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{Support,,Supported languages}.
199 For more information, see @ref{C,,C and C++}.
202 Support for Modula-2 is partial. For information on Modula-2, see
203 @ref{Modula-2,,Modula-2}.
206 Debugging Pascal programs which use sets, subranges, file variables, or
207 nested functions does not currently work. @value{GDBN} does not support
208 entering expressions, printing values, or similar features using Pascal
212 @value{GDBN} can be used to debug programs written in Fortran, although
213 it may be necessary to refer to some variables with a trailing
216 @value{GDBN} can be used to debug programs written in Objective-C,
217 using either the Apple/NeXT or the GNU Objective-C runtime.
220 * Free Software:: Freely redistributable software
221 * Contributors:: Contributors to GDB
225 @unnumberedsec Free software
227 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
228 General Public License
229 (GPL). The GPL gives you the freedom to copy or adapt a licensed
230 program---but every person getting a copy also gets with it the
231 freedom to modify that copy (which means that they must get access to
232 the source code), and the freedom to distribute further copies.
233 Typical software companies use copyrights to limit your freedoms; the
234 Free Software Foundation uses the GPL to preserve these freedoms.
236 Fundamentally, the General Public License is a license which says that
237 you have these freedoms and that you cannot take these freedoms away
240 @unnumberedsec Free Software Needs Free Documentation
242 The biggest deficiency in the free software community today is not in
243 the software---it is the lack of good free documentation that we can
244 include with the free software. Many of our most important
245 programs do not come with free reference manuals and free introductory
246 texts. Documentation is an essential part of any software package;
247 when an important free software package does not come with a free
248 manual and a free tutorial, that is a major gap. We have many such
251 Consider Perl, for instance. The tutorial manuals that people
252 normally use are non-free. How did this come about? Because the
253 authors of those manuals published them with restrictive terms---no
254 copying, no modification, source files not available---which exclude
255 them from the free software world.
257 That wasn't the first time this sort of thing happened, and it was far
258 from the last. Many times we have heard a GNU user eagerly describe a
259 manual that he is writing, his intended contribution to the community,
260 only to learn that he had ruined everything by signing a publication
261 contract to make it non-free.
263 Free documentation, like free software, is a matter of freedom, not
264 price. The problem with the non-free manual is not that publishers
265 charge a price for printed copies---that in itself is fine. (The Free
266 Software Foundation sells printed copies of manuals, too.) The
267 problem is the restrictions on the use of the manual. Free manuals
268 are available in source code form, and give you permission to copy and
269 modify. Non-free manuals do not allow this.
271 The criteria of freedom for a free manual are roughly the same as for
272 free software. Redistribution (including the normal kinds of
273 commercial redistribution) must be permitted, so that the manual can
274 accompany every copy of the program, both on-line and on paper.
276 Permission for modification of the technical content is crucial too.
277 When people modify the software, adding or changing features, if they
278 are conscientious they will change the manual too---so they can
279 provide accurate and clear documentation for the modified program. A
280 manual that leaves you no choice but to write a new manual to document
281 a changed version of the program is not really available to our
284 Some kinds of limits on the way modification is handled are
285 acceptable. For example, requirements to preserve the original
286 author's copyright notice, the distribution terms, or the list of
287 authors, are ok. It is also no problem to require modified versions
288 to include notice that they were modified. Even entire sections that
289 may not be deleted or changed are acceptable, as long as they deal
290 with nontechnical topics (like this one). These kinds of restrictions
291 are acceptable because they don't obstruct the community's normal use
294 However, it must be possible to modify all the @emph{technical}
295 content of the manual, and then distribute the result in all the usual
296 media, through all the usual channels. Otherwise, the restrictions
297 obstruct the use of the manual, it is not free, and we need another
298 manual to replace it.
300 Please spread the word about this issue. Our community continues to
301 lose manuals to proprietary publishing. If we spread the word that
302 free software needs free reference manuals and free tutorials, perhaps
303 the next person who wants to contribute by writing documentation will
304 realize, before it is too late, that only free manuals contribute to
305 the free software community.
307 If you are writing documentation, please insist on publishing it under
308 the GNU Free Documentation License or another free documentation
309 license. Remember that this decision requires your approval---you
310 don't have to let the publisher decide. Some commercial publishers
311 will use a free license if you insist, but they will not propose the
312 option; it is up to you to raise the issue and say firmly that this is
313 what you want. If the publisher you are dealing with refuses, please
314 try other publishers. If you're not sure whether a proposed license
315 is free, write to @email{licensing@@gnu.org}.
317 You can encourage commercial publishers to sell more free, copylefted
318 manuals and tutorials by buying them, and particularly by buying
319 copies from the publishers that paid for their writing or for major
320 improvements. Meanwhile, try to avoid buying non-free documentation
321 at all. Check the distribution terms of a manual before you buy it,
322 and insist that whoever seeks your business must respect your freedom.
323 Check the history of the book, and try to reward the publishers that
324 have paid or pay the authors to work on it.
326 The Free Software Foundation maintains a list of free documentation
327 published by other publishers, at
328 @url{http://www.fsf.org/doc/other-free-books.html}.
331 @unnumberedsec Contributors to @value{GDBN}
333 Richard Stallman was the original author of @value{GDBN}, and of many
334 other @sc{gnu} programs. Many others have contributed to its
335 development. This section attempts to credit major contributors. One
336 of the virtues of free software is that everyone is free to contribute
337 to it; with regret, we cannot actually acknowledge everyone here. The
338 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
339 blow-by-blow account.
341 Changes much prior to version 2.0 are lost in the mists of time.
344 @emph{Plea:} Additions to this section are particularly welcome. If you
345 or your friends (or enemies, to be evenhanded) have been unfairly
346 omitted from this list, we would like to add your names!
349 So that they may not regard their many labors as thankless, we
350 particularly thank those who shepherded @value{GDBN} through major
352 Andrew Cagney (releases 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
353 Jim Blandy (release 4.18);
354 Jason Molenda (release 4.17);
355 Stan Shebs (release 4.14);
356 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
357 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
358 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
359 Jim Kingdon (releases 3.5, 3.4, and 3.3);
360 and Randy Smith (releases 3.2, 3.1, and 3.0).
362 Richard Stallman, assisted at various times by Peter TerMaat, Chris
363 Hanson, and Richard Mlynarik, handled releases through 2.8.
365 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
366 in @value{GDBN}, with significant additional contributions from Per
367 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
368 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
369 much general update work leading to release 3.0).
371 @value{GDBN} uses the BFD subroutine library to examine multiple
372 object-file formats; BFD was a joint project of David V.
373 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
375 David Johnson wrote the original COFF support; Pace Willison did
376 the original support for encapsulated COFF.
378 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
380 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
381 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
383 Jean-Daniel Fekete contributed Sun 386i support.
384 Chris Hanson improved the HP9000 support.
385 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
386 David Johnson contributed Encore Umax support.
387 Jyrki Kuoppala contributed Altos 3068 support.
388 Jeff Law contributed HP PA and SOM support.
389 Keith Packard contributed NS32K support.
390 Doug Rabson contributed Acorn Risc Machine support.
391 Bob Rusk contributed Harris Nighthawk CX-UX support.
392 Chris Smith contributed Convex support (and Fortran debugging).
393 Jonathan Stone contributed Pyramid support.
394 Michael Tiemann contributed SPARC support.
395 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
396 Pace Willison contributed Intel 386 support.
397 Jay Vosburgh contributed Symmetry support.
398 Marko Mlinar contributed OpenRISC 1000 support.
400 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
402 Rich Schaefer and Peter Schauer helped with support of SunOS shared
405 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
406 about several machine instruction sets.
408 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
409 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
410 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
411 and RDI targets, respectively.
413 Brian Fox is the author of the readline libraries providing
414 command-line editing and command history.
416 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
417 Modula-2 support, and contributed the Languages chapter of this manual.
419 Fred Fish wrote most of the support for Unix System Vr4.
420 He also enhanced the command-completion support to cover C@t{++} overloaded
423 Hitachi America (now Renesas America), Ltd. sponsored the support for
424 H8/300, H8/500, and Super-H processors.
426 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
428 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
431 Toshiba sponsored the support for the TX39 Mips processor.
433 Matsushita sponsored the support for the MN10200 and MN10300 processors.
435 Fujitsu sponsored the support for SPARClite and FR30 processors.
437 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
440 Michael Snyder added support for tracepoints.
442 Stu Grossman wrote gdbserver.
444 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
445 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
447 The following people at the Hewlett-Packard Company contributed
448 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
449 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
450 compiler, and the Text User Interface (nee Terminal User Interface):
451 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
452 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
453 provided HP-specific information in this manual.
455 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
456 Robert Hoehne made significant contributions to the DJGPP port.
458 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
459 development since 1991. Cygnus engineers who have worked on @value{GDBN}
460 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
461 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
462 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
463 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
464 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
465 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
466 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
467 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
468 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
469 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
470 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
471 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
472 Zuhn have made contributions both large and small.
474 Jim Blandy added support for preprocessor macros, while working for Red
478 @chapter A Sample @value{GDBN} Session
480 You can use this manual at your leisure to read all about @value{GDBN}.
481 However, a handful of commands are enough to get started using the
482 debugger. This chapter illustrates those commands.
485 In this sample session, we emphasize user input like this: @b{input},
486 to make it easier to pick out from the surrounding output.
489 @c FIXME: this example may not be appropriate for some configs, where
490 @c FIXME...primary interest is in remote use.
492 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
493 processor) exhibits the following bug: sometimes, when we change its
494 quote strings from the default, the commands used to capture one macro
495 definition within another stop working. In the following short @code{m4}
496 session, we define a macro @code{foo} which expands to @code{0000}; we
497 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
498 same thing. However, when we change the open quote string to
499 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
500 procedure fails to define a new synonym @code{baz}:
509 @b{define(bar,defn(`foo'))}
513 @b{changequote(<QUOTE>,<UNQUOTE>)}
515 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
518 m4: End of input: 0: fatal error: EOF in string
522 Let us use @value{GDBN} to try to see what is going on.
525 $ @b{@value{GDBP} m4}
526 @c FIXME: this falsifies the exact text played out, to permit smallbook
527 @c FIXME... format to come out better.
528 @value{GDBN} is free software and you are welcome to distribute copies
529 of it under certain conditions; type "show copying" to see
531 There is absolutely no warranty for @value{GDBN}; type "show warranty"
534 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
539 @value{GDBN} reads only enough symbol data to know where to find the
540 rest when needed; as a result, the first prompt comes up very quickly.
541 We now tell @value{GDBN} to use a narrower display width than usual, so
542 that examples fit in this manual.
545 (@value{GDBP}) @b{set width 70}
549 We need to see how the @code{m4} built-in @code{changequote} works.
550 Having looked at the source, we know the relevant subroutine is
551 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
552 @code{break} command.
555 (@value{GDBP}) @b{break m4_changequote}
556 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
560 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
561 control; as long as control does not reach the @code{m4_changequote}
562 subroutine, the program runs as usual:
565 (@value{GDBP}) @b{run}
566 Starting program: /work/Editorial/gdb/gnu/m4/m4
574 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
575 suspends execution of @code{m4}, displaying information about the
576 context where it stops.
579 @b{changequote(<QUOTE>,<UNQUOTE>)}
581 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
583 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
587 Now we use the command @code{n} (@code{next}) to advance execution to
588 the next line of the current function.
592 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
597 @code{set_quotes} looks like a promising subroutine. We can go into it
598 by using the command @code{s} (@code{step}) instead of @code{next}.
599 @code{step} goes to the next line to be executed in @emph{any}
600 subroutine, so it steps into @code{set_quotes}.
604 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
606 530 if (lquote != def_lquote)
610 The display that shows the subroutine where @code{m4} is now
611 suspended (and its arguments) is called a stack frame display. It
612 shows a summary of the stack. We can use the @code{backtrace}
613 command (which can also be spelled @code{bt}), to see where we are
614 in the stack as a whole: the @code{backtrace} command displays a
615 stack frame for each active subroutine.
618 (@value{GDBP}) @b{bt}
619 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
621 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
623 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
624 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
626 #4 0x79dc in expand_input () at macro.c:40
627 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
631 We step through a few more lines to see what happens. The first two
632 times, we can use @samp{s}; the next two times we use @code{n} to avoid
633 falling into the @code{xstrdup} subroutine.
637 0x3b5c 532 if (rquote != def_rquote)
639 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
640 def_lquote : xstrdup(lq);
642 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
645 538 len_lquote = strlen(rquote);
649 The last line displayed looks a little odd; we can examine the variables
650 @code{lquote} and @code{rquote} to see if they are in fact the new left
651 and right quotes we specified. We use the command @code{p}
652 (@code{print}) to see their values.
655 (@value{GDBP}) @b{p lquote}
656 $1 = 0x35d40 "<QUOTE>"
657 (@value{GDBP}) @b{p rquote}
658 $2 = 0x35d50 "<UNQUOTE>"
662 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
663 To look at some context, we can display ten lines of source
664 surrounding the current line with the @code{l} (@code{list}) command.
670 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
672 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
675 538 len_lquote = strlen(rquote);
676 539 len_rquote = strlen(lquote);
683 Let us step past the two lines that set @code{len_lquote} and
684 @code{len_rquote}, and then examine the values of those variables.
688 539 len_rquote = strlen(lquote);
691 (@value{GDBP}) @b{p len_lquote}
693 (@value{GDBP}) @b{p len_rquote}
698 That certainly looks wrong, assuming @code{len_lquote} and
699 @code{len_rquote} are meant to be the lengths of @code{lquote} and
700 @code{rquote} respectively. We can set them to better values using
701 the @code{p} command, since it can print the value of
702 any expression---and that expression can include subroutine calls and
706 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
708 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
713 Is that enough to fix the problem of using the new quotes with the
714 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
715 executing with the @code{c} (@code{continue}) command, and then try the
716 example that caused trouble initially:
722 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
729 Success! The new quotes now work just as well as the default ones. The
730 problem seems to have been just the two typos defining the wrong
731 lengths. We allow @code{m4} exit by giving it an EOF as input:
735 Program exited normally.
739 The message @samp{Program exited normally.} is from @value{GDBN}; it
740 indicates @code{m4} has finished executing. We can end our @value{GDBN}
741 session with the @value{GDBN} @code{quit} command.
744 (@value{GDBP}) @b{quit}
748 @chapter Getting In and Out of @value{GDBN}
750 This chapter discusses how to start @value{GDBN}, and how to get out of it.
754 type @samp{@value{GDBP}} to start @value{GDBN}.
756 type @kbd{quit} or @kbd{C-d} to exit.
760 * Invoking GDB:: How to start @value{GDBN}
761 * Quitting GDB:: How to quit @value{GDBN}
762 * Shell Commands:: How to use shell commands inside @value{GDBN}
763 * Logging output:: How to log @value{GDBN}'s output to a file
767 @section Invoking @value{GDBN}
769 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
770 @value{GDBN} reads commands from the terminal until you tell it to exit.
772 You can also run @code{@value{GDBP}} with a variety of arguments and options,
773 to specify more of your debugging environment at the outset.
775 The command-line options described here are designed
776 to cover a variety of situations; in some environments, some of these
777 options may effectively be unavailable.
779 The most usual way to start @value{GDBN} is with one argument,
780 specifying an executable program:
783 @value{GDBP} @var{program}
787 You can also start with both an executable program and a core file
791 @value{GDBP} @var{program} @var{core}
794 You can, instead, specify a process ID as a second argument, if you want
795 to debug a running process:
798 @value{GDBP} @var{program} 1234
802 would attach @value{GDBN} to process @code{1234} (unless you also have a file
803 named @file{1234}; @value{GDBN} does check for a core file first).
805 Taking advantage of the second command-line argument requires a fairly
806 complete operating system; when you use @value{GDBN} as a remote
807 debugger attached to a bare board, there may not be any notion of
808 ``process'', and there is often no way to get a core dump. @value{GDBN}
809 will warn you if it is unable to attach or to read core dumps.
811 You can optionally have @code{@value{GDBP}} pass any arguments after the
812 executable file to the inferior using @code{--args}. This option stops
815 gdb --args gcc -O2 -c foo.c
817 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
818 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
820 You can run @code{@value{GDBP}} without printing the front material, which describes
821 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
828 You can further control how @value{GDBN} starts up by using command-line
829 options. @value{GDBN} itself can remind you of the options available.
839 to display all available options and briefly describe their use
840 (@samp{@value{GDBP} -h} is a shorter equivalent).
842 All options and command line arguments you give are processed
843 in sequential order. The order makes a difference when the
844 @samp{-x} option is used.
848 * File Options:: Choosing files
849 * Mode Options:: Choosing modes
853 @subsection Choosing files
855 When @value{GDBN} starts, it reads any arguments other than options as
856 specifying an executable file and core file (or process ID). This is
857 the same as if the arguments were specified by the @samp{-se} and
858 @samp{-c} (or @samp{-p} options respectively. (@value{GDBN} reads the
859 first argument that does not have an associated option flag as
860 equivalent to the @samp{-se} option followed by that argument; and the
861 second argument that does not have an associated option flag, if any, as
862 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
863 If the second argument begins with a decimal digit, @value{GDBN} will
864 first attempt to attach to it as a process, and if that fails, attempt
865 to open it as a corefile. If you have a corefile whose name begins with
866 a digit, you can prevent @value{GDBN} from treating it as a pid by
867 prefixing it with @file{./}, eg. @file{./12345}.
869 If @value{GDBN} has not been configured to included core file support,
870 such as for most embedded targets, then it will complain about a second
871 argument and ignore it.
873 Many options have both long and short forms; both are shown in the
874 following list. @value{GDBN} also recognizes the long forms if you truncate
875 them, so long as enough of the option is present to be unambiguous.
876 (If you prefer, you can flag option arguments with @samp{--} rather
877 than @samp{-}, though we illustrate the more usual convention.)
879 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
880 @c way, both those who look for -foo and --foo in the index, will find
884 @item -symbols @var{file}
886 @cindex @code{--symbols}
888 Read symbol table from file @var{file}.
890 @item -exec @var{file}
892 @cindex @code{--exec}
894 Use file @var{file} as the executable file to execute when appropriate,
895 and for examining pure data in conjunction with a core dump.
899 Read symbol table from file @var{file} and use it as the executable
902 @item -core @var{file}
904 @cindex @code{--core}
906 Use file @var{file} as a core dump to examine.
908 @item -c @var{number}
909 @item -pid @var{number}
910 @itemx -p @var{number}
913 Connect to process ID @var{number}, as with the @code{attach} command.
914 If there is no such process, @value{GDBN} will attempt to open a core
915 file named @var{number}.
917 @item -command @var{file}
919 @cindex @code{--command}
921 Execute @value{GDBN} commands from file @var{file}. @xref{Command
922 Files,, Command files}.
924 @item -directory @var{directory}
925 @itemx -d @var{directory}
926 @cindex @code{--directory}
928 Add @var{directory} to the path to search for source files.
932 @cindex @code{--mapped}
934 @emph{Warning: this option depends on operating system facilities that are not
935 supported on all systems.}@*
936 If memory-mapped files are available on your system through the @code{mmap}
937 system call, you can use this option
938 to have @value{GDBN} write the symbols from your
939 program into a reusable file in the current directory. If the program you are debugging is
940 called @file{/tmp/fred}, the mapped symbol file is @file{/tmp/fred.syms}.
941 Future @value{GDBN} debugging sessions notice the presence of this file,
942 and can quickly map in symbol information from it, rather than reading
943 the symbol table from the executable program.
945 The @file{.syms} file is specific to the host machine where @value{GDBN}
946 is run. It holds an exact image of the internal @value{GDBN} symbol
947 table. It cannot be shared across multiple host platforms.
951 @cindex @code{--readnow}
953 Read each symbol file's entire symbol table immediately, rather than
954 the default, which is to read it incrementally as it is needed.
955 This makes startup slower, but makes future operations faster.
959 You typically combine the @code{-mapped} and @code{-readnow} options in
960 order to build a @file{.syms} file that contains complete symbol
961 information. (@xref{Files,,Commands to specify files}, for information
962 on @file{.syms} files.) A simple @value{GDBN} invocation to do nothing
963 but build a @file{.syms} file for future use is:
966 gdb -batch -nx -mapped -readnow programname
970 @subsection Choosing modes
972 You can run @value{GDBN} in various alternative modes---for example, in
973 batch mode or quiet mode.
980 Do not execute commands found in any initialization files. Normally,
981 @value{GDBN} executes the commands in these files after all the command
982 options and arguments have been processed. @xref{Command Files,,Command
988 @cindex @code{--quiet}
989 @cindex @code{--silent}
991 ``Quiet''. Do not print the introductory and copyright messages. These
992 messages are also suppressed in batch mode.
995 @cindex @code{--batch}
996 Run in batch mode. Exit with status @code{0} after processing all the
997 command files specified with @samp{-x} (and all commands from
998 initialization files, if not inhibited with @samp{-n}). Exit with
999 nonzero status if an error occurs in executing the @value{GDBN} commands
1000 in the command files.
1002 Batch mode may be useful for running @value{GDBN} as a filter, for
1003 example to download and run a program on another computer; in order to
1004 make this more useful, the message
1007 Program exited normally.
1011 (which is ordinarily issued whenever a program running under
1012 @value{GDBN} control terminates) is not issued when running in batch
1017 @cindex @code{--nowindows}
1019 ``No windows''. If @value{GDBN} comes with a graphical user interface
1020 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1021 interface. If no GUI is available, this option has no effect.
1025 @cindex @code{--windows}
1027 If @value{GDBN} includes a GUI, then this option requires it to be
1030 @item -cd @var{directory}
1032 Run @value{GDBN} using @var{directory} as its working directory,
1033 instead of the current directory.
1037 @cindex @code{--fullname}
1039 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1040 subprocess. It tells @value{GDBN} to output the full file name and line
1041 number in a standard, recognizable fashion each time a stack frame is
1042 displayed (which includes each time your program stops). This
1043 recognizable format looks like two @samp{\032} characters, followed by
1044 the file name, line number and character position separated by colons,
1045 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1046 @samp{\032} characters as a signal to display the source code for the
1050 @cindex @code{--epoch}
1051 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1052 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1053 routines so as to allow Epoch to display values of expressions in a
1056 @item -annotate @var{level}
1057 @cindex @code{--annotate}
1058 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1059 effect is identical to using @samp{set annotate @var{level}}
1060 (@pxref{Annotations}). The annotation @var{level} controls how much
1061 information @value{GDBN} prints together with its prompt, values of
1062 expressions, source lines, and other types of output. Level 0 is the
1063 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1064 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1065 that control @value{GDBN}, and level 2 has been deprecated.
1067 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
1071 @cindex @code{--args}
1072 Change interpretation of command line so that arguments following the
1073 executable file are passed as command line arguments to the inferior.
1074 This option stops option processing.
1076 @item -baud @var{bps}
1078 @cindex @code{--baud}
1080 Set the line speed (baud rate or bits per second) of any serial
1081 interface used by @value{GDBN} for remote debugging.
1083 @item -l @var{timeout}
1085 Set the timeout (in seconds) of any communication used by @value{GDBN}
1086 for remote debugging.
1088 @item -tty @var{device}
1089 @itemx -t @var{device}
1090 @cindex @code{--tty}
1092 Run using @var{device} for your program's standard input and output.
1093 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1095 @c resolve the situation of these eventually
1097 @cindex @code{--tui}
1098 Activate the @dfn{Text User Interface} when starting. The Text User
1099 Interface manages several text windows on the terminal, showing
1100 source, assembly, registers and @value{GDBN} command outputs
1101 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1102 Text User Interface can be enabled by invoking the program
1103 @samp{gdbtui}. Do not use this option if you run @value{GDBN} from
1104 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1107 @c @cindex @code{--xdb}
1108 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1109 @c For information, see the file @file{xdb_trans.html}, which is usually
1110 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1113 @item -interpreter @var{interp}
1114 @cindex @code{--interpreter}
1115 Use the interpreter @var{interp} for interface with the controlling
1116 program or device. This option is meant to be set by programs which
1117 communicate with @value{GDBN} using it as a back end.
1118 @xref{Interpreters, , Command Interpreters}.
1120 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1121 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1122 The @sc{gdb/mi} Interface}) included since @var{GDBN} version 6.0. The
1123 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1124 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1125 @sc{gdb/mi} interfaces are no longer supported.
1128 @cindex @code{--write}
1129 Open the executable and core files for both reading and writing. This
1130 is equivalent to the @samp{set write on} command inside @value{GDBN}
1134 @cindex @code{--statistics}
1135 This option causes @value{GDBN} to print statistics about time and
1136 memory usage after it completes each command and returns to the prompt.
1139 @cindex @code{--version}
1140 This option causes @value{GDBN} to print its version number and
1141 no-warranty blurb, and exit.
1146 @section Quitting @value{GDBN}
1147 @cindex exiting @value{GDBN}
1148 @cindex leaving @value{GDBN}
1151 @kindex quit @r{[}@var{expression}@r{]}
1152 @kindex q @r{(@code{quit})}
1153 @item quit @r{[}@var{expression}@r{]}
1155 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1156 @code{q}), or type an end-of-file character (usually @kbd{C-d}). If you
1157 do not supply @var{expression}, @value{GDBN} will terminate normally;
1158 otherwise it will terminate using the result of @var{expression} as the
1163 An interrupt (often @kbd{C-c}) does not exit from @value{GDBN}, but rather
1164 terminates the action of any @value{GDBN} command that is in progress and
1165 returns to @value{GDBN} command level. It is safe to type the interrupt
1166 character at any time because @value{GDBN} does not allow it to take effect
1167 until a time when it is safe.
1169 If you have been using @value{GDBN} to control an attached process or
1170 device, you can release it with the @code{detach} command
1171 (@pxref{Attach, ,Debugging an already-running process}).
1173 @node Shell Commands
1174 @section Shell commands
1176 If you need to execute occasional shell commands during your
1177 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1178 just use the @code{shell} command.
1182 @cindex shell escape
1183 @item shell @var{command string}
1184 Invoke a standard shell to execute @var{command string}.
1185 If it exists, the environment variable @code{SHELL} determines which
1186 shell to run. Otherwise @value{GDBN} uses the default shell
1187 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1190 The utility @code{make} is often needed in development environments.
1191 You do not have to use the @code{shell} command for this purpose in
1196 @cindex calling make
1197 @item make @var{make-args}
1198 Execute the @code{make} program with the specified
1199 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1202 @node Logging output
1203 @section Logging output
1204 @cindex logging @value{GDBN} output
1206 You may want to save the output of @value{GDBN} commands to a file.
1207 There are several commands to control @value{GDBN}'s logging.
1211 @item set logging on
1213 @item set logging off
1215 @item set logging file @var{file}
1216 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1217 @item set logging overwrite [on|off]
1218 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1219 you want @code{set logging on} to overwrite the logfile instead.
1220 @item set logging redirect [on|off]
1221 By default, @value{GDBN} output will go to both the terminal and the logfile.
1222 Set @code{redirect} if you want output to go only to the log file.
1223 @kindex show logging
1225 Show the current values of the logging settings.
1229 @chapter @value{GDBN} Commands
1231 You can abbreviate a @value{GDBN} command to the first few letters of the command
1232 name, if that abbreviation is unambiguous; and you can repeat certain
1233 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1234 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1235 show you the alternatives available, if there is more than one possibility).
1238 * Command Syntax:: How to give commands to @value{GDBN}
1239 * Completion:: Command completion
1240 * Help:: How to ask @value{GDBN} for help
1243 @node Command Syntax
1244 @section Command syntax
1246 A @value{GDBN} command is a single line of input. There is no limit on
1247 how long it can be. It starts with a command name, which is followed by
1248 arguments whose meaning depends on the command name. For example, the
1249 command @code{step} accepts an argument which is the number of times to
1250 step, as in @samp{step 5}. You can also use the @code{step} command
1251 with no arguments. Some commands do not allow any arguments.
1253 @cindex abbreviation
1254 @value{GDBN} command names may always be truncated if that abbreviation is
1255 unambiguous. Other possible command abbreviations are listed in the
1256 documentation for individual commands. In some cases, even ambiguous
1257 abbreviations are allowed; for example, @code{s} is specially defined as
1258 equivalent to @code{step} even though there are other commands whose
1259 names start with @code{s}. You can test abbreviations by using them as
1260 arguments to the @code{help} command.
1262 @cindex repeating commands
1263 @kindex RET @r{(repeat last command)}
1264 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1265 repeat the previous command. Certain commands (for example, @code{run})
1266 will not repeat this way; these are commands whose unintentional
1267 repetition might cause trouble and which you are unlikely to want to
1270 The @code{list} and @code{x} commands, when you repeat them with
1271 @key{RET}, construct new arguments rather than repeating
1272 exactly as typed. This permits easy scanning of source or memory.
1274 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1275 output, in a way similar to the common utility @code{more}
1276 (@pxref{Screen Size,,Screen size}). Since it is easy to press one
1277 @key{RET} too many in this situation, @value{GDBN} disables command
1278 repetition after any command that generates this sort of display.
1280 @kindex # @r{(a comment)}
1282 Any text from a @kbd{#} to the end of the line is a comment; it does
1283 nothing. This is useful mainly in command files (@pxref{Command
1284 Files,,Command files}).
1286 @cindex repeating command sequences
1287 @kindex C-o @r{(operate-and-get-next)}
1288 The @kbd{C-o} binding is useful for repeating a complex sequence of
1289 commands. This command accepts the current line, like @kbd{RET}, and
1290 then fetches the next line relative to the current line from the history
1294 @section Command completion
1297 @cindex word completion
1298 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1299 only one possibility; it can also show you what the valid possibilities
1300 are for the next word in a command, at any time. This works for @value{GDBN}
1301 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1303 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1304 of a word. If there is only one possibility, @value{GDBN} fills in the
1305 word, and waits for you to finish the command (or press @key{RET} to
1306 enter it). For example, if you type
1308 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1309 @c complete accuracy in these examples; space introduced for clarity.
1310 @c If texinfo enhancements make it unnecessary, it would be nice to
1311 @c replace " @key" by "@key" in the following...
1313 (@value{GDBP}) info bre @key{TAB}
1317 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1318 the only @code{info} subcommand beginning with @samp{bre}:
1321 (@value{GDBP}) info breakpoints
1325 You can either press @key{RET} at this point, to run the @code{info
1326 breakpoints} command, or backspace and enter something else, if
1327 @samp{breakpoints} does not look like the command you expected. (If you
1328 were sure you wanted @code{info breakpoints} in the first place, you
1329 might as well just type @key{RET} immediately after @samp{info bre},
1330 to exploit command abbreviations rather than command completion).
1332 If there is more than one possibility for the next word when you press
1333 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1334 characters and try again, or just press @key{TAB} a second time;
1335 @value{GDBN} displays all the possible completions for that word. For
1336 example, you might want to set a breakpoint on a subroutine whose name
1337 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1338 just sounds the bell. Typing @key{TAB} again displays all the
1339 function names in your program that begin with those characters, for
1343 (@value{GDBP}) b make_ @key{TAB}
1344 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1345 make_a_section_from_file make_environ
1346 make_abs_section make_function_type
1347 make_blockvector make_pointer_type
1348 make_cleanup make_reference_type
1349 make_command make_symbol_completion_list
1350 (@value{GDBP}) b make_
1354 After displaying the available possibilities, @value{GDBN} copies your
1355 partial input (@samp{b make_} in the example) so you can finish the
1358 If you just want to see the list of alternatives in the first place, you
1359 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1360 means @kbd{@key{META} ?}. You can type this either by holding down a
1361 key designated as the @key{META} shift on your keyboard (if there is
1362 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1364 @cindex quotes in commands
1365 @cindex completion of quoted strings
1366 Sometimes the string you need, while logically a ``word'', may contain
1367 parentheses or other characters that @value{GDBN} normally excludes from
1368 its notion of a word. To permit word completion to work in this
1369 situation, you may enclose words in @code{'} (single quote marks) in
1370 @value{GDBN} commands.
1372 The most likely situation where you might need this is in typing the
1373 name of a C@t{++} function. This is because C@t{++} allows function
1374 overloading (multiple definitions of the same function, distinguished
1375 by argument type). For example, when you want to set a breakpoint you
1376 may need to distinguish whether you mean the version of @code{name}
1377 that takes an @code{int} parameter, @code{name(int)}, or the version
1378 that takes a @code{float} parameter, @code{name(float)}. To use the
1379 word-completion facilities in this situation, type a single quote
1380 @code{'} at the beginning of the function name. This alerts
1381 @value{GDBN} that it may need to consider more information than usual
1382 when you press @key{TAB} or @kbd{M-?} to request word completion:
1385 (@value{GDBP}) b 'bubble( @kbd{M-?}
1386 bubble(double,double) bubble(int,int)
1387 (@value{GDBP}) b 'bubble(
1390 In some cases, @value{GDBN} can tell that completing a name requires using
1391 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1392 completing as much as it can) if you do not type the quote in the first
1396 (@value{GDBP}) b bub @key{TAB}
1397 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1398 (@value{GDBP}) b 'bubble(
1402 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1403 you have not yet started typing the argument list when you ask for
1404 completion on an overloaded symbol.
1406 For more information about overloaded functions, see @ref{C plus plus
1407 expressions, ,C@t{++} expressions}. You can use the command @code{set
1408 overload-resolution off} to disable overload resolution;
1409 see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
1413 @section Getting help
1414 @cindex online documentation
1417 You can always ask @value{GDBN} itself for information on its commands,
1418 using the command @code{help}.
1421 @kindex h @r{(@code{help})}
1424 You can use @code{help} (abbreviated @code{h}) with no arguments to
1425 display a short list of named classes of commands:
1429 List of classes of commands:
1431 aliases -- Aliases of other commands
1432 breakpoints -- Making program stop at certain points
1433 data -- Examining data
1434 files -- Specifying and examining files
1435 internals -- Maintenance commands
1436 obscure -- Obscure features
1437 running -- Running the program
1438 stack -- Examining the stack
1439 status -- Status inquiries
1440 support -- Support facilities
1441 tracepoints -- Tracing of program execution without@*
1442 stopping the program
1443 user-defined -- User-defined commands
1445 Type "help" followed by a class name for a list of
1446 commands in that class.
1447 Type "help" followed by command name for full
1449 Command name abbreviations are allowed if unambiguous.
1452 @c the above line break eliminates huge line overfull...
1454 @item help @var{class}
1455 Using one of the general help classes as an argument, you can get a
1456 list of the individual commands in that class. For example, here is the
1457 help display for the class @code{status}:
1460 (@value{GDBP}) help status
1465 @c Line break in "show" line falsifies real output, but needed
1466 @c to fit in smallbook page size.
1467 info -- Generic command for showing things
1468 about the program being debugged
1469 show -- Generic command for showing things
1472 Type "help" followed by command name for full
1474 Command name abbreviations are allowed if unambiguous.
1478 @item help @var{command}
1479 With a command name as @code{help} argument, @value{GDBN} displays a
1480 short paragraph on how to use that command.
1483 @item apropos @var{args}
1484 The @code{apropos} command searches through all of the @value{GDBN}
1485 commands, and their documentation, for the regular expression specified in
1486 @var{args}. It prints out all matches found. For example:
1497 set symbol-reloading -- Set dynamic symbol table reloading
1498 multiple times in one run
1499 show symbol-reloading -- Show dynamic symbol table reloading
1500 multiple times in one run
1505 @item complete @var{args}
1506 The @code{complete @var{args}} command lists all the possible completions
1507 for the beginning of a command. Use @var{args} to specify the beginning of the
1508 command you want completed. For example:
1514 @noindent results in:
1525 @noindent This is intended for use by @sc{gnu} Emacs.
1528 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1529 and @code{show} to inquire about the state of your program, or the state
1530 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1531 manual introduces each of them in the appropriate context. The listings
1532 under @code{info} and under @code{show} in the Index point to
1533 all the sub-commands. @xref{Index}.
1538 @kindex i @r{(@code{info})}
1540 This command (abbreviated @code{i}) is for describing the state of your
1541 program. For example, you can list the arguments given to your program
1542 with @code{info args}, list the registers currently in use with @code{info
1543 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1544 You can get a complete list of the @code{info} sub-commands with
1545 @w{@code{help info}}.
1549 You can assign the result of an expression to an environment variable with
1550 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1551 @code{set prompt $}.
1555 In contrast to @code{info}, @code{show} is for describing the state of
1556 @value{GDBN} itself.
1557 You can change most of the things you can @code{show}, by using the
1558 related command @code{set}; for example, you can control what number
1559 system is used for displays with @code{set radix}, or simply inquire
1560 which is currently in use with @code{show radix}.
1563 To display all the settable parameters and their current
1564 values, you can use @code{show} with no arguments; you may also use
1565 @code{info set}. Both commands produce the same display.
1566 @c FIXME: "info set" violates the rule that "info" is for state of
1567 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1568 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1572 Here are three miscellaneous @code{show} subcommands, all of which are
1573 exceptional in lacking corresponding @code{set} commands:
1576 @kindex show version
1577 @cindex version number
1579 Show what version of @value{GDBN} is running. You should include this
1580 information in @value{GDBN} bug-reports. If multiple versions of
1581 @value{GDBN} are in use at your site, you may need to determine which
1582 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1583 commands are introduced, and old ones may wither away. Also, many
1584 system vendors ship variant versions of @value{GDBN}, and there are
1585 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1586 The version number is the same as the one announced when you start
1589 @kindex show copying
1590 @kindex info copying
1593 Display information about permission for copying @value{GDBN}.
1595 @kindex show warranty
1596 @kindex info warranty
1598 @itemx info warranty
1599 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1600 if your version of @value{GDBN} comes with one.
1605 @chapter Running Programs Under @value{GDBN}
1607 When you run a program under @value{GDBN}, you must first generate
1608 debugging information when you compile it.
1610 You may start @value{GDBN} with its arguments, if any, in an environment
1611 of your choice. If you are doing native debugging, you may redirect
1612 your program's input and output, debug an already running process, or
1613 kill a child process.
1616 * Compilation:: Compiling for debugging
1617 * Starting:: Starting your program
1618 * Arguments:: Your program's arguments
1619 * Environment:: Your program's environment
1621 * Working Directory:: Your program's working directory
1622 * Input/Output:: Your program's input and output
1623 * Attach:: Debugging an already-running process
1624 * Kill Process:: Killing the child process
1626 * Threads:: Debugging programs with multiple threads
1627 * Processes:: Debugging programs with multiple processes
1631 @section Compiling for debugging
1633 In order to debug a program effectively, you need to generate
1634 debugging information when you compile it. This debugging information
1635 is stored in the object file; it describes the data type of each
1636 variable or function and the correspondence between source line numbers
1637 and addresses in the executable code.
1639 To request debugging information, specify the @samp{-g} option when you run
1642 Most compilers do not include information about preprocessor macros in
1643 the debugging information if you specify the @option{-g} flag alone,
1644 because this information is rather large. Version 3.1 of @value{NGCC},
1645 the @sc{gnu} C compiler, provides macro information if you specify the
1646 options @option{-gdwarf-2} and @option{-g3}; the former option requests
1647 debugging information in the Dwarf 2 format, and the latter requests
1648 ``extra information''. In the future, we hope to find more compact ways
1649 to represent macro information, so that it can be included with
1652 Many C compilers are unable to handle the @samp{-g} and @samp{-O}
1653 options together. Using those compilers, you cannot generate optimized
1654 executables containing debugging information.
1656 @value{NGCC}, the @sc{gnu} C compiler, supports @samp{-g} with or
1657 without @samp{-O}, making it possible to debug optimized code. We
1658 recommend that you @emph{always} use @samp{-g} whenever you compile a
1659 program. You may think your program is correct, but there is no sense
1660 in pushing your luck.
1662 @cindex optimized code, debugging
1663 @cindex debugging optimized code
1664 When you debug a program compiled with @samp{-g -O}, remember that the
1665 optimizer is rearranging your code; the debugger shows you what is
1666 really there. Do not be too surprised when the execution path does not
1667 exactly match your source file! An extreme example: if you define a
1668 variable, but never use it, @value{GDBN} never sees that
1669 variable---because the compiler optimizes it out of existence.
1671 Some things do not work as well with @samp{-g -O} as with just
1672 @samp{-g}, particularly on machines with instruction scheduling. If in
1673 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1674 please report it to us as a bug (including a test case!).
1675 @xref{Variables}, for more information about debugging optimized code.
1677 Older versions of the @sc{gnu} C compiler permitted a variant option
1678 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1679 format; if your @sc{gnu} C compiler has this option, do not use it.
1683 @section Starting your program
1689 @kindex r @r{(@code{run})}
1692 Use the @code{run} command to start your program under @value{GDBN}.
1693 You must first specify the program name (except on VxWorks) with an
1694 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1695 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1696 (@pxref{Files, ,Commands to specify files}).
1700 If you are running your program in an execution environment that
1701 supports processes, @code{run} creates an inferior process and makes
1702 that process run your program. (In environments without processes,
1703 @code{run} jumps to the start of your program.)
1705 The execution of a program is affected by certain information it
1706 receives from its superior. @value{GDBN} provides ways to specify this
1707 information, which you must do @emph{before} starting your program. (You
1708 can change it after starting your program, but such changes only affect
1709 your program the next time you start it.) This information may be
1710 divided into four categories:
1713 @item The @emph{arguments.}
1714 Specify the arguments to give your program as the arguments of the
1715 @code{run} command. If a shell is available on your target, the shell
1716 is used to pass the arguments, so that you may use normal conventions
1717 (such as wildcard expansion or variable substitution) in describing
1719 In Unix systems, you can control which shell is used with the
1720 @code{SHELL} environment variable.
1721 @xref{Arguments, ,Your program's arguments}.
1723 @item The @emph{environment.}
1724 Your program normally inherits its environment from @value{GDBN}, but you can
1725 use the @value{GDBN} commands @code{set environment} and @code{unset
1726 environment} to change parts of the environment that affect
1727 your program. @xref{Environment, ,Your program's environment}.
1729 @item The @emph{working directory.}
1730 Your program inherits its working directory from @value{GDBN}. You can set
1731 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1732 @xref{Working Directory, ,Your program's working directory}.
1734 @item The @emph{standard input and output.}
1735 Your program normally uses the same device for standard input and
1736 standard output as @value{GDBN} is using. You can redirect input and output
1737 in the @code{run} command line, or you can use the @code{tty} command to
1738 set a different device for your program.
1739 @xref{Input/Output, ,Your program's input and output}.
1742 @emph{Warning:} While input and output redirection work, you cannot use
1743 pipes to pass the output of the program you are debugging to another
1744 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1748 When you issue the @code{run} command, your program begins to execute
1749 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1750 of how to arrange for your program to stop. Once your program has
1751 stopped, you may call functions in your program, using the @code{print}
1752 or @code{call} commands. @xref{Data, ,Examining Data}.
1754 If the modification time of your symbol file has changed since the last
1755 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1756 table, and reads it again. When it does this, @value{GDBN} tries to retain
1757 your current breakpoints.
1762 @cindex run to main procedure
1763 The name of the main procedure can vary from language to language.
1764 With C or C@t{++}, the main procedure name is always @code{main}, but
1765 other languages such as Ada do not require a specific name for their
1766 main procedure. The debugger provides a convenient way to start the
1767 execution of the program and to stop at the beginning of the main
1768 procedure, depending on the language used.
1770 The @samp{start} command does the equivalent of setting a temporary
1771 breakpoint at the beginning of the main procedure and then invoking
1772 the @samp{run} command.
1774 @cindex elaboration phase
1775 Some programs contain an @dfn{elaboration} phase where some startup code is
1776 executed before the main procedure is called. This depends on the
1777 languages used to write your program. In C@t{++}, for instance,
1778 constructors for static and global objects are executed before
1779 @code{main} is called. It is therefore possible that the debugger stops
1780 before reaching the main procedure. However, the temporary breakpoint
1781 will remain to halt execution.
1783 Specify the arguments to give to your program as arguments to the
1784 @samp{start} command. These arguments will be given verbatim to the
1785 underlying @samp{run} command. Note that the same arguments will be
1786 reused if no argument is provided during subsequent calls to
1787 @samp{start} or @samp{run}.
1789 It is sometimes necessary to debug the program during elaboration. In
1790 these cases, using the @code{start} command would stop the execution of
1791 your program too late, as the program would have already completed the
1792 elaboration phase. Under these circumstances, insert breakpoints in your
1793 elaboration code before running your program.
1797 @section Your program's arguments
1799 @cindex arguments (to your program)
1800 The arguments to your program can be specified by the arguments of the
1802 They are passed to a shell, which expands wildcard characters and
1803 performs redirection of I/O, and thence to your program. Your
1804 @code{SHELL} environment variable (if it exists) specifies what shell
1805 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1806 the default shell (@file{/bin/sh} on Unix).
1808 On non-Unix systems, the program is usually invoked directly by
1809 @value{GDBN}, which emulates I/O redirection via the appropriate system
1810 calls, and the wildcard characters are expanded by the startup code of
1811 the program, not by the shell.
1813 @code{run} with no arguments uses the same arguments used by the previous
1814 @code{run}, or those set by the @code{set args} command.
1819 Specify the arguments to be used the next time your program is run. If
1820 @code{set args} has no arguments, @code{run} executes your program
1821 with no arguments. Once you have run your program with arguments,
1822 using @code{set args} before the next @code{run} is the only way to run
1823 it again without arguments.
1827 Show the arguments to give your program when it is started.
1831 @section Your program's environment
1833 @cindex environment (of your program)
1834 The @dfn{environment} consists of a set of environment variables and
1835 their values. Environment variables conventionally record such things as
1836 your user name, your home directory, your terminal type, and your search
1837 path for programs to run. Usually you set up environment variables with
1838 the shell and they are inherited by all the other programs you run. When
1839 debugging, it can be useful to try running your program with a modified
1840 environment without having to start @value{GDBN} over again.
1844 @item path @var{directory}
1845 Add @var{directory} to the front of the @code{PATH} environment variable
1846 (the search path for executables) that will be passed to your program.
1847 The value of @code{PATH} used by @value{GDBN} does not change.
1848 You may specify several directory names, separated by whitespace or by a
1849 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1850 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1851 is moved to the front, so it is searched sooner.
1853 You can use the string @samp{$cwd} to refer to whatever is the current
1854 working directory at the time @value{GDBN} searches the path. If you
1855 use @samp{.} instead, it refers to the directory where you executed the
1856 @code{path} command. @value{GDBN} replaces @samp{.} in the
1857 @var{directory} argument (with the current path) before adding
1858 @var{directory} to the search path.
1859 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1860 @c document that, since repeating it would be a no-op.
1864 Display the list of search paths for executables (the @code{PATH}
1865 environment variable).
1867 @kindex show environment
1868 @item show environment @r{[}@var{varname}@r{]}
1869 Print the value of environment variable @var{varname} to be given to
1870 your program when it starts. If you do not supply @var{varname},
1871 print the names and values of all environment variables to be given to
1872 your program. You can abbreviate @code{environment} as @code{env}.
1874 @kindex set environment
1875 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1876 Set environment variable @var{varname} to @var{value}. The value
1877 changes for your program only, not for @value{GDBN} itself. @var{value} may
1878 be any string; the values of environment variables are just strings, and
1879 any interpretation is supplied by your program itself. The @var{value}
1880 parameter is optional; if it is eliminated, the variable is set to a
1882 @c "any string" here does not include leading, trailing
1883 @c blanks. Gnu asks: does anyone care?
1885 For example, this command:
1892 tells the debugged program, when subsequently run, that its user is named
1893 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
1894 are not actually required.)
1896 @kindex unset environment
1897 @item unset environment @var{varname}
1898 Remove variable @var{varname} from the environment to be passed to your
1899 program. This is different from @samp{set env @var{varname} =};
1900 @code{unset environment} removes the variable from the environment,
1901 rather than assigning it an empty value.
1904 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
1906 by your @code{SHELL} environment variable if it exists (or
1907 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
1908 that runs an initialization file---such as @file{.cshrc} for C-shell, or
1909 @file{.bashrc} for BASH---any variables you set in that file affect
1910 your program. You may wish to move setting of environment variables to
1911 files that are only run when you sign on, such as @file{.login} or
1914 @node Working Directory
1915 @section Your program's working directory
1917 @cindex working directory (of your program)
1918 Each time you start your program with @code{run}, it inherits its
1919 working directory from the current working directory of @value{GDBN}.
1920 The @value{GDBN} working directory is initially whatever it inherited
1921 from its parent process (typically the shell), but you can specify a new
1922 working directory in @value{GDBN} with the @code{cd} command.
1924 The @value{GDBN} working directory also serves as a default for the commands
1925 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
1930 @item cd @var{directory}
1931 Set the @value{GDBN} working directory to @var{directory}.
1935 Print the @value{GDBN} working directory.
1938 It is generally impossible to find the current working directory of
1939 the process being debugged (since a program can change its directory
1940 during its run). If you work on a system where @value{GDBN} is
1941 configured with the @file{/proc} support, you can use the @code{info
1942 proc} command (@pxref{SVR4 Process Information}) to find out the
1943 current working directory of the debuggee.
1946 @section Your program's input and output
1951 By default, the program you run under @value{GDBN} does input and output to
1952 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
1953 to its own terminal modes to interact with you, but it records the terminal
1954 modes your program was using and switches back to them when you continue
1955 running your program.
1958 @kindex info terminal
1960 Displays information recorded by @value{GDBN} about the terminal modes your
1964 You can redirect your program's input and/or output using shell
1965 redirection with the @code{run} command. For example,
1972 starts your program, diverting its output to the file @file{outfile}.
1975 @cindex controlling terminal
1976 Another way to specify where your program should do input and output is
1977 with the @code{tty} command. This command accepts a file name as
1978 argument, and causes this file to be the default for future @code{run}
1979 commands. It also resets the controlling terminal for the child
1980 process, for future @code{run} commands. For example,
1987 directs that processes started with subsequent @code{run} commands
1988 default to do input and output on the terminal @file{/dev/ttyb} and have
1989 that as their controlling terminal.
1991 An explicit redirection in @code{run} overrides the @code{tty} command's
1992 effect on the input/output device, but not its effect on the controlling
1995 When you use the @code{tty} command or redirect input in the @code{run}
1996 command, only the input @emph{for your program} is affected. The input
1997 for @value{GDBN} still comes from your terminal.
2000 @section Debugging an already-running process
2005 @item attach @var{process-id}
2006 This command attaches to a running process---one that was started
2007 outside @value{GDBN}. (@code{info files} shows your active
2008 targets.) The command takes as argument a process ID. The usual way to
2009 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2010 or with the @samp{jobs -l} shell command.
2012 @code{attach} does not repeat if you press @key{RET} a second time after
2013 executing the command.
2016 To use @code{attach}, your program must be running in an environment
2017 which supports processes; for example, @code{attach} does not work for
2018 programs on bare-board targets that lack an operating system. You must
2019 also have permission to send the process a signal.
2021 When you use @code{attach}, the debugger finds the program running in
2022 the process first by looking in the current working directory, then (if
2023 the program is not found) by using the source file search path
2024 (@pxref{Source Path, ,Specifying source directories}). You can also use
2025 the @code{file} command to load the program. @xref{Files, ,Commands to
2028 The first thing @value{GDBN} does after arranging to debug the specified
2029 process is to stop it. You can examine and modify an attached process
2030 with all the @value{GDBN} commands that are ordinarily available when
2031 you start processes with @code{run}. You can insert breakpoints; you
2032 can step and continue; you can modify storage. If you would rather the
2033 process continue running, you may use the @code{continue} command after
2034 attaching @value{GDBN} to the process.
2039 When you have finished debugging the attached process, you can use the
2040 @code{detach} command to release it from @value{GDBN} control. Detaching
2041 the process continues its execution. After the @code{detach} command,
2042 that process and @value{GDBN} become completely independent once more, and you
2043 are ready to @code{attach} another process or start one with @code{run}.
2044 @code{detach} does not repeat if you press @key{RET} again after
2045 executing the command.
2048 If you exit @value{GDBN} or use the @code{run} command while you have an
2049 attached process, you kill that process. By default, @value{GDBN} asks
2050 for confirmation if you try to do either of these things; you can
2051 control whether or not you need to confirm by using the @code{set
2052 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
2056 @section Killing the child process
2061 Kill the child process in which your program is running under @value{GDBN}.
2064 This command is useful if you wish to debug a core dump instead of a
2065 running process. @value{GDBN} ignores any core dump file while your program
2068 On some operating systems, a program cannot be executed outside @value{GDBN}
2069 while you have breakpoints set on it inside @value{GDBN}. You can use the
2070 @code{kill} command in this situation to permit running your program
2071 outside the debugger.
2073 The @code{kill} command is also useful if you wish to recompile and
2074 relink your program, since on many systems it is impossible to modify an
2075 executable file while it is running in a process. In this case, when you
2076 next type @code{run}, @value{GDBN} notices that the file has changed, and
2077 reads the symbol table again (while trying to preserve your current
2078 breakpoint settings).
2081 @section Debugging programs with multiple threads
2083 @cindex threads of execution
2084 @cindex multiple threads
2085 @cindex switching threads
2086 In some operating systems, such as HP-UX and Solaris, a single program
2087 may have more than one @dfn{thread} of execution. The precise semantics
2088 of threads differ from one operating system to another, but in general
2089 the threads of a single program are akin to multiple processes---except
2090 that they share one address space (that is, they can all examine and
2091 modify the same variables). On the other hand, each thread has its own
2092 registers and execution stack, and perhaps private memory.
2094 @value{GDBN} provides these facilities for debugging multi-thread
2098 @item automatic notification of new threads
2099 @item @samp{thread @var{threadno}}, a command to switch among threads
2100 @item @samp{info threads}, a command to inquire about existing threads
2101 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2102 a command to apply a command to a list of threads
2103 @item thread-specific breakpoints
2107 @emph{Warning:} These facilities are not yet available on every
2108 @value{GDBN} configuration where the operating system supports threads.
2109 If your @value{GDBN} does not support threads, these commands have no
2110 effect. For example, a system without thread support shows no output
2111 from @samp{info threads}, and always rejects the @code{thread} command,
2115 (@value{GDBP}) info threads
2116 (@value{GDBP}) thread 1
2117 Thread ID 1 not known. Use the "info threads" command to
2118 see the IDs of currently known threads.
2120 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2121 @c doesn't support threads"?
2124 @cindex focus of debugging
2125 @cindex current thread
2126 The @value{GDBN} thread debugging facility allows you to observe all
2127 threads while your program runs---but whenever @value{GDBN} takes
2128 control, one thread in particular is always the focus of debugging.
2129 This thread is called the @dfn{current thread}. Debugging commands show
2130 program information from the perspective of the current thread.
2132 @cindex @code{New} @var{systag} message
2133 @cindex thread identifier (system)
2134 @c FIXME-implementors!! It would be more helpful if the [New...] message
2135 @c included GDB's numeric thread handle, so you could just go to that
2136 @c thread without first checking `info threads'.
2137 Whenever @value{GDBN} detects a new thread in your program, it displays
2138 the target system's identification for the thread with a message in the
2139 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2140 whose form varies depending on the particular system. For example, on
2141 LynxOS, you might see
2144 [New process 35 thread 27]
2148 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2149 the @var{systag} is simply something like @samp{process 368}, with no
2152 @c FIXME!! (1) Does the [New...] message appear even for the very first
2153 @c thread of a program, or does it only appear for the
2154 @c second---i.e.@: when it becomes obvious we have a multithread
2156 @c (2) *Is* there necessarily a first thread always? Or do some
2157 @c multithread systems permit starting a program with multiple
2158 @c threads ab initio?
2160 @cindex thread number
2161 @cindex thread identifier (GDB)
2162 For debugging purposes, @value{GDBN} associates its own thread
2163 number---always a single integer---with each thread in your program.
2166 @kindex info threads
2168 Display a summary of all threads currently in your
2169 program. @value{GDBN} displays for each thread (in this order):
2173 the thread number assigned by @value{GDBN}
2176 the target system's thread identifier (@var{systag})
2179 the current stack frame summary for that thread
2183 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2184 indicates the current thread.
2188 @c end table here to get a little more width for example
2191 (@value{GDBP}) info threads
2192 3 process 35 thread 27 0x34e5 in sigpause ()
2193 2 process 35 thread 23 0x34e5 in sigpause ()
2194 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2200 @cindex debugging multithreaded programs (on HP-UX)
2201 @cindex thread identifier (GDB), on HP-UX
2202 For debugging purposes, @value{GDBN} associates its own thread
2203 number---a small integer assigned in thread-creation order---with each
2204 thread in your program.
2206 @cindex @code{New} @var{systag} message, on HP-UX
2207 @cindex thread identifier (system), on HP-UX
2208 @c FIXME-implementors!! It would be more helpful if the [New...] message
2209 @c included GDB's numeric thread handle, so you could just go to that
2210 @c thread without first checking `info threads'.
2211 Whenever @value{GDBN} detects a new thread in your program, it displays
2212 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2213 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2214 whose form varies depending on the particular system. For example, on
2218 [New thread 2 (system thread 26594)]
2222 when @value{GDBN} notices a new thread.
2225 @kindex info threads (HP-UX)
2227 Display a summary of all threads currently in your
2228 program. @value{GDBN} displays for each thread (in this order):
2231 @item the thread number assigned by @value{GDBN}
2233 @item the target system's thread identifier (@var{systag})
2235 @item the current stack frame summary for that thread
2239 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2240 indicates the current thread.
2244 @c end table here to get a little more width for example
2247 (@value{GDBP}) info threads
2248 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2250 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2251 from /usr/lib/libc.2
2252 1 system thread 27905 0x7b003498 in _brk () \@*
2253 from /usr/lib/libc.2
2257 @kindex thread @var{threadno}
2258 @item thread @var{threadno}
2259 Make thread number @var{threadno} the current thread. The command
2260 argument @var{threadno} is the internal @value{GDBN} thread number, as
2261 shown in the first field of the @samp{info threads} display.
2262 @value{GDBN} responds by displaying the system identifier of the thread
2263 you selected, and its current stack frame summary:
2266 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2267 (@value{GDBP}) thread 2
2268 [Switching to process 35 thread 23]
2269 0x34e5 in sigpause ()
2273 As with the @samp{[New @dots{}]} message, the form of the text after
2274 @samp{Switching to} depends on your system's conventions for identifying
2277 @item thread apply [@var{threadno}] [@var{all}] @var{args}
2278 The @code{thread apply} command allows you to apply a command to one or
2279 more threads. Specify the numbers of the threads that you want affected
2280 with the command argument @var{threadno}. @var{threadno} is the internal
2281 @value{GDBN} thread number, as shown in the first field of the @samp{info
2282 threads} display. To apply a command to all threads, use
2283 @code{thread apply all} @var{args}.
2286 @cindex automatic thread selection
2287 @cindex switching threads automatically
2288 @cindex threads, automatic switching
2289 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2290 signal, it automatically selects the thread where that breakpoint or
2291 signal happened. @value{GDBN} alerts you to the context switch with a
2292 message of the form @samp{[Switching to @var{systag}]} to identify the
2295 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2296 more information about how @value{GDBN} behaves when you stop and start
2297 programs with multiple threads.
2299 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2300 watchpoints in programs with multiple threads.
2303 @section Debugging programs with multiple processes
2305 @cindex fork, debugging programs which call
2306 @cindex multiple processes
2307 @cindex processes, multiple
2308 On most systems, @value{GDBN} has no special support for debugging
2309 programs which create additional processes using the @code{fork}
2310 function. When a program forks, @value{GDBN} will continue to debug the
2311 parent process and the child process will run unimpeded. If you have
2312 set a breakpoint in any code which the child then executes, the child
2313 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2314 will cause it to terminate.
2316 However, if you want to debug the child process there is a workaround
2317 which isn't too painful. Put a call to @code{sleep} in the code which
2318 the child process executes after the fork. It may be useful to sleep
2319 only if a certain environment variable is set, or a certain file exists,
2320 so that the delay need not occur when you don't want to run @value{GDBN}
2321 on the child. While the child is sleeping, use the @code{ps} program to
2322 get its process ID. Then tell @value{GDBN} (a new invocation of
2323 @value{GDBN} if you are also debugging the parent process) to attach to
2324 the child process (@pxref{Attach}). From that point on you can debug
2325 the child process just like any other process which you attached to.
2327 On some systems, @value{GDBN} provides support for debugging programs that
2328 create additional processes using the @code{fork} or @code{vfork} functions.
2329 Currently, the only platforms with this feature are HP-UX (11.x and later
2330 only?) and GNU/Linux (kernel version 2.5.60 and later).
2332 By default, when a program forks, @value{GDBN} will continue to debug
2333 the parent process and the child process will run unimpeded.
2335 If you want to follow the child process instead of the parent process,
2336 use the command @w{@code{set follow-fork-mode}}.
2339 @kindex set follow-fork-mode
2340 @item set follow-fork-mode @var{mode}
2341 Set the debugger response to a program call of @code{fork} or
2342 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2343 process. The @var{mode} can be:
2347 The original process is debugged after a fork. The child process runs
2348 unimpeded. This is the default.
2351 The new process is debugged after a fork. The parent process runs
2356 @item show follow-fork-mode
2357 Display the current debugger response to a @code{fork} or @code{vfork} call.
2360 If you ask to debug a child process and a @code{vfork} is followed by an
2361 @code{exec}, @value{GDBN} executes the new target up to the first
2362 breakpoint in the new target. If you have a breakpoint set on
2363 @code{main} in your original program, the breakpoint will also be set on
2364 the child process's @code{main}.
2366 When a child process is spawned by @code{vfork}, you cannot debug the
2367 child or parent until an @code{exec} call completes.
2369 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2370 call executes, the new target restarts. To restart the parent process,
2371 use the @code{file} command with the parent executable name as its
2374 You can use the @code{catch} command to make @value{GDBN} stop whenever
2375 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2376 Catchpoints, ,Setting catchpoints}.
2379 @chapter Stopping and Continuing
2381 The principal purposes of using a debugger are so that you can stop your
2382 program before it terminates; or so that, if your program runs into
2383 trouble, you can investigate and find out why.
2385 Inside @value{GDBN}, your program may stop for any of several reasons,
2386 such as a signal, a breakpoint, or reaching a new line after a
2387 @value{GDBN} command such as @code{step}. You may then examine and
2388 change variables, set new breakpoints or remove old ones, and then
2389 continue execution. Usually, the messages shown by @value{GDBN} provide
2390 ample explanation of the status of your program---but you can also
2391 explicitly request this information at any time.
2394 @kindex info program
2396 Display information about the status of your program: whether it is
2397 running or not, what process it is, and why it stopped.
2401 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2402 * Continuing and Stepping:: Resuming execution
2404 * Thread Stops:: Stopping and starting multi-thread programs
2408 @section Breakpoints, watchpoints, and catchpoints
2411 A @dfn{breakpoint} makes your program stop whenever a certain point in
2412 the program is reached. For each breakpoint, you can add conditions to
2413 control in finer detail whether your program stops. You can set
2414 breakpoints with the @code{break} command and its variants (@pxref{Set
2415 Breaks, ,Setting breakpoints}), to specify the place where your program
2416 should stop by line number, function name or exact address in the
2419 On some systems, you can set breakpoints in shared libraries before
2420 the executable is run. There is a minor limitation on HP-UX systems:
2421 you must wait until the executable is run in order to set breakpoints
2422 in shared library routines that are not called directly by the program
2423 (for example, routines that are arguments in a @code{pthread_create}
2427 @cindex memory tracing
2428 @cindex breakpoint on memory address
2429 @cindex breakpoint on variable modification
2430 A @dfn{watchpoint} is a special breakpoint that stops your program
2431 when the value of an expression changes. You must use a different
2432 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2433 watchpoints}), but aside from that, you can manage a watchpoint like
2434 any other breakpoint: you enable, disable, and delete both breakpoints
2435 and watchpoints using the same commands.
2437 You can arrange to have values from your program displayed automatically
2438 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2442 @cindex breakpoint on events
2443 A @dfn{catchpoint} is another special breakpoint that stops your program
2444 when a certain kind of event occurs, such as the throwing of a C@t{++}
2445 exception or the loading of a library. As with watchpoints, you use a
2446 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2447 catchpoints}), but aside from that, you can manage a catchpoint like any
2448 other breakpoint. (To stop when your program receives a signal, use the
2449 @code{handle} command; see @ref{Signals, ,Signals}.)
2451 @cindex breakpoint numbers
2452 @cindex numbers for breakpoints
2453 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2454 catchpoint when you create it; these numbers are successive integers
2455 starting with one. In many of the commands for controlling various
2456 features of breakpoints you use the breakpoint number to say which
2457 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2458 @dfn{disabled}; if disabled, it has no effect on your program until you
2461 @cindex breakpoint ranges
2462 @cindex ranges of breakpoints
2463 Some @value{GDBN} commands accept a range of breakpoints on which to
2464 operate. A breakpoint range is either a single breakpoint number, like
2465 @samp{5}, or two such numbers, in increasing order, separated by a
2466 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2467 all breakpoint in that range are operated on.
2470 * Set Breaks:: Setting breakpoints
2471 * Set Watchpoints:: Setting watchpoints
2472 * Set Catchpoints:: Setting catchpoints
2473 * Delete Breaks:: Deleting breakpoints
2474 * Disabling:: Disabling breakpoints
2475 * Conditions:: Break conditions
2476 * Break Commands:: Breakpoint command lists
2477 * Breakpoint Menus:: Breakpoint menus
2478 * Error in Breakpoints:: ``Cannot insert breakpoints''
2479 * Breakpoint related warnings:: ``Breakpoint address adjusted...''
2483 @subsection Setting breakpoints
2485 @c FIXME LMB what does GDB do if no code on line of breakpt?
2486 @c consider in particular declaration with/without initialization.
2488 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2491 @kindex b @r{(@code{break})}
2492 @vindex $bpnum@r{, convenience variable}
2493 @cindex latest breakpoint
2494 Breakpoints are set with the @code{break} command (abbreviated
2495 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2496 number of the breakpoint you've set most recently; see @ref{Convenience
2497 Vars,, Convenience variables}, for a discussion of what you can do with
2498 convenience variables.
2500 You have several ways to say where the breakpoint should go.
2503 @item break @var{function}
2504 Set a breakpoint at entry to function @var{function}.
2505 When using source languages that permit overloading of symbols, such as
2506 C@t{++}, @var{function} may refer to more than one possible place to break.
2507 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2509 @item break +@var{offset}
2510 @itemx break -@var{offset}
2511 Set a breakpoint some number of lines forward or back from the position
2512 at which execution stopped in the currently selected @dfn{stack frame}.
2513 (@xref{Frames, ,Frames}, for a description of stack frames.)
2515 @item break @var{linenum}
2516 Set a breakpoint at line @var{linenum} in the current source file.
2517 The current source file is the last file whose source text was printed.
2518 The breakpoint will stop your program just before it executes any of the
2521 @item break @var{filename}:@var{linenum}
2522 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2524 @item break @var{filename}:@var{function}
2525 Set a breakpoint at entry to function @var{function} found in file
2526 @var{filename}. Specifying a file name as well as a function name is
2527 superfluous except when multiple files contain similarly named
2530 @item break *@var{address}
2531 Set a breakpoint at address @var{address}. You can use this to set
2532 breakpoints in parts of your program which do not have debugging
2533 information or source files.
2536 When called without any arguments, @code{break} sets a breakpoint at
2537 the next instruction to be executed in the selected stack frame
2538 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2539 innermost, this makes your program stop as soon as control
2540 returns to that frame. This is similar to the effect of a
2541 @code{finish} command in the frame inside the selected frame---except
2542 that @code{finish} does not leave an active breakpoint. If you use
2543 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2544 the next time it reaches the current location; this may be useful
2547 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2548 least one instruction has been executed. If it did not do this, you
2549 would be unable to proceed past a breakpoint without first disabling the
2550 breakpoint. This rule applies whether or not the breakpoint already
2551 existed when your program stopped.
2553 @item break @dots{} if @var{cond}
2554 Set a breakpoint with condition @var{cond}; evaluate the expression
2555 @var{cond} each time the breakpoint is reached, and stop only if the
2556 value is nonzero---that is, if @var{cond} evaluates as true.
2557 @samp{@dots{}} stands for one of the possible arguments described
2558 above (or no argument) specifying where to break. @xref{Conditions,
2559 ,Break conditions}, for more information on breakpoint conditions.
2562 @item tbreak @var{args}
2563 Set a breakpoint enabled only for one stop. @var{args} are the
2564 same as for the @code{break} command, and the breakpoint is set in the same
2565 way, but the breakpoint is automatically deleted after the first time your
2566 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2569 @item hbreak @var{args}
2570 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2571 @code{break} command and the breakpoint is set in the same way, but the
2572 breakpoint requires hardware support and some target hardware may not
2573 have this support. The main purpose of this is EPROM/ROM code
2574 debugging, so you can set a breakpoint at an instruction without
2575 changing the instruction. This can be used with the new trap-generation
2576 provided by SPARClite DSU and most x86-based targets. These targets
2577 will generate traps when a program accesses some data or instruction
2578 address that is assigned to the debug registers. However the hardware
2579 breakpoint registers can take a limited number of breakpoints. For
2580 example, on the DSU, only two data breakpoints can be set at a time, and
2581 @value{GDBN} will reject this command if more than two are used. Delete
2582 or disable unused hardware breakpoints before setting new ones
2583 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2584 @xref{set remote hardware-breakpoint-limit}.
2588 @item thbreak @var{args}
2589 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2590 are the same as for the @code{hbreak} command and the breakpoint is set in
2591 the same way. However, like the @code{tbreak} command,
2592 the breakpoint is automatically deleted after the
2593 first time your program stops there. Also, like the @code{hbreak}
2594 command, the breakpoint requires hardware support and some target hardware
2595 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2596 See also @ref{Conditions, ,Break conditions}.
2599 @cindex regular expression
2600 @item rbreak @var{regex}
2601 Set breakpoints on all functions matching the regular expression
2602 @var{regex}. This command sets an unconditional breakpoint on all
2603 matches, printing a list of all breakpoints it set. Once these
2604 breakpoints are set, they are treated just like the breakpoints set with
2605 the @code{break} command. You can delete them, disable them, or make
2606 them conditional the same way as any other breakpoint.
2608 The syntax of the regular expression is the standard one used with tools
2609 like @file{grep}. Note that this is different from the syntax used by
2610 shells, so for instance @code{foo*} matches all functions that include
2611 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2612 @code{.*} leading and trailing the regular expression you supply, so to
2613 match only functions that begin with @code{foo}, use @code{^foo}.
2615 @cindex non-member C@t{++} functions, set breakpoint in
2616 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2617 breakpoints on overloaded functions that are not members of any special
2620 @cindex set breakpoints on all functions
2621 The @code{rbreak} command can be used to set breakpoints in
2622 @strong{all} the functions in a program, like this:
2625 (@value{GDBP}) rbreak .
2628 @kindex info breakpoints
2629 @cindex @code{$_} and @code{info breakpoints}
2630 @item info breakpoints @r{[}@var{n}@r{]}
2631 @itemx info break @r{[}@var{n}@r{]}
2632 @itemx info watchpoints @r{[}@var{n}@r{]}
2633 Print a table of all breakpoints, watchpoints, and catchpoints set and
2634 not deleted, with the following columns for each breakpoint:
2637 @item Breakpoint Numbers
2639 Breakpoint, watchpoint, or catchpoint.
2641 Whether the breakpoint is marked to be disabled or deleted when hit.
2642 @item Enabled or Disabled
2643 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2644 that are not enabled.
2646 Where the breakpoint is in your program, as a memory address. If the
2647 breakpoint is pending (see below for details) on a future load of a shared library, the address
2648 will be listed as @samp{<PENDING>}.
2650 Where the breakpoint is in the source for your program, as a file and
2651 line number. For a pending breakpoint, the original string passed to
2652 the breakpoint command will be listed as it cannot be resolved until
2653 the appropriate shared library is loaded in the future.
2657 If a breakpoint is conditional, @code{info break} shows the condition on
2658 the line following the affected breakpoint; breakpoint commands, if any,
2659 are listed after that. A pending breakpoint is allowed to have a condition
2660 specified for it. The condition is not parsed for validity until a shared
2661 library is loaded that allows the pending breakpoint to resolve to a
2665 @code{info break} with a breakpoint
2666 number @var{n} as argument lists only that breakpoint. The
2667 convenience variable @code{$_} and the default examining-address for
2668 the @code{x} command are set to the address of the last breakpoint
2669 listed (@pxref{Memory, ,Examining memory}).
2672 @code{info break} displays a count of the number of times the breakpoint
2673 has been hit. This is especially useful in conjunction with the
2674 @code{ignore} command. You can ignore a large number of breakpoint
2675 hits, look at the breakpoint info to see how many times the breakpoint
2676 was hit, and then run again, ignoring one less than that number. This
2677 will get you quickly to the last hit of that breakpoint.
2680 @value{GDBN} allows you to set any number of breakpoints at the same place in
2681 your program. There is nothing silly or meaningless about this. When
2682 the breakpoints are conditional, this is even useful
2683 (@pxref{Conditions, ,Break conditions}).
2685 @cindex pending breakpoints
2686 If a specified breakpoint location cannot be found, it may be due to the fact
2687 that the location is in a shared library that is yet to be loaded. In such
2688 a case, you may want @value{GDBN} to create a special breakpoint (known as
2689 a @dfn{pending breakpoint}) that
2690 attempts to resolve itself in the future when an appropriate shared library
2693 Pending breakpoints are useful to set at the start of your
2694 @value{GDBN} session for locations that you know will be dynamically loaded
2695 later by the program being debugged. When shared libraries are loaded,
2696 a check is made to see if the load resolves any pending breakpoint locations.
2697 If a pending breakpoint location gets resolved,
2698 a regular breakpoint is created and the original pending breakpoint is removed.
2700 @value{GDBN} provides some additional commands for controlling pending
2703 @kindex set breakpoint pending
2704 @kindex show breakpoint pending
2706 @item set breakpoint pending auto
2707 This is the default behavior. When @value{GDBN} cannot find the breakpoint
2708 location, it queries you whether a pending breakpoint should be created.
2710 @item set breakpoint pending on
2711 This indicates that an unrecognized breakpoint location should automatically
2712 result in a pending breakpoint being created.
2714 @item set breakpoint pending off
2715 This indicates that pending breakpoints are not to be created. Any
2716 unrecognized breakpoint location results in an error. This setting does
2717 not affect any pending breakpoints previously created.
2719 @item show breakpoint pending
2720 Show the current behavior setting for creating pending breakpoints.
2723 @cindex operations allowed on pending breakpoints
2724 Normal breakpoint operations apply to pending breakpoints as well. You may
2725 specify a condition for a pending breakpoint and/or commands to run when the
2726 breakpoint is reached. You can also enable or disable
2727 the pending breakpoint. When you specify a condition for a pending breakpoint,
2728 the parsing of the condition will be deferred until the point where the
2729 pending breakpoint location is resolved. Disabling a pending breakpoint
2730 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
2731 shared library load. When a pending breakpoint is re-enabled,
2732 @value{GDBN} checks to see if the location is already resolved.
2733 This is done because any number of shared library loads could have
2734 occurred since the time the breakpoint was disabled and one or more
2735 of these loads could resolve the location.
2737 @cindex negative breakpoint numbers
2738 @cindex internal @value{GDBN} breakpoints
2739 @value{GDBN} itself sometimes sets breakpoints in your program for
2740 special purposes, such as proper handling of @code{longjmp} (in C
2741 programs). These internal breakpoints are assigned negative numbers,
2742 starting with @code{-1}; @samp{info breakpoints} does not display them.
2743 You can see these breakpoints with the @value{GDBN} maintenance command
2744 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
2747 @node Set Watchpoints
2748 @subsection Setting watchpoints
2750 @cindex setting watchpoints
2751 You can use a watchpoint to stop execution whenever the value of an
2752 expression changes, without having to predict a particular place where
2755 @cindex software watchpoints
2756 @cindex hardware watchpoints
2757 Depending on your system, watchpoints may be implemented in software or
2758 hardware. @value{GDBN} does software watchpointing by single-stepping your
2759 program and testing the variable's value each time, which is hundreds of
2760 times slower than normal execution. (But this may still be worth it, to
2761 catch errors where you have no clue what part of your program is the
2764 On some systems, such as HP-UX, @sc{gnu}/Linux and most other
2765 x86-based targets, @value{GDBN} includes support for hardware
2766 watchpoints, which do not slow down the running of your program.
2770 @item watch @var{expr}
2771 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
2772 is written into by the program and its value changes.
2775 @item rwatch @var{expr}
2776 Set a watchpoint that will break when the value of @var{expr} is read
2780 @item awatch @var{expr}
2781 Set a watchpoint that will break when @var{expr} is either read from
2782 or written into by the program.
