where @value{GDBN} is running (the @dfn{host}
12189 machine). In general terms, the scheme looks like this:
12193 @value{GDBN} already understands how to use this protocol; when everything
12194 else is set up, you can simply use the @samp{target remote} command
12195 (@pxref{Targets,,Specifying a Debugging Target}).
12197 @item On the target,
12198 you must link with your program a few special-purpose subroutines that
12199 implement the @value{GDBN} remote serial protocol. The file containing these
12200 subroutines is called a @dfn{debugging stub}.
12202 On certain remote targets, you can use an auxiliary program
12203 @code{gdbserver} instead of linking a stub into your program.
12204 @xref{Server,,Using the @code{gdbserver} program}, for details.
12207 The debugging stub is specific to the architecture of the remote
12208 machine; for example, use @file{sparc-stub.c} to debug programs on
12211 @cindex remote serial stub list
12212 These working remote stubs are distributed with @value{GDBN}:
12217 @cindex @file{i386-stub.c}
12220 For Intel 386 and compatible architectures.
12223 @cindex @file{m68k-stub.c}
12224 @cindex Motorola 680x0
12226 For Motorola 680x0 architectures.
12229 @cindex @file{sh-stub.c}
12232 For Renesas SH architectures.
12235 @cindex @file{sparc-stub.c}
12237 For @sc{sparc} architectures.
12239 @item sparcl-stub.c
12240 @cindex @file{sparcl-stub.c}
12243 For Fujitsu @sc{sparclite} architectures.
12247 The @file{README} file in the @value{GDBN} distribution may list other
12248 recently added stubs.
12251 * Stub Contents:: What the stub can do for you
12252 * Bootstrapping:: What you must do for the stub
12253 * Debug Session:: Putting it all together
12256 @node Stub Contents
12257 @subsection What the stub can do for you
12259 @cindex remote serial stub
12260 The debugging stub for your architecture supplies these three
12264 @item set_debug_traps
12265 @findex set_debug_traps
12266 @cindex remote serial stub, initialization
12267 This routine arranges for @code{handle_exception} to run when your
12268 program stops. You must call this subroutine explicitly near the
12269 beginning of your program.
12271 @item handle_exception
12272 @findex handle_exception
12273 @cindex remote serial stub, main routine
12274 This is the central workhorse, but your program never calls it
12275 explicitly---the setup code arranges for @code{handle_exception} to
12276 run when a trap is triggered.
12278 @code{handle_exception} takes control when your program stops during
12279 execution (for example, on a breakpoint), and mediates communications
12280 with @value{GDBN} on the host machine. This is where the communications
12281 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
12282 representative on the target machine. It begins by sending summary
12283 information on the state of your program, then continues to execute,
12284 retrieving and transmitting any information @value{GDBN} needs, until you
12285 execute a @value{GDBN} command that makes your program resume; at that point,
12286 @code{handle_exception} returns control to your own code on the target
12290 @cindex @code{breakpoint} subroutine, remote
12291 Use this auxiliary subroutine to make your program contain a
12292 breakpoint. Depending on the particular situation, this may be the only
12293 way for @value{GDBN} to get control. For instance, if your target
12294 machine has some sort of interrupt button, you won't need to call this;
12295 pressing the interrupt button transfers control to
12296 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
12297 simply receiving characters on the serial port may also trigger a trap;
12298 again, in that situation, you don't need to call @code{breakpoint} from
12299 your own program---simply running @samp{target remote} from the host
12300 @value{GDBN} session gets control.
12302 Call @code{breakpoint} if none of these is true, or if you simply want
12303 to make certain your program stops at a predetermined point for the
12304 start of your debugging session.
12307 @node Bootstrapping
12308 @subsection What you must do for the stub
12310 @cindex remote stub, support routines
12311 The debugging stubs that come with @value{GDBN} are set up for a particular
12312 chip architecture, but they have no information about the rest of your
12313 debugging target machine.
12315 First of all you need to tell the stub how to communicate with the
12319 @item int getDebugChar()
12320 @findex getDebugChar
12321 Write this subroutine to read a single character from the serial port.
12322 It may be identical to @code{getchar} for your target system; a
12323 different name is used to allow you to distinguish the two if you wish.
12325 @item void putDebugChar(int)
12326 @findex putDebugChar
12327 Write this subroutine to write a single character to the serial port.
12328 It may be identical to @code{putchar} for your target system; a
12329 different name is used to allow you to distinguish the two if you wish.
12332 @cindex control C, and remote debugging
12333 @cindex interrupting remote targets
12334 If you want @value{GDBN} to be able to stop your program while it is
12335 running, you need to use an interrupt-driven serial driver, and arrange
12336 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
12337 character). That is the character which @value{GDBN} uses to tell the
12338 remote system to stop.
12340 Getting the debugging target to return the proper status to @value{GDBN}
12341 probably requires changes to the standard stub; one quick and dirty way
12342 is to just execute a breakpoint instruction (the ``dirty'' part is that
12343 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
12345 Other routines you need to supply are:
12348 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
12349 @findex exceptionHandler
12350 Write this function to install @var{exception_address} in the exception
12351 handling tables. You need to do this because the stub does not have any
12352 way of knowing what the exception handling tables on your target system
12353 are like (for example, the processor's table might be in @sc{rom},
12354 containing entries which point to a table in @sc{ram}).
12355 @var{exception_number} is the exception number which should be changed;
12356 its meaning is architecture-dependent (for example, different numbers
12357 might represent divide by zero, misaligned access, etc). When this
12358 exception occurs, control should be transferred directly to
12359 @var{exception_address}, and the processor state (stack, registers,
12360 and so on) should be just as it is when a processor exception occurs. So if
12361 you want to use a jump instruction to reach @var{exception_address}, it
12362 should be a simple jump, not a jump to subroutine.
12364 For the 386, @var{exception_address} should be installed as an interrupt
12365 gate so that interrupts are masked while the handler runs. The gate
12366 should be at privilege level 0 (the most privileged level). The
12367 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
12368 help from @code{exceptionHandler}.
12370 @item void flush_i_cache()
12371 @findex flush_i_cache
12372 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
12373 instruction cache, if any, on your target machine. If there is no
12374 instruction cache, this subroutine may be a no-op.
12376 On target machines that have instruction caches, @value{GDBN} requires this
12377 function to make certain that the state of your program is stable.
12381 You must also make sure this library routine is available:
12384 @item void *memset(void *, int, int)
12386 This is the standard library function @code{memset} that sets an area of
12387 memory to a known value. If you have one of the free versions of
12388 @code{libc.a}, @code{memset} can be found there; otherwise, you must
12389 either obtain it from your hardware manufacturer, or write your own.
12392 If you do not use the GNU C compiler, you may need other standard
12393 library subroutines as well; this varies from one stub to another,
12394 but in general the stubs are likely to use any of the common library
12395 subroutines which @code{@value{GCC}} generates as inline code.
12398 @node Debug Session
12399 @subsection Putting it all together
12401 @cindex remote serial debugging summary
12402 In summary, when your program is ready to debug, you must follow these
12407 Make sure you have defined the supporting low-level routines
12408 (@pxref{Bootstrapping,,What you must do for the stub}):
12410 @code{getDebugChar}, @code{putDebugChar},
12411 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
12415 Insert these lines near the top of your program:
12423 For the 680x0 stub only, you need to provide a variable called
12424 @code{exceptionHook}. Normally you just use:
12427 void (*exceptionHook)() = 0;
12431 but if before calling @code{set_debug_traps}, you set it to point to a
12432 function in your program, that function is called when
12433 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
12434 error). The function indicated by @code{exceptionHook} is called with
12435 one parameter: an @code{int} which is the exception number.
12438 Compile and link together: your program, the @value{GDBN} debugging stub for
12439 your target architecture, and the supporting subroutines.
12442 Make sure you have a serial connection between your target machine and
12443 the @value{GDBN} host, and identify the serial port on the host.
12446 @c The "remote" target now provides a `load' command, so we should
12447 @c document that. FIXME.
12448 Download your program to your target machine (or get it there by
12449 whatever means the manufacturer provides), and start it.
12452 Start @value{GDBN} on the host, and connect to the target
12453 (@pxref{Connecting,,Connecting to a remote target}).
12457 @node Configurations
12458 @chapter Configuration-Specific Information
12460 While nearly all @value{GDBN} commands are available for all native and
12461 cross versions of the debugger, there are some exceptions. This chapter
12462 describes things that are only available in certain configurations.
12464 There are three major categories of configurations: native
12465 configurations, where the host and target are the same, embedded
12466 operating system configurations, which are usually the same for several
12467 different processor architectures, and bare embedded processors, which
12468 are quite different from each other.
12473 * Embedded Processors::
12480 This section describes details specific to particular native
12485 * BSD libkvm Interface:: Debugging BSD kernel memory images
12486 * SVR4 Process Information:: SVR4 process information
12487 * DJGPP Native:: Features specific to the DJGPP port
12488 * Cygwin Native:: Features specific to the Cygwin port
12489 * Hurd Native:: Features specific to @sc{gnu} Hurd
12490 * Neutrino:: Features specific to QNX Neutrino
12496 On HP-UX systems, if you refer to a function or variable name that
12497 begins with a dollar sign, @value{GDBN} searches for a user or system
12498 name first, before it searches for a convenience variable.
12501 @node BSD libkvm Interface
12502 @subsection BSD libkvm Interface
12505 @cindex kernel memory image
12506 @cindex kernel crash dump
12508 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
12509 interface that provides a uniform interface for accessing kernel virtual
12510 memory images, including live systems and crash dumps. @value{GDBN}
12511 uses this interface to allow you to debug live kernels and kernel crash
12512 dumps on many native BSD configurations. This is implemented as a
12513 special @code{kvm} debugging target. For debugging a live system, load
12514 the currently running kernel into @value{GDBN} and connect to the
12518 (@value{GDBP}) @b{target kvm}
12521 For debugging crash dumps, provide the file name of the crash dump as an
12525 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
12528 Once connected to the @code{kvm} target, the following commands are
12534 Set current context from the @dfn{Process Control Block} (PCB) address.
12537 Set current context from proc address. This command isn't available on
12538 modern FreeBSD systems.
12541 @node SVR4 Process Information
12542 @subsection SVR4 process information
12544 @cindex examine process image
12545 @cindex process info via @file{/proc}
12547 Many versions of SVR4 and compatible systems provide a facility called
12548 @samp{/proc} that can be used to examine the image of a running
12549 process using file-system subroutines. If @value{GDBN} is configured
12550 for an operating system with this facility, the command @code{info
12551 proc} is available to report information about the process running
12552 your program, or about any process running on your system. @code{info
12553 proc} works only on SVR4 systems that include the @code{procfs} code.
12554 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
12555 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
12561 @itemx info proc @var{process-id}
12562 Summarize available information about any running process. If a
12563 process ID is specified by @var{process-id}, display information about
12564 that process; otherwise display information about the program being
12565 debugged. The summary includes the debugged process ID, the command
12566 line used to invoke it, its current working directory, and its
12567 executable file's absolute file name.
12569 On some systems, @var{process-id} can be of the form
12570 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
12571 within a process. If the optional @var{pid} part is missing, it means
12572 a thread from the process being debugged (the leading @samp{/} still
12573 needs to be present, or else @value{GDBN} will interpret the number as
12574 a process ID rather than a thread ID).
12576 @item info proc mappings
12577 @cindex memory address space mappings
12578 Report the memory address space ranges accessible in the program, with
12579 information on whether the process has read, write, or execute access
12580 rights to each range. On @sc{gnu}/Linux systems, each memory range
12581 includes the object file which is mapped to that range, instead of the
12582 memory access rights to that range.
12584 @item info proc stat
12585 @itemx info proc status
12586 @cindex process detailed status information
12587 These subcommands are specific to @sc{gnu}/Linux systems. They show
12588 the process-related information, including the user ID and group ID;
12589 how many threads are there in the process; its virtual memory usage;
12590 the signals that are pending, blocked, and ignored; its TTY; its
12591 consumption of system and user time; its stack size; its @samp{nice}
12592 value; etc. For more information, see the @samp{proc} man page
12593 (type @kbd{man 5 proc} from your shell prompt).
12595 @item info proc all
12596 Show all the information about the process described under all of the
12597 above @code{info proc} subcommands.
12600 @comment These sub-options of 'info proc' were not included when
12601 @comment procfs.c was re-written. Keep their descriptions around
12602 @comment against the day when someone finds the time to put them back in.
12603 @kindex info proc times
12604 @item info proc times
12605 Starting time, user CPU time, and system CPU time for your program and
12608 @kindex info proc id
12610 Report on the process IDs related to your program: its own process ID,
12611 the ID of its parent, the process group ID, and the session ID.
12614 @item set procfs-trace
12615 @kindex set procfs-trace
12616 @cindex @code{procfs} API calls
12617 This command enables and disables tracing of @code{procfs} API calls.
12619 @item show procfs-trace
12620 @kindex show procfs-trace
12621 Show the current state of @code{procfs} API call tracing.
12623 @item set procfs-file @var{file}
12624 @kindex set procfs-file
12625 Tell @value{GDBN} to write @code{procfs} API trace to the named
12626 @var{file}. @value{GDBN} appends the trace info to the previous
12627 contents of the file. The default is to display the trace on the
12630 @item show procfs-file
12631 @kindex show procfs-file
12632 Show the file to which @code{procfs} API trace is written.
12634 @item proc-trace-entry
12635 @itemx proc-trace-exit
12636 @itemx proc-untrace-entry
12637 @itemx proc-untrace-exit
12638 @kindex proc-trace-entry
12639 @kindex proc-trace-exit
12640 @kindex proc-untrace-entry
12641 @kindex proc-untrace-exit
12642 These commands enable and disable tracing of entries into and exits
12643 from the @code{syscall} interface.
12646 @kindex info pidlist
12647 @cindex process list, QNX Neutrino
12648 For QNX Neutrino only, this command displays the list of all the
12649 processes and all the threads within each process.
12652 @kindex info meminfo
12653 @cindex mapinfo list, QNX Neutrino
12654 For QNX Neutrino only, this command displays the list of all mapinfos.
12658 @subsection Features for Debugging @sc{djgpp} Programs
12659 @cindex @sc{djgpp} debugging
12660 @cindex native @sc{djgpp} debugging
12661 @cindex MS-DOS-specific commands
12664 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
12665 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
12666 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
12667 top of real-mode DOS systems and their emulations.
12669 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
12670 defines a few commands specific to the @sc{djgpp} port. This
12671 subsection describes those commands.
12676 This is a prefix of @sc{djgpp}-specific commands which print
12677 information about the target system and important OS structures.
12680 @cindex MS-DOS system info
12681 @cindex free memory information (MS-DOS)
12682 @item info dos sysinfo
12683 This command displays assorted information about the underlying
12684 platform: the CPU type and features, the OS version and flavor, the
12685 DPMI version, and the available conventional and DPMI memory.
12690 @cindex segment descriptor tables
12691 @cindex descriptor tables display
12693 @itemx info dos ldt
12694 @itemx info dos idt
12695 These 3 commands display entries from, respectively, Global, Local,
12696 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
12697 tables are data structures which store a descriptor for each segment
12698 that is currently in use. The segment's selector is an index into a
12699 descriptor table; the table entry for that index holds the
12700 descriptor's base address and limit, and its attributes and access
12703 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
12704 segment (used for both data and the stack), and a DOS segment (which
12705 allows access to DOS/BIOS data structures and absolute addresses in
12706 conventional memory). However, the DPMI host will usually define
12707 additional segments in order to support the DPMI environment.
12709 @cindex garbled pointers
12710 These commands allow to display entries from the descriptor tables.
12711 Without an argument, all entries from the specified table are
12712 displayed. An argument, which should be an integer expression, means
12713 display a single entry whose index is given by the argument. For
12714 example, here's a convenient way to display information about the
12715 debugged program's data segment:
12718 @exdent @code{(@value{GDBP}) info dos ldt $ds}
12719 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
12723 This comes in handy when you want to see whether a pointer is outside
12724 the data segment's limit (i.e.@: @dfn{garbled}).
12726 @cindex page tables display (MS-DOS)
12728 @itemx info dos pte
12729 These two commands display entries from, respectively, the Page
12730 Directory and the Page Tables. Page Directories and Page Tables are
12731 data structures which control how virtual memory addresses are mapped
12732 into physical addresses. A Page Table includes an entry for every
12733 page of memory that is mapped into the program's address space; there
12734 may be several Page Tables, each one holding up to 4096 entries. A
12735 Page Directory has up to 4096 entries, one each for every Page Table
12736 that is currently in use.
12738 Without an argument, @kbd{info dos pde} displays the entire Page
12739 Directory, and @kbd{info dos pte} displays all the entries in all of
12740 the Page Tables. An argument, an integer expression, given to the
12741 @kbd{info dos pde} command means display only that entry from the Page
12742 Directory table. An argument given to the @kbd{info dos pte} command
12743 means display entries from a single Page Table, the one pointed to by
12744 the specified entry in the Page Directory.
12746 @cindex direct memory access (DMA) on MS-DOS
12747 These commands are useful when your program uses @dfn{DMA} (Direct
12748 Memory Access), which needs physical addresses to program the DMA
12751 These commands are supported only with some DPMI servers.
12753 @cindex physical address from linear address
12754 @item info dos address-pte @var{addr}
12755 This command displays the Page Table entry for a specified linear
12756 address. The argument @var{addr} is a linear address which should
12757 already have the appropriate segment's base address added to it,
12758 because this command accepts addresses which may belong to @emph{any}
12759 segment. For example, here's how to display the Page Table entry for
12760 the page where a variable @code{i} is stored:
12763 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
12764 @exdent @code{Page Table entry for address 0x11a00d30:}
12765 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
12769 This says that @code{i} is stored at offset @code{0xd30} from the page
12770 whose physical base address is @code{0x02698000}, and shows all the
12771 attributes of that page.
12773 Note that you must cast the addresses of variables to a @code{char *},
12774 since otherwise the value of @code{__djgpp_base_address}, the base
12775 address of all variables and functions in a @sc{djgpp} program, will
12776 be added using the rules of C pointer arithmetics: if @code{i} is
12777 declared an @code{int}, @value{GDBN} will add 4 times the value of
12778 @code{__djgpp_base_address} to the address of @code{i}.
12780 Here's another example, it displays the Page Table entry for the
12784 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
12785 @exdent @code{Page Table entry for address 0x29110:}
12786 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
12790 (The @code{+ 3} offset is because the transfer buffer's address is the
12791 3rd member of the @code{_go32_info_block} structure.) The output
12792 clearly shows that this DPMI server maps the addresses in conventional
12793 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
12794 linear (@code{0x29110}) addresses are identical.
12796 This command is supported only with some DPMI servers.
12799 @cindex DOS serial data link, remote debugging
12800 In addition to native debugging, the DJGPP port supports remote
12801 debugging via a serial data link. The following commands are specific
12802 to remote serial debugging in the DJGPP port of @value{GDBN}.
12805 @kindex set com1base
12806 @kindex set com1irq
12807 @kindex set com2base
12808 @kindex set com2irq
12809 @kindex set com3base
12810 @kindex set com3irq
12811 @kindex set com4base
12812 @kindex set com4irq
12813 @item set com1base @var{addr}
12814 This command sets the base I/O port address of the @file{COM1} serial
12817 @item set com1irq @var{irq}
12818 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
12819 for the @file{COM1} serial port.
12821 There are similar commands @samp{set com2base}, @samp{set com3irq},
12822 etc.@: for setting the port address and the @code{IRQ} lines for the
12825 @kindex show com1base
12826 @kindex show com1irq
12827 @kindex show com2base
12828 @kindex show com2irq
12829 @kindex show com3base
12830 @kindex show com3irq
12831 @kindex show com4base
12832 @kindex show com4irq
12833 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
12834 display the current settings of the base address and the @code{IRQ}
12835 lines used by the COM ports.
12838 @kindex info serial
12839 @cindex DOS serial port status
12840 This command prints the status of the 4 DOS serial ports. For each
12841 port, it prints whether it's active or not, its I/O base address and
12842 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
12843 counts of various errors encountered so far.
12847 @node Cygwin Native
12848 @subsection Features for Debugging MS Windows PE executables
12849 @cindex MS Windows debugging
12850 @cindex native Cygwin debugging
12851 @cindex Cygwin-specific commands
12853 @value{GDBN} supports native debugging of MS Windows programs, including
12854 DLLs with and without symbolic debugging information. There are various
12855 additional Cygwin-specific commands, described in this subsection. The
12856 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
12857 that have no debugging symbols.
12863 This is a prefix of MS Windows specific commands which print
12864 information about the target system and important OS structures.
12866 @item info w32 selector
12867 This command displays information returned by
12868 the Win32 API @code{GetThreadSelectorEntry} function.
12869 It takes an optional argument that is evaluated to
12870 a long value to give the information about this given selector.
12871 Without argument, this command displays information
12872 about the the six segment registers.
12876 This is a Cygwin specific alias of info shared.
12878 @kindex dll-symbols
12880 This command loads symbols from a dll similarly to
12881 add-sym command but without the need to specify a base address.
12883 @kindex set new-console
12884 @item set new-console @var{mode}
12885 If @var{mode} is @code{on} the debuggee will
12886 be started in a new console on next start.
12887 If @var{mode} is @code{off}i, the debuggee will
12888 be started in the same console as the debugger.
12890 @kindex show new-console
12891 @item show new-console
12892 Displays whether a new console is used
12893 when the debuggee is started.
12895 @kindex set new-group
12896 @item set new-group @var{mode}
12897 This boolean value controls whether the debuggee should
12898 start a new group or stay in the same group as the debugger.
12899 This affects the way the Windows OS handles
12902 @kindex show new-group
12903 @item show new-group
12904 Displays current value of new-group boolean.
12906 @kindex set debugevents
12907 @item set debugevents
12908 This boolean value adds debug output concerning events seen by the debugger.
12910 @kindex set debugexec
12911 @item set debugexec
12912 This boolean value adds debug output concerning execute events
12913 seen by the debugger.
12915 @kindex set debugexceptions
12916 @item set debugexceptions
12917 This boolean value adds debug ouptut concerning exception events
12918 seen by the debugger.
12920 @kindex set debugmemory
12921 @item set debugmemory
12922 This boolean value adds debug ouptut concerning memory events
12923 seen by the debugger.
12927 This boolean values specifies whether the debuggee is called
12928 via a shell or directly (default value is on).
12932 Displays if the debuggee will be started with a shell.
12937 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
12940 @node Non-debug DLL symbols
12941 @subsubsection Support for DLLs without debugging symbols
12942 @cindex DLLs with no debugging symbols
12943 @cindex Minimal symbols and DLLs
12945 Very often on windows, some of the DLLs that your program relies on do
12946 not include symbolic debugging information (for example,
12947 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
12948 symbols in a DLL, it relies on the minimal amount of symbolic
12949 information contained in the DLL's export table. This subsubsection
12950 describes working with such symbols, known internally to @value{GDBN} as
12951 ``minimal symbols''.
12953 Note that before the debugged program has started execution, no DLLs
12954 will have been loaded. The easiest way around this problem is simply to
12955 start the program --- either by setting a breakpoint or letting the
12956 program run once to completion. It is also possible to force
12957 @value{GDBN} to load a particular DLL before starting the executable ---
12958 see the shared library information in @pxref{Files} or the
12959 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
12960 explicitly loading symbols from a DLL with no debugging information will
12961 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
12962 which may adversely affect symbol lookup performance.
12964 @subsubsection DLL name prefixes
12966 In keeping with the naming conventions used by the Microsoft debugging
12967 tools, DLL export symbols are made available with a prefix based on the
12968 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
12969 also entered into the symbol table, so @code{CreateFileA} is often
12970 sufficient. In some cases there will be name clashes within a program
12971 (particularly if the executable itself includes full debugging symbols)
12972 necessitating the use of the fully qualified name when referring to the
12973 contents of the DLL. Use single-quotes around the name to avoid the
12974 exclamation mark (``!'') being interpreted as a language operator.
12976 Note that the internal name of the DLL may be all upper-case, even
12977 though the file name of the DLL is lower-case, or vice-versa. Since
12978 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
12979 some confusion. If in doubt, try the @code{info functions} and
12980 @code{info variables} commands or even @code{maint print msymbols} (see
12981 @pxref{Symbols}). Here's an example:
12984 (@value{GDBP}) info function CreateFileA
12985 All functions matching regular expression "CreateFileA":
12987 Non-debugging symbols:
12988 0x77e885f4 CreateFileA
12989 0x77e885f4 KERNEL32!CreateFileA
12993 (@value{GDBP}) info function !
12994 All functions matching regular expression "!":
12996 Non-debugging symbols:
12997 0x6100114c cygwin1!__assert
12998 0x61004034 cygwin1!_dll_crt0@@0
12999 0x61004240 cygwin1!dll_crt0(per_process *)
13003 @subsubsection Working with minimal symbols
13005 Symbols extracted from a DLL's export table do not contain very much
13006 type information. All that @value{GDBN} can do is guess whether a symbol
13007 refers to a function or variable depending on the linker section that
13008 contains the symbol. Also note that the actual contents of the memory
13009 contained in a DLL are not available unless the program is running. This
13010 means that you cannot examine the contents of a variable or disassemble
13011 a function within a DLL without a running program.
13013 Variables are generally treated as pointers and dereferenced
13014 automatically. For this reason, it is often necessary to prefix a
13015 variable name with the address-of operator (``&'') and provide explicit
13016 type information in the command. Here's an example of the type of
13020 (@value{GDBP}) print 'cygwin1!__argv'
13025 (@value{GDBP}) x 'cygwin1!__argv'
13026 0x10021610: "\230y\""
13029 And two possible solutions:
13032 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
13033 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
13037 (@value{GDBP}) x/2x &'cygwin1!__argv'
13038 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
13039 (@value{GDBP}) x/x 0x10021608
13040 0x10021608: 0x0022fd98
13041 (@value{GDBP}) x/s 0x0022fd98
13042 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
13045 Setting a break point within a DLL is possible even before the program
13046 starts execution. However, under these circumstances, @value{GDBN} can't
13047 examine the initial instructions of the function in order to skip the
13048 function's frame set-up code. You can work around this by using ``*&''
13049 to set the breakpoint at a raw memory address:
13052 (@value{GDBP}) break *&'python22!PyOS_Readline'
13053 Breakpoint 1 at 0x1e04eff0
13056 The author of these extensions is not entirely convinced that setting a
13057 break point within a shared DLL like @file{kernel32.dll} is completely
13061 @subsection Commands specific to @sc{gnu} Hurd systems
13062 @cindex @sc{gnu} Hurd debugging
13064 This subsection describes @value{GDBN} commands specific to the
13065 @sc{gnu} Hurd native debugging.
13070 @kindex set signals@r{, Hurd command}
13071 @kindex set sigs@r{, Hurd command}
13072 This command toggles the state of inferior signal interception by
13073 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
13074 affected by this command. @code{sigs} is a shorthand alias for
13079 @kindex show signals@r{, Hurd command}
13080 @kindex show sigs@r{, Hurd command}
13081 Show the current state of intercepting inferior's signals.
13083 @item set signal-thread
13084 @itemx set sigthread
13085 @kindex set signal-thread
13086 @kindex set sigthread
13087 This command tells @value{GDBN} which thread is the @code{libc} signal
13088 thread. That thread is run when a signal is delivered to a running
13089 process. @code{set sigthread} is the shorthand alias of @code{set
13092 @item show signal-thread
13093 @itemx show sigthread
13094 @kindex show signal-thread
13095 @kindex show sigthread
13096 These two commands show which thread will run when the inferior is
13097 delivered a signal.
13100 @kindex set stopped@r{, Hurd command}
13101 This commands tells @value{GDBN} that the inferior process is stopped,
13102 as with the @code{SIGSTOP} signal. The stopped process can be
13103 continued by delivering a signal to it.
13106 @kindex show stopped@r{, Hurd command}
13107 This command shows whether @value{GDBN} thinks the debuggee is
13110 @item set exceptions
13111 @kindex set exceptions@r{, Hurd command}
13112 Use this command to turn off trapping of exceptions in the inferior.
13113 When exception trapping is off, neither breakpoints nor
13114 single-stepping will work. To restore the default, set exception
13117 @item show exceptions
13118 @kindex show exceptions@r{, Hurd command}
13119 Show the current state of trapping exceptions in the inferior.
13121 @item set task pause
13122 @kindex set task@r{, Hurd commands}
13123 @cindex task attributes (@sc{gnu} Hurd)
13124 @cindex pause current task (@sc{gnu} Hurd)
13125 This command toggles task suspension when @value{GDBN} has control.
13126 Setting it to on takes effect immediately, and the task is suspended
13127 whenever @value{GDBN} gets control. Setting it to off will take
13128 effect the next time the inferior is continued. If this option is set
13129 to off, you can use @code{set thread default pause on} or @code{set
13130 thread pause on} (see below) to pause individual threads.
13132 @item show task pause
13133 @kindex show task@r{, Hurd commands}
13134 Show the current state of task suspension.
13136 @item set task detach-suspend-count
13137 @cindex task suspend count
13138 @cindex detach from task, @sc{gnu} Hurd
13139 This command sets the suspend count the task will be left with when
13140 @value{GDBN} detaches from it.
13142 @item show task detach-suspend-count
13143 Show the suspend count the task will be left with when detaching.
13145 @item set task exception-port
13146 @itemx set task excp
13147 @cindex task exception port, @sc{gnu} Hurd
13148 This command sets the task exception port to which @value{GDBN} will
13149 forward exceptions. The argument should be the value of the @dfn{send
13150 rights} of the task. @code{set task excp} is a shorthand alias.
13152 @item set noninvasive
13153 @cindex noninvasive task options
13154 This command switches @value{GDBN} to a mode that is the least
13155 invasive as far as interfering with the inferior is concerned. This
13156 is the same as using @code{set task pause}, @code{set exceptions}, and
13157 @code{set signals} to values opposite to the defaults.
13159 @item info send-rights
13160 @itemx info receive-rights
13161 @itemx info port-rights
13162 @itemx info port-sets
13163 @itemx info dead-names
13166 @cindex send rights, @sc{gnu} Hurd
13167 @cindex receive rights, @sc{gnu} Hurd
13168 @cindex port rights, @sc{gnu} Hurd
13169 @cindex port sets, @sc{gnu} Hurd
13170 @cindex dead names, @sc{gnu} Hurd
13171 These commands display information about, respectively, send rights,
13172 receive rights, port rights, port sets, and dead names of a task.
13173 There are also shorthand aliases: @code{info ports} for @code{info
13174 port-rights} and @code{info psets} for @code{info port-sets}.
13176 @item set thread pause
13177 @kindex set thread@r{, Hurd command}
13178 @cindex thread properties, @sc{gnu} Hurd
13179 @cindex pause current thread (@sc{gnu} Hurd)
13180 This command toggles current thread suspension when @value{GDBN} has
13181 control. Setting it to on takes effect immediately, and the current
13182 thread is suspended whenever @value{GDBN} gets control. Setting it to
13183 off will take effect the next time the inferior is continued.
13184 Normally, this command has no effect, since when @value{GDBN} has
13185 control, the whole task is suspended. However, if you used @code{set
13186 task pause off} (see above), this command comes in handy to suspend
13187 only the current thread.
13189 @item show thread pause
13190 @kindex show thread@r{, Hurd command}
13191 This command shows the state of current thread suspension.
13193 @item set thread run
13194 This comamnd sets whether the current thread is allowed to run.
13196 @item show thread run
13197 Show whether the current thread is allowed to run.
13199 @item set thread detach-suspend-count
13200 @cindex thread suspend count, @sc{gnu} Hurd
13201 @cindex detach from thread, @sc{gnu} Hurd
13202 This command sets the suspend count @value{GDBN} will leave on a
13203 thread when detaching. This number is relative to the suspend count
13204 found by @value{GDBN} when it notices the thread; use @code{set thread
13205 takeover-suspend-count} to force it to an absolute value.
13207 @item show thread detach-suspend-count
13208 Show the suspend count @value{GDBN} will leave on the thread when
13211 @item set thread exception-port
13212 @itemx set thread excp
13213 Set the thread exception port to which to forward exceptions. This
13214 overrides the port set by @code{set task exception-port} (see above).
13215 @code{set thread excp} is the shorthand alias.
13217 @item set thread takeover-suspend-count
13218 Normally, @value{GDBN}'s thread suspend counts are relative to the
13219 value @value{GDBN} finds when it notices each thread. This command
13220 changes the suspend counts to be absolute instead.
13222 @item set thread default
13223 @itemx show thread default
13224 @cindex thread default settings, @sc{gnu} Hurd
13225 Each of the above @code{set thread} commands has a @code{set thread
13226 default} counterpart (e.g., @code{set thread default pause}, @code{set
13227 thread default exception-port}, etc.). The @code{thread default}
13228 variety of commands sets the default thread properties for all
13229 threads; you can then change the properties of individual threads with
13230 the non-default commands.
13235 @subsection QNX Neutrino
13236 @cindex QNX Neutrino
13238 @value{GDBN} provides the following commands specific to the QNX
13242 @item set debug nto-debug
13243 @kindex set debug nto-debug
13244 When set to on, enables debugging messages specific to the QNX
13247 @item show debug nto-debug
13248 @kindex show debug nto-debug
13249 Show the current state of QNX Neutrino messages.
13254 @section Embedded Operating Systems
13256 This section describes configurations involving the debugging of
13257 embedded operating systems that are available for several different
13261 * VxWorks:: Using @value{GDBN} with VxWorks
13264 @value{GDBN} includes the ability to debug programs running on
13265 various real-time operating systems.
13268 @subsection Using @value{GDBN} with VxWorks
13274 @kindex target vxworks
13275 @item target vxworks @var{machinename}
13276 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
13277 is the target system's machine name or IP address.
13281 On VxWorks, @code{load} links @var{filename} dynamically on the
13282 current target system as well as adding its symbols in @value{GDBN}.
13284 @value{GDBN} enables developers to spawn and debug tasks running on networked
13285 VxWorks targets from a Unix host. Already-running tasks spawned from
13286 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
13287 both the Unix host and on the VxWorks target. The program
13288 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
13289 installed with the name @code{vxgdb}, to distinguish it from a
13290 @value{GDBN} for debugging programs on the host itself.)
13293 @item VxWorks-timeout @var{args}
13294 @kindex vxworks-timeout
13295 All VxWorks-based targets now support the option @code{vxworks-timeout}.
13296 This option is set by the user, and @var{args} represents the number of
13297 seconds @value{GDBN} waits for responses to rpc's. You might use this if
13298 your VxWorks target is a slow software simulator or is on the far side
13299 of a thin network line.
13302 The following information on connecting to VxWorks was current when
13303 this manual was produced; newer releases of VxWorks may use revised
13306 @findex INCLUDE_RDB
13307 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
13308 to include the remote debugging interface routines in the VxWorks
13309 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
13310 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
13311 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
13312 source debugging task @code{tRdbTask} when VxWorks is booted. For more
13313 information on configuring and remaking VxWorks, see the manufacturer's
13315 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
13317 Once you have included @file{rdb.a} in your VxWorks system image and set
13318 your Unix execution search path to find @value{GDBN}, you are ready to
13319 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
13320 @code{vxgdb}, depending on your installation).
13322 @value{GDBN} comes up showing the prompt:
13329 * VxWorks Connection:: Connecting to VxWorks
13330 * VxWorks Download:: VxWorks download
13331 * VxWorks Attach:: Running tasks
13334 @node VxWorks Connection
13335 @subsubsection Connecting to VxWorks
13337 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
13338 network. To connect to a target whose host name is ``@code{tt}'', type:
13341 (vxgdb) target vxworks tt
13345 @value{GDBN} displays messages like these:
13348 Attaching remote machine across net...
13353 @value{GDBN} then attempts to read the symbol tables of any object modules
13354 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
13355 these files by searching the directories listed in the command search
13356 path (@pxref{Environment, ,Your program's environment}); if it fails
13357 to find an object file, it displays a message such as:
13360 prog.o: No such file or directory.
13363 When this happens, add the appropriate directory to the search path with
13364 the @value{GDBN} command @code{path}, and execute the @code{target}
13367 @node VxWorks Download
13368 @subsubsection VxWorks download
13370 @cindex download to VxWorks
13371 If you have connected to the VxWorks target and you want to debug an
13372 object that has not yet been loaded, you can use the @value{GDBN}
13373 @code{load} command to download a file from Unix to VxWorks
13374 incrementally. The object file given as an argument to the @code{load}
13375 command is actually opened twice: first by the VxWorks target in order
13376 to download the code, then by @value{GDBN} in order to read the symbol
13377 table. This can lead to problems if the current working directories on
13378 the two systems differ. If both systems have NFS mounted the same
13379 filesystems, you can avoid these problems by using absolute paths.
13380 Otherwise, it is simplest to set the working directory on both systems
13381 to the directory in which the object file resides, and then to reference
13382 the file by its name, without any path. For instance, a program
13383 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
13384 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
13385 program, type this on VxWorks:
13388 -> cd "@var{vxpath}/vw/demo/rdb"
13392 Then, in @value{GDBN}, type:
13395 (vxgdb) cd @var{hostpath}/vw/demo/rdb
13396 (vxgdb) load prog.o
13399 @value{GDBN} displays a response similar to this:
13402 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
13405 You can also use the @code{load} command to reload an object module
13406 after editing and recompiling the corresponding source file. Note that
13407 this makes @value{GDBN} delete all currently-defined breakpoints,
13408 auto-displays, and convenience variables, and to clear the value
13409 history. (This is necessary in order to preserve the integrity of
13410 debugger's data structures that reference the target system's symbol
13413 @node VxWorks Attach
13414 @subsubsection Running tasks
13416 @cindex running VxWorks tasks
13417 You can also attach to an existing task using the @code{attach} command as
13421 (vxgdb) attach @var{task}
13425 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
13426 or suspended when you attach to it. Running tasks are suspended at
13427 the time of attachment.
