1 \input texinfo @c -*-texinfo-*-
2 @c Copyright 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003, 2004, 2005
4 @c Free Software Foundation, Inc.
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
25 @c readline appendices use @vindex, @findex and @ftable,
26 @c annotate.texi and gdbmi use @findex.
30 @c !!set GDB manual's edition---not the same as GDB version!
31 @c This is updated by GNU Press.
34 @c !!set GDB edit command default editor
37 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
39 @c This is a dir.info fragment to support semi-automated addition of
40 @c manuals to an info tree.
41 @dircategory Software development
43 * Gdb: (gdb). The GNU debugger.
47 This file documents the @sc{gnu} debugger @value{GDBN}.
50 This is the @value{EDITION} Edition, of @cite{Debugging with
51 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
52 Version @value{GDBVN}.
54 Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,@*
55 1999, 2000, 2001, 2002, 2003, 2004, 2005@*
56 Free Software Foundation, Inc.
58 Permission is granted to copy, distribute and/or modify this document
59 under the terms of the GNU Free Documentation License, Version 1.1 or
60 any later version published by the Free Software Foundation; with the
61 Invariant Sections being ``Free Software'' and ``Free Software Needs
62 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
63 and with the Back-Cover Texts as in (a) below.
65 (a) The Free Software Foundation's Back-Cover Text is: ``You have
66 freedom to copy and modify this GNU Manual, like GNU software. Copies
67 published by the Free Software Foundation raise funds for GNU
72 @title Debugging with @value{GDBN}
73 @subtitle The @sc{gnu} Source-Level Debugger
75 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
76 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
80 \hfill (Send bugs and comments on @value{GDBN} to bug-gdb\@gnu.org.)\par
81 \hfill {\it Debugging with @value{GDBN}}\par
82 \hfill \TeX{}info \texinfoversion\par
86 @vskip 0pt plus 1filll
87 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
88 1996, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
89 Free Software Foundation, Inc.
91 Published by the Free Software Foundation @*
92 59 Temple Place - Suite 330, @*
93 Boston, MA 02111-1307 USA @*
96 Permission is granted to copy, distribute and/or modify this document
97 under the terms of the GNU Free Documentation License, Version 1.1 or
98 any later version published by the Free Software Foundation; with the
99 Invariant Sections being ``Free Software'' and ``Free Software Needs
100 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
101 and with the Back-Cover Texts as in (a) below.
103 (a) The Free Software Foundation's Back-Cover Text is: ``You have
104 freedom to copy and modify this GNU Manual, like GNU software. Copies
105 published by the Free Software Foundation raise funds for GNU
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN} Version
120 Copyright (C) 1988-2005 Free Software Foundation, Inc.
123 * Summary:: Summary of @value{GDBN}
124 * Sample Session:: A sample @value{GDBN} session
126 * Invocation:: Getting in and out of @value{GDBN}
127 * Commands:: @value{GDBN} commands
128 * Running:: Running programs under @value{GDBN}
129 * Stopping:: Stopping and continuing
130 * Stack:: Examining the stack
131 * Source:: Examining source files
132 * Data:: Examining data
133 * Macros:: Preprocessor Macros
134 * Tracepoints:: Debugging remote targets non-intrusively
135 * Overlays:: Debugging programs that use overlays
137 * Languages:: Using @value{GDBN} with different languages
139 * Symbols:: Examining the symbol table
140 * Altering:: Altering execution
141 * GDB Files:: @value{GDBN} files
142 * Targets:: Specifying a debugging target
143 * Remote Debugging:: Debugging remote programs
144 * Configurations:: Configuration-specific information
145 * Controlling GDB:: Controlling @value{GDBN}
146 * Sequences:: Canned sequences of commands
147 * TUI:: @value{GDBN} Text User Interface
148 * Interpreters:: Command Interpreters
149 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
150 * Annotations:: @value{GDBN}'s annotation interface.
151 * GDB/MI:: @value{GDBN}'s Machine Interface.
153 * GDB Bugs:: Reporting bugs in @value{GDBN}
154 * Formatting Documentation:: How to format and print @value{GDBN} documentation
156 * Command Line Editing:: Command Line Editing
157 * Using History Interactively:: Using History Interactively
158 * Installing GDB:: Installing GDB
159 * Maintenance Commands:: Maintenance Commands
160 * Remote Protocol:: GDB Remote Serial Protocol
161 * Agent Expressions:: The GDB Agent Expression Mechanism
162 * Copying:: GNU General Public License says
163 how you can copy and share GDB
164 * GNU Free Documentation License:: The license for this documentation
173 @unnumbered Summary of @value{GDBN}
175 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
176 going on ``inside'' another program while it executes---or what another
177 program was doing at the moment it crashed.
179 @value{GDBN} can do four main kinds of things (plus other things in support of
180 these) to help you catch bugs in the act:
184 Start your program, specifying anything that might affect its behavior.
187 Make your program stop on specified conditions.
190 Examine what has happened, when your program has stopped.
193 Change things in your program, so you can experiment with correcting the
194 effects of one bug and go on to learn about another.
197 You can use @value{GDBN} to debug programs written in C and C@t{++}.
198 For more information, see @ref{Supported languages,,Supported languages}.
199 For more information, see @ref{C,,C and C++}.
202 Support for Modula-2 is partial. For information on Modula-2, see
203 @ref{Modula-2,,Modula-2}.
206 Debugging Pascal programs which use sets, subranges, file variables, or
207 nested functions does not currently work. @value{GDBN} does not support
208 entering expressions, printing values, or similar features using Pascal
212 @value{GDBN} can be used to debug programs written in Fortran, although
213 it may be necessary to refer to some variables with a trailing
216 @value{GDBN} can be used to debug programs written in Objective-C,
217 using either the Apple/NeXT or the GNU Objective-C runtime.
220 * Free Software:: Freely redistributable software
221 * Contributors:: Contributors to GDB
225 @unnumberedsec Free software
227 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
228 General Public License
229 (GPL). The GPL gives you the freedom to copy or adapt a licensed
230 program---but every person getting a copy also gets with it the
231 freedom to modify that copy (which means that they must get access to
232 the source code), and the freedom to distribute further copies.
233 Typical software companies use copyrights to limit your freedoms; the
234 Free Software Foundation uses the GPL to preserve these freedoms.
236 Fundamentally, the General Public License is a license which says that
237 you have these freedoms and that you cannot take these freedoms away
240 @unnumberedsec Free Software Needs Free Documentation
242 The biggest deficiency in the free software community today is not in
243 the software---it is the lack of good free documentation that we can
244 include with the free software. Many of our most important
245 programs do not come with free reference manuals and free introductory
246 texts. Documentation is an essential part of any software package;
247 when an important free software package does not come with a free
248 manual and a free tutorial, that is a major gap. We have many such
251 Consider Perl, for instance. The tutorial manuals that people
252 normally use are non-free. How did this come about? Because the
253 authors of those manuals published them with restrictive terms---no
254 copying, no modification, source files not available---which exclude
255 them from the free software world.
257 That wasn't the first time this sort of thing happened, and it was far
258 from the last. Many times we have heard a GNU user eagerly describe a
259 manual that he is writing, his intended contribution to the community,
260 only to learn that he had ruined everything by signing a publication
261 contract to make it non-free.
263 Free documentation, like free software, is a matter of freedom, not
264 price. The problem with the non-free manual is not that publishers
265 charge a price for printed copies---that in itself is fine. (The Free
266 Software Foundation sells printed copies of manuals, too.) The
267 problem is the restrictions on the use of the manual. Free manuals
268 are available in source code form, and give you permission to copy and
269 modify. Non-free manuals do not allow this.
271 The criteria of freedom for a free manual are roughly the same as for
272 free software. Redistribution (including the normal kinds of
273 commercial redistribution) must be permitted, so that the manual can
274 accompany every copy of the program, both on-line and on paper.
276 Permission for modification of the technical content is crucial too.
277 When people modify the software, adding or changing features, if they
278 are conscientious they will change the manual too---so they can
279 provide accurate and clear documentation for the modified program. A
280 manual that leaves you no choice but to write a new manual to document
281 a changed version of the program is not really available to our
284 Some kinds of limits on the way modification is handled are
285 acceptable. For example, requirements to preserve the original
286 author's copyright notice, the distribution terms, or the list of
287 authors, are ok. It is also no problem to require modified versions
288 to include notice that they were modified. Even entire sections that
289 may not be deleted or changed are acceptable, as long as they deal
290 with nontechnical topics (like this one). These kinds of restrictions
291 are acceptable because they don't obstruct the community's normal use
294 However, it must be possible to modify all the @emph{technical}
295 content of the manual, and then distribute the result in all the usual
296 media, through all the usual channels. Otherwise, the restrictions
297 obstruct the use of the manual, it is not free, and we need another
298 manual to replace it.
300 Please spread the word about this issue. Our community continues to
301 lose manuals to proprietary publishing. If we spread the word that
302 free software needs free reference manuals and free tutorials, perhaps
303 the next person who wants to contribute by writing documentation will
304 realize, before it is too late, that only free manuals contribute to
305 the free software community.
307 If you are writing documentation, please insist on publishing it under
308 the GNU Free Documentation License or another free documentation
309 license. Remember that this decision requires your approval---you
310 don't have to let the publisher decide. Some commercial publishers
311 will use a free license if you insist, but they will not propose the
312 option; it is up to you to raise the issue and say firmly that this is
313 what you want. If the publisher you are dealing with refuses, please
314 try other publishers. If you're not sure whether a proposed license
315 is free, write to @email{licensing@@gnu.org}.
317 You can encourage commercial publishers to sell more free, copylefted
318 manuals and tutorials by buying them, and particularly by buying
319 copies from the publishers that paid for their writing or for major
320 improvements. Meanwhile, try to avoid buying non-free documentation
321 at all. Check the distribution terms of a manual before you buy it,
322 and insist that whoever seeks your business must respect your freedom.
323 Check the history of the book, and try to reward the publishers that
324 have paid or pay the authors to work on it.
326 The Free Software Foundation maintains a list of free documentation
327 published by other publishers, at
328 @url{http://www.fsf.org/doc/other-free-books.html}.
331 @unnumberedsec Contributors to @value{GDBN}
333 Richard Stallman was the original author of @value{GDBN}, and of many
334 other @sc{gnu} programs. Many others have contributed to its
335 development. This section attempts to credit major contributors. One
336 of the virtues of free software is that everyone is free to contribute
337 to it; with regret, we cannot actually acknowledge everyone here. The
338 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
339 blow-by-blow account.
341 Changes much prior to version 2.0 are lost in the mists of time.
344 @emph{Plea:} Additions to this section are particularly welcome. If you
345 or your friends (or enemies, to be evenhanded) have been unfairly
346 omitted from this list, we would like to add your names!
349 So that they may not regard their many labors as thankless, we
350 particularly thank those who shepherded @value{GDBN} through major
352 Andrew Cagney (releases 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
353 Jim Blandy (release 4.18);
354 Jason Molenda (release 4.17);
355 Stan Shebs (release 4.14);
356 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
357 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
358 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
359 Jim Kingdon (releases 3.5, 3.4, and 3.3);
360 and Randy Smith (releases 3.2, 3.1, and 3.0).
362 Richard Stallman, assisted at various times by Peter TerMaat, Chris
363 Hanson, and Richard Mlynarik, handled releases through 2.8.
365 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
366 in @value{GDBN}, with significant additional contributions from Per
367 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
368 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
369 much general update work leading to release 3.0).
371 @value{GDBN} uses the BFD subroutine library to examine multiple
372 object-file formats; BFD was a joint project of David V.
373 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
375 David Johnson wrote the original COFF support; Pace Willison did
376 the original support for encapsulated COFF.
378 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
380 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
381 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
383 Jean-Daniel Fekete contributed Sun 386i support.
384 Chris Hanson improved the HP9000 support.
385 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
386 David Johnson contributed Encore Umax support.
387 Jyrki Kuoppala contributed Altos 3068 support.
388 Jeff Law contributed HP PA and SOM support.
389 Keith Packard contributed NS32K support.
390 Doug Rabson contributed Acorn Risc Machine support.
391 Bob Rusk contributed Harris Nighthawk CX-UX support.
392 Chris Smith contributed Convex support (and Fortran debugging).
393 Jonathan Stone contributed Pyramid support.
394 Michael Tiemann contributed SPARC support.
395 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
396 Pace Willison contributed Intel 386 support.
397 Jay Vosburgh contributed Symmetry support.
398 Marko Mlinar contributed OpenRISC 1000 support.
400 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
402 Rich Schaefer and Peter Schauer helped with support of SunOS shared
405 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
406 about several machine instruction sets.
408 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
409 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
410 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
411 and RDI targets, respectively.
413 Brian Fox is the author of the readline libraries providing
414 command-line editing and command history.
416 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
417 Modula-2 support, and contributed the Languages chapter of this manual.
419 Fred Fish wrote most of the support for Unix System Vr4.
420 He also enhanced the command-completion support to cover C@t{++} overloaded
423 Hitachi America (now Renesas America), Ltd. sponsored the support for
424 H8/300, H8/500, and Super-H processors.
426 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
428 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
431 Toshiba sponsored the support for the TX39 Mips processor.
433 Matsushita sponsored the support for the MN10200 and MN10300 processors.
435 Fujitsu sponsored the support for SPARClite and FR30 processors.
437 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
440 Michael Snyder added support for tracepoints.
442 Stu Grossman wrote gdbserver.
444 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
445 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
447 The following people at the Hewlett-Packard Company contributed
448 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
449 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
450 compiler, and the Text User Interface (nee Terminal User Interface):
451 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
452 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
453 provided HP-specific information in this manual.
455 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
456 Robert Hoehne made significant contributions to the DJGPP port.
458 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
459 development since 1991. Cygnus engineers who have worked on @value{GDBN}
460 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
461 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
462 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
463 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
464 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
465 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
466 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
467 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
468 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
469 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
470 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
471 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
472 Zuhn have made contributions both large and small.
474 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
475 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
477 Jim Blandy added support for preprocessor macros, while working for Red
480 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
481 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
482 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
483 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
484 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
485 with the migration of old architectures to this new framework.
488 @chapter A Sample @value{GDBN} Session
490 You can use this manual at your leisure to read all about @value{GDBN}.
491 However, a handful of commands are enough to get started using the
492 debugger. This chapter illustrates those commands.
495 In this sample session, we emphasize user input like this: @b{input},
496 to make it easier to pick out from the surrounding output.
499 @c FIXME: this example may not be appropriate for some configs, where
500 @c FIXME...primary interest is in remote use.
502 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
503 processor) exhibits the following bug: sometimes, when we change its
504 quote strings from the default, the commands used to capture one macro
505 definition within another stop working. In the following short @code{m4}
506 session, we define a macro @code{foo} which expands to @code{0000}; we
507 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
508 same thing. However, when we change the open quote string to
509 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
510 procedure fails to define a new synonym @code{baz}:
519 @b{define(bar,defn(`foo'))}
523 @b{changequote(<QUOTE>,<UNQUOTE>)}
525 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
528 m4: End of input: 0: fatal error: EOF in string
532 Let us use @value{GDBN} to try to see what is going on.
535 $ @b{@value{GDBP} m4}
536 @c FIXME: this falsifies the exact text played out, to permit smallbook
537 @c FIXME... format to come out better.
538 @value{GDBN} is free software and you are welcome to distribute copies
539 of it under certain conditions; type "show copying" to see
541 There is absolutely no warranty for @value{GDBN}; type "show warranty"
544 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
549 @value{GDBN} reads only enough symbol data to know where to find the
550 rest when needed; as a result, the first prompt comes up very quickly.
551 We now tell @value{GDBN} to use a narrower display width than usual, so
552 that examples fit in this manual.
555 (@value{GDBP}) @b{set width 70}
559 We need to see how the @code{m4} built-in @code{changequote} works.
560 Having looked at the source, we know the relevant subroutine is
561 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
562 @code{break} command.
565 (@value{GDBP}) @b{break m4_changequote}
566 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
570 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
571 control; as long as control does not reach the @code{m4_changequote}
572 subroutine, the program runs as usual:
575 (@value{GDBP}) @b{run}
576 Starting program: /work/Editorial/gdb/gnu/m4/m4
584 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
585 suspends execution of @code{m4}, displaying information about the
586 context where it stops.
589 @b{changequote(<QUOTE>,<UNQUOTE>)}
591 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
593 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
597 Now we use the command @code{n} (@code{next}) to advance execution to
598 the next line of the current function.
602 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
607 @code{set_quotes} looks like a promising subroutine. We can go into it
608 by using the command @code{s} (@code{step}) instead of @code{next}.
609 @code{step} goes to the next line to be executed in @emph{any}
610 subroutine, so it steps into @code{set_quotes}.
614 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
616 530 if (lquote != def_lquote)
620 The display that shows the subroutine where @code{m4} is now
621 suspended (and its arguments) is called a stack frame display. It
622 shows a summary of the stack. We can use the @code{backtrace}
623 command (which can also be spelled @code{bt}), to see where we are
624 in the stack as a whole: the @code{backtrace} command displays a
625 stack frame for each active subroutine.
628 (@value{GDBP}) @b{bt}
629 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
631 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
633 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
634 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
636 #4 0x79dc in expand_input () at macro.c:40
637 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
641 We step through a few more lines to see what happens. The first two
642 times, we can use @samp{s}; the next two times we use @code{n} to avoid
643 falling into the @code{xstrdup} subroutine.
647 0x3b5c 532 if (rquote != def_rquote)
649 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
650 def_lquote : xstrdup(lq);
652 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
655 538 len_lquote = strlen(rquote);
659 The last line displayed looks a little odd; we can examine the variables
660 @code{lquote} and @code{rquote} to see if they are in fact the new left
661 and right quotes we specified. We use the command @code{p}
662 (@code{print}) to see their values.
665 (@value{GDBP}) @b{p lquote}
666 $1 = 0x35d40 "<QUOTE>"
667 (@value{GDBP}) @b{p rquote}
668 $2 = 0x35d50 "<UNQUOTE>"
672 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
673 To look at some context, we can display ten lines of source
674 surrounding the current line with the @code{l} (@code{list}) command.
680 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
682 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
685 538 len_lquote = strlen(rquote);
686 539 len_rquote = strlen(lquote);
693 Let us step past the two lines that set @code{len_lquote} and
694 @code{len_rquote}, and then examine the values of those variables.
698 539 len_rquote = strlen(lquote);
701 (@value{GDBP}) @b{p len_lquote}
703 (@value{GDBP}) @b{p len_rquote}
708 That certainly looks wrong, assuming @code{len_lquote} and
709 @code{len_rquote} are meant to be the lengths of @code{lquote} and
710 @code{rquote} respectively. We can set them to better values using
711 the @code{p} command, since it can print the value of
712 any expression---and that expression can include subroutine calls and
716 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
718 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
723 Is that enough to fix the problem of using the new quotes with the
724 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
725 executing with the @code{c} (@code{continue}) command, and then try the
726 example that caused trouble initially:
732 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
739 Success! The new quotes now work just as well as the default ones. The
740 problem seems to have been just the two typos defining the wrong
741 lengths. We allow @code{m4} exit by giving it an EOF as input:
745 Program exited normally.
749 The message @samp{Program exited normally.} is from @value{GDBN}; it
750 indicates @code{m4} has finished executing. We can end our @value{GDBN}
751 session with the @value{GDBN} @code{quit} command.
754 (@value{GDBP}) @b{quit}
758 @chapter Getting In and Out of @value{GDBN}
760 This chapter discusses how to start @value{GDBN}, and how to get out of it.
764 type @samp{@value{GDBP}} to start @value{GDBN}.
766 type @kbd{quit} or @kbd{C-d} to exit.
770 * Invoking GDB:: How to start @value{GDBN}
771 * Quitting GDB:: How to quit @value{GDBN}
772 * Shell Commands:: How to use shell commands inside @value{GDBN}
773 * Logging output:: How to log @value{GDBN}'s output to a file
777 @section Invoking @value{GDBN}
779 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
780 @value{GDBN} reads commands from the terminal until you tell it to exit.
782 You can also run @code{@value{GDBP}} with a variety of arguments and options,
783 to specify more of your debugging environment at the outset.
785 The command-line options described here are designed
786 to cover a variety of situations; in some environments, some of these
787 options may effectively be unavailable.
789 The most usual way to start @value{GDBN} is with one argument,
790 specifying an executable program:
793 @value{GDBP} @var{program}
797 You can also start with both an executable program and a core file
801 @value{GDBP} @var{program} @var{core}
804 You can, instead, specify a process ID as a second argument, if you want
805 to debug a running process:
808 @value{GDBP} @var{program} 1234
812 would attach @value{GDBN} to process @code{1234} (unless you also have a file
813 named @file{1234}; @value{GDBN} does check for a core file first).
815 Taking advantage of the second command-line argument requires a fairly
816 complete operating system; when you use @value{GDBN} as a remote
817 debugger attached to a bare board, there may not be any notion of
818 ``process'', and there is often no way to get a core dump. @value{GDBN}
819 will warn you if it is unable to attach or to read core dumps.
821 You can optionally have @code{@value{GDBP}} pass any arguments after the
822 executable file to the inferior using @code{--args}. This option stops
825 gdb --args gcc -O2 -c foo.c
827 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
828 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
830 You can run @code{@value{GDBP}} without printing the front material, which describes
831 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
838 You can further control how @value{GDBN} starts up by using command-line
839 options. @value{GDBN} itself can remind you of the options available.
849 to display all available options and briefly describe their use
850 (@samp{@value{GDBP} -h} is a shorter equivalent).
852 All options and command line arguments you give are processed
853 in sequential order. The order makes a difference when the
854 @samp{-x} option is used.
858 * File Options:: Choosing files
859 * Mode Options:: Choosing modes
860 * Startup:: What @value{GDBN} does during startup
864 @subsection Choosing files
866 When @value{GDBN} starts, it reads any arguments other than options as
867 specifying an executable file and core file (or process ID). This is
868 the same as if the arguments were specified by the @samp{-se} and
869 @samp{-c} (or @samp{-p} options respectively. (@value{GDBN} reads the
870 first argument that does not have an associated option flag as
871 equivalent to the @samp{-se} option followed by that argument; and the
872 second argument that does not have an associated option flag, if any, as
873 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
874 If the second argument begins with a decimal digit, @value{GDBN} will
875 first attempt to attach to it as a process, and if that fails, attempt
876 to open it as a corefile. If you have a corefile whose name begins with
877 a digit, you can prevent @value{GDBN} from treating it as a pid by
878 prefixing it with @file{./}, eg. @file{./12345}.
880 If @value{GDBN} has not been configured to included core file support,
881 such as for most embedded targets, then it will complain about a second
882 argument and ignore it.
884 Many options have both long and short forms; both are shown in the
885 following list. @value{GDBN} also recognizes the long forms if you truncate
886 them, so long as enough of the option is present to be unambiguous.
887 (If you prefer, you can flag option arguments with @samp{--} rather
888 than @samp{-}, though we illustrate the more usual convention.)
890 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
891 @c way, both those who look for -foo and --foo in the index, will find
895 @item -symbols @var{file}
897 @cindex @code{--symbols}
899 Read symbol table from file @var{file}.
901 @item -exec @var{file}
903 @cindex @code{--exec}
905 Use file @var{file} as the executable file to execute when appropriate,
906 and for examining pure data in conjunction with a core dump.
910 Read symbol table from file @var{file} and use it as the executable
913 @item -core @var{file}
915 @cindex @code{--core}
917 Use file @var{file} as a core dump to examine.
919 @item -c @var{number}
920 @item -pid @var{number}
921 @itemx -p @var{number}
924 Connect to process ID @var{number}, as with the @code{attach} command.
925 If there is no such process, @value{GDBN} will attempt to open a core
926 file named @var{number}.
928 @item -command @var{file}
930 @cindex @code{--command}
932 Execute @value{GDBN} commands from file @var{file}. @xref{Command
933 Files,, Command files}.
935 @item -directory @var{directory}
936 @itemx -d @var{directory}
937 @cindex @code{--directory}
939 Add @var{directory} to the path to search for source files.
943 @cindex @code{--mapped}
945 @emph{Warning: this option depends on operating system facilities that are not
946 supported on all systems.}@*
947 If memory-mapped files are available on your system through the @code{mmap}
948 system call, you can use this option
949 to have @value{GDBN} write the symbols from your
950 program into a reusable file in the current directory. If the program you are debugging is
951 called @file{/tmp/fred}, the mapped symbol file is @file{/tmp/fred.syms}.
952 Future @value{GDBN} debugging sessions notice the presence of this file,
953 and can quickly map in symbol information from it, rather than reading
954 the symbol table from the executable program.
956 The @file{.syms} file is specific to the host machine where @value{GDBN}
957 is run. It holds an exact image of the internal @value{GDBN} symbol
958 table. It cannot be shared across multiple host platforms.
962 @cindex @code{--readnow}
964 Read each symbol file's entire symbol table immediately, rather than
965 the default, which is to read it incrementally as it is needed.
966 This makes startup slower, but makes future operations faster.
970 You typically combine the @code{-mapped} and @code{-readnow} options in
971 order to build a @file{.syms} file that contains complete symbol
972 information. (@xref{Files,,Commands to specify files}, for information
973 on @file{.syms} files.) A simple @value{GDBN} invocation to do nothing
974 but build a @file{.syms} file for future use is:
977 gdb -batch -nx -mapped -readnow programname
981 @subsection Choosing modes
983 You can run @value{GDBN} in various alternative modes---for example, in
984 batch mode or quiet mode.
991 Do not execute commands found in any initialization files. Normally,
992 @value{GDBN} executes the commands in these files after all the command
993 options and arguments have been processed. @xref{Command Files,,Command
999 @cindex @code{--quiet}
1000 @cindex @code{--silent}
1002 ``Quiet''. Do not print the introductory and copyright messages. These
1003 messages are also suppressed in batch mode.
1006 @cindex @code{--batch}
1007 Run in batch mode. Exit with status @code{0} after processing all the
1008 command files specified with @samp{-x} (and all commands from
1009 initialization files, if not inhibited with @samp{-n}). Exit with
1010 nonzero status if an error occurs in executing the @value{GDBN} commands
1011 in the command files.
1013 Batch mode may be useful for running @value{GDBN} as a filter, for
1014 example to download and run a program on another computer; in order to
1015 make this more useful, the message
1018 Program exited normally.
1022 (which is ordinarily issued whenever a program running under
1023 @value{GDBN} control terminates) is not issued when running in batch
1028 @cindex @code{--nowindows}
1030 ``No windows''. If @value{GDBN} comes with a graphical user interface
1031 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1032 interface. If no GUI is available, this option has no effect.
1036 @cindex @code{--windows}
1038 If @value{GDBN} includes a GUI, then this option requires it to be
1041 @item -cd @var{directory}
1043 Run @value{GDBN} using @var{directory} as its working directory,
1044 instead of the current directory.
1048 @cindex @code{--fullname}
1050 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1051 subprocess. It tells @value{GDBN} to output the full file name and line
1052 number in a standard, recognizable fashion each time a stack frame is
1053 displayed (which includes each time your program stops). This
1054 recognizable format looks like two @samp{\032} characters, followed by
1055 the file name, line number and character position separated by colons,
1056 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1057 @samp{\032} characters as a signal to display the source code for the
1061 @cindex @code{--epoch}
1062 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1063 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1064 routines so as to allow Epoch to display values of expressions in a
1067 @item -annotate @var{level}
1068 @cindex @code{--annotate}
1069 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1070 effect is identical to using @samp{set annotate @var{level}}
1071 (@pxref{Annotations}). The annotation @var{level} controls how much
1072 information @value{GDBN} prints together with its prompt, values of
1073 expressions, source lines, and other types of output. Level 0 is the
1074 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1075 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1076 that control @value{GDBN}, and level 2 has been deprecated.
1078 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
1082 @cindex @code{--args}
1083 Change interpretation of command line so that arguments following the
1084 executable file are passed as command line arguments to the inferior.
1085 This option stops option processing.
1087 @item -baud @var{bps}
1089 @cindex @code{--baud}
1091 Set the line speed (baud rate or bits per second) of any serial
1092 interface used by @value{GDBN} for remote debugging.
1094 @item -l @var{timeout}
1096 Set the timeout (in seconds) of any communication used by @value{GDBN}
1097 for remote debugging.
1099 @item -tty @var{device}
1100 @itemx -t @var{device}
1101 @cindex @code{--tty}
1103 Run using @var{device} for your program's standard input and output.
1104 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1106 @c resolve the situation of these eventually
1108 @cindex @code{--tui}
1109 Activate the @dfn{Text User Interface} when starting. The Text User
1110 Interface manages several text windows on the terminal, showing
1111 source, assembly, registers and @value{GDBN} command outputs
1112 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1113 Text User Interface can be enabled by invoking the program
1114 @samp{gdbtui}. Do not use this option if you run @value{GDBN} from
1115 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1118 @c @cindex @code{--xdb}
1119 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1120 @c For information, see the file @file{xdb_trans.html}, which is usually
1121 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1124 @item -interpreter @var{interp}
1125 @cindex @code{--interpreter}
1126 Use the interpreter @var{interp} for interface with the controlling
1127 program or device. This option is meant to be set by programs which
1128 communicate with @value{GDBN} using it as a back end.
1129 @xref{Interpreters, , Command Interpreters}.
1131 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1132 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1133 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1134 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1135 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1136 @sc{gdb/mi} interfaces are no longer supported.
1139 @cindex @code{--write}
1140 Open the executable and core files for both reading and writing. This
1141 is equivalent to the @samp{set write on} command inside @value{GDBN}
1145 @cindex @code{--statistics}
1146 This option causes @value{GDBN} to print statistics about time and
1147 memory usage after it completes each command and returns to the prompt.
1150 @cindex @code{--version}
1151 This option causes @value{GDBN} to print its version number and
1152 no-warranty blurb, and exit.
1157 @subsection What @value{GDBN} does during startup
1158 @cindex @value{GDBN} startup
1160 Here's the description of what @value{GDBN} does during session startup:
1164 Sets up the command interpreter as specified by the command line
1165 (@pxref{Mode Options, interpreter}).
1169 Reads the @dfn{init file} (if any) in your home directory@footnote{On
1170 DOS/Windows systems, the home directory is the one pointed to by the
1171 @code{HOME} environment variable.} and executes all the commands in
1175 Processes command line options and operands.
1178 Reads and executes the commands from init file (if any) in the current
1179 working directory. This is only done if the current directory is
1180 different from your home directory. Thus, you can have more than one
1181 init file, one generic in your home directory, and another, specific
1182 to the program you are debugging, in the directory where you invoke
1186 Reads command files specified by the @samp{-x} option. @xref{Command
1187 Files}, for more details about @value{GDBN} command files.
1190 Reads the command history recorded in the @dfn{history file}.
1191 @xref{History}, for more details about the command history and the
1192 files where @value{GDBN} records it.
1195 Init files use the same syntax as @dfn{command files} (@pxref{Command
1196 Files}) and are processed by @value{GDBN} in the same way. The init
1197 file in your home directory can set options (such as @samp{set
1198 complaints}) that affect subsequent processing of command line options
1199 and operands. Init files are not executed if you use the @samp{-nx}
1200 option (@pxref{Mode Options, ,Choosing modes}).
1202 @cindex init file name
1203 @cindex @file{.gdbinit}
1204 The @value{GDBN} init files are normally called @file{.gdbinit}.
1205 On some configurations of @value{GDBN}, the init file is known by a
1206 different name (these are typically environments where a specialized
1207 form of @value{GDBN} may need to coexist with other forms, hence a
1208 different name for the specialized version's init file). These are the
1209 environments with special init file names:
1212 @cindex @file{gdb.ini}
1214 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1215 the limitations of file names imposed by DOS filesystems. The Windows
1216 ports of @value{GDBN} use the standard name, but if they find a
1217 @file{gdb.ini} file, they warn you about that and suggest to rename
1218 the file to the standard name.
1220 @cindex @file{.vxgdbinit}
1222 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
1224 @cindex @file{.os68gdbinit}
1226 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
1228 @cindex @file{.esgdbinit}
1230 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
1233 CISCO 68k: @file{.cisco-gdbinit}
1238 @section Quitting @value{GDBN}
1239 @cindex exiting @value{GDBN}
1240 @cindex leaving @value{GDBN}
1243 @kindex quit @r{[}@var{expression}@r{]}
1244 @kindex q @r{(@code{quit})}
1245 @item quit @r{[}@var{expression}@r{]}
1247 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1248 @code{q}), or type an end-of-file character (usually @kbd{C-d}). If you
1249 do not supply @var{expression}, @value{GDBN} will terminate normally;
1250 otherwise it will terminate using the result of @var{expression} as the
1255 An interrupt (often @kbd{C-c}) does not exit from @value{GDBN}, but rather
1256 terminates the action of any @value{GDBN} command that is in progress and
1257 returns to @value{GDBN} command level. It is safe to type the interrupt
1258 character at any time because @value{GDBN} does not allow it to take effect
1259 until a time when it is safe.
1261 If you have been using @value{GDBN} to control an attached process or
1262 device, you can release it with the @code{detach} command
1263 (@pxref{Attach, ,Debugging an already-running process}).
1265 @node Shell Commands
1266 @section Shell commands
1268 If you need to execute occasional shell commands during your
1269 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1270 just use the @code{shell} command.
1274 @cindex shell escape
1275 @item shell @var{command string}
1276 Invoke a standard shell to execute @var{command string}.
1277 If it exists, the environment variable @code{SHELL} determines which
1278 shell to run. Otherwise @value{GDBN} uses the default shell
1279 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1282 The utility @code{make} is often needed in development environments.
1283 You do not have to use the @code{shell} command for this purpose in
1288 @cindex calling make
1289 @item make @var{make-args}
1290 Execute the @code{make} program with the specified
1291 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1294 @node Logging output
1295 @section Logging output
1296 @cindex logging @value{GDBN} output
1297 @cindex save @value{GDBN} output to a file
1299 You may want to save the output of @value{GDBN} commands to a file.
1300 There are several commands to control @value{GDBN}'s logging.
1304 @item set logging on
1306 @item set logging off
1308 @cindex logging file name
1309 @item set logging file @var{file}
1310 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1311 @item set logging overwrite [on|off]
1312 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1313 you want @code{set logging on} to overwrite the logfile instead.
1314 @item set logging redirect [on|off]
1315 By default, @value{GDBN} output will go to both the terminal and the logfile.
1316 Set @code{redirect} if you want output to go only to the log file.
1317 @kindex show logging
1319 Show the current values of the logging settings.
1323 @chapter @value{GDBN} Commands
1325 You can abbreviate a @value{GDBN} command to the first few letters of the command
1326 name, if that abbreviation is unambiguous; and you can repeat certain
1327 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1328 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1329 show you the alternatives available, if there is more than one possibility).
1332 * Command Syntax:: How to give commands to @value{GDBN}
1333 * Completion:: Command completion
1334 * Help:: How to ask @value{GDBN} for help
1337 @node Command Syntax
1338 @section Command syntax
1340 A @value{GDBN} command is a single line of input. There is no limit on
1341 how long it can be. It starts with a command name, which is followed by
1342 arguments whose meaning depends on the command name. For example, the
1343 command @code{step} accepts an argument which is the number of times to
1344 step, as in @samp{step 5}. You can also use the @code{step} command
1345 with no arguments. Some commands do not allow any arguments.
1347 @cindex abbreviation
1348 @value{GDBN} command names may always be truncated if that abbreviation is
1349 unambiguous. Other possible command abbreviations are listed in the
1350 documentation for individual commands. In some cases, even ambiguous
1351 abbreviations are allowed; for example, @code{s} is specially defined as
1352 equivalent to @code{step} even though there are other commands whose
1353 names start with @code{s}. You can test abbreviations by using them as
1354 arguments to the @code{help} command.
1356 @cindex repeating commands
1357 @kindex RET @r{(repeat last command)}
1358 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1359 repeat the previous command. Certain commands (for example, @code{run})
1360 will not repeat this way; these are commands whose unintentional
1361 repetition might cause trouble and which you are unlikely to want to
1362 repeat. User-defined commands can disable this feature; see
1363 @ref{Define, dont-repeat}.
1365 The @code{list} and @code{x} commands, when you repeat them with
1366 @key{RET}, construct new arguments rather than repeating
1367 exactly as typed. This permits easy scanning of source or memory.
1369 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1370 output, in a way similar to the common utility @code{more}
1371 (@pxref{Screen Size,,Screen size}). Since it is easy to press one
1372 @key{RET} too many in this situation, @value{GDBN} disables command
1373 repetition after any command that generates this sort of display.
1375 @kindex # @r{(a comment)}
1377 Any text from a @kbd{#} to the end of the line is a comment; it does
1378 nothing. This is useful mainly in command files (@pxref{Command
1379 Files,,Command files}).
1381 @cindex repeating command sequences
1382 @kindex C-o @r{(operate-and-get-next)}
1383 The @kbd{C-o} binding is useful for repeating a complex sequence of
1384 commands. This command accepts the current line, like @kbd{RET}, and
1385 then fetches the next line relative to the current line from the history
1389 @section Command completion
1392 @cindex word completion
1393 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1394 only one possibility; it can also show you what the valid possibilities
1395 are for the next word in a command, at any time. This works for @value{GDBN}
1396 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1398 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1399 of a word. If there is only one possibility, @value{GDBN} fills in the
1400 word, and waits for you to finish the command (or press @key{RET} to
1401 enter it). For example, if you type
1403 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1404 @c complete accuracy in these examples; space introduced for clarity.
1405 @c If texinfo enhancements make it unnecessary, it would be nice to
1406 @c replace " @key" by "@key" in the following...
1408 (@value{GDBP}) info bre @key{TAB}
1412 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1413 the only @code{info} subcommand beginning with @samp{bre}:
1416 (@value{GDBP}) info breakpoints
1420 You can either press @key{RET} at this point, to run the @code{info
1421 breakpoints} command, or backspace and enter something else, if
1422 @samp{breakpoints} does not look like the command you expected. (If you
1423 were sure you wanted @code{info breakpoints} in the first place, you
1424 might as well just type @key{RET} immediately after @samp{info bre},
1425 to exploit command abbreviations rather than command completion).
1427 If there is more than one possibility for the next word when you press
1428 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1429 characters and try again, or just press @key{TAB} a second time;
1430 @value{GDBN} displays all the possible completions for that word. For
1431 example, you might want to set a breakpoint on a subroutine whose name
1432 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1433 just sounds the bell. Typing @key{TAB} again displays all the
1434 function names in your program that begin with those characters, for
1438 (@value{GDBP}) b make_ @key{TAB}
1439 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1440 make_a_section_from_file make_environ
1441 make_abs_section make_function_type
1442 make_blockvector make_pointer_type
1443 make_cleanup make_reference_type
1444 make_command make_symbol_completion_list
1445 (@value{GDBP}) b make_
1449 After displaying the available possibilities, @value{GDBN} copies your
1450 partial input (@samp{b make_} in the example) so you can finish the
1453 If you just want to see the list of alternatives in the first place, you
1454 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1455 means @kbd{@key{META} ?}. You can type this either by holding down a
1456 key designated as the @key{META} shift on your keyboard (if there is
1457 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1459 @cindex quotes in commands
1460 @cindex completion of quoted strings
1461 Sometimes the string you need, while logically a ``word'', may contain
1462 parentheses or other characters that @value{GDBN} normally excludes from
1463 its notion of a word. To permit word completion to work in this
1464 situation, you may enclose words in @code{'} (single quote marks) in
1465 @value{GDBN} commands.
1467 The most likely situation where you might need this is in typing the
1468 name of a C@t{++} function. This is because C@t{++} allows function
1469 overloading (multiple definitions of the same function, distinguished
1470 by argument type). For example, when you want to set a breakpoint you
1471 may need to distinguish whether you mean the version of @code{name}
1472 that takes an @code{int} parameter, @code{name(int)}, or the version
1473 that takes a @code{float} parameter, @code{name(float)}. To use the
1474 word-completion facilities in this situation, type a single quote
1475 @code{'} at the beginning of the function name. This alerts
1476 @value{GDBN} that it may need to consider more information than usual
1477 when you press @key{TAB} or @kbd{M-?} to request word completion:
1480 (@value{GDBP}) b 'bubble( @kbd{M-?}
1481 bubble(double,double) bubble(int,int)
1482 (@value{GDBP}) b 'bubble(
1485 In some cases, @value{GDBN} can tell that completing a name requires using
1486 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1487 completing as much as it can) if you do not type the quote in the first
1491 (@value{GDBP}) b bub @key{TAB}
1492 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1493 (@value{GDBP}) b 'bubble(
1497 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1498 you have not yet started typing the argument list when you ask for
1499 completion on an overloaded symbol.
1501 For more information about overloaded functions, see @ref{C plus plus
1502 expressions, ,C@t{++} expressions}. You can use the command @code{set
1503 overload-resolution off} to disable overload resolution;
1504 see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
1508 @section Getting help
1509 @cindex online documentation
1512 You can always ask @value{GDBN} itself for information on its commands,
1513 using the command @code{help}.
1516 @kindex h @r{(@code{help})}
1519 You can use @code{help} (abbreviated @code{h}) with no arguments to
1520 display a short list of named classes of commands:
1524 List of classes of commands:
1526 aliases -- Aliases of other commands
1527 breakpoints -- Making program stop at certain points
1528 data -- Examining data
1529 files -- Specifying and examining files
1530 internals -- Maintenance commands
1531 obscure -- Obscure features
1532 running -- Running the program
1533 stack -- Examining the stack
1534 status -- Status inquiries
1535 support -- Support facilities
1536 tracepoints -- Tracing of program execution without@*
1537 stopping the program
1538 user-defined -- User-defined commands
1540 Type "help" followed by a class name for a list of
1541 commands in that class.
1542 Type "help" followed by command name for full
1544 Command name abbreviations are allowed if unambiguous.
1547 @c the above line break eliminates huge line overfull...
1549 @item help @var{class}
1550 Using one of the general help classes as an argument, you can get a
1551 list of the individual commands in that class. For example, here is the
1552 help display for the class @code{status}:
1555 (@value{GDBP}) help status
1560 @c Line break in "show" line falsifies real output, but needed
1561 @c to fit in smallbook page size.
1562 info -- Generic command for showing things
1563 about the program being debugged
1564 show -- Generic command for showing things
1567 Type "help" followed by command name for full
1569 Command name abbreviations are allowed if unambiguous.
1573 @item help @var{command}
1574 With a command name as @code{help} argument, @value{GDBN} displays a
1575 short paragraph on how to use that command.
1578 @item apropos @var{args}
1579 The @code{apropos} command searches through all of the @value{GDBN}
1580 commands, and their documentation, for the regular expression specified in
1581 @var{args}. It prints out all matches found. For example:
1592 set symbol-reloading -- Set dynamic symbol table reloading
1593 multiple times in one run
1594 show symbol-reloading -- Show dynamic symbol table reloading
1595 multiple times in one run
1600 @item complete @var{args}
1601 The @code{complete @var{args}} command lists all the possible completions
1602 for the beginning of a command. Use @var{args} to specify the beginning of the
1603 command you want completed. For example:
1609 @noindent results in:
1620 @noindent This is intended for use by @sc{gnu} Emacs.
1623 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1624 and @code{show} to inquire about the state of your program, or the state
1625 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1626 manual introduces each of them in the appropriate context. The listings
1627 under @code{info} and under @code{show} in the Index point to
1628 all the sub-commands. @xref{Index}.
1633 @kindex i @r{(@code{info})}
1635 This command (abbreviated @code{i}) is for describing the state of your
1636 program. For example, you can list the arguments given to your program
1637 with @code{info args}, list the registers currently in use with @code{info
1638 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1639 You can get a complete list of the @code{info} sub-commands with
1640 @w{@code{help info}}.
1644 You can assign the result of an expression to an environment variable with
1645 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1646 @code{set prompt $}.
1650 In contrast to @code{info}, @code{show} is for describing the state of
1651 @value{GDBN} itself.
1652 You can change most of the things you can @code{show}, by using the
1653 related command @code{set}; for example, you can control what number
1654 system is used for displays with @code{set radix}, or simply inquire
1655 which is currently in use with @code{show radix}.
1658 To display all the settable parameters and their current
1659 values, you can use @code{show} with no arguments; you may also use
1660 @code{info set}. Both commands produce the same display.
1661 @c FIXME: "info set" violates the rule that "info" is for state of
1662 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1663 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1667 Here are three miscellaneous @code{show} subcommands, all of which are
1668 exceptional in lacking corresponding @code{set} commands:
1671 @kindex show version
1672 @cindex @value{GDBN} version number
1674 Show what version of @value{GDBN} is running. You should include this
1675 information in @value{GDBN} bug-reports. If multiple versions of
1676 @value{GDBN} are in use at your site, you may need to determine which
1677 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1678 commands are introduced, and old ones may wither away. Also, many
1679 system vendors ship variant versions of @value{GDBN}, and there are
1680 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1681 The version number is the same as the one announced when you start
1684 @kindex show copying
1685 @kindex info copying
1686 @cindex display @value{GDBN} copyright
1689 Display information about permission for copying @value{GDBN}.
1691 @kindex show warranty
1692 @kindex info warranty
1694 @itemx info warranty
1695 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1696 if your version of @value{GDBN} comes with one.
1701 @chapter Running Programs Under @value{GDBN}
1703 When you run a program under @value{GDBN}, you must first generate
1704 debugging information when you compile it.
1706 You may start @value{GDBN} with its arguments, if any, in an environment
1707 of your choice. If you are doing native debugging, you may redirect
1708 your program's input and output, debug an already running process, or
1709 kill a child process.
1712 * Compilation:: Compiling for debugging
1713 * Starting:: Starting your program
1714 * Arguments:: Your program's arguments
1715 * Environment:: Your program's environment
1717 * Working Directory:: Your program's working directory
1718 * Input/Output:: Your program's input and output
1719 * Attach:: Debugging an already-running process
1720 * Kill Process:: Killing the child process
1722 * Threads:: Debugging programs with multiple threads
1723 * Processes:: Debugging programs with multiple processes
1727 @section Compiling for debugging
1729 In order to debug a program effectively, you need to generate
1730 debugging information when you compile it. This debugging information
1731 is stored in the object file; it describes the data type of each
1732 variable or function and the correspondence between source line numbers
1733 and addresses in the executable code.
1735 To request debugging information, specify the @samp{-g} option when you run
1738 Programs that are to be shipped to your customers are compiled with
1739 optimizations, using the @samp{-O} compiler option. However, many
1740 compilers are unable to handle the @samp{-g} and @samp{-O} options
1741 together. Using those compilers, you cannot generate optimized
1742 executables containing debugging information.
1744 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1745 without @samp{-O}, making it possible to debug optimized code. We
1746 recommend that you @emph{always} use @samp{-g} whenever you compile a
1747 program. You may think your program is correct, but there is no sense
1748 in pushing your luck.
1750 @cindex optimized code, debugging
1751 @cindex debugging optimized code
1752 When you debug a program compiled with @samp{-g -O}, remember that the
1753 optimizer is rearranging your code; the debugger shows you what is
1754 really there. Do not be too surprised when the execution path does not
1755 exactly match your source file! An extreme example: if you define a
1756 variable, but never use it, @value{GDBN} never sees that
1757 variable---because the compiler optimizes it out of existence.
1759 Some things do not work as well with @samp{-g -O} as with just
1760 @samp{-g}, particularly on machines with instruction scheduling. If in
1761 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1762 please report it to us as a bug (including a test case!).
1763 @xref{Variables}, for more information about debugging optimized code.
1765 Older versions of the @sc{gnu} C compiler permitted a variant option
1766 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1767 format; if your @sc{gnu} C compiler has this option, do not use it.
1769 @value{GDBN} knows about preprocessor macros and can show you their
1770 expansion (@pxref{Macros}). Most compilers do not include information
1771 about preprocessor macros in the debugging information if you specify
1772 the @option{-g} flag alone, because this information is rather large.
1773 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1774 provides macro information if you specify the options
1775 @option{-gdwarf-2} and @option{-g3}; the former option requests
1776 debugging information in the Dwarf 2 format, and the latter requests
1777 ``extra information''. In the future, we hope to find more compact
1778 ways to represent macro information, so that it can be included with
1783 @section Starting your program
1789 @kindex r @r{(@code{run})}
1792 Use the @code{run} command to start your program under @value{GDBN}.
1793 You must first specify the program name (except on VxWorks) with an
1794 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1795 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1796 (@pxref{Files, ,Commands to specify files}).
1800 If you are running your program in an execution environment that
1801 supports processes, @code{run} creates an inferior process and makes
1802 that process run your program. (In environments without processes,
1803 @code{run} jumps to the start of your program.)
1805 The execution of a program is affected by certain information it
1806 receives from its superior. @value{GDBN} provides ways to specify this
1807 information, which you must do @emph{before} starting your program. (You
1808 can change it after starting your program, but such changes only affect
1809 your program the next time you start it.) This information may be
1810 divided into four categories:
1813 @item The @emph{arguments.}
1814 Specify the arguments to give your program as the arguments of the
1815 @code{run} command. If a shell is available on your target, the shell
1816 is used to pass the arguments, so that you may use normal conventions
1817 (such as wildcard expansion or variable substitution) in describing
1819 In Unix systems, you can control which shell is used with the
1820 @code{SHELL} environment variable.
1821 @xref{Arguments, ,Your program's arguments}.
1823 @item The @emph{environment.}
1824 Your program normally inherits its environment from @value{GDBN}, but you can
1825 use the @value{GDBN} commands @code{set environment} and @code{unset
1826 environment} to change parts of the environment that affect
1827 your program. @xref{Environment, ,Your program's environment}.
1829 @item The @emph{working directory.}
1830 Your program inherits its working directory from @value{GDBN}. You can set
1831 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1832 @xref{Working Directory, ,Your program's working directory}.
1834 @item The @emph{standard input and output.}
1835 Your program normally uses the same device for standard input and
1836 standard output as @value{GDBN} is using. You can redirect input and output
1837 in the @code{run} command line, or you can use the @code{tty} command to
1838 set a different device for your program.
1839 @xref{Input/Output, ,Your program's input and output}.
1842 @emph{Warning:} While input and output redirection work, you cannot use
1843 pipes to pass the output of the program you are debugging to another
1844 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1848 When you issue the @code{run} command, your program begins to execute
1849 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1850 of how to arrange for your program to stop. Once your program has
1851 stopped, you may call functions in your program, using the @code{print}
1852 or @code{call} commands. @xref{Data, ,Examining Data}.
1854 If the modification time of your symbol file has changed since the last
1855 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1856 table, and reads it again. When it does this, @value{GDBN} tries to retain
1857 your current breakpoints.
1862 @cindex run to main procedure
1863 The name of the main procedure can vary from language to language.
1864 With C or C@t{++}, the main procedure name is always @code{main}, but
1865 other languages such as Ada do not require a specific name for their
1866 main procedure. The debugger provides a convenient way to start the
1867 execution of the program and to stop at the beginning of the main
1868 procedure, depending on the language used.
1870 The @samp{start} command does the equivalent of setting a temporary
1871 breakpoint at the beginning of the main procedure and then invoking
1872 the @samp{run} command.
1874 @cindex elaboration phase
1875 Some programs contain an @dfn{elaboration} phase where some startup code is
1876 executed before the main procedure is called. This depends on the
1877 languages used to write your program. In C@t{++}, for instance,
1878 constructors for static and global objects are executed before
1879 @code{main} is called. It is therefore possible that the debugger stops
1880 before reaching the main procedure. However, the temporary breakpoint
1881 will remain to halt execution.
1883 Specify the arguments to give to your program as arguments to the
1884 @samp{start} command. These arguments will be given verbatim to the
1885 underlying @samp{run} command. Note that the same arguments will be
1886 reused if no argument is provided during subsequent calls to
1887 @samp{start} or @samp{run}.
1889 It is sometimes necessary to debug the program during elaboration. In
1890 these cases, using the @code{start} command would stop the execution of
1891 your program too late, as the program would have already completed the
1892 elaboration phase. Under these circumstances, insert breakpoints in your
1893 elaboration code before running your program.
1897 @section Your program's arguments
1899 @cindex arguments (to your program)
1900 The arguments to your program can be specified by the arguments of the
1902 They are passed to a shell, which expands wildcard characters and
1903 performs redirection of I/O, and thence to your program. Your
1904 @code{SHELL} environment variable (if it exists) specifies what shell
1905 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1906 the default shell (@file{/bin/sh} on Unix).
1908 On non-Unix systems, the program is usually invoked directly by
1909 @value{GDBN}, which emulates I/O redirection via the appropriate system
1910 calls, and the wildcard characters are expanded by the startup code of
1911 the program, not by the shell.
1913 @code{run} with no arguments uses the same arguments used by the previous
1914 @code{run}, or those set by the @code{set args} command.
1919 Specify the arguments to be used the next time your program is run. If
1920 @code{set args} has no arguments, @code{run} executes your program
1921 with no arguments. Once you have run your program with arguments,
1922 using @code{set args} before the next @code{run} is the only way to run
1923 it again without arguments.
1927 Show the arguments to give your program when it is started.
1931 @section Your program's environment
1933 @cindex environment (of your program)
1934 The @dfn{environment} consists of a set of environment variables and
1935 their values. Environment variables conventionally record such things as
1936 your user name, your home directory, your terminal type, and your search
1937 path for programs to run. Usually you set up environment variables with
1938 the shell and they are inherited by all the other programs you run. When
1939 debugging, it can be useful to try running your program with a modified
1940 environment without having to start @value{GDBN} over again.
1944 @item path @var{directory}
1945 Add @var{directory} to the front of the @code{PATH} environment variable
1946 (the search path for executables) that will be passed to your program.
1947 The value of @code{PATH} used by @value{GDBN} does not change.
1948 You may specify several directory names, separated by whitespace or by a
1949 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1950 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1951 is moved to the front, so it is searched sooner.
1953 You can use the string @samp{$cwd} to refer to whatever is the current
1954 working directory at the time @value{GDBN} searches the path. If you
1955 use @samp{.} instead, it refers to the directory where you executed the
1956 @code{path} command. @value{GDBN} replaces @samp{.} in the
1957 @var{directory} argument (with the current path) before adding
1958 @var{directory} to the search path.
1959 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1960 @c document that, since repeating it would be a no-op.
1964 Display the list of search paths for executables (the @code{PATH}
1965 environment variable).
1967 @kindex show environment
1968 @item show environment @r{[}@var{varname}@r{]}
1969 Print the value of environment variable @var{varname} to be given to
1970 your program when it starts. If you do not supply @var{varname},
1971 print the names and values of all environment variables to be given to
1972 your program. You can abbreviate @code{environment} as @code{env}.
1974 @kindex set environment
1975 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1976 Set environment variable @var{varname} to @var{value}. The value
1977 changes for your program only, not for @value{GDBN} itself. @var{value} may
1978 be any string; the values of environment variables are just strings, and
1979 any interpretation is supplied by your program itself. The @var{value}
1980 parameter is optional; if it is eliminated, the variable is set to a
1982 @c "any string" here does not include leading, trailing
1983 @c blanks. Gnu asks: does anyone care?
1985 For example, this command:
1992 tells the debugged program, when subsequently run, that its user is named
1993 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
1994 are not actually required.)
1996 @kindex unset environment
1997 @item unset environment @var{varname}
1998 Remove variable @var{varname} from the environment to be passed to your
1999 program. This is different from @samp{set env @var{varname} =};
2000 @code{unset environment} removes the variable from the environment,
2001 rather than assigning it an empty value.
2004 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2006 by your @code{SHELL} environment variable if it exists (or
2007 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2008 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2009 @file{.bashrc} for BASH---any variables you set in that file affect
2010 your program. You may wish to move setting of environment variables to
2011 files that are only run when you sign on, such as @file{.login} or
2014 @node Working Directory
2015 @section Your program's working directory
2017 @cindex working directory (of your program)
2018 Each time you start your program with @code{run}, it inherits its
2019 working directory from the current working directory of @value{GDBN}.
2020 The @value{GDBN} working directory is initially whatever it inherited
2021 from its parent process (typically the shell), but you can specify a new
2022 working directory in @value{GDBN} with the @code{cd} command.
2024 The @value{GDBN} working directory also serves as a default for the commands
2025 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2030 @cindex change working directory
2031 @item cd @var{directory}
2032 Set the @value{GDBN} working directory to @var{directory}.
2036 Print the @value{GDBN} working directory.
2039 It is generally impossible to find the current working directory of
2040 the process being debugged (since a program can change its directory
2041 during its run). If you work on a system where @value{GDBN} is
2042 configured with the @file{/proc} support, you can use the @code{info
2043 proc} command (@pxref{SVR4 Process Information}) to find out the
2044 current working directory of the debuggee.
2047 @section Your program's input and output
2052 By default, the program you run under @value{GDBN} does input and output to
2053 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2054 to its own terminal modes to interact with you, but it records the terminal
2055 modes your program was using and switches back to them when you continue
2056 running your program.
2059 @kindex info terminal
2061 Displays information recorded by @value{GDBN} about the terminal modes your
2065 You can redirect your program's input and/or output using shell
2066 redirection with the @code{run} command. For example,
2073 starts your program, diverting its output to the file @file{outfile}.
2076 @cindex controlling terminal
2077 Another way to specify where your program should do input and output is
2078 with the @code{tty} command. This command accepts a file name as
2079 argument, and causes this file to be the default for future @code{run}
2080 commands. It also resets the controlling terminal for the child
2081 process, for future @code{run} commands. For example,
2088 directs that processes started with subsequent @code{run} commands
2089 default to do input and output on the terminal @file{/dev/ttyb} and have
2090 that as their controlling terminal.
2092 An explicit redirection in @code{run} overrides the @code{tty} command's
2093 effect on the input/output device, but not its effect on the controlling
2096 When you use the @code{tty} command or redirect input in the @code{run}
2097 command, only the input @emph{for your program} is affected. The input
2098 for @value{GDBN} still comes from your terminal.
2101 @section Debugging an already-running process
2106 @item attach @var{process-id}
2107 This command attaches to a running process---one that was started
2108 outside @value{GDBN}. (@code{info files} shows your active
2109 targets.) The command takes as argument a process ID. The usual way to
2110 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2111 or with the @samp{jobs -l} shell command.
2113 @code{attach} does not repeat if you press @key{RET} a second time after
2114 executing the command.
2117 To use @code{attach}, your program must be running in an environment
2118 which supports processes; for example, @code{attach} does not work for
2119 programs on bare-board targets that lack an operating system. You must
2120 also have permission to send the process a signal.
2122 When you use @code{attach}, the debugger finds the program running in
2123 the process first by looking in the current working directory, then (if
2124 the program is not found) by using the source file search path
2125 (@pxref{Source Path, ,Specifying source directories}). You can also use
2126 the @code{file} command to load the program. @xref{Files, ,Commands to
2129 The first thing @value{GDBN} does after arranging to debug the specified
2130 process is to stop it. You can examine and modify an attached process
2131 with all the @value{GDBN} commands that are ordinarily available when
2132 you start processes with @code{run}. You can insert breakpoints; you
2133 can step and continue; you can modify storage. If you would rather the
2134 process continue running, you may use the @code{continue} command after
2135 attaching @value{GDBN} to the process.
2140 When you have finished debugging the attached process, you can use the
2141 @code{detach} command to release it from @value{GDBN} control. Detaching
2142 the process continues its execution. After the @code{detach} command,
2143 that process and @value{GDBN} become completely independent once more, and you
2144 are ready to @code{attach} another process or start one with @code{run}.
2145 @code{detach} does not repeat if you press @key{RET} again after
2146 executing the command.
2149 If you exit @value{GDBN} or use the @code{run} command while you have an
2150 attached process, you kill that process. By default, @value{GDBN} asks
2151 for confirmation if you try to do either of these things; you can
2152 control whether or not you need to confirm by using the @code{set
2153 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
2157 @section Killing the child process
2162 Kill the child process in which your program is running under @value{GDBN}.
2165 This command is useful if you wish to debug a core dump instead of a
2166 running process. @value{GDBN} ignores any core dump file while your program
2169 On some operating systems, a program cannot be executed outside @value{GDBN}
2170 while you have breakpoints set on it inside @value{GDBN}. You can use the
2171 @code{kill} command in this situation to permit running your program
2172 outside the debugger.
2174 The @code{kill} command is also useful if you wish to recompile and
2175 relink your program, since on many systems it is impossible to modify an
2176 executable file while it is running in a process. In this case, when you
2177 next type @code{run}, @value{GDBN} notices that the file has changed, and
2178 reads the symbol table again (while trying to preserve your current
2179 breakpoint settings).
2182 @section Debugging programs with multiple threads
2184 @cindex threads of execution
2185 @cindex multiple threads
2186 @cindex switching threads
2187 In some operating systems, such as HP-UX and Solaris, a single program
2188 may have more than one @dfn{thread} of execution. The precise semantics
2189 of threads differ from one operating system to another, but in general
2190 the threads of a single program are akin to multiple processes---except
2191 that they share one address space (that is, they can all examine and
2192 modify the same variables). On the other hand, each thread has its own
2193 registers and execution stack, and perhaps private memory.
2195 @value{GDBN} provides these facilities for debugging multi-thread
2199 @item automatic notification of new threads
2200 @item @samp{thread @var{threadno}}, a command to switch among threads
2201 @item @samp{info threads}, a command to inquire about existing threads
2202 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2203 a command to apply a command to a list of threads
2204 @item thread-specific breakpoints
2208 @emph{Warning:} These facilities are not yet available on every
2209 @value{GDBN} configuration where the operating system supports threads.
2210 If your @value{GDBN} does not support threads, these commands have no
2211 effect. For example, a system without thread support shows no output
2212 from @samp{info threads}, and always rejects the @code{thread} command,
2216 (@value{GDBP}) info threads
2217 (@value{GDBP}) thread 1
2218 Thread ID 1 not known. Use the "info threads" command to
2219 see the IDs of currently known threads.
2221 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2222 @c doesn't support threads"?
2225 @cindex focus of debugging
2226 @cindex current thread
2227 The @value{GDBN} thread debugging facility allows you to observe all
2228 threads while your program runs---but whenever @value{GDBN} takes
2229 control, one thread in particular is always the focus of debugging.
2230 This thread is called the @dfn{current thread}. Debugging commands show
2231 program information from the perspective of the current thread.
2233 @cindex @code{New} @var{systag} message
2234 @cindex thread identifier (system)
2235 @c FIXME-implementors!! It would be more helpful if the [New...] message
2236 @c included GDB's numeric thread handle, so you could just go to that
2237 @c thread without first checking `info threads'.
2238 Whenever @value{GDBN} detects a new thread in your program, it displays
2239 the target system's identification for the thread with a message in the
2240 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2241 whose form varies depending on the particular system. For example, on
2242 LynxOS, you might see
2245 [New process 35 thread 27]
2249 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2250 the @var{systag} is simply something like @samp{process 368}, with no
2253 @c FIXME!! (1) Does the [New...] message appear even for the very first
2254 @c thread of a program, or does it only appear for the
2255 @c second---i.e.@: when it becomes obvious we have a multithread
2257 @c (2) *Is* there necessarily a first thread always? Or do some
2258 @c multithread systems permit starting a program with multiple
2259 @c threads ab initio?
2261 @cindex thread number
2262 @cindex thread identifier (GDB)
2263 For debugging purposes, @value{GDBN} associates its own thread
2264 number---always a single integer---with each thread in your program.
2267 @kindex info threads
2269 Display a summary of all threads currently in your
2270 program. @value{GDBN} displays for each thread (in this order):
2274 the thread number assigned by @value{GDBN}
2277 the target system's thread identifier (@var{systag})
2280 the current stack frame summary for that thread
2284 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2285 indicates the current thread.
2289 @c end table here to get a little more width for example
2292 (@value{GDBP}) info threads
2293 3 process 35 thread 27 0x34e5 in sigpause ()
2294 2 process 35 thread 23 0x34e5 in sigpause ()
2295 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2301 @cindex debugging multithreaded programs (on HP-UX)
2302 @cindex thread identifier (GDB), on HP-UX
2303 For debugging purposes, @value{GDBN} associates its own thread
2304 number---a small integer assigned in thread-creation order---with each
2305 thread in your program.
2307 @cindex @code{New} @var{systag} message, on HP-UX
2308 @cindex thread identifier (system), on HP-UX
2309 @c FIXME-implementors!! It would be more helpful if the [New...] message
2310 @c included GDB's numeric thread handle, so you could just go to that
2311 @c thread without first checking `info threads'.
2312 Whenever @value{GDBN} detects a new thread in your program, it displays
2313 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2314 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2315 whose form varies depending on the particular system. For example, on
2319 [New thread 2 (system thread 26594)]
2323 when @value{GDBN} notices a new thread.
2326 @kindex info threads (HP-UX)
2328 Display a summary of all threads currently in your
2329 program. @value{GDBN} displays for each thread (in this order):
2332 @item the thread number assigned by @value{GDBN}
2334 @item the target system's thread identifier (@var{systag})
2336 @item the current stack frame summary for that thread
2340 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2341 indicates the current thread.
2345 @c end table here to get a little more width for example
2348 (@value{GDBP}) info threads
2349 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2351 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2352 from /usr/lib/libc.2
2353 1 system thread 27905 0x7b003498 in _brk () \@*
2354 from /usr/lib/libc.2
2357 On Solaris, you can display more information about user threads with a
2358 Solaris-specific command:
2361 @item maint info sol-threads
2362 @kindex maint info sol-threads
2363 @cindex thread info (Solaris)
2364 Display info on Solaris user threads.
2368 @kindex thread @var{threadno}
2369 @item thread @var{threadno}
2370 Make thread number @var{threadno} the current thread. The command
2371 argument @var{threadno} is the internal @value{GDBN} thread number, as
2372 shown in the first field of the @samp{info threads} display.
2373 @value{GDBN} responds by displaying the system identifier of the thread
2374 you selected, and its current stack frame summary:
2377 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2378 (@value{GDBP}) thread 2
2379 [Switching to process 35 thread 23]
2380 0x34e5 in sigpause ()
2384 As with the @samp{[New @dots{}]} message, the form of the text after
2385 @samp{Switching to} depends on your system's conventions for identifying
2388 @kindex thread apply
2389 @cindex apply command to several threads
2390 @item thread apply [@var{threadno}] [@var{all}] @var{args}
2391 The @code{thread apply} command allows you to apply a command to one or
2392 more threads. Specify the numbers of the threads that you want affected
2393 with the command argument @var{threadno}. @var{threadno} is the internal
2394 @value{GDBN} thread number, as shown in the first field of the @samp{info
2395 threads} display. To apply a command to all threads, use
2396 @code{thread apply all} @var{args}.
2399 @cindex automatic thread selection
2400 @cindex switching threads automatically
2401 @cindex threads, automatic switching
2402 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2403 signal, it automatically selects the thread where that breakpoint or
2404 signal happened. @value{GDBN} alerts you to the context switch with a
2405 message of the form @samp{[Switching to @var{systag}]} to identify the
2408 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2409 more information about how @value{GDBN} behaves when you stop and start
2410 programs with multiple threads.
2412 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2413 watchpoints in programs with multiple threads.
2416 @section Debugging programs with multiple processes
2418 @cindex fork, debugging programs which call
2419 @cindex multiple processes
2420 @cindex processes, multiple
2421 On most systems, @value{GDBN} has no special support for debugging
2422 programs which create additional processes using the @code{fork}
2423 function. When a program forks, @value{GDBN} will continue to debug the
2424 parent process and the child process will run unimpeded. If you have
2425 set a breakpoint in any code which the child then executes, the child
2426 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2427 will cause it to terminate.
2429 However, if you want to debug the child process there is a workaround
2430 which isn't too painful. Put a call to @code{sleep} in the code which
2431 the child process executes after the fork. It may be useful to sleep
2432 only if a certain environment variable is set, or a certain file exists,
2433 so that the delay need not occur when you don't want to run @value{GDBN}
2434 on the child. While the child is sleeping, use the @code{ps} program to
2435 get its process ID. Then tell @value{GDBN} (a new invocation of
2436 @value{GDBN} if you are also debugging the parent process) to attach to
2437 the child process (@pxref{Attach}). From that point on you can debug
2438 the child process just like any other process which you attached to.
2440 On some systems, @value{GDBN} provides support for debugging programs that
2441 create additional processes using the @code{fork} or @code{vfork} functions.
2442 Currently, the only platforms with this feature are HP-UX (11.x and later
2443 only?) and GNU/Linux (kernel version 2.5.60 and later).
2445 By default, when a program forks, @value{GDBN} will continue to debug
2446 the parent process and the child process will run unimpeded.
2448 If you want to follow the child process instead of the parent process,
2449 use the command @w{@code{set follow-fork-mode}}.
2452 @kindex set follow-fork-mode
2453 @item set follow-fork-mode @var{mode}
2454 Set the debugger response to a program call of @code{fork} or
2455 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2456 process. The @var{mode} argument can be:
2460 The original process is debugged after a fork. The child process runs
2461 unimpeded. This is the default.
2464 The new process is debugged after a fork. The parent process runs
2469 @kindex show follow-fork-mode
2470 @item show follow-fork-mode
2471 Display the current debugger response to a @code{fork} or @code{vfork} call.
2474 If you ask to debug a child process and a @code{vfork} is followed by an
2475 @code{exec}, @value{GDBN} executes the new target up to the first
2476 breakpoint in the new target. If you have a breakpoint set on
2477 @code{main} in your original program, the breakpoint will also be set on
2478 the child process's @code{main}.
2480 When a child process is spawned by @code{vfork}, you cannot debug the
2481 child or parent until an @code{exec} call completes.
2483 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2484 call executes, the new target restarts. To restart the parent process,
2485 use the @code{file} command with the parent executable name as its
2488 You can use the @code{catch} command to make @value{GDBN} stop whenever
2489 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2490 Catchpoints, ,Setting catchpoints}.
2493 @chapter Stopping and Continuing
2495 The principal purposes of using a debugger are so that you can stop your
2496 program before it terminates; or so that, if your program runs into
2497 trouble, you can investigate and find out why.
2499 Inside @value{GDBN}, your program may stop for any of several reasons,
2500 such as a signal, a breakpoint, or reaching a new line after a
2501 @value{GDBN} command such as @code{step}. You may then examine and
2502 change variables, set new breakpoints or remove old ones, and then
2503 continue execution. Usually, the messages shown by @value{GDBN} provide
2504 ample explanation of the status of your program---but you can also
2505 explicitly request this information at any time.
2508 @kindex info program
2510 Display information about the status of your program: whether it is
2511 running or not, what process it is, and why it stopped.
2515 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2516 * Continuing and Stepping:: Resuming execution
2518 * Thread Stops:: Stopping and starting multi-thread programs
2522 @section Breakpoints, watchpoints, and catchpoints
2525 A @dfn{breakpoint} makes your program stop whenever a certain point in
2526 the program is reached. For each breakpoint, you can add conditions to
2527 control in finer detail whether your program stops. You can set
2528 breakpoints with the @code{break} command and its variants (@pxref{Set
2529 Breaks, ,Setting breakpoints}), to specify the place where your program
2530 should stop by line number, function name or exact address in the
2533 On some systems, you can set breakpoints in shared libraries before
2534 the executable is run. There is a minor limitation on HP-UX systems:
2535 you must wait until the executable is run in order to set breakpoints
2536 in shared library routines that are not called directly by the program
2537 (for example, routines that are arguments in a @code{pthread_create}
2541 @cindex memory tracing
2542 @cindex breakpoint on memory address
2543 @cindex breakpoint on variable modification
2544 A @dfn{watchpoint} is a special breakpoint that stops your program
2545 when the value of an expression changes. You must use a different
2546 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2547 watchpoints}), but aside from that, you can manage a watchpoint like
2548 any other breakpoint: you enable, disable, and delete both breakpoints
2549 and watchpoints using the same commands.
2551 You can arrange to have values from your program displayed automatically
2552 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2556 @cindex breakpoint on events
2557 A @dfn{catchpoint} is another special breakpoint that stops your program
2558 when a certain kind of event occurs, such as the throwing of a C@t{++}
2559 exception or the loading of a library. As with watchpoints, you use a
2560 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2561 catchpoints}), but aside from that, you can manage a catchpoint like any
2562 other breakpoint. (To stop when your program receives a signal, use the
2563 @code{handle} command; see @ref{Signals, ,Signals}.)
2565 @cindex breakpoint numbers
2566 @cindex numbers for breakpoints
2567 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2568 catchpoint when you create it; these numbers are successive integers
2569 starting with one. In many of the commands for controlling various
2570 features of breakpoints you use the breakpoint number to say which
2571 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2572 @dfn{disabled}; if disabled, it has no effect on your program until you
2575 @cindex breakpoint ranges
2576 @cindex ranges of breakpoints
2577 Some @value{GDBN} commands accept a range of breakpoints on which to
2578 operate. A breakpoint range is either a single breakpoint number, like
2579 @samp{5}, or two such numbers, in increasing order, separated by a
2580 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2581 all breakpoint in that range are operated on.
2584 * Set Breaks:: Setting breakpoints
2585 * Set Watchpoints:: Setting watchpoints
2586 * Set Catchpoints:: Setting catchpoints
2587 * Delete Breaks:: Deleting breakpoints
2588 * Disabling:: Disabling breakpoints
2589 * Conditions:: Break conditions
2590 * Break Commands:: Breakpoint command lists
2591 * Breakpoint Menus:: Breakpoint menus
2592 * Error in Breakpoints:: ``Cannot insert breakpoints''
2593 * Breakpoint related warnings:: ``Breakpoint address adjusted...''
2597 @subsection Setting breakpoints
2599 @c FIXME LMB what does GDB do if no code on line of breakpt?
2600 @c consider in particular declaration with/without initialization.
2602 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2605 @kindex b @r{(@code{break})}
2606 @vindex $bpnum@r{, convenience variable}
2607 @cindex latest breakpoint
2608 Breakpoints are set with the @code{break} command (abbreviated
2609 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2610 number of the breakpoint you've set most recently; see @ref{Convenience
2611 Vars,, Convenience variables}, for a discussion of what you can do with
2612 convenience variables.
2614 You have several ways to say where the breakpoint should go.
2617 @item break @var{function}
2618 Set a breakpoint at entry to function @var{function}.
2619 When using source languages that permit overloading of symbols, such as
2620 C@t{++}, @var{function} may refer to more than one possible place to break.
2621 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2623 @item break +@var{offset}
2624 @itemx break -@var{offset}
2625 Set a breakpoint some number of lines forward or back from the position
2626 at which execution stopped in the currently selected @dfn{stack frame}.
2627 (@xref{Frames, ,Frames}, for a description of stack frames.)
2629 @item break @var{linenum}
2630 Set a breakpoint at line @var{linenum} in the current source file.
2631 The current source file is the last file whose source text was printed.
2632 The breakpoint will stop your program just before it executes any of the
2635 @item break @var{filename}:@var{linenum}
2636 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2638 @item break @var{filename}:@var{function}
2639 Set a breakpoint at entry to function @var{function} found in file
2640 @var{filename}. Specifying a file name as well as a function name is
2641 superfluous except when multiple files contain similarly named
2644 @item break *@var{address}
2645 Set a breakpoint at address @var{address}. You can use this to set
2646 breakpoints in parts of your program which do not have debugging
2647 information or source files.
2650 When called without any arguments, @code{break} sets a breakpoint at
2651 the next instruction to be executed in the selected stack frame
2652 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2653 innermost, this makes your program stop as soon as control
2654 returns to that frame. This is similar to the effect of a
2655 @code{finish} command in the frame inside the selected frame---except
2656 that @code{finish} does not leave an active breakpoint. If you use
2657 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2658 the next time it reaches the current location; this may be useful
2661 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2662 least one instruction has been executed. If it did not do this, you
2663 would be unable to proceed past a breakpoint without first disabling the
2664 breakpoint. This rule applies whether or not the breakpoint already
2665 existed when your program stopped.
2667 @item break @dots{} if @var{cond}
2668 Set a breakpoint with condition @var{cond}; evaluate the expression
2669 @var{cond} each time the breakpoint is reached, and stop only if the
2670 value is nonzero---that is, if @var{cond} evaluates as true.
2671 @samp{@dots{}} stands for one of the possible arguments described
2672 above (or no argument) specifying where to break. @xref{Conditions,
2673 ,Break conditions}, for more information on breakpoint conditions.
2676 @item tbreak @var{args}
2677 Set a breakpoint enabled only for one stop. @var{args} are the
2678 same as for the @code{break} command, and the breakpoint is set in the same
2679 way, but the breakpoint is automatically deleted after the first time your
2680 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2683 @cindex hardware breakpoints
2684 @item hbreak @var{args}
2685 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2686 @code{break} command and the breakpoint is set in the same way, but the
2687 breakpoint requires hardware support and some target hardware may not
2688 have this support. The main purpose of this is EPROM/ROM code
2689 debugging, so you can set a breakpoint at an instruction without
2690 changing the instruction. This can be used with the new trap-generation
2691 provided by SPARClite DSU and most x86-based targets. These targets
2692 will generate traps when a program accesses some data or instruction
2693 address that is assigned to the debug registers. However the hardware
2694 breakpoint registers can take a limited number of breakpoints. For
2695 example, on the DSU, only two data breakpoints can be set at a time, and
2696 @value{GDBN} will reject this command if more than two are used. Delete
2697 or disable unused hardware breakpoints before setting new ones
2698 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2699 For remote targets, you can restrict the number of hardware
2700 breakpoints @value{GDBN} will use, see @ref{set remote
2701 hardware-breakpoint-limit}.
2705 @item thbreak @var{args}
2706 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2707 are the same as for the @code{hbreak} command and the breakpoint is set in
2708 the same way. However, like the @code{tbreak} command,
2709 the breakpoint is automatically deleted after the
2710 first time your program stops there. Also, like the @code{hbreak}
2711 command, the breakpoint requires hardware support and some target hardware
2712 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2713 See also @ref{Conditions, ,Break conditions}.
2716 @cindex regular expression
2717 @cindex breakpoints in functions matching a regexp
2718 @cindex set breakpoints in many functions
2719 @item rbreak @var{regex}
2720 Set breakpoints on all functions matching the regular expression
2721 @var{regex}. This command sets an unconditional breakpoint on all
2722 matches, printing a list of all breakpoints it set. Once these
2723 breakpoints are set, they are treated just like the breakpoints set with
2724 the @code{break} command. You can delete them, disable them, or make
2725 them conditional the same way as any other breakpoint.
2727 The syntax of the regular expression is the standard one used with tools
2728 like @file{grep}. Note that this is different from the syntax used by
2729 shells, so for instance @code{foo*} matches all functions that include
2730 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2731 @code{.*} leading and trailing the regular expression you supply, so to
2732 match only functions that begin with @code{foo}, use @code{^foo}.
2734 @cindex non-member C@t{++} functions, set breakpoint in
2735 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2736 breakpoints on overloaded functions that are not members of any special
2739 @cindex set breakpoints on all functions
2740 The @code{rbreak} command can be used to set breakpoints in
2741 @strong{all} the functions in a program, like this:
2744 (@value{GDBP}) rbreak .
2747 @kindex info breakpoints
2748 @cindex @code{$_} and @code{info breakpoints}
2749 @item info breakpoints @r{[}@var{n}@r{]}
2750 @itemx info break @r{[}@var{n}@r{]}
2751 @itemx info watchpoints @r{[}@var{n}@r{]}
2752 Print a table of all breakpoints, watchpoints, and catchpoints set and
2753 not deleted, with the following columns for each breakpoint:
2756 @item Breakpoint Numbers
2758 Breakpoint, watchpoint, or catchpoint.
2760 Whether the breakpoint is marked to be disabled or deleted when hit.
2761 @item Enabled or Disabled
2762 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2763 that are not enabled.
2765 Where the breakpoint is in your program, as a memory address. If the
2766 breakpoint is pending (see below for details) on a future load of a shared library, the address
2767 will be listed as @samp{<PENDING>}.
2769 Where the breakpoint is in the source for your program, as a file and
2770 line number. For a pending breakpoint, the original string passed to
2771 the breakpoint command will be listed as it cannot be resolved until
2772 the appropriate shared library is loaded in the future.
2776 If a breakpoint is conditional, @code{info break} shows the condition on
2777 the line following the affected breakpoint; breakpoint commands, if any,
2778 are listed after that. A pending breakpoint is allowed to have a condition
2779 specified for it. The condition is not parsed for validity until a shared
2780 library is loaded that allows the pending breakpoint to resolve to a
2784 @code{info break} with a breakpoint
2785 number @var{n} as argument lists only that breakpoint. The
2786 convenience variable @code{$_} and the default examining-address for
2787 the @code{x} command are set to the address of the last breakpoint
2788 listed (@pxref{Memory, ,Examining memory}).
2791 @code{info break} displays a count of the number of times the breakpoint
2792 has been hit. This is especially useful in conjunction with the
2793 @code{ignore} command. You can ignore a large number of breakpoint
2794 hits, look at the breakpoint info to see how many times the breakpoint
2795 was hit, and then run again, ignoring one less than that number. This
2796 will get you quickly to the last hit of that breakpoint.