2784 @kindex info watchpoints
2785 @item info watchpoints
2786 This command prints a list of watchpoints, breakpoints, and catchpoints;
2787 it is the same as @code{info break} (@pxref{Set Breaks}).
2790 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
2791 watchpoints execute very quickly, and the debugger reports a change in
2792 value at the exact instruction where the change occurs. If @value{GDBN}
2793 cannot set a hardware watchpoint, it sets a software watchpoint, which
2794 executes more slowly and reports the change in value at the next
2795 @emph{statement}, not the instruction, after the change occurs.
2797 @vindex can-use-hw-watchpoints
2798 @cindex use only software watchpoints
2799 You can force @value{GDBN} to use only software watchpoints with the
2800 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
2801 zero, @value{GDBN} will never try to use hardware watchpoints, even if
2802 the underlying system supports them. (Note that hardware-assisted
2803 watchpoints that were set @emph{before} setting
2804 @code{can-use-hw-watchpoints} to zero will still use the hardware
2805 mechanism of watching expressiion values.)
2807 When you issue the @code{watch} command, @value{GDBN} reports
2810 Hardware watchpoint @var{num}: @var{expr}
2814 if it was able to set a hardware watchpoint.
2816 Currently, the @code{awatch} and @code{rwatch} commands can only set
2817 hardware watchpoints, because accesses to data that don't change the
2818 value of the watched expression cannot be detected without examining
2819 every instruction as it is being executed, and @value{GDBN} does not do
2820 that currently. If @value{GDBN} finds that it is unable to set a
2821 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
2822 will print a message like this:
2825 Expression cannot be implemented with read/access watchpoint.
2828 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
2829 data type of the watched expression is wider than what a hardware
2830 watchpoint on the target machine can handle. For example, some systems
2831 can only watch regions that are up to 4 bytes wide; on such systems you
2832 cannot set hardware watchpoints for an expression that yields a
2833 double-precision floating-point number (which is typically 8 bytes
2834 wide). As a work-around, it might be possible to break the large region
2835 into a series of smaller ones and watch them with separate watchpoints.
2837 If you set too many hardware watchpoints, @value{GDBN} might be unable
2838 to insert all of them when you resume the execution of your program.
2839 Since the precise number of active watchpoints is unknown until such
2840 time as the program is about to be resumed, @value{GDBN} might not be
2841 able to warn you about this when you set the watchpoints, and the
2842 warning will be printed only when the program is resumed:
2845 Hardware watchpoint @var{num}: Could not insert watchpoint
2849 If this happens, delete or disable some of the watchpoints.
2851 The SPARClite DSU will generate traps when a program accesses some data
2852 or instruction address that is assigned to the debug registers. For the
2853 data addresses, DSU facilitates the @code{watch} command. However the
2854 hardware breakpoint registers can only take two data watchpoints, and
2855 both watchpoints must be the same kind. For example, you can set two
2856 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
2857 @strong{or} two with @code{awatch} commands, but you cannot set one
2858 watchpoint with one command and the other with a different command.
2859 @value{GDBN} will reject the command if you try to mix watchpoints.
2860 Delete or disable unused watchpoint commands before setting new ones.
2862 If you call a function interactively using @code{print} or @code{call},
2863 any watchpoints you have set will be inactive until @value{GDBN} reaches another
2864 kind of breakpoint or the call completes.
2866 @value{GDBN} automatically deletes watchpoints that watch local
2867 (automatic) variables, or expressions that involve such variables, when
2868 they go out of scope, that is, when the execution leaves the block in
2869 which these variables were defined. In particular, when the program
2870 being debugged terminates, @emph{all} local variables go out of scope,
2871 and so only watchpoints that watch global variables remain set. If you
2872 rerun the program, you will need to set all such watchpoints again. One
2873 way of doing that would be to set a code breakpoint at the entry to the
2874 @code{main} function and when it breaks, set all the watchpoints.
2877 @cindex watchpoints and threads
2878 @cindex threads and watchpoints
2879 @emph{Warning:} In multi-thread programs, watchpoints have only limited
2880 usefulness. With the current watchpoint implementation, @value{GDBN}
2881 can only watch the value of an expression @emph{in a single thread}. If
2882 you are confident that the expression can only change due to the current
2883 thread's activity (and if you are also confident that no other thread
2884 can become current), then you can use watchpoints as usual. However,
2885 @value{GDBN} may not notice when a non-current thread's activity changes
2888 @c FIXME: this is almost identical to the previous paragraph.
2889 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
2890 have only limited usefulness. If @value{GDBN} creates a software
2891 watchpoint, it can only watch the value of an expression @emph{in a
2892 single thread}. If you are confident that the expression can only
2893 change due to the current thread's activity (and if you are also
2894 confident that no other thread can become current), then you can use
2895 software watchpoints as usual. However, @value{GDBN} may not notice
2896 when a non-current thread's activity changes the expression. (Hardware
2897 watchpoints, in contrast, watch an expression in all threads.)
2900 @xref{set remote hardware-watchpoint-limit}.
2902 @node Set Catchpoints
2903 @subsection Setting catchpoints
2904 @cindex catchpoints, setting
2905 @cindex exception handlers
2906 @cindex event handling
2908 You can use @dfn{catchpoints} to cause the debugger to stop for certain
2909 kinds of program events, such as C@t{++} exceptions or the loading of a
2910 shared library. Use the @code{catch} command to set a catchpoint.
2914 @item catch @var{event}
2915 Stop when @var{event} occurs. @var{event} can be any of the following:
2918 @cindex stop on C@t{++} exceptions
2919 The throwing of a C@t{++} exception.
2922 The catching of a C@t{++} exception.
2925 @cindex break on fork/exec
2926 A call to @code{exec}. This is currently only available for HP-UX.
2929 A call to @code{fork}. This is currently only available for HP-UX.
2932 A call to @code{vfork}. This is currently only available for HP-UX.
2935 @itemx load @var{libname}
2936 @cindex break on load/unload of shared library
2937 The dynamic loading of any shared library, or the loading of the library
2938 @var{libname}. This is currently only available for HP-UX.
2941 @itemx unload @var{libname}
2942 The unloading of any dynamically loaded shared library, or the unloading
2943 of the library @var{libname}. This is currently only available for HP-UX.
2946 @item tcatch @var{event}
2947 Set a catchpoint that is enabled only for one stop. The catchpoint is
2948 automatically deleted after the first time the event is caught.
2952 Use the @code{info break} command to list the current catchpoints.
2954 There are currently some limitations to C@t{++} exception handling
2955 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
2959 If you call a function interactively, @value{GDBN} normally returns
2960 control to you when the function has finished executing. If the call
2961 raises an exception, however, the call may bypass the mechanism that
2962 returns control to you and cause your program either to abort or to
2963 simply continue running until it hits a breakpoint, catches a signal
2964 that @value{GDBN} is listening for, or exits. This is the case even if
2965 you set a catchpoint for the exception; catchpoints on exceptions are
2966 disabled within interactive calls.
2969 You cannot raise an exception interactively.
2972 You cannot install an exception handler interactively.
2975 @cindex raise exceptions
2976 Sometimes @code{catch} is not the best way to debug exception handling:
2977 if you need to know exactly where an exception is raised, it is better to
2978 stop @emph{before} the exception handler is called, since that way you
2979 can see the stack before any unwinding takes place. If you set a
2980 breakpoint in an exception handler instead, it may not be easy to find
2981 out where the exception was raised.
2983 To stop just before an exception handler is called, you need some
2984 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
2985 raised by calling a library function named @code{__raise_exception}
2986 which has the following ANSI C interface:
2989 /* @var{addr} is where the exception identifier is stored.
2990 @var{id} is the exception identifier. */
2991 void __raise_exception (void **addr, void *id);
2995 To make the debugger catch all exceptions before any stack
2996 unwinding takes place, set a breakpoint on @code{__raise_exception}
2997 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
2999 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
3000 that depends on the value of @var{id}, you can stop your program when
3001 a specific exception is raised. You can use multiple conditional
3002 breakpoints to stop your program when any of a number of exceptions are
3007 @subsection Deleting breakpoints
3009 @cindex clearing breakpoints, watchpoints, catchpoints
3010 @cindex deleting breakpoints, watchpoints, catchpoints
3011 It is often necessary to eliminate a breakpoint, watchpoint, or
3012 catchpoint once it has done its job and you no longer want your program
3013 to stop there. This is called @dfn{deleting} the breakpoint. A
3014 breakpoint that has been deleted no longer exists; it is forgotten.
3016 With the @code{clear} command you can delete breakpoints according to
3017 where they are in your program. With the @code{delete} command you can
3018 delete individual breakpoints, watchpoints, or catchpoints by specifying
3019 their breakpoint numbers.
3021 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3022 automatically ignores breakpoints on the first instruction to be executed
3023 when you continue execution without changing the execution address.
3028 Delete any breakpoints at the next instruction to be executed in the
3029 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
3030 the innermost frame is selected, this is a good way to delete a
3031 breakpoint where your program just stopped.
3033 @item clear @var{function}
3034 @itemx clear @var{filename}:@var{function}
3035 Delete any breakpoints set at entry to the named @var{function}.
3037 @item clear @var{linenum}
3038 @itemx clear @var{filename}:@var{linenum}
3039 Delete any breakpoints set at or within the code of the specified
3040 @var{linenum} of the specified @var{filename}.
3042 @cindex delete breakpoints
3044 @kindex d @r{(@code{delete})}
3045 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3046 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3047 ranges specified as arguments. If no argument is specified, delete all
3048 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3049 confirm off}). You can abbreviate this command as @code{d}.
3053 @subsection Disabling breakpoints
3055 @cindex enable/disable a breakpoint
3056 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3057 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3058 it had been deleted, but remembers the information on the breakpoint so
3059 that you can @dfn{enable} it again later.
3061 You disable and enable breakpoints, watchpoints, and catchpoints with
3062 the @code{enable} and @code{disable} commands, optionally specifying one
3063 or more breakpoint numbers as arguments. Use @code{info break} or
3064 @code{info watch} to print a list of breakpoints, watchpoints, and
3065 catchpoints if you do not know which numbers to use.
3067 A breakpoint, watchpoint, or catchpoint can have any of four different
3068 states of enablement:
3072 Enabled. The breakpoint stops your program. A breakpoint set
3073 with the @code{break} command starts out in this state.
3075 Disabled. The breakpoint has no effect on your program.
3077 Enabled once. The breakpoint stops your program, but then becomes
3080 Enabled for deletion. The breakpoint stops your program, but
3081 immediately after it does so it is deleted permanently. A breakpoint
3082 set with the @code{tbreak} command starts out in this state.
3085 You can use the following commands to enable or disable breakpoints,
3086 watchpoints, and catchpoints:
3090 @kindex dis @r{(@code{disable})}
3091 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3092 Disable the specified breakpoints---or all breakpoints, if none are
3093 listed. A disabled breakpoint has no effect but is not forgotten. All
3094 options such as ignore-counts, conditions and commands are remembered in
3095 case the breakpoint is enabled again later. You may abbreviate
3096 @code{disable} as @code{dis}.
3099 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3100 Enable the specified breakpoints (or all defined breakpoints). They
3101 become effective once again in stopping your program.
3103 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3104 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3105 of these breakpoints immediately after stopping your program.
3107 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3108 Enable the specified breakpoints to work once, then die. @value{GDBN}
3109 deletes any of these breakpoints as soon as your program stops there.
3110 Breakpoints set by the @code{tbreak} command start out in this state.
3113 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3114 @c confusing: tbreak is also initially enabled.
3115 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3116 ,Setting breakpoints}), breakpoints that you set are initially enabled;
3117 subsequently, they become disabled or enabled only when you use one of
3118 the commands above. (The command @code{until} can set and delete a
3119 breakpoint of its own, but it does not change the state of your other
3120 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3124 @subsection Break conditions
3125 @cindex conditional breakpoints
3126 @cindex breakpoint conditions
3128 @c FIXME what is scope of break condition expr? Context where wanted?
3129 @c in particular for a watchpoint?
3130 The simplest sort of breakpoint breaks every time your program reaches a
3131 specified place. You can also specify a @dfn{condition} for a
3132 breakpoint. A condition is just a Boolean expression in your
3133 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3134 a condition evaluates the expression each time your program reaches it,
3135 and your program stops only if the condition is @emph{true}.
3137 This is the converse of using assertions for program validation; in that
3138 situation, you want to stop when the assertion is violated---that is,
3139 when the condition is false. In C, if you want to test an assertion expressed
3140 by the condition @var{assert}, you should set the condition
3141 @samp{! @var{assert}} on the appropriate breakpoint.
3143 Conditions are also accepted for watchpoints; you may not need them,
3144 since a watchpoint is inspecting the value of an expression anyhow---but
3145 it might be simpler, say, to just set a watchpoint on a variable name,
3146 and specify a condition that tests whether the new value is an interesting
3149 Break conditions can have side effects, and may even call functions in
3150 your program. This can be useful, for example, to activate functions
3151 that log program progress, or to use your own print functions to
3152 format special data structures. The effects are completely predictable
3153 unless there is another enabled breakpoint at the same address. (In
3154 that case, @value{GDBN} might see the other breakpoint first and stop your
3155 program without checking the condition of this one.) Note that
3156 breakpoint commands are usually more convenient and flexible than break
3158 purpose of performing side effects when a breakpoint is reached
3159 (@pxref{Break Commands, ,Breakpoint command lists}).
3161 Break conditions can be specified when a breakpoint is set, by using
3162 @samp{if} in the arguments to the @code{break} command. @xref{Set
3163 Breaks, ,Setting breakpoints}. They can also be changed at any time
3164 with the @code{condition} command.
3166 You can also use the @code{if} keyword with the @code{watch} command.
3167 The @code{catch} command does not recognize the @code{if} keyword;
3168 @code{condition} is the only way to impose a further condition on a
3173 @item condition @var{bnum} @var{expression}
3174 Specify @var{expression} as the break condition for breakpoint,
3175 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3176 breakpoint @var{bnum} stops your program only if the value of
3177 @var{expression} is true (nonzero, in C). When you use
3178 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3179 syntactic correctness, and to determine whether symbols in it have
3180 referents in the context of your breakpoint. If @var{expression} uses
3181 symbols not referenced in the context of the breakpoint, @value{GDBN}
3182 prints an error message:
3185 No symbol "foo" in current context.
3190 not actually evaluate @var{expression} at the time the @code{condition}
3191 command (or a command that sets a breakpoint with a condition, like
3192 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3194 @item condition @var{bnum}
3195 Remove the condition from breakpoint number @var{bnum}. It becomes
3196 an ordinary unconditional breakpoint.
3199 @cindex ignore count (of breakpoint)
3200 A special case of a breakpoint condition is to stop only when the
3201 breakpoint has been reached a certain number of times. This is so
3202 useful that there is a special way to do it, using the @dfn{ignore
3203 count} of the breakpoint. Every breakpoint has an ignore count, which
3204 is an integer. Most of the time, the ignore count is zero, and
3205 therefore has no effect. But if your program reaches a breakpoint whose
3206 ignore count is positive, then instead of stopping, it just decrements
3207 the ignore count by one and continues. As a result, if the ignore count
3208 value is @var{n}, the breakpoint does not stop the next @var{n} times
3209 your program reaches it.
3213 @item ignore @var{bnum} @var{count}
3214 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3215 The next @var{count} times the breakpoint is reached, your program's
3216 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3219 To make the breakpoint stop the next time it is reached, specify
3222 When you use @code{continue} to resume execution of your program from a
3223 breakpoint, you can specify an ignore count directly as an argument to
3224 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3225 Stepping,,Continuing and stepping}.
3227 If a breakpoint has a positive ignore count and a condition, the
3228 condition is not checked. Once the ignore count reaches zero,
3229 @value{GDBN} resumes checking the condition.
3231 You could achieve the effect of the ignore count with a condition such
3232 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3233 is decremented each time. @xref{Convenience Vars, ,Convenience
3237 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3240 @node Break Commands
3241 @subsection Breakpoint command lists
3243 @cindex breakpoint commands
3244 You can give any breakpoint (or watchpoint or catchpoint) a series of
3245 commands to execute when your program stops due to that breakpoint. For
3246 example, you might want to print the values of certain expressions, or
3247 enable other breakpoints.
3252 @item commands @r{[}@var{bnum}@r{]}
3253 @itemx @dots{} @var{command-list} @dots{}
3255 Specify a list of commands for breakpoint number @var{bnum}. The commands
3256 themselves appear on the following lines. Type a line containing just
3257 @code{end} to terminate the commands.
3259 To remove all commands from a breakpoint, type @code{commands} and
3260 follow it immediately with @code{end}; that is, give no commands.
3262 With no @var{bnum} argument, @code{commands} refers to the last
3263 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3264 recently encountered).
3267 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3268 disabled within a @var{command-list}.
3270 You can use breakpoint commands to start your program up again. Simply
3271 use the @code{continue} command, or @code{step}, or any other command
3272 that resumes execution.
3274 Any other commands in the command list, after a command that resumes
3275 execution, are ignored. This is because any time you resume execution
3276 (even with a simple @code{next} or @code{step}), you may encounter
3277 another breakpoint---which could have its own command list, leading to
3278 ambiguities about which list to execute.
3281 If the first command you specify in a command list is @code{silent}, the
3282 usual message about stopping at a breakpoint is not printed. This may
3283 be desirable for breakpoints that are to print a specific message and
3284 then continue. If none of the remaining commands print anything, you
3285 see no sign that the breakpoint was reached. @code{silent} is
3286 meaningful only at the beginning of a breakpoint command list.
3288 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3289 print precisely controlled output, and are often useful in silent
3290 breakpoints. @xref{Output, ,Commands for controlled output}.
3292 For example, here is how you could use breakpoint commands to print the
3293 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3299 printf "x is %d\n",x
3304 One application for breakpoint commands is to compensate for one bug so
3305 you can test for another. Put a breakpoint just after the erroneous line
3306 of code, give it a condition to detect the case in which something
3307 erroneous has been done, and give it commands to assign correct values
3308 to any variables that need them. End with the @code{continue} command
3309 so that your program does not stop, and start with the @code{silent}
3310 command so that no output is produced. Here is an example:
3321 @node Breakpoint Menus
3322 @subsection Breakpoint menus
3324 @cindex symbol overloading
3326 Some programming languages (notably C@t{++} and Objective-C) permit a
3327 single function name
3328 to be defined several times, for application in different contexts.
3329 This is called @dfn{overloading}. When a function name is overloaded,
3330 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3331 a breakpoint. If you realize this is a problem, you can use
3332 something like @samp{break @var{function}(@var{types})} to specify which
3333 particular version of the function you want. Otherwise, @value{GDBN} offers
3334 you a menu of numbered choices for different possible breakpoints, and
3335 waits for your selection with the prompt @samp{>}. The first two
3336 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3337 sets a breakpoint at each definition of @var{function}, and typing
3338 @kbd{0} aborts the @code{break} command without setting any new
3341 For example, the following session excerpt shows an attempt to set a
3342 breakpoint at the overloaded symbol @code{String::after}.
3343 We choose three particular definitions of that function name:
3345 @c FIXME! This is likely to change to show arg type lists, at least
3348 (@value{GDBP}) b String::after
3351 [2] file:String.cc; line number:867
3352 [3] file:String.cc; line number:860
3353 [4] file:String.cc; line number:875
3354 [5] file:String.cc; line number:853
3355 [6] file:String.cc; line number:846
3356 [7] file:String.cc; line number:735
3358 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3359 Breakpoint 2 at 0xb344: file String.cc, line 875.
3360 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3361 Multiple breakpoints were set.
3362 Use the "delete" command to delete unwanted
3368 @c @ifclear BARETARGET
3369 @node Error in Breakpoints
3370 @subsection ``Cannot insert breakpoints''
3372 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3374 Under some operating systems, breakpoints cannot be used in a program if
3375 any other process is running that program. In this situation,
3376 attempting to run or continue a program with a breakpoint causes
3377 @value{GDBN} to print an error message:
3380 Cannot insert breakpoints.
3381 The same program may be running in another process.
3384 When this happens, you have three ways to proceed:
3388 Remove or disable the breakpoints, then continue.
3391 Suspend @value{GDBN}, and copy the file containing your program to a new
3392 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3393 that @value{GDBN} should run your program under that name.
3394 Then start your program again.
3397 Relink your program so that the text segment is nonsharable, using the
3398 linker option @samp{-N}. The operating system limitation may not apply
3399 to nonsharable executables.
3403 A similar message can be printed if you request too many active
3404 hardware-assisted breakpoints and watchpoints:
3406 @c FIXME: the precise wording of this message may change; the relevant
3407 @c source change is not committed yet (Sep 3, 1999).
3409 Stopped; cannot insert breakpoints.
3410 You may have requested too many hardware breakpoints and watchpoints.
3414 This message is printed when you attempt to resume the program, since
3415 only then @value{GDBN} knows exactly how many hardware breakpoints and
3416 watchpoints it needs to insert.
3418 When this message is printed, you need to disable or remove some of the
3419 hardware-assisted breakpoints and watchpoints, and then continue.
3421 @node Breakpoint related warnings
3422 @subsection ``Breakpoint address adjusted...''
3423 @cindex breakpoint address adjusted
3425 Some processor architectures place constraints on the addresses at
3426 which breakpoints may be placed. For architectures thus constrained,
3427 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3428 with the constraints dictated by the architecture.
3430 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3431 a VLIW architecture in which a number of RISC-like instructions may be
3432 bundled together for parallel execution. The FR-V architecture
3433 constrains the location of a breakpoint instruction within such a
3434 bundle to the instruction with the lowest address. @value{GDBN}
3435 honors this constraint by adjusting a breakpoint's address to the
3436 first in the bundle.
3438 It is not uncommon for optimized code to have bundles which contain
3439 instructions from different source statements, thus it may happen that
3440 a breakpoint's address will be adjusted from one source statement to
3441 another. Since this adjustment may significantly alter @value{GDBN}'s
3442 breakpoint related behavior from what the user expects, a warning is
3443 printed when the breakpoint is first set and also when the breakpoint
3446 A warning like the one below is printed when setting a breakpoint
3447 that's been subject to address adjustment:
3450 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3453 Such warnings are printed both for user settable and @value{GDBN}'s
3454 internal breakpoints. If you see one of these warnings, you should
3455 verify that a breakpoint set at the adjusted address will have the
3456 desired affect. If not, the breakpoint in question may be removed and
3457 other breakpoints may be set which will have the desired behavior.
3458 E.g., it may be sufficient to place the breakpoint at a later
3459 instruction. A conditional breakpoint may also be useful in some
3460 cases to prevent the breakpoint from triggering too often.
3462 @value{GDBN} will also issue a warning when stopping at one of these
3463 adjusted breakpoints:
3466 warning: Breakpoint 1 address previously adjusted from 0x00010414
3470 When this warning is encountered, it may be too late to take remedial
3471 action except in cases where the breakpoint is hit earlier or more
3472 frequently than expected.
3474 @node Continuing and Stepping
3475 @section Continuing and stepping
3479 @cindex resuming execution
3480 @dfn{Continuing} means resuming program execution until your program
3481 completes normally. In contrast, @dfn{stepping} means executing just
3482 one more ``step'' of your program, where ``step'' may mean either one
3483 line of source code, or one machine instruction (depending on what
3484 particular command you use). Either when continuing or when stepping,
3485 your program may stop even sooner, due to a breakpoint or a signal. (If
3486 it stops due to a signal, you may want to use @code{handle}, or use
3487 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3491 @kindex c @r{(@code{continue})}
3492 @kindex fg @r{(resume foreground execution)}
3493 @item continue @r{[}@var{ignore-count}@r{]}
3494 @itemx c @r{[}@var{ignore-count}@r{]}
3495 @itemx fg @r{[}@var{ignore-count}@r{]}
3496 Resume program execution, at the address where your program last stopped;
3497 any breakpoints set at that address are bypassed. The optional argument
3498 @var{ignore-count} allows you to specify a further number of times to
3499 ignore a breakpoint at this location; its effect is like that of
3500 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3502 The argument @var{ignore-count} is meaningful only when your program
3503 stopped due to a breakpoint. At other times, the argument to
3504 @code{continue} is ignored.
3506 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3507 debugged program is deemed to be the foreground program) are provided
3508 purely for convenience, and have exactly the same behavior as
3512 To resume execution at a different place, you can use @code{return}
3513 (@pxref{Returning, ,Returning from a function}) to go back to the
3514 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3515 different address}) to go to an arbitrary location in your program.
3517 A typical technique for using stepping is to set a breakpoint
3518 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3519 beginning of the function or the section of your program where a problem
3520 is believed to lie, run your program until it stops at that breakpoint,
3521 and then step through the suspect area, examining the variables that are
3522 interesting, until you see the problem happen.
3526 @kindex s @r{(@code{step})}
3528 Continue running your program until control reaches a different source
3529 line, then stop it and return control to @value{GDBN}. This command is
3530 abbreviated @code{s}.
3533 @c "without debugging information" is imprecise; actually "without line
3534 @c numbers in the debugging information". (gcc -g1 has debugging info but
3535 @c not line numbers). But it seems complex to try to make that
3536 @c distinction here.
3537 @emph{Warning:} If you use the @code{step} command while control is
3538 within a function that was compiled without debugging information,
3539 execution proceeds until control reaches a function that does have
3540 debugging information. Likewise, it will not step into a function which
3541 is compiled without debugging information. To step through functions
3542 without debugging information, use the @code{stepi} command, described
3546 The @code{step} command only stops at the first instruction of a source
3547 line. This prevents the multiple stops that could otherwise occur in
3548 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3549 to stop if a function that has debugging information is called within
3550 the line. In other words, @code{step} @emph{steps inside} any functions
3551 called within the line.
3553 Also, the @code{step} command only enters a function if there is line
3554 number information for the function. Otherwise it acts like the
3555 @code{next} command. This avoids problems when using @code{cc -gl}
3556 on MIPS machines. Previously, @code{step} entered subroutines if there
3557 was any debugging information about the routine.
3559 @item step @var{count}
3560 Continue running as in @code{step}, but do so @var{count} times. If a
3561 breakpoint is reached, or a signal not related to stepping occurs before
3562 @var{count} steps, stepping stops right away.
3565 @kindex n @r{(@code{next})}
3566 @item next @r{[}@var{count}@r{]}
3567 Continue to the next source line in the current (innermost) stack frame.
3568 This is similar to @code{step}, but function calls that appear within
3569 the line of code are executed without stopping. Execution stops when
3570 control reaches a different line of code at the original stack level
3571 that was executing when you gave the @code{next} command. This command
3572 is abbreviated @code{n}.
3574 An argument @var{count} is a repeat count, as for @code{step}.
3577 @c FIX ME!! Do we delete this, or is there a way it fits in with
3578 @c the following paragraph? --- Vctoria
3580 @c @code{next} within a function that lacks debugging information acts like
3581 @c @code{step}, but any function calls appearing within the code of the
3582 @c function are executed without stopping.
3584 The @code{next} command only stops at the first instruction of a
3585 source line. This prevents multiple stops that could otherwise occur in
3586 @code{switch} statements, @code{for} loops, etc.
3588 @kindex set step-mode
3590 @cindex functions without line info, and stepping
3591 @cindex stepping into functions with no line info
3592 @itemx set step-mode on
3593 The @code{set step-mode on} command causes the @code{step} command to
3594 stop at the first instruction of a function which contains no debug line
3595 information rather than stepping over it.
3597 This is useful in cases where you may be interested in inspecting the
3598 machine instructions of a function which has no symbolic info and do not
3599 want @value{GDBN} to automatically skip over this function.
3601 @item set step-mode off
3602 Causes the @code{step} command to step over any functions which contains no
3603 debug information. This is the default.
3607 Continue running until just after function in the selected stack frame
3608 returns. Print the returned value (if any).
3610 Contrast this with the @code{return} command (@pxref{Returning,
3611 ,Returning from a function}).
3614 @kindex u @r{(@code{until})}
3615 @cindex run until specified location
3618 Continue running until a source line past the current line, in the
3619 current stack frame, is reached. This command is used to avoid single
3620 stepping through a loop more than once. It is like the @code{next}
3621 command, except that when @code{until} encounters a jump, it
3622 automatically continues execution until the program counter is greater
3623 than the address of the jump.
3625 This means that when you reach the end of a loop after single stepping
3626 though it, @code{until} makes your program continue execution until it
3627 exits the loop. In contrast, a @code{next} command at the end of a loop
3628 simply steps back to the beginning of the loop, which forces you to step
3629 through the next iteration.
3631 @code{until} always stops your program if it attempts to exit the current
3634 @code{until} may produce somewhat counterintuitive results if the order
3635 of machine code does not match the order of the source lines. For
3636 example, in the following excerpt from a debugging session, the @code{f}
3637 (@code{frame}) command shows that execution is stopped at line
3638 @code{206}; yet when we use @code{until}, we get to line @code{195}:
3642 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
3644 (@value{GDBP}) until
3645 195 for ( ; argc > 0; NEXTARG) @{
3648 This happened because, for execution efficiency, the compiler had
3649 generated code for the loop closure test at the end, rather than the
3650 start, of the loop---even though the test in a C @code{for}-loop is
3651 written before the body of the loop. The @code{until} command appeared
3652 to step back to the beginning of the loop when it advanced to this
3653 expression; however, it has not really gone to an earlier
3654 statement---not in terms of the actual machine code.
3656 @code{until} with no argument works by means of single
3657 instruction stepping, and hence is slower than @code{until} with an
3660 @item until @var{location}
3661 @itemx u @var{location}
3662 Continue running your program until either the specified location is
3663 reached, or the current stack frame returns. @var{location} is any of
3664 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
3665 ,Setting breakpoints}). This form of the command uses breakpoints, and
3666 hence is quicker than @code{until} without an argument. The specified
3667 location is actually reached only if it is in the current frame. This
3668 implies that @code{until} can be used to skip over recursive function
3669 invocations. For instance in the code below, if the current location is
3670 line @code{96}, issuing @code{until 99} will execute the program up to
3671 line @code{99} in the same invocation of factorial, i.e. after the inner
3672 invocations have returned.
3675 94 int factorial (int value)
3677 96 if (value > 1) @{
3678 97 value *= factorial (value - 1);
3685 @kindex advance @var{location}
3686 @itemx advance @var{location}
3687 Continue running the program up to the given @var{location}. An argument is
3688 required, which should be of the same form as arguments for the @code{break}
3689 command. Execution will also stop upon exit from the current stack
3690 frame. This command is similar to @code{until}, but @code{advance} will
3691 not skip over recursive function calls, and the target location doesn't
3692 have to be in the same frame as the current one.
3696 @kindex si @r{(@code{stepi})}
3698 @itemx stepi @var{arg}
3700 Execute one machine instruction, then stop and return to the debugger.
3702 It is often useful to do @samp{display/i $pc} when stepping by machine
3703 instructions. This makes @value{GDBN} automatically display the next
3704 instruction to be executed, each time your program stops. @xref{Auto
3705 Display,, Automatic display}.
3707 An argument is a repeat count, as in @code{step}.
3711 @kindex ni @r{(@code{nexti})}
3713 @itemx nexti @var{arg}
3715 Execute one machine instruction, but if it is a function call,
3716 proceed until the function returns.
3718 An argument is a repeat count, as in @code{next}.
3725 A signal is an asynchronous event that can happen in a program. The
3726 operating system defines the possible kinds of signals, and gives each
3727 kind a name and a number. For example, in Unix @code{SIGINT} is the
3728 signal a program gets when you type an interrupt character (often @kbd{C-c});
3729 @code{SIGSEGV} is the signal a program gets from referencing a place in
3730 memory far away from all the areas in use; @code{SIGALRM} occurs when
3731 the alarm clock timer goes off (which happens only if your program has
3732 requested an alarm).
3734 @cindex fatal signals
3735 Some signals, including @code{SIGALRM}, are a normal part of the
3736 functioning of your program. Others, such as @code{SIGSEGV}, indicate
3737 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
3738 program has not specified in advance some other way to handle the signal.
3739 @code{SIGINT} does not indicate an error in your program, but it is normally
3740 fatal so it can carry out the purpose of the interrupt: to kill the program.
3742 @value{GDBN} has the ability to detect any occurrence of a signal in your
3743 program. You can tell @value{GDBN} in advance what to do for each kind of
3746 @cindex handling signals
3747 Normally, @value{GDBN} is set up to let the non-erroneous signals like
3748 @code{SIGALRM} be silently passed to your program
3749 (so as not to interfere with their role in the program's functioning)
3750 but to stop your program immediately whenever an error signal happens.
3751 You can change these settings with the @code{handle} command.
3754 @kindex info signals
3758 Print a table of all the kinds of signals and how @value{GDBN} has been told to
3759 handle each one. You can use this to see the signal numbers of all
3760 the defined types of signals.
3762 @code{info handle} is an alias for @code{info signals}.
3765 @item handle @var{signal} @var{keywords}@dots{}
3766 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
3767 can be the number of a signal or its name (with or without the
3768 @samp{SIG} at the beginning); a list of signal numbers of the form
3769 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
3770 known signals. The @var{keywords} say what change to make.
3774 The keywords allowed by the @code{handle} command can be abbreviated.
3775 Their full names are:
3779 @value{GDBN} should not stop your program when this signal happens. It may
3780 still print a message telling you that the signal has come in.
3783 @value{GDBN} should stop your program when this signal happens. This implies
3784 the @code{print} keyword as well.
3787 @value{GDBN} should print a message when this signal happens.
3790 @value{GDBN} should not mention the occurrence of the signal at all. This
3791 implies the @code{nostop} keyword as well.
3795 @value{GDBN} should allow your program to see this signal; your program
3796 can handle the signal, or else it may terminate if the signal is fatal
3797 and not handled. @code{pass} and @code{noignore} are synonyms.
3801 @value{GDBN} should not allow your program to see this signal.
3802 @code{nopass} and @code{ignore} are synonyms.
3806 When a signal stops your program, the signal is not visible to the
3808 continue. Your program sees the signal then, if @code{pass} is in
3809 effect for the signal in question @emph{at that time}. In other words,
3810 after @value{GDBN} reports a signal, you can use the @code{handle}
3811 command with @code{pass} or @code{nopass} to control whether your
3812 program sees that signal when you continue.
3814 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
3815 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
3816 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
3819 You can also use the @code{signal} command to prevent your program from
3820 seeing a signal, or cause it to see a signal it normally would not see,
3821 or to give it any signal at any time. For example, if your program stopped
3822 due to some sort of memory reference error, you might store correct
3823 values into the erroneous variables and continue, hoping to see more
3824 execution; but your program would probably terminate immediately as
3825 a result of the fatal signal once it saw the signal. To prevent this,
3826 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
3830 @section Stopping and starting multi-thread programs
3832 When your program has multiple threads (@pxref{Threads,, Debugging
3833 programs with multiple threads}), you can choose whether to set
3834 breakpoints on all threads, or on a particular thread.
3837 @cindex breakpoints and threads
3838 @cindex thread breakpoints
3839 @kindex break @dots{} thread @var{threadno}
3840 @item break @var{linespec} thread @var{threadno}
3841 @itemx break @var{linespec} thread @var{threadno} if @dots{}
3842 @var{linespec} specifies source lines; there are several ways of
3843 writing them, but the effect is always to specify some source line.
3845 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
3846 to specify that you only want @value{GDBN} to stop the program when a
3847 particular thread reaches this breakpoint. @var{threadno} is one of the
3848 numeric thread identifiers assigned by @value{GDBN}, shown in the first
3849 column of the @samp{info threads} display.
3851 If you do not specify @samp{thread @var{threadno}} when you set a
3852 breakpoint, the breakpoint applies to @emph{all} threads of your
3855 You can use the @code{thread} qualifier on conditional breakpoints as
3856 well; in this case, place @samp{thread @var{threadno}} before the
3857 breakpoint condition, like this:
3860 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
3865 @cindex stopped threads
3866 @cindex threads, stopped
3867 Whenever your program stops under @value{GDBN} for any reason,
3868 @emph{all} threads of execution stop, not just the current thread. This
3869 allows you to examine the overall state of the program, including
3870 switching between threads, without worrying that things may change
3873 @cindex thread breakpoints and system calls
3874 @cindex system calls and thread breakpoints
3875 @cindex premature return from system calls
3876 There is an unfortunate side effect. If one thread stops for a
3877 breakpoint, or for some other reason, and another thread is blocked in a
3878 system call, then the system call may return prematurely. This is a
3879 consequence of the interaction between multiple threads and the signals
3880 that @value{GDBN} uses to implement breakpoints and other events that
3883 To handle this problem, your program should check the return value of
3884 each system call and react appropriately. This is good programming
3887 For example, do not write code like this:
3893 The call to @code{sleep} will return early if a different thread stops
3894 at a breakpoint or for some other reason.
3896 Instead, write this:
3901 unslept = sleep (unslept);
3904 A system call is allowed to return early, so the system is still
3905 conforming to its specification. But @value{GDBN} does cause your
3906 multi-threaded program to behave differently than it would without
3909 Also, @value{GDBN} uses internal breakpoints in the thread library to
3910 monitor certain events such as thread creation and thread destruction.
3911 When such an event happens, a system call in another thread may return
3912 prematurely, even though your program does not appear to stop.
3914 @cindex continuing threads
3915 @cindex threads, continuing
3916 Conversely, whenever you restart the program, @emph{all} threads start
3917 executing. @emph{This is true even when single-stepping} with commands
3918 like @code{step} or @code{next}.
3920 In particular, @value{GDBN} cannot single-step all threads in lockstep.
3921 Since thread scheduling is up to your debugging target's operating
3922 system (not controlled by @value{GDBN}), other threads may
3923 execute more than one statement while the current thread completes a
3924 single step. Moreover, in general other threads stop in the middle of a
3925 statement, rather than at a clean statement boundary, when the program
3928 You might even find your program stopped in another thread after
3929 continuing or even single-stepping. This happens whenever some other
3930 thread runs into a breakpoint, a signal, or an exception before the
3931 first thread completes whatever you requested.
3933 On some OSes, you can lock the OS scheduler and thus allow only a single
3937 @item set scheduler-locking @var{mode}
3938 Set the scheduler locking mode. If it is @code{off}, then there is no
3939 locking and any thread may run at any time. If @code{on}, then only the
3940 current thread may run when the inferior is resumed. The @code{step}
3941 mode optimizes for single-stepping. It stops other threads from
3942 ``seizing the prompt'' by preempting the current thread while you are
3943 stepping. Other threads will only rarely (or never) get a chance to run
3944 when you step. They are more likely to run when you @samp{next} over a
3945 function call, and they are completely free to run when you use commands
3946 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
3947 thread hits a breakpoint during its timeslice, they will never steal the
3948 @value{GDBN} prompt away from the thread that you are debugging.
3950 @item show scheduler-locking
3951 Display the current scheduler locking mode.
3956 @chapter Examining the Stack
3958 When your program has stopped, the first thing you need to know is where it
3959 stopped and how it got there.
3962 Each time your program performs a function call, information about the call
3964 That information includes the location of the call in your program,
3965 the arguments of the call,
3966 and the local variables of the function being called.
3967 The information is saved in a block of data called a @dfn{stack frame}.
3968 The stack frames are allocated in a region of memory called the @dfn{call
3971 When your program stops, the @value{GDBN} commands for examining the
3972 stack allow you to see all of this information.
3974 @cindex selected frame
3975 One of the stack frames is @dfn{selected} by @value{GDBN} and many
3976 @value{GDBN} commands refer implicitly to the selected frame. In
3977 particular, whenever you ask @value{GDBN} for the value of a variable in
3978 your program, the value is found in the selected frame. There are
3979 special @value{GDBN} commands to select whichever frame you are
3980 interested in. @xref{Selection, ,Selecting a frame}.
3982 When your program stops, @value{GDBN} automatically selects the
3983 currently executing frame and describes it briefly, similar to the
3984 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
3987 * Frames:: Stack frames
3988 * Backtrace:: Backtraces
3989 * Selection:: Selecting a frame
3990 * Frame Info:: Information on a frame
3995 @section Stack frames
3997 @cindex frame, definition
3999 The call stack is divided up into contiguous pieces called @dfn{stack
4000 frames}, or @dfn{frames} for short; each frame is the data associated
4001 with one call to one function. The frame contains the arguments given
4002 to the function, the function's local variables, and the address at
4003 which the function is executing.
4005 @cindex initial frame
4006 @cindex outermost frame
4007 @cindex innermost frame
4008 When your program is started, the stack has only one frame, that of the
4009 function @code{main}. This is called the @dfn{initial} frame or the
4010 @dfn{outermost} frame. Each time a function is called, a new frame is
4011 made. Each time a function returns, the frame for that function invocation
4012 is eliminated. If a function is recursive, there can be many frames for
4013 the same function. The frame for the function in which execution is
4014 actually occurring is called the @dfn{innermost} frame. This is the most
4015 recently created of all the stack frames that still exist.
4017 @cindex frame pointer
4018 Inside your program, stack frames are identified by their addresses. A
4019 stack frame consists of many bytes, each of which has its own address; each
4020 kind of computer has a convention for choosing one byte whose
4021 address serves as the address of the frame. Usually this address is kept
4022 in a register called the @dfn{frame pointer register} while execution is
4023 going on in that frame.
4025 @cindex frame number
4026 @value{GDBN} assigns numbers to all existing stack frames, starting with
4027 zero for the innermost frame, one for the frame that called it,
4028 and so on upward. These numbers do not really exist in your program;
4029 they are assigned by @value{GDBN} to give you a way of designating stack
4030 frames in @value{GDBN} commands.
4032 @c The -fomit-frame-pointer below perennially causes hbox overflow
4033 @c underflow problems.
4034 @cindex frameless execution
4035 Some compilers provide a way to compile functions so that they operate
4036 without stack frames. (For example, the @value{GCC} option
4038 @samp{-fomit-frame-pointer}
4040 generates functions without a frame.)
4041 This is occasionally done with heavily used library functions to save
4042 the frame setup time. @value{GDBN} has limited facilities for dealing
4043 with these function invocations. If the innermost function invocation
4044 has no stack frame, @value{GDBN} nevertheless regards it as though
4045 it had a separate frame, which is numbered zero as usual, allowing
4046 correct tracing of the function call chain. However, @value{GDBN} has
4047 no provision for frameless functions elsewhere in the stack.
4050 @kindex frame@r{, command}
4051 @cindex current stack frame
4052 @item frame @var{args}
4053 The @code{frame} command allows you to move from one stack frame to another,
4054 and to print the stack frame you select. @var{args} may be either the
4055 address of the frame or the stack frame number. Without an argument,
4056 @code{frame} prints the current stack frame.
4058 @kindex select-frame
4059 @cindex selecting frame silently
4061 The @code{select-frame} command allows you to move from one stack frame
4062 to another without printing the frame. This is the silent version of
4070 @cindex call stack traces
4071 A backtrace is a summary of how your program got where it is. It shows one
4072 line per frame, for many frames, starting with the currently executing
4073 frame (frame zero), followed by its caller (frame one), and on up the
4078 @kindex bt @r{(@code{backtrace})}
4081 Print a backtrace of the entire stack: one line per frame for all
4082 frames in the stack.
4084 You can stop the backtrace at any time by typing the system interrupt
4085 character, normally @kbd{C-c}.
4087 @item backtrace @var{n}
4089 Similar, but print only the innermost @var{n} frames.
4091 @item backtrace -@var{n}
4093 Similar, but print only the outermost @var{n} frames.
4098 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4099 are additional aliases for @code{backtrace}.
4101 Each line in the backtrace shows the frame number and the function name.
4102 The program counter value is also shown---unless you use @code{set
4103 print address off}. The backtrace also shows the source file name and
4104 line number, as well as the arguments to the function. The program
4105 counter value is omitted if it is at the beginning of the code for that
4108 Here is an example of a backtrace. It was made with the command
4109 @samp{bt 3}, so it shows the innermost three frames.
4113 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4115 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4116 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4118 (More stack frames follow...)
4123 The display for frame zero does not begin with a program counter
4124 value, indicating that your program has stopped at the beginning of the
4125 code for line @code{993} of @code{builtin.c}.
4127 @cindex backtrace beyond @code{main} function
4128 @cindex program entry point
4129 @cindex startup code, and backtrace
4130 Most programs have a standard user entry point---a place where system
4131 libraries and startup code transition into user code. For C this is
4132 @code{main}. When @value{GDBN} finds the entry function in a backtrace
4133 it will terminate the backtrace, to avoid tracing into highly
4134 system-specific (and generally uninteresting) code.
4136 If you need to examine the startup code, or limit the number of levels
4137 in a backtrace, you can change this behavior:
4140 @item set backtrace past-main
4141 @itemx set backtrace past-main on
4142 @kindex set backtrace
4143 Backtraces will continue past the user entry point.
4145 @item set backtrace past-main off
4146 Backtraces will stop when they encounter the user entry point. This is the
4149 @item show backtrace past-main
4150 @kindex show backtrace
4151 Display the current user entry point backtrace policy.
4153 @item set backtrace past-entry
4154 @itemx set backtrace past-entry on
4155 Backtraces will continue past the internal entry point of an application.
4156 This entry point is encoded by the linker when the application is built,
4157 and is likely before the user entry point @code{main} (or equivalent) is called.
4159 @item set backtrace past-entry off
4160 Backtraces will stop when they encouter the internal entry point of an
4161 application. This is the default.
4163 @item show backtrace past-entry
4164 Display the current internal entry point backtrace policy.
4166 @item set backtrace limit @var{n}
4167 @itemx set backtrace limit 0
4168 @cindex backtrace limit
4169 Limit the backtrace to @var{n} levels. A value of zero means
4172 @item show backtrace limit
4173 Display the current limit on backtrace levels.
4177 @section Selecting a frame
4179 Most commands for examining the stack and other data in your program work on
4180 whichever stack frame is selected at the moment. Here are the commands for
4181 selecting a stack frame; all of them finish by printing a brief description
4182 of the stack frame just selected.
4185 @kindex frame@r{, selecting}
4186 @kindex f @r{(@code{frame})}
4189 Select frame number @var{n}. Recall that frame zero is the innermost
4190 (currently executing) frame, frame one is the frame that called the
4191 innermost one, and so on. The highest-numbered frame is the one for
4194 @item frame @var{addr}
4196 Select the frame at address @var{addr}. This is useful mainly if the
4197 chaining of stack frames has been damaged by a bug, making it
4198 impossible for @value{GDBN} to assign numbers properly to all frames. In
4199 addition, this can be useful when your program has multiple stacks and
4200 switches between them.
4202 On the SPARC architecture, @code{frame} needs two addresses to
4203 select an arbitrary frame: a frame pointer and a stack pointer.
4205 On the MIPS and Alpha architecture, it needs two addresses: a stack
4206 pointer and a program counter.
4208 On the 29k architecture, it needs three addresses: a register stack
4209 pointer, a program counter, and a memory stack pointer.
4210 @c note to future updaters: this is conditioned on a flag
4211 @c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date
4212 @c as of 27 Jan 1994.
4216 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4217 advances toward the outermost frame, to higher frame numbers, to frames
4218 that have existed longer. @var{n} defaults to one.
4221 @kindex do @r{(@code{down})}
4223 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4224 advances toward the innermost frame, to lower frame numbers, to frames
4225 that were created more recently. @var{n} defaults to one. You may
4226 abbreviate @code{down} as @code{do}.
4229 All of these commands end by printing two lines of output describing the
4230 frame. The first line shows the frame number, the function name, the
4231 arguments, and the source file and line number of execution in that
4232 frame. The second line shows the text of that source line.
4240 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4242 10 read_input_file (argv[i]);
4246 After such a printout, the @code{list} command with no arguments
4247 prints ten lines centered on the point of execution in the frame.
4248 You can also edit the program at the point of execution with your favorite
4249 editing program by typing @code{edit}.
4250 @xref{List, ,Printing source lines},
4254 @kindex down-silently
4256 @item up-silently @var{n}
4257 @itemx down-silently @var{n}
4258 These two commands are variants of @code{up} and @code{down},
4259 respectively; they differ in that they do their work silently, without
4260 causing display of the new frame. They are intended primarily for use
4261 in @value{GDBN} command scripts, where the output might be unnecessary and
4266 @section Information about a frame
4268 There are several other commands to print information about the selected
4274 When used without any argument, this command does not change which
4275 frame is selected, but prints a brief description of the currently
4276 selected stack frame. It can be abbreviated @code{f}. With an
4277 argument, this command is used to select a stack frame.
4278 @xref{Selection, ,Selecting a frame}.
4281 @kindex info f @r{(@code{info frame})}
4284 This command prints a verbose description of the selected stack frame,
4289 the address of the frame
4291 the address of the next frame down (called by this frame)
4293 the address of the next frame up (caller of this frame)
4295 the language in which the source code corresponding to this frame is written
4297 the address of the frame's arguments
4299 the address of the frame's local variables
4301 the program counter saved in it (the address of execution in the caller frame)
4303 which registers were saved in the frame
4306 @noindent The verbose description is useful when
4307 something has gone wrong that has made the stack format fail to fit
4308 the usual conventions.
4310 @item info frame @var{addr}
4311 @itemx info f @var{addr}
4312 Print a verbose description of the frame at address @var{addr}, without
4313 selecting that frame. The selected frame remains unchanged by this
4314 command. This requires the same kind of address (more than one for some
4315 architectures) that you specify in the @code{frame} command.
4316 @xref{Selection, ,Selecting a frame}.
4320 Print the arguments of the selected frame, each on a separate line.
4324 Print the local variables of the selected frame, each on a separate
4325 line. These are all variables (declared either static or automatic)
4326 accessible at the point of execution of the selected frame.
4329 @cindex catch exceptions, list active handlers
4330 @cindex exception handlers, how to list
4332 Print a list of all the exception handlers that are active in the
4333 current stack frame at the current point of execution. To see other
4334 exception handlers, visit the associated frame (using the @code{up},
4335 @code{down}, or @code{frame} commands); then type @code{info catch}.
4336 @xref{Set Catchpoints, , Setting catchpoints}.
4342 @chapter Examining Source Files
4344 @value{GDBN} can print parts of your program's source, since the debugging
4345 information recorded in the program tells @value{GDBN} what source files were
4346 used to build it. When your program stops, @value{GDBN} spontaneously prints
4347 the line where it stopped. Likewise, when you select a stack frame
4348 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4349 execution in that frame has stopped. You can print other portions of
4350 source files by explicit command.
4352 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4353 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4354 @value{GDBN} under @sc{gnu} Emacs}.
4357 * List:: Printing source lines
4358 * Edit:: Editing source files
4359 * Search:: Searching source files
4360 * Source Path:: Specifying source directories
4361 * Machine Code:: Source and machine code
4365 @section Printing source lines
4368 @kindex l @r{(@code{list})}
4369 To print lines from a source file, use the @code{list} command
4370 (abbreviated @code{l}). By default, ten lines are printed.
4371 There are several ways to specify what part of the file you want to print.
4373 Here are the forms of the @code{list} command most commonly used:
4376 @item list @var{linenum}
4377 Print lines centered around line number @var{linenum} in the
4378 current source file.
4380 @item list @var{function}
4381 Print lines centered around the beginning of function
4385 Print more lines. If the last lines printed were printed with a
4386 @code{list} command, this prints lines following the last lines
4387 printed; however, if the last line printed was a solitary line printed
4388 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4389 Stack}), this prints lines centered around that line.
4392 Print lines just before the lines last printed.
4395 By default, @value{GDBN} prints ten source lines with any of these forms of
4396 the @code{list} command. You can change this using @code{set listsize}:
4399 @kindex set listsize
4400 @item set listsize @var{count}
4401 Make the @code{list} command display @var{count} source lines (unless
4402 the @code{list} argument explicitly specifies some other number).
4404 @kindex show listsize
4406 Display the number of lines that @code{list} prints.
4409 Repeating a @code{list} command with @key{RET} discards the argument,
4410 so it is equivalent to typing just @code{list}. This is more useful
4411 than listing the same lines again. An exception is made for an
4412 argument of @samp{-}; that argument is preserved in repetition so that
4413 each repetition moves up in the source file.
4416 In general, the @code{list} command expects you to supply zero, one or two
4417 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4418 of writing them, but the effect is always to specify some source line.
4419 Here is a complete description of the possible arguments for @code{list}:
4422 @item list @var{linespec}
4423 Print lines centered around the line specified by @var{linespec}.
4425 @item list @var{first},@var{last}
4426 Print lines from @var{first} to @var{last}. Both arguments are
4429 @item list ,@var{last}
4430 Print lines ending with @var{last}.
4432 @item list @var{first},
4433 Print lines starting with @var{first}.
4436 Print lines just after the lines last printed.
4439 Print lines just before the lines last printed.
4442 As described in the preceding table.
4445 Here are the ways of specifying a single source line---all the
4450 Specifies line @var{number} of the current source file.
4451 When a @code{list} command has two linespecs, this refers to
4452 the same source file as the first linespec.
4455 Specifies the line @var{offset} lines after the last line printed.
4456 When used as the second linespec in a @code{list} command that has
4457 two, this specifies the line @var{offset} lines down from the
4461 Specifies the line @var{offset} lines before the last line printed.
4463 @item @var{filename}:@var{number}
4464 Specifies line @var{number} in the source file @var{filename}.
4466 @item @var{function}
4467 Specifies the line that begins the body of the function @var{function}.
4468 For example: in C, this is the line with the open brace.
4470 @item @var{filename}:@var{function}
4471 Specifies the line of the open-brace that begins the body of the
4472 function @var{function} in the file @var{filename}. You only need the
4473 file name with a function name to avoid ambiguity when there are
4474 identically named functions in different source files.
4476 @item *@var{address}
4477 Specifies the line containing the program address @var{address}.
4478 @var{address} may be any expression.
4482 @section Editing source files
4483 @cindex editing source files
4486 @kindex e @r{(@code{edit})}
4487 To edit the lines in a source file, use the @code{edit} command.
4488 The editing program of your choice
4489 is invoked with the current line set to
4490 the active line in the program.
4491 Alternatively, there are several ways to specify what part of the file you
4492 want to print if you want to see other parts of the program.
4494 Here are the forms of the @code{edit} command most commonly used:
4498 Edit the current source file at the active line number in the program.
4500 @item edit @var{number}
4501 Edit the current source file with @var{number} as the active line number.
4503 @item edit @var{function}
4504 Edit the file containing @var{function} at the beginning of its definition.
4506 @item edit @var{filename}:@var{number}
4507 Specifies line @var{number} in the source file @var{filename}.
4509 @item edit @var{filename}:@var{function}
4510 Specifies the line that begins the body of the
4511 function @var{function} in the file @var{filename}. You only need the
4512 file name with a function name to avoid ambiguity when there are
4513 identically named functions in different source files.
4515 @item edit *@var{address}
4516 Specifies the line containing the program address @var{address}.
4517 @var{address} may be any expression.
4520 @subsection Choosing your editor
4521 You can customize @value{GDBN} to use any editor you want
4523 The only restriction is that your editor (say @code{ex}), recognizes the
4524 following command-line syntax:
4526 ex +@var{number} file
4528 The optional numeric value +@var{number} specifies the number of the line in
4529 the file where to start editing.}.
4530 By default, it is @file{@value{EDITOR}}, but you can change this
4531 by setting the environment variable @code{EDITOR} before using
4532 @value{GDBN}. For example, to configure @value{GDBN} to use the
4533 @code{vi} editor, you could use these commands with the @code{sh} shell:
4539 or in the @code{csh} shell,
4541 setenv EDITOR /usr/bin/vi
4546 @section Searching source files
4547 @cindex searching source files
4549 There are two commands for searching through the current source file for a
4554 @kindex forward-search
4555 @item forward-search @var{regexp}
4556 @itemx search @var{regexp}
4557 The command @samp{forward-search @var{regexp}} checks each line,
4558 starting with the one following the last line listed, for a match for
4559 @var{regexp}. It lists the line that is found. You can use the
4560 synonym @samp{search @var{regexp}} or abbreviate the command name as
4563 @kindex reverse-search
4564 @item reverse-search @var{regexp}
4565 The command @samp{reverse-search @var{regexp}} checks each line, starting
4566 with the one before the last line listed and going backward, for a match
4567 for @var{regexp}. It lists the line that is found. You can abbreviate
4568 this command as @code{rev}.
4572 @section Specifying source directories
4575 @cindex directories for source files
4576 Executable programs sometimes do not record the directories of the source
4577 files from which they were compiled, just the names. Even when they do,
4578 the directories could be moved between the compilation and your debugging
4579 session. @value{GDBN} has a list of directories to search for source files;
4580 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4581 it tries all the directories in the list, in the order they are present
4582 in the list, until it finds a file with the desired name.
4584 For example, suppose an executable references the file
4585 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
4586 @file{/mnt/cross}. The file is first looked up literally; if this
4587 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
4588 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
4589 message is printed. @value{GDBN} does not look up the parts of the
4590 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
4591 Likewise, the subdirectories of the source path are not searched: if
4592 the source path is @file{/mnt/cross}, and the binary refers to
4593 @file{foo.c}, @value{GDBN} would not find it under
4594 @file{/mnt/cross/usr/src/foo-1.0/lib}.
4596 Plain file names, relative file names with leading directories, file
4597 names containing dots, etc.@: are all treated as described above; for
4598 instance, if the source path is @file{/mnt/cross}, and the source file
4599 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
4600 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
4601 that---@file{/mnt/cross/foo.c}.
4603 Note that the executable search path is @emph{not} used to locate the
4604 source files. Neither is the current working directory, unless it
4605 happens to be in the source path.
4607 Whenever you reset or rearrange the source path, @value{GDBN} clears out
4608 any information it has cached about where source files are found and where
4609 each line is in the file.
4613 When you start @value{GDBN}, its source path includes only @samp{cdir}
4614 and @samp{cwd}, in that order.
4615 To add other directories, use the @code{directory} command.
4618 @item directory @var{dirname} @dots{}
4619 @item dir @var{dirname} @dots{}
4620 Add directory @var{dirname} to the front of the source path. Several
4621 directory names may be given to this command, separated by @samp{:}
4622 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4623 part of absolute file names) or
4624 whitespace. You may specify a directory that is already in the source
4625 path; this moves it forward, so @value{GDBN} searches it sooner.
4629 @vindex $cdir@r{, convenience variable}
4630 @vindex $cwdr@r{, convenience variable}
4631 @cindex compilation directory
4632 @cindex current directory
4633 @cindex working directory
4634 @cindex directory, current
4635 @cindex directory, compilation
4636 You can use the string @samp{$cdir} to refer to the compilation
4637 directory (if one is recorded), and @samp{$cwd} to refer to the current
4638 working directory. @samp{$cwd} is not the same as @samp{.}---the former
4639 tracks the current working directory as it changes during your @value{GDBN}
4640 session, while the latter is immediately expanded to the current
4641 directory at the time you add an entry to the source path.
4644 Reset the source path to empty again. This requires confirmation.
4646 @c RET-repeat for @code{directory} is explicitly disabled, but since
4647 @c repeating it would be a no-op we do not say that. (thanks to RMS)
4649 @item show directories
4650 @kindex show directories
4651 Print the source path: show which directories it contains.
4654 If your source path is cluttered with directories that are no longer of
4655 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4656 versions of source. You can correct the situation as follows:
4660 Use @code{directory} with no argument to reset the source path to empty.
4663 Use @code{directory} with suitable arguments to reinstall the
4664 directories you want in the source path. You can add all the
4665 directories in one command.
4669 @section Source and machine code
4670 @cindex source line and its code address
4672 You can use the command @code{info line} to map source lines to program
4673 addresses (and vice versa), and the command @code{disassemble} to display
4674 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
4675 mode, the @code{info line} command causes the arrow to point to the
4676 line specified. Also, @code{info line} prints addresses in symbolic form as
4681 @item info line @var{linespec}
4682 Print the starting and ending addresses of the compiled code for
4683 source line @var{linespec}. You can specify source lines in any of
4684 the ways understood by the @code{list} command (@pxref{List, ,Printing
4688 For example, we can use @code{info line} to discover the location of
4689 the object code for the first line of function
4690 @code{m4_changequote}:
4692 @c FIXME: I think this example should also show the addresses in
4693 @c symbolic form, as they usually would be displayed.
4695 (@value{GDBP}) info line m4_changequote
4696 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4700 @cindex code address and its source line
4701 We can also inquire (using @code{*@var{addr}} as the form for
4702 @var{linespec}) what source line covers a particular address:
4704 (@value{GDBP}) info line *0x63ff
4705 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4708 @cindex @code{$_} and @code{info line}
4709 @cindex @code{x} command, default address
4710 @kindex x@r{(examine), and} info line
4711 After @code{info line}, the default address for the @code{x} command
4712 is changed to the starting address of the line, so that @samp{x/i} is
4713 sufficient to begin examining the machine code (@pxref{Memory,
4714 ,Examining memory}). Also, this address is saved as the value of the
4715 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4720 @cindex assembly instructions
4721 @cindex instructions, assembly
4722 @cindex machine instructions
4723 @cindex listing machine instructions
4725 This specialized command dumps a range of memory as machine
4726 instructions. The default memory range is the function surrounding the
4727 program counter of the selected frame. A single argument to this
4728 command is a program counter value; @value{GDBN} dumps the function
4729 surrounding this value. Two arguments specify a range of addresses
4730 (first inclusive, second exclusive) to dump.
4733 The following example shows the disassembly of a range of addresses of
4734 HP PA-RISC 2.0 code:
4737 (@value{GDBP}) disas 0x32c4 0x32e4
4738 Dump of assembler code from 0x32c4 to 0x32e4:
4739 0x32c4 <main+204>: addil 0,dp
4740 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
4741 0x32cc <main+212>: ldil 0x3000,r31
4742 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
4743 0x32d4 <main+220>: ldo 0(r31),rp
4744 0x32d8 <main+224>: addil -0x800,dp
4745 0x32dc <main+228>: ldo 0x588(r1),r26
4746 0x32e0 <main+232>: ldil 0x3000,r31
4747 End of assembler dump.
4750 Some architectures have more than one commonly-used set of instruction
4751 mnemonics or other syntax.
4754 @kindex set disassembly-flavor
4755 @cindex Intel disassembly flavor
4756 @cindex AT&T disassembly flavor
4757 @item set disassembly-flavor @var{instruction-set}
4758 Select the instruction set to use when disassembling the
4759 program via the @code{disassemble} or @code{x/i} commands.
4761 Currently this command is only defined for the Intel x86 family. You
4762 can set @var{instruction-set} to either @code{intel} or @code{att}.
4763 The default is @code{att}, the AT&T flavor used by default by Unix
4764 assemblers for x86-based targets.
4769 @chapter Examining Data
4771 @cindex printing data
4772 @cindex examining data
4775 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
4776 @c document because it is nonstandard... Under Epoch it displays in a
4777 @c different window or something like that.
4778 The usual way to examine data in your program is with the @code{print}
4779 command (abbreviated @code{p}), or its synonym @code{inspect}. It
4780 evaluates and prints the value of an expression of the language your
4781 program is written in (@pxref{Languages, ,Using @value{GDBN} with
4782 Different Languages}).
4785 @item print @var{expr}
4786 @itemx print /@var{f} @var{expr}
4787 @var{expr} is an expression (in the source language). By default the
4788 value of @var{expr} is printed in a format appropriate to its data type;
4789 you can choose a different format by specifying @samp{/@var{f}}, where
4790 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
4794 @itemx print /@var{f}
4795 @cindex reprint the last value
4796 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
4797 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
4798 conveniently inspect the same value in an alternative format.
4801 A more low-level way of examining data is with the @code{x} command.
4802 It examines data in memory at a specified address and prints it in a
4803 specified format. @xref{Memory, ,Examining memory}.
4805 If you are interested in information about types, or about how the
4806 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
4807 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
4811 * Expressions:: Expressions
4812 * Variables:: Program variables
4813 * Arrays:: Artificial arrays
4814 * Output Formats:: Output formats
4815 * Memory:: Examining memory
4816 * Auto Display:: Automatic display
4817 * Print Settings:: Print settings
4818 * Value History:: Value history
4819 * Convenience Vars:: Convenience variables
4820 * Registers:: Registers
4821 * Floating Point Hardware:: Floating point hardware
4822 * Vector Unit:: Vector Unit
4823 * Auxiliary Vector:: Auxiliary data provided by operating system
4824 * Memory Region Attributes:: Memory region attributes
4825 * Dump/Restore Files:: Copy between memory and a file
4826 * Core File Generation:: Cause a program dump its core
4827 * Character Sets:: Debugging programs that use a different
4828 character set than GDB does
4829 * Caching Remote Data:: Data caching for remote targets
4833 @section Expressions
4836 @code{print} and many other @value{GDBN} commands accept an expression and
4837 compute its value. Any kind of constant, variable or operator defined
4838 by the programming language you are using is valid in an expression in
4839 @value{GDBN}. This includes conditional expressions, function calls,
4840 casts, and string constants. It also includes preprocessor macros, if
4841 you compiled your program to include this information; see
4844 @cindex arrays in expressions
4845 @value{GDBN} supports array constants in expressions input by
4846 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
4847 you can use the command @code{print @{1, 2, 3@}} to build up an array in
4848 memory that is @code{malloc}ed in the target program.
4850 Because C is so widespread, most of the expressions shown in examples in
4851 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
4852 Languages}, for information on how to use expressions in other
4855 In this section, we discuss operators that you can use in @value{GDBN}
4856 expressions regardless of your programming language.
4858 @cindex casts, in expressions
4859 Casts are supported in all languages, not just in C, because it is so
4860 useful to cast a number into a pointer in order to examine a structure
4861 at that address in memory.
4862 @c FIXME: casts supported---Mod2 true?
4864 @value{GDBN} supports these operators, in addition to those common
4865 to programming languages:
4869 @samp{@@} is a binary operator for treating parts of memory as arrays.
4870 @xref{Arrays, ,Artificial arrays}, for more information.
4873 @samp{::} allows you to specify a variable in terms of the file or
4874 function where it is defined. @xref{Variables, ,Program variables}.
4876 @cindex @{@var{type}@}
4877 @cindex type casting memory
4878 @cindex memory, viewing as typed object
4879 @cindex casts, to view memory
4880 @item @{@var{type}@} @var{addr}
4881 Refers to an object of type @var{type} stored at address @var{addr} in
4882 memory. @var{addr} may be any expression whose value is an integer or
4883 pointer (but parentheses are required around binary operators, just as in
4884 a cast). This construct is allowed regardless of what kind of data is
4885 normally supposed to reside at @var{addr}.
4889 @section Program variables
4891 The most common kind of expression to use is the name of a variable
4894 Variables in expressions are understood in the selected stack frame
4895 (@pxref{Selection, ,Selecting a frame}); they must be either:
4899 global (or file-static)
4906 visible according to the scope rules of the
4907 programming language from the point of execution in that frame
4910 @noindent This means that in the function
4925 you can examine and use the variable @code{a} whenever your program is
4926 executing within the function @code{foo}, but you can only use or
4927 examine the variable @code{b} while your program is executing inside
4928 the block where @code{b} is declared.
4930 @cindex variable name conflict
4931 There is an exception: you can refer to a variable or function whose
4932 scope is a single source file even if the current execution point is not
4933 in this file. But it is possible to have more than one such variable or
4934 function with the same name (in different source files). If that
4935 happens, referring to that name has unpredictable effects. If you wish,
4936 you can specify a static variable in a particular function or file,
4937 using the colon-colon (@code{::}) notation:
4939 @cindex colon-colon, context for variables/functions
4941 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
4942 @cindex @code{::}, context for variables/functions
4945 @var{file}::@var{variable}
4946 @var{function}::@var{variable}
4950 Here @var{file} or @var{function} is the name of the context for the
4951 static @var{variable}. In the case of file names, you can use quotes to
4952 make sure @value{GDBN} parses the file name as a single word---for example,
4953 to print a global value of @code{x} defined in @file{f2.c}:
4956 (@value{GDBP}) p 'f2.c'::x
4959 @cindex C@t{++} scope resolution
4960 This use of @samp{::} is very rarely in conflict with the very similar
4961 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
4962 scope resolution operator in @value{GDBN} expressions.
4963 @c FIXME: Um, so what happens in one of those rare cases where it's in
4966 @cindex wrong values
4967 @cindex variable values, wrong
4968 @cindex function entry/exit, wrong values of variables
4969 @cindex optimized code, wrong values of variables
4971 @emph{Warning:} Occasionally, a local variable may appear to have the
4972 wrong value at certain points in a function---just after entry to a new
4973 scope, and just before exit.
4975 You may see this problem when you are stepping by machine instructions.
4976 This is because, on most machines, it takes more than one instruction to
4977 set up a stack frame (including local variable definitions); if you are
4978 stepping by machine instructions, variables may appear to have the wrong
4979 values until the stack frame is completely built. On exit, it usually
4980 also takes more than one machine instruction to destroy a stack frame;
4981 after you begin stepping through that group of instructions, local
4982 variable definitions may be gone.
4984 This may also happen when the compiler does significant optimizations.
4985 To be sure of always seeing accurate values, turn off all optimization
4988 @cindex ``No symbol "foo" in current context''
4989 Another possible effect of compiler optimizations is to optimize
4990 unused variables out of existence, or assign variables to registers (as
4991 opposed to memory addresses). Depending on the support for such cases
4992 offered by the debug info format used by the compiler, @value{GDBN}
4993 might not be able to display values for such local variables. If that
4994 happens, @value{GDBN} will print a message like this:
4997 No symbol "foo" in current context.
5000 To solve such problems, either recompile without optimizations, or use a
5001 different debug info format, if the compiler supports several such
5002 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5003 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5004 produces debug info in a format that is superior to formats such as
5005 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5006 an effective form for debug info. @xref{Debugging Options,,Options
5007 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
5008 @xref{C, , Debugging C++}, for more info about debug info formats
5009 that are best suited to C@t{++} programs.
5012 @section Artificial arrays
5014 @cindex artificial array
5016 @kindex @@@r{, referencing memory as an array}
5017 It is often useful to print out several successive objects of the
5018 same type in memory; a section of an array, or an array of
5019 dynamically determined size for which only a pointer exists in the
5022 You can do this by referring to a contiguous span of memory as an
5023 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5024 operand of @samp{@@} should be the first element of the desired array
5025 and be an individual object. The right operand should be the desired length
5026 of the array. The result is an array value whose elements are all of
5027 the type of the left argument. The first element is actually the left
5028 argument; the second element comes from bytes of memory immediately
5029 following those that hold the first element, and so on. Here is an
5030 example. If a program says
5033 int *array = (int *) malloc (len * sizeof (int));
5037 you can print the contents of @code{array} with
5043 The left operand of @samp{@@} must reside in memory. Array values made
5044 with @samp{@@} in this way behave just like other arrays in terms of
5045 subscripting, and are coerced to pointers when used in expressions.
5046 Artificial arrays most often appear in expressions via the value history
5047 (@pxref{Value History, ,Value history}), after printing one out.
5049 Another way to create an artificial array is to use a cast.
5050 This re-interprets a value as if it were an array.
5051 The value need not be in memory:
5053 (@value{GDBP}) p/x (short[2])0x12345678
5054 $1 = @{0x1234, 0x5678@}
5057 As a convenience, if you leave the array length out (as in
5058 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5059 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5061 (@value{GDBP}) p/x (short[])0x12345678
5062 $2 = @{0x1234, 0x5678@}
5065 Sometimes the artificial array mechanism is not quite enough; in
5066 moderately complex data structures, the elements of interest may not
5067 actually be adjacent---for example, if you are interested in the values
5068 of pointers in an array. One useful work-around in this situation is
5069 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5070 variables}) as a counter in an expression that prints the first
5071 interesting value, and then repeat that expression via @key{RET}. For
5072 instance, suppose you have an array @code{dtab} of pointers to
5073 structures, and you are interested in the values of a field @code{fv}
5074 in each structure. Here is an example of what you might type:
5084 @node Output Formats
5085 @section Output formats
5087 @cindex formatted output
5088 @cindex output formats
5089 By default, @value{GDBN} prints a value according to its data type. Sometimes
5090 this is not what you want. For example, you might want to print a number
5091 in hex, or a pointer in decimal. Or you might want to view data in memory
5092 at a certain address as a character string or as an instruction. To do
5093 these things, specify an @dfn{output format} when you print a value.
5095 The simplest use of output formats is to say how to print a value
5096 already computed. This is done by starting the arguments of the
5097 @code{print} command with a slash and a format letter. The format
5098 letters supported are:
5102 Regard the bits of the value as an integer, and print the integer in
5106 Print as integer in signed decimal.
5109 Print as integer in unsigned decimal.
5112 Print as integer in octal.
5115 Print as integer in binary. The letter @samp{t} stands for ``two''.
5116 @footnote{@samp{b} cannot be used because these format letters are also
5117 used with the @code{x} command, where @samp{b} stands for ``byte'';
5118 see @ref{Memory,,Examining memory}.}
5121 @cindex unknown address, locating
5122 @cindex locate address
5123 Print as an address, both absolute in hexadecimal and as an offset from
5124 the nearest preceding symbol. You can use this format used to discover
5125 where (in what function) an unknown address is located:
5128 (@value{GDBP}) p/a 0x54320
5129 $3 = 0x54320 <_initialize_vx+396>
5133 The command @code{info symbol 0x54320} yields similar results.
5134 @xref{Symbols, info symbol}.
5137 Regard as an integer and print it as a character constant.
5140 Regard the bits of the value as a floating point number and print
5141 using typical floating point syntax.
5144 For example, to print the program counter in hex (@pxref{Registers}), type
5151 Note that no space is required before the slash; this is because command
5152 names in @value{GDBN} cannot contain a slash.
5154 To reprint the last value in the value history with a different format,
5155 you can use the @code{print} command with just a format and no
5156 expression. For example, @samp{p/x} reprints the last value in hex.
5159 @section Examining memory
5161 You can use the command @code{x} (for ``examine'') to examine memory in
5162 any of several formats, independently of your program's data types.
5164 @cindex examining memory
5166 @kindex x @r{(examine memory)}
5167 @item x/@var{nfu} @var{addr}
5170 Use the @code{x} command to examine memory.
5173 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5174 much memory to display and how to format it; @var{addr} is an
5175 expression giving the address where you want to start displaying memory.
5176 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5177 Several commands set convenient defaults for @var{addr}.
5180 @item @var{n}, the repeat count
5181 The repeat count is a decimal integer; the default is 1. It specifies
5182 how much memory (counting by units @var{u}) to display.
5183 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5186 @item @var{f}, the display format
5187 The display format is one of the formats used by @code{print},
5188 @samp{s} (null-terminated string), or @samp{i} (machine instruction).
5189 The default is @samp{x} (hexadecimal) initially.
5190 The default changes each time you use either @code{x} or @code{print}.
5192 @item @var{u}, the unit size
5193 The unit size is any of
5199 Halfwords (two bytes).
5201 Words (four bytes). This is the initial default.
5203 Giant words (eight bytes).
5206 Each time you specify a unit size with @code{x}, that size becomes the
5207 default unit the next time you use @code{x}. (For the @samp{s} and
5208 @samp{i} formats, the unit size is ignored and is normally not written.)
5210 @item @var{addr}, starting display address
5211 @var{addr} is the address where you want @value{GDBN} to begin displaying
5212 memory. The expression need not have a pointer value (though it may);
5213 it is always interpreted as an integer address of a byte of memory.
5214 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5215 @var{addr} is usually just after the last address examined---but several
5216 other commands also set the default address: @code{info breakpoints} (to
5217 the address of the last breakpoint listed), @code{info line} (to the
5218 starting address of a line), and @code{print} (if you use it to display
5219 a value from memory).
5222 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5223 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5224 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5225 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5226 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5228 Since the letters indicating unit sizes are all distinct from the
5229 letters specifying output formats, you do not have to remember whether
5230 unit size or format comes first; either order works. The output
5231 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5232 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5234 Even though the unit size @var{u} is ignored for the formats @samp{s}
5235 and @samp{i}, you might still want to use a count @var{n}; for example,
5236 @samp{3i} specifies that you want to see three machine instructions,
5237 including any operands. The command @code{disassemble} gives an
5238 alternative way of inspecting machine instructions; see @ref{Machine
5239 Code,,Source and machine code}.
5241 All the defaults for the arguments to @code{x} are designed to make it
5242 easy to continue scanning memory with minimal specifications each time
5243 you use @code{x}. For example, after you have inspected three machine
5244 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5245 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5246 the repeat count @var{n} is used again; the other arguments default as
5247 for successive uses of @code{x}.