13429 @node Embedded Processors
13430 @section Embedded Processors
13432 This section goes into details specific to particular embedded
13435 @cindex send command to simulator
13436 Whenever a specific embedded processor has a simulator, @value{GDBN}
13437 allows to send an arbitrary command to the simulator.
13440 @item sim @var{command}
13441 @kindex sim@r{, a command}
13442 Send an arbitrary @var{command} string to the simulator. Consult the
13443 documentation for the specific simulator in use for information about
13444 acceptable commands.
13450 * H8/300:: Renesas H8/300
13451 * H8/500:: Renesas H8/500
13452 * M32R/D:: Renesas M32R/D
13453 * M68K:: Motorola M68K
13454 * MIPS Embedded:: MIPS Embedded
13455 * OpenRISC 1000:: OpenRisc 1000
13456 * PA:: HP PA Embedded
13459 * Sparclet:: Tsqware Sparclet
13460 * Sparclite:: Fujitsu Sparclite
13461 * ST2000:: Tandem ST2000
13462 * Z8000:: Zilog Z8000
13465 * Super-H:: Renesas Super-H
13466 * WinCE:: Windows CE child processes
13475 @item target rdi @var{dev}
13476 ARM Angel monitor, via RDI library interface to ADP protocol. You may
13477 use this target to communicate with both boards running the Angel
13478 monitor, or with the EmbeddedICE JTAG debug device.
13481 @item target rdp @var{dev}
13486 @value{GDBN} provides the following ARM-specific commands:
13489 @item set arm disassembler
13491 This commands selects from a list of disassembly styles. The
13492 @code{"std"} style is the standard style.
13494 @item show arm disassembler
13496 Show the current disassembly style.
13498 @item set arm apcs32
13499 @cindex ARM 32-bit mode
13500 This command toggles ARM operation mode between 32-bit and 26-bit.
13502 @item show arm apcs32
13503 Display the current usage of the ARM 32-bit mode.
13505 @item set arm fpu @var{fputype}
13506 This command sets the ARM floating-point unit (FPU) type. The
13507 argument @var{fputype} can be one of these:
13511 Determine the FPU type by querying the OS ABI.
13513 Software FPU, with mixed-endian doubles on little-endian ARM
13516 GCC-compiled FPA co-processor.
13518 Software FPU with pure-endian doubles.
13524 Show the current type of the FPU.
13527 This command forces @value{GDBN} to use the specified ABI.
13530 Show the currently used ABI.
13532 @item set debug arm
13533 Toggle whether to display ARM-specific debugging messages from the ARM
13534 target support subsystem.
13536 @item show debug arm
13537 Show whether ARM-specific debugging messages are enabled.
13540 The following commands are available when an ARM target is debugged
13541 using the RDI interface:
13544 @item rdilogfile @r{[}@var{file}@r{]}
13546 @cindex ADP (Angel Debugger Protocol) logging
13547 Set the filename for the ADP (Angel Debugger Protocol) packet log.
13548 With an argument, sets the log file to the specified @var{file}. With
13549 no argument, show the current log file name. The default log file is
13552 @item rdilogenable @r{[}@var{arg}@r{]}
13553 @kindex rdilogenable
13554 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
13555 enables logging, with an argument 0 or @code{"no"} disables it. With
13556 no arguments displays the current setting. When logging is enabled,
13557 ADP packets exchanged between @value{GDBN} and the RDI target device
13558 are logged to a file.
13560 @item set rdiromatzero
13561 @kindex set rdiromatzero
13562 @cindex ROM at zero address, RDI
13563 Tell @value{GDBN} whether the target has ROM at address 0. If on,
13564 vector catching is disabled, so that zero address can be used. If off
13565 (the default), vector catching is enabled. For this command to take
13566 effect, it needs to be invoked prior to the @code{target rdi} command.
13568 @item show rdiromatzero
13569 @kindex show rdiromatzero
13570 Show the current setting of ROM at zero address.
13572 @item set rdiheartbeat
13573 @kindex set rdiheartbeat
13574 @cindex RDI heartbeat
13575 Enable or disable RDI heartbeat packets. It is not recommended to
13576 turn on this option, since it confuses ARM and EPI JTAG interface, as
13577 well as the Angel monitor.
13579 @item show rdiheartbeat
13580 @kindex show rdiheartbeat
13581 Show the setting of RDI heartbeat packets.
13586 @subsection Renesas H8/300
13590 @kindex target hms@r{, with H8/300}
13591 @item target hms @var{dev}
13592 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
13593 Use special commands @code{device} and @code{speed} to control the serial
13594 line and the communications speed used.
13596 @kindex target e7000@r{, with H8/300}
13597 @item target e7000 @var{dev}
13598 E7000 emulator for Renesas H8 and SH.
13600 @kindex target sh3@r{, with H8/300}
13601 @kindex target sh3e@r{, with H8/300}
13602 @item target sh3 @var{dev}
13603 @itemx target sh3e @var{dev}
13604 Renesas SH-3 and SH-3E target systems.
13608 @cindex download to H8/300 or H8/500
13609 @cindex H8/300 or H8/500 download
13610 @cindex download to Renesas SH
13611 @cindex Renesas SH download
13612 When you select remote debugging to a Renesas SH, H8/300, or H8/500
13613 board, the @code{load} command downloads your program to the Renesas
13614 board and also opens it as the current executable target for
13615 @value{GDBN} on your host (like the @code{file} command).
13617 @value{GDBN} needs to know these things to talk to your
13618 Renesas SH, H8/300, or H8/500:
13622 that you want to use @samp{target hms}, the remote debugging interface
13623 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
13624 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
13625 the default when @value{GDBN} is configured specifically for the Renesas SH,
13626 H8/300, or H8/500.)
13629 what serial device connects your host to your Renesas board (the first
13630 serial device available on your host is the default).
13633 what speed to use over the serial device.
13637 * Renesas Boards:: Connecting to Renesas boards.
13638 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
13639 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
13642 @node Renesas Boards
13643 @subsubsection Connecting to Renesas boards
13645 @c only for Unix hosts
13647 @cindex serial device, Renesas micros
13648 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
13649 need to explicitly set the serial device. The default @var{port} is the
13650 first available port on your host. This is only necessary on Unix
13651 hosts, where it is typically something like @file{/dev/ttya}.
13654 @cindex serial line speed, Renesas micros
13655 @code{@value{GDBN}} has another special command to set the communications
13656 speed: @samp{speed @var{bps}}. This command also is only used from Unix
13657 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
13658 the DOS @code{mode} command (for instance,
13659 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
13661 The @samp{device} and @samp{speed} commands are available only when you
13662 use a Unix host to debug your Renesas microprocessor programs. If you
13664 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
13665 called @code{asynctsr} to communicate with the development board
13666 through a PC serial port. You must also use the DOS @code{mode} command
13667 to set up the serial port on the DOS side.
13669 The following sample session illustrates the steps needed to start a
13670 program under @value{GDBN} control on an H8/300. The example uses a
13671 sample H8/300 program called @file{t.x}. The procedure is the same for
13672 the Renesas SH and the H8/500.
13674 First hook up your development board. In this example, we use a
13675 board attached to serial port @code{COM2}; if you use a different serial
13676 port, substitute its name in the argument of the @code{mode} command.
13677 When you call @code{asynctsr}, the auxiliary comms program used by the
13678 debugger, you give it just the numeric part of the serial port's name;
13679 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
13683 C:\H8300\TEST> asynctsr 2
13684 C:\H8300\TEST> mode com2:9600,n,8,1,p
13686 Resident portion of MODE loaded
13688 COM2: 9600, n, 8, 1, p
13693 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
13694 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
13695 disable it, or even boot without it, to use @code{asynctsr} to control
13696 your development board.
13699 @kindex target hms@r{, and serial protocol}
13700 Now that serial communications are set up, and the development board is
13701 connected, you can start up @value{GDBN}. Call @code{@value{GDBN}} with
13702 the name of your program as the argument. @code{@value{GDBN}} prompts
13703 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
13704 commands to begin your debugging session: @samp{target hms} to specify
13705 cross-debugging to the Renesas board, and the @code{load} command to
13706 download your program to the board. @code{load} displays the names of
13707 the program's sections, and a @samp{*} for each 2K of data downloaded.
13708 (If you want to refresh @value{GDBN} data on symbols or on the
13709 executable file without downloading, use the @value{GDBN} commands
13710 @code{file} or @code{symbol-file}. These commands, and @code{load}
13711 itself, are described in @ref{Files,,Commands to specify files}.)
13714 (eg-C:\H8300\TEST) @value{GDBP} t.x
13715 @value{GDBN} is free software and you are welcome to distribute copies
13716 of it under certain conditions; type "show copying" to see
13718 There is absolutely no warranty for @value{GDBN}; type "show warranty"
13720 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
13721 (@value{GDBP}) target hms
13722 Connected to remote H8/300 HMS system.
13723 (@value{GDBP}) load t.x
13724 .text : 0x8000 .. 0xabde ***********
13725 .data : 0xabde .. 0xad30 *
13726 .stack : 0xf000 .. 0xf014 *
13729 At this point, you're ready to run or debug your program. From here on,
13730 you can use all the usual @value{GDBN} commands. The @code{break} command
13731 sets breakpoints; the @code{run} command starts your program;
13732 @code{print} or @code{x} display data; the @code{continue} command
13733 resumes execution after stopping at a breakpoint. You can use the
13734 @code{help} command at any time to find out more about @value{GDBN} commands.
13736 Remember, however, that @emph{operating system} facilities aren't
13737 available on your development board; for example, if your program hangs,
13738 you can't send an interrupt---but you can press the @sc{reset} switch!
13740 Use the @sc{reset} button on the development board
13743 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
13744 no way to pass an interrupt signal to the development board); and
13747 to return to the @value{GDBN} command prompt after your program finishes
13748 normally. The communications protocol provides no other way for @value{GDBN}
13749 to detect program completion.
13752 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
13753 development board as a ``normal exit'' of your program.
13756 @subsubsection Using the E7000 in-circuit emulator
13758 @kindex target e7000@r{, with Renesas ICE}
13759 You can use the E7000 in-circuit emulator to develop code for either the
13760 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
13761 e7000} command to connect @value{GDBN} to your E7000:
13764 @item target e7000 @var{port} @var{speed}
13765 Use this form if your E7000 is connected to a serial port. The
13766 @var{port} argument identifies what serial port to use (for example,
13767 @samp{com2}). The third argument is the line speed in bits per second
13768 (for example, @samp{9600}).
13770 @item target e7000 @var{hostname}
13771 If your E7000 is installed as a host on a TCP/IP network, you can just
13772 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
13775 The following special commands are available when debugging with the
13779 @item e7000 @var{command}
13781 @cindex send command to E7000 monitor
13782 This sends the specified @var{command} to the E7000 monitor.
13784 @item ftplogin @var{machine} @var{username} @var{password} @var{dir}
13785 @kindex ftplogin@r{, E7000}
13786 This command records information for subsequent interface with the
13787 E7000 monitor via the FTP protocol: @value{GDBN} will log into the
13788 named @var{machine} using specified @var{username} and @var{password},
13789 and then chdir to the named directory @var{dir}.
13791 @item ftpload @var{file}
13792 @kindex ftpload@r{, E7000}
13793 This command uses credentials recorded by @code{ftplogin} to fetch and
13794 load the named @var{file} from the E7000 monitor.
13797 @kindex drain@r{, E7000}
13798 This command drains any pending text buffers stored on the E7000.
13800 @item set usehardbreakpoints
13801 @itemx show usehardbreakpoints
13802 @kindex set usehardbreakpoints@r{, E7000}
13803 @kindex show usehardbreakpoints@r{, E7000}
13804 @cindex hardware breakpoints, and E7000
13805 These commands set and show the use of hardware breakpoints for all
13806 breakpoints. @xref{Set Breaks, hardware-assisted breakpoint}, for
13807 more information about using hardware breakpoints selectively.
13810 @node Renesas Special
13811 @subsubsection Special @value{GDBN} commands for Renesas micros
13813 Some @value{GDBN} commands are available only for the H8/300:
13817 @kindex set machine
13818 @kindex show machine
13819 @item set machine h8300
13820 @itemx set machine h8300h
13821 Condition @value{GDBN} for one of the two variants of the H8/300
13822 architecture with @samp{set machine}. You can use @samp{show machine}
13823 to check which variant is currently in effect.
13832 @kindex set memory @var{mod}
13833 @cindex memory models, H8/500
13834 @item set memory @var{mod}
13836 Specify which H8/500 memory model (@var{mod}) you are using with
13837 @samp{set memory}; check which memory model is in effect with @samp{show
13838 memory}. The accepted values for @var{mod} are @code{small},
13839 @code{big}, @code{medium}, and @code{compact}.
13844 @subsection Renesas M32R/D and M32R/SDI
13847 @kindex target m32r
13848 @item target m32r @var{dev}
13849 Renesas M32R/D ROM monitor.
13851 @kindex target m32rsdi
13852 @item target m32rsdi @var{dev}
13853 Renesas M32R SDI server, connected via parallel port to the board.
13856 The following @value{GDBN} commands are specific to the M32R monitor:
13859 @item set download-path @var{path}
13860 @kindex set download-path
13861 @cindex find downloadable @sc{srec} files (M32R)
13862 Set the default path for finding donwloadable @sc{srec} files.
13864 @item show download-path
13865 @kindex show download-path
13866 Show the default path for downloadable @sc{srec} files.
13868 @item set board-address @var{addr}
13869 @kindex set board-address
13870 @cindex M32-EVA target board address
13871 Set the IP address for the M32R-EVA target board.
13873 @item show board-address
13874 @kindex show board-address
13875 Show the current IP address of the target board.
13877 @item set server-address @var{addr}
13878 @kindex set server-address
13879 @cindex download server address (M32R)
13880 Set the IP address for the download server, which is the @value{GDBN}'s
13883 @item show server-address
13884 @kindex show server-address
13885 Display the IP address of the download server.
13887 @item upload @r{[}@var{file}@r{]}
13888 @kindex upload@r{, M32R}
13889 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
13890 upload capability. If no @var{file} argument is given, the current
13891 executable file is uploaded.
13893 @item tload @r{[}@var{file}@r{]}
13894 @kindex tload@r{, M32R}
13895 Test the @code{upload} command.
13898 The following commands are available for M32R/SDI:
13903 @cindex reset SDI connection, M32R
13904 This command resets the SDI connection.
13908 This command shows the SDI connection status.
13911 @kindex debug_chaos
13912 @cindex M32R/Chaos debugging
13913 Instructs the remote that M32R/Chaos debugging is to be used.
13915 @item use_debug_dma
13916 @kindex use_debug_dma
13917 Instructs the remote to use the DEBUG_DMA method of accessing memory.
13920 @kindex use_mon_code
13921 Instructs the remote to use the MON_CODE method of accessing memory.
13924 @kindex use_ib_break
13925 Instructs the remote to set breakpoints by IB break.
13927 @item use_dbt_break
13928 @kindex use_dbt_break
13929 Instructs the remote to set breakpoints by DBT.
13935 The Motorola m68k configuration includes ColdFire support, and
13936 target command for the following ROM monitors.
13940 @kindex target abug
13941 @item target abug @var{dev}
13942 ABug ROM monitor for M68K.
13944 @kindex target cpu32bug
13945 @item target cpu32bug @var{dev}
13946 CPU32BUG monitor, running on a CPU32 (M68K) board.
13948 @kindex target dbug
13949 @item target dbug @var{dev}
13950 dBUG ROM monitor for Motorola ColdFire.
13953 @item target est @var{dev}
13954 EST-300 ICE monitor, running on a CPU32 (M68K) board.
13956 @kindex target rom68k
13957 @item target rom68k @var{dev}
13958 ROM 68K monitor, running on an M68K IDP board.
13964 @kindex target rombug
13965 @item target rombug @var{dev}
13966 ROMBUG ROM monitor for OS/9000.
13970 @node MIPS Embedded
13971 @subsection MIPS Embedded
13973 @cindex MIPS boards
13974 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
13975 MIPS board attached to a serial line. This is available when
13976 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
13979 Use these @value{GDBN} commands to specify the connection to your target board:
13982 @item target mips @var{port}
13983 @kindex target mips @var{port}
13984 To run a program on the board, start up @code{@value{GDBP}} with the
13985 name of your program as the argument. To connect to the board, use the
13986 command @samp{target mips @var{port}}, where @var{port} is the name of
13987 the serial port connected to the board. If the program has not already
13988 been downloaded to the board, you may use the @code{load} command to
13989 download it. You can then use all the usual @value{GDBN} commands.
13991 For example, this sequence connects to the target board through a serial
13992 port, and loads and runs a program called @var{prog} through the
13996 host$ @value{GDBP} @var{prog}
13997 @value{GDBN} is free software and @dots{}
13998 (@value{GDBP}) target mips /dev/ttyb
13999 (@value{GDBP}) load @var{prog}
14003 @item target mips @var{hostname}:@var{portnumber}
14004 On some @value{GDBN} host configurations, you can specify a TCP
14005 connection (for instance, to a serial line managed by a terminal
14006 concentrator) instead of a serial port, using the syntax
14007 @samp{@var{hostname}:@var{portnumber}}.
14009 @item target pmon @var{port}
14010 @kindex target pmon @var{port}
14013 @item target ddb @var{port}
14014 @kindex target ddb @var{port}
14015 NEC's DDB variant of PMON for Vr4300.
14017 @item target lsi @var{port}
14018 @kindex target lsi @var{port}
14019 LSI variant of PMON.
14021 @kindex target r3900
14022 @item target r3900 @var{dev}
14023 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
14025 @kindex target array
14026 @item target array @var{dev}
14027 Array Tech LSI33K RAID controller board.
14033 @value{GDBN} also supports these special commands for MIPS targets:
14036 @item set mipsfpu double
14037 @itemx set mipsfpu single
14038 @itemx set mipsfpu none
14039 @itemx set mipsfpu auto
14040 @itemx show mipsfpu
14041 @kindex set mipsfpu
14042 @kindex show mipsfpu
14043 @cindex MIPS remote floating point
14044 @cindex floating point, MIPS remote
14045 If your target board does not support the MIPS floating point
14046 coprocessor, you should use the command @samp{set mipsfpu none} (if you
14047 need this, you may wish to put the command in your @value{GDBN} init
14048 file). This tells @value{GDBN} how to find the return value of
14049 functions which return floating point values. It also allows
14050 @value{GDBN} to avoid saving the floating point registers when calling
14051 functions on the board. If you are using a floating point coprocessor
14052 with only single precision floating point support, as on the @sc{r4650}
14053 processor, use the command @samp{set mipsfpu single}. The default
14054 double precision floating point coprocessor may be selected using
14055 @samp{set mipsfpu double}.
14057 In previous versions the only choices were double precision or no
14058 floating point, so @samp{set mipsfpu on} will select double precision
14059 and @samp{set mipsfpu off} will select no floating point.
14061 As usual, you can inquire about the @code{mipsfpu} variable with
14062 @samp{show mipsfpu}.
14064 @item set timeout @var{seconds}
14065 @itemx set retransmit-timeout @var{seconds}
14066 @itemx show timeout
14067 @itemx show retransmit-timeout
14068 @cindex @code{timeout}, MIPS protocol
14069 @cindex @code{retransmit-timeout}, MIPS protocol
14070 @kindex set timeout
14071 @kindex show timeout
14072 @kindex set retransmit-timeout
14073 @kindex show retransmit-timeout
14074 You can control the timeout used while waiting for a packet, in the MIPS
14075 remote protocol, with the @code{set timeout @var{seconds}} command. The
14076 default is 5 seconds. Similarly, you can control the timeout used while
14077 waiting for an acknowledgement of a packet with the @code{set
14078 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
14079 You can inspect both values with @code{show timeout} and @code{show
14080 retransmit-timeout}. (These commands are @emph{only} available when
14081 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
14083 The timeout set by @code{set timeout} does not apply when @value{GDBN}
14084 is waiting for your program to stop. In that case, @value{GDBN} waits
14085 forever because it has no way of knowing how long the program is going
14086 to run before stopping.
14088 @item set syn-garbage-limit @var{num}
14089 @kindex set syn-garbage-limit@r{, MIPS remote}
14090 @cindex synchronize with remote MIPS target
14091 Limit the maximum number of characters @value{GDBN} should ignore when
14092 it tries to synchronize with the remote target. The default is 10
14093 characters. Setting the limit to -1 means there's no limit.
14095 @item show syn-garbage-limit
14096 @kindex show syn-garbage-limit@r{, MIPS remote}
14097 Show the current limit on the number of characters to ignore when
14098 trying to synchronize with the remote system.
14100 @item set monitor-prompt @var{prompt}
14101 @kindex set monitor-prompt@r{, MIPS remote}
14102 @cindex remote monitor prompt
14103 Tell @value{GDBN} to expect the specified @var{prompt} string from the
14104 remote monitor. The default depends on the target:
14114 @item show monitor-prompt
14115 @kindex show monitor-prompt@r{, MIPS remote}
14116 Show the current strings @value{GDBN} expects as the prompt from the
14119 @item set monitor-warnings
14120 @kindex set monitor-warnings@r{, MIPS remote}
14121 Enable or disable monitor warnings about hardware breakpoints. This
14122 has effect only for the @code{lsi} target. When on, @value{GDBN} will
14123 display warning messages whose codes are returned by the @code{lsi}
14124 PMON monitor for breakpoint commands.
14126 @item show monitor-warnings
14127 @kindex show monitor-warnings@r{, MIPS remote}
14128 Show the current setting of printing monitor warnings.
14130 @item pmon @var{command}
14131 @kindex pmon@r{, MIPS remote}
14132 @cindex send PMON command
14133 This command allows sending an arbitrary @var{command} string to the
14134 monitor. The monitor must be in debug mode for this to work.
14137 @node OpenRISC 1000
14138 @subsection OpenRISC 1000
14139 @cindex OpenRISC 1000
14141 @cindex or1k boards
14142 See OR1k Architecture document (@uref{www.opencores.org}) for more information
14143 about platform and commands.
14147 @kindex target jtag
14148 @item target jtag jtag://@var{host}:@var{port}
14150 Connects to remote JTAG server.
14151 JTAG remote server can be either an or1ksim or JTAG server,
14152 connected via parallel port to the board.
14154 Example: @code{target jtag jtag://localhost:9999}
14157 @item or1ksim @var{command}
14158 If connected to @code{or1ksim} OpenRISC 1000 Architectural
14159 Simulator, proprietary commands can be executed.
14161 @kindex info or1k spr
14162 @item info or1k spr
14163 Displays spr groups.
14165 @item info or1k spr @var{group}
14166 @itemx info or1k spr @var{groupno}
14167 Displays register names in selected group.
14169 @item info or1k spr @var{group} @var{register}
14170 @itemx info or1k spr @var{register}
14171 @itemx info or1k spr @var{groupno} @var{registerno}
14172 @itemx info or1k spr @var{registerno}
14173 Shows information about specified spr register.
14176 @item spr @var{group} @var{register} @var{value}
14177 @itemx spr @var{register @var{value}}
14178 @itemx spr @var{groupno} @var{registerno @var{value}}
14179 @itemx spr @var{registerno @var{value}}
14180 Writes @var{value} to specified spr register.
14183 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
14184 It is very similar to @value{GDBN} trace, except it does not interfere with normal
14185 program execution and is thus much faster. Hardware breakpoints/watchpoint
14186 triggers can be set using:
14189 Load effective address/data
14191 Store effective address/data
14193 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
14198 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
14199 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
14201 @code{htrace} commands:
14202 @cindex OpenRISC 1000 htrace
14205 @item hwatch @var{conditional}
14206 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
14207 or Data. For example:
14209 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14211 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14215 Display information about current HW trace configuration.
14217 @item htrace trigger @var{conditional}
14218 Set starting criteria for HW trace.
14220 @item htrace qualifier @var{conditional}
14221 Set acquisition qualifier for HW trace.
14223 @item htrace stop @var{conditional}
14224 Set HW trace stopping criteria.
14226 @item htrace record [@var{data}]*
14227 Selects the data to be recorded, when qualifier is met and HW trace was
14230 @item htrace enable
14231 @itemx htrace disable
14232 Enables/disables the HW trace.
14234 @item htrace rewind [@var{filename}]
14235 Clears currently recorded trace data.
14237 If filename is specified, new trace file is made and any newly collected data
14238 will be written there.
14240 @item htrace print [@var{start} [@var{len}]]
14241 Prints trace buffer, using current record configuration.
14243 @item htrace mode continuous
14244 Set continuous trace mode.
14246 @item htrace mode suspend
14247 Set suspend trace mode.
14252 @subsection PowerPC
14255 @kindex target dink32
14256 @item target dink32 @var{dev}
14257 DINK32 ROM monitor.
14259 @kindex target ppcbug
14260 @item target ppcbug @var{dev}
14261 @kindex target ppcbug1
14262 @item target ppcbug1 @var{dev}
14263 PPCBUG ROM monitor for PowerPC.
14266 @item target sds @var{dev}
14267 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
14270 @cindex SDS protocol
14271 The following commands specifi to the SDS protocol are supported
14275 @item set sdstimeout @var{nsec}
14276 @kindex set sdstimeout
14277 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
14278 default is 2 seconds.
14280 @item show sdstimeout
14281 @kindex show sdstimeout
14282 Show the current value of the SDS timeout.
14284 @item sds @var{command}
14285 @kindex sds@r{, a command}
14286 Send the specified @var{command} string to the SDS monitor.
14291 @subsection HP PA Embedded
14295 @kindex target op50n
14296 @item target op50n @var{dev}
14297 OP50N monitor, running on an OKI HPPA board.
14299 @kindex target w89k
14300 @item target w89k @var{dev}
14301 W89K monitor, running on a Winbond HPPA board.
14306 @subsection Renesas SH
14310 @kindex target hms@r{, with Renesas SH}
14311 @item target hms @var{dev}
14312 A Renesas SH board attached via serial line to your host. Use special
14313 commands @code{device} and @code{speed} to control the serial line and
14314 the communications speed used.
14316 @kindex target e7000@r{, with Renesas SH}
14317 @item target e7000 @var{dev}
14318 E7000 emulator for Renesas SH.
14320 @kindex target sh3@r{, with SH}
14321 @kindex target sh3e@r{, with SH}
14322 @item target sh3 @var{dev}
14323 @item target sh3e @var{dev}
14324 Renesas SH-3 and SH-3E target systems.
14329 @subsection Tsqware Sparclet
14333 @value{GDBN} enables developers to debug tasks running on
14334 Sparclet targets from a Unix host.
14335 @value{GDBN} uses code that runs on
14336 both the Unix host and on the Sparclet target. The program
14337 @code{@value{GDBP}} is installed and executed on the Unix host.
14340 @item remotetimeout @var{args}
14341 @kindex remotetimeout
14342 @value{GDBN} supports the option @code{remotetimeout}.
14343 This option is set by the user, and @var{args} represents the number of
14344 seconds @value{GDBN} waits for responses.
14347 @cindex compiling, on Sparclet
14348 When compiling for debugging, include the options @samp{-g} to get debug
14349 information and @samp{-Ttext} to relocate the program to where you wish to
14350 load it on the target. You may also want to add the options @samp{-n} or
14351 @samp{-N} in order to reduce the size of the sections. Example:
14354 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
14357 You can use @code{objdump} to verify that the addresses are what you intended:
14360 sparclet-aout-objdump --headers --syms prog
14363 @cindex running, on Sparclet
14365 your Unix execution search path to find @value{GDBN}, you are ready to
14366 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
14367 (or @code{sparclet-aout-gdb}, depending on your installation).
14369 @value{GDBN} comes up showing the prompt:
14376 * Sparclet File:: Setting the file to debug
14377 * Sparclet Connection:: Connecting to Sparclet
14378 * Sparclet Download:: Sparclet download
14379 * Sparclet Execution:: Running and debugging
14382 @node Sparclet File
14383 @subsubsection Setting file to debug
14385 The @value{GDBN} command @code{file} lets you choose with program to debug.
14388 (gdbslet) file prog
14392 @value{GDBN} then attempts to read the symbol table of @file{prog}.
14393 @value{GDBN} locates
14394 the file by searching the directories listed in the command search
14396 If the file was compiled with debug information (option "-g"), source
14397 files will be searched as well.
14398 @value{GDBN} locates
14399 the source files by searching the directories listed in the directory search
14400 path (@pxref{Environment, ,Your program's environment}).
14402 to find a file, it displays a message such as:
14405 prog: No such file or directory.
14408 When this happens, add the appropriate directories to the search paths with
14409 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
14410 @code{target} command again.
14412 @node Sparclet Connection
14413 @subsubsection Connecting to Sparclet
14415 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
14416 To connect to a target on serial port ``@code{ttya}'', type:
14419 (gdbslet) target sparclet /dev/ttya
14420 Remote target sparclet connected to /dev/ttya
14421 main () at ../prog.c:3
14425 @value{GDBN} displays messages like these:
14431 @node Sparclet Download
14432 @subsubsection Sparclet download
14434 @cindex download to Sparclet
14435 Once connected to the Sparclet target,
14436 you can use the @value{GDBN}
14437 @code{load} command to download the file from the host to the target.
14438 The file name and load offset should be given as arguments to the @code{load}
14440 Since the file format is aout, the program must be loaded to the starting
14441 address. You can use @code{objdump} to find out what this value is. The load
14442 offset is an offset which is added to the VMA (virtual memory address)
14443 of each of the file's sections.
14444 For instance, if the program
14445 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
14446 and bss at 0x12010170, in @value{GDBN}, type:
14449 (gdbslet) load prog 0x12010000
14450 Loading section .text, size 0xdb0 vma 0x12010000
14453 If the code is loaded at a different address then what the program was linked
14454 to, you may need to use the @code{section} and @code{add-symbol-file} commands
14455 to tell @value{GDBN} where to map the symbol table.
14457 @node Sparclet Execution
14458 @subsubsection Running and debugging
14460 @cindex running and debugging Sparclet programs
14461 You can now begin debugging the task using @value{GDBN}'s execution control
14462 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
14463 manual for the list of commands.
14467 Breakpoint 1 at 0x12010000: file prog.c, line 3.
14469 Starting program: prog
14470 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
14471 3 char *symarg = 0;
14473 4 char *execarg = "hello!";
14478 @subsection Fujitsu Sparclite
14482 @kindex target sparclite
14483 @item target sparclite @var{dev}
14484 Fujitsu sparclite boards, used only for the purpose of loading.
14485 You must use an additional command to debug the program.
14486 For example: target remote @var{dev} using @value{GDBN} standard
14492 @subsection Tandem ST2000
14494 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
14497 To connect your ST2000 to the host system, see the manufacturer's
14498 manual. Once the ST2000 is physically attached, you can run:
14501 target st2000 @var{dev} @var{speed}
14505 to establish it as your debugging environment. @var{dev} is normally
14506 the name of a serial device, such as @file{/dev/ttya}, connected to the
14507 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
14508 connection (for example, to a serial line attached via a terminal
14509 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
14511 The @code{load} and @code{attach} commands are @emph{not} defined for
14512 this target; you must load your program into the ST2000 as you normally
14513 would for standalone operation. @value{GDBN} reads debugging information
14514 (such as symbols) from a separate, debugging version of the program
14515 available on your host computer.
14516 @c FIXME!! This is terribly vague; what little content is here is
14517 @c basically hearsay.
14519 @cindex ST2000 auxiliary commands
14520 These auxiliary @value{GDBN} commands are available to help you with the ST2000
14524 @item st2000 @var{command}
14525 @kindex st2000 @var{cmd}
14526 @cindex STDBUG commands (ST2000)
14527 @cindex commands to STDBUG (ST2000)
14528 Send a @var{command} to the STDBUG monitor. See the manufacturer's
14529 manual for available commands.
14532 @cindex connect (to STDBUG)
14533 Connect the controlling terminal to the STDBUG command monitor. When
14534 you are done interacting with STDBUG, typing either of two character
14535 sequences gets you back to the @value{GDBN} command prompt:
14536 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
14537 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
14541 @subsection Zilog Z8000
14544 @cindex simulator, Z8000
14545 @cindex Zilog Z8000 simulator
14547 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
14550 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
14551 unsegmented variant of the Z8000 architecture) or the Z8001 (the
14552 segmented variant). The simulator recognizes which architecture is
14553 appropriate by inspecting the object code.
14556 @item target sim @var{args}
14558 @kindex target sim@r{, with Z8000}
14559 Debug programs on a simulated CPU. If the simulator supports setup
14560 options, specify them via @var{args}.
14564 After specifying this target, you can debug programs for the simulated
14565 CPU in the same style as programs for your host computer; use the
14566 @code{file} command to load a new program image, the @code{run} command
14567 to run your program, and so on.
14569 As well as making available all the usual machine registers
14570 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
14571 additional items of information as specially named registers:
14576 Counts clock-ticks in the simulator.
14579 Counts instructions run in the simulator.
14582 Execution time in 60ths of a second.
14586 You can refer to these values in @value{GDBN} expressions with the usual
14587 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
14588 conditional breakpoint that suspends only after at least 5000
14589 simulated clock ticks.
14592 @subsection Atmel AVR
14595 When configured for debugging the Atmel AVR, @value{GDBN} supports the
14596 following AVR-specific commands:
14599 @item info io_registers
14600 @kindex info io_registers@r{, AVR}
14601 @cindex I/O registers (Atmel AVR)
14602 This command displays information about the AVR I/O registers. For
14603 each register, @value{GDBN} prints its number and value.
14610 When configured for debugging CRIS, @value{GDBN} provides the
14611 following CRIS-specific commands:
14614 @item set cris-version @var{ver}
14615 @cindex CRIS version
14616 Set the current CRIS version to @var{ver}. The CRIS version affects
14617 register names and sizes. This command is useful in case
14618 autodetection of the CRIS version fails.
14620 @item show cris-version
14621 Show the current CRIS version.
14623 @item set cris-dwarf2-cfi
14624 @cindex DWARF-2 CFI and CRIS
14625 Set the usage of DWARF-2 CFI for CRIS debugging. The default is off
14626 if using @code{gcc-cris} whose version is below @code{R59}, otherwise
14629 @item show cris-dwarf2-cfi
14630 Show the current state of using DWARF-2 CFI.
14634 @subsection Renesas Super-H
14637 For the Renesas Super-H processor, @value{GDBN} provides these
14642 @kindex regs@r{, Super-H}
14643 Show the values of all Super-H registers.
14647 @subsection Windows CE
14650 The following commands are available for Windows CE:
14653 @item set remotedirectory @var{dir}
14654 @kindex set remotedirectory
14655 Tell @value{GDBN} to upload files from the named directory @var{dir}.
14656 The default is @file{/gdb}, i.e.@: the root directory on the current
14659 @item show remotedirectory
14660 @kindex show remotedirectory
14661 Show the current value of the upload directory.
14663 @item set remoteupload @var{method}
14664 @kindex set remoteupload
14665 Set the method used to upload files to remote device. Valid values
14666 for @var{method} are @samp{always}, @samp{newer}, and @samp{never}.
14667 The default is @samp{newer}.
14669 @item show remoteupload
14670 @kindex show remoteupload
14671 Show the current setting of the upload method.
14673 @item set remoteaddhost
14674 @kindex set remoteaddhost
14675 Tell @value{GDBN} whether to add this host to the remote stub's
14676 arguments when you debug over a network.
14678 @item show remoteaddhost
14679 @kindex show remoteaddhost
14680 Show whether to add this host to remote stub's arguments when
14681 debugging over a network.
14685 @node Architectures
14686 @section Architectures
14688 This section describes characteristics of architectures that affect
14689 all uses of @value{GDBN} with the architecture, both native and cross.
14696 * HPPA:: HP PA architecture
14700 @subsection x86 Architecture-specific issues.
14703 @item set struct-convention @var{mode}
14704 @kindex set struct-convention
14705 @cindex struct return convention
14706 @cindex struct/union returned in registers
14707 Set the convention used by the inferior to return @code{struct}s and
14708 @code{union}s from functions to @var{mode}. Possible values of
14709 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
14710 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
14711 are returned on the stack, while @code{"reg"} means that a
14712 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
14713 be returned in a register.
14715 @item show struct-convention
14716 @kindex show struct-convention
14717 Show the current setting of the convention to return @code{struct}s
14726 @kindex set rstack_high_address
14727 @cindex AMD 29K register stack
14728 @cindex register stack, AMD29K
14729 @item set rstack_high_address @var{address}
14730 On AMD 29000 family processors, registers are saved in a separate
14731 @dfn{register stack}. There is no way for @value{GDBN} to determine the
14732 extent of this stack. Normally, @value{GDBN} just assumes that the
14733 stack is ``large enough''. This may result in @value{GDBN} referencing
14734 memory locations that do not exist. If necessary, you can get around
14735 this problem by specifying the ending address of the register stack with
14736 the @code{set rstack_high_address} command. The argument should be an
14737 address, which you probably want to precede with @samp{0x} to specify in
14740 @kindex show rstack_high_address
14741 @item show rstack_high_address
14742 Display the current limit of the register stack, on AMD 29000 family
14750 See the following section.
14755 @cindex stack on Alpha
14756 @cindex stack on MIPS
14757 @cindex Alpha stack
14759 Alpha- and MIPS-based computers use an unusual stack frame, which
14760 sometimes requires @value{GDBN} to search backward in the object code to
14761 find the beginning of a function.