2799 @value{GDBN} allows you to set any number of breakpoints at the same place in
2800 your program. There is nothing silly or meaningless about this. When
2801 the breakpoints are conditional, this is even useful
2802 (@pxref{Conditions, ,Break conditions}).
2804 @cindex pending breakpoints
2805 If a specified breakpoint location cannot be found, it may be due to the fact
2806 that the location is in a shared library that is yet to be loaded. In such
2807 a case, you may want @value{GDBN} to create a special breakpoint (known as
2808 a @dfn{pending breakpoint}) that
2809 attempts to resolve itself in the future when an appropriate shared library
2812 Pending breakpoints are useful to set at the start of your
2813 @value{GDBN} session for locations that you know will be dynamically loaded
2814 later by the program being debugged. When shared libraries are loaded,
2815 a check is made to see if the load resolves any pending breakpoint locations.
2816 If a pending breakpoint location gets resolved,
2817 a regular breakpoint is created and the original pending breakpoint is removed.
2819 @value{GDBN} provides some additional commands for controlling pending
2822 @kindex set breakpoint pending
2823 @kindex show breakpoint pending
2825 @item set breakpoint pending auto
2826 This is the default behavior. When @value{GDBN} cannot find the breakpoint
2827 location, it queries you whether a pending breakpoint should be created.
2829 @item set breakpoint pending on
2830 This indicates that an unrecognized breakpoint location should automatically
2831 result in a pending breakpoint being created.
2833 @item set breakpoint pending off
2834 This indicates that pending breakpoints are not to be created. Any
2835 unrecognized breakpoint location results in an error. This setting does
2836 not affect any pending breakpoints previously created.
2838 @item show breakpoint pending
2839 Show the current behavior setting for creating pending breakpoints.
2842 @cindex operations allowed on pending breakpoints
2843 Normal breakpoint operations apply to pending breakpoints as well. You may
2844 specify a condition for a pending breakpoint and/or commands to run when the
2845 breakpoint is reached. You can also enable or disable
2846 the pending breakpoint. When you specify a condition for a pending breakpoint,
2847 the parsing of the condition will be deferred until the point where the
2848 pending breakpoint location is resolved. Disabling a pending breakpoint
2849 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
2850 shared library load. When a pending breakpoint is re-enabled,
2851 @value{GDBN} checks to see if the location is already resolved.
2852 This is done because any number of shared library loads could have
2853 occurred since the time the breakpoint was disabled and one or more
2854 of these loads could resolve the location.
2856 @cindex negative breakpoint numbers
2857 @cindex internal @value{GDBN} breakpoints
2858 @value{GDBN} itself sometimes sets breakpoints in your program for
2859 special purposes, such as proper handling of @code{longjmp} (in C
2860 programs). These internal breakpoints are assigned negative numbers,
2861 starting with @code{-1}; @samp{info breakpoints} does not display them.
2862 You can see these breakpoints with the @value{GDBN} maintenance command
2863 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
2866 @node Set Watchpoints
2867 @subsection Setting watchpoints
2869 @cindex setting watchpoints
2870 You can use a watchpoint to stop execution whenever the value of an
2871 expression changes, without having to predict a particular place where
2874 @cindex software watchpoints
2875 @cindex hardware watchpoints
2876 Depending on your system, watchpoints may be implemented in software or
2877 hardware. @value{GDBN} does software watchpointing by single-stepping your
2878 program and testing the variable's value each time, which is hundreds of
2879 times slower than normal execution. (But this may still be worth it, to
2880 catch errors where you have no clue what part of your program is the
2883 On some systems, such as HP-UX, @sc{gnu}/Linux and most other
2884 x86-based targets, @value{GDBN} includes support for hardware
2885 watchpoints, which do not slow down the running of your program.
2889 @item watch @var{expr}
2890 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
2891 is written into by the program and its value changes.
2894 @item rwatch @var{expr}
2895 Set a watchpoint that will break when the value of @var{expr} is read
2899 @item awatch @var{expr}
2900 Set a watchpoint that will break when @var{expr} is either read from
2901 or written into by the program.
2903 @kindex info watchpoints
2904 @item info watchpoints
2905 This command prints a list of watchpoints, breakpoints, and catchpoints;
2906 it is the same as @code{info break} (@pxref{Set Breaks}).
2909 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
2910 watchpoints execute very quickly, and the debugger reports a change in
2911 value at the exact instruction where the change occurs. If @value{GDBN}
2912 cannot set a hardware watchpoint, it sets a software watchpoint, which
2913 executes more slowly and reports the change in value at the next
2914 @emph{statement}, not the instruction, after the change occurs.
2916 @cindex use only software watchpoints
2917 You can force @value{GDBN} to use only software watchpoints with the
2918 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
2919 zero, @value{GDBN} will never try to use hardware watchpoints, even if
2920 the underlying system supports them. (Note that hardware-assisted
2921 watchpoints that were set @emph{before} setting
2922 @code{can-use-hw-watchpoints} to zero will still use the hardware
2923 mechanism of watching expressiion values.)
2926 @item set can-use-hw-watchpoints
2927 @kindex set can-use-hw-watchpoints
2928 Set whether or not to use hardware watchpoints.
2930 @item show can-use-hw-watchpoints
2931 @kindex show can-use-hw-watchpoints
2932 Show the current mode of using hardware watchpoints.
2935 For remote targets, you can restrict the number of hardware
2936 watchpoints @value{GDBN} will use, see @ref{set remote
2937 hardware-breakpoint-limit}.
2939 When you issue the @code{watch} command, @value{GDBN} reports
2942 Hardware watchpoint @var{num}: @var{expr}
2946 if it was able to set a hardware watchpoint.
2948 Currently, the @code{awatch} and @code{rwatch} commands can only set
2949 hardware watchpoints, because accesses to data that don't change the
2950 value of the watched expression cannot be detected without examining
2951 every instruction as it is being executed, and @value{GDBN} does not do
2952 that currently. If @value{GDBN} finds that it is unable to set a
2953 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
2954 will print a message like this:
2957 Expression cannot be implemented with read/access watchpoint.
2960 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
2961 data type of the watched expression is wider than what a hardware
2962 watchpoint on the target machine can handle. For example, some systems
2963 can only watch regions that are up to 4 bytes wide; on such systems you
2964 cannot set hardware watchpoints for an expression that yields a
2965 double-precision floating-point number (which is typically 8 bytes
2966 wide). As a work-around, it might be possible to break the large region
2967 into a series of smaller ones and watch them with separate watchpoints.
2969 If you set too many hardware watchpoints, @value{GDBN} might be unable
2970 to insert all of them when you resume the execution of your program.
2971 Since the precise number of active watchpoints is unknown until such
2972 time as the program is about to be resumed, @value{GDBN} might not be
2973 able to warn you about this when you set the watchpoints, and the
2974 warning will be printed only when the program is resumed:
2977 Hardware watchpoint @var{num}: Could not insert watchpoint
2981 If this happens, delete or disable some of the watchpoints.
2983 The SPARClite DSU will generate traps when a program accesses some data
2984 or instruction address that is assigned to the debug registers. For the
2985 data addresses, DSU facilitates the @code{watch} command. However the
2986 hardware breakpoint registers can only take two data watchpoints, and
2987 both watchpoints must be the same kind. For example, you can set two
2988 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
2989 @strong{or} two with @code{awatch} commands, but you cannot set one
2990 watchpoint with one command and the other with a different command.
2991 @value{GDBN} will reject the command if you try to mix watchpoints.
2992 Delete or disable unused watchpoint commands before setting new ones.
2994 If you call a function interactively using @code{print} or @code{call},
2995 any watchpoints you have set will be inactive until @value{GDBN} reaches another
2996 kind of breakpoint or the call completes.
2998 @value{GDBN} automatically deletes watchpoints that watch local
2999 (automatic) variables, or expressions that involve such variables, when
3000 they go out of scope, that is, when the execution leaves the block in
3001 which these variables were defined. In particular, when the program
3002 being debugged terminates, @emph{all} local variables go out of scope,
3003 and so only watchpoints that watch global variables remain set. If you
3004 rerun the program, you will need to set all such watchpoints again. One
3005 way of doing that would be to set a code breakpoint at the entry to the
3006 @code{main} function and when it breaks, set all the watchpoints.
3009 @cindex watchpoints and threads
3010 @cindex threads and watchpoints
3011 @emph{Warning:} In multi-thread programs, watchpoints have only limited
3012 usefulness. With the current watchpoint implementation, @value{GDBN}
3013 can only watch the value of an expression @emph{in a single thread}. If
3014 you are confident that the expression can only change due to the current
3015 thread's activity (and if you are also confident that no other thread
3016 can become current), then you can use watchpoints as usual. However,
3017 @value{GDBN} may not notice when a non-current thread's activity changes
3020 @c FIXME: this is almost identical to the previous paragraph.
3021 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
3022 have only limited usefulness. If @value{GDBN} creates a software
3023 watchpoint, it can only watch the value of an expression @emph{in a
3024 single thread}. If you are confident that the expression can only
3025 change due to the current thread's activity (and if you are also
3026 confident that no other thread can become current), then you can use
3027 software watchpoints as usual. However, @value{GDBN} may not notice
3028 when a non-current thread's activity changes the expression. (Hardware
3029 watchpoints, in contrast, watch an expression in all threads.)
3032 @xref{set remote hardware-watchpoint-limit}.
3034 @node Set Catchpoints
3035 @subsection Setting catchpoints
3036 @cindex catchpoints, setting
3037 @cindex exception handlers
3038 @cindex event handling
3040 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3041 kinds of program events, such as C@t{++} exceptions or the loading of a
3042 shared library. Use the @code{catch} command to set a catchpoint.
3046 @item catch @var{event}
3047 Stop when @var{event} occurs. @var{event} can be any of the following:
3050 @cindex stop on C@t{++} exceptions
3051 The throwing of a C@t{++} exception.
3054 The catching of a C@t{++} exception.
3057 @cindex break on fork/exec
3058 A call to @code{exec}. This is currently only available for HP-UX.
3061 A call to @code{fork}. This is currently only available for HP-UX.
3064 A call to @code{vfork}. This is currently only available for HP-UX.
3067 @itemx load @var{libname}
3068 @cindex break on load/unload of shared library
3069 The dynamic loading of any shared library, or the loading of the library
3070 @var{libname}. This is currently only available for HP-UX.
3073 @itemx unload @var{libname}
3074 The unloading of any dynamically loaded shared library, or the unloading
3075 of the library @var{libname}. This is currently only available for HP-UX.
3078 @item tcatch @var{event}
3079 Set a catchpoint that is enabled only for one stop. The catchpoint is
3080 automatically deleted after the first time the event is caught.
3084 Use the @code{info break} command to list the current catchpoints.
3086 There are currently some limitations to C@t{++} exception handling
3087 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3091 If you call a function interactively, @value{GDBN} normally returns
3092 control to you when the function has finished executing. If the call
3093 raises an exception, however, the call may bypass the mechanism that
3094 returns control to you and cause your program either to abort or to
3095 simply continue running until it hits a breakpoint, catches a signal
3096 that @value{GDBN} is listening for, or exits. This is the case even if
3097 you set a catchpoint for the exception; catchpoints on exceptions are
3098 disabled within interactive calls.
3101 You cannot raise an exception interactively.
3104 You cannot install an exception handler interactively.
3107 @cindex raise exceptions
3108 Sometimes @code{catch} is not the best way to debug exception handling:
3109 if you need to know exactly where an exception is raised, it is better to
3110 stop @emph{before} the exception handler is called, since that way you
3111 can see the stack before any unwinding takes place. If you set a
3112 breakpoint in an exception handler instead, it may not be easy to find
3113 out where the exception was raised.
3115 To stop just before an exception handler is called, you need some
3116 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3117 raised by calling a library function named @code{__raise_exception}
3118 which has the following ANSI C interface:
3121 /* @var{addr} is where the exception identifier is stored.
3122 @var{id} is the exception identifier. */
3123 void __raise_exception (void **addr, void *id);
3127 To make the debugger catch all exceptions before any stack
3128 unwinding takes place, set a breakpoint on @code{__raise_exception}
3129 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
3131 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
3132 that depends on the value of @var{id}, you can stop your program when
3133 a specific exception is raised. You can use multiple conditional
3134 breakpoints to stop your program when any of a number of exceptions are
3139 @subsection Deleting breakpoints
3141 @cindex clearing breakpoints, watchpoints, catchpoints
3142 @cindex deleting breakpoints, watchpoints, catchpoints
3143 It is often necessary to eliminate a breakpoint, watchpoint, or
3144 catchpoint once it has done its job and you no longer want your program
3145 to stop there. This is called @dfn{deleting} the breakpoint. A
3146 breakpoint that has been deleted no longer exists; it is forgotten.
3148 With the @code{clear} command you can delete breakpoints according to
3149 where they are in your program. With the @code{delete} command you can
3150 delete individual breakpoints, watchpoints, or catchpoints by specifying
3151 their breakpoint numbers.
3153 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3154 automatically ignores breakpoints on the first instruction to be executed
3155 when you continue execution without changing the execution address.
3160 Delete any breakpoints at the next instruction to be executed in the
3161 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
3162 the innermost frame is selected, this is a good way to delete a
3163 breakpoint where your program just stopped.
3165 @item clear @var{function}
3166 @itemx clear @var{filename}:@var{function}
3167 Delete any breakpoints set at entry to the named @var{function}.
3169 @item clear @var{linenum}
3170 @itemx clear @var{filename}:@var{linenum}
3171 Delete any breakpoints set at or within the code of the specified
3172 @var{linenum} of the specified @var{filename}.
3174 @cindex delete breakpoints
3176 @kindex d @r{(@code{delete})}
3177 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3178 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3179 ranges specified as arguments. If no argument is specified, delete all
3180 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3181 confirm off}). You can abbreviate this command as @code{d}.
3185 @subsection Disabling breakpoints
3187 @cindex enable/disable a breakpoint
3188 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3189 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3190 it had been deleted, but remembers the information on the breakpoint so
3191 that you can @dfn{enable} it again later.
3193 You disable and enable breakpoints, watchpoints, and catchpoints with
3194 the @code{enable} and @code{disable} commands, optionally specifying one
3195 or more breakpoint numbers as arguments. Use @code{info break} or
3196 @code{info watch} to print a list of breakpoints, watchpoints, and
3197 catchpoints if you do not know which numbers to use.
3199 A breakpoint, watchpoint, or catchpoint can have any of four different
3200 states of enablement:
3204 Enabled. The breakpoint stops your program. A breakpoint set
3205 with the @code{break} command starts out in this state.
3207 Disabled. The breakpoint has no effect on your program.
3209 Enabled once. The breakpoint stops your program, but then becomes
3212 Enabled for deletion. The breakpoint stops your program, but
3213 immediately after it does so it is deleted permanently. A breakpoint
3214 set with the @code{tbreak} command starts out in this state.
3217 You can use the following commands to enable or disable breakpoints,
3218 watchpoints, and catchpoints:
3222 @kindex dis @r{(@code{disable})}
3223 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3224 Disable the specified breakpoints---or all breakpoints, if none are
3225 listed. A disabled breakpoint has no effect but is not forgotten. All
3226 options such as ignore-counts, conditions and commands are remembered in
3227 case the breakpoint is enabled again later. You may abbreviate
3228 @code{disable} as @code{dis}.
3231 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3232 Enable the specified breakpoints (or all defined breakpoints). They
3233 become effective once again in stopping your program.
3235 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3236 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3237 of these breakpoints immediately after stopping your program.
3239 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3240 Enable the specified breakpoints to work once, then die. @value{GDBN}
3241 deletes any of these breakpoints as soon as your program stops there.
3242 Breakpoints set by the @code{tbreak} command start out in this state.
3245 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3246 @c confusing: tbreak is also initially enabled.
3247 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3248 ,Setting breakpoints}), breakpoints that you set are initially enabled;
3249 subsequently, they become disabled or enabled only when you use one of
3250 the commands above. (The command @code{until} can set and delete a
3251 breakpoint of its own, but it does not change the state of your other
3252 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3256 @subsection Break conditions
3257 @cindex conditional breakpoints
3258 @cindex breakpoint conditions
3260 @c FIXME what is scope of break condition expr? Context where wanted?
3261 @c in particular for a watchpoint?
3262 The simplest sort of breakpoint breaks every time your program reaches a
3263 specified place. You can also specify a @dfn{condition} for a
3264 breakpoint. A condition is just a Boolean expression in your
3265 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3266 a condition evaluates the expression each time your program reaches it,
3267 and your program stops only if the condition is @emph{true}.
3269 This is the converse of using assertions for program validation; in that
3270 situation, you want to stop when the assertion is violated---that is,
3271 when the condition is false. In C, if you want to test an assertion expressed
3272 by the condition @var{assert}, you should set the condition
3273 @samp{! @var{assert}} on the appropriate breakpoint.
3275 Conditions are also accepted for watchpoints; you may not need them,
3276 since a watchpoint is inspecting the value of an expression anyhow---but
3277 it might be simpler, say, to just set a watchpoint on a variable name,
3278 and specify a condition that tests whether the new value is an interesting
3281 Break conditions can have side effects, and may even call functions in
3282 your program. This can be useful, for example, to activate functions
3283 that log program progress, or to use your own print functions to
3284 format special data structures. The effects are completely predictable
3285 unless there is another enabled breakpoint at the same address. (In
3286 that case, @value{GDBN} might see the other breakpoint first and stop your
3287 program without checking the condition of this one.) Note that
3288 breakpoint commands are usually more convenient and flexible than break
3290 purpose of performing side effects when a breakpoint is reached
3291 (@pxref{Break Commands, ,Breakpoint command lists}).
3293 Break conditions can be specified when a breakpoint is set, by using
3294 @samp{if} in the arguments to the @code{break} command. @xref{Set
3295 Breaks, ,Setting breakpoints}. They can also be changed at any time
3296 with the @code{condition} command.
3298 You can also use the @code{if} keyword with the @code{watch} command.
3299 The @code{catch} command does not recognize the @code{if} keyword;
3300 @code{condition} is the only way to impose a further condition on a
3305 @item condition @var{bnum} @var{expression}
3306 Specify @var{expression} as the break condition for breakpoint,
3307 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3308 breakpoint @var{bnum} stops your program only if the value of
3309 @var{expression} is true (nonzero, in C). When you use
3310 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3311 syntactic correctness, and to determine whether symbols in it have
3312 referents in the context of your breakpoint. If @var{expression} uses
3313 symbols not referenced in the context of the breakpoint, @value{GDBN}
3314 prints an error message:
3317 No symbol "foo" in current context.
3322 not actually evaluate @var{expression} at the time the @code{condition}
3323 command (or a command that sets a breakpoint with a condition, like
3324 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3326 @item condition @var{bnum}
3327 Remove the condition from breakpoint number @var{bnum}. It becomes
3328 an ordinary unconditional breakpoint.
3331 @cindex ignore count (of breakpoint)
3332 A special case of a breakpoint condition is to stop only when the
3333 breakpoint has been reached a certain number of times. This is so
3334 useful that there is a special way to do it, using the @dfn{ignore
3335 count} of the breakpoint. Every breakpoint has an ignore count, which
3336 is an integer. Most of the time, the ignore count is zero, and
3337 therefore has no effect. But if your program reaches a breakpoint whose
3338 ignore count is positive, then instead of stopping, it just decrements
3339 the ignore count by one and continues. As a result, if the ignore count
3340 value is @var{n}, the breakpoint does not stop the next @var{n} times
3341 your program reaches it.
3345 @item ignore @var{bnum} @var{count}
3346 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3347 The next @var{count} times the breakpoint is reached, your program's
3348 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3351 To make the breakpoint stop the next time it is reached, specify
3354 When you use @code{continue} to resume execution of your program from a
3355 breakpoint, you can specify an ignore count directly as an argument to
3356 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3357 Stepping,,Continuing and stepping}.
3359 If a breakpoint has a positive ignore count and a condition, the
3360 condition is not checked. Once the ignore count reaches zero,
3361 @value{GDBN} resumes checking the condition.
3363 You could achieve the effect of the ignore count with a condition such
3364 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3365 is decremented each time. @xref{Convenience Vars, ,Convenience
3369 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3372 @node Break Commands
3373 @subsection Breakpoint command lists
3375 @cindex breakpoint commands
3376 You can give any breakpoint (or watchpoint or catchpoint) a series of
3377 commands to execute when your program stops due to that breakpoint. For
3378 example, you might want to print the values of certain expressions, or
3379 enable other breakpoints.
3384 @item commands @r{[}@var{bnum}@r{]}
3385 @itemx @dots{} @var{command-list} @dots{}
3387 Specify a list of commands for breakpoint number @var{bnum}. The commands
3388 themselves appear on the following lines. Type a line containing just
3389 @code{end} to terminate the commands.
3391 To remove all commands from a breakpoint, type @code{commands} and
3392 follow it immediately with @code{end}; that is, give no commands.
3394 With no @var{bnum} argument, @code{commands} refers to the last
3395 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3396 recently encountered).
3399 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3400 disabled within a @var{command-list}.
3402 You can use breakpoint commands to start your program up again. Simply
3403 use the @code{continue} command, or @code{step}, or any other command
3404 that resumes execution.
3406 Any other commands in the command list, after a command that resumes
3407 execution, are ignored. This is because any time you resume execution
3408 (even with a simple @code{next} or @code{step}), you may encounter
3409 another breakpoint---which could have its own command list, leading to
3410 ambiguities about which list to execute.
3413 If the first command you specify in a command list is @code{silent}, the
3414 usual message about stopping at a breakpoint is not printed. This may
3415 be desirable for breakpoints that are to print a specific message and
3416 then continue. If none of the remaining commands print anything, you
3417 see no sign that the breakpoint was reached. @code{silent} is
3418 meaningful only at the beginning of a breakpoint command list.
3420 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3421 print precisely controlled output, and are often useful in silent
3422 breakpoints. @xref{Output, ,Commands for controlled output}.
3424 For example, here is how you could use breakpoint commands to print the
3425 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3431 printf "x is %d\n",x
3436 One application for breakpoint commands is to compensate for one bug so
3437 you can test for another. Put a breakpoint just after the erroneous line
3438 of code, give it a condition to detect the case in which something
3439 erroneous has been done, and give it commands to assign correct values
3440 to any variables that need them. End with the @code{continue} command
3441 so that your program does not stop, and start with the @code{silent}
3442 command so that no output is produced. Here is an example:
3453 @node Breakpoint Menus
3454 @subsection Breakpoint menus
3456 @cindex symbol overloading
3458 Some programming languages (notably C@t{++} and Objective-C) permit a
3459 single function name
3460 to be defined several times, for application in different contexts.
3461 This is called @dfn{overloading}. When a function name is overloaded,
3462 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3463 a breakpoint. If you realize this is a problem, you can use
3464 something like @samp{break @var{function}(@var{types})} to specify which
3465 particular version of the function you want. Otherwise, @value{GDBN} offers
3466 you a menu of numbered choices for different possible breakpoints, and
3467 waits for your selection with the prompt @samp{>}. The first two
3468 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3469 sets a breakpoint at each definition of @var{function}, and typing
3470 @kbd{0} aborts the @code{break} command without setting any new
3473 For example, the following session excerpt shows an attempt to set a
3474 breakpoint at the overloaded symbol @code{String::after}.
3475 We choose three particular definitions of that function name:
3477 @c FIXME! This is likely to change to show arg type lists, at least
3480 (@value{GDBP}) b String::after
3483 [2] file:String.cc; line number:867
3484 [3] file:String.cc; line number:860
3485 [4] file:String.cc; line number:875
3486 [5] file:String.cc; line number:853
3487 [6] file:String.cc; line number:846
3488 [7] file:String.cc; line number:735
3490 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3491 Breakpoint 2 at 0xb344: file String.cc, line 875.
3492 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3493 Multiple breakpoints were set.
3494 Use the "delete" command to delete unwanted
3500 @c @ifclear BARETARGET
3501 @node Error in Breakpoints
3502 @subsection ``Cannot insert breakpoints''
3504 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3506 Under some operating systems, breakpoints cannot be used in a program if
3507 any other process is running that program. In this situation,
3508 attempting to run or continue a program with a breakpoint causes
3509 @value{GDBN} to print an error message:
3512 Cannot insert breakpoints.
3513 The same program may be running in another process.
3516 When this happens, you have three ways to proceed:
3520 Remove or disable the breakpoints, then continue.
3523 Suspend @value{GDBN}, and copy the file containing your program to a new
3524 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3525 that @value{GDBN} should run your program under that name.
3526 Then start your program again.
3529 Relink your program so that the text segment is nonsharable, using the
3530 linker option @samp{-N}. The operating system limitation may not apply
3531 to nonsharable executables.
3535 A similar message can be printed if you request too many active
3536 hardware-assisted breakpoints and watchpoints:
3538 @c FIXME: the precise wording of this message may change; the relevant
3539 @c source change is not committed yet (Sep 3, 1999).
3541 Stopped; cannot insert breakpoints.
3542 You may have requested too many hardware breakpoints and watchpoints.
3546 This message is printed when you attempt to resume the program, since
3547 only then @value{GDBN} knows exactly how many hardware breakpoints and
3548 watchpoints it needs to insert.
3550 When this message is printed, you need to disable or remove some of the
3551 hardware-assisted breakpoints and watchpoints, and then continue.
3553 @node Breakpoint related warnings
3554 @subsection ``Breakpoint address adjusted...''
3555 @cindex breakpoint address adjusted
3557 Some processor architectures place constraints on the addresses at
3558 which breakpoints may be placed. For architectures thus constrained,
3559 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3560 with the constraints dictated by the architecture.
3562 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3563 a VLIW architecture in which a number of RISC-like instructions may be
3564 bundled together for parallel execution. The FR-V architecture
3565 constrains the location of a breakpoint instruction within such a
3566 bundle to the instruction with the lowest address. @value{GDBN}
3567 honors this constraint by adjusting a breakpoint's address to the
3568 first in the bundle.
3570 It is not uncommon for optimized code to have bundles which contain
3571 instructions from different source statements, thus it may happen that
3572 a breakpoint's address will be adjusted from one source statement to
3573 another. Since this adjustment may significantly alter @value{GDBN}'s
3574 breakpoint related behavior from what the user expects, a warning is
3575 printed when the breakpoint is first set and also when the breakpoint
3578 A warning like the one below is printed when setting a breakpoint
3579 that's been subject to address adjustment:
3582 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3585 Such warnings are printed both for user settable and @value{GDBN}'s
3586 internal breakpoints. If you see one of these warnings, you should
3587 verify that a breakpoint set at the adjusted address will have the
3588 desired affect. If not, the breakpoint in question may be removed and
3589 other breakpoints may be set which will have the desired behavior.
3590 E.g., it may be sufficient to place the breakpoint at a later
3591 instruction. A conditional breakpoint may also be useful in some
3592 cases to prevent the breakpoint from triggering too often.
3594 @value{GDBN} will also issue a warning when stopping at one of these
3595 adjusted breakpoints:
3598 warning: Breakpoint 1 address previously adjusted from 0x00010414
3602 When this warning is encountered, it may be too late to take remedial
3603 action except in cases where the breakpoint is hit earlier or more
3604 frequently than expected.
3606 @node Continuing and Stepping
3607 @section Continuing and stepping
3611 @cindex resuming execution
3612 @dfn{Continuing} means resuming program execution until your program
3613 completes normally. In contrast, @dfn{stepping} means executing just
3614 one more ``step'' of your program, where ``step'' may mean either one
3615 line of source code, or one machine instruction (depending on what
3616 particular command you use). Either when continuing or when stepping,
3617 your program may stop even sooner, due to a breakpoint or a signal. (If
3618 it stops due to a signal, you may want to use @code{handle}, or use
3619 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3623 @kindex c @r{(@code{continue})}
3624 @kindex fg @r{(resume foreground execution)}
3625 @item continue @r{[}@var{ignore-count}@r{]}
3626 @itemx c @r{[}@var{ignore-count}@r{]}
3627 @itemx fg @r{[}@var{ignore-count}@r{]}
3628 Resume program execution, at the address where your program last stopped;
3629 any breakpoints set at that address are bypassed. The optional argument
3630 @var{ignore-count} allows you to specify a further number of times to
3631 ignore a breakpoint at this location; its effect is like that of
3632 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3634 The argument @var{ignore-count} is meaningful only when your program
3635 stopped due to a breakpoint. At other times, the argument to
3636 @code{continue} is ignored.
3638 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3639 debugged program is deemed to be the foreground program) are provided
3640 purely for convenience, and have exactly the same behavior as
3644 To resume execution at a different place, you can use @code{return}
3645 (@pxref{Returning, ,Returning from a function}) to go back to the
3646 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3647 different address}) to go to an arbitrary location in your program.
3649 A typical technique for using stepping is to set a breakpoint
3650 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3651 beginning of the function or the section of your program where a problem
3652 is believed to lie, run your program until it stops at that breakpoint,
3653 and then step through the suspect area, examining the variables that are
3654 interesting, until you see the problem happen.
3658 @kindex s @r{(@code{step})}
3660 Continue running your program until control reaches a different source
3661 line, then stop it and return control to @value{GDBN}. This command is
3662 abbreviated @code{s}.
3665 @c "without debugging information" is imprecise; actually "without line
3666 @c numbers in the debugging information". (gcc -g1 has debugging info but
3667 @c not line numbers). But it seems complex to try to make that
3668 @c distinction here.
3669 @emph{Warning:} If you use the @code{step} command while control is
3670 within a function that was compiled without debugging information,
3671 execution proceeds until control reaches a function that does have
3672 debugging information. Likewise, it will not step into a function which
3673 is compiled without debugging information. To step through functions
3674 without debugging information, use the @code{stepi} command, described
3678 The @code{step} command only stops at the first instruction of a source
3679 line. This prevents the multiple stops that could otherwise occur in
3680 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3681 to stop if a function that has debugging information is called within
3682 the line. In other words, @code{step} @emph{steps inside} any functions
3683 called within the line.
3685 Also, the @code{step} command only enters a function if there is line
3686 number information for the function. Otherwise it acts like the
3687 @code{next} command. This avoids problems when using @code{cc -gl}
3688 on MIPS machines. Previously, @code{step} entered subroutines if there
3689 was any debugging information about the routine.
3691 @item step @var{count}
3692 Continue running as in @code{step}, but do so @var{count} times. If a
3693 breakpoint is reached, or a signal not related to stepping occurs before
3694 @var{count} steps, stepping stops right away.
3697 @kindex n @r{(@code{next})}
3698 @item next @r{[}@var{count}@r{]}
3699 Continue to the next source line in the current (innermost) stack frame.
3700 This is similar to @code{step}, but function calls that appear within
3701 the line of code are executed without stopping. Execution stops when
3702 control reaches a different line of code at the original stack level
3703 that was executing when you gave the @code{next} command. This command
3704 is abbreviated @code{n}.
3706 An argument @var{count} is a repeat count, as for @code{step}.
3709 @c FIX ME!! Do we delete this, or is there a way it fits in with
3710 @c the following paragraph? --- Vctoria
3712 @c @code{next} within a function that lacks debugging information acts like
3713 @c @code{step}, but any function calls appearing within the code of the
3714 @c function are executed without stopping.
3716 The @code{next} command only stops at the first instruction of a
3717 source line. This prevents multiple stops that could otherwise occur in
3718 @code{switch} statements, @code{for} loops, etc.
3720 @kindex set step-mode
3722 @cindex functions without line info, and stepping
3723 @cindex stepping into functions with no line info
3724 @itemx set step-mode on
3725 The @code{set step-mode on} command causes the @code{step} command to
3726 stop at the first instruction of a function which contains no debug line
3727 information rather than stepping over it.
3729 This is useful in cases where you may be interested in inspecting the
3730 machine instructions of a function which has no symbolic info and do not
3731 want @value{GDBN} to automatically skip over this function.
3733 @item set step-mode off
3734 Causes the @code{step} command to step over any functions which contains no
3735 debug information. This is the default.
3737 @item show step-mode
3738 Show whether @value{GDBN} will stop in or step over functions without
3739 source line debug information.
3743 Continue running until just after function in the selected stack frame
3744 returns. Print the returned value (if any).
3746 Contrast this with the @code{return} command (@pxref{Returning,
3747 ,Returning from a function}).
3750 @kindex u @r{(@code{until})}
3751 @cindex run until specified location
3754 Continue running until a source line past the current line, in the
3755 current stack frame, is reached. This command is used to avoid single
3756 stepping through a loop more than once. It is like the @code{next}
3757 command, except that when @code{until} encounters a jump, it
3758 automatically continues execution until the program counter is greater
3759 than the address of the jump.
3761 This means that when you reach the end of a loop after single stepping
3762 though it, @code{until} makes your program continue execution until it
3763 exits the loop. In contrast, a @code{next} command at the end of a loop
3764 simply steps back to the beginning of the loop, which forces you to step
3765 through the next iteration.
3767 @code{until} always stops your program if it attempts to exit the current
3770 @code{until} may produce somewhat counterintuitive results if the order
3771 of machine code does not match the order of the source lines. For
3772 example, in the following excerpt from a debugging session, the @code{f}
3773 (@code{frame}) command shows that execution is stopped at line
3774 @code{206}; yet when we use @code{until}, we get to line @code{195}:
3778 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
3780 (@value{GDBP}) until
3781 195 for ( ; argc > 0; NEXTARG) @{
3784 This happened because, for execution efficiency, the compiler had
3785 generated code for the loop closure test at the end, rather than the
3786 start, of the loop---even though the test in a C @code{for}-loop is
3787 written before the body of the loop. The @code{until} command appeared
3788 to step back to the beginning of the loop when it advanced to this
3789 expression; however, it has not really gone to an earlier
3790 statement---not in terms of the actual machine code.
3792 @code{until} with no argument works by means of single
3793 instruction stepping, and hence is slower than @code{until} with an
3796 @item until @var{location}
3797 @itemx u @var{location}
3798 Continue running your program until either the specified location is
3799 reached, or the current stack frame returns. @var{location} is any of
3800 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
3801 ,Setting breakpoints}). This form of the command uses breakpoints, and
3802 hence is quicker than @code{until} without an argument. The specified
3803 location is actually reached only if it is in the current frame. This
3804 implies that @code{until} can be used to skip over recursive function
3805 invocations. For instance in the code below, if the current location is
3806 line @code{96}, issuing @code{until 99} will execute the program up to
3807 line @code{99} in the same invocation of factorial, i.e. after the inner
3808 invocations have returned.
3811 94 int factorial (int value)
3813 96 if (value > 1) @{
3814 97 value *= factorial (value - 1);
3821 @kindex advance @var{location}
3822 @itemx advance @var{location}
3823 Continue running the program up to the given @var{location}. An argument is
3824 required, which should be of the same form as arguments for the @code{break}
3825 command. Execution will also stop upon exit from the current stack
3826 frame. This command is similar to @code{until}, but @code{advance} will
3827 not skip over recursive function calls, and the target location doesn't
3828 have to be in the same frame as the current one.
3832 @kindex si @r{(@code{stepi})}
3834 @itemx stepi @var{arg}
3836 Execute one machine instruction, then stop and return to the debugger.
3838 It is often useful to do @samp{display/i $pc} when stepping by machine
3839 instructions. This makes @value{GDBN} automatically display the next
3840 instruction to be executed, each time your program stops. @xref{Auto
3841 Display,, Automatic display}.
3843 An argument is a repeat count, as in @code{step}.
3847 @kindex ni @r{(@code{nexti})}
3849 @itemx nexti @var{arg}
3851 Execute one machine instruction, but if it is a function call,
3852 proceed until the function returns.
3854 An argument is a repeat count, as in @code{next}.
3861 A signal is an asynchronous event that can happen in a program. The
3862 operating system defines the possible kinds of signals, and gives each
3863 kind a name and a number. For example, in Unix @code{SIGINT} is the
3864 signal a program gets when you type an interrupt character (often @kbd{C-c});
3865 @code{SIGSEGV} is the signal a program gets from referencing a place in
3866 memory far away from all the areas in use; @code{SIGALRM} occurs when
3867 the alarm clock timer goes off (which happens only if your program has
3868 requested an alarm).
3870 @cindex fatal signals
3871 Some signals, including @code{SIGALRM}, are a normal part of the
3872 functioning of your program. Others, such as @code{SIGSEGV}, indicate
3873 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
3874 program has not specified in advance some other way to handle the signal.
3875 @code{SIGINT} does not indicate an error in your program, but it is normally
3876 fatal so it can carry out the purpose of the interrupt: to kill the program.
3878 @value{GDBN} has the ability to detect any occurrence of a signal in your
3879 program. You can tell @value{GDBN} in advance what to do for each kind of
3882 @cindex handling signals
3883 Normally, @value{GDBN} is set up to let the non-erroneous signals like
3884 @code{SIGALRM} be silently passed to your program
3885 (so as not to interfere with their role in the program's functioning)
3886 but to stop your program immediately whenever an error signal happens.
3887 You can change these settings with the @code{handle} command.
3890 @kindex info signals
3894 Print a table of all the kinds of signals and how @value{GDBN} has been told to
3895 handle each one. You can use this to see the signal numbers of all
3896 the defined types of signals.
3898 @code{info handle} is an alias for @code{info signals}.
3901 @item handle @var{signal} @var{keywords}@dots{}
3902 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
3903 can be the number of a signal or its name (with or without the
3904 @samp{SIG} at the beginning); a list of signal numbers of the form
3905 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
3906 known signals. The @var{keywords} say what change to make.
3910 The keywords allowed by the @code{handle} command can be abbreviated.
3911 Their full names are:
3915 @value{GDBN} should not stop your program when this signal happens. It may
3916 still print a message telling you that the signal has come in.
3919 @value{GDBN} should stop your program when this signal happens. This implies
3920 the @code{print} keyword as well.
3923 @value{GDBN} should print a message when this signal happens.
3926 @value{GDBN} should not mention the occurrence of the signal at all. This
3927 implies the @code{nostop} keyword as well.
3931 @value{GDBN} should allow your program to see this signal; your program
3932 can handle the signal, or else it may terminate if the signal is fatal
3933 and not handled. @code{pass} and @code{noignore} are synonyms.
3937 @value{GDBN} should not allow your program to see this signal.
3938 @code{nopass} and @code{ignore} are synonyms.
3942 When a signal stops your program, the signal is not visible to the
3944 continue. Your program sees the signal then, if @code{pass} is in
3945 effect for the signal in question @emph{at that time}. In other words,
3946 after @value{GDBN} reports a signal, you can use the @code{handle}
3947 command with @code{pass} or @code{nopass} to control whether your
3948 program sees that signal when you continue.
3950 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
3951 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
3952 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
3955 You can also use the @code{signal} command to prevent your program from
3956 seeing a signal, or cause it to see a signal it normally would not see,
3957 or to give it any signal at any time. For example, if your program stopped
3958 due to some sort of memory reference error, you might store correct
3959 values into the erroneous variables and continue, hoping to see more
3960 execution; but your program would probably terminate immediately as
3961 a result of the fatal signal once it saw the signal. To prevent this,
3962 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
3966 @section Stopping and starting multi-thread programs
3968 When your program has multiple threads (@pxref{Threads,, Debugging
3969 programs with multiple threads}), you can choose whether to set
3970 breakpoints on all threads, or on a particular thread.
3973 @cindex breakpoints and threads
3974 @cindex thread breakpoints
3975 @kindex break @dots{} thread @var{threadno}
3976 @item break @var{linespec} thread @var{threadno}
3977 @itemx break @var{linespec} thread @var{threadno} if @dots{}
3978 @var{linespec} specifies source lines; there are several ways of
3979 writing them, but the effect is always to specify some source line.
3981 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
3982 to specify that you only want @value{GDBN} to stop the program when a
3983 particular thread reaches this breakpoint. @var{threadno} is one of the
3984 numeric thread identifiers assigned by @value{GDBN}, shown in the first
3985 column of the @samp{info threads} display.
3987 If you do not specify @samp{thread @var{threadno}} when you set a
3988 breakpoint, the breakpoint applies to @emph{all} threads of your
3991 You can use the @code{thread} qualifier on conditional breakpoints as
3992 well; in this case, place @samp{thread @var{threadno}} before the
3993 breakpoint condition, like this:
3996 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4001 @cindex stopped threads
4002 @cindex threads, stopped
4003 Whenever your program stops under @value{GDBN} for any reason,
4004 @emph{all} threads of execution stop, not just the current thread. This
4005 allows you to examine the overall state of the program, including
4006 switching between threads, without worrying that things may change
4009 @cindex thread breakpoints and system calls
4010 @cindex system calls and thread breakpoints
4011 @cindex premature return from system calls
4012 There is an unfortunate side effect. If one thread stops for a
4013 breakpoint, or for some other reason, and another thread is blocked in a
4014 system call, then the system call may return prematurely. This is a
4015 consequence of the interaction between multiple threads and the signals
4016 that @value{GDBN} uses to implement breakpoints and other events that
4019 To handle this problem, your program should check the return value of
4020 each system call and react appropriately. This is good programming
4023 For example, do not write code like this:
4029 The call to @code{sleep} will return early if a different thread stops
4030 at a breakpoint or for some other reason.
4032 Instead, write this:
4037 unslept = sleep (unslept);
4040 A system call is allowed to return early, so the system is still
4041 conforming to its specification. But @value{GDBN} does cause your
4042 multi-threaded program to behave differently than it would without
4045 Also, @value{GDBN} uses internal breakpoints in the thread library to
4046 monitor certain events such as thread creation and thread destruction.
4047 When such an event happens, a system call in another thread may return
4048 prematurely, even though your program does not appear to stop.
4050 @cindex continuing threads
4051 @cindex threads, continuing
4052 Conversely, whenever you restart the program, @emph{all} threads start
4053 executing. @emph{This is true even when single-stepping} with commands
4054 like @code{step} or @code{next}.
4056 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4057 Since thread scheduling is up to your debugging target's operating
4058 system (not controlled by @value{GDBN}), other threads may
4059 execute more than one statement while the current thread completes a
4060 single step. Moreover, in general other threads stop in the middle of a
4061 statement, rather than at a clean statement boundary, when the program
4064 You might even find your program stopped in another thread after
4065 continuing or even single-stepping. This happens whenever some other
4066 thread runs into a breakpoint, a signal, or an exception before the
4067 first thread completes whatever you requested.
4069 On some OSes, you can lock the OS scheduler and thus allow only a single
4073 @item set scheduler-locking @var{mode}
4074 @cindex scheduler locking mode
4075 @cindex lock scheduler
4076 Set the scheduler locking mode. If it is @code{off}, then there is no
4077 locking and any thread may run at any time. If @code{on}, then only the
4078 current thread may run when the inferior is resumed. The @code{step}
4079 mode optimizes for single-stepping. It stops other threads from
4080 ``seizing the prompt'' by preempting the current thread while you are
4081 stepping. Other threads will only rarely (or never) get a chance to run
4082 when you step. They are more likely to run when you @samp{next} over a
4083 function call, and they are completely free to run when you use commands
4084 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4085 thread hits a breakpoint during its timeslice, they will never steal the
4086 @value{GDBN} prompt away from the thread that you are debugging.
4088 @item show scheduler-locking
4089 Display the current scheduler locking mode.
4094 @chapter Examining the Stack
4096 When your program has stopped, the first thing you need to know is where it
4097 stopped and how it got there.
4100 Each time your program performs a function call, information about the call
4102 That information includes the location of the call in your program,
4103 the arguments of the call,
4104 and the local variables of the function being called.
4105 The information is saved in a block of data called a @dfn{stack frame}.
4106 The stack frames are allocated in a region of memory called the @dfn{call
4109 When your program stops, the @value{GDBN} commands for examining the
4110 stack allow you to see all of this information.
4112 @cindex selected frame
4113 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4114 @value{GDBN} commands refer implicitly to the selected frame. In
4115 particular, whenever you ask @value{GDBN} for the value of a variable in
4116 your program, the value is found in the selected frame. There are
4117 special @value{GDBN} commands to select whichever frame you are
4118 interested in. @xref{Selection, ,Selecting a frame}.
4120 When your program stops, @value{GDBN} automatically selects the
4121 currently executing frame and describes it briefly, similar to the
4122 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
4125 * Frames:: Stack frames
4126 * Backtrace:: Backtraces
4127 * Selection:: Selecting a frame
4128 * Frame Info:: Information on a frame
4133 @section Stack frames
4135 @cindex frame, definition
4137 The call stack is divided up into contiguous pieces called @dfn{stack
4138 frames}, or @dfn{frames} for short; each frame is the data associated
4139 with one call to one function. The frame contains the arguments given
4140 to the function, the function's local variables, and the address at
4141 which the function is executing.
4143 @cindex initial frame
4144 @cindex outermost frame
4145 @cindex innermost frame
4146 When your program is started, the stack has only one frame, that of the
4147 function @code{main}. This is called the @dfn{initial} frame or the
4148 @dfn{outermost} frame. Each time a function is called, a new frame is
4149 made. Each time a function returns, the frame for that function invocation
4150 is eliminated. If a function is recursive, there can be many frames for
4151 the same function. The frame for the function in which execution is
4152 actually occurring is called the @dfn{innermost} frame. This is the most
4153 recently created of all the stack frames that still exist.
4155 @cindex frame pointer
4156 Inside your program, stack frames are identified by their addresses. A
4157 stack frame consists of many bytes, each of which has its own address; each
4158 kind of computer has a convention for choosing one byte whose
4159 address serves as the address of the frame. Usually this address is kept
4160 in a register called the @dfn{frame pointer register}
4161 (@pxref{Registers, $fp}) while execution is going on in that frame.
4163 @cindex frame number
4164 @value{GDBN} assigns numbers to all existing stack frames, starting with
4165 zero for the innermost frame, one for the frame that called it,
4166 and so on upward. These numbers do not really exist in your program;
4167 they are assigned by @value{GDBN} to give you a way of designating stack
4168 frames in @value{GDBN} commands.
4170 @c The -fomit-frame-pointer below perennially causes hbox overflow
4171 @c underflow problems.
4172 @cindex frameless execution
4173 Some compilers provide a way to compile functions so that they operate
4174 without stack frames. (For example, the @value{GCC} option
4176 @samp{-fomit-frame-pointer}
4178 generates functions without a frame.)
4179 This is occasionally done with heavily used library functions to save
4180 the frame setup time. @value{GDBN} has limited facilities for dealing
4181 with these function invocations. If the innermost function invocation
4182 has no stack frame, @value{GDBN} nevertheless regards it as though
4183 it had a separate frame, which is numbered zero as usual, allowing
4184 correct tracing of the function call chain. However, @value{GDBN} has
4185 no provision for frameless functions elsewhere in the stack.
4188 @kindex frame@r{, command}
4189 @cindex current stack frame
4190 @item frame @var{args}
4191 The @code{frame} command allows you to move from one stack frame to another,
4192 and to print the stack frame you select. @var{args} may be either the
4193 address of the frame or the stack frame number. Without an argument,
4194 @code{frame} prints the current stack frame.
4196 @kindex select-frame
4197 @cindex selecting frame silently
4199 The @code{select-frame} command allows you to move from one stack frame
4200 to another without printing the frame. This is the silent version of
4208 @cindex call stack traces
4209 A backtrace is a summary of how your program got where it is. It shows one
4210 line per frame, for many frames, starting with the currently executing
4211 frame (frame zero), followed by its caller (frame one), and on up the
4216 @kindex bt @r{(@code{backtrace})}
4219 Print a backtrace of the entire stack: one line per frame for all
4220 frames in the stack.
4222 You can stop the backtrace at any time by typing the system interrupt
4223 character, normally @kbd{C-c}.
4225 @item backtrace @var{n}
4227 Similar, but print only the innermost @var{n} frames.
4229 @item backtrace -@var{n}
4231 Similar, but print only the outermost @var{n} frames.
4233 @item backtrace full
4234 Print the values of the local variables also.
4240 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4241 are additional aliases for @code{backtrace}.
4243 Each line in the backtrace shows the frame number and the function name.
4244 The program counter value is also shown---unless you use @code{set
4245 print address off}. The backtrace also shows the source file name and
4246 line number, as well as the arguments to the function. The program
4247 counter value is omitted if it is at the beginning of the code for that
4250 Here is an example of a backtrace. It was made with the command
4251 @samp{bt 3}, so it shows the innermost three frames.
4255 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4257 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4258 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4260 (More stack frames follow...)
4265 The display for frame zero does not begin with a program counter
4266 value, indicating that your program has stopped at the beginning of the
4267 code for line @code{993} of @code{builtin.c}.
4269 @cindex value optimized out, in backtrace
4270 @cindex function call arguments, optimized out
4271 If your program was compiled with optimizations, some compilers will
4272 optimize away arguments passed to functions if those arguments are
4273 never used after the call. Such optimizations generate code that
4274 passes arguments through registers, but doesn't store those arguments
4275 in the stack frame. @value{GDBN} has no way of displaying such
4276 arguments in stack frames other than the innermost one. Here's what
4277 such a backtrace might look like:
4281 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4283 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4284 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4286 (More stack frames follow...)
4291 The values of arguments that were not saved in their stack frames are
4292 shown as @samp{<value optimized out>}.
4294 If you need to display the values of such optimized-out arguments,
4295 either deduce that from other variables whose values depend on the one
4296 you are interested in, or recompile without optimizations.
4298 @cindex backtrace beyond @code{main} function
4299 @cindex program entry point
4300 @cindex startup code, and backtrace
4301 Most programs have a standard user entry point---a place where system
4302 libraries and startup code transition into user code. For C this is
4303 @code{main}. When @value{GDBN} finds the entry function in a backtrace
4304 it will terminate the backtrace, to avoid tracing into highly
4305 system-specific (and generally uninteresting) code.
4307 If you need to examine the startup code, or limit the number of levels
4308 in a backtrace, you can change this behavior:
4311 @item set backtrace past-main
4312 @itemx set backtrace past-main on
4313 @kindex set backtrace
4314 Backtraces will continue past the user entry point.
4316 @item set backtrace past-main off
4317 Backtraces will stop when they encounter the user entry point. This is the
4320 @item show backtrace past-main
4321 @kindex show backtrace
4322 Display the current user entry point backtrace policy.
4324 @item set backtrace past-entry
4325 @itemx set backtrace past-entry on
4326 Backtraces will continue past the internal entry point of an application.
4327 This entry point is encoded by the linker when the application is built,
4328 and is likely before the user entry point @code{main} (or equivalent) is called.
4330 @item set backtrace past-entry off
4331 Backtraces will stop when they encouter the internal entry point of an
4332 application. This is the default.
4334 @item show backtrace past-entry
4335 Display the current internal entry point backtrace policy.
4337 @item set backtrace limit @var{n}
4338 @itemx set backtrace limit 0
4339 @cindex backtrace limit
4340 Limit the backtrace to @var{n} levels. A value of zero means
4343 @item show backtrace limit
4344 Display the current limit on backtrace levels.
4348 @section Selecting a frame
4350 Most commands for examining the stack and other data in your program work on
4351 whichever stack frame is selected at the moment. Here are the commands for
4352 selecting a stack frame; all of them finish by printing a brief description
4353 of the stack frame just selected.
4356 @kindex frame@r{, selecting}
4357 @kindex f @r{(@code{frame})}
4360 Select frame number @var{n}. Recall that frame zero is the innermost
4361 (currently executing) frame, frame one is the frame that called the
4362 innermost one, and so on. The highest-numbered frame is the one for
4365 @item frame @var{addr}
4367 Select the frame at address @var{addr}. This is useful mainly if the
4368 chaining of stack frames has been damaged by a bug, making it
4369 impossible for @value{GDBN} to assign numbers properly to all frames. In
4370 addition, this can be useful when your program has multiple stacks and
4371 switches between them.
4373 On the SPARC architecture, @code{frame} needs two addresses to
4374 select an arbitrary frame: a frame pointer and a stack pointer.
4376 On the MIPS and Alpha architecture, it needs two addresses: a stack
4377 pointer and a program counter.
4379 On the 29k architecture, it needs three addresses: a register stack
4380 pointer, a program counter, and a memory stack pointer.
4381 @c note to future updaters: this is conditioned on a flag
4382 @c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date
4383 @c as of 27 Jan 1994.
4387 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4388 advances toward the outermost frame, to higher frame numbers, to frames
4389 that have existed longer. @var{n} defaults to one.
4392 @kindex do @r{(@code{down})}
4394 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4395 advances toward the innermost frame, to lower frame numbers, to frames
4396 that were created more recently. @var{n} defaults to one. You may
4397 abbreviate @code{down} as @code{do}.
4400 All of these commands end by printing two lines of output describing the
4401 frame. The first line shows the frame number, the function name, the
4402 arguments, and the source file and line number of execution in that
4403 frame. The second line shows the text of that source line.
4411 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4413 10 read_input_file (argv[i]);
4417 After such a printout, the @code{list} command with no arguments
4418 prints ten lines centered on the point of execution in the frame.
4419 You can also edit the program at the point of execution with your favorite
4420 editing program by typing @code{edit}.
4421 @xref{List, ,Printing source lines},
4425 @kindex down-silently
4427 @item up-silently @var{n}
4428 @itemx down-silently @var{n}
4429 These two commands are variants of @code{up} and @code{down},
4430 respectively; they differ in that they do their work silently, without
4431 causing display of the new frame. They are intended primarily for use
4432 in @value{GDBN} command scripts, where the output might be unnecessary and
4437 @section Information about a frame
4439 There are several other commands to print information about the selected
4445 When used without any argument, this command does not change which
4446 frame is selected, but prints a brief description of the currently
4447 selected stack frame. It can be abbreviated @code{f}. With an
4448 argument, this command is used to select a stack frame.
4449 @xref{Selection, ,Selecting a frame}.
4452 @kindex info f @r{(@code{info frame})}
4455 This command prints a verbose description of the selected stack frame,
4460 the address of the frame
4462 the address of the next frame down (called by this frame)
4464 the address of the next frame up (caller of this frame)
4466 the language in which the source code corresponding to this frame is written
4468 the address of the frame's arguments
4470 the address of the frame's local variables
4472 the program counter saved in it (the address of execution in the caller frame)
4474 which registers were saved in the frame
4477 @noindent The verbose description is useful when
4478 something has gone wrong that has made the stack format fail to fit
4479 the usual conventions.
4481 @item info frame @var{addr}
4482 @itemx info f @var{addr}
4483 Print a verbose description of the frame at address @var{addr}, without
4484 selecting that frame. The selected frame remains unchanged by this
4485 command. This requires the same kind of address (more than one for some
4486 architectures) that you specify in the @code{frame} command.
4487 @xref{Selection, ,Selecting a frame}.
4491 Print the arguments of the selected frame, each on a separate line.
4495 Print the local variables of the selected frame, each on a separate
4496 line. These are all variables (declared either static or automatic)
4497 accessible at the point of execution of the selected frame.
4500 @cindex catch exceptions, list active handlers
4501 @cindex exception handlers, how to list
4503 Print a list of all the exception handlers that are active in the
4504 current stack frame at the current point of execution. To see other
4505 exception handlers, visit the associated frame (using the @code{up},
4506 @code{down}, or @code{frame} commands); then type @code{info catch}.
4507 @xref{Set Catchpoints, , Setting catchpoints}.
4513 @chapter Examining Source Files
4515 @value{GDBN} can print parts of your program's source, since the debugging
4516 information recorded in the program tells @value{GDBN} what source files were
4517 used to build it. When your program stops, @value{GDBN} spontaneously prints
4518 the line where it stopped. Likewise, when you select a stack frame
4519 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4520 execution in that frame has stopped. You can print other portions of
4521 source files by explicit command.
4523 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4524 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4525 @value{GDBN} under @sc{gnu} Emacs}.
4528 * List:: Printing source lines
4529 * Edit:: Editing source files
4530 * Search:: Searching source files
4531 * Source Path:: Specifying source directories
4532 * Machine Code:: Source and machine code
4536 @section Printing source lines
4539 @kindex l @r{(@code{list})}
4540 To print lines from a source file, use the @code{list} command
4541 (abbreviated @code{l}). By default, ten lines are printed.
4542 There are several ways to specify what part of the file you want to print.
4544 Here are the forms of the @code{list} command most commonly used:
4547 @item list @var{linenum}
4548 Print lines centered around line number @var{linenum} in the
4549 current source file.
4551 @item list @var{function}
4552 Print lines centered around the beginning of function
4556 Print more lines. If the last lines printed were printed with a
4557 @code{list} command, this prints lines following the last lines
4558 printed; however, if the last line printed was a solitary line printed
4559 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4560 Stack}), this prints lines centered around that line.
4563 Print lines just before the lines last printed.
4566 @cindex @code{list}, how many lines to display
4567 By default, @value{GDBN} prints ten source lines with any of these forms of
4568 the @code{list} command. You can change this using @code{set listsize}:
4571 @kindex set listsize
4572 @item set listsize @var{count}
4573 Make the @code{list} command display @var{count} source lines (unless
4574 the @code{list} argument explicitly specifies some other number).
4576 @kindex show listsize
4578 Display the number of lines that @code{list} prints.
4581 Repeating a @code{list} command with @key{RET} discards the argument,
4582 so it is equivalent to typing just @code{list}. This is more useful
4583 than listing the same lines again. An exception is made for an
4584 argument of @samp{-}; that argument is preserved in repetition so that
4585 each repetition moves up in the source file.
4588 In general, the @code{list} command expects you to supply zero, one or two
4589 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4590 of writing them, but the effect is always to specify some source line.
4591 Here is a complete description of the possible arguments for @code{list}:
4594 @item list @var{linespec}
4595 Print lines centered around the line specified by @var{linespec}.
4597 @item list @var{first},@var{last}
4598 Print lines from @var{first} to @var{last}. Both arguments are
4601 @item list ,@var{last}
4602 Print lines ending with @var{last}.
4604 @item list @var{first},
4605 Print lines starting with @var{first}.
4608 Print lines just after the lines last printed.
4611 Print lines just before the lines last printed.
4614 As described in the preceding table.
4617 Here are the ways of specifying a single source line---all the
4622 Specifies line @var{number} of the current source file.
4623 When a @code{list} command has two linespecs, this refers to
4624 the same source file as the first linespec.
4627 Specifies the line @var{offset} lines after the last line printed.
4628 When used as the second linespec in a @code{list} command that has
4629 two, this specifies the line @var{offset} lines down from the
4633 Specifies the line @var{offset} lines before the last line printed.
4635 @item @var{filename}:@var{number}
4636 Specifies line @var{number} in the source file @var{filename}.
4638 @item @var{function}
4639 Specifies the line that begins the body of the function @var{function}.
4640 For example: in C, this is the line with the open brace.
4642 @item @var{filename}:@var{function}
4643 Specifies the line of the open-brace that begins the body of the
4644 function @var{function} in the file @var{filename}. You only need the
4645 file name with a function name to avoid ambiguity when there are
4646 identically named functions in different source files.
4648 @item *@var{address}
4649 Specifies the line containing the program address @var{address}.
4650 @var{address} may be any expression.
4654 @section Editing source files
4655 @cindex editing source files
4658 @kindex e @r{(@code{edit})}
4659 To edit the lines in a source file, use the @code{edit} command.
4660 The editing program of your choice
4661 is invoked with the current line set to
4662 the active line in the program.
4663 Alternatively, there are several ways to specify what part of the file you
4664 want to print if you want to see other parts of the program.
4666 Here are the forms of the @code{edit} command most commonly used:
4670 Edit the current source file at the active line number in the program.
4672 @item edit @var{number}
4673 Edit the current source file with @var{number} as the active line number.
4675 @item edit @var{function}
4676 Edit the file containing @var{function} at the beginning of its definition.
4678 @item edit @var{filename}:@var{number}
4679 Specifies line @var{number} in the source file @var{filename}.
4681 @item edit @var{filename}:@var{function}
4682 Specifies the line that begins the body of the
4683 function @var{function} in the file @var{filename}. You only need the
4684 file name with a function name to avoid ambiguity when there are
4685 identically named functions in different source files.
4687 @item edit *@var{address}
4688 Specifies the line containing the program address @var{address}.
4689 @var{address} may be any expression.
4692 @subsection Choosing your editor
4693 You can customize @value{GDBN} to use any editor you want
4695 The only restriction is that your editor (say @code{ex}), recognizes the
4696 following command-line syntax:
4698 ex +@var{number} file
4700 The optional numeric value +@var{number} specifies the number of the line in
4701 the file where to start editing.}.
4702 By default, it is @file{@value{EDITOR}}, but you can change this
4703 by setting the environment variable @code{EDITOR} before using
4704 @value{GDBN}. For example, to configure @value{GDBN} to use the
4705 @code{vi} editor, you could use these commands with the @code{sh} shell:
4711 or in the @code{csh} shell,
4713 setenv EDITOR /usr/bin/vi
4718 @section Searching source files
4719 @cindex searching source files
4721 There are two commands for searching through the current source file for a
4726 @kindex forward-search
4727 @item forward-search @var{regexp}
4728 @itemx search @var{regexp}
4729 The command @samp{forward-search @var{regexp}} checks each line,
4730 starting with the one following the last line listed, for a match for
4731 @var{regexp}. It lists the line that is found. You can use the
4732 synonym @samp{search @var{regexp}} or abbreviate the command name as
4735 @kindex reverse-search
4736 @item reverse-search @var{regexp}
4737 The command @samp{reverse-search @var{regexp}} checks each line, starting
4738 with the one before the last line listed and going backward, for a match
4739 for @var{regexp}. It lists the line that is found. You can abbreviate
4740 this command as @code{rev}.
4744 @section Specifying source directories
4747 @cindex directories for source files
4748 Executable programs sometimes do not record the directories of the source
4749 files from which they were compiled, just the names. Even when they do,
4750 the directories could be moved between the compilation and your debugging
4751 session. @value{GDBN} has a list of directories to search for source files;
4752 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4753 it tries all the directories in the list, in the order they are present
4754 in the list, until it finds a file with the desired name.
4756 For example, suppose an executable references the file
4757 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
4758 @file{/mnt/cross}. The file is first looked up literally; if this
4759 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
4760 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
4761 message is printed. @value{GDBN} does not look up the parts of the
4762 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
4763 Likewise, the subdirectories of the source path are not searched: if
4764 the source path is @file{/mnt/cross}, and the binary refers to
4765 @file{foo.c}, @value{GDBN} would not find it under
4766 @file{/mnt/cross/usr/src/foo-1.0/lib}.
4768 Plain file names, relative file names with leading directories, file
4769 names containing dots, etc.@: are all treated as described above; for
4770 instance, if the source path is @file{/mnt/cross}, and the source file
4771 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
4772 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
4773 that---@file{/mnt/cross/foo.c}.
4775 Note that the executable search path is @emph{not} used to locate the
4776 source files. Neither is the current working directory, unless it
4777 happens to be in the source path.
4779 Whenever you reset or rearrange the source path, @value{GDBN} clears out
4780 any information it has cached about where source files are found and where
4781 each line is in the file.
4785 When you start @value{GDBN}, its source path includes only @samp{cdir}
4786 and @samp{cwd}, in that order.
4787 To add other directories, use the @code{directory} command.
4790 @item directory @var{dirname} @dots{}
4791 @item dir @var{dirname} @dots{}
4792 Add directory @var{dirname} to the front of the source path. Several
4793 directory names may be given to this command, separated by @samp{:}
4794 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4795 part of absolute file names) or
4796 whitespace. You may specify a directory that is already in the source
4797 path; this moves it forward, so @value{GDBN} searches it sooner.
4801 @vindex $cdir@r{, convenience variable}
4802 @vindex $cwdr@r{, convenience variable}
4803 @cindex compilation directory
4804 @cindex current directory
4805 @cindex working directory
4806 @cindex directory, current
4807 @cindex directory, compilation
4808 You can use the string @samp{$cdir} to refer to the compilation
4809 directory (if one is recorded), and @samp{$cwd} to refer to the current
4810 working directory. @samp{$cwd} is not the same as @samp{.}---the former
4811 tracks the current working directory as it changes during your @value{GDBN}
4812 session, while the latter is immediately expanded to the current
4813 directory at the time you add an entry to the source path.
4816 Reset the source path to empty again. This requires confirmation.
4818 @c RET-repeat for @code{directory} is explicitly disabled, but since
4819 @c repeating it would be a no-op we do not say that. (thanks to RMS)
4821 @item show directories
4822 @kindex show directories
4823 Print the source path: show which directories it contains.
4826 If your source path is cluttered with directories that are no longer of
4827 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4828 versions of source. You can correct the situation as follows:
4832 Use @code{directory} with no argument to reset the source path to empty.
4835 Use @code{directory} with suitable arguments to reinstall the
4836 directories you want in the source path. You can add all the
4837 directories in one command.
4841 @section Source and machine code
4842 @cindex source line and its code address
4844 You can use the command @code{info line} to map source lines to program
4845 addresses (and vice versa), and the command @code{disassemble} to display
4846 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
4847 mode, the @code{info line} command causes the arrow to point to the
4848 line specified. Also, @code{info line} prints addresses in symbolic form as
4853 @item info line @var{linespec}
4854 Print the starting and ending addresses of the compiled code for
4855 source line @var{linespec}. You can specify source lines in any of
4856 the ways understood by the @code{list} command (@pxref{List, ,Printing
4860 For example, we can use @code{info line} to discover the location of
4861 the object code for the first line of function
4862 @code{m4_changequote}:
4864 @c FIXME: I think this example should also show the addresses in
4865 @c symbolic form, as they usually would be displayed.
4867 (@value{GDBP}) info line m4_changequote
4868 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4872 @cindex code address and its source line
4873 We can also inquire (using @code{*@var{addr}} as the form for
4874 @var{linespec}) what source line covers a particular address:
4876 (@value{GDBP}) info line *0x63ff
4877 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4880 @cindex @code{$_} and @code{info line}
4881 @cindex @code{x} command, default address
4882 @kindex x@r{(examine), and} info line
4883 After @code{info line}, the default address for the @code{x} command
4884 is changed to the starting address of the line, so that @samp{x/i} is
4885 sufficient to begin examining the machine code (@pxref{Memory,
4886 ,Examining memory}). Also, this address is saved as the value of the
4887 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4892 @cindex assembly instructions
4893 @cindex instructions, assembly
4894 @cindex machine instructions
4895 @cindex listing machine instructions
4897 This specialized command dumps a range of memory as machine
4898 instructions. The default memory range is the function surrounding the
4899 program counter of the selected frame. A single argument to this
4900 command is a program counter value; @value{GDBN} dumps the function
4901 surrounding this value. Two arguments specify a range of addresses
4902 (first inclusive, second exclusive) to dump.
4905 The following example shows the disassembly of a range of addresses of
4906 HP PA-RISC 2.0 code:
4909 (@value{GDBP}) disas 0x32c4 0x32e4
4910 Dump of assembler code from 0x32c4 to 0x32e4:
4911 0x32c4 <main+204>: addil 0,dp
4912 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
4913 0x32cc <main+212>: ldil 0x3000,r31
4914 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
4915 0x32d4 <main+220>: ldo 0(r31),rp
4916 0x32d8 <main+224>: addil -0x800,dp
4917 0x32dc <main+228>: ldo 0x588(r1),r26
4918 0x32e0 <main+232>: ldil 0x3000,r31
4919 End of assembler dump.
4922 Some architectures have more than one commonly-used set of instruction
4923 mnemonics or other syntax.
4926 @kindex set disassembly-flavor
4927 @cindex Intel disassembly flavor
4928 @cindex AT&T disassembly flavor
4929 @item set disassembly-flavor @var{instruction-set}
4930 Select the instruction set to use when disassembling the
4931 program via the @code{disassemble} or @code{x/i} commands.
4933 Currently this command is only defined for the Intel x86 family. You
4934 can set @var{instruction-set} to either @code{intel} or @code{att}.
4935 The default is @code{att}, the AT&T flavor used by default by Unix
4936 assemblers for x86-based targets.
4938 @kindex show disassembly-flavor
4939 @item show disassembly-flavor
4940 Show the current setting of the disassembly flavor.
4945 @chapter Examining Data
4947 @cindex printing data
4948 @cindex examining data
4951 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
4952 @c document because it is nonstandard... Under Epoch it displays in a
4953 @c different window or something like that.
4954 The usual way to examine data in your program is with the @code{print}
4955 command (abbreviated @code{p}), or its synonym @code{inspect}. It
4956 evaluates and prints the value of an expression of the language your
4957 program is written in (@pxref{Languages, ,Using @value{GDBN} with
4958 Different Languages}).
4961 @item print @var{expr}
4962 @itemx print /@var{f} @var{expr}
4963 @var{expr} is an expression (in the source language). By default the
4964 value of @var{expr} is printed in a format appropriate to its data type;
4965 you can choose a different format by specifying @samp{/@var{f}}, where
4966 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
4970 @itemx print /@var{f}
4971 @cindex reprint the last value
4972 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
4973 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
4974 conveniently inspect the same value in an alternative format.
4977 A more low-level way of examining data is with the @code{x} command.
4978 It examines data in memory at a specified address and prints it in a
4979 specified format. @xref{Memory, ,Examining memory}.
4981 If you are interested in information about types, or about how the
4982 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
4983 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
4987 * Expressions:: Expressions
4988 * Variables:: Program variables
4989 * Arrays:: Artificial arrays
4990 * Output Formats:: Output formats
4991 * Memory:: Examining memory
4992 * Auto Display:: Automatic display
4993 * Print Settings:: Print settings
4994 * Value History:: Value history
4995 * Convenience Vars:: Convenience variables
4996 * Registers:: Registers
4997 * Floating Point Hardware:: Floating point hardware
4998 * Vector Unit:: Vector Unit
4999 * OS Information:: Auxiliary data provided by operating system
5000 * Memory Region Attributes:: Memory region attributes
5001 * Dump/Restore Files:: Copy between memory and a file
5002 * Core File Generation:: Cause a program dump its core
5003 * Character Sets:: Debugging programs that use a different
5004 character set than GDB does
5005 * Caching Remote Data:: Data caching for remote targets
5009 @section Expressions
5012 @code{print} and many other @value{GDBN} commands accept an expression and
5013 compute its value. Any kind of constant, variable or operator defined
5014 by the programming language you are using is valid in an expression in
5015 @value{GDBN}. This includes conditional expressions, function calls,
5016 casts, and string constants. It also includes preprocessor macros, if
5017 you compiled your program to include this information; see
5020 @cindex arrays in expressions
5021 @value{GDBN} supports array constants in expressions input by
5022 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5023 you can use the command @code{print @{1, 2, 3@}} to build up an array in
5024 memory that is @code{malloc}ed in the target program.
5026 Because C is so widespread, most of the expressions shown in examples in
5027 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5028 Languages}, for information on how to use expressions in other
5031 In this section, we discuss operators that you can use in @value{GDBN}
5032 expressions regardless of your programming language.
5034 @cindex casts, in expressions
5035 Casts are supported in all languages, not just in C, because it is so
5036 useful to cast a number into a pointer in order to examine a structure
5037 at that address in memory.
5038 @c FIXME: casts supported---Mod2 true?
5040 @value{GDBN} supports these operators, in addition to those common
5041 to programming languages:
5045 @samp{@@} is a binary operator for treating parts of memory as arrays.
5046 @xref{Arrays, ,Artificial arrays}, for more information.
5049 @samp{::} allows you to specify a variable in terms of the file or
5050 function where it is defined. @xref{Variables, ,Program variables}.
5052 @cindex @{@var{type}@}
5053 @cindex type casting memory
5054 @cindex memory, viewing as typed object
5055 @cindex casts, to view memory
5056 @item @{@var{type}@} @var{addr}
5057 Refers to an object of type @var{type} stored at address @var{addr} in
5058 memory. @var{addr} may be any expression whose value is an integer or
5059 pointer (but parentheses are required around binary operators, just as in
5060 a cast). This construct is allowed regardless of what kind of data is
5061 normally supposed to reside at @var{addr}.
5065 @section Program variables
5067 The most common kind of expression to use is the name of a variable
5070 Variables in expressions are understood in the selected stack frame
5071 (@pxref{Selection, ,Selecting a frame}); they must be either:
5075 global (or file-static)
5082 visible according to the scope rules of the
5083 programming language from the point of execution in that frame
5086 @noindent This means that in the function
5101 you can examine and use the variable @code{a} whenever your program is
5102 executing within the function @code{foo}, but you can only use or
5103 examine the variable @code{b} while your program is executing inside
5104 the block where @code{b} is declared.
5106 @cindex variable name conflict
5107 There is an exception: you can refer to a variable or function whose
5108 scope is a single source file even if the current execution point is not
5109 in this file. But it is possible to have more than one such variable or
5110 function with the same name (in different source files). If that
5111 happens, referring to that name has unpredictable effects. If you wish,
5112 you can specify a static variable in a particular function or file,
5113 using the colon-colon (@code{::}) notation:
5115 @cindex colon-colon, context for variables/functions
5117 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5118 @cindex @code{::}, context for variables/functions
5121 @var{file}::@var{variable}
5122 @var{function}::@var{variable}
5126 Here @var{file} or @var{function} is the name of the context for the
5127 static @var{variable}. In the case of file names, you can use quotes to
5128 make sure @value{GDBN} parses the file name as a single word---for example,
5129 to print a global value of @code{x} defined in @file{f2.c}:
5132 (@value{GDBP}) p 'f2.c'::x
5135 @cindex C@t{++} scope resolution
5136 This use of @samp{::} is very rarely in conflict with the very similar
5137 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5138 scope resolution operator in @value{GDBN} expressions.
5139 @c FIXME: Um, so what happens in one of those rare cases where it's in
5142 @cindex wrong values
5143 @cindex variable values, wrong
5144 @cindex function entry/exit, wrong values of variables
5145 @cindex optimized code, wrong values of variables
5147 @emph{Warning:} Occasionally, a local variable may appear to have the
5148 wrong value at certain points in a function---just after entry to a new
5149 scope, and just before exit.
5151 You may see this problem when you are stepping by machine instructions.
5152 This is because, on most machines, it takes more than one instruction to
5153 set up a stack frame (including local variable definitions); if you are
5154 stepping by machine instructions, variables may appear to have the wrong
5155 values until the stack frame is completely built. On exit, it usually
5156 also takes more than one machine instruction to destroy a stack frame;
5157 after you begin stepping through that group of instructions, local
5158 variable definitions may be gone.
5160 This may also happen when the compiler does significant optimizations.
5161 To be sure of always seeing accurate values, turn off all optimization
5164 @cindex ``No symbol "foo" in current context''
5165 Another possible effect of compiler optimizations is to optimize
5166 unused variables out of existence, or assign variables to registers (as
5167 opposed to memory addresses). Depending on the support for such cases
5168 offered by the debug info format used by the compiler, @value{GDBN}
5169 might not be able to display values for such local variables. If that
5170 happens, @value{GDBN} will print a message like this:
5173 No symbol "foo" in current context.
5176 To solve such problems, either recompile without optimizations, or use a
5177 different debug info format, if the compiler supports several such
5178 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5179 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5180 produces debug info in a format that is superior to formats such as
5181 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5182 an effective form for debug info. @xref{Debugging Options,,Options
5183 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
5184 @xref{C, , Debugging C++}, for more info about debug info formats
5185 that are best suited to C@t{++} programs.
5188 @section Artificial arrays
5190 @cindex artificial array
5192 @kindex @@@r{, referencing memory as an array}
5193 It is often useful to print out several successive objects of the
5194 same type in memory; a section of an array, or an array of
5195 dynamically determined size for which only a pointer exists in the
5198 You can do this by referring to a contiguous span of memory as an
5199 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5200 operand of @samp{@@} should be the first element of the desired array
5201 and be an individual object. The right operand should be the desired length
5202 of the array. The result is an array value whose elements are all of
5203 the type of the left argument. The first element is actually the left
5204 argument; the second element comes from bytes of memory immediately
5205 following those that hold the first element, and so on. Here is an
5206 example. If a program says
5209 int *array = (int *) malloc (len * sizeof (int));
5213 you can print the contents of @code{array} with
5219 The left operand of @samp{@@} must reside in memory. Array values made
5220 with @samp{@@} in this way behave just like other arrays in terms of
5221 subscripting, and are coerced to pointers when used in expressions.
5222 Artificial arrays most often appear in expressions via the value history
5223 (@pxref{Value History, ,Value history}), after printing one out.
5225 Another way to create an artificial array is to use a cast.
5226 This re-interprets a value as if it were an array.
5227 The value need not be in memory:
5229 (@value{GDBP}) p/x (short[2])0x12345678
5230 $1 = @{0x1234, 0x5678@}
5233 As a convenience, if you leave the array length out (as in
5234 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5235 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5237 (@value{GDBP}) p/x (short[])0x12345678
5238 $2 = @{0x1234, 0x5678@}
5241 Sometimes the artificial array mechanism is not quite enough; in
5242 moderately complex data structures, the elements of interest may not
5243 actually be adjacent---for example, if you are interested in the values
5244 of pointers in an array. One useful work-around in this situation is
5245 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5246 variables}) as a counter in an expression that prints the first
5247 interesting value, and then repeat that expression via @key{RET}. For
5248 instance, suppose you have an array @code{dtab} of pointers to
5249 structures, and you are interested in the values of a field @code{fv}
5250 in each structure. Here is an example of what you might type:
5260 @node Output Formats
5261 @section Output formats
5263 @cindex formatted output
5264 @cindex output formats
5265 By default, @value{GDBN} prints a value according to its data type. Sometimes
5266 this is not what you want. For example, you might want to print a number
5267 in hex, or a pointer in decimal. Or you might want to view data in memory
5268 at a certain address as a character string or as an instruction. To do
5269 these things, specify an @dfn{output format} when you print a value.
5271 The simplest use of output formats is to say how to print a value
5272 already computed. This is done by starting the arguments of the
5273 @code{print} command with a slash and a format letter. The format
5274 letters supported are:
5278 Regard the bits of the value as an integer, and print the integer in
5282 Print as integer in signed decimal.
5285 Print as integer in unsigned decimal.
5288 Print as integer in octal.
5291 Print as integer in binary. The letter @samp{t} stands for ``two''.
5292 @footnote{@samp{b} cannot be used because these format letters are also
5293 used with the @code{x} command, where @samp{b} stands for ``byte'';
5294 see @ref{Memory,,Examining memory}.}
5297 @cindex unknown address, locating
5298 @cindex locate address
5299 Print as an address, both absolute in hexadecimal and as an offset from
5300 the nearest preceding symbol. You can use this format used to discover
5301 where (in what function) an unknown address is located:
5304 (@value{GDBP}) p/a 0x54320
5305 $3 = 0x54320 <_initialize_vx+396>
5309 The command @code{info symbol 0x54320} yields similar results.
5310 @xref{Symbols, info symbol}.
5313 Regard as an integer and print it as a character constant. This
5314 prints both the numerical value and its character representation. The
5315 character representation is replaced with the octal escape @samp{\nnn}
5316 for characters outside the 7-bit @sc{ascii} range.
5319 Regard the bits of the value as a floating point number and print
5320 using typical floating point syntax.
5323 For example, to print the program counter in hex (@pxref{Registers}), type
5330 Note that no space is required before the slash; this is because command
5331 names in @value{GDBN} cannot contain a slash.
5333 To reprint the last value in the value history with a different format,
5334 you can use the @code{print} command with just a format and no
5335 expression. For example, @samp{p/x} reprints the last value in hex.
5338 @section Examining memory
5340 You can use the command @code{x} (for ``examine'') to examine memory in
5341 any of several formats, independently of your program's data types.
5343 @cindex examining memory
5345 @kindex x @r{(examine memory)}
5346 @item x/@var{nfu} @var{addr}
5349 Use the @code{x} command to examine memory.
5352 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5353 much memory to display and how to format it; @var{addr} is an
5354 expression giving the address where you want to start displaying memory.
5355 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5356 Several commands set convenient defaults for @var{addr}.
5359 @item @var{n}, the repeat count
5360 The repeat count is a decimal integer; the default is 1. It specifies
5361 how much memory (counting by units @var{u}) to display.
5362 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5365 @item @var{f}, the display format
5366 The display format is one of the formats used by @code{print}
5367 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
5368 @samp{f}), and in addition @samp{s} (for null-terminated strings) and
5369 @samp{i} (for machine instructions). The default is @samp{x}
5370 (hexadecimal) initially. The default changes each time you use either
5371 @code{x} or @code{print}.
5373 @item @var{u}, the unit size
5374 The unit size is any of
5380 Halfwords (two bytes).
5382 Words (four bytes). This is the initial default.
5384 Giant words (eight bytes).
5387 Each time you specify a unit size with @code{x}, that size becomes the
5388 default unit the next time you use @code{x}. (For the @samp{s} and
5389 @samp{i} formats, the unit size is ignored and is normally not written.)
5391 @item @var{addr}, starting display address
5392 @var{addr} is the address where you want @value{GDBN} to begin displaying
5393 memory. The expression need not have a pointer value (though it may);
5394 it is always interpreted as an integer address of a byte of memory.
5395 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5396 @var{addr} is usually just after the last address examined---but several
5397 other commands also set the default address: @code{info breakpoints} (to
5398 the address of the last breakpoint listed), @code{info line} (to the
5399 starting address of a line), and @code{print} (if you use it to display
5400 a value from memory).