5249 @cindex @code{$_}, @code{$__}, and value history
5250 The addresses and contents printed by the @code{x} command are not saved
5251 in the value history because there is often too much of them and they
5252 would get in the way. Instead, @value{GDBN} makes these values available for
5253 subsequent use in expressions as values of the convenience variables
5254 @code{$_} and @code{$__}. After an @code{x} command, the last address
5255 examined is available for use in expressions in the convenience variable
5256 @code{$_}. The contents of that address, as examined, are available in
5257 the convenience variable @code{$__}.
5259 If the @code{x} command has a repeat count, the address and contents saved
5260 are from the last memory unit printed; this is not the same as the last
5261 address printed if several units were printed on the last line of output.
5263 @cindex remote memory comparison
5264 @cindex verify remote memory image
5265 When you are debugging a program running on a remote target machine
5266 (@pxref{Remote}), you may wish to verify the program's image in the
5267 remote machine's memory against the executable file you downloaded to
5268 the target. The @code{compare-sections} command is provided for such
5272 @kindex compare-sections
5273 @item compare-sections @r{[}@var{section-name}@r{]}
5274 Compare the data of a loadable section @var{section-name} in the
5275 executable file of the program being debugged with the same section in
5276 the remote machine's memory, and report any mismatches. With no
5277 arguments, compares all loadable sections. This command's
5278 availability depends on the target's support for the @code{"qCRC"}
5283 @section Automatic display
5284 @cindex automatic display
5285 @cindex display of expressions
5287 If you find that you want to print the value of an expression frequently
5288 (to see how it changes), you might want to add it to the @dfn{automatic
5289 display list} so that @value{GDBN} prints its value each time your program stops.
5290 Each expression added to the list is given a number to identify it;
5291 to remove an expression from the list, you specify that number.
5292 The automatic display looks like this:
5296 3: bar[5] = (struct hack *) 0x3804
5300 This display shows item numbers, expressions and their current values. As with
5301 displays you request manually using @code{x} or @code{print}, you can
5302 specify the output format you prefer; in fact, @code{display} decides
5303 whether to use @code{print} or @code{x} depending on how elaborate your
5304 format specification is---it uses @code{x} if you specify a unit size,
5305 or one of the two formats (@samp{i} and @samp{s}) that are only
5306 supported by @code{x}; otherwise it uses @code{print}.
5310 @item display @var{expr}
5311 Add the expression @var{expr} to the list of expressions to display
5312 each time your program stops. @xref{Expressions, ,Expressions}.
5314 @code{display} does not repeat if you press @key{RET} again after using it.
5316 @item display/@var{fmt} @var{expr}
5317 For @var{fmt} specifying only a display format and not a size or
5318 count, add the expression @var{expr} to the auto-display list but
5319 arrange to display it each time in the specified format @var{fmt}.
5320 @xref{Output Formats,,Output formats}.
5322 @item display/@var{fmt} @var{addr}
5323 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5324 number of units, add the expression @var{addr} as a memory address to
5325 be examined each time your program stops. Examining means in effect
5326 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5329 For example, @samp{display/i $pc} can be helpful, to see the machine
5330 instruction about to be executed each time execution stops (@samp{$pc}
5331 is a common name for the program counter; @pxref{Registers, ,Registers}).
5334 @kindex delete display
5336 @item undisplay @var{dnums}@dots{}
5337 @itemx delete display @var{dnums}@dots{}
5338 Remove item numbers @var{dnums} from the list of expressions to display.
5340 @code{undisplay} does not repeat if you press @key{RET} after using it.
5341 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5343 @kindex disable display
5344 @item disable display @var{dnums}@dots{}
5345 Disable the display of item numbers @var{dnums}. A disabled display
5346 item is not printed automatically, but is not forgotten. It may be
5347 enabled again later.
5349 @kindex enable display
5350 @item enable display @var{dnums}@dots{}
5351 Enable display of item numbers @var{dnums}. It becomes effective once
5352 again in auto display of its expression, until you specify otherwise.
5355 Display the current values of the expressions on the list, just as is
5356 done when your program stops.
5358 @kindex info display
5360 Print the list of expressions previously set up to display
5361 automatically, each one with its item number, but without showing the
5362 values. This includes disabled expressions, which are marked as such.
5363 It also includes expressions which would not be displayed right now
5364 because they refer to automatic variables not currently available.
5367 @cindex display disabled out of scope
5368 If a display expression refers to local variables, then it does not make
5369 sense outside the lexical context for which it was set up. Such an
5370 expression is disabled when execution enters a context where one of its
5371 variables is not defined. For example, if you give the command
5372 @code{display last_char} while inside a function with an argument
5373 @code{last_char}, @value{GDBN} displays this argument while your program
5374 continues to stop inside that function. When it stops elsewhere---where
5375 there is no variable @code{last_char}---the display is disabled
5376 automatically. The next time your program stops where @code{last_char}
5377 is meaningful, you can enable the display expression once again.
5379 @node Print Settings
5380 @section Print settings
5382 @cindex format options
5383 @cindex print settings
5384 @value{GDBN} provides the following ways to control how arrays, structures,
5385 and symbols are printed.
5388 These settings are useful for debugging programs in any language:
5392 @item set print address
5393 @itemx set print address on
5394 @cindex print/don't print memory addresses
5395 @value{GDBN} prints memory addresses showing the location of stack
5396 traces, structure values, pointer values, breakpoints, and so forth,
5397 even when it also displays the contents of those addresses. The default
5398 is @code{on}. For example, this is what a stack frame display looks like with
5399 @code{set print address on}:
5404 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5406 530 if (lquote != def_lquote)
5410 @item set print address off
5411 Do not print addresses when displaying their contents. For example,
5412 this is the same stack frame displayed with @code{set print address off}:
5416 (@value{GDBP}) set print addr off
5418 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5419 530 if (lquote != def_lquote)
5423 You can use @samp{set print address off} to eliminate all machine
5424 dependent displays from the @value{GDBN} interface. For example, with
5425 @code{print address off}, you should get the same text for backtraces on
5426 all machines---whether or not they involve pointer arguments.
5429 @item show print address
5430 Show whether or not addresses are to be printed.
5433 When @value{GDBN} prints a symbolic address, it normally prints the
5434 closest earlier symbol plus an offset. If that symbol does not uniquely
5435 identify the address (for example, it is a name whose scope is a single
5436 source file), you may need to clarify. One way to do this is with
5437 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5438 you can set @value{GDBN} to print the source file and line number when
5439 it prints a symbolic address:
5442 @item set print symbol-filename on
5443 @cindex closest symbol and offset for an address
5444 Tell @value{GDBN} to print the source file name and line number of a
5445 symbol in the symbolic form of an address.
5447 @item set print symbol-filename off
5448 Do not print source file name and line number of a symbol. This is the
5451 @item show print symbol-filename
5452 Show whether or not @value{GDBN} will print the source file name and
5453 line number of a symbol in the symbolic form of an address.
5456 Another situation where it is helpful to show symbol filenames and line
5457 numbers is when disassembling code; @value{GDBN} shows you the line
5458 number and source file that corresponds to each instruction.
5460 Also, you may wish to see the symbolic form only if the address being
5461 printed is reasonably close to the closest earlier symbol:
5464 @item set print max-symbolic-offset @var{max-offset}
5465 @cindex maximum value for offset of closest symbol
5466 Tell @value{GDBN} to only display the symbolic form of an address if the
5467 offset between the closest earlier symbol and the address is less than
5468 @var{max-offset}. The default is 0, which tells @value{GDBN}
5469 to always print the symbolic form of an address if any symbol precedes it.
5471 @item show print max-symbolic-offset
5472 Ask how large the maximum offset is that @value{GDBN} prints in a
5476 @cindex wild pointer, interpreting
5477 @cindex pointer, finding referent
5478 If you have a pointer and you are not sure where it points, try
5479 @samp{set print symbol-filename on}. Then you can determine the name
5480 and source file location of the variable where it points, using
5481 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5482 For example, here @value{GDBN} shows that a variable @code{ptt} points
5483 at another variable @code{t}, defined in @file{hi2.c}:
5486 (@value{GDBP}) set print symbol-filename on
5487 (@value{GDBP}) p/a ptt
5488 $4 = 0xe008 <t in hi2.c>
5492 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5493 does not show the symbol name and filename of the referent, even with
5494 the appropriate @code{set print} options turned on.
5497 Other settings control how different kinds of objects are printed:
5500 @item set print array
5501 @itemx set print array on
5502 @cindex pretty print arrays
5503 Pretty print arrays. This format is more convenient to read,
5504 but uses more space. The default is off.
5506 @item set print array off
5507 Return to compressed format for arrays.
5509 @item show print array
5510 Show whether compressed or pretty format is selected for displaying
5513 @item set print elements @var{number-of-elements}
5514 @cindex number of array elements to print
5515 Set a limit on how many elements of an array @value{GDBN} will print.
5516 If @value{GDBN} is printing a large array, it stops printing after it has
5517 printed the number of elements set by the @code{set print elements} command.
5518 This limit also applies to the display of strings.
5519 When @value{GDBN} starts, this limit is set to 200.
5520 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5522 @item show print elements
5523 Display the number of elements of a large array that @value{GDBN} will print.
5524 If the number is 0, then the printing is unlimited.
5526 @item set print null-stop
5527 @cindex @sc{null} elements in arrays
5528 Cause @value{GDBN} to stop printing the characters of an array when the first
5529 @sc{null} is encountered. This is useful when large arrays actually
5530 contain only short strings.
5533 @item set print pretty on
5534 Cause @value{GDBN} to print structures in an indented format with one member
5535 per line, like this:
5550 @item set print pretty off
5551 Cause @value{GDBN} to print structures in a compact format, like this:
5555 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5556 meat = 0x54 "Pork"@}
5561 This is the default format.
5563 @item show print pretty
5564 Show which format @value{GDBN} is using to print structures.
5566 @item set print sevenbit-strings on
5567 @cindex eight-bit characters in strings
5568 @cindex octal escapes in strings
5569 Print using only seven-bit characters; if this option is set,
5570 @value{GDBN} displays any eight-bit characters (in strings or
5571 character values) using the notation @code{\}@var{nnn}. This setting is
5572 best if you are working in English (@sc{ascii}) and you use the
5573 high-order bit of characters as a marker or ``meta'' bit.
5575 @item set print sevenbit-strings off
5576 Print full eight-bit characters. This allows the use of more
5577 international character sets, and is the default.
5579 @item show print sevenbit-strings
5580 Show whether or not @value{GDBN} is printing only seven-bit characters.
5582 @item set print union on
5583 @cindex unions in structures, printing
5584 Tell @value{GDBN} to print unions which are contained in structures. This
5585 is the default setting.
5587 @item set print union off
5588 Tell @value{GDBN} not to print unions which are contained in structures.
5590 @item show print union
5591 Ask @value{GDBN} whether or not it will print unions which are contained in
5594 For example, given the declarations
5597 typedef enum @{Tree, Bug@} Species;
5598 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5599 typedef enum @{Caterpillar, Cocoon, Butterfly@}
5610 struct thing foo = @{Tree, @{Acorn@}@};
5614 with @code{set print union on} in effect @samp{p foo} would print
5617 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5621 and with @code{set print union off} in effect it would print
5624 $1 = @{it = Tree, form = @{...@}@}
5630 These settings are of interest when debugging C@t{++} programs:
5633 @cindex demangling C@t{++} names
5634 @item set print demangle
5635 @itemx set print demangle on
5636 Print C@t{++} names in their source form rather than in the encoded
5637 (``mangled'') form passed to the assembler and linker for type-safe
5638 linkage. The default is on.
5640 @item show print demangle
5641 Show whether C@t{++} names are printed in mangled or demangled form.
5643 @item set print asm-demangle
5644 @itemx set print asm-demangle on
5645 Print C@t{++} names in their source form rather than their mangled form, even
5646 in assembler code printouts such as instruction disassemblies.
5649 @item show print asm-demangle
5650 Show whether C@t{++} names in assembly listings are printed in mangled
5653 @cindex C@t{++} symbol decoding style
5654 @cindex symbol decoding style, C@t{++}
5655 @kindex set demangle-style
5656 @item set demangle-style @var{style}
5657 Choose among several encoding schemes used by different compilers to
5658 represent C@t{++} names. The choices for @var{style} are currently:
5662 Allow @value{GDBN} to choose a decoding style by inspecting your program.
5665 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
5666 This is the default.
5669 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
5672 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
5675 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
5676 @strong{Warning:} this setting alone is not sufficient to allow
5677 debugging @code{cfront}-generated executables. @value{GDBN} would
5678 require further enhancement to permit that.
5681 If you omit @var{style}, you will see a list of possible formats.
5683 @item show demangle-style
5684 Display the encoding style currently in use for decoding C@t{++} symbols.
5686 @item set print object
5687 @itemx set print object on
5688 @cindex derived type of an object, printing
5689 When displaying a pointer to an object, identify the @emph{actual}
5690 (derived) type of the object rather than the @emph{declared} type, using
5691 the virtual function table.
5693 @item set print object off
5694 Display only the declared type of objects, without reference to the
5695 virtual function table. This is the default setting.
5697 @item show print object
5698 Show whether actual, or declared, object types are displayed.
5700 @item set print static-members
5701 @itemx set print static-members on
5702 @cindex static members of C@t{++} objects
5703 Print static members when displaying a C@t{++} object. The default is on.
5705 @item set print static-members off
5706 Do not print static members when displaying a C@t{++} object.
5708 @item show print static-members
5709 Show whether C@t{++} static members are printed, or not.
5711 @c These don't work with HP ANSI C++ yet.
5712 @item set print vtbl
5713 @itemx set print vtbl on
5714 @cindex pretty print C@t{++} virtual function tables
5715 Pretty print C@t{++} virtual function tables. The default is off.
5716 (The @code{vtbl} commands do not work on programs compiled with the HP
5717 ANSI C@t{++} compiler (@code{aCC}).)
5719 @item set print vtbl off
5720 Do not pretty print C@t{++} virtual function tables.
5722 @item show print vtbl
5723 Show whether C@t{++} virtual function tables are pretty printed, or not.
5727 @section Value history
5729 @cindex value history
5730 Values printed by the @code{print} command are saved in the @value{GDBN}
5731 @dfn{value history}. This allows you to refer to them in other expressions.
5732 Values are kept until the symbol table is re-read or discarded
5733 (for example with the @code{file} or @code{symbol-file} commands).
5734 When the symbol table changes, the value history is discarded,
5735 since the values may contain pointers back to the types defined in the
5740 @cindex history number
5741 The values printed are given @dfn{history numbers} by which you can
5742 refer to them. These are successive integers starting with one.
5743 @code{print} shows you the history number assigned to a value by
5744 printing @samp{$@var{num} = } before the value; here @var{num} is the
5747 To refer to any previous value, use @samp{$} followed by the value's
5748 history number. The way @code{print} labels its output is designed to
5749 remind you of this. Just @code{$} refers to the most recent value in
5750 the history, and @code{$$} refers to the value before that.
5751 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
5752 is the value just prior to @code{$$}, @code{$$1} is equivalent to
5753 @code{$$}, and @code{$$0} is equivalent to @code{$}.
5755 For example, suppose you have just printed a pointer to a structure and
5756 want to see the contents of the structure. It suffices to type
5762 If you have a chain of structures where the component @code{next} points
5763 to the next one, you can print the contents of the next one with this:
5770 You can print successive links in the chain by repeating this
5771 command---which you can do by just typing @key{RET}.
5773 Note that the history records values, not expressions. If the value of
5774 @code{x} is 4 and you type these commands:
5782 then the value recorded in the value history by the @code{print} command
5783 remains 4 even though the value of @code{x} has changed.
5788 Print the last ten values in the value history, with their item numbers.
5789 This is like @samp{p@ $$9} repeated ten times, except that @code{show
5790 values} does not change the history.
5792 @item show values @var{n}
5793 Print ten history values centered on history item number @var{n}.
5796 Print ten history values just after the values last printed. If no more
5797 values are available, @code{show values +} produces no display.
5800 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
5801 same effect as @samp{show values +}.
5803 @node Convenience Vars
5804 @section Convenience variables
5806 @cindex convenience variables
5807 @value{GDBN} provides @dfn{convenience variables} that you can use within
5808 @value{GDBN} to hold on to a value and refer to it later. These variables
5809 exist entirely within @value{GDBN}; they are not part of your program, and
5810 setting a convenience variable has no direct effect on further execution
5811 of your program. That is why you can use them freely.
5813 Convenience variables are prefixed with @samp{$}. Any name preceded by
5814 @samp{$} can be used for a convenience variable, unless it is one of
5815 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
5816 (Value history references, in contrast, are @emph{numbers} preceded
5817 by @samp{$}. @xref{Value History, ,Value history}.)
5819 You can save a value in a convenience variable with an assignment
5820 expression, just as you would set a variable in your program.
5824 set $foo = *object_ptr
5828 would save in @code{$foo} the value contained in the object pointed to by
5831 Using a convenience variable for the first time creates it, but its
5832 value is @code{void} until you assign a new value. You can alter the
5833 value with another assignment at any time.
5835 Convenience variables have no fixed types. You can assign a convenience
5836 variable any type of value, including structures and arrays, even if
5837 that variable already has a value of a different type. The convenience
5838 variable, when used as an expression, has the type of its current value.
5841 @kindex show convenience
5842 @item show convenience
5843 Print a list of convenience variables used so far, and their values.
5844 Abbreviated @code{show conv}.
5847 One of the ways to use a convenience variable is as a counter to be
5848 incremented or a pointer to be advanced. For example, to print
5849 a field from successive elements of an array of structures:
5853 print bar[$i++]->contents
5857 Repeat that command by typing @key{RET}.
5859 Some convenience variables are created automatically by @value{GDBN} and given
5860 values likely to be useful.
5863 @vindex $_@r{, convenience variable}
5865 The variable @code{$_} is automatically set by the @code{x} command to
5866 the last address examined (@pxref{Memory, ,Examining memory}). Other
5867 commands which provide a default address for @code{x} to examine also
5868 set @code{$_} to that address; these commands include @code{info line}
5869 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
5870 except when set by the @code{x} command, in which case it is a pointer
5871 to the type of @code{$__}.
5873 @vindex $__@r{, convenience variable}
5875 The variable @code{$__} is automatically set by the @code{x} command
5876 to the value found in the last address examined. Its type is chosen
5877 to match the format in which the data was printed.
5880 @vindex $_exitcode@r{, convenience variable}
5881 The variable @code{$_exitcode} is automatically set to the exit code when
5882 the program being debugged terminates.
5885 On HP-UX systems, if you refer to a function or variable name that
5886 begins with a dollar sign, @value{GDBN} searches for a user or system
5887 name first, before it searches for a convenience variable.
5893 You can refer to machine register contents, in expressions, as variables
5894 with names starting with @samp{$}. The names of registers are different
5895 for each machine; use @code{info registers} to see the names used on
5899 @kindex info registers
5900 @item info registers
5901 Print the names and values of all registers except floating-point
5902 and vector registers (in the selected stack frame).
5904 @kindex info all-registers
5905 @cindex floating point registers
5906 @item info all-registers
5907 Print the names and values of all registers, including floating-point
5908 and vector registers (in the selected stack frame).
5910 @item info registers @var{regname} @dots{}
5911 Print the @dfn{relativized} value of each specified register @var{regname}.
5912 As discussed in detail below, register values are normally relative to
5913 the selected stack frame. @var{regname} may be any register name valid on
5914 the machine you are using, with or without the initial @samp{$}.
5917 @value{GDBN} has four ``standard'' register names that are available (in
5918 expressions) on most machines---whenever they do not conflict with an
5919 architecture's canonical mnemonics for registers. The register names
5920 @code{$pc} and @code{$sp} are used for the program counter register and
5921 the stack pointer. @code{$fp} is used for a register that contains a
5922 pointer to the current stack frame, and @code{$ps} is used for a
5923 register that contains the processor status. For example,
5924 you could print the program counter in hex with
5931 or print the instruction to be executed next with
5938 or add four to the stack pointer@footnote{This is a way of removing
5939 one word from the stack, on machines where stacks grow downward in
5940 memory (most machines, nowadays). This assumes that the innermost
5941 stack frame is selected; setting @code{$sp} is not allowed when other
5942 stack frames are selected. To pop entire frames off the stack,
5943 regardless of machine architecture, use @code{return};
5944 see @ref{Returning, ,Returning from a function}.} with
5950 Whenever possible, these four standard register names are available on
5951 your machine even though the machine has different canonical mnemonics,
5952 so long as there is no conflict. The @code{info registers} command
5953 shows the canonical names. For example, on the SPARC, @code{info
5954 registers} displays the processor status register as @code{$psr} but you
5955 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
5956 is an alias for the @sc{eflags} register.
5958 @value{GDBN} always considers the contents of an ordinary register as an
5959 integer when the register is examined in this way. Some machines have
5960 special registers which can hold nothing but floating point; these
5961 registers are considered to have floating point values. There is no way
5962 to refer to the contents of an ordinary register as floating point value
5963 (although you can @emph{print} it as a floating point value with
5964 @samp{print/f $@var{regname}}).
5966 Some registers have distinct ``raw'' and ``virtual'' data formats. This
5967 means that the data format in which the register contents are saved by
5968 the operating system is not the same one that your program normally
5969 sees. For example, the registers of the 68881 floating point
5970 coprocessor are always saved in ``extended'' (raw) format, but all C
5971 programs expect to work with ``double'' (virtual) format. In such
5972 cases, @value{GDBN} normally works with the virtual format only (the format
5973 that makes sense for your program), but the @code{info registers} command
5974 prints the data in both formats.
5976 Normally, register values are relative to the selected stack frame
5977 (@pxref{Selection, ,Selecting a frame}). This means that you get the
5978 value that the register would contain if all stack frames farther in
5979 were exited and their saved registers restored. In order to see the
5980 true contents of hardware registers, you must select the innermost
5981 frame (with @samp{frame 0}).
5983 However, @value{GDBN} must deduce where registers are saved, from the machine
5984 code generated by your compiler. If some registers are not saved, or if
5985 @value{GDBN} is unable to locate the saved registers, the selected stack
5986 frame makes no difference.
5988 @node Floating Point Hardware
5989 @section Floating point hardware
5990 @cindex floating point
5992 Depending on the configuration, @value{GDBN} may be able to give
5993 you more information about the status of the floating point hardware.
5998 Display hardware-dependent information about the floating
5999 point unit. The exact contents and layout vary depending on the
6000 floating point chip. Currently, @samp{info float} is supported on
6001 the ARM and x86 machines.
6005 @section Vector Unit
6008 Depending on the configuration, @value{GDBN} may be able to give you
6009 more information about the status of the vector unit.
6014 Display information about the vector unit. The exact contents and
6015 layout vary depending on the hardware.
6018 @node Auxiliary Vector
6019 @section Operating system auxiliary vector
6020 @cindex auxiliary vector
6021 @cindex vector, auxiliary
6023 Some operating systems supply an @dfn{auxiliary vector} to programs at
6024 startup. This is akin to the arguments and environment that you
6025 specify for a program, but contains a system-dependent variety of
6026 binary values that tell system libraries important details about the
6027 hardware, operating system, and process. Each value's purpose is
6028 identified by an integer tag; the meanings are well-known but system-specific.
6029 Depending on the configuration and operating system facilities,
6030 @value{GDBN} may be able to show you this information.
6035 Display the auxiliary vector of the inferior, which can be either a
6036 live process or a core dump file. @value{GDBN} prints each tag value
6037 numerically, and also shows names and text descriptions for recognized
6038 tags. Some values in the vector are numbers, some bit masks, and some
6039 pointers to strings or other data. @value{GDBN} displays each value in the
6040 most appropriate form for a recognized tag, and in hexadecimal for
6041 an unrecognized tag.
6044 @node Memory Region Attributes
6045 @section Memory region attributes
6046 @cindex memory region attributes
6048 @dfn{Memory region attributes} allow you to describe special handling
6049 required by regions of your target's memory. @value{GDBN} uses attributes
6050 to determine whether to allow certain types of memory accesses; whether to
6051 use specific width accesses; and whether to cache target memory.
6053 Defined memory regions can be individually enabled and disabled. When a
6054 memory region is disabled, @value{GDBN} uses the default attributes when
6055 accessing memory in that region. Similarly, if no memory regions have
6056 been defined, @value{GDBN} uses the default attributes when accessing
6059 When a memory region is defined, it is given a number to identify it;
6060 to enable, disable, or remove a memory region, you specify that number.
6064 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6065 Define a memory region bounded by @var{lower} and @var{upper} with
6066 attributes @var{attributes}@dots{}, and add it to the list of regions
6067 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
6068 case: it is treated as the the target's maximum memory address.
6069 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6072 @item delete mem @var{nums}@dots{}
6073 Remove memory regions @var{nums}@dots{} from the list of regions
6074 monitored by @value{GDBN}.
6077 @item disable mem @var{nums}@dots{}
6078 Disable monitoring of memory regions @var{nums}@dots{}.
6079 A disabled memory region is not forgotten.
6080 It may be enabled again later.
6083 @item enable mem @var{nums}@dots{}
6084 Enable monitoring of memory regions @var{nums}@dots{}.
6088 Print a table of all defined memory regions, with the following columns
6092 @item Memory Region Number
6093 @item Enabled or Disabled.
6094 Enabled memory regions are marked with @samp{y}.
6095 Disabled memory regions are marked with @samp{n}.
6098 The address defining the inclusive lower bound of the memory region.
6101 The address defining the exclusive upper bound of the memory region.
6104 The list of attributes set for this memory region.
6109 @subsection Attributes
6111 @subsubsection Memory Access Mode
6112 The access mode attributes set whether @value{GDBN} may make read or
6113 write accesses to a memory region.
6115 While these attributes prevent @value{GDBN} from performing invalid
6116 memory accesses, they do nothing to prevent the target system, I/O DMA,
6117 etc. from accessing memory.
6121 Memory is read only.
6123 Memory is write only.
6125 Memory is read/write. This is the default.
6128 @subsubsection Memory Access Size
6129 The acccess size attributes tells @value{GDBN} to use specific sized
6130 accesses in the memory region. Often memory mapped device registers
6131 require specific sized accesses. If no access size attribute is
6132 specified, @value{GDBN} may use accesses of any size.
6136 Use 8 bit memory accesses.
6138 Use 16 bit memory accesses.
6140 Use 32 bit memory accesses.
6142 Use 64 bit memory accesses.
6145 @c @subsubsection Hardware/Software Breakpoints
6146 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6147 @c will use hardware or software breakpoints for the internal breakpoints
6148 @c used by the step, next, finish, until, etc. commands.
6152 @c Always use hardware breakpoints
6153 @c @item swbreak (default)
6156 @subsubsection Data Cache
6157 The data cache attributes set whether @value{GDBN} will cache target
6158 memory. While this generally improves performance by reducing debug
6159 protocol overhead, it can lead to incorrect results because @value{GDBN}
6160 does not know about volatile variables or memory mapped device
6165 Enable @value{GDBN} to cache target memory.
6167 Disable @value{GDBN} from caching target memory. This is the default.
6170 @c @subsubsection Memory Write Verification
6171 @c The memory write verification attributes set whether @value{GDBN}
6172 @c will re-reads data after each write to verify the write was successful.
6176 @c @item noverify (default)
6179 @node Dump/Restore Files
6180 @section Copy between memory and a file
6181 @cindex dump/restore files
6182 @cindex append data to a file
6183 @cindex dump data to a file
6184 @cindex restore data from a file
6186 You can use the commands @code{dump}, @code{append}, and
6187 @code{restore} to copy data between target memory and a file. The
6188 @code{dump} and @code{append} commands write data to a file, and the
6189 @code{restore} command reads data from a file back into the inferior's
6190 memory. Files may be in binary, Motorola S-record, Intel hex, or
6191 Tektronix Hex format; however, @value{GDBN} can only append to binary
6197 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6198 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6199 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6200 or the value of @var{expr}, to @var{filename} in the given format.
6202 The @var{format} parameter may be any one of:
6209 Motorola S-record format.
6211 Tektronix Hex format.
6214 @value{GDBN} uses the same definitions of these formats as the
6215 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
6216 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
6220 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6221 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
6222 Append the contents of memory from @var{start_addr} to @var{end_addr},
6223 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
6224 (@value{GDBN} can only append data to files in raw binary form.)
6227 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
6228 Restore the contents of file @var{filename} into memory. The
6229 @code{restore} command can automatically recognize any known @sc{bfd}
6230 file format, except for raw binary. To restore a raw binary file you
6231 must specify the optional keyword @code{binary} after the filename.
6233 If @var{bias} is non-zero, its value will be added to the addresses
6234 contained in the file. Binary files always start at address zero, so
6235 they will be restored at address @var{bias}. Other bfd files have
6236 a built-in location; they will be restored at offset @var{bias}
6239 If @var{start} and/or @var{end} are non-zero, then only data between
6240 file offset @var{start} and file offset @var{end} will be restored.
6241 These offsets are relative to the addresses in the file, before
6242 the @var{bias} argument is applied.
6246 @node Core File Generation
6247 @section How to Produce a Core File from Your Program
6248 @cindex dump core from inferior
6250 A @dfn{core file} or @dfn{core dump} is a file that records the memory
6251 image of a running process and its process status (register values
6252 etc.). Its primary use is post-mortem debugging of a program that
6253 crashed while it ran outside a debugger. A program that crashes
6254 automatically produces a core file, unless this feature is disabled by
6255 the user. @xref{Files}, for information on invoking @value{GDBN} in
6256 the post-mortem debugging mode.
6258 Occasionally, you may wish to produce a core file of the program you
6259 are debugging in order to preserve a snapshot of its state.
6260 @value{GDBN} has a special command for that.
6264 @kindex generate-core-file
6265 @item generate-core-file [@var{file}]
6266 @itemx gcore [@var{file}]
6267 Produce a core dump of the inferior process. The optional argument
6268 @var{file} specifies the file name where to put the core dump. If not
6269 specified, the file name defaults to @file{core.@var{pid}}, where
6270 @var{pid} is the inferior process ID.
6272 Note that this command is implemented only for some systems (as of
6273 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
6276 @node Character Sets
6277 @section Character Sets
6278 @cindex character sets
6280 @cindex translating between character sets
6281 @cindex host character set
6282 @cindex target character set
6284 If the program you are debugging uses a different character set to
6285 represent characters and strings than the one @value{GDBN} uses itself,
6286 @value{GDBN} can automatically translate between the character sets for
6287 you. The character set @value{GDBN} uses we call the @dfn{host
6288 character set}; the one the inferior program uses we call the
6289 @dfn{target character set}.
6291 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
6292 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
6293 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
6294 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
6295 then the host character set is Latin-1, and the target character set is
6296 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
6297 target-charset EBCDIC-US}, then @value{GDBN} translates between
6298 @sc{ebcdic} and Latin 1 as you print character or string values, or use
6299 character and string literals in expressions.
6301 @value{GDBN} has no way to automatically recognize which character set
6302 the inferior program uses; you must tell it, using the @code{set
6303 target-charset} command, described below.
6305 Here are the commands for controlling @value{GDBN}'s character set
6309 @item set target-charset @var{charset}
6310 @kindex set target-charset
6311 Set the current target character set to @var{charset}. We list the
6312 character set names @value{GDBN} recognizes below, but if you type
6313 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6314 list the target character sets it supports.
6318 @item set host-charset @var{charset}
6319 @kindex set host-charset
6320 Set the current host character set to @var{charset}.
6322 By default, @value{GDBN} uses a host character set appropriate to the
6323 system it is running on; you can override that default using the
6324 @code{set host-charset} command.
6326 @value{GDBN} can only use certain character sets as its host character
6327 set. We list the character set names @value{GDBN} recognizes below, and
6328 indicate which can be host character sets, but if you type
6329 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6330 list the host character sets it supports.
6332 @item set charset @var{charset}
6334 Set the current host and target character sets to @var{charset}. As
6335 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
6336 @value{GDBN} will list the name of the character sets that can be used
6337 for both host and target.
6341 @kindex show charset
6342 Show the names of the current host and target charsets.
6344 @itemx show host-charset
6345 @kindex show host-charset
6346 Show the name of the current host charset.
6348 @itemx show target-charset
6349 @kindex show target-charset
6350 Show the name of the current target charset.
6354 @value{GDBN} currently includes support for the following character
6360 @cindex ASCII character set
6361 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6365 @cindex ISO 8859-1 character set
6366 @cindex ISO Latin 1 character set
6367 The ISO Latin 1 character set. This extends @sc{ascii} with accented
6368 characters needed for French, German, and Spanish. @value{GDBN} can use
6369 this as its host character set.
6373 @cindex EBCDIC character set
6374 @cindex IBM1047 character set
6375 Variants of the @sc{ebcdic} character set, used on some of IBM's
6376 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6377 @value{GDBN} cannot use these as its host character set.
6381 Note that these are all single-byte character sets. More work inside
6382 GDB is needed to support multi-byte or variable-width character
6383 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6385 Here is an example of @value{GDBN}'s character set support in action.
6386 Assume that the following source code has been placed in the file
6387 @file{charset-test.c}:
6393 = @{72, 101, 108, 108, 111, 44, 32, 119,
6394 111, 114, 108, 100, 33, 10, 0@};
6395 char ibm1047_hello[]
6396 = @{200, 133, 147, 147, 150, 107, 64, 166,
6397 150, 153, 147, 132, 90, 37, 0@};
6401 printf ("Hello, world!\n");
6405 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6406 containing the string @samp{Hello, world!} followed by a newline,
6407 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6409 We compile the program, and invoke the debugger on it:
6412 $ gcc -g charset-test.c -o charset-test
6413 $ gdb -nw charset-test
6414 GNU gdb 2001-12-19-cvs
6415 Copyright 2001 Free Software Foundation, Inc.
6420 We can use the @code{show charset} command to see what character sets
6421 @value{GDBN} is currently using to interpret and display characters and
6425 (@value{GDBP}) show charset
6426 The current host and target character set is `ISO-8859-1'.
6430 For the sake of printing this manual, let's use @sc{ascii} as our
6431 initial character set:
6433 (@value{GDBP}) set charset ASCII
6434 (@value{GDBP}) show charset
6435 The current host and target character set is `ASCII'.
6439 Let's assume that @sc{ascii} is indeed the correct character set for our
6440 host system --- in other words, let's assume that if @value{GDBN} prints
6441 characters using the @sc{ascii} character set, our terminal will display
6442 them properly. Since our current target character set is also
6443 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
6446 (@value{GDBP}) print ascii_hello
6447 $1 = 0x401698 "Hello, world!\n"
6448 (@value{GDBP}) print ascii_hello[0]
6453 @value{GDBN} uses the target character set for character and string
6454 literals you use in expressions:
6457 (@value{GDBP}) print '+'
6462 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
6465 @value{GDBN} relies on the user to tell it which character set the
6466 target program uses. If we print @code{ibm1047_hello} while our target
6467 character set is still @sc{ascii}, we get jibberish:
6470 (@value{GDBP}) print ibm1047_hello
6471 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
6472 (@value{GDBP}) print ibm1047_hello[0]
6477 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
6478 @value{GDBN} tells us the character sets it supports:
6481 (@value{GDBP}) set target-charset
6482 ASCII EBCDIC-US IBM1047 ISO-8859-1
6483 (@value{GDBP}) set target-charset
6486 We can select @sc{ibm1047} as our target character set, and examine the
6487 program's strings again. Now the @sc{ascii} string is wrong, but
6488 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
6489 target character set, @sc{ibm1047}, to the host character set,
6490 @sc{ascii}, and they display correctly:
6493 (@value{GDBP}) set target-charset IBM1047
6494 (@value{GDBP}) show charset
6495 The current host character set is `ASCII'.
6496 The current target character set is `IBM1047'.
6497 (@value{GDBP}) print ascii_hello
6498 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
6499 (@value{GDBP}) print ascii_hello[0]
6501 (@value{GDBP}) print ibm1047_hello
6502 $8 = 0x4016a8 "Hello, world!\n"
6503 (@value{GDBP}) print ibm1047_hello[0]
6508 As above, @value{GDBN} uses the target character set for character and
6509 string literals you use in expressions:
6512 (@value{GDBP}) print '+'
6517 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
6520 @node Caching Remote Data
6521 @section Caching Data of Remote Targets
6522 @cindex caching data of remote targets
6524 @value{GDBN} can cache data exchanged between the debugger and a
6525 remote target (@pxref{Remote}). Such caching generally improves
6526 performance, because it reduces the overhead of the remote protocol by
6527 bundling memory reads and writes into large chunks. Unfortunately,
6528 @value{GDBN} does not currently know anything about volatile
6529 registers, and thus data caching will produce incorrect results when
6530 volatile registers are in use.
6533 @kindex set remotecache
6534 @item set remotecache on
6535 @itemx set remotecache off
6536 Set caching state for remote targets. When @code{ON}, use data
6537 caching. By default, this option is @code{OFF}.
6539 @kindex show remotecache
6540 @item show remotecache
6541 Show the current state of data caching for remote targets.
6545 Print the information about the data cache performance. The
6546 information displayed includes: the dcache width and depth; and for
6547 each cache line, how many times it was referenced, and its data and
6548 state (dirty, bad, ok, etc.). This command is useful for debugging
6549 the data cache operation.
6554 @chapter C Preprocessor Macros
6556 Some languages, such as C and C@t{++}, provide a way to define and invoke
6557 ``preprocessor macros'' which expand into strings of tokens.
6558 @value{GDBN} can evaluate expressions containing macro invocations, show
6559 the result of macro expansion, and show a macro's definition, including
6560 where it was defined.
6562 You may need to compile your program specially to provide @value{GDBN}
6563 with information about preprocessor macros. Most compilers do not
6564 include macros in their debugging information, even when you compile
6565 with the @option{-g} flag. @xref{Compilation}.
6567 A program may define a macro at one point, remove that definition later,
6568 and then provide a different definition after that. Thus, at different
6569 points in the program, a macro may have different definitions, or have
6570 no definition at all. If there is a current stack frame, @value{GDBN}
6571 uses the macros in scope at that frame's source code line. Otherwise,
6572 @value{GDBN} uses the macros in scope at the current listing location;
6575 At the moment, @value{GDBN} does not support the @code{##}
6576 token-splicing operator, the @code{#} stringification operator, or
6577 variable-arity macros.
6579 Whenever @value{GDBN} evaluates an expression, it always expands any
6580 macro invocations present in the expression. @value{GDBN} also provides
6581 the following commands for working with macros explicitly.
6585 @kindex macro expand
6586 @cindex macro expansion, showing the results of preprocessor
6587 @cindex preprocessor macro expansion, showing the results of
6588 @cindex expanding preprocessor macros
6589 @item macro expand @var{expression}
6590 @itemx macro exp @var{expression}
6591 Show the results of expanding all preprocessor macro invocations in
6592 @var{expression}. Since @value{GDBN} simply expands macros, but does
6593 not parse the result, @var{expression} need not be a valid expression;
6594 it can be any string of tokens.
6597 @item macro expand-once @var{expression}
6598 @itemx macro exp1 @var{expression}
6599 @cindex expand macro once
6600 @i{(This command is not yet implemented.)} Show the results of
6601 expanding those preprocessor macro invocations that appear explicitly in
6602 @var{expression}. Macro invocations appearing in that expansion are
6603 left unchanged. This command allows you to see the effect of a
6604 particular macro more clearly, without being confused by further
6605 expansions. Since @value{GDBN} simply expands macros, but does not
6606 parse the result, @var{expression} need not be a valid expression; it
6607 can be any string of tokens.
6610 @cindex macro definition, showing
6611 @cindex definition, showing a macro's
6612 @item info macro @var{macro}
6613 Show the definition of the macro named @var{macro}, and describe the
6614 source location where that definition was established.
6616 @kindex macro define
6617 @cindex user-defined macros
6618 @cindex defining macros interactively
6619 @cindex macros, user-defined
6620 @item macro define @var{macro} @var{replacement-list}
6621 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
6622 @i{(This command is not yet implemented.)} Introduce a definition for a
6623 preprocessor macro named @var{macro}, invocations of which are replaced
6624 by the tokens given in @var{replacement-list}. The first form of this
6625 command defines an ``object-like'' macro, which takes no arguments; the
6626 second form defines a ``function-like'' macro, which takes the arguments
6627 given in @var{arglist}.
6629 A definition introduced by this command is in scope in every expression
6630 evaluated in @value{GDBN}, until it is removed with the @command{macro
6631 undef} command, described below. The definition overrides all
6632 definitions for @var{macro} present in the program being debugged, as
6633 well as any previous user-supplied definition.
6636 @item macro undef @var{macro}
6637 @i{(This command is not yet implemented.)} Remove any user-supplied
6638 definition for the macro named @var{macro}. This command only affects
6639 definitions provided with the @command{macro define} command, described
6640 above; it cannot remove definitions present in the program being
6645 @i{(This command is not yet implemented.)} List all the macros
6646 defined using the @code{macro define} command.
6649 @cindex macros, example of debugging with
6650 Here is a transcript showing the above commands in action. First, we
6651 show our source files:
6659 #define ADD(x) (M + x)
6664 printf ("Hello, world!\n");
6666 printf ("We're so creative.\n");
6668 printf ("Goodbye, world!\n");
6675 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
6676 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
6677 compiler includes information about preprocessor macros in the debugging
6681 $ gcc -gdwarf-2 -g3 sample.c -o sample
6685 Now, we start @value{GDBN} on our sample program:
6689 GNU gdb 2002-05-06-cvs
6690 Copyright 2002 Free Software Foundation, Inc.
6691 GDB is free software, @dots{}
6695 We can expand macros and examine their definitions, even when the
6696 program is not running. @value{GDBN} uses the current listing position
6697 to decide which macro definitions are in scope:
6700 (@value{GDBP}) list main
6703 5 #define ADD(x) (M + x)
6708 10 printf ("Hello, world!\n");
6710 12 printf ("We're so creative.\n");
6711 (@value{GDBP}) info macro ADD
6712 Defined at /home/jimb/gdb/macros/play/sample.c:5
6713 #define ADD(x) (M + x)
6714 (@value{GDBP}) info macro Q
6715 Defined at /home/jimb/gdb/macros/play/sample.h:1
6716 included at /home/jimb/gdb/macros/play/sample.c:2
6718 (@value{GDBP}) macro expand ADD(1)
6719 expands to: (42 + 1)
6720 (@value{GDBP}) macro expand-once ADD(1)
6721 expands to: once (M + 1)
6725 In the example above, note that @command{macro expand-once} expands only
6726 the macro invocation explicit in the original text --- the invocation of
6727 @code{ADD} --- but does not expand the invocation of the macro @code{M},
6728 which was introduced by @code{ADD}.
6730 Once the program is running, GDB uses the macro definitions in force at
6731 the source line of the current stack frame:
6734 (@value{GDBP}) break main
6735 Breakpoint 1 at 0x8048370: file sample.c, line 10.
6737 Starting program: /home/jimb/gdb/macros/play/sample
6739 Breakpoint 1, main () at sample.c:10
6740 10 printf ("Hello, world!\n");
6744 At line 10, the definition of the macro @code{N} at line 9 is in force:
6747 (@value{GDBP}) info macro N
6748 Defined at /home/jimb/gdb/macros/play/sample.c:9
6750 (@value{GDBP}) macro expand N Q M
6752 (@value{GDBP}) print N Q M
6757 As we step over directives that remove @code{N}'s definition, and then
6758 give it a new definition, @value{GDBN} finds the definition (or lack
6759 thereof) in force at each point:
6764 12 printf ("We're so creative.\n");
6765 (@value{GDBP}) info macro N
6766 The symbol `N' has no definition as a C/C++ preprocessor macro
6767 at /home/jimb/gdb/macros/play/sample.c:12
6770 14 printf ("Goodbye, world!\n");
6771 (@value{GDBP}) info macro N
6772 Defined at /home/jimb/gdb/macros/play/sample.c:13
6774 (@value{GDBP}) macro expand N Q M
6775 expands to: 1729 < 42
6776 (@value{GDBP}) print N Q M
6783 @chapter Tracepoints
6784 @c This chapter is based on the documentation written by Michael
6785 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
6788 In some applications, it is not feasible for the debugger to interrupt
6789 the program's execution long enough for the developer to learn
6790 anything helpful about its behavior. If the program's correctness
6791 depends on its real-time behavior, delays introduced by a debugger
6792 might cause the program to change its behavior drastically, or perhaps
6793 fail, even when the code itself is correct. It is useful to be able
6794 to observe the program's behavior without interrupting it.
6796 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
6797 specify locations in the program, called @dfn{tracepoints}, and
6798 arbitrary expressions to evaluate when those tracepoints are reached.
6799 Later, using the @code{tfind} command, you can examine the values
6800 those expressions had when the program hit the tracepoints. The
6801 expressions may also denote objects in memory---structures or arrays,
6802 for example---whose values @value{GDBN} should record; while visiting
6803 a particular tracepoint, you may inspect those objects as if they were
6804 in memory at that moment. However, because @value{GDBN} records these
6805 values without interacting with you, it can do so quickly and
6806 unobtrusively, hopefully not disturbing the program's behavior.
6808 The tracepoint facility is currently available only for remote
6809 targets. @xref{Targets}. In addition, your remote target must know how
6810 to collect trace data. This functionality is implemented in the remote
6811 stub; however, none of the stubs distributed with @value{GDBN} support
6812 tracepoints as of this writing.
6814 This chapter describes the tracepoint commands and features.
6818 * Analyze Collected Data::
6819 * Tracepoint Variables::
6822 @node Set Tracepoints
6823 @section Commands to Set Tracepoints
6825 Before running such a @dfn{trace experiment}, an arbitrary number of
6826 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
6827 tracepoint has a number assigned to it by @value{GDBN}. Like with
6828 breakpoints, tracepoint numbers are successive integers starting from
6829 one. Many of the commands associated with tracepoints take the
6830 tracepoint number as their argument, to identify which tracepoint to
6833 For each tracepoint, you can specify, in advance, some arbitrary set
6834 of data that you want the target to collect in the trace buffer when
6835 it hits that tracepoint. The collected data can include registers,
6836 local variables, or global data. Later, you can use @value{GDBN}
6837 commands to examine the values these data had at the time the
6840 This section describes commands to set tracepoints and associated
6841 conditions and actions.
6844 * Create and Delete Tracepoints::
6845 * Enable and Disable Tracepoints::
6846 * Tracepoint Passcounts::
6847 * Tracepoint Actions::
6848 * Listing Tracepoints::
6849 * Starting and Stopping Trace Experiment::
6852 @node Create and Delete Tracepoints
6853 @subsection Create and Delete Tracepoints
6856 @cindex set tracepoint
6859 The @code{trace} command is very similar to the @code{break} command.
6860 Its argument can be a source line, a function name, or an address in
6861 the target program. @xref{Set Breaks}. The @code{trace} command
6862 defines a tracepoint, which is a point in the target program where the
6863 debugger will briefly stop, collect some data, and then allow the
6864 program to continue. Setting a tracepoint or changing its commands
6865 doesn't take effect until the next @code{tstart} command; thus, you
6866 cannot change the tracepoint attributes once a trace experiment is
6869 Here are some examples of using the @code{trace} command:
6872 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
6874 (@value{GDBP}) @b{trace +2} // 2 lines forward
6876 (@value{GDBP}) @b{trace my_function} // first source line of function
6878 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
6880 (@value{GDBP}) @b{trace *0x2117c4} // an address
6884 You can abbreviate @code{trace} as @code{tr}.
6887 @cindex last tracepoint number
6888 @cindex recent tracepoint number
6889 @cindex tracepoint number
6890 The convenience variable @code{$tpnum} records the tracepoint number
6891 of the most recently set tracepoint.
6893 @kindex delete tracepoint
6894 @cindex tracepoint deletion
6895 @item delete tracepoint @r{[}@var{num}@r{]}
6896 Permanently delete one or more tracepoints. With no argument, the
6897 default is to delete all tracepoints.
6902 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
6904 (@value{GDBP}) @b{delete trace} // remove all tracepoints
6908 You can abbreviate this command as @code{del tr}.
6911 @node Enable and Disable Tracepoints
6912 @subsection Enable and Disable Tracepoints
6915 @kindex disable tracepoint
6916 @item disable tracepoint @r{[}@var{num}@r{]}
6917 Disable tracepoint @var{num}, or all tracepoints if no argument
6918 @var{num} is given. A disabled tracepoint will have no effect during
6919 the next trace experiment, but it is not forgotten. You can re-enable
6920 a disabled tracepoint using the @code{enable tracepoint} command.
6922 @kindex enable tracepoint
6923 @item enable tracepoint @r{[}@var{num}@r{]}
6924 Enable tracepoint @var{num}, or all tracepoints. The enabled
6925 tracepoints will become effective the next time a trace experiment is
6929 @node Tracepoint Passcounts
6930 @subsection Tracepoint Passcounts
6934 @cindex tracepoint pass count
6935 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
6936 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
6937 automatically stop a trace experiment. If a tracepoint's passcount is
6938 @var{n}, then the trace experiment will be automatically stopped on
6939 the @var{n}'th time that tracepoint is hit. If the tracepoint number
6940 @var{num} is not specified, the @code{passcount} command sets the
6941 passcount of the most recently defined tracepoint. If no passcount is
6942 given, the trace experiment will run until stopped explicitly by the
6948 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
6949 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
6951 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
6952 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
6953 (@value{GDBP}) @b{trace foo}
6954 (@value{GDBP}) @b{pass 3}
6955 (@value{GDBP}) @b{trace bar}
6956 (@value{GDBP}) @b{pass 2}
6957 (@value{GDBP}) @b{trace baz}
6958 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
6959 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
6960 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
6961 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
6965 @node Tracepoint Actions
6966 @subsection Tracepoint Action Lists
6970 @cindex tracepoint actions
6971 @item actions @r{[}@var{num}@r{]}
6972 This command will prompt for a list of actions to be taken when the
6973 tracepoint is hit. If the tracepoint number @var{num} is not
6974 specified, this command sets the actions for the one that was most
6975 recently defined (so that you can define a tracepoint and then say
6976 @code{actions} without bothering about its number). You specify the
6977 actions themselves on the following lines, one action at a time, and
6978 terminate the actions list with a line containing just @code{end}. So
6979 far, the only defined actions are @code{collect} and
6980 @code{while-stepping}.
6982 @cindex remove actions from a tracepoint
6983 To remove all actions from a tracepoint, type @samp{actions @var{num}}
6984 and follow it immediately with @samp{end}.
6987 (@value{GDBP}) @b{collect @var{data}} // collect some data
6989 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
6991 (@value{GDBP}) @b{end} // signals the end of actions.
6994 In the following example, the action list begins with @code{collect}
6995 commands indicating the things to be collected when the tracepoint is
6996 hit. Then, in order to single-step and collect additional data
6997 following the tracepoint, a @code{while-stepping} command is used,
6998 followed by the list of things to be collected while stepping. The
6999 @code{while-stepping} command is terminated by its own separate
7000 @code{end} command. Lastly, the action list is terminated by an
7004 (@value{GDBP}) @b{trace foo}
7005 (@value{GDBP}) @b{actions}
7006 Enter actions for tracepoint 1, one per line:
7015 @kindex collect @r{(tracepoints)}
7016 @item collect @var{expr1}, @var{expr2}, @dots{}
7017 Collect values of the given expressions when the tracepoint is hit.
7018 This command accepts a comma-separated list of any valid expressions.
7019 In addition to global, static, or local variables, the following
7020 special arguments are supported:
7024 collect all registers
7027 collect all function arguments
7030 collect all local variables.
7033 You can give several consecutive @code{collect} commands, each one
7034 with a single argument, or one @code{collect} command with several
7035 arguments separated by commas: the effect is the same.
7037 The command @code{info scope} (@pxref{Symbols, info scope}) is
7038 particularly useful for figuring out what data to collect.
7040 @kindex while-stepping @r{(tracepoints)}
7041 @item while-stepping @var{n}
7042 Perform @var{n} single-step traces after the tracepoint, collecting
7043 new data at each step. The @code{while-stepping} command is
7044 followed by the list of what to collect while stepping (followed by
7045 its own @code{end} command):
7049 > collect $regs, myglobal
7055 You may abbreviate @code{while-stepping} as @code{ws} or
7059 @node Listing Tracepoints
7060 @subsection Listing Tracepoints
7063 @kindex info tracepoints
7065 @cindex information about tracepoints
7066 @item info tracepoints @r{[}@var{num}@r{]}
7067 Display information about the tracepoint @var{num}. If you don't specify
7068 a tracepoint number, displays information about all the tracepoints
7069 defined so far. For each tracepoint, the following information is
7076 whether it is enabled or disabled
7080 its passcount as given by the @code{passcount @var{n}} command
7082 its step count as given by the @code{while-stepping @var{n}} command
7084 where in the source files is the tracepoint set
7086 its action list as given by the @code{actions} command
7090 (@value{GDBP}) @b{info trace}
7091 Num Enb Address PassC StepC What
7092 1 y 0x002117c4 0 0 <gdb_asm>
7093 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
7094 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
7099 This command can be abbreviated @code{info tp}.
7102 @node Starting and Stopping Trace Experiment
7103 @subsection Starting and Stopping Trace Experiment
7107 @cindex start a new trace experiment
7108 @cindex collected data discarded
7110 This command takes no arguments. It starts the trace experiment, and
7111 begins collecting data. This has the side effect of discarding all
7112 the data collected in the trace buffer during the previous trace
7116 @cindex stop a running trace experiment
7118 This command takes no arguments. It ends the trace experiment, and
7119 stops collecting data.
7121 @strong{Note}: a trace experiment and data collection may stop
7122 automatically if any tracepoint's passcount is reached
7123 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
7126 @cindex status of trace data collection
7127 @cindex trace experiment, status of
7129 This command displays the status of the current trace data
7133 Here is an example of the commands we described so far:
7136 (@value{GDBP}) @b{trace gdb_c_test}
7137 (@value{GDBP}) @b{actions}
7138 Enter actions for tracepoint #1, one per line.
7139 > collect $regs,$locals,$args
7144 (@value{GDBP}) @b{tstart}
7145 [time passes @dots{}]
7146 (@value{GDBP}) @b{tstop}
7150 @node Analyze Collected Data
7151 @section Using the collected data
7153 After the tracepoint experiment ends, you use @value{GDBN} commands
7154 for examining the trace data. The basic idea is that each tracepoint
7155 collects a trace @dfn{snapshot} every time it is hit and another
7156 snapshot every time it single-steps. All these snapshots are
7157 consecutively numbered from zero and go into a buffer, and you can
7158 examine them later. The way you examine them is to @dfn{focus} on a
7159 specific trace snapshot. When the remote stub is focused on a trace
7160 snapshot, it will respond to all @value{GDBN} requests for memory and
7161 registers by reading from the buffer which belongs to that snapshot,
7162 rather than from @emph{real} memory or registers of the program being
7163 debugged. This means that @strong{all} @value{GDBN} commands
7164 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
7165 behave as if we were currently debugging the program state as it was
7166 when the tracepoint occurred. Any requests for data that are not in
7167 the buffer will fail.
7170 * tfind:: How to select a trace snapshot
7171 * tdump:: How to display all data for a snapshot
7172 * save-tracepoints:: How to save tracepoints for a future run
7176 @subsection @code{tfind @var{n}}
7179 @cindex select trace snapshot
7180 @cindex find trace snapshot
7181 The basic command for selecting a trace snapshot from the buffer is
7182 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
7183 counting from zero. If no argument @var{n} is given, the next
7184 snapshot is selected.
7186 Here are the various forms of using the @code{tfind} command.
7190 Find the first snapshot in the buffer. This is a synonym for
7191 @code{tfind 0} (since 0 is the number of the first snapshot).
7194 Stop debugging trace snapshots, resume @emph{live} debugging.
7197 Same as @samp{tfind none}.
7200 No argument means find the next trace snapshot.
7203 Find the previous trace snapshot before the current one. This permits
7204 retracing earlier steps.
7206 @item tfind tracepoint @var{num}
7207 Find the next snapshot associated with tracepoint @var{num}. Search
7208 proceeds forward from the last examined trace snapshot. If no
7209 argument @var{num} is given, it means find the next snapshot collected
7210 for the same tracepoint as the current snapshot.
7212 @item tfind pc @var{addr}
7213 Find the next snapshot associated with the value @var{addr} of the
7214 program counter. Search proceeds forward from the last examined trace
7215 snapshot. If no argument @var{addr} is given, it means find the next
7216 snapshot with the same value of PC as the current snapshot.
7218 @item tfind outside @var{addr1}, @var{addr2}
7219 Find the next snapshot whose PC is outside the given range of
7222 @item tfind range @var{addr1}, @var{addr2}
7223 Find the next snapshot whose PC is between @var{addr1} and
7224 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
7226 @item tfind line @r{[}@var{file}:@r{]}@var{n}
7227 Find the next snapshot associated with the source line @var{n}. If
7228 the optional argument @var{file} is given, refer to line @var{n} in
7229 that source file. Search proceeds forward from the last examined
7230 trace snapshot. If no argument @var{n} is given, it means find the
7231 next line other than the one currently being examined; thus saying
7232 @code{tfind line} repeatedly can appear to have the same effect as
7233 stepping from line to line in a @emph{live} debugging session.
7236 The default arguments for the @code{tfind} commands are specifically
7237 designed to make it easy to scan through the trace buffer. For
7238 instance, @code{tfind} with no argument selects the next trace
7239 snapshot, and @code{tfind -} with no argument selects the previous
7240 trace snapshot. So, by giving one @code{tfind} command, and then
7241 simply hitting @key{RET} repeatedly you can examine all the trace
7242 snapshots in order. Or, by saying @code{tfind -} and then hitting
7243 @key{RET} repeatedly you can examine the snapshots in reverse order.
7244 The @code{tfind line} command with no argument selects the snapshot
7245 for the next source line executed. The @code{tfind pc} command with
7246 no argument selects the next snapshot with the same program counter
7247 (PC) as the current frame. The @code{tfind tracepoint} command with
7248 no argument selects the next trace snapshot collected by the same
7249 tracepoint as the current one.
7251 In addition to letting you scan through the trace buffer manually,
7252 these commands make it easy to construct @value{GDBN} scripts that
7253 scan through the trace buffer and print out whatever collected data
7254 you are interested in. Thus, if we want to examine the PC, FP, and SP
7255 registers from each trace frame in the buffer, we can say this:
7258 (@value{GDBP}) @b{tfind start}
7259 (@value{GDBP}) @b{while ($trace_frame != -1)}
7260 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
7261 $trace_frame, $pc, $sp, $fp
7265 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
7266 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
7267 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
7268 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
7269 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
7270 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
7271 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
7272 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
7273 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
7274 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
7275 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
7278 Or, if we want to examine the variable @code{X} at each source line in
7282 (@value{GDBP}) @b{tfind start}
7283 (@value{GDBP}) @b{while ($trace_frame != -1)}
7284 > printf "Frame %d, X == %d\n", $trace_frame, X
7294 @subsection @code{tdump}
7296 @cindex dump all data collected at tracepoint
7297 @cindex tracepoint data, display
7299 This command takes no arguments. It prints all the data collected at
7300 the current trace snapshot.
7303 (@value{GDBP}) @b{trace 444}
7304 (@value{GDBP}) @b{actions}
7305 Enter actions for tracepoint #2, one per line:
7306 > collect $regs, $locals, $args, gdb_long_test
7309 (@value{GDBP}) @b{tstart}
7311 (@value{GDBP}) @b{tfind line 444}
7312 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
7314 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
7316 (@value{GDBP}) @b{tdump}
7317 Data collected at tracepoint 2, trace frame 1:
7318 d0 0xc4aa0085 -995491707
7322 d4 0x71aea3d 119204413
7327 a1 0x3000668 50333288
7330 a4 0x3000698 50333336
7332 fp 0x30bf3c 0x30bf3c
7333 sp 0x30bf34 0x30bf34
7335 pc 0x20b2c8 0x20b2c8
7339 p = 0x20e5b4 "gdb-test"
7346 gdb_long_test = 17 '\021'
7351 @node save-tracepoints
7352 @subsection @code{save-tracepoints @var{filename}}
7353 @kindex save-tracepoints
7354 @cindex save tracepoints for future sessions
7356 This command saves all current tracepoint definitions together with
7357 their actions and passcounts, into a file @file{@var{filename}}
7358 suitable for use in a later debugging session. To read the saved
7359 tracepoint definitions, use the @code{source} command (@pxref{Command
7362 @node Tracepoint Variables
7363 @section Convenience Variables for Tracepoints
7364 @cindex tracepoint variables
7365 @cindex convenience variables for tracepoints
7368 @vindex $trace_frame
7369 @item (int) $trace_frame
7370 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
7371 snapshot is selected.
7374 @item (int) $tracepoint
7375 The tracepoint for the current trace snapshot.
7378 @item (int) $trace_line
7379 The line number for the current trace snapshot.
7382 @item (char []) $trace_file
7383 The source file for the current trace snapshot.
7386 @item (char []) $trace_func
7387 The name of the function containing @code{$tracepoint}.
7390 Note: @code{$trace_file} is not suitable for use in @code{printf},
7391 use @code{output} instead.
7393 Here's a simple example of using these convenience variables for
7394 stepping through all the trace snapshots and printing some of their
7398 (@value{GDBP}) @b{tfind start}
7400 (@value{GDBP}) @b{while $trace_frame != -1}
7401 > output $trace_file
7402 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7408 @chapter Debugging Programs That Use Overlays
7411 If your program is too large to fit completely in your target system's
7412 memory, you can sometimes use @dfn{overlays} to work around this
7413 problem. @value{GDBN} provides some support for debugging programs that
7417 * How Overlays Work:: A general explanation of overlays.
7418 * Overlay Commands:: Managing overlays in @value{GDBN}.
7419 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7420 mapped by asking the inferior.
7421 * Overlay Sample Program:: A sample program using overlays.
7424 @node How Overlays Work
7425 @section How Overlays Work
7426 @cindex mapped overlays
7427 @cindex unmapped overlays
7428 @cindex load address, overlay's
7429 @cindex mapped address
7430 @cindex overlay area
7432 Suppose you have a computer whose instruction address space is only 64
7433 kilobytes long, but which has much more memory which can be accessed by
7434 other means: special instructions, segment registers, or memory
7435 management hardware, for example. Suppose further that you want to
7436 adapt a program which is larger than 64 kilobytes to run on this system.
7438 One solution is to identify modules of your program which are relatively
7439 independent, and need not call each other directly; call these modules
7440 @dfn{overlays}. Separate the overlays from the main program, and place
7441 their machine code in the larger memory. Place your main program in
7442 instruction memory, but leave at least enough space there to hold the
7443 largest overlay as well.
7445 Now, to call a function located in an overlay, you must first copy that
7446 overlay's machine code from the large memory into the space set aside
7447 for it in the instruction memory, and then jump to its entry point
7450 @c NB: In the below the mapped area's size is greater or equal to the
7451 @c size of all overlays. This is intentional to remind the developer
7452 @c that overlays don't necessarily need to be the same size.
7456 Data Instruction Larger
7457 Address Space Address Space Address Space
7458 +-----------+ +-----------+ +-----------+
7460 +-----------+ +-----------+ +-----------+<-- overlay 1
7461 | program | | main | .----| overlay 1 | load address
7462 | variables | | program | | +-----------+
7463 | and heap | | | | | |
7464 +-----------+ | | | +-----------+<-- overlay 2
7465 | | +-----------+ | | | load address
7466 +-----------+ | | | .-| overlay 2 |
7468 mapped --->+-----------+ | | +-----------+
7470 | overlay | <-' | | |
7471 | area | <---' +-----------+<-- overlay 3
7472 | | <---. | | load address
7473 +-----------+ `--| overlay 3 |
7480 @anchor{A code overlay}A code overlay
7484 The diagram (@pxref{A code overlay}) shows a system with separate data
7485 and instruction address spaces. To map an overlay, the program copies
7486 its code from the larger address space to the instruction address space.
7487 Since the overlays shown here all use the same mapped address, only one
7488 may be mapped at a time. For a system with a single address space for
7489 data and instructions, the diagram would be similar, except that the
7490 program variables and heap would share an address space with the main
7491 program and the overlay area.
7493 An overlay loaded into instruction memory and ready for use is called a
7494 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
7495 instruction memory. An overlay not present (or only partially present)
7496 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
7497 is its address in the larger memory. The mapped address is also called
7498 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
7499 called the @dfn{load memory address}, or @dfn{LMA}.
7501 Unfortunately, overlays are not a completely transparent way to adapt a
7502 program to limited instruction memory. They introduce a new set of
7503 global constraints you must keep in mind as you design your program:
7508 Before calling or returning to a function in an overlay, your program
7509 must make sure that overlay is actually mapped. Otherwise, the call or
7510 return will transfer control to the right address, but in the wrong
7511 overlay, and your program will probably crash.
7514 If the process of mapping an overlay is expensive on your system, you
7515 will need to choose your overlays carefully to minimize their effect on
7516 your program's performance.
7519 The executable file you load onto your system must contain each
7520 overlay's instructions, appearing at the overlay's load address, not its
7521 mapped address. However, each overlay's instructions must be relocated
7522 and its symbols defined as if the overlay were at its mapped address.
7523 You can use GNU linker scripts to specify different load and relocation
7524 addresses for pieces of your program; see @ref{Overlay Description,,,
7525 ld.info, Using ld: the GNU linker}.
7528 The procedure for loading executable files onto your system must be able
7529 to load their contents into the larger address space as well as the
7530 instruction and data spaces.
7534 The overlay system described above is rather simple, and could be
7535 improved in many ways:
7540 If your system has suitable bank switch registers or memory management
7541 hardware, you could use those facilities to make an overlay's load area
7542 contents simply appear at their mapped address in instruction space.
7543 This would probably be faster than copying the overlay to its mapped
7544 area in the usual way.
7547 If your overlays are small enough, you could set aside more than one
7548 overlay area, and have more than one overlay mapped at a time.
7551 You can use overlays to manage data, as well as instructions. In
7552 general, data overlays are even less transparent to your design than
7553 code overlays: whereas code overlays only require care when you call or
7554 return to functions, data overlays require care every time you access
7555 the data. Also, if you change the contents of a data overlay, you
7556 must copy its contents back out to its load address before you can copy a
7557 different data overlay into the same mapped area.
7562 @node Overlay Commands
7563 @section Overlay Commands
7565 To use @value{GDBN}'s overlay support, each overlay in your program must
7566 correspond to a separate section of the executable file. The section's
7567 virtual memory address and load memory address must be the overlay's
7568 mapped and load addresses. Identifying overlays with sections allows
7569 @value{GDBN} to determine the appropriate address of a function or
7570 variable, depending on whether the overlay is mapped or not.
7572 @value{GDBN}'s overlay commands all start with the word @code{overlay};
7573 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
7578 Disable @value{GDBN}'s overlay support. When overlay support is
7579 disabled, @value{GDBN} assumes that all functions and variables are
7580 always present at their mapped addresses. By default, @value{GDBN}'s
7581 overlay support is disabled.
7583 @item overlay manual
7584 @cindex manual overlay debugging
7585 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
7586 relies on you to tell it which overlays are mapped, and which are not,
7587 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
7588 commands described below.
7590 @item overlay map-overlay @var{overlay}
7591 @itemx overlay map @var{overlay}
7592 @cindex map an overlay
7593 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
7594 be the name of the object file section containing the overlay. When an
7595 overlay is mapped, @value{GDBN} assumes it can find the overlay's
7596 functions and variables at their mapped addresses. @value{GDBN} assumes
7597 that any other overlays whose mapped ranges overlap that of
7598 @var{overlay} are now unmapped.
7600 @item overlay unmap-overlay @var{overlay}
7601 @itemx overlay unmap @var{overlay}
7602 @cindex unmap an overlay
7603 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
7604 must be the name of the object file section containing the overlay.
7605 When an overlay is unmapped, @value{GDBN} assumes it can find the
7606 overlay's functions and variables at their load addresses.
7609 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
7610 consults a data structure the overlay manager maintains in the inferior
7611 to see which overlays are mapped. For details, see @ref{Automatic
7614 @item overlay load-target
7616 @cindex reloading the overlay table
7617 Re-read the overlay table from the inferior. Normally, @value{GDBN}
7618 re-reads the table @value{GDBN} automatically each time the inferior
7619 stops, so this command should only be necessary if you have changed the
7620 overlay mapping yourself using @value{GDBN}. This command is only
7621 useful when using automatic overlay debugging.
7623 @item overlay list-overlays
7625 @cindex listing mapped overlays
7626 Display a list of the overlays currently mapped, along with their mapped
7627 addresses, load addresses, and sizes.
7631 Normally, when @value{GDBN} prints a code address, it includes the name
7632 of the function the address falls in:
7635 (@value{GDBP}) print main
7636 $3 = @{int ()@} 0x11a0 <main>
7639 When overlay debugging is enabled, @value{GDBN} recognizes code in
7640 unmapped overlays, and prints the names of unmapped functions with
7641 asterisks around them. For example, if @code{foo} is a function in an
7642 unmapped overlay, @value{GDBN} prints it this way:
7645 (@value{GDBP}) overlay list
7646 No sections are mapped.
7647 (@value{GDBP}) print foo
7648 $5 = @{int (int)@} 0x100000 <*foo*>
7651 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
7655 (@value{GDBP}) overlay list
7656 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
7657 mapped at 0x1016 - 0x104a
7658 (@value{GDBP}) print foo
7659 $6 = @{int (int)@} 0x1016 <foo>
7662 When overlay debugging is enabled, @value{GDBN} can find the correct
7663 address for functions and variables in an overlay, whether or not the
7664 overlay is mapped. This allows most @value{GDBN} commands, like
7665 @code{break} and @code{disassemble}, to work normally, even on unmapped
7666 code. However, @value{GDBN}'s breakpoint support has some limitations:
7670 @cindex breakpoints in overlays
7671 @cindex overlays, setting breakpoints in
7672 You can set breakpoints in functions in unmapped overlays, as long as
7673 @value{GDBN} can write to the overlay at its load address.
7675 @value{GDBN} can not set hardware or simulator-based breakpoints in
7676 unmapped overlays. However, if you set a breakpoint at the end of your
7677 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
7678 you are using manual overlay management), @value{GDBN} will re-set its
7679 breakpoints properly.
7683 @node Automatic Overlay Debugging
7684 @section Automatic Overlay Debugging
7685 @cindex automatic overlay debugging
7687 @value{GDBN} can automatically track which overlays are mapped and which
7688 are not, given some simple co-operation from the overlay manager in the
7689 inferior. If you enable automatic overlay debugging with the
7690 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
7691 looks in the inferior's memory for certain variables describing the
7692 current state of the overlays.
7694 Here are the variables your overlay manager must define to support
7695 @value{GDBN}'s automatic overlay debugging:
7699 @item @code{_ovly_table}:
7700 This variable must be an array of the following structures:
7705 /* The overlay's mapped address. */
7708 /* The size of the overlay, in bytes. */
7711 /* The overlay's load address. */
7714 /* Non-zero if the overlay is currently mapped;
7716 unsigned long mapped;
7720 @item @code{_novlys}:
7721 This variable must be a four-byte signed integer, holding the total
7722 number of elements in @code{_ovly_table}.
7726 To decide whether a particular overlay is mapped or not, @value{GDBN}
7727 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
7728 @code{lma} members equal the VMA and LMA of the overlay's section in the
7729 executable file. When @value{GDBN} finds a matching entry, it consults
7730 the entry's @code{mapped} member to determine whether the overlay is
7733 In addition, your overlay manager may define a function called
7734 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
7735 will silently set a breakpoint there. If the overlay manager then
7736 calls this function whenever it has changed the overlay table, this
7737 will enable @value{GDBN} to accurately keep track of which overlays
7738 are in program memory, and update any breakpoints that may be set
7739 in overlays. This will allow breakpoints to work even if the
7740 overlays are kept in ROM or other non-writable memory while they
7741 are not being executed.
7743 @node Overlay Sample Program
7744 @section Overlay Sample Program
7745 @cindex overlay example program
7747 When linking a program which uses overlays, you must place the overlays
7748 at their load addresses, while relocating them to run at their mapped
7749 addresses. To do this, you must write a linker script (@pxref{Overlay
7750 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
7751 since linker scripts are specific to a particular host system, target
7752 architecture, and target memory layout, this manual cannot provide
7753 portable sample code demonstrating @value{GDBN}'s overlay support.
7755 However, the @value{GDBN} source distribution does contain an overlaid
7756 program, with linker scripts for a few systems, as part of its test
7757 suite. The program consists of the following files from
7758 @file{gdb/testsuite/gdb.base}:
7762 The main program file.
7764 A simple overlay manager, used by @file{overlays.c}.
7769 Overlay modules, loaded and used by @file{overlays.c}.
7772 Linker scripts for linking the test program on the @code{d10v-elf}
7773 and @code{m32r-elf} targets.
7776 You can build the test program using the @code{d10v-elf} GCC
7777 cross-compiler like this:
7780 $ d10v-elf-gcc -g -c overlays.c
7781 $ d10v-elf-gcc -g -c ovlymgr.c
7782 $ d10v-elf-gcc -g -c foo.c
7783 $ d10v-elf-gcc -g -c bar.c
7784 $ d10v-elf-gcc -g -c baz.c
7785 $ d10v-elf-gcc -g -c grbx.c
7786 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
7787 baz.o grbx.o -Wl,-Td10v.ld -o overlays
7790 The build process is identical for any other architecture, except that
7791 you must substitute the appropriate compiler and linker script for the
7792 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
7796 @chapter Using @value{GDBN} with Different Languages
7799 Although programming languages generally have common aspects, they are
7800 rarely expressed in the same manner. For instance, in ANSI C,
7801 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
7802 Modula-2, it is accomplished by @code{p^}. Values can also be
7803 represented (and displayed) differently. Hex numbers in C appear as
7804 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
7806 @cindex working language
7807 Language-specific information is built into @value{GDBN} for some languages,
7808 allowing you to express operations like the above in your program's
7809 native language, and allowing @value{GDBN} to output values in a manner
7810 consistent with the syntax of your program's native language. The
7811 language you use to build expressions is called the @dfn{working
7815 * Setting:: Switching between source languages
7816 * Show:: Displaying the language
7817 * Checks:: Type and range checks
7818 * Support:: Supported languages
7819 * Unsupported languages:: Unsupported languages
7823 @section Switching between source languages
7825 There are two ways to control the working language---either have @value{GDBN}
7826 set it automatically, or select it manually yourself. You can use the
7827 @code{set language} command for either purpose. On startup, @value{GDBN}
7828 defaults to setting the language automatically. The working language is
7829 used to determine how expressions you type are interpreted, how values
7832 In addition to the working language, every source file that
7833 @value{GDBN} knows about has its own working language. For some object
7834 file formats, the compiler might indicate which language a particular
7835 source file is in. However, most of the time @value{GDBN} infers the
7836 language from the name of the file. The language of a source file
7837 controls whether C@t{++} names are demangled---this way @code{backtrace} can
7838 show each frame appropriately for its own language. There is no way to
7839 set the language of a source file from within @value{GDBN}, but you can
7840 set the language associated with a filename extension. @xref{Show, ,
7841 Displaying the language}.
7843 This is most commonly a problem when you use a program, such
7844 as @code{cfront} or @code{f2c}, that generates C but is written in
7845 another language. In that case, make the
7846 program use @code{#line} directives in its C output; that way
7847 @value{GDBN} will know the correct language of the source code of the original
7848 program, and will display that source code, not the generated C code.
7851 * Filenames:: Filename extensions and languages.
7852 * Manually:: Setting the working language manually
7853 * Automatically:: Having @value{GDBN} infer the source language
7857 @subsection List of filename extensions and languages
7859 If a source file name ends in one of the following extensions, then
7860 @value{GDBN} infers that its language is the one indicated.
7881 Objective-C source file
7888 Modula-2 source file
7892 Assembler source file. This actually behaves almost like C, but
7893 @value{GDBN} does not skip over function prologues when stepping.
7896 In addition, you may set the language associated with a filename
7897 extension. @xref{Show, , Displaying the language}.
7900 @subsection Setting the working language
7902 If you allow @value{GDBN} to set the language automatically,
7903 expressions are interpreted the same way in your debugging session and
7906 @kindex set language
7907 If you wish, you may set the language manually. To do this, issue the
7908 command @samp{set language @var{lang}}, where @var{lang} is the name of
7910 @code{c} or @code{modula-2}.