14763 @cindex response time, MIPS debugging
14764 To improve response time (especially for embedded applications, where
14765 @value{GDBN} may be restricted to a slow serial line for this search)
14766 you may want to limit the size of this search, using one of these
14770 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
14771 @item set heuristic-fence-post @var{limit}
14772 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
14773 search for the beginning of a function. A value of @var{0} (the
14774 default) means there is no limit. However, except for @var{0}, the
14775 larger the limit the more bytes @code{heuristic-fence-post} must search
14776 and therefore the longer it takes to run. You should only need to use
14777 this command when debugging a stripped executable.
14779 @item show heuristic-fence-post
14780 Display the current limit.
14784 These commands are available @emph{only} when @value{GDBN} is configured
14785 for debugging programs on Alpha or MIPS processors.
14787 Several MIPS-specific commands are available when debugging MIPS
14791 @item set mips saved-gpreg-size @var{size}
14792 @kindex set mips saved-gpreg-size
14793 @cindex MIPS GP register size on stack
14794 Set the size of MIPS general-purpose registers saved on the stack.
14795 The argument @var{size} can be one of the following:
14799 32-bit GP registers
14801 64-bit GP registers
14803 Use the target's default setting or autodetect the saved size from the
14804 information contained in the executable. This is the default
14807 @item show mips saved-gpreg-size
14808 @kindex show mips saved-gpreg-size
14809 Show the current size of MIPS GP registers on the stack.
14811 @item set mips stack-arg-size @var{size}
14812 @kindex set mips stack-arg-size
14813 @cindex MIPS stack space for arguments
14814 Set the amount of stack space reserved for arguments to functions.
14815 The argument can be one of @code{"32"}, @code{"64"} or @code{"auto"}
14818 @item set mips abi @var{arg}
14819 @kindex set mips abi
14820 @cindex set ABI for MIPS
14821 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
14822 values of @var{arg} are:
14826 The default ABI associated with the current binary (this is the
14837 @item show mips abi
14838 @kindex show mips abi
14839 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
14842 @itemx show mipsfpu
14843 @xref{MIPS Embedded, set mipsfpu}.
14845 @item set mips mask-address @var{arg}
14846 @kindex set mips mask-address
14847 @cindex MIPS addresses, masking
14848 This command determines whether the most-significant 32 bits of 64-bit
14849 MIPS addresses are masked off. The argument @var{arg} can be
14850 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
14851 setting, which lets @value{GDBN} determine the correct value.
14853 @item show mips mask-address
14854 @kindex show mips mask-address
14855 Show whether the upper 32 bits of MIPS addresses are masked off or
14858 @item set remote-mips64-transfers-32bit-regs
14859 @kindex set remote-mips64-transfers-32bit-regs
14860 This command controls compatibility with 64-bit MIPS targets that
14861 transfer data in 32-bit quantities. If you have an old MIPS 64 target
14862 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
14863 and 64 bits for other registers, set this option to @samp{on}.
14865 @item show remote-mips64-transfers-32bit-regs
14866 @kindex show remote-mips64-transfers-32bit-regs
14867 Show the current setting of compatibility with older MIPS 64 targets.
14869 @item set debug mips
14870 @kindex set debug mips
14871 This command turns on and off debugging messages for the MIPS-specific
14872 target code in @value{GDBN}.
14874 @item show debug mips
14875 @kindex show debug mips
14876 Show the current setting of MIPS debugging messages.
14882 @cindex HPPA support
14884 When @value{GDBN} is debugging te HP PA architecture, it provides the
14885 following special commands:
14888 @item set debug hppa
14889 @kindex set debug hppa
14890 THis command determines whether HPPA architecture specific debugging
14891 messages are to be displayed.
14893 @item show debug hppa
14894 Show whether HPPA debugging messages are displayed.
14896 @item maint print unwind @var{address}
14897 @kindex maint print unwind@r{, HPPA}
14898 This command displays the contents of the unwind table entry at the
14899 given @var{address}.
14904 @node Controlling GDB
14905 @chapter Controlling @value{GDBN}
14907 You can alter the way @value{GDBN} interacts with you by using the
14908 @code{set} command. For commands controlling how @value{GDBN} displays
14909 data, see @ref{Print Settings, ,Print settings}. Other settings are
14914 * Editing:: Command editing
14915 * History:: Command history
14916 * Screen Size:: Screen size
14917 * Numbers:: Numbers
14918 * ABI:: Configuring the current ABI
14919 * Messages/Warnings:: Optional warnings and messages
14920 * Debugging Output:: Optional messages about internal happenings
14928 @value{GDBN} indicates its readiness to read a command by printing a string
14929 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
14930 can change the prompt string with the @code{set prompt} command. For
14931 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
14932 the prompt in one of the @value{GDBN} sessions so that you can always tell
14933 which one you are talking to.
14935 @emph{Note:} @code{set prompt} does not add a space for you after the
14936 prompt you set. This allows you to set a prompt which ends in a space
14937 or a prompt that does not.
14941 @item set prompt @var{newprompt}
14942 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
14944 @kindex show prompt
14946 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
14950 @section Command editing
14952 @cindex command line editing
14954 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
14955 @sc{gnu} library provides consistent behavior for programs which provide a
14956 command line interface to the user. Advantages are @sc{gnu} Emacs-style
14957 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
14958 substitution, and a storage and recall of command history across
14959 debugging sessions.
14961 You may control the behavior of command line editing in @value{GDBN} with the
14962 command @code{set}.
14965 @kindex set editing
14968 @itemx set editing on
14969 Enable command line editing (enabled by default).
14971 @item set editing off
14972 Disable command line editing.
14974 @kindex show editing
14976 Show whether command line editing is enabled.
14979 @xref{Command Line Editing}, for more details about the Readline
14980 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
14981 encouraged to read that chapter.
14984 @section Command history
14985 @cindex command history
14987 @value{GDBN} can keep track of the commands you type during your
14988 debugging sessions, so that you can be certain of precisely what
14989 happened. Use these commands to manage the @value{GDBN} command
14992 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
14993 package, to provide the history facility. @xref{Using History
14994 Interactively}, for the detailed description of the History library.
14996 Here is the description of @value{GDBN} commands related to command
15000 @cindex history substitution
15001 @cindex history file
15002 @kindex set history filename
15003 @cindex @env{GDBHISTFILE}, environment variable
15004 @item set history filename @var{fname}
15005 Set the name of the @value{GDBN} command history file to @var{fname}.
15006 This is the file where @value{GDBN} reads an initial command history
15007 list, and where it writes the command history from this session when it
15008 exits. You can access this list through history expansion or through
15009 the history command editing characters listed below. This file defaults
15010 to the value of the environment variable @code{GDBHISTFILE}, or to
15011 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
15014 @cindex save command history
15015 @kindex set history save
15016 @item set history save
15017 @itemx set history save on
15018 Record command history in a file, whose name may be specified with the
15019 @code{set history filename} command. By default, this option is disabled.
15021 @item set history save off
15022 Stop recording command history in a file.
15024 @cindex history size
15025 @kindex set history size
15026 @item set history size @var{size}
15027 Set the number of commands which @value{GDBN} keeps in its history list.
15028 This defaults to the value of the environment variable
15029 @code{HISTSIZE}, or to 256 if this variable is not set.
15032 History expansion assigns special meaning to the character @kbd{!}.
15033 @xref{Event Designators}, for more details.
15035 @cindex history expansion, turn on/off
15036 Since @kbd{!} is also the logical not operator in C, history expansion
15037 is off by default. If you decide to enable history expansion with the
15038 @code{set history expansion on} command, you may sometimes need to
15039 follow @kbd{!} (when it is used as logical not, in an expression) with
15040 a space or a tab to prevent it from being expanded. The readline
15041 history facilities do not attempt substitution on the strings
15042 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
15044 The commands to control history expansion are:
15047 @item set history expansion on
15048 @itemx set history expansion
15049 @kindex set history expansion
15050 Enable history expansion. History expansion is off by default.
15052 @item set history expansion off
15053 Disable history expansion.
15056 @kindex show history
15058 @itemx show history filename
15059 @itemx show history save
15060 @itemx show history size
15061 @itemx show history expansion
15062 These commands display the state of the @value{GDBN} history parameters.
15063 @code{show history} by itself displays all four states.
15068 @kindex show commands
15069 @cindex show last commands
15070 @cindex display command history
15071 @item show commands
15072 Display the last ten commands in the command history.
15074 @item show commands @var{n}
15075 Print ten commands centered on command number @var{n}.
15077 @item show commands +
15078 Print ten commands just after the commands last printed.
15082 @section Screen size
15083 @cindex size of screen
15084 @cindex pauses in output
15086 Certain commands to @value{GDBN} may produce large amounts of
15087 information output to the screen. To help you read all of it,
15088 @value{GDBN} pauses and asks you for input at the end of each page of
15089 output. Type @key{RET} when you want to continue the output, or @kbd{q}
15090 to discard the remaining output. Also, the screen width setting
15091 determines when to wrap lines of output. Depending on what is being
15092 printed, @value{GDBN} tries to break the line at a readable place,
15093 rather than simply letting it overflow onto the following line.
15095 Normally @value{GDBN} knows the size of the screen from the terminal
15096 driver software. For example, on Unix @value{GDBN} uses the termcap data base
15097 together with the value of the @code{TERM} environment variable and the
15098 @code{stty rows} and @code{stty cols} settings. If this is not correct,
15099 you can override it with the @code{set height} and @code{set
15106 @kindex show height
15107 @item set height @var{lpp}
15109 @itemx set width @var{cpl}
15111 These @code{set} commands specify a screen height of @var{lpp} lines and
15112 a screen width of @var{cpl} characters. The associated @code{show}
15113 commands display the current settings.
15115 If you specify a height of zero lines, @value{GDBN} does not pause during
15116 output no matter how long the output is. This is useful if output is to a
15117 file or to an editor buffer.
15119 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
15120 from wrapping its output.
15122 @item set pagination on
15123 @itemx set pagination off
15124 @kindex set pagination
15125 Turn the output pagination on or off; the default is on. Turning
15126 pagination off is the alternative to @code{set height 0}.
15128 @item show pagination
15129 @kindex show pagination
15130 Show the current pagination mode.
15135 @cindex number representation
15136 @cindex entering numbers
15138 You can always enter numbers in octal, decimal, or hexadecimal in
15139 @value{GDBN} by the usual conventions: octal numbers begin with
15140 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
15141 begin with @samp{0x}. Numbers that begin with none of these are, by
15142 default, entered in base 10; likewise, the default display for
15143 numbers---when no particular format is specified---is base 10. You can
15144 change the default base for both input and output with the @code{set
15148 @kindex set input-radix
15149 @item set input-radix @var{base}
15150 Set the default base for numeric input. Supported choices
15151 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15152 specified either unambiguously or using the current default radix; for
15156 set input-radix 012
15157 set input-radix 10.
15158 set input-radix 0xa
15162 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
15163 leaves the input radix unchanged, no matter what it was.
15165 @kindex set output-radix
15166 @item set output-radix @var{base}
15167 Set the default base for numeric display. Supported choices
15168 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15169 specified either unambiguously or using the current default radix.
15171 @kindex show input-radix
15172 @item show input-radix
15173 Display the current default base for numeric input.
15175 @kindex show output-radix
15176 @item show output-radix
15177 Display the current default base for numeric display.
15179 @item set radix @r{[}@var{base}@r{]}
15183 These commands set and show the default base for both input and output
15184 of numbers. @code{set radix} sets the radix of input and output to
15185 the same base; without an argument, it resets the radix back to its
15186 default value of 10.
15191 @section Configuring the current ABI
15193 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
15194 application automatically. However, sometimes you need to override its
15195 conclusions. Use these commands to manage @value{GDBN}'s view of the
15202 One @value{GDBN} configuration can debug binaries for multiple operating
15203 system targets, either via remote debugging or native emulation.
15204 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
15205 but you can override its conclusion using the @code{set osabi} command.
15206 One example where this is useful is in debugging of binaries which use
15207 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
15208 not have the same identifying marks that the standard C library for your
15213 Show the OS ABI currently in use.
15216 With no argument, show the list of registered available OS ABI's.
15218 @item set osabi @var{abi}
15219 Set the current OS ABI to @var{abi}.
15222 @cindex float promotion
15224 Generally, the way that an argument of type @code{float} is passed to a
15225 function depends on whether the function is prototyped. For a prototyped
15226 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
15227 according to the architecture's convention for @code{float}. For unprototyped
15228 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
15229 @code{double} and then passed.
15231 Unfortunately, some forms of debug information do not reliably indicate whether
15232 a function is prototyped. If @value{GDBN} calls a function that is not marked
15233 as prototyped, it consults @kbd{set coerce-float-to-double}.
15236 @kindex set coerce-float-to-double
15237 @item set coerce-float-to-double
15238 @itemx set coerce-float-to-double on
15239 Arguments of type @code{float} will be promoted to @code{double} when passed
15240 to an unprototyped function. This is the default setting.
15242 @item set coerce-float-to-double off
15243 Arguments of type @code{float} will be passed directly to unprototyped
15246 @kindex show coerce-float-to-double
15247 @item show coerce-float-to-double
15248 Show the current setting of promoting @code{float} to @code{double}.
15252 @kindex show cp-abi
15253 @value{GDBN} needs to know the ABI used for your program's C@t{++}
15254 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
15255 used to build your application. @value{GDBN} only fully supports
15256 programs with a single C@t{++} ABI; if your program contains code using
15257 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
15258 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
15259 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
15260 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
15261 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
15262 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
15267 Show the C@t{++} ABI currently in use.
15270 With no argument, show the list of supported C@t{++} ABI's.
15272 @item set cp-abi @var{abi}
15273 @itemx set cp-abi auto
15274 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
15277 @node Messages/Warnings
15278 @section Optional warnings and messages
15280 @cindex verbose operation
15281 @cindex optional warnings
15282 By default, @value{GDBN} is silent about its inner workings. If you are
15283 running on a slow machine, you may want to use the @code{set verbose}
15284 command. This makes @value{GDBN} tell you when it does a lengthy
15285 internal operation, so you will not think it has crashed.
15287 Currently, the messages controlled by @code{set verbose} are those
15288 which announce that the symbol table for a source file is being read;
15289 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
15292 @kindex set verbose
15293 @item set verbose on
15294 Enables @value{GDBN} output of certain informational messages.
15296 @item set verbose off
15297 Disables @value{GDBN} output of certain informational messages.
15299 @kindex show verbose
15301 Displays whether @code{set verbose} is on or off.
15304 By default, if @value{GDBN} encounters bugs in the symbol table of an
15305 object file, it is silent; but if you are debugging a compiler, you may
15306 find this information useful (@pxref{Symbol Errors, ,Errors reading
15311 @kindex set complaints
15312 @item set complaints @var{limit}
15313 Permits @value{GDBN} to output @var{limit} complaints about each type of
15314 unusual symbols before becoming silent about the problem. Set
15315 @var{limit} to zero to suppress all complaints; set it to a large number
15316 to prevent complaints from being suppressed.
15318 @kindex show complaints
15319 @item show complaints
15320 Displays how many symbol complaints @value{GDBN} is permitted to produce.
15324 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
15325 lot of stupid questions to confirm certain commands. For example, if
15326 you try to run a program which is already running:
15330 The program being debugged has been started already.
15331 Start it from the beginning? (y or n)
15334 If you are willing to unflinchingly face the consequences of your own
15335 commands, you can disable this ``feature'':
15339 @kindex set confirm
15341 @cindex confirmation
15342 @cindex stupid questions
15343 @item set confirm off
15344 Disables confirmation requests.
15346 @item set confirm on
15347 Enables confirmation requests (the default).
15349 @kindex show confirm
15351 Displays state of confirmation requests.
15355 @node Debugging Output
15356 @section Optional messages about internal happenings
15357 @cindex optional debugging messages
15359 @value{GDBN} has commands that enable optional debugging messages from
15360 various @value{GDBN} subsystems; normally these commands are of
15361 interest to @value{GDBN} maintainers, or when reporting a bug. This
15362 section documents those commands.
15365 @kindex set exec-done-display
15366 @item set exec-done-display
15367 Turns on or off the notification of asynchronous commands'
15368 completion. When on, @value{GDBN} will print a message when an
15369 asynchronous command finishes its execution. The default is off.
15370 @kindex show exec-done-display
15371 @item show exec-done-display
15372 Displays the current setting of asynchronous command completion
15375 @cindex gdbarch debugging info
15376 @cindex architecture debugging info
15377 @item set debug arch
15378 Turns on or off display of gdbarch debugging info. The default is off
15380 @item show debug arch
15381 Displays the current state of displaying gdbarch debugging info.
15382 @item set debug aix-thread
15383 @cindex AIX threads
15384 Display debugging messages about inner workings of the AIX thread
15386 @item show debug aix-thread
15387 Show the current state of AIX thread debugging info display.
15388 @item set debug event
15389 @cindex event debugging info
15390 Turns on or off display of @value{GDBN} event debugging info. The
15392 @item show debug event
15393 Displays the current state of displaying @value{GDBN} event debugging
15395 @item set debug expression
15396 @cindex expression debugging info
15397 Turns on or off display of debugging info about @value{GDBN}
15398 expression parsing. The default is off.
15399 @item show debug expression
15400 Displays the current state of displaying debugging info about
15401 @value{GDBN} expression parsing.
15402 @item set debug frame
15403 @cindex frame debugging info
15404 Turns on or off display of @value{GDBN} frame debugging info. The
15406 @item show debug frame
15407 Displays the current state of displaying @value{GDBN} frame debugging
15409 @item set debug infrun
15410 @cindex inferior debugging info
15411 Turns on or off display of @value{GDBN} debugging info for running the inferior.
15412 The default is off. @file{infrun.c} contains GDB's runtime state machine used
15413 for implementing operations such as single-stepping the inferior.
15414 @item show debug infrun
15415 Displays the current state of @value{GDBN} inferior debugging.
15416 @item set debug lin-lwp
15417 @cindex @sc{gnu}/Linux LWP debug messages
15418 @cindex Linux lightweight processes
15419 Turns on or off debugging messages from the Linux LWP debug support.
15420 @item show debug lin-lwp
15421 Show the current state of Linux LWP debugging messages.
15422 @item set debug observer
15423 @cindex observer debugging info
15424 Turns on or off display of @value{GDBN} observer debugging. This
15425 includes info such as the notification of observable events.
15426 @item show debug observer
15427 Displays the current state of observer debugging.
15428 @item set debug overload
15429 @cindex C@t{++} overload debugging info
15430 Turns on or off display of @value{GDBN} C@t{++} overload debugging
15431 info. This includes info such as ranking of functions, etc. The default
15433 @item show debug overload
15434 Displays the current state of displaying @value{GDBN} C@t{++} overload
15436 @cindex packets, reporting on stdout
15437 @cindex serial connections, debugging
15438 @item set debug remote
15439 Turns on or off display of reports on all packets sent back and forth across
15440 the serial line to the remote machine. The info is printed on the
15441 @value{GDBN} standard output stream. The default is off.
15442 @item show debug remote
15443 Displays the state of display of remote packets.
15444 @item set debug serial
15445 Turns on or off display of @value{GDBN} serial debugging info. The
15447 @item show debug serial
15448 Displays the current state of displaying @value{GDBN} serial debugging
15450 @item set debug solib-frv
15451 @cindex FR-V shared-library debugging
15452 Turns on or off debugging messages for FR-V shared-library code.
15453 @item show debug solib-frv
15454 Display the current state of FR-V shared-library code debugging
15456 @item set debug target
15457 @cindex target debugging info
15458 Turns on or off display of @value{GDBN} target debugging info. This info
15459 includes what is going on at the target level of GDB, as it happens. The
15460 default is 0. Set it to 1 to track events, and to 2 to also track the
15461 value of large memory transfers. Changes to this flag do not take effect
15462 until the next time you connect to a target or use the @code{run} command.
15463 @item show debug target
15464 Displays the current state of displaying @value{GDBN} target debugging
15466 @item set debugvarobj
15467 @cindex variable object debugging info
15468 Turns on or off display of @value{GDBN} variable object debugging
15469 info. The default is off.
15470 @item show debugvarobj
15471 Displays the current state of displaying @value{GDBN} variable object
15476 @chapter Canned Sequences of Commands
15478 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
15479 command lists}), @value{GDBN} provides two ways to store sequences of
15480 commands for execution as a unit: user-defined commands and command
15484 * Define:: User-defined commands
15485 * Hooks:: User-defined command hooks
15486 * Command Files:: Command files
15487 * Output:: Commands for controlled output
15491 @section User-defined commands
15493 @cindex user-defined command
15494 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
15495 which you assign a new name as a command. This is done with the
15496 @code{define} command. User commands may accept up to 10 arguments
15497 separated by whitespace. Arguments are accessed within the user command
15498 via @var{$arg0@dots{}$arg9}. A trivial example:
15502 print $arg0 + $arg1 + $arg2
15506 To execute the command use:
15513 This defines the command @code{adder}, which prints the sum of
15514 its three arguments. Note the arguments are text substitutions, so they may
15515 reference variables, use complex expressions, or even perform inferior
15521 @item define @var{commandname}
15522 Define a command named @var{commandname}. If there is already a command
15523 by that name, you are asked to confirm that you want to redefine it.
15525 The definition of the command is made up of other @value{GDBN} command lines,
15526 which are given following the @code{define} command. The end of these
15527 commands is marked by a line containing @code{end}.
15533 Takes a single argument, which is an expression to evaluate.
15534 It is followed by a series of commands that are executed
15535 only if the expression is true (nonzero).
15536 There can then optionally be a line @code{else}, followed
15537 by a series of commands that are only executed if the expression
15538 was false. The end of the list is marked by a line containing @code{end}.
15542 The syntax is similar to @code{if}: the command takes a single argument,
15543 which is an expression to evaluate, and must be followed by the commands to
15544 execute, one per line, terminated by an @code{end}.
15545 The commands are executed repeatedly as long as the expression
15549 @item document @var{commandname}
15550 Document the user-defined command @var{commandname}, so that it can be
15551 accessed by @code{help}. The command @var{commandname} must already be
15552 defined. This command reads lines of documentation just as @code{define}
15553 reads the lines of the command definition, ending with @code{end}.
15554 After the @code{document} command is finished, @code{help} on command
15555 @var{commandname} displays the documentation you have written.
15557 You may use the @code{document} command again to change the
15558 documentation of a command. Redefining the command with @code{define}
15559 does not change the documentation.
15561 @kindex dont-repeat
15562 @cindex don't repeat command
15564 Used inside a user-defined command, this tells @value{GDBN} that this
15565 command should not be repeated when the user hits @key{RET}
15566 (@pxref{Command Syntax, repeat last command}).
15568 @kindex help user-defined
15569 @item help user-defined
15570 List all user-defined commands, with the first line of the documentation
15575 @itemx show user @var{commandname}
15576 Display the @value{GDBN} commands used to define @var{commandname} (but
15577 not its documentation). If no @var{commandname} is given, display the
15578 definitions for all user-defined commands.
15580 @cindex infinite recusrion in user-defined commands
15581 @kindex show max-user-call-depth
15582 @kindex set max-user-call-depth
15583 @item show max-user-call-depth
15584 @itemx set max-user-call-depth
15585 The value of @code{max-user-call-depth} controls how many recursion
15586 levels are allowed in user-defined commands before GDB suspects an
15587 infinite recursion and aborts the command.
15591 When user-defined commands are executed, the
15592 commands of the definition are not printed. An error in any command
15593 stops execution of the user-defined command.
15595 If used interactively, commands that would ask for confirmation proceed
15596 without asking when used inside a user-defined command. Many @value{GDBN}
15597 commands that normally print messages to say what they are doing omit the
15598 messages when used in a user-defined command.
15601 @section User-defined command hooks
15602 @cindex command hooks
15603 @cindex hooks, for commands
15604 @cindex hooks, pre-command
15607 You may define @dfn{hooks}, which are a special kind of user-defined
15608 command. Whenever you run the command @samp{foo}, if the user-defined
15609 command @samp{hook-foo} exists, it is executed (with no arguments)
15610 before that command.
15612 @cindex hooks, post-command
15614 A hook may also be defined which is run after the command you executed.
15615 Whenever you run the command @samp{foo}, if the user-defined command
15616 @samp{hookpost-foo} exists, it is executed (with no arguments) after
15617 that command. Post-execution hooks may exist simultaneously with
15618 pre-execution hooks, for the same command.
15620 It is valid for a hook to call the command which it hooks. If this
15621 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
15623 @c It would be nice if hookpost could be passed a parameter indicating
15624 @c if the command it hooks executed properly or not. FIXME!
15626 @kindex stop@r{, a pseudo-command}
15627 In addition, a pseudo-command, @samp{stop} exists. Defining
15628 (@samp{hook-stop}) makes the associated commands execute every time
15629 execution stops in your program: before breakpoint commands are run,
15630 displays are printed, or the stack frame is printed.
15632 For example, to ignore @code{SIGALRM} signals while
15633 single-stepping, but treat them normally during normal execution,
15638 handle SIGALRM nopass
15642 handle SIGALRM pass
15645 define hook-continue
15646 handle SIGLARM pass
15650 As a further example, to hook at the begining and end of the @code{echo}
15651 command, and to add extra text to the beginning and end of the message,
15659 define hookpost-echo
15663 (@value{GDBP}) echo Hello World
15664 <<<---Hello World--->>>
15669 You can define a hook for any single-word command in @value{GDBN}, but
15670 not for command aliases; you should define a hook for the basic command
15671 name, e.g. @code{backtrace} rather than @code{bt}.
15672 @c FIXME! So how does Joe User discover whether a command is an alias
15674 If an error occurs during the execution of your hook, execution of
15675 @value{GDBN} commands stops and @value{GDBN} issues a prompt
15676 (before the command that you actually typed had a chance to run).
15678 If you try to define a hook which does not match any known command, you
15679 get a warning from the @code{define} command.
15681 @node Command Files
15682 @section Command files
15684 @cindex command files
15685 A command file for @value{GDBN} is a file of lines that are @value{GDBN}
15686 commands. Comments (lines starting with @kbd{#}) may also be included.
15687 An empty line in a command file does nothing; it does not mean to repeat
15688 the last command, as it would from the terminal.
15691 @cindex @file{.gdbinit}
15692 @cindex @file{gdb.ini}
15693 When you start @value{GDBN}, it automatically executes commands from its
15694 @dfn{init files}, normally called @file{.gdbinit}@footnote{The DJGPP
15695 port of @value{GDBN} uses the name @file{gdb.ini} instead, due to the
15696 limitations of file names imposed by DOS filesystems.}.
15697 During startup, @value{GDBN} does the following:
15701 Reads the init file (if any) in your home directory@footnote{On
15702 DOS/Windows systems, the home directory is the one pointed to by the
15703 @code{HOME} environment variable.}.
15706 Processes command line options and operands.
15709 Reads the init file (if any) in the current working directory.
15712 Reads command files specified by the @samp{-x} option.
15715 The init file in your home directory can set options (such as @samp{set
15716 complaints}) that affect subsequent processing of command line options
15717 and operands. Init files are not executed if you use the @samp{-nx}
15718 option (@pxref{Mode Options, ,Choosing modes}).
15720 @cindex init file name
15721 On some configurations of @value{GDBN}, the init file is known by a
15722 different name (these are typically environments where a specialized
15723 form of @value{GDBN} may need to coexist with other forms, hence a
15724 different name for the specialized version's init file). These are the
15725 environments with special init file names:
15727 @cindex @file{.vxgdbinit}
15730 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
15732 @cindex @file{.os68gdbinit}
15734 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
15736 @cindex @file{.esgdbinit}
15738 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
15741 You can also request the execution of a command file with the
15742 @code{source} command:
15746 @item source @var{filename}
15747 Execute the command file @var{filename}.
15750 The lines in a command file are executed sequentially. They are not
15751 printed as they are executed. An error in any command terminates
15752 execution of the command file and control is returned to the console.
15754 Commands that would ask for confirmation if used interactively proceed
15755 without asking when used in a command file. Many @value{GDBN} commands that
15756 normally print messages to say what they are doing omit the messages
15757 when called from command files.
15759 @value{GDBN} also accepts command input from standard input. In this
15760 mode, normal output goes to standard output and error output goes to
15761 standard error. Errors in a command file supplied on standard input do
15762 not terminate execution of the command file --- execution continues with
15766 gdb < cmds > log 2>&1
15769 (The syntax above will vary depending on the shell used.) This example
15770 will execute commands from the file @file{cmds}. All output and errors
15771 would be directed to @file{log}.
15774 @section Commands for controlled output
15776 During the execution of a command file or a user-defined command, normal
15777 @value{GDBN} output is suppressed; the only output that appears is what is
15778 explicitly printed by the commands in the definition. This section
15779 describes three commands useful for generating exactly the output you
15784 @item echo @var{text}
15785 @c I do not consider backslash-space a standard C escape sequence
15786 @c because it is not in ANSI.
15787 Print @var{text}. Nonprinting characters can be included in
15788 @var{text} using C escape sequences, such as @samp{\n} to print a
15789 newline. @strong{No newline is printed unless you specify one.}
15790 In addition to the standard C escape sequences, a backslash followed
15791 by a space stands for a space. This is useful for displaying a
15792 string with spaces at the beginning or the end, since leading and
15793 trailing spaces are otherwise trimmed from all arguments.
15794 To print @samp{@w{ }and foo =@w{ }}, use the command
15795 @samp{echo \@w{ }and foo = \@w{ }}.
15797 A backslash at the end of @var{text} can be used, as in C, to continue
15798 the command onto subsequent lines. For example,
15801 echo This is some text\n\
15802 which is continued\n\
15803 onto several lines.\n
15806 produces the same output as
15809 echo This is some text\n
15810 echo which is continued\n
15811 echo onto several lines.\n
15815 @item output @var{expression}
15816 Print the value of @var{expression} and nothing but that value: no
15817 newlines, no @samp{$@var{nn} = }. The value is not entered in the
15818 value history either. @xref{Expressions, ,Expressions}, for more information
15821 @item output/@var{fmt} @var{expression}
15822 Print the value of @var{expression} in format @var{fmt}. You can use
15823 the same formats as for @code{print}. @xref{Output Formats,,Output
15824 formats}, for more information.
15827 @item printf @var{string}, @var{expressions}@dots{}
15828 Print the values of the @var{expressions} under the control of
15829 @var{string}. The @var{expressions} are separated by commas and may be
15830 either numbers or pointers. Their values are printed as specified by
15831 @var{string}, exactly as if your program were to execute the C
15833 @c FIXME: the above implies that at least all ANSI C formats are
15834 @c supported, but it isn't true: %E and %G don't work (or so it seems).
15835 @c Either this is a bug, or the manual should document what formats are
15839 printf (@var{string}, @var{expressions}@dots{});
15842 For example, you can print two values in hex like this:
15845 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
15848 The only backslash-escape sequences that you can use in the format
15849 string are the simple ones that consist of backslash followed by a
15854 @chapter Command Interpreters
15855 @cindex command interpreters
15857 @value{GDBN} supports multiple command interpreters, and some command
15858 infrastructure to allow users or user interface writers to switch
15859 between interpreters or run commands in other interpreters.
15861 @value{GDBN} currently supports two command interpreters, the console
15862 interpreter (sometimes called the command-line interpreter or @sc{cli})
15863 and the machine interface interpreter (or @sc{gdb/mi}). This manual
15864 describes both of these interfaces in great detail.
15866 By default, @value{GDBN} will start with the console interpreter.
15867 However, the user may choose to start @value{GDBN} with another
15868 interpreter by specifying the @option{-i} or @option{--interpreter}
15869 startup options. Defined interpreters include:
15873 @cindex console interpreter
15874 The traditional console or command-line interpreter. This is the most often
15875 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
15876 @value{GDBN} will use this interpreter.
15879 @cindex mi interpreter
15880 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
15881 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
15882 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
15886 @cindex mi2 interpreter
15887 The current @sc{gdb/mi} interface.
15890 @cindex mi1 interpreter
15891 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
15895 @cindex invoke another interpreter
15896 The interpreter being used by @value{GDBN} may not be dynamically
15897 switched at runtime. Although possible, this could lead to a very
15898 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
15899 enters the command "interpreter-set console" in a console view,
15900 @value{GDBN} would switch to using the console interpreter, rendering
15901 the IDE inoperable!
15903 @kindex interpreter-exec
15904 Although you may only choose a single interpreter at startup, you may execute
15905 commands in any interpreter from the current interpreter using the appropriate
15906 command. If you are running the console interpreter, simply use the
15907 @code{interpreter-exec} command:
15910 interpreter-exec mi "-data-list-register-names"
15913 @sc{gdb/mi} has a similar command, although it is only available in versions of
15914 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
15917 @chapter @value{GDBN} Text User Interface
15919 @cindex Text User Interface
15922 * TUI Overview:: TUI overview
15923 * TUI Keys:: TUI key bindings
15924 * TUI Single Key Mode:: TUI single key mode
15925 * TUI Commands:: TUI specific commands
15926 * TUI Configuration:: TUI configuration variables
15929 The @value{GDBN} Text User Interface, TUI in short, is a terminal
15930 interface which uses the @code{curses} library to show the source
15931 file, the assembly output, the program registers and @value{GDBN}
15932 commands in separate text windows.
15934 The TUI is enabled by invoking @value{GDBN} using either
15936 @samp{gdbtui} or @samp{gdb -tui}.
15939 @section TUI overview
15941 The TUI has two display modes that can be switched while
15946 A curses (or TUI) mode in which it displays several text
15947 windows on the terminal.
15950 A standard mode which corresponds to the @value{GDBN} configured without
15954 In the TUI mode, @value{GDBN} can display several text window
15959 This window is the @value{GDBN} command window with the @value{GDBN}
15960 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
15961 managed using readline but through the TUI. The @emph{command}
15962 window is always visible.
15965 The source window shows the source file of the program. The current
15966 line as well as active breakpoints are displayed in this window.
15969 The assembly window shows the disassembly output of the program.
15972 This window shows the processor registers. It detects when
15973 a register is changed and when this is the case, registers that have
15974 changed are highlighted.
15978 The source and assembly windows show the current program position
15979 by highlighting the current line and marking them with the @samp{>} marker.
15980 Breakpoints are also indicated with two markers. A first one
15981 indicates the breakpoint type:
15985 Breakpoint which was hit at least once.
15988 Breakpoint which was never hit.
15991 Hardware breakpoint which was hit at least once.
15994 Hardware breakpoint which was never hit.
15998 The second marker indicates whether the breakpoint is enabled or not:
16002 Breakpoint is enabled.
16005 Breakpoint is disabled.
16009 The source, assembly and register windows are attached to the thread
16010 and the frame position. They are updated when the current thread
16011 changes, when the frame changes or when the program counter changes.
16012 These three windows are arranged by the TUI according to several
16013 layouts. The layout defines which of these three windows are visible.
16014 The following layouts are available:
16024 source and assembly
16027 source and registers
16030 assembly and registers
16034 On top of the command window a status line gives various information
16035 concerning the current process begin debugged. The status line is
16036 updated when the information it shows changes. The following fields
16041 Indicates the current gdb target
16042 (@pxref{Targets, ,Specifying a Debugging Target}).
16045 Gives information about the current process or thread number.
16046 When no process is being debugged, this field is set to @code{No process}.
16049 Gives the current function name for the selected frame.
16050 The name is demangled if demangling is turned on (@pxref{Print Settings}).
16051 When there is no symbol corresponding to the current program counter
16052 the string @code{??} is displayed.
16055 Indicates the current line number for the selected frame.
16056 When the current line number is not known the string @code{??} is displayed.
16059 Indicates the current program counter address.
16064 @section TUI Key Bindings
16065 @cindex TUI key bindings
16067 The TUI installs several key bindings in the readline keymaps
16068 (@pxref{Command Line Editing}).
16069 They allow to leave or enter in the TUI mode or they operate
16070 directly on the TUI layout and windows. The TUI also provides
16071 a @emph{SingleKey} keymap which binds several keys directly to
16072 @value{GDBN} commands. The following key bindings
16073 are installed for both TUI mode and the @value{GDBN} standard mode.
16082 Enter or leave the TUI mode. When the TUI mode is left,
16083 the curses window management is left and @value{GDBN} operates using
16084 its standard mode writing on the terminal directly. When the TUI
16085 mode is entered, the control is given back to the curses windows.
16086 The screen is then refreshed.
16090 Use a TUI layout with only one window. The layout will
16091 either be @samp{source} or @samp{assembly}. When the TUI mode
16092 is not active, it will switch to the TUI mode.
16094 Think of this key binding as the Emacs @kbd{C-x 1} binding.
16098 Use a TUI layout with at least two windows. When the current
16099 layout shows already two windows, a next layout with two windows is used.
16100 When a new layout is chosen, one window will always be common to the
16101 previous layout and the new one.
16103 Think of it as the Emacs @kbd{C-x 2} binding.
16107 Change the active window. The TUI associates several key bindings
16108 (like scrolling and arrow keys) to the active window. This command
16109 gives the focus to the next TUI window.