5403 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5404 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5405 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5406 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5407 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5409 Since the letters indicating unit sizes are all distinct from the
5410 letters specifying output formats, you do not have to remember whether
5411 unit size or format comes first; either order works. The output
5412 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5413 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5415 Even though the unit size @var{u} is ignored for the formats @samp{s}
5416 and @samp{i}, you might still want to use a count @var{n}; for example,
5417 @samp{3i} specifies that you want to see three machine instructions,
5418 including any operands. The command @code{disassemble} gives an
5419 alternative way of inspecting machine instructions; see @ref{Machine
5420 Code,,Source and machine code}.
5422 All the defaults for the arguments to @code{x} are designed to make it
5423 easy to continue scanning memory with minimal specifications each time
5424 you use @code{x}. For example, after you have inspected three machine
5425 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5426 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5427 the repeat count @var{n} is used again; the other arguments default as
5428 for successive uses of @code{x}.
5430 @cindex @code{$_}, @code{$__}, and value history
5431 The addresses and contents printed by the @code{x} command are not saved
5432 in the value history because there is often too much of them and they
5433 would get in the way. Instead, @value{GDBN} makes these values available for
5434 subsequent use in expressions as values of the convenience variables
5435 @code{$_} and @code{$__}. After an @code{x} command, the last address
5436 examined is available for use in expressions in the convenience variable
5437 @code{$_}. The contents of that address, as examined, are available in
5438 the convenience variable @code{$__}.
5440 If the @code{x} command has a repeat count, the address and contents saved
5441 are from the last memory unit printed; this is not the same as the last
5442 address printed if several units were printed on the last line of output.
5444 @cindex remote memory comparison
5445 @cindex verify remote memory image
5446 When you are debugging a program running on a remote target machine
5447 (@pxref{Remote}), you may wish to verify the program's image in the
5448 remote machine's memory against the executable file you downloaded to
5449 the target. The @code{compare-sections} command is provided for such
5453 @kindex compare-sections
5454 @item compare-sections @r{[}@var{section-name}@r{]}
5455 Compare the data of a loadable section @var{section-name} in the
5456 executable file of the program being debugged with the same section in
5457 the remote machine's memory, and report any mismatches. With no
5458 arguments, compares all loadable sections. This command's
5459 availability depends on the target's support for the @code{"qCRC"}
5464 @section Automatic display
5465 @cindex automatic display
5466 @cindex display of expressions
5468 If you find that you want to print the value of an expression frequently
5469 (to see how it changes), you might want to add it to the @dfn{automatic
5470 display list} so that @value{GDBN} prints its value each time your program stops.
5471 Each expression added to the list is given a number to identify it;
5472 to remove an expression from the list, you specify that number.
5473 The automatic display looks like this:
5477 3: bar[5] = (struct hack *) 0x3804
5481 This display shows item numbers, expressions and their current values. As with
5482 displays you request manually using @code{x} or @code{print}, you can
5483 specify the output format you prefer; in fact, @code{display} decides
5484 whether to use @code{print} or @code{x} depending on how elaborate your
5485 format specification is---it uses @code{x} if you specify a unit size,
5486 or one of the two formats (@samp{i} and @samp{s}) that are only
5487 supported by @code{x}; otherwise it uses @code{print}.
5491 @item display @var{expr}
5492 Add the expression @var{expr} to the list of expressions to display
5493 each time your program stops. @xref{Expressions, ,Expressions}.
5495 @code{display} does not repeat if you press @key{RET} again after using it.
5497 @item display/@var{fmt} @var{expr}
5498 For @var{fmt} specifying only a display format and not a size or
5499 count, add the expression @var{expr} to the auto-display list but
5500 arrange to display it each time in the specified format @var{fmt}.
5501 @xref{Output Formats,,Output formats}.
5503 @item display/@var{fmt} @var{addr}
5504 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5505 number of units, add the expression @var{addr} as a memory address to
5506 be examined each time your program stops. Examining means in effect
5507 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5510 For example, @samp{display/i $pc} can be helpful, to see the machine
5511 instruction about to be executed each time execution stops (@samp{$pc}
5512 is a common name for the program counter; @pxref{Registers, ,Registers}).
5515 @kindex delete display
5517 @item undisplay @var{dnums}@dots{}
5518 @itemx delete display @var{dnums}@dots{}
5519 Remove item numbers @var{dnums} from the list of expressions to display.
5521 @code{undisplay} does not repeat if you press @key{RET} after using it.
5522 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5524 @kindex disable display
5525 @item disable display @var{dnums}@dots{}
5526 Disable the display of item numbers @var{dnums}. A disabled display
5527 item is not printed automatically, but is not forgotten. It may be
5528 enabled again later.
5530 @kindex enable display
5531 @item enable display @var{dnums}@dots{}
5532 Enable display of item numbers @var{dnums}. It becomes effective once
5533 again in auto display of its expression, until you specify otherwise.
5536 Display the current values of the expressions on the list, just as is
5537 done when your program stops.
5539 @kindex info display
5541 Print the list of expressions previously set up to display
5542 automatically, each one with its item number, but without showing the
5543 values. This includes disabled expressions, which are marked as such.
5544 It also includes expressions which would not be displayed right now
5545 because they refer to automatic variables not currently available.
5548 @cindex display disabled out of scope
5549 If a display expression refers to local variables, then it does not make
5550 sense outside the lexical context for which it was set up. Such an
5551 expression is disabled when execution enters a context where one of its
5552 variables is not defined. For example, if you give the command
5553 @code{display last_char} while inside a function with an argument
5554 @code{last_char}, @value{GDBN} displays this argument while your program
5555 continues to stop inside that function. When it stops elsewhere---where
5556 there is no variable @code{last_char}---the display is disabled
5557 automatically. The next time your program stops where @code{last_char}
5558 is meaningful, you can enable the display expression once again.
5560 @node Print Settings
5561 @section Print settings
5563 @cindex format options
5564 @cindex print settings
5565 @value{GDBN} provides the following ways to control how arrays, structures,
5566 and symbols are printed.
5569 These settings are useful for debugging programs in any language:
5573 @item set print address
5574 @itemx set print address on
5575 @cindex print/don't print memory addresses
5576 @value{GDBN} prints memory addresses showing the location of stack
5577 traces, structure values, pointer values, breakpoints, and so forth,
5578 even when it also displays the contents of those addresses. The default
5579 is @code{on}. For example, this is what a stack frame display looks like with
5580 @code{set print address on}:
5585 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5587 530 if (lquote != def_lquote)
5591 @item set print address off
5592 Do not print addresses when displaying their contents. For example,
5593 this is the same stack frame displayed with @code{set print address off}:
5597 (@value{GDBP}) set print addr off
5599 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5600 530 if (lquote != def_lquote)
5604 You can use @samp{set print address off} to eliminate all machine
5605 dependent displays from the @value{GDBN} interface. For example, with
5606 @code{print address off}, you should get the same text for backtraces on
5607 all machines---whether or not they involve pointer arguments.
5610 @item show print address
5611 Show whether or not addresses are to be printed.
5614 When @value{GDBN} prints a symbolic address, it normally prints the
5615 closest earlier symbol plus an offset. If that symbol does not uniquely
5616 identify the address (for example, it is a name whose scope is a single
5617 source file), you may need to clarify. One way to do this is with
5618 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5619 you can set @value{GDBN} to print the source file and line number when
5620 it prints a symbolic address:
5623 @item set print symbol-filename on
5624 @cindex source file and line of a symbol
5625 @cindex symbol, source file and line
5626 Tell @value{GDBN} to print the source file name and line number of a
5627 symbol in the symbolic form of an address.
5629 @item set print symbol-filename off
5630 Do not print source file name and line number of a symbol. This is the
5633 @item show print symbol-filename
5634 Show whether or not @value{GDBN} will print the source file name and
5635 line number of a symbol in the symbolic form of an address.
5638 Another situation where it is helpful to show symbol filenames and line
5639 numbers is when disassembling code; @value{GDBN} shows you the line
5640 number and source file that corresponds to each instruction.
5642 Also, you may wish to see the symbolic form only if the address being
5643 printed is reasonably close to the closest earlier symbol:
5646 @item set print max-symbolic-offset @var{max-offset}
5647 @cindex maximum value for offset of closest symbol
5648 Tell @value{GDBN} to only display the symbolic form of an address if the
5649 offset between the closest earlier symbol and the address is less than
5650 @var{max-offset}. The default is 0, which tells @value{GDBN}
5651 to always print the symbolic form of an address if any symbol precedes it.
5653 @item show print max-symbolic-offset
5654 Ask how large the maximum offset is that @value{GDBN} prints in a
5658 @cindex wild pointer, interpreting
5659 @cindex pointer, finding referent
5660 If you have a pointer and you are not sure where it points, try
5661 @samp{set print symbol-filename on}. Then you can determine the name
5662 and source file location of the variable where it points, using
5663 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5664 For example, here @value{GDBN} shows that a variable @code{ptt} points
5665 at another variable @code{t}, defined in @file{hi2.c}:
5668 (@value{GDBP}) set print symbol-filename on
5669 (@value{GDBP}) p/a ptt
5670 $4 = 0xe008 <t in hi2.c>
5674 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5675 does not show the symbol name and filename of the referent, even with
5676 the appropriate @code{set print} options turned on.
5679 Other settings control how different kinds of objects are printed:
5682 @item set print array
5683 @itemx set print array on
5684 @cindex pretty print arrays
5685 Pretty print arrays. This format is more convenient to read,
5686 but uses more space. The default is off.
5688 @item set print array off
5689 Return to compressed format for arrays.
5691 @item show print array
5692 Show whether compressed or pretty format is selected for displaying
5695 @item set print elements @var{number-of-elements}
5696 @cindex number of array elements to print
5697 @cindex limit on number of printed array elements
5698 Set a limit on how many elements of an array @value{GDBN} will print.
5699 If @value{GDBN} is printing a large array, it stops printing after it has
5700 printed the number of elements set by the @code{set print elements} command.
5701 This limit also applies to the display of strings.
5702 When @value{GDBN} starts, this limit is set to 200.
5703 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5705 @item show print elements
5706 Display the number of elements of a large array that @value{GDBN} will print.
5707 If the number is 0, then the printing is unlimited.
5709 @item set print repeats
5710 @cindex repeated array elements
5711 Set the threshold for suppressing display of repeated array
5712 elelments. When the number of consecutive identical elements of an
5713 array exceeds the threshold, @value{GDBN} prints the string
5714 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
5715 identical repetitions, instead of displaying the identical elements
5716 themselves. Setting the threshold to zero will cause all elements to
5717 be individually printed. The default threshold is 10.
5719 @item show print repeats
5720 Display the current threshold for printing repeated identical
5723 @item set print null-stop
5724 @cindex @sc{null} elements in arrays
5725 Cause @value{GDBN} to stop printing the characters of an array when the first
5726 @sc{null} is encountered. This is useful when large arrays actually
5727 contain only short strings.
5730 @item show print null-stop
5731 Show whether @value{GDBN} stops printing an array on the first
5732 @sc{null} character.
5734 @item set print pretty on
5735 @cindex print structures in indented form
5736 @cindex indentation in structure display
5737 Cause @value{GDBN} to print structures in an indented format with one member
5738 per line, like this:
5753 @item set print pretty off
5754 Cause @value{GDBN} to print structures in a compact format, like this:
5758 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5759 meat = 0x54 "Pork"@}
5764 This is the default format.
5766 @item show print pretty
5767 Show which format @value{GDBN} is using to print structures.
5769 @item set print sevenbit-strings on
5770 @cindex eight-bit characters in strings
5771 @cindex octal escapes in strings
5772 Print using only seven-bit characters; if this option is set,
5773 @value{GDBN} displays any eight-bit characters (in strings or
5774 character values) using the notation @code{\}@var{nnn}. This setting is
5775 best if you are working in English (@sc{ascii}) and you use the
5776 high-order bit of characters as a marker or ``meta'' bit.
5778 @item set print sevenbit-strings off
5779 Print full eight-bit characters. This allows the use of more
5780 international character sets, and is the default.
5782 @item show print sevenbit-strings
5783 Show whether or not @value{GDBN} is printing only seven-bit characters.
5785 @item set print union on
5786 @cindex unions in structures, printing
5787 Tell @value{GDBN} to print unions which are contained in structures
5788 and other unions. This is the default setting.
5790 @item set print union off
5791 Tell @value{GDBN} not to print unions which are contained in
5792 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
5795 @item show print union
5796 Ask @value{GDBN} whether or not it will print unions which are contained in
5797 structures and other unions.
5799 For example, given the declarations
5802 typedef enum @{Tree, Bug@} Species;
5803 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5804 typedef enum @{Caterpillar, Cocoon, Butterfly@}
5815 struct thing foo = @{Tree, @{Acorn@}@};
5819 with @code{set print union on} in effect @samp{p foo} would print
5822 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5826 and with @code{set print union off} in effect it would print
5829 $1 = @{it = Tree, form = @{...@}@}
5833 @code{set print union} affects programs written in C-like languages
5839 These settings are of interest when debugging C@t{++} programs:
5842 @cindex demangling C@t{++} names
5843 @item set print demangle
5844 @itemx set print demangle on
5845 Print C@t{++} names in their source form rather than in the encoded
5846 (``mangled'') form passed to the assembler and linker for type-safe
5847 linkage. The default is on.
5849 @item show print demangle
5850 Show whether C@t{++} names are printed in mangled or demangled form.
5852 @item set print asm-demangle
5853 @itemx set print asm-demangle on
5854 Print C@t{++} names in their source form rather than their mangled form, even
5855 in assembler code printouts such as instruction disassemblies.
5858 @item show print asm-demangle
5859 Show whether C@t{++} names in assembly listings are printed in mangled
5862 @cindex C@t{++} symbol decoding style
5863 @cindex symbol decoding style, C@t{++}
5864 @kindex set demangle-style
5865 @item set demangle-style @var{style}
5866 Choose among several encoding schemes used by different compilers to
5867 represent C@t{++} names. The choices for @var{style} are currently:
5871 Allow @value{GDBN} to choose a decoding style by inspecting your program.
5874 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
5875 This is the default.
5878 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
5881 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
5884 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
5885 @strong{Warning:} this setting alone is not sufficient to allow
5886 debugging @code{cfront}-generated executables. @value{GDBN} would
5887 require further enhancement to permit that.
5890 If you omit @var{style}, you will see a list of possible formats.
5892 @item show demangle-style
5893 Display the encoding style currently in use for decoding C@t{++} symbols.
5895 @item set print object
5896 @itemx set print object on
5897 @cindex derived type of an object, printing
5898 @cindex display derived types
5899 When displaying a pointer to an object, identify the @emph{actual}
5900 (derived) type of the object rather than the @emph{declared} type, using
5901 the virtual function table.
5903 @item set print object off
5904 Display only the declared type of objects, without reference to the
5905 virtual function table. This is the default setting.
5907 @item show print object
5908 Show whether actual, or declared, object types are displayed.
5910 @item set print static-members
5911 @itemx set print static-members on
5912 @cindex static members of C@t{++} objects
5913 Print static members when displaying a C@t{++} object. The default is on.
5915 @item set print static-members off
5916 Do not print static members when displaying a C@t{++} object.
5918 @item show print static-members
5919 Show whether C@t{++} static members are printed or not.
5921 @item set print pascal_static-members
5922 @itemx set print pascal_static-members on
5923 @cindex static members of Pacal objects
5924 @cindex Pacal objects, static members display
5925 Print static members when displaying a Pascal object. The default is on.
5927 @item set print pascal_static-members off
5928 Do not print static members when displaying a Pascal object.
5930 @item show print pascal_static-members
5931 Show whether Pascal static members are printed or not.
5933 @c These don't work with HP ANSI C++ yet.
5934 @item set print vtbl
5935 @itemx set print vtbl on
5936 @cindex pretty print C@t{++} virtual function tables
5937 @cindex virtual functions (C@t{++}) display
5938 @cindex VTBL display
5939 Pretty print C@t{++} virtual function tables. The default is off.
5940 (The @code{vtbl} commands do not work on programs compiled with the HP
5941 ANSI C@t{++} compiler (@code{aCC}).)
5943 @item set print vtbl off
5944 Do not pretty print C@t{++} virtual function tables.
5946 @item show print vtbl
5947 Show whether C@t{++} virtual function tables are pretty printed, or not.
5951 @section Value history
5953 @cindex value history
5954 @cindex history of values printed by @value{GDBN}
5955 Values printed by the @code{print} command are saved in the @value{GDBN}
5956 @dfn{value history}. This allows you to refer to them in other expressions.
5957 Values are kept until the symbol table is re-read or discarded
5958 (for example with the @code{file} or @code{symbol-file} commands).
5959 When the symbol table changes, the value history is discarded,
5960 since the values may contain pointers back to the types defined in the
5965 @cindex history number
5966 The values printed are given @dfn{history numbers} by which you can
5967 refer to them. These are successive integers starting with one.
5968 @code{print} shows you the history number assigned to a value by
5969 printing @samp{$@var{num} = } before the value; here @var{num} is the
5972 To refer to any previous value, use @samp{$} followed by the value's
5973 history number. The way @code{print} labels its output is designed to
5974 remind you of this. Just @code{$} refers to the most recent value in
5975 the history, and @code{$$} refers to the value before that.
5976 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
5977 is the value just prior to @code{$$}, @code{$$1} is equivalent to
5978 @code{$$}, and @code{$$0} is equivalent to @code{$}.
5980 For example, suppose you have just printed a pointer to a structure and
5981 want to see the contents of the structure. It suffices to type
5987 If you have a chain of structures where the component @code{next} points
5988 to the next one, you can print the contents of the next one with this:
5995 You can print successive links in the chain by repeating this
5996 command---which you can do by just typing @key{RET}.
5998 Note that the history records values, not expressions. If the value of
5999 @code{x} is 4 and you type these commands:
6007 then the value recorded in the value history by the @code{print} command
6008 remains 4 even though the value of @code{x} has changed.
6013 Print the last ten values in the value history, with their item numbers.
6014 This is like @samp{p@ $$9} repeated ten times, except that @code{show
6015 values} does not change the history.
6017 @item show values @var{n}
6018 Print ten history values centered on history item number @var{n}.
6021 Print ten history values just after the values last printed. If no more
6022 values are available, @code{show values +} produces no display.
6025 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
6026 same effect as @samp{show values +}.
6028 @node Convenience Vars
6029 @section Convenience variables
6031 @cindex convenience variables
6032 @cindex user-defined variables
6033 @value{GDBN} provides @dfn{convenience variables} that you can use within
6034 @value{GDBN} to hold on to a value and refer to it later. These variables
6035 exist entirely within @value{GDBN}; they are not part of your program, and
6036 setting a convenience variable has no direct effect on further execution
6037 of your program. That is why you can use them freely.
6039 Convenience variables are prefixed with @samp{$}. Any name preceded by
6040 @samp{$} can be used for a convenience variable, unless it is one of
6041 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
6042 (Value history references, in contrast, are @emph{numbers} preceded
6043 by @samp{$}. @xref{Value History, ,Value history}.)
6045 You can save a value in a convenience variable with an assignment
6046 expression, just as you would set a variable in your program.
6050 set $foo = *object_ptr
6054 would save in @code{$foo} the value contained in the object pointed to by
6057 Using a convenience variable for the first time creates it, but its
6058 value is @code{void} until you assign a new value. You can alter the
6059 value with another assignment at any time.
6061 Convenience variables have no fixed types. You can assign a convenience
6062 variable any type of value, including structures and arrays, even if
6063 that variable already has a value of a different type. The convenience
6064 variable, when used as an expression, has the type of its current value.
6067 @kindex show convenience
6068 @cindex show all user variables
6069 @item show convenience
6070 Print a list of convenience variables used so far, and their values.
6071 Abbreviated @code{show conv}.
6074 One of the ways to use a convenience variable is as a counter to be
6075 incremented or a pointer to be advanced. For example, to print
6076 a field from successive elements of an array of structures:
6080 print bar[$i++]->contents
6084 Repeat that command by typing @key{RET}.
6086 Some convenience variables are created automatically by @value{GDBN} and given
6087 values likely to be useful.
6090 @vindex $_@r{, convenience variable}
6092 The variable @code{$_} is automatically set by the @code{x} command to
6093 the last address examined (@pxref{Memory, ,Examining memory}). Other
6094 commands which provide a default address for @code{x} to examine also
6095 set @code{$_} to that address; these commands include @code{info line}
6096 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
6097 except when set by the @code{x} command, in which case it is a pointer
6098 to the type of @code{$__}.
6100 @vindex $__@r{, convenience variable}
6102 The variable @code{$__} is automatically set by the @code{x} command
6103 to the value found in the last address examined. Its type is chosen
6104 to match the format in which the data was printed.
6107 @vindex $_exitcode@r{, convenience variable}
6108 The variable @code{$_exitcode} is automatically set to the exit code when
6109 the program being debugged terminates.
6112 On HP-UX systems, if you refer to a function or variable name that
6113 begins with a dollar sign, @value{GDBN} searches for a user or system
6114 name first, before it searches for a convenience variable.
6120 You can refer to machine register contents, in expressions, as variables
6121 with names starting with @samp{$}. The names of registers are different
6122 for each machine; use @code{info registers} to see the names used on
6126 @kindex info registers
6127 @item info registers
6128 Print the names and values of all registers except floating-point
6129 and vector registers (in the selected stack frame).
6131 @kindex info all-registers
6132 @cindex floating point registers
6133 @item info all-registers
6134 Print the names and values of all registers, including floating-point
6135 and vector registers (in the selected stack frame).
6137 @item info registers @var{regname} @dots{}
6138 Print the @dfn{relativized} value of each specified register @var{regname}.
6139 As discussed in detail below, register values are normally relative to
6140 the selected stack frame. @var{regname} may be any register name valid on
6141 the machine you are using, with or without the initial @samp{$}.
6144 @cindex stack pointer register
6145 @cindex program counter register
6146 @cindex process status register
6147 @cindex frame pointer register
6148 @cindex standard registers
6149 @value{GDBN} has four ``standard'' register names that are available (in
6150 expressions) on most machines---whenever they do not conflict with an
6151 architecture's canonical mnemonics for registers. The register names
6152 @code{$pc} and @code{$sp} are used for the program counter register and
6153 the stack pointer. @code{$fp} is used for a register that contains a
6154 pointer to the current stack frame, and @code{$ps} is used for a
6155 register that contains the processor status. For example,
6156 you could print the program counter in hex with
6163 or print the instruction to be executed next with
6170 or add four to the stack pointer@footnote{This is a way of removing
6171 one word from the stack, on machines where stacks grow downward in
6172 memory (most machines, nowadays). This assumes that the innermost
6173 stack frame is selected; setting @code{$sp} is not allowed when other
6174 stack frames are selected. To pop entire frames off the stack,
6175 regardless of machine architecture, use @code{return};
6176 see @ref{Returning, ,Returning from a function}.} with
6182 Whenever possible, these four standard register names are available on
6183 your machine even though the machine has different canonical mnemonics,
6184 so long as there is no conflict. The @code{info registers} command
6185 shows the canonical names. For example, on the SPARC, @code{info
6186 registers} displays the processor status register as @code{$psr} but you
6187 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6188 is an alias for the @sc{eflags} register.
6190 @value{GDBN} always considers the contents of an ordinary register as an
6191 integer when the register is examined in this way. Some machines have
6192 special registers which can hold nothing but floating point; these
6193 registers are considered to have floating point values. There is no way
6194 to refer to the contents of an ordinary register as floating point value
6195 (although you can @emph{print} it as a floating point value with
6196 @samp{print/f $@var{regname}}).
6198 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6199 means that the data format in which the register contents are saved by
6200 the operating system is not the same one that your program normally
6201 sees. For example, the registers of the 68881 floating point
6202 coprocessor are always saved in ``extended'' (raw) format, but all C
6203 programs expect to work with ``double'' (virtual) format. In such
6204 cases, @value{GDBN} normally works with the virtual format only (the format
6205 that makes sense for your program), but the @code{info registers} command
6206 prints the data in both formats.
6208 Normally, register values are relative to the selected stack frame
6209 (@pxref{Selection, ,Selecting a frame}). This means that you get the
6210 value that the register would contain if all stack frames farther in
6211 were exited and their saved registers restored. In order to see the
6212 true contents of hardware registers, you must select the innermost
6213 frame (with @samp{frame 0}).
6215 However, @value{GDBN} must deduce where registers are saved, from the machine
6216 code generated by your compiler. If some registers are not saved, or if
6217 @value{GDBN} is unable to locate the saved registers, the selected stack
6218 frame makes no difference.
6220 @node Floating Point Hardware
6221 @section Floating point hardware
6222 @cindex floating point
6224 Depending on the configuration, @value{GDBN} may be able to give
6225 you more information about the status of the floating point hardware.
6230 Display hardware-dependent information about the floating
6231 point unit. The exact contents and layout vary depending on the
6232 floating point chip. Currently, @samp{info float} is supported on
6233 the ARM and x86 machines.
6237 @section Vector Unit
6240 Depending on the configuration, @value{GDBN} may be able to give you
6241 more information about the status of the vector unit.
6246 Display information about the vector unit. The exact contents and
6247 layout vary depending on the hardware.
6250 @node OS Information
6251 @section Operating system auxiliary information
6252 @cindex OS information
6254 @value{GDBN} provides interfaces to useful OS facilities that can help
6255 you debug your program.
6257 @cindex @code{ptrace} system call
6258 @cindex @code{struct user} contents
6259 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
6260 machines), it interfaces with the inferior via the @code{ptrace}
6261 system call. The operating system creates a special sata structure,
6262 called @code{struct user}, for this interface. You can use the
6263 command @code{info udot} to display the contents of this data
6269 Display the contents of the @code{struct user} maintained by the OS
6270 kernel for the program being debugged. @value{GDBN} displays the
6271 contents of @code{struct user} as a list of hex numbers, similar to
6272 the @code{examine} command.
6275 @cindex auxiliary vector
6276 @cindex vector, auxiliary
6277 Some operating systems supply an @dfn{auxiliary vector} to programs at
6278 startup. This is akin to the arguments and environment that you
6279 specify for a program, but contains a system-dependent variety of
6280 binary values that tell system libraries important details about the
6281 hardware, operating system, and process. Each value's purpose is
6282 identified by an integer tag; the meanings are well-known but system-specific.
6283 Depending on the configuration and operating system facilities,
6284 @value{GDBN} may be able to show you this information. For remote
6285 targets, this functionality may further depend on the remote stub's
6286 support of the @samp{qPart:auxv:read} packet, see @ref{Remote
6287 configuration, auxiliary vector}.
6292 Display the auxiliary vector of the inferior, which can be either a
6293 live process or a core dump file. @value{GDBN} prints each tag value
6294 numerically, and also shows names and text descriptions for recognized
6295 tags. Some values in the vector are numbers, some bit masks, and some
6296 pointers to strings or other data. @value{GDBN} displays each value in the
6297 most appropriate form for a recognized tag, and in hexadecimal for
6298 an unrecognized tag.
6302 @node Memory Region Attributes
6303 @section Memory region attributes
6304 @cindex memory region attributes
6306 @dfn{Memory region attributes} allow you to describe special handling
6307 required by regions of your target's memory. @value{GDBN} uses attributes
6308 to determine whether to allow certain types of memory accesses; whether to
6309 use specific width accesses; and whether to cache target memory.
6311 Defined memory regions can be individually enabled and disabled. When a
6312 memory region is disabled, @value{GDBN} uses the default attributes when
6313 accessing memory in that region. Similarly, if no memory regions have
6314 been defined, @value{GDBN} uses the default attributes when accessing
6317 When a memory region is defined, it is given a number to identify it;
6318 to enable, disable, or remove a memory region, you specify that number.
6322 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6323 Define a memory region bounded by @var{lower} and @var{upper} with
6324 attributes @var{attributes}@dots{}, and add it to the list of regions
6325 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
6326 case: it is treated as the the target's maximum memory address.
6327 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6330 @item delete mem @var{nums}@dots{}
6331 Remove memory regions @var{nums}@dots{} from the list of regions
6332 monitored by @value{GDBN}.
6335 @item disable mem @var{nums}@dots{}
6336 Disable monitoring of memory regions @var{nums}@dots{}.
6337 A disabled memory region is not forgotten.
6338 It may be enabled again later.
6341 @item enable mem @var{nums}@dots{}
6342 Enable monitoring of memory regions @var{nums}@dots{}.
6346 Print a table of all defined memory regions, with the following columns
6350 @item Memory Region Number
6351 @item Enabled or Disabled.
6352 Enabled memory regions are marked with @samp{y}.
6353 Disabled memory regions are marked with @samp{n}.
6356 The address defining the inclusive lower bound of the memory region.
6359 The address defining the exclusive upper bound of the memory region.
6362 The list of attributes set for this memory region.
6367 @subsection Attributes
6369 @subsubsection Memory Access Mode
6370 The access mode attributes set whether @value{GDBN} may make read or
6371 write accesses to a memory region.
6373 While these attributes prevent @value{GDBN} from performing invalid
6374 memory accesses, they do nothing to prevent the target system, I/O DMA,
6375 etc. from accessing memory.
6379 Memory is read only.
6381 Memory is write only.
6383 Memory is read/write. This is the default.
6386 @subsubsection Memory Access Size
6387 The acccess size attributes tells @value{GDBN} to use specific sized
6388 accesses in the memory region. Often memory mapped device registers
6389 require specific sized accesses. If no access size attribute is
6390 specified, @value{GDBN} may use accesses of any size.
6394 Use 8 bit memory accesses.
6396 Use 16 bit memory accesses.
6398 Use 32 bit memory accesses.
6400 Use 64 bit memory accesses.
6403 @c @subsubsection Hardware/Software Breakpoints
6404 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6405 @c will use hardware or software breakpoints for the internal breakpoints
6406 @c used by the step, next, finish, until, etc. commands.
6410 @c Always use hardware breakpoints
6411 @c @item swbreak (default)
6414 @subsubsection Data Cache
6415 The data cache attributes set whether @value{GDBN} will cache target
6416 memory. While this generally improves performance by reducing debug
6417 protocol overhead, it can lead to incorrect results because @value{GDBN}
6418 does not know about volatile variables or memory mapped device
6423 Enable @value{GDBN} to cache target memory.
6425 Disable @value{GDBN} from caching target memory. This is the default.
6428 @c @subsubsection Memory Write Verification
6429 @c The memory write verification attributes set whether @value{GDBN}
6430 @c will re-reads data after each write to verify the write was successful.
6434 @c @item noverify (default)
6437 @node Dump/Restore Files
6438 @section Copy between memory and a file
6439 @cindex dump/restore files
6440 @cindex append data to a file
6441 @cindex dump data to a file
6442 @cindex restore data from a file
6444 You can use the commands @code{dump}, @code{append}, and
6445 @code{restore} to copy data between target memory and a file. The
6446 @code{dump} and @code{append} commands write data to a file, and the
6447 @code{restore} command reads data from a file back into the inferior's
6448 memory. Files may be in binary, Motorola S-record, Intel hex, or
6449 Tektronix Hex format; however, @value{GDBN} can only append to binary
6455 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6456 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6457 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6458 or the value of @var{expr}, to @var{filename} in the given format.
6460 The @var{format} parameter may be any one of:
6467 Motorola S-record format.
6469 Tektronix Hex format.
6472 @value{GDBN} uses the same definitions of these formats as the
6473 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
6474 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
6478 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6479 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
6480 Append the contents of memory from @var{start_addr} to @var{end_addr},
6481 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
6482 (@value{GDBN} can only append data to files in raw binary form.)
6485 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
6486 Restore the contents of file @var{filename} into memory. The
6487 @code{restore} command can automatically recognize any known @sc{bfd}
6488 file format, except for raw binary. To restore a raw binary file you
6489 must specify the optional keyword @code{binary} after the filename.
6491 If @var{bias} is non-zero, its value will be added to the addresses
6492 contained in the file. Binary files always start at address zero, so
6493 they will be restored at address @var{bias}. Other bfd files have
6494 a built-in location; they will be restored at offset @var{bias}
6497 If @var{start} and/or @var{end} are non-zero, then only data between
6498 file offset @var{start} and file offset @var{end} will be restored.
6499 These offsets are relative to the addresses in the file, before
6500 the @var{bias} argument is applied.
6504 @node Core File Generation
6505 @section How to Produce a Core File from Your Program
6506 @cindex dump core from inferior
6508 A @dfn{core file} or @dfn{core dump} is a file that records the memory
6509 image of a running process and its process status (register values
6510 etc.). Its primary use is post-mortem debugging of a program that
6511 crashed while it ran outside a debugger. A program that crashes
6512 automatically produces a core file, unless this feature is disabled by
6513 the user. @xref{Files}, for information on invoking @value{GDBN} in
6514 the post-mortem debugging mode.
6516 Occasionally, you may wish to produce a core file of the program you
6517 are debugging in order to preserve a snapshot of its state.
6518 @value{GDBN} has a special command for that.
6522 @kindex generate-core-file
6523 @item generate-core-file [@var{file}]
6524 @itemx gcore [@var{file}]
6525 Produce a core dump of the inferior process. The optional argument
6526 @var{file} specifies the file name where to put the core dump. If not
6527 specified, the file name defaults to @file{core.@var{pid}}, where
6528 @var{pid} is the inferior process ID.
6530 Note that this command is implemented only for some systems (as of
6531 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
6534 @node Character Sets
6535 @section Character Sets
6536 @cindex character sets
6538 @cindex translating between character sets
6539 @cindex host character set
6540 @cindex target character set
6542 If the program you are debugging uses a different character set to
6543 represent characters and strings than the one @value{GDBN} uses itself,
6544 @value{GDBN} can automatically translate between the character sets for
6545 you. The character set @value{GDBN} uses we call the @dfn{host
6546 character set}; the one the inferior program uses we call the
6547 @dfn{target character set}.
6549 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
6550 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
6551 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
6552 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
6553 then the host character set is Latin-1, and the target character set is
6554 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
6555 target-charset EBCDIC-US}, then @value{GDBN} translates between
6556 @sc{ebcdic} and Latin 1 as you print character or string values, or use
6557 character and string literals in expressions.
6559 @value{GDBN} has no way to automatically recognize which character set
6560 the inferior program uses; you must tell it, using the @code{set
6561 target-charset} command, described below.
6563 Here are the commands for controlling @value{GDBN}'s character set
6567 @item set target-charset @var{charset}
6568 @kindex set target-charset
6569 Set the current target character set to @var{charset}. We list the
6570 character set names @value{GDBN} recognizes below, but if you type
6571 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6572 list the target character sets it supports.
6576 @item set host-charset @var{charset}
6577 @kindex set host-charset
6578 Set the current host character set to @var{charset}.
6580 By default, @value{GDBN} uses a host character set appropriate to the
6581 system it is running on; you can override that default using the
6582 @code{set host-charset} command.
6584 @value{GDBN} can only use certain character sets as its host character
6585 set. We list the character set names @value{GDBN} recognizes below, and
6586 indicate which can be host character sets, but if you type
6587 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6588 list the host character sets it supports.
6590 @item set charset @var{charset}
6592 Set the current host and target character sets to @var{charset}. As
6593 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
6594 @value{GDBN} will list the name of the character sets that can be used
6595 for both host and target.
6599 @kindex show charset
6600 Show the names of the current host and target charsets.
6602 @itemx show host-charset
6603 @kindex show host-charset
6604 Show the name of the current host charset.
6606 @itemx show target-charset
6607 @kindex show target-charset
6608 Show the name of the current target charset.
6612 @value{GDBN} currently includes support for the following character
6618 @cindex ASCII character set
6619 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6623 @cindex ISO 8859-1 character set
6624 @cindex ISO Latin 1 character set
6625 The ISO Latin 1 character set. This extends @sc{ascii} with accented
6626 characters needed for French, German, and Spanish. @value{GDBN} can use
6627 this as its host character set.
6631 @cindex EBCDIC character set
6632 @cindex IBM1047 character set
6633 Variants of the @sc{ebcdic} character set, used on some of IBM's
6634 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6635 @value{GDBN} cannot use these as its host character set.
6639 Note that these are all single-byte character sets. More work inside
6640 GDB is needed to support multi-byte or variable-width character
6641 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6643 Here is an example of @value{GDBN}'s character set support in action.
6644 Assume that the following source code has been placed in the file
6645 @file{charset-test.c}:
6651 = @{72, 101, 108, 108, 111, 44, 32, 119,
6652 111, 114, 108, 100, 33, 10, 0@};
6653 char ibm1047_hello[]
6654 = @{200, 133, 147, 147, 150, 107, 64, 166,
6655 150, 153, 147, 132, 90, 37, 0@};
6659 printf ("Hello, world!\n");
6663 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6664 containing the string @samp{Hello, world!} followed by a newline,
6665 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6667 We compile the program, and invoke the debugger on it:
6670 $ gcc -g charset-test.c -o charset-test
6671 $ gdb -nw charset-test
6672 GNU gdb 2001-12-19-cvs
6673 Copyright 2001 Free Software Foundation, Inc.
6678 We can use the @code{show charset} command to see what character sets
6679 @value{GDBN} is currently using to interpret and display characters and
6683 (@value{GDBP}) show charset
6684 The current host and target character set is `ISO-8859-1'.
6688 For the sake of printing this manual, let's use @sc{ascii} as our
6689 initial character set:
6691 (@value{GDBP}) set charset ASCII
6692 (@value{GDBP}) show charset
6693 The current host and target character set is `ASCII'.
6697 Let's assume that @sc{ascii} is indeed the correct character set for our
6698 host system --- in other words, let's assume that if @value{GDBN} prints
6699 characters using the @sc{ascii} character set, our terminal will display
6700 them properly. Since our current target character set is also
6701 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
6704 (@value{GDBP}) print ascii_hello
6705 $1 = 0x401698 "Hello, world!\n"
6706 (@value{GDBP}) print ascii_hello[0]
6711 @value{GDBN} uses the target character set for character and string
6712 literals you use in expressions:
6715 (@value{GDBP}) print '+'
6720 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
6723 @value{GDBN} relies on the user to tell it which character set the
6724 target program uses. If we print @code{ibm1047_hello} while our target
6725 character set is still @sc{ascii}, we get jibberish:
6728 (@value{GDBP}) print ibm1047_hello
6729 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
6730 (@value{GDBP}) print ibm1047_hello[0]
6735 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
6736 @value{GDBN} tells us the character sets it supports:
6739 (@value{GDBP}) set target-charset
6740 ASCII EBCDIC-US IBM1047 ISO-8859-1
6741 (@value{GDBP}) set target-charset
6744 We can select @sc{ibm1047} as our target character set, and examine the
6745 program's strings again. Now the @sc{ascii} string is wrong, but
6746 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
6747 target character set, @sc{ibm1047}, to the host character set,
6748 @sc{ascii}, and they display correctly:
6751 (@value{GDBP}) set target-charset IBM1047
6752 (@value{GDBP}) show charset
6753 The current host character set is `ASCII'.
6754 The current target character set is `IBM1047'.
6755 (@value{GDBP}) print ascii_hello
6756 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
6757 (@value{GDBP}) print ascii_hello[0]
6759 (@value{GDBP}) print ibm1047_hello
6760 $8 = 0x4016a8 "Hello, world!\n"
6761 (@value{GDBP}) print ibm1047_hello[0]
6766 As above, @value{GDBN} uses the target character set for character and
6767 string literals you use in expressions:
6770 (@value{GDBP}) print '+'
6775 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
6778 @node Caching Remote Data
6779 @section Caching Data of Remote Targets
6780 @cindex caching data of remote targets
6782 @value{GDBN} can cache data exchanged between the debugger and a
6783 remote target (@pxref{Remote}). Such caching generally improves
6784 performance, because it reduces the overhead of the remote protocol by
6785 bundling memory reads and writes into large chunks. Unfortunately,
6786 @value{GDBN} does not currently know anything about volatile
6787 registers, and thus data caching will produce incorrect results when
6788 volatile registers are in use.
6791 @kindex set remotecache
6792 @item set remotecache on
6793 @itemx set remotecache off
6794 Set caching state for remote targets. When @code{ON}, use data
6795 caching. By default, this option is @code{OFF}.
6797 @kindex show remotecache
6798 @item show remotecache
6799 Show the current state of data caching for remote targets.
6803 Print the information about the data cache performance. The
6804 information displayed includes: the dcache width and depth; and for
6805 each cache line, how many times it was referenced, and its data and
6806 state (dirty, bad, ok, etc.). This command is useful for debugging
6807 the data cache operation.
6812 @chapter C Preprocessor Macros
6814 Some languages, such as C and C@t{++}, provide a way to define and invoke
6815 ``preprocessor macros'' which expand into strings of tokens.
6816 @value{GDBN} can evaluate expressions containing macro invocations, show
6817 the result of macro expansion, and show a macro's definition, including
6818 where it was defined.
6820 You may need to compile your program specially to provide @value{GDBN}
6821 with information about preprocessor macros. Most compilers do not
6822 include macros in their debugging information, even when you compile
6823 with the @option{-g} flag. @xref{Compilation}.
6825 A program may define a macro at one point, remove that definition later,
6826 and then provide a different definition after that. Thus, at different
6827 points in the program, a macro may have different definitions, or have
6828 no definition at all. If there is a current stack frame, @value{GDBN}
6829 uses the macros in scope at that frame's source code line. Otherwise,
6830 @value{GDBN} uses the macros in scope at the current listing location;
6833 At the moment, @value{GDBN} does not support the @code{##}
6834 token-splicing operator, the @code{#} stringification operator, or
6835 variable-arity macros.
6837 Whenever @value{GDBN} evaluates an expression, it always expands any
6838 macro invocations present in the expression. @value{GDBN} also provides
6839 the following commands for working with macros explicitly.
6843 @kindex macro expand
6844 @cindex macro expansion, showing the results of preprocessor
6845 @cindex preprocessor macro expansion, showing the results of
6846 @cindex expanding preprocessor macros
6847 @item macro expand @var{expression}
6848 @itemx macro exp @var{expression}
6849 Show the results of expanding all preprocessor macro invocations in
6850 @var{expression}. Since @value{GDBN} simply expands macros, but does
6851 not parse the result, @var{expression} need not be a valid expression;
6852 it can be any string of tokens.
6855 @item macro expand-once @var{expression}
6856 @itemx macro exp1 @var{expression}
6857 @cindex expand macro once
6858 @i{(This command is not yet implemented.)} Show the results of
6859 expanding those preprocessor macro invocations that appear explicitly in
6860 @var{expression}. Macro invocations appearing in that expansion are
6861 left unchanged. This command allows you to see the effect of a
6862 particular macro more clearly, without being confused by further
6863 expansions. Since @value{GDBN} simply expands macros, but does not
6864 parse the result, @var{expression} need not be a valid expression; it
6865 can be any string of tokens.
6868 @cindex macro definition, showing
6869 @cindex definition, showing a macro's
6870 @item info macro @var{macro}
6871 Show the definition of the macro named @var{macro}, and describe the
6872 source location where that definition was established.
6874 @kindex macro define
6875 @cindex user-defined macros
6876 @cindex defining macros interactively
6877 @cindex macros, user-defined
6878 @item macro define @var{macro} @var{replacement-list}
6879 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
6880 @i{(This command is not yet implemented.)} Introduce a definition for a
6881 preprocessor macro named @var{macro}, invocations of which are replaced
6882 by the tokens given in @var{replacement-list}. The first form of this
6883 command defines an ``object-like'' macro, which takes no arguments; the
6884 second form defines a ``function-like'' macro, which takes the arguments
6885 given in @var{arglist}.
6887 A definition introduced by this command is in scope in every expression
6888 evaluated in @value{GDBN}, until it is removed with the @command{macro
6889 undef} command, described below. The definition overrides all
6890 definitions for @var{macro} present in the program being debugged, as
6891 well as any previous user-supplied definition.
6894 @item macro undef @var{macro}
6895 @i{(This command is not yet implemented.)} Remove any user-supplied
6896 definition for the macro named @var{macro}. This command only affects
6897 definitions provided with the @command{macro define} command, described
6898 above; it cannot remove definitions present in the program being
6903 @i{(This command is not yet implemented.)} List all the macros
6904 defined using the @code{macro define} command.
6907 @cindex macros, example of debugging with
6908 Here is a transcript showing the above commands in action. First, we
6909 show our source files:
6917 #define ADD(x) (M + x)
6922 printf ("Hello, world!\n");
6924 printf ("We're so creative.\n");
6926 printf ("Goodbye, world!\n");
6933 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
6934 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
6935 compiler includes information about preprocessor macros in the debugging
6939 $ gcc -gdwarf-2 -g3 sample.c -o sample
6943 Now, we start @value{GDBN} on our sample program:
6947 GNU gdb 2002-05-06-cvs
6948 Copyright 2002 Free Software Foundation, Inc.
6949 GDB is free software, @dots{}
6953 We can expand macros and examine their definitions, even when the
6954 program is not running. @value{GDBN} uses the current listing position
6955 to decide which macro definitions are in scope:
6958 (@value{GDBP}) list main
6961 5 #define ADD(x) (M + x)
6966 10 printf ("Hello, world!\n");
6968 12 printf ("We're so creative.\n");
6969 (@value{GDBP}) info macro ADD
6970 Defined at /home/jimb/gdb/macros/play/sample.c:5
6971 #define ADD(x) (M + x)
6972 (@value{GDBP}) info macro Q
6973 Defined at /home/jimb/gdb/macros/play/sample.h:1
6974 included at /home/jimb/gdb/macros/play/sample.c:2
6976 (@value{GDBP}) macro expand ADD(1)
6977 expands to: (42 + 1)
6978 (@value{GDBP}) macro expand-once ADD(1)
6979 expands to: once (M + 1)
6983 In the example above, note that @command{macro expand-once} expands only
6984 the macro invocation explicit in the original text --- the invocation of
6985 @code{ADD} --- but does not expand the invocation of the macro @code{M},
6986 which was introduced by @code{ADD}.
6988 Once the program is running, GDB uses the macro definitions in force at
6989 the source line of the current stack frame:
6992 (@value{GDBP}) break main
6993 Breakpoint 1 at 0x8048370: file sample.c, line 10.
6995 Starting program: /home/jimb/gdb/macros/play/sample
6997 Breakpoint 1, main () at sample.c:10
6998 10 printf ("Hello, world!\n");
7002 At line 10, the definition of the macro @code{N} at line 9 is in force:
7005 (@value{GDBP}) info macro N
7006 Defined at /home/jimb/gdb/macros/play/sample.c:9
7008 (@value{GDBP}) macro expand N Q M
7010 (@value{GDBP}) print N Q M
7015 As we step over directives that remove @code{N}'s definition, and then
7016 give it a new definition, @value{GDBN} finds the definition (or lack
7017 thereof) in force at each point:
7022 12 printf ("We're so creative.\n");
7023 (@value{GDBP}) info macro N
7024 The symbol `N' has no definition as a C/C++ preprocessor macro
7025 at /home/jimb/gdb/macros/play/sample.c:12
7028 14 printf ("Goodbye, world!\n");
7029 (@value{GDBP}) info macro N
7030 Defined at /home/jimb/gdb/macros/play/sample.c:13
7032 (@value{GDBP}) macro expand N Q M
7033 expands to: 1729 < 42
7034 (@value{GDBP}) print N Q M
7041 @chapter Tracepoints
7042 @c This chapter is based on the documentation written by Michael
7043 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
7046 In some applications, it is not feasible for the debugger to interrupt
7047 the program's execution long enough for the developer to learn
7048 anything helpful about its behavior. If the program's correctness
7049 depends on its real-time behavior, delays introduced by a debugger
7050 might cause the program to change its behavior drastically, or perhaps
7051 fail, even when the code itself is correct. It is useful to be able
7052 to observe the program's behavior without interrupting it.
7054 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
7055 specify locations in the program, called @dfn{tracepoints}, and
7056 arbitrary expressions to evaluate when those tracepoints are reached.
7057 Later, using the @code{tfind} command, you can examine the values
7058 those expressions had when the program hit the tracepoints. The
7059 expressions may also denote objects in memory---structures or arrays,
7060 for example---whose values @value{GDBN} should record; while visiting
7061 a particular tracepoint, you may inspect those objects as if they were
7062 in memory at that moment. However, because @value{GDBN} records these
7063 values without interacting with you, it can do so quickly and
7064 unobtrusively, hopefully not disturbing the program's behavior.
7066 The tracepoint facility is currently available only for remote
7067 targets. @xref{Targets}. In addition, your remote target must know how
7068 to collect trace data. This functionality is implemented in the remote
7069 stub; however, none of the stubs distributed with @value{GDBN} support
7070 tracepoints as of this writing.
7072 This chapter describes the tracepoint commands and features.
7076 * Analyze Collected Data::
7077 * Tracepoint Variables::
7080 @node Set Tracepoints
7081 @section Commands to Set Tracepoints
7083 Before running such a @dfn{trace experiment}, an arbitrary number of
7084 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
7085 tracepoint has a number assigned to it by @value{GDBN}. Like with
7086 breakpoints, tracepoint numbers are successive integers starting from
7087 one. Many of the commands associated with tracepoints take the
7088 tracepoint number as their argument, to identify which tracepoint to
7091 For each tracepoint, you can specify, in advance, some arbitrary set
7092 of data that you want the target to collect in the trace buffer when
7093 it hits that tracepoint. The collected data can include registers,
7094 local variables, or global data. Later, you can use @value{GDBN}
7095 commands to examine the values these data had at the time the
7098 This section describes commands to set tracepoints and associated
7099 conditions and actions.
7102 * Create and Delete Tracepoints::
7103 * Enable and Disable Tracepoints::
7104 * Tracepoint Passcounts::
7105 * Tracepoint Actions::
7106 * Listing Tracepoints::
7107 * Starting and Stopping Trace Experiment::
7110 @node Create and Delete Tracepoints
7111 @subsection Create and Delete Tracepoints
7114 @cindex set tracepoint
7117 The @code{trace} command is very similar to the @code{break} command.
7118 Its argument can be a source line, a function name, or an address in
7119 the target program. @xref{Set Breaks}. The @code{trace} command
7120 defines a tracepoint, which is a point in the target program where the
7121 debugger will briefly stop, collect some data, and then allow the
7122 program to continue. Setting a tracepoint or changing its commands
7123 doesn't take effect until the next @code{tstart} command; thus, you
7124 cannot change the tracepoint attributes once a trace experiment is
7127 Here are some examples of using the @code{trace} command:
7130 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
7132 (@value{GDBP}) @b{trace +2} // 2 lines forward
7134 (@value{GDBP}) @b{trace my_function} // first source line of function
7136 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
7138 (@value{GDBP}) @b{trace *0x2117c4} // an address
7142 You can abbreviate @code{trace} as @code{tr}.
7145 @cindex last tracepoint number
7146 @cindex recent tracepoint number
7147 @cindex tracepoint number
7148 The convenience variable @code{$tpnum} records the tracepoint number
7149 of the most recently set tracepoint.
7151 @kindex delete tracepoint
7152 @cindex tracepoint deletion
7153 @item delete tracepoint @r{[}@var{num}@r{]}
7154 Permanently delete one or more tracepoints. With no argument, the
7155 default is to delete all tracepoints.
7160 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
7162 (@value{GDBP}) @b{delete trace} // remove all tracepoints
7166 You can abbreviate this command as @code{del tr}.
7169 @node Enable and Disable Tracepoints
7170 @subsection Enable and Disable Tracepoints
7173 @kindex disable tracepoint
7174 @item disable tracepoint @r{[}@var{num}@r{]}
7175 Disable tracepoint @var{num}, or all tracepoints if no argument
7176 @var{num} is given. A disabled tracepoint will have no effect during
7177 the next trace experiment, but it is not forgotten. You can re-enable
7178 a disabled tracepoint using the @code{enable tracepoint} command.
7180 @kindex enable tracepoint
7181 @item enable tracepoint @r{[}@var{num}@r{]}
7182 Enable tracepoint @var{num}, or all tracepoints. The enabled
7183 tracepoints will become effective the next time a trace experiment is
7187 @node Tracepoint Passcounts
7188 @subsection Tracepoint Passcounts
7192 @cindex tracepoint pass count
7193 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
7194 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
7195 automatically stop a trace experiment. If a tracepoint's passcount is
7196 @var{n}, then the trace experiment will be automatically stopped on
7197 the @var{n}'th time that tracepoint is hit. If the tracepoint number
7198 @var{num} is not specified, the @code{passcount} command sets the
7199 passcount of the most recently defined tracepoint. If no passcount is
7200 given, the trace experiment will run until stopped explicitly by the
7206 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
7207 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
7209 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
7210 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
7211 (@value{GDBP}) @b{trace foo}
7212 (@value{GDBP}) @b{pass 3}
7213 (@value{GDBP}) @b{trace bar}
7214 (@value{GDBP}) @b{pass 2}
7215 (@value{GDBP}) @b{trace baz}
7216 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
7217 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
7218 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
7219 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
7223 @node Tracepoint Actions
7224 @subsection Tracepoint Action Lists
7228 @cindex tracepoint actions
7229 @item actions @r{[}@var{num}@r{]}
7230 This command will prompt for a list of actions to be taken when the
7231 tracepoint is hit. If the tracepoint number @var{num} is not
7232 specified, this command sets the actions for the one that was most
7233 recently defined (so that you can define a tracepoint and then say
7234 @code{actions} without bothering about its number). You specify the
7235 actions themselves on the following lines, one action at a time, and
7236 terminate the actions list with a line containing just @code{end}. So
7237 far, the only defined actions are @code{collect} and
7238 @code{while-stepping}.
7240 @cindex remove actions from a tracepoint
7241 To remove all actions from a tracepoint, type @samp{actions @var{num}}
7242 and follow it immediately with @samp{end}.
7245 (@value{GDBP}) @b{collect @var{data}} // collect some data
7247 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
7249 (@value{GDBP}) @b{end} // signals the end of actions.
7252 In the following example, the action list begins with @code{collect}
7253 commands indicating the things to be collected when the tracepoint is
7254 hit. Then, in order to single-step and collect additional data
7255 following the tracepoint, a @code{while-stepping} command is used,
7256 followed by the list of things to be collected while stepping. The
7257 @code{while-stepping} command is terminated by its own separate
7258 @code{end} command. Lastly, the action list is terminated by an
7262 (@value{GDBP}) @b{trace foo}
7263 (@value{GDBP}) @b{actions}
7264 Enter actions for tracepoint 1, one per line:
7273 @kindex collect @r{(tracepoints)}
7274 @item collect @var{expr1}, @var{expr2}, @dots{}
7275 Collect values of the given expressions when the tracepoint is hit.
7276 This command accepts a comma-separated list of any valid expressions.
7277 In addition to global, static, or local variables, the following
7278 special arguments are supported:
7282 collect all registers
7285 collect all function arguments
7288 collect all local variables.
7291 You can give several consecutive @code{collect} commands, each one
7292 with a single argument, or one @code{collect} command with several
7293 arguments separated by commas: the effect is the same.
7295 The command @code{info scope} (@pxref{Symbols, info scope}) is
7296 particularly useful for figuring out what data to collect.
7298 @kindex while-stepping @r{(tracepoints)}
7299 @item while-stepping @var{n}
7300 Perform @var{n} single-step traces after the tracepoint, collecting
7301 new data at each step. The @code{while-stepping} command is
7302 followed by the list of what to collect while stepping (followed by
7303 its own @code{end} command):
7307 > collect $regs, myglobal
7313 You may abbreviate @code{while-stepping} as @code{ws} or
7317 @node Listing Tracepoints
7318 @subsection Listing Tracepoints
7321 @kindex info tracepoints
7323 @cindex information about tracepoints
7324 @item info tracepoints @r{[}@var{num}@r{]}
7325 Display information about the tracepoint @var{num}. If you don't specify
7326 a tracepoint number, displays information about all the tracepoints
7327 defined so far. For each tracepoint, the following information is
7334 whether it is enabled or disabled
7338 its passcount as given by the @code{passcount @var{n}} command
7340 its step count as given by the @code{while-stepping @var{n}} command
7342 where in the source files is the tracepoint set
7344 its action list as given by the @code{actions} command
7348 (@value{GDBP}) @b{info trace}
7349 Num Enb Address PassC StepC What
7350 1 y 0x002117c4 0 0 <gdb_asm>
7351 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
7352 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
7357 This command can be abbreviated @code{info tp}.
7360 @node Starting and Stopping Trace Experiment
7361 @subsection Starting and Stopping Trace Experiment
7365 @cindex start a new trace experiment
7366 @cindex collected data discarded
7368 This command takes no arguments. It starts the trace experiment, and
7369 begins collecting data. This has the side effect of discarding all
7370 the data collected in the trace buffer during the previous trace
7374 @cindex stop a running trace experiment
7376 This command takes no arguments. It ends the trace experiment, and
7377 stops collecting data.
7379 @strong{Note}: a trace experiment and data collection may stop
7380 automatically if any tracepoint's passcount is reached
7381 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
7384 @cindex status of trace data collection
7385 @cindex trace experiment, status of
7387 This command displays the status of the current trace data
7391 Here is an example of the commands we described so far:
7394 (@value{GDBP}) @b{trace gdb_c_test}
7395 (@value{GDBP}) @b{actions}
7396 Enter actions for tracepoint #1, one per line.
7397 > collect $regs,$locals,$args
7402 (@value{GDBP}) @b{tstart}
7403 [time passes @dots{}]
7404 (@value{GDBP}) @b{tstop}
7408 @node Analyze Collected Data
7409 @section Using the collected data
7411 After the tracepoint experiment ends, you use @value{GDBN} commands
7412 for examining the trace data. The basic idea is that each tracepoint
7413 collects a trace @dfn{snapshot} every time it is hit and another
7414 snapshot every time it single-steps. All these snapshots are
7415 consecutively numbered from zero and go into a buffer, and you can
7416 examine them later. The way you examine them is to @dfn{focus} on a
7417 specific trace snapshot. When the remote stub is focused on a trace
7418 snapshot, it will respond to all @value{GDBN} requests for memory and
7419 registers by reading from the buffer which belongs to that snapshot,
7420 rather than from @emph{real} memory or registers of the program being
7421 debugged. This means that @strong{all} @value{GDBN} commands
7422 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
7423 behave as if we were currently debugging the program state as it was
7424 when the tracepoint occurred. Any requests for data that are not in
7425 the buffer will fail.
7428 * tfind:: How to select a trace snapshot
7429 * tdump:: How to display all data for a snapshot
7430 * save-tracepoints:: How to save tracepoints for a future run
7434 @subsection @code{tfind @var{n}}
7437 @cindex select trace snapshot
7438 @cindex find trace snapshot
7439 The basic command for selecting a trace snapshot from the buffer is
7440 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
7441 counting from zero. If no argument @var{n} is given, the next
7442 snapshot is selected.
7444 Here are the various forms of using the @code{tfind} command.
7448 Find the first snapshot in the buffer. This is a synonym for
7449 @code{tfind 0} (since 0 is the number of the first snapshot).
7452 Stop debugging trace snapshots, resume @emph{live} debugging.
7455 Same as @samp{tfind none}.
7458 No argument means find the next trace snapshot.
7461 Find the previous trace snapshot before the current one. This permits
7462 retracing earlier steps.
7464 @item tfind tracepoint @var{num}
7465 Find the next snapshot associated with tracepoint @var{num}. Search
7466 proceeds forward from the last examined trace snapshot. If no
7467 argument @var{num} is given, it means find the next snapshot collected
7468 for the same tracepoint as the current snapshot.
7470 @item tfind pc @var{addr}
7471 Find the next snapshot associated with the value @var{addr} of the
7472 program counter. Search proceeds forward from the last examined trace
7473 snapshot. If no argument @var{addr} is given, it means find the next
7474 snapshot with the same value of PC as the current snapshot.
7476 @item tfind outside @var{addr1}, @var{addr2}
7477 Find the next snapshot whose PC is outside the given range of
7480 @item tfind range @var{addr1}, @var{addr2}
7481 Find the next snapshot whose PC is between @var{addr1} and
7482 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
7484 @item tfind line @r{[}@var{file}:@r{]}@var{n}
7485 Find the next snapshot associated with the source line @var{n}. If
7486 the optional argument @var{file} is given, refer to line @var{n} in
7487 that source file. Search proceeds forward from the last examined
7488 trace snapshot. If no argument @var{n} is given, it means find the
7489 next line other than the one currently being examined; thus saying
7490 @code{tfind line} repeatedly can appear to have the same effect as
7491 stepping from line to line in a @emph{live} debugging session.
7494 The default arguments for the @code{tfind} commands are specifically
7495 designed to make it easy to scan through the trace buffer. For
7496 instance, @code{tfind} with no argument selects the next trace
7497 snapshot, and @code{tfind -} with no argument selects the previous
7498 trace snapshot. So, by giving one @code{tfind} command, and then
7499 simply hitting @key{RET} repeatedly you can examine all the trace
7500 snapshots in order. Or, by saying @code{tfind -} and then hitting
7501 @key{RET} repeatedly you can examine the snapshots in reverse order.
7502 The @code{tfind line} command with no argument selects the snapshot
7503 for the next source line executed. The @code{tfind pc} command with
7504 no argument selects the next snapshot with the same program counter
7505 (PC) as the current frame. The @code{tfind tracepoint} command with
7506 no argument selects the next trace snapshot collected by the same
7507 tracepoint as the current one.
7509 In addition to letting you scan through the trace buffer manually,
7510 these commands make it easy to construct @value{GDBN} scripts that
7511 scan through the trace buffer and print out whatever collected data
7512 you are interested in. Thus, if we want to examine the PC, FP, and SP
7513 registers from each trace frame in the buffer, we can say this:
7516 (@value{GDBP}) @b{tfind start}
7517 (@value{GDBP}) @b{while ($trace_frame != -1)}
7518 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
7519 $trace_frame, $pc, $sp, $fp
7523 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
7524 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
7525 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
7526 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
7527 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
7528 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
7529 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
7530 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
7531 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
7532 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
7533 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
7536 Or, if we want to examine the variable @code{X} at each source line in
7540 (@value{GDBP}) @b{tfind start}
7541 (@value{GDBP}) @b{while ($trace_frame != -1)}
7542 > printf "Frame %d, X == %d\n", $trace_frame, X
7552 @subsection @code{tdump}
7554 @cindex dump all data collected at tracepoint
7555 @cindex tracepoint data, display
7557 This command takes no arguments. It prints all the data collected at
7558 the current trace snapshot.
7561 (@value{GDBP}) @b{trace 444}
7562 (@value{GDBP}) @b{actions}
7563 Enter actions for tracepoint #2, one per line:
7564 > collect $regs, $locals, $args, gdb_long_test
7567 (@value{GDBP}) @b{tstart}
7569 (@value{GDBP}) @b{tfind line 444}
7570 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
7572 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
7574 (@value{GDBP}) @b{tdump}
7575 Data collected at tracepoint 2, trace frame 1:
7576 d0 0xc4aa0085 -995491707
7580 d4 0x71aea3d 119204413
7585 a1 0x3000668 50333288
7588 a4 0x3000698 50333336
7590 fp 0x30bf3c 0x30bf3c
7591 sp 0x30bf34 0x30bf34
7593 pc 0x20b2c8 0x20b2c8
7597 p = 0x20e5b4 "gdb-test"
7604 gdb_long_test = 17 '\021'
7609 @node save-tracepoints
7610 @subsection @code{save-tracepoints @var{filename}}
7611 @kindex save-tracepoints
7612 @cindex save tracepoints for future sessions
7614 This command saves all current tracepoint definitions together with
7615 their actions and passcounts, into a file @file{@var{filename}}
7616 suitable for use in a later debugging session. To read the saved
7617 tracepoint definitions, use the @code{source} command (@pxref{Command
7620 @node Tracepoint Variables
7621 @section Convenience Variables for Tracepoints
7622 @cindex tracepoint variables
7623 @cindex convenience variables for tracepoints
7626 @vindex $trace_frame
7627 @item (int) $trace_frame
7628 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
7629 snapshot is selected.
7632 @item (int) $tracepoint
7633 The tracepoint for the current trace snapshot.
7636 @item (int) $trace_line
7637 The line number for the current trace snapshot.
7640 @item (char []) $trace_file
7641 The source file for the current trace snapshot.
7644 @item (char []) $trace_func
7645 The name of the function containing @code{$tracepoint}.
7648 Note: @code{$trace_file} is not suitable for use in @code{printf},
7649 use @code{output} instead.
7651 Here's a simple example of using these convenience variables for
7652 stepping through all the trace snapshots and printing some of their
7656 (@value{GDBP}) @b{tfind start}
7658 (@value{GDBP}) @b{while $trace_frame != -1}
7659 > output $trace_file
7660 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7666 @chapter Debugging Programs That Use Overlays
7669 If your program is too large to fit completely in your target system's
7670 memory, you can sometimes use @dfn{overlays} to work around this
7671 problem. @value{GDBN} provides some support for debugging programs that
7675 * How Overlays Work:: A general explanation of overlays.
7676 * Overlay Commands:: Managing overlays in @value{GDBN}.
7677 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7678 mapped by asking the inferior.
7679 * Overlay Sample Program:: A sample program using overlays.
7682 @node How Overlays Work
7683 @section How Overlays Work
7684 @cindex mapped overlays
7685 @cindex unmapped overlays
7686 @cindex load address, overlay's
7687 @cindex mapped address
7688 @cindex overlay area
7690 Suppose you have a computer whose instruction address space is only 64
7691 kilobytes long, but which has much more memory which can be accessed by
7692 other means: special instructions, segment registers, or memory
7693 management hardware, for example. Suppose further that you want to
7694 adapt a program which is larger than 64 kilobytes to run on this system.
7696 One solution is to identify modules of your program which are relatively
7697 independent, and need not call each other directly; call these modules
7698 @dfn{overlays}. Separate the overlays from the main program, and place
7699 their machine code in the larger memory. Place your main program in
7700 instruction memory, but leave at least enough space there to hold the
7701 largest overlay as well.
7703 Now, to call a function located in an overlay, you must first copy that
7704 overlay's machine code from the large memory into the space set aside
7705 for it in the instruction memory, and then jump to its entry point
7708 @c NB: In the below the mapped area's size is greater or equal to the
7709 @c size of all overlays. This is intentional to remind the developer
7710 @c that overlays don't necessarily need to be the same size.
7714 Data Instruction Larger
7715 Address Space Address Space Address Space
7716 +-----------+ +-----------+ +-----------+
7718 +-----------+ +-----------+ +-----------+<-- overlay 1
7719 | program | | main | .----| overlay 1 | load address
7720 | variables | | program | | +-----------+
7721 | and heap | | | | | |
7722 +-----------+ | | | +-----------+<-- overlay 2
7723 | | +-----------+ | | | load address
7724 +-----------+ | | | .-| overlay 2 |
7726 mapped --->+-----------+ | | +-----------+
7728 | overlay | <-' | | |
7729 | area | <---' +-----------+<-- overlay 3
7730 | | <---. | | load address
7731 +-----------+ `--| overlay 3 |
7738 @anchor{A code overlay}A code overlay
7742 The diagram (@pxref{A code overlay}) shows a system with separate data
7743 and instruction address spaces. To map an overlay, the program copies
7744 its code from the larger address space to the instruction address space.
7745 Since the overlays shown here all use the same mapped address, only one
7746 may be mapped at a time. For a system with a single address space for
7747 data and instructions, the diagram would be similar, except that the
7748 program variables and heap would share an address space with the main
7749 program and the overlay area.
7751 An overlay loaded into instruction memory and ready for use is called a
7752 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
7753 instruction memory. An overlay not present (or only partially present)
7754 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
7755 is its address in the larger memory. The mapped address is also called
7756 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
7757 called the @dfn{load memory address}, or @dfn{LMA}.
7759 Unfortunately, overlays are not a completely transparent way to adapt a
7760 program to limited instruction memory. They introduce a new set of
7761 global constraints you must keep in mind as you design your program:
7766 Before calling or returning to a function in an overlay, your program
7767 must make sure that overlay is actually mapped. Otherwise, the call or
7768 return will transfer control to the right address, but in the wrong
7769 overlay, and your program will probably crash.
7772 If the process of mapping an overlay is expensive on your system, you
7773 will need to choose your overlays carefully to minimize their effect on
7774 your program's performance.
7777 The executable file you load onto your system must contain each
7778 overlay's instructions, appearing at the overlay's load address, not its
7779 mapped address. However, each overlay's instructions must be relocated
7780 and its symbols defined as if the overlay were at its mapped address.
7781 You can use GNU linker scripts to specify different load and relocation
7782 addresses for pieces of your program; see @ref{Overlay Description,,,
7783 ld.info, Using ld: the GNU linker}.
7786 The procedure for loading executable files onto your system must be able
7787 to load their contents into the larger address space as well as the
7788 instruction and data spaces.
7792 The overlay system described above is rather simple, and could be
7793 improved in many ways:
7798 If your system has suitable bank switch registers or memory management
7799 hardware, you could use those facilities to make an overlay's load area
7800 contents simply appear at their mapped address in instruction space.
7801 This would probably be faster than copying the overlay to its mapped
7802 area in the usual way.
7805 If your overlays are small enough, you could set aside more than one
7806 overlay area, and have more than one overlay mapped at a time.
7809 You can use overlays to manage data, as well as instructions. In
7810 general, data overlays are even less transparent to your design than
7811 code overlays: whereas code overlays only require care when you call or
7812 return to functions, data overlays require care every time you access
7813 the data. Also, if you change the contents of a data overlay, you
7814 must copy its contents back out to its load address before you can copy a
7815 different data overlay into the same mapped area.
7820 @node Overlay Commands
7821 @section Overlay Commands
7823 To use @value{GDBN}'s overlay support, each overlay in your program must
7824 correspond to a separate section of the executable file. The section's
7825 virtual memory address and load memory address must be the overlay's
7826 mapped and load addresses. Identifying overlays with sections allows
7827 @value{GDBN} to determine the appropriate address of a function or
7828 variable, depending on whether the overlay is mapped or not.
7830 @value{GDBN}'s overlay commands all start with the word @code{overlay};
7831 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
7836 Disable @value{GDBN}'s overlay support. When overlay support is
7837 disabled, @value{GDBN} assumes that all functions and variables are
7838 always present at their mapped addresses. By default, @value{GDBN}'s
7839 overlay support is disabled.
7841 @item overlay manual
7842 @cindex manual overlay debugging
7843 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
7844 relies on you to tell it which overlays are mapped, and which are not,
7845 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
7846 commands described below.
7848 @item overlay map-overlay @var{overlay}
7849 @itemx overlay map @var{overlay}
7850 @cindex map an overlay
7851 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
7852 be the name of the object file section containing the overlay. When an
7853 overlay is mapped, @value{GDBN} assumes it can find the overlay's
7854 functions and variables at their mapped addresses. @value{GDBN} assumes
7855 that any other overlays whose mapped ranges overlap that of
7856 @var{overlay} are now unmapped.
7858 @item overlay unmap-overlay @var{overlay}
7859 @itemx overlay unmap @var{overlay}
7860 @cindex unmap an overlay
7861 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
7862 must be the name of the object file section containing the overlay.
7863 When an overlay is unmapped, @value{GDBN} assumes it can find the
7864 overlay's functions and variables at their load addresses.
7867 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
7868 consults a data structure the overlay manager maintains in the inferior
7869 to see which overlays are mapped. For details, see @ref{Automatic
7872 @item overlay load-target
7874 @cindex reloading the overlay table
7875 Re-read the overlay table from the inferior. Normally, @value{GDBN}
7876 re-reads the table @value{GDBN} automatically each time the inferior
7877 stops, so this command should only be necessary if you have changed the
7878 overlay mapping yourself using @value{GDBN}. This command is only
7879 useful when using automatic overlay debugging.
7881 @item overlay list-overlays
7883 @cindex listing mapped overlays
7884 Display a list of the overlays currently mapped, along with their mapped
7885 addresses, load addresses, and sizes.
7889 Normally, when @value{GDBN} prints a code address, it includes the name
7890 of the function the address falls in:
7893 (@value{GDBP}) print main
7894 $3 = @{int ()@} 0x11a0 <main>
7897 When overlay debugging is enabled, @value{GDBN} recognizes code in
7898 unmapped overlays, and prints the names of unmapped functions with
7899 asterisks around them. For example, if @code{foo} is a function in an
7900 unmapped overlay, @value{GDBN} prints it this way:
7903 (@value{GDBP}) overlay list
7904 No sections are mapped.
7905 (@value{GDBP}) print foo
7906 $5 = @{int (int)@} 0x100000 <*foo*>
7909 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
7913 (@value{GDBP}) overlay list
7914 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
7915 mapped at 0x1016 - 0x104a
7916 (@value{GDBP}) print foo
7917 $6 = @{int (int)@} 0x1016 <foo>
7920 When overlay debugging is enabled, @value{GDBN} can find the correct
7921 address for functions and variables in an overlay, whether or not the
7922 overlay is mapped. This allows most @value{GDBN} commands, like
7923 @code{break} and @code{disassemble}, to work normally, even on unmapped
7924 code. However, @value{GDBN}'s breakpoint support has some limitations:
7928 @cindex breakpoints in overlays
7929 @cindex overlays, setting breakpoints in
7930 You can set breakpoints in functions in unmapped overlays, as long as
7931 @value{GDBN} can write to the overlay at its load address.
7933 @value{GDBN} can not set hardware or simulator-based breakpoints in
7934 unmapped overlays. However, if you set a breakpoint at the end of your
7935 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
7936 you are using manual overlay management), @value{GDBN} will re-set its
7937 breakpoints properly.
7941 @node Automatic Overlay Debugging
7942 @section Automatic Overlay Debugging
7943 @cindex automatic overlay debugging
7945 @value{GDBN} can automatically track which overlays are mapped and which
7946 are not, given some simple co-operation from the overlay manager in the
7947 inferior. If you enable automatic overlay debugging with the
7948 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
7949 looks in the inferior's memory for certain variables describing the
7950 current state of the overlays.
7952 Here are the variables your overlay manager must define to support
7953 @value{GDBN}'s automatic overlay debugging:
7957 @item @code{_ovly_table}:
7958 This variable must be an array of the following structures:
7963 /* The overlay's mapped address. */
7966 /* The size of the overlay, in bytes. */
7969 /* The overlay's load address. */
7972 /* Non-zero if the overlay is currently mapped;
7974 unsigned long mapped;
7978 @item @code{_novlys}:
7979 This variable must be a four-byte signed integer, holding the total
7980 number of elements in @code{_ovly_table}.
7984 To decide whether a particular overlay is mapped or not, @value{GDBN}
7985 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
7986 @code{lma} members equal the VMA and LMA of the overlay's section in the
7987 executable file. When @value{GDBN} finds a matching entry, it consults
7988 the entry's @code{mapped} member to determine whether the overlay is
7991 In addition, your overlay manager may define a function called
7992 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
7993 will silently set a breakpoint there. If the overlay manager then
7994 calls this function whenever it has changed the overlay table, this
7995 will enable @value{GDBN} to accurately keep track of which overlays
7996 are in program memory, and update any breakpoints that may be set
7997 in overlays. This will allow breakpoints to work even if the
7998 overlays are kept in ROM or other non-writable memory while they
7999 are not being executed.
8001 @node Overlay Sample Program
8002 @section Overlay Sample Program
8003 @cindex overlay example program
8005 When linking a program which uses overlays, you must place the overlays
8006 at their load addresses, while relocating them to run at their mapped
8007 addresses. To do this, you must write a linker script (@pxref{Overlay
8008 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
8009 since linker scripts are specific to a particular host system, target
8010 architecture, and target memory layout, this manual cannot provide
8011 portable sample code demonstrating @value{GDBN}'s overlay support.
8013 However, the @value{GDBN} source distribution does contain an overlaid
8014 program, with linker scripts for a few systems, as part of its test
8015 suite. The program consists of the following files from
8016 @file{gdb/testsuite/gdb.base}:
8020 The main program file.
8022 A simple overlay manager, used by @file{overlays.c}.
8027 Overlay modules, loaded and used by @file{overlays.c}.
8030 Linker scripts for linking the test program on the @code{d10v-elf}
8031 and @code{m32r-elf} targets.
8034 You can build the test program using the @code{d10v-elf} GCC
8035 cross-compiler like this:
8038 $ d10v-elf-gcc -g -c overlays.c
8039 $ d10v-elf-gcc -g -c ovlymgr.c
8040 $ d10v-elf-gcc -g -c foo.c
8041 $ d10v-elf-gcc -g -c bar.c
8042 $ d10v-elf-gcc -g -c baz.c
8043 $ d10v-elf-gcc -g -c grbx.c
8044 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
8045 baz.o grbx.o -Wl,-Td10v.ld -o overlays
8048 The build process is identical for any other architecture, except that
8049 you must substitute the appropriate compiler and linker script for the
8050 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
8054 @chapter Using @value{GDBN} with Different Languages
8057 Although programming languages generally have common aspects, they are
8058 rarely expressed in the same manner. For instance, in ANSI C,
8059 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
8060 Modula-2, it is accomplished by @code{p^}. Values can also be
8061 represented (and displayed) differently. Hex numbers in C appear as
8062 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
8064 @cindex working language
8065 Language-specific information is built into @value{GDBN} for some languages,
8066 allowing you to express operations like the above in your program's
8067 native language, and allowing @value{GDBN} to output values in a manner
8068 consistent with the syntax of your program's native language. The
8069 language you use to build expressions is called the @dfn{working
8073 * Setting:: Switching between source languages
8074 * Show:: Displaying the language
8075 * Checks:: Type and range checks
8076 * Supported languages:: Supported languages
8077 * Unsupported languages:: Unsupported languages
8081 @section Switching between source languages
8083 There are two ways to control the working language---either have @value{GDBN}
8084 set it automatically, or select it manually yourself. You can use the
8085 @code{set language} command for either purpose. On startup, @value{GDBN}
8086 defaults to setting the language automatically. The working language is
8087 used to determine how expressions you type are interpreted, how values
8090 In addition to the working language, every source file that
8091 @value{GDBN} knows about has its own working language. For some object
8092 file formats, the compiler might indicate which language a particular
8093 source file is in. However, most of the time @value{GDBN} infers the
8094 language from the name of the file. The language of a source file
8095 controls whether C@t{++} names are demangled---this way @code{backtrace} can
8096 show each frame appropriately for its own language. There is no way to
8097 set the language of a source file from within @value{GDBN}, but you can
8098 set the language associated with a filename extension. @xref{Show, ,
8099 Displaying the language}.
8101 This is most commonly a problem when you use a program, such
8102 as @code{cfront} or @code{f2c}, that generates C but is written in
8103 another language. In that case, make the
8104 program use @code{#line} directives in its C output; that way
8105 @value{GDBN} will know the correct language of the source code of the original
8106 program, and will display that source code, not the generated C code.
8109 * Filenames:: Filename extensions and languages.
8110 * Manually:: Setting the working language manually
8111 * Automatically:: Having @value{GDBN} infer the source language
8115 @subsection List of filename extensions and languages
8117 If a source file name ends in one of the following extensions, then
8118 @value{GDBN} infers that its language is the one indicated.
8139 Objective-C source file
8146 Modula-2 source file
8150 Assembler source file. This actually behaves almost like C, but
8151 @value{GDBN} does not skip over function prologues when stepping.
8154 In addition, you may set the language associated with a filename
8155 extension. @xref{Show, , Displaying the language}.
8158 @subsection Setting the working language
8160 If you allow @value{GDBN} to set the language automatically,
8161 expressions are interpreted the same way in your debugging session and
8164 @kindex set language
8165 If you wish, you may set the language manually. To do this, issue the
8166 command @samp{set language @var{lang}}, where @var{lang} is the name of
8168 @code{c} or @code{modula-2}.
8169 For a list of the supported languages, type @samp{set language}.
8171 Setting the language manually prevents @value{GDBN} from updating the working
8172 language automatically. This can lead to confusion if you try
8173 to debug a program when the working language is not the same as the
8174 source language, when an expression is acceptable to both
8175 languages---but means different things. For instance, if the current
8176 source file were written in C, and @value{GDBN} was parsing Modula-2, a
8184 might not have the effect you intended. In C, this means to add
8185 @code{b} and @code{c} and place the result in @code{a}. The result
8186 printed would be the value of @code{a}. In Modula-2, this means to compare
8187 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
8190 @subsection Having @value{GDBN} infer the source language
8192 To have @value{GDBN} set the working language automatically, use
8193 @samp{set language local} or @samp{set language auto}. @value{GDBN}
8194 then infers the working language. That is, when your program stops in a
8195 frame (usually by encountering a breakpoint), @value{GDBN} sets the
8196 working language to the language recorded for the function in that
8197 frame. If the language for a frame is unknown (that is, if the function
8198 or block corresponding to the frame was defined in a source file that
8199 does not have a recognized extension), the current working language is
8200 not changed, and @value{GDBN} issues a warning.
8202 This may not seem necessary for most programs, which are written
8203 entirely in one source language. However, program modules and libraries
8204 written in one source language can be used by a main program written in
8205 a different source language. Using @samp{set language auto} in this
8206 case frees you from having to set the working language manually.
8209 @section Displaying the language
8211 The following commands help you find out which language is the
8212 working language, and also what language source files were written in.