7911 For a list of the supported languages, type @samp{set language}.
7913 Setting the language manually prevents @value{GDBN} from updating the working
7914 language automatically. This can lead to confusion if you try
7915 to debug a program when the working language is not the same as the
7916 source language, when an expression is acceptable to both
7917 languages---but means different things. For instance, if the current
7918 source file were written in C, and @value{GDBN} was parsing Modula-2, a
7926 might not have the effect you intended. In C, this means to add
7927 @code{b} and @code{c} and place the result in @code{a}. The result
7928 printed would be the value of @code{a}. In Modula-2, this means to compare
7929 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
7932 @subsection Having @value{GDBN} infer the source language
7934 To have @value{GDBN} set the working language automatically, use
7935 @samp{set language local} or @samp{set language auto}. @value{GDBN}
7936 then infers the working language. That is, when your program stops in a
7937 frame (usually by encountering a breakpoint), @value{GDBN} sets the
7938 working language to the language recorded for the function in that
7939 frame. If the language for a frame is unknown (that is, if the function
7940 or block corresponding to the frame was defined in a source file that
7941 does not have a recognized extension), the current working language is
7942 not changed, and @value{GDBN} issues a warning.
7944 This may not seem necessary for most programs, which are written
7945 entirely in one source language. However, program modules and libraries
7946 written in one source language can be used by a main program written in
7947 a different source language. Using @samp{set language auto} in this
7948 case frees you from having to set the working language manually.
7951 @section Displaying the language
7953 The following commands help you find out which language is the
7954 working language, and also what language source files were written in.
7956 @kindex show language
7959 Display the current working language. This is the
7960 language you can use with commands such as @code{print} to
7961 build and compute expressions that may involve variables in your program.
7964 @kindex info frame@r{, show the source language}
7965 Display the source language for this frame. This language becomes the
7966 working language if you use an identifier from this frame.
7967 @xref{Frame Info, ,Information about a frame}, to identify the other
7968 information listed here.
7971 @kindex info source@r{, show the source language}
7972 Display the source language of this source file.
7973 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
7974 information listed here.
7977 In unusual circumstances, you may have source files with extensions
7978 not in the standard list. You can then set the extension associated
7979 with a language explicitly:
7981 @kindex set extension-language
7982 @kindex info extensions
7984 @item set extension-language @var{ext} @var{language}
7985 Tell @value{GDBN} that source files with extension @var{ext} are to be
7986 assumed as written in the source language @var{language}.
7988 @item info extensions
7989 List all the filename extensions and the associated languages.
7993 @section Type and range checking
7996 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
7997 checking are included, but they do not yet have any effect. This
7998 section documents the intended facilities.
8000 @c FIXME remove warning when type/range code added
8002 Some languages are designed to guard you against making seemingly common
8003 errors through a series of compile- and run-time checks. These include
8004 checking the type of arguments to functions and operators, and making
8005 sure mathematical overflows are caught at run time. Checks such as
8006 these help to ensure a program's correctness once it has been compiled
8007 by eliminating type mismatches, and providing active checks for range
8008 errors when your program is running.
8010 @value{GDBN} can check for conditions like the above if you wish.
8011 Although @value{GDBN} does not check the statements in your program, it
8012 can check expressions entered directly into @value{GDBN} for evaluation via
8013 the @code{print} command, for example. As with the working language,
8014 @value{GDBN} can also decide whether or not to check automatically based on
8015 your program's source language. @xref{Support, ,Supported languages},
8016 for the default settings of supported languages.
8019 * Type Checking:: An overview of type checking
8020 * Range Checking:: An overview of range checking
8023 @cindex type checking
8024 @cindex checks, type
8026 @subsection An overview of type checking
8028 Some languages, such as Modula-2, are strongly typed, meaning that the
8029 arguments to operators and functions have to be of the correct type,
8030 otherwise an error occurs. These checks prevent type mismatch
8031 errors from ever causing any run-time problems. For example,
8039 The second example fails because the @code{CARDINAL} 1 is not
8040 type-compatible with the @code{REAL} 2.3.
8042 For the expressions you use in @value{GDBN} commands, you can tell the
8043 @value{GDBN} type checker to skip checking;
8044 to treat any mismatches as errors and abandon the expression;
8045 or to only issue warnings when type mismatches occur,
8046 but evaluate the expression anyway. When you choose the last of
8047 these, @value{GDBN} evaluates expressions like the second example above, but
8048 also issues a warning.
8050 Even if you turn type checking off, there may be other reasons
8051 related to type that prevent @value{GDBN} from evaluating an expression.
8052 For instance, @value{GDBN} does not know how to add an @code{int} and
8053 a @code{struct foo}. These particular type errors have nothing to do
8054 with the language in use, and usually arise from expressions, such as
8055 the one described above, which make little sense to evaluate anyway.
8057 Each language defines to what degree it is strict about type. For
8058 instance, both Modula-2 and C require the arguments to arithmetical
8059 operators to be numbers. In C, enumerated types and pointers can be
8060 represented as numbers, so that they are valid arguments to mathematical
8061 operators. @xref{Support, ,Supported languages}, for further
8062 details on specific languages.
8064 @value{GDBN} provides some additional commands for controlling the type checker:
8066 @kindex set check type
8067 @kindex show check type
8069 @item set check type auto
8070 Set type checking on or off based on the current working language.
8071 @xref{Support, ,Supported languages}, for the default settings for
8074 @item set check type on
8075 @itemx set check type off
8076 Set type checking on or off, overriding the default setting for the
8077 current working language. Issue a warning if the setting does not
8078 match the language default. If any type mismatches occur in
8079 evaluating an expression while type checking is on, @value{GDBN} prints a
8080 message and aborts evaluation of the expression.
8082 @item set check type warn
8083 Cause the type checker to issue warnings, but to always attempt to
8084 evaluate the expression. Evaluating the expression may still
8085 be impossible for other reasons. For example, @value{GDBN} cannot add
8086 numbers and structures.
8089 Show the current setting of the type checker, and whether or not @value{GDBN}
8090 is setting it automatically.
8093 @cindex range checking
8094 @cindex checks, range
8095 @node Range Checking
8096 @subsection An overview of range checking
8098 In some languages (such as Modula-2), it is an error to exceed the
8099 bounds of a type; this is enforced with run-time checks. Such range
8100 checking is meant to ensure program correctness by making sure
8101 computations do not overflow, or indices on an array element access do
8102 not exceed the bounds of the array.
8104 For expressions you use in @value{GDBN} commands, you can tell
8105 @value{GDBN} to treat range errors in one of three ways: ignore them,
8106 always treat them as errors and abandon the expression, or issue
8107 warnings but evaluate the expression anyway.
8109 A range error can result from numerical overflow, from exceeding an
8110 array index bound, or when you type a constant that is not a member
8111 of any type. Some languages, however, do not treat overflows as an
8112 error. In many implementations of C, mathematical overflow causes the
8113 result to ``wrap around'' to lower values---for example, if @var{m} is
8114 the largest integer value, and @var{s} is the smallest, then
8117 @var{m} + 1 @result{} @var{s}
8120 This, too, is specific to individual languages, and in some cases
8121 specific to individual compilers or machines. @xref{Support, ,
8122 Supported languages}, for further details on specific languages.
8124 @value{GDBN} provides some additional commands for controlling the range checker:
8126 @kindex set check range
8127 @kindex show check range
8129 @item set check range auto
8130 Set range checking on or off based on the current working language.
8131 @xref{Support, ,Supported languages}, for the default settings for
8134 @item set check range on
8135 @itemx set check range off
8136 Set range checking on or off, overriding the default setting for the
8137 current working language. A warning is issued if the setting does not
8138 match the language default. If a range error occurs and range checking is on,
8139 then a message is printed and evaluation of the expression is aborted.
8141 @item set check range warn
8142 Output messages when the @value{GDBN} range checker detects a range error,
8143 but attempt to evaluate the expression anyway. Evaluating the
8144 expression may still be impossible for other reasons, such as accessing
8145 memory that the process does not own (a typical example from many Unix
8149 Show the current setting of the range checker, and whether or not it is
8150 being set automatically by @value{GDBN}.
8154 @section Supported languages
8156 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, assembly, Modula-2, and Ada.
8157 @c This is false ...
8158 Some @value{GDBN} features may be used in expressions regardless of the
8159 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
8160 and the @samp{@{type@}addr} construct (@pxref{Expressions,
8161 ,Expressions}) can be used with the constructs of any supported
8164 The following sections detail to what degree each source language is
8165 supported by @value{GDBN}. These sections are not meant to be language
8166 tutorials or references, but serve only as a reference guide to what the
8167 @value{GDBN} expression parser accepts, and what input and output
8168 formats should look like for different languages. There are many good
8169 books written on each of these languages; please look to these for a
8170 language reference or tutorial.
8174 * Objective-C:: Objective-C
8176 * Modula-2:: Modula-2
8181 @subsection C and C@t{++}
8183 @cindex C and C@t{++}
8184 @cindex expressions in C or C@t{++}
8186 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
8187 to both languages. Whenever this is the case, we discuss those languages
8191 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
8192 @cindex @sc{gnu} C@t{++}
8193 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
8194 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
8195 effectively, you must compile your C@t{++} programs with a supported
8196 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
8197 compiler (@code{aCC}).
8199 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
8200 format; if it doesn't work on your system, try the stabs+ debugging
8201 format. You can select those formats explicitly with the @code{g++}
8202 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
8203 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
8204 CC, gcc.info, Using @sc{gnu} CC}.
8207 * C Operators:: C and C@t{++} operators
8208 * C Constants:: C and C@t{++} constants
8209 * C plus plus expressions:: C@t{++} expressions
8210 * C Defaults:: Default settings for C and C@t{++}
8211 * C Checks:: C and C@t{++} type and range checks
8212 * Debugging C:: @value{GDBN} and C
8213 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
8217 @subsubsection C and C@t{++} operators
8219 @cindex C and C@t{++} operators
8221 Operators must be defined on values of specific types. For instance,
8222 @code{+} is defined on numbers, but not on structures. Operators are
8223 often defined on groups of types.
8225 For the purposes of C and C@t{++}, the following definitions hold:
8230 @emph{Integral types} include @code{int} with any of its storage-class
8231 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
8234 @emph{Floating-point types} include @code{float}, @code{double}, and
8235 @code{long double} (if supported by the target platform).
8238 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
8241 @emph{Scalar types} include all of the above.
8246 The following operators are supported. They are listed here
8247 in order of increasing precedence:
8251 The comma or sequencing operator. Expressions in a comma-separated list
8252 are evaluated from left to right, with the result of the entire
8253 expression being the last expression evaluated.
8256 Assignment. The value of an assignment expression is the value
8257 assigned. Defined on scalar types.
8260 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
8261 and translated to @w{@code{@var{a} = @var{a op b}}}.
8262 @w{@code{@var{op}=}} and @code{=} have the same precedence.
8263 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
8264 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
8267 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
8268 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
8272 Logical @sc{or}. Defined on integral types.
8275 Logical @sc{and}. Defined on integral types.
8278 Bitwise @sc{or}. Defined on integral types.
8281 Bitwise exclusive-@sc{or}. Defined on integral types.
8284 Bitwise @sc{and}. Defined on integral types.
8287 Equality and inequality. Defined on scalar types. The value of these
8288 expressions is 0 for false and non-zero for true.
8290 @item <@r{, }>@r{, }<=@r{, }>=
8291 Less than, greater than, less than or equal, greater than or equal.
8292 Defined on scalar types. The value of these expressions is 0 for false
8293 and non-zero for true.
8296 left shift, and right shift. Defined on integral types.
8299 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8302 Addition and subtraction. Defined on integral types, floating-point types and
8305 @item *@r{, }/@r{, }%
8306 Multiplication, division, and modulus. Multiplication and division are
8307 defined on integral and floating-point types. Modulus is defined on
8311 Increment and decrement. When appearing before a variable, the
8312 operation is performed before the variable is used in an expression;
8313 when appearing after it, the variable's value is used before the
8314 operation takes place.
8317 Pointer dereferencing. Defined on pointer types. Same precedence as
8321 Address operator. Defined on variables. Same precedence as @code{++}.
8323 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
8324 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
8325 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
8326 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
8330 Negative. Defined on integral and floating-point types. Same
8331 precedence as @code{++}.
8334 Logical negation. Defined on integral types. Same precedence as
8338 Bitwise complement operator. Defined on integral types. Same precedence as
8343 Structure member, and pointer-to-structure member. For convenience,
8344 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
8345 pointer based on the stored type information.
8346 Defined on @code{struct} and @code{union} data.
8349 Dereferences of pointers to members.
8352 Array indexing. @code{@var{a}[@var{i}]} is defined as
8353 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
8356 Function parameter list. Same precedence as @code{->}.
8359 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
8360 and @code{class} types.
8363 Doubled colons also represent the @value{GDBN} scope operator
8364 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
8368 If an operator is redefined in the user code, @value{GDBN} usually
8369 attempts to invoke the redefined version instead of using the operator's
8377 @subsubsection C and C@t{++} constants
8379 @cindex C and C@t{++} constants
8381 @value{GDBN} allows you to express the constants of C and C@t{++} in the
8386 Integer constants are a sequence of digits. Octal constants are
8387 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
8388 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
8389 @samp{l}, specifying that the constant should be treated as a
8393 Floating point constants are a sequence of digits, followed by a decimal
8394 point, followed by a sequence of digits, and optionally followed by an
8395 exponent. An exponent is of the form:
8396 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8397 sequence of digits. The @samp{+} is optional for positive exponents.
8398 A floating-point constant may also end with a letter @samp{f} or
8399 @samp{F}, specifying that the constant should be treated as being of
8400 the @code{float} (as opposed to the default @code{double}) type; or with
8401 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8405 Enumerated constants consist of enumerated identifiers, or their
8406 integral equivalents.
8409 Character constants are a single character surrounded by single quotes
8410 (@code{'}), or a number---the ordinal value of the corresponding character
8411 (usually its @sc{ascii} value). Within quotes, the single character may
8412 be represented by a letter or by @dfn{escape sequences}, which are of
8413 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8414 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8415 @samp{@var{x}} is a predefined special character---for example,
8416 @samp{\n} for newline.
8419 String constants are a sequence of character constants surrounded by
8420 double quotes (@code{"}). Any valid character constant (as described
8421 above) may appear. Double quotes within the string must be preceded by
8422 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8426 Pointer constants are an integral value. You can also write pointers
8427 to constants using the C operator @samp{&}.
8430 Array constants are comma-separated lists surrounded by braces @samp{@{}
8431 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8432 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8433 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8437 * C plus plus expressions::
8444 @node C plus plus expressions
8445 @subsubsection C@t{++} expressions
8447 @cindex expressions in C@t{++}
8448 @value{GDBN} expression handling can interpret most C@t{++} expressions.
8450 @cindex debugging C@t{++} programs
8451 @cindex C@t{++} compilers
8452 @cindex debug formats and C@t{++}
8453 @cindex @value{NGCC} and C@t{++}
8455 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
8456 proper compiler and the proper debug format. Currently, @value{GDBN}
8457 works best when debugging C@t{++} code that is compiled with
8458 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
8459 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
8460 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
8461 stabs+ as their default debug format, so you usually don't need to
8462 specify a debug format explicitly. Other compilers and/or debug formats
8463 are likely to work badly or not at all when using @value{GDBN} to debug
8469 @cindex member functions
8471 Member function calls are allowed; you can use expressions like
8474 count = aml->GetOriginal(x, y)
8477 @vindex this@r{, inside C@t{++} member functions}
8478 @cindex namespace in C@t{++}
8480 While a member function is active (in the selected stack frame), your
8481 expressions have the same namespace available as the member function;
8482 that is, @value{GDBN} allows implicit references to the class instance
8483 pointer @code{this} following the same rules as C@t{++}.
8485 @cindex call overloaded functions
8486 @cindex overloaded functions, calling
8487 @cindex type conversions in C@t{++}
8489 You can call overloaded functions; @value{GDBN} resolves the function
8490 call to the right definition, with some restrictions. @value{GDBN} does not
8491 perform overload resolution involving user-defined type conversions,
8492 calls to constructors, or instantiations of templates that do not exist
8493 in the program. It also cannot handle ellipsis argument lists or
8496 It does perform integral conversions and promotions, floating-point
8497 promotions, arithmetic conversions, pointer conversions, conversions of
8498 class objects to base classes, and standard conversions such as those of
8499 functions or arrays to pointers; it requires an exact match on the
8500 number of function arguments.
8502 Overload resolution is always performed, unless you have specified
8503 @code{set overload-resolution off}. @xref{Debugging C plus plus,
8504 ,@value{GDBN} features for C@t{++}}.
8506 You must specify @code{set overload-resolution off} in order to use an
8507 explicit function signature to call an overloaded function, as in
8509 p 'foo(char,int)'('x', 13)
8512 The @value{GDBN} command-completion facility can simplify this;
8513 see @ref{Completion, ,Command completion}.
8515 @cindex reference declarations
8517 @value{GDBN} understands variables declared as C@t{++} references; you can use
8518 them in expressions just as you do in C@t{++} source---they are automatically
8521 In the parameter list shown when @value{GDBN} displays a frame, the values of
8522 reference variables are not displayed (unlike other variables); this
8523 avoids clutter, since references are often used for large structures.
8524 The @emph{address} of a reference variable is always shown, unless
8525 you have specified @samp{set print address off}.
8528 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
8529 expressions can use it just as expressions in your program do. Since
8530 one scope may be defined in another, you can use @code{::} repeatedly if
8531 necessary, for example in an expression like
8532 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
8533 resolving name scope by reference to source files, in both C and C@t{++}
8534 debugging (@pxref{Variables, ,Program variables}).
8537 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
8538 calling virtual functions correctly, printing out virtual bases of
8539 objects, calling functions in a base subobject, casting objects, and
8540 invoking user-defined operators.
8543 @subsubsection C and C@t{++} defaults
8545 @cindex C and C@t{++} defaults
8547 If you allow @value{GDBN} to set type and range checking automatically, they
8548 both default to @code{off} whenever the working language changes to
8549 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
8550 selects the working language.
8552 If you allow @value{GDBN} to set the language automatically, it
8553 recognizes source files whose names end with @file{.c}, @file{.C}, or
8554 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
8555 these files, it sets the working language to C or C@t{++}.
8556 @xref{Automatically, ,Having @value{GDBN} infer the source language},
8557 for further details.
8559 @c Type checking is (a) primarily motivated by Modula-2, and (b)
8560 @c unimplemented. If (b) changes, it might make sense to let this node
8561 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
8564 @subsubsection C and C@t{++} type and range checks
8566 @cindex C and C@t{++} checks
8568 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
8569 is not used. However, if you turn type checking on, @value{GDBN}
8570 considers two variables type equivalent if:
8574 The two variables are structured and have the same structure, union, or
8578 The two variables have the same type name, or types that have been
8579 declared equivalent through @code{typedef}.
8582 @c leaving this out because neither J Gilmore nor R Pesch understand it.
8585 The two @code{struct}, @code{union}, or @code{enum} variables are
8586 declared in the same declaration. (Note: this may not be true for all C
8591 Range checking, if turned on, is done on mathematical operations. Array
8592 indices are not checked, since they are often used to index a pointer
8593 that is not itself an array.
8596 @subsubsection @value{GDBN} and C
8598 The @code{set print union} and @code{show print union} commands apply to
8599 the @code{union} type. When set to @samp{on}, any @code{union} that is
8600 inside a @code{struct} or @code{class} is also printed. Otherwise, it
8601 appears as @samp{@{...@}}.
8603 The @code{@@} operator aids in the debugging of dynamic arrays, formed
8604 with pointers and a memory allocation function. @xref{Expressions,
8608 * Debugging C plus plus::
8611 @node Debugging C plus plus
8612 @subsubsection @value{GDBN} features for C@t{++}
8614 @cindex commands for C@t{++}
8616 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
8617 designed specifically for use with C@t{++}. Here is a summary:
8620 @cindex break in overloaded functions
8621 @item @r{breakpoint menus}
8622 When you want a breakpoint in a function whose name is overloaded,
8623 @value{GDBN} breakpoint menus help you specify which function definition
8624 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
8626 @cindex overloading in C@t{++}
8627 @item rbreak @var{regex}
8628 Setting breakpoints using regular expressions is helpful for setting
8629 breakpoints on overloaded functions that are not members of any special
8631 @xref{Set Breaks, ,Setting breakpoints}.
8633 @cindex C@t{++} exception handling
8636 Debug C@t{++} exception handling using these commands. @xref{Set
8637 Catchpoints, , Setting catchpoints}.
8640 @item ptype @var{typename}
8641 Print inheritance relationships as well as other information for type
8643 @xref{Symbols, ,Examining the Symbol Table}.
8645 @cindex C@t{++} symbol display
8646 @item set print demangle
8647 @itemx show print demangle
8648 @itemx set print asm-demangle
8649 @itemx show print asm-demangle
8650 Control whether C@t{++} symbols display in their source form, both when
8651 displaying code as C@t{++} source and when displaying disassemblies.
8652 @xref{Print Settings, ,Print settings}.
8654 @item set print object
8655 @itemx show print object
8656 Choose whether to print derived (actual) or declared types of objects.
8657 @xref{Print Settings, ,Print settings}.
8659 @item set print vtbl
8660 @itemx show print vtbl
8661 Control the format for printing virtual function tables.
8662 @xref{Print Settings, ,Print settings}.
8663 (The @code{vtbl} commands do not work on programs compiled with the HP
8664 ANSI C@t{++} compiler (@code{aCC}).)
8666 @kindex set overload-resolution
8667 @cindex overloaded functions, overload resolution
8668 @item set overload-resolution on
8669 Enable overload resolution for C@t{++} expression evaluation. The default
8670 is on. For overloaded functions, @value{GDBN} evaluates the arguments
8671 and searches for a function whose signature matches the argument types,
8672 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
8673 expressions}, for details). If it cannot find a match, it emits a
8676 @item set overload-resolution off
8677 Disable overload resolution for C@t{++} expression evaluation. For
8678 overloaded functions that are not class member functions, @value{GDBN}
8679 chooses the first function of the specified name that it finds in the
8680 symbol table, whether or not its arguments are of the correct type. For
8681 overloaded functions that are class member functions, @value{GDBN}
8682 searches for a function whose signature @emph{exactly} matches the
8685 @item @r{Overloaded symbol names}
8686 You can specify a particular definition of an overloaded symbol, using
8687 the same notation that is used to declare such symbols in C@t{++}: type
8688 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
8689 also use the @value{GDBN} command-line word completion facilities to list the
8690 available choices, or to finish the type list for you.
8691 @xref{Completion,, Command completion}, for details on how to do this.
8695 @subsection Objective-C
8698 This section provides information about some commands and command
8699 options that are useful for debugging Objective-C code.
8702 * Method Names in Commands::
8703 * The Print Command with Objective-C::
8706 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
8707 @subsubsection Method Names in Commands
8709 The following commands have been extended to accept Objective-C method
8710 names as line specifications:
8712 @kindex clear@r{, and Objective-C}
8713 @kindex break@r{, and Objective-C}
8714 @kindex info line@r{, and Objective-C}
8715 @kindex jump@r{, and Objective-C}
8716 @kindex list@r{, and Objective-C}
8720 @item @code{info line}
8725 A fully qualified Objective-C method name is specified as
8728 -[@var{Class} @var{methodName}]
8731 where the minus sign is used to indicate an instance method and a
8732 plus sign (not shown) is used to indicate a class method. The class
8733 name @var{Class} and method name @var{methodName} are enclosed in
8734 brackets, similar to the way messages are specified in Objective-C
8735 source code. For example, to set a breakpoint at the @code{create}
8736 instance method of class @code{Fruit} in the program currently being
8740 break -[Fruit create]
8743 To list ten program lines around the @code{initialize} class method,
8747 list +[NSText initialize]
8750 In the current version of @value{GDBN}, the plus or minus sign is
8751 required. In future versions of @value{GDBN}, the plus or minus
8752 sign will be optional, but you can use it to narrow the search. It
8753 is also possible to specify just a method name:
8759 You must specify the complete method name, including any colons. If
8760 your program's source files contain more than one @code{create} method,
8761 you'll be presented with a numbered list of classes that implement that
8762 method. Indicate your choice by number, or type @samp{0} to exit if
8765 As another example, to clear a breakpoint established at the
8766 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
8769 clear -[NSWindow makeKeyAndOrderFront:]
8772 @node The Print Command with Objective-C
8773 @subsubsection The Print Command With Objective-C
8774 @kindex print-object
8775 @kindex po @r{(@code{print-object})}
8777 The print command has also been extended to accept methods. For example:
8780 print -[@var{object} hash]
8783 @cindex print an Objective-C object description
8784 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
8786 will tell @value{GDBN} to send the @code{hash} message to @var{object}
8787 and print the result. Also, an additional command has been added,
8788 @code{print-object} or @code{po} for short, which is meant to print
8789 the description of an object. However, this command may only work
8790 with certain Objective-C libraries that have a particular hook
8791 function, @code{_NSPrintForDebugger}, defined.
8795 @cindex Fortran-specific support in @value{GDBN}
8798 @cindex @code{COMMON} blocks, Fortran
8800 @item info common @r{[}@var{common-name}@r{]}
8801 This command prints the values contained in the Fortran @code{COMMON}
8802 block whose name is @var{common-name}. With no argument, the names of
8803 all @code{COMMON} blocks visible at current program location are
8807 Fortran symbols are usually case-insensitive, so @value{GDBN} by
8808 default uses case-insensitive matches for Fortran symbols. You can
8809 change that with the @samp{set case-insensitive} command, see
8810 @ref{Symbols}, for the details.
8813 @subsection Modula-2
8815 @cindex Modula-2, @value{GDBN} support
8817 The extensions made to @value{GDBN} to support Modula-2 only support
8818 output from the @sc{gnu} Modula-2 compiler (which is currently being
8819 developed). Other Modula-2 compilers are not currently supported, and
8820 attempting to debug executables produced by them is most likely
8821 to give an error as @value{GDBN} reads in the executable's symbol
8824 @cindex expressions in Modula-2
8826 * M2 Operators:: Built-in operators
8827 * Built-In Func/Proc:: Built-in functions and procedures
8828 * M2 Constants:: Modula-2 constants
8829 * M2 Defaults:: Default settings for Modula-2
8830 * Deviations:: Deviations from standard Modula-2
8831 * M2 Checks:: Modula-2 type and range checks
8832 * M2 Scope:: The scope operators @code{::} and @code{.}
8833 * GDB/M2:: @value{GDBN} and Modula-2
8837 @subsubsection Operators
8838 @cindex Modula-2 operators
8840 Operators must be defined on values of specific types. For instance,
8841 @code{+} is defined on numbers, but not on structures. Operators are
8842 often defined on groups of types. For the purposes of Modula-2, the
8843 following definitions hold:
8848 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
8852 @emph{Character types} consist of @code{CHAR} and its subranges.
8855 @emph{Floating-point types} consist of @code{REAL}.
8858 @emph{Pointer types} consist of anything declared as @code{POINTER TO
8862 @emph{Scalar types} consist of all of the above.
8865 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
8868 @emph{Boolean types} consist of @code{BOOLEAN}.
8872 The following operators are supported, and appear in order of
8873 increasing precedence:
8877 Function argument or array index separator.
8880 Assignment. The value of @var{var} @code{:=} @var{value} is
8884 Less than, greater than on integral, floating-point, or enumerated
8888 Less than or equal to, greater than or equal to
8889 on integral, floating-point and enumerated types, or set inclusion on
8890 set types. Same precedence as @code{<}.
8892 @item =@r{, }<>@r{, }#
8893 Equality and two ways of expressing inequality, valid on scalar types.
8894 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
8895 available for inequality, since @code{#} conflicts with the script
8899 Set membership. Defined on set types and the types of their members.
8900 Same precedence as @code{<}.
8903 Boolean disjunction. Defined on boolean types.
8906 Boolean conjunction. Defined on boolean types.
8909 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8912 Addition and subtraction on integral and floating-point types, or union
8913 and difference on set types.
8916 Multiplication on integral and floating-point types, or set intersection
8920 Division on floating-point types, or symmetric set difference on set
8921 types. Same precedence as @code{*}.
8924 Integer division and remainder. Defined on integral types. Same
8925 precedence as @code{*}.
8928 Negative. Defined on @code{INTEGER} and @code{REAL} data.
8931 Pointer dereferencing. Defined on pointer types.
8934 Boolean negation. Defined on boolean types. Same precedence as
8938 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
8939 precedence as @code{^}.
8942 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
8945 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
8949 @value{GDBN} and Modula-2 scope operators.
8953 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
8954 treats the use of the operator @code{IN}, or the use of operators
8955 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
8956 @code{<=}, and @code{>=} on sets as an error.
8960 @node Built-In Func/Proc
8961 @subsubsection Built-in functions and procedures
8962 @cindex Modula-2 built-ins
8964 Modula-2 also makes available several built-in procedures and functions.
8965 In describing these, the following metavariables are used:
8970 represents an @code{ARRAY} variable.
8973 represents a @code{CHAR} constant or variable.
8976 represents a variable or constant of integral type.
8979 represents an identifier that belongs to a set. Generally used in the
8980 same function with the metavariable @var{s}. The type of @var{s} should
8981 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
8984 represents a variable or constant of integral or floating-point type.
8987 represents a variable or constant of floating-point type.
8993 represents a variable.
8996 represents a variable or constant of one of many types. See the
8997 explanation of the function for details.
9000 All Modula-2 built-in procedures also return a result, described below.
9004 Returns the absolute value of @var{n}.
9007 If @var{c} is a lower case letter, it returns its upper case
9008 equivalent, otherwise it returns its argument.
9011 Returns the character whose ordinal value is @var{i}.
9014 Decrements the value in the variable @var{v} by one. Returns the new value.
9016 @item DEC(@var{v},@var{i})
9017 Decrements the value in the variable @var{v} by @var{i}. Returns the
9020 @item EXCL(@var{m},@var{s})
9021 Removes the element @var{m} from the set @var{s}. Returns the new
9024 @item FLOAT(@var{i})
9025 Returns the floating point equivalent of the integer @var{i}.
9028 Returns the index of the last member of @var{a}.
9031 Increments the value in the variable @var{v} by one. Returns the new value.
9033 @item INC(@var{v},@var{i})
9034 Increments the value in the variable @var{v} by @var{i}. Returns the
9037 @item INCL(@var{m},@var{s})
9038 Adds the element @var{m} to the set @var{s} if it is not already
9039 there. Returns the new set.
9042 Returns the maximum value of the type @var{t}.
9045 Returns the minimum value of the type @var{t}.
9048 Returns boolean TRUE if @var{i} is an odd number.
9051 Returns the ordinal value of its argument. For example, the ordinal
9052 value of a character is its @sc{ascii} value (on machines supporting the
9053 @sc{ascii} character set). @var{x} must be of an ordered type, which include
9054 integral, character and enumerated types.
9057 Returns the size of its argument. @var{x} can be a variable or a type.
9059 @item TRUNC(@var{r})
9060 Returns the integral part of @var{r}.
9062 @item VAL(@var{t},@var{i})
9063 Returns the member of the type @var{t} whose ordinal value is @var{i}.
9067 @emph{Warning:} Sets and their operations are not yet supported, so
9068 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
9072 @cindex Modula-2 constants
9074 @subsubsection Constants
9076 @value{GDBN} allows you to express the constants of Modula-2 in the following
9082 Integer constants are simply a sequence of digits. When used in an
9083 expression, a constant is interpreted to be type-compatible with the
9084 rest of the expression. Hexadecimal integers are specified by a
9085 trailing @samp{H}, and octal integers by a trailing @samp{B}.
9088 Floating point constants appear as a sequence of digits, followed by a
9089 decimal point and another sequence of digits. An optional exponent can
9090 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
9091 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
9092 digits of the floating point constant must be valid decimal (base 10)
9096 Character constants consist of a single character enclosed by a pair of
9097 like quotes, either single (@code{'}) or double (@code{"}). They may
9098 also be expressed by their ordinal value (their @sc{ascii} value, usually)
9099 followed by a @samp{C}.
9102 String constants consist of a sequence of characters enclosed by a
9103 pair of like quotes, either single (@code{'}) or double (@code{"}).
9104 Escape sequences in the style of C are also allowed. @xref{C
9105 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
9109 Enumerated constants consist of an enumerated identifier.
9112 Boolean constants consist of the identifiers @code{TRUE} and
9116 Pointer constants consist of integral values only.
9119 Set constants are not yet supported.
9123 @subsubsection Modula-2 defaults
9124 @cindex Modula-2 defaults
9126 If type and range checking are set automatically by @value{GDBN}, they
9127 both default to @code{on} whenever the working language changes to
9128 Modula-2. This happens regardless of whether you or @value{GDBN}
9129 selected the working language.
9131 If you allow @value{GDBN} to set the language automatically, then entering
9132 code compiled from a file whose name ends with @file{.mod} sets the
9133 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
9134 the language automatically}, for further details.
9137 @subsubsection Deviations from standard Modula-2
9138 @cindex Modula-2, deviations from
9140 A few changes have been made to make Modula-2 programs easier to debug.
9141 This is done primarily via loosening its type strictness:
9145 Unlike in standard Modula-2, pointer constants can be formed by
9146 integers. This allows you to modify pointer variables during
9147 debugging. (In standard Modula-2, the actual address contained in a
9148 pointer variable is hidden from you; it can only be modified
9149 through direct assignment to another pointer variable or expression that
9150 returned a pointer.)
9153 C escape sequences can be used in strings and characters to represent
9154 non-printable characters. @value{GDBN} prints out strings with these
9155 escape sequences embedded. Single non-printable characters are
9156 printed using the @samp{CHR(@var{nnn})} format.
9159 The assignment operator (@code{:=}) returns the value of its right-hand
9163 All built-in procedures both modify @emph{and} return their argument.
9167 @subsubsection Modula-2 type and range checks
9168 @cindex Modula-2 checks
9171 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
9174 @c FIXME remove warning when type/range checks added
9176 @value{GDBN} considers two Modula-2 variables type equivalent if:
9180 They are of types that have been declared equivalent via a @code{TYPE
9181 @var{t1} = @var{t2}} statement
9184 They have been declared on the same line. (Note: This is true of the
9185 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
9188 As long as type checking is enabled, any attempt to combine variables
9189 whose types are not equivalent is an error.
9191 Range checking is done on all mathematical operations, assignment, array
9192 index bounds, and all built-in functions and procedures.
9195 @subsubsection The scope operators @code{::} and @code{.}
9197 @cindex @code{.}, Modula-2 scope operator
9198 @cindex colon, doubled as scope operator
9200 @vindex colon-colon@r{, in Modula-2}
9201 @c Info cannot handle :: but TeX can.
9204 @vindex ::@r{, in Modula-2}
9207 There are a few subtle differences between the Modula-2 scope operator
9208 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
9213 @var{module} . @var{id}
9214 @var{scope} :: @var{id}
9218 where @var{scope} is the name of a module or a procedure,
9219 @var{module} the name of a module, and @var{id} is any declared
9220 identifier within your program, except another module.
9222 Using the @code{::} operator makes @value{GDBN} search the scope
9223 specified by @var{scope} for the identifier @var{id}. If it is not
9224 found in the specified scope, then @value{GDBN} searches all scopes
9225 enclosing the one specified by @var{scope}.
9227 Using the @code{.} operator makes @value{GDBN} search the current scope for
9228 the identifier specified by @var{id} that was imported from the
9229 definition module specified by @var{module}. With this operator, it is
9230 an error if the identifier @var{id} was not imported from definition
9231 module @var{module}, or if @var{id} is not an identifier in
9235 @subsubsection @value{GDBN} and Modula-2
9237 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
9238 Five subcommands of @code{set print} and @code{show print} apply
9239 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
9240 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
9241 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
9242 analogue in Modula-2.
9244 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
9245 with any language, is not useful with Modula-2. Its
9246 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
9247 created in Modula-2 as they can in C or C@t{++}. However, because an
9248 address can be specified by an integral constant, the construct
9249 @samp{@{@var{type}@}@var{adrexp}} is still useful.
9251 @cindex @code{#} in Modula-2
9252 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
9253 interpreted as the beginning of a comment. Use @code{<>} instead.
9259 The extensions made to @value{GDBN} for Ada only support
9260 output from the @sc{gnu} Ada (GNAT) compiler.
9261 Other Ada compilers are not currently supported, and
9262 attempting to debug executables produced by them is most likely
9266 @cindex expressions in Ada
9268 * Ada Mode Intro:: General remarks on the Ada syntax
9269 and semantics supported by Ada mode
9271 * Omissions from Ada:: Restrictions on the Ada expression syntax.
9272 * Additions to Ada:: Extensions of the Ada expression syntax.
9273 * Stopping Before Main Program:: Debugging the program during elaboration.
9274 * Ada Glitches:: Known peculiarities of Ada mode.
9277 @node Ada Mode Intro
9278 @subsubsection Introduction
9279 @cindex Ada mode, general
9281 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
9282 syntax, with some extensions.
9283 The philosophy behind the design of this subset is
9287 That @value{GDBN} should provide basic literals and access to operations for
9288 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
9289 leaving more sophisticated computations to subprograms written into the
9290 program (which therefore may be called from @value{GDBN}).
9293 That type safety and strict adherence to Ada language restrictions
9294 are not particularly important to the @value{GDBN} user.
9297 That brevity is important to the @value{GDBN} user.
9300 Thus, for brevity, the debugger acts as if there were
9301 implicit @code{with} and @code{use} clauses in effect for all user-written
9302 packages, making it unnecessary to fully qualify most names with
9303 their packages, regardless of context. Where this causes ambiguity,
9304 @value{GDBN} asks the user's intent.
9306 The debugger will start in Ada mode if it detects an Ada main program.
9307 As for other languages, it will enter Ada mode when stopped in a program that
9308 was translated from an Ada source file.
9310 While in Ada mode, you may use `@t{--}' for comments. This is useful
9311 mostly for documenting command files. The standard @value{GDBN} comment
9312 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
9313 middle (to allow based literals).
9315 The debugger supports limited overloading. Given a subprogram call in which
9316 the function symbol has multiple definitions, it will use the number of
9317 actual parameters and some information about their types to attempt to narrow
9318 the set of definitions. It also makes very limited use of context, preferring
9319 procedures to functions in the context of the @code{call} command, and
9320 functions to procedures elsewhere.
9322 @node Omissions from Ada
9323 @subsubsection Omissions from Ada
9324 @cindex Ada, omissions from
9326 Here are the notable omissions from the subset:
9330 Only a subset of the attributes are supported:
9334 @t{'First}, @t{'Last}, and @t{'Length}
9335 on array objects (not on types and subtypes).
9338 @t{'Min} and @t{'Max}.
9341 @t{'Pos} and @t{'Val}.
9347 @t{'Range} on array objects (not subtypes), but only as the right
9348 operand of the membership (@code{in}) operator.
9351 @t{'Access}, @t{'Unchecked_Access}, and
9352 @t{'Unrestricted_Access} (a GNAT extension).
9360 @code{Characters.Latin_1} are not available and
9361 concatenation is not implemented. Thus, escape characters in strings are
9362 not currently available.
9365 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
9366 equality of representations. They will generally work correctly
9367 for strings and arrays whose elements have integer or enumeration types.
9368 They may not work correctly for arrays whose element
9369 types have user-defined equality, for arrays of real values
9370 (in particular, IEEE-conformant floating point, because of negative
9371 zeroes and NaNs), and for arrays whose elements contain unused bits with
9372 indeterminate values.
9375 The other component-by-component array operations (@code{and}, @code{or},
9376 @code{xor}, @code{not}, and relational tests other than equality)
9377 are not implemented.
9380 There are no record or array aggregates.
9383 Calls to dispatching subprograms are not implemented.
9386 The overloading algorithm is much more limited (i.e., less selective)
9387 than that of real Ada. It makes only limited use of the context in which a subexpression
9388 appears to resolve its meaning, and it is much looser in its rules for allowing
9389 type matches. As a result, some function calls will be ambiguous, and the user
9390 will be asked to choose the proper resolution.
9393 The @code{new} operator is not implemented.
9396 Entry calls are not implemented.
9399 Aside from printing, arithmetic operations on the native VAX floating-point
9400 formats are not supported.
9403 It is not possible to slice a packed array.
9406 @node Additions to Ada
9407 @subsubsection Additions to Ada
9408 @cindex Ada, deviations from
9410 As it does for other languages, @value{GDBN} makes certain generic
9411 extensions to Ada (@pxref{Expressions}):
9415 If the expression @var{E} is a variable residing in memory
9416 (typically a local variable or array element) and @var{N} is
9417 a positive integer, then @code{@var{E}@@@var{N}} displays the values of
9418 @var{E} and the @var{N}-1 adjacent variables following it in memory as an array.
9419 In Ada, this operator is generally not necessary, since its prime use
9420 is in displaying parts of an array, and slicing will usually do this in Ada.
9421 However, there are occasional uses when debugging programs
9422 in which certain debugging information has been optimized away.
9425 @code{@var{B}::@var{var}} means ``the variable named @var{var} that appears
9426 in function or file @var{B}.'' When @var{B} is a file name, you must typically
9427 surround it in single quotes.
9430 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
9431 @var{type} that appears at address @var{addr}.''
9434 A name starting with @samp{$} is a convenience variable
9435 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
9438 In addition, @value{GDBN} provides a few other shortcuts and outright additions specific
9443 The assignment statement is allowed as an expression, returning
9444 its right-hand operand as its value. Thus, you may enter
9448 print A(tmp := y + 1)
9452 The semicolon is allowed as an ``operator,'' returning as its value
9453 the value of its right-hand operand.
9454 This allows, for example,
9455 complex conditional breaks:
9459 condition 1 (report(i); k += 1; A(k) > 100)
9463 Rather than use catenation and symbolic character names to introduce special
9464 characters into strings, one may instead use a special bracket notation,
9465 which is also used to print strings. A sequence of characters of the form
9466 @samp{["@var{XX}"]} within a string or character literal denotes the
9467 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
9468 sequence of characters @samp{["""]} also denotes a single quotation mark
9469 in strings. For example,
9471 "One line.["0a"]Next line.["0a"]"
9474 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF}) after each
9478 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
9479 @t{'Max} is optional (and is ignored in any case). For example, it is valid
9487 When printing arrays, @value{GDBN} uses positional notation when the
9488 array has a lower bound of 1, and uses a modified named notation otherwise.
9489 For example, a one-dimensional array of three integers with a lower bound of 3 might print as
9496 That is, in contrast to valid Ada, only the first component has a @code{=>}
9500 You may abbreviate attributes in expressions with any unique,
9501 multi-character subsequence of
9502 their names (an exact match gets preference).
9503 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
9504 in place of @t{a'length}.
9507 @cindex quoting Ada internal identifiers
9508 Since Ada is case-insensitive, the debugger normally maps identifiers you type
9509 to lower case. The GNAT compiler uses upper-case characters for
9510 some of its internal identifiers, which are normally of no interest to users.
9511 For the rare occasions when you actually have to look at them,
9512 enclose them in angle brackets to avoid the lower-case mapping.
9515 @value{GDBP} print <JMPBUF_SAVE>[0]
9519 Printing an object of class-wide type or dereferencing an
9520 access-to-class-wide value will display all the components of the object's
9521 specific type (as indicated by its run-time tag). Likewise, component
9522 selection on such a value will operate on the specific type of the
9527 @node Stopping Before Main Program
9528 @subsubsection Stopping at the Very Beginning
9530 @cindex breakpointing Ada elaboration code
9531 It is sometimes necessary to debug the program during elaboration, and
9532 before reaching the main procedure.
9533 As defined in the Ada Reference
9534 Manual, the elaboration code is invoked from a procedure called
9535 @code{adainit}. To run your program up to the beginning of
9536 elaboration, simply use the following two commands:
9537 @code{tbreak adainit} and @code{run}.
9540 @subsubsection Known Peculiarities of Ada Mode
9541 @cindex Ada, problems
9543 Besides the omissions listed previously (@pxref{Omissions from Ada}),
9544 we know of several problems with and limitations of Ada mode in
9546 some of which will be fixed with planned future releases of the debugger
9547 and the GNU Ada compiler.
9551 Currently, the debugger
9552 has insufficient information to determine whether certain pointers represent
9553 pointers to objects or the objects themselves.
9554 Thus, the user may have to tack an extra @code{.all} after an expression
9555 to get it printed properly.
9558 Static constants that the compiler chooses not to materialize as objects in
9559 storage are invisible to the debugger.
9562 Named parameter associations in function argument lists are ignored (the
9563 argument lists are treated as positional).
9566 Many useful library packages are currently invisible to the debugger.
9569 Fixed-point arithmetic, conversions, input, and output is carried out using
9570 floating-point arithmetic, and may give results that only approximate those on
9574 The type of the @t{'Address} attribute may not be @code{System.Address}.
9577 The GNAT compiler never generates the prefix @code{Standard} for any of
9578 the standard symbols defined by the Ada language. @value{GDBN} knows about
9579 this: it will strip the prefix from names when you use it, and will never
9580 look for a name you have so qualified among local symbols, nor match against
9581 symbols in other packages or subprograms. If you have
9582 defined entities anywhere in your program other than parameters and
9583 local variables whose simple names match names in @code{Standard},
9584 GNAT's lack of qualification here can cause confusion. When this happens,
9585 you can usually resolve the confusion
9586 by qualifying the problematic names with package
9587 @code{Standard} explicitly.
9590 @node Unsupported languages
9591 @section Unsupported languages
9593 @cindex unsupported languages
9594 @cindex minimal language
9595 In addition to the other fully-supported programming languages,
9596 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
9597 It does not represent a real programming language, but provides a set
9598 of capabilities close to what the C or assembly languages provide.
9599 This should allow most simple operations to be performed while debugging
9600 an application that uses a language currently not supported by @value{GDBN}.
9602 If the language is set to @code{auto}, @value{GDBN} will automatically
9603 select this language if the current frame corresponds to an unsupported
9607 @chapter Examining the Symbol Table
9609 The commands described in this chapter allow you to inquire about the
9610 symbols (names of variables, functions and types) defined in your
9611 program. This information is inherent in the text of your program and
9612 does not change as your program executes. @value{GDBN} finds it in your
9613 program's symbol table, in the file indicated when you started @value{GDBN}
9614 (@pxref{File Options, ,Choosing files}), or by one of the
9615 file-management commands (@pxref{Files, ,Commands to specify files}).
9617 @cindex symbol names
9618 @cindex names of symbols
9619 @cindex quoting names
9620 Occasionally, you may need to refer to symbols that contain unusual
9621 characters, which @value{GDBN} ordinarily treats as word delimiters. The
9622 most frequent case is in referring to static variables in other
9623 source files (@pxref{Variables,,Program variables}). File names
9624 are recorded in object files as debugging symbols, but @value{GDBN} would
9625 ordinarily parse a typical file name, like @file{foo.c}, as the three words
9626 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
9627 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
9634 looks up the value of @code{x} in the scope of the file @file{foo.c}.
9637 @cindex case-insensitive symbol names
9638 @cindex case sensitivity in symbol names
9639 @kindex set case-sensitive
9640 @item set case-sensitive on
9641 @itemx set case-sensitive off
9642 @itemx set case-sensitive auto
9643 Normally, when @value{GDBN} looks up symbols, it matches their names
9644 with case sensitivity determined by the current source language.
9645 Occasionally, you may wish to control that. The command @code{set
9646 case-sensitive} lets you do that by specifying @code{on} for
9647 case-sensitive matches or @code{off} for case-insensitive ones. If
9648 you specify @code{auto}, case sensitivity is reset to the default
9649 suitable for the source language. The default is case-sensitive
9650 matches for all languages except for Fortran, for which the default is
9651 case-insensitive matches.
9653 @kindex show case-insensitive
9654 @item show case-insensitive
9655 This command shows the current setting of case sensitivity for symbols
9658 @kindex info address
9659 @cindex address of a symbol
9660 @item info address @var{symbol}
9661 Describe where the data for @var{symbol} is stored. For a register
9662 variable, this says which register it is kept in. For a non-register
9663 local variable, this prints the stack-frame offset at which the variable
9666 Note the contrast with @samp{print &@var{symbol}}, which does not work
9667 at all for a register variable, and for a stack local variable prints
9668 the exact address of the current instantiation of the variable.
9671 @cindex symbol from address
9672 @item info symbol @var{addr}
9673 Print the name of a symbol which is stored at the address @var{addr}.
9674 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
9675 nearest symbol and an offset from it:
9678 (@value{GDBP}) info symbol 0x54320
9679 _initialize_vx + 396 in section .text
9683 This is the opposite of the @code{info address} command. You can use
9684 it to find out the name of a variable or a function given its address.
9687 @item whatis @var{expr}
9688 Print the data type of expression @var{expr}. @var{expr} is not
9689 actually evaluated, and any side-effecting operations (such as
9690 assignments or function calls) inside it do not take place.
9691 @xref{Expressions, ,Expressions}.
9694 Print the data type of @code{$}, the last value in the value history.
9697 @item ptype @var{typename}
9698 Print a description of data type @var{typename}. @var{typename} may be
9699 the name of a type, or for C code it may have the form @samp{class
9700 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
9701 @var{union-tag}} or @samp{enum @var{enum-tag}}.
9703 @item ptype @var{expr}
9705 Print a description of the type of expression @var{expr}. @code{ptype}
9706 differs from @code{whatis} by printing a detailed description, instead
9707 of just the name of the type.
9709 For example, for this variable declaration:
9712 struct complex @{double real; double imag;@} v;
9716 the two commands give this output:
9720 (@value{GDBP}) whatis v
9721 type = struct complex
9722 (@value{GDBP}) ptype v
9723 type = struct complex @{
9731 As with @code{whatis}, using @code{ptype} without an argument refers to
9732 the type of @code{$}, the last value in the value history.
9735 @item info types @var{regexp}
9737 Print a brief description of all types whose names match the regular
9738 expression @var{regexp} (or all types in your program, if you supply
9739 no argument). Each complete typename is matched as though it were a
9740 complete line; thus, @samp{i type value} gives information on all
9741 types in your program whose names include the string @code{value}, but
9742 @samp{i type ^value$} gives information only on types whose complete
9743 name is @code{value}.
9745 This command differs from @code{ptype} in two ways: first, like
9746 @code{whatis}, it does not print a detailed description; second, it
9747 lists all source files where a type is defined.
9750 @cindex local variables
9751 @item info scope @var{location}
9752 List all the variables local to a particular scope. This command
9753 accepts a @var{location} argument---a function name, a source line, or
9754 an address preceded by a @samp{*}, and prints all the variables local
9755 to the scope defined by that location. For example:
9758 (@value{GDBP}) @b{info scope command_line_handler}
9759 Scope for command_line_handler:
9760 Symbol rl is an argument at stack/frame offset 8, length 4.
9761 Symbol linebuffer is in static storage at address 0x150a18, length 4.
9762 Symbol linelength is in static storage at address 0x150a1c, length 4.
9763 Symbol p is a local variable in register $esi, length 4.
9764 Symbol p1 is a local variable in register $ebx, length 4.
9765 Symbol nline is a local variable in register $edx, length 4.
9766 Symbol repeat is a local variable at frame offset -8, length 4.
9770 This command is especially useful for determining what data to collect
9771 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
9776 Show information about the current source file---that is, the source file for
9777 the function containing the current point of execution:
9780 the name of the source file, and the directory containing it,
9782 the directory it was compiled in,
9784 its length, in lines,
9786 which programming language it is written in,
9788 whether the executable includes debugging information for that file, and
9789 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
9791 whether the debugging information includes information about
9792 preprocessor macros.
9796 @kindex info sources
9798 Print the names of all source files in your program for which there is
9799 debugging information, organized into two lists: files whose symbols
9800 have already been read, and files whose symbols will be read when needed.
9802 @kindex info functions
9803 @item info functions
9804 Print the names and data types of all defined functions.
9806 @item info functions @var{regexp}
9807 Print the names and data types of all defined functions
9808 whose names contain a match for regular expression @var{regexp}.
9809 Thus, @samp{info fun step} finds all functions whose names
9810 include @code{step}; @samp{info fun ^step} finds those whose names
9811 start with @code{step}. If a function name contains characters
9812 that conflict with the regular expression language (eg.
9813 @samp{operator*()}), they may be quoted with a backslash.
9815 @kindex info variables
9816 @item info variables
9817 Print the names and data types of all variables that are declared
9818 outside of functions (i.e.@: excluding local variables).
9820 @item info variables @var{regexp}
9821 Print the names and data types of all variables (except for local
9822 variables) whose names contain a match for regular expression
9825 @kindex info classes
9827 @itemx info classes @var{regexp}
9828 Display all Objective-C classes in your program, or
9829 (with the @var{regexp} argument) all those matching a particular regular
9832 @kindex info selectors
9833 @item info selectors
9834 @itemx info selectors @var{regexp}
9835 Display all Objective-C selectors in your program, or
9836 (with the @var{regexp} argument) all those matching a particular regular
9840 This was never implemented.
9841 @kindex info methods
9843 @itemx info methods @var{regexp}
9844 The @code{info methods} command permits the user to examine all defined
9845 methods within C@t{++} program, or (with the @var{regexp} argument) a
9846 specific set of methods found in the various C@t{++} classes. Many
9847 C@t{++} classes provide a large number of methods. Thus, the output
9848 from the @code{ptype} command can be overwhelming and hard to use. The
9849 @code{info-methods} command filters the methods, printing only those
9850 which match the regular-expression @var{regexp}.
9853 @cindex reloading symbols
9854 Some systems allow individual object files that make up your program to
9855 be replaced without stopping and restarting your program. For example,
9856 in VxWorks you can simply recompile a defective object file and keep on
9857 running. If you are running on one of these systems, you can allow
9858 @value{GDBN} to reload the symbols for automatically relinked modules:
9861 @kindex set symbol-reloading
9862 @item set symbol-reloading on
9863 Replace symbol definitions for the corresponding source file when an
9864 object file with a particular name is seen again.
9866 @item set symbol-reloading off
9867 Do not replace symbol definitions when encountering object files of the
9868 same name more than once. This is the default state; if you are not
9869 running on a system that permits automatic relinking of modules, you
9870 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
9871 may discard symbols when linking large programs, that may contain
9872 several modules (from different directories or libraries) with the same
9875 @kindex show symbol-reloading
9876 @item show symbol-reloading
9877 Show the current @code{on} or @code{off} setting.
9880 @kindex set opaque-type-resolution
9881 @item set opaque-type-resolution on
9882 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
9883 declared as a pointer to a @code{struct}, @code{class}, or
9884 @code{union}---for example, @code{struct MyType *}---that is used in one
9885 source file although the full declaration of @code{struct MyType} is in
9886 another source file. The default is on.
9888 A change in the setting of this subcommand will not take effect until
9889 the next time symbols for a file are loaded.
9891 @item set opaque-type-resolution off
9892 Tell @value{GDBN} not to resolve opaque types. In this case, the type
9893 is printed as follows:
9895 @{<no data fields>@}
9898 @kindex show opaque-type-resolution
9899 @item show opaque-type-resolution
9900 Show whether opaque types are resolved or not.
9902 @kindex maint print symbols
9904 @kindex maint print psymbols
9905 @cindex partial symbol dump
9906 @item maint print symbols @var{filename}
9907 @itemx maint print psymbols @var{filename}
9908 @itemx maint print msymbols @var{filename}
9909 Write a dump of debugging symbol data into the file @var{filename}.
9910 These commands are used to debug the @value{GDBN} symbol-reading code. Only
9911 symbols with debugging data are included. If you use @samp{maint print
9912 symbols}, @value{GDBN} includes all the symbols for which it has already
9913 collected full details: that is, @var{filename} reflects symbols for
9914 only those files whose symbols @value{GDBN} has read. You can use the
9915 command @code{info sources} to find out which files these are. If you
9916 use @samp{maint print psymbols} instead, the dump shows information about
9917 symbols that @value{GDBN} only knows partially---that is, symbols defined in
9918 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
9919 @samp{maint print msymbols} dumps just the minimal symbol information
9920 required for each object file from which @value{GDBN} has read some symbols.
9921 @xref{Files, ,Commands to specify files}, for a discussion of how
9922 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
9924 @kindex maint info symtabs
9925 @kindex maint info psymtabs
9926 @cindex listing @value{GDBN}'s internal symbol tables
9927 @cindex symbol tables, listing @value{GDBN}'s internal
9928 @cindex full symbol tables, listing @value{GDBN}'s internal
9929 @cindex partial symbol tables, listing @value{GDBN}'s internal
9930 @item maint info symtabs @r{[} @var{regexp} @r{]}
9931 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
9933 List the @code{struct symtab} or @code{struct partial_symtab}
9934 structures whose names match @var{regexp}. If @var{regexp} is not
9935 given, list them all. The output includes expressions which you can
9936 copy into a @value{GDBN} debugging this one to examine a particular
9937 structure in more detail. For example:
9940 (@value{GDBP}) maint info psymtabs dwarf2read
9941 @{ objfile /home/gnu/build/gdb/gdb
9942 ((struct objfile *) 0x82e69d0)
9943 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
9944 ((struct partial_symtab *) 0x8474b10)
9947 text addresses 0x814d3c8 -- 0x8158074
9948 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
9949 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
9953 (@value{GDBP}) maint info symtabs
9957 We see that there is one partial symbol table whose filename contains
9958 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
9959 and we see that @value{GDBN} has not read in any symtabs yet at all.
9960 If we set a breakpoint on a function, that will cause @value{GDBN} to
9961 read the symtab for the compilation unit containing that function:
9964 (@value{GDBP}) break dwarf2_psymtab_to_symtab
9965 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
9967 (@value{GDBP}) maint info symtabs
9968 @{ objfile /home/gnu/build/gdb/gdb
9969 ((struct objfile *) 0x82e69d0)
9970 @{ symtab /home/gnu/src/gdb/dwarf2read.c
9971 ((struct symtab *) 0x86c1f38)
9974 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
9984 @chapter Altering Execution
9986 Once you think you have found an error in your program, you might want to
9987 find out for certain whether correcting the apparent error would lead to
9988 correct results in the rest of the run. You can find the answer by
9989 experiment, using the @value{GDBN} features for altering execution of the
9992 For example, you can store new values into variables or memory
9993 locations, give your program a signal, restart it at a different
9994 address, or even return prematurely from a function.
9997 * Assignment:: Assignment to variables
9998 * Jumping:: Continuing at a different address
9999 * Signaling:: Giving your program a signal
10000 * Returning:: Returning from a function
10001 * Calling:: Calling your program's functions
10002 * Patching:: Patching your program
10006 @section Assignment to variables
10009 @cindex setting variables
10010 To alter the value of a variable, evaluate an assignment expression.
10011 @xref{Expressions, ,Expressions}. For example,
10018 stores the value 4 into the variable @code{x}, and then prints the
10019 value of the assignment expression (which is 4).
10020 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
10021 information on operators in supported languages.
10023 @kindex set variable
10024 @cindex variables, setting
10025 If you are not interested in seeing the value of the assignment, use the
10026 @code{set} command instead of the @code{print} command. @code{set} is
10027 really the same as @code{print} except that the expression's value is
10028 not printed and is not put in the value history (@pxref{Value History,
10029 ,Value history}). The expression is evaluated only for its effects.
10031 If the beginning of the argument string of the @code{set} command
10032 appears identical to a @code{set} subcommand, use the @code{set
10033 variable} command instead of just @code{set}. This command is identical
10034 to @code{set} except for its lack of subcommands. For example, if your
10035 program has a variable @code{width}, you get an error if you try to set
10036 a new value with just @samp{set width=13}, because @value{GDBN} has the
10037 command @code{set width}:
10040 (@value{GDBP}) whatis width
10042 (@value{GDBP}) p width
10044 (@value{GDBP}) set width=47
10045 Invalid syntax in expression.
10049 The invalid expression, of course, is @samp{=47}. In
10050 order to actually set the program's variable @code{width}, use
10053 (@value{GDBP}) set var width=47
10056 Because the @code{set} command has many subcommands that can conflict
10057 with the names of program variables, it is a good idea to use the
10058 @code{set variable} command instead of just @code{set}. For example, if
10059 your program has a variable @code{g}, you run into problems if you try
10060 to set a new value with just @samp{set g=4}, because @value{GDBN} has
10061 the command @code{set gnutarget}, abbreviated @code{set g}:
10065 (@value{GDBP}) whatis g
10069 (@value{GDBP}) set g=4
10073 The program being debugged has been started already.
10074 Start it from the beginning? (y or n) y
10075 Starting program: /home/smith/cc_progs/a.out
10076 "/home/smith/cc_progs/a.out": can't open to read symbols:
10077 Invalid bfd target.
10078 (@value{GDBP}) show g
10079 The current BFD target is "=4".
10084 The program variable @code{g} did not change, and you silently set the
10085 @code{gnutarget} to an invalid value. In order to set the variable
10089 (@value{GDBP}) set var g=4
10092 @value{GDBN} allows more implicit conversions in assignments than C; you can
10093 freely store an integer value into a pointer variable or vice versa,
10094 and you can convert any structure to any other structure that is the
10095 same length or shorter.
10096 @comment FIXME: how do structs align/pad in these conversions?
10097 @comment /doc@cygnus.com 18dec1990
10099 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
10100 construct to generate a value of specified type at a specified address
10101 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
10102 to memory location @code{0x83040} as an integer (which implies a certain size
10103 and representation in memory), and
10106 set @{int@}0x83040 = 4
10110 stores the value 4 into that memory location.
10113 @section Continuing at a different address
10115 Ordinarily, when you continue your program, you do so at the place where
10116 it stopped, with the @code{continue} command. You can instead continue at
10117 an address of your own choosing, with the following commands:
10121 @item jump @var{linespec}
10122 Resume execution at line @var{linespec}. Execution stops again
10123 immediately if there is a breakpoint there. @xref{List, ,Printing
10124 source lines}, for a description of the different forms of
10125 @var{linespec}. It is common practice to use the @code{tbreak} command
10126 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
10129 The @code{jump} command does not change the current stack frame, or
10130 the stack pointer, or the contents of any memory location or any
10131 register other than the program counter. If line @var{linespec} is in
10132 a different function from the one currently executing, the results may
10133 be bizarre if the two functions expect different patterns of arguments or
10134 of local variables. For this reason, the @code{jump} command requests
10135 confirmation if the specified line is not in the function currently
10136 executing. However, even bizarre results are predictable if you are
10137 well acquainted with the machine-language code of your program.
10139 @item jump *@var{address}
10140 Resume execution at the instruction at address @var{address}.
10143 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
10144 On many systems, you can get much the same effect as the @code{jump}
10145 command by storing a new value into the register @code{$pc}. The
10146 difference is that this does not start your program running; it only
10147 changes the address of where it @emph{will} run when you continue. For
10155 makes the next @code{continue} command or stepping command execute at
10156 address @code{0x485}, rather than at the address where your program stopped.
10157 @xref{Continuing and Stepping, ,Continuing and stepping}.
10159 The most common occasion to use the @code{jump} command is to back
10160 up---perhaps with more breakpoints set---over a portion of a program
10161 that has already executed, in order to examine its execution in more
10166 @section Giving your program a signal
10170 @item signal @var{signal}
10171 Resume execution where your program stopped, but immediately give it the
10172 signal @var{signal}. @var{signal} can be the name or the number of a
10173 signal. For example, on many systems @code{signal 2} and @code{signal
10174 SIGINT} are both ways of sending an interrupt signal.
10176 Alternatively, if @var{signal} is zero, continue execution without
10177 giving a signal. This is useful when your program stopped on account of
10178 a signal and would ordinary see the signal when resumed with the
10179 @code{continue} command; @samp{signal 0} causes it to resume without a
10182 @code{signal} does not repeat when you press @key{RET} a second time
10183 after executing the command.
10187 Invoking the @code{signal} command is not the same as invoking the
10188 @code{kill} utility from the shell. Sending a signal with @code{kill}
10189 causes @value{GDBN} to decide what to do with the signal depending on
10190 the signal handling tables (@pxref{Signals}). The @code{signal} command
10191 passes the signal directly to your program.
10195 @section Returning from a function
10198 @cindex returning from a function
10201 @itemx return @var{expression}
10202 You can cancel execution of a function call with the @code{return}
10203 command. If you give an
10204 @var{expression} argument, its value is used as the function's return
10208 When you use @code{return}, @value{GDBN} discards the selected stack frame
10209 (and all frames within it). You can think of this as making the
10210 discarded frame return prematurely. If you wish to specify a value to
10211 be returned, give that value as the argument to @code{return}.
10213 This pops the selected stack frame (@pxref{Selection, ,Selecting a
10214 frame}), and any other frames inside of it, leaving its caller as the
10215 innermost remaining frame. That frame becomes selected. The
10216 specified value is stored in the registers used for returning values
10219 The @code{return} command does not resume execution; it leaves the
10220 program stopped in the state that would exist if the function had just
10221 returned. In contrast, the @code{finish} command (@pxref{Continuing
10222 and Stepping, ,Continuing and stepping}) resumes execution until the
10223 selected stack frame returns naturally.
10226 @section Calling program functions
10229 @cindex calling functions
10230 @cindex inferior functions, calling
10231 @item print @var{expr}
10232 Evaluate the expression @var{expr} and displaying the resuling value.
10233 @var{expr} may include calls to functions in the program being
10237 @item call @var{expr}
10238 Evaluate the expression @var{expr} without displaying @code{void}
10241 You can use this variant of the @code{print} command if you want to
10242 execute a function from your program that does not return anything
10243 (a.k.a.@: @dfn{a void function}), but without cluttering the output
10244 with @code{void} returned values that @value{GDBN} will otherwise
10245 print. If the result is not void, it is printed and saved in the
10249 @cindex weak alias functions
10250 Sometimes, a function you wish to call is actually a @dfn{weak alias}
10251 for another function. In such case, @value{GDBN} might not pick up
10252 the type information, including the types of the function arguments,
10253 which causes @value{GDBN} to call the inferior function incorrectly.
10254 As a result, the called function will function erroneously and may
10255 even crash. A solution to that is to use the name of the aliased
10259 @section Patching programs
10261 @cindex patching binaries
10262 @cindex writing into executables
10263 @cindex writing into corefiles
10265 By default, @value{GDBN} opens the file containing your program's
10266 executable code (or the corefile) read-only. This prevents accidental
10267 alterations to machine code; but it also prevents you from intentionally
10268 patching your program's binary.
10270 If you'd like to be able to patch the binary, you can specify that
10271 explicitly with the @code{set write} command. For example, you might
10272 want to turn on internal debugging flags, or even to make emergency
10278 @itemx set write off
10279 If you specify @samp{set write on}, @value{GDBN} opens executable and
10280 core files for both reading and writing; if you specify @samp{set write
10281 off} (the default), @value{GDBN} opens them read-only.
10283 If you have already loaded a file, you must load it again (using the
10284 @code{exec-file} or @code{core-file} command) after changing @code{set
10285 write}, for your new setting to take effect.
10289 Display whether executable files and core files are opened for writing
10290 as well as reading.
10294 @chapter @value{GDBN} Files
10296 @value{GDBN} needs to know the file name of the program to be debugged,
10297 both in order to read its symbol table and in order to start your
10298 program. To debug a core dump of a previous run, you must also tell
10299 @value{GDBN} the name of the core dump file.
10302 * Files:: Commands to specify files
10303 * Separate Debug Files:: Debugging information in separate files
10304 * Symbol Errors:: Errors reading symbol files
10308 @section Commands to specify files
10310 @cindex symbol table
10311 @cindex core dump file
10313 You may want to specify executable and core dump file names. The usual
10314 way to do this is at start-up time, using the arguments to
10315 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
10316 Out of @value{GDBN}}).
10318 Occasionally it is necessary to change to a different file during a
10319 @value{GDBN} session. Or you may run @value{GDBN} and forget to specify
10320 a file you want to use. In these situations the @value{GDBN} commands
10321 to specify new files are useful.
10324 @cindex executable file
10326 @item file @var{filename}
10327 Use @var{filename} as the program to be debugged. It is read for its
10328 symbols and for the contents of pure memory. It is also the program
10329 executed when you use the @code{run} command. If you do not specify a
10330 directory and the file is not found in the @value{GDBN} working directory,
10331 @value{GDBN} uses the environment variable @code{PATH} as a list of
10332 directories to search, just as the shell does when looking for a program
10333 to run. You can change the value of this variable, for both @value{GDBN}
10334 and your program, using the @code{path} command.
10336 On systems with memory-mapped files, an auxiliary file named
10337 @file{@var{filename}.syms} may hold symbol table information for
10338 @var{filename}. If so, @value{GDBN} maps in the symbol table from
10339 @file{@var{filename}.syms}, starting up more quickly. See the
10340 descriptions of the file options @samp{-mapped} and @samp{-readnow}
10341 (available on the command line, see @ref{File Options, , -readnow},
10342 and with the commands @code{file}, @code{symbol-file}, or
10343 @code{add-symbol-file}, described below), for more information.
10346 @code{file} with no argument makes @value{GDBN} discard any information it
10347 has on both executable file and the symbol table.
10350 @item exec-file @r{[} @var{filename} @r{]}
10351 Specify that the program to be run (but not the symbol table) is found
10352 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
10353 if necessary to locate your program. Omitting @var{filename} means to
10354 discard information on the executable file.
10356 @kindex symbol-file
10357 @item symbol-file @r{[} @var{filename} @r{]}
10358 Read symbol table information from file @var{filename}. @code{PATH} is
10359 searched when necessary. Use the @code{file} command to get both symbol
10360 table and program to run from the same file.
10362 @code{symbol-file} with no argument clears out @value{GDBN} information on your
10363 program's symbol table.
10365 The @code{symbol-file} command causes @value{GDBN} to forget the contents
10366 of its convenience variables, the value history, and all breakpoints and
10367 auto-display expressions. This is because they may contain pointers to
10368 the internal data recording symbols and data types, which are part of
10369 the old symbol table data being discarded inside @value{GDBN}.
10371 @code{symbol-file} does not repeat if you press @key{RET} again after
10374 When @value{GDBN} is configured for a particular environment, it
10375 understands debugging information in whatever format is the standard
10376 generated for that environment; you may use either a @sc{gnu} compiler, or
10377 other compilers that adhere to the local conventions.
10378 Best results are usually obtained from @sc{gnu} compilers; for example,
10379 using @code{@value{GCC}} you can generate debugging information for
10382 For most kinds of object files, with the exception of old SVR3 systems
10383 using COFF, the @code{symbol-file} command does not normally read the
10384 symbol table in full right away. Instead, it scans the symbol table
10385 quickly to find which source files and which symbols are present. The
10386 details are read later, one source file at a time, as they are needed.
10388 The purpose of this two-stage reading strategy is to make @value{GDBN}
10389 start up faster. For the most part, it is invisible except for
10390 occasional pauses while the symbol table details for a particular source
10391 file are being read. (The @code{set verbose} command can turn these
10392 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
10393 warnings and messages}.)
10395 We have not implemented the two-stage strategy for COFF yet. When the
10396 symbol table is stored in COFF format, @code{symbol-file} reads the
10397 symbol table data in full right away. Note that ``stabs-in-COFF''
10398 still does the two-stage strategy, since the debug info is actually
10402 @cindex reading symbols immediately
10403 @cindex symbols, reading immediately
10405 @cindex memory-mapped symbol file
10406 @cindex saving symbol table
10407 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10408 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10409 You can override the @value{GDBN} two-stage strategy for reading symbol
10410 tables by using the @samp{-readnow} option with any of the commands that
10411 load symbol table information, if you want to be sure @value{GDBN} has the
10412 entire symbol table available.
10414 If memory-mapped files are available on your system through the
10415 @code{mmap} system call, you can use another option, @samp{-mapped}, to
10416 cause @value{GDBN} to write the symbols for your program into a reusable
10417 file. Future @value{GDBN} debugging sessions map in symbol information
10418 from this auxiliary symbol file (if the program has not changed), rather
10419 than spending time reading the symbol table from the executable
10420 program. Using the @samp{-mapped} option has the same effect as
10421 starting @value{GDBN} with the @samp{-mapped} command-line option.
10423 You can use both options together, to make sure the auxiliary symbol
10424 file has all the symbol information for your program.
10426 The auxiliary symbol file for a program called @var{myprog} is called
10427 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
10428 than the corresponding executable), @value{GDBN} always attempts to use
10429 it when you debug @var{myprog}; no special options or commands are
10432 The @file{.syms} file is specific to the host machine where you run
10433 @value{GDBN}. It holds an exact image of the internal @value{GDBN}
10434 symbol table. It cannot be shared across multiple host platforms.
10436 @c FIXME: for now no mention of directories, since this seems to be in
10437 @c flux. 13mar1992 status is that in theory GDB would look either in
10438 @c current dir or in same dir as myprog; but issues like competing
10439 @c GDB's, or clutter in system dirs, mean that in practice right now
10440 @c only current dir is used. FFish says maybe a special GDB hierarchy
10441 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
10445 @item core-file @r{[}@var{filename}@r{]}
10447 Specify the whereabouts of a core dump file to be used as the ``contents
10448 of memory''. Traditionally, core files contain only some parts of the
10449 address space of the process that generated them; @value{GDBN} can access the
10450 executable file itself for other parts.
10452 @code{core-file} with no argument specifies that no core file is
10455 Note that the core file is ignored when your program is actually running
10456 under @value{GDBN}. So, if you have been running your program and you
10457 wish to debug a core file instead, you must kill the subprocess in which
10458 the program is running. To do this, use the @code{kill} command
10459 (@pxref{Kill Process, ,Killing the child process}).
10461 @kindex add-symbol-file
10462 @cindex dynamic linking
10463 @item add-symbol-file @var{filename} @var{address}
10464 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10465 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
10466 The @code{add-symbol-file} command reads additional symbol table
10467 information from the file @var{filename}. You would use this command
10468 when @var{filename} has been dynamically loaded (by some other means)
10469 into the program that is running. @var{address} should be the memory
10470 address at which the file has been loaded; @value{GDBN} cannot figure
10471 this out for itself. You can additionally specify an arbitrary number
10472 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
10473 section name and base address for that section. You can specify any
10474 @var{address} as an expression.
10476 The symbol table of the file @var{filename} is added to the symbol table
10477 originally read with the @code{symbol-file} command. You can use the
10478 @code{add-symbol-file} command any number of times; the new symbol data
10479 thus read keeps adding to the old. To discard all old symbol data
10480 instead, use the @code{symbol-file} command without any arguments.
10482 @cindex relocatable object files, reading symbols from
10483 @cindex object files, relocatable, reading symbols from
10484 @cindex reading symbols from relocatable object files
10485 @cindex symbols, reading from relocatable object files
10486 @cindex @file{.o} files, reading symbols from
10487 Although @var{filename} is typically a shared library file, an
10488 executable file, or some other object file which has been fully
10489 relocated for loading into a process, you can also load symbolic
10490 information from relocatable @file{.o} files, as long as:
10494 the file's symbolic information refers only to linker symbols defined in
10495 that file, not to symbols defined by other object files,
10497 every section the file's symbolic information refers to has actually
10498 been loaded into the inferior, as it appears in the file, and
10500 you can determine the address at which every section was loaded, and
10501 provide these to the @code{add-symbol-file} command.
10505 Some embedded operating systems, like Sun Chorus and VxWorks, can load
10506 relocatable files into an already running program; such systems
10507 typically make the requirements above easy to meet. However, it's
10508 important to recognize that many native systems use complex link
10509 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
10510 assembly, for example) that make the requirements difficult to meet. In
10511 general, one cannot assume that using @code{add-symbol-file} to read a
10512 relocatable object file's symbolic information will have the same effect
10513 as linking the relocatable object file into the program in the normal
10516 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
10518 You can use the @samp{-mapped} and @samp{-readnow} options just as with
10519 the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
10520 table information for @var{filename}.
10522 @kindex add-shared-symbol-files
10524 @item add-shared-symbol-files @var{library-file}
10525 @itemx assf @var{library-file}
10526 The @code{add-shared-symbol-files} command can currently be used only
10527 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
10528 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
10529 @value{GDBN} automatically looks for shared libraries, however if
10530 @value{GDBN} does not find yours, you can invoke
10531 @code{add-shared-symbol-files}. It takes one argument: the shared
10532 library's file name. @code{assf} is a shorthand alias for
10533 @code{add-shared-symbol-files}.