16111 Think of it as the Emacs @kbd{C-x o} binding.
16115 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
16116 (@pxref{TUI Single Key Mode}).
16120 The following key bindings are handled only by the TUI mode:
16125 Scroll the active window one page up.
16129 Scroll the active window one page down.
16133 Scroll the active window one line up.
16137 Scroll the active window one line down.
16141 Scroll the active window one column left.
16145 Scroll the active window one column right.
16149 Refresh the screen.
16153 In the TUI mode, the arrow keys are used by the active window
16154 for scrolling. This means they are available for readline when the
16155 active window is the command window. When the command window
16156 does not have the focus, it is necessary to use other readline
16157 key bindings such as @key{C-p}, @key{C-n}, @key{C-b} and @key{C-f}.
16159 @node TUI Single Key Mode
16160 @section TUI Single Key Mode
16161 @cindex TUI single key mode
16163 The TUI provides a @emph{SingleKey} mode in which it installs a particular
16164 key binding in the readline keymaps to connect single keys to
16168 @kindex c @r{(SingleKey TUI key)}
16172 @kindex d @r{(SingleKey TUI key)}
16176 @kindex f @r{(SingleKey TUI key)}
16180 @kindex n @r{(SingleKey TUI key)}
16184 @kindex q @r{(SingleKey TUI key)}
16186 exit the @emph{SingleKey} mode.
16188 @kindex r @r{(SingleKey TUI key)}
16192 @kindex s @r{(SingleKey TUI key)}
16196 @kindex u @r{(SingleKey TUI key)}
16200 @kindex v @r{(SingleKey TUI key)}
16204 @kindex w @r{(SingleKey TUI key)}
16210 Other keys temporarily switch to the @value{GDBN} command prompt.
16211 The key that was pressed is inserted in the editing buffer so that
16212 it is possible to type most @value{GDBN} commands without interaction
16213 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
16214 @emph{SingleKey} mode is restored. The only way to permanently leave
16215 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
16219 @section TUI specific commands
16220 @cindex TUI commands
16222 The TUI has specific commands to control the text windows.
16223 These commands are always available, that is they do not depend on
16224 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
16225 is in the standard mode, using these commands will automatically switch
16231 List and give the size of all displayed windows.
16235 Display the next layout.
16238 Display the previous layout.
16241 Display the source window only.
16244 Display the assembly window only.
16247 Display the source and assembly window.
16250 Display the register window together with the source or assembly window.
16252 @item focus next | prev | src | asm | regs | split
16254 Set the focus to the named window.
16255 This command allows to change the active window so that scrolling keys
16256 can be affected to another window.
16260 Refresh the screen. This is similar to using @key{C-L} key.
16262 @item tui reg float
16264 Show the floating point registers in the register window.
16266 @item tui reg general
16267 Show the general registers in the register window.
16270 Show the next register group. The list of register groups as well as
16271 their order is target specific. The predefined register groups are the
16272 following: @code{general}, @code{float}, @code{system}, @code{vector},
16273 @code{all}, @code{save}, @code{restore}.
16275 @item tui reg system
16276 Show the system registers in the register window.
16280 Update the source window and the current execution point.
16282 @item winheight @var{name} +@var{count}
16283 @itemx winheight @var{name} -@var{count}
16285 Change the height of the window @var{name} by @var{count}
16286 lines. Positive counts increase the height, while negative counts
16290 @kindex tabset @var{nchars}
16291 Set the width of tab stops to be @var{nchars} characters.
16295 @node TUI Configuration
16296 @section TUI configuration variables
16297 @cindex TUI configuration variables
16299 The TUI has several configuration variables that control the
16300 appearance of windows on the terminal.
16303 @item set tui border-kind @var{kind}
16304 @kindex set tui border-kind
16305 Select the border appearance for the source, assembly and register windows.
16306 The possible values are the following:
16309 Use a space character to draw the border.
16312 Use ascii characters + - and | to draw the border.
16315 Use the Alternate Character Set to draw the border. The border is
16316 drawn using character line graphics if the terminal supports them.
16320 @item set tui active-border-mode @var{mode}
16321 @kindex set tui active-border-mode
16322 Select the attributes to display the border of the active window.
16323 The possible values are @code{normal}, @code{standout}, @code{reverse},
16324 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
16326 @item set tui border-mode @var{mode}
16327 @kindex set tui border-mode
16328 Select the attributes to display the border of other windows.
16329 The @var{mode} can be one of the following:
16332 Use normal attributes to display the border.
16338 Use reverse video mode.
16341 Use half bright mode.
16343 @item half-standout
16344 Use half bright and standout mode.
16347 Use extra bright or bold mode.
16349 @item bold-standout
16350 Use extra bright or bold and standout mode.
16357 @chapter Using @value{GDBN} under @sc{gnu} Emacs
16360 @cindex @sc{gnu} Emacs
16361 A special interface allows you to use @sc{gnu} Emacs to view (and
16362 edit) the source files for the program you are debugging with
16365 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
16366 executable file you want to debug as an argument. This command starts
16367 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
16368 created Emacs buffer.
16369 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
16371 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
16376 All ``terminal'' input and output goes through the Emacs buffer.
16379 This applies both to @value{GDBN} commands and their output, and to the input
16380 and output done by the program you are debugging.
16382 This is useful because it means that you can copy the text of previous
16383 commands and input them again; you can even use parts of the output
16386 All the facilities of Emacs' Shell mode are available for interacting
16387 with your program. In particular, you can send signals the usual
16388 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
16393 @value{GDBN} displays source code through Emacs.
16396 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
16397 source file for that frame and puts an arrow (@samp{=>}) at the
16398 left margin of the current line. Emacs uses a separate buffer for
16399 source display, and splits the screen to show both your @value{GDBN} session
16402 Explicit @value{GDBN} @code{list} or search commands still produce output as
16403 usual, but you probably have no reason to use them from Emacs.
16405 If you specify an absolute file name when prompted for the @kbd{M-x
16406 gdb} argument, then Emacs sets your current working directory to where
16407 your program resides. If you only specify the file name, then Emacs
16408 sets your current working directory to to the directory associated
16409 with the previous buffer. In this case, @value{GDBN} may find your
16410 program by searching your environment's @code{PATH} variable, but on
16411 some operating systems it might not find the source. So, although the
16412 @value{GDBN} input and output session proceeds normally, the auxiliary
16413 buffer does not display the current source and line of execution.
16415 The initial working directory of @value{GDBN} is printed on the top
16416 line of the @value{GDBN} I/O buffer and this serves as a default for
16417 the commands that specify files for @value{GDBN} to operate
16418 on. @xref{Files, ,Commands to specify files}.
16420 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
16421 need to call @value{GDBN} by a different name (for example, if you
16422 keep several configurations around, with different names) you can
16423 customize the Emacs variable @code{gud-gdb-command-name} to run the
16426 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
16427 addition to the standard Shell mode commands:
16431 Describe the features of Emacs' @value{GDBN} Mode.
16434 Execute to another source line, like the @value{GDBN} @code{step} command; also
16435 update the display window to show the current file and location.
16438 Execute to next source line in this function, skipping all function
16439 calls, like the @value{GDBN} @code{next} command. Then update the display window
16440 to show the current file and location.
16443 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
16444 display window accordingly.
16447 Execute until exit from the selected stack frame, like the @value{GDBN}
16448 @code{finish} command.
16451 Continue execution of your program, like the @value{GDBN} @code{continue}
16455 Go up the number of frames indicated by the numeric argument
16456 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
16457 like the @value{GDBN} @code{up} command.
16460 Go down the number of frames indicated by the numeric argument, like the
16461 @value{GDBN} @code{down} command.
16464 In any source file, the Emacs command @kbd{C-x SPC} (@code{gud-break})
16465 tells @value{GDBN} to set a breakpoint on the source line point is on.
16467 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
16468 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
16469 point to any frame in the stack and type @key{RET} to make it become the
16470 current frame and display the associated source in the source buffer.
16471 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
16474 If you accidentally delete the source-display buffer, an easy way to get
16475 it back is to type the command @code{f} in the @value{GDBN} buffer, to
16476 request a frame display; when you run under Emacs, this recreates
16477 the source buffer if necessary to show you the context of the current
16480 The source files displayed in Emacs are in ordinary Emacs buffers
16481 which are visiting the source files in the usual way. You can edit
16482 the files with these buffers if you wish; but keep in mind that @value{GDBN}
16483 communicates with Emacs in terms of line numbers. If you add or
16484 delete lines from the text, the line numbers that @value{GDBN} knows cease
16485 to correspond properly with the code.
16487 The description given here is for GNU Emacs version 21.3 and a more
16488 detailed description of its interaction with @value{GDBN} is given in
16489 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
16491 @c The following dropped because Epoch is nonstandard. Reactivate
16492 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
16494 @kindex Emacs Epoch environment
16498 Version 18 of @sc{gnu} Emacs has a built-in window system
16499 called the @code{epoch}
16500 environment. Users of this environment can use a new command,
16501 @code{inspect} which performs identically to @code{print} except that
16502 each value is printed in its own window.
16507 @chapter The @sc{gdb/mi} Interface
16509 @unnumberedsec Function and Purpose
16511 @cindex @sc{gdb/mi}, its purpose
16512 @sc{gdb/mi} is a line based machine oriented text interface to
16513 @value{GDBN} and is activated by specifying using the
16514 @option{--interpreter} command line option (@pxref{Mode Options}). It
16515 is specifically intended to support the development of systems which
16516 use the debugger as just one small component of a larger system.
16518 This chapter is a specification of the @sc{gdb/mi} interface. It is written
16519 in the form of a reference manual.
16521 Note that @sc{gdb/mi} is still under construction, so some of the
16522 features described below are incomplete and subject to change.
16524 @unnumberedsec Notation and Terminology
16526 @cindex notational conventions, for @sc{gdb/mi}
16527 This chapter uses the following notation:
16531 @code{|} separates two alternatives.
16534 @code{[ @var{something} ]} indicates that @var{something} is optional:
16535 it may or may not be given.
16538 @code{( @var{group} )*} means that @var{group} inside the parentheses
16539 may repeat zero or more times.
16542 @code{( @var{group} )+} means that @var{group} inside the parentheses
16543 may repeat one or more times.
16546 @code{"@var{string}"} means a literal @var{string}.
16550 @heading Dependencies
16553 @heading Acknowledgments
16555 In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
16559 * GDB/MI Command Syntax::
16560 * GDB/MI Compatibility with CLI::
16561 * GDB/MI Output Records::
16562 * GDB/MI Command Description Format::
16563 * GDB/MI Breakpoint Table Commands::
16564 * GDB/MI Data Manipulation::
16565 * GDB/MI Program Control::
16566 * GDB/MI Miscellaneous Commands::
16568 * GDB/MI Kod Commands::
16569 * GDB/MI Memory Overlay Commands::
16570 * GDB/MI Signal Handling Commands::
16572 * GDB/MI Stack Manipulation::
16573 * GDB/MI Symbol Query::
16574 * GDB/MI Target Manipulation::
16575 * GDB/MI Thread Commands::
16576 * GDB/MI Tracepoint Commands::
16577 * GDB/MI Variable Objects::
16580 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16581 @node GDB/MI Command Syntax
16582 @section @sc{gdb/mi} Command Syntax
16585 * GDB/MI Input Syntax::
16586 * GDB/MI Output Syntax::
16587 * GDB/MI Simple Examples::
16590 @node GDB/MI Input Syntax
16591 @subsection @sc{gdb/mi} Input Syntax
16593 @cindex input syntax for @sc{gdb/mi}
16594 @cindex @sc{gdb/mi}, input syntax
16596 @item @var{command} @expansion{}
16597 @code{@var{cli-command} | @var{mi-command}}
16599 @item @var{cli-command} @expansion{}
16600 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
16601 @var{cli-command} is any existing @value{GDBN} CLI command.
16603 @item @var{mi-command} @expansion{}
16604 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
16605 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
16607 @item @var{token} @expansion{}
16608 "any sequence of digits"
16610 @item @var{option} @expansion{}
16611 @code{"-" @var{parameter} [ " " @var{parameter} ]}
16613 @item @var{parameter} @expansion{}
16614 @code{@var{non-blank-sequence} | @var{c-string}}
16616 @item @var{operation} @expansion{}
16617 @emph{any of the operations described in this chapter}
16619 @item @var{non-blank-sequence} @expansion{}
16620 @emph{anything, provided it doesn't contain special characters such as
16621 "-", @var{nl}, """ and of course " "}
16623 @item @var{c-string} @expansion{}
16624 @code{""" @var{seven-bit-iso-c-string-content} """}
16626 @item @var{nl} @expansion{}
16635 The CLI commands are still handled by the @sc{mi} interpreter; their
16636 output is described below.
16639 The @code{@var{token}}, when present, is passed back when the command
16643 Some @sc{mi} commands accept optional arguments as part of the parameter
16644 list. Each option is identified by a leading @samp{-} (dash) and may be
16645 followed by an optional argument parameter. Options occur first in the
16646 parameter list and can be delimited from normal parameters using
16647 @samp{--} (this is useful when some parameters begin with a dash).
16654 We want easy access to the existing CLI syntax (for debugging).
16657 We want it to be easy to spot a @sc{mi} operation.
16660 @node GDB/MI Output Syntax
16661 @subsection @sc{gdb/mi} Output Syntax
16663 @cindex output syntax of @sc{gdb/mi}
16664 @cindex @sc{gdb/mi}, output syntax
16665 The output from @sc{gdb/mi} consists of zero or more out-of-band records
16666 followed, optionally, by a single result record. This result record
16667 is for the most recent command. The sequence of output records is
16668 terminated by @samp{(@value{GDBP})}.
16670 If an input command was prefixed with a @code{@var{token}} then the
16671 corresponding output for that command will also be prefixed by that same
16675 @item @var{output} @expansion{}
16676 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(@value{GDBP})" @var{nl}}
16678 @item @var{result-record} @expansion{}
16679 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
16681 @item @var{out-of-band-record} @expansion{}
16682 @code{@var{async-record} | @var{stream-record}}
16684 @item @var{async-record} @expansion{}
16685 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
16687 @item @var{exec-async-output} @expansion{}
16688 @code{[ @var{token} ] "*" @var{async-output}}
16690 @item @var{status-async-output} @expansion{}
16691 @code{[ @var{token} ] "+" @var{async-output}}
16693 @item @var{notify-async-output} @expansion{}
16694 @code{[ @var{token} ] "=" @var{async-output}}
16696 @item @var{async-output} @expansion{}
16697 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
16699 @item @var{result-class} @expansion{}
16700 @code{"done" | "running" | "connected" | "error" | "exit"}
16702 @item @var{async-class} @expansion{}
16703 @code{"stopped" | @var{others}} (where @var{others} will be added
16704 depending on the needs---this is still in development).
16706 @item @var{result} @expansion{}
16707 @code{ @var{variable} "=" @var{value}}
16709 @item @var{variable} @expansion{}
16710 @code{ @var{string} }
16712 @item @var{value} @expansion{}
16713 @code{ @var{const} | @var{tuple} | @var{list} }
16715 @item @var{const} @expansion{}
16716 @code{@var{c-string}}
16718 @item @var{tuple} @expansion{}
16719 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
16721 @item @var{list} @expansion{}
16722 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
16723 @var{result} ( "," @var{result} )* "]" }
16725 @item @var{stream-record} @expansion{}
16726 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
16728 @item @var{console-stream-output} @expansion{}
16729 @code{"~" @var{c-string}}
16731 @item @var{target-stream-output} @expansion{}
16732 @code{"@@" @var{c-string}}
16734 @item @var{log-stream-output} @expansion{}
16735 @code{"&" @var{c-string}}
16737 @item @var{nl} @expansion{}
16740 @item @var{token} @expansion{}
16741 @emph{any sequence of digits}.
16749 All output sequences end in a single line containing a period.
16752 The @code{@var{token}} is from the corresponding request. If an execution
16753 command is interrupted by the @samp{-exec-interrupt} command, the
16754 @var{token} associated with the @samp{*stopped} message is the one of the
16755 original execution command, not the one of the interrupt command.
16758 @cindex status output in @sc{gdb/mi}
16759 @var{status-async-output} contains on-going status information about the
16760 progress of a slow operation. It can be discarded. All status output is
16761 prefixed by @samp{+}.
16764 @cindex async output in @sc{gdb/mi}
16765 @var{exec-async-output} contains asynchronous state change on the target
16766 (stopped, started, disappeared). All async output is prefixed by
16770 @cindex notify output in @sc{gdb/mi}
16771 @var{notify-async-output} contains supplementary information that the
16772 client should handle (e.g., a new breakpoint information). All notify
16773 output is prefixed by @samp{=}.
16776 @cindex console output in @sc{gdb/mi}
16777 @var{console-stream-output} is output that should be displayed as is in the
16778 console. It is the textual response to a CLI command. All the console
16779 output is prefixed by @samp{~}.
16782 @cindex target output in @sc{gdb/mi}
16783 @var{target-stream-output} is the output produced by the target program.
16784 All the target output is prefixed by @samp{@@}.
16787 @cindex log output in @sc{gdb/mi}
16788 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
16789 instance messages that should be displayed as part of an error log. All
16790 the log output is prefixed by @samp{&}.
16793 @cindex list output in @sc{gdb/mi}
16794 New @sc{gdb/mi} commands should only output @var{lists} containing
16800 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
16801 details about the various output records.
16803 @node GDB/MI Simple Examples
16804 @subsection Simple Examples of @sc{gdb/mi} Interaction
16805 @cindex @sc{gdb/mi}, simple examples
16807 This subsection presents several simple examples of interaction using
16808 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
16809 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
16810 the output received from @sc{gdb/mi}.
16812 @subsubheading Target Stop
16813 @c Ummm... There is no "-stop" command. This assumes async, no?
16814 Here's an example of stopping the inferior process:
16825 <- *stop,reason="stop",address="0x123",source="a.c:123"
16829 @subsubheading Simple CLI Command
16831 Here's an example of a simple CLI command being passed through
16832 @sc{gdb/mi} and on to the CLI.
16842 @subsubheading Command With Side Effects
16845 -> -symbol-file xyz.exe
16846 <- *breakpoint,nr="3",address="0x123",source="a.c:123"
16850 @subsubheading A Bad Command
16852 Here's what happens if you pass a non-existent command:
16856 <- ^error,msg="Undefined MI command: rubbish"
16860 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16861 @node GDB/MI Compatibility with CLI
16862 @section @sc{gdb/mi} Compatibility with CLI
16864 @cindex compatibility, @sc{gdb/mi} and CLI
16865 @cindex @sc{gdb/mi}, compatibility with CLI
16866 To help users familiar with @value{GDBN}'s existing CLI interface, @sc{gdb/mi}
16867 accepts existing CLI commands. As specified by the syntax, such
16868 commands can be directly entered into the @sc{gdb/mi} interface and @value{GDBN} will
16871 This mechanism is provided as an aid to developers of @sc{gdb/mi}
16872 clients and not as a reliable interface into the CLI. Since the command
16873 is being interpreteted in an environment that assumes @sc{gdb/mi}
16874 behaviour, the exact output of such commands is likely to end up being
16875 an un-supported hybrid of @sc{gdb/mi} and CLI output.
16877 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16878 @node GDB/MI Output Records
16879 @section @sc{gdb/mi} Output Records
16882 * GDB/MI Result Records::
16883 * GDB/MI Stream Records::
16884 * GDB/MI Out-of-band Records::
16887 @node GDB/MI Result Records
16888 @subsection @sc{gdb/mi} Result Records
16890 @cindex result records in @sc{gdb/mi}
16891 @cindex @sc{gdb/mi}, result records
16892 In addition to a number of out-of-band notifications, the response to a
16893 @sc{gdb/mi} command includes one of the following result indications:
16897 @item "^done" [ "," @var{results} ]
16898 The synchronous operation was successful, @code{@var{results}} are the return
16903 @c Is this one correct? Should it be an out-of-band notification?
16904 The asynchronous operation was successfully started. The target is
16907 @item "^error" "," @var{c-string}
16909 The operation failed. The @code{@var{c-string}} contains the corresponding
16913 @node GDB/MI Stream Records
16914 @subsection @sc{gdb/mi} Stream Records
16916 @cindex @sc{gdb/mi}, stream records
16917 @cindex stream records in @sc{gdb/mi}
16918 @value{GDBN} internally maintains a number of output streams: the console, the
16919 target, and the log. The output intended for each of these streams is
16920 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
16922 Each stream record begins with a unique @dfn{prefix character} which
16923 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
16924 Syntax}). In addition to the prefix, each stream record contains a
16925 @code{@var{string-output}}. This is either raw text (with an implicit new
16926 line) or a quoted C string (which does not contain an implicit newline).
16929 @item "~" @var{string-output}
16930 The console output stream contains text that should be displayed in the
16931 CLI console window. It contains the textual responses to CLI commands.
16933 @item "@@" @var{string-output}
16934 The target output stream contains any textual output from the running
16937 @item "&" @var{string-output}
16938 The log stream contains debugging messages being produced by @value{GDBN}'s
16942 @node GDB/MI Out-of-band Records
16943 @subsection @sc{gdb/mi} Out-of-band Records
16945 @cindex out-of-band records in @sc{gdb/mi}
16946 @cindex @sc{gdb/mi}, out-of-band records
16947 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
16948 additional changes that have occurred. Those changes can either be a
16949 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
16950 target activity (e.g., target stopped).
16952 The following is a preliminary list of possible out-of-band records.
16959 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16960 @node GDB/MI Command Description Format
16961 @section @sc{gdb/mi} Command Description Format
16963 The remaining sections describe blocks of commands. Each block of
16964 commands is laid out in a fashion similar to this section.
16966 Note the the line breaks shown in the examples are here only for
16967 readability. They don't appear in the real output.
16968 Also note that the commands with a non-available example (N.A.@:) are
16969 not yet implemented.
16971 @subheading Motivation
16973 The motivation for this collection of commands.
16975 @subheading Introduction
16977 A brief introduction to this collection of commands as a whole.
16979 @subheading Commands
16981 For each command in the block, the following is described:
16983 @subsubheading Synopsis
16986 -command @var{args}@dots{}
16989 @subsubheading @value{GDBN} Command
16991 The corresponding @value{GDBN} CLI command.
16993 @subsubheading Result
16995 @subsubheading Out-of-band
16997 @subsubheading Notes
16999 @subsubheading Example
17002 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17003 @node GDB/MI Breakpoint Table Commands
17004 @section @sc{gdb/mi} Breakpoint table commands
17006 @cindex breakpoint commands for @sc{gdb/mi}
17007 @cindex @sc{gdb/mi}, breakpoint commands
17008 This section documents @sc{gdb/mi} commands for manipulating
17011 @subheading The @code{-break-after} Command
17012 @findex -break-after
17014 @subsubheading Synopsis
17017 -break-after @var{number} @var{count}
17020 The breakpoint number @var{number} is not in effect until it has been
17021 hit @var{count} times. To see how this is reflected in the output of
17022 the @samp{-break-list} command, see the description of the
17023 @samp{-break-list} command below.
17025 @subsubheading @value{GDBN} Command
17027 The corresponding @value{GDBN} command is @samp{ignore}.
17029 @subsubheading Example
17034 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",line="5"@}
17041 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17042 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17043 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17044 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17045 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17046 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17047 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17048 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17049 addr="0x000100d0",func="main",file="hello.c",line="5",times="0",
17055 @subheading The @code{-break-catch} Command
17056 @findex -break-catch
17058 @subheading The @code{-break-commands} Command
17059 @findex -break-commands
17063 @subheading The @code{-break-condition} Command
17064 @findex -break-condition
17066 @subsubheading Synopsis
17069 -break-condition @var{number} @var{expr}
17072 Breakpoint @var{number} will stop the program only if the condition in
17073 @var{expr} is true. The condition becomes part of the
17074 @samp{-break-list} output (see the description of the @samp{-break-list}
17077 @subsubheading @value{GDBN} Command
17079 The corresponding @value{GDBN} command is @samp{condition}.
17081 @subsubheading Example
17085 -break-condition 1 1
17089 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17090 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17091 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17092 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17093 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17094 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17095 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17096 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17097 addr="0x000100d0",func="main",file="hello.c",line="5",cond="1",
17098 times="0",ignore="3"@}]@}
17102 @subheading The @code{-break-delete} Command
17103 @findex -break-delete
17105 @subsubheading Synopsis
17108 -break-delete ( @var{breakpoint} )+
17111 Delete the breakpoint(s) whose number(s) are specified in the argument
17112 list. This is obviously reflected in the breakpoint list.
17114 @subsubheading @value{GDBN} command
17116 The corresponding @value{GDBN} command is @samp{delete}.
17118 @subsubheading Example
17126 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17127 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17128 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17129 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17130 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17131 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17132 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17137 @subheading The @code{-break-disable} Command
17138 @findex -break-disable
17140 @subsubheading Synopsis
17143 -break-disable ( @var{breakpoint} )+
17146 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
17147 break list is now set to @samp{n} for the named @var{breakpoint}(s).
17149 @subsubheading @value{GDBN} Command
17151 The corresponding @value{GDBN} command is @samp{disable}.
17153 @subsubheading Example
17161 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17162 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17163 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17164 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17165 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17166 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17167 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17168 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
17169 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
17173 @subheading The @code{-break-enable} Command
17174 @findex -break-enable
17176 @subsubheading Synopsis
17179 -break-enable ( @var{breakpoint} )+
17182 Enable (previously disabled) @var{breakpoint}(s).
17184 @subsubheading @value{GDBN} Command
17186 The corresponding @value{GDBN} command is @samp{enable}.
17188 @subsubheading Example
17196 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17197 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17198 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17199 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17200 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17201 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17202 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17203 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17204 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
17208 @subheading The @code{-break-info} Command
17209 @findex -break-info
17211 @subsubheading Synopsis
17214 -break-info @var{breakpoint}
17218 Get information about a single breakpoint.
17220 @subsubheading @value{GDBN} command
17222 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
17224 @subsubheading Example
17227 @subheading The @code{-break-insert} Command
17228 @findex -break-insert
17230 @subsubheading Synopsis
17233 -break-insert [ -t ] [ -h ] [ -r ]
17234 [ -c @var{condition} ] [ -i @var{ignore-count} ]
17235 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
17239 If specified, @var{line}, can be one of:
17246 @item filename:linenum
17247 @item filename:function
17251 The possible optional parameters of this command are:
17255 Insert a tempoary breakpoint.
17257 Insert a hardware breakpoint.
17258 @item -c @var{condition}
17259 Make the breakpoint conditional on @var{condition}.
17260 @item -i @var{ignore-count}
17261 Initialize the @var{ignore-count}.
17263 Insert a regular breakpoint in all the functions whose names match the
17264 given regular expression. Other flags are not applicable to regular
17268 @subsubheading Result
17270 The result is in the form:
17273 ^done,bkptno="@var{number}",func="@var{funcname}",
17274 file="@var{filename}",line="@var{lineno}"
17278 where @var{number} is the @value{GDBN} number for this breakpoint, @var{funcname}
17279 is the name of the function where the breakpoint was inserted,
17280 @var{filename} is the name of the source file which contains this
17281 function, and @var{lineno} is the source line number within that file.
17283 Note: this format is open to change.
17284 @c An out-of-band breakpoint instead of part of the result?
17286 @subsubheading @value{GDBN} Command
17288 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
17289 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
17291 @subsubheading Example
17296 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
17298 -break-insert -t foo
17299 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",line="11"@}
17302 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17303 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17304 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17305 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17306 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17307 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17308 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17309 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17310 addr="0x0001072c", func="main",file="recursive2.c",line="4",times="0"@},
17311 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
17312 addr="0x00010774",func="foo",file="recursive2.c",line="11",times="0"@}]@}
17314 -break-insert -r foo.*
17315 ~int foo(int, int);
17316 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c",line="11"@}
17320 @subheading The @code{-break-list} Command
17321 @findex -break-list
17323 @subsubheading Synopsis
17329 Displays the list of inserted breakpoints, showing the following fields:
17333 number of the breakpoint
17335 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
17337 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
17340 is the breakpoint enabled or no: @samp{y} or @samp{n}
17342 memory location at which the breakpoint is set
17344 logical location of the breakpoint, expressed by function name, file
17347 number of times the breakpoint has been hit
17350 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
17351 @code{body} field is an empty list.
17353 @subsubheading @value{GDBN} Command
17355 The corresponding @value{GDBN} command is @samp{info break}.
17357 @subsubheading Example
17362 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17363 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17364 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17365 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17366 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17367 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17368 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17369 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17370 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
17371 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17372 addr="0x00010114",func="foo",file="hello.c",line="13",times="0"@}]@}
17376 Here's an example of the result when there are no breakpoints:
17381 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17382 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17383 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17384 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17385 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17386 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17387 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17392 @subheading The @code{-break-watch} Command
17393 @findex -break-watch
17395 @subsubheading Synopsis
17398 -break-watch [ -a | -r ]
17401 Create a watchpoint. With the @samp{-a} option it will create an
17402 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
17403 read from or on a write to the memory location. With the @samp{-r}
17404 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
17405 trigger only when the memory location is accessed for reading. Without
17406 either of the options, the watchpoint created is a regular watchpoint,
17407 i.e. it will trigger when the memory location is accessed for writing.
17408 @xref{Set Watchpoints, , Setting watchpoints}.
17410 Note that @samp{-break-list} will report a single list of watchpoints and
17411 breakpoints inserted.
17413 @subsubheading @value{GDBN} Command
17415 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
17418 @subsubheading Example
17420 Setting a watchpoint on a variable in the @code{main} function:
17425 ^done,wpt=@{number="2",exp="x"@}
17429 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
17430 value=@{old="-268439212",new="55"@},
17431 frame=@{func="main",args=[],file="recursive2.c",line="5"@}
17435 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
17436 the program execution twice: first for the variable changing value, then
17437 for the watchpoint going out of scope.
17442 ^done,wpt=@{number="5",exp="C"@}
17446 ^done,reason="watchpoint-trigger",
17447 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
17448 frame=@{func="callee4",args=[],
17449 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
17453 ^done,reason="watchpoint-scope",wpnum="5",
17454 frame=@{func="callee3",args=[@{name="strarg",
17455 value="0x11940 \"A string argument.\""@}],
17456 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
17460 Listing breakpoints and watchpoints, at different points in the program
17461 execution. Note that once the watchpoint goes out of scope, it is
17467 ^done,wpt=@{number="2",exp="C"@}
17470 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17471 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17472 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17473 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17474 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17475 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17476 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17477 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17478 addr="0x00010734",func="callee4",
17479 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
17480 bkpt=@{number="2",type="watchpoint",disp="keep",
17481 enabled="y",addr="",what="C",times="0"@}]@}
17485 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
17486 value=@{old="-276895068",new="3"@},
17487 frame=@{func="callee4",args=[],
17488 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
17491 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17492 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17493 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17494 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17495 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17496 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17497 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17498 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17499 addr="0x00010734",func="callee4",
17500 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
17501 bkpt=@{number="2",type="watchpoint",disp="keep",
17502 enabled="y",addr="",what="C",times="-5"@}]@}
17506 ^done,reason="watchpoint-scope",wpnum="2",
17507 frame=@{func="callee3",args=[@{name="strarg",
17508 value="0x11940 \"A string argument.\""@}],
17509 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
17512 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17513 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17514 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17515 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17516 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17517 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17518 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17519 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17520 addr="0x00010734",func="callee4",
17521 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@}]@}
17525 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17526 @node GDB/MI Data Manipulation
17527 @section @sc{gdb/mi} Data Manipulation
17529 @cindex data manipulation, in @sc{gdb/mi}
17530 @cindex @sc{gdb/mi}, data manipulation
17531 This section describes the @sc{gdb/mi} commands that manipulate data:
17532 examine memory and registers, evaluate expressions, etc.
17534 @c REMOVED FROM THE INTERFACE.
17535 @c @subheading -data-assign
17536 @c Change the value of a program variable. Plenty of side effects.
17537 @c @subsubheading GDB command
17539 @c @subsubheading Example
17542 @subheading The @code{-data-disassemble} Command
17543 @findex -data-disassemble
17545 @subsubheading Synopsis
17549 [ -s @var{start-addr} -e @var{end-addr} ]
17550 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
17558 @item @var{start-addr}
17559 is the beginning address (or @code{$pc})
17560 @item @var{end-addr}
17562 @item @var{filename}
17563 is the name of the file to disassemble
17564 @item @var{linenum}
17565 is the line number to disassemble around
17567 is the the number of disassembly lines to be produced. If it is -1,
17568 the whole function will be disassembled, in case no @var{end-addr} is
17569 specified. If @var{end-addr} is specified as a non-zero value, and
17570 @var{lines} is lower than the number of disassembly lines between
17571 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
17572 displayed; if @var{lines} is higher than the number of lines between
17573 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
17576 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
17580 @subsubheading Result
17582 The output for each instruction is composed of four fields:
17591 Note that whatever included in the instruction field, is not manipulated
17592 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
17594 @subsubheading @value{GDBN} Command
17596 There's no direct mapping from this command to the CLI.
17598 @subsubheading Example
17600 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
17604 -data-disassemble -s $pc -e "$pc + 20" -- 0
17607 @{address="0x000107c0",func-name="main",offset="4",
17608 inst="mov 2, %o0"@},
17609 @{address="0x000107c4",func-name="main",offset="8",
17610 inst="sethi %hi(0x11800), %o2"@},
17611 @{address="0x000107c8",func-name="main",offset="12",
17612 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
17613 @{address="0x000107cc",func-name="main",offset="16",
17614 inst="sethi %hi(0x11800), %o2"@},
17615 @{address="0x000107d0",func-name="main",offset="20",
17616 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
17620 Disassemble the whole @code{main} function. Line 32 is part of
17624 -data-disassemble -f basics.c -l 32 -- 0
17626 @{address="0x000107bc",func-name="main",offset="0",
17627 inst="save %sp, -112, %sp"@},
17628 @{address="0x000107c0",func-name="main",offset="4",
17629 inst="mov 2, %o0"@},
17630 @{address="0x000107c4",func-name="main",offset="8",
17631 inst="sethi %hi(0x11800), %o2"@},
17633 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
17634 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
17638 Disassemble 3 instructions from the start of @code{main}:
17642 -data-disassemble -f basics.c -l 32 -n 3 -- 0
17644 @{address="0x000107bc",func-name="main",offset="0",
17645 inst="save %sp, -112, %sp"@},
17646 @{address="0x000107c0",func-name="main",offset="4",
17647 inst="mov 2, %o0"@},
17648 @{address="0x000107c4",func-name="main",offset="8",
17649 inst="sethi %hi(0x11800), %o2"@}]
17653 Disassemble 3 instructions from the start of @code{main} in mixed mode:
17657 -data-disassemble -f basics.c -l 32 -n 3 -- 1
17659 src_and_asm_line=@{line="31",
17660 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
17661 testsuite/gdb.mi/basics.c",line_asm_insn=[
17662 @{address="0x000107bc",func-name="main",offset="0",
17663 inst="save %sp, -112, %sp"@}]@},
17664 src_and_asm_line=@{line="32",
17665 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
17666 testsuite/gdb.mi/basics.c",line_asm_insn=[
17667 @{address="0x000107c0",func-name="main",offset="4",
17668 inst="mov 2, %o0"@},
17669 @{address="0x000107c4",func-name="main",offset="8",
17670 inst="sethi %hi(0x11800), %o2"@}]@}]
17675 @subheading The @code{-data-evaluate-expression} Command
17676 @findex -data-evaluate-expression
17678 @subsubheading Synopsis
17681 -data-evaluate-expression @var{expr}
17684 Evaluate @var{expr} as an expression. The expression could contain an
17685 inferior function call. The function call will execute synchronously.
17686 If the expression contains spaces, it must be enclosed in double quotes.
17688 @subsubheading @value{GDBN} Command
17690 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
17691 @samp{call}. In @code{gdbtk} only, there's a corresponding
17692 @samp{gdb_eval} command.
17694 @subsubheading Example
17696 In the following example, the numbers that precede the commands are the
17697 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
17698 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
17702 211-data-evaluate-expression A
17705 311-data-evaluate-expression &A
17706 311^done,value="0xefffeb7c"
17708 411-data-evaluate-expression A+3
17711 511-data-evaluate-expression "A + 3"
17717 @subheading The @code{-data-list-changed-registers} Command
17718 @findex -data-list-changed-registers
17720 @subsubheading Synopsis
17723 -data-list-changed-registers
17726 Display a list of the registers that have changed.
17728 @subsubheading @value{GDBN} Command
17730 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
17731 has the corresponding command @samp{gdb_changed_register_list}.
17733 @subsubheading Example
17735 On a PPC MBX board:
17743 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
17744 args=[],file="try.c",line="5"@}
17746 -data-list-changed-registers
17747 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
17748 "10","11","13","14","15","16","17","18","19","20","21","22","23",
17749 "24","25","26","27","28","30","31","64","65","66","67","69"]
17754 @subheading The @code{-data-list-register-names} Command
17755 @findex -data-list-register-names
17757 @subsubheading Synopsis
17760 -data-list-register-names [ ( @var{regno} )+ ]
17763 Show a list of register names for the current target. If no arguments
17764 are given, it shows a list of the names of all the registers. If
17765 integer numbers are given as arguments, it will print a list of the
17766 names of the registers corresponding to the arguments. To ensure
17767 consistency between a register name and its number, the output list may
17768 include empty register names.