8216 @kindex show language
8217 Display the current working language. This is the
8218 language you can use with commands such as @code{print} to
8219 build and compute expressions that may involve variables in your program.
8222 @kindex info frame@r{, show the source language}
8223 Display the source language for this frame. This language becomes the
8224 working language if you use an identifier from this frame.
8225 @xref{Frame Info, ,Information about a frame}, to identify the other
8226 information listed here.
8229 @kindex info source@r{, show the source language}
8230 Display the source language of this source file.
8231 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
8232 information listed here.
8235 In unusual circumstances, you may have source files with extensions
8236 not in the standard list. You can then set the extension associated
8237 with a language explicitly:
8240 @item set extension-language @var{ext} @var{language}
8241 @kindex set extension-language
8242 Tell @value{GDBN} that source files with extension @var{ext} are to be
8243 assumed as written in the source language @var{language}.
8245 @item info extensions
8246 @kindex info extensions
8247 List all the filename extensions and the associated languages.
8251 @section Type and range checking
8254 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
8255 checking are included, but they do not yet have any effect. This
8256 section documents the intended facilities.
8258 @c FIXME remove warning when type/range code added
8260 Some languages are designed to guard you against making seemingly common
8261 errors through a series of compile- and run-time checks. These include
8262 checking the type of arguments to functions and operators, and making
8263 sure mathematical overflows are caught at run time. Checks such as
8264 these help to ensure a program's correctness once it has been compiled
8265 by eliminating type mismatches, and providing active checks for range
8266 errors when your program is running.
8268 @value{GDBN} can check for conditions like the above if you wish.
8269 Although @value{GDBN} does not check the statements in your program,
8270 it can check expressions entered directly into @value{GDBN} for
8271 evaluation via the @code{print} command, for example. As with the
8272 working language, @value{GDBN} can also decide whether or not to check
8273 automatically based on your program's source language.
8274 @xref{Supported languages, ,Supported languages}, for the default
8275 settings of supported languages.
8278 * Type Checking:: An overview of type checking
8279 * Range Checking:: An overview of range checking
8282 @cindex type checking
8283 @cindex checks, type
8285 @subsection An overview of type checking
8287 Some languages, such as Modula-2, are strongly typed, meaning that the
8288 arguments to operators and functions have to be of the correct type,
8289 otherwise an error occurs. These checks prevent type mismatch
8290 errors from ever causing any run-time problems. For example,
8298 The second example fails because the @code{CARDINAL} 1 is not
8299 type-compatible with the @code{REAL} 2.3.
8301 For the expressions you use in @value{GDBN} commands, you can tell the
8302 @value{GDBN} type checker to skip checking;
8303 to treat any mismatches as errors and abandon the expression;
8304 or to only issue warnings when type mismatches occur,
8305 but evaluate the expression anyway. When you choose the last of
8306 these, @value{GDBN} evaluates expressions like the second example above, but
8307 also issues a warning.
8309 Even if you turn type checking off, there may be other reasons
8310 related to type that prevent @value{GDBN} from evaluating an expression.
8311 For instance, @value{GDBN} does not know how to add an @code{int} and
8312 a @code{struct foo}. These particular type errors have nothing to do
8313 with the language in use, and usually arise from expressions, such as
8314 the one described above, which make little sense to evaluate anyway.
8316 Each language defines to what degree it is strict about type. For
8317 instance, both Modula-2 and C require the arguments to arithmetical
8318 operators to be numbers. In C, enumerated types and pointers can be
8319 represented as numbers, so that they are valid arguments to mathematical
8320 operators. @xref{Supported languages, ,Supported languages}, for further
8321 details on specific languages.
8323 @value{GDBN} provides some additional commands for controlling the type checker:
8325 @kindex set check type
8326 @kindex show check type
8328 @item set check type auto
8329 Set type checking on or off based on the current working language.
8330 @xref{Supported languages, ,Supported languages}, for the default settings for
8333 @item set check type on
8334 @itemx set check type off
8335 Set type checking on or off, overriding the default setting for the
8336 current working language. Issue a warning if the setting does not
8337 match the language default. If any type mismatches occur in
8338 evaluating an expression while type checking is on, @value{GDBN} prints a
8339 message and aborts evaluation of the expression.
8341 @item set check type warn
8342 Cause the type checker to issue warnings, but to always attempt to
8343 evaluate the expression. Evaluating the expression may still
8344 be impossible for other reasons. For example, @value{GDBN} cannot add
8345 numbers and structures.
8348 Show the current setting of the type checker, and whether or not @value{GDBN}
8349 is setting it automatically.
8352 @cindex range checking
8353 @cindex checks, range
8354 @node Range Checking
8355 @subsection An overview of range checking
8357 In some languages (such as Modula-2), it is an error to exceed the
8358 bounds of a type; this is enforced with run-time checks. Such range
8359 checking is meant to ensure program correctness by making sure
8360 computations do not overflow, or indices on an array element access do
8361 not exceed the bounds of the array.
8363 For expressions you use in @value{GDBN} commands, you can tell
8364 @value{GDBN} to treat range errors in one of three ways: ignore them,
8365 always treat them as errors and abandon the expression, or issue
8366 warnings but evaluate the expression anyway.
8368 A range error can result from numerical overflow, from exceeding an
8369 array index bound, or when you type a constant that is not a member
8370 of any type. Some languages, however, do not treat overflows as an
8371 error. In many implementations of C, mathematical overflow causes the
8372 result to ``wrap around'' to lower values---for example, if @var{m} is
8373 the largest integer value, and @var{s} is the smallest, then
8376 @var{m} + 1 @result{} @var{s}
8379 This, too, is specific to individual languages, and in some cases
8380 specific to individual compilers or machines. @xref{Supported languages, ,
8381 Supported languages}, for further details on specific languages.
8383 @value{GDBN} provides some additional commands for controlling the range checker:
8385 @kindex set check range
8386 @kindex show check range
8388 @item set check range auto
8389 Set range checking on or off based on the current working language.
8390 @xref{Supported languages, ,Supported languages}, for the default settings for
8393 @item set check range on
8394 @itemx set check range off
8395 Set range checking on or off, overriding the default setting for the
8396 current working language. A warning is issued if the setting does not
8397 match the language default. If a range error occurs and range checking is on,
8398 then a message is printed and evaluation of the expression is aborted.
8400 @item set check range warn
8401 Output messages when the @value{GDBN} range checker detects a range error,
8402 but attempt to evaluate the expression anyway. Evaluating the
8403 expression may still be impossible for other reasons, such as accessing
8404 memory that the process does not own (a typical example from many Unix
8408 Show the current setting of the range checker, and whether or not it is
8409 being set automatically by @value{GDBN}.
8412 @node Supported languages
8413 @section Supported languages
8415 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
8416 assembly, Modula-2, and Ada.
8417 @c This is false ...
8418 Some @value{GDBN} features may be used in expressions regardless of the
8419 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
8420 and the @samp{@{type@}addr} construct (@pxref{Expressions,
8421 ,Expressions}) can be used with the constructs of any supported
8424 The following sections detail to what degree each source language is
8425 supported by @value{GDBN}. These sections are not meant to be language
8426 tutorials or references, but serve only as a reference guide to what the
8427 @value{GDBN} expression parser accepts, and what input and output
8428 formats should look like for different languages. There are many good
8429 books written on each of these languages; please look to these for a
8430 language reference or tutorial.
8434 * Objective-C:: Objective-C
8437 * Modula-2:: Modula-2
8442 @subsection C and C@t{++}
8444 @cindex C and C@t{++}
8445 @cindex expressions in C or C@t{++}
8447 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
8448 to both languages. Whenever this is the case, we discuss those languages
8452 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
8453 @cindex @sc{gnu} C@t{++}
8454 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
8455 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
8456 effectively, you must compile your C@t{++} programs with a supported
8457 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
8458 compiler (@code{aCC}).
8460 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
8461 format; if it doesn't work on your system, try the stabs+ debugging
8462 format. You can select those formats explicitly with the @code{g++}
8463 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
8464 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
8465 CC, gcc.info, Using @sc{gnu} CC}.
8468 * C Operators:: C and C@t{++} operators
8469 * C Constants:: C and C@t{++} constants
8470 * C plus plus expressions:: C@t{++} expressions
8471 * C Defaults:: Default settings for C and C@t{++}
8472 * C Checks:: C and C@t{++} type and range checks
8473 * Debugging C:: @value{GDBN} and C
8474 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
8478 @subsubsection C and C@t{++} operators
8480 @cindex C and C@t{++} operators
8482 Operators must be defined on values of specific types. For instance,
8483 @code{+} is defined on numbers, but not on structures. Operators are
8484 often defined on groups of types.
8486 For the purposes of C and C@t{++}, the following definitions hold:
8491 @emph{Integral types} include @code{int} with any of its storage-class
8492 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
8495 @emph{Floating-point types} include @code{float}, @code{double}, and
8496 @code{long double} (if supported by the target platform).
8499 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
8502 @emph{Scalar types} include all of the above.
8507 The following operators are supported. They are listed here
8508 in order of increasing precedence:
8512 The comma or sequencing operator. Expressions in a comma-separated list
8513 are evaluated from left to right, with the result of the entire
8514 expression being the last expression evaluated.
8517 Assignment. The value of an assignment expression is the value
8518 assigned. Defined on scalar types.
8521 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
8522 and translated to @w{@code{@var{a} = @var{a op b}}}.
8523 @w{@code{@var{op}=}} and @code{=} have the same precedence.
8524 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
8525 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
8528 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
8529 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
8533 Logical @sc{or}. Defined on integral types.
8536 Logical @sc{and}. Defined on integral types.
8539 Bitwise @sc{or}. Defined on integral types.
8542 Bitwise exclusive-@sc{or}. Defined on integral types.
8545 Bitwise @sc{and}. Defined on integral types.
8548 Equality and inequality. Defined on scalar types. The value of these
8549 expressions is 0 for false and non-zero for true.
8551 @item <@r{, }>@r{, }<=@r{, }>=
8552 Less than, greater than, less than or equal, greater than or equal.
8553 Defined on scalar types. The value of these expressions is 0 for false
8554 and non-zero for true.
8557 left shift, and right shift. Defined on integral types.
8560 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8563 Addition and subtraction. Defined on integral types, floating-point types and
8566 @item *@r{, }/@r{, }%
8567 Multiplication, division, and modulus. Multiplication and division are
8568 defined on integral and floating-point types. Modulus is defined on
8572 Increment and decrement. When appearing before a variable, the
8573 operation is performed before the variable is used in an expression;
8574 when appearing after it, the variable's value is used before the
8575 operation takes place.
8578 Pointer dereferencing. Defined on pointer types. Same precedence as
8582 Address operator. Defined on variables. Same precedence as @code{++}.
8584 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
8585 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
8586 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
8587 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
8591 Negative. Defined on integral and floating-point types. Same
8592 precedence as @code{++}.
8595 Logical negation. Defined on integral types. Same precedence as
8599 Bitwise complement operator. Defined on integral types. Same precedence as
8604 Structure member, and pointer-to-structure member. For convenience,
8605 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
8606 pointer based on the stored type information.
8607 Defined on @code{struct} and @code{union} data.
8610 Dereferences of pointers to members.
8613 Array indexing. @code{@var{a}[@var{i}]} is defined as
8614 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
8617 Function parameter list. Same precedence as @code{->}.
8620 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
8621 and @code{class} types.
8624 Doubled colons also represent the @value{GDBN} scope operator
8625 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
8629 If an operator is redefined in the user code, @value{GDBN} usually
8630 attempts to invoke the redefined version instead of using the operator's
8638 @subsubsection C and C@t{++} constants
8640 @cindex C and C@t{++} constants
8642 @value{GDBN} allows you to express the constants of C and C@t{++} in the
8647 Integer constants are a sequence of digits. Octal constants are
8648 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
8649 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
8650 @samp{l}, specifying that the constant should be treated as a
8654 Floating point constants are a sequence of digits, followed by a decimal
8655 point, followed by a sequence of digits, and optionally followed by an
8656 exponent. An exponent is of the form:
8657 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8658 sequence of digits. The @samp{+} is optional for positive exponents.
8659 A floating-point constant may also end with a letter @samp{f} or
8660 @samp{F}, specifying that the constant should be treated as being of
8661 the @code{float} (as opposed to the default @code{double}) type; or with
8662 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8666 Enumerated constants consist of enumerated identifiers, or their
8667 integral equivalents.
8670 Character constants are a single character surrounded by single quotes
8671 (@code{'}), or a number---the ordinal value of the corresponding character
8672 (usually its @sc{ascii} value). Within quotes, the single character may
8673 be represented by a letter or by @dfn{escape sequences}, which are of
8674 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8675 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8676 @samp{@var{x}} is a predefined special character---for example,
8677 @samp{\n} for newline.
8680 String constants are a sequence of character constants surrounded by
8681 double quotes (@code{"}). Any valid character constant (as described
8682 above) may appear. Double quotes within the string must be preceded by
8683 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8687 Pointer constants are an integral value. You can also write pointers
8688 to constants using the C operator @samp{&}.
8691 Array constants are comma-separated lists surrounded by braces @samp{@{}
8692 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8693 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8694 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8698 * C plus plus expressions::
8705 @node C plus plus expressions
8706 @subsubsection C@t{++} expressions
8708 @cindex expressions in C@t{++}
8709 @value{GDBN} expression handling can interpret most C@t{++} expressions.
8711 @cindex debugging C@t{++} programs
8712 @cindex C@t{++} compilers
8713 @cindex debug formats and C@t{++}
8714 @cindex @value{NGCC} and C@t{++}
8716 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
8717 proper compiler and the proper debug format. Currently, @value{GDBN}
8718 works best when debugging C@t{++} code that is compiled with
8719 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
8720 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
8721 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
8722 stabs+ as their default debug format, so you usually don't need to
8723 specify a debug format explicitly. Other compilers and/or debug formats
8724 are likely to work badly or not at all when using @value{GDBN} to debug
8730 @cindex member functions
8732 Member function calls are allowed; you can use expressions like
8735 count = aml->GetOriginal(x, y)
8738 @vindex this@r{, inside C@t{++} member functions}
8739 @cindex namespace in C@t{++}
8741 While a member function is active (in the selected stack frame), your
8742 expressions have the same namespace available as the member function;
8743 that is, @value{GDBN} allows implicit references to the class instance
8744 pointer @code{this} following the same rules as C@t{++}.
8746 @cindex call overloaded functions
8747 @cindex overloaded functions, calling
8748 @cindex type conversions in C@t{++}
8750 You can call overloaded functions; @value{GDBN} resolves the function
8751 call to the right definition, with some restrictions. @value{GDBN} does not
8752 perform overload resolution involving user-defined type conversions,
8753 calls to constructors, or instantiations of templates that do not exist
8754 in the program. It also cannot handle ellipsis argument lists or
8757 It does perform integral conversions and promotions, floating-point
8758 promotions, arithmetic conversions, pointer conversions, conversions of
8759 class objects to base classes, and standard conversions such as those of
8760 functions or arrays to pointers; it requires an exact match on the
8761 number of function arguments.
8763 Overload resolution is always performed, unless you have specified
8764 @code{set overload-resolution off}. @xref{Debugging C plus plus,
8765 ,@value{GDBN} features for C@t{++}}.
8767 You must specify @code{set overload-resolution off} in order to use an
8768 explicit function signature to call an overloaded function, as in
8770 p 'foo(char,int)'('x', 13)
8773 The @value{GDBN} command-completion facility can simplify this;
8774 see @ref{Completion, ,Command completion}.
8776 @cindex reference declarations
8778 @value{GDBN} understands variables declared as C@t{++} references; you can use
8779 them in expressions just as you do in C@t{++} source---they are automatically
8782 In the parameter list shown when @value{GDBN} displays a frame, the values of
8783 reference variables are not displayed (unlike other variables); this
8784 avoids clutter, since references are often used for large structures.
8785 The @emph{address} of a reference variable is always shown, unless
8786 you have specified @samp{set print address off}.
8789 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
8790 expressions can use it just as expressions in your program do. Since
8791 one scope may be defined in another, you can use @code{::} repeatedly if
8792 necessary, for example in an expression like
8793 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
8794 resolving name scope by reference to source files, in both C and C@t{++}
8795 debugging (@pxref{Variables, ,Program variables}).
8798 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
8799 calling virtual functions correctly, printing out virtual bases of
8800 objects, calling functions in a base subobject, casting objects, and
8801 invoking user-defined operators.
8804 @subsubsection C and C@t{++} defaults
8806 @cindex C and C@t{++} defaults
8808 If you allow @value{GDBN} to set type and range checking automatically, they
8809 both default to @code{off} whenever the working language changes to
8810 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
8811 selects the working language.
8813 If you allow @value{GDBN} to set the language automatically, it
8814 recognizes source files whose names end with @file{.c}, @file{.C}, or
8815 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
8816 these files, it sets the working language to C or C@t{++}.
8817 @xref{Automatically, ,Having @value{GDBN} infer the source language},
8818 for further details.
8820 @c Type checking is (a) primarily motivated by Modula-2, and (b)
8821 @c unimplemented. If (b) changes, it might make sense to let this node
8822 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
8825 @subsubsection C and C@t{++} type and range checks
8827 @cindex C and C@t{++} checks
8829 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
8830 is not used. However, if you turn type checking on, @value{GDBN}
8831 considers two variables type equivalent if:
8835 The two variables are structured and have the same structure, union, or
8839 The two variables have the same type name, or types that have been
8840 declared equivalent through @code{typedef}.
8843 @c leaving this out because neither J Gilmore nor R Pesch understand it.
8846 The two @code{struct}, @code{union}, or @code{enum} variables are
8847 declared in the same declaration. (Note: this may not be true for all C
8852 Range checking, if turned on, is done on mathematical operations. Array
8853 indices are not checked, since they are often used to index a pointer
8854 that is not itself an array.
8857 @subsubsection @value{GDBN} and C
8859 The @code{set print union} and @code{show print union} commands apply to
8860 the @code{union} type. When set to @samp{on}, any @code{union} that is
8861 inside a @code{struct} or @code{class} is also printed. Otherwise, it
8862 appears as @samp{@{...@}}.
8864 The @code{@@} operator aids in the debugging of dynamic arrays, formed
8865 with pointers and a memory allocation function. @xref{Expressions,
8869 * Debugging C plus plus::
8872 @node Debugging C plus plus
8873 @subsubsection @value{GDBN} features for C@t{++}
8875 @cindex commands for C@t{++}
8877 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
8878 designed specifically for use with C@t{++}. Here is a summary:
8881 @cindex break in overloaded functions
8882 @item @r{breakpoint menus}
8883 When you want a breakpoint in a function whose name is overloaded,
8884 @value{GDBN} breakpoint menus help you specify which function definition
8885 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
8887 @cindex overloading in C@t{++}
8888 @item rbreak @var{regex}
8889 Setting breakpoints using regular expressions is helpful for setting
8890 breakpoints on overloaded functions that are not members of any special
8892 @xref{Set Breaks, ,Setting breakpoints}.
8894 @cindex C@t{++} exception handling
8897 Debug C@t{++} exception handling using these commands. @xref{Set
8898 Catchpoints, , Setting catchpoints}.
8901 @item ptype @var{typename}
8902 Print inheritance relationships as well as other information for type
8904 @xref{Symbols, ,Examining the Symbol Table}.
8906 @cindex C@t{++} symbol display
8907 @item set print demangle
8908 @itemx show print demangle
8909 @itemx set print asm-demangle
8910 @itemx show print asm-demangle
8911 Control whether C@t{++} symbols display in their source form, both when
8912 displaying code as C@t{++} source and when displaying disassemblies.
8913 @xref{Print Settings, ,Print settings}.
8915 @item set print object
8916 @itemx show print object
8917 Choose whether to print derived (actual) or declared types of objects.
8918 @xref{Print Settings, ,Print settings}.
8920 @item set print vtbl
8921 @itemx show print vtbl
8922 Control the format for printing virtual function tables.
8923 @xref{Print Settings, ,Print settings}.
8924 (The @code{vtbl} commands do not work on programs compiled with the HP
8925 ANSI C@t{++} compiler (@code{aCC}).)
8927 @kindex set overload-resolution
8928 @cindex overloaded functions, overload resolution
8929 @item set overload-resolution on
8930 Enable overload resolution for C@t{++} expression evaluation. The default
8931 is on. For overloaded functions, @value{GDBN} evaluates the arguments
8932 and searches for a function whose signature matches the argument types,
8933 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
8934 expressions}, for details). If it cannot find a match, it emits a
8937 @item set overload-resolution off
8938 Disable overload resolution for C@t{++} expression evaluation. For
8939 overloaded functions that are not class member functions, @value{GDBN}
8940 chooses the first function of the specified name that it finds in the
8941 symbol table, whether or not its arguments are of the correct type. For
8942 overloaded functions that are class member functions, @value{GDBN}
8943 searches for a function whose signature @emph{exactly} matches the
8946 @kindex show overload-resolution
8947 @item show overload-resolution
8948 Show the current setting of overload resolution.
8950 @item @r{Overloaded symbol names}
8951 You can specify a particular definition of an overloaded symbol, using
8952 the same notation that is used to declare such symbols in C@t{++}: type
8953 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
8954 also use the @value{GDBN} command-line word completion facilities to list the
8955 available choices, or to finish the type list for you.
8956 @xref{Completion,, Command completion}, for details on how to do this.
8960 @subsection Objective-C
8963 This section provides information about some commands and command
8964 options that are useful for debugging Objective-C code. See also
8965 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
8966 few more commands specific to Objective-C support.
8969 * Method Names in Commands::
8970 * The Print Command with Objective-C::
8973 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
8974 @subsubsection Method Names in Commands
8976 The following commands have been extended to accept Objective-C method
8977 names as line specifications:
8979 @kindex clear@r{, and Objective-C}
8980 @kindex break@r{, and Objective-C}
8981 @kindex info line@r{, and Objective-C}
8982 @kindex jump@r{, and Objective-C}
8983 @kindex list@r{, and Objective-C}
8987 @item @code{info line}
8992 A fully qualified Objective-C method name is specified as
8995 -[@var{Class} @var{methodName}]
8998 where the minus sign is used to indicate an instance method and a
8999 plus sign (not shown) is used to indicate a class method. The class
9000 name @var{Class} and method name @var{methodName} are enclosed in
9001 brackets, similar to the way messages are specified in Objective-C
9002 source code. For example, to set a breakpoint at the @code{create}
9003 instance method of class @code{Fruit} in the program currently being
9007 break -[Fruit create]
9010 To list ten program lines around the @code{initialize} class method,
9014 list +[NSText initialize]
9017 In the current version of @value{GDBN}, the plus or minus sign is
9018 required. In future versions of @value{GDBN}, the plus or minus
9019 sign will be optional, but you can use it to narrow the search. It
9020 is also possible to specify just a method name:
9026 You must specify the complete method name, including any colons. If
9027 your program's source files contain more than one @code{create} method,
9028 you'll be presented with a numbered list of classes that implement that
9029 method. Indicate your choice by number, or type @samp{0} to exit if
9032 As another example, to clear a breakpoint established at the
9033 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
9036 clear -[NSWindow makeKeyAndOrderFront:]
9039 @node The Print Command with Objective-C
9040 @subsubsection The Print Command With Objective-C
9041 @cindex Objective-C, print objects
9042 @kindex print-object
9043 @kindex po @r{(@code{print-object})}
9045 The print command has also been extended to accept methods. For example:
9048 print -[@var{object} hash]
9051 @cindex print an Objective-C object description
9052 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
9054 will tell @value{GDBN} to send the @code{hash} message to @var{object}
9055 and print the result. Also, an additional command has been added,
9056 @code{print-object} or @code{po} for short, which is meant to print
9057 the description of an object. However, this command may only work
9058 with certain Objective-C libraries that have a particular hook
9059 function, @code{_NSPrintForDebugger}, defined.
9063 @cindex Fortran-specific support in @value{GDBN}
9066 @cindex @code{COMMON} blocks, Fortran
9068 @item info common @r{[}@var{common-name}@r{]}
9069 This command prints the values contained in the Fortran @code{COMMON}
9070 block whose name is @var{common-name}. With no argument, the names of
9071 all @code{COMMON} blocks visible at current program location are
9075 Fortran symbols are usually case-insensitive, so @value{GDBN} by
9076 default uses case-insensitive matches for Fortran symbols. You can
9077 change that with the @samp{set case-insensitive} command, see
9078 @ref{Symbols}, for the details.
9083 @cindex Pascal support in @value{GDBN}, limitations
9084 Debugging Pascal programs which use sets, subranges, file variables, or
9085 nested functions does not currently work. @value{GDBN} does not support
9086 entering expressions, printing values, or similar features using Pascal
9089 The Pascal-specific command @code{set print pascal_static-members}
9090 controls whether static members of Pascal objects are displayed.
9091 @xref{Print Settings, pascal_static-members}.
9094 @subsection Modula-2
9096 @cindex Modula-2, @value{GDBN} support
9098 The extensions made to @value{GDBN} to support Modula-2 only support
9099 output from the @sc{gnu} Modula-2 compiler (which is currently being
9100 developed). Other Modula-2 compilers are not currently supported, and
9101 attempting to debug executables produced by them is most likely
9102 to give an error as @value{GDBN} reads in the executable's symbol
9105 @cindex expressions in Modula-2
9107 * M2 Operators:: Built-in operators
9108 * Built-In Func/Proc:: Built-in functions and procedures
9109 * M2 Constants:: Modula-2 constants
9110 * M2 Defaults:: Default settings for Modula-2
9111 * Deviations:: Deviations from standard Modula-2
9112 * M2 Checks:: Modula-2 type and range checks
9113 * M2 Scope:: The scope operators @code{::} and @code{.}
9114 * GDB/M2:: @value{GDBN} and Modula-2
9118 @subsubsection Operators
9119 @cindex Modula-2 operators
9121 Operators must be defined on values of specific types. For instance,
9122 @code{+} is defined on numbers, but not on structures. Operators are
9123 often defined on groups of types. For the purposes of Modula-2, the
9124 following definitions hold:
9129 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
9133 @emph{Character types} consist of @code{CHAR} and its subranges.
9136 @emph{Floating-point types} consist of @code{REAL}.
9139 @emph{Pointer types} consist of anything declared as @code{POINTER TO
9143 @emph{Scalar types} consist of all of the above.
9146 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
9149 @emph{Boolean types} consist of @code{BOOLEAN}.
9153 The following operators are supported, and appear in order of
9154 increasing precedence:
9158 Function argument or array index separator.
9161 Assignment. The value of @var{var} @code{:=} @var{value} is
9165 Less than, greater than on integral, floating-point, or enumerated
9169 Less than or equal to, greater than or equal to
9170 on integral, floating-point and enumerated types, or set inclusion on
9171 set types. Same precedence as @code{<}.
9173 @item =@r{, }<>@r{, }#
9174 Equality and two ways of expressing inequality, valid on scalar types.
9175 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
9176 available for inequality, since @code{#} conflicts with the script
9180 Set membership. Defined on set types and the types of their members.
9181 Same precedence as @code{<}.
9184 Boolean disjunction. Defined on boolean types.
9187 Boolean conjunction. Defined on boolean types.
9190 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9193 Addition and subtraction on integral and floating-point types, or union
9194 and difference on set types.
9197 Multiplication on integral and floating-point types, or set intersection
9201 Division on floating-point types, or symmetric set difference on set
9202 types. Same precedence as @code{*}.
9205 Integer division and remainder. Defined on integral types. Same
9206 precedence as @code{*}.
9209 Negative. Defined on @code{INTEGER} and @code{REAL} data.
9212 Pointer dereferencing. Defined on pointer types.
9215 Boolean negation. Defined on boolean types. Same precedence as
9219 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
9220 precedence as @code{^}.
9223 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
9226 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
9230 @value{GDBN} and Modula-2 scope operators.
9234 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
9235 treats the use of the operator @code{IN}, or the use of operators
9236 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
9237 @code{<=}, and @code{>=} on sets as an error.
9241 @node Built-In Func/Proc
9242 @subsubsection Built-in functions and procedures
9243 @cindex Modula-2 built-ins
9245 Modula-2 also makes available several built-in procedures and functions.
9246 In describing these, the following metavariables are used:
9251 represents an @code{ARRAY} variable.
9254 represents a @code{CHAR} constant or variable.
9257 represents a variable or constant of integral type.
9260 represents an identifier that belongs to a set. Generally used in the
9261 same function with the metavariable @var{s}. The type of @var{s} should
9262 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
9265 represents a variable or constant of integral or floating-point type.
9268 represents a variable or constant of floating-point type.
9274 represents a variable.
9277 represents a variable or constant of one of many types. See the
9278 explanation of the function for details.
9281 All Modula-2 built-in procedures also return a result, described below.
9285 Returns the absolute value of @var{n}.
9288 If @var{c} is a lower case letter, it returns its upper case
9289 equivalent, otherwise it returns its argument.
9292 Returns the character whose ordinal value is @var{i}.
9295 Decrements the value in the variable @var{v} by one. Returns the new value.
9297 @item DEC(@var{v},@var{i})
9298 Decrements the value in the variable @var{v} by @var{i}. Returns the
9301 @item EXCL(@var{m},@var{s})
9302 Removes the element @var{m} from the set @var{s}. Returns the new
9305 @item FLOAT(@var{i})
9306 Returns the floating point equivalent of the integer @var{i}.
9309 Returns the index of the last member of @var{a}.
9312 Increments the value in the variable @var{v} by one. Returns the new value.
9314 @item INC(@var{v},@var{i})
9315 Increments the value in the variable @var{v} by @var{i}. Returns the
9318 @item INCL(@var{m},@var{s})
9319 Adds the element @var{m} to the set @var{s} if it is not already
9320 there. Returns the new set.
9323 Returns the maximum value of the type @var{t}.
9326 Returns the minimum value of the type @var{t}.
9329 Returns boolean TRUE if @var{i} is an odd number.
9332 Returns the ordinal value of its argument. For example, the ordinal
9333 value of a character is its @sc{ascii} value (on machines supporting the
9334 @sc{ascii} character set). @var{x} must be of an ordered type, which include
9335 integral, character and enumerated types.
9338 Returns the size of its argument. @var{x} can be a variable or a type.
9340 @item TRUNC(@var{r})
9341 Returns the integral part of @var{r}.
9343 @item VAL(@var{t},@var{i})
9344 Returns the member of the type @var{t} whose ordinal value is @var{i}.
9348 @emph{Warning:} Sets and their operations are not yet supported, so
9349 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
9353 @cindex Modula-2 constants
9355 @subsubsection Constants
9357 @value{GDBN} allows you to express the constants of Modula-2 in the following
9363 Integer constants are simply a sequence of digits. When used in an
9364 expression, a constant is interpreted to be type-compatible with the
9365 rest of the expression. Hexadecimal integers are specified by a
9366 trailing @samp{H}, and octal integers by a trailing @samp{B}.
9369 Floating point constants appear as a sequence of digits, followed by a
9370 decimal point and another sequence of digits. An optional exponent can
9371 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
9372 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
9373 digits of the floating point constant must be valid decimal (base 10)
9377 Character constants consist of a single character enclosed by a pair of
9378 like quotes, either single (@code{'}) or double (@code{"}). They may
9379 also be expressed by their ordinal value (their @sc{ascii} value, usually)
9380 followed by a @samp{C}.
9383 String constants consist of a sequence of characters enclosed by a
9384 pair of like quotes, either single (@code{'}) or double (@code{"}).
9385 Escape sequences in the style of C are also allowed. @xref{C
9386 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
9390 Enumerated constants consist of an enumerated identifier.
9393 Boolean constants consist of the identifiers @code{TRUE} and
9397 Pointer constants consist of integral values only.
9400 Set constants are not yet supported.
9404 @subsubsection Modula-2 defaults
9405 @cindex Modula-2 defaults
9407 If type and range checking are set automatically by @value{GDBN}, they
9408 both default to @code{on} whenever the working language changes to
9409 Modula-2. This happens regardless of whether you or @value{GDBN}
9410 selected the working language.
9412 If you allow @value{GDBN} to set the language automatically, then entering
9413 code compiled from a file whose name ends with @file{.mod} sets the
9414 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
9415 the language automatically}, for further details.
9418 @subsubsection Deviations from standard Modula-2
9419 @cindex Modula-2, deviations from
9421 A few changes have been made to make Modula-2 programs easier to debug.
9422 This is done primarily via loosening its type strictness:
9426 Unlike in standard Modula-2, pointer constants can be formed by
9427 integers. This allows you to modify pointer variables during
9428 debugging. (In standard Modula-2, the actual address contained in a
9429 pointer variable is hidden from you; it can only be modified
9430 through direct assignment to another pointer variable or expression that
9431 returned a pointer.)
9434 C escape sequences can be used in strings and characters to represent
9435 non-printable characters. @value{GDBN} prints out strings with these
9436 escape sequences embedded. Single non-printable characters are
9437 printed using the @samp{CHR(@var{nnn})} format.
9440 The assignment operator (@code{:=}) returns the value of its right-hand
9444 All built-in procedures both modify @emph{and} return their argument.
9448 @subsubsection Modula-2 type and range checks
9449 @cindex Modula-2 checks
9452 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
9455 @c FIXME remove warning when type/range checks added
9457 @value{GDBN} considers two Modula-2 variables type equivalent if:
9461 They are of types that have been declared equivalent via a @code{TYPE
9462 @var{t1} = @var{t2}} statement
9465 They have been declared on the same line. (Note: This is true of the
9466 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
9469 As long as type checking is enabled, any attempt to combine variables
9470 whose types are not equivalent is an error.
9472 Range checking is done on all mathematical operations, assignment, array
9473 index bounds, and all built-in functions and procedures.
9476 @subsubsection The scope operators @code{::} and @code{.}
9478 @cindex @code{.}, Modula-2 scope operator
9479 @cindex colon, doubled as scope operator
9481 @vindex colon-colon@r{, in Modula-2}
9482 @c Info cannot handle :: but TeX can.
9485 @vindex ::@r{, in Modula-2}
9488 There are a few subtle differences between the Modula-2 scope operator
9489 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
9494 @var{module} . @var{id}
9495 @var{scope} :: @var{id}
9499 where @var{scope} is the name of a module or a procedure,
9500 @var{module} the name of a module, and @var{id} is any declared
9501 identifier within your program, except another module.
9503 Using the @code{::} operator makes @value{GDBN} search the scope
9504 specified by @var{scope} for the identifier @var{id}. If it is not
9505 found in the specified scope, then @value{GDBN} searches all scopes
9506 enclosing the one specified by @var{scope}.
9508 Using the @code{.} operator makes @value{GDBN} search the current scope for
9509 the identifier specified by @var{id} that was imported from the
9510 definition module specified by @var{module}. With this operator, it is
9511 an error if the identifier @var{id} was not imported from definition
9512 module @var{module}, or if @var{id} is not an identifier in
9516 @subsubsection @value{GDBN} and Modula-2
9518 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
9519 Five subcommands of @code{set print} and @code{show print} apply
9520 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
9521 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
9522 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
9523 analogue in Modula-2.
9525 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
9526 with any language, is not useful with Modula-2. Its
9527 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
9528 created in Modula-2 as they can in C or C@t{++}. However, because an
9529 address can be specified by an integral constant, the construct
9530 @samp{@{@var{type}@}@var{adrexp}} is still useful.
9532 @cindex @code{#} in Modula-2
9533 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
9534 interpreted as the beginning of a comment. Use @code{<>} instead.
9540 The extensions made to @value{GDBN} for Ada only support
9541 output from the @sc{gnu} Ada (GNAT) compiler.
9542 Other Ada compilers are not currently supported, and
9543 attempting to debug executables produced by them is most likely
9547 @cindex expressions in Ada
9549 * Ada Mode Intro:: General remarks on the Ada syntax
9550 and semantics supported by Ada mode
9552 * Omissions from Ada:: Restrictions on the Ada expression syntax.
9553 * Additions to Ada:: Extensions of the Ada expression syntax.
9554 * Stopping Before Main Program:: Debugging the program during elaboration.
9555 * Ada Glitches:: Known peculiarities of Ada mode.
9558 @node Ada Mode Intro
9559 @subsubsection Introduction
9560 @cindex Ada mode, general
9562 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
9563 syntax, with some extensions.
9564 The philosophy behind the design of this subset is
9568 That @value{GDBN} should provide basic literals and access to operations for
9569 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
9570 leaving more sophisticated computations to subprograms written into the
9571 program (which therefore may be called from @value{GDBN}).
9574 That type safety and strict adherence to Ada language restrictions
9575 are not particularly important to the @value{GDBN} user.
9578 That brevity is important to the @value{GDBN} user.
9581 Thus, for brevity, the debugger acts as if there were
9582 implicit @code{with} and @code{use} clauses in effect for all user-written
9583 packages, making it unnecessary to fully qualify most names with
9584 their packages, regardless of context. Where this causes ambiguity,
9585 @value{GDBN} asks the user's intent.
9587 The debugger will start in Ada mode if it detects an Ada main program.
9588 As for other languages, it will enter Ada mode when stopped in a program that
9589 was translated from an Ada source file.
9591 While in Ada mode, you may use `@t{--}' for comments. This is useful
9592 mostly for documenting command files. The standard @value{GDBN} comment
9593 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
9594 middle (to allow based literals).
9596 The debugger supports limited overloading. Given a subprogram call in which
9597 the function symbol has multiple definitions, it will use the number of
9598 actual parameters and some information about their types to attempt to narrow
9599 the set of definitions. It also makes very limited use of context, preferring
9600 procedures to functions in the context of the @code{call} command, and
9601 functions to procedures elsewhere.
9603 @node Omissions from Ada
9604 @subsubsection Omissions from Ada
9605 @cindex Ada, omissions from
9607 Here are the notable omissions from the subset:
9611 Only a subset of the attributes are supported:
9615 @t{'First}, @t{'Last}, and @t{'Length}
9616 on array objects (not on types and subtypes).
9619 @t{'Min} and @t{'Max}.
9622 @t{'Pos} and @t{'Val}.
9628 @t{'Range} on array objects (not subtypes), but only as the right
9629 operand of the membership (@code{in}) operator.
9632 @t{'Access}, @t{'Unchecked_Access}, and
9633 @t{'Unrestricted_Access} (a GNAT extension).
9641 @code{Characters.Latin_1} are not available and
9642 concatenation is not implemented. Thus, escape characters in strings are
9643 not currently available.
9646 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
9647 equality of representations. They will generally work correctly
9648 for strings and arrays whose elements have integer or enumeration types.
9649 They may not work correctly for arrays whose element
9650 types have user-defined equality, for arrays of real values
9651 (in particular, IEEE-conformant floating point, because of negative
9652 zeroes and NaNs), and for arrays whose elements contain unused bits with
9653 indeterminate values.
9656 The other component-by-component array operations (@code{and}, @code{or},
9657 @code{xor}, @code{not}, and relational tests other than equality)
9658 are not implemented.
9661 There are no record or array aggregates.
9664 Calls to dispatching subprograms are not implemented.
9667 The overloading algorithm is much more limited (i.e., less selective)
9668 than that of real Ada. It makes only limited use of the context in which a subexpression
9669 appears to resolve its meaning, and it is much looser in its rules for allowing
9670 type matches. As a result, some function calls will be ambiguous, and the user
9671 will be asked to choose the proper resolution.
9674 The @code{new} operator is not implemented.
9677 Entry calls are not implemented.
9680 Aside from printing, arithmetic operations on the native VAX floating-point
9681 formats are not supported.
9684 It is not possible to slice a packed array.
9687 @node Additions to Ada
9688 @subsubsection Additions to Ada
9689 @cindex Ada, deviations from
9691 As it does for other languages, @value{GDBN} makes certain generic
9692 extensions to Ada (@pxref{Expressions}):
9696 If the expression @var{E} is a variable residing in memory
9697 (typically a local variable or array element) and @var{N} is
9698 a positive integer, then @code{@var{E}@@@var{N}} displays the values of
9699 @var{E} and the @var{N}-1 adjacent variables following it in memory as an array.
9700 In Ada, this operator is generally not necessary, since its prime use
9701 is in displaying parts of an array, and slicing will usually do this in Ada.
9702 However, there are occasional uses when debugging programs
9703 in which certain debugging information has been optimized away.
9706 @code{@var{B}::@var{var}} means ``the variable named @var{var} that appears
9707 in function or file @var{B}.'' When @var{B} is a file name, you must typically
9708 surround it in single quotes.
9711 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
9712 @var{type} that appears at address @var{addr}.''
9715 A name starting with @samp{$} is a convenience variable
9716 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
9719 In addition, @value{GDBN} provides a few other shortcuts and outright additions specific
9724 The assignment statement is allowed as an expression, returning
9725 its right-hand operand as its value. Thus, you may enter
9729 print A(tmp := y + 1)
9733 The semicolon is allowed as an ``operator,'' returning as its value
9734 the value of its right-hand operand.
9735 This allows, for example,
9736 complex conditional breaks:
9740 condition 1 (report(i); k += 1; A(k) > 100)
9744 Rather than use catenation and symbolic character names to introduce special
9745 characters into strings, one may instead use a special bracket notation,
9746 which is also used to print strings. A sequence of characters of the form
9747 @samp{["@var{XX}"]} within a string or character literal denotes the
9748 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
9749 sequence of characters @samp{["""]} also denotes a single quotation mark
9750 in strings. For example,
9752 "One line.["0a"]Next line.["0a"]"
9755 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF}) after each
9759 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
9760 @t{'Max} is optional (and is ignored in any case). For example, it is valid
9768 When printing arrays, @value{GDBN} uses positional notation when the
9769 array has a lower bound of 1, and uses a modified named notation otherwise.
9770 For example, a one-dimensional array of three integers with a lower bound of 3 might print as
9777 That is, in contrast to valid Ada, only the first component has a @code{=>}
9781 You may abbreviate attributes in expressions with any unique,
9782 multi-character subsequence of
9783 their names (an exact match gets preference).
9784 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
9785 in place of @t{a'length}.
9788 @cindex quoting Ada internal identifiers
9789 Since Ada is case-insensitive, the debugger normally maps identifiers you type
9790 to lower case. The GNAT compiler uses upper-case characters for
9791 some of its internal identifiers, which are normally of no interest to users.
9792 For the rare occasions when you actually have to look at them,
9793 enclose them in angle brackets to avoid the lower-case mapping.
9796 @value{GDBP} print <JMPBUF_SAVE>[0]
9800 Printing an object of class-wide type or dereferencing an
9801 access-to-class-wide value will display all the components of the object's
9802 specific type (as indicated by its run-time tag). Likewise, component
9803 selection on such a value will operate on the specific type of the
9808 @node Stopping Before Main Program
9809 @subsubsection Stopping at the Very Beginning
9811 @cindex breakpointing Ada elaboration code
9812 It is sometimes necessary to debug the program during elaboration, and
9813 before reaching the main procedure.
9814 As defined in the Ada Reference
9815 Manual, the elaboration code is invoked from a procedure called
9816 @code{adainit}. To run your program up to the beginning of
9817 elaboration, simply use the following two commands:
9818 @code{tbreak adainit} and @code{run}.
9821 @subsubsection Known Peculiarities of Ada Mode
9822 @cindex Ada, problems
9824 Besides the omissions listed previously (@pxref{Omissions from Ada}),
9825 we know of several problems with and limitations of Ada mode in
9827 some of which will be fixed with planned future releases of the debugger
9828 and the GNU Ada compiler.
9832 Currently, the debugger
9833 has insufficient information to determine whether certain pointers represent
9834 pointers to objects or the objects themselves.
9835 Thus, the user may have to tack an extra @code{.all} after an expression
9836 to get it printed properly.
9839 Static constants that the compiler chooses not to materialize as objects in
9840 storage are invisible to the debugger.
9843 Named parameter associations in function argument lists are ignored (the
9844 argument lists are treated as positional).
9847 Many useful library packages are currently invisible to the debugger.
9850 Fixed-point arithmetic, conversions, input, and output is carried out using
9851 floating-point arithmetic, and may give results that only approximate those on
9855 The type of the @t{'Address} attribute may not be @code{System.Address}.
9858 The GNAT compiler never generates the prefix @code{Standard} for any of
9859 the standard symbols defined by the Ada language. @value{GDBN} knows about
9860 this: it will strip the prefix from names when you use it, and will never
9861 look for a name you have so qualified among local symbols, nor match against
9862 symbols in other packages or subprograms. If you have
9863 defined entities anywhere in your program other than parameters and
9864 local variables whose simple names match names in @code{Standard},
9865 GNAT's lack of qualification here can cause confusion. When this happens,
9866 you can usually resolve the confusion
9867 by qualifying the problematic names with package
9868 @code{Standard} explicitly.
9871 @node Unsupported languages
9872 @section Unsupported languages
9874 @cindex unsupported languages
9875 @cindex minimal language
9876 In addition to the other fully-supported programming languages,
9877 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
9878 It does not represent a real programming language, but provides a set
9879 of capabilities close to what the C or assembly languages provide.
9880 This should allow most simple operations to be performed while debugging
9881 an application that uses a language currently not supported by @value{GDBN}.
9883 If the language is set to @code{auto}, @value{GDBN} will automatically
9884 select this language if the current frame corresponds to an unsupported
9888 @chapter Examining the Symbol Table
9890 The commands described in this chapter allow you to inquire about the
9891 symbols (names of variables, functions and types) defined in your
9892 program. This information is inherent in the text of your program and
9893 does not change as your program executes. @value{GDBN} finds it in your
9894 program's symbol table, in the file indicated when you started @value{GDBN}
9895 (@pxref{File Options, ,Choosing files}), or by one of the
9896 file-management commands (@pxref{Files, ,Commands to specify files}).
9898 @cindex symbol names
9899 @cindex names of symbols
9900 @cindex quoting names
9901 Occasionally, you may need to refer to symbols that contain unusual
9902 characters, which @value{GDBN} ordinarily treats as word delimiters. The
9903 most frequent case is in referring to static variables in other
9904 source files (@pxref{Variables,,Program variables}). File names
9905 are recorded in object files as debugging symbols, but @value{GDBN} would
9906 ordinarily parse a typical file name, like @file{foo.c}, as the three words
9907 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
9908 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
9915 looks up the value of @code{x} in the scope of the file @file{foo.c}.
9918 @cindex case-insensitive symbol names
9919 @cindex case sensitivity in symbol names
9920 @kindex set case-sensitive
9921 @item set case-sensitive on
9922 @itemx set case-sensitive off
9923 @itemx set case-sensitive auto
9924 Normally, when @value{GDBN} looks up symbols, it matches their names
9925 with case sensitivity determined by the current source language.
9926 Occasionally, you may wish to control that. The command @code{set
9927 case-sensitive} lets you do that by specifying @code{on} for
9928 case-sensitive matches or @code{off} for case-insensitive ones. If
9929 you specify @code{auto}, case sensitivity is reset to the default
9930 suitable for the source language. The default is case-sensitive
9931 matches for all languages except for Fortran, for which the default is
9932 case-insensitive matches.
9934 @kindex show case-sensitive
9935 @item show case-sensitive
9936 This command shows the current setting of case sensitivity for symbols
9939 @kindex info address
9940 @cindex address of a symbol
9941 @item info address @var{symbol}
9942 Describe where the data for @var{symbol} is stored. For a register
9943 variable, this says which register it is kept in. For a non-register
9944 local variable, this prints the stack-frame offset at which the variable
9947 Note the contrast with @samp{print &@var{symbol}}, which does not work
9948 at all for a register variable, and for a stack local variable prints
9949 the exact address of the current instantiation of the variable.
9952 @cindex symbol from address
9953 @cindex closest symbol and offset for an address
9954 @item info symbol @var{addr}
9955 Print the name of a symbol which is stored at the address @var{addr}.
9956 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
9957 nearest symbol and an offset from it:
9960 (@value{GDBP}) info symbol 0x54320
9961 _initialize_vx + 396 in section .text
9965 This is the opposite of the @code{info address} command. You can use
9966 it to find out the name of a variable or a function given its address.
9969 @item whatis @var{expr}
9970 Print the data type of expression @var{expr}. @var{expr} is not
9971 actually evaluated, and any side-effecting operations (such as
9972 assignments or function calls) inside it do not take place.
9973 @xref{Expressions, ,Expressions}.
9976 Print the data type of @code{$}, the last value in the value history.
9979 @item ptype @var{typename}
9980 Print a description of data type @var{typename}. @var{typename} may be
9981 the name of a type, or for C code it may have the form @samp{class
9982 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
9983 @var{union-tag}} or @samp{enum @var{enum-tag}}.
9985 @item ptype @var{expr}
9987 Print a description of the type of expression @var{expr}. @code{ptype}
9988 differs from @code{whatis} by printing a detailed description, instead
9989 of just the name of the type.
9991 For example, for this variable declaration:
9994 struct complex @{double real; double imag;@} v;
9998 the two commands give this output:
10002 (@value{GDBP}) whatis v
10003 type = struct complex
10004 (@value{GDBP}) ptype v
10005 type = struct complex @{
10013 As with @code{whatis}, using @code{ptype} without an argument refers to
10014 the type of @code{$}, the last value in the value history.
10017 @item info types @var{regexp}
10019 Print a brief description of all types whose names match the regular
10020 expression @var{regexp} (or all types in your program, if you supply
10021 no argument). Each complete typename is matched as though it were a
10022 complete line; thus, @samp{i type value} gives information on all
10023 types in your program whose names include the string @code{value}, but
10024 @samp{i type ^value$} gives information only on types whose complete
10025 name is @code{value}.
10027 This command differs from @code{ptype} in two ways: first, like
10028 @code{whatis}, it does not print a detailed description; second, it
10029 lists all source files where a type is defined.
10032 @cindex local variables
10033 @item info scope @var{location}
10034 List all the variables local to a particular scope. This command
10035 accepts a @var{location} argument---a function name, a source line, or
10036 an address preceded by a @samp{*}, and prints all the variables local
10037 to the scope defined by that location. For example:
10040 (@value{GDBP}) @b{info scope command_line_handler}
10041 Scope for command_line_handler:
10042 Symbol rl is an argument at stack/frame offset 8, length 4.
10043 Symbol linebuffer is in static storage at address 0x150a18, length 4.
10044 Symbol linelength is in static storage at address 0x150a1c, length 4.
10045 Symbol p is a local variable in register $esi, length 4.
10046 Symbol p1 is a local variable in register $ebx, length 4.
10047 Symbol nline is a local variable in register $edx, length 4.
10048 Symbol repeat is a local variable at frame offset -8, length 4.
10052 This command is especially useful for determining what data to collect
10053 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
10056 @kindex info source
10058 Show information about the current source file---that is, the source file for
10059 the function containing the current point of execution:
10062 the name of the source file, and the directory containing it,
10064 the directory it was compiled in,
10066 its length, in lines,
10068 which programming language it is written in,
10070 whether the executable includes debugging information for that file, and
10071 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
10073 whether the debugging information includes information about
10074 preprocessor macros.
10078 @kindex info sources
10080 Print the names of all source files in your program for which there is
10081 debugging information, organized into two lists: files whose symbols
10082 have already been read, and files whose symbols will be read when needed.
10084 @kindex info functions
10085 @item info functions
10086 Print the names and data types of all defined functions.
10088 @item info functions @var{regexp}
10089 Print the names and data types of all defined functions
10090 whose names contain a match for regular expression @var{regexp}.
10091 Thus, @samp{info fun step} finds all functions whose names
10092 include @code{step}; @samp{info fun ^step} finds those whose names
10093 start with @code{step}. If a function name contains characters
10094 that conflict with the regular expression language (eg.
10095 @samp{operator*()}), they may be quoted with a backslash.
10097 @kindex info variables
10098 @item info variables
10099 Print the names and data types of all variables that are declared
10100 outside of functions (i.e.@: excluding local variables).
10102 @item info variables @var{regexp}
10103 Print the names and data types of all variables (except for local
10104 variables) whose names contain a match for regular expression
10107 @kindex info classes
10108 @cindex Objective-C, classes and selectors
10110 @itemx info classes @var{regexp}
10111 Display all Objective-C classes in your program, or
10112 (with the @var{regexp} argument) all those matching a particular regular
10115 @kindex info selectors
10116 @item info selectors
10117 @itemx info selectors @var{regexp}
10118 Display all Objective-C selectors in your program, or
10119 (with the @var{regexp} argument) all those matching a particular regular
10123 This was never implemented.
10124 @kindex info methods
10126 @itemx info methods @var{regexp}
10127 The @code{info methods} command permits the user to examine all defined
10128 methods within C@t{++} program, or (with the @var{regexp} argument) a
10129 specific set of methods found in the various C@t{++} classes. Many
10130 C@t{++} classes provide a large number of methods. Thus, the output
10131 from the @code{ptype} command can be overwhelming and hard to use. The
10132 @code{info-methods} command filters the methods, printing only those
10133 which match the regular-expression @var{regexp}.
10136 @cindex reloading symbols
10137 Some systems allow individual object files that make up your program to
10138 be replaced without stopping and restarting your program. For example,
10139 in VxWorks you can simply recompile a defective object file and keep on
10140 running. If you are running on one of these systems, you can allow
10141 @value{GDBN} to reload the symbols for automatically relinked modules:
10144 @kindex set symbol-reloading
10145 @item set symbol-reloading on
10146 Replace symbol definitions for the corresponding source file when an
10147 object file with a particular name is seen again.
10149 @item set symbol-reloading off
10150 Do not replace symbol definitions when encountering object files of the
10151 same name more than once. This is the default state; if you are not
10152 running on a system that permits automatic relinking of modules, you
10153 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
10154 may discard symbols when linking large programs, that may contain
10155 several modules (from different directories or libraries) with the same
10158 @kindex show symbol-reloading
10159 @item show symbol-reloading
10160 Show the current @code{on} or @code{off} setting.
10163 @cindex opaque data types
10164 @kindex set opaque-type-resolution
10165 @item set opaque-type-resolution on
10166 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
10167 declared as a pointer to a @code{struct}, @code{class}, or
10168 @code{union}---for example, @code{struct MyType *}---that is used in one
10169 source file although the full declaration of @code{struct MyType} is in
10170 another source file. The default is on.
10172 A change in the setting of this subcommand will not take effect until
10173 the next time symbols for a file are loaded.
10175 @item set opaque-type-resolution off
10176 Tell @value{GDBN} not to resolve opaque types. In this case, the type
10177 is printed as follows:
10179 @{<no data fields>@}
10182 @kindex show opaque-type-resolution
10183 @item show opaque-type-resolution
10184 Show whether opaque types are resolved or not.
10186 @kindex maint print symbols
10187 @cindex symbol dump
10188 @kindex maint print psymbols
10189 @cindex partial symbol dump
10190 @item maint print symbols @var{filename}
10191 @itemx maint print psymbols @var{filename}
10192 @itemx maint print msymbols @var{filename}
10193 Write a dump of debugging symbol data into the file @var{filename}.
10194 These commands are used to debug the @value{GDBN} symbol-reading code. Only
10195 symbols with debugging data are included. If you use @samp{maint print
10196 symbols}, @value{GDBN} includes all the symbols for which it has already
10197 collected full details: that is, @var{filename} reflects symbols for
10198 only those files whose symbols @value{GDBN} has read. You can use the
10199 command @code{info sources} to find out which files these are. If you
10200 use @samp{maint print psymbols} instead, the dump shows information about
10201 symbols that @value{GDBN} only knows partially---that is, symbols defined in
10202 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
10203 @samp{maint print msymbols} dumps just the minimal symbol information
10204 required for each object file from which @value{GDBN} has read some symbols.
10205 @xref{Files, ,Commands to specify files}, for a discussion of how
10206 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
10208 @kindex maint info symtabs
10209 @kindex maint info psymtabs
10210 @cindex listing @value{GDBN}'s internal symbol tables
10211 @cindex symbol tables, listing @value{GDBN}'s internal
10212 @cindex full symbol tables, listing @value{GDBN}'s internal
10213 @cindex partial symbol tables, listing @value{GDBN}'s internal
10214 @item maint info symtabs @r{[} @var{regexp} @r{]}
10215 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
10217 List the @code{struct symtab} or @code{struct partial_symtab}
10218 structures whose names match @var{regexp}. If @var{regexp} is not
10219 given, list them all. The output includes expressions which you can
10220 copy into a @value{GDBN} debugging this one to examine a particular
10221 structure in more detail. For example:
10224 (@value{GDBP}) maint info psymtabs dwarf2read
10225 @{ objfile /home/gnu/build/gdb/gdb
10226 ((struct objfile *) 0x82e69d0)
10227 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
10228 ((struct partial_symtab *) 0x8474b10)
10231 text addresses 0x814d3c8 -- 0x8158074
10232 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
10233 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
10234 dependencies (none)
10237 (@value{GDBP}) maint info symtabs
10241 We see that there is one partial symbol table whose filename contains
10242 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
10243 and we see that @value{GDBN} has not read in any symtabs yet at all.
10244 If we set a breakpoint on a function, that will cause @value{GDBN} to
10245 read the symtab for the compilation unit containing that function:
10248 (@value{GDBP}) break dwarf2_psymtab_to_symtab
10249 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
10251 (@value{GDBP}) maint info symtabs
10252 @{ objfile /home/gnu/build/gdb/gdb
10253 ((struct objfile *) 0x82e69d0)
10254 @{ symtab /home/gnu/src/gdb/dwarf2read.c
10255 ((struct symtab *) 0x86c1f38)
10258 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
10259 debugformat DWARF 2
10268 @chapter Altering Execution
10270 Once you think you have found an error in your program, you might want to
10271 find out for certain whether correcting the apparent error would lead to
10272 correct results in the rest of the run. You can find the answer by
10273 experiment, using the @value{GDBN} features for altering execution of the
10276 For example, you can store new values into variables or memory
10277 locations, give your program a signal, restart it at a different
10278 address, or even return prematurely from a function.
10281 * Assignment:: Assignment to variables
10282 * Jumping:: Continuing at a different address
10283 * Signaling:: Giving your program a signal
10284 * Returning:: Returning from a function
10285 * Calling:: Calling your program's functions
10286 * Patching:: Patching your program
10290 @section Assignment to variables
10293 @cindex setting variables
10294 To alter the value of a variable, evaluate an assignment expression.
10295 @xref{Expressions, ,Expressions}. For example,
10302 stores the value 4 into the variable @code{x}, and then prints the
10303 value of the assignment expression (which is 4).
10304 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
10305 information on operators in supported languages.
10307 @kindex set variable
10308 @cindex variables, setting
10309 If you are not interested in seeing the value of the assignment, use the
10310 @code{set} command instead of the @code{print} command. @code{set} is
10311 really the same as @code{print} except that the expression's value is
10312 not printed and is not put in the value history (@pxref{Value History,
10313 ,Value history}). The expression is evaluated only for its effects.
10315 If the beginning of the argument string of the @code{set} command
10316 appears identical to a @code{set} subcommand, use the @code{set
10317 variable} command instead of just @code{set}. This command is identical
10318 to @code{set} except for its lack of subcommands. For example, if your
10319 program has a variable @code{width}, you get an error if you try to set
10320 a new value with just @samp{set width=13}, because @value{GDBN} has the
10321 command @code{set width}:
10324 (@value{GDBP}) whatis width
10326 (@value{GDBP}) p width
10328 (@value{GDBP}) set width=47
10329 Invalid syntax in expression.
10333 The invalid expression, of course, is @samp{=47}. In
10334 order to actually set the program's variable @code{width}, use
10337 (@value{GDBP}) set var width=47
10340 Because the @code{set} command has many subcommands that can conflict
10341 with the names of program variables, it is a good idea to use the
10342 @code{set variable} command instead of just @code{set}. For example, if
10343 your program has a variable @code{g}, you run into problems if you try
10344 to set a new value with just @samp{set g=4}, because @value{GDBN} has
10345 the command @code{set gnutarget}, abbreviated @code{set g}:
10349 (@value{GDBP}) whatis g
10353 (@value{GDBP}) set g=4
10357 The program being debugged has been started already.
10358 Start it from the beginning? (y or n) y
10359 Starting program: /home/smith/cc_progs/a.out
10360 "/home/smith/cc_progs/a.out": can't open to read symbols:
10361 Invalid bfd target.
10362 (@value{GDBP}) show g
10363 The current BFD target is "=4".
10368 The program variable @code{g} did not change, and you silently set the
10369 @code{gnutarget} to an invalid value. In order to set the variable
10373 (@value{GDBP}) set var g=4
10376 @value{GDBN} allows more implicit conversions in assignments than C; you can
10377 freely store an integer value into a pointer variable or vice versa,
10378 and you can convert any structure to any other structure that is the
10379 same length or shorter.
10380 @comment FIXME: how do structs align/pad in these conversions?
10381 @comment /doc@cygnus.com 18dec1990
10383 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
10384 construct to generate a value of specified type at a specified address
10385 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
10386 to memory location @code{0x83040} as an integer (which implies a certain size
10387 and representation in memory), and
10390 set @{int@}0x83040 = 4
10394 stores the value 4 into that memory location.
10397 @section Continuing at a different address
10399 Ordinarily, when you continue your program, you do so at the place where
10400 it stopped, with the @code{continue} command. You can instead continue at
10401 an address of your own choosing, with the following commands:
10405 @item jump @var{linespec}
10406 Resume execution at line @var{linespec}. Execution stops again
10407 immediately if there is a breakpoint there. @xref{List, ,Printing
10408 source lines}, for a description of the different forms of
10409 @var{linespec}. It is common practice to use the @code{tbreak} command
10410 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
10413 The @code{jump} command does not change the current stack frame, or
10414 the stack pointer, or the contents of any memory location or any
10415 register other than the program counter. If line @var{linespec} is in
10416 a different function from the one currently executing, the results may
10417 be bizarre if the two functions expect different patterns of arguments or
10418 of local variables. For this reason, the @code{jump} command requests
10419 confirmation if the specified line is not in the function currently
10420 executing. However, even bizarre results are predictable if you are
10421 well acquainted with the machine-language code of your program.
10423 @item jump *@var{address}
10424 Resume execution at the instruction at address @var{address}.
10427 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
10428 On many systems, you can get much the same effect as the @code{jump}
10429 command by storing a new value into the register @code{$pc}. The
10430 difference is that this does not start your program running; it only
10431 changes the address of where it @emph{will} run when you continue. For
10439 makes the next @code{continue} command or stepping command execute at
10440 address @code{0x485}, rather than at the address where your program stopped.
10441 @xref{Continuing and Stepping, ,Continuing and stepping}.
10443 The most common occasion to use the @code{jump} command is to back
10444 up---perhaps with more breakpoints set---over a portion of a program
10445 that has already executed, in order to examine its execution in more
10450 @section Giving your program a signal
10451 @cindex deliver a signal to a program
10455 @item signal @var{signal}
10456 Resume execution where your program stopped, but immediately give it the
10457 signal @var{signal}. @var{signal} can be the name or the number of a
10458 signal. For example, on many systems @code{signal 2} and @code{signal
10459 SIGINT} are both ways of sending an interrupt signal.
10461 Alternatively, if @var{signal} is zero, continue execution without
10462 giving a signal. This is useful when your program stopped on account of
10463 a signal and would ordinary see the signal when resumed with the
10464 @code{continue} command; @samp{signal 0} causes it to resume without a
10467 @code{signal} does not repeat when you press @key{RET} a second time
10468 after executing the command.
10472 Invoking the @code{signal} command is not the same as invoking the
10473 @code{kill} utility from the shell. Sending a signal with @code{kill}
10474 causes @value{GDBN} to decide what to do with the signal depending on
10475 the signal handling tables (@pxref{Signals}). The @code{signal} command
10476 passes the signal directly to your program.
10480 @section Returning from a function
10483 @cindex returning from a function
10486 @itemx return @var{expression}
10487 You can cancel execution of a function call with the @code{return}
10488 command. If you give an
10489 @var{expression} argument, its value is used as the function's return
10493 When you use @code{return}, @value{GDBN} discards the selected stack frame
10494 (and all frames within it). You can think of this as making the
10495 discarded frame return prematurely. If you wish to specify a value to
10496 be returned, give that value as the argument to @code{return}.
10498 This pops the selected stack frame (@pxref{Selection, ,Selecting a
10499 frame}), and any other frames inside of it, leaving its caller as the
10500 innermost remaining frame. That frame becomes selected. The
10501 specified value is stored in the registers used for returning values
10504 The @code{return} command does not resume execution; it leaves the
10505 program stopped in the state that would exist if the function had just
10506 returned. In contrast, the @code{finish} command (@pxref{Continuing
10507 and Stepping, ,Continuing and stepping}) resumes execution until the
10508 selected stack frame returns naturally.
10511 @section Calling program functions
10514 @cindex calling functions
10515 @cindex inferior functions, calling
10516 @item print @var{expr}
10517 Evaluate the expression @var{expr} and display the resuling value.
10518 @var{expr} may include calls to functions in the program being
10522 @item call @var{expr}
10523 Evaluate the expression @var{expr} without displaying @code{void}
10526 You can use this variant of the @code{print} command if you want to
10527 execute a function from your program that does not return anything
10528 (a.k.a.@: @dfn{a void function}), but without cluttering the output
10529 with @code{void} returned values that @value{GDBN} will otherwise
10530 print. If the result is not void, it is printed and saved in the
10534 It is possible for the function you call via the @code{print} or
10535 @code{call} command to generate a signal (e.g., if there's a bug in
10536 the function, or if you passed it incorrect arguments). What happens
10537 in that case is controlled by the @code{set unwindonsignal} command.
10540 @item set unwindonsignal
10541 @kindex set unwindonsignal
10542 @cindex unwind stack in called functions
10543 @cindex call dummy stack unwinding
10544 Set unwinding of the stack if a signal is received while in a function
10545 that @value{GDBN} called in the program being debugged. If set to on,
10546 @value{GDBN} unwinds the stack it created for the call and restores
10547 the context to what it was before the call. If set to off (the
10548 default), @value{GDBN} stops in the frame where the signal was
10551 @item show unwindonsignal
10552 @kindex show unwindonsignal
10553 Show the current setting of stack unwinding in the functions called by
10557 @cindex weak alias functions
10558 Sometimes, a function you wish to call is actually a @dfn{weak alias}
10559 for another function. In such case, @value{GDBN} might not pick up
10560 the type information, including the types of the function arguments,
10561 which causes @value{GDBN} to call the inferior function incorrectly.
10562 As a result, the called function will function erroneously and may
10563 even crash. A solution to that is to use the name of the aliased
10567 @section Patching programs
10569 @cindex patching binaries
10570 @cindex writing into executables
10571 @cindex writing into corefiles
10573 By default, @value{GDBN} opens the file containing your program's
10574 executable code (or the corefile) read-only. This prevents accidental
10575 alterations to machine code; but it also prevents you from intentionally
10576 patching your program's binary.
10578 If you'd like to be able to patch the binary, you can specify that
10579 explicitly with the @code{set write} command. For example, you might
10580 want to turn on internal debugging flags, or even to make emergency
10586 @itemx set write off
10587 If you specify @samp{set write on}, @value{GDBN} opens executable and
10588 core files for both reading and writing; if you specify @samp{set write
10589 off} (the default), @value{GDBN} opens them read-only.
10591 If you have already loaded a file, you must load it again (using the
10592 @code{exec-file} or @code{core-file} command) after changing @code{set
10593 write}, for your new setting to take effect.
10597 Display whether executable files and core files are opened for writing
10598 as well as reading.
10602 @chapter @value{GDBN} Files
10604 @value{GDBN} needs to know the file name of the program to be debugged,
10605 both in order to read its symbol table and in order to start your
10606 program. To debug a core dump of a previous run, you must also tell
10607 @value{GDBN} the name of the core dump file.
10610 * Files:: Commands to specify files
10611 * Separate Debug Files:: Debugging information in separate files
10612 * Symbol Errors:: Errors reading symbol files
10616 @section Commands to specify files
10618 @cindex symbol table
10619 @cindex core dump file
10621 You may want to specify executable and core dump file names. The usual
10622 way to do this is at start-up time, using the arguments to
10623 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
10624 Out of @value{GDBN}}).
10626 Occasionally it is necessary to change to a different file during a
10627 @value{GDBN} session. Or you may run @value{GDBN} and forget to
10628 specify a file you want to use. Or you are debugging a remote target
10629 via @code{gdbserver} (@pxref{Server, file}). In these situations the
10630 @value{GDBN} commands to specify new files are useful.
10633 @cindex executable file
10635 @item file @var{filename}
10636 Use @var{filename} as the program to be debugged. It is read for its
10637 symbols and for the contents of pure memory. It is also the program
10638 executed when you use the @code{run} command. If you do not specify a
10639 directory and the file is not found in the @value{GDBN} working directory,
10640 @value{GDBN} uses the environment variable @code{PATH} as a list of
10641 directories to search, just as the shell does when looking for a program
10642 to run. You can change the value of this variable, for both @value{GDBN}
10643 and your program, using the @code{path} command.
10645 On systems with memory-mapped files, an auxiliary file named
10646 @file{@var{filename}.syms} may hold symbol table information for
10647 @var{filename}. If so, @value{GDBN} maps in the symbol table from
10648 @file{@var{filename}.syms}, starting up more quickly. See the
10649 descriptions of the file options @samp{-mapped} and @samp{-readnow}
10650 (available on the command line, see @ref{File Options, , -readnow},
10651 and with the commands @code{file}, @code{symbol-file}, or
10652 @code{add-symbol-file}, described below), for more information.
10654 @cindex unlinked object files
10655 @cindex patching object files
10656 You can load unlinked object @file{.o} files into @value{GDBN} using
10657 the @code{file} command. You will not be able to ``run'' an object
10658 file, but you can disassemble functions and inspect variables. Also,
10659 if the underlying BFD functionality supports it, you could use
10660 @kbd{gdb -write} to patch object files using this technique. Note
10661 that @value{GDBN} can neither interpret nor modify relocations in this
10662 case, so branches and some initialized variables will appear to go to
10663 the wrong place. But this feature is still handy from time to time.
10666 @code{file} with no argument makes @value{GDBN} discard any information it
10667 has on both executable file and the symbol table.
10670 @item exec-file @r{[} @var{filename} @r{]}
10671 Specify that the program to be run (but not the symbol table) is found
10672 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
10673 if necessary to locate your program. Omitting @var{filename} means to
10674 discard information on the executable file.
10676 @kindex symbol-file
10677 @item symbol-file @r{[} @var{filename} @r{]}
10678 Read symbol table information from file @var{filename}. @code{PATH} is
10679 searched when necessary. Use the @code{file} command to get both symbol
10680 table and program to run from the same file.
10682 @code{symbol-file} with no argument clears out @value{GDBN} information on your
10683 program's symbol table.
10685 The @code{symbol-file} command causes @value{GDBN} to forget the contents
10686 of its convenience variables, the value history, and all breakpoints and
10687 auto-display expressions. This is because they may contain pointers to
10688 the internal data recording symbols and data types, which are part of
10689 the old symbol table data being discarded inside @value{GDBN}.
10691 @code{symbol-file} does not repeat if you press @key{RET} again after
10694 When @value{GDBN} is configured for a particular environment, it
10695 understands debugging information in whatever format is the standard
10696 generated for that environment; you may use either a @sc{gnu} compiler, or
10697 other compilers that adhere to the local conventions.
10698 Best results are usually obtained from @sc{gnu} compilers; for example,
10699 using @code{@value{GCC}} you can generate debugging information for
10702 For most kinds of object files, with the exception of old SVR3 systems
10703 using COFF, the @code{symbol-file} command does not normally read the
10704 symbol table in full right away. Instead, it scans the symbol table
10705 quickly to find which source files and which symbols are present. The
10706 details are read later, one source file at a time, as they are needed.
10708 The purpose of this two-stage reading strategy is to make @value{GDBN}
10709 start up faster. For the most part, it is invisible except for
10710 occasional pauses while the symbol table details for a particular source
10711 file are being read. (The @code{set verbose} command can turn these
10712 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
10713 warnings and messages}.)
10715 We have not implemented the two-stage strategy for COFF yet. When the
10716 symbol table is stored in COFF format, @code{symbol-file} reads the
10717 symbol table data in full right away. Note that ``stabs-in-COFF''
10718 still does the two-stage strategy, since the debug info is actually
10722 @cindex reading symbols immediately
10723 @cindex symbols, reading immediately
10725 @cindex memory-mapped symbol file
10726 @cindex saving symbol table
10727 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10728 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10729 You can override the @value{GDBN} two-stage strategy for reading symbol
10730 tables by using the @samp{-readnow} option with any of the commands that
10731 load symbol table information, if you want to be sure @value{GDBN} has the
10732 entire symbol table available.
10734 If memory-mapped files are available on your system through the
10735 @code{mmap} system call, you can use another option, @samp{-mapped}, to
10736 cause @value{GDBN} to write the symbols for your program into a reusable
10737 file. Future @value{GDBN} debugging sessions map in symbol information
10738 from this auxiliary symbol file (if the program has not changed), rather
10739 than spending time reading the symbol table from the executable
10740 program. Using the @samp{-mapped} option has the same effect as
10741 starting @value{GDBN} with the @samp{-mapped} command-line option.
10743 You can use both options together, to make sure the auxiliary symbol
10744 file has all the symbol information for your program.
10746 The auxiliary symbol file for a program called @var{myprog} is called
10747 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
10748 than the corresponding executable), @value{GDBN} always attempts to use
10749 it when you debug @var{myprog}; no special options or commands are
10752 The @file{.syms} file is specific to the host machine where you run
10753 @value{GDBN}. It holds an exact image of the internal @value{GDBN}
10754 symbol table. It cannot be shared across multiple host platforms.
10756 @c FIXME: for now no mention of directories, since this seems to be in
10757 @c flux. 13mar1992 status is that in theory GDB would look either in
10758 @c current dir or in same dir as myprog; but issues like competing
10759 @c GDB's, or clutter in system dirs, mean that in practice right now
10760 @c only current dir is used. FFish says maybe a special GDB hierarchy
10761 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
10765 @item core-file @r{[}@var{filename}@r{]}
10767 Specify the whereabouts of a core dump file to be used as the ``contents
10768 of memory''. Traditionally, core files contain only some parts of the
10769 address space of the process that generated them; @value{GDBN} can access the
10770 executable file itself for other parts.
10772 @code{core-file} with no argument specifies that no core file is
10775 Note that the core file is ignored when your program is actually running
10776 under @value{GDBN}. So, if you have been running your program and you
10777 wish to debug a core file instead, you must kill the subprocess in which
10778 the program is running. To do this, use the @code{kill} command
10779 (@pxref{Kill Process, ,Killing the child process}).
10781 @kindex add-symbol-file
10782 @cindex dynamic linking
10783 @item add-symbol-file @var{filename} @var{address}
10784 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10785 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
10786 The @code{add-symbol-file} command reads additional symbol table
10787 information from the file @var{filename}. You would use this command
10788 when @var{filename} has been dynamically loaded (by some other means)
10789 into the program that is running. @var{address} should be the memory
10790 address at which the file has been loaded; @value{GDBN} cannot figure
10791 this out for itself. You can additionally specify an arbitrary number
10792 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
10793 section name and base address for that section. You can specify any
10794 @var{address} as an expression.
10796 The symbol table of the file @var{filename} is added to the symbol table
10797 originally read with the @code{symbol-file} command. You can use the
10798 @code{add-symbol-file} command any number of times; the new symbol data
10799 thus read keeps adding to the old. To discard all old symbol data
10800 instead, use the @code{symbol-file} command without any arguments.
10802 @cindex relocatable object files, reading symbols from
10803 @cindex object files, relocatable, reading symbols from
10804 @cindex reading symbols from relocatable object files
10805 @cindex symbols, reading from relocatable object files
10806 @cindex @file{.o} files, reading symbols from
10807 Although @var{filename} is typically a shared library file, an
10808 executable file, or some other object file which has been fully
10809 relocated for loading into a process, you can also load symbolic
10810 information from relocatable @file{.o} files, as long as:
10814 the file's symbolic information refers only to linker symbols defined in
10815 that file, not to symbols defined by other object files,
10817 every section the file's symbolic information refers to has actually
10818 been loaded into the inferior, as it appears in the file, and
10820 you can determine the address at which every section was loaded, and
10821 provide these to the @code{add-symbol-file} command.
10825 Some embedded operating systems, like Sun Chorus and VxWorks, can load
10826 relocatable files into an already running program; such systems
10827 typically make the requirements above easy to meet. However, it's
10828 important to recognize that many native systems use complex link
10829 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
10830 assembly, for example) that make the requirements difficult to meet. In
10831 general, one cannot assume that using @code{add-symbol-file} to read a
10832 relocatable object file's symbolic information will have the same effect
10833 as linking the relocatable object file into the program in the normal
10836 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
10838 You can use the @samp{-mapped} and @samp{-readnow} options just as with
10839 the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
10840 table information for @var{filename}.
10842 @kindex add-symbol-file-from-memory
10843 @cindex @code{syscall DSO}
10844 @cindex load symbols from memory
10845 @item add-symbol-file-from-memory @var{address}
10846 Load symbols from the given @var{address} in a dynamically loaded
10847 object file whose image is mapped directly into the inferior's memory.
10848 For example, the Linux kernel maps a @code{syscall DSO} into each
10849 process's address space; this DSO provides kernel-specific code for
10850 some system calls. The argument can be any expression whose
10851 evaluation yields the address of the file's shared object file header.
10852 For this command to work, you must have used @code{symbol-file} or
10853 @code{exec-file} commands in advance.
10855 @kindex add-shared-symbol-files
10857 @item add-shared-symbol-files @var{library-file}
10858 @itemx assf @var{library-file}
10859 The @code{add-shared-symbol-files} command can currently be used only
10860 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
10861 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
10862 @value{GDBN} automatically looks for shared libraries, however if
10863 @value{GDBN} does not find yours, you can invoke
10864 @code{add-shared-symbol-files}. It takes one argument: the shared
10865 library's file name. @code{assf} is a shorthand alias for
10866 @code{add-shared-symbol-files}.
10869 @item section @var{section} @var{addr}
10870 The @code{section} command changes the base address of the named
10871 @var{section} of the exec file to @var{addr}. This can be used if the
10872 exec file does not contain section addresses, (such as in the
10873 @code{a.out} format), or when the addresses specified in the file
10874 itself are wrong. Each section must be changed separately. The
10875 @code{info files} command, described below, lists all the sections and
10879 @kindex info target
10882 @code{info files} and @code{info target} are synonymous; both print the
10883 current target (@pxref{Targets, ,Specifying a Debugging Target}),
10884 including the names of the executable and core dump files currently in
10885 use by @value{GDBN}, and the files from which symbols were loaded. The
10886 command @code{help target} lists all possible targets rather than
10889 @kindex maint info sections
10890 @item maint info sections
10891 Another command that can give you extra information about program sections
10892 is @code{maint info sections}. In addition to the section information
10893 displayed by @code{info files}, this command displays the flags and file
10894 offset of each section in the executable and core dump files. In addition,
10895 @code{maint info sections} provides the following command options (which
10896 may be arbitrarily combined):
10900 Display sections for all loaded object files, including shared libraries.
10901 @item @var{sections}
10902 Display info only for named @var{sections}.
10903 @item @var{section-flags}
10904 Display info only for sections for which @var{section-flags} are true.
10905 The section flags that @value{GDBN} currently knows about are:
10908 Section will have space allocated in the process when loaded.
10909 Set for all sections except those containing debug information.
10911 Section will be loaded from the file into the child process memory.
10912 Set for pre-initialized code and data, clear for @code{.bss} sections.
10914 Section needs to be relocated before loading.
10916 Section cannot be modified by the child process.
10918 Section contains executable code only.
10920 Section contains data only (no executable code).
10922 Section will reside in ROM.
10924 Section contains data for constructor/destructor lists.
10926 Section is not empty.
10928 An instruction to the linker to not output the section.
10929 @item COFF_SHARED_LIBRARY
10930 A notification to the linker that the section contains
10931 COFF shared library information.
10933 Section contains common symbols.
10936 @kindex set trust-readonly-sections
10937 @cindex read-only sections
10938 @item set trust-readonly-sections on
10939 Tell @value{GDBN} that readonly sections in your object file
10940 really are read-only (i.e.@: that their contents will not change).
10941 In that case, @value{GDBN} can fetch values from these sections
10942 out of the object file, rather than from the target program.
10943 For some targets (notably embedded ones), this can be a significant
10944 enhancement to debugging performance.
10946 The default is off.
10948 @item set trust-readonly-sections off
10949 Tell @value{GDBN} not to trust readonly sections. This means that
10950 the contents of the section might change while the program is running,
10951 and must therefore be fetched from the target when needed.
10953 @item show trust-readonly-sections
10954 Show the current setting of trusting readonly sections.
10957 All file-specifying commands allow both absolute and relative file names
10958 as arguments. @value{GDBN} always converts the file name to an absolute file
10959 name and remembers it that way.
10961 @cindex shared libraries
10962 @value{GDBN} supports GNU/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
10963 and IBM RS/6000 AIX shared libraries.
10965 @value{GDBN} automatically loads symbol definitions from shared libraries
10966 when you use the @code{run} command, or when you examine a core file.
10967 (Before you issue the @code{run} command, @value{GDBN} does not understand
10968 references to a function in a shared library, however---unless you are
10969 debugging a core file).