10536 @item section @var{section} @var{addr}
10537 The @code{section} command changes the base address of the named
10538 @var{section} of the exec file to @var{addr}. This can be used if the
10539 exec file does not contain section addresses, (such as in the
10540 @code{a.out} format), or when the addresses specified in the file
10541 itself are wrong. Each section must be changed separately. The
10542 @code{info files} command, described below, lists all the sections and
10546 @kindex info target
10549 @code{info files} and @code{info target} are synonymous; both print the
10550 current target (@pxref{Targets, ,Specifying a Debugging Target}),
10551 including the names of the executable and core dump files currently in
10552 use by @value{GDBN}, and the files from which symbols were loaded. The
10553 command @code{help target} lists all possible targets rather than
10556 @kindex maint info sections
10557 @item maint info sections
10558 Another command that can give you extra information about program sections
10559 is @code{maint info sections}. In addition to the section information
10560 displayed by @code{info files}, this command displays the flags and file
10561 offset of each section in the executable and core dump files. In addition,
10562 @code{maint info sections} provides the following command options (which
10563 may be arbitrarily combined):
10567 Display sections for all loaded object files, including shared libraries.
10568 @item @var{sections}
10569 Display info only for named @var{sections}.
10570 @item @var{section-flags}
10571 Display info only for sections for which @var{section-flags} are true.
10572 The section flags that @value{GDBN} currently knows about are:
10575 Section will have space allocated in the process when loaded.
10576 Set for all sections except those containing debug information.
10578 Section will be loaded from the file into the child process memory.
10579 Set for pre-initialized code and data, clear for @code{.bss} sections.
10581 Section needs to be relocated before loading.
10583 Section cannot be modified by the child process.
10585 Section contains executable code only.
10587 Section contains data only (no executable code).
10589 Section will reside in ROM.
10591 Section contains data for constructor/destructor lists.
10593 Section is not empty.
10595 An instruction to the linker to not output the section.
10596 @item COFF_SHARED_LIBRARY
10597 A notification to the linker that the section contains
10598 COFF shared library information.
10600 Section contains common symbols.
10603 @kindex set trust-readonly-sections
10604 @item set trust-readonly-sections on
10605 Tell @value{GDBN} that readonly sections in your object file
10606 really are read-only (i.e.@: that their contents will not change).
10607 In that case, @value{GDBN} can fetch values from these sections
10608 out of the object file, rather than from the target program.
10609 For some targets (notably embedded ones), this can be a significant
10610 enhancement to debugging performance.
10612 The default is off.
10614 @item set trust-readonly-sections off
10615 Tell @value{GDBN} not to trust readonly sections. This means that
10616 the contents of the section might change while the program is running,
10617 and must therefore be fetched from the target when needed.
10620 All file-specifying commands allow both absolute and relative file names
10621 as arguments. @value{GDBN} always converts the file name to an absolute file
10622 name and remembers it that way.
10624 @cindex shared libraries
10625 @value{GDBN} supports GNU/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix
10626 5, and IBM RS/6000 shared libraries.
10628 @value{GDBN} automatically loads symbol definitions from shared libraries
10629 when you use the @code{run} command, or when you examine a core file.
10630 (Before you issue the @code{run} command, @value{GDBN} does not understand
10631 references to a function in a shared library, however---unless you are
10632 debugging a core file).
10634 On HP-UX, if the program loads a library explicitly, @value{GDBN}
10635 automatically loads the symbols at the time of the @code{shl_load} call.
10637 @c FIXME: some @value{GDBN} release may permit some refs to undef
10638 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
10639 @c FIXME...lib; check this from time to time when updating manual
10641 There are times, however, when you may wish to not automatically load
10642 symbol definitions from shared libraries, such as when they are
10643 particularly large or there are many of them.
10645 To control the automatic loading of shared library symbols, use the
10649 @kindex set auto-solib-add
10650 @item set auto-solib-add @var{mode}
10651 If @var{mode} is @code{on}, symbols from all shared object libraries
10652 will be loaded automatically when the inferior begins execution, you
10653 attach to an independently started inferior, or when the dynamic linker
10654 informs @value{GDBN} that a new library has been loaded. If @var{mode}
10655 is @code{off}, symbols must be loaded manually, using the
10656 @code{sharedlibrary} command. The default value is @code{on}.
10658 @cindex memory used for symbol tables
10659 If your program uses lots of shared libraries with debug info that
10660 takes large amounts of memory, you can decrease the @value{GDBN}
10661 memory footprint by preventing it from automatically loading the
10662 symbols from shared libraries. To that end, type @kbd{set
10663 auto-solib-add off} before running the inferior, then load each
10664 library whose debug symbols you do need with @kbd{sharedlibrary
10665 @var{regexp}}, where @var{regexp} is a regular expresion that matches
10666 the libraries whose symbols you want to be loaded.
10668 @kindex show auto-solib-add
10669 @item show auto-solib-add
10670 Display the current autoloading mode.
10673 To explicitly load shared library symbols, use the @code{sharedlibrary}
10677 @kindex info sharedlibrary
10680 @itemx info sharedlibrary
10681 Print the names of the shared libraries which are currently loaded.
10683 @kindex sharedlibrary
10685 @item sharedlibrary @var{regex}
10686 @itemx share @var{regex}
10687 Load shared object library symbols for files matching a
10688 Unix regular expression.
10689 As with files loaded automatically, it only loads shared libraries
10690 required by your program for a core file or after typing @code{run}. If
10691 @var{regex} is omitted all shared libraries required by your program are
10695 On some systems, such as HP-UX systems, @value{GDBN} supports
10696 autoloading shared library symbols until a limiting threshold size is
10697 reached. This provides the benefit of allowing autoloading to remain on
10698 by default, but avoids autoloading excessively large shared libraries,
10699 up to a threshold that is initially set, but which you can modify if you
10702 Beyond that threshold, symbols from shared libraries must be explicitly
10703 loaded. To load these symbols, use the command @code{sharedlibrary
10704 @var{filename}}. The base address of the shared library is determined
10705 automatically by @value{GDBN} and need not be specified.
10707 To display or set the threshold, use the commands:
10710 @kindex set auto-solib-limit
10711 @item set auto-solib-limit @var{threshold}
10712 Set the autoloading size threshold, in an integral number of megabytes.
10713 If @var{threshold} is nonzero and shared library autoloading is enabled,
10714 symbols from all shared object libraries will be loaded until the total
10715 size of the loaded shared library symbols exceeds this threshold.
10716 Otherwise, symbols must be loaded manually, using the
10717 @code{sharedlibrary} command. The default threshold is 100 (i.e.@: 100
10720 @kindex show auto-solib-limit
10721 @item show auto-solib-limit
10722 Display the current autoloading size threshold, in megabytes.
10725 Shared libraries are also supported in many cross or remote debugging
10726 configurations. A copy of the target's libraries need to be present on the
10727 host system; they need to be the same as the target libraries, although the
10728 copies on the target can be stripped as long as the copies on the host are
10731 You need to tell @value{GDBN} where the target libraries are, so that it can
10732 load the correct copies---otherwise, it may try to load the host's libraries.
10733 @value{GDBN} has two variables to specify the search directories for target
10737 @kindex set solib-absolute-prefix
10738 @item set solib-absolute-prefix @var{path}
10739 If this variable is set, @var{path} will be used as a prefix for any
10740 absolute shared library paths; many runtime loaders store the absolute
10741 paths to the shared library in the target program's memory. If you use
10742 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
10743 out in the same way that they are on the target, with e.g.@: a
10744 @file{/usr/lib} hierarchy under @var{path}.
10746 You can set the default value of @samp{solib-absolute-prefix} by using the
10747 configure-time @samp{--with-sysroot} option.
10749 @kindex show solib-absolute-prefix
10750 @item show solib-absolute-prefix
10751 Display the current shared library prefix.
10753 @kindex set solib-search-path
10754 @item set solib-search-path @var{path}
10755 If this variable is set, @var{path} is a colon-separated list of directories
10756 to search for shared libraries. @samp{solib-search-path} is used after
10757 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
10758 the library is relative instead of absolute. If you want to use
10759 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
10760 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
10761 @value{GDBN} from finding your host's libraries.
10763 @kindex show solib-search-path
10764 @item show solib-search-path
10765 Display the current shared library search path.
10769 @node Separate Debug Files
10770 @section Debugging Information in Separate Files
10771 @cindex separate debugging information files
10772 @cindex debugging information in separate files
10773 @cindex @file{.debug} subdirectories
10774 @cindex debugging information directory, global
10775 @cindex global debugging information directory
10777 @value{GDBN} allows you to put a program's debugging information in a
10778 file separate from the executable itself, in a way that allows
10779 @value{GDBN} to find and load the debugging information automatically.
10780 Since debugging information can be very large --- sometimes larger
10781 than the executable code itself --- some systems distribute debugging
10782 information for their executables in separate files, which users can
10783 install only when they need to debug a problem.
10785 If an executable's debugging information has been extracted to a
10786 separate file, the executable should contain a @dfn{debug link} giving
10787 the name of the debugging information file (with no directory
10788 components), and a checksum of its contents. (The exact form of a
10789 debug link is described below.) If the full name of the directory
10790 containing the executable is @var{execdir}, and the executable has a
10791 debug link that specifies the name @var{debugfile}, then @value{GDBN}
10792 will automatically search for the debugging information file in three
10797 the directory containing the executable file (that is, it will look
10798 for a file named @file{@var{execdir}/@var{debugfile}},
10800 a subdirectory of that directory named @file{.debug} (that is, the
10801 file @file{@var{execdir}/.debug/@var{debugfile}}, and
10803 a subdirectory of the global debug file directory that includes the
10804 executable's full path, and the name from the link (that is, the file
10805 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
10806 @var{globaldebugdir} is the global debug file directory, and
10807 @var{execdir} has been turned into a relative path).
10810 @value{GDBN} checks under each of these names for a debugging
10811 information file whose checksum matches that given in the link, and
10812 reads the debugging information from the first one it finds.
10814 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
10815 which has a link containing the name @file{ls.debug}, and the global
10816 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
10817 for debug information in @file{/usr/bin/ls.debug},
10818 @file{/usr/bin/.debug/ls.debug}, and
10819 @file{/usr/lib/debug/usr/bin/ls.debug}.
10821 You can set the global debugging info directory's name, and view the
10822 name @value{GDBN} is currently using.
10826 @kindex set debug-file-directory
10827 @item set debug-file-directory @var{directory}
10828 Set the directory which @value{GDBN} searches for separate debugging
10829 information files to @var{directory}.
10831 @kindex show debug-file-directory
10832 @item show debug-file-directory
10833 Show the directory @value{GDBN} searches for separate debugging
10838 @cindex @code{.gnu_debuglink} sections
10839 @cindex debug links
10840 A debug link is a special section of the executable file named
10841 @code{.gnu_debuglink}. The section must contain:
10845 A filename, with any leading directory components removed, followed by
10848 zero to three bytes of padding, as needed to reach the next four-byte
10849 boundary within the section, and
10851 a four-byte CRC checksum, stored in the same endianness used for the
10852 executable file itself. The checksum is computed on the debugging
10853 information file's full contents by the function given below, passing
10854 zero as the @var{crc} argument.
10857 Any executable file format can carry a debug link, as long as it can
10858 contain a section named @code{.gnu_debuglink} with the contents
10861 The debugging information file itself should be an ordinary
10862 executable, containing a full set of linker symbols, sections, and
10863 debugging information. The sections of the debugging information file
10864 should have the same names, addresses and sizes as the original file,
10865 but they need not contain any data --- much like a @code{.bss} section
10866 in an ordinary executable.
10868 As of December 2002, there is no standard GNU utility to produce
10869 separated executable / debugging information file pairs. Ulrich
10870 Drepper's @file{elfutils} package, starting with version 0.53,
10871 contains a version of the @code{strip} command such that the command
10872 @kbd{strip foo -f foo.debug} removes the debugging information from
10873 the executable file @file{foo}, places it in the file
10874 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
10876 Since there are many different ways to compute CRC's (different
10877 polynomials, reversals, byte ordering, etc.), the simplest way to
10878 describe the CRC used in @code{.gnu_debuglink} sections is to give the
10879 complete code for a function that computes it:
10881 @kindex gnu_debuglink_crc32
10884 gnu_debuglink_crc32 (unsigned long crc,
10885 unsigned char *buf, size_t len)
10887 static const unsigned long crc32_table[256] =
10889 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
10890 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
10891 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
10892 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
10893 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
10894 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
10895 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
10896 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
10897 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
10898 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
10899 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
10900 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
10901 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
10902 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
10903 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
10904 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
10905 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
10906 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
10907 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
10908 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
10909 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
10910 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
10911 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
10912 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
10913 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
10914 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
10915 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
10916 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
10917 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
10918 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
10919 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
10920 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
10921 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
10922 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
10923 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
10924 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
10925 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
10926 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
10927 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
10928 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
10929 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
10930 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
10931 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
10932 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
10933 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
10934 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
10935 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
10936 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
10937 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
10938 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
10939 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
10942 unsigned char *end;
10944 crc = ~crc & 0xffffffff;
10945 for (end = buf + len; buf < end; ++buf)
10946 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
10947 return ~crc & 0xffffffff;
10952 @node Symbol Errors
10953 @section Errors reading symbol files
10955 While reading a symbol file, @value{GDBN} occasionally encounters problems,
10956 such as symbol types it does not recognize, or known bugs in compiler
10957 output. By default, @value{GDBN} does not notify you of such problems, since
10958 they are relatively common and primarily of interest to people
10959 debugging compilers. If you are interested in seeing information
10960 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
10961 only one message about each such type of problem, no matter how many
10962 times the problem occurs; or you can ask @value{GDBN} to print more messages,
10963 to see how many times the problems occur, with the @code{set
10964 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
10967 The messages currently printed, and their meanings, include:
10970 @item inner block not inside outer block in @var{symbol}
10972 The symbol information shows where symbol scopes begin and end
10973 (such as at the start of a function or a block of statements). This
10974 error indicates that an inner scope block is not fully contained
10975 in its outer scope blocks.
10977 @value{GDBN} circumvents the problem by treating the inner block as if it had
10978 the same scope as the outer block. In the error message, @var{symbol}
10979 may be shown as ``@code{(don't know)}'' if the outer block is not a
10982 @item block at @var{address} out of order
10984 The symbol information for symbol scope blocks should occur in
10985 order of increasing addresses. This error indicates that it does not
10988 @value{GDBN} does not circumvent this problem, and has trouble
10989 locating symbols in the source file whose symbols it is reading. (You
10990 can often determine what source file is affected by specifying
10991 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
10994 @item bad block start address patched
10996 The symbol information for a symbol scope block has a start address
10997 smaller than the address of the preceding source line. This is known
10998 to occur in the SunOS 4.1.1 (and earlier) C compiler.
11000 @value{GDBN} circumvents the problem by treating the symbol scope block as
11001 starting on the previous source line.
11003 @item bad string table offset in symbol @var{n}
11006 Symbol number @var{n} contains a pointer into the string table which is
11007 larger than the size of the string table.
11009 @value{GDBN} circumvents the problem by considering the symbol to have the
11010 name @code{foo}, which may cause other problems if many symbols end up
11013 @item unknown symbol type @code{0x@var{nn}}
11015 The symbol information contains new data types that @value{GDBN} does
11016 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
11017 uncomprehended information, in hexadecimal.
11019 @value{GDBN} circumvents the error by ignoring this symbol information.
11020 This usually allows you to debug your program, though certain symbols
11021 are not accessible. If you encounter such a problem and feel like
11022 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
11023 on @code{complain}, then go up to the function @code{read_dbx_symtab}
11024 and examine @code{*bufp} to see the symbol.
11026 @item stub type has NULL name
11028 @value{GDBN} could not find the full definition for a struct or class.
11030 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
11031 The symbol information for a C@t{++} member function is missing some
11032 information that recent versions of the compiler should have output for
11035 @item info mismatch between compiler and debugger
11037 @value{GDBN} could not parse a type specification output by the compiler.
11042 @chapter Specifying a Debugging Target
11044 @cindex debugging target
11045 A @dfn{target} is the execution environment occupied by your program.
11047 Often, @value{GDBN} runs in the same host environment as your program;
11048 in that case, the debugging target is specified as a side effect when
11049 you use the @code{file} or @code{core} commands. When you need more
11050 flexibility---for example, running @value{GDBN} on a physically separate
11051 host, or controlling a standalone system over a serial port or a
11052 realtime system over a TCP/IP connection---you can use the @code{target}
11053 command to specify one of the target types configured for @value{GDBN}
11054 (@pxref{Target Commands, ,Commands for managing targets}).
11056 @cindex target architecture
11057 It is possible to build @value{GDBN} for several different @dfn{target
11058 architectures}. When @value{GDBN} is built like that, you can choose
11059 one of the available architectures with the @kbd{set architecture}
11063 @kindex set architecture
11064 @kindex show architecture
11065 @item set architecture @var{arch}
11066 This command sets the current target architecture to @var{arch}. The
11067 value of @var{arch} can be @code{"auto"}, in addition to one of the
11068 supported architectures.
11070 @item show architecture
11071 Show the current target architecture.
11075 * Active Targets:: Active targets
11076 * Target Commands:: Commands for managing targets
11077 * Byte Order:: Choosing target byte order
11078 * Remote:: Remote debugging
11079 * KOD:: Kernel Object Display
11083 @node Active Targets
11084 @section Active targets
11086 @cindex stacking targets
11087 @cindex active targets
11088 @cindex multiple targets
11090 There are three classes of targets: processes, core files, and
11091 executable files. @value{GDBN} can work concurrently on up to three
11092 active targets, one in each class. This allows you to (for example)
11093 start a process and inspect its activity without abandoning your work on
11096 For example, if you execute @samp{gdb a.out}, then the executable file
11097 @code{a.out} is the only active target. If you designate a core file as
11098 well---presumably from a prior run that crashed and coredumped---then
11099 @value{GDBN} has two active targets and uses them in tandem, looking
11100 first in the corefile target, then in the executable file, to satisfy
11101 requests for memory addresses. (Typically, these two classes of target
11102 are complementary, since core files contain only a program's
11103 read-write memory---variables and so on---plus machine status, while
11104 executable files contain only the program text and initialized data.)
11106 When you type @code{run}, your executable file becomes an active process
11107 target as well. When a process target is active, all @value{GDBN}
11108 commands requesting memory addresses refer to that target; addresses in
11109 an active core file or executable file target are obscured while the
11110 process target is active.
11112 Use the @code{core-file} and @code{exec-file} commands to select a new
11113 core file or executable target (@pxref{Files, ,Commands to specify
11114 files}). To specify as a target a process that is already running, use
11115 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
11118 @node Target Commands
11119 @section Commands for managing targets
11122 @item target @var{type} @var{parameters}
11123 Connects the @value{GDBN} host environment to a target machine or
11124 process. A target is typically a protocol for talking to debugging
11125 facilities. You use the argument @var{type} to specify the type or
11126 protocol of the target machine.
11128 Further @var{parameters} are interpreted by the target protocol, but
11129 typically include things like device names or host names to connect
11130 with, process numbers, and baud rates.
11132 The @code{target} command does not repeat if you press @key{RET} again
11133 after executing the command.
11135 @kindex help target
11137 Displays the names of all targets available. To display targets
11138 currently selected, use either @code{info target} or @code{info files}
11139 (@pxref{Files, ,Commands to specify files}).
11141 @item help target @var{name}
11142 Describe a particular target, including any parameters necessary to
11145 @kindex set gnutarget
11146 @item set gnutarget @var{args}
11147 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
11148 knows whether it is reading an @dfn{executable},
11149 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
11150 with the @code{set gnutarget} command. Unlike most @code{target} commands,
11151 with @code{gnutarget} the @code{target} refers to a program, not a machine.
11154 @emph{Warning:} To specify a file format with @code{set gnutarget},
11155 you must know the actual BFD name.
11159 @xref{Files, , Commands to specify files}.
11161 @kindex show gnutarget
11162 @item show gnutarget
11163 Use the @code{show gnutarget} command to display what file format
11164 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
11165 @value{GDBN} will determine the file format for each file automatically,
11166 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
11169 @cindex common targets
11170 Here are some common targets (available, or not, depending on the GDB
11175 @item target exec @var{program}
11176 @cindex executable file target
11177 An executable file. @samp{target exec @var{program}} is the same as
11178 @samp{exec-file @var{program}}.
11180 @item target core @var{filename}
11181 @cindex core dump file target
11182 A core dump file. @samp{target core @var{filename}} is the same as
11183 @samp{core-file @var{filename}}.
11185 @item target remote @var{dev}
11186 @cindex remote target
11187 Remote serial target in GDB-specific protocol. The argument @var{dev}
11188 specifies what serial device to use for the connection (e.g.
11189 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
11190 supports the @code{load} command. This is only useful if you have
11191 some other way of getting the stub to the target system, and you can put
11192 it somewhere in memory where it won't get clobbered by the download.
11195 @cindex built-in simulator target
11196 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
11204 works; however, you cannot assume that a specific memory map, device
11205 drivers, or even basic I/O is available, although some simulators do
11206 provide these. For info about any processor-specific simulator details,
11207 see the appropriate section in @ref{Embedded Processors, ,Embedded
11212 Some configurations may include these targets as well:
11216 @item target nrom @var{dev}
11217 @cindex NetROM ROM emulator target
11218 NetROM ROM emulator. This target only supports downloading.
11222 Different targets are available on different configurations of @value{GDBN};
11223 your configuration may have more or fewer targets.
11225 Many remote targets require you to download the executable's code
11226 once you've successfully established a connection. You may wish to
11227 control the size of the data chunks used by @value{GDBN} to download
11228 program parts to the remote target.
11231 @kindex set download-write-size
11232 @item set download-write-size @var{size}
11233 Set the write size used when downloading a program. Only used when
11234 downloading a program onto a remote target. Specify zero or a
11235 negative value to disable blocked writes. The actual size of each
11236 transfer is also limited by the size of the target packet and the
11239 @kindex show download-write-size
11240 @item show download-write-size
11241 Show the current value of the write size.
11246 @kindex load @var{filename}
11247 @item load @var{filename}
11248 Depending on what remote debugging facilities are configured into
11249 @value{GDBN}, the @code{load} command may be available. Where it exists, it
11250 is meant to make @var{filename} (an executable) available for debugging
11251 on the remote system---by downloading, or dynamic linking, for example.
11252 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
11253 the @code{add-symbol-file} command.
11255 If your @value{GDBN} does not have a @code{load} command, attempting to
11256 execute it gets the error message ``@code{You can't do that when your
11257 target is @dots{}}''
11259 The file is loaded at whatever address is specified in the executable.
11260 For some object file formats, you can specify the load address when you
11261 link the program; for other formats, like a.out, the object file format
11262 specifies a fixed address.
11263 @c FIXME! This would be a good place for an xref to the GNU linker doc.
11265 @code{load} does not repeat if you press @key{RET} again after using it.
11269 @section Choosing target byte order
11271 @cindex choosing target byte order
11272 @cindex target byte order
11274 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
11275 offer the ability to run either big-endian or little-endian byte
11276 orders. Usually the executable or symbol will include a bit to
11277 designate the endian-ness, and you will not need to worry about
11278 which to use. However, you may still find it useful to adjust
11279 @value{GDBN}'s idea of processor endian-ness manually.
11283 @item set endian big
11284 Instruct @value{GDBN} to assume the target is big-endian.
11286 @item set endian little
11287 Instruct @value{GDBN} to assume the target is little-endian.
11289 @item set endian auto
11290 Instruct @value{GDBN} to use the byte order associated with the
11294 Display @value{GDBN}'s current idea of the target byte order.
11298 Note that these commands merely adjust interpretation of symbolic
11299 data on the host, and that they have absolutely no effect on the
11303 @section Remote debugging
11304 @cindex remote debugging
11306 If you are trying to debug a program running on a machine that cannot run
11307 @value{GDBN} in the usual way, it is often useful to use remote debugging.
11308 For example, you might use remote debugging on an operating system kernel,
11309 or on a small system which does not have a general purpose operating system
11310 powerful enough to run a full-featured debugger.
11312 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
11313 to make this work with particular debugging targets. In addition,
11314 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
11315 but not specific to any particular target system) which you can use if you
11316 write the remote stubs---the code that runs on the remote system to
11317 communicate with @value{GDBN}.
11319 Other remote targets may be available in your
11320 configuration of @value{GDBN}; use @code{help target} to list them.
11323 @section Kernel Object Display
11324 @cindex kernel object display
11327 Some targets support kernel object display. Using this facility,
11328 @value{GDBN} communicates specially with the underlying operating system
11329 and can display information about operating system-level objects such as
11330 mutexes and other synchronization objects. Exactly which objects can be
11331 displayed is determined on a per-OS basis.
11334 Use the @code{set os} command to set the operating system. This tells
11335 @value{GDBN} which kernel object display module to initialize:
11338 (@value{GDBP}) set os cisco
11342 The associated command @code{show os} displays the operating system
11343 set with the @code{set os} command; if no operating system has been
11344 set, @code{show os} will display an empty string @samp{""}.
11346 If @code{set os} succeeds, @value{GDBN} will display some information
11347 about the operating system, and will create a new @code{info} command
11348 which can be used to query the target. The @code{info} command is named
11349 after the operating system:
11353 (@value{GDBP}) info cisco
11354 List of Cisco Kernel Objects
11356 any Any and all objects
11359 Further subcommands can be used to query about particular objects known
11362 There is currently no way to determine whether a given operating
11363 system is supported other than to try setting it with @kbd{set os
11364 @var{name}}, where @var{name} is the name of the operating system you
11368 @node Remote Debugging
11369 @chapter Debugging remote programs
11372 * Connecting:: Connecting to a remote target
11373 * Server:: Using the gdbserver program
11374 * NetWare:: Using the gdbserve.nlm program
11375 * Remote configuration:: Remote configuration
11376 * remote stub:: Implementing a remote stub
11380 @section Connecting to a remote target
11382 On the @value{GDBN} host machine, you will need an unstripped copy of
11383 your program, since @value{GDBN} needs symobl and debugging information.
11384 Start up @value{GDBN} as usual, using the name of the local copy of your
11385 program as the first argument.
11387 @cindex serial line, @code{target remote}
11388 If you're using a serial line, you may want to give @value{GDBN} the
11389 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
11390 before the @code{target} command.
11392 After that, use @code{target remote} to establish communications with
11393 the target machine. Its argument specifies how to communicate---either
11394 via a devicename attached to a direct serial line, or a TCP or UDP port
11395 (possibly to a terminal server which in turn has a serial line to the
11396 target). For example, to use a serial line connected to the device
11397 named @file{/dev/ttyb}:
11400 target remote /dev/ttyb
11403 @cindex TCP port, @code{target remote}
11404 To use a TCP connection, use an argument of the form
11405 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
11406 For example, to connect to port 2828 on a
11407 terminal server named @code{manyfarms}:
11410 target remote manyfarms:2828
11413 If your remote target is actually running on the same machine as
11414 your debugger session (e.g.@: a simulator of your target running on
11415 the same host), you can omit the hostname. For example, to connect
11416 to port 1234 on your local machine:
11419 target remote :1234
11423 Note that the colon is still required here.
11425 @cindex UDP port, @code{target remote}
11426 To use a UDP connection, use an argument of the form
11427 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
11428 on a terminal server named @code{manyfarms}:
11431 target remote udp:manyfarms:2828
11434 When using a UDP connection for remote debugging, you should keep in mind
11435 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
11436 busy or unreliable networks, which will cause havoc with your debugging
11439 Now you can use all the usual commands to examine and change data and to
11440 step and continue the remote program.
11442 @cindex interrupting remote programs
11443 @cindex remote programs, interrupting
11444 Whenever @value{GDBN} is waiting for the remote program, if you type the
11445 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
11446 program. This may or may not succeed, depending in part on the hardware
11447 and the serial drivers the remote system uses. If you type the
11448 interrupt character once again, @value{GDBN} displays this prompt:
11451 Interrupted while waiting for the program.
11452 Give up (and stop debugging it)? (y or n)
11455 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
11456 (If you decide you want to try again later, you can use @samp{target
11457 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
11458 goes back to waiting.
11461 @kindex detach (remote)
11463 When you have finished debugging the remote program, you can use the
11464 @code{detach} command to release it from @value{GDBN} control.
11465 Detaching from the target normally resumes its execution, but the results
11466 will depend on your particular remote stub. After the @code{detach}
11467 command, @value{GDBN} is free to connect to another target.
11471 The @code{disconnect} command behaves like @code{detach}, except that
11472 the target is generally not resumed. It will wait for @value{GDBN}
11473 (this instance or another one) to connect and continue debugging. After
11474 the @code{disconnect} command, @value{GDBN} is again free to connect to
11477 @cindex send command to remote monitor
11479 @item monitor @var{cmd}
11480 This command allows you to send commands directly to the remote
11485 @section Using the @code{gdbserver} program
11488 @cindex remote connection without stubs
11489 @code{gdbserver} is a control program for Unix-like systems, which
11490 allows you to connect your program with a remote @value{GDBN} via
11491 @code{target remote}---but without linking in the usual debugging stub.
11493 @code{gdbserver} is not a complete replacement for the debugging stubs,
11494 because it requires essentially the same operating-system facilities
11495 that @value{GDBN} itself does. In fact, a system that can run
11496 @code{gdbserver} to connect to a remote @value{GDBN} could also run
11497 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
11498 because it is a much smaller program than @value{GDBN} itself. It is
11499 also easier to port than all of @value{GDBN}, so you may be able to get
11500 started more quickly on a new system by using @code{gdbserver}.
11501 Finally, if you develop code for real-time systems, you may find that
11502 the tradeoffs involved in real-time operation make it more convenient to
11503 do as much development work as possible on another system, for example
11504 by cross-compiling. You can use @code{gdbserver} to make a similar
11505 choice for debugging.
11507 @value{GDBN} and @code{gdbserver} communicate via either a serial line
11508 or a TCP connection, using the standard @value{GDBN} remote serial
11512 @item On the target machine,
11513 you need to have a copy of the program you want to debug.
11514 @code{gdbserver} does not need your program's symbol table, so you can
11515 strip the program if necessary to save space. @value{GDBN} on the host
11516 system does all the symbol handling.
11518 To use the server, you must tell it how to communicate with @value{GDBN};
11519 the name of your program; and the arguments for your program. The usual
11523 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
11526 @var{comm} is either a device name (to use a serial line) or a TCP
11527 hostname and portnumber. For example, to debug Emacs with the argument
11528 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
11532 target> gdbserver /dev/com1 emacs foo.txt
11535 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
11538 To use a TCP connection instead of a serial line:
11541 target> gdbserver host:2345 emacs foo.txt
11544 The only difference from the previous example is the first argument,
11545 specifying that you are communicating with the host @value{GDBN} via
11546 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
11547 expect a TCP connection from machine @samp{host} to local TCP port 2345.
11548 (Currently, the @samp{host} part is ignored.) You can choose any number
11549 you want for the port number as long as it does not conflict with any
11550 TCP ports already in use on the target system (for example, @code{23} is
11551 reserved for @code{telnet}).@footnote{If you choose a port number that
11552 conflicts with another service, @code{gdbserver} prints an error message
11553 and exits.} You must use the same port number with the host @value{GDBN}
11554 @code{target remote} command.
11556 On some targets, @code{gdbserver} can also attach to running programs.
11557 This is accomplished via the @code{--attach} argument. The syntax is:
11560 target> gdbserver @var{comm} --attach @var{pid}
11563 @var{pid} is the process ID of a currently running process. It isn't necessary
11564 to point @code{gdbserver} at a binary for the running process.
11567 @cindex attach to a program by name
11568 You can debug processes by name instead of process ID if your target has the
11569 @code{pidof} utility:
11572 target> gdbserver @var{comm} --attach `pidof @var{PROGRAM}`
11575 In case more than one copy of @var{PROGRAM} is running, or @var{PROGRAM}
11576 has multiple threads, most versions of @code{pidof} support the
11577 @code{-s} option to only return the first process ID.
11579 @item On the host machine,
11580 connect to your target (@pxref{Connecting,,Connecting to a remote target}).
11581 For TCP connections, you must start up @code{gdbserver} prior to using
11582 the @code{target remote} command. Otherwise you may get an error whose
11583 text depends on the host system, but which usually looks something like
11584 @samp{Connection refused}. You don't need to use the @code{load}
11585 command in @value{GDBN} when using gdbserver, since the program is
11586 already on the target.
11591 @section Using the @code{gdbserve.nlm} program
11593 @kindex gdbserve.nlm
11594 @code{gdbserve.nlm} is a control program for NetWare systems, which
11595 allows you to connect your program with a remote @value{GDBN} via
11596 @code{target remote}.
11598 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
11599 using the standard @value{GDBN} remote serial protocol.
11602 @item On the target machine,
11603 you need to have a copy of the program you want to debug.
11604 @code{gdbserve.nlm} does not need your program's symbol table, so you
11605 can strip the program if necessary to save space. @value{GDBN} on the
11606 host system does all the symbol handling.
11608 To use the server, you must tell it how to communicate with
11609 @value{GDBN}; the name of your program; and the arguments for your
11610 program. The syntax is:
11613 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
11614 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
11617 @var{board} and @var{port} specify the serial line; @var{baud} specifies
11618 the baud rate used by the connection. @var{port} and @var{node} default
11619 to 0, @var{baud} defaults to 9600@dmn{bps}.
11621 For example, to debug Emacs with the argument @samp{foo.txt}and
11622 communicate with @value{GDBN} over serial port number 2 or board 1
11623 using a 19200@dmn{bps} connection:
11626 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
11630 On the @value{GDBN} host machine, connect to your target (@pxref{Connecting,,
11631 Connecting to a remote target}).
11635 @node Remote configuration
11636 @section Remote configuration
11638 The following configuration options are available when debugging remote
11642 @kindex set remote hardware-watchpoint-limit
11643 @kindex set remote hardware-breakpoint-limit
11644 @anchor{set remote hardware-watchpoint-limit}
11645 @anchor{set remote hardware-breakpoint-limit}
11646 @item set remote hardware-watchpoint-limit @var{limit}
11647 @itemx set remote hardware-breakpoint-limit @var{limit}
11648 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
11649 watchpoints. A limit of -1, the default, is treated as unlimited.
11653 @section Implementing a remote stub
11655 @cindex debugging stub, example
11656 @cindex remote stub, example
11657 @cindex stub example, remote debugging
11658 The stub files provided with @value{GDBN} implement the target side of the
11659 communication protocol, and the @value{GDBN} side is implemented in the
11660 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
11661 these subroutines to communicate, and ignore the details. (If you're
11662 implementing your own stub file, you can still ignore the details: start
11663 with one of the existing stub files. @file{sparc-stub.c} is the best
11664 organized, and therefore the easiest to read.)
11666 @cindex remote serial debugging, overview
11667 To debug a program running on another machine (the debugging
11668 @dfn{target} machine), you must first arrange for all the usual
11669 prerequisites for the program to run by itself. For example, for a C
11674 A startup routine to set up the C runtime environment; these usually
11675 have a name like @file{crt0}. The startup routine may be supplied by
11676 your hardware supplier, or you may have to write your own.
11679 A C subroutine library to support your program's
11680 subroutine calls, notably managing input and output.
11683 A way of getting your program to the other machine---for example, a
11684 download program. These are often supplied by the hardware
11685 manufacturer, but you may have to write your own from hardware
11689 The next step is to arrange for your program to use a serial port to
11690 communicate with the machine where @value{GDBN} is running (the @dfn{host}
11691 machine). In general terms, the scheme looks like this:
11695 @value{GDBN} already understands how to use this protocol; when everything
11696 else is set up, you can simply use the @samp{target remote} command
11697 (@pxref{Targets,,Specifying a Debugging Target}).
11699 @item On the target,
11700 you must link with your program a few special-purpose subroutines that
11701 implement the @value{GDBN} remote serial protocol. The file containing these
11702 subroutines is called a @dfn{debugging stub}.
11704 On certain remote targets, you can use an auxiliary program
11705 @code{gdbserver} instead of linking a stub into your program.
11706 @xref{Server,,Using the @code{gdbserver} program}, for details.
11709 The debugging stub is specific to the architecture of the remote
11710 machine; for example, use @file{sparc-stub.c} to debug programs on
11713 @cindex remote serial stub list
11714 These working remote stubs are distributed with @value{GDBN}:
11719 @cindex @file{i386-stub.c}
11722 For Intel 386 and compatible architectures.
11725 @cindex @file{m68k-stub.c}
11726 @cindex Motorola 680x0
11728 For Motorola 680x0 architectures.
11731 @cindex @file{sh-stub.c}
11734 For Renesas SH architectures.
11737 @cindex @file{sparc-stub.c}
11739 For @sc{sparc} architectures.
11741 @item sparcl-stub.c
11742 @cindex @file{sparcl-stub.c}
11745 For Fujitsu @sc{sparclite} architectures.
11749 The @file{README} file in the @value{GDBN} distribution may list other
11750 recently added stubs.
11753 * Stub Contents:: What the stub can do for you
11754 * Bootstrapping:: What you must do for the stub
11755 * Debug Session:: Putting it all together
11758 @node Stub Contents
11759 @subsection What the stub can do for you
11761 @cindex remote serial stub
11762 The debugging stub for your architecture supplies these three
11766 @item set_debug_traps
11767 @findex set_debug_traps
11768 @cindex remote serial stub, initialization
11769 This routine arranges for @code{handle_exception} to run when your
11770 program stops. You must call this subroutine explicitly near the
11771 beginning of your program.
11773 @item handle_exception
11774 @findex handle_exception
11775 @cindex remote serial stub, main routine
11776 This is the central workhorse, but your program never calls it
11777 explicitly---the setup code arranges for @code{handle_exception} to
11778 run when a trap is triggered.
11780 @code{handle_exception} takes control when your program stops during
11781 execution (for example, on a breakpoint), and mediates communications
11782 with @value{GDBN} on the host machine. This is where the communications
11783 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
11784 representative on the target machine. It begins by sending summary
11785 information on the state of your program, then continues to execute,
11786 retrieving and transmitting any information @value{GDBN} needs, until you
11787 execute a @value{GDBN} command that makes your program resume; at that point,
11788 @code{handle_exception} returns control to your own code on the target
11792 @cindex @code{breakpoint} subroutine, remote
11793 Use this auxiliary subroutine to make your program contain a
11794 breakpoint. Depending on the particular situation, this may be the only
11795 way for @value{GDBN} to get control. For instance, if your target
11796 machine has some sort of interrupt button, you won't need to call this;
11797 pressing the interrupt button transfers control to
11798 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
11799 simply receiving characters on the serial port may also trigger a trap;
11800 again, in that situation, you don't need to call @code{breakpoint} from
11801 your own program---simply running @samp{target remote} from the host
11802 @value{GDBN} session gets control.
11804 Call @code{breakpoint} if none of these is true, or if you simply want
11805 to make certain your program stops at a predetermined point for the
11806 start of your debugging session.
11809 @node Bootstrapping
11810 @subsection What you must do for the stub
11812 @cindex remote stub, support routines
11813 The debugging stubs that come with @value{GDBN} are set up for a particular
11814 chip architecture, but they have no information about the rest of your
11815 debugging target machine.
11817 First of all you need to tell the stub how to communicate with the
11821 @item int getDebugChar()
11822 @findex getDebugChar
11823 Write this subroutine to read a single character from the serial port.
11824 It may be identical to @code{getchar} for your target system; a
11825 different name is used to allow you to distinguish the two if you wish.
11827 @item void putDebugChar(int)
11828 @findex putDebugChar
11829 Write this subroutine to write a single character to the serial port.
11830 It may be identical to @code{putchar} for your target system; a
11831 different name is used to allow you to distinguish the two if you wish.
11834 @cindex control C, and remote debugging
11835 @cindex interrupting remote targets
11836 If you want @value{GDBN} to be able to stop your program while it is
11837 running, you need to use an interrupt-driven serial driver, and arrange
11838 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
11839 character). That is the character which @value{GDBN} uses to tell the
11840 remote system to stop.
11842 Getting the debugging target to return the proper status to @value{GDBN}
11843 probably requires changes to the standard stub; one quick and dirty way
11844 is to just execute a breakpoint instruction (the ``dirty'' part is that
11845 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
11847 Other routines you need to supply are:
11850 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
11851 @findex exceptionHandler
11852 Write this function to install @var{exception_address} in the exception
11853 handling tables. You need to do this because the stub does not have any
11854 way of knowing what the exception handling tables on your target system
11855 are like (for example, the processor's table might be in @sc{rom},
11856 containing entries which point to a table in @sc{ram}).
11857 @var{exception_number} is the exception number which should be changed;
11858 its meaning is architecture-dependent (for example, different numbers
11859 might represent divide by zero, misaligned access, etc). When this
11860 exception occurs, control should be transferred directly to
11861 @var{exception_address}, and the processor state (stack, registers,
11862 and so on) should be just as it is when a processor exception occurs. So if
11863 you want to use a jump instruction to reach @var{exception_address}, it
11864 should be a simple jump, not a jump to subroutine.
11866 For the 386, @var{exception_address} should be installed as an interrupt
11867 gate so that interrupts are masked while the handler runs. The gate
11868 should be at privilege level 0 (the most privileged level). The
11869 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
11870 help from @code{exceptionHandler}.
11872 @item void flush_i_cache()
11873 @findex flush_i_cache
11874 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
11875 instruction cache, if any, on your target machine. If there is no
11876 instruction cache, this subroutine may be a no-op.
11878 On target machines that have instruction caches, @value{GDBN} requires this
11879 function to make certain that the state of your program is stable.
11883 You must also make sure this library routine is available:
11886 @item void *memset(void *, int, int)
11888 This is the standard library function @code{memset} that sets an area of
11889 memory to a known value. If you have one of the free versions of
11890 @code{libc.a}, @code{memset} can be found there; otherwise, you must
11891 either obtain it from your hardware manufacturer, or write your own.
11894 If you do not use the GNU C compiler, you may need other standard
11895 library subroutines as well; this varies from one stub to another,
11896 but in general the stubs are likely to use any of the common library
11897 subroutines which @code{@value{GCC}} generates as inline code.
11900 @node Debug Session
11901 @subsection Putting it all together
11903 @cindex remote serial debugging summary
11904 In summary, when your program is ready to debug, you must follow these
11909 Make sure you have defined the supporting low-level routines
11910 (@pxref{Bootstrapping,,What you must do for the stub}):
11912 @code{getDebugChar}, @code{putDebugChar},
11913 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
11917 Insert these lines near the top of your program:
11925 For the 680x0 stub only, you need to provide a variable called
11926 @code{exceptionHook}. Normally you just use:
11929 void (*exceptionHook)() = 0;
11933 but if before calling @code{set_debug_traps}, you set it to point to a
11934 function in your program, that function is called when
11935 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
11936 error). The function indicated by @code{exceptionHook} is called with
11937 one parameter: an @code{int} which is the exception number.
11940 Compile and link together: your program, the @value{GDBN} debugging stub for
11941 your target architecture, and the supporting subroutines.
11944 Make sure you have a serial connection between your target machine and
11945 the @value{GDBN} host, and identify the serial port on the host.
11948 @c The "remote" target now provides a `load' command, so we should
11949 @c document that. FIXME.
11950 Download your program to your target machine (or get it there by
11951 whatever means the manufacturer provides), and start it.
11954 Start @value{GDBN} on the host, and connect to the target
11955 (@pxref{Connecting,,Connecting to a remote target}).
11959 @node Configurations
11960 @chapter Configuration-Specific Information
11962 While nearly all @value{GDBN} commands are available for all native and
11963 cross versions of the debugger, there are some exceptions. This chapter
11964 describes things that are only available in certain configurations.
11966 There are three major categories of configurations: native
11967 configurations, where the host and target are the same, embedded
11968 operating system configurations, which are usually the same for several
11969 different processor architectures, and bare embedded processors, which
11970 are quite different from each other.
11975 * Embedded Processors::
11982 This section describes details specific to particular native
11987 * BSD libkvm Interface:: Debugging BSD kernel memory images
11988 * SVR4 Process Information:: SVR4 process information
11989 * DJGPP Native:: Features specific to the DJGPP port
11990 * Cygwin Native:: Features specific to the Cygwin port
11996 On HP-UX systems, if you refer to a function or variable name that
11997 begins with a dollar sign, @value{GDBN} searches for a user or system
11998 name first, before it searches for a convenience variable.
12000 @node BSD libkvm Interface
12001 @subsection BSD libkvm Interface
12004 @cindex kernel memory image
12005 @cindex kernel crash dump
12007 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
12008 interface that provides a uniform interface for accessing kernel virtual
12009 memory images, including live systems and crash dumps. @value{GDBN}
12010 uses this interface to allow you to debug live kernels and kernel crash
12011 dumps on many native BSD configurations. This is implemented as a
12012 special @code{kvm} debugging target. For debugging a live system, load
12013 the currently running kernel into @value{GDBN} and connect to the
12017 (@value{GDBP}) @b{target kvm}
12020 For debugging crash dumps, provide the file name of the crash dump as an
12024 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
12027 Once connected to the @code{kvm} target, the following commands are
12033 Set current context from pcb address.
12036 Set current context from proc address. This command isn't available on
12037 modern FreeBSD systems.
12040 @node SVR4 Process Information
12041 @subsection SVR4 process information
12043 @cindex examine process image
12044 @cindex process info via @file{/proc}
12046 Many versions of SVR4 and compatible systems provide a facility called
12047 @samp{/proc} that can be used to examine the image of a running
12048 process using file-system subroutines. If @value{GDBN} is configured
12049 for an operating system with this facility, the command @code{info
12050 proc} is available to report information about the process running
12051 your program, or about any process running on your system. @code{info
12052 proc} works only on SVR4 systems that include the @code{procfs} code.
12053 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
12054 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
12060 @itemx info proc @var{process-id}
12061 Summarize available information about any running process. If a
12062 process ID is specified by @var{process-id}, display information about
12063 that process; otherwise display information about the program being
12064 debugged. The summary includes the debugged process ID, the command
12065 line used to invoke it, its current working directory, and its
12066 executable file's absolute file name.
12068 On some systems, @var{process-id} can be of the form
12069 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
12070 within a process. If the optional @var{pid} part is missing, it means
12071 a thread from the process being debugged (the leading @samp{/} still
12072 needs to be present, or else @value{GDBN} will interpret the number as
12073 a process ID rather than a thread ID).
12075 @item info proc mappings
12076 @cindex memory address space mappings
12077 Report the memory address space ranges accessible in the program, with
12078 information on whether the process has read, write, or execute access
12079 rights to each range. On @sc{gnu}/Linux systems, each memory range
12080 includes the object file which is mapped to that range, instead of the
12081 memory access rights to that range.
12083 @item info proc stat
12084 @itemx info proc status
12085 @cindex process detailed status information
12086 These subcommands are specific to @sc{gnu}/Linux systems. They show
12087 the process-related information, including the user ID and group ID;
12088 how many threads are there in the process; its virtual memory usage;
12089 the signals that are pending, blocked, and ignored; its TTY; its
12090 consumption of system and user time; its stack size; its @samp{nice}
12091 value; etc. For more information, see the @samp{proc(5)} man page
12092 (type @kbd{man 5 proc} from your shell prompt).
12094 @item info proc all
12095 Show all the information about the process described under all of the
12096 above @code{info proc} subcommands.
12099 @comment These sub-options of 'info proc' were not included when
12100 @comment procfs.c was re-written. Keep their descriptions around
12101 @comment against the day when someone finds the time to put them back in.
12102 @kindex info proc times
12103 @item info proc times
12104 Starting time, user CPU time, and system CPU time for your program and
12107 @kindex info proc id
12109 Report on the process IDs related to your program: its own process ID,
12110 the ID of its parent, the process group ID, and the session ID.
12115 @subsection Features for Debugging @sc{djgpp} Programs
12116 @cindex @sc{djgpp} debugging
12117 @cindex native @sc{djgpp} debugging
12118 @cindex MS-DOS-specific commands
12120 @sc{djgpp} is the port of @sc{gnu} development tools to MS-DOS and
12121 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
12122 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
12123 top of real-mode DOS systems and their emulations.
12125 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
12126 defines a few commands specific to the @sc{djgpp} port. This
12127 subsection describes those commands.
12132 This is a prefix of @sc{djgpp}-specific commands which print
12133 information about the target system and important OS structures.
12136 @cindex MS-DOS system info
12137 @cindex free memory information (MS-DOS)
12138 @item info dos sysinfo
12139 This command displays assorted information about the underlying
12140 platform: the CPU type and features, the OS version and flavor, the
12141 DPMI version, and the available conventional and DPMI memory.
12146 @cindex segment descriptor tables
12147 @cindex descriptor tables display
12149 @itemx info dos ldt
12150 @itemx info dos idt
12151 These 3 commands display entries from, respectively, Global, Local,
12152 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
12153 tables are data structures which store a descriptor for each segment
12154 that is currently in use. The segment's selector is an index into a
12155 descriptor table; the table entry for that index holds the
12156 descriptor's base address and limit, and its attributes and access
12159 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
12160 segment (used for both data and the stack), and a DOS segment (which
12161 allows access to DOS/BIOS data structures and absolute addresses in
12162 conventional memory). However, the DPMI host will usually define
12163 additional segments in order to support the DPMI environment.
12165 @cindex garbled pointers
12166 These commands allow to display entries from the descriptor tables.
12167 Without an argument, all entries from the specified table are
12168 displayed. An argument, which should be an integer expression, means
12169 display a single entry whose index is given by the argument. For
12170 example, here's a convenient way to display information about the
12171 debugged program's data segment:
12174 @exdent @code{(@value{GDBP}) info dos ldt $ds}
12175 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
12179 This comes in handy when you want to see whether a pointer is outside
12180 the data segment's limit (i.e.@: @dfn{garbled}).
12182 @cindex page tables display (MS-DOS)
12184 @itemx info dos pte
12185 These two commands display entries from, respectively, the Page
12186 Directory and the Page Tables. Page Directories and Page Tables are
12187 data structures which control how virtual memory addresses are mapped
12188 into physical addresses. A Page Table includes an entry for every
12189 page of memory that is mapped into the program's address space; there
12190 may be several Page Tables, each one holding up to 4096 entries. A
12191 Page Directory has up to 4096 entries, one each for every Page Table
12192 that is currently in use.
12194 Without an argument, @kbd{info dos pde} displays the entire Page
12195 Directory, and @kbd{info dos pte} displays all the entries in all of
12196 the Page Tables. An argument, an integer expression, given to the
12197 @kbd{info dos pde} command means display only that entry from the Page
12198 Directory table. An argument given to the @kbd{info dos pte} command
12199 means display entries from a single Page Table, the one pointed to by
12200 the specified entry in the Page Directory.
12202 @cindex direct memory access (DMA) on MS-DOS
12203 These commands are useful when your program uses @dfn{DMA} (Direct
12204 Memory Access), which needs physical addresses to program the DMA
12207 These commands are supported only with some DPMI servers.
12209 @cindex physical address from linear address
12210 @item info dos address-pte @var{addr}
12211 This command displays the Page Table entry for a specified linear
12212 address. The argument linear address @var{addr} should already have the
12213 appropriate segment's base address added to it, because this command
12214 accepts addresses which may belong to @emph{any} segment. For
12215 example, here's how to display the Page Table entry for the page where
12216 the variable @code{i} is stored:
12219 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
12220 @exdent @code{Page Table entry for address 0x11a00d30:}
12221 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
12225 This says that @code{i} is stored at offset @code{0xd30} from the page
12226 whose physical base address is @code{0x02698000}, and prints all the
12227 attributes of that page.
12229 Note that you must cast the addresses of variables to a @code{char *},
12230 since otherwise the value of @code{__djgpp_base_address}, the base
12231 address of all variables and functions in a @sc{djgpp} program, will
12232 be added using the rules of C pointer arithmetics: if @code{i} is
12233 declared an @code{int}, @value{GDBN} will add 4 times the value of
12234 @code{__djgpp_base_address} to the address of @code{i}.
12236 Here's another example, it displays the Page Table entry for the
12240 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
12241 @exdent @code{Page Table entry for address 0x29110:}
12242 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
12246 (The @code{+ 3} offset is because the transfer buffer's address is the
12247 3rd member of the @code{_go32_info_block} structure.) The output of
12248 this command clearly shows that addresses in conventional memory are
12249 mapped 1:1, i.e.@: the physical and linear addresses are identical.
12251 This command is supported only with some DPMI servers.
12254 In addition to native debugging, the DJGPP port supports remote
12255 debugging via a serial data link. The following commands are specific
12256 to remote serial debugging in the DJGPP port of @value{GDBN}.
12259 @kindex set com1base
12260 @kindex set com1irq
12261 @kindex set com2base
12262 @kindex set com2irq
12263 @kindex set com3base
12264 @kindex set com3irq
12265 @kindex set com4base
12266 @kindex set com4irq
12267 @item set com1base @var{addr}
12268 This command sets the base I/O port address of the @file{COM1} serial
12271 @item set com1irq @var{irq}
12272 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
12273 for the @file{COM1} serial port.
12275 There are similar commands @samp{set com2base}, @samp{set com3irq},
12276 etc.@: for setting the port address and the @code{IRQ} lines for the
12279 @kindex show com1base
12280 @kindex show com1irq
12281 @kindex show com2base
12282 @kindex show com2irq
12283 @kindex show com3base
12284 @kindex show com3irq
12285 @kindex show com4base
12286 @kindex show com4irq
12287 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
12288 display the current settings of the base address and the @code{IRQ}
12289 lines used by the COM ports.
12293 @node Cygwin Native
12294 @subsection Features for Debugging MS Windows PE executables
12295 @cindex MS Windows debugging
12296 @cindex native Cygwin debugging
12297 @cindex Cygwin-specific commands
12299 @value{GDBN} supports native debugging of MS Windows programs, including
12300 DLLs with and without symbolic debugging information. There are various
12301 additional Cygwin-specific commands, described in this subsection. The
12302 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
12303 that have no debugging symbols.
12309 This is a prefix of MS Windows specific commands which print
12310 information about the target system and important OS structures.
12312 @item info w32 selector
12313 This command displays information returned by
12314 the Win32 API @code{GetThreadSelectorEntry} function.
12315 It takes an optional argument that is evaluated to
12316 a long value to give the information about this given selector.
12317 Without argument, this command displays information
12318 about the the six segment registers.
12322 This is a Cygwin specific alias of info shared.
12324 @kindex dll-symbols
12326 This command loads symbols from a dll similarly to
12327 add-sym command but without the need to specify a base address.
12329 @kindex set new-console
12330 @item set new-console @var{mode}
12331 If @var{mode} is @code{on} the debuggee will
12332 be started in a new console on next start.
12333 If @var{mode} is @code{off}i, the debuggee will
12334 be started in the same console as the debugger.
12336 @kindex show new-console
12337 @item show new-console
12338 Displays whether a new console is used
12339 when the debuggee is started.
12341 @kindex set new-group
12342 @item set new-group @var{mode}
12343 This boolean value controls whether the debuggee should
12344 start a new group or stay in the same group as the debugger.
12345 This affects the way the Windows OS handles
12348 @kindex show new-group
12349 @item show new-group
12350 Displays current value of new-group boolean.
12352 @kindex set debugevents
12353 @item set debugevents
12354 This boolean value adds debug output concerning events seen by the debugger.
12356 @kindex set debugexec
12357 @item set debugexec
12358 This boolean value adds debug output concerning execute events
12359 seen by the debugger.
12361 @kindex set debugexceptions
12362 @item set debugexceptions
12363 This boolean value adds debug ouptut concerning exception events
12364 seen by the debugger.
12366 @kindex set debugmemory
12367 @item set debugmemory
12368 This boolean value adds debug ouptut concerning memory events
12369 seen by the debugger.
12373 This boolean values specifies whether the debuggee is called
12374 via a shell or directly (default value is on).
12378 Displays if the debuggee will be started with a shell.
12383 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
12386 @node Non-debug DLL symbols
12387 @subsubsection Support for DLLs without debugging symbols
12388 @cindex DLLs with no debugging symbols
12389 @cindex Minimal symbols and DLLs
12391 Very often on windows, some of the DLLs that your program relies on do
12392 not include symbolic debugging information (for example,
12393 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
12394 symbols in a DLL, it relies on the minimal amount of symbolic
12395 information contained in the DLL's export table. This subsubsection
12396 describes working with such symbols, known internally to @value{GDBN} as
12397 ``minimal symbols''.
12399 Note that before the debugged program has started execution, no DLLs
12400 will have been loaded. The easiest way around this problem is simply to
12401 start the program --- either by setting a breakpoint or letting the
12402 program run once to completion. It is also possible to force
12403 @value{GDBN} to load a particular DLL before starting the executable ---
12404 see the shared library information in @pxref{Files} or the
12405 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
12406 explicitly loading symbols from a DLL with no debugging information will
12407 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
12408 which may adversely affect symbol lookup performance.
12410 @subsubsection DLL name prefixes
12412 In keeping with the naming conventions used by the Microsoft debugging
12413 tools, DLL export symbols are made available with a prefix based on the
12414 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
12415 also entered into the symbol table, so @code{CreateFileA} is often
12416 sufficient. In some cases there will be name clashes within a program
12417 (particularly if the executable itself includes full debugging symbols)
12418 necessitating the use of the fully qualified name when referring to the
12419 contents of the DLL. Use single-quotes around the name to avoid the
12420 exclamation mark (``!'') being interpreted as a language operator.
12422 Note that the internal name of the DLL may be all upper-case, even
12423 though the file name of the DLL is lower-case, or vice-versa. Since
12424 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
12425 some confusion. If in doubt, try the @code{info functions} and
12426 @code{info variables} commands or even @code{maint print msymbols} (see
12427 @pxref{Symbols}). Here's an example:
12430 (@value{GDBP}) info function CreateFileA
12431 All functions matching regular expression "CreateFileA":
12433 Non-debugging symbols:
12434 0x77e885f4 CreateFileA
12435 0x77e885f4 KERNEL32!CreateFileA
12439 (@value{GDBP}) info function !
12440 All functions matching regular expression "!":
12442 Non-debugging symbols:
12443 0x6100114c cygwin1!__assert
12444 0x61004034 cygwin1!_dll_crt0@@0
12445 0x61004240 cygwin1!dll_crt0(per_process *)
12449 @subsubsection Working with minimal symbols
12451 Symbols extracted from a DLL's export table do not contain very much
12452 type information. All that @value{GDBN} can do is guess whether a symbol
12453 refers to a function or variable depending on the linker section that
12454 contains the symbol. Also note that the actual contents of the memory
12455 contained in a DLL are not available unless the program is running. This
12456 means that you cannot examine the contents of a variable or disassemble
12457 a function within a DLL without a running program.
12459 Variables are generally treated as pointers and dereferenced
12460 automatically. For this reason, it is often necessary to prefix a
12461 variable name with the address-of operator (``&'') and provide explicit
12462 type information in the command. Here's an example of the type of
12466 (@value{GDBP}) print 'cygwin1!__argv'
12471 (@value{GDBP}) x 'cygwin1!__argv'
12472 0x10021610: "\230y\""
12475 And two possible solutions:
12478 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
12479 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
12483 (@value{GDBP}) x/2x &'cygwin1!__argv'
12484 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
12485 (@value{GDBP}) x/x 0x10021608
12486 0x10021608: 0x0022fd98
12487 (@value{GDBP}) x/s 0x0022fd98
12488 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
12491 Setting a break point within a DLL is possible even before the program
12492 starts execution. However, under these circumstances, @value{GDBN} can't
12493 examine the initial instructions of the function in order to skip the
12494 function's frame set-up code. You can work around this by using ``*&''
12495 to set the breakpoint at a raw memory address:
12498 (@value{GDBP}) break *&'python22!PyOS_Readline'
12499 Breakpoint 1 at 0x1e04eff0
12502 The author of these extensions is not entirely convinced that setting a
12503 break point within a shared DLL like @file{kernel32.dll} is completely
12507 @section Embedded Operating Systems
12509 This section describes configurations involving the debugging of
12510 embedded operating systems that are available for several different
12514 * VxWorks:: Using @value{GDBN} with VxWorks
12517 @value{GDBN} includes the ability to debug programs running on
12518 various real-time operating systems.
12521 @subsection Using @value{GDBN} with VxWorks
12527 @kindex target vxworks
12528 @item target vxworks @var{machinename}
12529 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
12530 is the target system's machine name or IP address.
12534 On VxWorks, @code{load} links @var{filename} dynamically on the
12535 current target system as well as adding its symbols in @value{GDBN}.
12537 @value{GDBN} enables developers to spawn and debug tasks running on networked
12538 VxWorks targets from a Unix host. Already-running tasks spawned from
12539 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
12540 both the Unix host and on the VxWorks target. The program
12541 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
12542 installed with the name @code{vxgdb}, to distinguish it from a
12543 @value{GDBN} for debugging programs on the host itself.)
12546 @item VxWorks-timeout @var{args}
12547 @kindex vxworks-timeout
12548 All VxWorks-based targets now support the option @code{vxworks-timeout}.
12549 This option is set by the user, and @var{args} represents the number of
12550 seconds @value{GDBN} waits for responses to rpc's. You might use this if
12551 your VxWorks target is a slow software simulator or is on the far side
12552 of a thin network line.
12555 The following information on connecting to VxWorks was current when
12556 this manual was produced; newer releases of VxWorks may use revised
12559 @findex INCLUDE_RDB
12560 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
12561 to include the remote debugging interface routines in the VxWorks
12562 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
12563 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
12564 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
12565 source debugging task @code{tRdbTask} when VxWorks is booted. For more
12566 information on configuring and remaking VxWorks, see the manufacturer's
12568 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
12570 Once you have included @file{rdb.a} in your VxWorks system image and set
12571 your Unix execution search path to find @value{GDBN}, you are ready to
12572 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
12573 @code{vxgdb}, depending on your installation).
12575 @value{GDBN} comes up showing the prompt:
12582 * VxWorks Connection:: Connecting to VxWorks
12583 * VxWorks Download:: VxWorks download
12584 * VxWorks Attach:: Running tasks
12587 @node VxWorks Connection
12588 @subsubsection Connecting to VxWorks
12590 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
12591 network. To connect to a target whose host name is ``@code{tt}'', type:
12594 (vxgdb) target vxworks tt
12598 @value{GDBN} displays messages like these:
12601 Attaching remote machine across net...
12606 @value{GDBN} then attempts to read the symbol tables of any object modules
12607 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
12608 these files by searching the directories listed in the command search
12609 path (@pxref{Environment, ,Your program's environment}); if it fails
12610 to find an object file, it displays a message such as:
12613 prog.o: No such file or directory.
12616 When this happens, add the appropriate directory to the search path with
12617 the @value{GDBN} command @code{path}, and execute the @code{target}
12620 @node VxWorks Download
12621 @subsubsection VxWorks download
12623 @cindex download to VxWorks
12624 If you have connected to the VxWorks target and you want to debug an
12625 object that has not yet been loaded, you can use the @value{GDBN}
12626 @code{load} command to download a file from Unix to VxWorks
12627 incrementally. The object file given as an argument to the @code{load}
12628 command is actually opened twice: first by the VxWorks target in order
12629 to download the code, then by @value{GDBN} in order to read the symbol
12630 table. This can lead to problems if the current working directories on
12631 the two systems differ. If both systems have NFS mounted the same
12632 filesystems, you can avoid these problems by using absolute paths.
12633 Otherwise, it is simplest to set the working directory on both systems
12634 to the directory in which the object file resides, and then to reference
12635 the file by its name, without any path. For instance, a program
12636 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
12637 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
12638 program, type this on VxWorks:
12641 -> cd "@var{vxpath}/vw/demo/rdb"
12645 Then, in @value{GDBN}, type:
12648 (vxgdb) cd @var{hostpath}/vw/demo/rdb
12649 (vxgdb) load prog.o
12652 @value{GDBN} displays a response similar to this:
12655 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
12658 You can also use the @code{load} command to reload an object module
12659 after editing and recompiling the corresponding source file. Note that
12660 this makes @value{GDBN} delete all currently-defined breakpoints,
12661 auto-displays, and convenience variables, and to clear the value
12662 history. (This is necessary in order to preserve the integrity of
12663 debugger's data structures that reference the target system's symbol
12666 @node VxWorks Attach
12667 @subsubsection Running tasks
12669 @cindex running VxWorks tasks
12670 You can also attach to an existing task using the @code{attach} command as
12674 (vxgdb) attach @var{task}
12678 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
12679 or suspended when you attach to it. Running tasks are suspended at
12680 the time of attachment.
12682 @node Embedded Processors
12683 @section Embedded Processors
12685 This section goes into details specific to particular embedded
12691 * H8/300:: Renesas H8/300
12692 * H8/500:: Renesas H8/500
12693 * M32R/D:: Renesas M32R/D
12694 * M68K:: Motorola M68K
12695 * MIPS Embedded:: MIPS Embedded
12696 * OpenRISC 1000:: OpenRisc 1000
12697 * PA:: HP PA Embedded
12700 * Sparclet:: Tsqware Sparclet
12701 * Sparclite:: Fujitsu Sparclite
12702 * ST2000:: Tandem ST2000
12703 * Z8000:: Zilog Z8000
12712 @item target rdi @var{dev}
12713 ARM Angel monitor, via RDI library interface to ADP protocol. You may
12714 use this target to communicate with both boards running the Angel
12715 monitor, or with the EmbeddedICE JTAG debug device.
12718 @item target rdp @var{dev}
12724 @subsection Renesas H8/300
12728 @kindex target hms@r{, with H8/300}
12729 @item target hms @var{dev}
12730 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
12731 Use special commands @code{device} and @code{speed} to control the serial
12732 line and the communications speed used.
12734 @kindex target e7000@r{, with H8/300}
12735 @item target e7000 @var{dev}
12736 E7000 emulator for Renesas H8 and SH.
12738 @kindex target sh3@r{, with H8/300}
12739 @kindex target sh3e@r{, with H8/300}
12740 @item target sh3 @var{dev}
12741 @itemx target sh3e @var{dev}
12742 Renesas SH-3 and SH-3E target systems.
12746 @cindex download to H8/300 or H8/500
12747 @cindex H8/300 or H8/500 download
12748 @cindex download to Renesas SH
12749 @cindex Renesas SH download
12750 When you select remote debugging to a Renesas SH, H8/300, or H8/500
12751 board, the @code{load} command downloads your program to the Renesas
12752 board and also opens it as the current executable target for
12753 @value{GDBN} on your host (like the @code{file} command).
12755 @value{GDBN} needs to know these things to talk to your
12756 Renesas SH, H8/300, or H8/500:
12760 that you want to use @samp{target hms}, the remote debugging interface
12761 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
12762 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
12763 the default when @value{GDBN} is configured specifically for the Renesas SH,
12764 H8/300, or H8/500.)
12767 what serial device connects your host to your Renesas board (the first
12768 serial device available on your host is the default).
12771 what speed to use over the serial device.
12775 * Renesas Boards:: Connecting to Renesas boards.
12776 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
12777 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
12780 @node Renesas Boards
12781 @subsubsection Connecting to Renesas boards
12783 @c only for Unix hosts
12785 @cindex serial device, Renesas micros
12786 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
12787 need to explicitly set the serial device. The default @var{port} is the
12788 first available port on your host. This is only necessary on Unix
12789 hosts, where it is typically something like @file{/dev/ttya}.
12792 @cindex serial line speed, Renesas micros
12793 @code{@value{GDBN}} has another special command to set the communications
12794 speed: @samp{speed @var{bps}}. This command also is only used from Unix
12795 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
12796 the DOS @code{mode} command (for instance,
12797 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
12799 The @samp{device} and @samp{speed} commands are available only when you
12800 use a Unix host to debug your Renesas microprocessor programs. If you
12802 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
12803 called @code{asynctsr} to communicate with the development board
12804 through a PC serial port. You must also use the DOS @code{mode} command
12805 to set up the serial port on the DOS side.
12807 The following sample session illustrates the steps needed to start a
12808 program under @value{GDBN} control on an H8/300. The example uses a
12809 sample H8/300 program called @file{t.x}. The procedure is the same for
12810 the Renesas SH and the H8/500.
12812 First hook up your development board. In this example, we use a
12813 board attached to serial port @code{COM2}; if you use a different serial
12814 port, substitute its name in the argument of the @code{mode} command.
12815 When you call @code{asynctsr}, the auxiliary comms program used by the
12816 debugger, you give it just the numeric part of the serial port's name;
12817 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
12821 C:\H8300\TEST> asynctsr 2
12822 C:\H8300\TEST> mode com2:9600,n,8,1,p
12824 Resident portion of MODE loaded
12826 COM2: 9600, n, 8, 1, p
12831 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
12832 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
12833 disable it, or even boot without it, to use @code{asynctsr} to control
12834 your development board.
12837 @kindex target hms@r{, and serial protocol}
12838 Now that serial communications are set up, and the development board is
12839 connected, you can start up @value{GDBN}. Call @code{@value{GDBP}} with
12840 the name of your program as the argument. @code{@value{GDBN}} prompts
12841 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
12842 commands to begin your debugging session: @samp{target hms} to specify
12843 cross-debugging to the Renesas board, and the @code{load} command to
12844 download your program to the board. @code{load} displays the names of
12845 the program's sections, and a @samp{*} for each 2K of data downloaded.
12846 (If you want to refresh @value{GDBN} data on symbols or on the
12847 executable file without downloading, use the @value{GDBN} commands
12848 @code{file} or @code{symbol-file}. These commands, and @code{load}
12849 itself, are described in @ref{Files,,Commands to specify files}.)
12852 (eg-C:\H8300\TEST) @value{GDBP} t.x
12853 @value{GDBN} is free software and you are welcome to distribute copies
12854 of it under certain conditions; type "show copying" to see
12856 There is absolutely no warranty for @value{GDBN}; type "show warranty"
12858 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
12859 (@value{GDBP}) target hms
12860 Connected to remote H8/300 HMS system.
12861 (@value{GDBP}) load t.x
12862 .text : 0x8000 .. 0xabde ***********
12863 .data : 0xabde .. 0xad30 *
12864 .stack : 0xf000 .. 0xf014 *
12867 At this point, you're ready to run or debug your program. From here on,
12868 you can use all the usual @value{GDBN} commands. The @code{break} command
12869 sets breakpoints; the @code{run} command starts your program;
12870 @code{print} or @code{x} display data; the @code{continue} command
12871 resumes execution after stopping at a breakpoint. You can use the
12872 @code{help} command at any time to find out more about @value{GDBN} commands.
12874 Remember, however, that @emph{operating system} facilities aren't
12875 available on your development board; for example, if your program hangs,
12876 you can't send an interrupt---but you can press the @sc{reset} switch!
12878 Use the @sc{reset} button on the development board
12881 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
12882 no way to pass an interrupt signal to the development board); and
12885 to return to the @value{GDBN} command prompt after your program finishes
12886 normally. The communications protocol provides no other way for @value{GDBN}
12887 to detect program completion.
12890 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
12891 development board as a ``normal exit'' of your program.
12894 @subsubsection Using the E7000 in-circuit emulator
12896 @kindex target e7000@r{, with Renesas ICE}
12897 You can use the E7000 in-circuit emulator to develop code for either the
12898 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
12899 e7000} command to connect @value{GDBN} to your E7000:
12902 @item target e7000 @var{port} @var{speed}
12903 Use this form if your E7000 is connected to a serial port. The
12904 @var{port} argument identifies what serial port to use (for example,
12905 @samp{com2}). The third argument is the line speed in bits per second
12906 (for example, @samp{9600}).
12908 @item target e7000 @var{hostname}
12909 If your E7000 is installed as a host on a TCP/IP network, you can just
12910 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
12913 @node Renesas Special
12914 @subsubsection Special @value{GDBN} commands for Renesas micros
12916 Some @value{GDBN} commands are available only for the H8/300:
12920 @kindex set machine
12921 @kindex show machine
12922 @item set machine h8300
12923 @itemx set machine h8300h
12924 Condition @value{GDBN} for one of the two variants of the H8/300
12925 architecture with @samp{set machine}. You can use @samp{show machine}
12926 to check which variant is currently in effect.
12935 @kindex set memory @var{mod}
12936 @cindex memory models, H8/500
12937 @item set memory @var{mod}
12939 Specify which H8/500 memory model (@var{mod}) you are using with
12940 @samp{set memory}; check which memory model is in effect with @samp{show
12941 memory}. The accepted values for @var{mod} are @code{small},
12942 @code{big}, @code{medium}, and @code{compact}.
12947 @subsection Renesas M32R/D
12951 @kindex target m32r
12952 @item target m32r @var{dev}
12953 Renesas M32R/D ROM monitor.
12955 @kindex target m32rsdi
12956 @item target m32rsdi @var{dev}
12957 Renesas M32R SDI server, connected via parallel port to the board.
12964 The Motorola m68k configuration includes ColdFire support, and
12965 target command for the following ROM monitors.
12969 @kindex target abug
12970 @item target abug @var{dev}
12971 ABug ROM monitor for M68K.
12973 @kindex target cpu32bug
12974 @item target cpu32bug @var{dev}
12975 CPU32BUG monitor, running on a CPU32 (M68K) board.
12977 @kindex target dbug
12978 @item target dbug @var{dev}
12979 dBUG ROM monitor for Motorola ColdFire.
12982 @item target est @var{dev}
12983 EST-300 ICE monitor, running on a CPU32 (M68K) board.
12985 @kindex target rom68k
12986 @item target rom68k @var{dev}
12987 ROM 68K monitor, running on an M68K IDP board.
12993 @kindex target rombug
12994 @item target rombug @var{dev}
12995 ROMBUG ROM monitor for OS/9000.
12999 @node MIPS Embedded
13000 @subsection MIPS Embedded
13002 @cindex MIPS boards
13003 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
13004 MIPS board attached to a serial line. This is available when
13005 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
13008 Use these @value{GDBN} commands to specify the connection to your target board:
13011 @item target mips @var{port}
13012 @kindex target mips @var{port}
13013 To run a program on the board, start up @code{@value{GDBP}} with the
13014 name of your program as the argument. To connect to the board, use the
13015 command @samp{target mips @var{port}}, where @var{port} is the name of
13016 the serial port connected to the board. If the program has not already
13017 been downloaded to the board, you may use the @code{load} command to
13018 download it. You can then use all the usual @value{GDBN} commands.
13020 For example, this sequence connects to the target board through a serial
13021 port, and loads and runs a program called @var{prog} through the
13025 host$ @value{GDBP} @var{prog}
13026 @value{GDBN} is free software and @dots{}
13027 (@value{GDBP}) target mips /dev/ttyb
13028 (@value{GDBP}) load @var{prog}
13032 @item target mips @var{hostname}:@var{portnumber}
13033 On some @value{GDBN} host configurations, you can specify a TCP
13034 connection (for instance, to a serial line managed by a terminal
13035 concentrator) instead of a serial port, using the syntax
13036 @samp{@var{hostname}:@var{portnumber}}.
13038 @item target pmon @var{port}
13039 @kindex target pmon @var{port}
13042 @item target ddb @var{port}
13043 @kindex target ddb @var{port}
13044 NEC's DDB variant of PMON for Vr4300.
13046 @item target lsi @var{port}
13047 @kindex target lsi @var{port}
13048 LSI variant of PMON.
13050 @kindex target r3900
13051 @item target r3900 @var{dev}
13052 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
13054 @kindex target array
13055 @item target array @var{dev}
13056 Array Tech LSI33K RAID controller board.
13062 @value{GDBN} also supports these special commands for MIPS targets:
13065 @item set processor @var{args}
13066 @itemx show processor
13067 @kindex set processor @var{args}
13068 @kindex show processor
13069 Use the @code{set processor} command to set the type of MIPS
13070 processor when you want to access processor-type-specific registers.
13071 For example, @code{set processor @var{r3041}} tells @value{GDBN}
13072 to use the CPU registers appropriate for the 3041 chip.
13073 Use the @code{show processor} command to see what MIPS processor @value{GDBN}
13074 is using. Use the @code{info reg} command to see what registers
13075 @value{GDBN} is using.
13077 @item set mipsfpu double
13078 @itemx set mipsfpu single
13079 @itemx set mipsfpu none
13080 @itemx show mipsfpu
13081 @kindex set mipsfpu
13082 @kindex show mipsfpu
13083 @cindex MIPS remote floating point
13084 @cindex floating point, MIPS remote
13085 If your target board does not support the MIPS floating point
13086 coprocessor, you should use the command @samp{set mipsfpu none} (if you
13087 need this, you may wish to put the command in your @value{GDBN} init
13088 file). This tells @value{GDBN} how to find the return value of
13089 functions which return floating point values. It also allows
13090 @value{GDBN} to avoid saving the floating point registers when calling
13091 functions on the board. If you are using a floating point coprocessor
13092 with only single precision floating point support, as on the @sc{r4650}
13093 processor, use the command @samp{set mipsfpu single}. The default
13094 double precision floating point coprocessor may be selected using
13095 @samp{set mipsfpu double}.
13097 In previous versions the only choices were double precision or no
13098 floating point, so @samp{set mipsfpu on} will select double precision
13099 and @samp{set mipsfpu off} will select no floating point.
13101 As usual, you can inquire about the @code{mipsfpu} variable with
13102 @samp{show mipsfpu}.