17770 @subsubheading @value{GDBN} Command
17772 @value{GDBN} does not have a command which corresponds to
17773 @samp{-data-list-register-names}. In @code{gdbtk} there is a
17774 corresponding command @samp{gdb_regnames}.
17776 @subsubheading Example
17778 For the PPC MBX board:
17781 -data-list-register-names
17782 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
17783 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
17784 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
17785 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
17786 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
17787 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
17788 "", "pc","ps","cr","lr","ctr","xer"]
17790 -data-list-register-names 1 2 3
17791 ^done,register-names=["r1","r2","r3"]
17795 @subheading The @code{-data-list-register-values} Command
17796 @findex -data-list-register-values
17798 @subsubheading Synopsis
17801 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
17804 Display the registers' contents. @var{fmt} is the format according to
17805 which the registers' contents are to be returned, followed by an optional
17806 list of numbers specifying the registers to display. A missing list of
17807 numbers indicates that the contents of all the registers must be returned.
17809 Allowed formats for @var{fmt} are:
17826 @subsubheading @value{GDBN} Command
17828 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
17829 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
17831 @subsubheading Example
17833 For a PPC MBX board (note: line breaks are for readability only, they
17834 don't appear in the actual output):
17838 -data-list-register-values r 64 65
17839 ^done,register-values=[@{number="64",value="0xfe00a300"@},
17840 @{number="65",value="0x00029002"@}]
17842 -data-list-register-values x
17843 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
17844 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
17845 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
17846 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
17847 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
17848 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
17849 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
17850 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
17851 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
17852 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
17853 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
17854 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
17855 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
17856 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
17857 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
17858 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
17859 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
17860 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
17861 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
17862 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
17863 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
17864 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
17865 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
17866 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
17867 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
17868 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
17869 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
17870 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
17871 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
17872 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
17873 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
17874 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
17875 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
17876 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
17877 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
17878 @{number="69",value="0x20002b03"@}]
17883 @subheading The @code{-data-read-memory} Command
17884 @findex -data-read-memory
17886 @subsubheading Synopsis
17889 -data-read-memory [ -o @var{byte-offset} ]
17890 @var{address} @var{word-format} @var{word-size}
17891 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
17898 @item @var{address}
17899 An expression specifying the address of the first memory word to be
17900 read. Complex expressions containing embedded white space should be
17901 quoted using the C convention.
17903 @item @var{word-format}
17904 The format to be used to print the memory words. The notation is the
17905 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
17908 @item @var{word-size}
17909 The size of each memory word in bytes.
17911 @item @var{nr-rows}
17912 The number of rows in the output table.
17914 @item @var{nr-cols}
17915 The number of columns in the output table.
17918 If present, indicates that each row should include an @sc{ascii} dump. The
17919 value of @var{aschar} is used as a padding character when a byte is not a
17920 member of the printable @sc{ascii} character set (printable @sc{ascii}
17921 characters are those whose code is between 32 and 126, inclusively).
17923 @item @var{byte-offset}
17924 An offset to add to the @var{address} before fetching memory.
17927 This command displays memory contents as a table of @var{nr-rows} by
17928 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
17929 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
17930 (returned as @samp{total-bytes}). Should less than the requested number
17931 of bytes be returned by the target, the missing words are identified
17932 using @samp{N/A}. The number of bytes read from the target is returned
17933 in @samp{nr-bytes} and the starting address used to read memory in
17936 The address of the next/previous row or page is available in
17937 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
17940 @subsubheading @value{GDBN} Command
17942 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
17943 @samp{gdb_get_mem} memory read command.
17945 @subsubheading Example
17947 Read six bytes of memory starting at @code{bytes+6} but then offset by
17948 @code{-6} bytes. Format as three rows of two columns. One byte per
17949 word. Display each word in hex.
17953 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
17954 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
17955 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
17956 prev-page="0x0000138a",memory=[
17957 @{addr="0x00001390",data=["0x00","0x01"]@},
17958 @{addr="0x00001392",data=["0x02","0x03"]@},
17959 @{addr="0x00001394",data=["0x04","0x05"]@}]
17963 Read two bytes of memory starting at address @code{shorts + 64} and
17964 display as a single word formatted in decimal.
17968 5-data-read-memory shorts+64 d 2 1 1
17969 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
17970 next-row="0x00001512",prev-row="0x0000150e",
17971 next-page="0x00001512",prev-page="0x0000150e",memory=[
17972 @{addr="0x00001510",data=["128"]@}]
17976 Read thirty two bytes of memory starting at @code{bytes+16} and format
17977 as eight rows of four columns. Include a string encoding with @samp{x}
17978 used as the non-printable character.
17982 4-data-read-memory bytes+16 x 1 8 4 x
17983 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
17984 next-row="0x000013c0",prev-row="0x0000139c",
17985 next-page="0x000013c0",prev-page="0x00001380",memory=[
17986 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
17987 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
17988 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
17989 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
17990 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
17991 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
17992 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
17993 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
17997 @subheading The @code{-display-delete} Command
17998 @findex -display-delete
18000 @subsubheading Synopsis
18003 -display-delete @var{number}
18006 Delete the display @var{number}.
18008 @subsubheading @value{GDBN} Command
18010 The corresponding @value{GDBN} command is @samp{delete display}.
18012 @subsubheading Example
18016 @subheading The @code{-display-disable} Command
18017 @findex -display-disable
18019 @subsubheading Synopsis
18022 -display-disable @var{number}
18025 Disable display @var{number}.
18027 @subsubheading @value{GDBN} Command
18029 The corresponding @value{GDBN} command is @samp{disable display}.
18031 @subsubheading Example
18035 @subheading The @code{-display-enable} Command
18036 @findex -display-enable
18038 @subsubheading Synopsis
18041 -display-enable @var{number}
18044 Enable display @var{number}.
18046 @subsubheading @value{GDBN} Command
18048 The corresponding @value{GDBN} command is @samp{enable display}.
18050 @subsubheading Example
18054 @subheading The @code{-display-insert} Command
18055 @findex -display-insert
18057 @subsubheading Synopsis
18060 -display-insert @var{expression}
18063 Display @var{expression} every time the program stops.
18065 @subsubheading @value{GDBN} Command
18067 The corresponding @value{GDBN} command is @samp{display}.
18069 @subsubheading Example
18073 @subheading The @code{-display-list} Command
18074 @findex -display-list
18076 @subsubheading Synopsis
18082 List the displays. Do not show the current values.
18084 @subsubheading @value{GDBN} Command
18086 The corresponding @value{GDBN} command is @samp{info display}.
18088 @subsubheading Example
18092 @subheading The @code{-environment-cd} Command
18093 @findex -environment-cd
18095 @subsubheading Synopsis
18098 -environment-cd @var{pathdir}
18101 Set @value{GDBN}'s working directory.
18103 @subsubheading @value{GDBN} Command
18105 The corresponding @value{GDBN} command is @samp{cd}.
18107 @subsubheading Example
18111 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18117 @subheading The @code{-environment-directory} Command
18118 @findex -environment-directory
18120 @subsubheading Synopsis
18123 -environment-directory [ -r ] [ @var{pathdir} ]+
18126 Add directories @var{pathdir} to beginning of search path for source files.
18127 If the @samp{-r} option is used, the search path is reset to the default
18128 search path. If directories @var{pathdir} are supplied in addition to the
18129 @samp{-r} option, the search path is first reset and then addition
18131 Multiple directories may be specified, separated by blanks. Specifying
18132 multiple directories in a single command
18133 results in the directories added to the beginning of the
18134 search path in the same order they were presented in the command.
18135 If blanks are needed as
18136 part of a directory name, double-quotes should be used around
18137 the name. In the command output, the path will show up separated
18138 by the system directory-separator character. The directory-seperator
18139 character must not be used
18140 in any directory name.
18141 If no directories are specified, the current search path is displayed.
18143 @subsubheading @value{GDBN} Command
18145 The corresponding @value{GDBN} command is @samp{dir}.
18147 @subsubheading Example
18151 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18152 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18154 -environment-directory ""
18155 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18157 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
18158 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
18160 -environment-directory -r
18161 ^done,source-path="$cdir:$cwd"
18166 @subheading The @code{-environment-path} Command
18167 @findex -environment-path
18169 @subsubheading Synopsis
18172 -environment-path [ -r ] [ @var{pathdir} ]+
18175 Add directories @var{pathdir} to beginning of search path for object files.
18176 If the @samp{-r} option is used, the search path is reset to the original
18177 search path that existed at gdb start-up. If directories @var{pathdir} are
18178 supplied in addition to the
18179 @samp{-r} option, the search path is first reset and then addition
18181 Multiple directories may be specified, separated by blanks. Specifying
18182 multiple directories in a single command
18183 results in the directories added to the beginning of the
18184 search path in the same order they were presented in the command.
18185 If blanks are needed as
18186 part of a directory name, double-quotes should be used around
18187 the name. In the command output, the path will show up separated
18188 by the system directory-separator character. The directory-seperator
18189 character must not be used
18190 in any directory name.
18191 If no directories are specified, the current path is displayed.
18194 @subsubheading @value{GDBN} Command
18196 The corresponding @value{GDBN} command is @samp{path}.
18198 @subsubheading Example
18203 ^done,path="/usr/bin"
18205 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
18206 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
18208 -environment-path -r /usr/local/bin
18209 ^done,path="/usr/local/bin:/usr/bin"
18214 @subheading The @code{-environment-pwd} Command
18215 @findex -environment-pwd
18217 @subsubheading Synopsis
18223 Show the current working directory.
18225 @subsubheading @value{GDBN} command
18227 The corresponding @value{GDBN} command is @samp{pwd}.
18229 @subsubheading Example
18234 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
18238 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18239 @node GDB/MI Program Control
18240 @section @sc{gdb/mi} Program control
18242 @subsubheading Program termination
18244 As a result of execution, the inferior program can run to completion, if
18245 it doesn't encounter any breakpoints. In this case the output will
18246 include an exit code, if the program has exited exceptionally.
18248 @subsubheading Examples
18251 Program exited normally:
18259 *stopped,reason="exited-normally"
18264 Program exited exceptionally:
18272 *stopped,reason="exited",exit-code="01"
18276 Another way the program can terminate is if it receives a signal such as
18277 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
18281 *stopped,reason="exited-signalled",signal-name="SIGINT",
18282 signal-meaning="Interrupt"
18286 @subheading The @code{-exec-abort} Command
18287 @findex -exec-abort
18289 @subsubheading Synopsis
18295 Kill the inferior running program.
18297 @subsubheading @value{GDBN} Command
18299 The corresponding @value{GDBN} command is @samp{kill}.
18301 @subsubheading Example
18305 @subheading The @code{-exec-arguments} Command
18306 @findex -exec-arguments
18308 @subsubheading Synopsis
18311 -exec-arguments @var{args}
18314 Set the inferior program arguments, to be used in the next
18317 @subsubheading @value{GDBN} Command
18319 The corresponding @value{GDBN} command is @samp{set args}.
18321 @subsubheading Example
18324 Don't have one around.
18327 @subheading The @code{-exec-continue} Command
18328 @findex -exec-continue
18330 @subsubheading Synopsis
18336 Asynchronous command. Resumes the execution of the inferior program
18337 until a breakpoint is encountered, or until the inferior exits.
18339 @subsubheading @value{GDBN} Command
18341 The corresponding @value{GDBN} corresponding is @samp{continue}.
18343 @subsubheading Example
18350 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
18351 file="hello.c",line="13"@}
18356 @subheading The @code{-exec-finish} Command
18357 @findex -exec-finish
18359 @subsubheading Synopsis
18365 Asynchronous command. Resumes the execution of the inferior program
18366 until the current function is exited. Displays the results returned by
18369 @subsubheading @value{GDBN} Command
18371 The corresponding @value{GDBN} command is @samp{finish}.
18373 @subsubheading Example
18375 Function returning @code{void}.
18382 *stopped,reason="function-finished",frame=@{func="main",args=[],
18383 file="hello.c",line="7"@}
18387 Function returning other than @code{void}. The name of the internal
18388 @value{GDBN} variable storing the result is printed, together with the
18395 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
18396 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
18397 file="recursive2.c",line="14"@},
18398 gdb-result-var="$1",return-value="0"
18403 @subheading The @code{-exec-interrupt} Command
18404 @findex -exec-interrupt
18406 @subsubheading Synopsis
18412 Asynchronous command. Interrupts the background execution of the target.
18413 Note how the token associated with the stop message is the one for the
18414 execution command that has been interrupted. The token for the interrupt
18415 itself only appears in the @samp{^done} output. If the user is trying to
18416 interrupt a non-running program, an error message will be printed.
18418 @subsubheading @value{GDBN} Command
18420 The corresponding @value{GDBN} command is @samp{interrupt}.
18422 @subsubheading Example
18433 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
18434 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",line="13"@}
18439 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
18444 @subheading The @code{-exec-next} Command
18447 @subsubheading Synopsis
18453 Asynchronous command. Resumes execution of the inferior program, stopping
18454 when the beginning of the next source line is reached.
18456 @subsubheading @value{GDBN} Command
18458 The corresponding @value{GDBN} command is @samp{next}.
18460 @subsubheading Example
18466 *stopped,reason="end-stepping-range",line="8",file="hello.c"
18471 @subheading The @code{-exec-next-instruction} Command
18472 @findex -exec-next-instruction
18474 @subsubheading Synopsis
18477 -exec-next-instruction
18480 Asynchronous command. Executes one machine instruction. If the
18481 instruction is a function call continues until the function returns. If
18482 the program stops at an instruction in the middle of a source line, the
18483 address will be printed as well.
18485 @subsubheading @value{GDBN} Command
18487 The corresponding @value{GDBN} command is @samp{nexti}.
18489 @subsubheading Example
18493 -exec-next-instruction
18497 *stopped,reason="end-stepping-range",
18498 addr="0x000100d4",line="5",file="hello.c"
18503 @subheading The @code{-exec-return} Command
18504 @findex -exec-return
18506 @subsubheading Synopsis
18512 Makes current function return immediately. Doesn't execute the inferior.
18513 Displays the new current frame.
18515 @subsubheading @value{GDBN} Command
18517 The corresponding @value{GDBN} command is @samp{return}.
18519 @subsubheading Example
18523 200-break-insert callee4
18524 200^done,bkpt=@{number="1",addr="0x00010734",
18525 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18530 000*stopped,reason="breakpoint-hit",bkptno="1",
18531 frame=@{func="callee4",args=[],
18532 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18538 111^done,frame=@{level="0",func="callee3",
18539 args=[@{name="strarg",
18540 value="0x11940 \"A string argument.\""@}],
18541 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18546 @subheading The @code{-exec-run} Command
18549 @subsubheading Synopsis
18555 Asynchronous command. Starts execution of the inferior from the
18556 beginning. The inferior executes until either a breakpoint is
18557 encountered or the program exits.
18559 @subsubheading @value{GDBN} Command
18561 The corresponding @value{GDBN} command is @samp{run}.
18563 @subsubheading Example
18568 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
18573 *stopped,reason="breakpoint-hit",bkptno="1",
18574 frame=@{func="main",args=[],file="recursive2.c",line="4"@}
18579 @subheading The @code{-exec-show-arguments} Command
18580 @findex -exec-show-arguments
18582 @subsubheading Synopsis
18585 -exec-show-arguments
18588 Print the arguments of the program.
18590 @subsubheading @value{GDBN} Command
18592 The corresponding @value{GDBN} command is @samp{show args}.
18594 @subsubheading Example
18597 @c @subheading -exec-signal
18599 @subheading The @code{-exec-step} Command
18602 @subsubheading Synopsis
18608 Asynchronous command. Resumes execution of the inferior program, stopping
18609 when the beginning of the next source line is reached, if the next
18610 source line is not a function call. If it is, stop at the first
18611 instruction of the called function.
18613 @subsubheading @value{GDBN} Command
18615 The corresponding @value{GDBN} command is @samp{step}.
18617 @subsubheading Example
18619 Stepping into a function:
18625 *stopped,reason="end-stepping-range",
18626 frame=@{func="foo",args=[@{name="a",value="10"@},
18627 @{name="b",value="0"@}],file="recursive2.c",line="11"@}
18637 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
18642 @subheading The @code{-exec-step-instruction} Command
18643 @findex -exec-step-instruction
18645 @subsubheading Synopsis
18648 -exec-step-instruction
18651 Asynchronous command. Resumes the inferior which executes one machine
18652 instruction. The output, once @value{GDBN} has stopped, will vary depending on
18653 whether we have stopped in the middle of a source line or not. In the
18654 former case, the address at which the program stopped will be printed as
18657 @subsubheading @value{GDBN} Command
18659 The corresponding @value{GDBN} command is @samp{stepi}.
18661 @subsubheading Example
18665 -exec-step-instruction
18669 *stopped,reason="end-stepping-range",
18670 frame=@{func="foo",args=[],file="try.c",line="10"@}
18672 -exec-step-instruction
18676 *stopped,reason="end-stepping-range",
18677 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",line="10"@}
18682 @subheading The @code{-exec-until} Command
18683 @findex -exec-until
18685 @subsubheading Synopsis
18688 -exec-until [ @var{location} ]
18691 Asynchronous command. Executes the inferior until the @var{location}
18692 specified in the argument is reached. If there is no argument, the inferior
18693 executes until a source line greater than the current one is reached.
18694 The reason for stopping in this case will be @samp{location-reached}.
18696 @subsubheading @value{GDBN} Command
18698 The corresponding @value{GDBN} command is @samp{until}.
18700 @subsubheading Example
18704 -exec-until recursive2.c:6
18708 *stopped,reason="location-reached",frame=@{func="main",args=[],
18709 file="recursive2.c",line="6"@}
18714 @subheading -file-clear
18715 Is this going away????
18719 @subheading The @code{-file-exec-and-symbols} Command
18720 @findex -file-exec-and-symbols
18722 @subsubheading Synopsis
18725 -file-exec-and-symbols @var{file}
18728 Specify the executable file to be debugged. This file is the one from
18729 which the symbol table is also read. If no file is specified, the
18730 command clears the executable and symbol information. If breakpoints
18731 are set when using this command with no arguments, @value{GDBN} will produce
18732 error messages. Otherwise, no output is produced, except a completion
18735 @subsubheading @value{GDBN} Command
18737 The corresponding @value{GDBN} command is @samp{file}.
18739 @subsubheading Example
18743 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18749 @subheading The @code{-file-exec-file} Command
18750 @findex -file-exec-file
18752 @subsubheading Synopsis
18755 -file-exec-file @var{file}
18758 Specify the executable file to be debugged. Unlike
18759 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
18760 from this file. If used without argument, @value{GDBN} clears the information
18761 about the executable file. No output is produced, except a completion
18764 @subsubheading @value{GDBN} Command
18766 The corresponding @value{GDBN} command is @samp{exec-file}.
18768 @subsubheading Example
18772 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18778 @subheading The @code{-file-list-exec-sections} Command
18779 @findex -file-list-exec-sections
18781 @subsubheading Synopsis
18784 -file-list-exec-sections
18787 List the sections of the current executable file.
18789 @subsubheading @value{GDBN} Command
18791 The @value{GDBN} command @samp{info file} shows, among the rest, the same
18792 information as this command. @code{gdbtk} has a corresponding command
18793 @samp{gdb_load_info}.
18795 @subsubheading Example
18799 @subheading The @code{-file-list-exec-source-file} Command
18800 @findex -file-list-exec-source-file
18802 @subsubheading Synopsis
18805 -file-list-exec-source-file
18808 List the line number, the current source file, and the absolute path
18809 to the current source file for the current executable.
18811 @subsubheading @value{GDBN} Command
18813 There's no @value{GDBN} command which directly corresponds to this one.
18815 @subsubheading Example
18819 123-file-list-exec-source-file
18820 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
18825 @subheading The @code{-file-list-exec-source-files} Command
18826 @findex -file-list-exec-source-files
18828 @subsubheading Synopsis
18831 -file-list-exec-source-files
18834 List the source files for the current executable.
18836 It will always output the filename, but only when GDB can find the absolute
18837 file name of a source file, will it output the fullname.
18839 @subsubheading @value{GDBN} Command
18841 There's no @value{GDBN} command which directly corresponds to this one.
18842 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
18844 @subsubheading Example
18847 -file-list-exec-source-files
18849 @{file=foo.c,fullname=/home/foo.c@},
18850 @{file=/home/bar.c,fullname=/home/bar.c@},
18851 @{file=gdb_could_not_find_fullpath.c@}]
18855 @subheading The @code{-file-list-shared-libraries} Command
18856 @findex -file-list-shared-libraries
18858 @subsubheading Synopsis
18861 -file-list-shared-libraries
18864 List the shared libraries in the program.
18866 @subsubheading @value{GDBN} Command
18868 The corresponding @value{GDBN} command is @samp{info shared}.
18870 @subsubheading Example
18874 @subheading The @code{-file-list-symbol-files} Command
18875 @findex -file-list-symbol-files
18877 @subsubheading Synopsis
18880 -file-list-symbol-files
18885 @subsubheading @value{GDBN} Command
18887 The corresponding @value{GDBN} command is @samp{info file} (part of it).
18889 @subsubheading Example
18893 @subheading The @code{-file-symbol-file} Command
18894 @findex -file-symbol-file
18896 @subsubheading Synopsis
18899 -file-symbol-file @var{file}
18902 Read symbol table info from the specified @var{file} argument. When
18903 used without arguments, clears @value{GDBN}'s symbol table info. No output is
18904 produced, except for a completion notification.
18906 @subsubheading @value{GDBN} Command
18908 The corresponding @value{GDBN} command is @samp{symbol-file}.
18910 @subsubheading Example
18914 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18919 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18920 @node GDB/MI Miscellaneous Commands
18921 @section Miscellaneous @value{GDBN} commands in @sc{gdb/mi}
18923 @c @subheading -gdb-complete
18925 @subheading The @code{-gdb-exit} Command
18928 @subsubheading Synopsis
18934 Exit @value{GDBN} immediately.
18936 @subsubheading @value{GDBN} Command
18938 Approximately corresponds to @samp{quit}.
18940 @subsubheading Example
18947 @subheading The @code{-gdb-set} Command
18950 @subsubheading Synopsis
18956 Set an internal @value{GDBN} variable.
18957 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
18959 @subsubheading @value{GDBN} Command
18961 The corresponding @value{GDBN} command is @samp{set}.
18963 @subsubheading Example
18973 @subheading The @code{-gdb-show} Command
18976 @subsubheading Synopsis
18982 Show the current value of a @value{GDBN} variable.
18984 @subsubheading @value{GDBN} command
18986 The corresponding @value{GDBN} command is @samp{show}.
18988 @subsubheading Example
18997 @c @subheading -gdb-source
19000 @subheading The @code{-gdb-version} Command
19001 @findex -gdb-version
19003 @subsubheading Synopsis
19009 Show version information for @value{GDBN}. Used mostly in testing.
19011 @subsubheading @value{GDBN} Command
19013 There's no equivalent @value{GDBN} command. @value{GDBN} by default shows this
19014 information when you start an interactive session.
19016 @subsubheading Example
19018 @c This example modifies the actual output from GDB to avoid overfull
19024 ~Copyright 2000 Free Software Foundation, Inc.
19025 ~GDB is free software, covered by the GNU General Public License, and
19026 ~you are welcome to change it and/or distribute copies of it under
19027 ~ certain conditions.
19028 ~Type "show copying" to see the conditions.
19029 ~There is absolutely no warranty for GDB. Type "show warranty" for
19031 ~This GDB was configured as
19032 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
19037 @subheading The @code{-interpreter-exec} Command
19038 @findex -interpreter-exec
19040 @subheading Synopsis
19043 -interpreter-exec @var{interpreter} @var{command}
19046 Execute the specified @var{command} in the given @var{interpreter}.
19048 @subheading @value{GDBN} Command
19050 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
19052 @subheading Example
19056 -interpreter-exec console "break main"
19057 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
19058 &"During symbol reading, bad structure-type format.\n"
19059 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
19065 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19066 @node GDB/MI Kod Commands
19067 @section @sc{gdb/mi} Kod Commands
19069 The Kod commands are not implemented.
19071 @c @subheading -kod-info
19073 @c @subheading -kod-list
19075 @c @subheading -kod-list-object-types
19077 @c @subheading -kod-show
19079 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19080 @node GDB/MI Memory Overlay Commands
19081 @section @sc{gdb/mi} Memory Overlay Commands
19083 The memory overlay commands are not implemented.
19085 @c @subheading -overlay-auto
19087 @c @subheading -overlay-list-mapping-state
19089 @c @subheading -overlay-list-overlays
19091 @c @subheading -overlay-map
19093 @c @subheading -overlay-off
19095 @c @subheading -overlay-on
19097 @c @subheading -overlay-unmap
19099 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19100 @node GDB/MI Signal Handling Commands
19101 @section @sc{gdb/mi} Signal Handling Commands
19103 Signal handling commands are not implemented.
19105 @c @subheading -signal-handle
19107 @c @subheading -signal-list-handle-actions
19109 @c @subheading -signal-list-signal-types
19113 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19114 @node GDB/MI Stack Manipulation
19115 @section @sc{gdb/mi} Stack Manipulation Commands
19118 @subheading The @code{-stack-info-frame} Command
19119 @findex -stack-info-frame
19121 @subsubheading Synopsis
19127 Get info on the current frame.
19129 @subsubheading @value{GDBN} Command
19131 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
19132 (without arguments).
19134 @subsubheading Example
19137 @subheading The @code{-stack-info-depth} Command
19138 @findex -stack-info-depth
19140 @subsubheading Synopsis
19143 -stack-info-depth [ @var{max-depth} ]
19146 Return the depth of the stack. If the integer argument @var{max-depth}
19147 is specified, do not count beyond @var{max-depth} frames.
19149 @subsubheading @value{GDBN} Command
19151 There's no equivalent @value{GDBN} command.
19153 @subsubheading Example
19155 For a stack with frame levels 0 through 11:
19162 -stack-info-depth 4
19165 -stack-info-depth 12
19168 -stack-info-depth 11
19171 -stack-info-depth 13
19176 @subheading The @code{-stack-list-arguments} Command
19177 @findex -stack-list-arguments
19179 @subsubheading Synopsis
19182 -stack-list-arguments @var{show-values}
19183 [ @var{low-frame} @var{high-frame} ]
19186 Display a list of the arguments for the frames between @var{low-frame}
19187 and @var{high-frame} (inclusive). If @var{low-frame} and
19188 @var{high-frame} are not provided, list the arguments for the whole call
19191 The @var{show-values} argument must have a value of 0 or 1. A value of
19192 0 means that only the names of the arguments are listed, a value of 1
19193 means that both names and values of the arguments are printed.
19195 @subsubheading @value{GDBN} Command
19197 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19198 @samp{gdb_get_args} command which partially overlaps with the
19199 functionality of @samp{-stack-list-arguments}.
19201 @subsubheading Example
19208 frame=@{level="0",addr="0x00010734",func="callee4",
19209 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19210 frame=@{level="1",addr="0x0001076c",func="callee3",
19211 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19212 frame=@{level="2",addr="0x0001078c",func="callee2",
19213 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19214 frame=@{level="3",addr="0x000107b4",func="callee1",
19215 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19216 frame=@{level="4",addr="0x000107e0",func="main",
19217 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19219 -stack-list-arguments 0
19222 frame=@{level="0",args=[]@},
19223 frame=@{level="1",args=[name="strarg"]@},
19224 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19225 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19226 frame=@{level="4",args=[]@}]
19228 -stack-list-arguments 1
19231 frame=@{level="0",args=[]@},
19233 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19234 frame=@{level="2",args=[
19235 @{name="intarg",value="2"@},
19236 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19237 @{frame=@{level="3",args=[
19238 @{name="intarg",value="2"@},
19239 @{name="strarg",value="0x11940 \"A string argument.\""@},
19240 @{name="fltarg",value="3.5"@}]@},
19241 frame=@{level="4",args=[]@}]
19243 -stack-list-arguments 0 2 2
19244 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19246 -stack-list-arguments 1 2 2
19247 ^done,stack-args=[frame=@{level="2",
19248 args=[@{name="intarg",value="2"@},
19249 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19253 @c @subheading -stack-list-exception-handlers
19256 @subheading The @code{-stack-list-frames} Command
19257 @findex -stack-list-frames
19259 @subsubheading Synopsis
19262 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19265 List the frames currently on the stack. For each frame it displays the
19270 The frame number, 0 being the topmost frame, i.e. the innermost function.
19272 The @code{$pc} value for that frame.
19276 File name of the source file where the function lives.
19278 Line number corresponding to the @code{$pc}.
19281 If invoked without arguments, this command prints a backtrace for the
19282 whole stack. If given two integer arguments, it shows the frames whose
19283 levels are between the two arguments (inclusive). If the two arguments
19284 are equal, it shows the single frame at the corresponding level.
19286 @subsubheading @value{GDBN} Command
19288 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19290 @subsubheading Example
19292 Full stack backtrace:
19298 [frame=@{level="0",addr="0x0001076c",func="foo",
19299 file="recursive2.c",line="11"@},
19300 frame=@{level="1",addr="0x000107a4",func="foo",
19301 file="recursive2.c",line="14"@},
19302 frame=@{level="2",addr="0x000107a4",func="foo",
19303 file="recursive2.c",line="14"@},
19304 frame=@{level="3",addr="0x000107a4",func="foo",
19305 file="recursive2.c",line="14"@},
19306 frame=@{level="4",addr="0x000107a4",func="foo",
19307 file="recursive2.c",line="14"@},
19308 frame=@{level="5",addr="0x000107a4",func="foo",
19309 file="recursive2.c",line="14"@},
19310 frame=@{level="6",addr="0x000107a4",func="foo",
19311 file="recursive2.c",line="14"@},
19312 frame=@{level="7",addr="0x000107a4",func="foo",
19313 file="recursive2.c",line="14"@},
19314 frame=@{level="8",addr="0x000107a4",func="foo",
19315 file="recursive2.c",line="14"@},
19316 frame=@{level="9",addr="0x000107a4",func="foo",
19317 file="recursive2.c",line="14"@},
19318 frame=@{level="10",addr="0x000107a4",func="foo",
19319 file="recursive2.c",line="14"@},
19320 frame=@{level="11",addr="0x00010738",func="main",
19321 file="recursive2.c",line="4"@}]
19325 Show frames between @var{low_frame} and @var{high_frame}:
19329 -stack-list-frames 3 5
19331 [frame=@{level="3",addr="0x000107a4",func="foo",
19332 file="recursive2.c",line="14"@},
19333 frame=@{level="4",addr="0x000107a4",func="foo",
19334 file="recursive2.c",line="14"@},
19335 frame=@{level="5",addr="0x000107a4",func="foo",
19336 file="recursive2.c",line="14"@}]
19340 Show a single frame:
19344 -stack-list-frames 3 3
19346 [frame=@{level="3",addr="0x000107a4",func="foo",
19347 file="recursive2.c",line="14"@}]
19352 @subheading The @code{-stack-list-locals} Command
19353 @findex -stack-list-locals
19355 @subsubheading Synopsis
19358 -stack-list-locals @var{print-values}
19361 Display the local variable names for the current frame. With an
19362 argument of 0 or @code{--no-values}, prints only the names of the variables.
19363 With argument of 1 or @code{--all-values}, prints also their values. With
19364 argument of 2 or @code{--simple-values}, prints the name, type and value for
19365 simple data types and the name and type for arrays, structures and
19366 unions. In this last case, the idea is that the user can see the
19367 value of simple data types immediately and he can create variable
19368 objects for other data types if he wishes to explore their values in
19371 @subsubheading @value{GDBN} Command
19373 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
19375 @subsubheading Example
19379 -stack-list-locals 0
19380 ^done,locals=[name="A",name="B",name="C"]
19382 -stack-list-locals --all-values
19383 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
19384 @{name="C",value="@{1, 2, 3@}"@}]
19385 -stack-list-locals --simple-values
19386 ^done,locals=[@{name="A",type="int",value="1"@},
19387 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
19392 @subheading The @code{-stack-select-frame} Command
19393 @findex -stack-select-frame
19395 @subsubheading Synopsis
19398 -stack-select-frame @var{framenum}
19401 Change the current frame. Select a different frame @var{framenum} on
19404 @subsubheading @value{GDBN} Command
19406 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
19407 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
19409 @subsubheading Example
19413 -stack-select-frame 2
19418 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19419 @node GDB/MI Symbol Query
19420 @section @sc{gdb/mi} Symbol Query Commands
19423 @subheading The @code{-symbol-info-address} Command
19424 @findex -symbol-info-address
19426 @subsubheading Synopsis
19429 -symbol-info-address @var{symbol}
19432 Describe where @var{symbol} is stored.
19434 @subsubheading @value{GDBN} Command
19436 The corresponding @value{GDBN} command is @samp{info address}.
19438 @subsubheading Example
19442 @subheading The @code{-symbol-info-file} Command
19443 @findex -symbol-info-file
19445 @subsubheading Synopsis
19451 Show the file for the symbol.
19453 @subsubheading @value{GDBN} Command
19455 There's no equivalent @value{GDBN} command. @code{gdbtk} has
19456 @samp{gdb_find_file}.
19458 @subsubheading Example
19462 @subheading The @code{-symbol-info-function} Command
19463 @findex -symbol-info-function
19465 @subsubheading Synopsis
19468 -symbol-info-function
19471 Show which function the symbol lives in.
19473 @subsubheading @value{GDBN} Command
19475 @samp{gdb_get_function} in @code{gdbtk}.
19477 @subsubheading Example
19481 @subheading The @code{-symbol-info-line} Command
19482 @findex -symbol-info-line
19484 @subsubheading Synopsis
19490 Show the core addresses of the code for a source line.
19492 @subsubheading @value{GDBN} Command
19494 The corresponding @value{GDBN} command is @samp{info line}.
19495 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
19497 @subsubheading Example
19501 @subheading The @code{-symbol-info-symbol} Command
19502 @findex -symbol-info-symbol
19504 @subsubheading Synopsis
19507 -symbol-info-symbol @var{addr}
19510 Describe what symbol is at location @var{addr}.
19512 @subsubheading @value{GDBN} Command
19514 The corresponding @value{GDBN} command is @samp{info symbol}.
19516 @subsubheading Example
19520 @subheading The @code{-symbol-list-functions} Command
19521 @findex -symbol-list-functions
19523 @subsubheading Synopsis
19526 -symbol-list-functions
19529 List the functions in the executable.
19531 @subsubheading @value{GDBN} Command
19533 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
19534 @samp{gdb_search} in @code{gdbtk}.
19536 @subsubheading Example
19540 @subheading The @code{-symbol-list-lines} Command
19541 @findex -symbol-list-lines
19543 @subsubheading Synopsis
19546 -symbol-list-lines @var{filename}
19549 Print the list of lines that contain code and their associated program
19550 addresses for the given source filename. The entries are sorted in
19551 ascending PC order.
19553 @subsubheading @value{GDBN} Command
19555 There is no corresponding @value{GDBN} command.
19557 @subsubheading Example
19560 -symbol-list-lines basics.c
19561 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
19566 @subheading The @code{-symbol-list-types} Command
19567 @findex -symbol-list-types
19569 @subsubheading Synopsis
19575 List all the type names.
19577 @subsubheading @value{GDBN} Command
19579 The corresponding commands are @samp{info types} in @value{GDBN},
19580 @samp{gdb_search} in @code{gdbtk}.
19582 @subsubheading Example
19586 @subheading The @code{-symbol-list-variables} Command
19587 @findex -symbol-list-variables
19589 @subsubheading Synopsis
19592 -symbol-list-variables
19595 List all the global and static variable names.
19597 @subsubheading @value{GDBN} Command
19599 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
19601 @subsubheading Example
19605 @subheading The @code{-symbol-locate} Command
19606 @findex -symbol-locate
19608 @subsubheading Synopsis
19614 @subsubheading @value{GDBN} Command
19616 @samp{gdb_loc} in @code{gdbtk}.
19618 @subsubheading Example
19622 @subheading The @code{-symbol-type} Command
19623 @findex -symbol-type
19625 @subsubheading Synopsis
19628 -symbol-type @var{variable}
19631 Show type of @var{variable}.
19633 @subsubheading @value{GDBN} Command
19635 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
19636 @samp{gdb_obj_variable}.
19638 @subsubheading Example
19642 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19643 @node GDB/MI Target Manipulation
19644 @section @sc{gdb/mi} Target Manipulation Commands
19647 @subheading The @code{-target-attach} Command
19648 @findex -target-attach
19650 @subsubheading Synopsis
19653 -target-attach @var{pid} | @var{file}
19656 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
19658 @subsubheading @value{GDBN} command
19660 The corresponding @value{GDBN} command is @samp{attach}.
19662 @subsubheading Example
19666 @subheading The @code{-target-compare-sections} Command
19667 @findex -target-compare-sections
19669 @subsubheading Synopsis
19672 -target-compare-sections [ @var{section} ]
19675 Compare data of section @var{section} on target to the exec file.
19676 Without the argument, all sections are compared.
19678 @subsubheading @value{GDBN} Command
19680 The @value{GDBN} equivalent is @samp{compare-sections}.
19682 @subsubheading Example
19686 @subheading The @code{-target-detach} Command
19687 @findex -target-detach
19689 @subsubheading Synopsis
19695 Disconnect from the remote target. There's no output.
19697 @subsubheading @value{GDBN} command
19699 The corresponding @value{GDBN} command is @samp{detach}.
19701 @subsubheading Example
19711 @subheading The @code{-target-disconnect} Command
19712 @findex -target-disconnect
19714 @subsubheading Synopsis
19720 Disconnect from the remote target. There's no output.
19722 @subsubheading @value{GDBN} command
19724 The corresponding @value{GDBN} command is @samp{disconnect}.
19726 @subsubheading Example
19736 @subheading The @code{-target-download} Command
19737 @findex -target-download
19739 @subsubheading Synopsis
19745 Loads the executable onto the remote target.
19746 It prints out an update message every half second, which includes the fields:
19750 The name of the section.
19752 The size of what has been sent so far for that section.
19754 The size of the section.
19756 The total size of what was sent so far (the current and the previous sections).
19758 The size of the overall executable to download.
19762 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
19763 @sc{gdb/mi} Output Syntax}).