10971 On HP-UX, if the program loads a library explicitly, @value{GDBN}
10972 automatically loads the symbols at the time of the @code{shl_load} call.
10974 @c FIXME: some @value{GDBN} release may permit some refs to undef
10975 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
10976 @c FIXME...lib; check this from time to time when updating manual
10978 There are times, however, when you may wish to not automatically load
10979 symbol definitions from shared libraries, such as when they are
10980 particularly large or there are many of them.
10982 To control the automatic loading of shared library symbols, use the
10986 @kindex set auto-solib-add
10987 @item set auto-solib-add @var{mode}
10988 If @var{mode} is @code{on}, symbols from all shared object libraries
10989 will be loaded automatically when the inferior begins execution, you
10990 attach to an independently started inferior, or when the dynamic linker
10991 informs @value{GDBN} that a new library has been loaded. If @var{mode}
10992 is @code{off}, symbols must be loaded manually, using the
10993 @code{sharedlibrary} command. The default value is @code{on}.
10995 @cindex memory used for symbol tables
10996 If your program uses lots of shared libraries with debug info that
10997 takes large amounts of memory, you can decrease the @value{GDBN}
10998 memory footprint by preventing it from automatically loading the
10999 symbols from shared libraries. To that end, type @kbd{set
11000 auto-solib-add off} before running the inferior, then load each
11001 library whose debug symbols you do need with @kbd{sharedlibrary
11002 @var{regexp}}, where @var{regexp} is a regular expresion that matches
11003 the libraries whose symbols you want to be loaded.
11005 @kindex show auto-solib-add
11006 @item show auto-solib-add
11007 Display the current autoloading mode.
11010 @cindex load shared library
11011 To explicitly load shared library symbols, use the @code{sharedlibrary}
11015 @kindex info sharedlibrary
11018 @itemx info sharedlibrary
11019 Print the names of the shared libraries which are currently loaded.
11021 @kindex sharedlibrary
11023 @item sharedlibrary @var{regex}
11024 @itemx share @var{regex}
11025 Load shared object library symbols for files matching a
11026 Unix regular expression.
11027 As with files loaded automatically, it only loads shared libraries
11028 required by your program for a core file or after typing @code{run}. If
11029 @var{regex} is omitted all shared libraries required by your program are
11032 @item nosharedlibrary
11033 @kindex nosharedlibrary
11034 @cindex unload symbols from shared libraries
11035 Unload all shared object library symbols. This discards all symbols
11036 that have been loaded from all shared libraries. Symbols from shared
11037 libraries that were loaded by explicit user requests are not
11041 Sometimes you may wish that @value{GDBN} stops and gives you control
11042 when any of shared library events happen. Use the @code{set
11043 stop-on-solib-events} command for this:
11046 @item set stop-on-solib-events
11047 @kindex set stop-on-solib-events
11048 This command controls whether @value{GDBN} should give you control
11049 when the dynamic linker notifies it about some shared library event.
11050 The most common event of interest is loading or unloading of a new
11053 @item show stop-on-solib-events
11054 @kindex show stop-on-solib-events
11055 Show whether @value{GDBN} stops and gives you control when shared
11056 library events happen.
11059 Shared libraries are also supported in many cross or remote debugging
11060 configurations. A copy of the target's libraries need to be present on the
11061 host system; they need to be the same as the target libraries, although the
11062 copies on the target can be stripped as long as the copies on the host are
11065 @cindex where to look for shared libraries
11066 For remote debugging, you need to tell @value{GDBN} where the target
11067 libraries are, so that it can load the correct copies---otherwise, it
11068 may try to load the host's libraries. @value{GDBN} has two variables
11069 to specify the search directories for target libraries.
11072 @cindex prefix for shared library file names
11073 @kindex set solib-absolute-prefix
11074 @item set solib-absolute-prefix @var{path}
11075 If this variable is set, @var{path} will be used as a prefix for any
11076 absolute shared library paths; many runtime loaders store the absolute
11077 paths to the shared library in the target program's memory. If you use
11078 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
11079 out in the same way that they are on the target, with e.g.@: a
11080 @file{/usr/lib} hierarchy under @var{path}.
11082 @cindex default value of @samp{solib-absolute-prefix}
11083 @cindex @samp{--with-sysroot}
11084 You can set the default value of @samp{solib-absolute-prefix} by using the
11085 configure-time @samp{--with-sysroot} option.
11087 @kindex show solib-absolute-prefix
11088 @item show solib-absolute-prefix
11089 Display the current shared library prefix.
11091 @kindex set solib-search-path
11092 @item set solib-search-path @var{path}
11093 If this variable is set, @var{path} is a colon-separated list of directories
11094 to search for shared libraries. @samp{solib-search-path} is used after
11095 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
11096 the library is relative instead of absolute. If you want to use
11097 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
11098 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
11099 @value{GDBN} from finding your host's libraries.
11101 @kindex show solib-search-path
11102 @item show solib-search-path
11103 Display the current shared library search path.
11107 @node Separate Debug Files
11108 @section Debugging Information in Separate Files
11109 @cindex separate debugging information files
11110 @cindex debugging information in separate files
11111 @cindex @file{.debug} subdirectories
11112 @cindex debugging information directory, global
11113 @cindex global debugging information directory
11115 @value{GDBN} allows you to put a program's debugging information in a
11116 file separate from the executable itself, in a way that allows
11117 @value{GDBN} to find and load the debugging information automatically.
11118 Since debugging information can be very large --- sometimes larger
11119 than the executable code itself --- some systems distribute debugging
11120 information for their executables in separate files, which users can
11121 install only when they need to debug a problem.
11123 If an executable's debugging information has been extracted to a
11124 separate file, the executable should contain a @dfn{debug link} giving
11125 the name of the debugging information file (with no directory
11126 components), and a checksum of its contents. (The exact form of a
11127 debug link is described below.) If the full name of the directory
11128 containing the executable is @var{execdir}, and the executable has a
11129 debug link that specifies the name @var{debugfile}, then @value{GDBN}
11130 will automatically search for the debugging information file in three
11135 the directory containing the executable file (that is, it will look
11136 for a file named @file{@var{execdir}/@var{debugfile}},
11138 a subdirectory of that directory named @file{.debug} (that is, the
11139 file @file{@var{execdir}/.debug/@var{debugfile}}, and
11141 a subdirectory of the global debug file directory that includes the
11142 executable's full path, and the name from the link (that is, the file
11143 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
11144 @var{globaldebugdir} is the global debug file directory, and
11145 @var{execdir} has been turned into a relative path).
11148 @value{GDBN} checks under each of these names for a debugging
11149 information file whose checksum matches that given in the link, and
11150 reads the debugging information from the first one it finds.
11152 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
11153 which has a link containing the name @file{ls.debug}, and the global
11154 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
11155 for debug information in @file{/usr/bin/ls.debug},
11156 @file{/usr/bin/.debug/ls.debug}, and
11157 @file{/usr/lib/debug/usr/bin/ls.debug}.
11159 You can set the global debugging info directory's name, and view the
11160 name @value{GDBN} is currently using.
11164 @kindex set debug-file-directory
11165 @item set debug-file-directory @var{directory}
11166 Set the directory which @value{GDBN} searches for separate debugging
11167 information files to @var{directory}.
11169 @kindex show debug-file-directory
11170 @item show debug-file-directory
11171 Show the directory @value{GDBN} searches for separate debugging
11176 @cindex @code{.gnu_debuglink} sections
11177 @cindex debug links
11178 A debug link is a special section of the executable file named
11179 @code{.gnu_debuglink}. The section must contain:
11183 A filename, with any leading directory components removed, followed by
11186 zero to three bytes of padding, as needed to reach the next four-byte
11187 boundary within the section, and
11189 a four-byte CRC checksum, stored in the same endianness used for the
11190 executable file itself. The checksum is computed on the debugging
11191 information file's full contents by the function given below, passing
11192 zero as the @var{crc} argument.
11195 Any executable file format can carry a debug link, as long as it can
11196 contain a section named @code{.gnu_debuglink} with the contents
11199 The debugging information file itself should be an ordinary
11200 executable, containing a full set of linker symbols, sections, and
11201 debugging information. The sections of the debugging information file
11202 should have the same names, addresses and sizes as the original file,
11203 but they need not contain any data --- much like a @code{.bss} section
11204 in an ordinary executable.
11206 As of December 2002, there is no standard GNU utility to produce
11207 separated executable / debugging information file pairs. Ulrich
11208 Drepper's @file{elfutils} package, starting with version 0.53,
11209 contains a version of the @code{strip} command such that the command
11210 @kbd{strip foo -f foo.debug} removes the debugging information from
11211 the executable file @file{foo}, places it in the file
11212 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
11214 Since there are many different ways to compute CRC's (different
11215 polynomials, reversals, byte ordering, etc.), the simplest way to
11216 describe the CRC used in @code{.gnu_debuglink} sections is to give the
11217 complete code for a function that computes it:
11219 @kindex gnu_debuglink_crc32
11222 gnu_debuglink_crc32 (unsigned long crc,
11223 unsigned char *buf, size_t len)
11225 static const unsigned long crc32_table[256] =
11227 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
11228 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
11229 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
11230 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
11231 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
11232 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
11233 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
11234 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
11235 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
11236 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
11237 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
11238 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
11239 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
11240 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
11241 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
11242 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
11243 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
11244 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
11245 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
11246 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
11247 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
11248 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
11249 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
11250 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
11251 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
11252 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
11253 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
11254 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
11255 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
11256 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
11257 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
11258 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
11259 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
11260 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
11261 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
11262 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
11263 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
11264 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
11265 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
11266 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
11267 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
11268 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
11269 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
11270 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
11271 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
11272 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
11273 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
11274 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
11275 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
11276 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
11277 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
11280 unsigned char *end;
11282 crc = ~crc & 0xffffffff;
11283 for (end = buf + len; buf < end; ++buf)
11284 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
11285 return ~crc & 0xffffffff;
11290 @node Symbol Errors
11291 @section Errors reading symbol files
11293 While reading a symbol file, @value{GDBN} occasionally encounters problems,
11294 such as symbol types it does not recognize, or known bugs in compiler
11295 output. By default, @value{GDBN} does not notify you of such problems, since
11296 they are relatively common and primarily of interest to people
11297 debugging compilers. If you are interested in seeing information
11298 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
11299 only one message about each such type of problem, no matter how many
11300 times the problem occurs; or you can ask @value{GDBN} to print more messages,
11301 to see how many times the problems occur, with the @code{set
11302 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
11305 The messages currently printed, and their meanings, include:
11308 @item inner block not inside outer block in @var{symbol}
11310 The symbol information shows where symbol scopes begin and end
11311 (such as at the start of a function or a block of statements). This
11312 error indicates that an inner scope block is not fully contained
11313 in its outer scope blocks.
11315 @value{GDBN} circumvents the problem by treating the inner block as if it had
11316 the same scope as the outer block. In the error message, @var{symbol}
11317 may be shown as ``@code{(don't know)}'' if the outer block is not a
11320 @item block at @var{address} out of order
11322 The symbol information for symbol scope blocks should occur in
11323 order of increasing addresses. This error indicates that it does not
11326 @value{GDBN} does not circumvent this problem, and has trouble
11327 locating symbols in the source file whose symbols it is reading. (You
11328 can often determine what source file is affected by specifying
11329 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
11332 @item bad block start address patched
11334 The symbol information for a symbol scope block has a start address
11335 smaller than the address of the preceding source line. This is known
11336 to occur in the SunOS 4.1.1 (and earlier) C compiler.
11338 @value{GDBN} circumvents the problem by treating the symbol scope block as
11339 starting on the previous source line.
11341 @item bad string table offset in symbol @var{n}
11344 Symbol number @var{n} contains a pointer into the string table which is
11345 larger than the size of the string table.
11347 @value{GDBN} circumvents the problem by considering the symbol to have the
11348 name @code{foo}, which may cause other problems if many symbols end up
11351 @item unknown symbol type @code{0x@var{nn}}
11353 The symbol information contains new data types that @value{GDBN} does
11354 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
11355 uncomprehended information, in hexadecimal.
11357 @value{GDBN} circumvents the error by ignoring this symbol information.
11358 This usually allows you to debug your program, though certain symbols
11359 are not accessible. If you encounter such a problem and feel like
11360 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
11361 on @code{complain}, then go up to the function @code{read_dbx_symtab}
11362 and examine @code{*bufp} to see the symbol.
11364 @item stub type has NULL name
11366 @value{GDBN} could not find the full definition for a struct or class.
11368 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
11369 The symbol information for a C@t{++} member function is missing some
11370 information that recent versions of the compiler should have output for
11373 @item info mismatch between compiler and debugger
11375 @value{GDBN} could not parse a type specification output by the compiler.
11380 @chapter Specifying a Debugging Target
11382 @cindex debugging target
11383 A @dfn{target} is the execution environment occupied by your program.
11385 Often, @value{GDBN} runs in the same host environment as your program;
11386 in that case, the debugging target is specified as a side effect when
11387 you use the @code{file} or @code{core} commands. When you need more
11388 flexibility---for example, running @value{GDBN} on a physically separate
11389 host, or controlling a standalone system over a serial port or a
11390 realtime system over a TCP/IP connection---you can use the @code{target}
11391 command to specify one of the target types configured for @value{GDBN}
11392 (@pxref{Target Commands, ,Commands for managing targets}).
11394 @cindex target architecture
11395 It is possible to build @value{GDBN} for several different @dfn{target
11396 architectures}. When @value{GDBN} is built like that, you can choose
11397 one of the available architectures with the @kbd{set architecture}
11401 @kindex set architecture
11402 @kindex show architecture
11403 @item set architecture @var{arch}
11404 This command sets the current target architecture to @var{arch}. The
11405 value of @var{arch} can be @code{"auto"}, in addition to one of the
11406 supported architectures.
11408 @item show architecture
11409 Show the current target architecture.
11411 @item set processor
11413 @kindex set processor
11414 @kindex show processor
11415 These are alias commands for, respectively, @code{set architecture}
11416 and @code{show architecture}.
11420 * Active Targets:: Active targets
11421 * Target Commands:: Commands for managing targets
11422 * Byte Order:: Choosing target byte order
11423 * Remote:: Remote debugging
11424 * KOD:: Kernel Object Display
11428 @node Active Targets
11429 @section Active targets
11431 @cindex stacking targets
11432 @cindex active targets
11433 @cindex multiple targets
11435 There are three classes of targets: processes, core files, and
11436 executable files. @value{GDBN} can work concurrently on up to three
11437 active targets, one in each class. This allows you to (for example)
11438 start a process and inspect its activity without abandoning your work on
11441 For example, if you execute @samp{gdb a.out}, then the executable file
11442 @code{a.out} is the only active target. If you designate a core file as
11443 well---presumably from a prior run that crashed and coredumped---then
11444 @value{GDBN} has two active targets and uses them in tandem, looking
11445 first in the corefile target, then in the executable file, to satisfy
11446 requests for memory addresses. (Typically, these two classes of target
11447 are complementary, since core files contain only a program's
11448 read-write memory---variables and so on---plus machine status, while
11449 executable files contain only the program text and initialized data.)
11451 When you type @code{run}, your executable file becomes an active process
11452 target as well. When a process target is active, all @value{GDBN}
11453 commands requesting memory addresses refer to that target; addresses in
11454 an active core file or executable file target are obscured while the
11455 process target is active.
11457 Use the @code{core-file} and @code{exec-file} commands to select a new
11458 core file or executable target (@pxref{Files, ,Commands to specify
11459 files}). To specify as a target a process that is already running, use
11460 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
11463 @node Target Commands
11464 @section Commands for managing targets
11467 @item target @var{type} @var{parameters}
11468 Connects the @value{GDBN} host environment to a target machine or
11469 process. A target is typically a protocol for talking to debugging
11470 facilities. You use the argument @var{type} to specify the type or
11471 protocol of the target machine.
11473 Further @var{parameters} are interpreted by the target protocol, but
11474 typically include things like device names or host names to connect
11475 with, process numbers, and baud rates.
11477 The @code{target} command does not repeat if you press @key{RET} again
11478 after executing the command.
11480 @kindex help target
11482 Displays the names of all targets available. To display targets
11483 currently selected, use either @code{info target} or @code{info files}
11484 (@pxref{Files, ,Commands to specify files}).
11486 @item help target @var{name}
11487 Describe a particular target, including any parameters necessary to
11490 @kindex set gnutarget
11491 @item set gnutarget @var{args}
11492 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
11493 knows whether it is reading an @dfn{executable},
11494 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
11495 with the @code{set gnutarget} command. Unlike most @code{target} commands,
11496 with @code{gnutarget} the @code{target} refers to a program, not a machine.
11499 @emph{Warning:} To specify a file format with @code{set gnutarget},
11500 you must know the actual BFD name.
11504 @xref{Files, , Commands to specify files}.
11506 @kindex show gnutarget
11507 @item show gnutarget
11508 Use the @code{show gnutarget} command to display what file format
11509 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
11510 @value{GDBN} will determine the file format for each file automatically,
11511 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
11514 @cindex common targets
11515 Here are some common targets (available, or not, depending on the GDB
11520 @item target exec @var{program}
11521 @cindex executable file target
11522 An executable file. @samp{target exec @var{program}} is the same as
11523 @samp{exec-file @var{program}}.
11525 @item target core @var{filename}
11526 @cindex core dump file target
11527 A core dump file. @samp{target core @var{filename}} is the same as
11528 @samp{core-file @var{filename}}.
11530 @item target remote @var{dev}
11531 @cindex remote target
11532 Remote serial target in GDB-specific protocol. The argument @var{dev}
11533 specifies what serial device to use for the connection (e.g.
11534 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
11535 supports the @code{load} command. This is only useful if you have
11536 some other way of getting the stub to the target system, and you can put
11537 it somewhere in memory where it won't get clobbered by the download.
11540 @cindex built-in simulator target
11541 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
11549 works; however, you cannot assume that a specific memory map, device
11550 drivers, or even basic I/O is available, although some simulators do
11551 provide these. For info about any processor-specific simulator details,
11552 see the appropriate section in @ref{Embedded Processors, ,Embedded
11557 Some configurations may include these targets as well:
11561 @item target nrom @var{dev}
11562 @cindex NetROM ROM emulator target
11563 NetROM ROM emulator. This target only supports downloading.
11567 Different targets are available on different configurations of @value{GDBN};
11568 your configuration may have more or fewer targets.
11570 Many remote targets require you to download the executable's code once
11571 you've successfully established a connection. You may wish to control
11572 various aspects of this process, such as the size of the data chunks
11573 used by @value{GDBN} to download program parts to the remote target.
11576 @kindex set download-write-size
11577 @item set download-write-size @var{size}
11578 Set the write size used when downloading a program. Only used when
11579 downloading a program onto a remote target. Specify zero or a
11580 negative value to disable blocked writes. The actual size of each
11581 transfer is also limited by the size of the target packet and the
11584 @kindex show download-write-size
11585 @item show download-write-size
11586 @kindex show download-write-size
11587 Show the current value of the write size.
11590 @kindex set hash@r{, for remote monitors}
11591 @cindex hash mark while downloading
11592 This command controls whether a hash mark @samp{#} is displayed while
11593 downloading a file to the remote monitor. If on, a hash mark is
11594 displayed after each S-record is successfully downloaded to the
11598 @kindex show hash@r{, for remote monitors}
11599 Show the current status of displaying the hash mark.
11601 @item set debug monitor
11602 @kindex set debug monitor
11603 @cindex display remote monitor communications
11604 Enable or disable display of communications messages between
11605 @value{GDBN} and the remote monitor.
11607 @item show debug monitor
11608 @kindex show debug monitor
11609 Show the current status of displaying communications between
11610 @value{GDBN} and the remote monitor.
11615 @kindex load @var{filename}
11616 @item load @var{filename}
11617 Depending on what remote debugging facilities are configured into
11618 @value{GDBN}, the @code{load} command may be available. Where it exists, it
11619 is meant to make @var{filename} (an executable) available for debugging
11620 on the remote system---by downloading, or dynamic linking, for example.
11621 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
11622 the @code{add-symbol-file} command.
11624 If your @value{GDBN} does not have a @code{load} command, attempting to
11625 execute it gets the error message ``@code{You can't do that when your
11626 target is @dots{}}''
11628 The file is loaded at whatever address is specified in the executable.
11629 For some object file formats, you can specify the load address when you
11630 link the program; for other formats, like a.out, the object file format
11631 specifies a fixed address.
11632 @c FIXME! This would be a good place for an xref to the GNU linker doc.
11634 @code{load} does not repeat if you press @key{RET} again after using it.
11638 @section Choosing target byte order
11640 @cindex choosing target byte order
11641 @cindex target byte order
11643 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
11644 offer the ability to run either big-endian or little-endian byte
11645 orders. Usually the executable or symbol will include a bit to
11646 designate the endian-ness, and you will not need to worry about
11647 which to use. However, you may still find it useful to adjust
11648 @value{GDBN}'s idea of processor endian-ness manually.
11652 @item set endian big
11653 Instruct @value{GDBN} to assume the target is big-endian.
11655 @item set endian little
11656 Instruct @value{GDBN} to assume the target is little-endian.
11658 @item set endian auto
11659 Instruct @value{GDBN} to use the byte order associated with the
11663 Display @value{GDBN}'s current idea of the target byte order.
11667 Note that these commands merely adjust interpretation of symbolic
11668 data on the host, and that they have absolutely no effect on the
11672 @section Remote debugging
11673 @cindex remote debugging
11675 If you are trying to debug a program running on a machine that cannot run
11676 @value{GDBN} in the usual way, it is often useful to use remote debugging.
11677 For example, you might use remote debugging on an operating system kernel,
11678 or on a small system which does not have a general purpose operating system
11679 powerful enough to run a full-featured debugger.
11681 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
11682 to make this work with particular debugging targets. In addition,
11683 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
11684 but not specific to any particular target system) which you can use if you
11685 write the remote stubs---the code that runs on the remote system to
11686 communicate with @value{GDBN}.
11688 Other remote targets may be available in your
11689 configuration of @value{GDBN}; use @code{help target} to list them.
11691 Once you've connected to the remote target, @value{GDBN} allows you to
11692 send arbitrary commands to the remote monitor:
11695 @item remote @var{command}
11696 @kindex remote@r{, a command}
11697 @cindex send command to remote monitor
11698 Send an arbitrary @var{command} string to the remote monitor.
11703 @section Kernel Object Display
11704 @cindex kernel object display
11707 Some targets support kernel object display. Using this facility,
11708 @value{GDBN} communicates specially with the underlying operating system
11709 and can display information about operating system-level objects such as
11710 mutexes and other synchronization objects. Exactly which objects can be
11711 displayed is determined on a per-OS basis.
11714 Use the @code{set os} command to set the operating system. This tells
11715 @value{GDBN} which kernel object display module to initialize:
11718 (@value{GDBP}) set os cisco
11722 The associated command @code{show os} displays the operating system
11723 set with the @code{set os} command; if no operating system has been
11724 set, @code{show os} will display an empty string @samp{""}.
11726 If @code{set os} succeeds, @value{GDBN} will display some information
11727 about the operating system, and will create a new @code{info} command
11728 which can be used to query the target. The @code{info} command is named
11729 after the operating system:
11733 (@value{GDBP}) info cisco
11734 List of Cisco Kernel Objects
11736 any Any and all objects
11739 Further subcommands can be used to query about particular objects known
11742 There is currently no way to determine whether a given operating
11743 system is supported other than to try setting it with @kbd{set os
11744 @var{name}}, where @var{name} is the name of the operating system you
11748 @node Remote Debugging
11749 @chapter Debugging remote programs
11752 * Connecting:: Connecting to a remote target
11753 * Server:: Using the gdbserver program
11754 * NetWare:: Using the gdbserve.nlm program
11755 * Remote configuration:: Remote configuration
11756 * remote stub:: Implementing a remote stub
11760 @section Connecting to a remote target
11762 On the @value{GDBN} host machine, you will need an unstripped copy of
11763 your program, since @value{GDBN} needs symobl and debugging information.
11764 Start up @value{GDBN} as usual, using the name of the local copy of your
11765 program as the first argument.
11767 @cindex serial line, @code{target remote}
11768 If you're using a serial line, you may want to give @value{GDBN} the
11769 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
11770 (@pxref{Remote configuration, set remotebaud}) before the
11771 @code{target} command.
11773 After that, use @code{target remote} to establish communications with
11774 the target machine. Its argument specifies how to communicate---either
11775 via a devicename attached to a direct serial line, or a TCP or UDP port
11776 (possibly to a terminal server which in turn has a serial line to the
11777 target). For example, to use a serial line connected to the device
11778 named @file{/dev/ttyb}:
11781 target remote /dev/ttyb
11784 @cindex TCP port, @code{target remote}
11785 To use a TCP connection, use an argument of the form
11786 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
11787 For example, to connect to port 2828 on a
11788 terminal server named @code{manyfarms}:
11791 target remote manyfarms:2828
11794 If your remote target is actually running on the same machine as
11795 your debugger session (e.g.@: a simulator of your target running on
11796 the same host), you can omit the hostname. For example, to connect
11797 to port 1234 on your local machine:
11800 target remote :1234
11804 Note that the colon is still required here.
11806 @cindex UDP port, @code{target remote}
11807 To use a UDP connection, use an argument of the form
11808 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
11809 on a terminal server named @code{manyfarms}:
11812 target remote udp:manyfarms:2828
11815 When using a UDP connection for remote debugging, you should keep in mind
11816 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
11817 busy or unreliable networks, which will cause havoc with your debugging
11820 Now you can use all the usual commands to examine and change data and to
11821 step and continue the remote program.
11823 @cindex interrupting remote programs
11824 @cindex remote programs, interrupting
11825 Whenever @value{GDBN} is waiting for the remote program, if you type the
11826 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
11827 program. This may or may not succeed, depending in part on the hardware
11828 and the serial drivers the remote system uses. If you type the
11829 interrupt character once again, @value{GDBN} displays this prompt:
11832 Interrupted while waiting for the program.
11833 Give up (and stop debugging it)? (y or n)
11836 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
11837 (If you decide you want to try again later, you can use @samp{target
11838 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
11839 goes back to waiting.
11842 @kindex detach (remote)
11844 When you have finished debugging the remote program, you can use the
11845 @code{detach} command to release it from @value{GDBN} control.
11846 Detaching from the target normally resumes its execution, but the results
11847 will depend on your particular remote stub. After the @code{detach}
11848 command, @value{GDBN} is free to connect to another target.
11852 The @code{disconnect} command behaves like @code{detach}, except that
11853 the target is generally not resumed. It will wait for @value{GDBN}
11854 (this instance or another one) to connect and continue debugging. After
11855 the @code{disconnect} command, @value{GDBN} is again free to connect to
11858 @cindex send command to remote monitor
11860 @item monitor @var{cmd}
11861 This command allows you to send commands directly to the remote
11866 @section Using the @code{gdbserver} program
11869 @cindex remote connection without stubs
11870 @code{gdbserver} is a control program for Unix-like systems, which
11871 allows you to connect your program with a remote @value{GDBN} via
11872 @code{target remote}---but without linking in the usual debugging stub.
11874 @code{gdbserver} is not a complete replacement for the debugging stubs,
11875 because it requires essentially the same operating-system facilities
11876 that @value{GDBN} itself does. In fact, a system that can run
11877 @code{gdbserver} to connect to a remote @value{GDBN} could also run
11878 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
11879 because it is a much smaller program than @value{GDBN} itself. It is
11880 also easier to port than all of @value{GDBN}, so you may be able to get
11881 started more quickly on a new system by using @code{gdbserver}.
11882 Finally, if you develop code for real-time systems, you may find that
11883 the tradeoffs involved in real-time operation make it more convenient to
11884 do as much development work as possible on another system, for example
11885 by cross-compiling. You can use @code{gdbserver} to make a similar
11886 choice for debugging.
11888 @value{GDBN} and @code{gdbserver} communicate via either a serial line
11889 or a TCP connection, using the standard @value{GDBN} remote serial
11893 @item On the target machine,
11894 you need to have a copy of the program you want to debug.
11895 @code{gdbserver} does not need your program's symbol table, so you can
11896 strip the program if necessary to save space. @value{GDBN} on the host
11897 system does all the symbol handling.
11899 To use the server, you must tell it how to communicate with @value{GDBN};
11900 the name of your program; and the arguments for your program. The usual
11904 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
11907 @var{comm} is either a device name (to use a serial line) or a TCP
11908 hostname and portnumber. For example, to debug Emacs with the argument
11909 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
11913 target> gdbserver /dev/com1 emacs foo.txt
11916 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
11919 To use a TCP connection instead of a serial line:
11922 target> gdbserver host:2345 emacs foo.txt
11925 The only difference from the previous example is the first argument,
11926 specifying that you are communicating with the host @value{GDBN} via
11927 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
11928 expect a TCP connection from machine @samp{host} to local TCP port 2345.
11929 (Currently, the @samp{host} part is ignored.) You can choose any number
11930 you want for the port number as long as it does not conflict with any
11931 TCP ports already in use on the target system (for example, @code{23} is
11932 reserved for @code{telnet}).@footnote{If you choose a port number that
11933 conflicts with another service, @code{gdbserver} prints an error message
11934 and exits.} You must use the same port number with the host @value{GDBN}
11935 @code{target remote} command.
11937 On some targets, @code{gdbserver} can also attach to running programs.
11938 This is accomplished via the @code{--attach} argument. The syntax is:
11941 target> gdbserver @var{comm} --attach @var{pid}
11944 @var{pid} is the process ID of a currently running process. It isn't necessary
11945 to point @code{gdbserver} at a binary for the running process.
11948 @cindex attach to a program by name
11949 You can debug processes by name instead of process ID if your target has the
11950 @code{pidof} utility:
11953 target> gdbserver @var{comm} --attach `pidof @var{PROGRAM}`
11956 In case more than one copy of @var{PROGRAM} is running, or @var{PROGRAM}
11957 has multiple threads, most versions of @code{pidof} support the
11958 @code{-s} option to only return the first process ID.
11960 @item On the host machine,
11961 connect to your target (@pxref{Connecting,,Connecting to a remote target}).
11962 For TCP connections, you must start up @code{gdbserver} prior to using
11963 the @code{target remote} command. Otherwise you may get an error whose
11964 text depends on the host system, but which usually looks something like
11965 @samp{Connection refused}. You don't need to use the @code{load}
11966 command in @value{GDBN} when using @code{gdbserver}, since the program is
11967 already on the target. However, if you want to load the symbols (as
11968 you normally would), do that with the @code{file} command, and issue
11969 it @emph{before} connecting to the server; otherwise, you will get an
11970 error message saying @code{"Program is already running"}, since the
11971 program is considered running after the connection.
11976 @section Using the @code{gdbserve.nlm} program
11978 @kindex gdbserve.nlm
11979 @code{gdbserve.nlm} is a control program for NetWare systems, which
11980 allows you to connect your program with a remote @value{GDBN} via
11981 @code{target remote}.
11983 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
11984 using the standard @value{GDBN} remote serial protocol.
11987 @item On the target machine,
11988 you need to have a copy of the program you want to debug.
11989 @code{gdbserve.nlm} does not need your program's symbol table, so you
11990 can strip the program if necessary to save space. @value{GDBN} on the
11991 host system does all the symbol handling.
11993 To use the server, you must tell it how to communicate with
11994 @value{GDBN}; the name of your program; and the arguments for your
11995 program. The syntax is:
11998 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
11999 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
12002 @var{board} and @var{port} specify the serial line; @var{baud} specifies
12003 the baud rate used by the connection. @var{port} and @var{node} default
12004 to 0, @var{baud} defaults to 9600@dmn{bps}.
12006 For example, to debug Emacs with the argument @samp{foo.txt}and
12007 communicate with @value{GDBN} over serial port number 2 or board 1
12008 using a 19200@dmn{bps} connection:
12011 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
12015 On the @value{GDBN} host machine, connect to your target (@pxref{Connecting,,
12016 Connecting to a remote target}).
12020 @node Remote configuration
12021 @section Remote configuration
12024 @kindex show remote
12025 This section documents the configuration options available when
12026 debugging remote programs. For the options related to the File I/O
12027 extensions of the remote protocol, see @ref{The system call,
12028 system-call-allowed}.
12031 @item set remoteaddresssize @var{bits}
12032 @cindex adress size for remote targets
12033 @cindex bits in remote address
12034 Set the maximum size of address in a memory packet to the specified
12035 number of bits. @value{GDBN} will mask off the address bits above
12036 that number, when it passes addresses to the remote target. The
12037 default value is the number of bits in the target's address.
12039 @item show remoteaddresssize
12040 Show the current value of remote address size in bits.
12042 @item set remotebaud @var{n}
12043 @cindex baud rate for remote targets
12044 Set the baud rate for the remote serial I/O to @var{n} baud. The
12045 value is used to set the speed of the serial port used for debugging
12048 @item show remotebaud
12049 Show the current speed of the remote connection.
12051 @item set remotebreak
12052 @cindex interrupt remote programs
12053 @cindex BREAK signal instead of Ctrl-C
12054 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
12055 when you press the @key{Ctrl-C} key to interrupt the program running
12056 on the remote. If set to off, @value{GDBN} sends the @samp{Strl-C}
12057 character instead. The default is off, since most remote systems
12058 expect to see @samp{Ctrl-C} as the interrupt signal.
12060 @item show remotebreak
12061 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
12062 interrupt the remote program.
12064 @item set remotedebug
12065 @cindex debug remote protocol
12066 @cindex remote protocol debugging
12067 @cindex display remote packets
12068 Control the debugging of the remote protocol. When enabled, each
12069 packet sent to or received from the remote target is displayed. The
12072 @item show remotedebug
12073 Show the current setting of the remote protocol debugging.
12075 @item set remotedevice @var{device}
12076 @cindex serial port name
12077 Set the name of the serial port through which to communicate to the
12078 remote target to @var{device}. This is the device used by
12079 @value{GDBN} to open the serial communications line to the remote
12080 target. There's no default, so you must set a valid port name for the
12081 remote serial communications to work. (Some varieties of the
12082 @code{target} command accept the port name as part of their
12085 @item show remotedevice
12086 Show the current name of the serial port.
12088 @item set remotelogbase @var{base}
12089 Set the base (a.k.a.@: radix) of logging serial protocol
12090 communications to @var{base}. Supported values of @var{base} are:
12091 @code{ascii}, @code{octal}, and @code{hex}. The default is
12094 @item show remotelogbase
12095 Show the current setting of the radix for logging remote serial
12098 @item set remotelogfile @var{file}
12099 @cindex record serial communications on file
12100 Record remote serial communications on the named @var{file}. The
12101 default is not to record at all.
12103 @item show remotelogfile.
12104 Show the current setting of the file name on which to record the
12105 serial communications.
12107 @item set remotetimeout @var{num}
12108 @cindex timeout for serial communications
12109 @cindex remote timeout
12110 Set the timeout limit to wait for the remote target to respond to
12111 @var{num} seconds. The default is 2 seconds.
12113 @item show remotetimeout
12114 Show the current number of seconds to wait for the remote target
12117 @cindex limit hardware breakpoints and watchpoints
12118 @cindex remote target, limit break- and watchpoints
12119 @anchor{set remote hardware-watchpoint-limit}
12120 @anchor{set remote hardware-breakpoint-limit}
12121 @item set remote hardware-watchpoint-limit @var{limit}
12122 @itemx set remote hardware-breakpoint-limit @var{limit}
12123 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
12124 watchpoints. A limit of -1, the default, is treated as unlimited.
12126 @item set remote fetch-register-packet
12127 @itemx set remote set-register-packet
12128 @itemx set remote P-packet
12129 @itemx set remote p-packet
12131 @cindex fetch registers from remote targets
12132 @cindex set registers in remote targets
12133 Determine whether @value{GDBN} can set and fetch registers from the
12134 remote target using the @samp{P} packets. The default depends on the
12135 remote stub's support of the @samp{P} packets (@value{GDBN} queries
12136 the stub when this packet is first required).
12138 @item show remote fetch-register-packet
12139 @itemx show remote set-register-packet
12140 @itemx show remote P-packet
12141 @itemx show remote p-packet
12142 Show the current setting of using the @samp{P} packets for setting and
12143 fetching registers from the remote target.
12145 @cindex binary downloads
12147 @item set remote binary-download-packet
12148 @itemx set remote X-packet
12149 Determine whether @value{GDBN} sends downloads in binary mode using
12150 the @samp{X} packets. The default is on.
12152 @item show remote binary-download-packet
12153 @itemx show remote X-packet
12154 Show the current setting of using the @samp{X} packets for binary
12157 @item set remote read-aux-vector-packet
12158 @cindex auxiliary vector of remote target
12159 @cindex @code{auxv}, and remote targets
12160 Set the use of the remote protocol's @samp{qPart:auxv:read} (target
12161 auxiliary vector read) request. This request is used to fetch the
12162 remote target's @dfn{auxiliary vector}, see @ref{OS Information,
12163 Auxiliary Vector}. The default setting depends on the remote stub's
12164 support of this request (@value{GDBN} queries the stub when this
12165 request is first required). @xref{General Query Packets, qPart}, for
12166 more information about this request.
12168 @item show remote read-aux-vector-packet
12169 Show the current setting of use of the @samp{qPart:auxv:read} request.
12171 @item set remote symbol-lookup-packet
12172 @cindex remote symbol lookup request
12173 Set the use of the remote protocol's @samp{qSymbol} (target symbol
12174 lookup) request. This request is used to communicate symbol
12175 information to the remote target, e.g., whenever a new shared library
12176 is loaded by the remote (@pxref{Files, shared libraries}). The
12177 default setting depends on the remote stub's support of this request
12178 (@value{GDBN} queries the stub when this request is first required).
12179 @xref{General Query Packets, qSymbol}, for more information about this
12182 @item show remote symbol-lookup-packet
12183 Show the current setting of use of the @samp{qSymbol} request.
12185 @item set remote verbose-resume-packet
12186 @cindex resume remote target
12187 @cindex signal thread, and remote targets
12188 @cindex single-step thread, and remote targets
12189 @cindex thread-specific operations on remote targets
12190 Set the use of the remote protocol's @samp{vCont} (descriptive resume)
12191 request. This request is used to resume specific threads in the
12192 remote target, and to single-step or signal them. The default setting
12193 depends on the remote stub's support of this request (@value{GDBN}
12194 queries the stub when this request is first required). This setting
12195 affects debugging of multithreaded programs: if @samp{vCont} cannot be
12196 used, @value{GDBN} might be unable to single-step a specific thread,
12197 especially under @code{set scheduler-locking off}; it is also
12198 impossible to pause a specific thread. @xref{Packets, vCont}, for
12201 @item show remote verbose-resume-packet
12202 Show the current setting of use of the @samp{vCont} request
12204 @item set remote software-breakpoint-packet
12205 @itemx set remote hardware-breakpoint-packet
12206 @itemx set remote write-watchpoint-packet
12207 @itemx set remote read-watchpoint-packet
12208 @itemx set remote access-watchpoint-packet
12209 @itemx set remote Z-packet
12211 @cindex remote hardware breakpoints and watchpoints
12212 These commands enable or disable the use of @samp{Z} packets for
12213 setting breakpoints and watchpoints in the remote target. The default
12214 depends on the remote stub's support of the @samp{Z} packets
12215 (@value{GDBN} queries the stub when each packet is first required).
12216 The command @code{set remote Z-packet}, kept for back-compatibility,
12217 turns on or off all the features that require the use of @samp{Z}
12220 @item show remote software-breakpoint-packet
12221 @itemx show remote hardware-breakpoint-packet
12222 @itemx show remote write-watchpoint-packet
12223 @itemx show remote read-watchpoint-packet
12224 @itemx show remote access-watchpoint-packet
12225 @itemx show remote Z-packet
12226 Show the current setting of @samp{Z} packets usage.
12228 @item set remote get-thread-local-storage-address
12229 @kindex set remote get-thread-local-storage-address
12230 @cindex thread local storage of remote targets
12231 This command enables or disables the use of the @samp{qGetTLSAddr}
12232 (Get Thread Local Storage Address) request packet. The default
12233 depends on whether the remote stub supports this request.
12234 @xref{General Query Packets, qGetTLSAddr}, for more details about this
12237 @item show remote get-thread-local-storage-address
12238 @kindex show remote get-thread-local-storage-address
12239 Show the current setting of @samp{qGetTLSAddr} packet usage.
12243 @section Implementing a remote stub
12245 @cindex debugging stub, example
12246 @cindex remote stub, example
12247 @cindex stub example, remote debugging
12248 The stub files provided with @value{GDBN} implement the target side of the
12249 communication protocol, and the @value{GDBN} side is implemented in the
12250 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
12251 these subroutines to communicate, and ignore the details. (If you're
12252 implementing your own stub file, you can still ignore the details: start
12253 with one of the existing stub files. @file{sparc-stub.c} is the best
12254 organized, and therefore the easiest to read.)
12256 @cindex remote serial debugging, overview
12257 To debug a program running on another machine (the debugging
12258 @dfn{target} machine), you must first arrange for all the usual
12259 prerequisites for the program to run by itself. For example, for a C
12264 A startup routine to set up the C runtime environment; these usually
12265 have a name like @file{crt0}. The startup routine may be supplied by
12266 your hardware supplier, or you may have to write your own.
12269 A C subroutine library to support your program's
12270 subroutine calls, notably managing input and output.
12273 A way of getting your program to the other machine---for example, a
12274 download program. These are often supplied by the hardware
12275 manufacturer, but you may have to write your own from hardware
12279 The next step is to arrange for your program to use a serial port to
12280 communicate with the machine where @value{GDBN} is running (the @dfn{host}
12281 machine). In general terms, the scheme looks like this:
12285 @value{GDBN} already understands how to use this protocol; when everything
12286 else is set up, you can simply use the @samp{target remote} command
12287 (@pxref{Targets,,Specifying a Debugging Target}).
12289 @item On the target,
12290 you must link with your program a few special-purpose subroutines that
12291 implement the @value{GDBN} remote serial protocol. The file containing these
12292 subroutines is called a @dfn{debugging stub}.
12294 On certain remote targets, you can use an auxiliary program
12295 @code{gdbserver} instead of linking a stub into your program.
12296 @xref{Server,,Using the @code{gdbserver} program}, for details.
12299 The debugging stub is specific to the architecture of the remote
12300 machine; for example, use @file{sparc-stub.c} to debug programs on
12303 @cindex remote serial stub list
12304 These working remote stubs are distributed with @value{GDBN}:
12309 @cindex @file{i386-stub.c}
12312 For Intel 386 and compatible architectures.
12315 @cindex @file{m68k-stub.c}
12316 @cindex Motorola 680x0
12318 For Motorola 680x0 architectures.
12321 @cindex @file{sh-stub.c}
12324 For Renesas SH architectures.
12327 @cindex @file{sparc-stub.c}
12329 For @sc{sparc} architectures.
12331 @item sparcl-stub.c
12332 @cindex @file{sparcl-stub.c}
12335 For Fujitsu @sc{sparclite} architectures.
12339 The @file{README} file in the @value{GDBN} distribution may list other
12340 recently added stubs.
12343 * Stub Contents:: What the stub can do for you
12344 * Bootstrapping:: What you must do for the stub
12345 * Debug Session:: Putting it all together
12348 @node Stub Contents
12349 @subsection What the stub can do for you
12351 @cindex remote serial stub
12352 The debugging stub for your architecture supplies these three
12356 @item set_debug_traps
12357 @findex set_debug_traps
12358 @cindex remote serial stub, initialization
12359 This routine arranges for @code{handle_exception} to run when your
12360 program stops. You must call this subroutine explicitly near the
12361 beginning of your program.
12363 @item handle_exception
12364 @findex handle_exception
12365 @cindex remote serial stub, main routine
12366 This is the central workhorse, but your program never calls it
12367 explicitly---the setup code arranges for @code{handle_exception} to
12368 run when a trap is triggered.
12370 @code{handle_exception} takes control when your program stops during
12371 execution (for example, on a breakpoint), and mediates communications
12372 with @value{GDBN} on the host machine. This is where the communications
12373 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
12374 representative on the target machine. It begins by sending summary
12375 information on the state of your program, then continues to execute,
12376 retrieving and transmitting any information @value{GDBN} needs, until you
12377 execute a @value{GDBN} command that makes your program resume; at that point,
12378 @code{handle_exception} returns control to your own code on the target
12382 @cindex @code{breakpoint} subroutine, remote
12383 Use this auxiliary subroutine to make your program contain a
12384 breakpoint. Depending on the particular situation, this may be the only
12385 way for @value{GDBN} to get control. For instance, if your target
12386 machine has some sort of interrupt button, you won't need to call this;
12387 pressing the interrupt button transfers control to
12388 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
12389 simply receiving characters on the serial port may also trigger a trap;
12390 again, in that situation, you don't need to call @code{breakpoint} from
12391 your own program---simply running @samp{target remote} from the host
12392 @value{GDBN} session gets control.
12394 Call @code{breakpoint} if none of these is true, or if you simply want
12395 to make certain your program stops at a predetermined point for the
12396 start of your debugging session.
12399 @node Bootstrapping
12400 @subsection What you must do for the stub
12402 @cindex remote stub, support routines
12403 The debugging stubs that come with @value{GDBN} are set up for a particular
12404 chip architecture, but they have no information about the rest of your
12405 debugging target machine.
12407 First of all you need to tell the stub how to communicate with the
12411 @item int getDebugChar()
12412 @findex getDebugChar
12413 Write this subroutine to read a single character from the serial port.
12414 It may be identical to @code{getchar} for your target system; a
12415 different name is used to allow you to distinguish the two if you wish.
12417 @item void putDebugChar(int)
12418 @findex putDebugChar
12419 Write this subroutine to write a single character to the serial port.
12420 It may be identical to @code{putchar} for your target system; a
12421 different name is used to allow you to distinguish the two if you wish.
12424 @cindex control C, and remote debugging
12425 @cindex interrupting remote targets
12426 If you want @value{GDBN} to be able to stop your program while it is
12427 running, you need to use an interrupt-driven serial driver, and arrange
12428 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
12429 character). That is the character which @value{GDBN} uses to tell the
12430 remote system to stop.
12432 Getting the debugging target to return the proper status to @value{GDBN}
12433 probably requires changes to the standard stub; one quick and dirty way
12434 is to just execute a breakpoint instruction (the ``dirty'' part is that
12435 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
12437 Other routines you need to supply are:
12440 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
12441 @findex exceptionHandler
12442 Write this function to install @var{exception_address} in the exception
12443 handling tables. You need to do this because the stub does not have any
12444 way of knowing what the exception handling tables on your target system
12445 are like (for example, the processor's table might be in @sc{rom},
12446 containing entries which point to a table in @sc{ram}).
12447 @var{exception_number} is the exception number which should be changed;
12448 its meaning is architecture-dependent (for example, different numbers
12449 might represent divide by zero, misaligned access, etc). When this
12450 exception occurs, control should be transferred directly to
12451 @var{exception_address}, and the processor state (stack, registers,
12452 and so on) should be just as it is when a processor exception occurs. So if
12453 you want to use a jump instruction to reach @var{exception_address}, it
12454 should be a simple jump, not a jump to subroutine.
12456 For the 386, @var{exception_address} should be installed as an interrupt
12457 gate so that interrupts are masked while the handler runs. The gate
12458 should be at privilege level 0 (the most privileged level). The
12459 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
12460 help from @code{exceptionHandler}.
12462 @item void flush_i_cache()
12463 @findex flush_i_cache
12464 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
12465 instruction cache, if any, on your target machine. If there is no
12466 instruction cache, this subroutine may be a no-op.
12468 On target machines that have instruction caches, @value{GDBN} requires this
12469 function to make certain that the state of your program is stable.
12473 You must also make sure this library routine is available:
12476 @item void *memset(void *, int, int)
12478 This is the standard library function @code{memset} that sets an area of
12479 memory to a known value. If you have one of the free versions of
12480 @code{libc.a}, @code{memset} can be found there; otherwise, you must
12481 either obtain it from your hardware manufacturer, or write your own.
12484 If you do not use the GNU C compiler, you may need other standard
12485 library subroutines as well; this varies from one stub to another,
12486 but in general the stubs are likely to use any of the common library
12487 subroutines which @code{@value{GCC}} generates as inline code.
12490 @node Debug Session
12491 @subsection Putting it all together
12493 @cindex remote serial debugging summary
12494 In summary, when your program is ready to debug, you must follow these
12499 Make sure you have defined the supporting low-level routines
12500 (@pxref{Bootstrapping,,What you must do for the stub}):
12502 @code{getDebugChar}, @code{putDebugChar},
12503 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
12507 Insert these lines near the top of your program:
12515 For the 680x0 stub only, you need to provide a variable called
12516 @code{exceptionHook}. Normally you just use:
12519 void (*exceptionHook)() = 0;
12523 but if before calling @code{set_debug_traps}, you set it to point to a
12524 function in your program, that function is called when
12525 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
12526 error). The function indicated by @code{exceptionHook} is called with
12527 one parameter: an @code{int} which is the exception number.
12530 Compile and link together: your program, the @value{GDBN} debugging stub for
12531 your target architecture, and the supporting subroutines.
12534 Make sure you have a serial connection between your target machine and
12535 the @value{GDBN} host, and identify the serial port on the host.
12538 @c The "remote" target now provides a `load' command, so we should
12539 @c document that. FIXME.
12540 Download your program to your target machine (or get it there by
12541 whatever means the manufacturer provides), and start it.
12544 Start @value{GDBN} on the host, and connect to the target
12545 (@pxref{Connecting,,Connecting to a remote target}).
12549 @node Configurations
12550 @chapter Configuration-Specific Information
12552 While nearly all @value{GDBN} commands are available for all native and
12553 cross versions of the debugger, there are some exceptions. This chapter
12554 describes things that are only available in certain configurations.
12556 There are three major categories of configurations: native
12557 configurations, where the host and target are the same, embedded
12558 operating system configurations, which are usually the same for several
12559 different processor architectures, and bare embedded processors, which
12560 are quite different from each other.
12565 * Embedded Processors::
12572 This section describes details specific to particular native
12577 * BSD libkvm Interface:: Debugging BSD kernel memory images
12578 * SVR4 Process Information:: SVR4 process information
12579 * DJGPP Native:: Features specific to the DJGPP port
12580 * Cygwin Native:: Features specific to the Cygwin port
12581 * Hurd Native:: Features specific to @sc{gnu} Hurd
12582 * Neutrino:: Features specific to QNX Neutrino
12588 On HP-UX systems, if you refer to a function or variable name that
12589 begins with a dollar sign, @value{GDBN} searches for a user or system
12590 name first, before it searches for a convenience variable.
12593 @node BSD libkvm Interface
12594 @subsection BSD libkvm Interface
12597 @cindex kernel memory image
12598 @cindex kernel crash dump
12600 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
12601 interface that provides a uniform interface for accessing kernel virtual
12602 memory images, including live systems and crash dumps. @value{GDBN}
12603 uses this interface to allow you to debug live kernels and kernel crash
12604 dumps on many native BSD configurations. This is implemented as a
12605 special @code{kvm} debugging target. For debugging a live system, load
12606 the currently running kernel into @value{GDBN} and connect to the
12610 (@value{GDBP}) @b{target kvm}
12613 For debugging crash dumps, provide the file name of the crash dump as an
12617 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
12620 Once connected to the @code{kvm} target, the following commands are
12626 Set current context from the @dfn{Process Control Block} (PCB) address.
12629 Set current context from proc address. This command isn't available on
12630 modern FreeBSD systems.
12633 @node SVR4 Process Information
12634 @subsection SVR4 process information
12636 @cindex examine process image
12637 @cindex process info via @file{/proc}
12639 Many versions of SVR4 and compatible systems provide a facility called
12640 @samp{/proc} that can be used to examine the image of a running
12641 process using file-system subroutines. If @value{GDBN} is configured
12642 for an operating system with this facility, the command @code{info
12643 proc} is available to report information about the process running
12644 your program, or about any process running on your system. @code{info
12645 proc} works only on SVR4 systems that include the @code{procfs} code.
12646 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
12647 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
12653 @itemx info proc @var{process-id}
12654 Summarize available information about any running process. If a
12655 process ID is specified by @var{process-id}, display information about
12656 that process; otherwise display information about the program being
12657 debugged. The summary includes the debugged process ID, the command
12658 line used to invoke it, its current working directory, and its
12659 executable file's absolute file name.
12661 On some systems, @var{process-id} can be of the form
12662 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
12663 within a process. If the optional @var{pid} part is missing, it means
12664 a thread from the process being debugged (the leading @samp{/} still
12665 needs to be present, or else @value{GDBN} will interpret the number as
12666 a process ID rather than a thread ID).
12668 @item info proc mappings
12669 @cindex memory address space mappings
12670 Report the memory address space ranges accessible in the program, with
12671 information on whether the process has read, write, or execute access
12672 rights to each range. On @sc{gnu}/Linux systems, each memory range
12673 includes the object file which is mapped to that range, instead of the
12674 memory access rights to that range.
12676 @item info proc stat
12677 @itemx info proc status
12678 @cindex process detailed status information
12679 These subcommands are specific to @sc{gnu}/Linux systems. They show
12680 the process-related information, including the user ID and group ID;
12681 how many threads are there in the process; its virtual memory usage;
12682 the signals that are pending, blocked, and ignored; its TTY; its
12683 consumption of system and user time; its stack size; its @samp{nice}
12684 value; etc. For more information, see the @samp{proc} man page
12685 (type @kbd{man 5 proc} from your shell prompt).
12687 @item info proc all
12688 Show all the information about the process described under all of the
12689 above @code{info proc} subcommands.
12692 @comment These sub-options of 'info proc' were not included when
12693 @comment procfs.c was re-written. Keep their descriptions around
12694 @comment against the day when someone finds the time to put them back in.
12695 @kindex info proc times
12696 @item info proc times
12697 Starting time, user CPU time, and system CPU time for your program and
12700 @kindex info proc id
12702 Report on the process IDs related to your program: its own process ID,
12703 the ID of its parent, the process group ID, and the session ID.
12706 @item set procfs-trace
12707 @kindex set procfs-trace
12708 @cindex @code{procfs} API calls
12709 This command enables and disables tracing of @code{procfs} API calls.
12711 @item show procfs-trace
12712 @kindex show procfs-trace
12713 Show the current state of @code{procfs} API call tracing.
12715 @item set procfs-file @var{file}
12716 @kindex set procfs-file
12717 Tell @value{GDBN} to write @code{procfs} API trace to the named
12718 @var{file}. @value{GDBN} appends the trace info to the previous
12719 contents of the file. The default is to display the trace on the
12722 @item show procfs-file
12723 @kindex show procfs-file
12724 Show the file to which @code{procfs} API trace is written.
12726 @item proc-trace-entry
12727 @itemx proc-trace-exit
12728 @itemx proc-untrace-entry
12729 @itemx proc-untrace-exit
12730 @kindex proc-trace-entry
12731 @kindex proc-trace-exit
12732 @kindex proc-untrace-entry
12733 @kindex proc-untrace-exit
12734 These commands enable and disable tracing of entries into and exits
12735 from the @code{syscall} interface.
12738 @kindex info pidlist
12739 @cindex process list, QNX Neutrino
12740 For QNX Neutrino only, this command displays the list of all the
12741 processes and all the threads within each process.
12744 @kindex info meminfo
12745 @cindex mapinfo list, QNX Neutrino
12746 For QNX Neutrino only, this command displays the list of all mapinfos.
12750 @subsection Features for Debugging @sc{djgpp} Programs
12751 @cindex @sc{djgpp} debugging
12752 @cindex native @sc{djgpp} debugging
12753 @cindex MS-DOS-specific commands
12756 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
12757 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
12758 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
12759 top of real-mode DOS systems and their emulations.
12761 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
12762 defines a few commands specific to the @sc{djgpp} port. This
12763 subsection describes those commands.
12768 This is a prefix of @sc{djgpp}-specific commands which print
12769 information about the target system and important OS structures.
12772 @cindex MS-DOS system info
12773 @cindex free memory information (MS-DOS)
12774 @item info dos sysinfo
12775 This command displays assorted information about the underlying
12776 platform: the CPU type and features, the OS version and flavor, the
12777 DPMI version, and the available conventional and DPMI memory.
12782 @cindex segment descriptor tables
12783 @cindex descriptor tables display
12785 @itemx info dos ldt
12786 @itemx info dos idt
12787 These 3 commands display entries from, respectively, Global, Local,
12788 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
12789 tables are data structures which store a descriptor for each segment
12790 that is currently in use. The segment's selector is an index into a
12791 descriptor table; the table entry for that index holds the
12792 descriptor's base address and limit, and its attributes and access
12795 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
12796 segment (used for both data and the stack), and a DOS segment (which
12797 allows access to DOS/BIOS data structures and absolute addresses in
12798 conventional memory). However, the DPMI host will usually define
12799 additional segments in order to support the DPMI environment.
12801 @cindex garbled pointers
12802 These commands allow to display entries from the descriptor tables.
12803 Without an argument, all entries from the specified table are
12804 displayed. An argument, which should be an integer expression, means
12805 display a single entry whose index is given by the argument. For
12806 example, here's a convenient way to display information about the
12807 debugged program's data segment:
12810 @exdent @code{(@value{GDBP}) info dos ldt $ds}
12811 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
12815 This comes in handy when you want to see whether a pointer is outside
12816 the data segment's limit (i.e.@: @dfn{garbled}).
12818 @cindex page tables display (MS-DOS)
12820 @itemx info dos pte
12821 These two commands display entries from, respectively, the Page
12822 Directory and the Page Tables. Page Directories and Page Tables are
12823 data structures which control how virtual memory addresses are mapped
12824 into physical addresses. A Page Table includes an entry for every
12825 page of memory that is mapped into the program's address space; there
12826 may be several Page Tables, each one holding up to 4096 entries. A
12827 Page Directory has up to 4096 entries, one each for every Page Table
12828 that is currently in use.
12830 Without an argument, @kbd{info dos pde} displays the entire Page
12831 Directory, and @kbd{info dos pte} displays all the entries in all of
12832 the Page Tables. An argument, an integer expression, given to the
12833 @kbd{info dos pde} command means display only that entry from the Page
12834 Directory table. An argument given to the @kbd{info dos pte} command
12835 means display entries from a single Page Table, the one pointed to by
12836 the specified entry in the Page Directory.
12838 @cindex direct memory access (DMA) on MS-DOS
12839 These commands are useful when your program uses @dfn{DMA} (Direct
12840 Memory Access), which needs physical addresses to program the DMA
12843 These commands are supported only with some DPMI servers.
12845 @cindex physical address from linear address
12846 @item info dos address-pte @var{addr}
12847 This command displays the Page Table entry for a specified linear
12848 address. The argument @var{addr} is a linear address which should
12849 already have the appropriate segment's base address added to it,
12850 because this command accepts addresses which may belong to @emph{any}
12851 segment. For example, here's how to display the Page Table entry for
12852 the page where a variable @code{i} is stored:
12855 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
12856 @exdent @code{Page Table entry for address 0x11a00d30:}
12857 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
12861 This says that @code{i} is stored at offset @code{0xd30} from the page
12862 whose physical base address is @code{0x02698000}, and shows all the
12863 attributes of that page.
12865 Note that you must cast the addresses of variables to a @code{char *},
12866 since otherwise the value of @code{__djgpp_base_address}, the base
12867 address of all variables and functions in a @sc{djgpp} program, will
12868 be added using the rules of C pointer arithmetics: if @code{i} is
12869 declared an @code{int}, @value{GDBN} will add 4 times the value of
12870 @code{__djgpp_base_address} to the address of @code{i}.
12872 Here's another example, it displays the Page Table entry for the
12876 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
12877 @exdent @code{Page Table entry for address 0x29110:}
12878 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
12882 (The @code{+ 3} offset is because the transfer buffer's address is the
12883 3rd member of the @code{_go32_info_block} structure.) The output
12884 clearly shows that this DPMI server maps the addresses in conventional
12885 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
12886 linear (@code{0x29110}) addresses are identical.
12888 This command is supported only with some DPMI servers.
12891 @cindex DOS serial data link, remote debugging
12892 In addition to native debugging, the DJGPP port supports remote
12893 debugging via a serial data link. The following commands are specific
12894 to remote serial debugging in the DJGPP port of @value{GDBN}.
12897 @kindex set com1base
12898 @kindex set com1irq
12899 @kindex set com2base
12900 @kindex set com2irq
12901 @kindex set com3base
12902 @kindex set com3irq
12903 @kindex set com4base
12904 @kindex set com4irq
12905 @item set com1base @var{addr}
12906 This command sets the base I/O port address of the @file{COM1} serial
12909 @item set com1irq @var{irq}
12910 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
12911 for the @file{COM1} serial port.
12913 There are similar commands @samp{set com2base}, @samp{set com3irq},
12914 etc.@: for setting the port address and the @code{IRQ} lines for the
12917 @kindex show com1base
12918 @kindex show com1irq
12919 @kindex show com2base
12920 @kindex show com2irq
12921 @kindex show com3base
12922 @kindex show com3irq
12923 @kindex show com4base
12924 @kindex show com4irq
12925 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
12926 display the current settings of the base address and the @code{IRQ}
12927 lines used by the COM ports.
12930 @kindex info serial
12931 @cindex DOS serial port status
12932 This command prints the status of the 4 DOS serial ports. For each
12933 port, it prints whether it's active or not, its I/O base address and
12934 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
12935 counts of various errors encountered so far.
12939 @node Cygwin Native
12940 @subsection Features for Debugging MS Windows PE executables
12941 @cindex MS Windows debugging
12942 @cindex native Cygwin debugging
12943 @cindex Cygwin-specific commands
12945 @value{GDBN} supports native debugging of MS Windows programs, including
12946 DLLs with and without symbolic debugging information. There are various
12947 additional Cygwin-specific commands, described in this subsection. The
12948 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
12949 that have no debugging symbols.
12955 This is a prefix of MS Windows specific commands which print
12956 information about the target system and important OS structures.
12958 @item info w32 selector
12959 This command displays information returned by
12960 the Win32 API @code{GetThreadSelectorEntry} function.
12961 It takes an optional argument that is evaluated to
12962 a long value to give the information about this given selector.
12963 Without argument, this command displays information
12964 about the the six segment registers.
12968 This is a Cygwin specific alias of info shared.
12970 @kindex dll-symbols
12972 This command loads symbols from a dll similarly to
12973 add-sym command but without the need to specify a base address.
12975 @kindex set new-console
12976 @item set new-console @var{mode}
12977 If @var{mode} is @code{on} the debuggee will
12978 be started in a new console on next start.
12979 If @var{mode} is @code{off}i, the debuggee will
12980 be started in the same console as the debugger.
12982 @kindex show new-console
12983 @item show new-console
12984 Displays whether a new console is used
12985 when the debuggee is started.
12987 @kindex set new-group
12988 @item set new-group @var{mode}
12989 This boolean value controls whether the debuggee should
12990 start a new group or stay in the same group as the debugger.
12991 This affects the way the Windows OS handles
12994 @kindex show new-group
12995 @item show new-group
12996 Displays current value of new-group boolean.
12998 @kindex set debugevents
12999 @item set debugevents
13000 This boolean value adds debug output concerning events seen by the debugger.
13002 @kindex set debugexec
13003 @item set debugexec
13004 This boolean value adds debug output concerning execute events
13005 seen by the debugger.
13007 @kindex set debugexceptions
13008 @item set debugexceptions
13009 This boolean value adds debug ouptut concerning exception events
13010 seen by the debugger.
13012 @kindex set debugmemory
13013 @item set debugmemory
13014 This boolean value adds debug ouptut concerning memory events
13015 seen by the debugger.
13019 This boolean values specifies whether the debuggee is called
13020 via a shell or directly (default value is on).
13024 Displays if the debuggee will be started with a shell.
13029 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
13032 @node Non-debug DLL symbols
13033 @subsubsection Support for DLLs without debugging symbols
13034 @cindex DLLs with no debugging symbols
13035 @cindex Minimal symbols and DLLs
13037 Very often on windows, some of the DLLs that your program relies on do
13038 not include symbolic debugging information (for example,
13039 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
13040 symbols in a DLL, it relies on the minimal amount of symbolic
13041 information contained in the DLL's export table. This subsubsection
13042 describes working with such symbols, known internally to @value{GDBN} as
13043 ``minimal symbols''.
13045 Note that before the debugged program has started execution, no DLLs
13046 will have been loaded. The easiest way around this problem is simply to
13047 start the program --- either by setting a breakpoint or letting the
13048 program run once to completion. It is also possible to force
13049 @value{GDBN} to load a particular DLL before starting the executable ---
13050 see the shared library information in @pxref{Files} or the
13051 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
13052 explicitly loading symbols from a DLL with no debugging information will
13053 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
13054 which may adversely affect symbol lookup performance.
13056 @subsubsection DLL name prefixes
13058 In keeping with the naming conventions used by the Microsoft debugging
13059 tools, DLL export symbols are made available with a prefix based on the
13060 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
13061 also entered into the symbol table, so @code{CreateFileA} is often
13062 sufficient. In some cases there will be name clashes within a program
13063 (particularly if the executable itself includes full debugging symbols)
13064 necessitating the use of the fully qualified name when referring to the
13065 contents of the DLL. Use single-quotes around the name to avoid the
13066 exclamation mark (``!'') being interpreted as a language operator.
13068 Note that the internal name of the DLL may be all upper-case, even
13069 though the file name of the DLL is lower-case, or vice-versa. Since
13070 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
13071 some confusion. If in doubt, try the @code{info functions} and
13072 @code{info variables} commands or even @code{maint print msymbols} (see
13073 @pxref{Symbols}). Here's an example:
13076 (@value{GDBP}) info function CreateFileA
13077 All functions matching regular expression "CreateFileA":
13079 Non-debugging symbols:
13080 0x77e885f4 CreateFileA
13081 0x77e885f4 KERNEL32!CreateFileA
13085 (@value{GDBP}) info function !
13086 All functions matching regular expression "!":
13088 Non-debugging symbols:
13089 0x6100114c cygwin1!__assert
13090 0x61004034 cygwin1!_dll_crt0@@0
13091 0x61004240 cygwin1!dll_crt0(per_process *)
13095 @subsubsection Working with minimal symbols
13097 Symbols extracted from a DLL's export table do not contain very much
13098 type information. All that @value{GDBN} can do is guess whether a symbol
13099 refers to a function or variable depending on the linker section that
13100 contains the symbol. Also note that the actual contents of the memory
13101 contained in a DLL are not available unless the program is running. This
13102 means that you cannot examine the contents of a variable or disassemble
13103 a function within a DLL without a running program.
13105 Variables are generally treated as pointers and dereferenced
13106 automatically. For this reason, it is often necessary to prefix a
13107 variable name with the address-of operator (``&'') and provide explicit
13108 type information in the command. Here's an example of the type of
13112 (@value{GDBP}) print 'cygwin1!__argv'
13117 (@value{GDBP}) x 'cygwin1!__argv'
13118 0x10021610: "\230y\""
13121 And two possible solutions:
13124 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
13125 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
13129 (@value{GDBP}) x/2x &'cygwin1!__argv'
13130 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
13131 (@value{GDBP}) x/x 0x10021608
13132 0x10021608: 0x0022fd98
13133 (@value{GDBP}) x/s 0x0022fd98
13134 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
13137 Setting a break point within a DLL is possible even before the program
13138 starts execution. However, under these circumstances, @value{GDBN} can't
13139 examine the initial instructions of the function in order to skip the
13140 function's frame set-up code. You can work around this by using ``*&''
13141 to set the breakpoint at a raw memory address:
13144 (@value{GDBP}) break *&'python22!PyOS_Readline'
13145 Breakpoint 1 at 0x1e04eff0
13148 The author of these extensions is not entirely convinced that setting a
13149 break point within a shared DLL like @file{kernel32.dll} is completely
13153 @subsection Commands specific to @sc{gnu} Hurd systems
13154 @cindex @sc{gnu} Hurd debugging
13156 This subsection describes @value{GDBN} commands specific to the
13157 @sc{gnu} Hurd native debugging.
13162 @kindex set signals@r{, Hurd command}
13163 @kindex set sigs@r{, Hurd command}
13164 This command toggles the state of inferior signal interception by
13165 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
13166 affected by this command. @code{sigs} is a shorthand alias for
13171 @kindex show signals@r{, Hurd command}
13172 @kindex show sigs@r{, Hurd command}
13173 Show the current state of intercepting inferior's signals.
13175 @item set signal-thread
13176 @itemx set sigthread
13177 @kindex set signal-thread
13178 @kindex set sigthread
13179 This command tells @value{GDBN} which thread is the @code{libc} signal
13180 thread. That thread is run when a signal is delivered to a running
13181 process. @code{set sigthread} is the shorthand alias of @code{set
13184 @item show signal-thread
13185 @itemx show sigthread
13186 @kindex show signal-thread
13187 @kindex show sigthread
13188 These two commands show which thread will run when the inferior is
13189 delivered a signal.
13192 @kindex set stopped@r{, Hurd command}
13193 This commands tells @value{GDBN} that the inferior process is stopped,
13194 as with the @code{SIGSTOP} signal. The stopped process can be
13195 continued by delivering a signal to it.
13198 @kindex show stopped@r{, Hurd command}
13199 This command shows whether @value{GDBN} thinks the debuggee is
13202 @item set exceptions
13203 @kindex set exceptions@r{, Hurd command}
13204 Use this command to turn off trapping of exceptions in the inferior.
13205 When exception trapping is off, neither breakpoints nor
13206 single-stepping will work. To restore the default, set exception
13209 @item show exceptions
13210 @kindex show exceptions@r{, Hurd command}
13211 Show the current state of trapping exceptions in the inferior.
13213 @item set task pause
13214 @kindex set task@r{, Hurd commands}
13215 @cindex task attributes (@sc{gnu} Hurd)
13216 @cindex pause current task (@sc{gnu} Hurd)
13217 This command toggles task suspension when @value{GDBN} has control.
13218 Setting it to on takes effect immediately, and the task is suspended
13219 whenever @value{GDBN} gets control. Setting it to off will take
13220 effect the next time the inferior is continued. If this option is set
13221 to off, you can use @code{set thread default pause on} or @code{set
13222 thread pause on} (see below) to pause individual threads.
13224 @item show task pause
13225 @kindex show task@r{, Hurd commands}
13226 Show the current state of task suspension.
13228 @item set task detach-suspend-count
13229 @cindex task suspend count
13230 @cindex detach from task, @sc{gnu} Hurd
13231 This command sets the suspend count the task will be left with when
13232 @value{GDBN} detaches from it.
13234 @item show task detach-suspend-count
13235 Show the suspend count the task will be left with when detaching.
13237 @item set task exception-port
13238 @itemx set task excp
13239 @cindex task exception port, @sc{gnu} Hurd
13240 This command sets the task exception port to which @value{GDBN} will
13241 forward exceptions. The argument should be the value of the @dfn{send
13242 rights} of the task. @code{set task excp} is a shorthand alias.
13244 @item set noninvasive
13245 @cindex noninvasive task options
13246 This command switches @value{GDBN} to a mode that is the least
13247 invasive as far as interfering with the inferior is concerned. This
13248 is the same as using @code{set task pause}, @code{set exceptions}, and
13249 @code{set signals} to values opposite to the defaults.
13251 @item info send-rights
13252 @itemx info receive-rights
13253 @itemx info port-rights
13254 @itemx info port-sets
13255 @itemx info dead-names
13258 @cindex send rights, @sc{gnu} Hurd
13259 @cindex receive rights, @sc{gnu} Hurd
13260 @cindex port rights, @sc{gnu} Hurd
13261 @cindex port sets, @sc{gnu} Hurd
13262 @cindex dead names, @sc{gnu} Hurd
13263 These commands display information about, respectively, send rights,
13264 receive rights, port rights, port sets, and dead names of a task.
13265 There are also shorthand aliases: @code{info ports} for @code{info
13266 port-rights} and @code{info psets} for @code{info port-sets}.
13268 @item set thread pause
13269 @kindex set thread@r{, Hurd command}
13270 @cindex thread properties, @sc{gnu} Hurd
13271 @cindex pause current thread (@sc{gnu} Hurd)
13272 This command toggles current thread suspension when @value{GDBN} has
13273 control. Setting it to on takes effect immediately, and the current
13274 thread is suspended whenever @value{GDBN} gets control. Setting it to
13275 off will take effect the next time the inferior is continued.
13276 Normally, this command has no effect, since when @value{GDBN} has
13277 control, the whole task is suspended. However, if you used @code{set
13278 task pause off} (see above), this command comes in handy to suspend
13279 only the current thread.
13281 @item show thread pause
13282 @kindex show thread@r{, Hurd command}
13283 This command shows the state of current thread suspension.
13285 @item set thread run
13286 This comamnd sets whether the current thread is allowed to run.
13288 @item show thread run
13289 Show whether the current thread is allowed to run.
13291 @item set thread detach-suspend-count
13292 @cindex thread suspend count, @sc{gnu} Hurd
13293 @cindex detach from thread, @sc{gnu} Hurd
13294 This command sets the suspend count @value{GDBN} will leave on a
13295 thread when detaching. This number is relative to the suspend count
13296 found by @value{GDBN} when it notices the thread; use @code{set thread
13297 takeover-suspend-count} to force it to an absolute value.
13299 @item show thread detach-suspend-count
13300 Show the suspend count @value{GDBN} will leave on the thread when
13303 @item set thread exception-port
13304 @itemx set thread excp
13305 Set the thread exception port to which to forward exceptions. This
13306 overrides the port set by @code{set task exception-port} (see above).
13307 @code{set thread excp} is the shorthand alias.
13309 @item set thread takeover-suspend-count
13310 Normally, @value{GDBN}'s thread suspend counts are relative to the
13311 value @value{GDBN} finds when it notices each thread. This command
13312 changes the suspend counts to be absolute instead.
13314 @item set thread default
13315 @itemx show thread default
13316 @cindex thread default settings, @sc{gnu} Hurd
13317 Each of the above @code{set thread} commands has a @code{set thread
13318 default} counterpart (e.g., @code{set thread default pause}, @code{set
13319 thread default exception-port}, etc.). The @code{thread default}
13320 variety of commands sets the default thread properties for all
13321 threads; you can then change the properties of individual threads with
13322 the non-default commands.
13327 @subsection QNX Neutrino
13328 @cindex QNX Neutrino
13330 @value{GDBN} provides the following commands specific to the QNX
13334 @item set debug nto-debug
13335 @kindex set debug nto-debug
13336 When set to on, enables debugging messages specific to the QNX
13339 @item show debug nto-debug
13340 @kindex show debug nto-debug
13341 Show the current state of QNX Neutrino messages.
13346 @section Embedded Operating Systems
13348 This section describes configurations involving the debugging of
13349 embedded operating systems that are available for several different
13353 * VxWorks:: Using @value{GDBN} with VxWorks
13356 @value{GDBN} includes the ability to debug programs running on
13357 various real-time operating systems.
13360 @subsection Using @value{GDBN} with VxWorks
13366 @kindex target vxworks
13367 @item target vxworks @var{machinename}
13368 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
13369 is the target system's machine name or IP address.
13373 On VxWorks, @code{load} links @var{filename} dynamically on the
13374 current target system as well as adding its symbols in @value{GDBN}.
13376 @value{GDBN} enables developers to spawn and debug tasks running on networked
13377 VxWorks targets from a Unix host. Already-running tasks spawned from
13378 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
13379 both the Unix host and on the VxWorks target. The program
13380 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
13381 installed with the name @code{vxgdb}, to distinguish it from a
13382 @value{GDBN} for debugging programs on the host itself.)
13385 @item VxWorks-timeout @var{args}
13386 @kindex vxworks-timeout
13387 All VxWorks-based targets now support the option @code{vxworks-timeout}.
13388 This option is set by the user, and @var{args} represents the number of
13389 seconds @value{GDBN} waits for responses to rpc's. You might use this if
13390 your VxWorks target is a slow software simulator or is on the far side
13391 of a thin network line.
13394 The following information on connecting to VxWorks was current when
13395 this manual was produced; newer releases of VxWorks may use revised
13398 @findex INCLUDE_RDB
13399 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
13400 to include the remote debugging interface routines in the VxWorks
13401 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
13402 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
13403 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
13404 source debugging task @code{tRdbTask} when VxWorks is booted. For more
13405 information on configuring and remaking VxWorks, see the manufacturer's
13407 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
13409 Once you have included @file{rdb.a} in your VxWorks system image and set
13410 your Unix execution search path to find @value{GDBN}, you are ready to
13411 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
13412 @code{vxgdb}, depending on your installation).
13414 @value{GDBN} comes up showing the prompt:
13421 * VxWorks Connection:: Connecting to VxWorks
13422 * VxWorks Download:: VxWorks download
13423 * VxWorks Attach:: Running tasks
13426 @node VxWorks Connection
13427 @subsubsection Connecting to VxWorks
13429 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
13430 network. To connect to a target whose host name is ``@code{tt}'', type:
13433 (vxgdb) target vxworks tt
13437 @value{GDBN} displays messages like these:
13440 Attaching remote machine across net...
13445 @value{GDBN} then attempts to read the symbol tables of any object modules
13446 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
13447 these files by searching the directories listed in the command search
13448 path (@pxref{Environment, ,Your program's environment}); if it fails
13449 to find an object file, it displays a message such as:
13452 prog.o: No such file or directory.
13455 When this happens, add the appropriate directory to the search path with
13456 the @value{GDBN} command @code{path}, and execute the @code{target}
13459 @node VxWorks Download
13460 @subsubsection VxWorks download
13462 @cindex download to VxWorks
13463 If you have connected to the VxWorks target and you want to debug an
13464 object that has not yet been loaded, you can use the @value{GDBN}
13465 @code{load} command to download a file from Unix to VxWorks
13466 incrementally. The object file given as an argument to the @code{load}
13467 command is actually opened twice: first by the VxWorks target in order
13468 to download the code, then by @value{GDBN} in order to read the symbol
13469 table. This can lead to problems if the current working directories on
13470 the two systems differ. If both systems have NFS mounted the same
13471 filesystems, you can avoid these problems by using absolute paths.
13472 Otherwise, it is simplest to set the working directory on both systems
13473 to the directory in which the object file resides, and then to reference
13474 the file by its name, without any path. For instance, a program
13475 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
13476 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
13477 program, type this on VxWorks:
13480 -> cd "@var{vxpath}/vw/demo/rdb"
13484 Then, in @value{GDBN}, type:
13487 (vxgdb) cd @var{hostpath}/vw/demo/rdb
13488 (vxgdb) load prog.o
13491 @value{GDBN} displays a response similar to this:
13494 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
13497 You can also use the @code{load} command to reload an object module
13498 after editing and recompiling the corresponding source file. Note that
13499 this makes @value{GDBN} delete all currently-defined breakpoints,
13500 auto-displays, and convenience variables, and to clear the value
13501 history. (This is necessary in order to preserve the integrity of
13502 debugger's data structures that reference the target system's symbol
13505 @node VxWorks Attach
13506 @subsubsection Running tasks
13508 @cindex running VxWorks tasks
13509 You can also attach to an existing task using the @code{attach} command as
13513 (vxgdb) attach @var{task}
13517 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
13518 or suspended when you attach to it. Running tasks are suspended at
13519 the time of attachment.
13521 @node Embedded Processors
13522 @section Embedded Processors
13524 This section goes into details specific to particular embedded
13527 @cindex send command to simulator
13528 Whenever a specific embedded processor has a simulator, @value{GDBN}
13529 allows to send an arbitrary command to the simulator.
13532 @item sim @var{command}
13533 @kindex sim@r{, a command}
13534 Send an arbitrary @var{command} string to the simulator. Consult the
13535 documentation for the specific simulator in use for information about
13536 acceptable commands.
13542 * H8/300:: Renesas H8/300
13543 * H8/500:: Renesas H8/500
13544 * M32R/D:: Renesas M32R/D
13545 * M68K:: Motorola M68K
13546 * MIPS Embedded:: MIPS Embedded
13547 * OpenRISC 1000:: OpenRisc 1000
13548 * PA:: HP PA Embedded
13551 * Sparclet:: Tsqware Sparclet
13552 * Sparclite:: Fujitsu Sparclite
13553 * ST2000:: Tandem ST2000
13554 * Z8000:: Zilog Z8000
13557 * Super-H:: Renesas Super-H
13558 * WinCE:: Windows CE child processes
13567 @item target rdi @var{dev}
13568 ARM Angel monitor, via RDI library interface to ADP protocol. You may
13569 use this target to communicate with both boards running the Angel
13570 monitor, or with the EmbeddedICE JTAG debug device.
13573 @item target rdp @var{dev}
13578 @value{GDBN} provides the following ARM-specific commands:
13581 @item set arm disassembler
13583 This commands selects from a list of disassembly styles. The
13584 @code{"std"} style is the standard style.