13104 @item set remotedebug @var{n}
13105 @itemx show remotedebug
13106 @kindex set remotedebug@r{, MIPS protocol}
13107 @kindex show remotedebug@r{, MIPS protocol}
13108 @cindex @code{remotedebug}, MIPS protocol
13109 @cindex MIPS @code{remotedebug} protocol
13110 @c FIXME! For this to be useful, you must know something about the MIPS
13111 @c FIXME...protocol. Where is it described?
13112 You can see some debugging information about communications with the board
13113 by setting the @code{remotedebug} variable. If you set it to @code{1} using
13114 @samp{set remotedebug 1}, every packet is displayed. If you set it
13115 to @code{2}, every character is displayed. You can check the current value
13116 at any time with the command @samp{show remotedebug}.
13118 @item set timeout @var{seconds}
13119 @itemx set retransmit-timeout @var{seconds}
13120 @itemx show timeout
13121 @itemx show retransmit-timeout
13122 @cindex @code{timeout}, MIPS protocol
13123 @cindex @code{retransmit-timeout}, MIPS protocol
13124 @kindex set timeout
13125 @kindex show timeout
13126 @kindex set retransmit-timeout
13127 @kindex show retransmit-timeout
13128 You can control the timeout used while waiting for a packet, in the MIPS
13129 remote protocol, with the @code{set timeout @var{seconds}} command. The
13130 default is 5 seconds. Similarly, you can control the timeout used while
13131 waiting for an acknowledgement of a packet with the @code{set
13132 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
13133 You can inspect both values with @code{show timeout} and @code{show
13134 retransmit-timeout}. (These commands are @emph{only} available when
13135 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
13137 The timeout set by @code{set timeout} does not apply when @value{GDBN}
13138 is waiting for your program to stop. In that case, @value{GDBN} waits
13139 forever because it has no way of knowing how long the program is going
13140 to run before stopping.
13143 @node OpenRISC 1000
13144 @subsection OpenRISC 1000
13145 @cindex OpenRISC 1000
13147 @cindex or1k boards
13148 See OR1k Architecture document (@uref{www.opencores.org}) for more information
13149 about platform and commands.
13153 @kindex target jtag
13154 @item target jtag jtag://@var{host}:@var{port}
13156 Connects to remote JTAG server.
13157 JTAG remote server can be either an or1ksim or JTAG server,
13158 connected via parallel port to the board.
13160 Example: @code{target jtag jtag://localhost:9999}
13163 @item or1ksim @var{command}
13164 If connected to @code{or1ksim} OpenRISC 1000 Architectural
13165 Simulator, proprietary commands can be executed.
13167 @kindex info or1k spr
13168 @item info or1k spr
13169 Displays spr groups.
13171 @item info or1k spr @var{group}
13172 @itemx info or1k spr @var{groupno}
13173 Displays register names in selected group.
13175 @item info or1k spr @var{group} @var{register}
13176 @itemx info or1k spr @var{register}
13177 @itemx info or1k spr @var{groupno} @var{registerno}
13178 @itemx info or1k spr @var{registerno}
13179 Shows information about specified spr register.
13182 @item spr @var{group} @var{register} @var{value}
13183 @itemx spr @var{register @var{value}}
13184 @itemx spr @var{groupno} @var{registerno @var{value}}
13185 @itemx spr @var{registerno @var{value}}
13186 Writes @var{value} to specified spr register.
13189 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
13190 It is very similar to @value{GDBN} trace, except it does not interfere with normal
13191 program execution and is thus much faster. Hardware breakpoints/watchpoint
13192 triggers can be set using:
13195 Load effective address/data
13197 Store effective address/data
13199 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
13204 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
13205 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
13207 @code{htrace} commands:
13208 @cindex OpenRISC 1000 htrace
13211 @item hwatch @var{conditional}
13212 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
13213 or Data. For example:
13215 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
13217 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
13221 Display information about current HW trace configuration.
13223 @item htrace trigger @var{conditional}
13224 Set starting criteria for HW trace.
13226 @item htrace qualifier @var{conditional}
13227 Set acquisition qualifier for HW trace.
13229 @item htrace stop @var{conditional}
13230 Set HW trace stopping criteria.
13232 @item htrace record [@var{data}]*
13233 Selects the data to be recorded, when qualifier is met and HW trace was
13236 @item htrace enable
13237 @itemx htrace disable
13238 Enables/disables the HW trace.
13240 @item htrace rewind [@var{filename}]
13241 Clears currently recorded trace data.
13243 If filename is specified, new trace file is made and any newly collected data
13244 will be written there.
13246 @item htrace print [@var{start} [@var{len}]]
13247 Prints trace buffer, using current record configuration.
13249 @item htrace mode continuous
13250 Set continuous trace mode.
13252 @item htrace mode suspend
13253 Set suspend trace mode.
13258 @subsection PowerPC
13262 @kindex target dink32
13263 @item target dink32 @var{dev}
13264 DINK32 ROM monitor.
13266 @kindex target ppcbug
13267 @item target ppcbug @var{dev}
13268 @kindex target ppcbug1
13269 @item target ppcbug1 @var{dev}
13270 PPCBUG ROM monitor for PowerPC.
13273 @item target sds @var{dev}
13274 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
13279 @subsection HP PA Embedded
13283 @kindex target op50n
13284 @item target op50n @var{dev}
13285 OP50N monitor, running on an OKI HPPA board.
13287 @kindex target w89k
13288 @item target w89k @var{dev}
13289 W89K monitor, running on a Winbond HPPA board.
13294 @subsection Renesas SH
13298 @kindex target hms@r{, with Renesas SH}
13299 @item target hms @var{dev}
13300 A Renesas SH board attached via serial line to your host. Use special
13301 commands @code{device} and @code{speed} to control the serial line and
13302 the communications speed used.
13304 @kindex target e7000@r{, with Renesas SH}
13305 @item target e7000 @var{dev}
13306 E7000 emulator for Renesas SH.
13308 @kindex target sh3@r{, with SH}
13309 @kindex target sh3e@r{, with SH}
13310 @item target sh3 @var{dev}
13311 @item target sh3e @var{dev}
13312 Renesas SH-3 and SH-3E target systems.
13317 @subsection Tsqware Sparclet
13321 @value{GDBN} enables developers to debug tasks running on
13322 Sparclet targets from a Unix host.
13323 @value{GDBN} uses code that runs on
13324 both the Unix host and on the Sparclet target. The program
13325 @code{@value{GDBP}} is installed and executed on the Unix host.
13328 @item remotetimeout @var{args}
13329 @kindex remotetimeout
13330 @value{GDBN} supports the option @code{remotetimeout}.
13331 This option is set by the user, and @var{args} represents the number of
13332 seconds @value{GDBN} waits for responses.
13335 @cindex compiling, on Sparclet
13336 When compiling for debugging, include the options @samp{-g} to get debug
13337 information and @samp{-Ttext} to relocate the program to where you wish to
13338 load it on the target. You may also want to add the options @samp{-n} or
13339 @samp{-N} in order to reduce the size of the sections. Example:
13342 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
13345 You can use @code{objdump} to verify that the addresses are what you intended:
13348 sparclet-aout-objdump --headers --syms prog
13351 @cindex running, on Sparclet
13353 your Unix execution search path to find @value{GDBN}, you are ready to
13354 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
13355 (or @code{sparclet-aout-gdb}, depending on your installation).
13357 @value{GDBN} comes up showing the prompt:
13364 * Sparclet File:: Setting the file to debug
13365 * Sparclet Connection:: Connecting to Sparclet
13366 * Sparclet Download:: Sparclet download
13367 * Sparclet Execution:: Running and debugging
13370 @node Sparclet File
13371 @subsubsection Setting file to debug
13373 The @value{GDBN} command @code{file} lets you choose with program to debug.
13376 (gdbslet) file prog
13380 @value{GDBN} then attempts to read the symbol table of @file{prog}.
13381 @value{GDBN} locates
13382 the file by searching the directories listed in the command search
13384 If the file was compiled with debug information (option "-g"), source
13385 files will be searched as well.
13386 @value{GDBN} locates
13387 the source files by searching the directories listed in the directory search
13388 path (@pxref{Environment, ,Your program's environment}).
13390 to find a file, it displays a message such as:
13393 prog: No such file or directory.
13396 When this happens, add the appropriate directories to the search paths with
13397 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
13398 @code{target} command again.
13400 @node Sparclet Connection
13401 @subsubsection Connecting to Sparclet
13403 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
13404 To connect to a target on serial port ``@code{ttya}'', type:
13407 (gdbslet) target sparclet /dev/ttya
13408 Remote target sparclet connected to /dev/ttya
13409 main () at ../prog.c:3
13413 @value{GDBN} displays messages like these:
13419 @node Sparclet Download
13420 @subsubsection Sparclet download
13422 @cindex download to Sparclet
13423 Once connected to the Sparclet target,
13424 you can use the @value{GDBN}
13425 @code{load} command to download the file from the host to the target.
13426 The file name and load offset should be given as arguments to the @code{load}
13428 Since the file format is aout, the program must be loaded to the starting
13429 address. You can use @code{objdump} to find out what this value is. The load
13430 offset is an offset which is added to the VMA (virtual memory address)
13431 of each of the file's sections.
13432 For instance, if the program
13433 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
13434 and bss at 0x12010170, in @value{GDBN}, type:
13437 (gdbslet) load prog 0x12010000
13438 Loading section .text, size 0xdb0 vma 0x12010000
13441 If the code is loaded at a different address then what the program was linked
13442 to, you may need to use the @code{section} and @code{add-symbol-file} commands
13443 to tell @value{GDBN} where to map the symbol table.
13445 @node Sparclet Execution
13446 @subsubsection Running and debugging
13448 @cindex running and debugging Sparclet programs
13449 You can now begin debugging the task using @value{GDBN}'s execution control
13450 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
13451 manual for the list of commands.
13455 Breakpoint 1 at 0x12010000: file prog.c, line 3.
13457 Starting program: prog
13458 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
13459 3 char *symarg = 0;
13461 4 char *execarg = "hello!";
13466 @subsection Fujitsu Sparclite
13470 @kindex target sparclite
13471 @item target sparclite @var{dev}
13472 Fujitsu sparclite boards, used only for the purpose of loading.
13473 You must use an additional command to debug the program.
13474 For example: target remote @var{dev} using @value{GDBN} standard
13480 @subsection Tandem ST2000
13482 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
13485 To connect your ST2000 to the host system, see the manufacturer's
13486 manual. Once the ST2000 is physically attached, you can run:
13489 target st2000 @var{dev} @var{speed}
13493 to establish it as your debugging environment. @var{dev} is normally
13494 the name of a serial device, such as @file{/dev/ttya}, connected to the
13495 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
13496 connection (for example, to a serial line attached via a terminal
13497 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
13499 The @code{load} and @code{attach} commands are @emph{not} defined for
13500 this target; you must load your program into the ST2000 as you normally
13501 would for standalone operation. @value{GDBN} reads debugging information
13502 (such as symbols) from a separate, debugging version of the program
13503 available on your host computer.
13504 @c FIXME!! This is terribly vague; what little content is here is
13505 @c basically hearsay.
13507 @cindex ST2000 auxiliary commands
13508 These auxiliary @value{GDBN} commands are available to help you with the ST2000
13512 @item st2000 @var{command}
13513 @kindex st2000 @var{cmd}
13514 @cindex STDBUG commands (ST2000)
13515 @cindex commands to STDBUG (ST2000)
13516 Send a @var{command} to the STDBUG monitor. See the manufacturer's
13517 manual for available commands.
13520 @cindex connect (to STDBUG)
13521 Connect the controlling terminal to the STDBUG command monitor. When
13522 you are done interacting with STDBUG, typing either of two character
13523 sequences gets you back to the @value{GDBN} command prompt:
13524 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
13525 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
13529 @subsection Zilog Z8000
13532 @cindex simulator, Z8000
13533 @cindex Zilog Z8000 simulator
13535 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
13538 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
13539 unsegmented variant of the Z8000 architecture) or the Z8001 (the
13540 segmented variant). The simulator recognizes which architecture is
13541 appropriate by inspecting the object code.
13544 @item target sim @var{args}
13546 @kindex target sim@r{, with Z8000}
13547 Debug programs on a simulated CPU. If the simulator supports setup
13548 options, specify them via @var{args}.
13552 After specifying this target, you can debug programs for the simulated
13553 CPU in the same style as programs for your host computer; use the
13554 @code{file} command to load a new program image, the @code{run} command
13555 to run your program, and so on.
13557 As well as making available all the usual machine registers
13558 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
13559 additional items of information as specially named registers:
13564 Counts clock-ticks in the simulator.
13567 Counts instructions run in the simulator.
13570 Execution time in 60ths of a second.
13574 You can refer to these values in @value{GDBN} expressions with the usual
13575 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
13576 conditional breakpoint that suspends only after at least 5000
13577 simulated clock ticks.
13579 @node Architectures
13580 @section Architectures
13582 This section describes characteristics of architectures that affect
13583 all uses of @value{GDBN} with the architecture, both native and cross.
13596 @kindex set rstack_high_address
13597 @cindex AMD 29K register stack
13598 @cindex register stack, AMD29K
13599 @item set rstack_high_address @var{address}
13600 On AMD 29000 family processors, registers are saved in a separate
13601 @dfn{register stack}. There is no way for @value{GDBN} to determine the
13602 extent of this stack. Normally, @value{GDBN} just assumes that the
13603 stack is ``large enough''. This may result in @value{GDBN} referencing
13604 memory locations that do not exist. If necessary, you can get around
13605 this problem by specifying the ending address of the register stack with
13606 the @code{set rstack_high_address} command. The argument should be an
13607 address, which you probably want to precede with @samp{0x} to specify in
13610 @kindex show rstack_high_address
13611 @item show rstack_high_address
13612 Display the current limit of the register stack, on AMD 29000 family
13620 See the following section.
13625 @cindex stack on Alpha
13626 @cindex stack on MIPS
13627 @cindex Alpha stack
13629 Alpha- and MIPS-based computers use an unusual stack frame, which
13630 sometimes requires @value{GDBN} to search backward in the object code to
13631 find the beginning of a function.
13633 @cindex response time, MIPS debugging
13634 To improve response time (especially for embedded applications, where
13635 @value{GDBN} may be restricted to a slow serial line for this search)
13636 you may want to limit the size of this search, using one of these
13640 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
13641 @item set heuristic-fence-post @var{limit}
13642 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
13643 search for the beginning of a function. A value of @var{0} (the
13644 default) means there is no limit. However, except for @var{0}, the
13645 larger the limit the more bytes @code{heuristic-fence-post} must search
13646 and therefore the longer it takes to run.
13648 @item show heuristic-fence-post
13649 Display the current limit.
13653 These commands are available @emph{only} when @value{GDBN} is configured
13654 for debugging programs on Alpha or MIPS processors.
13657 @node Controlling GDB
13658 @chapter Controlling @value{GDBN}
13660 You can alter the way @value{GDBN} interacts with you by using the
13661 @code{set} command. For commands controlling how @value{GDBN} displays
13662 data, see @ref{Print Settings, ,Print settings}. Other settings are
13667 * Editing:: Command editing
13668 * History:: Command history
13669 * Screen Size:: Screen size
13670 * Numbers:: Numbers
13671 * ABI:: Configuring the current ABI
13672 * Messages/Warnings:: Optional warnings and messages
13673 * Debugging Output:: Optional messages about internal happenings
13681 @value{GDBN} indicates its readiness to read a command by printing a string
13682 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
13683 can change the prompt string with the @code{set prompt} command. For
13684 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
13685 the prompt in one of the @value{GDBN} sessions so that you can always tell
13686 which one you are talking to.
13688 @emph{Note:} @code{set prompt} does not add a space for you after the
13689 prompt you set. This allows you to set a prompt which ends in a space
13690 or a prompt that does not.
13694 @item set prompt @var{newprompt}
13695 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
13697 @kindex show prompt
13699 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
13703 @section Command editing
13705 @cindex command line editing
13707 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
13708 @sc{gnu} library provides consistent behavior for programs which provide a
13709 command line interface to the user. Advantages are @sc{gnu} Emacs-style
13710 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
13711 substitution, and a storage and recall of command history across
13712 debugging sessions.
13714 You may control the behavior of command line editing in @value{GDBN} with the
13715 command @code{set}.
13718 @kindex set editing
13721 @itemx set editing on
13722 Enable command line editing (enabled by default).
13724 @item set editing off
13725 Disable command line editing.
13727 @kindex show editing
13729 Show whether command line editing is enabled.
13732 @xref{Command Line Editing}, for more details about the Readline
13733 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
13734 encouraged to read that chapter.
13737 @section Command history
13738 @cindex command history
13740 @value{GDBN} can keep track of the commands you type during your
13741 debugging sessions, so that you can be certain of precisely what
13742 happened. Use these commands to manage the @value{GDBN} command
13745 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
13746 package, to provide the history facility. @xref{Using History
13747 Interactively}, for the detailed description of the History library.
13749 Here is the description of @value{GDBN} commands related to command
13753 @cindex history substitution
13754 @cindex history file
13755 @kindex set history filename
13756 @cindex @env{GDBHISTFILE}, environment variable
13757 @item set history filename @var{fname}
13758 Set the name of the @value{GDBN} command history file to @var{fname}.
13759 This is the file where @value{GDBN} reads an initial command history
13760 list, and where it writes the command history from this session when it
13761 exits. You can access this list through history expansion or through
13762 the history command editing characters listed below. This file defaults
13763 to the value of the environment variable @code{GDBHISTFILE}, or to
13764 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
13767 @cindex history save
13768 @kindex set history
13769 @item set history save
13770 @itemx set history save on
13771 Record command history in a file, whose name may be specified with the
13772 @code{set history filename} command. By default, this option is disabled.
13774 @item set history save off
13775 Stop recording command history in a file.
13777 @cindex history size
13778 @item set history size @var{size}
13779 Set the number of commands which @value{GDBN} keeps in its history list.
13780 This defaults to the value of the environment variable
13781 @code{HISTSIZE}, or to 256 if this variable is not set.
13784 History expansion assigns special meaning to the character @kbd{!}.
13785 @xref{Event Designators}, for more details.
13787 @cindex history expansion, turn on/off
13788 Since @kbd{!} is also the logical not operator in C, history expansion
13789 is off by default. If you decide to enable history expansion with the
13790 @code{set history expansion on} command, you may sometimes need to
13791 follow @kbd{!} (when it is used as logical not, in an expression) with
13792 a space or a tab to prevent it from being expanded. The readline
13793 history facilities do not attempt substitution on the strings
13794 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
13796 The commands to control history expansion are:
13799 @item set history expansion on
13800 @itemx set history expansion
13801 @kindex set history expansion
13802 Enable history expansion. History expansion is off by default.
13804 @item set history expansion off
13805 Disable history expansion.
13808 @kindex show history
13810 @itemx show history filename
13811 @itemx show history save
13812 @itemx show history size
13813 @itemx show history expansion
13814 These commands display the state of the @value{GDBN} history parameters.
13815 @code{show history} by itself displays all four states.
13821 @item show commands
13822 Display the last ten commands in the command history.
13824 @item show commands @var{n}
13825 Print ten commands centered on command number @var{n}.
13827 @item show commands +
13828 Print ten commands just after the commands last printed.
13832 @section Screen size
13833 @cindex size of screen
13834 @cindex pauses in output
13836 Certain commands to @value{GDBN} may produce large amounts of
13837 information output to the screen. To help you read all of it,
13838 @value{GDBN} pauses and asks you for input at the end of each page of
13839 output. Type @key{RET} when you want to continue the output, or @kbd{q}
13840 to discard the remaining output. Also, the screen width setting
13841 determines when to wrap lines of output. Depending on what is being
13842 printed, @value{GDBN} tries to break the line at a readable place,
13843 rather than simply letting it overflow onto the following line.
13845 Normally @value{GDBN} knows the size of the screen from the terminal
13846 driver software. For example, on Unix @value{GDBN} uses the termcap data base
13847 together with the value of the @code{TERM} environment variable and the
13848 @code{stty rows} and @code{stty cols} settings. If this is not correct,
13849 you can override it with the @code{set height} and @code{set
13856 @kindex show height
13857 @item set height @var{lpp}
13859 @itemx set width @var{cpl}
13861 These @code{set} commands specify a screen height of @var{lpp} lines and
13862 a screen width of @var{cpl} characters. The associated @code{show}
13863 commands display the current settings.
13865 If you specify a height of zero lines, @value{GDBN} does not pause during
13866 output no matter how long the output is. This is useful if output is to a
13867 file or to an editor buffer.
13869 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
13870 from wrapping its output.
13875 @cindex number representation
13876 @cindex entering numbers
13878 You can always enter numbers in octal, decimal, or hexadecimal in
13879 @value{GDBN} by the usual conventions: octal numbers begin with
13880 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
13881 begin with @samp{0x}. Numbers that begin with none of these are, by
13882 default, entered in base 10; likewise, the default display for
13883 numbers---when no particular format is specified---is base 10. You can
13884 change the default base for both input and output with the @code{set
13888 @kindex set input-radix
13889 @item set input-radix @var{base}
13890 Set the default base for numeric input. Supported choices
13891 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
13892 specified either unambiguously or using the current default radix; for
13902 sets the base to decimal. On the other hand, @samp{set radix 10}
13903 leaves the radix unchanged no matter what it was.
13905 @kindex set output-radix
13906 @item set output-radix @var{base}
13907 Set the default base for numeric display. Supported choices
13908 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
13909 specified either unambiguously or using the current default radix.
13911 @kindex show input-radix
13912 @item show input-radix
13913 Display the current default base for numeric input.
13915 @kindex show output-radix
13916 @item show output-radix
13917 Display the current default base for numeric display.
13921 @section Configuring the current ABI
13923 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
13924 application automatically. However, sometimes you need to override its
13925 conclusions. Use these commands to manage @value{GDBN}'s view of the
13932 One @value{GDBN} configuration can debug binaries for multiple operating
13933 system targets, either via remote debugging or native emulation.
13934 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
13935 but you can override its conclusion using the @code{set osabi} command.
13936 One example where this is useful is in debugging of binaries which use
13937 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
13938 not have the same identifying marks that the standard C library for your
13943 Show the OS ABI currently in use.
13946 With no argument, show the list of registered available OS ABI's.
13948 @item set osabi @var{abi}
13949 Set the current OS ABI to @var{abi}.
13952 @cindex float promotion
13954 Generally, the way that an argument of type @code{float} is passed to a
13955 function depends on whether the function is prototyped. For a prototyped
13956 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
13957 according to the architecture's convention for @code{float}. For unprototyped
13958 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
13959 @code{double} and then passed.
13961 Unfortunately, some forms of debug information do not reliably indicate whether
13962 a function is prototyped. If @value{GDBN} calls a function that is not marked
13963 as prototyped, it consults @kbd{set coerce-float-to-double}.
13966 @kindex set coerce-float-to-double
13967 @item set coerce-float-to-double
13968 @itemx set coerce-float-to-double on
13969 Arguments of type @code{float} will be promoted to @code{double} when passed
13970 to an unprototyped function. This is the default setting.
13972 @item set coerce-float-to-double off
13973 Arguments of type @code{float} will be passed directly to unprototyped
13978 @kindex show cp-abi
13979 @value{GDBN} needs to know the ABI used for your program's C@t{++}
13980 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
13981 used to build your application. @value{GDBN} only fully supports
13982 programs with a single C@t{++} ABI; if your program contains code using
13983 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
13984 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
13985 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
13986 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
13987 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
13988 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
13993 Show the C@t{++} ABI currently in use.
13996 With no argument, show the list of supported C@t{++} ABI's.
13998 @item set cp-abi @var{abi}
13999 @itemx set cp-abi auto
14000 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
14003 @node Messages/Warnings
14004 @section Optional warnings and messages
14006 By default, @value{GDBN} is silent about its inner workings. If you are
14007 running on a slow machine, you may want to use the @code{set verbose}
14008 command. This makes @value{GDBN} tell you when it does a lengthy
14009 internal operation, so you will not think it has crashed.
14011 Currently, the messages controlled by @code{set verbose} are those
14012 which announce that the symbol table for a source file is being read;
14013 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
14016 @kindex set verbose
14017 @item set verbose on
14018 Enables @value{GDBN} output of certain informational messages.
14020 @item set verbose off
14021 Disables @value{GDBN} output of certain informational messages.
14023 @kindex show verbose
14025 Displays whether @code{set verbose} is on or off.
14028 By default, if @value{GDBN} encounters bugs in the symbol table of an
14029 object file, it is silent; but if you are debugging a compiler, you may
14030 find this information useful (@pxref{Symbol Errors, ,Errors reading
14035 @kindex set complaints
14036 @item set complaints @var{limit}
14037 Permits @value{GDBN} to output @var{limit} complaints about each type of
14038 unusual symbols before becoming silent about the problem. Set
14039 @var{limit} to zero to suppress all complaints; set it to a large number
14040 to prevent complaints from being suppressed.
14042 @kindex show complaints
14043 @item show complaints
14044 Displays how many symbol complaints @value{GDBN} is permitted to produce.
14048 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
14049 lot of stupid questions to confirm certain commands. For example, if
14050 you try to run a program which is already running:
14054 The program being debugged has been started already.
14055 Start it from the beginning? (y or n)
14058 If you are willing to unflinchingly face the consequences of your own
14059 commands, you can disable this ``feature'':
14063 @kindex set confirm
14065 @cindex confirmation
14066 @cindex stupid questions
14067 @item set confirm off
14068 Disables confirmation requests.
14070 @item set confirm on
14071 Enables confirmation requests (the default).
14073 @kindex show confirm
14075 Displays state of confirmation requests.
14079 @node Debugging Output
14080 @section Optional messages about internal happenings
14081 @cindex optional debugging messages
14084 @kindex set exec-done-display
14085 @item set exec-done-display
14086 Turns on or off the notification of asynchronous commands'
14087 completion. When on, @value{GDBN} will print a message when an
14088 asynchronous command finishes its execution. The default is off.
14089 @kindex show exec-done-display
14090 @item show exec-done-display
14091 Displays the current setting of asynchronous command completion
14094 @cindex gdbarch debugging info
14095 @cindex architecture debugging info
14096 @item set debug arch
14097 Turns on or off display of gdbarch debugging info. The default is off
14099 @item show debug arch
14100 Displays the current state of displaying gdbarch debugging info.
14101 @item set debug event
14102 @cindex event debugging info
14103 Turns on or off display of @value{GDBN} event debugging info. The
14105 @item show debug event
14106 Displays the current state of displaying @value{GDBN} event debugging
14108 @item set debug expression
14109 @cindex expression debugging info
14110 Turns on or off display of @value{GDBN} expression debugging info. The
14112 @item show debug expression
14113 Displays the current state of displaying @value{GDBN} expression
14115 @item set debug frame
14116 @cindex frame debugging info
14117 Turns on or off display of @value{GDBN} frame debugging info. The
14119 @item show debug frame
14120 Displays the current state of displaying @value{GDBN} frame debugging
14122 @item set debug infrun
14123 @cindex inferior debugging info
14124 Turns on or off display of @value{GDBN} debugging info for running the inferior.
14125 The default is off. @file{infrun.c} contains GDB's runtime state machine used
14126 for implementing operations such as single-stepping the inferior.
14127 @item show debug infrun
14128 Displays the current state of @value{GDBN} inferior debugging.
14129 @item set debug observer
14130 @cindex observer debugging info
14131 Turns on or off display of @value{GDBN} observer debugging. This
14132 includes info such as the notification of observable events.
14133 @item show debug observer
14134 Displays the current state of observer debugging.
14135 @item set debug overload
14136 @cindex C@t{++} overload debugging info
14137 Turns on or off display of @value{GDBN} C@t{++} overload debugging
14138 info. This includes info such as ranking of functions, etc. The default
14140 @item show debug overload
14141 Displays the current state of displaying @value{GDBN} C@t{++} overload
14143 @cindex packets, reporting on stdout
14144 @cindex serial connections, debugging
14145 @item set debug remote
14146 Turns on or off display of reports on all packets sent back and forth across
14147 the serial line to the remote machine. The info is printed on the
14148 @value{GDBN} standard output stream. The default is off.
14149 @item show debug remote
14150 Displays the state of display of remote packets.
14151 @item set debug serial
14152 Turns on or off display of @value{GDBN} serial debugging info. The
14154 @item show debug serial
14155 Displays the current state of displaying @value{GDBN} serial debugging
14157 @item set debug target
14158 @cindex target debugging info
14159 Turns on or off display of @value{GDBN} target debugging info. This info
14160 includes what is going on at the target level of GDB, as it happens. The
14161 default is 0. Set it to 1 to track events, and to 2 to also track the
14162 value of large memory transfers. Changes to this flag do not take effect
14163 until the next time you connect to a target or use the @code{run} command.
14164 @item show debug target
14165 Displays the current state of displaying @value{GDBN} target debugging
14167 @item set debug varobj
14168 @cindex variable object debugging info
14169 Turns on or off display of @value{GDBN} variable object debugging
14170 info. The default is off.
14171 @item show debug varobj
14172 Displays the current state of displaying @value{GDBN} variable object
14177 @chapter Canned Sequences of Commands
14179 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
14180 command lists}), @value{GDBN} provides two ways to store sequences of
14181 commands for execution as a unit: user-defined commands and command
14185 * Define:: User-defined commands
14186 * Hooks:: User-defined command hooks
14187 * Command Files:: Command files
14188 * Output:: Commands for controlled output
14192 @section User-defined commands
14194 @cindex user-defined command
14195 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
14196 which you assign a new name as a command. This is done with the
14197 @code{define} command. User commands may accept up to 10 arguments
14198 separated by whitespace. Arguments are accessed within the user command
14199 via @var{$arg0@dots{}$arg9}. A trivial example:
14203 print $arg0 + $arg1 + $arg2
14207 To execute the command use:
14214 This defines the command @code{adder}, which prints the sum of
14215 its three arguments. Note the arguments are text substitutions, so they may
14216 reference variables, use complex expressions, or even perform inferior
14222 @item define @var{commandname}
14223 Define a command named @var{commandname}. If there is already a command
14224 by that name, you are asked to confirm that you want to redefine it.
14226 The definition of the command is made up of other @value{GDBN} command lines,
14227 which are given following the @code{define} command. The end of these
14228 commands is marked by a line containing @code{end}.
14234 Takes a single argument, which is an expression to evaluate.
14235 It is followed by a series of commands that are executed
14236 only if the expression is true (nonzero).
14237 There can then optionally be a line @code{else}, followed
14238 by a series of commands that are only executed if the expression
14239 was false. The end of the list is marked by a line containing @code{end}.
14243 The syntax is similar to @code{if}: the command takes a single argument,
14244 which is an expression to evaluate, and must be followed by the commands to
14245 execute, one per line, terminated by an @code{end}.
14246 The commands are executed repeatedly as long as the expression
14250 @item document @var{commandname}
14251 Document the user-defined command @var{commandname}, so that it can be
14252 accessed by @code{help}. The command @var{commandname} must already be
14253 defined. This command reads lines of documentation just as @code{define}
14254 reads the lines of the command definition, ending with @code{end}.
14255 After the @code{document} command is finished, @code{help} on command
14256 @var{commandname} displays the documentation you have written.
14258 You may use the @code{document} command again to change the
14259 documentation of a command. Redefining the command with @code{define}
14260 does not change the documentation.
14262 @kindex help user-defined
14263 @item help user-defined
14264 List all user-defined commands, with the first line of the documentation
14269 @itemx show user @var{commandname}
14270 Display the @value{GDBN} commands used to define @var{commandname} (but
14271 not its documentation). If no @var{commandname} is given, display the
14272 definitions for all user-defined commands.
14274 @kindex show max-user-call-depth
14275 @kindex set max-user-call-depth
14276 @item show max-user-call-depth
14277 @itemx set max-user-call-depth
14278 The value of @code{max-user-call-depth} controls how many recursion
14279 levels are allowed in user-defined commands before GDB suspects an
14280 infinite recursion and aborts the command.
14284 When user-defined commands are executed, the
14285 commands of the definition are not printed. An error in any command
14286 stops execution of the user-defined command.
14288 If used interactively, commands that would ask for confirmation proceed
14289 without asking when used inside a user-defined command. Many @value{GDBN}
14290 commands that normally print messages to say what they are doing omit the
14291 messages when used in a user-defined command.
14294 @section User-defined command hooks
14295 @cindex command hooks
14296 @cindex hooks, for commands
14297 @cindex hooks, pre-command
14300 You may define @dfn{hooks}, which are a special kind of user-defined
14301 command. Whenever you run the command @samp{foo}, if the user-defined
14302 command @samp{hook-foo} exists, it is executed (with no arguments)
14303 before that command.
14305 @cindex hooks, post-command
14307 A hook may also be defined which is run after the command you executed.
14308 Whenever you run the command @samp{foo}, if the user-defined command
14309 @samp{hookpost-foo} exists, it is executed (with no arguments) after
14310 that command. Post-execution hooks may exist simultaneously with
14311 pre-execution hooks, for the same command.
14313 It is valid for a hook to call the command which it hooks. If this
14314 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
14316 @c It would be nice if hookpost could be passed a parameter indicating
14317 @c if the command it hooks executed properly or not. FIXME!
14319 @kindex stop@r{, a pseudo-command}
14320 In addition, a pseudo-command, @samp{stop} exists. Defining
14321 (@samp{hook-stop}) makes the associated commands execute every time
14322 execution stops in your program: before breakpoint commands are run,
14323 displays are printed, or the stack frame is printed.
14325 For example, to ignore @code{SIGALRM} signals while
14326 single-stepping, but treat them normally during normal execution,
14331 handle SIGALRM nopass
14335 handle SIGALRM pass
14338 define hook-continue
14339 handle SIGLARM pass
14343 As a further example, to hook at the begining and end of the @code{echo}
14344 command, and to add extra text to the beginning and end of the message,
14352 define hookpost-echo
14356 (@value{GDBP}) echo Hello World
14357 <<<---Hello World--->>>
14362 You can define a hook for any single-word command in @value{GDBN}, but
14363 not for command aliases; you should define a hook for the basic command
14364 name, e.g. @code{backtrace} rather than @code{bt}.
14365 @c FIXME! So how does Joe User discover whether a command is an alias
14367 If an error occurs during the execution of your hook, execution of
14368 @value{GDBN} commands stops and @value{GDBN} issues a prompt
14369 (before the command that you actually typed had a chance to run).
14371 If you try to define a hook which does not match any known command, you
14372 get a warning from the @code{define} command.
14374 @node Command Files
14375 @section Command files
14377 @cindex command files
14378 A command file for @value{GDBN} is a file of lines that are @value{GDBN}
14379 commands. Comments (lines starting with @kbd{#}) may also be included.
14380 An empty line in a command file does nothing; it does not mean to repeat
14381 the last command, as it would from the terminal.
14384 @cindex @file{.gdbinit}
14385 @cindex @file{gdb.ini}
14386 When you start @value{GDBN}, it automatically executes commands from its
14387 @dfn{init files}, normally called @file{.gdbinit}@footnote{The DJGPP
14388 port of @value{GDBN} uses the name @file{gdb.ini} instead, due to the
14389 limitations of file names imposed by DOS filesystems.}.
14390 During startup, @value{GDBN} does the following:
14394 Reads the init file (if any) in your home directory@footnote{On
14395 DOS/Windows systems, the home directory is the one pointed to by the
14396 @code{HOME} environment variable.}.
14399 Processes command line options and operands.
14402 Reads the init file (if any) in the current working directory.
14405 Reads command files specified by the @samp{-x} option.
14408 The init file in your home directory can set options (such as @samp{set
14409 complaints}) that affect subsequent processing of command line options
14410 and operands. Init files are not executed if you use the @samp{-nx}
14411 option (@pxref{Mode Options, ,Choosing modes}).
14413 @cindex init file name
14414 On some configurations of @value{GDBN}, the init file is known by a
14415 different name (these are typically environments where a specialized
14416 form of @value{GDBN} may need to coexist with other forms, hence a
14417 different name for the specialized version's init file). These are the
14418 environments with special init file names:
14420 @cindex @file{.vxgdbinit}
14423 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
14425 @cindex @file{.os68gdbinit}
14427 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
14429 @cindex @file{.esgdbinit}
14431 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
14434 You can also request the execution of a command file with the
14435 @code{source} command:
14439 @item source @var{filename}
14440 Execute the command file @var{filename}.
14443 The lines in a command file are executed sequentially. They are not
14444 printed as they are executed. An error in any command terminates
14445 execution of the command file and control is returned to the console.
14447 Commands that would ask for confirmation if used interactively proceed
14448 without asking when used in a command file. Many @value{GDBN} commands that
14449 normally print messages to say what they are doing omit the messages
14450 when called from command files.
14452 @value{GDBN} also accepts command input from standard input. In this
14453 mode, normal output goes to standard output and error output goes to
14454 standard error. Errors in a command file supplied on standard input do
14455 not terminate execution of the command file --- execution continues with
14459 gdb < cmds > log 2>&1
14462 (The syntax above will vary depending on the shell used.) This example
14463 will execute commands from the file @file{cmds}. All output and errors
14464 would be directed to @file{log}.
14467 @section Commands for controlled output
14469 During the execution of a command file or a user-defined command, normal
14470 @value{GDBN} output is suppressed; the only output that appears is what is
14471 explicitly printed by the commands in the definition. This section
14472 describes three commands useful for generating exactly the output you
14477 @item echo @var{text}
14478 @c I do not consider backslash-space a standard C escape sequence
14479 @c because it is not in ANSI.
14480 Print @var{text}. Nonprinting characters can be included in
14481 @var{text} using C escape sequences, such as @samp{\n} to print a
14482 newline. @strong{No newline is printed unless you specify one.}
14483 In addition to the standard C escape sequences, a backslash followed
14484 by a space stands for a space. This is useful for displaying a
14485 string with spaces at the beginning or the end, since leading and
14486 trailing spaces are otherwise trimmed from all arguments.
14487 To print @samp{@w{ }and foo =@w{ }}, use the command
14488 @samp{echo \@w{ }and foo = \@w{ }}.
14490 A backslash at the end of @var{text} can be used, as in C, to continue
14491 the command onto subsequent lines. For example,
14494 echo This is some text\n\
14495 which is continued\n\
14496 onto several lines.\n
14499 produces the same output as
14502 echo This is some text\n
14503 echo which is continued\n
14504 echo onto several lines.\n
14508 @item output @var{expression}
14509 Print the value of @var{expression} and nothing but that value: no
14510 newlines, no @samp{$@var{nn} = }. The value is not entered in the
14511 value history either. @xref{Expressions, ,Expressions}, for more information
14514 @item output/@var{fmt} @var{expression}
14515 Print the value of @var{expression} in format @var{fmt}. You can use
14516 the same formats as for @code{print}. @xref{Output Formats,,Output
14517 formats}, for more information.
14520 @item printf @var{string}, @var{expressions}@dots{}
14521 Print the values of the @var{expressions} under the control of
14522 @var{string}. The @var{expressions} are separated by commas and may be
14523 either numbers or pointers. Their values are printed as specified by
14524 @var{string}, exactly as if your program were to execute the C
14526 @c FIXME: the above implies that at least all ANSI C formats are
14527 @c supported, but it isn't true: %E and %G don't work (or so it seems).
14528 @c Either this is a bug, or the manual should document what formats are
14532 printf (@var{string}, @var{expressions}@dots{});
14535 For example, you can print two values in hex like this:
14538 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
14541 The only backslash-escape sequences that you can use in the format
14542 string are the simple ones that consist of backslash followed by a
14547 @chapter Command Interpreters
14548 @cindex command interpreters
14550 @value{GDBN} supports multiple command interpreters, and some command
14551 infrastructure to allow users or user interface writers to switch
14552 between interpreters or run commands in other interpreters.
14554 @value{GDBN} currently supports two command interpreters, the console
14555 interpreter (sometimes called the command-line interpreter or @sc{cli})
14556 and the machine interface interpreter (or @sc{gdb/mi}). This manual
14557 describes both of these interfaces in great detail.
14559 By default, @value{GDBN} will start with the console interpreter.
14560 However, the user may choose to start @value{GDBN} with another
14561 interpreter by specifying the @option{-i} or @option{--interpreter}
14562 startup options. Defined interpreters include:
14566 @cindex console interpreter
14567 The traditional console or command-line interpreter. This is the most often
14568 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
14569 @value{GDBN} will use this interpreter.
14572 @cindex mi interpreter
14573 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
14574 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
14575 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
14579 @cindex mi2 interpreter
14580 The current @sc{gdb/mi} interface.
14583 @cindex mi1 interpreter
14584 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
14588 @cindex invoke another interpreter
14589 The interpreter being used by @value{GDBN} may not be dynamically
14590 switched at runtime. Although possible, this could lead to a very
14591 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
14592 enters the command "interpreter-set console" in a console view,
14593 @value{GDBN} would switch to using the console interpreter, rendering
14594 the IDE inoperable!
14596 @kindex interpreter-exec
14597 Although you may only choose a single interpreter at startup, you may execute
14598 commands in any interpreter from the current interpreter using the appropriate
14599 command. If you are running the console interpreter, simply use the
14600 @code{interpreter-exec} command:
14603 interpreter-exec mi "-data-list-register-names"
14606 @sc{gdb/mi} has a similar command, although it is only available in versions of
14607 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
14610 @chapter @value{GDBN} Text User Interface
14612 @cindex Text User Interface
14615 * TUI Overview:: TUI overview
14616 * TUI Keys:: TUI key bindings
14617 * TUI Single Key Mode:: TUI single key mode
14618 * TUI Commands:: TUI specific commands
14619 * TUI Configuration:: TUI configuration variables
14622 The @value{GDBN} Text User Interface, TUI in short, is a terminal
14623 interface which uses the @code{curses} library to show the source
14624 file, the assembly output, the program registers and @value{GDBN}
14625 commands in separate text windows.
14627 The TUI is enabled by invoking @value{GDBN} using either
14629 @samp{gdbtui} or @samp{gdb -tui}.
14632 @section TUI overview
14634 The TUI has two display modes that can be switched while
14639 A curses (or TUI) mode in which it displays several text
14640 windows on the terminal.
14643 A standard mode which corresponds to the @value{GDBN} configured without
14647 In the TUI mode, @value{GDBN} can display several text window
14652 This window is the @value{GDBN} command window with the @value{GDBN}
14653 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
14654 managed using readline but through the TUI. The @emph{command}
14655 window is always visible.
14658 The source window shows the source file of the program. The current
14659 line as well as active breakpoints are displayed in this window.
14662 The assembly window shows the disassembly output of the program.
14665 This window shows the processor registers. It detects when
14666 a register is changed and when this is the case, registers that have
14667 changed are highlighted.
14671 The source and assembly windows show the current program position
14672 by highlighting the current line and marking them with the @samp{>} marker.
14673 Breakpoints are also indicated with two markers. A first one
14674 indicates the breakpoint type:
14678 Breakpoint which was hit at least once.
14681 Breakpoint which was never hit.
14684 Hardware breakpoint which was hit at least once.
14687 Hardware breakpoint which was never hit.
14691 The second marker indicates whether the breakpoint is enabled or not:
14695 Breakpoint is enabled.
14698 Breakpoint is disabled.
14702 The source, assembly and register windows are attached to the thread
14703 and the frame position. They are updated when the current thread
14704 changes, when the frame changes or when the program counter changes.
14705 These three windows are arranged by the TUI according to several
14706 layouts. The layout defines which of these three windows are visible.
14707 The following layouts are available:
14717 source and assembly
14720 source and registers
14723 assembly and registers
14727 On top of the command window a status line gives various information
14728 concerning the current process begin debugged. The status line is
14729 updated when the information it shows changes. The following fields
14734 Indicates the current gdb target
14735 (@pxref{Targets, ,Specifying a Debugging Target}).
14738 Gives information about the current process or thread number.
14739 When no process is being debugged, this field is set to @code{No process}.
14742 Gives the current function name for the selected frame.
14743 The name is demangled if demangling is turned on (@pxref{Print Settings}).
14744 When there is no symbol corresponding to the current program counter
14745 the string @code{??} is displayed.
14748 Indicates the current line number for the selected frame.
14749 When the current line number is not known the string @code{??} is displayed.
14752 Indicates the current program counter address.
14757 @section TUI Key Bindings
14758 @cindex TUI key bindings
14760 The TUI installs several key bindings in the readline keymaps
14761 (@pxref{Command Line Editing}).
14762 They allow to leave or enter in the TUI mode or they operate
14763 directly on the TUI layout and windows. The TUI also provides
14764 a @emph{SingleKey} keymap which binds several keys directly to
14765 @value{GDBN} commands. The following key bindings
14766 are installed for both TUI mode and the @value{GDBN} standard mode.
14775 Enter or leave the TUI mode. When the TUI mode is left,
14776 the curses window management is left and @value{GDBN} operates using
14777 its standard mode writing on the terminal directly. When the TUI
14778 mode is entered, the control is given back to the curses windows.
14779 The screen is then refreshed.
14783 Use a TUI layout with only one window. The layout will
14784 either be @samp{source} or @samp{assembly}. When the TUI mode
14785 is not active, it will switch to the TUI mode.
14787 Think of this key binding as the Emacs @kbd{C-x 1} binding.
14791 Use a TUI layout with at least two windows. When the current
14792 layout shows already two windows, a next layout with two windows is used.
14793 When a new layout is chosen, one window will always be common to the
14794 previous layout and the new one.
14796 Think of it as the Emacs @kbd{C-x 2} binding.
14800 Change the active window. The TUI associates several key bindings
14801 (like scrolling and arrow keys) to the active window. This command
14802 gives the focus to the next TUI window.
14804 Think of it as the Emacs @kbd{C-x o} binding.
14808 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
14809 (@pxref{TUI Single Key Mode}).
14813 The following key bindings are handled only by the TUI mode:
14818 Scroll the active window one page up.
14822 Scroll the active window one page down.
14826 Scroll the active window one line up.
14830 Scroll the active window one line down.
14834 Scroll the active window one column left.
14838 Scroll the active window one column right.
14842 Refresh the screen.
14846 In the TUI mode, the arrow keys are used by the active window
14847 for scrolling. This means they are available for readline when the
14848 active window is the command window. When the command window
14849 does not have the focus, it is necessary to use other readline
14850 key bindings such as @key{C-p}, @key{C-n}, @key{C-b} and @key{C-f}.
14852 @node TUI Single Key Mode
14853 @section TUI Single Key Mode
14854 @cindex TUI single key mode
14856 The TUI provides a @emph{SingleKey} mode in which it installs a particular
14857 key binding in the readline keymaps to connect single keys to
14861 @kindex c @r{(SingleKey TUI key)}
14865 @kindex d @r{(SingleKey TUI key)}
14869 @kindex f @r{(SingleKey TUI key)}
14873 @kindex n @r{(SingleKey TUI key)}
14877 @kindex q @r{(SingleKey TUI key)}
14879 exit the @emph{SingleKey} mode.
14881 @kindex r @r{(SingleKey TUI key)}
14885 @kindex s @r{(SingleKey TUI key)}
14889 @kindex u @r{(SingleKey TUI key)}
14893 @kindex v @r{(SingleKey TUI key)}
14897 @kindex w @r{(SingleKey TUI key)}
14903 Other keys temporarily switch to the @value{GDBN} command prompt.
14904 The key that was pressed is inserted in the editing buffer so that
14905 it is possible to type most @value{GDBN} commands without interaction
14906 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
14907 @emph{SingleKey} mode is restored. The only way to permanently leave
14908 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
14912 @section TUI specific commands
14913 @cindex TUI commands
14915 The TUI has specific commands to control the text windows.
14916 These commands are always available, that is they do not depend on
14917 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
14918 is in the standard mode, using these commands will automatically switch
14924 List and give the size of all displayed windows.
14928 Display the next layout.
14931 Display the previous layout.
14934 Display the source window only.
14937 Display the assembly window only.
14940 Display the source and assembly window.
14943 Display the register window together with the source or assembly window.
14945 @item focus next | prev | src | asm | regs | split
14947 Set the focus to the named window.
14948 This command allows to change the active window so that scrolling keys
14949 can be affected to another window.
14953 Refresh the screen. This is similar to using @key{C-L} key.
14955 @item tui reg float
14957 Show the floating point registers in the register window.
14959 @item tui reg general
14960 Show the general registers in the register window.
14963 Show the next register group. The list of register groups as well as
14964 their order is target specific. The predefined register groups are the
14965 following: @code{general}, @code{float}, @code{system}, @code{vector},
14966 @code{all}, @code{save}, @code{restore}.
14968 @item tui reg system
14969 Show the system registers in the register window.
14973 Update the source window and the current execution point.
14975 @item winheight @var{name} +@var{count}
14976 @itemx winheight @var{name} -@var{count}
14978 Change the height of the window @var{name} by @var{count}
14979 lines. Positive counts increase the height, while negative counts
14984 @node TUI Configuration
14985 @section TUI configuration variables
14986 @cindex TUI configuration variables
14988 The TUI has several configuration variables that control the
14989 appearance of windows on the terminal.
14992 @item set tui border-kind @var{kind}
14993 @kindex set tui border-kind
14994 Select the border appearance for the source, assembly and register windows.
14995 The possible values are the following:
14998 Use a space character to draw the border.
15001 Use ascii characters + - and | to draw the border.
15004 Use the Alternate Character Set to draw the border. The border is
15005 drawn using character line graphics if the terminal supports them.
15009 @item set tui active-border-mode @var{mode}
15010 @kindex set tui active-border-mode
15011 Select the attributes to display the border of the active window.
15012 The possible values are @code{normal}, @code{standout}, @code{reverse},
15013 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
15015 @item set tui border-mode @var{mode}
15016 @kindex set tui border-mode
15017 Select the attributes to display the border of other windows.
15018 The @var{mode} can be one of the following:
15021 Use normal attributes to display the border.
15027 Use reverse video mode.
15030 Use half bright mode.
15032 @item half-standout
15033 Use half bright and standout mode.
15036 Use extra bright or bold mode.
15038 @item bold-standout
15039 Use extra bright or bold and standout mode.
15046 @chapter Using @value{GDBN} under @sc{gnu} Emacs
15049 @cindex @sc{gnu} Emacs
15050 A special interface allows you to use @sc{gnu} Emacs to view (and
15051 edit) the source files for the program you are debugging with
15054 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
15055 executable file you want to debug as an argument. This command starts
15056 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
15057 created Emacs buffer.
15058 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
15060 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
15065 All ``terminal'' input and output goes through the Emacs buffer.
15068 This applies both to @value{GDBN} commands and their output, and to the input
15069 and output done by the program you are debugging.
15071 This is useful because it means that you can copy the text of previous
15072 commands and input them again; you can even use parts of the output
15075 All the facilities of Emacs' Shell mode are available for interacting
15076 with your program. In particular, you can send signals the usual
15077 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
15082 @value{GDBN} displays source code through Emacs.
15085 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
15086 source file for that frame and puts an arrow (@samp{=>}) at the
15087 left margin of the current line. Emacs uses a separate buffer for
15088 source display, and splits the screen to show both your @value{GDBN} session
15091 Explicit @value{GDBN} @code{list} or search commands still produce output as
15092 usual, but you probably have no reason to use them from Emacs.
15094 If you specify an absolute file name when prompted for the @kbd{M-x
15095 gdb} argument, then Emacs sets your current working directory to where
15096 your program resides. If you only specify the file name, then Emacs
15097 sets your current working directory to to the directory associated
15098 with the previous buffer. In this case, @value{GDBN} may find your
15099 program by searching your environment's @code{PATH} variable, but on
15100 some operating systems it might not find the source. So, although the
15101 @value{GDBN} input and output session proceeds normally, the auxiliary
15102 buffer does not display the current source and line of execution.
15104 The initial working directory of @value{GDBN} is printed on the top
15105 line of the @value{GDBN} I/O buffer and this serves as a default for
15106 the commands that specify files for @value{GDBN} to operate
15107 on. @xref{Files, ,Commands to specify files}.
15109 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
15110 need to call @value{GDBN} by a different name (for example, if you
15111 keep several configurations around, with different names) you can
15112 customize the Emacs variable @code{gud-gdb-command-name} to run the
15115 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
15116 addition to the standard Shell mode commands:
15120 Describe the features of Emacs' @value{GDBN} Mode.
15123 Execute to another source line, like the @value{GDBN} @code{step} command; also
15124 update the display window to show the current file and location.
15127 Execute to next source line in this function, skipping all function
15128 calls, like the @value{GDBN} @code{next} command. Then update the display window
15129 to show the current file and location.
15132 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
15133 display window accordingly.
15136 Execute until exit from the selected stack frame, like the @value{GDBN}
15137 @code{finish} command.
15140 Continue execution of your program, like the @value{GDBN} @code{continue}
15144 Go up the number of frames indicated by the numeric argument
15145 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
15146 like the @value{GDBN} @code{up} command.
15149 Go down the number of frames indicated by the numeric argument, like the
15150 @value{GDBN} @code{down} command.
15153 In any source file, the Emacs command @kbd{C-x SPC} (@code{gud-break})
15154 tells @value{GDBN} to set a breakpoint on the source line point is on.
15156 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
15157 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
15158 point to any frame in the stack and type @key{RET} to make it become the
15159 current frame and display the associated source in the source buffer.
15160 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
15163 If you accidentally delete the source-display buffer, an easy way to get
15164 it back is to type the command @code{f} in the @value{GDBN} buffer, to
15165 request a frame display; when you run under Emacs, this recreates
15166 the source buffer if necessary to show you the context of the current
15169 The source files displayed in Emacs are in ordinary Emacs buffers
15170 which are visiting the source files in the usual way. You can edit
15171 the files with these buffers if you wish; but keep in mind that @value{GDBN}
15172 communicates with Emacs in terms of line numbers. If you add or
15173 delete lines from the text, the line numbers that @value{GDBN} knows cease
15174 to correspond properly with the code.
15176 The description given here is for GNU Emacs version 21.3 and a more
15177 detailed description of its interaction with @value{GDBN} is given in
15178 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
15180 @c The following dropped because Epoch is nonstandard. Reactivate
15181 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
15183 @kindex Emacs Epoch environment
15187 Version 18 of @sc{gnu} Emacs has a built-in window system
15188 called the @code{epoch}
15189 environment. Users of this environment can use a new command,
15190 @code{inspect} which performs identically to @code{print} except that
15191 each value is printed in its own window.
15196 @chapter The @sc{gdb/mi} Interface
15198 @unnumberedsec Function and Purpose
15200 @cindex @sc{gdb/mi}, its purpose
15201 @sc{gdb/mi} is a line based machine oriented text interface to @value{GDBN}. It is
15202 specifically intended to support the development of systems which use
15203 the debugger as just one small component of a larger system.
15205 This chapter is a specification of the @sc{gdb/mi} interface. It is written
15206 in the form of a reference manual.
15208 Note that @sc{gdb/mi} is still under construction, so some of the
15209 features described below are incomplete and subject to change.
15211 @unnumberedsec Notation and Terminology
15213 @cindex notational conventions, for @sc{gdb/mi}
15214 This chapter uses the following notation:
15218 @code{|} separates two alternatives.
15221 @code{[ @var{something} ]} indicates that @var{something} is optional:
15222 it may or may not be given.
15225 @code{( @var{group} )*} means that @var{group} inside the parentheses
15226 may repeat zero or more times.
15229 @code{( @var{group} )+} means that @var{group} inside the parentheses
15230 may repeat one or more times.
15233 @code{"@var{string}"} means a literal @var{string}.
15237 @heading Dependencies
15240 @heading Acknowledgments
15242 In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
15246 * GDB/MI Command Syntax::
15247 * GDB/MI Compatibility with CLI::
15248 * GDB/MI Output Records::
15249 * GDB/MI Command Description Format::
15250 * GDB/MI Breakpoint Table Commands::
15251 * GDB/MI Data Manipulation::
15252 * GDB/MI Program Control::
15253 * GDB/MI Miscellaneous Commands::
15255 * GDB/MI Kod Commands::
15256 * GDB/MI Memory Overlay Commands::
15257 * GDB/MI Signal Handling Commands::
15259 * GDB/MI Stack Manipulation::
15260 * GDB/MI Symbol Query::
15261 * GDB/MI Target Manipulation::
15262 * GDB/MI Thread Commands::
15263 * GDB/MI Tracepoint Commands::
15264 * GDB/MI Variable Objects::
15267 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15268 @node GDB/MI Command Syntax
15269 @section @sc{gdb/mi} Command Syntax
15272 * GDB/MI Input Syntax::
15273 * GDB/MI Output Syntax::
15274 * GDB/MI Simple Examples::
15277 @node GDB/MI Input Syntax
15278 @subsection @sc{gdb/mi} Input Syntax
15280 @cindex input syntax for @sc{gdb/mi}
15281 @cindex @sc{gdb/mi}, input syntax
15283 @item @var{command} @expansion{}
15284 @code{@var{cli-command} | @var{mi-command}}
15286 @item @var{cli-command} @expansion{}
15287 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
15288 @var{cli-command} is any existing @value{GDBN} CLI command.
15290 @item @var{mi-command} @expansion{}
15291 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
15292 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
15294 @item @var{token} @expansion{}
15295 "any sequence of digits"
15297 @item @var{option} @expansion{}
15298 @code{"-" @var{parameter} [ " " @var{parameter} ]}
15300 @item @var{parameter} @expansion{}
15301 @code{@var{non-blank-sequence} | @var{c-string}}
15303 @item @var{operation} @expansion{}
15304 @emph{any of the operations described in this chapter}
15306 @item @var{non-blank-sequence} @expansion{}
15307 @emph{anything, provided it doesn't contain special characters such as
15308 "-", @var{nl}, """ and of course " "}
15310 @item @var{c-string} @expansion{}
15311 @code{""" @var{seven-bit-iso-c-string-content} """}
15313 @item @var{nl} @expansion{}
15322 The CLI commands are still handled by the @sc{mi} interpreter; their
15323 output is described below.
15326 The @code{@var{token}}, when present, is passed back when the command
15330 Some @sc{mi} commands accept optional arguments as part of the parameter
15331 list. Each option is identified by a leading @samp{-} (dash) and may be
15332 followed by an optional argument parameter. Options occur first in the
15333 parameter list and can be delimited from normal parameters using
15334 @samp{--} (this is useful when some parameters begin with a dash).
15341 We want easy access to the existing CLI syntax (for debugging).
15344 We want it to be easy to spot a @sc{mi} operation.
15347 @node GDB/MI Output Syntax
15348 @subsection @sc{gdb/mi} Output Syntax
15350 @cindex output syntax of @sc{gdb/mi}
15351 @cindex @sc{gdb/mi}, output syntax
15352 The output from @sc{gdb/mi} consists of zero or more out-of-band records
15353 followed, optionally, by a single result record. This result record
15354 is for the most recent command. The sequence of output records is
15355 terminated by @samp{(@value{GDBP})}.
15357 If an input command was prefixed with a @code{@var{token}} then the
15358 corresponding output for that command will also be prefixed by that same
15362 @item @var{output} @expansion{}
15363 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(@value{GDBP})" @var{nl}}
15365 @item @var{result-record} @expansion{}
15366 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
15368 @item @var{out-of-band-record} @expansion{}
15369 @code{@var{async-record} | @var{stream-record}}
15371 @item @var{async-record} @expansion{}
15372 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
15374 @item @var{exec-async-output} @expansion{}
15375 @code{[ @var{token} ] "*" @var{async-output}}
15377 @item @var{status-async-output} @expansion{}
15378 @code{[ @var{token} ] "+" @var{async-output}}
15380 @item @var{notify-async-output} @expansion{}
15381 @code{[ @var{token} ] "=" @var{async-output}}
15383 @item @var{async-output} @expansion{}
15384 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
15386 @item @var{result-class} @expansion{}
15387 @code{"done" | "running" | "connected" | "error" | "exit"}
15389 @item @var{async-class} @expansion{}
15390 @code{"stopped" | @var{others}} (where @var{others} will be added
15391 depending on the needs---this is still in development).
15393 @item @var{result} @expansion{}
15394 @code{ @var{variable} "=" @var{value}}
15396 @item @var{variable} @expansion{}
15397 @code{ @var{string} }
15399 @item @var{value} @expansion{}
15400 @code{ @var{const} | @var{tuple} | @var{list} }
15402 @item @var{const} @expansion{}
15403 @code{@var{c-string}}
15405 @item @var{tuple} @expansion{}
15406 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
15408 @item @var{list} @expansion{}
15409 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
15410 @var{result} ( "," @var{result} )* "]" }
15412 @item @var{stream-record} @expansion{}
15413 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
15415 @item @var{console-stream-output} @expansion{}
15416 @code{"~" @var{c-string}}
15418 @item @var{target-stream-output} @expansion{}
15419 @code{"@@" @var{c-string}}
15421 @item @var{log-stream-output} @expansion{}
15422 @code{"&" @var{c-string}}
15424 @item @var{nl} @expansion{}
15427 @item @var{token} @expansion{}
15428 @emph{any sequence of digits}.
15436 All output sequences end in a single line containing a period.
15439 The @code{@var{token}} is from the corresponding request. If an execution
15440 command is interrupted by the @samp{-exec-interrupt} command, the
15441 @var{token} associated with the @samp{*stopped} message is the one of the
15442 original execution command, not the one of the interrupt command.
15445 @cindex status output in @sc{gdb/mi}
15446 @var{status-async-output} contains on-going status information about the
15447 progress of a slow operation. It can be discarded. All status output is
15448 prefixed by @samp{+}.
15451 @cindex async output in @sc{gdb/mi}
15452 @var{exec-async-output} contains asynchronous state change on the target
15453 (stopped, started, disappeared). All async output is prefixed by
15457 @cindex notify output in @sc{gdb/mi}
15458 @var{notify-async-output} contains supplementary information that the
15459 client should handle (e.g., a new breakpoint information). All notify
15460 output is prefixed by @samp{=}.
15463 @cindex console output in @sc{gdb/mi}
15464 @var{console-stream-output} is output that should be displayed as is in the
15465 console. It is the textual response to a CLI command. All the console
15466 output is prefixed by @samp{~}.
15469 @cindex target output in @sc{gdb/mi}
15470 @var{target-stream-output} is the output produced by the target program.
15471 All the target output is prefixed by @samp{@@}.
15474 @cindex log output in @sc{gdb/mi}
15475 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
15476 instance messages that should be displayed as part of an error log. All
15477 the log output is prefixed by @samp{&}.
15480 @cindex list output in @sc{gdb/mi}
15481 New @sc{gdb/mi} commands should only output @var{lists} containing
15487 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
15488 details about the various output records.
15490 @node GDB/MI Simple Examples
15491 @subsection Simple Examples of @sc{gdb/mi} Interaction
15492 @cindex @sc{gdb/mi}, simple examples
15494 This subsection presents several simple examples of interaction using
15495 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
15496 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
15497 the output received from @sc{gdb/mi}.
15499 @subsubheading Target Stop
15500 @c Ummm... There is no "-stop" command. This assumes async, no?
15501 Here's an example of stopping the inferior process:
15512 <- *stop,reason="stop",address="0x123",source="a.c:123"
15516 @subsubheading Simple CLI Command
15518 Here's an example of a simple CLI command being passed through
15519 @sc{gdb/mi} and on to the CLI.
15529 @subsubheading Command With Side Effects
15532 -> -symbol-file xyz.exe
15533 <- *breakpoint,nr="3",address="0x123",source="a.c:123"
15537 @subsubheading A Bad Command
15539 Here's what happens if you pass a non-existent command:
15543 <- ^error,msg="Undefined MI command: rubbish"
15547 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15548 @node GDB/MI Compatibility with CLI
15549 @section @sc{gdb/mi} Compatibility with CLI
15551 @cindex compatibility, @sc{gdb/mi} and CLI
15552 @cindex @sc{gdb/mi}, compatibility with CLI
15553 To help users familiar with @value{GDBN}'s existing CLI interface, @sc{gdb/mi}
15554 accepts existing CLI commands. As specified by the syntax, such
15555 commands can be directly entered into the @sc{gdb/mi} interface and @value{GDBN} will
15558 This mechanism is provided as an aid to developers of @sc{gdb/mi}
15559 clients and not as a reliable interface into the CLI. Since the command
15560 is being interpreteted in an environment that assumes @sc{gdb/mi}
15561 behaviour, the exact output of such commands is likely to end up being
15562 an un-supported hybrid of @sc{gdb/mi} and CLI output.
15564 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15565 @node GDB/MI Output Records
15566 @section @sc{gdb/mi} Output Records
15569 * GDB/MI Result Records::
15570 * GDB/MI Stream Records::
15571 * GDB/MI Out-of-band Records::
15574 @node GDB/MI Result Records
15575 @subsection @sc{gdb/mi} Result Records
15577 @cindex result records in @sc{gdb/mi}
15578 @cindex @sc{gdb/mi}, result records
15579 In addition to a number of out-of-band notifications, the response to a
15580 @sc{gdb/mi} command includes one of the following result indications:
15584 @item "^done" [ "," @var{results} ]
15585 The synchronous operation was successful, @code{@var{results}} are the return
15590 @c Is this one correct? Should it be an out-of-band notification?
15591 The asynchronous operation was successfully started. The target is
15594 @item "^error" "," @var{c-string}
15596 The operation failed. The @code{@var{c-string}} contains the corresponding
15600 @node GDB/MI Stream Records
15601 @subsection @sc{gdb/mi} Stream Records
15603 @cindex @sc{gdb/mi}, stream records
15604 @cindex stream records in @sc{gdb/mi}
15605 @value{GDBN} internally maintains a number of output streams: the console, the
15606 target, and the log. The output intended for each of these streams is
15607 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
15609 Each stream record begins with a unique @dfn{prefix character} which
15610 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
15611 Syntax}). In addition to the prefix, each stream record contains a
15612 @code{@var{string-output}}. This is either raw text (with an implicit new
15613 line) or a quoted C string (which does not contain an implicit newline).
15616 @item "~" @var{string-output}
15617 The console output stream contains text that should be displayed in the
15618 CLI console window. It contains the textual responses to CLI commands.
15620 @item "@@" @var{string-output}
15621 The target output stream contains any textual output from the running
15624 @item "&" @var{string-output}
15625 The log stream contains debugging messages being produced by @value{GDBN}'s
15629 @node GDB/MI Out-of-band Records
15630 @subsection @sc{gdb/mi} Out-of-band Records
15632 @cindex out-of-band records in @sc{gdb/mi}
15633 @cindex @sc{gdb/mi}, out-of-band records
15634 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
15635 additional changes that have occurred. Those changes can either be a
15636 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
15637 target activity (e.g., target stopped).
15639 The following is a preliminary list of possible out-of-band records.
15646 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15647 @node GDB/MI Command Description Format
15648 @section @sc{gdb/mi} Command Description Format
15650 The remaining sections describe blocks of commands. Each block of
15651 commands is laid out in a fashion similar to this section.
15653 Note the the line breaks shown in the examples are here only for
15654 readability. They don't appear in the real output.
15655 Also note that the commands with a non-available example (N.A.@:) are
15656 not yet implemented.
15658 @subheading Motivation
15660 The motivation for this collection of commands.
15662 @subheading Introduction
15664 A brief introduction to this collection of commands as a whole.
15666 @subheading Commands
15668 For each command in the block, the following is described:
15670 @subsubheading Synopsis
15673 -command @var{args}@dots{}
15676 @subsubheading @value{GDBN} Command
15678 The corresponding @value{GDBN} CLI command.
15680 @subsubheading Result
15682 @subsubheading Out-of-band
15684 @subsubheading Notes
15686 @subsubheading Example
15689 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15690 @node GDB/MI Breakpoint Table Commands
15691 @section @sc{gdb/mi} Breakpoint table commands
15693 @cindex breakpoint commands for @sc{gdb/mi}
15694 @cindex @sc{gdb/mi}, breakpoint commands
15695 This section documents @sc{gdb/mi} commands for manipulating
15698 @subheading The @code{-break-after} Command
15699 @findex -break-after
15701 @subsubheading Synopsis
15704 -break-after @var{number} @var{count}
15707 The breakpoint number @var{number} is not in effect until it has been
15708 hit @var{count} times. To see how this is reflected in the output of
15709 the @samp{-break-list} command, see the description of the
15710 @samp{-break-list} command below.
15712 @subsubheading @value{GDBN} Command
15714 The corresponding @value{GDBN} command is @samp{ignore}.
15716 @subsubheading Example
15721 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",line="5"@}
15728 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15729 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15730 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15731 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15732 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15733 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15734 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15735 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15736 addr="0x000100d0",func="main",file="hello.c",line="5",times="0",
15742 @subheading The @code{-break-catch} Command
15743 @findex -break-catch
15745 @subheading The @code{-break-commands} Command
15746 @findex -break-commands
15750 @subheading The @code{-break-condition} Command
15751 @findex -break-condition
15753 @subsubheading Synopsis
15756 -break-condition @var{number} @var{expr}
15759 Breakpoint @var{number} will stop the program only if the condition in
15760 @var{expr} is true. The condition becomes part of the
15761 @samp{-break-list} output (see the description of the @samp{-break-list}
15764 @subsubheading @value{GDBN} Command
15766 The corresponding @value{GDBN} command is @samp{condition}.
15768 @subsubheading Example
15772 -break-condition 1 1
15776 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15777 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15778 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15779 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15780 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15781 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15782 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15783 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15784 addr="0x000100d0",func="main",file="hello.c",line="5",cond="1",
15785 times="0",ignore="3"@}]@}
15789 @subheading The @code{-break-delete} Command
15790 @findex -break-delete
15792 @subsubheading Synopsis
15795 -break-delete ( @var{breakpoint} )+
15798 Delete the breakpoint(s) whose number(s) are specified in the argument
15799 list. This is obviously reflected in the breakpoint list.
15801 @subsubheading @value{GDBN} command
15803 The corresponding @value{GDBN} command is @samp{delete}.
15805 @subsubheading Example
15813 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
15814 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15815 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15816 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15817 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15818 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15819 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15824 @subheading The @code{-break-disable} Command
15825 @findex -break-disable
15827 @subsubheading Synopsis
15830 -break-disable ( @var{breakpoint} )+
15833 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
15834 break list is now set to @samp{n} for the named @var{breakpoint}(s).
15836 @subsubheading @value{GDBN} Command
15838 The corresponding @value{GDBN} command is @samp{disable}.
15840 @subsubheading Example
15848 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15849 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15850 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15851 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15852 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15853 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15854 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15855 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
15856 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
15860 @subheading The @code{-break-enable} Command
15861 @findex -break-enable
15863 @subsubheading Synopsis
15866 -break-enable ( @var{breakpoint} )+
15869 Enable (previously disabled) @var{breakpoint}(s).
15871 @subsubheading @value{GDBN} Command
15873 The corresponding @value{GDBN} command is @samp{enable}.
15875 @subsubheading Example
15883 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15884 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15885 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15886 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15887 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15888 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15889 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15890 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
15891 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
15895 @subheading The @code{-break-info} Command
15896 @findex -break-info
15898 @subsubheading Synopsis
15901 -break-info @var{breakpoint}
15905 Get information about a single breakpoint.
15907 @subsubheading @value{GDBN} command
15909 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
15911 @subsubheading Example
15914 @subheading The @code{-break-insert} Command
15915 @findex -break-insert
15917 @subsubheading Synopsis
15920 -break-insert [ -t ] [ -h ] [ -r ]
15921 [ -c @var{condition} ] [ -i @var{ignore-count} ]
15922 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
15926 If specified, @var{line}, can be one of:
15933 @item filename:linenum
15934 @item filename:function
15938 The possible optional parameters of this command are:
15942 Insert a tempoary breakpoint.
15944 Insert a hardware breakpoint.
15945 @item -c @var{condition}
15946 Make the breakpoint conditional on @var{condition}.
15947 @item -i @var{ignore-count}
15948 Initialize the @var{ignore-count}.
15950 Insert a regular breakpoint in all the functions whose names match the
15951 given regular expression. Other flags are not applicable to regular
15955 @subsubheading Result
15957 The result is in the form:
15960 ^done,bkptno="@var{number}",func="@var{funcname}",
15961 file="@var{filename}",line="@var{lineno}"
15965 where @var{number} is the @value{GDBN} number for this breakpoint, @var{funcname}
15966 is the name of the function where the breakpoint was inserted,
15967 @var{filename} is the name of the source file which contains this
15968 function, and @var{lineno} is the source line number within that file.
15970 Note: this format is open to change.
15971 @c An out-of-band breakpoint instead of part of the result?
15973 @subsubheading @value{GDBN} Command
15975 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
15976 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
15978 @subsubheading Example
15983 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
15985 -break-insert -t foo
15986 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",line="11"@}
15989 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15990 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15991 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15992 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15993 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15994 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15995 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15996 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15997 addr="0x0001072c", func="main",file="recursive2.c",line="4",times="0"@},
15998 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
15999 addr="0x00010774",func="foo",file="recursive2.c",line="11",times="0"@}]@}
16001 -break-insert -r foo.*
16002 ~int foo(int, int);
16003 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c",line="11"@}
16007 @subheading The @code{-break-list} Command
16008 @findex -break-list
16010 @subsubheading Synopsis
16016 Displays the list of inserted breakpoints, showing the following fields:
16020 number of the breakpoint
16022 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
16024 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
16027 is the breakpoint enabled or no: @samp{y} or @samp{n}
16029 memory location at which the breakpoint is set
16031 logical location of the breakpoint, expressed by function name, file
16034 number of times the breakpoint has been hit
16037 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
16038 @code{body} field is an empty list.
16040 @subsubheading @value{GDBN} Command
16042 The corresponding @value{GDBN} command is @samp{info break}.
16044 @subsubheading Example
16049 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
16050 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
16051 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
16052 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
16053 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
16054 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
16055 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
16056 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
16057 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
16058 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
16059 addr="0x00010114",func="foo",file="hello.c",line="13",times="0"@}]@}
16063 Here's an example of the result when there are no breakpoints:
16068 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
16069 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
16070 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
16071 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
16072 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
16073 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
16074 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
16079 @subheading The @code{-break-watch} Command
16080 @findex -break-watch
16082 @subsubheading Synopsis
16085 -break-watch [ -a | -r ]
16088 Create a watchpoint. With the @samp{-a} option it will create an
16089 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
16090 read from or on a write to the memory location. With the @samp{-r}
16091 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
16092 trigger only when the memory location is accessed for reading. Without
16093 either of the options, the watchpoint created is a regular watchpoint,
16094 i.e. it will trigger when the memory location is accessed for writing.
16095 @xref{Set Watchpoints, , Setting watchpoints}.
16097 Note that @samp{-break-list} will report a single list of watchpoints and
16098 breakpoints inserted.
16100 @subsubheading @value{GDBN} Command
16102 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
16105 @subsubheading Example
16107 Setting a watchpoint on a variable in the @code{main} function:
16112 ^done,wpt=@{number="2",exp="x"@}
16116 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
16117 value=@{old="-268439212",new="55"@},
16118 frame=@{func="main",args=[],file="recursive2.c",line="5"@}
16122 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
16123 the program execution twice: first for the variable changing value, then
16124 for the watchpoint going out of scope.
16129 ^done,wpt=@{number="5",exp="C"@}
16133 ^done,reason="watchpoint-trigger",
16134 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
16135 frame=@{func="callee4",args=[],
16136 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
16140 ^done,reason="watchpoint-scope",wpnum="5",
16141 frame=@{func="callee3",args=[@{name="strarg",
16142 value="0x11940 \"A string argument.\""@}],
16143 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
16147 Listing breakpoints and watchpoints, at different points in the program
16148 execution. Note that once the watchpoint goes out of scope, it is
16154 ^done,wpt=@{number="2",exp="C"@}
16157 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
16158 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
16159 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
16160 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
16161 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
16162 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
16163 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
16164 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
16165 addr="0x00010734",func="callee4",
16166 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
16167 bkpt=@{number="2",type="watchpoint",disp="keep",
16168 enabled="y",addr="",what="C",times="0"@}]@}
16172 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
16173 value=@{old="-276895068",new="3"@},
16174 frame=@{func="callee4",args=[],
16175 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
16178 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
16179 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
16180 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
16181 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
16182 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
16183 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
16184 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
16185 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
16186 addr="0x00010734",func="callee4",
16187 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
16188 bkpt=@{number="2",type="watchpoint",disp="keep",
16189 enabled="y",addr="",what="C",times="-5"@}]@}
16193 ^done,reason="watchpoint-scope",wpnum="2",
16194 frame=@{func="callee3",args=[@{name="strarg",
16195 value="0x11940 \"A string argument.\""@}],
16196 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
16199 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
16200 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
16201 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
16202 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
16203 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
16204 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
16205 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
16206 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
16207 addr="0x00010734",func="callee4",
16208 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@}]@}
16212 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16213 @node GDB/MI Data Manipulation
16214 @section @sc{gdb/mi} Data Manipulation
16216 @cindex data manipulation, in @sc{gdb/mi}
16217 @cindex @sc{gdb/mi}, data manipulation
16218 This section describes the @sc{gdb/mi} commands that manipulate data:
16219 examine memory and registers, evaluate expressions, etc.