19765 In addition, it prints the name and size of the sections, as they are
19766 downloaded. These messages include the following fields:
19770 The name of the section.
19772 The size of the section.
19774 The size of the overall executable to download.
19778 At the end, a summary is printed.
19780 @subsubheading @value{GDBN} Command
19782 The corresponding @value{GDBN} command is @samp{load}.
19784 @subsubheading Example
19786 Note: each status message appears on a single line. Here the messages
19787 have been broken down so that they can fit onto a page.
19792 +download,@{section=".text",section-size="6668",total-size="9880"@}
19793 +download,@{section=".text",section-sent="512",section-size="6668",
19794 total-sent="512",total-size="9880"@}
19795 +download,@{section=".text",section-sent="1024",section-size="6668",
19796 total-sent="1024",total-size="9880"@}
19797 +download,@{section=".text",section-sent="1536",section-size="6668",
19798 total-sent="1536",total-size="9880"@}
19799 +download,@{section=".text",section-sent="2048",section-size="6668",
19800 total-sent="2048",total-size="9880"@}
19801 +download,@{section=".text",section-sent="2560",section-size="6668",
19802 total-sent="2560",total-size="9880"@}
19803 +download,@{section=".text",section-sent="3072",section-size="6668",
19804 total-sent="3072",total-size="9880"@}
19805 +download,@{section=".text",section-sent="3584",section-size="6668",
19806 total-sent="3584",total-size="9880"@}
19807 +download,@{section=".text",section-sent="4096",section-size="6668",
19808 total-sent="4096",total-size="9880"@}
19809 +download,@{section=".text",section-sent="4608",section-size="6668",
19810 total-sent="4608",total-size="9880"@}
19811 +download,@{section=".text",section-sent="5120",section-size="6668",
19812 total-sent="5120",total-size="9880"@}
19813 +download,@{section=".text",section-sent="5632",section-size="6668",
19814 total-sent="5632",total-size="9880"@}
19815 +download,@{section=".text",section-sent="6144",section-size="6668",
19816 total-sent="6144",total-size="9880"@}
19817 +download,@{section=".text",section-sent="6656",section-size="6668",
19818 total-sent="6656",total-size="9880"@}
19819 +download,@{section=".init",section-size="28",total-size="9880"@}
19820 +download,@{section=".fini",section-size="28",total-size="9880"@}
19821 +download,@{section=".data",section-size="3156",total-size="9880"@}
19822 +download,@{section=".data",section-sent="512",section-size="3156",
19823 total-sent="7236",total-size="9880"@}
19824 +download,@{section=".data",section-sent="1024",section-size="3156",
19825 total-sent="7748",total-size="9880"@}
19826 +download,@{section=".data",section-sent="1536",section-size="3156",
19827 total-sent="8260",total-size="9880"@}
19828 +download,@{section=".data",section-sent="2048",section-size="3156",
19829 total-sent="8772",total-size="9880"@}
19830 +download,@{section=".data",section-sent="2560",section-size="3156",
19831 total-sent="9284",total-size="9880"@}
19832 +download,@{section=".data",section-sent="3072",section-size="3156",
19833 total-sent="9796",total-size="9880"@}
19834 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
19840 @subheading The @code{-target-exec-status} Command
19841 @findex -target-exec-status
19843 @subsubheading Synopsis
19846 -target-exec-status
19849 Provide information on the state of the target (whether it is running or
19850 not, for instance).
19852 @subsubheading @value{GDBN} Command
19854 There's no equivalent @value{GDBN} command.
19856 @subsubheading Example
19860 @subheading The @code{-target-list-available-targets} Command
19861 @findex -target-list-available-targets
19863 @subsubheading Synopsis
19866 -target-list-available-targets
19869 List the possible targets to connect to.
19871 @subsubheading @value{GDBN} Command
19873 The corresponding @value{GDBN} command is @samp{help target}.
19875 @subsubheading Example
19879 @subheading The @code{-target-list-current-targets} Command
19880 @findex -target-list-current-targets
19882 @subsubheading Synopsis
19885 -target-list-current-targets
19888 Describe the current target.
19890 @subsubheading @value{GDBN} Command
19892 The corresponding information is printed by @samp{info file} (among
19895 @subsubheading Example
19899 @subheading The @code{-target-list-parameters} Command
19900 @findex -target-list-parameters
19902 @subsubheading Synopsis
19905 -target-list-parameters
19910 @subsubheading @value{GDBN} Command
19914 @subsubheading Example
19918 @subheading The @code{-target-select} Command
19919 @findex -target-select
19921 @subsubheading Synopsis
19924 -target-select @var{type} @var{parameters @dots{}}
19927 Connect @value{GDBN} to the remote target. This command takes two args:
19931 The type of target, for instance @samp{async}, @samp{remote}, etc.
19932 @item @var{parameters}
19933 Device names, host names and the like. @xref{Target Commands, ,
19934 Commands for managing targets}, for more details.
19937 The output is a connection notification, followed by the address at
19938 which the target program is, in the following form:
19941 ^connected,addr="@var{address}",func="@var{function name}",
19942 args=[@var{arg list}]
19945 @subsubheading @value{GDBN} Command
19947 The corresponding @value{GDBN} command is @samp{target}.
19949 @subsubheading Example
19953 -target-select async /dev/ttya
19954 ^connected,addr="0xfe00a300",func="??",args=[]
19958 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19959 @node GDB/MI Thread Commands
19960 @section @sc{gdb/mi} Thread Commands
19963 @subheading The @code{-thread-info} Command
19964 @findex -thread-info
19966 @subsubheading Synopsis
19972 @subsubheading @value{GDBN} command
19976 @subsubheading Example
19980 @subheading The @code{-thread-list-all-threads} Command
19981 @findex -thread-list-all-threads
19983 @subsubheading Synopsis
19986 -thread-list-all-threads
19989 @subsubheading @value{GDBN} Command
19991 The equivalent @value{GDBN} command is @samp{info threads}.
19993 @subsubheading Example
19997 @subheading The @code{-thread-list-ids} Command
19998 @findex -thread-list-ids
20000 @subsubheading Synopsis
20006 Produces a list of the currently known @value{GDBN} thread ids. At the
20007 end of the list it also prints the total number of such threads.
20009 @subsubheading @value{GDBN} Command
20011 Part of @samp{info threads} supplies the same information.
20013 @subsubheading Example
20015 No threads present, besides the main process:
20020 ^done,thread-ids=@{@},number-of-threads="0"
20030 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20031 number-of-threads="3"
20036 @subheading The @code{-thread-select} Command
20037 @findex -thread-select
20039 @subsubheading Synopsis
20042 -thread-select @var{threadnum}
20045 Make @var{threadnum} the current thread. It prints the number of the new
20046 current thread, and the topmost frame for that thread.
20048 @subsubheading @value{GDBN} Command
20050 The corresponding @value{GDBN} command is @samp{thread}.
20052 @subsubheading Example
20059 *stopped,reason="end-stepping-range",thread-id="2",line="187",
20060 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
20064 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20065 number-of-threads="3"
20068 ^done,new-thread-id="3",
20069 frame=@{level="0",func="vprintf",
20070 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
20071 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
20075 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20076 @node GDB/MI Tracepoint Commands
20077 @section @sc{gdb/mi} Tracepoint Commands
20079 The tracepoint commands are not yet implemented.
20081 @c @subheading -trace-actions
20083 @c @subheading -trace-delete
20085 @c @subheading -trace-disable
20087 @c @subheading -trace-dump
20089 @c @subheading -trace-enable
20091 @c @subheading -trace-exists
20093 @c @subheading -trace-find
20095 @c @subheading -trace-frame-number
20097 @c @subheading -trace-info
20099 @c @subheading -trace-insert
20101 @c @subheading -trace-list
20103 @c @subheading -trace-pass-count
20105 @c @subheading -trace-save
20107 @c @subheading -trace-start
20109 @c @subheading -trace-stop
20112 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20113 @node GDB/MI Variable Objects
20114 @section @sc{gdb/mi} Variable Objects
20117 @subheading Motivation for Variable Objects in @sc{gdb/mi}
20119 For the implementation of a variable debugger window (locals, watched
20120 expressions, etc.), we are proposing the adaptation of the existing code
20121 used by @code{Insight}.
20123 The two main reasons for that are:
20127 It has been proven in practice (it is already on its second generation).
20130 It will shorten development time (needless to say how important it is
20134 The original interface was designed to be used by Tcl code, so it was
20135 slightly changed so it could be used through @sc{gdb/mi}. This section
20136 describes the @sc{gdb/mi} operations that will be available and gives some
20137 hints about their use.
20139 @emph{Note}: In addition to the set of operations described here, we
20140 expect the @sc{gui} implementation of a variable window to require, at
20141 least, the following operations:
20144 @item @code{-gdb-show} @code{output-radix}
20145 @item @code{-stack-list-arguments}
20146 @item @code{-stack-list-locals}
20147 @item @code{-stack-select-frame}
20150 @subheading Introduction to Variable Objects in @sc{gdb/mi}
20152 @cindex variable objects in @sc{gdb/mi}
20153 The basic idea behind variable objects is the creation of a named object
20154 to represent a variable, an expression, a memory location or even a CPU
20155 register. For each object created, a set of operations is available for
20156 examining or changing its properties.
20158 Furthermore, complex data types, such as C structures, are represented
20159 in a tree format. For instance, the @code{struct} type variable is the
20160 root and the children will represent the struct members. If a child
20161 is itself of a complex type, it will also have children of its own.
20162 Appropriate language differences are handled for C, C@t{++} and Java.
20164 When returning the actual values of the objects, this facility allows
20165 for the individual selection of the display format used in the result
20166 creation. It can be chosen among: binary, decimal, hexadecimal, octal
20167 and natural. Natural refers to a default format automatically
20168 chosen based on the variable type (like decimal for an @code{int}, hex
20169 for pointers, etc.).
20171 The following is the complete set of @sc{gdb/mi} operations defined to
20172 access this functionality:
20174 @multitable @columnfractions .4 .6
20175 @item @strong{Operation}
20176 @tab @strong{Description}
20178 @item @code{-var-create}
20179 @tab create a variable object
20180 @item @code{-var-delete}
20181 @tab delete the variable object and its children
20182 @item @code{-var-set-format}
20183 @tab set the display format of this variable
20184 @item @code{-var-show-format}
20185 @tab show the display format of this variable
20186 @item @code{-var-info-num-children}
20187 @tab tells how many children this object has
20188 @item @code{-var-list-children}
20189 @tab return a list of the object's children
20190 @item @code{-var-info-type}
20191 @tab show the type of this variable object
20192 @item @code{-var-info-expression}
20193 @tab print what this variable object represents
20194 @item @code{-var-show-attributes}
20195 @tab is this variable editable? does it exist here?
20196 @item @code{-var-evaluate-expression}
20197 @tab get the value of this variable
20198 @item @code{-var-assign}
20199 @tab set the value of this variable
20200 @item @code{-var-update}
20201 @tab update the variable and its children
20204 In the next subsection we describe each operation in detail and suggest
20205 how it can be used.
20207 @subheading Description And Use of Operations on Variable Objects
20209 @subheading The @code{-var-create} Command
20210 @findex -var-create
20212 @subsubheading Synopsis
20215 -var-create @{@var{name} | "-"@}
20216 @{@var{frame-addr} | "*"@} @var{expression}
20219 This operation creates a variable object, which allows the monitoring of
20220 a variable, the result of an expression, a memory cell or a CPU
20223 The @var{name} parameter is the string by which the object can be
20224 referenced. It must be unique. If @samp{-} is specified, the varobj
20225 system will generate a string ``varNNNNNN'' automatically. It will be
20226 unique provided that one does not specify @var{name} on that format.
20227 The command fails if a duplicate name is found.
20229 The frame under which the expression should be evaluated can be
20230 specified by @var{frame-addr}. A @samp{*} indicates that the current
20231 frame should be used.
20233 @var{expression} is any expression valid on the current language set (must not
20234 begin with a @samp{*}), or one of the following:
20238 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
20241 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
20244 @samp{$@var{regname}} --- a CPU register name
20247 @subsubheading Result
20249 This operation returns the name, number of children and the type of the
20250 object created. Type is returned as a string as the ones generated by
20251 the @value{GDBN} CLI:
20254 name="@var{name}",numchild="N",type="@var{type}"
20258 @subheading The @code{-var-delete} Command
20259 @findex -var-delete
20261 @subsubheading Synopsis
20264 -var-delete @var{name}
20267 Deletes a previously created variable object and all of its children.
20269 Returns an error if the object @var{name} is not found.
20272 @subheading The @code{-var-set-format} Command
20273 @findex -var-set-format
20275 @subsubheading Synopsis
20278 -var-set-format @var{name} @var{format-spec}
20281 Sets the output format for the value of the object @var{name} to be
20284 The syntax for the @var{format-spec} is as follows:
20287 @var{format-spec} @expansion{}
20288 @{binary | decimal | hexadecimal | octal | natural@}
20292 @subheading The @code{-var-show-format} Command
20293 @findex -var-show-format
20295 @subsubheading Synopsis
20298 -var-show-format @var{name}
20301 Returns the format used to display the value of the object @var{name}.
20304 @var{format} @expansion{}
20309 @subheading The @code{-var-info-num-children} Command
20310 @findex -var-info-num-children
20312 @subsubheading Synopsis
20315 -var-info-num-children @var{name}
20318 Returns the number of children of a variable object @var{name}:
20325 @subheading The @code{-var-list-children} Command
20326 @findex -var-list-children
20328 @subsubheading Synopsis
20331 -var-list-children [@var{print-values}] @var{name}
20334 Returns a list of the children of the specified variable object. With
20335 just the variable object name as an argument or with an optional
20336 preceding argument of 0 or @code{--no-values}, prints only the names of the
20337 variables. With an optional preceding argument of 1 or @code{--all-values},
20338 also prints their values.
20340 @subsubheading Example
20344 -var-list-children n
20345 numchild=@var{n},children=[@{name=@var{name},
20346 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
20348 -var-list-children --all-values n
20349 numchild=@var{n},children=[@{name=@var{name},
20350 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
20354 @subheading The @code{-var-info-type} Command
20355 @findex -var-info-type
20357 @subsubheading Synopsis
20360 -var-info-type @var{name}
20363 Returns the type of the specified variable @var{name}. The type is
20364 returned as a string in the same format as it is output by the
20368 type=@var{typename}
20372 @subheading The @code{-var-info-expression} Command
20373 @findex -var-info-expression
20375 @subsubheading Synopsis
20378 -var-info-expression @var{name}
20381 Returns what is represented by the variable object @var{name}:
20384 lang=@var{lang-spec},exp=@var{expression}
20388 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
20390 @subheading The @code{-var-show-attributes} Command
20391 @findex -var-show-attributes
20393 @subsubheading Synopsis
20396 -var-show-attributes @var{name}
20399 List attributes of the specified variable object @var{name}:
20402 status=@var{attr} [ ( ,@var{attr} )* ]
20406 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
20408 @subheading The @code{-var-evaluate-expression} Command
20409 @findex -var-evaluate-expression
20411 @subsubheading Synopsis
20414 -var-evaluate-expression @var{name}
20417 Evaluates the expression that is represented by the specified variable
20418 object and returns its value as a string in the current format specified
20425 Note that one must invoke @code{-var-list-children} for a variable
20426 before the value of a child variable can be evaluated.
20428 @subheading The @code{-var-assign} Command
20429 @findex -var-assign
20431 @subsubheading Synopsis
20434 -var-assign @var{name} @var{expression}
20437 Assigns the value of @var{expression} to the variable object specified
20438 by @var{name}. The object must be @samp{editable}. If the variable's
20439 value is altered by the assign, the variable will show up in any
20440 subsequent @code{-var-update} list.
20442 @subsubheading Example
20450 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
20454 @subheading The @code{-var-update} Command
20455 @findex -var-update
20457 @subsubheading Synopsis
20460 -var-update @{@var{name} | "*"@}
20463 Update the value of the variable object @var{name} by evaluating its
20464 expression after fetching all the new values from memory or registers.
20465 A @samp{*} causes all existing variable objects to be updated.
20469 @chapter @value{GDBN} Annotations
20471 This chapter describes annotations in @value{GDBN}. Annotations were
20472 designed to interface @value{GDBN} to graphical user interfaces or other
20473 similar programs which want to interact with @value{GDBN} at a
20474 relatively high level.
20476 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
20480 This is Edition @value{EDITION}, @value{DATE}.
20484 * Annotations Overview:: What annotations are; the general syntax.
20485 * Server Prefix:: Issuing a command without affecting user state.
20486 * Prompting:: Annotations marking @value{GDBN}'s need for input.
20487 * Errors:: Annotations for error messages.
20488 * Invalidation:: Some annotations describe things now invalid.
20489 * Annotations for Running::
20490 Whether the program is running, how it stopped, etc.
20491 * Source Annotations:: Annotations describing source code.
20494 @node Annotations Overview
20495 @section What is an Annotation?
20496 @cindex annotations
20498 Annotations start with a newline character, two @samp{control-z}
20499 characters, and the name of the annotation. If there is no additional
20500 information associated with this annotation, the name of the annotation
20501 is followed immediately by a newline. If there is additional
20502 information, the name of the annotation is followed by a space, the
20503 additional information, and a newline. The additional information
20504 cannot contain newline characters.
20506 Any output not beginning with a newline and two @samp{control-z}
20507 characters denotes literal output from @value{GDBN}. Currently there is
20508 no need for @value{GDBN} to output a newline followed by two
20509 @samp{control-z} characters, but if there was such a need, the
20510 annotations could be extended with an @samp{escape} annotation which
20511 means those three characters as output.
20513 The annotation @var{level}, which is specified using the
20514 @option{--annotate} command line option (@pxref{Mode Options}), controls
20515 how much information @value{GDBN} prints together with its prompt,
20516 values of expressions, source lines, and other types of output. Level 0
20517 is for no anntations, level 1 is for use when @value{GDBN} is run as a
20518 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
20519 for programs that control @value{GDBN}, and level 2 annotations have
20520 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
20521 Interface, annotate, GDB's Obsolete Annotations}).
20524 @kindex set annotate
20525 @item set annotate @var{level}
20526 The @value{GDB} command @code{set annotate} sets the level of
20527 annotations to the specified @var{level}.
20529 @item show annotate
20530 @kindex show annotate
20531 Show the current annotation level.
20534 This chapter describes level 3 annotations.
20536 A simple example of starting up @value{GDBN} with annotations is:
20539 $ @kbd{gdb --annotate=3}
20541 Copyright 2003 Free Software Foundation, Inc.
20542 GDB is free software, covered by the GNU General Public License,
20543 and you are welcome to change it and/or distribute copies of it
20544 under certain conditions.
20545 Type "show copying" to see the conditions.
20546 There is absolutely no warranty for GDB. Type "show warranty"
20548 This GDB was configured as "i386-pc-linux-gnu"
20559 Here @samp{quit} is input to @value{GDBN}; the rest is output from
20560 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
20561 denotes a @samp{control-z} character) are annotations; the rest is
20562 output from @value{GDBN}.
20564 @node Server Prefix
20565 @section The Server Prefix
20566 @cindex server prefix for annotations
20568 To issue a command to @value{GDBN} without affecting certain aspects of
20569 the state which is seen by users, prefix it with @samp{server }. This
20570 means that this command will not affect the command history, nor will it
20571 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
20572 pressed on a line by itself.
20574 The server prefix does not affect the recording of values into the value
20575 history; to print a value without recording it into the value history,
20576 use the @code{output} command instead of the @code{print} command.
20579 @section Annotation for @value{GDBN} Input
20581 @cindex annotations for prompts
20582 When @value{GDBN} prompts for input, it annotates this fact so it is possible
20583 to know when to send output, when the output from a given command is
20586 Different kinds of input each have a different @dfn{input type}. Each
20587 input type has three annotations: a @code{pre-} annotation, which
20588 denotes the beginning of any prompt which is being output, a plain
20589 annotation, which denotes the end of the prompt, and then a @code{post-}
20590 annotation which denotes the end of any echo which may (or may not) be
20591 associated with the input. For example, the @code{prompt} input type
20592 features the following annotations:
20600 The input types are
20605 @findex post-prompt
20607 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
20609 @findex pre-commands
20611 @findex post-commands
20613 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
20614 command. The annotations are repeated for each command which is input.
20616 @findex pre-overload-choice
20617 @findex overload-choice
20618 @findex post-overload-choice
20619 @item overload-choice
20620 When @value{GDBN} wants the user to select between various overloaded functions.
20626 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
20628 @findex pre-prompt-for-continue
20629 @findex prompt-for-continue
20630 @findex post-prompt-for-continue
20631 @item prompt-for-continue
20632 When @value{GDBN} is asking the user to press return to continue. Note: Don't
20633 expect this to work well; instead use @code{set height 0} to disable
20634 prompting. This is because the counting of lines is buggy in the
20635 presence of annotations.
20640 @cindex annotations for errors, warnings and interrupts
20647 This annotation occurs right before @value{GDBN} responds to an interrupt.
20654 This annotation occurs right before @value{GDBN} responds to an error.
20656 Quit and error annotations indicate that any annotations which @value{GDBN} was
20657 in the middle of may end abruptly. For example, if a
20658 @code{value-history-begin} annotation is followed by a @code{error}, one
20659 cannot expect to receive the matching @code{value-history-end}. One
20660 cannot expect not to receive it either, however; an error annotation
20661 does not necessarily mean that @value{GDBN} is immediately returning all the way
20664 @findex error-begin
20665 A quit or error annotation may be preceded by
20671 Any output between that and the quit or error annotation is the error
20674 Warning messages are not yet annotated.
20675 @c If we want to change that, need to fix warning(), type_error(),
20676 @c range_error(), and possibly other places.
20679 @section Invalidation Notices
20681 @cindex annotations for invalidation messages
20682 The following annotations say that certain pieces of state may have
20686 @findex frames-invalid
20687 @item ^Z^Zframes-invalid
20689 The frames (for example, output from the @code{backtrace} command) may
20692 @findex breakpoints-invalid
20693 @item ^Z^Zbreakpoints-invalid
20695 The breakpoints may have changed. For example, the user just added or
20696 deleted a breakpoint.
20699 @node Annotations for Running
20700 @section Running the Program
20701 @cindex annotations for running programs
20705 When the program starts executing due to a @value{GDBN} command such as
20706 @code{step} or @code{continue},
20712 is output. When the program stops,
20718 is output. Before the @code{stopped} annotation, a variety of
20719 annotations describe how the program stopped.
20723 @item ^Z^Zexited @var{exit-status}
20724 The program exited, and @var{exit-status} is the exit status (zero for
20725 successful exit, otherwise nonzero).
20728 @findex signal-name
20729 @findex signal-name-end
20730 @findex signal-string
20731 @findex signal-string-end
20732 @item ^Z^Zsignalled
20733 The program exited with a signal. After the @code{^Z^Zsignalled}, the
20734 annotation continues:
20740 ^Z^Zsignal-name-end
20744 ^Z^Zsignal-string-end
20749 where @var{name} is the name of the signal, such as @code{SIGILL} or
20750 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
20751 as @code{Illegal Instruction} or @code{Segmentation fault}.
20752 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
20753 user's benefit and have no particular format.
20757 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
20758 just saying that the program received the signal, not that it was
20759 terminated with it.
20762 @item ^Z^Zbreakpoint @var{number}
20763 The program hit breakpoint number @var{number}.
20766 @item ^Z^Zwatchpoint @var{number}
20767 The program hit watchpoint number @var{number}.
20770 @node Source Annotations
20771 @section Displaying Source
20772 @cindex annotations for source display
20775 The following annotation is used instead of displaying source code:
20778 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
20781 where @var{filename} is an absolute file name indicating which source
20782 file, @var{line} is the line number within that file (where 1 is the
20783 first line in the file), @var{character} is the character position
20784 within the file (where 0 is the first character in the file) (for most
20785 debug formats this will necessarily point to the beginning of a line),
20786 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
20787 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
20788 @var{addr} is the address in the target program associated with the
20789 source which is being displayed. @var{addr} is in the form @samp{0x}
20790 followed by one or more lowercase hex digits (note that this does not
20791 depend on the language).
20794 @chapter Reporting Bugs in @value{GDBN}
20795 @cindex bugs in @value{GDBN}
20796 @cindex reporting bugs in @value{GDBN}
20798 Your bug reports play an essential role in making @value{GDBN} reliable.
20800 Reporting a bug may help you by bringing a solution to your problem, or it
20801 may not. But in any case the principal function of a bug report is to help
20802 the entire community by making the next version of @value{GDBN} work better. Bug
20803 reports are your contribution to the maintenance of @value{GDBN}.
20805 In order for a bug report to serve its purpose, you must include the
20806 information that enables us to fix the bug.
20809 * Bug Criteria:: Have you found a bug?
20810 * Bug Reporting:: How to report bugs
20814 @section Have you found a bug?
20815 @cindex bug criteria
20817 If you are not sure whether you have found a bug, here are some guidelines:
20820 @cindex fatal signal
20821 @cindex debugger crash
20822 @cindex crash of debugger
20824 If the debugger gets a fatal signal, for any input whatever, that is a
20825 @value{GDBN} bug. Reliable debuggers never crash.
20827 @cindex error on valid input
20829 If @value{GDBN} produces an error message for valid input, that is a
20830 bug. (Note that if you're cross debugging, the problem may also be
20831 somewhere in the connection to the target.)
20833 @cindex invalid input
20835 If @value{GDBN} does not produce an error message for invalid input,
20836 that is a bug. However, you should note that your idea of
20837 ``invalid input'' might be our idea of ``an extension'' or ``support
20838 for traditional practice''.
20841 If you are an experienced user of debugging tools, your suggestions
20842 for improvement of @value{GDBN} are welcome in any case.
20845 @node Bug Reporting
20846 @section How to report bugs
20847 @cindex bug reports
20848 @cindex @value{GDBN} bugs, reporting
20850 A number of companies and individuals offer support for @sc{gnu} products.
20851 If you obtained @value{GDBN} from a support organization, we recommend you
20852 contact that organization first.
20854 You can find contact information for many support companies and
20855 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
20857 @c should add a web page ref...
20859 In any event, we also recommend that you submit bug reports for
20860 @value{GDBN}. The prefered method is to submit them directly using
20861 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
20862 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
20865 @strong{Do not send bug reports to @samp{info-gdb}, or to
20866 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
20867 not want to receive bug reports. Those that do have arranged to receive
20870 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
20871 serves as a repeater. The mailing list and the newsgroup carry exactly
20872 the same messages. Often people think of posting bug reports to the
20873 newsgroup instead of mailing them. This appears to work, but it has one
20874 problem which can be crucial: a newsgroup posting often lacks a mail
20875 path back to the sender. Thus, if we need to ask for more information,
20876 we may be unable to reach you. For this reason, it is better to send
20877 bug reports to the mailing list.
20879 The fundamental principle of reporting bugs usefully is this:
20880 @strong{report all the facts}. If you are not sure whether to state a
20881 fact or leave it out, state it!
20883 Often people omit facts because they think they know what causes the
20884 problem and assume that some details do not matter. Thus, you might
20885 assume that the name of the variable you use in an example does not matter.
20886 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
20887 stray memory reference which happens to fetch from the location where that
20888 name is stored in memory; perhaps, if the name were different, the contents
20889 of that location would fool the debugger into doing the right thing despite
20890 the bug. Play it safe and give a specific, complete example. That is the
20891 easiest thing for you to do, and the most helpful.
20893 Keep in mind that the purpose of a bug report is to enable us to fix the
20894 bug. It may be that the bug has been reported previously, but neither
20895 you nor we can know that unless your bug report is complete and
20898 Sometimes people give a few sketchy facts and ask, ``Does this ring a
20899 bell?'' Those bug reports are useless, and we urge everyone to
20900 @emph{refuse to respond to them} except to chide the sender to report
20903 To enable us to fix the bug, you should include all these things:
20907 The version of @value{GDBN}. @value{GDBN} announces it if you start
20908 with no arguments; you can also print it at any time using @code{show
20911 Without this, we will not know whether there is any point in looking for
20912 the bug in the current version of @value{GDBN}.
20915 The type of machine you are using, and the operating system name and
20919 What compiler (and its version) was used to compile @value{GDBN}---e.g.
20920 ``@value{GCC}--2.8.1''.
20923 What compiler (and its version) was used to compile the program you are
20924 debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
20925 C Compiler''. For GCC, you can say @code{gcc --version} to get this
20926 information; for other compilers, see the documentation for those
20930 The command arguments you gave the compiler to compile your example and
20931 observe the bug. For example, did you use @samp{-O}? To guarantee
20932 you will not omit something important, list them all. A copy of the
20933 Makefile (or the output from make) is sufficient.
20935 If we were to try to guess the arguments, we would probably guess wrong
20936 and then we might not encounter the bug.
20939 A complete input script, and all necessary source files, that will
20943 A description of what behavior you observe that you believe is
20944 incorrect. For example, ``It gets a fatal signal.''
20946 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
20947 will certainly notice it. But if the bug is incorrect output, we might
20948 not notice unless it is glaringly wrong. You might as well not give us
20949 a chance to make a mistake.
20951 Even if the problem you experience is a fatal signal, you should still
20952 say so explicitly. Suppose something strange is going on, such as, your
20953 copy of @value{GDBN} is out of synch, or you have encountered a bug in
20954 the C library on your system. (This has happened!) Your copy might
20955 crash and ours would not. If you told us to expect a crash, then when
20956 ours fails to crash, we would know that the bug was not happening for
20957 us. If you had not told us to expect a crash, then we would not be able
20958 to draw any conclusion from our observations.
20961 @cindex recording a session script
20962 To collect all this information, you can use a session recording program
20963 such as @command{script}, which is available on many Unix systems.
20964 Just run your @value{GDBN} session inside @command{script} and then
20965 include the @file{typescript} file with your bug report.
20967 Another way to record a @value{GDBN} session is to run @value{GDBN}
20968 inside Emacs and then save the entire buffer to a file.
20971 If you wish to suggest changes to the @value{GDBN} source, send us context
20972 diffs. If you even discuss something in the @value{GDBN} source, refer to
20973 it by context, not by line number.
20975 The line numbers in our development sources will not match those in your
20976 sources. Your line numbers would convey no useful information to us.
20980 Here are some things that are not necessary:
20984 A description of the envelope of the bug.
20986 Often people who encounter a bug spend a lot of time investigating
20987 which changes to the input file will make the bug go away and which
20988 changes will not affect it.
20990 This is often time consuming and not very useful, because the way we
20991 will find the bug is by running a single example under the debugger
20992 with breakpoints, not by pure deduction from a series of examples.
20993 We recommend that you save your time for something else.
20995 Of course, if you can find a simpler example to report @emph{instead}
20996 of the original one, that is a convenience for us. Errors in the
20997 output will be easier to spot, running under the debugger will take
20998 less time, and so on.
21000 However, simplification is not vital; if you do not want to do this,
21001 report the bug anyway and send us the entire test case you used.
21004 A patch for the bug.
21006 A patch for the bug does help us if it is a good one. But do not omit
21007 the necessary information, such as the test case, on the assumption that
21008 a patch is all we need. We might see problems with your patch and decide
21009 to fix the problem another way, or we might not understand it at all.
21011 Sometimes with a program as complicated as @value{GDBN} it is very hard to
21012 construct an example that will make the program follow a certain path
21013 through the code. If you do not send us the example, we will not be able
21014 to construct one, so we will not be able to verify that the bug is fixed.
21016 And if we cannot understand what bug you are trying to fix, or why your
21017 patch should be an improvement, we will not install it. A test case will
21018 help us to understand.
21021 A guess about what the bug is or what it depends on.
21023 Such guesses are usually wrong. Even we cannot guess right about such
21024 things without first using the debugger to find the facts.
21027 @c The readline documentation is distributed with the readline code
21028 @c and consists of the two following files:
21030 @c inc-hist.texinfo
21031 @c Use -I with makeinfo to point to the appropriate directory,
21032 @c environment var TEXINPUTS with TeX.
21033 @include rluser.texinfo
21034 @include inc-hist.texinfo
21037 @node Formatting Documentation
21038 @appendix Formatting Documentation
21040 @cindex @value{GDBN} reference card
21041 @cindex reference card
21042 The @value{GDBN} 4 release includes an already-formatted reference card, ready
21043 for printing with PostScript or Ghostscript, in the @file{gdb}
21044 subdirectory of the main source directory@footnote{In
21045 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
21046 release.}. If you can use PostScript or Ghostscript with your printer,
21047 you can print the reference card immediately with @file{refcard.ps}.
21049 The release also includes the source for the reference card. You
21050 can format it, using @TeX{}, by typing:
21056 The @value{GDBN} reference card is designed to print in @dfn{landscape}
21057 mode on US ``letter'' size paper;
21058 that is, on a sheet 11 inches wide by 8.5 inches
21059 high. You will need to specify this form of printing as an option to
21060 your @sc{dvi} output program.
21062 @cindex documentation
21064 All the documentation for @value{GDBN} comes as part of the machine-readable
21065 distribution. The documentation is written in Texinfo format, which is
21066 a documentation system that uses a single source file to produce both
21067 on-line information and a printed manual. You can use one of the Info
21068 formatting commands to create the on-line version of the documentation
21069 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
21071 @value{GDBN} includes an already formatted copy of the on-line Info
21072 version of this manual in the @file{gdb} subdirectory. The main Info
21073 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
21074 subordinate files matching @samp{gdb.info*} in the same directory. If
21075 necessary, you can print out these files, or read them with any editor;
21076 but they are easier to read using the @code{info} subsystem in @sc{gnu}
21077 Emacs or the standalone @code{info} program, available as part of the
21078 @sc{gnu} Texinfo distribution.
21080 If you want to format these Info files yourself, you need one of the
21081 Info formatting programs, such as @code{texinfo-format-buffer} or
21084 If you have @code{makeinfo} installed, and are in the top level
21085 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
21086 version @value{GDBVN}), you can make the Info file by typing:
21093 If you want to typeset and print copies of this manual, you need @TeX{},
21094 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
21095 Texinfo definitions file.
21097 @TeX{} is a typesetting program; it does not print files directly, but
21098 produces output files called @sc{dvi} files. To print a typeset
21099 document, you need a program to print @sc{dvi} files. If your system
21100 has @TeX{} installed, chances are it has such a program. The precise
21101 command to use depends on your system; @kbd{lpr -d} is common; another
21102 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
21103 require a file name without any extension or a @samp{.dvi} extension.
21105 @TeX{} also requires a macro definitions file called
21106 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
21107 written in Texinfo format. On its own, @TeX{} cannot either read or
21108 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
21109 and is located in the @file{gdb-@var{version-number}/texinfo}
21112 If you have @TeX{} and a @sc{dvi} printer program installed, you can
21113 typeset and print this manual. First switch to the the @file{gdb}
21114 subdirectory of the main source directory (for example, to
21115 @file{gdb-@value{GDBVN}/gdb}) and type:
21121 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
21123 @node Installing GDB
21124 @appendix Installing @value{GDBN}
21125 @cindex configuring @value{GDBN}
21126 @cindex installation
21127 @cindex configuring @value{GDBN}, and source tree subdirectories
21129 @value{GDBN} comes with a @code{configure} script that automates the process
21130 of preparing @value{GDBN} for installation; you can then use @code{make} to
21131 build the @code{gdb} program.
21133 @c irrelevant in info file; it's as current as the code it lives with.
21134 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
21135 look at the @file{README} file in the sources; we may have improved the
21136 installation procedures since publishing this manual.}
21139 The @value{GDBN} distribution includes all the source code you need for
21140 @value{GDBN} in a single directory, whose name is usually composed by
21141 appending the version number to @samp{gdb}.
21143 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
21144 @file{gdb-@value{GDBVN}} directory. That directory contains:
21147 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
21148 script for configuring @value{GDBN} and all its supporting libraries
21150 @item gdb-@value{GDBVN}/gdb
21151 the source specific to @value{GDBN} itself
21153 @item gdb-@value{GDBVN}/bfd
21154 source for the Binary File Descriptor library
21156 @item gdb-@value{GDBVN}/include
21157 @sc{gnu} include files
21159 @item gdb-@value{GDBVN}/libiberty
21160 source for the @samp{-liberty} free software library
21162 @item gdb-@value{GDBVN}/opcodes
21163 source for the library of opcode tables and disassemblers
21165 @item gdb-@value{GDBVN}/readline
21166 source for the @sc{gnu} command-line interface
21168 @item gdb-@value{GDBVN}/glob
21169 source for the @sc{gnu} filename pattern-matching subroutine
21171 @item gdb-@value{GDBVN}/mmalloc
21172 source for the @sc{gnu} memory-mapped malloc package
21175 The simplest way to configure and build @value{GDBN} is to run @code{configure}
21176 from the @file{gdb-@var{version-number}} source directory, which in
21177 this example is the @file{gdb-@value{GDBVN}} directory.