13586 @item show arm disassembler
13588 Show the current disassembly style.
13590 @item set arm apcs32
13591 @cindex ARM 32-bit mode
13592 This command toggles ARM operation mode between 32-bit and 26-bit.
13594 @item show arm apcs32
13595 Display the current usage of the ARM 32-bit mode.
13597 @item set arm fpu @var{fputype}
13598 This command sets the ARM floating-point unit (FPU) type. The
13599 argument @var{fputype} can be one of these:
13603 Determine the FPU type by querying the OS ABI.
13605 Software FPU, with mixed-endian doubles on little-endian ARM
13608 GCC-compiled FPA co-processor.
13610 Software FPU with pure-endian doubles.
13616 Show the current type of the FPU.
13619 This command forces @value{GDBN} to use the specified ABI.
13622 Show the currently used ABI.
13624 @item set debug arm
13625 Toggle whether to display ARM-specific debugging messages from the ARM
13626 target support subsystem.
13628 @item show debug arm
13629 Show whether ARM-specific debugging messages are enabled.
13632 The following commands are available when an ARM target is debugged
13633 using the RDI interface:
13636 @item rdilogfile @r{[}@var{file}@r{]}
13638 @cindex ADP (Angel Debugger Protocol) logging
13639 Set the filename for the ADP (Angel Debugger Protocol) packet log.
13640 With an argument, sets the log file to the specified @var{file}. With
13641 no argument, show the current log file name. The default log file is
13644 @item rdilogenable @r{[}@var{arg}@r{]}
13645 @kindex rdilogenable
13646 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
13647 enables logging, with an argument 0 or @code{"no"} disables it. With
13648 no arguments displays the current setting. When logging is enabled,
13649 ADP packets exchanged between @value{GDBN} and the RDI target device
13650 are logged to a file.
13652 @item set rdiromatzero
13653 @kindex set rdiromatzero
13654 @cindex ROM at zero address, RDI
13655 Tell @value{GDBN} whether the target has ROM at address 0. If on,
13656 vector catching is disabled, so that zero address can be used. If off
13657 (the default), vector catching is enabled. For this command to take
13658 effect, it needs to be invoked prior to the @code{target rdi} command.
13660 @item show rdiromatzero
13661 @kindex show rdiromatzero
13662 Show the current setting of ROM at zero address.
13664 @item set rdiheartbeat
13665 @kindex set rdiheartbeat
13666 @cindex RDI heartbeat
13667 Enable or disable RDI heartbeat packets. It is not recommended to
13668 turn on this option, since it confuses ARM and EPI JTAG interface, as
13669 well as the Angel monitor.
13671 @item show rdiheartbeat
13672 @kindex show rdiheartbeat
13673 Show the setting of RDI heartbeat packets.
13678 @subsection Renesas H8/300
13682 @kindex target hms@r{, with H8/300}
13683 @item target hms @var{dev}
13684 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
13685 Use special commands @code{device} and @code{speed} to control the serial
13686 line and the communications speed used.
13688 @kindex target e7000@r{, with H8/300}
13689 @item target e7000 @var{dev}
13690 E7000 emulator for Renesas H8 and SH.
13692 @kindex target sh3@r{, with H8/300}
13693 @kindex target sh3e@r{, with H8/300}
13694 @item target sh3 @var{dev}
13695 @itemx target sh3e @var{dev}
13696 Renesas SH-3 and SH-3E target systems.
13700 @cindex download to H8/300 or H8/500
13701 @cindex H8/300 or H8/500 download
13702 @cindex download to Renesas SH
13703 @cindex Renesas SH download
13704 When you select remote debugging to a Renesas SH, H8/300, or H8/500
13705 board, the @code{load} command downloads your program to the Renesas
13706 board and also opens it as the current executable target for
13707 @value{GDBN} on your host (like the @code{file} command).
13709 @value{GDBN} needs to know these things to talk to your
13710 Renesas SH, H8/300, or H8/500:
13714 that you want to use @samp{target hms}, the remote debugging interface
13715 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
13716 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
13717 the default when @value{GDBN} is configured specifically for the Renesas SH,
13718 H8/300, or H8/500.)
13721 what serial device connects your host to your Renesas board (the first
13722 serial device available on your host is the default).
13725 what speed to use over the serial device.
13729 * Renesas Boards:: Connecting to Renesas boards.
13730 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
13731 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
13734 @node Renesas Boards
13735 @subsubsection Connecting to Renesas boards
13737 @c only for Unix hosts
13739 @cindex serial device, Renesas micros
13740 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
13741 need to explicitly set the serial device. The default @var{port} is the
13742 first available port on your host. This is only necessary on Unix
13743 hosts, where it is typically something like @file{/dev/ttya}.
13746 @cindex serial line speed, Renesas micros
13747 @code{@value{GDBN}} has another special command to set the communications
13748 speed: @samp{speed @var{bps}}. This command also is only used from Unix
13749 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
13750 the DOS @code{mode} command (for instance,
13751 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
13753 The @samp{device} and @samp{speed} commands are available only when you
13754 use a Unix host to debug your Renesas microprocessor programs. If you
13756 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
13757 called @code{asynctsr} to communicate with the development board
13758 through a PC serial port. You must also use the DOS @code{mode} command
13759 to set up the serial port on the DOS side.
13761 The following sample session illustrates the steps needed to start a
13762 program under @value{GDBN} control on an H8/300. The example uses a
13763 sample H8/300 program called @file{t.x}. The procedure is the same for
13764 the Renesas SH and the H8/500.
13766 First hook up your development board. In this example, we use a
13767 board attached to serial port @code{COM2}; if you use a different serial
13768 port, substitute its name in the argument of the @code{mode} command.
13769 When you call @code{asynctsr}, the auxiliary comms program used by the
13770 debugger, you give it just the numeric part of the serial port's name;
13771 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
13775 C:\H8300\TEST> asynctsr 2
13776 C:\H8300\TEST> mode com2:9600,n,8,1,p
13778 Resident portion of MODE loaded
13780 COM2: 9600, n, 8, 1, p
13785 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
13786 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
13787 disable it, or even boot without it, to use @code{asynctsr} to control
13788 your development board.
13791 @kindex target hms@r{, and serial protocol}
13792 Now that serial communications are set up, and the development board is
13793 connected, you can start up @value{GDBN}. Call @code{@value{GDBN}} with
13794 the name of your program as the argument. @code{@value{GDBN}} prompts
13795 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
13796 commands to begin your debugging session: @samp{target hms} to specify
13797 cross-debugging to the Renesas board, and the @code{load} command to
13798 download your program to the board. @code{load} displays the names of
13799 the program's sections, and a @samp{*} for each 2K of data downloaded.
13800 (If you want to refresh @value{GDBN} data on symbols or on the
13801 executable file without downloading, use the @value{GDBN} commands
13802 @code{file} or @code{symbol-file}. These commands, and @code{load}
13803 itself, are described in @ref{Files,,Commands to specify files}.)
13806 (eg-C:\H8300\TEST) @value{GDBP} t.x
13807 @value{GDBN} is free software and you are welcome to distribute copies
13808 of it under certain conditions; type "show copying" to see
13810 There is absolutely no warranty for @value{GDBN}; type "show warranty"
13812 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
13813 (@value{GDBP}) target hms
13814 Connected to remote H8/300 HMS system.
13815 (@value{GDBP}) load t.x
13816 .text : 0x8000 .. 0xabde ***********
13817 .data : 0xabde .. 0xad30 *
13818 .stack : 0xf000 .. 0xf014 *
13821 At this point, you're ready to run or debug your program. From here on,
13822 you can use all the usual @value{GDBN} commands. The @code{break} command
13823 sets breakpoints; the @code{run} command starts your program;
13824 @code{print} or @code{x} display data; the @code{continue} command
13825 resumes execution after stopping at a breakpoint. You can use the
13826 @code{help} command at any time to find out more about @value{GDBN} commands.
13828 Remember, however, that @emph{operating system} facilities aren't
13829 available on your development board; for example, if your program hangs,
13830 you can't send an interrupt---but you can press the @sc{reset} switch!
13832 Use the @sc{reset} button on the development board
13835 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
13836 no way to pass an interrupt signal to the development board); and
13839 to return to the @value{GDBN} command prompt after your program finishes
13840 normally. The communications protocol provides no other way for @value{GDBN}
13841 to detect program completion.
13844 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
13845 development board as a ``normal exit'' of your program.
13848 @subsubsection Using the E7000 in-circuit emulator
13850 @kindex target e7000@r{, with Renesas ICE}
13851 You can use the E7000 in-circuit emulator to develop code for either the
13852 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
13853 e7000} command to connect @value{GDBN} to your E7000:
13856 @item target e7000 @var{port} @var{speed}
13857 Use this form if your E7000 is connected to a serial port. The
13858 @var{port} argument identifies what serial port to use (for example,
13859 @samp{com2}). The third argument is the line speed in bits per second
13860 (for example, @samp{9600}).
13862 @item target e7000 @var{hostname}
13863 If your E7000 is installed as a host on a TCP/IP network, you can just
13864 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
13867 The following special commands are available when debugging with the
13871 @item e7000 @var{command}
13873 @cindex send command to E7000 monitor
13874 This sends the specified @var{command} to the E7000 monitor.
13876 @item ftplogin @var{machine} @var{username} @var{password} @var{dir}
13877 @kindex ftplogin@r{, E7000}
13878 This command records information for subsequent interface with the
13879 E7000 monitor via the FTP protocol: @value{GDBN} will log into the
13880 named @var{machine} using specified @var{username} and @var{password},
13881 and then chdir to the named directory @var{dir}.
13883 @item ftpload @var{file}
13884 @kindex ftpload@r{, E7000}
13885 This command uses credentials recorded by @code{ftplogin} to fetch and
13886 load the named @var{file} from the E7000 monitor.
13889 @kindex drain@r{, E7000}
13890 This command drains any pending text buffers stored on the E7000.
13892 @item set usehardbreakpoints
13893 @itemx show usehardbreakpoints
13894 @kindex set usehardbreakpoints@r{, E7000}
13895 @kindex show usehardbreakpoints@r{, E7000}
13896 @cindex hardware breakpoints, and E7000
13897 These commands set and show the use of hardware breakpoints for all
13898 breakpoints. @xref{Set Breaks, hardware-assisted breakpoint}, for
13899 more information about using hardware breakpoints selectively.
13902 @node Renesas Special
13903 @subsubsection Special @value{GDBN} commands for Renesas micros
13905 Some @value{GDBN} commands are available only for the H8/300:
13909 @kindex set machine
13910 @kindex show machine
13911 @item set machine h8300
13912 @itemx set machine h8300h
13913 Condition @value{GDBN} for one of the two variants of the H8/300
13914 architecture with @samp{set machine}. You can use @samp{show machine}
13915 to check which variant is currently in effect.
13924 @kindex set memory @var{mod}
13925 @cindex memory models, H8/500
13926 @item set memory @var{mod}
13928 Specify which H8/500 memory model (@var{mod}) you are using with
13929 @samp{set memory}; check which memory model is in effect with @samp{show
13930 memory}. The accepted values for @var{mod} are @code{small},
13931 @code{big}, @code{medium}, and @code{compact}.
13936 @subsection Renesas M32R/D and M32R/SDI
13939 @kindex target m32r
13940 @item target m32r @var{dev}
13941 Renesas M32R/D ROM monitor.
13943 @kindex target m32rsdi
13944 @item target m32rsdi @var{dev}
13945 Renesas M32R SDI server, connected via parallel port to the board.
13948 The following @value{GDBN} commands are specific to the M32R monitor:
13951 @item set download-path @var{path}
13952 @kindex set download-path
13953 @cindex find downloadable @sc{srec} files (M32R)
13954 Set the default path for finding donwloadable @sc{srec} files.
13956 @item show download-path
13957 @kindex show download-path
13958 Show the default path for downloadable @sc{srec} files.
13960 @item set board-address @var{addr}
13961 @kindex set board-address
13962 @cindex M32-EVA target board address
13963 Set the IP address for the M32R-EVA target board.
13965 @item show board-address
13966 @kindex show board-address
13967 Show the current IP address of the target board.
13969 @item set server-address @var{addr}
13970 @kindex set server-address
13971 @cindex download server address (M32R)
13972 Set the IP address for the download server, which is the @value{GDBN}'s
13975 @item show server-address
13976 @kindex show server-address
13977 Display the IP address of the download server.
13979 @item upload @r{[}@var{file}@r{]}
13980 @kindex upload@r{, M32R}
13981 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
13982 upload capability. If no @var{file} argument is given, the current
13983 executable file is uploaded.
13985 @item tload @r{[}@var{file}@r{]}
13986 @kindex tload@r{, M32R}
13987 Test the @code{upload} command.
13990 The following commands are available for M32R/SDI:
13995 @cindex reset SDI connection, M32R
13996 This command resets the SDI connection.
14000 This command shows the SDI connection status.
14003 @kindex debug_chaos
14004 @cindex M32R/Chaos debugging
14005 Instructs the remote that M32R/Chaos debugging is to be used.
14007 @item use_debug_dma
14008 @kindex use_debug_dma
14009 Instructs the remote to use the DEBUG_DMA method of accessing memory.
14012 @kindex use_mon_code
14013 Instructs the remote to use the MON_CODE method of accessing memory.
14016 @kindex use_ib_break
14017 Instructs the remote to set breakpoints by IB break.
14019 @item use_dbt_break
14020 @kindex use_dbt_break
14021 Instructs the remote to set breakpoints by DBT.
14027 The Motorola m68k configuration includes ColdFire support, and
14028 target command for the following ROM monitors.
14032 @kindex target abug
14033 @item target abug @var{dev}
14034 ABug ROM monitor for M68K.
14036 @kindex target cpu32bug
14037 @item target cpu32bug @var{dev}
14038 CPU32BUG monitor, running on a CPU32 (M68K) board.
14040 @kindex target dbug
14041 @item target dbug @var{dev}
14042 dBUG ROM monitor for Motorola ColdFire.
14045 @item target est @var{dev}
14046 EST-300 ICE monitor, running on a CPU32 (M68K) board.
14048 @kindex target rom68k
14049 @item target rom68k @var{dev}
14050 ROM 68K monitor, running on an M68K IDP board.
14056 @kindex target rombug
14057 @item target rombug @var{dev}
14058 ROMBUG ROM monitor for OS/9000.
14062 @node MIPS Embedded
14063 @subsection MIPS Embedded
14065 @cindex MIPS boards
14066 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
14067 MIPS board attached to a serial line. This is available when
14068 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
14071 Use these @value{GDBN} commands to specify the connection to your target board:
14074 @item target mips @var{port}
14075 @kindex target mips @var{port}
14076 To run a program on the board, start up @code{@value{GDBP}} with the
14077 name of your program as the argument. To connect to the board, use the
14078 command @samp{target mips @var{port}}, where @var{port} is the name of
14079 the serial port connected to the board. If the program has not already
14080 been downloaded to the board, you may use the @code{load} command to
14081 download it. You can then use all the usual @value{GDBN} commands.
14083 For example, this sequence connects to the target board through a serial
14084 port, and loads and runs a program called @var{prog} through the
14088 host$ @value{GDBP} @var{prog}
14089 @value{GDBN} is free software and @dots{}
14090 (@value{GDBP}) target mips /dev/ttyb
14091 (@value{GDBP}) load @var{prog}
14095 @item target mips @var{hostname}:@var{portnumber}
14096 On some @value{GDBN} host configurations, you can specify a TCP
14097 connection (for instance, to a serial line managed by a terminal
14098 concentrator) instead of a serial port, using the syntax
14099 @samp{@var{hostname}:@var{portnumber}}.
14101 @item target pmon @var{port}
14102 @kindex target pmon @var{port}
14105 @item target ddb @var{port}
14106 @kindex target ddb @var{port}
14107 NEC's DDB variant of PMON for Vr4300.
14109 @item target lsi @var{port}
14110 @kindex target lsi @var{port}
14111 LSI variant of PMON.
14113 @kindex target r3900
14114 @item target r3900 @var{dev}
14115 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
14117 @kindex target array
14118 @item target array @var{dev}
14119 Array Tech LSI33K RAID controller board.
14125 @value{GDBN} also supports these special commands for MIPS targets:
14128 @item set mipsfpu double
14129 @itemx set mipsfpu single
14130 @itemx set mipsfpu none
14131 @itemx set mipsfpu auto
14132 @itemx show mipsfpu
14133 @kindex set mipsfpu
14134 @kindex show mipsfpu
14135 @cindex MIPS remote floating point
14136 @cindex floating point, MIPS remote
14137 If your target board does not support the MIPS floating point
14138 coprocessor, you should use the command @samp{set mipsfpu none} (if you
14139 need this, you may wish to put the command in your @value{GDBN} init
14140 file). This tells @value{GDBN} how to find the return value of
14141 functions which return floating point values. It also allows
14142 @value{GDBN} to avoid saving the floating point registers when calling
14143 functions on the board. If you are using a floating point coprocessor
14144 with only single precision floating point support, as on the @sc{r4650}
14145 processor, use the command @samp{set mipsfpu single}. The default
14146 double precision floating point coprocessor may be selected using
14147 @samp{set mipsfpu double}.
14149 In previous versions the only choices were double precision or no
14150 floating point, so @samp{set mipsfpu on} will select double precision
14151 and @samp{set mipsfpu off} will select no floating point.
14153 As usual, you can inquire about the @code{mipsfpu} variable with
14154 @samp{show mipsfpu}.
14156 @item set timeout @var{seconds}
14157 @itemx set retransmit-timeout @var{seconds}
14158 @itemx show timeout
14159 @itemx show retransmit-timeout
14160 @cindex @code{timeout}, MIPS protocol
14161 @cindex @code{retransmit-timeout}, MIPS protocol
14162 @kindex set timeout
14163 @kindex show timeout
14164 @kindex set retransmit-timeout
14165 @kindex show retransmit-timeout
14166 You can control the timeout used while waiting for a packet, in the MIPS
14167 remote protocol, with the @code{set timeout @var{seconds}} command. The
14168 default is 5 seconds. Similarly, you can control the timeout used while
14169 waiting for an acknowledgement of a packet with the @code{set
14170 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
14171 You can inspect both values with @code{show timeout} and @code{show
14172 retransmit-timeout}. (These commands are @emph{only} available when
14173 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
14175 The timeout set by @code{set timeout} does not apply when @value{GDBN}
14176 is waiting for your program to stop. In that case, @value{GDBN} waits
14177 forever because it has no way of knowing how long the program is going
14178 to run before stopping.
14180 @item set syn-garbage-limit @var{num}
14181 @kindex set syn-garbage-limit@r{, MIPS remote}
14182 @cindex synchronize with remote MIPS target
14183 Limit the maximum number of characters @value{GDBN} should ignore when
14184 it tries to synchronize with the remote target. The default is 10
14185 characters. Setting the limit to -1 means there's no limit.
14187 @item show syn-garbage-limit
14188 @kindex show syn-garbage-limit@r{, MIPS remote}
14189 Show the current limit on the number of characters to ignore when
14190 trying to synchronize with the remote system.
14192 @item set monitor-prompt @var{prompt}
14193 @kindex set monitor-prompt@r{, MIPS remote}
14194 @cindex remote monitor prompt
14195 Tell @value{GDBN} to expect the specified @var{prompt} string from the
14196 remote monitor. The default depends on the target:
14206 @item show monitor-prompt
14207 @kindex show monitor-prompt@r{, MIPS remote}
14208 Show the current strings @value{GDBN} expects as the prompt from the
14211 @item set monitor-warnings
14212 @kindex set monitor-warnings@r{, MIPS remote}
14213 Enable or disable monitor warnings about hardware breakpoints. This
14214 has effect only for the @code{lsi} target. When on, @value{GDBN} will
14215 display warning messages whose codes are returned by the @code{lsi}
14216 PMON monitor for breakpoint commands.
14218 @item show monitor-warnings
14219 @kindex show monitor-warnings@r{, MIPS remote}
14220 Show the current setting of printing monitor warnings.
14222 @item pmon @var{command}
14223 @kindex pmon@r{, MIPS remote}
14224 @cindex send PMON command
14225 This command allows sending an arbitrary @var{command} string to the
14226 monitor. The monitor must be in debug mode for this to work.
14229 @node OpenRISC 1000
14230 @subsection OpenRISC 1000
14231 @cindex OpenRISC 1000
14233 @cindex or1k boards
14234 See OR1k Architecture document (@uref{www.opencores.org}) for more information
14235 about platform and commands.
14239 @kindex target jtag
14240 @item target jtag jtag://@var{host}:@var{port}
14242 Connects to remote JTAG server.
14243 JTAG remote server can be either an or1ksim or JTAG server,
14244 connected via parallel port to the board.
14246 Example: @code{target jtag jtag://localhost:9999}
14249 @item or1ksim @var{command}
14250 If connected to @code{or1ksim} OpenRISC 1000 Architectural
14251 Simulator, proprietary commands can be executed.
14253 @kindex info or1k spr
14254 @item info or1k spr
14255 Displays spr groups.
14257 @item info or1k spr @var{group}
14258 @itemx info or1k spr @var{groupno}
14259 Displays register names in selected group.
14261 @item info or1k spr @var{group} @var{register}
14262 @itemx info or1k spr @var{register}
14263 @itemx info or1k spr @var{groupno} @var{registerno}
14264 @itemx info or1k spr @var{registerno}
14265 Shows information about specified spr register.
14268 @item spr @var{group} @var{register} @var{value}
14269 @itemx spr @var{register @var{value}}
14270 @itemx spr @var{groupno} @var{registerno @var{value}}
14271 @itemx spr @var{registerno @var{value}}
14272 Writes @var{value} to specified spr register.
14275 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
14276 It is very similar to @value{GDBN} trace, except it does not interfere with normal
14277 program execution and is thus much faster. Hardware breakpoints/watchpoint
14278 triggers can be set using:
14281 Load effective address/data
14283 Store effective address/data
14285 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
14290 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
14291 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
14293 @code{htrace} commands:
14294 @cindex OpenRISC 1000 htrace
14297 @item hwatch @var{conditional}
14298 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
14299 or Data. For example:
14301 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14303 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14307 Display information about current HW trace configuration.
14309 @item htrace trigger @var{conditional}
14310 Set starting criteria for HW trace.
14312 @item htrace qualifier @var{conditional}
14313 Set acquisition qualifier for HW trace.
14315 @item htrace stop @var{conditional}
14316 Set HW trace stopping criteria.
14318 @item htrace record [@var{data}]*
14319 Selects the data to be recorded, when qualifier is met and HW trace was
14322 @item htrace enable
14323 @itemx htrace disable
14324 Enables/disables the HW trace.
14326 @item htrace rewind [@var{filename}]
14327 Clears currently recorded trace data.
14329 If filename is specified, new trace file is made and any newly collected data
14330 will be written there.
14332 @item htrace print [@var{start} [@var{len}]]
14333 Prints trace buffer, using current record configuration.
14335 @item htrace mode continuous
14336 Set continuous trace mode.
14338 @item htrace mode suspend
14339 Set suspend trace mode.
14344 @subsection PowerPC
14347 @kindex target dink32
14348 @item target dink32 @var{dev}
14349 DINK32 ROM monitor.
14351 @kindex target ppcbug
14352 @item target ppcbug @var{dev}
14353 @kindex target ppcbug1
14354 @item target ppcbug1 @var{dev}
14355 PPCBUG ROM monitor for PowerPC.
14358 @item target sds @var{dev}
14359 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
14362 @cindex SDS protocol
14363 The following commands specifi to the SDS protocol are supported
14367 @item set sdstimeout @var{nsec}
14368 @kindex set sdstimeout
14369 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
14370 default is 2 seconds.
14372 @item show sdstimeout
14373 @kindex show sdstimeout
14374 Show the current value of the SDS timeout.
14376 @item sds @var{command}
14377 @kindex sds@r{, a command}
14378 Send the specified @var{command} string to the SDS monitor.
14383 @subsection HP PA Embedded
14387 @kindex target op50n
14388 @item target op50n @var{dev}
14389 OP50N monitor, running on an OKI HPPA board.
14391 @kindex target w89k
14392 @item target w89k @var{dev}
14393 W89K monitor, running on a Winbond HPPA board.
14398 @subsection Renesas SH
14402 @kindex target hms@r{, with Renesas SH}
14403 @item target hms @var{dev}
14404 A Renesas SH board attached via serial line to your host. Use special
14405 commands @code{device} and @code{speed} to control the serial line and
14406 the communications speed used.
14408 @kindex target e7000@r{, with Renesas SH}
14409 @item target e7000 @var{dev}
14410 E7000 emulator for Renesas SH.
14412 @kindex target sh3@r{, with SH}
14413 @kindex target sh3e@r{, with SH}
14414 @item target sh3 @var{dev}
14415 @item target sh3e @var{dev}
14416 Renesas SH-3 and SH-3E target systems.
14421 @subsection Tsqware Sparclet
14425 @value{GDBN} enables developers to debug tasks running on
14426 Sparclet targets from a Unix host.
14427 @value{GDBN} uses code that runs on
14428 both the Unix host and on the Sparclet target. The program
14429 @code{@value{GDBP}} is installed and executed on the Unix host.
14432 @item remotetimeout @var{args}
14433 @kindex remotetimeout
14434 @value{GDBN} supports the option @code{remotetimeout}.
14435 This option is set by the user, and @var{args} represents the number of
14436 seconds @value{GDBN} waits for responses.
14439 @cindex compiling, on Sparclet
14440 When compiling for debugging, include the options @samp{-g} to get debug
14441 information and @samp{-Ttext} to relocate the program to where you wish to
14442 load it on the target. You may also want to add the options @samp{-n} or
14443 @samp{-N} in order to reduce the size of the sections. Example:
14446 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
14449 You can use @code{objdump} to verify that the addresses are what you intended:
14452 sparclet-aout-objdump --headers --syms prog
14455 @cindex running, on Sparclet
14457 your Unix execution search path to find @value{GDBN}, you are ready to
14458 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
14459 (or @code{sparclet-aout-gdb}, depending on your installation).
14461 @value{GDBN} comes up showing the prompt:
14468 * Sparclet File:: Setting the file to debug
14469 * Sparclet Connection:: Connecting to Sparclet
14470 * Sparclet Download:: Sparclet download
14471 * Sparclet Execution:: Running and debugging
14474 @node Sparclet File
14475 @subsubsection Setting file to debug
14477 The @value{GDBN} command @code{file} lets you choose with program to debug.
14480 (gdbslet) file prog
14484 @value{GDBN} then attempts to read the symbol table of @file{prog}.
14485 @value{GDBN} locates
14486 the file by searching the directories listed in the command search
14488 If the file was compiled with debug information (option "-g"), source
14489 files will be searched as well.
14490 @value{GDBN} locates
14491 the source files by searching the directories listed in the directory search
14492 path (@pxref{Environment, ,Your program's environment}).
14494 to find a file, it displays a message such as:
14497 prog: No such file or directory.
14500 When this happens, add the appropriate directories to the search paths with
14501 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
14502 @code{target} command again.
14504 @node Sparclet Connection
14505 @subsubsection Connecting to Sparclet
14507 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
14508 To connect to a target on serial port ``@code{ttya}'', type:
14511 (gdbslet) target sparclet /dev/ttya
14512 Remote target sparclet connected to /dev/ttya
14513 main () at ../prog.c:3
14517 @value{GDBN} displays messages like these:
14523 @node Sparclet Download
14524 @subsubsection Sparclet download
14526 @cindex download to Sparclet
14527 Once connected to the Sparclet target,
14528 you can use the @value{GDBN}
14529 @code{load} command to download the file from the host to the target.
14530 The file name and load offset should be given as arguments to the @code{load}
14532 Since the file format is aout, the program must be loaded to the starting
14533 address. You can use @code{objdump} to find out what this value is. The load
14534 offset is an offset which is added to the VMA (virtual memory address)
14535 of each of the file's sections.
14536 For instance, if the program
14537 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
14538 and bss at 0x12010170, in @value{GDBN}, type:
14541 (gdbslet) load prog 0x12010000
14542 Loading section .text, size 0xdb0 vma 0x12010000
14545 If the code is loaded at a different address then what the program was linked
14546 to, you may need to use the @code{section} and @code{add-symbol-file} commands
14547 to tell @value{GDBN} where to map the symbol table.
14549 @node Sparclet Execution
14550 @subsubsection Running and debugging
14552 @cindex running and debugging Sparclet programs
14553 You can now begin debugging the task using @value{GDBN}'s execution control
14554 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
14555 manual for the list of commands.
14559 Breakpoint 1 at 0x12010000: file prog.c, line 3.
14561 Starting program: prog
14562 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
14563 3 char *symarg = 0;
14565 4 char *execarg = "hello!";
14570 @subsection Fujitsu Sparclite
14574 @kindex target sparclite
14575 @item target sparclite @var{dev}
14576 Fujitsu sparclite boards, used only for the purpose of loading.
14577 You must use an additional command to debug the program.
14578 For example: target remote @var{dev} using @value{GDBN} standard
14584 @subsection Tandem ST2000
14586 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
14589 To connect your ST2000 to the host system, see the manufacturer's
14590 manual. Once the ST2000 is physically attached, you can run:
14593 target st2000 @var{dev} @var{speed}
14597 to establish it as your debugging environment. @var{dev} is normally
14598 the name of a serial device, such as @file{/dev/ttya}, connected to the
14599 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
14600 connection (for example, to a serial line attached via a terminal
14601 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
14603 The @code{load} and @code{attach} commands are @emph{not} defined for
14604 this target; you must load your program into the ST2000 as you normally
14605 would for standalone operation. @value{GDBN} reads debugging information
14606 (such as symbols) from a separate, debugging version of the program
14607 available on your host computer.
14608 @c FIXME!! This is terribly vague; what little content is here is
14609 @c basically hearsay.
14611 @cindex ST2000 auxiliary commands
14612 These auxiliary @value{GDBN} commands are available to help you with the ST2000
14616 @item st2000 @var{command}
14617 @kindex st2000 @var{cmd}
14618 @cindex STDBUG commands (ST2000)
14619 @cindex commands to STDBUG (ST2000)
14620 Send a @var{command} to the STDBUG monitor. See the manufacturer's
14621 manual for available commands.
14624 @cindex connect (to STDBUG)
14625 Connect the controlling terminal to the STDBUG command monitor. When
14626 you are done interacting with STDBUG, typing either of two character
14627 sequences gets you back to the @value{GDBN} command prompt:
14628 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
14629 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
14633 @subsection Zilog Z8000
14636 @cindex simulator, Z8000
14637 @cindex Zilog Z8000 simulator
14639 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
14642 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
14643 unsegmented variant of the Z8000 architecture) or the Z8001 (the
14644 segmented variant). The simulator recognizes which architecture is
14645 appropriate by inspecting the object code.
14648 @item target sim @var{args}
14650 @kindex target sim@r{, with Z8000}
14651 Debug programs on a simulated CPU. If the simulator supports setup
14652 options, specify them via @var{args}.
14656 After specifying this target, you can debug programs for the simulated
14657 CPU in the same style as programs for your host computer; use the
14658 @code{file} command to load a new program image, the @code{run} command
14659 to run your program, and so on.
14661 As well as making available all the usual machine registers
14662 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
14663 additional items of information as specially named registers:
14668 Counts clock-ticks in the simulator.
14671 Counts instructions run in the simulator.
14674 Execution time in 60ths of a second.
14678 You can refer to these values in @value{GDBN} expressions with the usual
14679 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
14680 conditional breakpoint that suspends only after at least 5000
14681 simulated clock ticks.
14684 @subsection Atmel AVR
14687 When configured for debugging the Atmel AVR, @value{GDBN} supports the
14688 following AVR-specific commands:
14691 @item info io_registers
14692 @kindex info io_registers@r{, AVR}
14693 @cindex I/O registers (Atmel AVR)
14694 This command displays information about the AVR I/O registers. For
14695 each register, @value{GDBN} prints its number and value.
14702 When configured for debugging CRIS, @value{GDBN} provides the
14703 following CRIS-specific commands:
14706 @item set cris-version @var{ver}
14707 @cindex CRIS version
14708 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
14709 The CRIS version affects register names and sizes. This command is useful in
14710 case autodetection of the CRIS version fails.
14712 @item show cris-version
14713 Show the current CRIS version.
14715 @item set cris-dwarf2-cfi
14716 @cindex DWARF-2 CFI and CRIS
14717 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
14718 Change to @samp{off} when using @code{gcc-cris} whose version is below
14721 @item show cris-dwarf2-cfi
14722 Show the current state of using DWARF-2 CFI.
14724 @item set cris-mode @var{mode}
14726 Set the current CRIS mode to @var{mode}. It should only be changed when
14727 debugging in guru mode, in which case it should be set to
14728 @samp{guru} (the default is @samp{normal}).
14730 @item show cris-mode
14731 Show the current CRIS mode.
14735 @subsection Renesas Super-H
14738 For the Renesas Super-H processor, @value{GDBN} provides these
14743 @kindex regs@r{, Super-H}
14744 Show the values of all Super-H registers.
14748 @subsection Windows CE
14751 The following commands are available for Windows CE:
14754 @item set remotedirectory @var{dir}
14755 @kindex set remotedirectory
14756 Tell @value{GDBN} to upload files from the named directory @var{dir}.
14757 The default is @file{/gdb}, i.e.@: the root directory on the current
14760 @item show remotedirectory
14761 @kindex show remotedirectory
14762 Show the current value of the upload directory.
14764 @item set remoteupload @var{method}
14765 @kindex set remoteupload
14766 Set the method used to upload files to remote device. Valid values
14767 for @var{method} are @samp{always}, @samp{newer}, and @samp{never}.
14768 The default is @samp{newer}.
14770 @item show remoteupload
14771 @kindex show remoteupload
14772 Show the current setting of the upload method.
14774 @item set remoteaddhost
14775 @kindex set remoteaddhost
14776 Tell @value{GDBN} whether to add this host to the remote stub's
14777 arguments when you debug over a network.
14779 @item show remoteaddhost
14780 @kindex show remoteaddhost
14781 Show whether to add this host to remote stub's arguments when
14782 debugging over a network.
14786 @node Architectures
14787 @section Architectures
14789 This section describes characteristics of architectures that affect
14790 all uses of @value{GDBN} with the architecture, both native and cross.
14797 * HPPA:: HP PA architecture
14801 @subsection x86 Architecture-specific issues.
14804 @item set struct-convention @var{mode}
14805 @kindex set struct-convention
14806 @cindex struct return convention
14807 @cindex struct/union returned in registers
14808 Set the convention used by the inferior to return @code{struct}s and
14809 @code{union}s from functions to @var{mode}. Possible values of
14810 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
14811 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
14812 are returned on the stack, while @code{"reg"} means that a
14813 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
14814 be returned in a register.
14816 @item show struct-convention
14817 @kindex show struct-convention
14818 Show the current setting of the convention to return @code{struct}s
14827 @kindex set rstack_high_address
14828 @cindex AMD 29K register stack
14829 @cindex register stack, AMD29K
14830 @item set rstack_high_address @var{address}
14831 On AMD 29000 family processors, registers are saved in a separate
14832 @dfn{register stack}. There is no way for @value{GDBN} to determine the
14833 extent of this stack. Normally, @value{GDBN} just assumes that the
14834 stack is ``large enough''. This may result in @value{GDBN} referencing
14835 memory locations that do not exist. If necessary, you can get around
14836 this problem by specifying the ending address of the register stack with
14837 the @code{set rstack_high_address} command. The argument should be an
14838 address, which you probably want to precede with @samp{0x} to specify in
14841 @kindex show rstack_high_address
14842 @item show rstack_high_address
14843 Display the current limit of the register stack, on AMD 29000 family
14851 See the following section.
14856 @cindex stack on Alpha
14857 @cindex stack on MIPS
14858 @cindex Alpha stack
14860 Alpha- and MIPS-based computers use an unusual stack frame, which
14861 sometimes requires @value{GDBN} to search backward in the object code to
14862 find the beginning of a function.
14864 @cindex response time, MIPS debugging
14865 To improve response time (especially for embedded applications, where
14866 @value{GDBN} may be restricted to a slow serial line for this search)
14867 you may want to limit the size of this search, using one of these
14871 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
14872 @item set heuristic-fence-post @var{limit}
14873 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
14874 search for the beginning of a function. A value of @var{0} (the
14875 default) means there is no limit. However, except for @var{0}, the
14876 larger the limit the more bytes @code{heuristic-fence-post} must search
14877 and therefore the longer it takes to run. You should only need to use
14878 this command when debugging a stripped executable.
14880 @item show heuristic-fence-post
14881 Display the current limit.
14885 These commands are available @emph{only} when @value{GDBN} is configured
14886 for debugging programs on Alpha or MIPS processors.
14888 Several MIPS-specific commands are available when debugging MIPS
14892 @item set mips saved-gpreg-size @var{size}
14893 @kindex set mips saved-gpreg-size
14894 @cindex MIPS GP register size on stack
14895 Set the size of MIPS general-purpose registers saved on the stack.
14896 The argument @var{size} can be one of the following:
14900 32-bit GP registers
14902 64-bit GP registers
14904 Use the target's default setting or autodetect the saved size from the
14905 information contained in the executable. This is the default
14908 @item show mips saved-gpreg-size
14909 @kindex show mips saved-gpreg-size
14910 Show the current size of MIPS GP registers on the stack.
14912 @item set mips stack-arg-size @var{size}
14913 @kindex set mips stack-arg-size
14914 @cindex MIPS stack space for arguments
14915 Set the amount of stack space reserved for arguments to functions.
14916 The argument can be one of @code{"32"}, @code{"64"} or @code{"auto"}
14919 @item set mips abi @var{arg}
14920 @kindex set mips abi
14921 @cindex set ABI for MIPS
14922 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
14923 values of @var{arg} are:
14927 The default ABI associated with the current binary (this is the
14938 @item show mips abi
14939 @kindex show mips abi
14940 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
14943 @itemx show mipsfpu
14944 @xref{MIPS Embedded, set mipsfpu}.
14946 @item set mips mask-address @var{arg}
14947 @kindex set mips mask-address
14948 @cindex MIPS addresses, masking
14949 This command determines whether the most-significant 32 bits of 64-bit
14950 MIPS addresses are masked off. The argument @var{arg} can be
14951 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
14952 setting, which lets @value{GDBN} determine the correct value.
14954 @item show mips mask-address
14955 @kindex show mips mask-address
14956 Show whether the upper 32 bits of MIPS addresses are masked off or
14959 @item set remote-mips64-transfers-32bit-regs
14960 @kindex set remote-mips64-transfers-32bit-regs
14961 This command controls compatibility with 64-bit MIPS targets that
14962 transfer data in 32-bit quantities. If you have an old MIPS 64 target
14963 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
14964 and 64 bits for other registers, set this option to @samp{on}.
14966 @item show remote-mips64-transfers-32bit-regs
14967 @kindex show remote-mips64-transfers-32bit-regs
14968 Show the current setting of compatibility with older MIPS 64 targets.
14970 @item set debug mips
14971 @kindex set debug mips
14972 This command turns on and off debugging messages for the MIPS-specific
14973 target code in @value{GDBN}.
14975 @item show debug mips
14976 @kindex show debug mips
14977 Show the current setting of MIPS debugging messages.
14983 @cindex HPPA support
14985 When @value{GDBN} is debugging te HP PA architecture, it provides the
14986 following special commands:
14989 @item set debug hppa
14990 @kindex set debug hppa
14991 THis command determines whether HPPA architecture specific debugging
14992 messages are to be displayed.
14994 @item show debug hppa
14995 Show whether HPPA debugging messages are displayed.
14997 @item maint print unwind @var{address}
14998 @kindex maint print unwind@r{, HPPA}
14999 This command displays the contents of the unwind table entry at the
15000 given @var{address}.
15005 @node Controlling GDB
15006 @chapter Controlling @value{GDBN}
15008 You can alter the way @value{GDBN} interacts with you by using the
15009 @code{set} command. For commands controlling how @value{GDBN} displays
15010 data, see @ref{Print Settings, ,Print settings}. Other settings are
15015 * Editing:: Command editing
15016 * History:: Command history
15017 * Screen Size:: Screen size
15018 * Numbers:: Numbers
15019 * ABI:: Configuring the current ABI
15020 * Messages/Warnings:: Optional warnings and messages
15021 * Debugging Output:: Optional messages about internal happenings
15029 @value{GDBN} indicates its readiness to read a command by printing a string
15030 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
15031 can change the prompt string with the @code{set prompt} command. For
15032 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
15033 the prompt in one of the @value{GDBN} sessions so that you can always tell
15034 which one you are talking to.
15036 @emph{Note:} @code{set prompt} does not add a space for you after the
15037 prompt you set. This allows you to set a prompt which ends in a space
15038 or a prompt that does not.
15042 @item set prompt @var{newprompt}
15043 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
15045 @kindex show prompt
15047 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
15051 @section Command editing
15053 @cindex command line editing
15055 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
15056 @sc{gnu} library provides consistent behavior for programs which provide a
15057 command line interface to the user. Advantages are @sc{gnu} Emacs-style
15058 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
15059 substitution, and a storage and recall of command history across
15060 debugging sessions.
15062 You may control the behavior of command line editing in @value{GDBN} with the
15063 command @code{set}.
15066 @kindex set editing
15069 @itemx set editing on
15070 Enable command line editing (enabled by default).
15072 @item set editing off
15073 Disable command line editing.
15075 @kindex show editing
15077 Show whether command line editing is enabled.
15080 @xref{Command Line Editing}, for more details about the Readline
15081 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
15082 encouraged to read that chapter.
15085 @section Command history
15086 @cindex command history
15088 @value{GDBN} can keep track of the commands you type during your
15089 debugging sessions, so that you can be certain of precisely what
15090 happened. Use these commands to manage the @value{GDBN} command
15093 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
15094 package, to provide the history facility. @xref{Using History
15095 Interactively}, for the detailed description of the History library.
15097 Here is the description of @value{GDBN} commands related to command
15101 @cindex history substitution
15102 @cindex history file
15103 @kindex set history filename
15104 @cindex @env{GDBHISTFILE}, environment variable
15105 @item set history filename @var{fname}
15106 Set the name of the @value{GDBN} command history file to @var{fname}.
15107 This is the file where @value{GDBN} reads an initial command history
15108 list, and where it writes the command history from this session when it
15109 exits. You can access this list through history expansion or through
15110 the history command editing characters listed below. This file defaults
15111 to the value of the environment variable @code{GDBHISTFILE}, or to
15112 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
15115 @cindex save command history
15116 @kindex set history save
15117 @item set history save
15118 @itemx set history save on
15119 Record command history in a file, whose name may be specified with the
15120 @code{set history filename} command. By default, this option is disabled.
15122 @item set history save off
15123 Stop recording command history in a file.
15125 @cindex history size
15126 @kindex set history size
15127 @cindex @env{HISTSIZE}, environment variable
15128 @item set history size @var{size}
15129 Set the number of commands which @value{GDBN} keeps in its history list.
15130 This defaults to the value of the environment variable
15131 @code{HISTSIZE}, or to 256 if this variable is not set.
15134 History expansion assigns special meaning to the character @kbd{!}.
15135 @xref{Event Designators}, for more details.
15137 @cindex history expansion, turn on/off
15138 Since @kbd{!} is also the logical not operator in C, history expansion
15139 is off by default. If you decide to enable history expansion with the
15140 @code{set history expansion on} command, you may sometimes need to
15141 follow @kbd{!} (when it is used as logical not, in an expression) with
15142 a space or a tab to prevent it from being expanded. The readline
15143 history facilities do not attempt substitution on the strings
15144 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
15146 The commands to control history expansion are:
15149 @item set history expansion on
15150 @itemx set history expansion
15151 @kindex set history expansion
15152 Enable history expansion. History expansion is off by default.
15154 @item set history expansion off
15155 Disable history expansion.
15158 @kindex show history
15160 @itemx show history filename
15161 @itemx show history save
15162 @itemx show history size
15163 @itemx show history expansion
15164 These commands display the state of the @value{GDBN} history parameters.
15165 @code{show history} by itself displays all four states.
15170 @kindex show commands
15171 @cindex show last commands
15172 @cindex display command history
15173 @item show commands
15174 Display the last ten commands in the command history.
15176 @item show commands @var{n}
15177 Print ten commands centered on command number @var{n}.
15179 @item show commands +
15180 Print ten commands just after the commands last printed.
15184 @section Screen size
15185 @cindex size of screen
15186 @cindex pauses in output
15188 Certain commands to @value{GDBN} may produce large amounts of
15189 information output to the screen. To help you read all of it,
15190 @value{GDBN} pauses and asks you for input at the end of each page of
15191 output. Type @key{RET} when you want to continue the output, or @kbd{q}
15192 to discard the remaining output. Also, the screen width setting
15193 determines when to wrap lines of output. Depending on what is being
15194 printed, @value{GDBN} tries to break the line at a readable place,
15195 rather than simply letting it overflow onto the following line.
15197 Normally @value{GDBN} knows the size of the screen from the terminal
15198 driver software. For example, on Unix @value{GDBN} uses the termcap data base
15199 together with the value of the @code{TERM} environment variable and the
15200 @code{stty rows} and @code{stty cols} settings. If this is not correct,
15201 you can override it with the @code{set height} and @code{set
15208 @kindex show height
15209 @item set height @var{lpp}
15211 @itemx set width @var{cpl}
15213 These @code{set} commands specify a screen height of @var{lpp} lines and
15214 a screen width of @var{cpl} characters. The associated @code{show}
15215 commands display the current settings.
15217 If you specify a height of zero lines, @value{GDBN} does not pause during
15218 output no matter how long the output is. This is useful if output is to a
15219 file or to an editor buffer.
15221 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
15222 from wrapping its output.
15224 @item set pagination on
15225 @itemx set pagination off
15226 @kindex set pagination
15227 Turn the output pagination on or off; the default is on. Turning
15228 pagination off is the alternative to @code{set height 0}.
15230 @item show pagination
15231 @kindex show pagination
15232 Show the current pagination mode.
15237 @cindex number representation
15238 @cindex entering numbers
15240 You can always enter numbers in octal, decimal, or hexadecimal in
15241 @value{GDBN} by the usual conventions: octal numbers begin with
15242 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
15243 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
15244 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
15245 10; likewise, the default display for numbers---when no particular
15246 format is specified---is base 10. You can change the default base for
15247 both input and output with the commands described below.
15250 @kindex set input-radix
15251 @item set input-radix @var{base}
15252 Set the default base for numeric input. Supported choices
15253 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15254 specified either unambiguously or using the current input radix; for
15258 set input-radix 012
15259 set input-radix 10.
15260 set input-radix 0xa
15264 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
15265 leaves the input radix unchanged, no matter what it was, since
15266 @samp{10}, being without any leading or trailing signs of its base, is
15267 interpreted in the current radix. Thus, if the current radix is 16,
15268 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
15271 @kindex set output-radix
15272 @item set output-radix @var{base}
15273 Set the default base for numeric display. Supported choices
15274 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15275 specified either unambiguously or using the current input radix.
15277 @kindex show input-radix
15278 @item show input-radix
15279 Display the current default base for numeric input.
15281 @kindex show output-radix
15282 @item show output-radix
15283 Display the current default base for numeric display.
15285 @item set radix @r{[}@var{base}@r{]}
15289 These commands set and show the default base for both input and output
15290 of numbers. @code{set radix} sets the radix of input and output to
15291 the same base; without an argument, it resets the radix back to its
15292 default value of 10.
15297 @section Configuring the current ABI
15299 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
15300 application automatically. However, sometimes you need to override its
15301 conclusions. Use these commands to manage @value{GDBN}'s view of the
15308 One @value{GDBN} configuration can debug binaries for multiple operating
15309 system targets, either via remote debugging or native emulation.
15310 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
15311 but you can override its conclusion using the @code{set osabi} command.
15312 One example where this is useful is in debugging of binaries which use
15313 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
15314 not have the same identifying marks that the standard C library for your
15319 Show the OS ABI currently in use.
15322 With no argument, show the list of registered available OS ABI's.
15324 @item set osabi @var{abi}
15325 Set the current OS ABI to @var{abi}.
15328 @cindex float promotion
15330 Generally, the way that an argument of type @code{float} is passed to a
15331 function depends on whether the function is prototyped. For a prototyped
15332 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
15333 according to the architecture's convention for @code{float}. For unprototyped
15334 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
15335 @code{double} and then passed.
15337 Unfortunately, some forms of debug information do not reliably indicate whether
15338 a function is prototyped. If @value{GDBN} calls a function that is not marked
15339 as prototyped, it consults @kbd{set coerce-float-to-double}.
15342 @kindex set coerce-float-to-double
15343 @item set coerce-float-to-double
15344 @itemx set coerce-float-to-double on
15345 Arguments of type @code{float} will be promoted to @code{double} when passed
15346 to an unprototyped function. This is the default setting.
15348 @item set coerce-float-to-double off
15349 Arguments of type @code{float} will be passed directly to unprototyped
15352 @kindex show coerce-float-to-double
15353 @item show coerce-float-to-double
15354 Show the current setting of promoting @code{float} to @code{double}.
15358 @kindex show cp-abi
15359 @value{GDBN} needs to know the ABI used for your program's C@t{++}
15360 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
15361 used to build your application. @value{GDBN} only fully supports
15362 programs with a single C@t{++} ABI; if your program contains code using
15363 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
15364 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
15365 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
15366 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
15367 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
15368 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
15373 Show the C@t{++} ABI currently in use.
15376 With no argument, show the list of supported C@t{++} ABI's.
15378 @item set cp-abi @var{abi}
15379 @itemx set cp-abi auto
15380 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
15383 @node Messages/Warnings
15384 @section Optional warnings and messages
15386 @cindex verbose operation
15387 @cindex optional warnings
15388 By default, @value{GDBN} is silent about its inner workings. If you are
15389 running on a slow machine, you may want to use the @code{set verbose}
15390 command. This makes @value{GDBN} tell you when it does a lengthy
15391 internal operation, so you will not think it has crashed.
15393 Currently, the messages controlled by @code{set verbose} are those
15394 which announce that the symbol table for a source file is being read;
15395 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
15398 @kindex set verbose
15399 @item set verbose on
15400 Enables @value{GDBN} output of certain informational messages.
15402 @item set verbose off
15403 Disables @value{GDBN} output of certain informational messages.
15405 @kindex show verbose
15407 Displays whether @code{set verbose} is on or off.
15410 By default, if @value{GDBN} encounters bugs in the symbol table of an
15411 object file, it is silent; but if you are debugging a compiler, you may
15412 find this information useful (@pxref{Symbol Errors, ,Errors reading
15417 @kindex set complaints
15418 @item set complaints @var{limit}
15419 Permits @value{GDBN} to output @var{limit} complaints about each type of
15420 unusual symbols before becoming silent about the problem. Set
15421 @var{limit} to zero to suppress all complaints; set it to a large number
15422 to prevent complaints from being suppressed.
15424 @kindex show complaints
15425 @item show complaints
15426 Displays how many symbol complaints @value{GDBN} is permitted to produce.
15430 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
15431 lot of stupid questions to confirm certain commands. For example, if
15432 you try to run a program which is already running:
15436 The program being debugged has been started already.
15437 Start it from the beginning? (y or n)
15440 If you are willing to unflinchingly face the consequences of your own
15441 commands, you can disable this ``feature'':
15445 @kindex set confirm
15447 @cindex confirmation
15448 @cindex stupid questions
15449 @item set confirm off
15450 Disables confirmation requests.
15452 @item set confirm on
15453 Enables confirmation requests (the default).
15455 @kindex show confirm
15457 Displays state of confirmation requests.
15461 @node Debugging Output
15462 @section Optional messages about internal happenings
15463 @cindex optional debugging messages
15465 @value{GDBN} has commands that enable optional debugging messages from
15466 various @value{GDBN} subsystems; normally these commands are of
15467 interest to @value{GDBN} maintainers, or when reporting a bug. This
15468 section documents those commands.
15471 @kindex set exec-done-display
15472 @item set exec-done-display
15473 Turns on or off the notification of asynchronous commands'
15474 completion. When on, @value{GDBN} will print a message when an
15475 asynchronous command finishes its execution. The default is off.
15476 @kindex show exec-done-display
15477 @item show exec-done-display
15478 Displays the current setting of asynchronous command completion
15481 @cindex gdbarch debugging info
15482 @cindex architecture debugging info
15483 @item set debug arch
15484 Turns on or off display of gdbarch debugging info. The default is off
15486 @item show debug arch
15487 Displays the current state of displaying gdbarch debugging info.
15488 @item set debug aix-thread
15489 @cindex AIX threads
15490 Display debugging messages about inner workings of the AIX thread
15492 @item show debug aix-thread
15493 Show the current state of AIX thread debugging info display.
15494 @item set debug event
15495 @cindex event debugging info
15496 Turns on or off display of @value{GDBN} event debugging info. The
15498 @item show debug event
15499 Displays the current state of displaying @value{GDBN} event debugging
15501 @item set debug expression
15502 @cindex expression debugging info
15503 Turns on or off display of debugging info about @value{GDBN}
15504 expression parsing. The default is off.
15505 @item show debug expression
15506 Displays the current state of displaying debugging info about
15507 @value{GDBN} expression parsing.
15508 @item set debug frame
15509 @cindex frame debugging info
15510 Turns on or off display of @value{GDBN} frame debugging info. The
15512 @item show debug frame
15513 Displays the current state of displaying @value{GDBN} frame debugging
15515 @item set debug infrun
15516 @cindex inferior debugging info
15517 Turns on or off display of @value{GDBN} debugging info for running the inferior.
15518 The default is off. @file{infrun.c} contains GDB's runtime state machine used
15519 for implementing operations such as single-stepping the inferior.
15520 @item show debug infrun
15521 Displays the current state of @value{GDBN} inferior debugging.
15522 @item set debug lin-lwp
15523 @cindex @sc{gnu}/Linux LWP debug messages
15524 @cindex Linux lightweight processes
15525 Turns on or off debugging messages from the Linux LWP debug support.
15526 @item show debug lin-lwp
15527 Show the current state of Linux LWP debugging messages.
15528 @item set debug observer
15529 @cindex observer debugging info
15530 Turns on or off display of @value{GDBN} observer debugging. This
15531 includes info such as the notification of observable events.
15532 @item show debug observer
15533 Displays the current state of observer debugging.
15534 @item set debug overload
15535 @cindex C@t{++} overload debugging info
15536 Turns on or off display of @value{GDBN} C@t{++} overload debugging
15537 info. This includes info such as ranking of functions, etc. The default
15539 @item show debug overload
15540 Displays the current state of displaying @value{GDBN} C@t{++} overload
15542 @cindex packets, reporting on stdout
15543 @cindex serial connections, debugging
15544 @item set debug remote
15545 Turns on or off display of reports on all packets sent back and forth across
15546 the serial line to the remote machine. The info is printed on the
15547 @value{GDBN} standard output stream. The default is off.
15548 @item show debug remote
15549 Displays the state of display of remote packets.
15550 @item set debug serial
15551 Turns on or off display of @value{GDBN} serial debugging info. The
15553 @item show debug serial
15554 Displays the current state of displaying @value{GDBN} serial debugging
15556 @item set debug solib-frv
15557 @cindex FR-V shared-library debugging
15558 Turns on or off debugging messages for FR-V shared-library code.
15559 @item show debug solib-frv
15560 Display the current state of FR-V shared-library code debugging
15562 @item set debug target
15563 @cindex target debugging info
15564 Turns on or off display of @value{GDBN} target debugging info. This info
15565 includes what is going on at the target level of GDB, as it happens. The
15566 default is 0. Set it to 1 to track events, and to 2 to also track the
15567 value of large memory transfers. Changes to this flag do not take effect
15568 until the next time you connect to a target or use the @code{run} command.
15569 @item show debug target
15570 Displays the current state of displaying @value{GDBN} target debugging
15572 @item set debugvarobj
15573 @cindex variable object debugging info
15574 Turns on or off display of @value{GDBN} variable object debugging
15575 info. The default is off.
15576 @item show debugvarobj
15577 Displays the current state of displaying @value{GDBN} variable object
15582 @chapter Canned Sequences of Commands
15584 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
15585 command lists}), @value{GDBN} provides two ways to store sequences of
15586 commands for execution as a unit: user-defined commands and command
15590 * Define:: User-defined commands
15591 * Hooks:: User-defined command hooks
15592 * Command Files:: Command files
15593 * Output:: Commands for controlled output
15597 @section User-defined commands
15599 @cindex user-defined command
15600 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
15601 which you assign a new name as a command. This is done with the
15602 @code{define} command. User commands may accept up to 10 arguments
15603 separated by whitespace. Arguments are accessed within the user command
15604 via @var{$arg0@dots{}$arg9}. A trivial example:
15608 print $arg0 + $arg1 + $arg2
15612 To execute the command use:
15619 This defines the command @code{adder}, which prints the sum of
15620 its three arguments. Note the arguments are text substitutions, so they may
15621 reference variables, use complex expressions, or even perform inferior
15627 @item define @var{commandname}
15628 Define a command named @var{commandname}. If there is already a command
15629 by that name, you are asked to confirm that you want to redefine it.
15631 The definition of the command is made up of other @value{GDBN} command lines,
15632 which are given following the @code{define} command. The end of these
15633 commands is marked by a line containing @code{end}.
15639 Takes a single argument, which is an expression to evaluate.
15640 It is followed by a series of commands that are executed
15641 only if the expression is true (nonzero).
15642 There can then optionally be a line @code{else}, followed
15643 by a series of commands that are only executed if the expression
15644 was false. The end of the list is marked by a line containing @code{end}.
15648 The syntax is similar to @code{if}: the command takes a single argument,
15649 which is an expression to evaluate, and must be followed by the commands to
15650 execute, one per line, terminated by an @code{end}.
15651 The commands are executed repeatedly as long as the expression
15655 @item document @var{commandname}
15656 Document the user-defined command @var{commandname}, so that it can be
15657 accessed by @code{help}. The command @var{commandname} must already be
15658 defined. This command reads lines of documentation just as @code{define}
15659 reads the lines of the command definition, ending with @code{end}.
15660 After the @code{document} command is finished, @code{help} on command
15661 @var{commandname} displays the documentation you have written.
15663 You may use the @code{document} command again to change the
15664 documentation of a command. Redefining the command with @code{define}
15665 does not change the documentation.
15667 @kindex dont-repeat
15668 @cindex don't repeat command
15670 Used inside a user-defined command, this tells @value{GDBN} that this
15671 command should not be repeated when the user hits @key{RET}
15672 (@pxref{Command Syntax, repeat last command}).
15674 @kindex help user-defined
15675 @item help user-defined
15676 List all user-defined commands, with the first line of the documentation
15681 @itemx show user @var{commandname}
15682 Display the @value{GDBN} commands used to define @var{commandname} (but
15683 not its documentation). If no @var{commandname} is given, display the
15684 definitions for all user-defined commands.
15686 @cindex infinite recusrion in user-defined commands
15687 @kindex show max-user-call-depth
15688 @kindex set max-user-call-depth
15689 @item show max-user-call-depth
15690 @itemx set max-user-call-depth
15691 The value of @code{max-user-call-depth} controls how many recursion
15692 levels are allowed in user-defined commands before GDB suspects an
15693 infinite recursion and aborts the command.
15697 When user-defined commands are executed, the
15698 commands of the definition are not printed. An error in any command
15699 stops execution of the user-defined command.
15701 If used interactively, commands that would ask for confirmation proceed
15702 without asking when used inside a user-defined command. Many @value{GDBN}
15703 commands that normally print messages to say what they are doing omit the
15704 messages when used in a user-defined command.
15707 @section User-defined command hooks
15708 @cindex command hooks
15709 @cindex hooks, for commands
15710 @cindex hooks, pre-command
15713 You may define @dfn{hooks}, which are a special kind of user-defined
15714 command. Whenever you run the command @samp{foo}, if the user-defined
15715 command @samp{hook-foo} exists, it is executed (with no arguments)
15716 before that command.
15718 @cindex hooks, post-command
15720 A hook may also be defined which is run after the command you executed.
15721 Whenever you run the command @samp{foo}, if the user-defined command
15722 @samp{hookpost-foo} exists, it is executed (with no arguments) after
15723 that command. Post-execution hooks may exist simultaneously with
15724 pre-execution hooks, for the same command.
15726 It is valid for a hook to call the command which it hooks. If this
15727 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
15729 @c It would be nice if hookpost could be passed a parameter indicating
15730 @c if the command it hooks executed properly or not. FIXME!
15732 @kindex stop@r{, a pseudo-command}
15733 In addition, a pseudo-command, @samp{stop} exists. Defining
15734 (@samp{hook-stop}) makes the associated commands execute every time
15735 execution stops in your program: before breakpoint commands are run,
15736 displays are printed, or the stack frame is printed.
15738 For example, to ignore @code{SIGALRM} signals while
15739 single-stepping, but treat them normally during normal execution,
15744 handle SIGALRM nopass
15748 handle SIGALRM pass
15751 define hook-continue
15752 handle SIGLARM pass
15756 As a further example, to hook at the begining and end of the @code{echo}
15757 command, and to add extra text to the beginning and end of the message,
15765 define hookpost-echo
15769 (@value{GDBP}) echo Hello World
15770 <<<---Hello World--->>>
15775 You can define a hook for any single-word command in @value{GDBN}, but
15776 not for command aliases; you should define a hook for the basic command
15777 name, e.g. @code{backtrace} rather than @code{bt}.
15778 @c FIXME! So how does Joe User discover whether a command is an alias
15780 If an error occurs during the execution of your hook, execution of
15781 @value{GDBN} commands stops and @value{GDBN} issues a prompt
15782 (before the command that you actually typed had a chance to run).
15784 If you try to define a hook which does not match any known command, you
15785 get a warning from the @code{define} command.
15787 @node Command Files
15788 @section Command files
15790 @cindex command files
15791 A command file for @value{GDBN} is a text file made of lines that are
15792 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
15793 also be included. An empty line in a command file does nothing; it
15794 does not mean to repeat the last command, as it would from the
15797 You can request the execution of a command file with the @code{source}
15802 @item source @var{filename}
15803 Execute the command file @var{filename}.
15806 The lines in a command file are executed sequentially. They are not
15807 printed as they are executed. An error in any command terminates
15808 execution of the command file and control is returned to the console.
15810 Commands that would ask for confirmation if used interactively proceed
15811 without asking when used in a command file. Many @value{GDBN} commands that
15812 normally print messages to say what they are doing omit the messages
15813 when called from command files.
15815 @value{GDBN} also accepts command input from standard input. In this
15816 mode, normal output goes to standard output and error output goes to
15817 standard error. Errors in a command file supplied on standard input do
15818 not terminate execution of the command file---execution continues with
15822 gdb < cmds > log 2>&1
15825 (The syntax above will vary depending on the shell used.) This example
15826 will execute commands from the file @file{cmds}. All output and errors
15827 would be directed to @file{log}.
15830 @section Commands for controlled output
15832 During the execution of a command file or a user-defined command, normal
15833 @value{GDBN} output is suppressed; the only output that appears is what is
15834 explicitly printed by the commands in the definition. This section
15835 describes three commands useful for generating exactly the output you
15840 @item echo @var{text}
15841 @c I do not consider backslash-space a standard C escape sequence
15842 @c because it is not in ANSI.
15843 Print @var{text}. Nonprinting characters can be included in
15844 @var{text} using C escape sequences, such as @samp{\n} to print a
15845 newline. @strong{No newline is printed unless you specify one.}
15846 In addition to the standard C escape sequences, a backslash followed
15847 by a space stands for a space. This is useful for displaying a
15848 string with spaces at the beginning or the end, since leading and
15849 trailing spaces are otherwise trimmed from all arguments.
15850 To print @samp{@w{ }and foo =@w{ }}, use the command
15851 @samp{echo \@w{ }and foo = \@w{ }}.
15853 A backslash at the end of @var{text} can be used, as in C, to continue
15854 the command onto subsequent lines. For example,
15857 echo This is some text\n\
15858 which is continued\n\
15859 onto several lines.\n
15862 produces the same output as
15865 echo This is some text\n
15866 echo which is continued\n
15867 echo onto several lines.\n
15871 @item output @var{expression}
15872 Print the value of @var{expression} and nothing but that value: no
15873 newlines, no @samp{$@var{nn} = }. The value is not entered in the
15874 value history either. @xref{Expressions, ,Expressions}, for more information
15877 @item output/@var{fmt} @var{expression}
15878 Print the value of @var{expression} in format @var{fmt}. You can use
15879 the same formats as for @code{print}. @xref{Output Formats,,Output
15880 formats}, for more information.
15883 @item printf @var{string}, @var{expressions}@dots{}
15884 Print the values of the @var{expressions} under the control of
15885 @var{string}. The @var{expressions} are separated by commas and may be
15886 either numbers or pointers. Their values are printed as specified by
15887 @var{string}, exactly as if your program were to execute the C
15889 @c FIXME: the above implies that at least all ANSI C formats are
15890 @c supported, but it isn't true: %E and %G don't work (or so it seems).
15891 @c Either this is a bug, or the manual should document what formats are
15895 printf (@var{string}, @var{expressions}@dots{});
15898 For example, you can print two values in hex like this:
15901 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
15904 The only backslash-escape sequences that you can use in the format
15905 string are the simple ones that consist of backslash followed by a
15910 @chapter Command Interpreters
15911 @cindex command interpreters
15913 @value{GDBN} supports multiple command interpreters, and some command
15914 infrastructure to allow users or user interface writers to switch
15915 between interpreters or run commands in other interpreters.
15917 @value{GDBN} currently supports two command interpreters, the console
15918 interpreter (sometimes called the command-line interpreter or @sc{cli})
15919 and the machine interface interpreter (or @sc{gdb/mi}). This manual
15920 describes both of these interfaces in great detail.
15922 By default, @value{GDBN} will start with the console interpreter.
15923 However, the user may choose to start @value{GDBN} with another
15924 interpreter by specifying the @option{-i} or @option{--interpreter}
15925 startup options. Defined interpreters include:
15929 @cindex console interpreter
15930 The traditional console or command-line interpreter. This is the most often
15931 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
15932 @value{GDBN} will use this interpreter.
15935 @cindex mi interpreter
15936 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
15937 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
15938 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
15942 @cindex mi2 interpreter
15943 The current @sc{gdb/mi} interface.
15946 @cindex mi1 interpreter
15947 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
15951 @cindex invoke another interpreter
15952 The interpreter being used by @value{GDBN} may not be dynamically
15953 switched at runtime. Although possible, this could lead to a very
15954 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
15955 enters the command "interpreter-set console" in a console view,
15956 @value{GDBN} would switch to using the console interpreter, rendering
15957 the IDE inoperable!
15959 @kindex interpreter-exec
15960 Although you may only choose a single interpreter at startup, you may execute
15961 commands in any interpreter from the current interpreter using the appropriate
15962 command. If you are running the console interpreter, simply use the
15963 @code{interpreter-exec} command:
15966 interpreter-exec mi "-data-list-register-names"
15969 @sc{gdb/mi} has a similar command, although it is only available in versions of
15970 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
15973 @chapter @value{GDBN} Text User Interface
15975 @cindex Text User Interface
15978 * TUI Overview:: TUI overview
15979 * TUI Keys:: TUI key bindings
15980 * TUI Single Key Mode:: TUI single key mode
15981 * TUI Commands:: TUI specific commands
15982 * TUI Configuration:: TUI configuration variables
15985 The @value{GDBN} Text User Interface, TUI in short, is a terminal
15986 interface which uses the @code{curses} library to show the source
15987 file, the assembly output, the program registers and @value{GDBN}
15988 commands in separate text windows.
15990 The TUI is enabled by invoking @value{GDBN} using either
15992 @samp{gdbtui} or @samp{gdb -tui}.
15995 @section TUI overview
15997 The TUI has two display modes that can be switched while
16002 A curses (or TUI) mode in which it displays several text
16003 windows on the terminal.
16006 A standard mode which corresponds to the @value{GDBN} configured without
16010 In the TUI mode, @value{GDBN} can display several text window
16015 This window is the @value{GDBN} command window with the @value{GDBN}
16016 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
16017 managed using readline but through the TUI. The @emph{command}
16018 window is always visible.
16021 The source window shows the source file of the program. The current
16022 line as well as active breakpoints are displayed in this window.
16025 The assembly window shows the disassembly output of the program.
16028 This window shows the processor registers. It detects when
16029 a register is changed and when this is the case, registers that have
16030 changed are highlighted.
16034 The source and assembly windows show the current program position
16035 by highlighting the current line and marking them with the @samp{>} marker.
16036 Breakpoints are also indicated with two markers. A first one
16037 indicates the breakpoint type:
16041 Breakpoint which was hit at least once.
16044 Breakpoint which was never hit.
16047 Hardware breakpoint which was hit at least once.
16050 Hardware breakpoint which was never hit.
16054 The second marker indicates whether the breakpoint is enabled or not:
16058 Breakpoint is enabled.
16061 Breakpoint is disabled.
16065 The source, assembly and register windows are attached to the thread
16066 and the frame position. They are updated when the current thread
16067 changes, when the frame changes or when the program counter changes.
16068 These three windows are arranged by the TUI according to several
16069 layouts. The layout defines which of these three windows are visible.
16070 The following layouts are available:
16080 source and assembly
16083 source and registers
16086 assembly and registers
16090 On top of the command window a status line gives various information
16091 concerning the current process begin debugged. The status line is
16092 updated when the information it shows changes. The following fields
16097 Indicates the current gdb target
16098 (@pxref{Targets, ,Specifying a Debugging Target}).
16101 Gives information about the current process or thread number.
16102 When no process is being debugged, this field is set to @code{No process}.
16105 Gives the current function name for the selected frame.
16106 The name is demangled if demangling is turned on (@pxref{Print Settings}).
16107 When there is no symbol corresponding to the current program counter
16108 the string @code{??} is displayed.
16111 Indicates the current line number for the selected frame.
16112 When the current line number is not known the string @code{??} is displayed.
16115 Indicates the current program counter address.
16120 @section TUI Key Bindings
16121 @cindex TUI key bindings
16123 The TUI installs several key bindings in the readline keymaps
16124 (@pxref{Command Line Editing}).
16125 They allow to leave or enter in the TUI mode or they operate
16126 directly on the TUI layout and windows. The TUI also provides
16127 a @emph{SingleKey} keymap which binds several keys directly to
16128 @value{GDBN} commands. The following key bindings
16129 are installed for both TUI mode and the @value{GDBN} standard mode.
16138 Enter or leave the TUI mode. When the TUI mode is left,
16139 the curses window management is left and @value{GDBN} operates using
16140 its standard mode writing on the terminal directly. When the TUI
16141 mode is entered, the control is given back to the curses windows.
16142 The screen is then refreshed.
16146 Use a TUI layout with only one window. The layout will
16147 either be @samp{source} or @samp{assembly}. When the TUI mode
16148 is not active, it will switch to the TUI mode.
16150 Think of this key binding as the Emacs @kbd{C-x 1} binding.
16154 Use a TUI layout with at least two windows. When the current
16155 layout shows already two windows, a next layout with two windows is used.
16156 When a new layout is chosen, one window will always be common to the
16157 previous layout and the new one.
16159 Think of it as the Emacs @kbd{C-x 2} binding.
16163 Change the active window. The TUI associates several key bindings
16164 (like scrolling and arrow keys) to the active window. This command
16165 gives the focus to the next TUI window.
16167 Think of it as the Emacs @kbd{C-x o} binding.
16171 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
16172 (@pxref{TUI Single Key Mode}).
16176 The following key bindings are handled only by the TUI mode:
16181 Scroll the active window one page up.
16185 Scroll the active window one page down.
16189 Scroll the active window one line up.
16193 Scroll the active window one line down.
16197 Scroll the active window one column left.
16201 Scroll the active window one column right.
16205 Refresh the screen.
16209 In the TUI mode, the arrow keys are used by the active window
16210 for scrolling. This means they are available for readline when the
16211 active window is the command window. When the command window
16212 does not have the focus, it is necessary to use other readline
16213 key bindings such as @key{C-p}, @key{C-n}, @key{C-b} and @key{C-f}.
16215 @node TUI Single Key Mode
16216 @section TUI Single Key Mode
16217 @cindex TUI single key mode
16219 The TUI provides a @emph{SingleKey} mode in which it installs a particular
16220 key binding in the readline keymaps to connect single keys to
16224 @kindex c @r{(SingleKey TUI key)}
16228 @kindex d @r{(SingleKey TUI key)}
16232 @kindex f @r{(SingleKey TUI key)}
16236 @kindex n @r{(SingleKey TUI key)}
16240 @kindex q @r{(SingleKey TUI key)}
16242 exit the @emph{SingleKey} mode.
16244 @kindex r @r{(SingleKey TUI key)}
16248 @kindex s @r{(SingleKey TUI key)}
16252 @kindex u @r{(SingleKey TUI key)}
16256 @kindex v @r{(SingleKey TUI key)}
16260 @kindex w @r{(SingleKey TUI key)}
16266 Other keys temporarily switch to the @value{GDBN} command prompt.
16267 The key that was pressed is inserted in the editing buffer so that
16268 it is possible to type most @value{GDBN} commands without interaction
16269 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
16270 @emph{SingleKey} mode is restored. The only way to permanently leave
16271 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
16275 @section TUI specific commands
16276 @cindex TUI commands
16278 The TUI has specific commands to control the text windows.
16279 These commands are always available, that is they do not depend on
16280 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
16281 is in the standard mode, using these commands will automatically switch
16287 List and give the size of all displayed windows.
16291 Display the next layout.
16294 Display the previous layout.
16297 Display the source window only.
16300 Display the assembly window only.
16303 Display the source and assembly window.
16306 Display the register window together with the source or assembly window.
16308 @item focus next | prev | src | asm | regs | split
16310 Set the focus to the named window.
16311 This command allows to change the active window so that scrolling keys
16312 can be affected to another window.
16316 Refresh the screen. This is similar to using @key{C-L} key.
16318 @item tui reg float
16320 Show the floating point registers in the register window.
16322 @item tui reg general
16323 Show the general registers in the register window.
16326 Show the next register group. The list of register groups as well as
16327 their order is target specific. The predefined register groups are the
16328 following: @code{general}, @code{float}, @code{system}, @code{vector},
16329 @code{all}, @code{save}, @code{restore}.
16331 @item tui reg system
16332 Show the system registers in the register window.
16336 Update the source window and the current execution point.
16338 @item winheight @var{name} +@var{count}
16339 @itemx winheight @var{name} -@var{count}
16341 Change the height of the window @var{name} by @var{count}
16342 lines. Positive counts increase the height, while negative counts
16346 @kindex tabset @var{nchars}
16347 Set the width of tab stops to be @var{nchars} characters.
16351 @node TUI Configuration
16352 @section TUI configuration variables
16353 @cindex TUI configuration variables
16355 The TUI has several configuration variables that control the
16356 appearance of windows on the terminal.
16359 @item set tui border-kind @var{kind}
16360 @kindex set tui border-kind
16361 Select the border appearance for the source, assembly and register windows.
16362 The possible values are the following:
16365 Use a space character to draw the border.
16368 Use ascii characters + - and | to draw the border.
16371 Use the Alternate Character Set to draw the border. The border is
16372 drawn using character line graphics if the terminal supports them.
16376 @item set tui active-border-mode @var{mode}
16377 @kindex set tui active-border-mode
16378 Select the attributes to display the border of the active window.
16379 The possible values are @code{normal}, @code{standout}, @code{reverse},
16380 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
16382 @item set tui border-mode @var{mode}
16383 @kindex set tui border-mode
16384 Select the attributes to display the border of other windows.
16385 The @var{mode} can be one of the following:
16388 Use normal attributes to display the border.
16394 Use reverse video mode.
16397 Use half bright mode.
16399 @item half-standout
16400 Use half bright and standout mode.
16403 Use extra bright or bold mode.
16405 @item bold-standout
16406 Use extra bright or bold and standout mode.
16413 @chapter Using @value{GDBN} under @sc{gnu} Emacs
16416 @cindex @sc{gnu} Emacs
16417 A special interface allows you to use @sc{gnu} Emacs to view (and
16418 edit) the source files for the program you are debugging with
16421 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
16422 executable file you want to debug as an argument. This command starts
16423 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
16424 created Emacs buffer.
16425 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
16427 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
16432 All ``terminal'' input and output goes through the Emacs buffer.
16435 This applies both to @value{GDBN} commands and their output, and to the input
16436 and output done by the program you are debugging.
16438 This is useful because it means that you can copy the text of previous
16439 commands and input them again; you can even use parts of the output
16442 All the facilities of Emacs' Shell mode are available for interacting
16443 with your program. In particular, you can send signals the usual
16444 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
16449 @value{GDBN} displays source code through Emacs.
16452 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
16453 source file for that frame and puts an arrow (@samp{=>}) at the
16454 left margin of the current line. Emacs uses a separate buffer for
16455 source display, and splits the screen to show both your @value{GDBN} session
16458 Explicit @value{GDBN} @code{list} or search commands still produce output as
16459 usual, but you probably have no reason to use them from Emacs.
16461 If you specify an absolute file name when prompted for the @kbd{M-x
16462 gdb} argument, then Emacs sets your current working directory to where
16463 your program resides. If you only specify the file name, then Emacs
16464 sets your current working directory to to the directory associated
16465 with the previous buffer. In this case, @value{GDBN} may find your
16466 program by searching your environment's @code{PATH} variable, but on
16467 some operating systems it might not find the source. So, although the
16468 @value{GDBN} input and output session proceeds normally, the auxiliary
16469 buffer does not display the current source and line of execution.
16471 The initial working directory of @value{GDBN} is printed on the top
16472 line of the @value{GDBN} I/O buffer and this serves as a default for
16473 the commands that specify files for @value{GDBN} to operate
16474 on. @xref{Files, ,Commands to specify files}.
16476 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
16477 need to call @value{GDBN} by a different name (for example, if you
16478 keep several configurations around, with different names) you can
16479 customize the Emacs variable @code{gud-gdb-command-name} to run the
16482 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
16483 addition to the standard Shell mode commands:
16487 Describe the features of Emacs' @value{GDBN} Mode.
16490 Execute to another source line, like the @value{GDBN} @code{step} command; also
16491 update the display window to show the current file and location.
16494 Execute to next source line in this function, skipping all function
16495 calls, like the @value{GDBN} @code{next} command. Then update the display window
16496 to show the current file and location.
16499 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
16500 display window accordingly.
16503 Execute until exit from the selected stack frame, like the @value{GDBN}
16504 @code{finish} command.
16507 Continue execution of your program, like the @value{GDBN} @code{continue}
16511 Go up the number of frames indicated by the numeric argument
16512 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
16513 like the @value{GDBN} @code{up} command.
16516 Go down the number of frames indicated by the numeric argument, like the
16517 @value{GDBN} @code{down} command.
16520 In any source file, the Emacs command @kbd{C-x SPC} (@code{gud-break})
16521 tells @value{GDBN} to set a breakpoint on the source line point is on.
16523 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
16524 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
16525 point to any frame in the stack and type @key{RET} to make it become the
16526 current frame and display the associated source in the source buffer.
16527 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
16530 If you accidentally delete the source-display buffer, an easy way to get
16531 it back is to type the command @code{f} in the @value{GDBN} buffer, to
16532 request a frame display; when you run under Emacs, this recreates
16533 the source buffer if necessary to show you the context of the current
16536 The source files displayed in Emacs are in ordinary Emacs buffers
16537 which are visiting the source files in the usual way. You can edit
16538 the files with these buffers if you wish; but keep in mind that @value{GDBN}
16539 communicates with Emacs in terms of line numbers. If you add or
16540 delete lines from the text, the line numbers that @value{GDBN} knows cease
16541 to correspond properly with the code.
16543 The description given here is for GNU Emacs version 21.3 and a more
16544 detailed description of its interaction with @value{GDBN} is given in
16545 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
16547 @c The following dropped because Epoch is nonstandard. Reactivate
16548 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
16550 @kindex Emacs Epoch environment
16554 Version 18 of @sc{gnu} Emacs has a built-in window system
16555 called the @code{epoch}
16556 environment. Users of this environment can use a new command,
16557 @code{inspect} which performs identically to @code{print} except that
16558 each value is printed in its own window.
16563 @chapter The @sc{gdb/mi} Interface
16565 @unnumberedsec Function and Purpose
16567 @cindex @sc{gdb/mi}, its purpose
16568 @sc{gdb/mi} is a line based machine oriented text interface to
16569 @value{GDBN} and is activated by specifying using the
16570 @option{--interpreter} command line option (@pxref{Mode Options}). It
16571 is specifically intended to support the development of systems which
16572 use the debugger as just one small component of a larger system.
16574 This chapter is a specification of the @sc{gdb/mi} interface. It is written
16575 in the form of a reference manual.
16577 Note that @sc{gdb/mi} is still under construction, so some of the
16578 features described below are incomplete and subject to change.
16580 @unnumberedsec Notation and Terminology
16582 @cindex notational conventions, for @sc{gdb/mi}
16583 This chapter uses the following notation:
16587 @code{|} separates two alternatives.
16590 @code{[ @var{something} ]} indicates that @var{something} is optional:
16591 it may or may not be given.
16594 @code{( @var{group} )*} means that @var{group} inside the parentheses
16595 may repeat zero or more times.
16598 @code{( @var{group} )+} means that @var{group} inside the parentheses
16599 may repeat one or more times.