16221 @c REMOVED FROM THE INTERFACE.
16222 @c @subheading -data-assign
16223 @c Change the value of a program variable. Plenty of side effects.
16224 @c @subsubheading GDB command
16226 @c @subsubheading Example
16229 @subheading The @code{-data-disassemble} Command
16230 @findex -data-disassemble
16232 @subsubheading Synopsis
16236 [ -s @var{start-addr} -e @var{end-addr} ]
16237 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
16245 @item @var{start-addr}
16246 is the beginning address (or @code{$pc})
16247 @item @var{end-addr}
16249 @item @var{filename}
16250 is the name of the file to disassemble
16251 @item @var{linenum}
16252 is the line number to disassemble around
16254 is the the number of disassembly lines to be produced. If it is -1,
16255 the whole function will be disassembled, in case no @var{end-addr} is
16256 specified. If @var{end-addr} is specified as a non-zero value, and
16257 @var{lines} is lower than the number of disassembly lines between
16258 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
16259 displayed; if @var{lines} is higher than the number of lines between
16260 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
16263 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
16267 @subsubheading Result
16269 The output for each instruction is composed of four fields:
16278 Note that whatever included in the instruction field, is not manipulated
16279 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
16281 @subsubheading @value{GDBN} Command
16283 There's no direct mapping from this command to the CLI.
16285 @subsubheading Example
16287 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
16291 -data-disassemble -s $pc -e "$pc + 20" -- 0
16294 @{address="0x000107c0",func-name="main",offset="4",
16295 inst="mov 2, %o0"@},
16296 @{address="0x000107c4",func-name="main",offset="8",
16297 inst="sethi %hi(0x11800), %o2"@},
16298 @{address="0x000107c8",func-name="main",offset="12",
16299 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
16300 @{address="0x000107cc",func-name="main",offset="16",
16301 inst="sethi %hi(0x11800), %o2"@},
16302 @{address="0x000107d0",func-name="main",offset="20",
16303 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
16307 Disassemble the whole @code{main} function. Line 32 is part of
16311 -data-disassemble -f basics.c -l 32 -- 0
16313 @{address="0x000107bc",func-name="main",offset="0",
16314 inst="save %sp, -112, %sp"@},
16315 @{address="0x000107c0",func-name="main",offset="4",
16316 inst="mov 2, %o0"@},
16317 @{address="0x000107c4",func-name="main",offset="8",
16318 inst="sethi %hi(0x11800), %o2"@},
16320 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
16321 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
16325 Disassemble 3 instructions from the start of @code{main}:
16329 -data-disassemble -f basics.c -l 32 -n 3 -- 0
16331 @{address="0x000107bc",func-name="main",offset="0",
16332 inst="save %sp, -112, %sp"@},
16333 @{address="0x000107c0",func-name="main",offset="4",
16334 inst="mov 2, %o0"@},
16335 @{address="0x000107c4",func-name="main",offset="8",
16336 inst="sethi %hi(0x11800), %o2"@}]
16340 Disassemble 3 instructions from the start of @code{main} in mixed mode:
16344 -data-disassemble -f basics.c -l 32 -n 3 -- 1
16346 src_and_asm_line=@{line="31",
16347 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
16348 testsuite/gdb.mi/basics.c",line_asm_insn=[
16349 @{address="0x000107bc",func-name="main",offset="0",
16350 inst="save %sp, -112, %sp"@}]@},
16351 src_and_asm_line=@{line="32",
16352 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
16353 testsuite/gdb.mi/basics.c",line_asm_insn=[
16354 @{address="0x000107c0",func-name="main",offset="4",
16355 inst="mov 2, %o0"@},
16356 @{address="0x000107c4",func-name="main",offset="8",
16357 inst="sethi %hi(0x11800), %o2"@}]@}]
16362 @subheading The @code{-data-evaluate-expression} Command
16363 @findex -data-evaluate-expression
16365 @subsubheading Synopsis
16368 -data-evaluate-expression @var{expr}
16371 Evaluate @var{expr} as an expression. The expression could contain an
16372 inferior function call. The function call will execute synchronously.
16373 If the expression contains spaces, it must be enclosed in double quotes.
16375 @subsubheading @value{GDBN} Command
16377 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
16378 @samp{call}. In @code{gdbtk} only, there's a corresponding
16379 @samp{gdb_eval} command.
16381 @subsubheading Example
16383 In the following example, the numbers that precede the commands are the
16384 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
16385 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
16389 211-data-evaluate-expression A
16392 311-data-evaluate-expression &A
16393 311^done,value="0xefffeb7c"
16395 411-data-evaluate-expression A+3
16398 511-data-evaluate-expression "A + 3"
16404 @subheading The @code{-data-list-changed-registers} Command
16405 @findex -data-list-changed-registers
16407 @subsubheading Synopsis
16410 -data-list-changed-registers
16413 Display a list of the registers that have changed.
16415 @subsubheading @value{GDBN} Command
16417 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
16418 has the corresponding command @samp{gdb_changed_register_list}.
16420 @subsubheading Example
16422 On a PPC MBX board:
16430 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
16431 args=[],file="try.c",line="5"@}
16433 -data-list-changed-registers
16434 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
16435 "10","11","13","14","15","16","17","18","19","20","21","22","23",
16436 "24","25","26","27","28","30","31","64","65","66","67","69"]
16441 @subheading The @code{-data-list-register-names} Command
16442 @findex -data-list-register-names
16444 @subsubheading Synopsis
16447 -data-list-register-names [ ( @var{regno} )+ ]
16450 Show a list of register names for the current target. If no arguments
16451 are given, it shows a list of the names of all the registers. If
16452 integer numbers are given as arguments, it will print a list of the
16453 names of the registers corresponding to the arguments. To ensure
16454 consistency between a register name and its number, the output list may
16455 include empty register names.
16457 @subsubheading @value{GDBN} Command
16459 @value{GDBN} does not have a command which corresponds to
16460 @samp{-data-list-register-names}. In @code{gdbtk} there is a
16461 corresponding command @samp{gdb_regnames}.
16463 @subsubheading Example
16465 For the PPC MBX board:
16468 -data-list-register-names
16469 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
16470 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
16471 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
16472 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
16473 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
16474 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
16475 "", "pc","ps","cr","lr","ctr","xer"]
16477 -data-list-register-names 1 2 3
16478 ^done,register-names=["r1","r2","r3"]
16482 @subheading The @code{-data-list-register-values} Command
16483 @findex -data-list-register-values
16485 @subsubheading Synopsis
16488 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
16491 Display the registers' contents. @var{fmt} is the format according to
16492 which the registers' contents are to be returned, followed by an optional
16493 list of numbers specifying the registers to display. A missing list of
16494 numbers indicates that the contents of all the registers must be returned.
16496 Allowed formats for @var{fmt} are:
16513 @subsubheading @value{GDBN} Command
16515 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
16516 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
16518 @subsubheading Example
16520 For a PPC MBX board (note: line breaks are for readability only, they
16521 don't appear in the actual output):
16525 -data-list-register-values r 64 65
16526 ^done,register-values=[@{number="64",value="0xfe00a300"@},
16527 @{number="65",value="0x00029002"@}]
16529 -data-list-register-values x
16530 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
16531 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
16532 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
16533 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
16534 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
16535 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
16536 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
16537 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
16538 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
16539 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
16540 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
16541 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
16542 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
16543 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
16544 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
16545 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
16546 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
16547 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
16548 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
16549 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
16550 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
16551 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
16552 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
16553 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
16554 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
16555 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
16556 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
16557 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
16558 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
16559 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
16560 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
16561 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
16562 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
16563 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
16564 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
16565 @{number="69",value="0x20002b03"@}]
16570 @subheading The @code{-data-read-memory} Command
16571 @findex -data-read-memory
16573 @subsubheading Synopsis
16576 -data-read-memory [ -o @var{byte-offset} ]
16577 @var{address} @var{word-format} @var{word-size}
16578 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
16585 @item @var{address}
16586 An expression specifying the address of the first memory word to be
16587 read. Complex expressions containing embedded white space should be
16588 quoted using the C convention.
16590 @item @var{word-format}
16591 The format to be used to print the memory words. The notation is the
16592 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
16595 @item @var{word-size}
16596 The size of each memory word in bytes.
16598 @item @var{nr-rows}
16599 The number of rows in the output table.
16601 @item @var{nr-cols}
16602 The number of columns in the output table.
16605 If present, indicates that each row should include an @sc{ascii} dump. The
16606 value of @var{aschar} is used as a padding character when a byte is not a
16607 member of the printable @sc{ascii} character set (printable @sc{ascii}
16608 characters are those whose code is between 32 and 126, inclusively).
16610 @item @var{byte-offset}
16611 An offset to add to the @var{address} before fetching memory.
16614 This command displays memory contents as a table of @var{nr-rows} by
16615 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
16616 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
16617 (returned as @samp{total-bytes}). Should less than the requested number
16618 of bytes be returned by the target, the missing words are identified
16619 using @samp{N/A}. The number of bytes read from the target is returned
16620 in @samp{nr-bytes} and the starting address used to read memory in
16623 The address of the next/previous row or page is available in
16624 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
16627 @subsubheading @value{GDBN} Command
16629 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
16630 @samp{gdb_get_mem} memory read command.
16632 @subsubheading Example
16634 Read six bytes of memory starting at @code{bytes+6} but then offset by
16635 @code{-6} bytes. Format as three rows of two columns. One byte per
16636 word. Display each word in hex.
16640 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
16641 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
16642 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
16643 prev-page="0x0000138a",memory=[
16644 @{addr="0x00001390",data=["0x00","0x01"]@},
16645 @{addr="0x00001392",data=["0x02","0x03"]@},
16646 @{addr="0x00001394",data=["0x04","0x05"]@}]
16650 Read two bytes of memory starting at address @code{shorts + 64} and
16651 display as a single word formatted in decimal.
16655 5-data-read-memory shorts+64 d 2 1 1
16656 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
16657 next-row="0x00001512",prev-row="0x0000150e",
16658 next-page="0x00001512",prev-page="0x0000150e",memory=[
16659 @{addr="0x00001510",data=["128"]@}]
16663 Read thirty two bytes of memory starting at @code{bytes+16} and format
16664 as eight rows of four columns. Include a string encoding with @samp{x}
16665 used as the non-printable character.
16669 4-data-read-memory bytes+16 x 1 8 4 x
16670 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
16671 next-row="0x000013c0",prev-row="0x0000139c",
16672 next-page="0x000013c0",prev-page="0x00001380",memory=[
16673 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
16674 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
16675 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
16676 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
16677 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
16678 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
16679 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
16680 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
16684 @subheading The @code{-display-delete} Command
16685 @findex -display-delete
16687 @subsubheading Synopsis
16690 -display-delete @var{number}
16693 Delete the display @var{number}.
16695 @subsubheading @value{GDBN} Command
16697 The corresponding @value{GDBN} command is @samp{delete display}.
16699 @subsubheading Example
16703 @subheading The @code{-display-disable} Command
16704 @findex -display-disable
16706 @subsubheading Synopsis
16709 -display-disable @var{number}
16712 Disable display @var{number}.
16714 @subsubheading @value{GDBN} Command
16716 The corresponding @value{GDBN} command is @samp{disable display}.
16718 @subsubheading Example
16722 @subheading The @code{-display-enable} Command
16723 @findex -display-enable
16725 @subsubheading Synopsis
16728 -display-enable @var{number}
16731 Enable display @var{number}.
16733 @subsubheading @value{GDBN} Command
16735 The corresponding @value{GDBN} command is @samp{enable display}.
16737 @subsubheading Example
16741 @subheading The @code{-display-insert} Command
16742 @findex -display-insert
16744 @subsubheading Synopsis
16747 -display-insert @var{expression}
16750 Display @var{expression} every time the program stops.
16752 @subsubheading @value{GDBN} Command
16754 The corresponding @value{GDBN} command is @samp{display}.
16756 @subsubheading Example
16760 @subheading The @code{-display-list} Command
16761 @findex -display-list
16763 @subsubheading Synopsis
16769 List the displays. Do not show the current values.
16771 @subsubheading @value{GDBN} Command
16773 The corresponding @value{GDBN} command is @samp{info display}.
16775 @subsubheading Example
16779 @subheading The @code{-environment-cd} Command
16780 @findex -environment-cd
16782 @subsubheading Synopsis
16785 -environment-cd @var{pathdir}
16788 Set @value{GDBN}'s working directory.
16790 @subsubheading @value{GDBN} Command
16792 The corresponding @value{GDBN} command is @samp{cd}.
16794 @subsubheading Example
16798 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
16804 @subheading The @code{-environment-directory} Command
16805 @findex -environment-directory
16807 @subsubheading Synopsis
16810 -environment-directory [ -r ] [ @var{pathdir} ]+
16813 Add directories @var{pathdir} to beginning of search path for source files.
16814 If the @samp{-r} option is used, the search path is reset to the default
16815 search path. If directories @var{pathdir} are supplied in addition to the
16816 @samp{-r} option, the search path is first reset and then addition
16818 Multiple directories may be specified, separated by blanks. Specifying
16819 multiple directories in a single command
16820 results in the directories added to the beginning of the
16821 search path in the same order they were presented in the command.
16822 If blanks are needed as
16823 part of a directory name, double-quotes should be used around
16824 the name. In the command output, the path will show up separated
16825 by the system directory-separator character. The directory-seperator
16826 character must not be used
16827 in any directory name.
16828 If no directories are specified, the current search path is displayed.
16830 @subsubheading @value{GDBN} Command
16832 The corresponding @value{GDBN} command is @samp{dir}.
16834 @subsubheading Example
16838 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
16839 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
16841 -environment-directory ""
16842 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
16844 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
16845 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
16847 -environment-directory -r
16848 ^done,source-path="$cdir:$cwd"
16853 @subheading The @code{-environment-path} Command
16854 @findex -environment-path
16856 @subsubheading Synopsis
16859 -environment-path [ -r ] [ @var{pathdir} ]+
16862 Add directories @var{pathdir} to beginning of search path for object files.
16863 If the @samp{-r} option is used, the search path is reset to the original
16864 search path that existed at gdb start-up. If directories @var{pathdir} are
16865 supplied in addition to the
16866 @samp{-r} option, the search path is first reset and then addition
16868 Multiple directories may be specified, separated by blanks. Specifying
16869 multiple directories in a single command
16870 results in the directories added to the beginning of the
16871 search path in the same order they were presented in the command.
16872 If blanks are needed as
16873 part of a directory name, double-quotes should be used around
16874 the name. In the command output, the path will show up separated
16875 by the system directory-separator character. The directory-seperator
16876 character must not be used
16877 in any directory name.
16878 If no directories are specified, the current path is displayed.
16881 @subsubheading @value{GDBN} Command
16883 The corresponding @value{GDBN} command is @samp{path}.
16885 @subsubheading Example
16890 ^done,path="/usr/bin"
16892 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
16893 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
16895 -environment-path -r /usr/local/bin
16896 ^done,path="/usr/local/bin:/usr/bin"
16901 @subheading The @code{-environment-pwd} Command
16902 @findex -environment-pwd
16904 @subsubheading Synopsis
16910 Show the current working directory.
16912 @subsubheading @value{GDBN} command
16914 The corresponding @value{GDBN} command is @samp{pwd}.
16916 @subsubheading Example
16921 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
16925 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16926 @node GDB/MI Program Control
16927 @section @sc{gdb/mi} Program control
16929 @subsubheading Program termination
16931 As a result of execution, the inferior program can run to completion, if
16932 it doesn't encounter any breakpoints. In this case the output will
16933 include an exit code, if the program has exited exceptionally.
16935 @subsubheading Examples
16938 Program exited normally:
16946 *stopped,reason="exited-normally"
16951 Program exited exceptionally:
16959 *stopped,reason="exited",exit-code="01"
16963 Another way the program can terminate is if it receives a signal such as
16964 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
16968 *stopped,reason="exited-signalled",signal-name="SIGINT",
16969 signal-meaning="Interrupt"
16973 @subheading The @code{-exec-abort} Command
16974 @findex -exec-abort
16976 @subsubheading Synopsis
16982 Kill the inferior running program.
16984 @subsubheading @value{GDBN} Command
16986 The corresponding @value{GDBN} command is @samp{kill}.
16988 @subsubheading Example
16992 @subheading The @code{-exec-arguments} Command
16993 @findex -exec-arguments
16995 @subsubheading Synopsis
16998 -exec-arguments @var{args}
17001 Set the inferior program arguments, to be used in the next
17004 @subsubheading @value{GDBN} Command
17006 The corresponding @value{GDBN} command is @samp{set args}.
17008 @subsubheading Example
17011 Don't have one around.
17014 @subheading The @code{-exec-continue} Command
17015 @findex -exec-continue
17017 @subsubheading Synopsis
17023 Asynchronous command. Resumes the execution of the inferior program
17024 until a breakpoint is encountered, or until the inferior exits.
17026 @subsubheading @value{GDBN} Command
17028 The corresponding @value{GDBN} corresponding is @samp{continue}.
17030 @subsubheading Example
17037 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
17038 file="hello.c",line="13"@}
17043 @subheading The @code{-exec-finish} Command
17044 @findex -exec-finish
17046 @subsubheading Synopsis
17052 Asynchronous command. Resumes the execution of the inferior program
17053 until the current function is exited. Displays the results returned by
17056 @subsubheading @value{GDBN} Command
17058 The corresponding @value{GDBN} command is @samp{finish}.
17060 @subsubheading Example
17062 Function returning @code{void}.
17069 *stopped,reason="function-finished",frame=@{func="main",args=[],
17070 file="hello.c",line="7"@}
17074 Function returning other than @code{void}. The name of the internal
17075 @value{GDBN} variable storing the result is printed, together with the
17082 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
17083 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
17084 file="recursive2.c",line="14"@},
17085 gdb-result-var="$1",return-value="0"
17090 @subheading The @code{-exec-interrupt} Command
17091 @findex -exec-interrupt
17093 @subsubheading Synopsis
17099 Asynchronous command. Interrupts the background execution of the target.
17100 Note how the token associated with the stop message is the one for the
17101 execution command that has been interrupted. The token for the interrupt
17102 itself only appears in the @samp{^done} output. If the user is trying to
17103 interrupt a non-running program, an error message will be printed.
17105 @subsubheading @value{GDBN} Command
17107 The corresponding @value{GDBN} command is @samp{interrupt}.
17109 @subsubheading Example
17120 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
17121 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",line="13"@}
17126 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
17131 @subheading The @code{-exec-next} Command
17134 @subsubheading Synopsis
17140 Asynchronous command. Resumes execution of the inferior program, stopping
17141 when the beginning of the next source line is reached.
17143 @subsubheading @value{GDBN} Command
17145 The corresponding @value{GDBN} command is @samp{next}.
17147 @subsubheading Example
17153 *stopped,reason="end-stepping-range",line="8",file="hello.c"
17158 @subheading The @code{-exec-next-instruction} Command
17159 @findex -exec-next-instruction
17161 @subsubheading Synopsis
17164 -exec-next-instruction
17167 Asynchronous command. Executes one machine instruction. If the
17168 instruction is a function call continues until the function returns. If
17169 the program stops at an instruction in the middle of a source line, the
17170 address will be printed as well.
17172 @subsubheading @value{GDBN} Command
17174 The corresponding @value{GDBN} command is @samp{nexti}.
17176 @subsubheading Example
17180 -exec-next-instruction
17184 *stopped,reason="end-stepping-range",
17185 addr="0x000100d4",line="5",file="hello.c"
17190 @subheading The @code{-exec-return} Command
17191 @findex -exec-return
17193 @subsubheading Synopsis
17199 Makes current function return immediately. Doesn't execute the inferior.
17200 Displays the new current frame.
17202 @subsubheading @value{GDBN} Command
17204 The corresponding @value{GDBN} command is @samp{return}.
17206 @subsubheading Example
17210 200-break-insert callee4
17211 200^done,bkpt=@{number="1",addr="0x00010734",
17212 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
17217 000*stopped,reason="breakpoint-hit",bkptno="1",
17218 frame=@{func="callee4",args=[],
17219 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
17225 111^done,frame=@{level="0",func="callee3",
17226 args=[@{name="strarg",
17227 value="0x11940 \"A string argument.\""@}],
17228 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
17233 @subheading The @code{-exec-run} Command
17236 @subsubheading Synopsis
17242 Asynchronous command. Starts execution of the inferior from the
17243 beginning. The inferior executes until either a breakpoint is
17244 encountered or the program exits.
17246 @subsubheading @value{GDBN} Command
17248 The corresponding @value{GDBN} command is @samp{run}.
17250 @subsubheading Example
17255 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
17260 *stopped,reason="breakpoint-hit",bkptno="1",
17261 frame=@{func="main",args=[],file="recursive2.c",line="4"@}
17266 @subheading The @code{-exec-show-arguments} Command
17267 @findex -exec-show-arguments
17269 @subsubheading Synopsis
17272 -exec-show-arguments
17275 Print the arguments of the program.
17277 @subsubheading @value{GDBN} Command
17279 The corresponding @value{GDBN} command is @samp{show args}.
17281 @subsubheading Example
17284 @c @subheading -exec-signal
17286 @subheading The @code{-exec-step} Command
17289 @subsubheading Synopsis
17295 Asynchronous command. Resumes execution of the inferior program, stopping
17296 when the beginning of the next source line is reached, if the next
17297 source line is not a function call. If it is, stop at the first
17298 instruction of the called function.
17300 @subsubheading @value{GDBN} Command
17302 The corresponding @value{GDBN} command is @samp{step}.
17304 @subsubheading Example
17306 Stepping into a function:
17312 *stopped,reason="end-stepping-range",
17313 frame=@{func="foo",args=[@{name="a",value="10"@},
17314 @{name="b",value="0"@}],file="recursive2.c",line="11"@}
17324 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
17329 @subheading The @code{-exec-step-instruction} Command
17330 @findex -exec-step-instruction
17332 @subsubheading Synopsis
17335 -exec-step-instruction
17338 Asynchronous command. Resumes the inferior which executes one machine
17339 instruction. The output, once @value{GDBN} has stopped, will vary depending on
17340 whether we have stopped in the middle of a source line or not. In the
17341 former case, the address at which the program stopped will be printed as
17344 @subsubheading @value{GDBN} Command
17346 The corresponding @value{GDBN} command is @samp{stepi}.
17348 @subsubheading Example
17352 -exec-step-instruction
17356 *stopped,reason="end-stepping-range",
17357 frame=@{func="foo",args=[],file="try.c",line="10"@}
17359 -exec-step-instruction
17363 *stopped,reason="end-stepping-range",
17364 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",line="10"@}
17369 @subheading The @code{-exec-until} Command
17370 @findex -exec-until
17372 @subsubheading Synopsis
17375 -exec-until [ @var{location} ]
17378 Asynchronous command. Executes the inferior until the @var{location}
17379 specified in the argument is reached. If there is no argument, the inferior
17380 executes until a source line greater than the current one is reached.
17381 The reason for stopping in this case will be @samp{location-reached}.
17383 @subsubheading @value{GDBN} Command
17385 The corresponding @value{GDBN} command is @samp{until}.
17387 @subsubheading Example
17391 -exec-until recursive2.c:6
17395 *stopped,reason="location-reached",frame=@{func="main",args=[],
17396 file="recursive2.c",line="6"@}
17401 @subheading -file-clear
17402 Is this going away????
17406 @subheading The @code{-file-exec-and-symbols} Command
17407 @findex -file-exec-and-symbols
17409 @subsubheading Synopsis
17412 -file-exec-and-symbols @var{file}
17415 Specify the executable file to be debugged. This file is the one from
17416 which the symbol table is also read. If no file is specified, the
17417 command clears the executable and symbol information. If breakpoints
17418 are set when using this command with no arguments, @value{GDBN} will produce
17419 error messages. Otherwise, no output is produced, except a completion
17422 @subsubheading @value{GDBN} Command
17424 The corresponding @value{GDBN} command is @samp{file}.
17426 @subsubheading Example
17430 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
17436 @subheading The @code{-file-exec-file} Command
17437 @findex -file-exec-file
17439 @subsubheading Synopsis
17442 -file-exec-file @var{file}
17445 Specify the executable file to be debugged. Unlike
17446 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
17447 from this file. If used without argument, @value{GDBN} clears the information
17448 about the executable file. No output is produced, except a completion
17451 @subsubheading @value{GDBN} Command
17453 The corresponding @value{GDBN} command is @samp{exec-file}.
17455 @subsubheading Example
17459 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
17465 @subheading The @code{-file-list-exec-sections} Command
17466 @findex -file-list-exec-sections
17468 @subsubheading Synopsis
17471 -file-list-exec-sections
17474 List the sections of the current executable file.
17476 @subsubheading @value{GDBN} Command
17478 The @value{GDBN} command @samp{info file} shows, among the rest, the same
17479 information as this command. @code{gdbtk} has a corresponding command
17480 @samp{gdb_load_info}.
17482 @subsubheading Example
17486 @subheading The @code{-file-list-exec-source-file} Command
17487 @findex -file-list-exec-source-file
17489 @subsubheading Synopsis
17492 -file-list-exec-source-file
17495 List the line number, the current source file, and the absolute path
17496 to the current source file for the current executable.
17498 @subsubheading @value{GDBN} Command
17500 There's no @value{GDBN} command which directly corresponds to this one.
17502 @subsubheading Example
17506 123-file-list-exec-source-file
17507 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
17512 @subheading The @code{-file-list-exec-source-files} Command
17513 @findex -file-list-exec-source-files
17515 @subsubheading Synopsis
17518 -file-list-exec-source-files
17521 List the source files for the current executable.
17523 It will always output the filename, but only when GDB can find the absolute
17524 file name of a source file, will it output the fullname.
17526 @subsubheading @value{GDBN} Command
17528 There's no @value{GDBN} command which directly corresponds to this one.
17529 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
17531 @subsubheading Example
17534 -file-list-exec-source-files
17536 @{file=foo.c,fullname=/home/foo.c@},
17537 @{file=/home/bar.c,fullname=/home/bar.c@},
17538 @{file=gdb_could_not_find_fullpath.c@}]
17542 @subheading The @code{-file-list-shared-libraries} Command
17543 @findex -file-list-shared-libraries
17545 @subsubheading Synopsis
17548 -file-list-shared-libraries
17551 List the shared libraries in the program.
17553 @subsubheading @value{GDBN} Command
17555 The corresponding @value{GDBN} command is @samp{info shared}.
17557 @subsubheading Example
17561 @subheading The @code{-file-list-symbol-files} Command
17562 @findex -file-list-symbol-files
17564 @subsubheading Synopsis
17567 -file-list-symbol-files
17572 @subsubheading @value{GDBN} Command
17574 The corresponding @value{GDBN} command is @samp{info file} (part of it).
17576 @subsubheading Example
17580 @subheading The @code{-file-symbol-file} Command
17581 @findex -file-symbol-file
17583 @subsubheading Synopsis
17586 -file-symbol-file @var{file}
17589 Read symbol table info from the specified @var{file} argument. When
17590 used without arguments, clears @value{GDBN}'s symbol table info. No output is
17591 produced, except for a completion notification.
17593 @subsubheading @value{GDBN} Command
17595 The corresponding @value{GDBN} command is @samp{symbol-file}.
17597 @subsubheading Example
17601 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
17606 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17607 @node GDB/MI Miscellaneous Commands
17608 @section Miscellaneous @value{GDBN} commands in @sc{gdb/mi}
17610 @c @subheading -gdb-complete
17612 @subheading The @code{-gdb-exit} Command
17615 @subsubheading Synopsis
17621 Exit @value{GDBN} immediately.
17623 @subsubheading @value{GDBN} Command
17625 Approximately corresponds to @samp{quit}.
17627 @subsubheading Example
17634 @subheading The @code{-gdb-set} Command
17637 @subsubheading Synopsis
17643 Set an internal @value{GDBN} variable.
17644 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
17646 @subsubheading @value{GDBN} Command
17648 The corresponding @value{GDBN} command is @samp{set}.
17650 @subsubheading Example
17660 @subheading The @code{-gdb-show} Command
17663 @subsubheading Synopsis
17669 Show the current value of a @value{GDBN} variable.
17671 @subsubheading @value{GDBN} command
17673 The corresponding @value{GDBN} command is @samp{show}.
17675 @subsubheading Example
17684 @c @subheading -gdb-source
17687 @subheading The @code{-gdb-version} Command
17688 @findex -gdb-version
17690 @subsubheading Synopsis
17696 Show version information for @value{GDBN}. Used mostly in testing.
17698 @subsubheading @value{GDBN} Command
17700 There's no equivalent @value{GDBN} command. @value{GDBN} by default shows this
17701 information when you start an interactive session.
17703 @subsubheading Example
17705 @c This example modifies the actual output from GDB to avoid overfull
17711 ~Copyright 2000 Free Software Foundation, Inc.
17712 ~GDB is free software, covered by the GNU General Public License, and
17713 ~you are welcome to change it and/or distribute copies of it under
17714 ~ certain conditions.
17715 ~Type "show copying" to see the conditions.
17716 ~There is absolutely no warranty for GDB. Type "show warranty" for
17718 ~This GDB was configured as
17719 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
17724 @subheading The @code{-interpreter-exec} Command
17725 @findex -interpreter-exec
17727 @subheading Synopsis
17730 -interpreter-exec @var{interpreter} @var{command}
17733 Execute the specified @var{command} in the given @var{interpreter}.
17735 @subheading @value{GDBN} Command
17737 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
17739 @subheading Example
17743 -interpreter-exec console "break main"
17744 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
17745 &"During symbol reading, bad structure-type format.\n"
17746 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
17752 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17753 @node GDB/MI Kod Commands
17754 @section @sc{gdb/mi} Kod Commands
17756 The Kod commands are not implemented.
17758 @c @subheading -kod-info
17760 @c @subheading -kod-list
17762 @c @subheading -kod-list-object-types
17764 @c @subheading -kod-show
17766 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17767 @node GDB/MI Memory Overlay Commands
17768 @section @sc{gdb/mi} Memory Overlay Commands
17770 The memory overlay commands are not implemented.
17772 @c @subheading -overlay-auto
17774 @c @subheading -overlay-list-mapping-state
17776 @c @subheading -overlay-list-overlays
17778 @c @subheading -overlay-map
17780 @c @subheading -overlay-off
17782 @c @subheading -overlay-on
17784 @c @subheading -overlay-unmap
17786 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17787 @node GDB/MI Signal Handling Commands
17788 @section @sc{gdb/mi} Signal Handling Commands
17790 Signal handling commands are not implemented.
17792 @c @subheading -signal-handle
17794 @c @subheading -signal-list-handle-actions
17796 @c @subheading -signal-list-signal-types
17800 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17801 @node GDB/MI Stack Manipulation
17802 @section @sc{gdb/mi} Stack Manipulation Commands
17805 @subheading The @code{-stack-info-frame} Command
17806 @findex -stack-info-frame
17808 @subsubheading Synopsis
17814 Get info on the current frame.
17816 @subsubheading @value{GDBN} Command
17818 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
17819 (without arguments).
17821 @subsubheading Example
17824 @subheading The @code{-stack-info-depth} Command
17825 @findex -stack-info-depth
17827 @subsubheading Synopsis
17830 -stack-info-depth [ @var{max-depth} ]
17833 Return the depth of the stack. If the integer argument @var{max-depth}
17834 is specified, do not count beyond @var{max-depth} frames.
17836 @subsubheading @value{GDBN} Command
17838 There's no equivalent @value{GDBN} command.
17840 @subsubheading Example
17842 For a stack with frame levels 0 through 11:
17849 -stack-info-depth 4
17852 -stack-info-depth 12
17855 -stack-info-depth 11
17858 -stack-info-depth 13
17863 @subheading The @code{-stack-list-arguments} Command
17864 @findex -stack-list-arguments
17866 @subsubheading Synopsis
17869 -stack-list-arguments @var{show-values}
17870 [ @var{low-frame} @var{high-frame} ]
17873 Display a list of the arguments for the frames between @var{low-frame}
17874 and @var{high-frame} (inclusive). If @var{low-frame} and
17875 @var{high-frame} are not provided, list the arguments for the whole call
17878 The @var{show-values} argument must have a value of 0 or 1. A value of
17879 0 means that only the names of the arguments are listed, a value of 1
17880 means that both names and values of the arguments are printed.
17882 @subsubheading @value{GDBN} Command
17884 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
17885 @samp{gdb_get_args} command which partially overlaps with the
17886 functionality of @samp{-stack-list-arguments}.
17888 @subsubheading Example
17895 frame=@{level="0",addr="0x00010734",func="callee4",
17896 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
17897 frame=@{level="1",addr="0x0001076c",func="callee3",
17898 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
17899 frame=@{level="2",addr="0x0001078c",func="callee2",
17900 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
17901 frame=@{level="3",addr="0x000107b4",func="callee1",
17902 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
17903 frame=@{level="4",addr="0x000107e0",func="main",
17904 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
17906 -stack-list-arguments 0
17909 frame=@{level="0",args=[]@},
17910 frame=@{level="1",args=[name="strarg"]@},
17911 frame=@{level="2",args=[name="intarg",name="strarg"]@},
17912 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
17913 frame=@{level="4",args=[]@}]
17915 -stack-list-arguments 1
17918 frame=@{level="0",args=[]@},
17920 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
17921 frame=@{level="2",args=[
17922 @{name="intarg",value="2"@},
17923 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
17924 @{frame=@{level="3",args=[
17925 @{name="intarg",value="2"@},
17926 @{name="strarg",value="0x11940 \"A string argument.\""@},
17927 @{name="fltarg",value="3.5"@}]@},
17928 frame=@{level="4",args=[]@}]
17930 -stack-list-arguments 0 2 2
17931 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
17933 -stack-list-arguments 1 2 2
17934 ^done,stack-args=[frame=@{level="2",
17935 args=[@{name="intarg",value="2"@},
17936 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
17940 @c @subheading -stack-list-exception-handlers
17943 @subheading The @code{-stack-list-frames} Command
17944 @findex -stack-list-frames
17946 @subsubheading Synopsis
17949 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
17952 List the frames currently on the stack. For each frame it displays the
17957 The frame number, 0 being the topmost frame, i.e. the innermost function.
17959 The @code{$pc} value for that frame.
17963 File name of the source file where the function lives.
17965 Line number corresponding to the @code{$pc}.
17968 If invoked without arguments, this command prints a backtrace for the
17969 whole stack. If given two integer arguments, it shows the frames whose
17970 levels are between the two arguments (inclusive). If the two arguments
17971 are equal, it shows the single frame at the corresponding level.
17973 @subsubheading @value{GDBN} Command
17975 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
17977 @subsubheading Example
17979 Full stack backtrace:
17985 [frame=@{level="0",addr="0x0001076c",func="foo",
17986 file="recursive2.c",line="11"@},
17987 frame=@{level="1",addr="0x000107a4",func="foo",
17988 file="recursive2.c",line="14"@},
17989 frame=@{level="2",addr="0x000107a4",func="foo",
17990 file="recursive2.c",line="14"@},
17991 frame=@{level="3",addr="0x000107a4",func="foo",
17992 file="recursive2.c",line="14"@},
17993 frame=@{level="4",addr="0x000107a4",func="foo",
17994 file="recursive2.c",line="14"@},
17995 frame=@{level="5",addr="0x000107a4",func="foo",
17996 file="recursive2.c",line="14"@},
17997 frame=@{level="6",addr="0x000107a4",func="foo",
17998 file="recursive2.c",line="14"@},
17999 frame=@{level="7",addr="0x000107a4",func="foo",
18000 file="recursive2.c",line="14"@},
18001 frame=@{level="8",addr="0x000107a4",func="foo",
18002 file="recursive2.c",line="14"@},
18003 frame=@{level="9",addr="0x000107a4",func="foo",
18004 file="recursive2.c",line="14"@},
18005 frame=@{level="10",addr="0x000107a4",func="foo",
18006 file="recursive2.c",line="14"@},
18007 frame=@{level="11",addr="0x00010738",func="main",
18008 file="recursive2.c",line="4"@}]
18012 Show frames between @var{low_frame} and @var{high_frame}:
18016 -stack-list-frames 3 5
18018 [frame=@{level="3",addr="0x000107a4",func="foo",
18019 file="recursive2.c",line="14"@},
18020 frame=@{level="4",addr="0x000107a4",func="foo",
18021 file="recursive2.c",line="14"@},
18022 frame=@{level="5",addr="0x000107a4",func="foo",
18023 file="recursive2.c",line="14"@}]
18027 Show a single frame:
18031 -stack-list-frames 3 3
18033 [frame=@{level="3",addr="0x000107a4",func="foo",
18034 file="recursive2.c",line="14"@}]
18039 @subheading The @code{-stack-list-locals} Command
18040 @findex -stack-list-locals
18042 @subsubheading Synopsis
18045 -stack-list-locals @var{print-values}
18048 Display the local variable names for the current frame. With an
18049 argument of 0 or @code{--no-values}, prints only the names of the variables.
18050 With argument of 1 or @code{--all-values}, prints also their values. With
18051 argument of 2 or @code{--simple-values}, prints the name, type and value for
18052 simple data types and the name and type for arrays, structures and
18053 unions. In this last case, the idea is that the user can see the
18054 value of simple data types immediately and he can create variable
18055 objects for other data types if he wishes to explore their values in
18058 @subsubheading @value{GDBN} Command
18060 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
18062 @subsubheading Example
18066 -stack-list-locals 0
18067 ^done,locals=[name="A",name="B",name="C"]
18069 -stack-list-locals --all-values
18070 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
18071 @{name="C",value="@{1, 2, 3@}"@}]
18072 -stack-list-locals --simple-values
18073 ^done,locals=[@{name="A",type="int",value="1"@},
18074 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
18079 @subheading The @code{-stack-select-frame} Command
18080 @findex -stack-select-frame
18082 @subsubheading Synopsis
18085 -stack-select-frame @var{framenum}
18088 Change the current frame. Select a different frame @var{framenum} on
18091 @subsubheading @value{GDBN} Command
18093 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
18094 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
18096 @subsubheading Example
18100 -stack-select-frame 2
18105 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18106 @node GDB/MI Symbol Query
18107 @section @sc{gdb/mi} Symbol Query Commands
18110 @subheading The @code{-symbol-info-address} Command
18111 @findex -symbol-info-address
18113 @subsubheading Synopsis
18116 -symbol-info-address @var{symbol}
18119 Describe where @var{symbol} is stored.
18121 @subsubheading @value{GDBN} Command
18123 The corresponding @value{GDBN} command is @samp{info address}.
18125 @subsubheading Example
18129 @subheading The @code{-symbol-info-file} Command
18130 @findex -symbol-info-file
18132 @subsubheading Synopsis
18138 Show the file for the symbol.
18140 @subsubheading @value{GDBN} Command
18142 There's no equivalent @value{GDBN} command. @code{gdbtk} has
18143 @samp{gdb_find_file}.
18145 @subsubheading Example
18149 @subheading The @code{-symbol-info-function} Command
18150 @findex -symbol-info-function
18152 @subsubheading Synopsis
18155 -symbol-info-function
18158 Show which function the symbol lives in.
18160 @subsubheading @value{GDBN} Command
18162 @samp{gdb_get_function} in @code{gdbtk}.
18164 @subsubheading Example
18168 @subheading The @code{-symbol-info-line} Command
18169 @findex -symbol-info-line
18171 @subsubheading Synopsis
18177 Show the core addresses of the code for a source line.
18179 @subsubheading @value{GDBN} Command
18181 The corresponding @value{GDBN} command is @samp{info line}.
18182 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
18184 @subsubheading Example
18188 @subheading The @code{-symbol-info-symbol} Command
18189 @findex -symbol-info-symbol
18191 @subsubheading Synopsis
18194 -symbol-info-symbol @var{addr}
18197 Describe what symbol is at location @var{addr}.
18199 @subsubheading @value{GDBN} Command
18201 The corresponding @value{GDBN} command is @samp{info symbol}.
18203 @subsubheading Example
18207 @subheading The @code{-symbol-list-functions} Command
18208 @findex -symbol-list-functions
18210 @subsubheading Synopsis
18213 -symbol-list-functions
18216 List the functions in the executable.
18218 @subsubheading @value{GDBN} Command
18220 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
18221 @samp{gdb_search} in @code{gdbtk}.
18223 @subsubheading Example
18227 @subheading The @code{-symbol-list-lines} Command
18228 @findex -symbol-list-lines
18230 @subsubheading Synopsis
18233 -symbol-list-lines @var{filename}
18236 Print the list of lines that contain code and their associated program
18237 addresses for the given source filename. The entries are sorted in
18238 ascending PC order.
18240 @subsubheading @value{GDBN} Command
18242 There is no corresponding @value{GDBN} command.
18244 @subsubheading Example
18247 -symbol-list-lines basics.c
18248 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
18253 @subheading The @code{-symbol-list-types} Command
18254 @findex -symbol-list-types
18256 @subsubheading Synopsis
18262 List all the type names.
18264 @subsubheading @value{GDBN} Command
18266 The corresponding commands are @samp{info types} in @value{GDBN},
18267 @samp{gdb_search} in @code{gdbtk}.
18269 @subsubheading Example
18273 @subheading The @code{-symbol-list-variables} Command
18274 @findex -symbol-list-variables
18276 @subsubheading Synopsis
18279 -symbol-list-variables
18282 List all the global and static variable names.
18284 @subsubheading @value{GDBN} Command
18286 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
18288 @subsubheading Example
18292 @subheading The @code{-symbol-locate} Command
18293 @findex -symbol-locate
18295 @subsubheading Synopsis
18301 @subsubheading @value{GDBN} Command
18303 @samp{gdb_loc} in @code{gdbtk}.
18305 @subsubheading Example
18309 @subheading The @code{-symbol-type} Command
18310 @findex -symbol-type
18312 @subsubheading Synopsis
18315 -symbol-type @var{variable}
18318 Show type of @var{variable}.
18320 @subsubheading @value{GDBN} Command
18322 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
18323 @samp{gdb_obj_variable}.
18325 @subsubheading Example
18329 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18330 @node GDB/MI Target Manipulation
18331 @section @sc{gdb/mi} Target Manipulation Commands
18334 @subheading The @code{-target-attach} Command
18335 @findex -target-attach
18337 @subsubheading Synopsis
18340 -target-attach @var{pid} | @var{file}
18343 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
18345 @subsubheading @value{GDBN} command
18347 The corresponding @value{GDBN} command is @samp{attach}.
18349 @subsubheading Example
18353 @subheading The @code{-target-compare-sections} Command
18354 @findex -target-compare-sections
18356 @subsubheading Synopsis
18359 -target-compare-sections [ @var{section} ]
18362 Compare data of section @var{section} on target to the exec file.
18363 Without the argument, all sections are compared.
18365 @subsubheading @value{GDBN} Command
18367 The @value{GDBN} equivalent is @samp{compare-sections}.
18369 @subsubheading Example
18373 @subheading The @code{-target-detach} Command
18374 @findex -target-detach
18376 @subsubheading Synopsis
18382 Disconnect from the remote target. There's no output.
18384 @subsubheading @value{GDBN} command
18386 The corresponding @value{GDBN} command is @samp{detach}.
18388 @subsubheading Example
18398 @subheading The @code{-target-disconnect} Command
18399 @findex -target-disconnect
18401 @subsubheading Synopsis
18407 Disconnect from the remote target. There's no output.
18409 @subsubheading @value{GDBN} command
18411 The corresponding @value{GDBN} command is @samp{disconnect}.
18413 @subsubheading Example
18423 @subheading The @code{-target-download} Command
18424 @findex -target-download
18426 @subsubheading Synopsis
18432 Loads the executable onto the remote target.
18433 It prints out an update message every half second, which includes the fields:
18437 The name of the section.
18439 The size of what has been sent so far for that section.
18441 The size of the section.
18443 The total size of what was sent so far (the current and the previous sections).
18445 The size of the overall executable to download.
18449 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
18450 @sc{gdb/mi} Output Syntax}).
18452 In addition, it prints the name and size of the sections, as they are
18453 downloaded. These messages include the following fields:
18457 The name of the section.
18459 The size of the section.
18461 The size of the overall executable to download.
18465 At the end, a summary is printed.
18467 @subsubheading @value{GDBN} Command
18469 The corresponding @value{GDBN} command is @samp{load}.
18471 @subsubheading Example
18473 Note: each status message appears on a single line. Here the messages
18474 have been broken down so that they can fit onto a page.
18479 +download,@{section=".text",section-size="6668",total-size="9880"@}
18480 +download,@{section=".text",section-sent="512",section-size="6668",
18481 total-sent="512",total-size="9880"@}
18482 +download,@{section=".text",section-sent="1024",section-size="6668",
18483 total-sent="1024",total-size="9880"@}
18484 +download,@{section=".text",section-sent="1536",section-size="6668",
18485 total-sent="1536",total-size="9880"@}
18486 +download,@{section=".text",section-sent="2048",section-size="6668",
18487 total-sent="2048",total-size="9880"@}
18488 +download,@{section=".text",section-sent="2560",section-size="6668",
18489 total-sent="2560",total-size="9880"@}
18490 +download,@{section=".text",section-sent="3072",section-size="6668",
18491 total-sent="3072",total-size="9880"@}
18492 +download,@{section=".text",section-sent="3584",section-size="6668",
18493 total-sent="3584",total-size="9880"@}
18494 +download,@{section=".text",section-sent="4096",section-size="6668",
18495 total-sent="4096",total-size="9880"@}
18496 +download,@{section=".text",section-sent="4608",section-size="6668",
18497 total-sent="4608",total-size="9880"@}
18498 +download,@{section=".text",section-sent="5120",section-size="6668",
18499 total-sent="5120",total-size="9880"@}
18500 +download,@{section=".text",section-sent="5632",section-size="6668",
18501 total-sent="5632",total-size="9880"@}
18502 +download,@{section=".text",section-sent="6144",section-size="6668",
18503 total-sent="6144",total-size="9880"@}
18504 +download,@{section=".text",section-sent="6656",section-size="6668",
18505 total-sent="6656",total-size="9880"@}
18506 +download,@{section=".init",section-size="28",total-size="9880"@}
18507 +download,@{section=".fini",section-size="28",total-size="9880"@}
18508 +download,@{section=".data",section-size="3156",total-size="9880"@}
18509 +download,@{section=".data",section-sent="512",section-size="3156",
18510 total-sent="7236",total-size="9880"@}
18511 +download,@{section=".data",section-sent="1024",section-size="3156",
18512 total-sent="7748",total-size="9880"@}
18513 +download,@{section=".data",section-sent="1536",section-size="3156",
18514 total-sent="8260",total-size="9880"@}
18515 +download,@{section=".data",section-sent="2048",section-size="3156",
18516 total-sent="8772",total-size="9880"@}
18517 +download,@{section=".data",section-sent="2560",section-size="3156",
18518 total-sent="9284",total-size="9880"@}
18519 +download,@{section=".data",section-sent="3072",section-size="3156",
18520 total-sent="9796",total-size="9880"@}
18521 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
18527 @subheading The @code{-target-exec-status} Command
18528 @findex -target-exec-status
18530 @subsubheading Synopsis
18533 -target-exec-status
18536 Provide information on the state of the target (whether it is running or
18537 not, for instance).
18539 @subsubheading @value{GDBN} Command
18541 There's no equivalent @value{GDBN} command.
18543 @subsubheading Example
18547 @subheading The @code{-target-list-available-targets} Command
18548 @findex -target-list-available-targets
18550 @subsubheading Synopsis
18553 -target-list-available-targets
18556 List the possible targets to connect to.
18558 @subsubheading @value{GDBN} Command
18560 The corresponding @value{GDBN} command is @samp{help target}.
18562 @subsubheading Example
18566 @subheading The @code{-target-list-current-targets} Command
18567 @findex -target-list-current-targets
18569 @subsubheading Synopsis
18572 -target-list-current-targets
18575 Describe the current target.
18577 @subsubheading @value{GDBN} Command
18579 The corresponding information is printed by @samp{info file} (among
18582 @subsubheading Example
18586 @subheading The @code{-target-list-parameters} Command
18587 @findex -target-list-parameters
18589 @subsubheading Synopsis
18592 -target-list-parameters
18597 @subsubheading @value{GDBN} Command
18601 @subsubheading Example
18605 @subheading The @code{-target-select} Command
18606 @findex -target-select
18608 @subsubheading Synopsis
18611 -target-select @var{type} @var{parameters @dots{}}
18614 Connect @value{GDBN} to the remote target. This command takes two args:
18618 The type of target, for instance @samp{async}, @samp{remote}, etc.
18619 @item @var{parameters}
18620 Device names, host names and the like. @xref{Target Commands, ,
18621 Commands for managing targets}, for more details.
18624 The output is a connection notification, followed by the address at
18625 which the target program is, in the following form:
18628 ^connected,addr="@var{address}",func="@var{function name}",
18629 args=[@var{arg list}]
18632 @subsubheading @value{GDBN} Command
18634 The corresponding @value{GDBN} command is @samp{target}.
18636 @subsubheading Example
18640 -target-select async /dev/ttya
18641 ^connected,addr="0xfe00a300",func="??",args=[]
18645 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18646 @node GDB/MI Thread Commands
18647 @section @sc{gdb/mi} Thread Commands
18650 @subheading The @code{-thread-info} Command
18651 @findex -thread-info
18653 @subsubheading Synopsis
18659 @subsubheading @value{GDBN} command
18663 @subsubheading Example
18667 @subheading The @code{-thread-list-all-threads} Command
18668 @findex -thread-list-all-threads
18670 @subsubheading Synopsis
18673 -thread-list-all-threads
18676 @subsubheading @value{GDBN} Command
18678 The equivalent @value{GDBN} command is @samp{info threads}.
18680 @subsubheading Example
18684 @subheading The @code{-thread-list-ids} Command
18685 @findex -thread-list-ids
18687 @subsubheading Synopsis
18693 Produces a list of the currently known @value{GDBN} thread ids. At the
18694 end of the list it also prints the total number of such threads.
18696 @subsubheading @value{GDBN} Command
18698 Part of @samp{info threads} supplies the same information.
18700 @subsubheading Example
18702 No threads present, besides the main process:
18707 ^done,thread-ids=@{@},number-of-threads="0"
18717 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18718 number-of-threads="3"
18723 @subheading The @code{-thread-select} Command
18724 @findex -thread-select
18726 @subsubheading Synopsis
18729 -thread-select @var{threadnum}
18732 Make @var{threadnum} the current thread. It prints the number of the new
18733 current thread, and the topmost frame for that thread.
18735 @subsubheading @value{GDBN} Command
18737 The corresponding @value{GDBN} command is @samp{thread}.
18739 @subsubheading Example
18746 *stopped,reason="end-stepping-range",thread-id="2",line="187",
18747 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
18751 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18752 number-of-threads="3"
18755 ^done,new-thread-id="3",
18756 frame=@{level="0",func="vprintf",
18757 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
18758 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
18762 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18763 @node GDB/MI Tracepoint Commands
18764 @section @sc{gdb/mi} Tracepoint Commands
18766 The tracepoint commands are not yet implemented.
18768 @c @subheading -trace-actions
18770 @c @subheading -trace-delete
18772 @c @subheading -trace-disable
18774 @c @subheading -trace-dump
18776 @c @subheading -trace-enable
18778 @c @subheading -trace-exists
18780 @c @subheading -trace-find
18782 @c @subheading -trace-frame-number
18784 @c @subheading -trace-info
18786 @c @subheading -trace-insert
18788 @c @subheading -trace-list
18790 @c @subheading -trace-pass-count
18792 @c @subheading -trace-save
18794 @c @subheading -trace-start
18796 @c @subheading -trace-stop
18799 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18800 @node GDB/MI Variable Objects
18801 @section @sc{gdb/mi} Variable Objects
18804 @subheading Motivation for Variable Objects in @sc{gdb/mi}
18806 For the implementation of a variable debugger window (locals, watched
18807 expressions, etc.), we are proposing the adaptation of the existing code
18808 used by @code{Insight}.
18810 The two main reasons for that are:
18814 It has been proven in practice (it is already on its second generation).
18817 It will shorten development time (needless to say how important it is
18821 The original interface was designed to be used by Tcl code, so it was
18822 slightly changed so it could be used through @sc{gdb/mi}. This section
18823 describes the @sc{gdb/mi} operations that will be available and gives some
18824 hints about their use.
18826 @emph{Note}: In addition to the set of operations described here, we
18827 expect the @sc{gui} implementation of a variable window to require, at
18828 least, the following operations:
18831 @item @code{-gdb-show} @code{output-radix}
18832 @item @code{-stack-list-arguments}
18833 @item @code{-stack-list-locals}
18834 @item @code{-stack-select-frame}
18837 @subheading Introduction to Variable Objects in @sc{gdb/mi}
18839 @cindex variable objects in @sc{gdb/mi}
18840 The basic idea behind variable objects is the creation of a named object
18841 to represent a variable, an expression, a memory location or even a CPU
18842 register. For each object created, a set of operations is available for
18843 examining or changing its properties.
18845 Furthermore, complex data types, such as C structures, are represented
18846 in a tree format. For instance, the @code{struct} type variable is the
18847 root and the children will represent the struct members. If a child
18848 is itself of a complex type, it will also have children of its own.
18849 Appropriate language differences are handled for C, C@t{++} and Java.
18851 When returning the actual values of the objects, this facility allows
18852 for the individual selection of the display format used in the result
18853 creation. It can be chosen among: binary, decimal, hexadecimal, octal
18854 and natural. Natural refers to a default format automatically
18855 chosen based on the variable type (like decimal for an @code{int}, hex
18856 for pointers, etc.).
18858 The following is the complete set of @sc{gdb/mi} operations defined to
18859 access this functionality:
18861 @multitable @columnfractions .4 .6
18862 @item @strong{Operation}
18863 @tab @strong{Description}
18865 @item @code{-var-create}
18866 @tab create a variable object
18867 @item @code{-var-delete}
18868 @tab delete the variable object and its children
18869 @item @code{-var-set-format}
18870 @tab set the display format of this variable
18871 @item @code{-var-show-format}
18872 @tab show the display format of this variable
18873 @item @code{-var-info-num-children}
18874 @tab tells how many children this object has
18875 @item @code{-var-list-children}
18876 @tab return a list of the object's children
18877 @item @code{-var-info-type}
18878 @tab show the type of this variable object
18879 @item @code{-var-info-expression}
18880 @tab print what this variable object represents
18881 @item @code{-var-show-attributes}
18882 @tab is this variable editable? does it exist here?
18883 @item @code{-var-evaluate-expression}
18884 @tab get the value of this variable
18885 @item @code{-var-assign}
18886 @tab set the value of this variable
18887 @item @code{-var-update}
18888 @tab update the variable and its children
18891 In the next subsection we describe each operation in detail and suggest
18892 how it can be used.
18894 @subheading Description And Use of Operations on Variable Objects
18896 @subheading The @code{-var-create} Command
18897 @findex -var-create
18899 @subsubheading Synopsis
18902 -var-create @{@var{name} | "-"@}
18903 @{@var{frame-addr} | "*"@} @var{expression}
18906 This operation creates a variable object, which allows the monitoring of
18907 a variable, the result of an expression, a memory cell or a CPU
18910 The @var{name} parameter is the string by which the object can be
18911 referenced. It must be unique. If @samp{-} is specified, the varobj
18912 system will generate a string ``varNNNNNN'' automatically. It will be
18913 unique provided that one does not specify @var{name} on that format.
18914 The command fails if a duplicate name is found.
18916 The frame under which the expression should be evaluated can be
18917 specified by @var{frame-addr}. A @samp{*} indicates that the current
18918 frame should be used.
18920 @var{expression} is any expression valid on the current language set (must not
18921 begin with a @samp{*}), or one of the following:
18925 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
18928 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
18931 @samp{$@var{regname}} --- a CPU register name
18934 @subsubheading Result
18936 This operation returns the name, number of children and the type of the
18937 object created. Type is returned as a string as the ones generated by
18938 the @value{GDBN} CLI:
18941 name="@var{name}",numchild="N",type="@var{type}"
18945 @subheading The @code{-var-delete} Command
18946 @findex -var-delete
18948 @subsubheading Synopsis
18951 -var-delete @var{name}
18954 Deletes a previously created variable object and all of its children.
18956 Returns an error if the object @var{name} is not found.
18959 @subheading The @code{-var-set-format} Command
18960 @findex -var-set-format
18962 @subsubheading Synopsis
18965 -var-set-format @var{name} @var{format-spec}
18968 Sets the output format for the value of the object @var{name} to be
18971 The syntax for the @var{format-spec} is as follows:
18974 @var{format-spec} @expansion{}
18975 @{binary | decimal | hexadecimal | octal | natural@}
18979 @subheading The @code{-var-show-format} Command
18980 @findex -var-show-format
18982 @subsubheading Synopsis
18985 -var-show-format @var{name}
18988 Returns the format used to display the value of the object @var{name}.
18991 @var{format} @expansion{}
18996 @subheading The @code{-var-info-num-children} Command
18997 @findex -var-info-num-children
18999 @subsubheading Synopsis
19002 -var-info-num-children @var{name}
19005 Returns the number of children of a variable object @var{name}:
19012 @subheading The @code{-var-list-children} Command
19013 @findex -var-list-children
19015 @subsubheading Synopsis
19018 -var-list-children [@var{print-values}] @var{name}
19021 Returns a list of the children of the specified variable object. With
19022 just the variable object name as an argument or with an optional
19023 preceding argument of 0 or @code{--no-values}, prints only the names of the
19024 variables. With an optional preceding argument of 1 or @code{--all-values},
19025 also prints their values.
19027 @subsubheading Example
19031 -var-list-children n
19032 numchild=@var{n},children=[@{name=@var{name},
19033 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
19035 -var-list-children --all-values n
19036 numchild=@var{n},children=[@{name=@var{name},
19037 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
19041 @subheading The @code{-var-info-type} Command
19042 @findex -var-info-type
19044 @subsubheading Synopsis
19047 -var-info-type @var{name}
19050 Returns the type of the specified variable @var{name}. The type is
19051 returned as a string in the same format as it is output by the
19055 type=@var{typename}
19059 @subheading The @code{-var-info-expression} Command
19060 @findex -var-info-expression
19062 @subsubheading Synopsis
19065 -var-info-expression @var{name}
19068 Returns what is represented by the variable object @var{name}:
19071 lang=@var{lang-spec},exp=@var{expression}
19075 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
19077 @subheading The @code{-var-show-attributes} Command
19078 @findex -var-show-attributes
19080 @subsubheading Synopsis
19083 -var-show-attributes @var{name}
19086 List attributes of the specified variable object @var{name}:
19089 status=@var{attr} [ ( ,@var{attr} )* ]
19093 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
19095 @subheading The @code{-var-evaluate-expression} Command
19096 @findex -var-evaluate-expression
19098 @subsubheading Synopsis
19101 -var-evaluate-expression @var{name}
19104 Evaluates the expression that is represented by the specified variable
19105 object and returns its value as a string in the current format specified
19112 Note that one must invoke @code{-var-list-children} for a variable
19113 before the value of a child variable can be evaluated.
19115 @subheading The @code{-var-assign} Command
19116 @findex -var-assign
19118 @subsubheading Synopsis
19121 -var-assign @var{name} @var{expression}
19124 Assigns the value of @var{expression} to the variable object specified
19125 by @var{name}. The object must be @samp{editable}. If the variable's
19126 value is altered by the assign, the variable will show up in any
19127 subsequent @code{-var-update} list.
19129 @subsubheading Example
19137 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
19141 @subheading The @code{-var-update} Command
19142 @findex -var-update
19144 @subsubheading Synopsis
19147 -var-update @{@var{name} | "*"@}
19150 Update the value of the variable object @var{name} by evaluating its
19151 expression after fetching all the new values from memory or registers.
19152 A @samp{*} causes all existing variable objects to be updated.
19156 @chapter @value{GDBN} Annotations
19158 This chapter describes annotations in @value{GDBN}. Annotations were
19159 designed to interface @value{GDBN} to graphical user interfaces or other
19160 similar programs which want to interact with @value{GDBN} at a
19161 relatively high level.
19163 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
19167 This is Edition @value{EDITION}, @value{DATE}.
19171 * Annotations Overview:: What annotations are; the general syntax.
19172 * Server Prefix:: Issuing a command without affecting user state.
19173 * Prompting:: Annotations marking @value{GDBN}'s need for input.
19174 * Errors:: Annotations for error messages.
19175 * Invalidation:: Some annotations describe things now invalid.
19176 * Annotations for Running::
19177 Whether the program is running, how it stopped, etc.
19178 * Source Annotations:: Annotations describing source code.
19181 @node Annotations Overview
19182 @section What is an Annotation?
19183 @cindex annotations
19185 Annotations start with a newline character, two @samp{control-z}
19186 characters, and the name of the annotation. If there is no additional
19187 information associated with this annotation, the name of the annotation
19188 is followed immediately by a newline. If there is additional
19189 information, the name of the annotation is followed by a space, the
19190 additional information, and a newline. The additional information
19191 cannot contain newline characters.
19193 Any output not beginning with a newline and two @samp{control-z}
19194 characters denotes literal output from @value{GDBN}. Currently there is
19195 no need for @value{GDBN} to output a newline followed by two
19196 @samp{control-z} characters, but if there was such a need, the
19197 annotations could be extended with an @samp{escape} annotation which
19198 means those three characters as output.
19200 The annotation @var{level}, which is specified using the
19201 @option{--annotate} command line option (@pxref{Mode Options}), controls
19202 how much information @value{GDBN} prints together with its prompt,
19203 values of expressions, source lines, and other types of output. Level 0
19204 is for no anntations, level 1 is for use when @value{GDBN} is run as a
19205 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
19206 for programs that control @value{GDBN}, and level 2 annotations have
19207 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
19208 Interface, annotate, GDB's Obsolete Annotations}).
19211 @kindex set annotate
19212 @item set annotate @var{level}
19213 The @value{GDB} command @code{set annotate} sets the level of
19214 annotations to the specified @var{level}.
19217 This chapter describes level 3 annotations.
19219 A simple example of starting up @value{GDBN} with annotations is:
19222 $ @kbd{gdb --annotate=3}
19224 Copyright 2003 Free Software Foundation, Inc.
19225 GDB is free software, covered by the GNU General Public License,
19226 and you are welcome to change it and/or distribute copies of it
19227 under certain conditions.
19228 Type "show copying" to see the conditions.
19229 There is absolutely no warranty for GDB. Type "show warranty"
19231 This GDB was configured as "i386-pc-linux-gnu"
19242 Here @samp{quit} is input to @value{GDBN}; the rest is output from
19243 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
19244 denotes a @samp{control-z} character) are annotations; the rest is
19245 output from @value{GDBN}.
19247 @node Server Prefix
19248 @section The Server Prefix
19249 @cindex server prefix for annotations
19251 To issue a command to @value{GDBN} without affecting certain aspects of
19252 the state which is seen by users, prefix it with @samp{server }. This
19253 means that this command will not affect the command history, nor will it
19254 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
19255 pressed on a line by itself.
19257 The server prefix does not affect the recording of values into the value
19258 history; to print a value without recording it into the value history,
19259 use the @code{output} command instead of the @code{print} command.
19262 @section Annotation for @value{GDBN} Input
19264 @cindex annotations for prompts
19265 When @value{GDBN} prompts for input, it annotates this fact so it is possible
19266 to know when to send output, when the output from a given command is
19269 Different kinds of input each have a different @dfn{input type}. Each
19270 input type has three annotations: a @code{pre-} annotation, which
19271 denotes the beginning of any prompt which is being output, a plain
19272 annotation, which denotes the end of the prompt, and then a @code{post-}
19273 annotation which denotes the end of any echo which may (or may not) be
19274 associated with the input. For example, the @code{prompt} input type
19275 features the following annotations:
19283 The input types are
19288 @findex post-prompt
19290 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
19292 @findex pre-commands
19294 @findex post-commands
19296 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
19297 command. The annotations are repeated for each command which is input.
19299 @findex pre-overload-choice
19300 @findex overload-choice
19301 @findex post-overload-choice
19302 @item overload-choice
19303 When @value{GDBN} wants the user to select between various overloaded functions.
19309 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
19311 @findex pre-prompt-for-continue
19312 @findex prompt-for-continue
19313 @findex post-prompt-for-continue
19314 @item prompt-for-continue
19315 When @value{GDBN} is asking the user to press return to continue. Note: Don't
19316 expect this to work well; instead use @code{set height 0} to disable
19317 prompting. This is because the counting of lines is buggy in the
19318 presence of annotations.
19323 @cindex annotations for errors, warnings and interrupts
19330 This annotation occurs right before @value{GDBN} responds to an interrupt.
19337 This annotation occurs right before @value{GDBN} responds to an error.
19339 Quit and error annotations indicate that any annotations which @value{GDBN} was
19340 in the middle of may end abruptly. For example, if a
19341 @code{value-history-begin} annotation is followed by a @code{error}, one
19342 cannot expect to receive the matching @code{value-history-end}. One
19343 cannot expect not to receive it either, however; an error annotation
19344 does not necessarily mean that @value{GDBN} is immediately returning all the way
19347 @findex error-begin
19348 A quit or error annotation may be preceded by
19354 Any output between that and the quit or error annotation is the error
19357 Warning messages are not yet annotated.
19358 @c If we want to change that, need to fix warning(), type_error(),
19359 @c range_error(), and possibly other places.
19362 @section Invalidation Notices
19364 @cindex annotations for invalidation messages
19365 The following annotations say that certain pieces of state may have
19369 @findex frames-invalid
19370 @item ^Z^Zframes-invalid
19372 The frames (for example, output from the @code{backtrace} command) may
19375 @findex breakpoints-invalid
19376 @item ^Z^Zbreakpoints-invalid
19378 The breakpoints may have changed. For example, the user just added or
19379 deleted a breakpoint.
19382 @node Annotations for Running
19383 @section Running the Program
19384 @cindex annotations for running programs
19388 When the program starts executing due to a @value{GDBN} command such as
19389 @code{step} or @code{continue},
19395 is output. When the program stops,
19401 is output. Before the @code{stopped} annotation, a variety of
19402 annotations describe how the program stopped.
19406 @item ^Z^Zexited @var{exit-status}
19407 The program exited, and @var{exit-status} is the exit status (zero for
19408 successful exit, otherwise nonzero).
19411 @findex signal-name
19412 @findex signal-name-end
19413 @findex signal-string
19414 @findex signal-string-end
19415 @item ^Z^Zsignalled
19416 The program exited with a signal. After the @code{^Z^Zsignalled}, the
19417 annotation continues:
19423 ^Z^Zsignal-name-end
19427 ^Z^Zsignal-string-end
19432 where @var{name} is the name of the signal, such as @code{SIGILL} or
19433 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
19434 as @code{Illegal Instruction} or @code{Segmentation fault}.
19435 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
19436 user's benefit and have no particular format.
19440 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
19441 just saying that the program received the signal, not that it was
19442 terminated with it.
19445 @item ^Z^Zbreakpoint @var{number}
19446 The program hit breakpoint number @var{number}.
19449 @item ^Z^Zwatchpoint @var{number}
19450 The program hit watchpoint number @var{number}.
19453 @node Source Annotations
19454 @section Displaying Source
19455 @cindex annotations for source display
19458 The following annotation is used instead of displaying source code:
19461 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
19464 where @var{filename} is an absolute file name indicating which source
19465 file, @var{line} is the line number within that file (where 1 is the
19466 first line in the file), @var{character} is the character position
19467 within the file (where 0 is the first character in the file) (for most
19468 debug formats this will necessarily point to the beginning of a line),
19469 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
19470 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
19471 @var{addr} is the address in the target program associated with the
19472 source which is being displayed. @var{addr} is in the form @samp{0x}
19473 followed by one or more lowercase hex digits (note that this does not
19474 depend on the language).
19477 @chapter Reporting Bugs in @value{GDBN}
19478 @cindex bugs in @value{GDBN}
19479 @cindex reporting bugs in @value{GDBN}
19481 Your bug reports play an essential role in making @value{GDBN} reliable.
19483 Reporting a bug may help you by bringing a solution to your problem, or it
19484 may not. But in any case the principal function of a bug report is to help
19485 the entire community by making the next version of @value{GDBN} work better. Bug
19486 reports are your contribution to the maintenance of @value{GDBN}.
19488 In order for a bug report to serve its purpose, you must include the
19489 information that enables us to fix the bug.
19492 * Bug Criteria:: Have you found a bug?
19493 * Bug Reporting:: How to report bugs
19497 @section Have you found a bug?
19498 @cindex bug criteria
19500 If you are not sure whether you have found a bug, here are some guidelines:
19503 @cindex fatal signal
19504 @cindex debugger crash
19505 @cindex crash of debugger
19507 If the debugger gets a fatal signal, for any input whatever, that is a
19508 @value{GDBN} bug. Reliable debuggers never crash.
19510 @cindex error on valid input
19512 If @value{GDBN} produces an error message for valid input, that is a
19513 bug. (Note that if you're cross debugging, the problem may also be
19514 somewhere in the connection to the target.)
19516 @cindex invalid input
19518 If @value{GDBN} does not produce an error message for invalid input,
19519 that is a bug. However, you should note that your idea of
19520 ``invalid input'' might be our idea of ``an extension'' or ``support
19521 for traditional practice''.
19524 If you are an experienced user of debugging tools, your suggestions
19525 for improvement of @value{GDBN} are welcome in any case.
19528 @node Bug Reporting
19529 @section How to report bugs
19530 @cindex bug reports
19531 @cindex @value{GDBN} bugs, reporting
19533 A number of companies and individuals offer support for @sc{gnu} products.
19534 If you obtained @value{GDBN} from a support organization, we recommend you
19535 contact that organization first.
19537 You can find contact information for many support companies and
19538 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
19540 @c should add a web page ref...
19542 In any event, we also recommend that you submit bug reports for
19543 @value{GDBN}. The prefered method is to submit them directly using
19544 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
19545 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
19548 @strong{Do not send bug reports to @samp{info-gdb}, or to
19549 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
19550 not want to receive bug reports. Those that do have arranged to receive
19553 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
19554 serves as a repeater. The mailing list and the newsgroup carry exactly
19555 the same messages. Often people think of posting bug reports to the
19556 newsgroup instead of mailing them. This appears to work, but it has one
19557 problem which can be crucial: a newsgroup posting often lacks a mail
19558 path back to the sender. Thus, if we need to ask for more information,
19559 we may be unable to reach you. For this reason, it is better to send
19560 bug reports to the mailing list.
19562 The fundamental principle of reporting bugs usefully is this:
19563 @strong{report all the facts}. If you are not sure whether to state a
19564 fact or leave it out, state it!
19566 Often people omit facts because they think they know what causes the
19567 problem and assume that some details do not matter. Thus, you might
19568 assume that the name of the variable you use in an example does not matter.
19569 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
19570 stray memory reference which happens to fetch from the location where that
19571 name is stored in memory; perhaps, if the name were different, the contents
19572 of that location would fool the debugger into doing the right thing despite
19573 the bug. Play it safe and give a specific, complete example. That is the
19574 easiest thing for you to do, and the most helpful.
19576 Keep in mind that the purpose of a bug report is to enable us to fix the
19577 bug. It may be that the bug has been reported previously, but neither
19578 you nor we can know that unless your bug report is complete and
19581 Sometimes people give a few sketchy facts and ask, ``Does this ring a
19582 bell?'' Those bug reports are useless, and we urge everyone to
19583 @emph{refuse to respond to them} except to chide the sender to report
19586 To enable us to fix the bug, you should include all these things:
19590 The version of @value{GDBN}. @value{GDBN} announces it if you start
19591 with no arguments; you can also print it at any time using @code{show
19594 Without this, we will not know whether there is any point in looking for
19595 the bug in the current version of @value{GDBN}.
19598 The type of machine you are using, and the operating system name and
19602 What compiler (and its version) was used to compile @value{GDBN}---e.g.
19603 ``@value{GCC}--2.8.1''.
19606 What compiler (and its version) was used to compile the program you are
19607 debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
19608 C Compiler''. For GCC, you can say @code{gcc --version} to get this
19609 information; for other compilers, see the documentation for those
19613 The command arguments you gave the compiler to compile your example and
19614 observe the bug. For example, did you use @samp{-O}? To guarantee
19615 you will not omit something important, list them all. A copy of the
19616 Makefile (or the output from make) is sufficient.
19618 If we were to try to guess the arguments, we would probably guess wrong
19619 and then we might not encounter the bug.
19622 A complete input script, and all necessary source files, that will
19626 A description of what behavior you observe that you believe is
19627 incorrect. For example, ``It gets a fatal signal.''
19629 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
19630 will certainly notice it. But if the bug is incorrect output, we might
19631 not notice unless it is glaringly wrong. You might as well not give us
19632 a chance to make a mistake.
19634 Even if the problem you experience is a fatal signal, you should still
19635 say so explicitly. Suppose something strange is going on, such as, your
19636 copy of @value{GDBN} is out of synch, or you have encountered a bug in
19637 the C library on your system. (This has happened!) Your copy might
19638 crash and ours would not. If you told us to expect a crash, then when
19639 ours fails to crash, we would know that the bug was not happening for
19640 us. If you had not told us to expect a crash, then we would not be able
19641 to draw any conclusion from our observations.
19644 @cindex recording a session script
19645 To collect all this information, you can use a session recording program
19646 such as @command{script}, which is available on many Unix systems.
19647 Just run your @value{GDBN} session inside @command{script} and then
19648 include the @file{typescript} file with your bug report.
19650 Another way to record a @value{GDBN} session is to run @value{GDBN}
19651 inside Emacs and then save the entire buffer to a file.
19654 If you wish to suggest changes to the @value{GDBN} source, send us context
19655 diffs. If you even discuss something in the @value{GDBN} source, refer to
19656 it by context, not by line number.
19658 The line numbers in our development sources will not match those in your
19659 sources. Your line numbers would convey no useful information to us.
19663 Here are some things that are not necessary:
19667 A description of the envelope of the bug.
19669 Often people who encounter a bug spend a lot of time investigating
19670 which changes to the input file will make the bug go away and which
19671 changes will not affect it.
19673 This is often time consuming and not very useful, because the way we
19674 will find the bug is by running a single example under the debugger
19675 with breakpoints, not by pure deduction from a series of examples.
19676 We recommend that you save your time for something else.
19678 Of course, if you can find a simpler example to report @emph{instead}
19679 of the original one, that is a convenience for us. Errors in the
19680 output will be easier to spot, running under the debugger will take
19681 less time, and so on.
19683 However, simplification is not vital; if you do not want to do this,
19684 report the bug anyway and send us the entire test case you used.
19687 A patch for the bug.
19689 A patch for the bug does help us if it is a good one. But do not omit
19690 the necessary information, such as the test case, on the assumption that
19691 a patch is all we need. We might see problems with your patch and decide
19692 to fix the problem another way, or we might not understand it at all.
19694 Sometimes with a program as complicated as @value{GDBN} it is very hard to
19695 construct an example that will make the program follow a certain path
19696 through the code. If you do not send us the example, we will not be able
19697 to construct one, so we will not be able to verify that the bug is fixed.
19699 And if we cannot understand what bug you are trying to fix, or why your
19700 patch should be an improvement, we will not install it. A test case will
19701 help us to understand.
19704 A guess about what the bug is or what it depends on.
19706 Such guesses are usually wrong. Even we cannot guess right about such
19707 things without first using the debugger to find the facts.
19710 @c The readline documentation is distributed with the readline code
19711 @c and consists of the two following files:
19713 @c inc-hist.texinfo
19714 @c Use -I with makeinfo to point to the appropriate directory,
19715 @c environment var TEXINPUTS with TeX.
19716 @include rluser.texinfo
19717 @include inc-hist.texinfo
19720 @node Formatting Documentation
19721 @appendix Formatting Documentation
19723 @cindex @value{GDBN} reference card
19724 @cindex reference card
19725 The @value{GDBN} 4 release includes an already-formatted reference card, ready
19726 for printing with PostScript or Ghostscript, in the @file{gdb}
19727 subdirectory of the main source directory@footnote{In
19728 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
19729 release.}. If you can use PostScript or Ghostscript with your printer,
19730 you can print the reference card immediately with @file{refcard.ps}.