21179 First switch to the @file{gdb-@var{version-number}} source directory
21180 if you are not already in it; then run @code{configure}. Pass the
21181 identifier for the platform on which @value{GDBN} will run as an
21187 cd gdb-@value{GDBVN}
21188 ./configure @var{host}
21193 where @var{host} is an identifier such as @samp{sun4} or
21194 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
21195 (You can often leave off @var{host}; @code{configure} tries to guess the
21196 correct value by examining your system.)
21198 Running @samp{configure @var{host}} and then running @code{make} builds the
21199 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
21200 libraries, then @code{gdb} itself. The configured source files, and the
21201 binaries, are left in the corresponding source directories.
21204 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
21205 system does not recognize this automatically when you run a different
21206 shell, you may need to run @code{sh} on it explicitly:
21209 sh configure @var{host}
21212 If you run @code{configure} from a directory that contains source
21213 directories for multiple libraries or programs, such as the
21214 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
21215 creates configuration files for every directory level underneath (unless
21216 you tell it not to, with the @samp{--norecursion} option).
21218 You should run the @code{configure} script from the top directory in the
21219 source tree, the @file{gdb-@var{version-number}} directory. If you run
21220 @code{configure} from one of the subdirectories, you will configure only
21221 that subdirectory. That is usually not what you want. In particular,
21222 if you run the first @code{configure} from the @file{gdb} subdirectory
21223 of the @file{gdb-@var{version-number}} directory, you will omit the
21224 configuration of @file{bfd}, @file{readline}, and other sibling
21225 directories of the @file{gdb} subdirectory. This leads to build errors
21226 about missing include files such as @file{bfd/bfd.h}.
21228 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
21229 However, you should make sure that the shell on your path (named by
21230 the @samp{SHELL} environment variable) is publicly readable. Remember
21231 that @value{GDBN} uses the shell to start your program---some systems refuse to
21232 let @value{GDBN} debug child processes whose programs are not readable.
21235 * Separate Objdir:: Compiling @value{GDBN} in another directory
21236 * Config Names:: Specifying names for hosts and targets
21237 * Configure Options:: Summary of options for configure
21240 @node Separate Objdir
21241 @section Compiling @value{GDBN} in another directory
21243 If you want to run @value{GDBN} versions for several host or target machines,
21244 you need a different @code{gdb} compiled for each combination of
21245 host and target. @code{configure} is designed to make this easy by
21246 allowing you to generate each configuration in a separate subdirectory,
21247 rather than in the source directory. If your @code{make} program
21248 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
21249 @code{make} in each of these directories builds the @code{gdb}
21250 program specified there.
21252 To build @code{gdb} in a separate directory, run @code{configure}
21253 with the @samp{--srcdir} option to specify where to find the source.
21254 (You also need to specify a path to find @code{configure}
21255 itself from your working directory. If the path to @code{configure}
21256 would be the same as the argument to @samp{--srcdir}, you can leave out
21257 the @samp{--srcdir} option; it is assumed.)
21259 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
21260 separate directory for a Sun 4 like this:
21264 cd gdb-@value{GDBVN}
21267 ../gdb-@value{GDBVN}/configure sun4
21272 When @code{configure} builds a configuration using a remote source
21273 directory, it creates a tree for the binaries with the same structure
21274 (and using the same names) as the tree under the source directory. In
21275 the example, you'd find the Sun 4 library @file{libiberty.a} in the
21276 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
21277 @file{gdb-sun4/gdb}.
21279 Make sure that your path to the @file{configure} script has just one
21280 instance of @file{gdb} in it. If your path to @file{configure} looks
21281 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
21282 one subdirectory of @value{GDBN}, not the whole package. This leads to
21283 build errors about missing include files such as @file{bfd/bfd.h}.
21285 One popular reason to build several @value{GDBN} configurations in separate
21286 directories is to configure @value{GDBN} for cross-compiling (where
21287 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
21288 programs that run on another machine---the @dfn{target}).
21289 You specify a cross-debugging target by
21290 giving the @samp{--target=@var{target}} option to @code{configure}.
21292 When you run @code{make} to build a program or library, you must run
21293 it in a configured directory---whatever directory you were in when you
21294 called @code{configure} (or one of its subdirectories).
21296 The @code{Makefile} that @code{configure} generates in each source
21297 directory also runs recursively. If you type @code{make} in a source
21298 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
21299 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
21300 will build all the required libraries, and then build GDB.
21302 When you have multiple hosts or targets configured in separate
21303 directories, you can run @code{make} on them in parallel (for example,
21304 if they are NFS-mounted on each of the hosts); they will not interfere
21308 @section Specifying names for hosts and targets
21310 The specifications used for hosts and targets in the @code{configure}
21311 script are based on a three-part naming scheme, but some short predefined
21312 aliases are also supported. The full naming scheme encodes three pieces
21313 of information in the following pattern:
21316 @var{architecture}-@var{vendor}-@var{os}
21319 For example, you can use the alias @code{sun4} as a @var{host} argument,
21320 or as the value for @var{target} in a @code{--target=@var{target}}
21321 option. The equivalent full name is @samp{sparc-sun-sunos4}.
21323 The @code{configure} script accompanying @value{GDBN} does not provide
21324 any query facility to list all supported host and target names or
21325 aliases. @code{configure} calls the Bourne shell script
21326 @code{config.sub} to map abbreviations to full names; you can read the
21327 script, if you wish, or you can use it to test your guesses on
21328 abbreviations---for example:
21331 % sh config.sub i386-linux
21333 % sh config.sub alpha-linux
21334 alpha-unknown-linux-gnu
21335 % sh config.sub hp9k700
21337 % sh config.sub sun4
21338 sparc-sun-sunos4.1.1
21339 % sh config.sub sun3
21340 m68k-sun-sunos4.1.1
21341 % sh config.sub i986v
21342 Invalid configuration `i986v': machine `i986v' not recognized
21346 @code{config.sub} is also distributed in the @value{GDBN} source
21347 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
21349 @node Configure Options
21350 @section @code{configure} options
21352 Here is a summary of the @code{configure} options and arguments that
21353 are most often useful for building @value{GDBN}. @code{configure} also has
21354 several other options not listed here. @inforef{What Configure
21355 Does,,configure.info}, for a full explanation of @code{configure}.
21358 configure @r{[}--help@r{]}
21359 @r{[}--prefix=@var{dir}@r{]}
21360 @r{[}--exec-prefix=@var{dir}@r{]}
21361 @r{[}--srcdir=@var{dirname}@r{]}
21362 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
21363 @r{[}--target=@var{target}@r{]}
21368 You may introduce options with a single @samp{-} rather than
21369 @samp{--} if you prefer; but you may abbreviate option names if you use
21374 Display a quick summary of how to invoke @code{configure}.
21376 @item --prefix=@var{dir}
21377 Configure the source to install programs and files under directory
21380 @item --exec-prefix=@var{dir}
21381 Configure the source to install programs under directory
21384 @c avoid splitting the warning from the explanation:
21386 @item --srcdir=@var{dirname}
21387 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
21388 @code{make} that implements the @code{VPATH} feature.}@*
21389 Use this option to make configurations in directories separate from the
21390 @value{GDBN} source directories. Among other things, you can use this to
21391 build (or maintain) several configurations simultaneously, in separate
21392 directories. @code{configure} writes configuration specific files in
21393 the current directory, but arranges for them to use the source in the
21394 directory @var{dirname}. @code{configure} creates directories under
21395 the working directory in parallel to the source directories below
21398 @item --norecursion
21399 Configure only the directory level where @code{configure} is executed; do not
21400 propagate configuration to subdirectories.
21402 @item --target=@var{target}
21403 Configure @value{GDBN} for cross-debugging programs running on the specified
21404 @var{target}. Without this option, @value{GDBN} is configured to debug
21405 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
21407 There is no convenient way to generate a list of all available targets.
21409 @item @var{host} @dots{}
21410 Configure @value{GDBN} to run on the specified @var{host}.
21412 There is no convenient way to generate a list of all available hosts.
21415 There are many other options available as well, but they are generally
21416 needed for special purposes only.
21418 @node Maintenance Commands
21419 @appendix Maintenance Commands
21420 @cindex maintenance commands
21421 @cindex internal commands
21423 In addition to commands intended for @value{GDBN} users, @value{GDBN}
21424 includes a number of commands intended for @value{GDBN} developers,
21425 that are not documented elsewhere in this manual. These commands are
21426 provided here for reference. (For commands that turn on debugging
21427 messages, see @ref{Debugging Output}.)
21430 @kindex maint agent
21431 @item maint agent @var{expression}
21432 Translate the given @var{expression} into remote agent bytecodes.
21433 This command is useful for debugging the Agent Expression mechanism
21434 (@pxref{Agent Expressions}).
21436 @kindex maint info breakpoints
21437 @item @anchor{maint info breakpoints}maint info breakpoints
21438 Using the same format as @samp{info breakpoints}, display both the
21439 breakpoints you've set explicitly, and those @value{GDBN} is using for
21440 internal purposes. Internal breakpoints are shown with negative
21441 breakpoint numbers. The type column identifies what kind of breakpoint
21446 Normal, explicitly set breakpoint.
21449 Normal, explicitly set watchpoint.
21452 Internal breakpoint, used to handle correctly stepping through
21453 @code{longjmp} calls.
21455 @item longjmp resume
21456 Internal breakpoint at the target of a @code{longjmp}.
21459 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
21462 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
21465 Shared library events.
21469 @kindex maint check-symtabs
21470 @item maint check-symtabs
21471 Check the consistency of psymtabs and symtabs.
21473 @kindex maint cplus first_component
21474 @item maint cplus first_component @var{name}
21475 Print the first C@t{++} class/namespace component of @var{name}.
21477 @kindex maint cplus namespace
21478 @item maint cplus namespace
21479 Print the list of possible C@t{++} namespaces.
21481 @kindex maint demangle
21482 @item maint demangle @var{name}
21483 Demangle a C@t{++} or Objective-C manled @var{name}.
21485 @kindex maint deprecate
21486 @kindex maint undeprecate
21487 @cindex deprecated commands
21488 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
21489 @itemx maint undeprecate @var{command}
21490 Deprecate or undeprecate the named @var{command}. Deprecated commands
21491 cause @value{GDBN} to issue a warning when you use them. The optional
21492 argument @var{replacement} says which newer command should be used in
21493 favor of the deprecated one; if it is given, @value{GDBN} will mention
21494 the replacement as part of the warning.
21496 @kindex maint dump-me
21497 @item maint dump-me
21498 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
21499 Cause a fatal signal in the debugger and force it to dump its core.
21500 This is supported only on systems which support aborting a program
21501 with the @code{SIGQUIT} signal.
21503 @kindex maint internal-error
21504 @kindex maint internal-warning
21505 @item maint internal-error @r{[}@var{message-text}@r{]}
21506 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
21507 Cause @value{GDBN} to call the internal function @code{internal_error}
21508 or @code{internal_warning} and hence behave as though an internal error
21509 or internal warning has been detected. In addition to reporting the
21510 internal problem, these functions give the user the opportunity to
21511 either quit @value{GDBN} or create a core file of the current
21512 @value{GDBN} session.
21514 These commands take an optional parameter @var{message-text} that is
21515 used as the text of the error or warning message.
21517 Here's an example of using @code{indernal-error}:
21520 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
21521 @dots{}/maint.c:121: internal-error: testing, 1, 2
21522 A problem internal to GDB has been detected. Further
21523 debugging may prove unreliable.
21524 Quit this debugging session? (y or n) @kbd{n}
21525 Create a core file? (y or n) @kbd{n}
21529 @kindex maint packet
21530 @item maint packet @var{text}
21531 If @value{GDBN} is talking to an inferior via the serial protocol,
21532 then this command sends the string @var{text} to the inferior, and
21533 displays the response packet. @value{GDBN} supplies the initial
21534 @samp{$} character, the terminating @samp{#} character, and the
21537 @kindex maint print architecture
21538 @item maint print architecture @r{[}@var{file}@r{]}
21539 Print the entire architecture configuration. The optional argument
21540 @var{file} names the file where the output goes.
21542 @kindex maint print dummy-frames
21543 @item maint print dummy-frames
21544 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
21547 (@value{GDBP}) @kbd{b add}
21549 (@value{GDBP}) @kbd{print add(2,3)}
21550 Breakpoint 2, add (a=2, b=3) at @dots{}
21552 The program being debugged stopped while in a function called from GDB.
21554 (@value{GDBP}) @kbd{maint print dummy-frames}
21555 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
21556 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
21557 call_lo=0x01014000 call_hi=0x01014001
21561 Takes an optional file parameter.
21563 @kindex maint print registers
21564 @kindex maint print raw-registers
21565 @kindex maint print cooked-registers
21566 @kindex maint print register-groups
21567 @item maint print registers @r{[}@var{file}@r{]}
21568 @itemx maint print raw-registers @r{[}@var{file}@r{]}
21569 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
21570 @itemx maint print register-groups @r{[}@var{file}@r{]}
21571 Print @value{GDBN}'s internal register data structures.
21573 The command @code{maint print raw-registers} includes the contents of
21574 the raw register cache; the command @code{maint print cooked-registers}
21575 includes the (cooked) value of all registers; and the command
21576 @code{maint print register-groups} includes the groups that each
21577 register is a member of. @xref{Registers,, Registers, gdbint,
21578 @value{GDBN} Internals}.
21580 These commands take an optional parameter, a file name to which to
21581 write the information.
21583 @kindex maint print reggroups
21584 @item maint print reggroups @r{[}@var{file}@r{]}
21585 Print @value{GDBN}'s internal register group data structures. The
21586 optional argument @var{file} tells to what file to write the
21589 The register groups info looks like this:
21592 (@value{GDBP}) @kbd{maint print reggroups}
21605 This command forces @value{GDBN} to flush its internal register cache.
21607 @kindex maint print objfiles
21608 @cindex info for known object files
21609 @item maint print objfiles
21610 Print a dump of all known object files. For each object file, this
21611 command prints its name, address in memory, and all of its psymtabs
21614 @kindex maint print statistics
21615 @cindex bcache statistics
21616 @item maint print statistics
21617 This command prints, for each object file in the program, various data
21618 about that object file followed by the byte cache (@dfn{bcache})
21619 statistics for the object file. The objfile data includes the number
21620 of minimal, partical, full, and stabs symbols, the number of types
21621 defined by the objfile, the number of as yet unexpanded psym tables,
21622 the number of line tables and string tables, and the amount of memory
21623 used by the various tables. The bcache statistics include the counts,
21624 sizes, and counts of duplicates of all and unique objects, max,
21625 average, and median entry size, total memory used and its overhead and
21626 savings, and various measures of the hash table size and chain
21629 @kindex maint print type
21630 @cindex type chain of a data type
21631 @item maint print type @var{expr}
21632 Print the type chain for a type specified by @var{expr}. The argument
21633 can be either a type name or a symbol. If it is a symbol, the type of
21634 that symbol is described. The type chain produced by this command is
21635 a recursive definition of the data type as stored in @value{GDBN}'s
21636 data structures, including its flags and contained types.
21638 @kindex maint set dwarf2 max-cache-age
21639 @kindex maint show dwarf2 max-cache-age
21640 @item maint set dwarf2 max-cache-age
21641 @itemx maint show dwarf2 max-cache-age
21642 Control the DWARF 2 compilation unit cache.
21644 @cindex DWARF 2 compilation units cache
21645 In object files with inter-compilation-unit references, such as those
21646 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
21647 reader needs to frequently refer to previously read compilation units.
21648 This setting controls how long a compilation unit will remain in the
21649 cache if it is not referenced. A higher limit means that cached
21650 compilation units will be stored in memory longer, and more total
21651 memory will be used. Setting it to zero disables caching, which will
21652 slow down @value{GDBN} startup, but reduce memory consumption.
21654 @kindex maint set profile
21655 @kindex maint show profile
21656 @cindex profiling GDB
21657 @item maint set profile
21658 @itemx maint show profile
21659 Control profiling of @value{GDBN}.
21661 Profiling will be disabled until you use the @samp{maint set profile}
21662 command to enable it. When you enable profiling, the system will begin
21663 collecting timing and execution count data; when you disable profiling or
21664 exit @value{GDBN}, the results will be written to a log file. Remember that
21665 if you use profiling, @value{GDBN} will overwrite the profiling log file
21666 (often called @file{gmon.out}). If you have a record of important profiling
21667 data in a @file{gmon.out} file, be sure to move it to a safe location.
21669 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
21670 compiled with the @samp{-pg} compiler option.
21672 @kindex maint show-debug-regs
21673 @cindex x86 hardware debug registers
21674 @item maint show-debug-regs
21675 Control whether to show variables that mirror the x86 hardware debug
21676 registers. Use @code{ON} to enable, @code{OFF} to disable. If
21677 enabled, the debug registers values are shown when GDB inserts or
21678 removes a hardware breakpoint or watchpoint, and when the inferior
21679 triggers a hardware-assisted breakpoint or watchpoint.
21681 @kindex maint space
21682 @cindex memory used by commands
21684 Control whether to display memory usage for each command. If set to a
21685 nonzero value, @value{GDBN} will display how much memory each command
21686 took, following the command's own output. This can also be requested
21687 by invoking @value{GDBN} with the @option{--statistics} command-line
21688 switch (@pxref{Mode Options}).
21691 @cindex time of command execution
21693 Control whether to display the execution time for each command. If
21694 set to a nonzero value, @value{GDBN} will display how much time it
21695 took to execute each command, following the command's own output.
21696 This can also be requested by invoking @value{GDBN} with the
21697 @option{--statistics} command-line switch (@pxref{Mode Options}).
21699 @kindex maint translate-address
21700 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
21701 Find the symbol stored at the location specified by the address
21702 @var{addr} and an optional section name @var{section}. If found,
21703 @value{GDBN} prints the name of the closest symbol and an offset from
21704 the symbol's location to the specified address. This is similar to
21705 the @code{info address} command (@pxref{Symbols}), except that this
21706 command also allows to find symbols in other sections.
21710 The following command is useful for non-interactive invocations of
21711 @value{GDBN}, such as in the test suite.
21714 @item set watchdog @var{nsec}
21715 @kindex set watchdog
21716 @cindex watchdog timer
21717 @cindex timeout for commands
21718 Set the maximum number of seconds @value{GDBN} will wait for the
21719 target operation to finish. If this time expires, @value{GDBN}
21720 reports and error and the command is aborted.
21722 @item show watchdog
21723 Show the current setting of the target wait timeout.
21726 @node Remote Protocol
21727 @appendix @value{GDBN} Remote Serial Protocol
21732 * Stop Reply Packets::
21733 * General Query Packets::
21734 * Register Packet Format::
21736 * File-I/O remote protocol extension::
21742 There may be occasions when you need to know something about the
21743 protocol---for example, if there is only one serial port to your target
21744 machine, you might want your program to do something special if it
21745 recognizes a packet meant for @value{GDBN}.
21747 In the examples below, @samp{->} and @samp{<-} are used to indicate
21748 transmitted and received data respectfully.
21750 @cindex protocol, @value{GDBN} remote serial
21751 @cindex serial protocol, @value{GDBN} remote
21752 @cindex remote serial protocol
21753 All @value{GDBN} commands and responses (other than acknowledgments) are
21754 sent as a @var{packet}. A @var{packet} is introduced with the character
21755 @samp{$}, the actual @var{packet-data}, and the terminating character
21756 @samp{#} followed by a two-digit @var{checksum}:
21759 @code{$}@var{packet-data}@code{#}@var{checksum}
21763 @cindex checksum, for @value{GDBN} remote
21765 The two-digit @var{checksum} is computed as the modulo 256 sum of all
21766 characters between the leading @samp{$} and the trailing @samp{#} (an
21767 eight bit unsigned checksum).
21769 Implementors should note that prior to @value{GDBN} 5.0 the protocol
21770 specification also included an optional two-digit @var{sequence-id}:
21773 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
21776 @cindex sequence-id, for @value{GDBN} remote
21778 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
21779 has never output @var{sequence-id}s. Stubs that handle packets added
21780 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
21782 @cindex acknowledgment, for @value{GDBN} remote
21783 When either the host or the target machine receives a packet, the first
21784 response expected is an acknowledgment: either @samp{+} (to indicate
21785 the package was received correctly) or @samp{-} (to request
21789 -> @code{$}@var{packet-data}@code{#}@var{checksum}
21794 The host (@value{GDBN}) sends @var{command}s, and the target (the
21795 debugging stub incorporated in your program) sends a @var{response}. In
21796 the case of step and continue @var{command}s, the response is only sent
21797 when the operation has completed (the target has again stopped).
21799 @var{packet-data} consists of a sequence of characters with the
21800 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
21803 Fields within the packet should be separated using @samp{,} @samp{;} or
21804 @cindex remote protocol, field separator
21805 @samp{:}. Except where otherwise noted all numbers are represented in
21806 @sc{hex} with leading zeros suppressed.
21808 Implementors should note that prior to @value{GDBN} 5.0, the character
21809 @samp{:} could not appear as the third character in a packet (as it
21810 would potentially conflict with the @var{sequence-id}).
21812 Response @var{data} can be run-length encoded to save space. A @samp{*}
21813 means that the next character is an @sc{ascii} encoding giving a repeat count
21814 which stands for that many repetitions of the character preceding the
21815 @samp{*}. The encoding is @code{n+29}, yielding a printable character
21816 where @code{n >=3} (which is where rle starts to win). The printable
21817 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
21818 value greater than 126 should not be used.
21825 means the same as "0000".
21827 The error response returned for some packets includes a two character
21828 error number. That number is not well defined.
21830 For any @var{command} not supported by the stub, an empty response
21831 (@samp{$#00}) should be returned. That way it is possible to extend the
21832 protocol. A newer @value{GDBN} can tell if a packet is supported based
21835 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
21836 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
21842 The following table provides a complete list of all currently defined
21843 @var{command}s and their corresponding response @var{data}.
21844 @xref{File-I/O remote protocol extension}, for details about the File
21845 I/O extension of the remote protocol.
21849 @item @code{!} --- extended mode
21850 @cindex @code{!} packet
21852 Enable extended mode. In extended mode, the remote server is made
21853 persistent. The @samp{R} packet is used to restart the program being
21859 The remote target both supports and has enabled extended mode.
21862 @item @code{?} --- last signal
21863 @cindex @code{?} packet
21865 Indicate the reason the target halted. The reply is the same as for
21869 @xref{Stop Reply Packets}, for the reply specifications.
21871 @item @code{a} --- reserved
21873 Reserved for future use.
21875 @item @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,@dots{}} --- set program arguments @strong{(reserved)}
21876 @cindex @code{A} packet
21878 Initialized @samp{argv[]} array passed into program. @var{arglen}
21879 specifies the number of bytes in the hex encoded byte stream @var{arg}.
21880 See @code{gdbserver} for more details.
21888 @item @code{b}@var{baud} --- set baud @strong{(deprecated)}
21889 @cindex @code{b} packet
21891 Change the serial line speed to @var{baud}.
21893 JTC: @emph{When does the transport layer state change? When it's
21894 received, or after the ACK is transmitted. In either case, there are
21895 problems if the command or the acknowledgment packet is dropped.}
21897 Stan: @emph{If people really wanted to add something like this, and get
21898 it working for the first time, they ought to modify ser-unix.c to send
21899 some kind of out-of-band message to a specially-setup stub and have the
21900 switch happen "in between" packets, so that from remote protocol's point
21901 of view, nothing actually happened.}
21903 @item @code{B}@var{addr},@var{mode} --- set breakpoint @strong{(deprecated)}
21904 @cindex @code{B} packet
21906 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
21907 breakpoint at @var{addr}.
21909 This packet has been replaced by the @samp{Z} and @samp{z} packets
21910 (@pxref{insert breakpoint or watchpoint packet}).
21912 @item @code{c}@var{addr} --- continue
21913 @cindex @code{c} packet
21915 @var{addr} is address to resume. If @var{addr} is omitted, resume at
21919 @xref{Stop Reply Packets}, for the reply specifications.
21921 @item @code{C}@var{sig}@code{;}@var{addr} --- continue with signal
21922 @cindex @code{C} packet
21924 Continue with signal @var{sig} (hex signal number). If
21925 @code{;}@var{addr} is omitted, resume at same address.
21928 @xref{Stop Reply Packets}, for the reply specifications.
21930 @item @code{d} --- toggle debug @strong{(deprecated)}
21931 @cindex @code{d} packet
21935 @item @code{D} --- detach
21936 @cindex @code{D} packet
21938 Detach @value{GDBN} from the remote system. Sent to the remote target
21939 before @value{GDBN} disconnects via the @code{detach} command.
21943 @item @emph{no response}
21944 @value{GDBN} does not check for any response after sending this packet.
21947 @item @code{e} --- reserved
21949 Reserved for future use.
21951 @item @code{E} --- reserved
21953 Reserved for future use.
21955 @item @code{f} --- reserved
21957 Reserved for future use.
21959 @item @code{F}@var{RC}@code{,}@var{EE}@code{,}@var{CF}@code{;}@var{XX} --- Reply to target's F packet.
21960 @cindex @code{F} packet
21962 This packet is send by @value{GDBN} as reply to a @code{F} request packet
21963 sent by the target. This is part of the File-I/O protocol extension.
21964 @xref{File-I/O remote protocol extension}, for the specification.
21966 @item @code{g} --- read registers
21967 @anchor{read registers packet}
21968 @cindex @code{g} packet
21970 Read general registers.
21974 @item @var{XX@dots{}}
21975 Each byte of register data is described by two hex digits. The bytes
21976 with the register are transmitted in target byte order. The size of
21977 each register and their position within the @samp{g} @var{packet} are
21978 determined by the @value{GDBN} internal macros
21979 @var{DEPRECATED_REGISTER_RAW_SIZE} and @var{REGISTER_NAME} macros. The
21980 specification of several standard @code{g} packets is specified below.
21985 @item @code{G}@var{XX@dots{}} --- write regs
21986 @cindex @code{G} packet
21988 @xref{read registers packet}, for a description of the @var{XX@dots{}}
21999 @item @code{h} --- reserved
22001 Reserved for future use.
22003 @item @code{H}@var{c}@var{t@dots{}} --- set thread
22004 @cindex @code{H} packet
22006 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
22007 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
22008 should be @samp{c} for step and continue operations, @samp{g} for other
22009 operations. The thread designator @var{t@dots{}} may be -1, meaning all
22010 the threads, a thread number, or zero which means pick any thread.
22021 @c 'H': How restrictive (or permissive) is the thread model. If a
22022 @c thread is selected and stopped, are other threads allowed
22023 @c to continue to execute? As I mentioned above, I think the
22024 @c semantics of each command when a thread is selected must be
22025 @c described. For example:
22027 @c 'g': If the stub supports threads and a specific thread is
22028 @c selected, returns the register block from that thread;
22029 @c otherwise returns current registers.
22031 @c 'G' If the stub supports threads and a specific thread is
22032 @c selected, sets the registers of the register block of
22033 @c that thread; otherwise sets current registers.
22035 @item @code{i}@var{addr}@code{,}@var{nnn} --- cycle step @strong{(draft)}
22036 @anchor{cycle step packet}
22037 @cindex @code{i} packet
22039 Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
22040 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
22041 step starting at that address.
22043 @item @code{I} --- signal then cycle step @strong{(reserved)}
22044 @cindex @code{I} packet
22046 @xref{step with signal packet}. @xref{cycle step packet}.
22048 @item @code{j} --- reserved
22050 Reserved for future use.
22052 @item @code{J} --- reserved
22054 Reserved for future use.
22056 @item @code{k} --- kill request
22057 @cindex @code{k} packet
22059 FIXME: @emph{There is no description of how to operate when a specific
22060 thread context has been selected (i.e.@: does 'k' kill only that
22063 @item @code{K} --- reserved
22065 Reserved for future use.
22067 @item @code{l} --- reserved
22069 Reserved for future use.
22071 @item @code{L} --- reserved
22073 Reserved for future use.
22075 @item @code{m}@var{addr}@code{,}@var{length} --- read memory
22076 @cindex @code{m} packet
22078 Read @var{length} bytes of memory starting at address @var{addr}.
22079 Neither @value{GDBN} nor the stub assume that sized memory transfers are
22080 assumed using word aligned accesses. FIXME: @emph{A word aligned memory
22081 transfer mechanism is needed.}
22085 @item @var{XX@dots{}}
22086 @var{XX@dots{}} is mem contents. Can be fewer bytes than requested if able
22087 to read only part of the data. Neither @value{GDBN} nor the stub assume
22088 that sized memory transfers are assumed using word aligned
22089 accesses. FIXME: @emph{A word aligned memory transfer mechanism is
22095 @item @code{M}@var{addr},@var{length}@code{:}@var{XX@dots{}} --- write mem
22096 @cindex @code{M} packet
22098 Write @var{length} bytes of memory starting at address @var{addr}.
22099 @var{XX@dots{}} is the data.
22106 for an error (this includes the case where only part of the data was
22110 @item @code{n} --- reserved
22112 Reserved for future use.
22114 @item @code{N} --- reserved
22116 Reserved for future use.
22118 @item @code{o} --- reserved
22120 Reserved for future use.
22122 @item @code{O} --- reserved
22124 @item @code{p}@var{hex number of register} --- read register packet
22125 @cindex @code{p} packet
22127 @xref{read registers packet}, for a description of how the returned
22128 register value is encoded.
22132 @item @var{XX@dots{}}
22133 the register's value
22137 Indicating an unrecognized @var{query}.
22140 @item @code{P}@var{n@dots{}}@code{=}@var{r@dots{}} --- write register
22141 @anchor{write register packet}
22142 @cindex @code{P} packet
22144 Write register @var{n@dots{}} with value @var{r@dots{}}, which contains two hex
22145 digits for each byte in the register (target byte order).
22155 @item @code{q}@var{query} --- general query
22156 @anchor{general query packet}
22157 @cindex @code{q} packet
22159 Request info about @var{query}. In general @value{GDBN} queries have a
22160 leading upper case letter. Custom vendor queries should use a company
22161 prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may optionally
22162 be followed by a @samp{,} or @samp{;} separated list. Stubs must ensure
22163 that they match the full @var{query} name.
22167 @item @var{XX@dots{}}
22168 Hex encoded data from query. The reply can not be empty.
22172 Indicating an unrecognized @var{query}.
22175 @item @code{Q}@var{var}@code{=}@var{val} --- general set
22176 @cindex @code{Q} packet
22178 Set value of @var{var} to @var{val}.
22180 @xref{general query packet}, for a discussion of naming conventions.
22182 @item @code{r} --- reset @strong{(deprecated)}
22183 @cindex @code{r} packet
22185 Reset the entire system.
22187 @item @code{R}@var{XX} --- remote restart
22188 @cindex @code{R} packet
22190 Restart the program being debugged. @var{XX}, while needed, is ignored.
22191 This packet is only available in extended mode.
22195 @item @emph{no reply}
22196 The @samp{R} packet has no reply.
22199 @item @code{s}@var{addr} --- step
22200 @cindex @code{s} packet
22202 @var{addr} is address to resume. If @var{addr} is omitted, resume at
22206 @xref{Stop Reply Packets}, for the reply specifications.
22208 @item @code{S}@var{sig}@code{;}@var{addr} --- step with signal
22209 @anchor{step with signal packet}
22210 @cindex @code{S} packet
22212 Like @samp{C} but step not continue.
22215 @xref{Stop Reply Packets}, for the reply specifications.
22217 @item @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} --- search
22218 @cindex @code{t} packet
22220 Search backwards starting at address @var{addr} for a match with pattern
22221 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
22222 @var{addr} must be at least 3 digits.
22224 @item @code{T}@var{XX} --- thread alive
22225 @cindex @code{T} packet
22227 Find out if the thread XX is alive.
22232 thread is still alive
22237 @item @code{u} --- reserved
22239 Reserved for future use.
22241 @item @code{U} --- reserved
22243 Reserved for future use.
22245 @item @code{v} --- verbose packet prefix
22247 Packets starting with @code{v} are identified by a multi-letter name,
22248 up to the first @code{;} or @code{?} (or the end of the packet).
22250 @item @code{vCont}[;@var{action}[@code{:}@var{tid}]]... --- extended resume
22251 @cindex @code{vCont} packet
22253 Resume the inferior. Different actions may be specified for each thread.
22254 If an action is specified with no @var{tid}, then it is applied to any
22255 threads that don't have a specific action specified; if no default action is
22256 specified then other threads should remain stopped. Specifying multiple
22257 default actions is an error; specifying no actions is also an error.
22258 Thread IDs are specified in hexadecimal. Currently supported actions are:
22264 Continue with signal @var{sig}. @var{sig} should be two hex digits.
22268 Step with signal @var{sig}. @var{sig} should be two hex digits.
22271 The optional @var{addr} argument normally associated with these packets is
22272 not supported in @code{vCont}.
22275 @xref{Stop Reply Packets}, for the reply specifications.
22277 @item @code{vCont?} --- extended resume query
22278 @cindex @code{vCont?} packet
22280 Query support for the @code{vCont} packet.
22284 @item @code{vCont}[;@var{action}]...
22285 The @code{vCont} packet is supported. Each @var{action} is a supported
22286 command in the @code{vCont} packet.
22288 The @code{vCont} packet is not supported.
22291 @item @code{V} --- reserved
22293 Reserved for future use.
22295 @item @code{w} --- reserved
22297 Reserved for future use.
22299 @item @code{W} --- reserved
22301 Reserved for future use.
22303 @item @code{x} --- reserved
22305 Reserved for future use.
22307 @item @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX@dots{}} --- write mem (binary)
22308 @cindex @code{X} packet
22310 @var{addr} is address, @var{length} is number of bytes, @var{XX@dots{}}
22311 is binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
22312 escaped using @code{0x7d}, and then XORed with @code{0x20}.
22313 For example, @code{0x7d} would be transmitted as @code{0x7d 0x5d}.
22323 @item @code{y} --- reserved
22325 Reserved for future use.
22327 @item @code{Y} reserved
22329 Reserved for future use.
22331 @item @code{z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- remove breakpoint or watchpoint @strong{(draft)}
22332 @itemx @code{Z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- insert breakpoint or watchpoint @strong{(draft)}
22333 @anchor{insert breakpoint or watchpoint packet}
22334 @cindex @code{z} packet
22335 @cindex @code{Z} packets
22337 Insert (@code{Z}) or remove (@code{z}) a @var{type} breakpoint or
22338 watchpoint starting at address @var{address} and covering the next
22339 @var{length} bytes.
22341 Each breakpoint and watchpoint packet @var{type} is documented
22344 @emph{Implementation notes: A remote target shall return an empty string
22345 for an unrecognized breakpoint or watchpoint packet @var{type}. A
22346 remote target shall support either both or neither of a given
22347 @code{Z}@var{type}@dots{} and @code{z}@var{type}@dots{} packet pair. To
22348 avoid potential problems with duplicate packets, the operations should
22349 be implemented in an idempotent way.}
22351 @item @code{z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- remove memory breakpoint @strong{(draft)}
22352 @item @code{Z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- insert memory breakpoint @strong{(draft)}
22353 @cindex @code{z0} packet
22354 @cindex @code{Z0} packet
22356 Insert (@code{Z0}) or remove (@code{z0}) a memory breakpoint at address
22357 @code{addr} of size @code{length}.
22359 A memory breakpoint is implemented by replacing the instruction at
22360 @var{addr} with a software breakpoint or trap instruction. The
22361 @code{length} is used by targets that indicates the size of the
22362 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
22363 @sc{mips} can insert either a 2 or 4 byte breakpoint).
22365 @emph{Implementation note: It is possible for a target to copy or move
22366 code that contains memory breakpoints (e.g., when implementing
22367 overlays). The behavior of this packet, in the presence of such a
22368 target, is not defined.}
22380 @item @code{z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- remove hardware breakpoint @strong{(draft)}
22381 @item @code{Z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- insert hardware breakpoint @strong{(draft)}
22382 @cindex @code{z1} packet
22383 @cindex @code{Z1} packet
22385 Insert (@code{Z1}) or remove (@code{z1}) a hardware breakpoint at
22386 address @code{addr} of size @code{length}.
22388 A hardware breakpoint is implemented using a mechanism that is not
22389 dependant on being able to modify the target's memory.
22391 @emph{Implementation note: A hardware breakpoint is not affected by code
22404 @item @code{z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- remove write watchpoint @strong{(draft)}
22405 @item @code{Z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- insert write watchpoint @strong{(draft)}
22406 @cindex @code{z2} packet
22407 @cindex @code{Z2} packet
22409 Insert (@code{Z2}) or remove (@code{z2}) a write watchpoint.
22421 @item @code{z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- remove read watchpoint @strong{(draft)}
22422 @item @code{Z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- insert read watchpoint @strong{(draft)}
22423 @cindex @code{z3} packet
22424 @cindex @code{Z3} packet
22426 Insert (@code{Z3}) or remove (@code{z3}) a read watchpoint.
22438 @item @code{z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- remove access watchpoint @strong{(draft)}
22439 @item @code{Z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- insert access watchpoint @strong{(draft)}
22440 @cindex @code{z4} packet
22441 @cindex @code{Z4} packet
22443 Insert (@code{Z4}) or remove (@code{z4}) an access watchpoint.
22457 @node Stop Reply Packets
22458 @section Stop Reply Packets
22459 @cindex stop reply packets
22461 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
22462 receive any of the below as a reply. In the case of the @samp{C},
22463 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
22464 when the target halts. In the below the exact meaning of @samp{signal
22465 number} is poorly defined. In general one of the UNIX signal numbering
22466 conventions is used.