16602 @code{"@var{string}"} means a literal @var{string}.
16606 @heading Dependencies
16609 @heading Acknowledgments
16611 In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
16615 * GDB/MI Command Syntax::
16616 * GDB/MI Compatibility with CLI::
16617 * GDB/MI Output Records::
16618 * GDB/MI Command Description Format::
16619 * GDB/MI Breakpoint Table Commands::
16620 * GDB/MI Data Manipulation::
16621 * GDB/MI Program Control::
16622 * GDB/MI Miscellaneous Commands::
16624 * GDB/MI Kod Commands::
16625 * GDB/MI Memory Overlay Commands::
16626 * GDB/MI Signal Handling Commands::
16628 * GDB/MI Stack Manipulation::
16629 * GDB/MI Symbol Query::
16630 * GDB/MI Target Manipulation::
16631 * GDB/MI Thread Commands::
16632 * GDB/MI Tracepoint Commands::
16633 * GDB/MI Variable Objects::
16636 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16637 @node GDB/MI Command Syntax
16638 @section @sc{gdb/mi} Command Syntax
16641 * GDB/MI Input Syntax::
16642 * GDB/MI Output Syntax::
16643 * GDB/MI Simple Examples::
16646 @node GDB/MI Input Syntax
16647 @subsection @sc{gdb/mi} Input Syntax
16649 @cindex input syntax for @sc{gdb/mi}
16650 @cindex @sc{gdb/mi}, input syntax
16652 @item @var{command} @expansion{}
16653 @code{@var{cli-command} | @var{mi-command}}
16655 @item @var{cli-command} @expansion{}
16656 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
16657 @var{cli-command} is any existing @value{GDBN} CLI command.
16659 @item @var{mi-command} @expansion{}
16660 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
16661 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
16663 @item @var{token} @expansion{}
16664 "any sequence of digits"
16666 @item @var{option} @expansion{}
16667 @code{"-" @var{parameter} [ " " @var{parameter} ]}
16669 @item @var{parameter} @expansion{}
16670 @code{@var{non-blank-sequence} | @var{c-string}}
16672 @item @var{operation} @expansion{}
16673 @emph{any of the operations described in this chapter}
16675 @item @var{non-blank-sequence} @expansion{}
16676 @emph{anything, provided it doesn't contain special characters such as
16677 "-", @var{nl}, """ and of course " "}
16679 @item @var{c-string} @expansion{}
16680 @code{""" @var{seven-bit-iso-c-string-content} """}
16682 @item @var{nl} @expansion{}
16691 The CLI commands are still handled by the @sc{mi} interpreter; their
16692 output is described below.
16695 The @code{@var{token}}, when present, is passed back when the command
16699 Some @sc{mi} commands accept optional arguments as part of the parameter
16700 list. Each option is identified by a leading @samp{-} (dash) and may be
16701 followed by an optional argument parameter. Options occur first in the
16702 parameter list and can be delimited from normal parameters using
16703 @samp{--} (this is useful when some parameters begin with a dash).
16710 We want easy access to the existing CLI syntax (for debugging).
16713 We want it to be easy to spot a @sc{mi} operation.
16716 @node GDB/MI Output Syntax
16717 @subsection @sc{gdb/mi} Output Syntax
16719 @cindex output syntax of @sc{gdb/mi}
16720 @cindex @sc{gdb/mi}, output syntax
16721 The output from @sc{gdb/mi} consists of zero or more out-of-band records
16722 followed, optionally, by a single result record. This result record
16723 is for the most recent command. The sequence of output records is
16724 terminated by @samp{(@value{GDBP})}.
16726 If an input command was prefixed with a @code{@var{token}} then the
16727 corresponding output for that command will also be prefixed by that same
16731 @item @var{output} @expansion{}
16732 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(@value{GDBP})" @var{nl}}
16734 @item @var{result-record} @expansion{}
16735 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
16737 @item @var{out-of-band-record} @expansion{}
16738 @code{@var{async-record} | @var{stream-record}}
16740 @item @var{async-record} @expansion{}
16741 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
16743 @item @var{exec-async-output} @expansion{}
16744 @code{[ @var{token} ] "*" @var{async-output}}
16746 @item @var{status-async-output} @expansion{}
16747 @code{[ @var{token} ] "+" @var{async-output}}
16749 @item @var{notify-async-output} @expansion{}
16750 @code{[ @var{token} ] "=" @var{async-output}}
16752 @item @var{async-output} @expansion{}
16753 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
16755 @item @var{result-class} @expansion{}
16756 @code{"done" | "running" | "connected" | "error" | "exit"}
16758 @item @var{async-class} @expansion{}
16759 @code{"stopped" | @var{others}} (where @var{others} will be added
16760 depending on the needs---this is still in development).
16762 @item @var{result} @expansion{}
16763 @code{ @var{variable} "=" @var{value}}
16765 @item @var{variable} @expansion{}
16766 @code{ @var{string} }
16768 @item @var{value} @expansion{}
16769 @code{ @var{const} | @var{tuple} | @var{list} }
16771 @item @var{const} @expansion{}
16772 @code{@var{c-string}}
16774 @item @var{tuple} @expansion{}
16775 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
16777 @item @var{list} @expansion{}
16778 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
16779 @var{result} ( "," @var{result} )* "]" }
16781 @item @var{stream-record} @expansion{}
16782 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
16784 @item @var{console-stream-output} @expansion{}
16785 @code{"~" @var{c-string}}
16787 @item @var{target-stream-output} @expansion{}
16788 @code{"@@" @var{c-string}}
16790 @item @var{log-stream-output} @expansion{}
16791 @code{"&" @var{c-string}}
16793 @item @var{nl} @expansion{}
16796 @item @var{token} @expansion{}
16797 @emph{any sequence of digits}.
16805 All output sequences end in a single line containing a period.
16808 The @code{@var{token}} is from the corresponding request. If an execution
16809 command is interrupted by the @samp{-exec-interrupt} command, the
16810 @var{token} associated with the @samp{*stopped} message is the one of the
16811 original execution command, not the one of the interrupt command.
16814 @cindex status output in @sc{gdb/mi}
16815 @var{status-async-output} contains on-going status information about the
16816 progress of a slow operation. It can be discarded. All status output is
16817 prefixed by @samp{+}.
16820 @cindex async output in @sc{gdb/mi}
16821 @var{exec-async-output} contains asynchronous state change on the target
16822 (stopped, started, disappeared). All async output is prefixed by
16826 @cindex notify output in @sc{gdb/mi}
16827 @var{notify-async-output} contains supplementary information that the
16828 client should handle (e.g., a new breakpoint information). All notify
16829 output is prefixed by @samp{=}.
16832 @cindex console output in @sc{gdb/mi}
16833 @var{console-stream-output} is output that should be displayed as is in the
16834 console. It is the textual response to a CLI command. All the console
16835 output is prefixed by @samp{~}.
16838 @cindex target output in @sc{gdb/mi}
16839 @var{target-stream-output} is the output produced by the target program.
16840 All the target output is prefixed by @samp{@@}.
16843 @cindex log output in @sc{gdb/mi}
16844 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
16845 instance messages that should be displayed as part of an error log. All
16846 the log output is prefixed by @samp{&}.
16849 @cindex list output in @sc{gdb/mi}
16850 New @sc{gdb/mi} commands should only output @var{lists} containing
16856 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
16857 details about the various output records.
16859 @node GDB/MI Simple Examples
16860 @subsection Simple Examples of @sc{gdb/mi} Interaction
16861 @cindex @sc{gdb/mi}, simple examples
16863 This subsection presents several simple examples of interaction using
16864 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
16865 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
16866 the output received from @sc{gdb/mi}.
16868 @subsubheading Target Stop
16869 @c Ummm... There is no "-stop" command. This assumes async, no?
16870 Here's an example of stopping the inferior process:
16881 <- *stop,reason="stop",address="0x123",source="a.c:123"
16885 @subsubheading Simple CLI Command
16887 Here's an example of a simple CLI command being passed through
16888 @sc{gdb/mi} and on to the CLI.
16898 @subsubheading Command With Side Effects
16901 -> -symbol-file xyz.exe
16902 <- *breakpoint,nr="3",address="0x123",source="a.c:123"
16906 @subsubheading A Bad Command
16908 Here's what happens if you pass a non-existent command:
16912 <- ^error,msg="Undefined MI command: rubbish"
16916 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16917 @node GDB/MI Compatibility with CLI
16918 @section @sc{gdb/mi} Compatibility with CLI
16920 @cindex compatibility, @sc{gdb/mi} and CLI
16921 @cindex @sc{gdb/mi}, compatibility with CLI
16922 To help users familiar with @value{GDBN}'s existing CLI interface, @sc{gdb/mi}
16923 accepts existing CLI commands. As specified by the syntax, such
16924 commands can be directly entered into the @sc{gdb/mi} interface and @value{GDBN} will
16927 This mechanism is provided as an aid to developers of @sc{gdb/mi}
16928 clients and not as a reliable interface into the CLI. Since the command
16929 is being interpreteted in an environment that assumes @sc{gdb/mi}
16930 behaviour, the exact output of such commands is likely to end up being
16931 an un-supported hybrid of @sc{gdb/mi} and CLI output.
16933 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16934 @node GDB/MI Output Records
16935 @section @sc{gdb/mi} Output Records
16938 * GDB/MI Result Records::
16939 * GDB/MI Stream Records::
16940 * GDB/MI Out-of-band Records::
16943 @node GDB/MI Result Records
16944 @subsection @sc{gdb/mi} Result Records
16946 @cindex result records in @sc{gdb/mi}
16947 @cindex @sc{gdb/mi}, result records
16948 In addition to a number of out-of-band notifications, the response to a
16949 @sc{gdb/mi} command includes one of the following result indications:
16953 @item "^done" [ "," @var{results} ]
16954 The synchronous operation was successful, @code{@var{results}} are the return
16959 @c Is this one correct? Should it be an out-of-band notification?
16960 The asynchronous operation was successfully started. The target is
16963 @item "^error" "," @var{c-string}
16965 The operation failed. The @code{@var{c-string}} contains the corresponding
16969 @node GDB/MI Stream Records
16970 @subsection @sc{gdb/mi} Stream Records
16972 @cindex @sc{gdb/mi}, stream records
16973 @cindex stream records in @sc{gdb/mi}
16974 @value{GDBN} internally maintains a number of output streams: the console, the
16975 target, and the log. The output intended for each of these streams is
16976 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
16978 Each stream record begins with a unique @dfn{prefix character} which
16979 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
16980 Syntax}). In addition to the prefix, each stream record contains a
16981 @code{@var{string-output}}. This is either raw text (with an implicit new
16982 line) or a quoted C string (which does not contain an implicit newline).
16985 @item "~" @var{string-output}
16986 The console output stream contains text that should be displayed in the
16987 CLI console window. It contains the textual responses to CLI commands.
16989 @item "@@" @var{string-output}
16990 The target output stream contains any textual output from the running
16993 @item "&" @var{string-output}
16994 The log stream contains debugging messages being produced by @value{GDBN}'s
16998 @node GDB/MI Out-of-band Records
16999 @subsection @sc{gdb/mi} Out-of-band Records
17001 @cindex out-of-band records in @sc{gdb/mi}
17002 @cindex @sc{gdb/mi}, out-of-band records
17003 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
17004 additional changes that have occurred. Those changes can either be a
17005 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
17006 target activity (e.g., target stopped).
17008 The following is a preliminary list of possible out-of-band records.
17009 In particular, the @var{exec-async-output} records.
17012 @item *stopped,reason="@var{reason}"
17015 @var{reason} can be one of the following:
17018 @item breakpoint-hit
17019 A breakpoint was reached.
17020 @item watchpoint-trigger
17021 A watchpoint was triggered.
17022 @item read-watchpoint-trigger
17023 A read watchpoint was triggered.
17024 @item access-watchpoint-trigger
17025 An access watchpoint was triggered.
17026 @item function-finished
17027 An -exec-finish or similar CLI command was accomplished.
17028 @item location-reached
17029 An -exec-until or similar CLI command was accomplished.
17030 @item watchpoint-scope
17031 A watchpoint has gone out of scope.
17032 @item end-stepping-range
17033 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
17034 similar CLI command was accomplished.
17035 @item exited-signalled
17036 The inferior exited because of a signal.
17038 The inferior exited.
17039 @item exited-normally
17040 The inferior exited normally.
17041 @item signal-received
17042 A signal was received by the inferior.
17046 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17047 @node GDB/MI Command Description Format
17048 @section @sc{gdb/mi} Command Description Format
17050 The remaining sections describe blocks of commands. Each block of
17051 commands is laid out in a fashion similar to this section.
17053 Note the the line breaks shown in the examples are here only for
17054 readability. They don't appear in the real output.
17055 Also note that the commands with a non-available example (N.A.@:) are
17056 not yet implemented.
17058 @subheading Motivation
17060 The motivation for this collection of commands.
17062 @subheading Introduction
17064 A brief introduction to this collection of commands as a whole.
17066 @subheading Commands
17068 For each command in the block, the following is described:
17070 @subsubheading Synopsis
17073 -command @var{args}@dots{}
17076 @subsubheading @value{GDBN} Command
17078 The corresponding @value{GDBN} CLI command.
17080 @subsubheading Result
17082 @subsubheading Out-of-band
17084 @subsubheading Notes
17086 @subsubheading Example
17089 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17090 @node GDB/MI Breakpoint Table Commands
17091 @section @sc{gdb/mi} Breakpoint table commands
17093 @cindex breakpoint commands for @sc{gdb/mi}
17094 @cindex @sc{gdb/mi}, breakpoint commands
17095 This section documents @sc{gdb/mi} commands for manipulating
17098 @subheading The @code{-break-after} Command
17099 @findex -break-after
17101 @subsubheading Synopsis
17104 -break-after @var{number} @var{count}
17107 The breakpoint number @var{number} is not in effect until it has been
17108 hit @var{count} times. To see how this is reflected in the output of
17109 the @samp{-break-list} command, see the description of the
17110 @samp{-break-list} command below.
17112 @subsubheading @value{GDBN} Command
17114 The corresponding @value{GDBN} command is @samp{ignore}.
17116 @subsubheading Example
17121 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",line="5"@}
17128 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17129 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17130 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17131 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17132 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17133 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17134 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17135 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17136 addr="0x000100d0",func="main",file="hello.c",line="5",times="0",
17142 @subheading The @code{-break-catch} Command
17143 @findex -break-catch
17145 @subheading The @code{-break-commands} Command
17146 @findex -break-commands
17150 @subheading The @code{-break-condition} Command
17151 @findex -break-condition
17153 @subsubheading Synopsis
17156 -break-condition @var{number} @var{expr}
17159 Breakpoint @var{number} will stop the program only if the condition in
17160 @var{expr} is true. The condition becomes part of the
17161 @samp{-break-list} output (see the description of the @samp{-break-list}
17164 @subsubheading @value{GDBN} Command
17166 The corresponding @value{GDBN} command is @samp{condition}.
17168 @subsubheading Example
17172 -break-condition 1 1
17176 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17177 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17178 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17179 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17180 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17181 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17182 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17183 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17184 addr="0x000100d0",func="main",file="hello.c",line="5",cond="1",
17185 times="0",ignore="3"@}]@}
17189 @subheading The @code{-break-delete} Command
17190 @findex -break-delete
17192 @subsubheading Synopsis
17195 -break-delete ( @var{breakpoint} )+
17198 Delete the breakpoint(s) whose number(s) are specified in the argument
17199 list. This is obviously reflected in the breakpoint list.
17201 @subsubheading @value{GDBN} command
17203 The corresponding @value{GDBN} command is @samp{delete}.
17205 @subsubheading Example
17213 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17214 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17215 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17216 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17217 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17218 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17219 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17224 @subheading The @code{-break-disable} Command
17225 @findex -break-disable
17227 @subsubheading Synopsis
17230 -break-disable ( @var{breakpoint} )+
17233 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
17234 break list is now set to @samp{n} for the named @var{breakpoint}(s).
17236 @subsubheading @value{GDBN} Command
17238 The corresponding @value{GDBN} command is @samp{disable}.
17240 @subsubheading Example
17248 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17249 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17250 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17251 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17252 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17253 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17254 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17255 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
17256 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
17260 @subheading The @code{-break-enable} Command
17261 @findex -break-enable
17263 @subsubheading Synopsis
17266 -break-enable ( @var{breakpoint} )+
17269 Enable (previously disabled) @var{breakpoint}(s).
17271 @subsubheading @value{GDBN} Command
17273 The corresponding @value{GDBN} command is @samp{enable}.
17275 @subsubheading Example
17283 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17284 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17285 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17286 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17287 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17288 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17289 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17290 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17291 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
17295 @subheading The @code{-break-info} Command
17296 @findex -break-info
17298 @subsubheading Synopsis
17301 -break-info @var{breakpoint}
17305 Get information about a single breakpoint.
17307 @subsubheading @value{GDBN} command
17309 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
17311 @subsubheading Example
17314 @subheading The @code{-break-insert} Command
17315 @findex -break-insert
17317 @subsubheading Synopsis
17320 -break-insert [ -t ] [ -h ] [ -r ]
17321 [ -c @var{condition} ] [ -i @var{ignore-count} ]
17322 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
17326 If specified, @var{line}, can be one of:
17333 @item filename:linenum
17334 @item filename:function
17338 The possible optional parameters of this command are:
17342 Insert a tempoary breakpoint.
17344 Insert a hardware breakpoint.
17345 @item -c @var{condition}
17346 Make the breakpoint conditional on @var{condition}.
17347 @item -i @var{ignore-count}
17348 Initialize the @var{ignore-count}.
17350 Insert a regular breakpoint in all the functions whose names match the
17351 given regular expression. Other flags are not applicable to regular
17355 @subsubheading Result
17357 The result is in the form:
17360 ^done,bkptno="@var{number}",func="@var{funcname}",
17361 file="@var{filename}",line="@var{lineno}"
17365 where @var{number} is the @value{GDBN} number for this breakpoint, @var{funcname}
17366 is the name of the function where the breakpoint was inserted,
17367 @var{filename} is the name of the source file which contains this
17368 function, and @var{lineno} is the source line number within that file.
17370 Note: this format is open to change.
17371 @c An out-of-band breakpoint instead of part of the result?
17373 @subsubheading @value{GDBN} Command
17375 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
17376 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
17378 @subsubheading Example
17383 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
17385 -break-insert -t foo
17386 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",line="11"@}
17389 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17390 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17391 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17392 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17393 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17394 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17395 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17396 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17397 addr="0x0001072c", func="main",file="recursive2.c",line="4",times="0"@},
17398 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
17399 addr="0x00010774",func="foo",file="recursive2.c",line="11",times="0"@}]@}
17401 -break-insert -r foo.*
17402 ~int foo(int, int);
17403 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c",line="11"@}
17407 @subheading The @code{-break-list} Command
17408 @findex -break-list
17410 @subsubheading Synopsis
17416 Displays the list of inserted breakpoints, showing the following fields:
17420 number of the breakpoint
17422 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
17424 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
17427 is the breakpoint enabled or no: @samp{y} or @samp{n}
17429 memory location at which the breakpoint is set
17431 logical location of the breakpoint, expressed by function name, file
17434 number of times the breakpoint has been hit
17437 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
17438 @code{body} field is an empty list.
17440 @subsubheading @value{GDBN} Command
17442 The corresponding @value{GDBN} command is @samp{info break}.
17444 @subsubheading Example
17449 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17450 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17451 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17452 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17453 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17454 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17455 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17456 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17457 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
17458 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17459 addr="0x00010114",func="foo",file="hello.c",line="13",times="0"@}]@}
17463 Here's an example of the result when there are no breakpoints:
17468 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17469 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17470 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17471 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17472 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17473 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17474 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17479 @subheading The @code{-break-watch} Command
17480 @findex -break-watch
17482 @subsubheading Synopsis
17485 -break-watch [ -a | -r ]
17488 Create a watchpoint. With the @samp{-a} option it will create an
17489 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
17490 read from or on a write to the memory location. With the @samp{-r}
17491 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
17492 trigger only when the memory location is accessed for reading. Without
17493 either of the options, the watchpoint created is a regular watchpoint,
17494 i.e. it will trigger when the memory location is accessed for writing.
17495 @xref{Set Watchpoints, , Setting watchpoints}.
17497 Note that @samp{-break-list} will report a single list of watchpoints and
17498 breakpoints inserted.
17500 @subsubheading @value{GDBN} Command
17502 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
17505 @subsubheading Example
17507 Setting a watchpoint on a variable in the @code{main} function:
17512 ^done,wpt=@{number="2",exp="x"@}
17516 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
17517 value=@{old="-268439212",new="55"@},
17518 frame=@{func="main",args=[],file="recursive2.c",
17519 fullname="/home/foo/bar/devo/myproject/recursive2.c",line="5"@}
17523 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
17524 the program execution twice: first for the variable changing value, then
17525 for the watchpoint going out of scope.
17530 ^done,wpt=@{number="5",exp="C"@}
17534 ^done,reason="watchpoint-trigger",
17535 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
17536 frame=@{func="callee4",args=[],
17537 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17538 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
17542 ^done,reason="watchpoint-scope",wpnum="5",
17543 frame=@{func="callee3",args=[@{name="strarg",
17544 value="0x11940 \"A string argument.\""@}],
17545 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17546 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
17550 Listing breakpoints and watchpoints, at different points in the program
17551 execution. Note that once the watchpoint goes out of scope, it is
17557 ^done,wpt=@{number="2",exp="C"@}
17560 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17561 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17562 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17563 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17564 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17565 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17566 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17567 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17568 addr="0x00010734",func="callee4",
17569 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
17570 bkpt=@{number="2",type="watchpoint",disp="keep",
17571 enabled="y",addr="",what="C",times="0"@}]@}
17575 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
17576 value=@{old="-276895068",new="3"@},
17577 frame=@{func="callee4",args=[],
17578 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17579 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
17582 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17583 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17584 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17585 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17586 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17587 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17588 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17589 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17590 addr="0x00010734",func="callee4",
17591 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
17592 bkpt=@{number="2",type="watchpoint",disp="keep",
17593 enabled="y",addr="",what="C",times="-5"@}]@}
17597 ^done,reason="watchpoint-scope",wpnum="2",
17598 frame=@{func="callee3",args=[@{name="strarg",
17599 value="0x11940 \"A string argument.\""@}],
17600 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17601 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
17604 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17605 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17606 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17607 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17608 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17609 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17610 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17611 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17612 addr="0x00010734",func="callee4",
17613 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@}]@}
17617 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17618 @node GDB/MI Data Manipulation
17619 @section @sc{gdb/mi} Data Manipulation
17621 @cindex data manipulation, in @sc{gdb/mi}
17622 @cindex @sc{gdb/mi}, data manipulation
17623 This section describes the @sc{gdb/mi} commands that manipulate data:
17624 examine memory and registers, evaluate expressions, etc.
17626 @c REMOVED FROM THE INTERFACE.
17627 @c @subheading -data-assign
17628 @c Change the value of a program variable. Plenty of side effects.
17629 @c @subsubheading GDB command
17631 @c @subsubheading Example
17634 @subheading The @code{-data-disassemble} Command
17635 @findex -data-disassemble
17637 @subsubheading Synopsis
17641 [ -s @var{start-addr} -e @var{end-addr} ]
17642 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
17650 @item @var{start-addr}
17651 is the beginning address (or @code{$pc})
17652 @item @var{end-addr}
17654 @item @var{filename}
17655 is the name of the file to disassemble
17656 @item @var{linenum}
17657 is the line number to disassemble around
17659 is the the number of disassembly lines to be produced. If it is -1,
17660 the whole function will be disassembled, in case no @var{end-addr} is
17661 specified. If @var{end-addr} is specified as a non-zero value, and
17662 @var{lines} is lower than the number of disassembly lines between
17663 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
17664 displayed; if @var{lines} is higher than the number of lines between
17665 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
17668 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
17672 @subsubheading Result
17674 The output for each instruction is composed of four fields:
17683 Note that whatever included in the instruction field, is not manipulated
17684 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
17686 @subsubheading @value{GDBN} Command
17688 There's no direct mapping from this command to the CLI.
17690 @subsubheading Example
17692 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
17696 -data-disassemble -s $pc -e "$pc + 20" -- 0
17699 @{address="0x000107c0",func-name="main",offset="4",
17700 inst="mov 2, %o0"@},
17701 @{address="0x000107c4",func-name="main",offset="8",
17702 inst="sethi %hi(0x11800), %o2"@},
17703 @{address="0x000107c8",func-name="main",offset="12",
17704 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
17705 @{address="0x000107cc",func-name="main",offset="16",
17706 inst="sethi %hi(0x11800), %o2"@},
17707 @{address="0x000107d0",func-name="main",offset="20",
17708 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
17712 Disassemble the whole @code{main} function. Line 32 is part of
17716 -data-disassemble -f basics.c -l 32 -- 0
17718 @{address="0x000107bc",func-name="main",offset="0",
17719 inst="save %sp, -112, %sp"@},
17720 @{address="0x000107c0",func-name="main",offset="4",
17721 inst="mov 2, %o0"@},
17722 @{address="0x000107c4",func-name="main",offset="8",
17723 inst="sethi %hi(0x11800), %o2"@},
17725 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
17726 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
17730 Disassemble 3 instructions from the start of @code{main}:
17734 -data-disassemble -f basics.c -l 32 -n 3 -- 0
17736 @{address="0x000107bc",func-name="main",offset="0",
17737 inst="save %sp, -112, %sp"@},
17738 @{address="0x000107c0",func-name="main",offset="4",
17739 inst="mov 2, %o0"@},
17740 @{address="0x000107c4",func-name="main",offset="8",
17741 inst="sethi %hi(0x11800), %o2"@}]
17745 Disassemble 3 instructions from the start of @code{main} in mixed mode:
17749 -data-disassemble -f basics.c -l 32 -n 3 -- 1
17751 src_and_asm_line=@{line="31",
17752 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
17753 testsuite/gdb.mi/basics.c",line_asm_insn=[
17754 @{address="0x000107bc",func-name="main",offset="0",
17755 inst="save %sp, -112, %sp"@}]@},
17756 src_and_asm_line=@{line="32",
17757 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
17758 testsuite/gdb.mi/basics.c",line_asm_insn=[
17759 @{address="0x000107c0",func-name="main",offset="4",
17760 inst="mov 2, %o0"@},
17761 @{address="0x000107c4",func-name="main",offset="8",
17762 inst="sethi %hi(0x11800), %o2"@}]@}]
17767 @subheading The @code{-data-evaluate-expression} Command
17768 @findex -data-evaluate-expression
17770 @subsubheading Synopsis
17773 -data-evaluate-expression @var{expr}
17776 Evaluate @var{expr} as an expression. The expression could contain an
17777 inferior function call. The function call will execute synchronously.
17778 If the expression contains spaces, it must be enclosed in double quotes.
17780 @subsubheading @value{GDBN} Command
17782 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
17783 @samp{call}. In @code{gdbtk} only, there's a corresponding
17784 @samp{gdb_eval} command.
17786 @subsubheading Example
17788 In the following example, the numbers that precede the commands are the
17789 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
17790 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
17794 211-data-evaluate-expression A
17797 311-data-evaluate-expression &A
17798 311^done,value="0xefffeb7c"
17800 411-data-evaluate-expression A+3
17803 511-data-evaluate-expression "A + 3"
17809 @subheading The @code{-data-list-changed-registers} Command
17810 @findex -data-list-changed-registers
17812 @subsubheading Synopsis
17815 -data-list-changed-registers
17818 Display a list of the registers that have changed.
17820 @subsubheading @value{GDBN} Command
17822 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
17823 has the corresponding command @samp{gdb_changed_register_list}.
17825 @subsubheading Example
17827 On a PPC MBX board:
17835 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
17836 args=[],file="try.c",fullname="/home/foo/bar/devo/myproject/try.c",line="5"@}
17838 -data-list-changed-registers
17839 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
17840 "10","11","13","14","15","16","17","18","19","20","21","22","23",
17841 "24","25","26","27","28","30","31","64","65","66","67","69"]
17846 @subheading The @code{-data-list-register-names} Command
17847 @findex -data-list-register-names
17849 @subsubheading Synopsis
17852 -data-list-register-names [ ( @var{regno} )+ ]
17855 Show a list of register names for the current target. If no arguments
17856 are given, it shows a list of the names of all the registers. If
17857 integer numbers are given as arguments, it will print a list of the
17858 names of the registers corresponding to the arguments. To ensure
17859 consistency between a register name and its number, the output list may
17860 include empty register names.
17862 @subsubheading @value{GDBN} Command
17864 @value{GDBN} does not have a command which corresponds to
17865 @samp{-data-list-register-names}. In @code{gdbtk} there is a
17866 corresponding command @samp{gdb_regnames}.
17868 @subsubheading Example
17870 For the PPC MBX board:
17873 -data-list-register-names
17874 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
17875 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
17876 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
17877 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
17878 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
17879 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
17880 "", "pc","ps","cr","lr","ctr","xer"]
17882 -data-list-register-names 1 2 3
17883 ^done,register-names=["r1","r2","r3"]
17887 @subheading The @code{-data-list-register-values} Command
17888 @findex -data-list-register-values
17890 @subsubheading Synopsis
17893 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
17896 Display the registers' contents. @var{fmt} is the format according to
17897 which the registers' contents are to be returned, followed by an optional
17898 list of numbers specifying the registers to display. A missing list of
17899 numbers indicates that the contents of all the registers must be returned.
17901 Allowed formats for @var{fmt} are:
17918 @subsubheading @value{GDBN} Command
17920 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
17921 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
17923 @subsubheading Example
17925 For a PPC MBX board (note: line breaks are for readability only, they
17926 don't appear in the actual output):
17930 -data-list-register-values r 64 65
17931 ^done,register-values=[@{number="64",value="0xfe00a300"@},
17932 @{number="65",value="0x00029002"@}]
17934 -data-list-register-values x
17935 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
17936 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
17937 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
17938 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
17939 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
17940 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
17941 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
17942 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
17943 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
17944 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
17945 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
17946 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
17947 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
17948 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
17949 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
17950 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
17951 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
17952 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
17953 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
17954 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
17955 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
17956 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
17957 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
17958 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
17959 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
17960 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
17961 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
17962 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
17963 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
17964 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
17965 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
17966 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
17967 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
17968 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
17969 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
17970 @{number="69",value="0x20002b03"@}]
17975 @subheading The @code{-data-read-memory} Command
17976 @findex -data-read-memory
17978 @subsubheading Synopsis
17981 -data-read-memory [ -o @var{byte-offset} ]
17982 @var{address} @var{word-format} @var{word-size}
17983 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
17990 @item @var{address}
17991 An expression specifying the address of the first memory word to be
17992 read. Complex expressions containing embedded white space should be
17993 quoted using the C convention.
17995 @item @var{word-format}
17996 The format to be used to print the memory words. The notation is the
17997 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
18000 @item @var{word-size}
18001 The size of each memory word in bytes.
18003 @item @var{nr-rows}
18004 The number of rows in the output table.
18006 @item @var{nr-cols}
18007 The number of columns in the output table.
18010 If present, indicates that each row should include an @sc{ascii} dump. The
18011 value of @var{aschar} is used as a padding character when a byte is not a
18012 member of the printable @sc{ascii} character set (printable @sc{ascii}
18013 characters are those whose code is between 32 and 126, inclusively).
18015 @item @var{byte-offset}
18016 An offset to add to the @var{address} before fetching memory.
18019 This command displays memory contents as a table of @var{nr-rows} by
18020 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
18021 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
18022 (returned as @samp{total-bytes}). Should less than the requested number
18023 of bytes be returned by the target, the missing words are identified
18024 using @samp{N/A}. The number of bytes read from the target is returned
18025 in @samp{nr-bytes} and the starting address used to read memory in
18028 The address of the next/previous row or page is available in
18029 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
18032 @subsubheading @value{GDBN} Command
18034 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
18035 @samp{gdb_get_mem} memory read command.
18037 @subsubheading Example
18039 Read six bytes of memory starting at @code{bytes+6} but then offset by
18040 @code{-6} bytes. Format as three rows of two columns. One byte per
18041 word. Display each word in hex.
18045 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
18046 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
18047 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
18048 prev-page="0x0000138a",memory=[
18049 @{addr="0x00001390",data=["0x00","0x01"]@},
18050 @{addr="0x00001392",data=["0x02","0x03"]@},
18051 @{addr="0x00001394",data=["0x04","0x05"]@}]
18055 Read two bytes of memory starting at address @code{shorts + 64} and
18056 display as a single word formatted in decimal.
18060 5-data-read-memory shorts+64 d 2 1 1
18061 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
18062 next-row="0x00001512",prev-row="0x0000150e",
18063 next-page="0x00001512",prev-page="0x0000150e",memory=[
18064 @{addr="0x00001510",data=["128"]@}]
18068 Read thirty two bytes of memory starting at @code{bytes+16} and format
18069 as eight rows of four columns. Include a string encoding with @samp{x}
18070 used as the non-printable character.
18074 4-data-read-memory bytes+16 x 1 8 4 x
18075 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
18076 next-row="0x000013c0",prev-row="0x0000139c",
18077 next-page="0x000013c0",prev-page="0x00001380",memory=[
18078 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
18079 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
18080 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
18081 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
18082 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
18083 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
18084 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
18085 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
18089 @subheading The @code{-display-delete} Command
18090 @findex -display-delete
18092 @subsubheading Synopsis
18095 -display-delete @var{number}
18098 Delete the display @var{number}.
18100 @subsubheading @value{GDBN} Command
18102 The corresponding @value{GDBN} command is @samp{delete display}.
18104 @subsubheading Example
18108 @subheading The @code{-display-disable} Command
18109 @findex -display-disable
18111 @subsubheading Synopsis
18114 -display-disable @var{number}
18117 Disable display @var{number}.
18119 @subsubheading @value{GDBN} Command
18121 The corresponding @value{GDBN} command is @samp{disable display}.
18123 @subsubheading Example
18127 @subheading The @code{-display-enable} Command
18128 @findex -display-enable
18130 @subsubheading Synopsis
18133 -display-enable @var{number}
18136 Enable display @var{number}.
18138 @subsubheading @value{GDBN} Command
18140 The corresponding @value{GDBN} command is @samp{enable display}.
18142 @subsubheading Example
18146 @subheading The @code{-display-insert} Command
18147 @findex -display-insert
18149 @subsubheading Synopsis
18152 -display-insert @var{expression}
18155 Display @var{expression} every time the program stops.
18157 @subsubheading @value{GDBN} Command
18159 The corresponding @value{GDBN} command is @samp{display}.
18161 @subsubheading Example
18165 @subheading The @code{-display-list} Command
18166 @findex -display-list
18168 @subsubheading Synopsis
18174 List the displays. Do not show the current values.
18176 @subsubheading @value{GDBN} Command
18178 The corresponding @value{GDBN} command is @samp{info display}.
18180 @subsubheading Example
18184 @subheading The @code{-environment-cd} Command
18185 @findex -environment-cd
18187 @subsubheading Synopsis
18190 -environment-cd @var{pathdir}
18193 Set @value{GDBN}'s working directory.
18195 @subsubheading @value{GDBN} Command
18197 The corresponding @value{GDBN} command is @samp{cd}.
18199 @subsubheading Example
18203 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18209 @subheading The @code{-environment-directory} Command
18210 @findex -environment-directory
18212 @subsubheading Synopsis
18215 -environment-directory [ -r ] [ @var{pathdir} ]+
18218 Add directories @var{pathdir} to beginning of search path for source files.
18219 If the @samp{-r} option is used, the search path is reset to the default
18220 search path. If directories @var{pathdir} are supplied in addition to the
18221 @samp{-r} option, the search path is first reset and then addition
18223 Multiple directories may be specified, separated by blanks. Specifying
18224 multiple directories in a single command
18225 results in the directories added to the beginning of the
18226 search path in the same order they were presented in the command.
18227 If blanks are needed as
18228 part of a directory name, double-quotes should be used around
18229 the name. In the command output, the path will show up separated
18230 by the system directory-separator character. The directory-seperator
18231 character must not be used
18232 in any directory name.
18233 If no directories are specified, the current search path is displayed.
18235 @subsubheading @value{GDBN} Command
18237 The corresponding @value{GDBN} command is @samp{dir}.
18239 @subsubheading Example
18243 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18244 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18246 -environment-directory ""
18247 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18249 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
18250 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
18252 -environment-directory -r
18253 ^done,source-path="$cdir:$cwd"
18258 @subheading The @code{-environment-path} Command
18259 @findex -environment-path
18261 @subsubheading Synopsis
18264 -environment-path [ -r ] [ @var{pathdir} ]+
18267 Add directories @var{pathdir} to beginning of search path for object files.
18268 If the @samp{-r} option is used, the search path is reset to the original
18269 search path that existed at gdb start-up. If directories @var{pathdir} are
18270 supplied in addition to the
18271 @samp{-r} option, the search path is first reset and then addition
18273 Multiple directories may be specified, separated by blanks. Specifying
18274 multiple directories in a single command
18275 results in the directories added to the beginning of the
18276 search path in the same order they were presented in the command.
18277 If blanks are needed as
18278 part of a directory name, double-quotes should be used around
18279 the name. In the command output, the path will show up separated
18280 by the system directory-separator character. The directory-seperator
18281 character must not be used
18282 in any directory name.
18283 If no directories are specified, the current path is displayed.
18286 @subsubheading @value{GDBN} Command
18288 The corresponding @value{GDBN} command is @samp{path}.
18290 @subsubheading Example
18295 ^done,path="/usr/bin"
18297 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
18298 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
18300 -environment-path -r /usr/local/bin
18301 ^done,path="/usr/local/bin:/usr/bin"
18306 @subheading The @code{-environment-pwd} Command
18307 @findex -environment-pwd
18309 @subsubheading Synopsis
18315 Show the current working directory.
18317 @subsubheading @value{GDBN} command
18319 The corresponding @value{GDBN} command is @samp{pwd}.
18321 @subsubheading Example
18326 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
18330 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18331 @node GDB/MI Program Control
18332 @section @sc{gdb/mi} Program control
18334 @subsubheading Program termination
18336 As a result of execution, the inferior program can run to completion, if
18337 it doesn't encounter any breakpoints. In this case the output will
18338 include an exit code, if the program has exited exceptionally.
18340 @subsubheading Examples
18343 Program exited normally:
18351 *stopped,reason="exited-normally"
18356 Program exited exceptionally:
18364 *stopped,reason="exited",exit-code="01"
18368 Another way the program can terminate is if it receives a signal such as
18369 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
18373 *stopped,reason="exited-signalled",signal-name="SIGINT",
18374 signal-meaning="Interrupt"
18378 @subheading The @code{-exec-abort} Command
18379 @findex -exec-abort
18381 @subsubheading Synopsis
18387 Kill the inferior running program.
18389 @subsubheading @value{GDBN} Command
18391 The corresponding @value{GDBN} command is @samp{kill}.
18393 @subsubheading Example
18397 @subheading The @code{-exec-arguments} Command
18398 @findex -exec-arguments
18400 @subsubheading Synopsis
18403 -exec-arguments @var{args}
18406 Set the inferior program arguments, to be used in the next
18409 @subsubheading @value{GDBN} Command
18411 The corresponding @value{GDBN} command is @samp{set args}.
18413 @subsubheading Example
18416 Don't have one around.
18419 @subheading The @code{-exec-continue} Command
18420 @findex -exec-continue
18422 @subsubheading Synopsis
18428 Asynchronous command. Resumes the execution of the inferior program
18429 until a breakpoint is encountered, or until the inferior exits.
18431 @subsubheading @value{GDBN} Command
18433 The corresponding @value{GDBN} corresponding is @samp{continue}.
18435 @subsubheading Example
18442 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
18443 file="hello.c",fullname="/home/foo/bar/devo/myproject/hello.c",line="13"@}
18448 @subheading The @code{-exec-finish} Command
18449 @findex -exec-finish
18451 @subsubheading Synopsis
18457 Asynchronous command. Resumes the execution of the inferior program
18458 until the current function is exited. Displays the results returned by
18461 @subsubheading @value{GDBN} Command
18463 The corresponding @value{GDBN} command is @samp{finish}.
18465 @subsubheading Example
18467 Function returning @code{void}.
18474 *stopped,reason="function-finished",frame=@{func="main",args=[],
18475 file="hello.c",fullname="/home/foo/bar/devo/myproject/hello.c",line="7"@}
18479 Function returning other than @code{void}. The name of the internal
18480 @value{GDBN} variable storing the result is printed, together with the
18487 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
18488 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
18489 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
18490 gdb-result-var="$1",return-value="0"
18495 @subheading The @code{-exec-interrupt} Command
18496 @findex -exec-interrupt
18498 @subsubheading Synopsis
18504 Asynchronous command. Interrupts the background execution of the target.
18505 Note how the token associated with the stop message is the one for the
18506 execution command that has been interrupted. The token for the interrupt
18507 itself only appears in the @samp{^done} output. If the user is trying to
18508 interrupt a non-running program, an error message will be printed.
18510 @subsubheading @value{GDBN} Command
18512 The corresponding @value{GDBN} command is @samp{interrupt}.
18514 @subsubheading Example
18525 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
18526 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
18527 fullname="/home/foo/bar/devo/myproject/try.c",line="13"@}
18532 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
18537 @subheading The @code{-exec-next} Command
18540 @subsubheading Synopsis
18546 Asynchronous command. Resumes execution of the inferior program, stopping
18547 when the beginning of the next source line is reached.
18549 @subsubheading @value{GDBN} Command
18551 The corresponding @value{GDBN} command is @samp{next}.
18553 @subsubheading Example
18559 *stopped,reason="end-stepping-range",line="8",file="hello.c"
18564 @subheading The @code{-exec-next-instruction} Command
18565 @findex -exec-next-instruction
18567 @subsubheading Synopsis
18570 -exec-next-instruction
18573 Asynchronous command. Executes one machine instruction. If the
18574 instruction is a function call continues until the function returns. If
18575 the program stops at an instruction in the middle of a source line, the
18576 address will be printed as well.
18578 @subsubheading @value{GDBN} Command
18580 The corresponding @value{GDBN} command is @samp{nexti}.
18582 @subsubheading Example
18586 -exec-next-instruction
18590 *stopped,reason="end-stepping-range",
18591 addr="0x000100d4",line="5",file="hello.c"
18596 @subheading The @code{-exec-return} Command
18597 @findex -exec-return
18599 @subsubheading Synopsis
18605 Makes current function return immediately. Doesn't execute the inferior.
18606 Displays the new current frame.
18608 @subsubheading @value{GDBN} Command
18610 The corresponding @value{GDBN} command is @samp{return}.
18612 @subsubheading Example
18616 200-break-insert callee4
18617 200^done,bkpt=@{number="1",addr="0x00010734",
18618 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18623 000*stopped,reason="breakpoint-hit",bkptno="1",
18624 frame=@{func="callee4",args=[],
18625 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18626 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18632 111^done,frame=@{level="0",func="callee3",
18633 args=[@{name="strarg",
18634 value="0x11940 \"A string argument.\""@}],
18635 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18636 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18641 @subheading The @code{-exec-run} Command
18644 @subsubheading Synopsis
18650 Asynchronous command. Starts execution of the inferior from the
18651 beginning. The inferior executes until either a breakpoint is
18652 encountered or the program exits.
18654 @subsubheading @value{GDBN} Command
18656 The corresponding @value{GDBN} command is @samp{run}.
18658 @subsubheading Example
18663 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
18668 *stopped,reason="breakpoint-hit",bkptno="1",
18669 frame=@{func="main",args=[],file="recursive2.c",
18670 fullname="/home/foo/bar/devo/myproject/recursive2.c",line="4"@}
18675 @subheading The @code{-exec-show-arguments} Command
18676 @findex -exec-show-arguments
18678 @subsubheading Synopsis
18681 -exec-show-arguments
18684 Print the arguments of the program.
18686 @subsubheading @value{GDBN} Command
18688 The corresponding @value{GDBN} command is @samp{show args}.
18690 @subsubheading Example
18693 @c @subheading -exec-signal
18695 @subheading The @code{-exec-step} Command
18698 @subsubheading Synopsis
18704 Asynchronous command. Resumes execution of the inferior program, stopping
18705 when the beginning of the next source line is reached, if the next
18706 source line is not a function call. If it is, stop at the first
18707 instruction of the called function.
18709 @subsubheading @value{GDBN} Command
18711 The corresponding @value{GDBN} command is @samp{step}.
18713 @subsubheading Example
18715 Stepping into a function:
18721 *stopped,reason="end-stepping-range",
18722 frame=@{func="foo",args=[@{name="a",value="10"@},
18723 @{name="b",value="0"@}],file="recursive2.c",
18724 fullname="/home/foo/bar/devo/myproject/recursive2.c",line="11"@}
18734 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
18739 @subheading The @code{-exec-step-instruction} Command
18740 @findex -exec-step-instruction
18742 @subsubheading Synopsis
18745 -exec-step-instruction
18748 Asynchronous command. Resumes the inferior which executes one machine
18749 instruction. The output, once @value{GDBN} has stopped, will vary depending on
18750 whether we have stopped in the middle of a source line or not. In the
18751 former case, the address at which the program stopped will be printed as
18754 @subsubheading @value{GDBN} Command
18756 The corresponding @value{GDBN} command is @samp{stepi}.
18758 @subsubheading Example
18762 -exec-step-instruction
18766 *stopped,reason="end-stepping-range",
18767 frame=@{func="foo",args=[],file="try.c",
18768 fullname="/home/foo/bar/devo/myproject/try.c",line="10"@}
18770 -exec-step-instruction
18774 *stopped,reason="end-stepping-range",
18775 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
18776 fullname="/home/foo/bar/devo/myproject/try.c",line="10"@}
18781 @subheading The @code{-exec-until} Command
18782 @findex -exec-until
18784 @subsubheading Synopsis
18787 -exec-until [ @var{location} ]
18790 Asynchronous command. Executes the inferior until the @var{location}
18791 specified in the argument is reached. If there is no argument, the inferior
18792 executes until a source line greater than the current one is reached.
18793 The reason for stopping in this case will be @samp{location-reached}.
18795 @subsubheading @value{GDBN} Command
18797 The corresponding @value{GDBN} command is @samp{until}.
18799 @subsubheading Example
18803 -exec-until recursive2.c:6
18807 *stopped,reason="location-reached",frame=@{func="main",args=[],
18808 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="6"@}
18813 @subheading -file-clear
18814 Is this going away????
18818 @subheading The @code{-file-exec-and-symbols} Command
18819 @findex -file-exec-and-symbols
18821 @subsubheading Synopsis
18824 -file-exec-and-symbols @var{file}
18827 Specify the executable file to be debugged. This file is the one from
18828 which the symbol table is also read. If no file is specified, the
18829 command clears the executable and symbol information. If breakpoints
18830 are set when using this command with no arguments, @value{GDBN} will produce
18831 error messages. Otherwise, no output is produced, except a completion
18834 @subsubheading @value{GDBN} Command
18836 The corresponding @value{GDBN} command is @samp{file}.
18838 @subsubheading Example
18842 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18848 @subheading The @code{-file-exec-file} Command
18849 @findex -file-exec-file
18851 @subsubheading Synopsis
18854 -file-exec-file @var{file}
18857 Specify the executable file to be debugged. Unlike
18858 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
18859 from this file. If used without argument, @value{GDBN} clears the information
18860 about the executable file. No output is produced, except a completion
18863 @subsubheading @value{GDBN} Command
18865 The corresponding @value{GDBN} command is @samp{exec-file}.
18867 @subsubheading Example
18871 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18877 @subheading The @code{-file-list-exec-sections} Command
18878 @findex -file-list-exec-sections
18880 @subsubheading Synopsis
18883 -file-list-exec-sections
18886 List the sections of the current executable file.
18888 @subsubheading @value{GDBN} Command
18890 The @value{GDBN} command @samp{info file} shows, among the rest, the same
18891 information as this command. @code{gdbtk} has a corresponding command
18892 @samp{gdb_load_info}.
18894 @subsubheading Example
18898 @subheading The @code{-file-list-exec-source-file} Command
18899 @findex -file-list-exec-source-file
18901 @subsubheading Synopsis
18904 -file-list-exec-source-file
18907 List the line number, the current source file, and the absolute path
18908 to the current source file for the current executable.
18910 @subsubheading @value{GDBN} Command
18912 There's no @value{GDBN} command which directly corresponds to this one.
18914 @subsubheading Example
18918 123-file-list-exec-source-file
18919 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
18924 @subheading The @code{-file-list-exec-source-files} Command
18925 @findex -file-list-exec-source-files
18927 @subsubheading Synopsis
18930 -file-list-exec-source-files
18933 List the source files for the current executable.
18935 It will always output the filename, but only when GDB can find the absolute
18936 file name of a source file, will it output the fullname.
18938 @subsubheading @value{GDBN} Command
18940 There's no @value{GDBN} command which directly corresponds to this one.
18941 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
18943 @subsubheading Example
18946 -file-list-exec-source-files
18948 @{file=foo.c,fullname=/home/foo.c@},
18949 @{file=/home/bar.c,fullname=/home/bar.c@},
18950 @{file=gdb_could_not_find_fullpath.c@}]
18954 @subheading The @code{-file-list-shared-libraries} Command
18955 @findex -file-list-shared-libraries
18957 @subsubheading Synopsis
18960 -file-list-shared-libraries
18963 List the shared libraries in the program.
18965 @subsubheading @value{GDBN} Command
18967 The corresponding @value{GDBN} command is @samp{info shared}.
18969 @subsubheading Example
18973 @subheading The @code{-file-list-symbol-files} Command
18974 @findex -file-list-symbol-files
18976 @subsubheading Synopsis
18979 -file-list-symbol-files
18984 @subsubheading @value{GDBN} Command
18986 The corresponding @value{GDBN} command is @samp{info file} (part of it).
18988 @subsubheading Example
18992 @subheading The @code{-file-symbol-file} Command
18993 @findex -file-symbol-file
18995 @subsubheading Synopsis
18998 -file-symbol-file @var{file}
19001 Read symbol table info from the specified @var{file} argument. When
19002 used without arguments, clears @value{GDBN}'s symbol table info. No output is
19003 produced, except for a completion notification.
19005 @subsubheading @value{GDBN} Command
19007 The corresponding @value{GDBN} command is @samp{symbol-file}.
19009 @subsubheading Example
19013 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
19018 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19019 @node GDB/MI Miscellaneous Commands
19020 @section Miscellaneous @value{GDBN} commands in @sc{gdb/mi}
19022 @c @subheading -gdb-complete
19024 @subheading The @code{-gdb-exit} Command
19027 @subsubheading Synopsis
19033 Exit @value{GDBN} immediately.
19035 @subsubheading @value{GDBN} Command
19037 Approximately corresponds to @samp{quit}.
19039 @subsubheading Example
19046 @subheading The @code{-gdb-set} Command
19049 @subsubheading Synopsis
19055 Set an internal @value{GDBN} variable.
19056 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
19058 @subsubheading @value{GDBN} Command
19060 The corresponding @value{GDBN} command is @samp{set}.
19062 @subsubheading Example
19072 @subheading The @code{-gdb-show} Command
19075 @subsubheading Synopsis
19081 Show the current value of a @value{GDBN} variable.
19083 @subsubheading @value{GDBN} command
19085 The corresponding @value{GDBN} command is @samp{show}.
19087 @subsubheading Example
19096 @c @subheading -gdb-source
19099 @subheading The @code{-gdb-version} Command
19100 @findex -gdb-version
19102 @subsubheading Synopsis
19108 Show version information for @value{GDBN}. Used mostly in testing.
19110 @subsubheading @value{GDBN} Command
19112 There's no equivalent @value{GDBN} command. @value{GDBN} by default shows this
19113 information when you start an interactive session.
19115 @subsubheading Example
19117 @c This example modifies the actual output from GDB to avoid overfull
19123 ~Copyright 2000 Free Software Foundation, Inc.
19124 ~GDB is free software, covered by the GNU General Public License, and
19125 ~you are welcome to change it and/or distribute copies of it under
19126 ~ certain conditions.
19127 ~Type "show copying" to see the conditions.
19128 ~There is absolutely no warranty for GDB. Type "show warranty" for
19130 ~This GDB was configured as
19131 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
19136 @subheading The @code{-interpreter-exec} Command
19137 @findex -interpreter-exec
19139 @subheading Synopsis
19142 -interpreter-exec @var{interpreter} @var{command}
19145 Execute the specified @var{command} in the given @var{interpreter}.
19147 @subheading @value{GDBN} Command
19149 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
19151 @subheading Example
19155 -interpreter-exec console "break main"
19156 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
19157 &"During symbol reading, bad structure-type format.\n"
19158 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
19164 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19165 @node GDB/MI Kod Commands
19166 @section @sc{gdb/mi} Kod Commands
19168 The Kod commands are not implemented.
19170 @c @subheading -kod-info
19172 @c @subheading -kod-list
19174 @c @subheading -kod-list-object-types
19176 @c @subheading -kod-show
19178 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19179 @node GDB/MI Memory Overlay Commands
19180 @section @sc{gdb/mi} Memory Overlay Commands
19182 The memory overlay commands are not implemented.
19184 @c @subheading -overlay-auto
19186 @c @subheading -overlay-list-mapping-state
19188 @c @subheading -overlay-list-overlays
19190 @c @subheading -overlay-map
19192 @c @subheading -overlay-off
19194 @c @subheading -overlay-on
19196 @c @subheading -overlay-unmap
19198 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19199 @node GDB/MI Signal Handling Commands
19200 @section @sc{gdb/mi} Signal Handling Commands
19202 Signal handling commands are not implemented.
19204 @c @subheading -signal-handle
19206 @c @subheading -signal-list-handle-actions
19208 @c @subheading -signal-list-signal-types
19212 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19213 @node GDB/MI Stack Manipulation
19214 @section @sc{gdb/mi} Stack Manipulation Commands
19216 @subheading The @code{-stack-info-depth} Command
19217 @findex -stack-info-depth
19219 @subsubheading Synopsis
19222 -stack-info-depth [ @var{max-depth} ]
19225 Return the depth of the stack. If the integer argument @var{max-depth}
19226 is specified, do not count beyond @var{max-depth} frames.
19228 @subsubheading @value{GDBN} Command
19230 There's no equivalent @value{GDBN} command.
19232 @subsubheading Example
19234 For a stack with frame levels 0 through 11:
19241 -stack-info-depth 4
19244 -stack-info-depth 12
19247 -stack-info-depth 11
19250 -stack-info-depth 13
19255 @subheading The @code{-stack-list-arguments} Command
19256 @findex -stack-list-arguments
19258 @subsubheading Synopsis
19261 -stack-list-arguments @var{show-values}
19262 [ @var{low-frame} @var{high-frame} ]
19265 Display a list of the arguments for the frames between @var{low-frame}
19266 and @var{high-frame} (inclusive). If @var{low-frame} and
19267 @var{high-frame} are not provided, list the arguments for the whole call
19270 The @var{show-values} argument must have a value of 0 or 1. A value of
19271 0 means that only the names of the arguments are listed, a value of 1
19272 means that both names and values of the arguments are printed.
19274 @subsubheading @value{GDBN} Command
19276 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19277 @samp{gdb_get_args} command which partially overlaps with the
19278 functionality of @samp{-stack-list-arguments}.
19280 @subsubheading Example
19287 frame=@{level="0",addr="0x00010734",func="callee4",
19288 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19289 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19290 frame=@{level="1",addr="0x0001076c",func="callee3",
19291 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19292 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19293 frame=@{level="2",addr="0x0001078c",func="callee2",
19294 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19295 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19296 frame=@{level="3",addr="0x000107b4",func="callee1",
19297 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19298 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19299 frame=@{level="4",addr="0x000107e0",func="main",
19300 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19301 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19303 -stack-list-arguments 0
19306 frame=@{level="0",args=[]@},
19307 frame=@{level="1",args=[name="strarg"]@},
19308 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19309 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19310 frame=@{level="4",args=[]@}]
19312 -stack-list-arguments 1
19315 frame=@{level="0",args=[]@},
19317 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19318 frame=@{level="2",args=[
19319 @{name="intarg",value="2"@},
19320 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19321 @{frame=@{level="3",args=[
19322 @{name="intarg",value="2"@},
19323 @{name="strarg",value="0x11940 \"A string argument.\""@},
19324 @{name="fltarg",value="3.5"@}]@},
19325 frame=@{level="4",args=[]@}]
19327 -stack-list-arguments 0 2 2
19328 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19330 -stack-list-arguments 1 2 2
19331 ^done,stack-args=[frame=@{level="2",
19332 args=[@{name="intarg",value="2"@},
19333 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19337 @c @subheading -stack-list-exception-handlers
19340 @subheading The @code{-stack-list-frames} Command
19341 @findex -stack-list-frames
19343 @subsubheading Synopsis
19346 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19349 List the frames currently on the stack. For each frame it displays the
19354 The frame number, 0 being the topmost frame, i.e. the innermost function.
19356 The @code{$pc} value for that frame.
19360 File name of the source file where the function lives.
19362 Line number corresponding to the @code{$pc}.
19365 If invoked without arguments, this command prints a backtrace for the
19366 whole stack. If given two integer arguments, it shows the frames whose
19367 levels are between the two arguments (inclusive). If the two arguments
19368 are equal, it shows the single frame at the corresponding level.
19370 @subsubheading @value{GDBN} Command
19372 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19374 @subsubheading Example
19376 Full stack backtrace:
19382 [frame=@{level="0",addr="0x0001076c",func="foo",
19383 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="11"@},
19384 frame=@{level="1",addr="0x000107a4",func="foo",
19385 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19386 frame=@{level="2",addr="0x000107a4",func="foo",
19387 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19388 frame=@{level="3",addr="0x000107a4",func="foo",
19389 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19390 frame=@{level="4",addr="0x000107a4",func="foo",
19391 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19392 frame=@{level="5",addr="0x000107a4",func="foo",
19393 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19394 frame=@{level="6",addr="0x000107a4",func="foo",
19395 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19396 frame=@{level="7",addr="0x000107a4",func="foo",
19397 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19398 frame=@{level="8",addr="0x000107a4",func="foo",
19399 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19400 frame=@{level="9",addr="0x000107a4",func="foo",
19401 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19402 frame=@{level="10",addr="0x000107a4",func="foo",
19403 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19404 frame=@{level="11",addr="0x00010738",func="main",
19405 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="4"@}]
19409 Show frames between @var{low_frame} and @var{high_frame}:
19413 -stack-list-frames 3 5
19415 [frame=@{level="3",addr="0x000107a4",func="foo",
19416 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19417 frame=@{level="4",addr="0x000107a4",func="foo",
19418 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19419 frame=@{level="5",addr="0x000107a4",func="foo",
19420 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@}]
19424 Show a single frame:
19428 -stack-list-frames 3 3
19430 [frame=@{level="3",addr="0x000107a4",func="foo",
19431 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@}]
19436 @subheading The @code{-stack-list-locals} Command
19437 @findex -stack-list-locals
19439 @subsubheading Synopsis
19442 -stack-list-locals @var{print-values}
19445 Display the local variable names for the current frame. With an
19446 argument of 0 or @code{--no-values}, prints only the names of the variables.
19447 With argument of 1 or @code{--all-values}, prints also their values. With
19448 argument of 2 or @code{--simple-values}, prints the name, type and value for
19449 simple data types and the name and type for arrays, structures and
19450 unions. In this last case, the idea is that the user can see the
19451 value of simple data types immediately and he can create variable
19452 objects for other data types if he wishes to explore their values in
19455 @subsubheading @value{GDBN} Command
19457 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
19459 @subsubheading Example
19463 -stack-list-locals 0
19464 ^done,locals=[name="A",name="B",name="C"]
19466 -stack-list-locals --all-values
19467 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
19468 @{name="C",value="@{1, 2, 3@}"@}]
19469 -stack-list-locals --simple-values
19470 ^done,locals=[@{name="A",type="int",value="1"@},
19471 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
19476 @subheading The @code{-stack-select-frame} Command
19477 @findex -stack-select-frame
19479 @subsubheading Synopsis
19482 -stack-select-frame @var{framenum}
19485 Change the current frame. Select a different frame @var{framenum} on
19488 @subsubheading @value{GDBN} Command
19490 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
19491 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
19493 @subsubheading Example
19497 -stack-select-frame 2
19502 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19503 @node GDB/MI Symbol Query
19504 @section @sc{gdb/mi} Symbol Query Commands
19507 @subheading The @code{-symbol-info-address} Command
19508 @findex -symbol-info-address
19510 @subsubheading Synopsis
19513 -symbol-info-address @var{symbol}
19516 Describe where @var{symbol} is stored.
19518 @subsubheading @value{GDBN} Command
19520 The corresponding @value{GDBN} command is @samp{info address}.
19522 @subsubheading Example
19526 @subheading The @code{-symbol-info-file} Command
19527 @findex -symbol-info-file
19529 @subsubheading Synopsis
19535 Show the file for the symbol.
19537 @subsubheading @value{GDBN} Command
19539 There's no equivalent @value{GDBN} command. @code{gdbtk} has
19540 @samp{gdb_find_file}.
19542 @subsubheading Example
19546 @subheading The @code{-symbol-info-function} Command
19547 @findex -symbol-info-function
19549 @subsubheading Synopsis
19552 -symbol-info-function
19555 Show which function the symbol lives in.
19557 @subsubheading @value{GDBN} Command
19559 @samp{gdb_get_function} in @code{gdbtk}.
19561 @subsubheading Example
19565 @subheading The @code{-symbol-info-line} Command
19566 @findex -symbol-info-line
19568 @subsubheading Synopsis
19574 Show the core addresses of the code for a source line.
19576 @subsubheading @value{GDBN} Command
19578 The corresponding @value{GDBN} command is @samp{info line}.
19579 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
19581 @subsubheading Example
19585 @subheading The @code{-symbol-info-symbol} Command
19586 @findex -symbol-info-symbol
19588 @subsubheading Synopsis
19591 -symbol-info-symbol @var{addr}
19594 Describe what symbol is at location @var{addr}.
19596 @subsubheading @value{GDBN} Command
19598 The corresponding @value{GDBN} command is @samp{info symbol}.
19600 @subsubheading Example
19604 @subheading The @code{-symbol-list-functions} Command
19605 @findex -symbol-list-functions
19607 @subsubheading Synopsis
19610 -symbol-list-functions
19613 List the functions in the executable.
19615 @subsubheading @value{GDBN} Command
19617 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
19618 @samp{gdb_search} in @code{gdbtk}.
19620 @subsubheading Example
19624 @subheading The @code{-symbol-list-lines} Command
19625 @findex -symbol-list-lines
19627 @subsubheading Synopsis
19630 -symbol-list-lines @var{filename}
19633 Print the list of lines that contain code and their associated program
19634 addresses for the given source filename. The entries are sorted in
19635 ascending PC order.
19637 @subsubheading @value{GDBN} Command
19639 There is no corresponding @value{GDBN} command.
19641 @subsubheading Example
19644 -symbol-list-lines basics.c
19645 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
19650 @subheading The @code{-symbol-list-types} Command
19651 @findex -symbol-list-types
19653 @subsubheading Synopsis
19659 List all the type names.
19661 @subsubheading @value{GDBN} Command
19663 The corresponding commands are @samp{info types} in @value{GDBN},
19664 @samp{gdb_search} in @code{gdbtk}.
19666 @subsubheading Example
19670 @subheading The @code{-symbol-list-variables} Command
19671 @findex -symbol-list-variables
19673 @subsubheading Synopsis
19676 -symbol-list-variables
19679 List all the global and static variable names.
19681 @subsubheading @value{GDBN} Command
19683 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
19685 @subsubheading Example
19689 @subheading The @code{-symbol-locate} Command
19690 @findex -symbol-locate
19692 @subsubheading Synopsis
19698 @subsubheading @value{GDBN} Command
19700 @samp{gdb_loc} in @code{gdbtk}.
19702 @subsubheading Example
19706 @subheading The @code{-symbol-type} Command
19707 @findex -symbol-type
19709 @subsubheading Synopsis
19712 -symbol-type @var{variable}
19715 Show type of @var{variable}.
19717 @subsubheading @value{GDBN} Command
19719 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
19720 @samp{gdb_obj_variable}.
19722 @subsubheading Example
19726 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19727 @node GDB/MI Target Manipulation
19728 @section @sc{gdb/mi} Target Manipulation Commands
19731 @subheading The @code{-target-attach} Command
19732 @findex -target-attach
19734 @subsubheading Synopsis
19737 -target-attach @var{pid} | @var{file}
19740 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
19742 @subsubheading @value{GDBN} command
19744 The corresponding @value{GDBN} command is @samp{attach}.
19746 @subsubheading Example
19750 @subheading The @code{-target-compare-sections} Command
19751 @findex -target-compare-sections
19753 @subsubheading Synopsis
19756 -target-compare-sections [ @var{section} ]
19759 Compare data of section @var{section} on target to the exec file.
19760 Without the argument, all sections are compared.
19762 @subsubheading @value{GDBN} Command
19764 The @value{GDBN} equivalent is @samp{compare-sections}.
19766 @subsubheading Example
19770 @subheading The @code{-target-detach} Command
19771 @findex -target-detach
19773 @subsubheading Synopsis
19779 Disconnect from the remote target. There's no output.
19781 @subsubheading @value{GDBN} command
19783 The corresponding @value{GDBN} command is @samp{detach}.
19785 @subsubheading Example
19795 @subheading The @code{-target-disconnect} Command
19796 @findex -target-disconnect
19798 @subsubheading Synopsis
19804 Disconnect from the remote target. There's no output.
19806 @subsubheading @value{GDBN} command
19808 The corresponding @value{GDBN} command is @samp{disconnect}.
19810 @subsubheading Example
19820 @subheading The @code{-target-download} Command
19821 @findex -target-download
19823 @subsubheading Synopsis
19829 Loads the executable onto the remote target.
19830 It prints out an update message every half second, which includes the fields:
19834 The name of the section.
19836 The size of what has been sent so far for that section.
19838 The size of the section.
19840 The total size of what was sent so far (the current and the previous sections).
19842 The size of the overall executable to download.
19846 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
19847 @sc{gdb/mi} Output Syntax}).
19849 In addition, it prints the name and size of the sections, as they are
19850 downloaded. These messages include the following fields:
19854 The name of the section.
19856 The size of the section.
19858 The size of the overall executable to download.
19862 At the end, a summary is printed.
19864 @subsubheading @value{GDBN} Command
19866 The corresponding @value{GDBN} command is @samp{load}.
19868 @subsubheading Example
19870 Note: each status message appears on a single line. Here the messages
19871 have been broken down so that they can fit onto a page.
19876 +download,@{section=".text",section-size="6668",total-size="9880"@}
19877 +download,@{section=".text",section-sent="512",section-size="6668",
19878 total-sent="512",total-size="9880"@}
19879 +download,@{section=".text",section-sent="1024",section-size="6668",
19880 total-sent="1024",total-size="9880"@}
19881 +download,@{section=".text",section-sent="1536",section-size="6668",
19882 total-sent="1536",total-size="9880"@}
19883 +download,@{section=".text",section-sent="2048",section-size="6668",
19884 total-sent="2048",total-size="9880"@}
19885 +download,@{section=".text",section-sent="2560",section-size="6668",
19886 total-sent="2560",total-size="9880"@}
19887 +download,@{section=".text",section-sent="3072",section-size="6668",
19888 total-sent="3072",total-size="9880"@}
19889 +download,@{section=".text",section-sent="3584",section-size="6668",
19890 total-sent="3584",total-size="9880"@}
19891 +download,@{section=".text",section-sent="4096",section-size="6668",
19892 total-sent="4096",total-size="9880"@}
19893 +download,@{section=".text",section-sent="4608",section-size="6668",
19894 total-sent="4608",total-size="9880"@}
19895 +download,@{section=".text",section-sent="5120",section-size="6668",
19896 total-sent="5120",total-size="9880"@}
19897 +download,@{section=".text",section-sent="5632",section-size="6668",
19898 total-sent="5632",total-size="9880"@}
19899 +download,@{section=".text",section-sent="6144",section-size="6668",
19900 total-sent="6144",total-size="9880"@}
19901 +download,@{section=".text",section-sent="6656",section-size="6668",
19902 total-sent="6656",total-size="9880"@}
19903 +download,@{section=".init",section-size="28",total-size="9880"@}
19904 +download,@{section=".fini",section-size="28",total-size="9880"@}
19905 +download,@{section=".data",section-size="3156",total-size="9880"@}
19906 +download,@{section=".data",section-sent="512",section-size="3156",
19907 total-sent="7236",total-size="9880"@}
19908 +download,@{section=".data",section-sent="1024",section-size="3156",
19909 total-sent="7748",total-size="9880"@}
19910 +download,@{section=".data",section-sent="1536",section-size="3156",
19911 total-sent="8260",total-size="9880"@}
19912 +download,@{section=".data",section-sent="2048",section-size="3156",
19913 total-sent="8772",total-size="9880"@}
19914 +download,@{section=".data",section-sent="2560",section-size="3156",
19915 total-sent="9284",total-size="9880"@}
19916 +download,@{section=".data",section-sent="3072",section-size="3156",
19917 total-sent="9796",total-size="9880"@}
19918 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
19924 @subheading The @code{-target-exec-status} Command
19925 @findex -target-exec-status
19927 @subsubheading Synopsis
19930 -target-exec-status
19933 Provide information on the state of the target (whether it is running or
19934 not, for instance).
19936 @subsubheading @value{GDBN} Command
19938 There's no equivalent @value{GDBN} command.
19940 @subsubheading Example
19944 @subheading The @code{-target-list-available-targets} Command
19945 @findex -target-list-available-targets
19947 @subsubheading Synopsis
19950 -target-list-available-targets
19953 List the possible targets to connect to.
19955 @subsubheading @value{GDBN} Command
19957 The corresponding @value{GDBN} command is @samp{help target}.
19959 @subsubheading Example
19963 @subheading The @code{-target-list-current-targets} Command
19964 @findex -target-list-current-targets
19966 @subsubheading Synopsis
19969 -target-list-current-targets
19972 Describe the current target.
19974 @subsubheading @value{GDBN} Command
19976 The corresponding information is printed by @samp{info file} (among
19979 @subsubheading Example
19983 @subheading The @code{-target-list-parameters} Command
19984 @findex -target-list-parameters
19986 @subsubheading Synopsis
19989 -target-list-parameters
19994 @subsubheading @value{GDBN} Command
19998 @subsubheading Example
20002 @subheading The @code{-target-select} Command
20003 @findex -target-select
20005 @subsubheading Synopsis
20008 -target-select @var{type} @var{parameters @dots{}}
20011 Connect @value{GDBN} to the remote target. This command takes two args:
20015 The type of target, for instance @samp{async}, @samp{remote}, etc.
20016 @item @var{parameters}
20017 Device names, host names and the like. @xref{Target Commands, ,
20018 Commands for managing targets}, for more details.
20021 The output is a connection notification, followed by the address at
20022 which the target program is, in the following form:
20025 ^connected,addr="@var{address}",func="@var{function name}",
20026 args=[@var{arg list}]
20029 @subsubheading @value{GDBN} Command
20031 The corresponding @value{GDBN} command is @samp{target}.
20033 @subsubheading Example
20037 -target-select async /dev/ttya
20038 ^connected,addr="0xfe00a300",func="??",args=[]
20042 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20043 @node GDB/MI Thread Commands
20044 @section @sc{gdb/mi} Thread Commands
20047 @subheading The @code{-thread-info} Command
20048 @findex -thread-info
20050 @subsubheading Synopsis
20056 @subsubheading @value{GDBN} command
20060 @subsubheading Example
20064 @subheading The @code{-thread-list-all-threads} Command
20065 @findex -thread-list-all-threads
20067 @subsubheading Synopsis
20070 -thread-list-all-threads
20073 @subsubheading @value{GDBN} Command
20075 The equivalent @value{GDBN} command is @samp{info threads}.
20077 @subsubheading Example
20081 @subheading The @code{-thread-list-ids} Command
20082 @findex -thread-list-ids
20084 @subsubheading Synopsis
20090 Produces a list of the currently known @value{GDBN} thread ids. At the
20091 end of the list it also prints the total number of such threads.
20093 @subsubheading @value{GDBN} Command
20095 Part of @samp{info threads} supplies the same information.
20097 @subsubheading Example
20099 No threads present, besides the main process:
20104 ^done,thread-ids=@{@},number-of-threads="0"
20114 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20115 number-of-threads="3"
20120 @subheading The @code{-thread-select} Command
20121 @findex -thread-select
20123 @subsubheading Synopsis
20126 -thread-select @var{threadnum}
20129 Make @var{threadnum} the current thread. It prints the number of the new
20130 current thread, and the topmost frame for that thread.
20132 @subsubheading @value{GDBN} Command
20134 The corresponding @value{GDBN} command is @samp{thread}.
20136 @subsubheading Example
20143 *stopped,reason="end-stepping-range",thread-id="2",line="187",
20144 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
20148 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20149 number-of-threads="3"
20152 ^done,new-thread-id="3",
20153 frame=@{level="0",func="vprintf",
20154 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
20155 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
20159 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20160 @node GDB/MI Tracepoint Commands
20161 @section @sc{gdb/mi} Tracepoint Commands
20163 The tracepoint commands are not yet implemented.
20165 @c @subheading -trace-actions
20167 @c @subheading -trace-delete
20169 @c @subheading -trace-disable
20171 @c @subheading -trace-dump
20173 @c @subheading -trace-enable
20175 @c @subheading -trace-exists
20177 @c @subheading -trace-find
20179 @c @subheading -trace-frame-number
20181 @c @subheading -trace-info
20183 @c @subheading -trace-insert
20185 @c @subheading -trace-list
20187 @c @subheading -trace-pass-count
20189 @c @subheading -trace-save
20191 @c @subheading -trace-start
20193 @c @subheading -trace-stop
20196 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20197 @node GDB/MI Variable Objects
20198 @section @sc{gdb/mi} Variable Objects
20201 @subheading Motivation for Variable Objects in @sc{gdb/mi}
20203 For the implementation of a variable debugger window (locals, watched
20204 expressions, etc.), we are proposing the adaptation of the existing code
20205 used by @code{Insight}.
20207 The two main reasons for that are:
20211 It has been proven in practice (it is already on its second generation).
20214 It will shorten development time (needless to say how important it is
20218 The original interface was designed to be used by Tcl code, so it was
20219 slightly changed so it could be used through @sc{gdb/mi}. This section
20220 describes the @sc{gdb/mi} operations that will be available and gives some
20221 hints about their use.
20223 @emph{Note}: In addition to the set of operations described here, we
20224 expect the @sc{gui} implementation of a variable window to require, at
20225 least, the following operations:
20228 @item @code{-gdb-show} @code{output-radix}
20229 @item @code{-stack-list-arguments}
20230 @item @code{-stack-list-locals}
20231 @item @code{-stack-select-frame}
20234 @subheading Introduction to Variable Objects in @sc{gdb/mi}
20236 @cindex variable objects in @sc{gdb/mi}
20237 The basic idea behind variable objects is the creation of a named object
20238 to represent a variable, an expression, a memory location or even a CPU
20239 register. For each object created, a set of operations is available for
20240 examining or changing its properties.
20242 Furthermore, complex data types, such as C structures, are represented
20243 in a tree format. For instance, the @code{struct} type variable is the
20244 root and the children will represent the struct members. If a child
20245 is itself of a complex type, it will also have children of its own.
20246 Appropriate language differences are handled for C, C@t{++} and Java.
20248 When returning the actual values of the objects, this facility allows
20249 for the individual selection of the display format used in the result
20250 creation. It can be chosen among: binary, decimal, hexadecimal, octal
20251 and natural. Natural refers to a default format automatically
20252 chosen based on the variable type (like decimal for an @code{int}, hex
20253 for pointers, etc.).
20255 The following is the complete set of @sc{gdb/mi} operations defined to
20256 access this functionality:
20258 @multitable @columnfractions .4 .6
20259 @item @strong{Operation}
20260 @tab @strong{Description}
20262 @item @code{-var-create}
20263 @tab create a variable object
20264 @item @code{-var-delete}
20265 @tab delete the variable object and its children
20266 @item @code{-var-set-format}
20267 @tab set the display format of this variable
20268 @item @code{-var-show-format}
20269 @tab show the display format of this variable
20270 @item @code{-var-info-num-children}
20271 @tab tells how many children this object has
20272 @item @code{-var-list-children}
20273 @tab return a list of the object's children
20274 @item @code{-var-info-type}
20275 @tab show the type of this variable object
20276 @item @code{-var-info-expression}
20277 @tab print what this variable object represents
20278 @item @code{-var-show-attributes}
20279 @tab is this variable editable? does it exist here?
20280 @item @code{-var-evaluate-expression}
20281 @tab get the value of this variable
20282 @item @code{-var-assign}
20283 @tab set the value of this variable
20284 @item @code{-var-update}
20285 @tab update the variable and its children
20288 In the next subsection we describe each operation in detail and suggest
20289 how it can be used.
20291 @subheading Description And Use of Operations on Variable Objects
20293 @subheading The @code{-var-create} Command
20294 @findex -var-create
20296 @subsubheading Synopsis
20299 -var-create @{@var{name} | "-"@}
20300 @{@var{frame-addr} | "*"@} @var{expression}
20303 This operation creates a variable object, which allows the monitoring of
20304 a variable, the result of an expression, a memory cell or a CPU
20307 The @var{name} parameter is the string by which the object can be
20308 referenced. It must be unique. If @samp{-} is specified, the varobj
20309 system will generate a string ``varNNNNNN'' automatically. It will be
20310 unique provided that one does not specify @var{name} on that format.
20311 The command fails if a duplicate name is found.
20313 The frame under which the expression should be evaluated can be
20314 specified by @var{frame-addr}. A @samp{*} indicates that the current
20315 frame should be used.
20317 @var{expression} is any expression valid on the current language set (must not
20318 begin with a @samp{*}), or one of the following:
20322 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
20325 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
20328 @samp{$@var{regname}} --- a CPU register name
20331 @subsubheading Result
20333 This operation returns the name, number of children and the type of the
20334 object created. Type is returned as a string as the ones generated by
20335 the @value{GDBN} CLI:
20338 name="@var{name}",numchild="N",type="@var{type}"
20342 @subheading The @code{-var-delete} Command
20343 @findex -var-delete
20345 @subsubheading Synopsis
20348 -var-delete @var{name}
20351 Deletes a previously created variable object and all of its children.
20353 Returns an error if the object @var{name} is not found.
20356 @subheading The @code{-var-set-format} Command
20357 @findex -var-set-format
20359 @subsubheading Synopsis
20362 -var-set-format @var{name} @var{format-spec}
20365 Sets the output format for the value of the object @var{name} to be
20368 The syntax for the @var{format-spec} is as follows:
20371 @var{format-spec} @expansion{}
20372 @{binary | decimal | hexadecimal | octal | natural@}
20376 @subheading The @code{-var-show-format} Command
20377 @findex -var-show-format
20379 @subsubheading Synopsis
20382 -var-show-format @var{name}
20385 Returns the format used to display the value of the object @var{name}.
20388 @var{format} @expansion{}
20393 @subheading The @code{-var-info-num-children} Command
20394 @findex -var-info-num-children
20396 @subsubheading Synopsis
20399 -var-info-num-children @var{name}
20402 Returns the number of children of a variable object @var{name}:
20409 @subheading The @code{-var-list-children} Command
20410 @findex -var-list-children
20412 @subsubheading Synopsis
20415 -var-list-children [@var{print-values}] @var{name}
20418 Returns a list of the children of the specified variable object. With
20419 just the variable object name as an argument or with an optional
20420 preceding argument of 0 or @code{--no-values}, prints only the names of the
20421 variables. With an optional preceding argument of 1 or @code{--all-values},
20422 also prints their values.
20424 @subsubheading Example
20428 -var-list-children n
20429 numchild=@var{n},children=[@{name=@var{name},
20430 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
20432 -var-list-children --all-values n
20433 numchild=@var{n},children=[@{name=@var{name},
20434 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
20438 @subheading The @code{-var-info-type} Command
20439 @findex -var-info-type
20441 @subsubheading Synopsis
20444 -var-info-type @var{name}
20447 Returns the type of the specified variable @var{name}. The type is
20448 returned as a string in the same format as it is output by the
20452 type=@var{typename}
20456 @subheading The @code{-var-info-expression} Command
20457 @findex -var-info-expression
20459 @subsubheading Synopsis
20462 -var-info-expression @var{name}
20465 Returns what is represented by the variable object @var{name}:
20468 lang=@var{lang-spec},exp=@var{expression}
20472 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
20474 @subheading The @code{-var-show-attributes} Command
20475 @findex -var-show-attributes
20477 @subsubheading Synopsis
20480 -var-show-attributes @var{name}
20483 List attributes of the specified variable object @var{name}:
20486 status=@var{attr} [ ( ,@var{attr} )* ]
20490 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
20492 @subheading The @code{-var-evaluate-expression} Command
20493 @findex -var-evaluate-expression
20495 @subsubheading Synopsis
20498 -var-evaluate-expression @var{name}
20501 Evaluates the expression that is represented by the specified variable
20502 object and returns its value as a string in the current format specified
20509 Note that one must invoke @code{-var-list-children} for a variable
20510 before the value of a child variable can be evaluated.