19732 The release also includes the source for the reference card. You
19733 can format it, using @TeX{}, by typing:
19739 The @value{GDBN} reference card is designed to print in @dfn{landscape}
19740 mode on US ``letter'' size paper;
19741 that is, on a sheet 11 inches wide by 8.5 inches
19742 high. You will need to specify this form of printing as an option to
19743 your @sc{dvi} output program.
19745 @cindex documentation
19747 All the documentation for @value{GDBN} comes as part of the machine-readable
19748 distribution. The documentation is written in Texinfo format, which is
19749 a documentation system that uses a single source file to produce both
19750 on-line information and a printed manual. You can use one of the Info
19751 formatting commands to create the on-line version of the documentation
19752 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
19754 @value{GDBN} includes an already formatted copy of the on-line Info
19755 version of this manual in the @file{gdb} subdirectory. The main Info
19756 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
19757 subordinate files matching @samp{gdb.info*} in the same directory. If
19758 necessary, you can print out these files, or read them with any editor;
19759 but they are easier to read using the @code{info} subsystem in @sc{gnu}
19760 Emacs or the standalone @code{info} program, available as part of the
19761 @sc{gnu} Texinfo distribution.
19763 If you want to format these Info files yourself, you need one of the
19764 Info formatting programs, such as @code{texinfo-format-buffer} or
19767 If you have @code{makeinfo} installed, and are in the top level
19768 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
19769 version @value{GDBVN}), you can make the Info file by typing:
19776 If you want to typeset and print copies of this manual, you need @TeX{},
19777 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
19778 Texinfo definitions file.
19780 @TeX{} is a typesetting program; it does not print files directly, but
19781 produces output files called @sc{dvi} files. To print a typeset
19782 document, you need a program to print @sc{dvi} files. If your system
19783 has @TeX{} installed, chances are it has such a program. The precise
19784 command to use depends on your system; @kbd{lpr -d} is common; another
19785 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
19786 require a file name without any extension or a @samp{.dvi} extension.
19788 @TeX{} also requires a macro definitions file called
19789 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
19790 written in Texinfo format. On its own, @TeX{} cannot either read or
19791 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
19792 and is located in the @file{gdb-@var{version-number}/texinfo}
19795 If you have @TeX{} and a @sc{dvi} printer program installed, you can
19796 typeset and print this manual. First switch to the the @file{gdb}
19797 subdirectory of the main source directory (for example, to
19798 @file{gdb-@value{GDBVN}/gdb}) and type:
19804 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
19806 @node Installing GDB
19807 @appendix Installing @value{GDBN}
19808 @cindex configuring @value{GDBN}
19809 @cindex installation
19810 @cindex configuring @value{GDBN}, and source tree subdirectories
19812 @value{GDBN} comes with a @code{configure} script that automates the process
19813 of preparing @value{GDBN} for installation; you can then use @code{make} to
19814 build the @code{gdb} program.
19816 @c irrelevant in info file; it's as current as the code it lives with.
19817 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
19818 look at the @file{README} file in the sources; we may have improved the
19819 installation procedures since publishing this manual.}
19822 The @value{GDBN} distribution includes all the source code you need for
19823 @value{GDBN} in a single directory, whose name is usually composed by
19824 appending the version number to @samp{gdb}.
19826 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
19827 @file{gdb-@value{GDBVN}} directory. That directory contains:
19830 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
19831 script for configuring @value{GDBN} and all its supporting libraries
19833 @item gdb-@value{GDBVN}/gdb
19834 the source specific to @value{GDBN} itself
19836 @item gdb-@value{GDBVN}/bfd
19837 source for the Binary File Descriptor library
19839 @item gdb-@value{GDBVN}/include
19840 @sc{gnu} include files
19842 @item gdb-@value{GDBVN}/libiberty
19843 source for the @samp{-liberty} free software library
19845 @item gdb-@value{GDBVN}/opcodes
19846 source for the library of opcode tables and disassemblers
19848 @item gdb-@value{GDBVN}/readline
19849 source for the @sc{gnu} command-line interface
19851 @item gdb-@value{GDBVN}/glob
19852 source for the @sc{gnu} filename pattern-matching subroutine
19854 @item gdb-@value{GDBVN}/mmalloc
19855 source for the @sc{gnu} memory-mapped malloc package
19858 The simplest way to configure and build @value{GDBN} is to run @code{configure}
19859 from the @file{gdb-@var{version-number}} source directory, which in
19860 this example is the @file{gdb-@value{GDBVN}} directory.
19862 First switch to the @file{gdb-@var{version-number}} source directory
19863 if you are not already in it; then run @code{configure}. Pass the
19864 identifier for the platform on which @value{GDBN} will run as an
19870 cd gdb-@value{GDBVN}
19871 ./configure @var{host}
19876 where @var{host} is an identifier such as @samp{sun4} or
19877 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
19878 (You can often leave off @var{host}; @code{configure} tries to guess the
19879 correct value by examining your system.)
19881 Running @samp{configure @var{host}} and then running @code{make} builds the
19882 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
19883 libraries, then @code{gdb} itself. The configured source files, and the
19884 binaries, are left in the corresponding source directories.
19887 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
19888 system does not recognize this automatically when you run a different
19889 shell, you may need to run @code{sh} on it explicitly:
19892 sh configure @var{host}
19895 If you run @code{configure} from a directory that contains source
19896 directories for multiple libraries or programs, such as the
19897 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
19898 creates configuration files for every directory level underneath (unless
19899 you tell it not to, with the @samp{--norecursion} option).
19901 You should run the @code{configure} script from the top directory in the
19902 source tree, the @file{gdb-@var{version-number}} directory. If you run
19903 @code{configure} from one of the subdirectories, you will configure only
19904 that subdirectory. That is usually not what you want. In particular,
19905 if you run the first @code{configure} from the @file{gdb} subdirectory
19906 of the @file{gdb-@var{version-number}} directory, you will omit the
19907 configuration of @file{bfd}, @file{readline}, and other sibling
19908 directories of the @file{gdb} subdirectory. This leads to build errors
19909 about missing include files such as @file{bfd/bfd.h}.
19911 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
19912 However, you should make sure that the shell on your path (named by
19913 the @samp{SHELL} environment variable) is publicly readable. Remember
19914 that @value{GDBN} uses the shell to start your program---some systems refuse to
19915 let @value{GDBN} debug child processes whose programs are not readable.
19918 * Separate Objdir:: Compiling @value{GDBN} in another directory
19919 * Config Names:: Specifying names for hosts and targets
19920 * Configure Options:: Summary of options for configure
19923 @node Separate Objdir
19924 @section Compiling @value{GDBN} in another directory
19926 If you want to run @value{GDBN} versions for several host or target machines,
19927 you need a different @code{gdb} compiled for each combination of
19928 host and target. @code{configure} is designed to make this easy by
19929 allowing you to generate each configuration in a separate subdirectory,
19930 rather than in the source directory. If your @code{make} program
19931 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
19932 @code{make} in each of these directories builds the @code{gdb}
19933 program specified there.
19935 To build @code{gdb} in a separate directory, run @code{configure}
19936 with the @samp{--srcdir} option to specify where to find the source.
19937 (You also need to specify a path to find @code{configure}
19938 itself from your working directory. If the path to @code{configure}
19939 would be the same as the argument to @samp{--srcdir}, you can leave out
19940 the @samp{--srcdir} option; it is assumed.)
19942 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
19943 separate directory for a Sun 4 like this:
19947 cd gdb-@value{GDBVN}
19950 ../gdb-@value{GDBVN}/configure sun4
19955 When @code{configure} builds a configuration using a remote source
19956 directory, it creates a tree for the binaries with the same structure
19957 (and using the same names) as the tree under the source directory. In
19958 the example, you'd find the Sun 4 library @file{libiberty.a} in the
19959 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
19960 @file{gdb-sun4/gdb}.
19962 Make sure that your path to the @file{configure} script has just one
19963 instance of @file{gdb} in it. If your path to @file{configure} looks
19964 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
19965 one subdirectory of @value{GDBN}, not the whole package. This leads to
19966 build errors about missing include files such as @file{bfd/bfd.h}.
19968 One popular reason to build several @value{GDBN} configurations in separate
19969 directories is to configure @value{GDBN} for cross-compiling (where
19970 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
19971 programs that run on another machine---the @dfn{target}).
19972 You specify a cross-debugging target by
19973 giving the @samp{--target=@var{target}} option to @code{configure}.
19975 When you run @code{make} to build a program or library, you must run
19976 it in a configured directory---whatever directory you were in when you
19977 called @code{configure} (or one of its subdirectories).
19979 The @code{Makefile} that @code{configure} generates in each source
19980 directory also runs recursively. If you type @code{make} in a source
19981 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
19982 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
19983 will build all the required libraries, and then build GDB.
19985 When you have multiple hosts or targets configured in separate
19986 directories, you can run @code{make} on them in parallel (for example,
19987 if they are NFS-mounted on each of the hosts); they will not interfere
19991 @section Specifying names for hosts and targets
19993 The specifications used for hosts and targets in the @code{configure}
19994 script are based on a three-part naming scheme, but some short predefined
19995 aliases are also supported. The full naming scheme encodes three pieces
19996 of information in the following pattern:
19999 @var{architecture}-@var{vendor}-@var{os}
20002 For example, you can use the alias @code{sun4} as a @var{host} argument,
20003 or as the value for @var{target} in a @code{--target=@var{target}}
20004 option. The equivalent full name is @samp{sparc-sun-sunos4}.
20006 The @code{configure} script accompanying @value{GDBN} does not provide
20007 any query facility to list all supported host and target names or
20008 aliases. @code{configure} calls the Bourne shell script
20009 @code{config.sub} to map abbreviations to full names; you can read the
20010 script, if you wish, or you can use it to test your guesses on
20011 abbreviations---for example:
20014 % sh config.sub i386-linux
20016 % sh config.sub alpha-linux
20017 alpha-unknown-linux-gnu
20018 % sh config.sub hp9k700
20020 % sh config.sub sun4
20021 sparc-sun-sunos4.1.1
20022 % sh config.sub sun3
20023 m68k-sun-sunos4.1.1
20024 % sh config.sub i986v
20025 Invalid configuration `i986v': machine `i986v' not recognized
20029 @code{config.sub} is also distributed in the @value{GDBN} source
20030 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
20032 @node Configure Options
20033 @section @code{configure} options
20035 Here is a summary of the @code{configure} options and arguments that
20036 are most often useful for building @value{GDBN}. @code{configure} also has
20037 several other options not listed here. @inforef{What Configure
20038 Does,,configure.info}, for a full explanation of @code{configure}.
20041 configure @r{[}--help@r{]}
20042 @r{[}--prefix=@var{dir}@r{]}
20043 @r{[}--exec-prefix=@var{dir}@r{]}
20044 @r{[}--srcdir=@var{dirname}@r{]}
20045 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
20046 @r{[}--target=@var{target}@r{]}
20051 You may introduce options with a single @samp{-} rather than
20052 @samp{--} if you prefer; but you may abbreviate option names if you use
20057 Display a quick summary of how to invoke @code{configure}.
20059 @item --prefix=@var{dir}
20060 Configure the source to install programs and files under directory
20063 @item --exec-prefix=@var{dir}
20064 Configure the source to install programs under directory
20067 @c avoid splitting the warning from the explanation:
20069 @item --srcdir=@var{dirname}
20070 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
20071 @code{make} that implements the @code{VPATH} feature.}@*
20072 Use this option to make configurations in directories separate from the
20073 @value{GDBN} source directories. Among other things, you can use this to
20074 build (or maintain) several configurations simultaneously, in separate
20075 directories. @code{configure} writes configuration specific files in
20076 the current directory, but arranges for them to use the source in the
20077 directory @var{dirname}. @code{configure} creates directories under
20078 the working directory in parallel to the source directories below
20081 @item --norecursion
20082 Configure only the directory level where @code{configure} is executed; do not
20083 propagate configuration to subdirectories.
20085 @item --target=@var{target}
20086 Configure @value{GDBN} for cross-debugging programs running on the specified
20087 @var{target}. Without this option, @value{GDBN} is configured to debug
20088 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
20090 There is no convenient way to generate a list of all available targets.
20092 @item @var{host} @dots{}
20093 Configure @value{GDBN} to run on the specified @var{host}.
20095 There is no convenient way to generate a list of all available hosts.
20098 There are many other options available as well, but they are generally
20099 needed for special purposes only.
20101 @node Maintenance Commands
20102 @appendix Maintenance Commands
20103 @cindex maintenance commands
20104 @cindex internal commands
20106 In addition to commands intended for @value{GDBN} users, @value{GDBN}
20107 includes a number of commands intended for @value{GDBN} developers,
20108 that are not documented elsewhere in this manual. These commands are
20109 provided here for reference.
20112 @kindex maint agent
20113 @item maint agent @var{expression}
20114 Translate the given @var{expression} into remote agent bytecodes.
20115 This command is useful for debugging the Agent Expression mechanism
20116 (@pxref{Agent Expressions}).
20118 @kindex maint info breakpoints
20119 @item @anchor{maint info breakpoints}maint info breakpoints
20120 Using the same format as @samp{info breakpoints}, display both the
20121 breakpoints you've set explicitly, and those @value{GDBN} is using for
20122 internal purposes. Internal breakpoints are shown with negative
20123 breakpoint numbers. The type column identifies what kind of breakpoint
20128 Normal, explicitly set breakpoint.
20131 Normal, explicitly set watchpoint.
20134 Internal breakpoint, used to handle correctly stepping through
20135 @code{longjmp} calls.
20137 @item longjmp resume
20138 Internal breakpoint at the target of a @code{longjmp}.
20141 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
20144 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
20147 Shared library events.
20151 @kindex maint check-symtabs
20152 @item maint check-symtabs
20153 Check the consistency of psymtabs and symtabs.
20155 @kindex maint cplus first_component
20156 @item maint cplus first_component @var{name}
20157 Print the first C@t{++} class/namespace component of @var{name}.
20159 @kindex maint cplus namespace
20160 @item maint cplus namespace
20161 Print the list of possible C@t{++} namespaces.
20163 @kindex maint demangle
20164 @item maint demangle @var{name}
20165 Demangle a C@t{++} or Objective-C manled @var{name}.
20167 @kindex maint deprecate
20168 @kindex maint undeprecate
20169 @cindex deprecated commands
20170 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
20171 @itemx maint undeprecate @var{command}
20172 Deprecate or undeprecate the named @var{command}. Deprecated commands
20173 cause @value{GDBN} to issue a warning when you use them. The optional
20174 argument @var{replacement} says which newer command should be used in
20175 favor of the deprecated one; if it is given, @value{GDBN} will mention
20176 the replacement as part of the warning.
20178 @kindex maint dump-me
20179 @item maint dump-me
20180 Cause a fatal signal in the debugger and force it to dump its core.
20182 @kindex maint internal-error
20183 @kindex maint internal-warning
20184 @item maint internal-error @r{[}@var{message-text}@r{]}
20185 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
20186 Cause @value{GDBN} to call the internal function @code{internal_error}
20187 or @code{internal_warning} and hence behave as though an internal error
20188 or internal warning has been detected. In addition to reporting the
20189 internal problem, these functions give the user the opportunity to
20190 either quit @value{GDBN} or create a core file of the current
20191 @value{GDBN} session.
20193 These commands take an optional parameter @var{message-text} that is
20194 used as the text of the error or warning message.
20196 Here's an example of using @code{indernal-error}:
20199 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
20200 @dots{}/maint.c:121: internal-error: testing, 1, 2
20201 A problem internal to GDB has been detected. Further
20202 debugging may prove unreliable.
20203 Quit this debugging session? (y or n) @kbd{n}
20204 Create a core file? (y or n) @kbd{n}
20208 @kindex maint packet
20209 @item maint packet @var{text}
20210 If @value{GDBN} is talking to an inferior via the serial protocol,
20211 then this command sends the string @var{text} to the inferior, and
20212 displays the response packet. @value{GDBN} supplies the initial
20213 @samp{$} character, the terminating @samp{#} character, and the
20216 @kindex maint print architecture
20217 @item maint print architecture @r{[}@var{file}@r{]}
20218 Print the entire architecture configuration. The optional argument
20219 @var{file} names the file where the output goes.
20221 @kindex maint print dummy-frames
20222 @item maint print dummy-frames
20224 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
20227 (@value{GDBP}) @kbd{b add}
20229 (@value{GDBP}) @kbd{print add(2,3)}
20230 Breakpoint 2, add (a=2, b=3) at @dots{}
20232 The program being debugged stopped while in a function called from GDB.
20234 (@value{GDBP}) @kbd{maint print dummy-frames}
20235 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
20236 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
20237 call_lo=0x01014000 call_hi=0x01014001
20241 Takes an optional file parameter.
20243 @kindex maint print registers
20244 @kindex maint print raw-registers
20245 @kindex maint print cooked-registers
20246 @kindex maint print register-groups
20247 @item maint print registers @r{[}@var{file}@r{]}
20248 @itemx maint print raw-registers @r{[}@var{file}@r{]}
20249 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
20250 @itemx maint print register-groups @r{[}@var{file}@r{]}
20251 Print @value{GDBN}'s internal register data structures.
20253 The command @code{maint print raw-registers} includes the contents of
20254 the raw register cache; the command @code{maint print cooked-registers}
20255 includes the (cooked) value of all registers; and the command
20256 @code{maint print register-groups} includes the groups that each
20257 register is a member of. @xref{Registers,, Registers, gdbint,
20258 @value{GDBN} Internals}.
20260 These commands take an optional parameter, a file name to which to
20261 write the information.
20263 @kindex maint print reggroups
20264 @item maint print reggroups @r{[}@var{file}@r{]}
20265 Print @value{GDBN}'s internal register group data structures. The
20266 optional argument @var{file} tells to what file to write the
20269 The register groups info looks like this:
20272 (@value{GDBP}) @kbd{maint print reggroups}
20285 This command forces @value{GDBN} to flush its internal register cache.
20287 @kindex maint print objfiles
20288 @cindex info for known object files
20289 @item maint print objfiles
20290 Print a dump of all known object files. For each object file, this
20291 command prints its name, address in memory, and all of its psymtabs
20294 @kindex maint print statistics
20295 @cindex bcache statistics
20296 @item maint print statistics
20297 This command prints, for each object file in the program, various data
20298 about that object file followed by the byte cache (@dfn{bcache})
20299 statistics for the object file. The objfile data includes the number
20300 of minimal, partical, full, and stabs symbols, the number of types
20301 defined by the objfile, the number of as yet unexpanded psym tables,
20302 the number of line tables and string tables, and the amount of memory
20303 used by the various tables. The bcache statistics include the counts,
20304 sizes, and counts of duplicates of all and unique objects, max,
20305 average, and median entry size, total memory used and its overhead and
20306 savings, and various measures of the hash table size and chain
20309 @kindex maint print type
20310 @cindex type chain of a data type
20311 @item maint print type @var{expr}
20312 Print the type chain for a type specified by @var{expr}. The argument
20313 can be either a type name or a symbol. If it is a symbol, the type of
20314 that symbol is described. The type chain produced by this command is
20315 a recursive definition of the data type as stored in @value{GDBN}'s
20316 data structures, including its flags and contained types.
20318 @kindex maint set dwarf2 max-cache-age
20319 @kindex maint show dwarf2 max-cache-age
20320 @item maint set dwarf2 max-cache-age
20321 @itemx maint show dwarf2 max-cache-age
20322 Control the DWARF 2 compilation unit cache.
20324 @cindex DWARF 2 compilation units cache
20325 In object files with inter-compilation-unit references, such as those
20326 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
20327 reader needs to frequently refer to previously read compilation units.
20328 This setting controls how long a compilation unit will remain in the
20329 cache if it is not referenced. A higher limit means that cached
20330 compilation units will be stored in memory longer, and more total
20331 memory will be used. Setting it to zero disables caching, which will
20332 slow down @value{GDBN} startup, but reduce memory consumption.
20334 @kindex maint set profile
20335 @kindex maint show profile
20336 @cindex profiling GDB
20337 @item maint set profile
20338 @itemx maint show profile
20339 Control profiling of @value{GDBN}.
20341 Profiling will be disabled until you use the @samp{maint set profile}
20342 command to enable it. When you enable profiling, the system will begin
20343 collecting timing and execution count data; when you disable profiling or
20344 exit @value{GDBN}, the results will be written to a log file. Remember that
20345 if you use profiling, @value{GDBN} will overwrite the profiling log file
20346 (often called @file{gmon.out}). If you have a record of important profiling
20347 data in a @file{gmon.out} file, be sure to move it to a safe location.
20349 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
20350 compiled with the @samp{-pg} compiler option.
20352 @kindex maint show-debug-regs
20353 @cindex x86 hardware debug registers
20354 @item maint show-debug-regs
20355 Control whether to show variables that mirror the x86 hardware debug
20356 registers. Use @code{ON} to enable, @code{OFF} to disable. If
20357 enabled, the debug registers values are shown when GDB inserts or
20358 removes a hardware breakpoint or watchpoint, and when the inferior
20359 triggers a hardware-assisted breakpoint or watchpoint.
20361 @kindex maint space
20362 @cindex memory used by commands
20364 Control whether to display memory usage for each command. If set to a
20365 nonzero value, @value{GDBN} will display how much memory each command
20366 took, following the command's own output. This can also be requested
20367 by invoking @value{GDBN} with the @option{--statistics} command-line
20368 switch (@pxref{Mode Options}).
20371 @cindex time of command execution
20373 Control whether to display the execution time for each command. If
20374 set to a nonzero value, @value{GDBN} will display how much time it
20375 took to execute each command, following the command's own output.
20376 This can also be requested by invoking @value{GDBN} with the
20377 @option{--statistics} command-line switch (@pxref{Mode Options}).
20379 @kindex maint translate-address
20380 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
20381 Find the symbol stored at the location specified by the address
20382 @var{addr} and an optional section name @var{section}. If found,
20383 @value{GDBN} prints the name of the closest symbol and an offset from
20384 the symbol's location to the specified address. This is similar to
20385 the @code{info address} command (@pxref{Symbols}), except that this
20386 command also allows to find symbols in other sections.
20391 @node Remote Protocol
20392 @appendix @value{GDBN} Remote Serial Protocol
20397 * Stop Reply Packets::
20398 * General Query Packets::
20399 * Register Packet Format::
20401 * File-I/O remote protocol extension::
20407 There may be occasions when you need to know something about the
20408 protocol---for example, if there is only one serial port to your target
20409 machine, you might want your program to do something special if it
20410 recognizes a packet meant for @value{GDBN}.
20412 In the examples below, @samp{->} and @samp{<-} are used to indicate
20413 transmitted and received data respectfully.
20415 @cindex protocol, @value{GDBN} remote serial
20416 @cindex serial protocol, @value{GDBN} remote
20417 @cindex remote serial protocol
20418 All @value{GDBN} commands and responses (other than acknowledgments) are
20419 sent as a @var{packet}. A @var{packet} is introduced with the character
20420 @samp{$}, the actual @var{packet-data}, and the terminating character
20421 @samp{#} followed by a two-digit @var{checksum}:
20424 @code{$}@var{packet-data}@code{#}@var{checksum}
20428 @cindex checksum, for @value{GDBN} remote
20430 The two-digit @var{checksum} is computed as the modulo 256 sum of all
20431 characters between the leading @samp{$} and the trailing @samp{#} (an
20432 eight bit unsigned checksum).
20434 Implementors should note that prior to @value{GDBN} 5.0 the protocol
20435 specification also included an optional two-digit @var{sequence-id}:
20438 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
20441 @cindex sequence-id, for @value{GDBN} remote
20443 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
20444 has never output @var{sequence-id}s. Stubs that handle packets added
20445 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
20447 @cindex acknowledgment, for @value{GDBN} remote
20448 When either the host or the target machine receives a packet, the first
20449 response expected is an acknowledgment: either @samp{+} (to indicate
20450 the package was received correctly) or @samp{-} (to request
20454 -> @code{$}@var{packet-data}@code{#}@var{checksum}
20459 The host (@value{GDBN}) sends @var{command}s, and the target (the
20460 debugging stub incorporated in your program) sends a @var{response}. In
20461 the case of step and continue @var{command}s, the response is only sent
20462 when the operation has completed (the target has again stopped).
20464 @var{packet-data} consists of a sequence of characters with the
20465 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
20468 Fields within the packet should be separated using @samp{,} @samp{;} or
20469 @cindex remote protocol, field separator
20470 @samp{:}. Except where otherwise noted all numbers are represented in
20471 @sc{hex} with leading zeros suppressed.
20473 Implementors should note that prior to @value{GDBN} 5.0, the character
20474 @samp{:} could not appear as the third character in a packet (as it
20475 would potentially conflict with the @var{sequence-id}).
20477 Response @var{data} can be run-length encoded to save space. A @samp{*}
20478 means that the next character is an @sc{ascii} encoding giving a repeat count
20479 which stands for that many repetitions of the character preceding the
20480 @samp{*}. The encoding is @code{n+29}, yielding a printable character
20481 where @code{n >=3} (which is where rle starts to win). The printable
20482 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
20483 value greater than 126 should not be used.
20490 means the same as "0000".
20492 The error response returned for some packets includes a two character
20493 error number. That number is not well defined.
20495 For any @var{command} not supported by the stub, an empty response
20496 (@samp{$#00}) should be returned. That way it is possible to extend the
20497 protocol. A newer @value{GDBN} can tell if a packet is supported based
20500 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
20501 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
20507 The following table provides a complete list of all currently defined
20508 @var{command}s and their corresponding response @var{data}.
20512 @item @code{!} --- extended mode
20513 @cindex @code{!} packet
20515 Enable extended mode. In extended mode, the remote server is made
20516 persistent. The @samp{R} packet is used to restart the program being
20522 The remote target both supports and has enabled extended mode.
20525 @item @code{?} --- last signal
20526 @cindex @code{?} packet
20528 Indicate the reason the target halted. The reply is the same as for
20532 @xref{Stop Reply Packets}, for the reply specifications.
20534 @item @code{a} --- reserved
20536 Reserved for future use.
20538 @item @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,@dots{}} --- set program arguments @strong{(reserved)}
20539 @cindex @code{A} packet
20541 Initialized @samp{argv[]} array passed into program. @var{arglen}
20542 specifies the number of bytes in the hex encoded byte stream @var{arg}.
20543 See @code{gdbserver} for more details.
20551 @item @code{b}@var{baud} --- set baud @strong{(deprecated)}
20552 @cindex @code{b} packet
20554 Change the serial line speed to @var{baud}.
20556 JTC: @emph{When does the transport layer state change? When it's
20557 received, or after the ACK is transmitted. In either case, there are
20558 problems if the command or the acknowledgment packet is dropped.}
20560 Stan: @emph{If people really wanted to add something like this, and get
20561 it working for the first time, they ought to modify ser-unix.c to send
20562 some kind of out-of-band message to a specially-setup stub and have the
20563 switch happen "in between" packets, so that from remote protocol's point
20564 of view, nothing actually happened.}
20566 @item @code{B}@var{addr},@var{mode} --- set breakpoint @strong{(deprecated)}
20567 @cindex @code{B} packet
20569 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
20570 breakpoint at @var{addr}.
20572 This packet has been replaced by the @samp{Z} and @samp{z} packets
20573 (@pxref{insert breakpoint or watchpoint packet}).
20575 @item @code{c}@var{addr} --- continue
20576 @cindex @code{c} packet
20578 @var{addr} is address to resume. If @var{addr} is omitted, resume at
20582 @xref{Stop Reply Packets}, for the reply specifications.
20584 @item @code{C}@var{sig}@code{;}@var{addr} --- continue with signal
20585 @cindex @code{C} packet
20587 Continue with signal @var{sig} (hex signal number). If
20588 @code{;}@var{addr} is omitted, resume at same address.
20591 @xref{Stop Reply Packets}, for the reply specifications.
20593 @item @code{d} --- toggle debug @strong{(deprecated)}
20594 @cindex @code{d} packet
20598 @item @code{D} --- detach
20599 @cindex @code{D} packet
20601 Detach @value{GDBN} from the remote system. Sent to the remote target
20602 before @value{GDBN} disconnects via the @code{detach} command.
20606 @item @emph{no response}
20607 @value{GDBN} does not check for any response after sending this packet.
20610 @item @code{e} --- reserved
20612 Reserved for future use.
20614 @item @code{E} --- reserved
20616 Reserved for future use.
20618 @item @code{f} --- reserved
20620 Reserved for future use.
20622 @item @code{F}@var{RC}@code{,}@var{EE}@code{,}@var{CF}@code{;}@var{XX} --- Reply to target's F packet.
20623 @cindex @code{F} packet
20625 This packet is send by @value{GDBN} as reply to a @code{F} request packet
20626 sent by the target. This is part of the File-I/O protocol extension.
20627 @xref{File-I/O remote protocol extension}, for the specification.
20629 @item @code{g} --- read registers
20630 @anchor{read registers packet}
20631 @cindex @code{g} packet
20633 Read general registers.
20637 @item @var{XX@dots{}}
20638 Each byte of register data is described by two hex digits. The bytes
20639 with the register are transmitted in target byte order. The size of
20640 each register and their position within the @samp{g} @var{packet} are
20641 determined by the @value{GDBN} internal macros
20642 @var{DEPRECATED_REGISTER_RAW_SIZE} and @var{REGISTER_NAME} macros. The
20643 specification of several standard @code{g} packets is specified below.
20648 @item @code{G}@var{XX@dots{}} --- write regs
20649 @cindex @code{G} packet
20651 @xref{read registers packet}, for a description of the @var{XX@dots{}}
20662 @item @code{h} --- reserved
20664 Reserved for future use.
20666 @item @code{H}@var{c}@var{t@dots{}} --- set thread
20667 @cindex @code{H} packet
20669 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
20670 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
20671 should be @samp{c} for step and continue operations, @samp{g} for other
20672 operations. The thread designator @var{t@dots{}} may be -1, meaning all
20673 the threads, a thread number, or zero which means pick any thread.
20684 @c 'H': How restrictive (or permissive) is the thread model. If a
20685 @c thread is selected and stopped, are other threads allowed
20686 @c to continue to execute? As I mentioned above, I think the
20687 @c semantics of each command when a thread is selected must be
20688 @c described. For example:
20690 @c 'g': If the stub supports threads and a specific thread is
20691 @c selected, returns the register block from that thread;
20692 @c otherwise returns current registers.
20694 @c 'G' If the stub supports threads and a specific thread is
20695 @c selected, sets the registers of the register block of
20696 @c that thread; otherwise sets current registers.
20698 @item @code{i}@var{addr}@code{,}@var{nnn} --- cycle step @strong{(draft)}
20699 @anchor{cycle step packet}
20700 @cindex @code{i} packet
20702 Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
20703 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
20704 step starting at that address.
20706 @item @code{I} --- signal then cycle step @strong{(reserved)}
20707 @cindex @code{I} packet
20709 @xref{step with signal packet}. @xref{cycle step packet}.
20711 @item @code{j} --- reserved
20713 Reserved for future use.
20715 @item @code{J} --- reserved
20717 Reserved for future use.
20719 @item @code{k} --- kill request
20720 @cindex @code{k} packet
20722 FIXME: @emph{There is no description of how to operate when a specific
20723 thread context has been selected (i.e.@: does 'k' kill only that
20726 @item @code{K} --- reserved
20728 Reserved for future use.
20730 @item @code{l} --- reserved
20732 Reserved for future use.
20734 @item @code{L} --- reserved
20736 Reserved for future use.
20738 @item @code{m}@var{addr}@code{,}@var{length} --- read memory
20739 @cindex @code{m} packet
20741 Read @var{length} bytes of memory starting at address @var{addr}.
20742 Neither @value{GDBN} nor the stub assume that sized memory transfers are
20743 assumed using word aligned accesses. FIXME: @emph{A word aligned memory
20744 transfer mechanism is needed.}
20748 @item @var{XX@dots{}}
20749 @var{XX@dots{}} is mem contents. Can be fewer bytes than requested if able
20750 to read only part of the data. Neither @value{GDBN} nor the stub assume
20751 that sized memory transfers are assumed using word aligned
20752 accesses. FIXME: @emph{A word aligned memory transfer mechanism is
20758 @item @code{M}@var{addr},@var{length}@code{:}@var{XX@dots{}} --- write mem
20759 @cindex @code{M} packet
20761 Write @var{length} bytes of memory starting at address @var{addr}.
20762 @var{XX@dots{}} is the data.
20769 for an error (this includes the case where only part of the data was
20773 @item @code{n} --- reserved
20775 Reserved for future use.
20777 @item @code{N} --- reserved
20779 Reserved for future use.
20781 @item @code{o} --- reserved
20783 Reserved for future use.
20785 @item @code{O} --- reserved
20787 @item @code{p}@var{hex number of register} --- read register packet
20788 @cindex @code{p} packet
20790 @xref{read registers packet}, for a description of how the returned
20791 register value is encoded.
20795 @item @var{XX@dots{}}
20796 the register's value
20800 Indicating an unrecognized @var{query}.
20803 @item @code{P}@var{n@dots{}}@code{=}@var{r@dots{}} --- write register
20804 @anchor{write register packet}
20805 @cindex @code{P} packet
20807 Write register @var{n@dots{}} with value @var{r@dots{}}, which contains two hex
20808 digits for each byte in the register (target byte order).
20818 @item @code{q}@var{query} --- general query
20819 @anchor{general query packet}
20820 @cindex @code{q} packet
20822 Request info about @var{query}. In general @value{GDBN} queries have a
20823 leading upper case letter. Custom vendor queries should use a company
20824 prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may optionally
20825 be followed by a @samp{,} or @samp{;} separated list. Stubs must ensure
20826 that they match the full @var{query} name.
20830 @item @var{XX@dots{}}
20831 Hex encoded data from query. The reply can not be empty.
20835 Indicating an unrecognized @var{query}.
20838 @item @code{Q}@var{var}@code{=}@var{val} --- general set
20839 @cindex @code{Q} packet
20841 Set value of @var{var} to @var{val}.
20843 @xref{general query packet}, for a discussion of naming conventions.
20845 @item @code{r} --- reset @strong{(deprecated)}
20846 @cindex @code{r} packet
20848 Reset the entire system.
20850 @item @code{R}@var{XX} --- remote restart
20851 @cindex @code{R} packet
20853 Restart the program being debugged. @var{XX}, while needed, is ignored.
20854 This packet is only available in extended mode.
20858 @item @emph{no reply}
20859 The @samp{R} packet has no reply.
20862 @item @code{s}@var{addr} --- step
20863 @cindex @code{s} packet
20865 @var{addr} is address to resume. If @var{addr} is omitted, resume at
20869 @xref{Stop Reply Packets}, for the reply specifications.
20871 @item @code{S}@var{sig}@code{;}@var{addr} --- step with signal
20872 @anchor{step with signal packet}
20873 @cindex @code{S} packet
20875 Like @samp{C} but step not continue.
20878 @xref{Stop Reply Packets}, for the reply specifications.
20880 @item @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} --- search
20881 @cindex @code{t} packet
20883 Search backwards starting at address @var{addr} for a match with pattern
20884 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
20885 @var{addr} must be at least 3 digits.
20887 @item @code{T}@var{XX} --- thread alive
20888 @cindex @code{T} packet
20890 Find out if the thread XX is alive.
20895 thread is still alive
20900 @item @code{u} --- reserved
20902 Reserved for future use.
20904 @item @code{U} --- reserved
20906 Reserved for future use.
20908 @item @code{v} --- verbose packet prefix
20910 Packets starting with @code{v} are identified by a multi-letter name,
20911 up to the first @code{;} or @code{?} (or the end of the packet).
20913 @item @code{vCont}[;@var{action}[@code{:}@var{tid}]]... --- extended resume
20914 @cindex @code{vCont} packet
20916 Resume the inferior. Different actions may be specified for each thread.
20917 If an action is specified with no @var{tid}, then it is applied to any
20918 threads that don't have a specific action specified; if no default action is
20919 specified then other threads should remain stopped. Specifying multiple
20920 default actions is an error; specifying no actions is also an error.
20921 Thread IDs are specified in hexadecimal. Currently supported actions are:
20927 Continue with signal @var{sig}. @var{sig} should be two hex digits.
20931 Step with signal @var{sig}. @var{sig} should be two hex digits.
20934 The optional @var{addr} argument normally associated with these packets is
20935 not supported in @code{vCont}.
20938 @xref{Stop Reply Packets}, for the reply specifications.
20940 @item @code{vCont?} --- extended resume query
20941 @cindex @code{vCont?} packet
20943 Query support for the @code{vCont} packet.
20947 @item @code{vCont}[;@var{action}]...
20948 The @code{vCont} packet is supported. Each @var{action} is a supported
20949 command in the @code{vCont} packet.
20951 The @code{vCont} packet is not supported.
20954 @item @code{V} --- reserved
20956 Reserved for future use.
20958 @item @code{w} --- reserved
20960 Reserved for future use.
20962 @item @code{W} --- reserved
20964 Reserved for future use.
20966 @item @code{x} --- reserved
20968 Reserved for future use.
20970 @item @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX@dots{}} --- write mem (binary)
20971 @cindex @code{X} packet
20973 @var{addr} is address, @var{length} is number of bytes, @var{XX@dots{}}
20974 is binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
20975 escaped using @code{0x7d}, and then XORed with @code{0x20}.
20976 For example, @code{0x7d} would be transmitted as @code{0x7d 0x5d}.
20986 @item @code{y} --- reserved
20988 Reserved for future use.
20990 @item @code{Y} reserved
20992 Reserved for future use.
20994 @item @code{z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- remove breakpoint or watchpoint @strong{(draft)}
20995 @itemx @code{Z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- insert breakpoint or watchpoint @strong{(draft)}
20996 @anchor{insert breakpoint or watchpoint packet}
20997 @cindex @code{z} packet
20998 @cindex @code{Z} packets
21000 Insert (@code{Z}) or remove (@code{z}) a @var{type} breakpoint or
21001 watchpoint starting at address @var{address} and covering the next
21002 @var{length} bytes.
21004 Each breakpoint and watchpoint packet @var{type} is documented
21007 @emph{Implementation notes: A remote target shall return an empty string
21008 for an unrecognized breakpoint or watchpoint packet @var{type}. A
21009 remote target shall support either both or neither of a given
21010 @code{Z}@var{type}@dots{} and @code{z}@var{type}@dots{} packet pair. To
21011 avoid potential problems with duplicate packets, the operations should
21012 be implemented in an idempotent way.}
21014 @item @code{z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- remove memory breakpoint @strong{(draft)}
21015 @item @code{Z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- insert memory breakpoint @strong{(draft)}
21016 @cindex @code{z0} packet
21017 @cindex @code{Z0} packet
21019 Insert (@code{Z0}) or remove (@code{z0}) a memory breakpoint at address
21020 @code{addr} of size @code{length}.
21022 A memory breakpoint is implemented by replacing the instruction at
21023 @var{addr} with a software breakpoint or trap instruction. The
21024 @code{length} is used by targets that indicates the size of the
21025 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
21026 @sc{mips} can insert either a 2 or 4 byte breakpoint).
21028 @emph{Implementation note: It is possible for a target to copy or move
21029 code that contains memory breakpoints (e.g., when implementing
21030 overlays). The behavior of this packet, in the presence of such a
21031 target, is not defined.}
21043 @item @code{z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- remove hardware breakpoint @strong{(draft)}
21044 @item @code{Z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- insert hardware breakpoint @strong{(draft)}
21045 @cindex @code{z1} packet
21046 @cindex @code{Z1} packet
21048 Insert (@code{Z1}) or remove (@code{z1}) a hardware breakpoint at
21049 address @code{addr} of size @code{length}.
21051 A hardware breakpoint is implemented using a mechanism that is not
21052 dependant on being able to modify the target's memory.
21054 @emph{Implementation note: A hardware breakpoint is not affected by code
21067 @item @code{z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- remove write watchpoint @strong{(draft)}
21068 @item @code{Z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- insert write watchpoint @strong{(draft)}
21069 @cindex @code{z2} packet
21070 @cindex @code{Z2} packet
21072 Insert (@code{Z2}) or remove (@code{z2}) a write watchpoint.
21084 @item @code{z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- remove read watchpoint @strong{(draft)}
21085 @item @code{Z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- insert read watchpoint @strong{(draft)}
21086 @cindex @code{z3} packet
21087 @cindex @code{Z3} packet
21089 Insert (@code{Z3}) or remove (@code{z3}) a read watchpoint.
21101 @item @code{z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- remove access watchpoint @strong{(draft)}
21102 @item @code{Z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- insert access watchpoint @strong{(draft)}
21103 @cindex @code{z4} packet
21104 @cindex @code{Z4} packet
21106 Insert (@code{Z4}) or remove (@code{z4}) an access watchpoint.
21120 @node Stop Reply Packets
21121 @section Stop Reply Packets
21122 @cindex stop reply packets
21124 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
21125 receive any of the below as a reply. In the case of the @samp{C},
21126 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
21127 when the target halts. In the below the exact meaning of @samp{signal
21128 number} is poorly defined. In general one of the UNIX signal numbering
21129 conventions is used.
21134 @var{AA} is the signal number
21136 @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
21137 @cindex @code{T} packet reply
21139 @var{AA} = two hex digit signal number; @var{n...} = register number
21140 (hex), @var{r...} = target byte ordered register contents, size defined
21141 by @code{DEPRECATED_REGISTER_RAW_SIZE}; @var{n...} = @samp{thread},
21142 @var{r...} = thread process ID, this is a hex integer; @var{n...} =
21143 (@samp{watch} | @samp{rwatch} | @samp{awatch}, @var{r...} = data
21144 address, this is a hex integer; @var{n...} = other string not starting
21145 with valid hex digit. @value{GDBN} should ignore this @var{n...},
21146 @var{r...} pair and go on to the next. This way we can extend the
21151 The process exited, and @var{AA} is the exit status. This is only
21152 applicable to certain targets.
21156 The process terminated with signal @var{AA}.
21158 @item O@var{XX@dots{}}
21160 @var{XX@dots{}} is hex encoding of @sc{ascii} data. This can happen at
21161 any time while the program is running and the debugger should continue
21162 to wait for @samp{W}, @samp{T}, etc.
21164 @item F@var{call-id}@code{,}@var{parameter@dots{}}
21166 @var{call-id} is the identifier which says which host system call should
21167 be called. This is just the name of the function. Translation into the
21168 correct system call is only applicable as it's defined in @value{GDBN}.
21169 @xref{File-I/O remote protocol extension}, for a list of implemented
21172 @var{parameter@dots{}} is a list of parameters as defined for this very
21175 The target replies with this packet when it expects @value{GDBN} to call
21176 a host system call on behalf of the target. @value{GDBN} replies with
21177 an appropriate @code{F} packet and keeps up waiting for the next reply
21178 packet from the target. The latest @samp{C}, @samp{c}, @samp{S} or
21179 @samp{s} action is expected to be continued.
21180 @xref{File-I/O remote protocol extension}, for more details.
21184 @node General Query Packets
21185 @section General Query Packets
21187 The following set and query packets have already been defined.
21191 @item @code{q}@code{C} --- current thread
21193 Return the current thread id.
21197 @item @code{QC}@var{pid}
21198 Where @var{pid} is an unsigned hexidecimal process id.
21200 Any other reply implies the old pid.
21203 @item @code{q}@code{fThreadInfo} -- all thread ids
21205 @code{q}@code{sThreadInfo}
21207 Obtain a list of active thread ids from the target (OS). Since there
21208 may be too many active threads to fit into one reply packet, this query
21209 works iteratively: it may require more than one query/reply sequence to
21210 obtain the entire list of threads. The first query of the sequence will
21211 be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
21212 sequence will be the @code{qs}@code{ThreadInfo} query.
21214 NOTE: replaces the @code{qL} query (see below).
21218 @item @code{m}@var{id}
21220 @item @code{m}@var{id},@var{id}@dots{}
21221 a comma-separated list of thread ids
21223 (lower case 'el') denotes end of list.
21226 In response to each query, the target will reply with a list of one or
21227 more thread ids, in big-endian unsigned hex, separated by commas.
21228 @value{GDBN} will respond to each reply with a request for more thread
21229 ids (using the @code{qs} form of the query), until the target responds
21230 with @code{l} (lower-case el, for @code{'last'}).
21232 @item @code{q}@code{ThreadExtraInfo}@code{,}@var{id} --- extra thread info
21234 Where @var{id} is a thread-id in big-endian hex. Obtain a printable
21235 string description of a thread's attributes from the target OS. This
21236 string may contain anything that the target OS thinks is interesting for
21237 @value{GDBN} to tell the user about the thread. The string is displayed
21238 in @value{GDBN}'s @samp{info threads} display. Some examples of
21239 possible thread extra info strings are ``Runnable'', or ``Blocked on
21244 @item @var{XX@dots{}}
21245 Where @var{XX@dots{}} is a hex encoding of @sc{ascii} data, comprising
21246 the printable string containing the extra information about the thread's
21250 @item @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} --- query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
21252 Obtain thread information from RTOS. Where: @var{startflag} (one hex
21253 digit) is one to indicate the first query and zero to indicate a
21254 subsequent query; @var{threadcount} (two hex digits) is the maximum
21255 number of threads the response packet can contain; and @var{nextthread}
21256 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
21257 returned in the response as @var{argthread}.
21259 NOTE: this query is replaced by the @code{q}@code{fThreadInfo} query
21264 @item @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread@dots{}}
21265 Where: @var{count} (two hex digits) is the number of threads being
21266 returned; @var{done} (one hex digit) is zero to indicate more threads
21267 and one indicates no further threads; @var{argthreadid} (eight hex
21268 digits) is @var{nextthread} from the request packet; @var{thread@dots{}}
21269 is a sequence of thread IDs from the target. @var{threadid} (eight hex
21270 digits). See @code{remote.c:parse_threadlist_response()}.
21273 @item @code{q}@code{CRC:}@var{addr}@code{,}@var{length} --- compute CRC of memory block
21277 @item @code{E}@var{NN}
21278 An error (such as memory fault)
21279 @item @code{C}@var{CRC32}
21280 A 32 bit cyclic redundancy check of the specified memory region.
21283 @item @code{q}@code{Offsets} --- query sect offs
21285 Get section offsets that the target used when re-locating the downloaded
21286 image. @emph{Note: while a @code{Bss} offset is included in the
21287 response, @value{GDBN} ignores this and instead applies the @code{Data}
21288 offset to the @code{Bss} section.}
21292 @item @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
21295 @item @code{q}@code{P}@var{mode}@var{threadid} --- thread info request
21297 Returns information on @var{threadid}. Where: @var{mode} is a hex
21298 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
21305 See @code{remote.c:remote_unpack_thread_info_response()}.
21307 @item @code{q}@code{Rcmd,}@var{command} --- remote command
21309 @var{command} (hex encoded) is passed to the local interpreter for
21310 execution. Invalid commands should be reported using the output string.
21311 Before the final result packet, the target may also respond with a
21312 number of intermediate @code{O}@var{output} console output packets.
21313 @emph{Implementors should note that providing access to a stubs's
21314 interpreter may have security implications}.
21319 A command response with no output.
21321 A command response with the hex encoded output string @var{OUTPUT}.
21322 @item @code{E}@var{NN}
21323 Indicate a badly formed request.
21325 When @samp{q}@samp{Rcmd} is not recognized.
21328 @item @code{qSymbol::} --- symbol lookup
21330 Notify the target that @value{GDBN} is prepared to serve symbol lookup
21331 requests. Accept requests from the target for the values of symbols.
21336 The target does not need to look up any (more) symbols.
21337 @item @code{qSymbol:}@var{sym_name}
21338 The target requests the value of symbol @var{sym_name} (hex encoded).
21339 @value{GDBN} may provide the value by using the
21340 @code{qSymbol:}@var{sym_value}:@var{sym_name} message, described below.
21343 @item @code{qSymbol:}@var{sym_value}:@var{sym_name} --- symbol value
21345 Set the value of @var{sym_name} to @var{sym_value}.
21347 @var{sym_name} (hex encoded) is the name of a symbol whose value the
21348 target has previously requested.
21350 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
21351 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
21357 The target does not need to look up any (more) symbols.
21358 @item @code{qSymbol:}@var{sym_name}
21359 The target requests the value of a new symbol @var{sym_name} (hex
21360 encoded). @value{GDBN} will continue to supply the values of symbols
21361 (if available), until the target ceases to request them.
21364 @item @code{qPart}:@var{object}:@code{read}:@var{annex}:@var{offset},@var{length} --- read special data
21366 Read uninterpreted bytes from the target's special data area
21367 identified by the keyword @code{object}.
21368 Request @var{length} bytes starting at @var{offset} bytes into the data.
21369 The content and encoding of @var{annex} is specific to the object;
21370 it can supply additional details about what data to access.
21372 Here are the specific requests of this form defined so far.
21373 All @samp{@code{qPart}:@var{object}:@code{read}:@dots{}}
21374 requests use the same reply formats, listed below.
21377 @item @code{qPart}:@code{auxv}:@code{read}::@var{offset},@var{length}
21378 Access the target's @dfn{auxiliary vector}. @xref{Auxiliary Vector}.
21379 Note @var{annex} must be empty.
21385 The @var{offset} in the request is at the end of the data.
21386 There is no more data to be read.
21388 @item @var{XX@dots{}}
21389 Hex encoded data bytes read.
21390 This may be fewer bytes than the @var{length} in the request.
21393 The request was malformed, or @var{annex} was invalid.
21395 @item @code{E}@var{nn}
21396 The offset was invalid, or there was an error encountered reading the data.
21397 @var{nn} is a hex-encoded @code{errno} value.
21399 @item @code{""} (empty)
21400 An empty reply indicates the @var{object} or @var{annex} string was not
21401 recognized by the stub.
21404 @item @code{qPart}:@var{object}:@code{write}:@var{annex}:@var{offset}:@var{data@dots{}}
21406 Write uninterpreted bytes into the target's special data area
21407 identified by the keyword @code{object},
21408 starting at @var{offset} bytes into the data.
21409 @var{data@dots{}} is the hex-encoded data to be written.
21410 The content and encoding of @var{annex} is specific to the object;
21411 it can supply additional details about what data to access.
21413 No requests of this form are presently in use. This specification
21414 serves as a placeholder to document the common format that new
21415 specific request specifications ought to use.
21420 @var{nn} (hex encoded) is the number of bytes written.
21421 This may be fewer bytes than supplied in the request.
21424 The request was malformed, or @var{annex} was invalid.
21426 @item @code{E}@var{nn}
21427 The offset was invalid, or there was an error encountered writing the data.
21428 @var{nn} is a hex-encoded @code{errno} value.
21430 @item @code{""} (empty)
21431 An empty reply indicates the @var{object} or @var{annex} string was not
21432 recognized by the stub, or that the object does not support writing.
21435 @item @code{qPart}:@var{object}:@var{operation}:@dots{}
21436 Requests of this form may be added in the future. When a stub does
21437 not recognize the @var{object} keyword, or its support for
21438 @var{object} does not recognize the @var{operation} keyword,
21439 the stub must respond with an empty packet.
21441 @item @code{qGetTLSAddr}:@var{thread-id},@var{offset},@var{lm} --- get thread local storage address
21443 Fetch the address associated with thread local storage specified
21444 by @var{thread-id}, @var{offset}, and @var{lm}.
21446 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
21447 thread for which to fetch the TLS address.
21449 @var{offset} is the (big endian, hex encoded) offset associated with the
21450 thread local variable. (This offset is obtained from the debug
21451 information associated with the variable.)
21453 @var{lm} is the (big endian, hex encoded) OS/ABI specific encoding of the
21454 the load module associated with the thread local storage. For example,
21455 a @sc{gnu}/Linux system will pass the link map address of the shared
21456 object associated with the thread local storage under consideration.
21457 Other operating environments may choose to represent the load module
21458 differently, so the precise meaning of this parameter will vary.
21462 @item @var{XX@dots{}}
21463 Hex encoded (big endian) bytes representing the address of the thread
21464 local storage requested.
21466 @item @code{E}@var{nn} (where @var{nn} are hex digits)
21469 @item @code{""} (empty)
21470 An empty reply indicates that @code{qGetTLSAddr} is not supported by the stub.
21475 @node Register Packet Format
21476 @section Register Packet Format
21478 The following @samp{g}/@samp{G} packets have previously been defined.
21479 In the below, some thirty-two bit registers are transferred as
21480 sixty-four bits. Those registers should be zero/sign extended (which?)
21481 to fill the space allocated. Register bytes are transfered in target
21482 byte order. The two nibbles within a register byte are transfered
21483 most-significant - least-significant.
21489 All registers are transfered as thirty-two bit quantities in the order:
21490 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
21491 registers; fsr; fir; fp.
21495 All registers are transfered as sixty-four bit quantities (including
21496 thirty-two bit registers such as @code{sr}). The ordering is the same
21504 Example sequence of a target being re-started. Notice how the restart
21505 does not get any direct output:
21510 @emph{target restarts}
21513 <- @code{T001:1234123412341234}
21517 Example sequence of a target being stepped by a single instruction:
21520 -> @code{G1445@dots{}}
21525 <- @code{T001:1234123412341234}
21529 <- @code{1455@dots{}}
21533 @node File-I/O remote protocol extension
21534 @section File-I/O remote protocol extension
21535 @cindex File-I/O remote protocol extension
21538 * File-I/O Overview::
21539 * Protocol basics::
21540 * The F request packet::
21541 * The F reply packet::
21542 * Memory transfer::
21543 * The Ctrl-C message::
21545 * The isatty call::
21546 * The system call::
21547 * List of supported calls::
21548 * Protocol specific representation of datatypes::
21550 * File-I/O Examples::
21553 @node File-I/O Overview
21554 @subsection File-I/O Overview
21555 @cindex file-i/o overview
21557 The File I/O remote protocol extension (short: File-I/O) allows the
21558 target to use the hosts file system and console I/O when calling various
21559 system calls. System calls on the target system are translated into a
21560 remote protocol packet to the host system which then performs the needed
21561 actions and returns with an adequate response packet to the target system.
21562 This simulates file system operations even on targets that lack file systems.
21564 The protocol is defined host- and target-system independent. It uses
21565 it's own independent representation of datatypes and values. Both,
21566 @value{GDBN} and the target's @value{GDBN} stub are responsible for
21567 translating the system dependent values into the unified protocol values
21568 when data is transmitted.
21570 The communication is synchronous. A system call is possible only
21571 when GDB is waiting for the @samp{C}, @samp{c}, @samp{S} or @samp{s}
21572 packets. While @value{GDBN} handles the request for a system call,
21573 the target is stopped to allow deterministic access to the target's
21574 memory. Therefore File-I/O is not interuptible by target signals. It
21575 is possible to interrupt File-I/O by a user interrupt (Ctrl-C), though.
21577 The target's request to perform a host system call does not finish
21578 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
21579 after finishing the system call, the target returns to continuing the
21580 previous activity (continue, step). No additional continue or step
21581 request from @value{GDBN} is required.
21584 (@value{GDBP}) continue
21585 <- target requests 'system call X'
21586 target is stopped, @value{GDBN} executes system call
21587 -> GDB returns result
21588 ... target continues, GDB returns to wait for the target
21589 <- target hits breakpoint and sends a Txx packet
21592 The protocol is only used for files on the host file system and
21593 for I/O on the console. Character or block special devices, pipes,
21594 named pipes or sockets or any other communication method on the host
21595 system are not supported by this protocol.
21597 @node Protocol basics
21598 @subsection Protocol basics
21599 @cindex protocol basics, file-i/o
21601 The File-I/O protocol uses the @code{F} packet, as request as well
21602 as as reply packet. Since a File-I/O system call can only occur when
21603 @value{GDBN} is waiting for the continuing or stepping target, the
21604 File-I/O request is a reply that @value{GDBN} has to expect as a result
21605 of a former @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
21606 This @code{F} packet contains all information needed to allow @value{GDBN}
21607 to call the appropriate host system call:
21611 A unique identifier for the requested system call.
21614 All parameters to the system call. Pointers are given as addresses
21615 in the target memory address space. Pointers to strings are given as
21616 pointer/length pair. Numerical values are given as they are.
21617 Numerical control values are given in a protocol specific representation.
21621 At that point @value{GDBN} has to perform the following actions.
21625 If parameter pointer values are given, which point to data needed as input
21626 to a system call, @value{GDBN} requests this data from the target with a
21627 standard @code{m} packet request. This additional communication has to be
21628 expected by the target implementation and is handled as any other @code{m}
21632 @value{GDBN} translates all value from protocol representation to host
21633 representation as needed. Datatypes are coerced into the host types.
21636 @value{GDBN} calls the system call
21639 It then coerces datatypes back to protocol representation.
21642 If pointer parameters in the request packet point to buffer space in which
21643 a system call is expected to copy data to, the data is transmitted to the
21644 target using a @code{M} or @code{X} packet. This packet has to be expected
21645 by the target implementation and is handled as any other @code{M} or @code{X}
21650 Eventually @value{GDBN} replies with another @code{F} packet which contains all
21651 necessary information for the target to continue. This at least contains
21658 @code{errno}, if has been changed by the system call.
21665 After having done the needed type and value coercion, the target continues
21666 the latest continue or step action.
21668 @node The F request packet
21669 @subsection The @code{F} request packet
21670 @cindex file-i/o request packet
21671 @cindex @code{F} request packet
21673 The @code{F} request packet has the following format:
21678 @code{F}@var{call-id}@code{,}@var{parameter@dots{}}
21681 @var{call-id} is the identifier to indicate the host system call to be called.
21682 This is just the name of the function.
21684 @var{parameter@dots{}} are the parameters to the system call.
21688 Parameters are hexadecimal integer values, either the real values in case
21689 of scalar datatypes, as pointers to target buffer space in case of compound
21690 datatypes and unspecified memory areas or as pointer/length pairs in case
21691 of string parameters. These are appended to the call-id, each separated
21692 from its predecessor by a comma. All values are transmitted in ASCII
21693 string representation, pointer/length pairs separated by a slash.
21695 @node The F reply packet
21696 @subsection The @code{F} reply packet
21697 @cindex file-i/o reply packet
21698 @cindex @code{F} reply packet
21700 The @code{F} reply packet has the following format:
21705 @code{F}@var{retcode}@code{,}@var{errno}@code{,}@var{Ctrl-C flag}@code{;}@var{call specific attachment}
21708 @var{retcode} is the return code of the system call as hexadecimal value.
21710 @var{errno} is the errno set by the call, in protocol specific representation.
21711 This parameter can be omitted if the call was successful.
21713 @var{Ctrl-C flag} is only send if the user requested a break. In this
21714 case, @var{errno} must be send as well, even if the call was successful.
21715 The @var{Ctrl-C flag} itself consists of the character 'C':
21722 or, if the call was interupted before the host call has been performed:
21729 assuming 4 is the protocol specific representation of @code{EINTR}.
21733 @node Memory transfer
21734 @subsection Memory transfer
21735 @cindex memory transfer, in file-i/o protocol
21737 Structured data which is transferred using a memory read or write as e.g.@:
21738 a @code{struct stat} is expected to be in a protocol specific format with
21739 all scalar multibyte datatypes being big endian. This should be done by
21740 the target before the @code{F} packet is sent resp.@: by @value{GDBN} before
21741 it transfers memory to the target. Transferred pointers to structured
21742 data should point to the already coerced data at any time.
21744 @node The Ctrl-C message
21745 @subsection The Ctrl-C message
21746 @cindex ctrl-c message, in file-i/o protocol
21748 A special case is, if the @var{Ctrl-C flag} is set in the @value{GDBN}
21749 reply packet. In this case the target should behave, as if it had
21750 gotten a break message. The meaning for the target is ``system call
21751 interupted by @code{SIGINT}''. Consequentially, the target should actually stop
21752 (as with a break message) and return to @value{GDBN} with a @code{T02}
21753 packet. In this case, it's important for the target to know, in which
21754 state the system call was interrupted. Since this action is by design
21755 not an atomic operation, we have to differ between two cases:
21759 The system call hasn't been performed on the host yet.
21762 The system call on the host has been finished.
21766 These two states can be distinguished by the target by the value of the
21767 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
21768 call hasn't been performed. This is equivalent to the @code{EINTR} handling
21769 on POSIX systems. In any other case, the target may presume that the
21770 system call has been finished --- successful or not --- and should behave
21771 as if the break message arrived right after the system call.
21773 @value{GDBN} must behave reliable. If the system call has not been called
21774 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
21775 @code{errno} in the packet. If the system call on the host has been finished
21776 before the user requests a break, the full action must be finshed by
21777 @value{GDBN}. This requires sending @code{M} or @code{X} packets as they fit.
21778 The @code{F} packet may only be send when either nothing has happened
21779 or the full action has been completed.
21782 @subsection Console I/O
21783 @cindex console i/o as part of file-i/o
21785 By default and if not explicitely closed by the target system, the file
21786 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
21787 on the @value{GDBN} console is handled as any other file output operation
21788 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
21789 by @value{GDBN} so that after the target read request from file descriptor
21790 0 all following typing is buffered until either one of the following
21795 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, the
21797 system call is treated as finished.
21800 The user presses @kbd{Enter}. This is treated as end of input with a trailing
21804 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
21805 character, especially no Ctrl-D is appended to the input.
21809 If the user has typed more characters as fit in the buffer given to
21810 the read call, the trailing characters are buffered in @value{GDBN} until
21811 either another @code{read(0, @dots{})} is requested by the target or debugging
21812 is stopped on users request.
21814 @node The isatty call
21815 @subsection The isatty(3) call
21816 @cindex isatty call, file-i/o protocol
21818 A special case in this protocol is the library call @code{isatty} which
21819 is implemented as it's own call inside of this protocol. It returns
21820 1 to the target if the file descriptor given as parameter is attached
21821 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
21822 would require implementing @code{ioctl} and would be more complex than
21825 @node The system call
21826 @subsection The system(3) call
21827 @cindex system call, file-i/o protocol
21829 The other special case in this protocol is the @code{system} call which
21830 is implemented as it's own call, too. @value{GDBN} is taking over the full
21831 task of calling the necessary host calls to perform the @code{system}
21832 call. The return value of @code{system} is simplified before it's returned
21833 to the target. Basically, the only signal transmitted back is @code{EINTR}
21834 in case the user pressed @kbd{Ctrl-C}. Otherwise the return value consists
21835 entirely of the exit status of the called command.
21837 Due to security concerns, the @code{system} call is refused to be called
21838 by @value{GDBN} by default. The user has to allow this call explicitly by
21842 @kindex set remote system-call-allowed 1
21843 @item @code{set remote system-call-allowed 1}
21846 Disabling the @code{system} call is done by
21849 @kindex set remote system-call-allowed 0
21850 @item @code{set remote system-call-allowed 0}
21853 The current setting is shown by typing
21856 @kindex show remote system-call-allowed
21857 @item @code{show remote system-call-allowed}
21860 @node List of supported calls
21861 @subsection List of supported calls
21862 @cindex list of supported file-i/o calls
21879 @unnumberedsubsubsec open
21880 @cindex open, file-i/o system call
21884 int open(const char *pathname, int flags);
21885 int open(const char *pathname, int flags, mode_t mode);
21888 Fopen,pathptr/len,flags,mode
21892 @code{flags} is the bitwise or of the following values:
21896 If the file does not exist it will be created. The host
21897 rules apply as far as file ownership and time stamps
21901 When used with O_CREAT, if the file already exists it is
21902 an error and open() fails.
21905 If the file already exists and the open mode allows
21906 writing (O_RDWR or O_WRONLY is given) it will be
21907 truncated to length 0.
21910 The file is opened in append mode.
21913 The file is opened for reading only.
21916 The file is opened for writing only.
21919 The file is opened for reading and writing.
21922 Each other bit is silently ignored.
21927 @code{mode} is the bitwise or of the following values:
21931 User has read permission.
21934 User has write permission.
21937 Group has read permission.
21940 Group has write permission.
21943 Others have read permission.
21946 Others have write permission.
21949 Each other bit is silently ignored.
21954 @exdent Return value:
21955 open returns the new file descriptor or -1 if an error
21963 pathname already exists and O_CREAT and O_EXCL were used.
21966 pathname refers to a directory.
21969 The requested access is not allowed.
21972 pathname was too long.
21975 A directory component in pathname does not exist.
21978 pathname refers to a device, pipe, named pipe or socket.
21981 pathname refers to a file on a read-only filesystem and
21982 write access was requested.
21985 pathname is an invalid pointer value.
21988 No space on device to create the file.
21991 The process already has the maximum number of files open.
21994 The limit on the total number of files open on the system
21998 The call was interrupted by the user.
22002 @unnumberedsubsubsec close
22003 @cindex close, file-i/o system call
22012 @exdent Return value:
22013 close returns zero on success, or -1 if an error occurred.
22020 fd isn't a valid open file descriptor.
22023 The call was interrupted by the user.
22027 @unnumberedsubsubsec read
22028 @cindex read, file-i/o system call
22032 int read(int fd, void *buf, unsigned int count);
22035 Fread,fd,bufptr,count
22037 @exdent Return value:
22038 On success, the number of bytes read is returned.
22039 Zero indicates end of file. If count is zero, read
22040 returns zero as well. On error, -1 is returned.
22047 fd is not a valid file descriptor or is not open for
22051 buf is an invalid pointer value.
22054 The call was interrupted by the user.
22058 @unnumberedsubsubsec write
22059 @cindex write, file-i/o system call
22063 int write(int fd, const void *buf, unsigned int count);
22066 Fwrite,fd,bufptr,count
22068 @exdent Return value:
22069 On success, the number of bytes written are returned.
22070 Zero indicates nothing was written. On error, -1
22078 fd is not a valid file descriptor or is not open for
22082 buf is an invalid pointer value.
22085 An attempt was made to write a file that exceeds the
22086 host specific maximum file size allowed.
22089 No space on device to write the data.
22092 The call was interrupted by the user.
22096 @unnumberedsubsubsec lseek
22097 @cindex lseek, file-i/o system call
22101 long lseek (int fd, long offset, int flag);
22104 Flseek,fd,offset,flag
22107 @code{flag} is one of:
22111 The offset is set to offset bytes.
22114 The offset is set to its current location plus offset
22118 The offset is set to the size of the file plus offset
22123 @exdent Return value:
22124 On success, the resulting unsigned offset in bytes from
22125 the beginning of the file is returned. Otherwise, a
22126 value of -1 is returned.
22133 fd is not a valid open file descriptor.
22136 fd is associated with the @value{GDBN} console.
22139 flag is not a proper value.
22142 The call was interrupted by the user.
22146 @unnumberedsubsubsec rename
22147 @cindex rename, file-i/o system call
22151 int rename(const char *oldpath, const char *newpath);
22154 Frename,oldpathptr/len,newpathptr/len
22156 @exdent Return value:
22157 On success, zero is returned. On error, -1 is returned.
22164 newpath is an existing directory, but oldpath is not a
22168 newpath is a non-empty directory.
22171 oldpath or newpath is a directory that is in use by some
22175 An attempt was made to make a directory a subdirectory
22179 A component used as a directory in oldpath or new
22180 path is not a directory. Or oldpath is a directory
22181 and newpath exists but is not a directory.
22184 oldpathptr or newpathptr are invalid pointer values.
22187 No access to the file or the path of the file.
22191 oldpath or newpath was too long.
22194 A directory component in oldpath or newpath does not exist.
22197 The file is on a read-only filesystem.
22200 The device containing the file has no room for the new
22204 The call was interrupted by the user.
22208 @unnumberedsubsubsec unlink
22209 @cindex unlink, file-i/o system call
22213 int unlink(const char *pathname);
22216 Funlink,pathnameptr/len
22218 @exdent Return value:
22219 On success, zero is returned. On error, -1 is returned.
22226 No access to the file or the path of the file.
22229 The system does not allow unlinking of directories.
22232 The file pathname cannot be unlinked because it's
22233 being used by another process.
22236 pathnameptr is an invalid pointer value.
22239 pathname was too long.
22242 A directory component in pathname does not exist.
22245 A component of the path is not a directory.
22248 The file is on a read-only filesystem.
22251 The call was interrupted by the user.
22255 @unnumberedsubsubsec stat/fstat
22256 @cindex fstat, file-i/o system call
22257 @cindex stat, file-i/o system call
22261 int stat(const char *pathname, struct stat *buf);
22262 int fstat(int fd, struct stat *buf);
22265 Fstat,pathnameptr/len,bufptr
22268 @exdent Return value:
22269 On success, zero is returned. On error, -1 is returned.
22276 fd is not a valid open file.
22279 A directory component in pathname does not exist or the
22280 path is an empty string.
22283 A component of the path is not a directory.
22286 pathnameptr is an invalid pointer value.
22289 No access to the file or the path of the file.
22292 pathname was too long.
22295 The call was interrupted by the user.
22299 @unnumberedsubsubsec gettimeofday
22300 @cindex gettimeofday, file-i/o system call
22304 int gettimeofday(struct timeval *tv, void *tz);
22307 Fgettimeofday,tvptr,tzptr
22309 @exdent Return value:
22310 On success, 0 is returned, -1 otherwise.
22317 tz is a non-NULL pointer.
22320 tvptr and/or tzptr is an invalid pointer value.
22324 @unnumberedsubsubsec isatty
22325 @cindex isatty, file-i/o system call
22329 int isatty(int fd);
22334 @exdent Return value:
22335 Returns 1 if fd refers to the @value{GDBN} console, 0 otherwise.
22342 The call was interrupted by the user.
22346 @unnumberedsubsubsec system
22347 @cindex system, file-i/o system call
22351 int system(const char *command);
22354 Fsystem,commandptr/len
22356 @exdent Return value:
22357 The value returned is -1 on error and the return status
22358 of the command otherwise. Only the exit status of the
22359 command is returned, which is extracted from the hosts
22360 system return value by calling WEXITSTATUS(retval).
22361 In case /bin/sh could not be executed, 127 is returned.
22368 The call was interrupted by the user.
22371 @node Protocol specific representation of datatypes
22372 @subsection Protocol specific representation of datatypes
22373 @cindex protocol specific representation of datatypes, in file-i/o protocol
22376 * Integral datatypes::
22382 @node Integral datatypes
22383 @unnumberedsubsubsec Integral datatypes
22384 @cindex integral datatypes, in file-i/o protocol
22386 The integral datatypes used in the system calls are
22389 int@r{,} unsigned int@r{,} long@r{,} unsigned long@r{,} mode_t @r{and} time_t
22392 @code{Int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
22393 implemented as 32 bit values in this protocol.
22395 @code{Long} and @code{unsigned long} are implemented as 64 bit types.
22397 @xref{Limits}, for corresponding MIN and MAX values (similar to those
22398 in @file{limits.h}) to allow range checking on host and target.
22400 @code{time_t} datatypes are defined as seconds since the Epoch.
22402 All integral datatypes transferred as part of a memory read or write of a
22403 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
22406 @node Pointer values
22407 @unnumberedsubsubsec Pointer values
22408 @cindex pointer values, in file-i/o protocol
22410 Pointers to target data are transmitted as they are. An exception
22411 is made for pointers to buffers for which the length isn't
22412 transmitted as part of the function call, namely strings. Strings
22413 are transmitted as a pointer/length pair, both as hex values, e.g.@:
22420 which is a pointer to data of length 18 bytes at position 0x1aaf.
22421 The length is defined as the full string length in bytes, including
22422 the trailing null byte. Example:
22425 ``hello, world'' at address 0x123456
22436 @unnumberedsubsubsec struct stat
22437 @cindex struct stat, in file-i/o protocol
22439 The buffer of type struct stat used by the target and @value{GDBN} is defined
22444 unsigned int st_dev; /* device */
22445 unsigned int st_ino; /* inode */
22446 mode_t st_mode; /* protection */
22447 unsigned int st_nlink; /* number of hard links */
22448 unsigned int st_uid; /* user ID of owner */
22449 unsigned int st_gid; /* group ID of owner */
22450 unsigned int st_rdev; /* device type (if inode device) */
22451 unsigned long st_size; /* total size, in bytes */
22452 unsigned long st_blksize; /* blocksize for filesystem I/O */
22453 unsigned long st_blocks; /* number of blocks allocated */
22454 time_t st_atime; /* time of last access */
22455 time_t st_mtime; /* time of last modification */
22456 time_t st_ctime; /* time of last change */
22460 The integral datatypes are conforming to the definitions given in the
22461 approriate section (see @ref{Integral datatypes}, for details) so this
22462 structure is of size 64 bytes.
22464 The values of several fields have a restricted meaning and/or
22471 st_ino: No valid meaning for the target. Transmitted unchanged.
22473 st_mode: Valid mode bits are described in Appendix C. Any other
22474 bits have currently no meaning for the target.
22476 st_uid: No valid meaning for the target. Transmitted unchanged.
22478 st_gid: No valid meaning for the target. Transmitted unchanged.
22480 st_rdev: No valid meaning for the target. Transmitted unchanged.
22482 st_atime, st_mtime, st_ctime:
22483 These values have a host and file system dependent
22484 accuracy. Especially on Windows hosts the file systems
22485 don't support exact timing values.
22488 The target gets a struct stat of the above representation and is
22489 responsible to coerce it to the target representation before
22492 Note that due to size differences between the host and target
22493 representation of stat members, these members could eventually
22494 get truncated on the target.
22496 @node struct timeval
22497 @unnumberedsubsubsec struct timeval
22498 @cindex struct timeval, in file-i/o protocol
22500 The buffer of type struct timeval used by the target and @value{GDBN}
22501 is defined as follows:
22505 time_t tv_sec; /* second */
22506 long tv_usec; /* microsecond */
22510 The integral datatypes are conforming to the definitions given in the
22511 approriate section (see @ref{Integral datatypes}, for details) so this
22512 structure is of size 8 bytes.
22515 @subsection Constants
22516 @cindex constants, in file-i/o protocol
22518 The following values are used for the constants inside of the
22519 protocol. @value{GDBN} and target are resposible to translate these
22520 values before and after the call as needed.
22531 @unnumberedsubsubsec Open flags
22532 @cindex open flags, in file-i/o protocol
22534 All values are given in hexadecimal representation.
22546 @node mode_t values
22547 @unnumberedsubsubsec mode_t values
22548 @cindex mode_t values, in file-i/o protocol
22550 All values are given in octal representation.
22567 @unnumberedsubsubsec Errno values
22568 @cindex errno values, in file-i/o protocol
22570 All values are given in decimal representation.
22595 EUNKNOWN is used as a fallback error value if a host system returns
22596 any error value not in the list of supported error numbers.
22599 @unnumberedsubsubsec Lseek flags
22600 @cindex lseek flags, in file-i/o protocol
22609 @unnumberedsubsubsec Limits
22610 @cindex limits, in file-i/o protocol
22612 All values are given in decimal representation.
22615 INT_MIN -2147483648
22617 UINT_MAX 4294967295
22618 LONG_MIN -9223372036854775808
22619 LONG_MAX 9223372036854775807
22620 ULONG_MAX 18446744073709551615
22623 @node File-I/O Examples
22624 @subsection File-I/O Examples
22625 @cindex file-i/o examples
22627 Example sequence of a write call, file descriptor 3, buffer is at target
22628 address 0x1234, 6 bytes should be written:
22631 <- @code{Fwrite,3,1234,6}
22632 @emph{request memory read from target}
22635 @emph{return "6 bytes written"}
22639 Example sequence of a read call, file descriptor 3, buffer is at target
22640 address 0x1234, 6 bytes should be read:
22643 <- @code{Fread,3,1234,6}
22644 @emph{request memory write to target}
22645 -> @code{X1234,6:XXXXXX}
22646 @emph{return "6 bytes read"}
22650 Example sequence of a read call, call fails on the host due to invalid
22651 file descriptor (EBADF):
22654 <- @code{Fread,3,1234,6}
22658 Example sequence of a read call, user presses Ctrl-C before syscall on
22662 <- @code{Fread,3,1234,6}
22667 Example sequence of a read call, user presses Ctrl-C after syscall on
22671 <- @code{Fread,3,1234,6}
22672 -> @code{X1234,6:XXXXXX}
22676 @include agentexpr.texi
22690 % I think something like @colophon should be in texinfo. In the
22692 \long\def\colophon{\hbox to0pt{}\vfill
22693 \centerline{The body of this manual is set in}
22694 \centerline{\fontname\tenrm,}
22695 \centerline{with headings in {\bf\fontname\tenbf}}
22696 \centerline{and examples in {\tt\fontname\tentt}.}
22697 \centerline{{\it\fontname\tenit\/},}
22698 \centerline{{\bf\fontname\tenbf}, and}
22699 \centerline{{\sl\fontname\tensl\/}}
22700 \centerline{are used for emphasis.}\vfill}
22702 % Blame: doc@cygnus.com, 1991.