22471 @var{AA} is the signal number
22473 @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
22474 @cindex @code{T} packet reply
22476 @var{AA} = two hex digit signal number; @var{n...} = register number
22477 (hex), @var{r...} = target byte ordered register contents, size defined
22478 by @code{DEPRECATED_REGISTER_RAW_SIZE}; @var{n...} = @samp{thread},
22479 @var{r...} = thread process ID, this is a hex integer; @var{n...} =
22480 (@samp{watch} | @samp{rwatch} | @samp{awatch}, @var{r...} = data
22481 address, this is a hex integer; @var{n...} = other string not starting
22482 with valid hex digit. @value{GDBN} should ignore this @var{n...},
22483 @var{r...} pair and go on to the next. This way we can extend the
22488 The process exited, and @var{AA} is the exit status. This is only
22489 applicable to certain targets.
22493 The process terminated with signal @var{AA}.
22495 @item O@var{XX@dots{}}
22497 @var{XX@dots{}} is hex encoding of @sc{ascii} data. This can happen at
22498 any time while the program is running and the debugger should continue
22499 to wait for @samp{W}, @samp{T}, etc.
22501 @item F@var{call-id}@code{,}@var{parameter@dots{}}
22503 @var{call-id} is the identifier which says which host system call should
22504 be called. This is just the name of the function. Translation into the
22505 correct system call is only applicable as it's defined in @value{GDBN}.
22506 @xref{File-I/O remote protocol extension}, for a list of implemented
22509 @var{parameter@dots{}} is a list of parameters as defined for this very
22512 The target replies with this packet when it expects @value{GDBN} to call
22513 a host system call on behalf of the target. @value{GDBN} replies with
22514 an appropriate @code{F} packet and keeps up waiting for the next reply
22515 packet from the target. The latest @samp{C}, @samp{c}, @samp{S} or
22516 @samp{s} action is expected to be continued.
22517 @xref{File-I/O remote protocol extension}, for more details.
22521 @node General Query Packets
22522 @section General Query Packets
22523 @cindex remote query requests
22525 The following set and query packets have already been defined.
22529 @item @code{q}@code{C} --- current thread
22530 @cindex current thread, remote request
22531 @cindex @code{qC} packet
22532 Return the current thread id.
22536 @item @code{QC}@var{pid}
22537 Where @var{pid} is an unsigned hexidecimal process id.
22539 Any other reply implies the old pid.
22542 @item @code{q}@code{fThreadInfo} -- all thread ids
22543 @cindex list active threads, remote request
22544 @cindex @code{qfThreadInfo} packet
22545 @code{q}@code{sThreadInfo}
22547 Obtain a list of active thread ids from the target (OS). Since there
22548 may be too many active threads to fit into one reply packet, this query
22549 works iteratively: it may require more than one query/reply sequence to
22550 obtain the entire list of threads. The first query of the sequence will
22551 be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
22552 sequence will be the @code{qs}@code{ThreadInfo} query.
22554 NOTE: replaces the @code{qL} query (see below).
22558 @item @code{m}@var{id}
22560 @item @code{m}@var{id},@var{id}@dots{}
22561 a comma-separated list of thread ids
22563 (lower case 'el') denotes end of list.
22566 In response to each query, the target will reply with a list of one or
22567 more thread ids, in big-endian unsigned hex, separated by commas.
22568 @value{GDBN} will respond to each reply with a request for more thread
22569 ids (using the @code{qs} form of the query), until the target responds
22570 with @code{l} (lower-case el, for @code{'last'}).
22572 @item @code{q}@code{ThreadExtraInfo}@code{,}@var{id} --- extra thread info
22573 @cindex thread attributes info, remote request
22574 @cindex @code{qThreadExtraInfo} packet
22575 Where @var{id} is a thread-id in big-endian hex. Obtain a printable
22576 string description of a thread's attributes from the target OS. This
22577 string may contain anything that the target OS thinks is interesting for
22578 @value{GDBN} to tell the user about the thread. The string is displayed
22579 in @value{GDBN}'s @samp{info threads} display. Some examples of
22580 possible thread extra info strings are ``Runnable'', or ``Blocked on
22585 @item @var{XX@dots{}}
22586 Where @var{XX@dots{}} is a hex encoding of @sc{ascii} data, comprising
22587 the printable string containing the extra information about the thread's
22591 @item @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} --- query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
22593 Obtain thread information from RTOS. Where: @var{startflag} (one hex
22594 digit) is one to indicate the first query and zero to indicate a
22595 subsequent query; @var{threadcount} (two hex digits) is the maximum
22596 number of threads the response packet can contain; and @var{nextthread}
22597 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
22598 returned in the response as @var{argthread}.
22600 NOTE: this query is replaced by the @code{q}@code{fThreadInfo} query
22605 @item @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread@dots{}}
22606 Where: @var{count} (two hex digits) is the number of threads being
22607 returned; @var{done} (one hex digit) is zero to indicate more threads
22608 and one indicates no further threads; @var{argthreadid} (eight hex
22609 digits) is @var{nextthread} from the request packet; @var{thread@dots{}}
22610 is a sequence of thread IDs from the target. @var{threadid} (eight hex
22611 digits). See @code{remote.c:parse_threadlist_response()}.
22614 @item @code{q}@code{CRC:}@var{addr}@code{,}@var{length} --- compute CRC of memory block
22615 @cindex CRC of memory block, remote request
22616 @cindex @code{qCRC} packet
22619 @item @code{E}@var{NN}
22620 An error (such as memory fault)
22621 @item @code{C}@var{CRC32}
22622 A 32 bit cyclic redundancy check of the specified memory region.
22625 @item @code{q}@code{Offsets} --- query sect offs
22626 @cindex section offsets, remote request
22627 @cindex @code{qOffsets} packet
22628 Get section offsets that the target used when re-locating the downloaded
22629 image. @emph{Note: while a @code{Bss} offset is included in the
22630 response, @value{GDBN} ignores this and instead applies the @code{Data}
22631 offset to the @code{Bss} section.}
22635 @item @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
22638 @item @code{q}@code{P}@var{mode}@var{threadid} --- thread info request
22639 @cindex thread information, remote request
22640 @cindex @code{qP} packet
22641 Returns information on @var{threadid}. Where: @var{mode} is a hex
22642 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
22649 See @code{remote.c:remote_unpack_thread_info_response()}.
22651 @item @code{q}@code{Rcmd,}@var{command} --- remote command
22652 @cindex execute remote command, remote request
22653 @cindex @code{qRcmd} packet
22654 @var{command} (hex encoded) is passed to the local interpreter for
22655 execution. Invalid commands should be reported using the output string.
22656 Before the final result packet, the target may also respond with a
22657 number of intermediate @code{O}@var{output} console output packets.
22658 @emph{Implementors should note that providing access to a stubs's
22659 interpreter may have security implications}.
22664 A command response with no output.
22666 A command response with the hex encoded output string @var{OUTPUT}.
22667 @item @code{E}@var{NN}
22668 Indicate a badly formed request.
22670 When @samp{q}@samp{Rcmd} is not recognized.
22673 @item @code{qSymbol::} --- symbol lookup
22674 @cindex symbol lookup, remote request
22675 @cindex @code{qSymbol} packet
22676 Notify the target that @value{GDBN} is prepared to serve symbol lookup
22677 requests. Accept requests from the target for the values of symbols.
22682 The target does not need to look up any (more) symbols.
22683 @item @code{qSymbol:}@var{sym_name}
22684 The target requests the value of symbol @var{sym_name} (hex encoded).
22685 @value{GDBN} may provide the value by using the
22686 @code{qSymbol:}@var{sym_value}:@var{sym_name} message, described below.
22689 @item @code{qSymbol:}@var{sym_value}:@var{sym_name} --- symbol value
22691 Set the value of @var{sym_name} to @var{sym_value}.
22693 @var{sym_name} (hex encoded) is the name of a symbol whose value the
22694 target has previously requested.
22696 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
22697 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
22703 The target does not need to look up any (more) symbols.
22704 @item @code{qSymbol:}@var{sym_name}
22705 The target requests the value of a new symbol @var{sym_name} (hex
22706 encoded). @value{GDBN} will continue to supply the values of symbols
22707 (if available), until the target ceases to request them.
22710 @item @code{qPart}:@var{object}:@code{read}:@var{annex}:@var{offset},@var{length} --- read special data
22711 @cindex read special object, remote request
22712 @cindex @code{qPart} packet
22713 Read uninterpreted bytes from the target's special data area
22714 identified by the keyword @code{object}.
22715 Request @var{length} bytes starting at @var{offset} bytes into the data.
22716 The content and encoding of @var{annex} is specific to the object;
22717 it can supply additional details about what data to access.
22719 Here are the specific requests of this form defined so far.
22720 All @samp{@code{qPart}:@var{object}:@code{read}:@dots{}}
22721 requests use the same reply formats, listed below.
22724 @item @code{qPart}:@code{auxv}:@code{read}::@var{offset},@var{length}
22725 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
22726 auxiliary vector}, and see @ref{Remote configuration,
22727 read-aux-vector-packet}. Note @var{annex} must be empty.
22733 The @var{offset} in the request is at the end of the data.
22734 There is no more data to be read.
22736 @item @var{XX@dots{}}
22737 Hex encoded data bytes read.
22738 This may be fewer bytes than the @var{length} in the request.
22741 The request was malformed, or @var{annex} was invalid.
22743 @item @code{E}@var{nn}
22744 The offset was invalid, or there was an error encountered reading the data.
22745 @var{nn} is a hex-encoded @code{errno} value.
22747 @item @code{""} (empty)
22748 An empty reply indicates the @var{object} or @var{annex} string was not
22749 recognized by the stub.
22752 @item @code{qPart}:@var{object}:@code{write}:@var{annex}:@var{offset}:@var{data@dots{}}
22753 @cindex write data into object, remote request
22754 Write uninterpreted bytes into the target's special data area
22755 identified by the keyword @code{object},
22756 starting at @var{offset} bytes into the data.
22757 @var{data@dots{}} is the hex-encoded data to be written.
22758 The content and encoding of @var{annex} is specific to the object;
22759 it can supply additional details about what data to access.
22761 No requests of this form are presently in use. This specification
22762 serves as a placeholder to document the common format that new
22763 specific request specifications ought to use.
22768 @var{nn} (hex encoded) is the number of bytes written.
22769 This may be fewer bytes than supplied in the request.
22772 The request was malformed, or @var{annex} was invalid.
22774 @item @code{E}@var{nn}
22775 The offset was invalid, or there was an error encountered writing the data.
22776 @var{nn} is a hex-encoded @code{errno} value.
22778 @item @code{""} (empty)
22779 An empty reply indicates the @var{object} or @var{annex} string was not
22780 recognized by the stub, or that the object does not support writing.
22783 @item @code{qPart}:@var{object}:@var{operation}:@dots{}
22784 Requests of this form may be added in the future. When a stub does
22785 not recognize the @var{object} keyword, or its support for
22786 @var{object} does not recognize the @var{operation} keyword,
22787 the stub must respond with an empty packet.
22789 @item @code{qGetTLSAddr}:@var{thread-id},@var{offset},@var{lm} --- get thread local storage address
22790 @cindex get thread-local storage address, remote request
22791 @cindex @code{qGetTLSAddr} packet
22792 Fetch the address associated with thread local storage specified
22793 by @var{thread-id}, @var{offset}, and @var{lm}.
22795 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
22796 thread for which to fetch the TLS address.
22798 @var{offset} is the (big endian, hex encoded) offset associated with the
22799 thread local variable. (This offset is obtained from the debug
22800 information associated with the variable.)
22802 @var{lm} is the (big endian, hex encoded) OS/ABI specific encoding of the
22803 the load module associated with the thread local storage. For example,
22804 a @sc{gnu}/Linux system will pass the link map address of the shared
22805 object associated with the thread local storage under consideration.
22806 Other operating environments may choose to represent the load module
22807 differently, so the precise meaning of this parameter will vary.
22811 @item @var{XX@dots{}}
22812 Hex encoded (big endian) bytes representing the address of the thread
22813 local storage requested.
22815 @item @code{E}@var{nn} (where @var{nn} are hex digits)
22818 @item @code{""} (empty)
22819 An empty reply indicates that @code{qGetTLSAddr} is not supported by the stub.
22822 Use of this request packet is controlled by the @code{set remote
22823 get-thread-local-storage-address} command (@pxref{Remote
22824 configuration, set remote get-thread-local-storage-address}).
22828 @node Register Packet Format
22829 @section Register Packet Format
22831 The following @samp{g}/@samp{G} packets have previously been defined.
22832 In the below, some thirty-two bit registers are transferred as
22833 sixty-four bits. Those registers should be zero/sign extended (which?)
22834 to fill the space allocated. Register bytes are transfered in target
22835 byte order. The two nibbles within a register byte are transfered
22836 most-significant - least-significant.
22842 All registers are transfered as thirty-two bit quantities in the order:
22843 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
22844 registers; fsr; fir; fp.
22848 All registers are transfered as sixty-four bit quantities (including
22849 thirty-two bit registers such as @code{sr}). The ordering is the same
22857 Example sequence of a target being re-started. Notice how the restart
22858 does not get any direct output:
22863 @emph{target restarts}
22866 <- @code{T001:1234123412341234}
22870 Example sequence of a target being stepped by a single instruction:
22873 -> @code{G1445@dots{}}
22878 <- @code{T001:1234123412341234}
22882 <- @code{1455@dots{}}
22886 @node File-I/O remote protocol extension
22887 @section File-I/O remote protocol extension
22888 @cindex File-I/O remote protocol extension
22891 * File-I/O Overview::
22892 * Protocol basics::
22893 * The F request packet::
22894 * The F reply packet::
22895 * Memory transfer::
22896 * The Ctrl-C message::
22898 * The isatty call::
22899 * The system call::
22900 * List of supported calls::
22901 * Protocol specific representation of datatypes::
22903 * File-I/O Examples::
22906 @node File-I/O Overview
22907 @subsection File-I/O Overview
22908 @cindex file-i/o overview
22910 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
22911 target to use the host's file system and console I/O when calling various
22912 system calls. System calls on the target system are translated into a
22913 remote protocol packet to the host system which then performs the needed
22914 actions and returns with an adequate response packet to the target system.
22915 This simulates file system operations even on targets that lack file systems.
22917 The protocol is defined host- and target-system independent. It uses
22918 its own independent representation of datatypes and values. Both,
22919 @value{GDBN} and the target's @value{GDBN} stub are responsible for
22920 translating the system dependent values into the unified protocol values
22921 when data is transmitted.
22923 The communication is synchronous. A system call is possible only
22924 when GDB is waiting for the @samp{C}, @samp{c}, @samp{S} or @samp{s}
22925 packets. While @value{GDBN} handles the request for a system call,
22926 the target is stopped to allow deterministic access to the target's
22927 memory. Therefore File-I/O is not interuptible by target signals. It
22928 is possible to interrupt File-I/O by a user interrupt (Ctrl-C), though.
22930 The target's request to perform a host system call does not finish
22931 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
22932 after finishing the system call, the target returns to continuing the
22933 previous activity (continue, step). No additional continue or step
22934 request from @value{GDBN} is required.
22937 (@value{GDBP}) continue
22938 <- target requests 'system call X'
22939 target is stopped, @value{GDBN} executes system call
22940 -> GDB returns result
22941 ... target continues, GDB returns to wait for the target
22942 <- target hits breakpoint and sends a Txx packet
22945 The protocol is only used for files on the host file system and
22946 for I/O on the console. Character or block special devices, pipes,
22947 named pipes or sockets or any other communication method on the host
22948 system are not supported by this protocol.
22950 @node Protocol basics
22951 @subsection Protocol basics
22952 @cindex protocol basics, file-i/o
22954 The File-I/O protocol uses the @code{F} packet, as request as well
22955 as as reply packet. Since a File-I/O system call can only occur when
22956 @value{GDBN} is waiting for the continuing or stepping target, the
22957 File-I/O request is a reply that @value{GDBN} has to expect as a result
22958 of a former @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
22959 This @code{F} packet contains all information needed to allow @value{GDBN}
22960 to call the appropriate host system call:
22964 A unique identifier for the requested system call.
22967 All parameters to the system call. Pointers are given as addresses
22968 in the target memory address space. Pointers to strings are given as
22969 pointer/length pair. Numerical values are given as they are.
22970 Numerical control values are given in a protocol specific representation.
22974 At that point @value{GDBN} has to perform the following actions.
22978 If parameter pointer values are given, which point to data needed as input
22979 to a system call, @value{GDBN} requests this data from the target with a
22980 standard @code{m} packet request. This additional communication has to be
22981 expected by the target implementation and is handled as any other @code{m}
22985 @value{GDBN} translates all value from protocol representation to host
22986 representation as needed. Datatypes are coerced into the host types.
22989 @value{GDBN} calls the system call
22992 It then coerces datatypes back to protocol representation.
22995 If pointer parameters in the request packet point to buffer space in which
22996 a system call is expected to copy data to, the data is transmitted to the
22997 target using a @code{M} or @code{X} packet. This packet has to be expected
22998 by the target implementation and is handled as any other @code{M} or @code{X}
23003 Eventually @value{GDBN} replies with another @code{F} packet which contains all
23004 necessary information for the target to continue. This at least contains
23011 @code{errno}, if has been changed by the system call.
23018 After having done the needed type and value coercion, the target continues
23019 the latest continue or step action.
23021 @node The F request packet
23022 @subsection The @code{F} request packet
23023 @cindex file-i/o request packet
23024 @cindex @code{F} request packet
23026 The @code{F} request packet has the following format:
23031 @code{F}@var{call-id}@code{,}@var{parameter@dots{}}
23034 @var{call-id} is the identifier to indicate the host system call to be called.
23035 This is just the name of the function.
23037 @var{parameter@dots{}} are the parameters to the system call.
23041 Parameters are hexadecimal integer values, either the real values in case
23042 of scalar datatypes, as pointers to target buffer space in case of compound
23043 datatypes and unspecified memory areas or as pointer/length pairs in case
23044 of string parameters. These are appended to the call-id, each separated
23045 from its predecessor by a comma. All values are transmitted in ASCII
23046 string representation, pointer/length pairs separated by a slash.
23048 @node The F reply packet
23049 @subsection The @code{F} reply packet
23050 @cindex file-i/o reply packet
23051 @cindex @code{F} reply packet
23053 The @code{F} reply packet has the following format:
23058 @code{F}@var{retcode}@code{,}@var{errno}@code{,}@var{Ctrl-C flag}@code{;}@var{call specific attachment}
23061 @var{retcode} is the return code of the system call as hexadecimal value.
23063 @var{errno} is the errno set by the call, in protocol specific representation.
23064 This parameter can be omitted if the call was successful.
23066 @var{Ctrl-C flag} is only send if the user requested a break. In this
23067 case, @var{errno} must be send as well, even if the call was successful.
23068 The @var{Ctrl-C flag} itself consists of the character 'C':
23075 or, if the call was interupted before the host call has been performed:
23082 assuming 4 is the protocol specific representation of @code{EINTR}.
23086 @node Memory transfer
23087 @subsection Memory transfer
23088 @cindex memory transfer, in file-i/o protocol
23090 Structured data which is transferred using a memory read or write as e.g.@:
23091 a @code{struct stat} is expected to be in a protocol specific format with
23092 all scalar multibyte datatypes being big endian. This should be done by
23093 the target before the @code{F} packet is sent resp.@: by @value{GDBN} before
23094 it transfers memory to the target. Transferred pointers to structured
23095 data should point to the already coerced data at any time.
23097 @node The Ctrl-C message
23098 @subsection The Ctrl-C message
23099 @cindex ctrl-c message, in file-i/o protocol
23101 A special case is, if the @var{Ctrl-C flag} is set in the @value{GDBN}
23102 reply packet. In this case the target should behave, as if it had
23103 gotten a break message. The meaning for the target is ``system call
23104 interupted by @code{SIGINT}''. Consequentially, the target should actually stop
23105 (as with a break message) and return to @value{GDBN} with a @code{T02}
23106 packet. In this case, it's important for the target to know, in which
23107 state the system call was interrupted. Since this action is by design
23108 not an atomic operation, we have to differ between two cases:
23112 The system call hasn't been performed on the host yet.
23115 The system call on the host has been finished.
23119 These two states can be distinguished by the target by the value of the
23120 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
23121 call hasn't been performed. This is equivalent to the @code{EINTR} handling
23122 on POSIX systems. In any other case, the target may presume that the
23123 system call has been finished --- successful or not --- and should behave
23124 as if the break message arrived right after the system call.
23126 @value{GDBN} must behave reliable. If the system call has not been called
23127 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
23128 @code{errno} in the packet. If the system call on the host has been finished
23129 before the user requests a break, the full action must be finshed by
23130 @value{GDBN}. This requires sending @code{M} or @code{X} packets as they fit.
23131 The @code{F} packet may only be send when either nothing has happened
23132 or the full action has been completed.
23135 @subsection Console I/O
23136 @cindex console i/o as part of file-i/o
23138 By default and if not explicitely closed by the target system, the file
23139 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
23140 on the @value{GDBN} console is handled as any other file output operation
23141 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
23142 by @value{GDBN} so that after the target read request from file descriptor
23143 0 all following typing is buffered until either one of the following
23148 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, the
23150 system call is treated as finished.
23153 The user presses @kbd{Enter}. This is treated as end of input with a trailing
23157 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
23158 character, especially no Ctrl-D is appended to the input.
23162 If the user has typed more characters as fit in the buffer given to
23163 the read call, the trailing characters are buffered in @value{GDBN} until
23164 either another @code{read(0, @dots{})} is requested by the target or debugging
23165 is stopped on users request.
23167 @node The isatty call
23168 @subsection The @samp{isatty} function call
23169 @cindex isatty call, file-i/o protocol
23171 A special case in this protocol is the library call @code{isatty} which
23172 is implemented as its own call inside of this protocol. It returns
23173 1 to the target if the file descriptor given as parameter is attached
23174 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
23175 would require implementing @code{ioctl} and would be more complex than
23178 @node The system call
23179 @subsection The @samp{system} function call
23180 @cindex system call, file-i/o protocol
23182 The other special case in this protocol is the @code{system} call which
23183 is implemented as its own call, too. @value{GDBN} is taking over the full
23184 task of calling the necessary host calls to perform the @code{system}
23185 call. The return value of @code{system} is simplified before it's returned
23186 to the target. Basically, the only signal transmitted back is @code{EINTR}
23187 in case the user pressed @kbd{Ctrl-C}. Otherwise the return value consists
23188 entirely of the exit status of the called command.
23190 Due to security concerns, the @code{system} call is by default refused
23191 by @value{GDBN}. The user has to allow this call explicitly with the
23192 @kbd{set remote system-call-allowed 1} command.
23195 @item set remote system-call-allowed
23196 @kindex set remote system-call-allowed
23197 Control whether to allow the @code{system} calls in the File I/O
23198 protocol for the remote target. The default is zero (disabled).
23200 @item show remote system-call-allowed
23201 @kindex show remote system-call-allowed
23202 Show the current setting of system calls for the remote File I/O
23206 @node List of supported calls
23207 @subsection List of supported calls
23208 @cindex list of supported file-i/o calls
23225 @unnumberedsubsubsec open
23226 @cindex open, file-i/o system call
23230 int open(const char *pathname, int flags);
23231 int open(const char *pathname, int flags, mode_t mode);
23234 Fopen,pathptr/len,flags,mode
23238 @code{flags} is the bitwise or of the following values:
23242 If the file does not exist it will be created. The host
23243 rules apply as far as file ownership and time stamps
23247 When used with O_CREAT, if the file already exists it is
23248 an error and open() fails.
23251 If the file already exists and the open mode allows
23252 writing (O_RDWR or O_WRONLY is given) it will be
23253 truncated to length 0.
23256 The file is opened in append mode.
23259 The file is opened for reading only.
23262 The file is opened for writing only.
23265 The file is opened for reading and writing.
23268 Each other bit is silently ignored.
23273 @code{mode} is the bitwise or of the following values:
23277 User has read permission.
23280 User has write permission.
23283 Group has read permission.
23286 Group has write permission.
23289 Others have read permission.
23292 Others have write permission.
23295 Each other bit is silently ignored.
23300 @exdent Return value:
23301 open returns the new file descriptor or -1 if an error
23309 pathname already exists and O_CREAT and O_EXCL were used.
23312 pathname refers to a directory.
23315 The requested access is not allowed.
23318 pathname was too long.
23321 A directory component in pathname does not exist.
23324 pathname refers to a device, pipe, named pipe or socket.
23327 pathname refers to a file on a read-only filesystem and
23328 write access was requested.
23331 pathname is an invalid pointer value.
23334 No space on device to create the file.
23337 The process already has the maximum number of files open.
23340 The limit on the total number of files open on the system
23344 The call was interrupted by the user.
23348 @unnumberedsubsubsec close
23349 @cindex close, file-i/o system call
23358 @exdent Return value:
23359 close returns zero on success, or -1 if an error occurred.
23366 fd isn't a valid open file descriptor.
23369 The call was interrupted by the user.
23373 @unnumberedsubsubsec read
23374 @cindex read, file-i/o system call
23378 int read(int fd, void *buf, unsigned int count);
23381 Fread,fd,bufptr,count
23383 @exdent Return value:
23384 On success, the number of bytes read is returned.
23385 Zero indicates end of file. If count is zero, read
23386 returns zero as well. On error, -1 is returned.
23393 fd is not a valid file descriptor or is not open for
23397 buf is an invalid pointer value.
23400 The call was interrupted by the user.
23404 @unnumberedsubsubsec write
23405 @cindex write, file-i/o system call
23409 int write(int fd, const void *buf, unsigned int count);
23412 Fwrite,fd,bufptr,count
23414 @exdent Return value:
23415 On success, the number of bytes written are returned.
23416 Zero indicates nothing was written. On error, -1
23424 fd is not a valid file descriptor or is not open for
23428 buf is an invalid pointer value.
23431 An attempt was made to write a file that exceeds the
23432 host specific maximum file size allowed.
23435 No space on device to write the data.
23438 The call was interrupted by the user.
23442 @unnumberedsubsubsec lseek
23443 @cindex lseek, file-i/o system call
23447 long lseek (int fd, long offset, int flag);
23450 Flseek,fd,offset,flag
23453 @code{flag} is one of:
23457 The offset is set to offset bytes.
23460 The offset is set to its current location plus offset
23464 The offset is set to the size of the file plus offset
23469 @exdent Return value:
23470 On success, the resulting unsigned offset in bytes from
23471 the beginning of the file is returned. Otherwise, a
23472 value of -1 is returned.
23479 fd is not a valid open file descriptor.
23482 fd is associated with the @value{GDBN} console.
23485 flag is not a proper value.
23488 The call was interrupted by the user.
23492 @unnumberedsubsubsec rename
23493 @cindex rename, file-i/o system call
23497 int rename(const char *oldpath, const char *newpath);
23500 Frename,oldpathptr/len,newpathptr/len
23502 @exdent Return value:
23503 On success, zero is returned. On error, -1 is returned.
23510 newpath is an existing directory, but oldpath is not a
23514 newpath is a non-empty directory.
23517 oldpath or newpath is a directory that is in use by some
23521 An attempt was made to make a directory a subdirectory
23525 A component used as a directory in oldpath or new
23526 path is not a directory. Or oldpath is a directory
23527 and newpath exists but is not a directory.
23530 oldpathptr or newpathptr are invalid pointer values.
23533 No access to the file or the path of the file.
23537 oldpath or newpath was too long.
23540 A directory component in oldpath or newpath does not exist.
23543 The file is on a read-only filesystem.
23546 The device containing the file has no room for the new
23550 The call was interrupted by the user.
23554 @unnumberedsubsubsec unlink
23555 @cindex unlink, file-i/o system call
23559 int unlink(const char *pathname);
23562 Funlink,pathnameptr/len
23564 @exdent Return value:
23565 On success, zero is returned. On error, -1 is returned.
23572 No access to the file or the path of the file.
23575 The system does not allow unlinking of directories.
23578 The file pathname cannot be unlinked because it's
23579 being used by another process.
23582 pathnameptr is an invalid pointer value.
23585 pathname was too long.
23588 A directory component in pathname does not exist.
23591 A component of the path is not a directory.
23594 The file is on a read-only filesystem.
23597 The call was interrupted by the user.
23601 @unnumberedsubsubsec stat/fstat
23602 @cindex fstat, file-i/o system call
23603 @cindex stat, file-i/o system call
23607 int stat(const char *pathname, struct stat *buf);
23608 int fstat(int fd, struct stat *buf);
23611 Fstat,pathnameptr/len,bufptr
23614 @exdent Return value:
23615 On success, zero is returned. On error, -1 is returned.
23622 fd is not a valid open file.
23625 A directory component in pathname does not exist or the
23626 path is an empty string.
23629 A component of the path is not a directory.
23632 pathnameptr is an invalid pointer value.
23635 No access to the file or the path of the file.
23638 pathname was too long.
23641 The call was interrupted by the user.
23645 @unnumberedsubsubsec gettimeofday
23646 @cindex gettimeofday, file-i/o system call
23650 int gettimeofday(struct timeval *tv, void *tz);
23653 Fgettimeofday,tvptr,tzptr
23655 @exdent Return value:
23656 On success, 0 is returned, -1 otherwise.
23663 tz is a non-NULL pointer.
23666 tvptr and/or tzptr is an invalid pointer value.
23670 @unnumberedsubsubsec isatty
23671 @cindex isatty, file-i/o system call
23675 int isatty(int fd);
23680 @exdent Return value:
23681 Returns 1 if fd refers to the @value{GDBN} console, 0 otherwise.
23688 The call was interrupted by the user.
23692 @unnumberedsubsubsec system
23693 @cindex system, file-i/o system call
23697 int system(const char *command);
23700 Fsystem,commandptr/len
23702 @exdent Return value:
23703 The value returned is -1 on error and the return status
23704 of the command otherwise. Only the exit status of the
23705 command is returned, which is extracted from the hosts
23706 system return value by calling WEXITSTATUS(retval).
23707 In case /bin/sh could not be executed, 127 is returned.
23714 The call was interrupted by the user.
23717 @node Protocol specific representation of datatypes
23718 @subsection Protocol specific representation of datatypes
23719 @cindex protocol specific representation of datatypes, in file-i/o protocol
23722 * Integral datatypes::
23728 @node Integral datatypes
23729 @unnumberedsubsubsec Integral datatypes
23730 @cindex integral datatypes, in file-i/o protocol
23732 The integral datatypes used in the system calls are
23735 int@r{,} unsigned int@r{,} long@r{,} unsigned long@r{,} mode_t @r{and} time_t
23738 @code{Int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
23739 implemented as 32 bit values in this protocol.
23741 @code{Long} and @code{unsigned long} are implemented as 64 bit types.
23743 @xref{Limits}, for corresponding MIN and MAX values (similar to those
23744 in @file{limits.h}) to allow range checking on host and target.
23746 @code{time_t} datatypes are defined as seconds since the Epoch.
23748 All integral datatypes transferred as part of a memory read or write of a
23749 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
23752 @node Pointer values
23753 @unnumberedsubsubsec Pointer values
23754 @cindex pointer values, in file-i/o protocol
23756 Pointers to target data are transmitted as they are. An exception
23757 is made for pointers to buffers for which the length isn't
23758 transmitted as part of the function call, namely strings. Strings
23759 are transmitted as a pointer/length pair, both as hex values, e.g.@:
23766 which is a pointer to data of length 18 bytes at position 0x1aaf.
23767 The length is defined as the full string length in bytes, including
23768 the trailing null byte. Example:
23771 ``hello, world'' at address 0x123456
23782 @unnumberedsubsubsec struct stat
23783 @cindex struct stat, in file-i/o protocol
23785 The buffer of type struct stat used by the target and @value{GDBN} is defined
23790 unsigned int st_dev; /* device */
23791 unsigned int st_ino; /* inode */
23792 mode_t st_mode; /* protection */
23793 unsigned int st_nlink; /* number of hard links */
23794 unsigned int st_uid; /* user ID of owner */
23795 unsigned int st_gid; /* group ID of owner */
23796 unsigned int st_rdev; /* device type (if inode device) */
23797 unsigned long st_size; /* total size, in bytes */
23798 unsigned long st_blksize; /* blocksize for filesystem I/O */
23799 unsigned long st_blocks; /* number of blocks allocated */
23800 time_t st_atime; /* time of last access */
23801 time_t st_mtime; /* time of last modification */
23802 time_t st_ctime; /* time of last change */
23806 The integral datatypes are conforming to the definitions given in the
23807 approriate section (see @ref{Integral datatypes}, for details) so this
23808 structure is of size 64 bytes.
23810 The values of several fields have a restricted meaning and/or
23817 st_ino: No valid meaning for the target. Transmitted unchanged.
23819 st_mode: Valid mode bits are described in Appendix C. Any other
23820 bits have currently no meaning for the target.
23822 st_uid: No valid meaning for the target. Transmitted unchanged.
23824 st_gid: No valid meaning for the target. Transmitted unchanged.
23826 st_rdev: No valid meaning for the target. Transmitted unchanged.
23828 st_atime, st_mtime, st_ctime:
23829 These values have a host and file system dependent
23830 accuracy. Especially on Windows hosts the file systems
23831 don't support exact timing values.
23834 The target gets a struct stat of the above representation and is
23835 responsible to coerce it to the target representation before
23838 Note that due to size differences between the host and target
23839 representation of stat members, these members could eventually
23840 get truncated on the target.
23842 @node struct timeval
23843 @unnumberedsubsubsec struct timeval
23844 @cindex struct timeval, in file-i/o protocol
23846 The buffer of type struct timeval used by the target and @value{GDBN}
23847 is defined as follows:
23851 time_t tv_sec; /* second */
23852 long tv_usec; /* microsecond */
23856 The integral datatypes are conforming to the definitions given in the
23857 approriate section (see @ref{Integral datatypes}, for details) so this
23858 structure is of size 8 bytes.
23861 @subsection Constants
23862 @cindex constants, in file-i/o protocol
23864 The following values are used for the constants inside of the
23865 protocol. @value{GDBN} and target are resposible to translate these
23866 values before and after the call as needed.
23877 @unnumberedsubsubsec Open flags
23878 @cindex open flags, in file-i/o protocol
23880 All values are given in hexadecimal representation.
23892 @node mode_t values
23893 @unnumberedsubsubsec mode_t values
23894 @cindex mode_t values, in file-i/o protocol
23896 All values are given in octal representation.
23913 @unnumberedsubsubsec Errno values
23914 @cindex errno values, in file-i/o protocol
23916 All values are given in decimal representation.
23941 EUNKNOWN is used as a fallback error value if a host system returns
23942 any error value not in the list of supported error numbers.
23945 @unnumberedsubsubsec Lseek flags
23946 @cindex lseek flags, in file-i/o protocol
23955 @unnumberedsubsubsec Limits
23956 @cindex limits, in file-i/o protocol
23958 All values are given in decimal representation.
23961 INT_MIN -2147483648
23963 UINT_MAX 4294967295
23964 LONG_MIN -9223372036854775808
23965 LONG_MAX 9223372036854775807
23966 ULONG_MAX 18446744073709551615
23969 @node File-I/O Examples
23970 @subsection File-I/O Examples
23971 @cindex file-i/o examples
23973 Example sequence of a write call, file descriptor 3, buffer is at target
23974 address 0x1234, 6 bytes should be written:
23977 <- @code{Fwrite,3,1234,6}
23978 @emph{request memory read from target}
23981 @emph{return "6 bytes written"}
23985 Example sequence of a read call, file descriptor 3, buffer is at target
23986 address 0x1234, 6 bytes should be read:
23989 <- @code{Fread,3,1234,6}
23990 @emph{request memory write to target}
23991 -> @code{X1234,6:XXXXXX}
23992 @emph{return "6 bytes read"}
23996 Example sequence of a read call, call fails on the host due to invalid
23997 file descriptor (EBADF):
24000 <- @code{Fread,3,1234,6}
24004 Example sequence of a read call, user presses Ctrl-C before syscall on
24008 <- @code{Fread,3,1234,6}
24013 Example sequence of a read call, user presses Ctrl-C after syscall on
24017 <- @code{Fread,3,1234,6}
24018 -> @code{X1234,6:XXXXXX}
24022 @include agentexpr.texi
24036 % I think something like @colophon should be in texinfo. In the
24038 \long\def\colophon{\hbox to0pt{}\vfill
24039 \centerline{The body of this manual is set in}
24040 \centerline{\fontname\tenrm,}
24041 \centerline{with headings in {\bf\fontname\tenbf}}
24042 \centerline{and examples in {\tt\fontname\tentt}.}
24043 \centerline{{\it\fontname\tenit\/},}
24044 \centerline{{\bf\fontname\tenbf}, and}
24045 \centerline{{\sl\fontname\tensl\/}}
24046 \centerline{are used for emphasis.}\vfill}
24048 % Blame: doc@cygnus.com, 1991.