20512 @subheading The @code{-var-assign} Command
20513 @findex -var-assign
20515 @subsubheading Synopsis
20518 -var-assign @var{name} @var{expression}
20521 Assigns the value of @var{expression} to the variable object specified
20522 by @var{name}. The object must be @samp{editable}. If the variable's
20523 value is altered by the assign, the variable will show up in any
20524 subsequent @code{-var-update} list.
20526 @subsubheading Example
20534 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
20538 @subheading The @code{-var-update} Command
20539 @findex -var-update
20541 @subsubheading Synopsis
20544 -var-update @{@var{name} | "*"@}
20547 Update the value of the variable object @var{name} by evaluating its
20548 expression after fetching all the new values from memory or registers.
20549 A @samp{*} causes all existing variable objects to be updated.
20553 @chapter @value{GDBN} Annotations
20555 This chapter describes annotations in @value{GDBN}. Annotations were
20556 designed to interface @value{GDBN} to graphical user interfaces or other
20557 similar programs which want to interact with @value{GDBN} at a
20558 relatively high level.
20560 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
20564 This is Edition @value{EDITION}, @value{DATE}.
20568 * Annotations Overview:: What annotations are; the general syntax.
20569 * Server Prefix:: Issuing a command without affecting user state.
20570 * Prompting:: Annotations marking @value{GDBN}'s need for input.
20571 * Errors:: Annotations for error messages.
20572 * Invalidation:: Some annotations describe things now invalid.
20573 * Annotations for Running::
20574 Whether the program is running, how it stopped, etc.
20575 * Source Annotations:: Annotations describing source code.
20578 @node Annotations Overview
20579 @section What is an Annotation?
20580 @cindex annotations
20582 Annotations start with a newline character, two @samp{control-z}
20583 characters, and the name of the annotation. If there is no additional
20584 information associated with this annotation, the name of the annotation
20585 is followed immediately by a newline. If there is additional
20586 information, the name of the annotation is followed by a space, the
20587 additional information, and a newline. The additional information
20588 cannot contain newline characters.
20590 Any output not beginning with a newline and two @samp{control-z}
20591 characters denotes literal output from @value{GDBN}. Currently there is
20592 no need for @value{GDBN} to output a newline followed by two
20593 @samp{control-z} characters, but if there was such a need, the
20594 annotations could be extended with an @samp{escape} annotation which
20595 means those three characters as output.
20597 The annotation @var{level}, which is specified using the
20598 @option{--annotate} command line option (@pxref{Mode Options}), controls
20599 how much information @value{GDBN} prints together with its prompt,
20600 values of expressions, source lines, and other types of output. Level 0
20601 is for no anntations, level 1 is for use when @value{GDBN} is run as a
20602 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
20603 for programs that control @value{GDBN}, and level 2 annotations have
20604 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
20605 Interface, annotate, GDB's Obsolete Annotations}).
20608 @kindex set annotate
20609 @item set annotate @var{level}
20610 The @value{GDBN} command @code{set annotate} sets the level of
20611 annotations to the specified @var{level}.
20613 @item show annotate
20614 @kindex show annotate
20615 Show the current annotation level.
20618 This chapter describes level 3 annotations.
20620 A simple example of starting up @value{GDBN} with annotations is:
20623 $ @kbd{gdb --annotate=3}
20625 Copyright 2003 Free Software Foundation, Inc.
20626 GDB is free software, covered by the GNU General Public License,
20627 and you are welcome to change it and/or distribute copies of it
20628 under certain conditions.
20629 Type "show copying" to see the conditions.
20630 There is absolutely no warranty for GDB. Type "show warranty"
20632 This GDB was configured as "i386-pc-linux-gnu"
20643 Here @samp{quit} is input to @value{GDBN}; the rest is output from
20644 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
20645 denotes a @samp{control-z} character) are annotations; the rest is
20646 output from @value{GDBN}.
20648 @node Server Prefix
20649 @section The Server Prefix
20650 @cindex server prefix for annotations
20652 To issue a command to @value{GDBN} without affecting certain aspects of
20653 the state which is seen by users, prefix it with @samp{server }. This
20654 means that this command will not affect the command history, nor will it
20655 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
20656 pressed on a line by itself.
20658 The server prefix does not affect the recording of values into the value
20659 history; to print a value without recording it into the value history,
20660 use the @code{output} command instead of the @code{print} command.
20663 @section Annotation for @value{GDBN} Input
20665 @cindex annotations for prompts
20666 When @value{GDBN} prompts for input, it annotates this fact so it is possible
20667 to know when to send output, when the output from a given command is
20670 Different kinds of input each have a different @dfn{input type}. Each
20671 input type has three annotations: a @code{pre-} annotation, which
20672 denotes the beginning of any prompt which is being output, a plain
20673 annotation, which denotes the end of the prompt, and then a @code{post-}
20674 annotation which denotes the end of any echo which may (or may not) be
20675 associated with the input. For example, the @code{prompt} input type
20676 features the following annotations:
20684 The input types are
20689 @findex post-prompt
20691 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
20693 @findex pre-commands
20695 @findex post-commands
20697 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
20698 command. The annotations are repeated for each command which is input.
20700 @findex pre-overload-choice
20701 @findex overload-choice
20702 @findex post-overload-choice
20703 @item overload-choice
20704 When @value{GDBN} wants the user to select between various overloaded functions.
20710 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
20712 @findex pre-prompt-for-continue
20713 @findex prompt-for-continue
20714 @findex post-prompt-for-continue
20715 @item prompt-for-continue
20716 When @value{GDBN} is asking the user to press return to continue. Note: Don't
20717 expect this to work well; instead use @code{set height 0} to disable
20718 prompting. This is because the counting of lines is buggy in the
20719 presence of annotations.
20724 @cindex annotations for errors, warnings and interrupts
20731 This annotation occurs right before @value{GDBN} responds to an interrupt.
20738 This annotation occurs right before @value{GDBN} responds to an error.
20740 Quit and error annotations indicate that any annotations which @value{GDBN} was
20741 in the middle of may end abruptly. For example, if a
20742 @code{value-history-begin} annotation is followed by a @code{error}, one
20743 cannot expect to receive the matching @code{value-history-end}. One
20744 cannot expect not to receive it either, however; an error annotation
20745 does not necessarily mean that @value{GDBN} is immediately returning all the way
20748 @findex error-begin
20749 A quit or error annotation may be preceded by
20755 Any output between that and the quit or error annotation is the error
20758 Warning messages are not yet annotated.
20759 @c If we want to change that, need to fix warning(), type_error(),
20760 @c range_error(), and possibly other places.
20763 @section Invalidation Notices
20765 @cindex annotations for invalidation messages
20766 The following annotations say that certain pieces of state may have
20770 @findex frames-invalid
20771 @item ^Z^Zframes-invalid
20773 The frames (for example, output from the @code{backtrace} command) may
20776 @findex breakpoints-invalid
20777 @item ^Z^Zbreakpoints-invalid
20779 The breakpoints may have changed. For example, the user just added or
20780 deleted a breakpoint.
20783 @node Annotations for Running
20784 @section Running the Program
20785 @cindex annotations for running programs
20789 When the program starts executing due to a @value{GDBN} command such as
20790 @code{step} or @code{continue},
20796 is output. When the program stops,
20802 is output. Before the @code{stopped} annotation, a variety of
20803 annotations describe how the program stopped.
20807 @item ^Z^Zexited @var{exit-status}
20808 The program exited, and @var{exit-status} is the exit status (zero for
20809 successful exit, otherwise nonzero).
20812 @findex signal-name
20813 @findex signal-name-end
20814 @findex signal-string
20815 @findex signal-string-end
20816 @item ^Z^Zsignalled
20817 The program exited with a signal. After the @code{^Z^Zsignalled}, the
20818 annotation continues:
20824 ^Z^Zsignal-name-end
20828 ^Z^Zsignal-string-end
20833 where @var{name} is the name of the signal, such as @code{SIGILL} or
20834 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
20835 as @code{Illegal Instruction} or @code{Segmentation fault}.
20836 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
20837 user's benefit and have no particular format.
20841 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
20842 just saying that the program received the signal, not that it was
20843 terminated with it.
20846 @item ^Z^Zbreakpoint @var{number}
20847 The program hit breakpoint number @var{number}.
20850 @item ^Z^Zwatchpoint @var{number}
20851 The program hit watchpoint number @var{number}.
20854 @node Source Annotations
20855 @section Displaying Source
20856 @cindex annotations for source display
20859 The following annotation is used instead of displaying source code:
20862 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
20865 where @var{filename} is an absolute file name indicating which source
20866 file, @var{line} is the line number within that file (where 1 is the
20867 first line in the file), @var{character} is the character position
20868 within the file (where 0 is the first character in the file) (for most
20869 debug formats this will necessarily point to the beginning of a line),
20870 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
20871 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
20872 @var{addr} is the address in the target program associated with the
20873 source which is being displayed. @var{addr} is in the form @samp{0x}
20874 followed by one or more lowercase hex digits (note that this does not
20875 depend on the language).
20878 @chapter Reporting Bugs in @value{GDBN}
20879 @cindex bugs in @value{GDBN}
20880 @cindex reporting bugs in @value{GDBN}
20882 Your bug reports play an essential role in making @value{GDBN} reliable.
20884 Reporting a bug may help you by bringing a solution to your problem, or it
20885 may not. But in any case the principal function of a bug report is to help
20886 the entire community by making the next version of @value{GDBN} work better. Bug
20887 reports are your contribution to the maintenance of @value{GDBN}.
20889 In order for a bug report to serve its purpose, you must include the
20890 information that enables us to fix the bug.
20893 * Bug Criteria:: Have you found a bug?
20894 * Bug Reporting:: How to report bugs
20898 @section Have you found a bug?
20899 @cindex bug criteria
20901 If you are not sure whether you have found a bug, here are some guidelines:
20904 @cindex fatal signal
20905 @cindex debugger crash
20906 @cindex crash of debugger
20908 If the debugger gets a fatal signal, for any input whatever, that is a
20909 @value{GDBN} bug. Reliable debuggers never crash.
20911 @cindex error on valid input
20913 If @value{GDBN} produces an error message for valid input, that is a
20914 bug. (Note that if you're cross debugging, the problem may also be
20915 somewhere in the connection to the target.)
20917 @cindex invalid input
20919 If @value{GDBN} does not produce an error message for invalid input,
20920 that is a bug. However, you should note that your idea of
20921 ``invalid input'' might be our idea of ``an extension'' or ``support
20922 for traditional practice''.
20925 If you are an experienced user of debugging tools, your suggestions
20926 for improvement of @value{GDBN} are welcome in any case.
20929 @node Bug Reporting
20930 @section How to report bugs
20931 @cindex bug reports
20932 @cindex @value{GDBN} bugs, reporting
20934 A number of companies and individuals offer support for @sc{gnu} products.
20935 If you obtained @value{GDBN} from a support organization, we recommend you
20936 contact that organization first.
20938 You can find contact information for many support companies and
20939 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
20941 @c should add a web page ref...
20943 In any event, we also recommend that you submit bug reports for
20944 @value{GDBN}. The prefered method is to submit them directly using
20945 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
20946 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
20949 @strong{Do not send bug reports to @samp{info-gdb}, or to
20950 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
20951 not want to receive bug reports. Those that do have arranged to receive
20954 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
20955 serves as a repeater. The mailing list and the newsgroup carry exactly
20956 the same messages. Often people think of posting bug reports to the
20957 newsgroup instead of mailing them. This appears to work, but it has one
20958 problem which can be crucial: a newsgroup posting often lacks a mail
20959 path back to the sender. Thus, if we need to ask for more information,
20960 we may be unable to reach you. For this reason, it is better to send
20961 bug reports to the mailing list.
20963 The fundamental principle of reporting bugs usefully is this:
20964 @strong{report all the facts}. If you are not sure whether to state a
20965 fact or leave it out, state it!
20967 Often people omit facts because they think they know what causes the
20968 problem and assume that some details do not matter. Thus, you might
20969 assume that the name of the variable you use in an example does not matter.
20970 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
20971 stray memory reference which happens to fetch from the location where that
20972 name is stored in memory; perhaps, if the name were different, the contents
20973 of that location would fool the debugger into doing the right thing despite
20974 the bug. Play it safe and give a specific, complete example. That is the
20975 easiest thing for you to do, and the most helpful.
20977 Keep in mind that the purpose of a bug report is to enable us to fix the
20978 bug. It may be that the bug has been reported previously, but neither
20979 you nor we can know that unless your bug report is complete and
20982 Sometimes people give a few sketchy facts and ask, ``Does this ring a
20983 bell?'' Those bug reports are useless, and we urge everyone to
20984 @emph{refuse to respond to them} except to chide the sender to report
20987 To enable us to fix the bug, you should include all these things:
20991 The version of @value{GDBN}. @value{GDBN} announces it if you start
20992 with no arguments; you can also print it at any time using @code{show
20995 Without this, we will not know whether there is any point in looking for
20996 the bug in the current version of @value{GDBN}.
20999 The type of machine you are using, and the operating system name and
21003 What compiler (and its version) was used to compile @value{GDBN}---e.g.
21004 ``@value{GCC}--2.8.1''.
21007 What compiler (and its version) was used to compile the program you are
21008 debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
21009 C Compiler''. For GCC, you can say @code{gcc --version} to get this
21010 information; for other compilers, see the documentation for those
21014 The command arguments you gave the compiler to compile your example and
21015 observe the bug. For example, did you use @samp{-O}? To guarantee
21016 you will not omit something important, list them all. A copy of the
21017 Makefile (or the output from make) is sufficient.
21019 If we were to try to guess the arguments, we would probably guess wrong
21020 and then we might not encounter the bug.
21023 A complete input script, and all necessary source files, that will
21027 A description of what behavior you observe that you believe is
21028 incorrect. For example, ``It gets a fatal signal.''
21030 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
21031 will certainly notice it. But if the bug is incorrect output, we might
21032 not notice unless it is glaringly wrong. You might as well not give us
21033 a chance to make a mistake.
21035 Even if the problem you experience is a fatal signal, you should still
21036 say so explicitly. Suppose something strange is going on, such as, your
21037 copy of @value{GDBN} is out of synch, or you have encountered a bug in
21038 the C library on your system. (This has happened!) Your copy might
21039 crash and ours would not. If you told us to expect a crash, then when
21040 ours fails to crash, we would know that the bug was not happening for
21041 us. If you had not told us to expect a crash, then we would not be able
21042 to draw any conclusion from our observations.
21045 @cindex recording a session script
21046 To collect all this information, you can use a session recording program
21047 such as @command{script}, which is available on many Unix systems.
21048 Just run your @value{GDBN} session inside @command{script} and then
21049 include the @file{typescript} file with your bug report.
21051 Another way to record a @value{GDBN} session is to run @value{GDBN}
21052 inside Emacs and then save the entire buffer to a file.
21055 If you wish to suggest changes to the @value{GDBN} source, send us context
21056 diffs. If you even discuss something in the @value{GDBN} source, refer to
21057 it by context, not by line number.
21059 The line numbers in our development sources will not match those in your
21060 sources. Your line numbers would convey no useful information to us.
21064 Here are some things that are not necessary:
21068 A description of the envelope of the bug.
21070 Often people who encounter a bug spend a lot of time investigating
21071 which changes to the input file will make the bug go away and which
21072 changes will not affect it.
21074 This is often time consuming and not very useful, because the way we
21075 will find the bug is by running a single example under the debugger
21076 with breakpoints, not by pure deduction from a series of examples.
21077 We recommend that you save your time for something else.
21079 Of course, if you can find a simpler example to report @emph{instead}
21080 of the original one, that is a convenience for us. Errors in the
21081 output will be easier to spot, running under the debugger will take
21082 less time, and so on.
21084 However, simplification is not vital; if you do not want to do this,
21085 report the bug anyway and send us the entire test case you used.
21088 A patch for the bug.
21090 A patch for the bug does help us if it is a good one. But do not omit
21091 the necessary information, such as the test case, on the assumption that
21092 a patch is all we need. We might see problems with your patch and decide
21093 to fix the problem another way, or we might not understand it at all.
21095 Sometimes with a program as complicated as @value{GDBN} it is very hard to
21096 construct an example that will make the program follow a certain path
21097 through the code. If you do not send us the example, we will not be able
21098 to construct one, so we will not be able to verify that the bug is fixed.
21100 And if we cannot understand what bug you are trying to fix, or why your
21101 patch should be an improvement, we will not install it. A test case will
21102 help us to understand.
21105 A guess about what the bug is or what it depends on.
21107 Such guesses are usually wrong. Even we cannot guess right about such
21108 things without first using the debugger to find the facts.
21111 @c The readline documentation is distributed with the readline code
21112 @c and consists of the two following files:
21114 @c inc-hist.texinfo
21115 @c Use -I with makeinfo to point to the appropriate directory,
21116 @c environment var TEXINPUTS with TeX.
21117 @include rluser.texinfo
21118 @include inc-hist.texinfo
21121 @node Formatting Documentation
21122 @appendix Formatting Documentation
21124 @cindex @value{GDBN} reference card
21125 @cindex reference card
21126 The @value{GDBN} 4 release includes an already-formatted reference card, ready
21127 for printing with PostScript or Ghostscript, in the @file{gdb}
21128 subdirectory of the main source directory@footnote{In
21129 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
21130 release.}. If you can use PostScript or Ghostscript with your printer,
21131 you can print the reference card immediately with @file{refcard.ps}.
21133 The release also includes the source for the reference card. You
21134 can format it, using @TeX{}, by typing:
21140 The @value{GDBN} reference card is designed to print in @dfn{landscape}
21141 mode on US ``letter'' size paper;
21142 that is, on a sheet 11 inches wide by 8.5 inches
21143 high. You will need to specify this form of printing as an option to
21144 your @sc{dvi} output program.
21146 @cindex documentation
21148 All the documentation for @value{GDBN} comes as part of the machine-readable
21149 distribution. The documentation is written in Texinfo format, which is
21150 a documentation system that uses a single source file to produce both
21151 on-line information and a printed manual. You can use one of the Info
21152 formatting commands to create the on-line version of the documentation
21153 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
21155 @value{GDBN} includes an already formatted copy of the on-line Info
21156 version of this manual in the @file{gdb} subdirectory. The main Info
21157 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
21158 subordinate files matching @samp{gdb.info*} in the same directory. If
21159 necessary, you can print out these files, or read them with any editor;
21160 but they are easier to read using the @code{info} subsystem in @sc{gnu}
21161 Emacs or the standalone @code{info} program, available as part of the
21162 @sc{gnu} Texinfo distribution.
21164 If you want to format these Info files yourself, you need one of the
21165 Info formatting programs, such as @code{texinfo-format-buffer} or
21168 If you have @code{makeinfo} installed, and are in the top level
21169 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
21170 version @value{GDBVN}), you can make the Info file by typing:
21177 If you want to typeset and print copies of this manual, you need @TeX{},
21178 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
21179 Texinfo definitions file.
21181 @TeX{} is a typesetting program; it does not print files directly, but
21182 produces output files called @sc{dvi} files. To print a typeset
21183 document, you need a program to print @sc{dvi} files. If your system
21184 has @TeX{} installed, chances are it has such a program. The precise
21185 command to use depends on your system; @kbd{lpr -d} is common; another
21186 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
21187 require a file name without any extension or a @samp{.dvi} extension.
21189 @TeX{} also requires a macro definitions file called
21190 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
21191 written in Texinfo format. On its own, @TeX{} cannot either read or
21192 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
21193 and is located in the @file{gdb-@var{version-number}/texinfo}
21196 If you have @TeX{} and a @sc{dvi} printer program installed, you can
21197 typeset and print this manual. First switch to the the @file{gdb}
21198 subdirectory of the main source directory (for example, to
21199 @file{gdb-@value{GDBVN}/gdb}) and type:
21205 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
21207 @node Installing GDB
21208 @appendix Installing @value{GDBN}
21209 @cindex configuring @value{GDBN}
21210 @cindex installation
21211 @cindex configuring @value{GDBN}, and source tree subdirectories
21213 @value{GDBN} comes with a @code{configure} script that automates the process
21214 of preparing @value{GDBN} for installation; you can then use @code{make} to
21215 build the @code{gdb} program.
21217 @c irrelevant in info file; it's as current as the code it lives with.
21218 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
21219 look at the @file{README} file in the sources; we may have improved the
21220 installation procedures since publishing this manual.}
21223 The @value{GDBN} distribution includes all the source code you need for
21224 @value{GDBN} in a single directory, whose name is usually composed by
21225 appending the version number to @samp{gdb}.
21227 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
21228 @file{gdb-@value{GDBVN}} directory. That directory contains:
21231 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
21232 script for configuring @value{GDBN} and all its supporting libraries
21234 @item gdb-@value{GDBVN}/gdb
21235 the source specific to @value{GDBN} itself
21237 @item gdb-@value{GDBVN}/bfd
21238 source for the Binary File Descriptor library
21240 @item gdb-@value{GDBVN}/include
21241 @sc{gnu} include files
21243 @item gdb-@value{GDBVN}/libiberty
21244 source for the @samp{-liberty} free software library
21246 @item gdb-@value{GDBVN}/opcodes
21247 source for the library of opcode tables and disassemblers
21249 @item gdb-@value{GDBVN}/readline
21250 source for the @sc{gnu} command-line interface
21252 @item gdb-@value{GDBVN}/glob
21253 source for the @sc{gnu} filename pattern-matching subroutine
21255 @item gdb-@value{GDBVN}/mmalloc
21256 source for the @sc{gnu} memory-mapped malloc package
21259 The simplest way to configure and build @value{GDBN} is to run @code{configure}
21260 from the @file{gdb-@var{version-number}} source directory, which in
21261 this example is the @file{gdb-@value{GDBVN}} directory.
21263 First switch to the @file{gdb-@var{version-number}} source directory
21264 if you are not already in it; then run @code{configure}. Pass the
21265 identifier for the platform on which @value{GDBN} will run as an
21271 cd gdb-@value{GDBVN}
21272 ./configure @var{host}
21277 where @var{host} is an identifier such as @samp{sun4} or
21278 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
21279 (You can often leave off @var{host}; @code{configure} tries to guess the
21280 correct value by examining your system.)
21282 Running @samp{configure @var{host}} and then running @code{make} builds the
21283 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
21284 libraries, then @code{gdb} itself. The configured source files, and the
21285 binaries, are left in the corresponding source directories.
21288 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
21289 system does not recognize this automatically when you run a different
21290 shell, you may need to run @code{sh} on it explicitly:
21293 sh configure @var{host}
21296 If you run @code{configure} from a directory that contains source
21297 directories for multiple libraries or programs, such as the
21298 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
21299 creates configuration files for every directory level underneath (unless
21300 you tell it not to, with the @samp{--norecursion} option).
21302 You should run the @code{configure} script from the top directory in the
21303 source tree, the @file{gdb-@var{version-number}} directory. If you run
21304 @code{configure} from one of the subdirectories, you will configure only
21305 that subdirectory. That is usually not what you want. In particular,
21306 if you run the first @code{configure} from the @file{gdb} subdirectory
21307 of the @file{gdb-@var{version-number}} directory, you will omit the
21308 configuration of @file{bfd}, @file{readline}, and other sibling
21309 directories of the @file{gdb} subdirectory. This leads to build errors
21310 about missing include files such as @file{bfd/bfd.h}.
21312 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
21313 However, you should make sure that the shell on your path (named by
21314 the @samp{SHELL} environment variable) is publicly readable. Remember
21315 that @value{GDBN} uses the shell to start your program---some systems refuse to
21316 let @value{GDBN} debug child processes whose programs are not readable.
21319 * Separate Objdir:: Compiling @value{GDBN} in another directory
21320 * Config Names:: Specifying names for hosts and targets
21321 * Configure Options:: Summary of options for configure
21324 @node Separate Objdir
21325 @section Compiling @value{GDBN} in another directory
21327 If you want to run @value{GDBN} versions for several host or target machines,
21328 you need a different @code{gdb} compiled for each combination of
21329 host and target. @code{configure} is designed to make this easy by
21330 allowing you to generate each configuration in a separate subdirectory,
21331 rather than in the source directory. If your @code{make} program
21332 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
21333 @code{make} in each of these directories builds the @code{gdb}
21334 program specified there.
21336 To build @code{gdb} in a separate directory, run @code{configure}
21337 with the @samp{--srcdir} option to specify where to find the source.
21338 (You also need to specify a path to find @code{configure}
21339 itself from your working directory. If the path to @code{configure}
21340 would be the same as the argument to @samp{--srcdir}, you can leave out
21341 the @samp{--srcdir} option; it is assumed.)
21343 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
21344 separate directory for a Sun 4 like this:
21348 cd gdb-@value{GDBVN}
21351 ../gdb-@value{GDBVN}/configure sun4
21356 When @code{configure} builds a configuration using a remote source
21357 directory, it creates a tree for the binaries with the same structure
21358 (and using the same names) as the tree under the source directory. In
21359 the example, you'd find the Sun 4 library @file{libiberty.a} in the
21360 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
21361 @file{gdb-sun4/gdb}.
21363 Make sure that your path to the @file{configure} script has just one
21364 instance of @file{gdb} in it. If your path to @file{configure} looks
21365 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
21366 one subdirectory of @value{GDBN}, not the whole package. This leads to
21367 build errors about missing include files such as @file{bfd/bfd.h}.
21369 One popular reason to build several @value{GDBN} configurations in separate
21370 directories is to configure @value{GDBN} for cross-compiling (where
21371 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
21372 programs that run on another machine---the @dfn{target}).
21373 You specify a cross-debugging target by
21374 giving the @samp{--target=@var{target}} option to @code{configure}.
21376 When you run @code{make} to build a program or library, you must run
21377 it in a configured directory---whatever directory you were in when you
21378 called @code{configure} (or one of its subdirectories).
21380 The @code{Makefile} that @code{configure} generates in each source
21381 directory also runs recursively. If you type @code{make} in a source
21382 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
21383 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
21384 will build all the required libraries, and then build GDB.
21386 When you have multiple hosts or targets configured in separate
21387 directories, you can run @code{make} on them in parallel (for example,
21388 if they are NFS-mounted on each of the hosts); they will not interfere
21392 @section Specifying names for hosts and targets
21394 The specifications used for hosts and targets in the @code{configure}
21395 script are based on a three-part naming scheme, but some short predefined
21396 aliases are also supported. The full naming scheme encodes three pieces
21397 of information in the following pattern:
21400 @var{architecture}-@var{vendor}-@var{os}
21403 For example, you can use the alias @code{sun4} as a @var{host} argument,
21404 or as the value for @var{target} in a @code{--target=@var{target}}
21405 option. The equivalent full name is @samp{sparc-sun-sunos4}.
21407 The @code{configure} script accompanying @value{GDBN} does not provide
21408 any query facility to list all supported host and target names or
21409 aliases. @code{configure} calls the Bourne shell script
21410 @code{config.sub} to map abbreviations to full names; you can read the
21411 script, if you wish, or you can use it to test your guesses on
21412 abbreviations---for example:
21415 % sh config.sub i386-linux
21417 % sh config.sub alpha-linux
21418 alpha-unknown-linux-gnu
21419 % sh config.sub hp9k700
21421 % sh config.sub sun4
21422 sparc-sun-sunos4.1.1
21423 % sh config.sub sun3
21424 m68k-sun-sunos4.1.1
21425 % sh config.sub i986v
21426 Invalid configuration `i986v': machine `i986v' not recognized
21430 @code{config.sub} is also distributed in the @value{GDBN} source
21431 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
21433 @node Configure Options
21434 @section @code{configure} options
21436 Here is a summary of the @code{configure} options and arguments that
21437 are most often useful for building @value{GDBN}. @code{configure} also has
21438 several other options not listed here. @inforef{What Configure
21439 Does,,configure.info}, for a full explanation of @code{configure}.
21442 configure @r{[}--help@r{]}
21443 @r{[}--prefix=@var{dir}@r{]}
21444 @r{[}--exec-prefix=@var{dir}@r{]}
21445 @r{[}--srcdir=@var{dirname}@r{]}
21446 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
21447 @r{[}--target=@var{target}@r{]}
21452 You may introduce options with a single @samp{-} rather than
21453 @samp{--} if you prefer; but you may abbreviate option names if you use
21458 Display a quick summary of how to invoke @code{configure}.
21460 @item --prefix=@var{dir}
21461 Configure the source to install programs and files under directory
21464 @item --exec-prefix=@var{dir}
21465 Configure the source to install programs under directory
21468 @c avoid splitting the warning from the explanation:
21470 @item --srcdir=@var{dirname}
21471 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
21472 @code{make} that implements the @code{VPATH} feature.}@*
21473 Use this option to make configurations in directories separate from the
21474 @value{GDBN} source directories. Among other things, you can use this to
21475 build (or maintain) several configurations simultaneously, in separate
21476 directories. @code{configure} writes configuration specific files in
21477 the current directory, but arranges for them to use the source in the
21478 directory @var{dirname}. @code{configure} creates directories under
21479 the working directory in parallel to the source directories below
21482 @item --norecursion
21483 Configure only the directory level where @code{configure} is executed; do not
21484 propagate configuration to subdirectories.
21486 @item --target=@var{target}
21487 Configure @value{GDBN} for cross-debugging programs running on the specified
21488 @var{target}. Without this option, @value{GDBN} is configured to debug
21489 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
21491 There is no convenient way to generate a list of all available targets.
21493 @item @var{host} @dots{}
21494 Configure @value{GDBN} to run on the specified @var{host}.
21496 There is no convenient way to generate a list of all available hosts.
21499 There are many other options available as well, but they are generally
21500 needed for special purposes only.
21502 @node Maintenance Commands
21503 @appendix Maintenance Commands
21504 @cindex maintenance commands
21505 @cindex internal commands
21507 In addition to commands intended for @value{GDBN} users, @value{GDBN}
21508 includes a number of commands intended for @value{GDBN} developers,
21509 that are not documented elsewhere in this manual. These commands are
21510 provided here for reference. (For commands that turn on debugging
21511 messages, see @ref{Debugging Output}.)
21514 @kindex maint agent
21515 @item maint agent @var{expression}
21516 Translate the given @var{expression} into remote agent bytecodes.
21517 This command is useful for debugging the Agent Expression mechanism
21518 (@pxref{Agent Expressions}).
21520 @kindex maint info breakpoints
21521 @item @anchor{maint info breakpoints}maint info breakpoints
21522 Using the same format as @samp{info breakpoints}, display both the
21523 breakpoints you've set explicitly, and those @value{GDBN} is using for
21524 internal purposes. Internal breakpoints are shown with negative
21525 breakpoint numbers. The type column identifies what kind of breakpoint
21530 Normal, explicitly set breakpoint.
21533 Normal, explicitly set watchpoint.
21536 Internal breakpoint, used to handle correctly stepping through
21537 @code{longjmp} calls.
21539 @item longjmp resume
21540 Internal breakpoint at the target of a @code{longjmp}.
21543 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
21546 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
21549 Shared library events.
21553 @kindex maint check-symtabs
21554 @item maint check-symtabs
21555 Check the consistency of psymtabs and symtabs.
21557 @kindex maint cplus first_component
21558 @item maint cplus first_component @var{name}
21559 Print the first C@t{++} class/namespace component of @var{name}.
21561 @kindex maint cplus namespace
21562 @item maint cplus namespace
21563 Print the list of possible C@t{++} namespaces.
21565 @kindex maint demangle
21566 @item maint demangle @var{name}
21567 Demangle a C@t{++} or Objective-C manled @var{name}.
21569 @kindex maint deprecate
21570 @kindex maint undeprecate
21571 @cindex deprecated commands
21572 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
21573 @itemx maint undeprecate @var{command}
21574 Deprecate or undeprecate the named @var{command}. Deprecated commands
21575 cause @value{GDBN} to issue a warning when you use them. The optional
21576 argument @var{replacement} says which newer command should be used in
21577 favor of the deprecated one; if it is given, @value{GDBN} will mention
21578 the replacement as part of the warning.
21580 @kindex maint dump-me
21581 @item maint dump-me
21582 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
21583 Cause a fatal signal in the debugger and force it to dump its core.
21584 This is supported only on systems which support aborting a program
21585 with the @code{SIGQUIT} signal.
21587 @kindex maint internal-error
21588 @kindex maint internal-warning
21589 @item maint internal-error @r{[}@var{message-text}@r{]}
21590 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
21591 Cause @value{GDBN} to call the internal function @code{internal_error}
21592 or @code{internal_warning} and hence behave as though an internal error
21593 or internal warning has been detected. In addition to reporting the
21594 internal problem, these functions give the user the opportunity to
21595 either quit @value{GDBN} or create a core file of the current
21596 @value{GDBN} session.
21598 These commands take an optional parameter @var{message-text} that is
21599 used as the text of the error or warning message.
21601 Here's an example of using @code{indernal-error}:
21604 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
21605 @dots{}/maint.c:121: internal-error: testing, 1, 2
21606 A problem internal to GDB has been detected. Further
21607 debugging may prove unreliable.
21608 Quit this debugging session? (y or n) @kbd{n}
21609 Create a core file? (y or n) @kbd{n}
21613 @kindex maint packet
21614 @item maint packet @var{text}
21615 If @value{GDBN} is talking to an inferior via the serial protocol,
21616 then this command sends the string @var{text} to the inferior, and
21617 displays the response packet. @value{GDBN} supplies the initial
21618 @samp{$} character, the terminating @samp{#} character, and the
21621 @kindex maint print architecture
21622 @item maint print architecture @r{[}@var{file}@r{]}
21623 Print the entire architecture configuration. The optional argument
21624 @var{file} names the file where the output goes.
21626 @kindex maint print dummy-frames
21627 @item maint print dummy-frames
21628 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
21631 (@value{GDBP}) @kbd{b add}
21633 (@value{GDBP}) @kbd{print add(2,3)}
21634 Breakpoint 2, add (a=2, b=3) at @dots{}
21636 The program being debugged stopped while in a function called from GDB.
21638 (@value{GDBP}) @kbd{maint print dummy-frames}
21639 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
21640 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
21641 call_lo=0x01014000 call_hi=0x01014001
21645 Takes an optional file parameter.
21647 @kindex maint print registers
21648 @kindex maint print raw-registers
21649 @kindex maint print cooked-registers
21650 @kindex maint print register-groups
21651 @item maint print registers @r{[}@var{file}@r{]}
21652 @itemx maint print raw-registers @r{[}@var{file}@r{]}
21653 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
21654 @itemx maint print register-groups @r{[}@var{file}@r{]}
21655 Print @value{GDBN}'s internal register data structures.
21657 The command @code{maint print raw-registers} includes the contents of
21658 the raw register cache; the command @code{maint print cooked-registers}
21659 includes the (cooked) value of all registers; and the command
21660 @code{maint print register-groups} includes the groups that each
21661 register is a member of. @xref{Registers,, Registers, gdbint,
21662 @value{GDBN} Internals}.
21664 These commands take an optional parameter, a file name to which to
21665 write the information.
21667 @kindex maint print reggroups
21668 @item maint print reggroups @r{[}@var{file}@r{]}
21669 Print @value{GDBN}'s internal register group data structures. The
21670 optional argument @var{file} tells to what file to write the
21673 The register groups info looks like this:
21676 (@value{GDBP}) @kbd{maint print reggroups}
21689 This command forces @value{GDBN} to flush its internal register cache.
21691 @kindex maint print objfiles
21692 @cindex info for known object files
21693 @item maint print objfiles
21694 Print a dump of all known object files. For each object file, this
21695 command prints its name, address in memory, and all of its psymtabs
21698 @kindex maint print statistics
21699 @cindex bcache statistics
21700 @item maint print statistics
21701 This command prints, for each object file in the program, various data
21702 about that object file followed by the byte cache (@dfn{bcache})
21703 statistics for the object file. The objfile data includes the number
21704 of minimal, partical, full, and stabs symbols, the number of types
21705 defined by the objfile, the number of as yet unexpanded psym tables,
21706 the number of line tables and string tables, and the amount of memory
21707 used by the various tables. The bcache statistics include the counts,
21708 sizes, and counts of duplicates of all and unique objects, max,
21709 average, and median entry size, total memory used and its overhead and
21710 savings, and various measures of the hash table size and chain
21713 @kindex maint print type
21714 @cindex type chain of a data type
21715 @item maint print type @var{expr}
21716 Print the type chain for a type specified by @var{expr}. The argument
21717 can be either a type name or a symbol. If it is a symbol, the type of
21718 that symbol is described. The type chain produced by this command is
21719 a recursive definition of the data type as stored in @value{GDBN}'s
21720 data structures, including its flags and contained types.
21722 @kindex maint set dwarf2 max-cache-age
21723 @kindex maint show dwarf2 max-cache-age
21724 @item maint set dwarf2 max-cache-age
21725 @itemx maint show dwarf2 max-cache-age
21726 Control the DWARF 2 compilation unit cache.
21728 @cindex DWARF 2 compilation units cache
21729 In object files with inter-compilation-unit references, such as those
21730 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
21731 reader needs to frequently refer to previously read compilation units.
21732 This setting controls how long a compilation unit will remain in the
21733 cache if it is not referenced. A higher limit means that cached
21734 compilation units will be stored in memory longer, and more total
21735 memory will be used. Setting it to zero disables caching, which will
21736 slow down @value{GDBN} startup, but reduce memory consumption.
21738 @kindex maint set profile
21739 @kindex maint show profile
21740 @cindex profiling GDB
21741 @item maint set profile
21742 @itemx maint show profile
21743 Control profiling of @value{GDBN}.
21745 Profiling will be disabled until you use the @samp{maint set profile}
21746 command to enable it. When you enable profiling, the system will begin
21747 collecting timing and execution count data; when you disable profiling or
21748 exit @value{GDBN}, the results will be written to a log file. Remember that
21749 if you use profiling, @value{GDBN} will overwrite the profiling log file
21750 (often called @file{gmon.out}). If you have a record of important profiling
21751 data in a @file{gmon.out} file, be sure to move it to a safe location.
21753 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
21754 compiled with the @samp{-pg} compiler option.
21756 @kindex maint show-debug-regs
21757 @cindex x86 hardware debug registers
21758 @item maint show-debug-regs
21759 Control whether to show variables that mirror the x86 hardware debug
21760 registers. Use @code{ON} to enable, @code{OFF} to disable. If
21761 enabled, the debug registers values are shown when GDB inserts or
21762 removes a hardware breakpoint or watchpoint, and when the inferior
21763 triggers a hardware-assisted breakpoint or watchpoint.
21765 @kindex maint space
21766 @cindex memory used by commands
21768 Control whether to display memory usage for each command. If set to a
21769 nonzero value, @value{GDBN} will display how much memory each command
21770 took, following the command's own output. This can also be requested
21771 by invoking @value{GDBN} with the @option{--statistics} command-line
21772 switch (@pxref{Mode Options}).
21775 @cindex time of command execution
21777 Control whether to display the execution time for each command. If
21778 set to a nonzero value, @value{GDBN} will display how much time it
21779 took to execute each command, following the command's own output.
21780 This can also be requested by invoking @value{GDBN} with the
21781 @option{--statistics} command-line switch (@pxref{Mode Options}).
21783 @kindex maint translate-address
21784 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
21785 Find the symbol stored at the location specified by the address
21786 @var{addr} and an optional section name @var{section}. If found,
21787 @value{GDBN} prints the name of the closest symbol and an offset from
21788 the symbol's location to the specified address. This is similar to
21789 the @code{info address} command (@pxref{Symbols}), except that this
21790 command also allows to find symbols in other sections.
21794 The following command is useful for non-interactive invocations of
21795 @value{GDBN}, such as in the test suite.
21798 @item set watchdog @var{nsec}
21799 @kindex set watchdog
21800 @cindex watchdog timer
21801 @cindex timeout for commands
21802 Set the maximum number of seconds @value{GDBN} will wait for the
21803 target operation to finish. If this time expires, @value{GDBN}
21804 reports and error and the command is aborted.
21806 @item show watchdog
21807 Show the current setting of the target wait timeout.
21810 @node Remote Protocol
21811 @appendix @value{GDBN} Remote Serial Protocol
21816 * Stop Reply Packets::
21817 * General Query Packets::
21818 * Register Packet Format::
21820 * File-I/O remote protocol extension::
21826 There may be occasions when you need to know something about the
21827 protocol---for example, if there is only one serial port to your target
21828 machine, you might want your program to do something special if it
21829 recognizes a packet meant for @value{GDBN}.
21831 In the examples below, @samp{->} and @samp{<-} are used to indicate
21832 transmitted and received data respectfully.
21834 @cindex protocol, @value{GDBN} remote serial
21835 @cindex serial protocol, @value{GDBN} remote
21836 @cindex remote serial protocol
21837 All @value{GDBN} commands and responses (other than acknowledgments) are
21838 sent as a @var{packet}. A @var{packet} is introduced with the character
21839 @samp{$}, the actual @var{packet-data}, and the terminating character
21840 @samp{#} followed by a two-digit @var{checksum}:
21843 @code{$}@var{packet-data}@code{#}@var{checksum}
21847 @cindex checksum, for @value{GDBN} remote
21849 The two-digit @var{checksum} is computed as the modulo 256 sum of all
21850 characters between the leading @samp{$} and the trailing @samp{#} (an
21851 eight bit unsigned checksum).
21853 Implementors should note that prior to @value{GDBN} 5.0 the protocol
21854 specification also included an optional two-digit @var{sequence-id}:
21857 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
21860 @cindex sequence-id, for @value{GDBN} remote
21862 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
21863 has never output @var{sequence-id}s. Stubs that handle packets added
21864 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
21866 @cindex acknowledgment, for @value{GDBN} remote
21867 When either the host or the target machine receives a packet, the first
21868 response expected is an acknowledgment: either @samp{+} (to indicate
21869 the package was received correctly) or @samp{-} (to request
21873 -> @code{$}@var{packet-data}@code{#}@var{checksum}
21878 The host (@value{GDBN}) sends @var{command}s, and the target (the
21879 debugging stub incorporated in your program) sends a @var{response}. In
21880 the case of step and continue @var{command}s, the response is only sent
21881 when the operation has completed (the target has again stopped).
21883 @var{packet-data} consists of a sequence of characters with the
21884 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
21887 Fields within the packet should be separated using @samp{,} @samp{;} or
21888 @cindex remote protocol, field separator
21889 @samp{:}. Except where otherwise noted all numbers are represented in
21890 @sc{hex} with leading zeros suppressed.
21892 Implementors should note that prior to @value{GDBN} 5.0, the character
21893 @samp{:} could not appear as the third character in a packet (as it
21894 would potentially conflict with the @var{sequence-id}).
21896 Response @var{data} can be run-length encoded to save space. A @samp{*}
21897 means that the next character is an @sc{ascii} encoding giving a repeat count
21898 which stands for that many repetitions of the character preceding the
21899 @samp{*}. The encoding is @code{n+29}, yielding a printable character
21900 where @code{n >=3} (which is where rle starts to win). The printable
21901 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
21902 value greater than 126 should not be used.
21909 means the same as "0000".
21911 The error response returned for some packets includes a two character
21912 error number. That number is not well defined.
21914 For any @var{command} not supported by the stub, an empty response
21915 (@samp{$#00}) should be returned. That way it is possible to extend the
21916 protocol. A newer @value{GDBN} can tell if a packet is supported based
21919 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
21920 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
21926 The following table provides a complete list of all currently defined
21927 @var{command}s and their corresponding response @var{data}.
21928 @xref{File-I/O remote protocol extension}, for details about the File
21929 I/O extension of the remote protocol.
21933 @item @code{!} --- extended mode
21934 @cindex @code{!} packet
21936 Enable extended mode. In extended mode, the remote server is made
21937 persistent. The @samp{R} packet is used to restart the program being
21943 The remote target both supports and has enabled extended mode.
21946 @item @code{?} --- last signal
21947 @cindex @code{?} packet
21949 Indicate the reason the target halted. The reply is the same as for
21953 @xref{Stop Reply Packets}, for the reply specifications.
21955 @item @code{a} --- reserved
21957 Reserved for future use.
21959 @item @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,@dots{}} --- set program arguments @strong{(reserved)}
21960 @cindex @code{A} packet
21962 Initialized @samp{argv[]} array passed into program. @var{arglen}
21963 specifies the number of bytes in the hex encoded byte stream @var{arg}.
21964 See @code{gdbserver} for more details.
21972 @item @code{b}@var{baud} --- set baud @strong{(deprecated)}
21973 @cindex @code{b} packet
21975 Change the serial line speed to @var{baud}.
21977 JTC: @emph{When does the transport layer state change? When it's
21978 received, or after the ACK is transmitted. In either case, there are
21979 problems if the command or the acknowledgment packet is dropped.}
21981 Stan: @emph{If people really wanted to add something like this, and get
21982 it working for the first time, they ought to modify ser-unix.c to send
21983 some kind of out-of-band message to a specially-setup stub and have the
21984 switch happen "in between" packets, so that from remote protocol's point
21985 of view, nothing actually happened.}
21987 @item @code{B}@var{addr},@var{mode} --- set breakpoint @strong{(deprecated)}
21988 @cindex @code{B} packet
21990 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
21991 breakpoint at @var{addr}.
21993 This packet has been replaced by the @samp{Z} and @samp{z} packets
21994 (@pxref{insert breakpoint or watchpoint packet}).
21996 @item @code{c}@var{addr} --- continue
21997 @cindex @code{c} packet
21999 @var{addr} is address to resume. If @var{addr} is omitted, resume at
22003 @xref{Stop Reply Packets}, for the reply specifications.
22005 @item @code{C}@var{sig}@code{;}@var{addr} --- continue with signal
22006 @cindex @code{C} packet
22008 Continue with signal @var{sig} (hex signal number). If
22009 @code{;}@var{addr} is omitted, resume at same address.
22012 @xref{Stop Reply Packets}, for the reply specifications.
22014 @item @code{d} --- toggle debug @strong{(deprecated)}
22015 @cindex @code{d} packet
22019 @item @code{D} --- detach
22020 @cindex @code{D} packet
22022 Detach @value{GDBN} from the remote system. Sent to the remote target
22023 before @value{GDBN} disconnects via the @code{detach} command.
22027 @item @emph{no response}
22028 @value{GDBN} does not check for any response after sending this packet.
22031 @item @code{e} --- reserved
22033 Reserved for future use.
22035 @item @code{E} --- reserved
22037 Reserved for future use.
22039 @item @code{f} --- reserved
22041 Reserved for future use.
22043 @item @code{F}@var{RC}@code{,}@var{EE}@code{,}@var{CF}@code{;}@var{XX} --- Reply to target's F packet.
22044 @cindex @code{F} packet
22046 This packet is send by @value{GDBN} as reply to a @code{F} request packet
22047 sent by the target. This is part of the File-I/O protocol extension.
22048 @xref{File-I/O remote protocol extension}, for the specification.
22050 @item @code{g} --- read registers
22051 @anchor{read registers packet}
22052 @cindex @code{g} packet
22054 Read general registers.
22058 @item @var{XX@dots{}}
22059 Each byte of register data is described by two hex digits. The bytes
22060 with the register are transmitted in target byte order. The size of
22061 each register and their position within the @samp{g} @var{packet} are
22062 determined by the @value{GDBN} internal macros
22063 @var{DEPRECATED_REGISTER_RAW_SIZE} and @var{REGISTER_NAME} macros. The
22064 specification of several standard @code{g} packets is specified below.
22069 @item @code{G}@var{XX@dots{}} --- write regs
22070 @cindex @code{G} packet
22072 @xref{read registers packet}, for a description of the @var{XX@dots{}}
22083 @item @code{h} --- reserved
22085 Reserved for future use.
22087 @item @code{H}@var{c}@var{t@dots{}} --- set thread
22088 @cindex @code{H} packet
22090 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
22091 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
22092 should be @samp{c} for step and continue operations, @samp{g} for other
22093 operations. The thread designator @var{t@dots{}} may be -1, meaning all
22094 the threads, a thread number, or zero which means pick any thread.
22105 @c 'H': How restrictive (or permissive) is the thread model. If a
22106 @c thread is selected and stopped, are other threads allowed
22107 @c to continue to execute? As I mentioned above, I think the
22108 @c semantics of each command when a thread is selected must be
22109 @c described. For example:
22111 @c 'g': If the stub supports threads and a specific thread is
22112 @c selected, returns the register block from that thread;
22113 @c otherwise returns current registers.
22115 @c 'G' If the stub supports threads and a specific thread is
22116 @c selected, sets the registers of the register block of
22117 @c that thread; otherwise sets current registers.
22119 @item @code{i}@var{addr}@code{,}@var{nnn} --- cycle step @strong{(draft)}
22120 @anchor{cycle step packet}
22121 @cindex @code{i} packet
22123 Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
22124 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
22125 step starting at that address.
22127 @item @code{I} --- signal then cycle step @strong{(reserved)}
22128 @cindex @code{I} packet
22130 @xref{step with signal packet}. @xref{cycle step packet}.
22132 @item @code{j} --- reserved
22134 Reserved for future use.
22136 @item @code{J} --- reserved
22138 Reserved for future use.
22140 @item @code{k} --- kill request
22141 @cindex @code{k} packet
22143 FIXME: @emph{There is no description of how to operate when a specific
22144 thread context has been selected (i.e.@: does 'k' kill only that
22147 @item @code{K} --- reserved
22149 Reserved for future use.
22151 @item @code{l} --- reserved
22153 Reserved for future use.
22155 @item @code{L} --- reserved
22157 Reserved for future use.
22159 @item @code{m}@var{addr}@code{,}@var{length} --- read memory
22160 @cindex @code{m} packet
22162 Read @var{length} bytes of memory starting at address @var{addr}.
22163 Neither @value{GDBN} nor the stub assume that sized memory transfers are
22164 assumed using word aligned accesses. FIXME: @emph{A word aligned memory
22165 transfer mechanism is needed.}
22169 @item @var{XX@dots{}}
22170 @var{XX@dots{}} is mem contents. Can be fewer bytes than requested if able
22171 to read only part of the data. Neither @value{GDBN} nor the stub assume
22172 that sized memory transfers are assumed using word aligned
22173 accesses. FIXME: @emph{A word aligned memory transfer mechanism is
22179 @item @code{M}@var{addr},@var{length}@code{:}@var{XX@dots{}} --- write mem
22180 @cindex @code{M} packet
22182 Write @var{length} bytes of memory starting at address @var{addr}.
22183 @var{XX@dots{}} is the data.
22190 for an error (this includes the case where only part of the data was
22194 @item @code{n} --- reserved
22196 Reserved for future use.
22198 @item @code{N} --- reserved
22200 Reserved for future use.
22202 @item @code{o} --- reserved
22204 Reserved for future use.
22206 @item @code{O} --- reserved
22208 @item @code{p}@var{hex number of register} --- read register packet
22209 @cindex @code{p} packet
22211 @xref{read registers packet}, for a description of how the returned
22212 register value is encoded.
22216 @item @var{XX@dots{}}
22217 the register's value
22221 Indicating an unrecognized @var{query}.
22224 @item @code{P}@var{n@dots{}}@code{=}@var{r@dots{}} --- write register
22225 @anchor{write register packet}
22226 @cindex @code{P} packet
22228 Write register @var{n@dots{}} with value @var{r@dots{}}, which contains two hex
22229 digits for each byte in the register (target byte order).
22239 @item @code{q}@var{query} --- general query
22240 @anchor{general query packet}
22241 @cindex @code{q} packet
22243 Request info about @var{query}. In general @value{GDBN} queries have a
22244 leading upper case letter. Custom vendor queries should use a company
22245 prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may optionally
22246 be followed by a @samp{,} or @samp{;} separated list. Stubs must ensure
22247 that they match the full @var{query} name.
22251 @item @var{XX@dots{}}
22252 Hex encoded data from query. The reply can not be empty.
22256 Indicating an unrecognized @var{query}.
22259 @item @code{Q}@var{var}@code{=}@var{val} --- general set
22260 @cindex @code{Q} packet
22262 Set value of @var{var} to @var{val}.
22264 @xref{general query packet}, for a discussion of naming conventions.
22266 @item @code{r} --- reset @strong{(deprecated)}
22267 @cindex @code{r} packet
22269 Reset the entire system.
22271 @item @code{R}@var{XX} --- remote restart
22272 @cindex @code{R} packet
22274 Restart the program being debugged. @var{XX}, while needed, is ignored.
22275 This packet is only available in extended mode.
22279 @item @emph{no reply}
22280 The @samp{R} packet has no reply.
22283 @item @code{s}@var{addr} --- step
22284 @cindex @code{s} packet
22286 @var{addr} is address to resume. If @var{addr} is omitted, resume at
22290 @xref{Stop Reply Packets}, for the reply specifications.
22292 @item @code{S}@var{sig}@code{;}@var{addr} --- step with signal
22293 @anchor{step with signal packet}
22294 @cindex @code{S} packet
22296 Like @samp{C} but step not continue.
22299 @xref{Stop Reply Packets}, for the reply specifications.
22301 @item @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} --- search
22302 @cindex @code{t} packet
22304 Search backwards starting at address @var{addr} for a match with pattern
22305 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
22306 @var{addr} must be at least 3 digits.
22308 @item @code{T}@var{XX} --- thread alive
22309 @cindex @code{T} packet
22311 Find out if the thread XX is alive.
22316 thread is still alive
22321 @item @code{u} --- reserved
22323 Reserved for future use.
22325 @item @code{U} --- reserved
22327 Reserved for future use.
22329 @item @code{v} --- verbose packet prefix
22331 Packets starting with @code{v} are identified by a multi-letter name,
22332 up to the first @code{;} or @code{?} (or the end of the packet).
22334 @item @code{vCont}[;@var{action}[@code{:}@var{tid}]]... --- extended resume
22335 @cindex @code{vCont} packet
22337 Resume the inferior. Different actions may be specified for each thread.
22338 If an action is specified with no @var{tid}, then it is applied to any
22339 threads that don't have a specific action specified; if no default action is
22340 specified then other threads should remain stopped. Specifying multiple
22341 default actions is an error; specifying no actions is also an error.
22342 Thread IDs are specified in hexadecimal. Currently supported actions are:
22348 Continue with signal @var{sig}. @var{sig} should be two hex digits.
22352 Step with signal @var{sig}. @var{sig} should be two hex digits.
22355 The optional @var{addr} argument normally associated with these packets is
22356 not supported in @code{vCont}.
22359 @xref{Stop Reply Packets}, for the reply specifications.
22361 @item @code{vCont?} --- extended resume query
22362 @cindex @code{vCont?} packet
22364 Query support for the @code{vCont} packet.
22368 @item @code{vCont}[;@var{action}]...
22369 The @code{vCont} packet is supported. Each @var{action} is a supported
22370 command in the @code{vCont} packet.
22372 The @code{vCont} packet is not supported.
22375 @item @code{V} --- reserved
22377 Reserved for future use.
22379 @item @code{w} --- reserved
22381 Reserved for future use.
22383 @item @code{W} --- reserved
22385 Reserved for future use.
22387 @item @code{x} --- reserved
22389 Reserved for future use.
22391 @item @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX@dots{}} --- write mem (binary)
22392 @cindex @code{X} packet
22394 @var{addr} is address, @var{length} is number of bytes, @var{XX@dots{}}
22395 is binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
22396 escaped using @code{0x7d}, and then XORed with @code{0x20}.
22397 For example, @code{0x7d} would be transmitted as @code{0x7d 0x5d}.
22407 @item @code{y} --- reserved
22409 Reserved for future use.
22411 @item @code{Y} reserved
22413 Reserved for future use.
22415 @item @code{z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- remove breakpoint or watchpoint @strong{(draft)}
22416 @itemx @code{Z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- insert breakpoint or watchpoint @strong{(draft)}
22417 @anchor{insert breakpoint or watchpoint packet}
22418 @cindex @code{z} packet
22419 @cindex @code{Z} packets
22421 Insert (@code{Z}) or remove (@code{z}) a @var{type} breakpoint or
22422 watchpoint starting at address @var{address} and covering the next
22423 @var{length} bytes.
22425 Each breakpoint and watchpoint packet @var{type} is documented
22428 @emph{Implementation notes: A remote target shall return an empty string
22429 for an unrecognized breakpoint or watchpoint packet @var{type}. A
22430 remote target shall support either both or neither of a given
22431 @code{Z}@var{type}@dots{} and @code{z}@var{type}@dots{} packet pair. To
22432 avoid potential problems with duplicate packets, the operations should
22433 be implemented in an idempotent way.}
22435 @item @code{z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- remove memory breakpoint @strong{(draft)}
22436 @item @code{Z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- insert memory breakpoint @strong{(draft)}
22437 @cindex @code{z0} packet
22438 @cindex @code{Z0} packet
22440 Insert (@code{Z0}) or remove (@code{z0}) a memory breakpoint at address
22441 @code{addr} of size @code{length}.
22443 A memory breakpoint is implemented by replacing the instruction at
22444 @var{addr} with a software breakpoint or trap instruction. The
22445 @code{length} is used by targets that indicates the size of the
22446 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
22447 @sc{mips} can insert either a 2 or 4 byte breakpoint).
22449 @emph{Implementation note: It is possible for a target to copy or move
22450 code that contains memory breakpoints (e.g., when implementing
22451 overlays). The behavior of this packet, in the presence of such a
22452 target, is not defined.}
22464 @item @code{z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- remove hardware breakpoint @strong{(draft)}
22465 @item @code{Z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- insert hardware breakpoint @strong{(draft)}
22466 @cindex @code{z1} packet
22467 @cindex @code{Z1} packet
22469 Insert (@code{Z1}) or remove (@code{z1}) a hardware breakpoint at
22470 address @code{addr} of size @code{length}.
22472 A hardware breakpoint is implemented using a mechanism that is not
22473 dependant on being able to modify the target's memory.
22475 @emph{Implementation note: A hardware breakpoint is not affected by code
22488 @item @code{z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- remove write watchpoint @strong{(draft)}
22489 @item @code{Z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- insert write watchpoint @strong{(draft)}
22490 @cindex @code{z2} packet
22491 @cindex @code{Z2} packet
22493 Insert (@code{Z2}) or remove (@code{z2}) a write watchpoint.
22505 @item @code{z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- remove read watchpoint @strong{(draft)}
22506 @item @code{Z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- insert read watchpoint @strong{(draft)}
22507 @cindex @code{z3} packet
22508 @cindex @code{Z3} packet
22510 Insert (@code{Z3}) or remove (@code{z3}) a read watchpoint.
22522 @item @code{z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- remove access watchpoint @strong{(draft)}
22523 @item @code{Z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- insert access watchpoint @strong{(draft)}
22524 @cindex @code{z4} packet
22525 @cindex @code{Z4} packet
22527 Insert (@code{Z4}) or remove (@code{z4}) an access watchpoint.
22541 @node Stop Reply Packets
22542 @section Stop Reply Packets
22543 @cindex stop reply packets
22545 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
22546 receive any of the below as a reply. In the case of the @samp{C},
22547 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
22548 when the target halts. In the below the exact meaning of @samp{signal
22549 number} is poorly defined. In general one of the UNIX signal numbering
22550 conventions is used.
22555 @var{AA} is the signal number
22557 @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
22558 @cindex @code{T} packet reply
22560 @var{AA} = two hex digit signal number; @var{n...} = register number
22561 (hex), @var{r...} = target byte ordered register contents, size defined
22562 by @code{DEPRECATED_REGISTER_RAW_SIZE}; @var{n...} = @samp{thread},
22563 @var{r...} = thread process ID, this is a hex integer; @var{n...} =
22564 (@samp{watch} | @samp{rwatch} | @samp{awatch}, @var{r...} = data
22565 address, this is a hex integer; @var{n...} = other string not starting
22566 with valid hex digit. @value{GDBN} should ignore this @var{n...},
22567 @var{r...} pair and go on to the next. This way we can extend the
22572 The process exited, and @var{AA} is the exit status. This is only
22573 applicable to certain targets.
22577 The process terminated with signal @var{AA}.
22579 @item O@var{XX@dots{}}
22581 @var{XX@dots{}} is hex encoding of @sc{ascii} data. This can happen at
22582 any time while the program is running and the debugger should continue
22583 to wait for @samp{W}, @samp{T}, etc.
22585 @item F@var{call-id}@code{,}@var{parameter@dots{}}
22587 @var{call-id} is the identifier which says which host system call should
22588 be called. This is just the name of the function. Translation into the
22589 correct system call is only applicable as it's defined in @value{GDBN}.
22590 @xref{File-I/O remote protocol extension}, for a list of implemented
22593 @var{parameter@dots{}} is a list of parameters as defined for this very
22596 The target replies with this packet when it expects @value{GDBN} to call
22597 a host system call on behalf of the target. @value{GDBN} replies with
22598 an appropriate @code{F} packet and keeps up waiting for the next reply
22599 packet from the target. The latest @samp{C}, @samp{c}, @samp{S} or
22600 @samp{s} action is expected to be continued.
22601 @xref{File-I/O remote protocol extension}, for more details.
22605 @node General Query Packets
22606 @section General Query Packets
22607 @cindex remote query requests
22609 The following set and query packets have already been defined.
22613 @item @code{q}@code{C} --- current thread
22614 @cindex current thread, remote request
22615 @cindex @code{qC} packet
22616 Return the current thread id.
22620 @item @code{QC}@var{pid}
22621 Where @var{pid} is an unsigned hexidecimal process id.
22623 Any other reply implies the old pid.
22626 @item @code{q}@code{fThreadInfo} -- all thread ids
22627 @cindex list active threads, remote request
22628 @cindex @code{qfThreadInfo} packet
22629 @code{q}@code{sThreadInfo}
22631 Obtain a list of active thread ids from the target (OS). Since there
22632 may be too many active threads to fit into one reply packet, this query
22633 works iteratively: it may require more than one query/reply sequence to
22634 obtain the entire list of threads. The first query of the sequence will
22635 be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
22636 sequence will be the @code{qs}@code{ThreadInfo} query.
22638 NOTE: replaces the @code{qL} query (see below).
22642 @item @code{m}@var{id}
22644 @item @code{m}@var{id},@var{id}@dots{}
22645 a comma-separated list of thread ids
22647 (lower case 'el') denotes end of list.
22650 In response to each query, the target will reply with a list of one or
22651 more thread ids, in big-endian unsigned hex, separated by commas.
22652 @value{GDBN} will respond to each reply with a request for more thread
22653 ids (using the @code{qs} form of the query), until the target responds
22654 with @code{l} (lower-case el, for @code{'last'}).
22656 @item @code{q}@code{ThreadExtraInfo}@code{,}@var{id} --- extra thread info
22657 @cindex thread attributes info, remote request
22658 @cindex @code{qThreadExtraInfo} packet
22659 Where @var{id} is a thread-id in big-endian hex. Obtain a printable
22660 string description of a thread's attributes from the target OS. This
22661 string may contain anything that the target OS thinks is interesting for
22662 @value{GDBN} to tell the user about the thread. The string is displayed
22663 in @value{GDBN}'s @samp{info threads} display. Some examples of
22664 possible thread extra info strings are ``Runnable'', or ``Blocked on
22669 @item @var{XX@dots{}}
22670 Where @var{XX@dots{}} is a hex encoding of @sc{ascii} data, comprising
22671 the printable string containing the extra information about the thread's
22675 @item @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} --- query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
22677 Obtain thread information from RTOS. Where: @var{startflag} (one hex
22678 digit) is one to indicate the first query and zero to indicate a
22679 subsequent query; @var{threadcount} (two hex digits) is the maximum
22680 number of threads the response packet can contain; and @var{nextthread}
22681 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
22682 returned in the response as @var{argthread}.
22684 NOTE: this query is replaced by the @code{q}@code{fThreadInfo} query
22689 @item @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread@dots{}}
22690 Where: @var{count} (two hex digits) is the number of threads being
22691 returned; @var{done} (one hex digit) is zero to indicate more threads
22692 and one indicates no further threads; @var{argthreadid} (eight hex
22693 digits) is @var{nextthread} from the request packet; @var{thread@dots{}}
22694 is a sequence of thread IDs from the target. @var{threadid} (eight hex
22695 digits). See @code{remote.c:parse_threadlist_response()}.
22698 @item @code{q}@code{CRC:}@var{addr}@code{,}@var{length} --- compute CRC of memory block
22699 @cindex CRC of memory block, remote request
22700 @cindex @code{qCRC} packet
22703 @item @code{E}@var{NN}
22704 An error (such as memory fault)
22705 @item @code{C}@var{CRC32}
22706 A 32 bit cyclic redundancy check of the specified memory region.
22709 @item @code{q}@code{Offsets} --- query sect offs
22710 @cindex section offsets, remote request
22711 @cindex @code{qOffsets} packet
22712 Get section offsets that the target used when re-locating the downloaded
22713 image. @emph{Note: while a @code{Bss} offset is included in the
22714 response, @value{GDBN} ignores this and instead applies the @code{Data}
22715 offset to the @code{Bss} section.}
22719 @item @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
22722 @item @code{q}@code{P}@var{mode}@var{threadid} --- thread info request
22723 @cindex thread information, remote request
22724 @cindex @code{qP} packet
22725 Returns information on @var{threadid}. Where: @var{mode} is a hex
22726 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
22733 See @code{remote.c:remote_unpack_thread_info_response()}.
22735 @item @code{q}@code{Rcmd,}@var{command} --- remote command
22736 @cindex execute remote command, remote request
22737 @cindex @code{qRcmd} packet
22738 @var{command} (hex encoded) is passed to the local interpreter for
22739 execution. Invalid commands should be reported using the output string.
22740 Before the final result packet, the target may also respond with a
22741 number of intermediate @code{O}@var{output} console output packets.
22742 @emph{Implementors should note that providing access to a stubs's
22743 interpreter may have security implications}.
22748 A command response with no output.
22750 A command response with the hex encoded output string @var{OUTPUT}.
22751 @item @code{E}@var{NN}
22752 Indicate a badly formed request.
22754 When @samp{q}@samp{Rcmd} is not recognized.
22757 @item @code{qSymbol::} --- symbol lookup
22758 @cindex symbol lookup, remote request
22759 @cindex @code{qSymbol} packet
22760 Notify the target that @value{GDBN} is prepared to serve symbol lookup
22761 requests. Accept requests from the target for the values of symbols.
22766 The target does not need to look up any (more) symbols.
22767 @item @code{qSymbol:}@var{sym_name}
22768 The target requests the value of symbol @var{sym_name} (hex encoded).
22769 @value{GDBN} may provide the value by using the
22770 @code{qSymbol:}@var{sym_value}:@var{sym_name} message, described below.
22773 @item @code{qSymbol:}@var{sym_value}:@var{sym_name} --- symbol value
22775 Set the value of @var{sym_name} to @var{sym_value}.
22777 @var{sym_name} (hex encoded) is the name of a symbol whose value the
22778 target has previously requested.
22780 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
22781 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
22787 The target does not need to look up any (more) symbols.
22788 @item @code{qSymbol:}@var{sym_name}
22789 The target requests the value of a new symbol @var{sym_name} (hex
22790 encoded). @value{GDBN} will continue to supply the values of symbols
22791 (if available), until the target ceases to request them.
22794 @item @code{qPart}:@var{object}:@code{read}:@var{annex}:@var{offset},@var{length} --- read special data
22795 @cindex read special object, remote request
22796 @cindex @code{qPart} packet
22797 Read uninterpreted bytes from the target's special data area
22798 identified by the keyword @code{object}.
22799 Request @var{length} bytes starting at @var{offset} bytes into the data.
22800 The content and encoding of @var{annex} is specific to the object;
22801 it can supply additional details about what data to access.
22803 Here are the specific requests of this form defined so far.
22804 All @samp{@code{qPart}:@var{object}:@code{read}:@dots{}}
22805 requests use the same reply formats, listed below.
22808 @item @code{qPart}:@code{auxv}:@code{read}::@var{offset},@var{length}
22809 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
22810 auxiliary vector}, and see @ref{Remote configuration,
22811 read-aux-vector-packet}. Note @var{annex} must be empty.
22817 The @var{offset} in the request is at the end of the data.
22818 There is no more data to be read.
22820 @item @var{XX@dots{}}
22821 Hex encoded data bytes read.
22822 This may be fewer bytes than the @var{length} in the request.
22825 The request was malformed, or @var{annex} was invalid.
22827 @item @code{E}@var{nn}
22828 The offset was invalid, or there was an error encountered reading the data.
22829 @var{nn} is a hex-encoded @code{errno} value.
22831 @item @code{""} (empty)
22832 An empty reply indicates the @var{object} or @var{annex} string was not
22833 recognized by the stub.
22836 @item @code{qPart}:@var{object}:@code{write}:@var{annex}:@var{offset}:@var{data@dots{}}
22837 @cindex write data into object, remote request
22838 Write uninterpreted bytes into the target's special data area
22839 identified by the keyword @code{object},
22840 starting at @var{offset} bytes into the data.
22841 @var{data@dots{}} is the hex-encoded data to be written.
22842 The content and encoding of @var{annex} is specific to the object;
22843 it can supply additional details about what data to access.
22845 No requests of this form are presently in use. This specification
22846 serves as a placeholder to document the common format that new
22847 specific request specifications ought to use.
22852 @var{nn} (hex encoded) is the number of bytes written.
22853 This may be fewer bytes than supplied in the request.
22856 The request was malformed, or @var{annex} was invalid.
22858 @item @code{E}@var{nn}
22859 The offset was invalid, or there was an error encountered writing the data.
22860 @var{nn} is a hex-encoded @code{errno} value.
22862 @item @code{""} (empty)
22863 An empty reply indicates the @var{object} or @var{annex} string was not
22864 recognized by the stub, or that the object does not support writing.
22867 @item @code{qPart}:@var{object}:@var{operation}:@dots{}
22868 Requests of this form may be added in the future. When a stub does
22869 not recognize the @var{object} keyword, or its support for
22870 @var{object} does not recognize the @var{operation} keyword,
22871 the stub must respond with an empty packet.
22873 @item @code{qGetTLSAddr}:@var{thread-id},@var{offset},@var{lm} --- get thread local storage address
22874 @cindex get thread-local storage address, remote request
22875 @cindex @code{qGetTLSAddr} packet
22876 Fetch the address associated with thread local storage specified
22877 by @var{thread-id}, @var{offset}, and @var{lm}.
22879 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
22880 thread for which to fetch the TLS address.
22882 @var{offset} is the (big endian, hex encoded) offset associated with the
22883 thread local variable. (This offset is obtained from the debug
22884 information associated with the variable.)
22886 @var{lm} is the (big endian, hex encoded) OS/ABI specific encoding of the
22887 the load module associated with the thread local storage. For example,
22888 a @sc{gnu}/Linux system will pass the link map address of the shared
22889 object associated with the thread local storage under consideration.
22890 Other operating environments may choose to represent the load module
22891 differently, so the precise meaning of this parameter will vary.
22895 @item @var{XX@dots{}}
22896 Hex encoded (big endian) bytes representing the address of the thread
22897 local storage requested.
22899 @item @code{E}@var{nn} (where @var{nn} are hex digits)
22902 @item @code{""} (empty)
22903 An empty reply indicates that @code{qGetTLSAddr} is not supported by the stub.
22906 Use of this request packet is controlled by the @code{set remote
22907 get-thread-local-storage-address} command (@pxref{Remote
22908 configuration, set remote get-thread-local-storage-address}).
22912 @node Register Packet Format
22913 @section Register Packet Format
22915 The following @samp{g}/@samp{G} packets have previously been defined.
22916 In the below, some thirty-two bit registers are transferred as
22917 sixty-four bits. Those registers should be zero/sign extended (which?)
22918 to fill the space allocated. Register bytes are transfered in target
22919 byte order. The two nibbles within a register byte are transfered
22920 most-significant - least-significant.
22926 All registers are transfered as thirty-two bit quantities in the order:
22927 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
22928 registers; fsr; fir; fp.
22932 All registers are transfered as sixty-four bit quantities (including
22933 thirty-two bit registers such as @code{sr}). The ordering is the same
22941 Example sequence of a target being re-started. Notice how the restart
22942 does not get any direct output:
22947 @emph{target restarts}
22950 <- @code{T001:1234123412341234}
22954 Example sequence of a target being stepped by a single instruction:
22957 -> @code{G1445@dots{}}
22962 <- @code{T001:1234123412341234}
22966 <- @code{1455@dots{}}
22970 @node File-I/O remote protocol extension
22971 @section File-I/O remote protocol extension
22972 @cindex File-I/O remote protocol extension
22975 * File-I/O Overview::
22976 * Protocol basics::
22977 * The F request packet::
22978 * The F reply packet::
22979 * Memory transfer::
22980 * The Ctrl-C message::
22982 * The isatty call::
22983 * The system call::
22984 * List of supported calls::
22985 * Protocol specific representation of datatypes::
22987 * File-I/O Examples::
22990 @node File-I/O Overview
22991 @subsection File-I/O Overview
22992 @cindex file-i/o overview
22994 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
22995 target to use the host's file system and console I/O when calling various
22996 system calls. System calls on the target system are translated into a
22997 remote protocol packet to the host system which then performs the needed
22998 actions and returns with an adequate response packet to the target system.
22999 This simulates file system operations even on targets that lack file systems.
23001 The protocol is defined host- and target-system independent. It uses
23002 its own independent representation of datatypes and values. Both,
23003 @value{GDBN} and the target's @value{GDBN} stub are responsible for
23004 translating the system dependent values into the unified protocol values
23005 when data is transmitted.
23007 The communication is synchronous. A system call is possible only
23008 when GDB is waiting for the @samp{C}, @samp{c}, @samp{S} or @samp{s}
23009 packets. While @value{GDBN} handles the request for a system call,
23010 the target is stopped to allow deterministic access to the target's
23011 memory. Therefore File-I/O is not interuptible by target signals. It
23012 is possible to interrupt File-I/O by a user interrupt (Ctrl-C), though.
23014 The target's request to perform a host system call does not finish
23015 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
23016 after finishing the system call, the target returns to continuing the
23017 previous activity (continue, step). No additional continue or step
23018 request from @value{GDBN} is required.
23021 (@value{GDBP}) continue
23022 <- target requests 'system call X'
23023 target is stopped, @value{GDBN} executes system call
23024 -> GDB returns result
23025 ... target continues, GDB returns to wait for the target
23026 <- target hits breakpoint and sends a Txx packet
23029 The protocol is only used for files on the host file system and
23030 for I/O on the console. Character or block special devices, pipes,
23031 named pipes or sockets or any other communication method on the host
23032 system are not supported by this protocol.
23034 @node Protocol basics
23035 @subsection Protocol basics
23036 @cindex protocol basics, file-i/o
23038 The File-I/O protocol uses the @code{F} packet, as request as well
23039 as as reply packet. Since a File-I/O system call can only occur when
23040 @value{GDBN} is waiting for the continuing or stepping target, the
23041 File-I/O request is a reply that @value{GDBN} has to expect as a result
23042 of a former @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
23043 This @code{F} packet contains all information needed to allow @value{GDBN}
23044 to call the appropriate host system call:
23048 A unique identifier for the requested system call.
23051 All parameters to the system call. Pointers are given as addresses
23052 in the target memory address space. Pointers to strings are given as
23053 pointer/length pair. Numerical values are given as they are.
23054 Numerical control values are given in a protocol specific representation.
23058 At that point @value{GDBN} has to perform the following actions.
23062 If parameter pointer values are given, which point to data needed as input
23063 to a system call, @value{GDBN} requests this data from the target with a
23064 standard @code{m} packet request. This additional communication has to be
23065 expected by the target implementation and is handled as any other @code{m}
23069 @value{GDBN} translates all value from protocol representation to host
23070 representation as needed. Datatypes are coerced into the host types.
23073 @value{GDBN} calls the system call
23076 It then coerces datatypes back to protocol representation.
23079 If pointer parameters in the request packet point to buffer space in which
23080 a system call is expected to copy data to, the data is transmitted to the
23081 target using a @code{M} or @code{X} packet. This packet has to be expected
23082 by the target implementation and is handled as any other @code{M} or @code{X}
23087 Eventually @value{GDBN} replies with another @code{F} packet which contains all
23088 necessary information for the target to continue. This at least contains
23095 @code{errno}, if has been changed by the system call.
23102 After having done the needed type and value coercion, the target continues
23103 the latest continue or step action.
23105 @node The F request packet
23106 @subsection The @code{F} request packet
23107 @cindex file-i/o request packet
23108 @cindex @code{F} request packet
23110 The @code{F} request packet has the following format:
23115 @code{F}@var{call-id}@code{,}@var{parameter@dots{}}
23118 @var{call-id} is the identifier to indicate the host system call to be called.
23119 This is just the name of the function.
23121 @var{parameter@dots{}} are the parameters to the system call.
23125 Parameters are hexadecimal integer values, either the real values in case
23126 of scalar datatypes, as pointers to target buffer space in case of compound
23127 datatypes and unspecified memory areas or as pointer/length pairs in case
23128 of string parameters. These are appended to the call-id, each separated
23129 from its predecessor by a comma. All values are transmitted in ASCII
23130 string representation, pointer/length pairs separated by a slash.
23132 @node The F reply packet
23133 @subsection The @code{F} reply packet
23134 @cindex file-i/o reply packet
23135 @cindex @code{F} reply packet
23137 The @code{F} reply packet has the following format:
23142 @code{F}@var{retcode}@code{,}@var{errno}@code{,}@var{Ctrl-C flag}@code{;}@var{call specific attachment}
23145 @var{retcode} is the return code of the system call as hexadecimal value.
23147 @var{errno} is the errno set by the call, in protocol specific representation.
23148 This parameter can be omitted if the call was successful.
23150 @var{Ctrl-C flag} is only send if the user requested a break. In this
23151 case, @var{errno} must be send as well, even if the call was successful.
23152 The @var{Ctrl-C flag} itself consists of the character 'C':
23159 or, if the call was interupted before the host call has been performed:
23166 assuming 4 is the protocol specific representation of @code{EINTR}.
23170 @node Memory transfer
23171 @subsection Memory transfer
23172 @cindex memory transfer, in file-i/o protocol
23174 Structured data which is transferred using a memory read or write as e.g.@:
23175 a @code{struct stat} is expected to be in a protocol specific format with
23176 all scalar multibyte datatypes being big endian. This should be done by
23177 the target before the @code{F} packet is sent resp.@: by @value{GDBN} before
23178 it transfers memory to the target. Transferred pointers to structured
23179 data should point to the already coerced data at any time.
23181 @node The Ctrl-C message
23182 @subsection The Ctrl-C message
23183 @cindex ctrl-c message, in file-i/o protocol
23185 A special case is, if the @var{Ctrl-C flag} is set in the @value{GDBN}
23186 reply packet. In this case the target should behave, as if it had
23187 gotten a break message. The meaning for the target is ``system call
23188 interupted by @code{SIGINT}''. Consequentially, the target should actually stop
23189 (as with a break message) and return to @value{GDBN} with a @code{T02}
23190 packet. In this case, it's important for the target to know, in which
23191 state the system call was interrupted. Since this action is by design
23192 not an atomic operation, we have to differ between two cases:
23196 The system call hasn't been performed on the host yet.
23199 The system call on the host has been finished.
23203 These two states can be distinguished by the target by the value of the
23204 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
23205 call hasn't been performed. This is equivalent to the @code{EINTR} handling
23206 on POSIX systems. In any other case, the target may presume that the
23207 system call has been finished --- successful or not --- and should behave
23208 as if the break message arrived right after the system call.
23210 @value{GDBN} must behave reliable. If the system call has not been called
23211 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
23212 @code{errno} in the packet. If the system call on the host has been finished
23213 before the user requests a break, the full action must be finshed by
23214 @value{GDBN}. This requires sending @code{M} or @code{X} packets as they fit.
23215 The @code{F} packet may only be send when either nothing has happened
23216 or the full action has been completed.
23219 @subsection Console I/O
23220 @cindex console i/o as part of file-i/o
23222 By default and if not explicitely closed by the target system, the file
23223 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
23224 on the @value{GDBN} console is handled as any other file output operation
23225 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
23226 by @value{GDBN} so that after the target read request from file descriptor
23227 0 all following typing is buffered until either one of the following
23232 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, the
23234 system call is treated as finished.
23237 The user presses @kbd{Enter}. This is treated as end of input with a trailing
23241 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
23242 character, especially no Ctrl-D is appended to the input.
23246 If the user has typed more characters as fit in the buffer given to
23247 the read call, the trailing characters are buffered in @value{GDBN} until
23248 either another @code{read(0, @dots{})} is requested by the target or debugging
23249 is stopped on users request.
23251 @node The isatty call
23252 @subsection The @samp{isatty} function call
23253 @cindex isatty call, file-i/o protocol
23255 A special case in this protocol is the library call @code{isatty} which
23256 is implemented as its own call inside of this protocol. It returns
23257 1 to the target if the file descriptor given as parameter is attached
23258 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
23259 would require implementing @code{ioctl} and would be more complex than
23262 @node The system call
23263 @subsection The @samp{system} function call
23264 @cindex system call, file-i/o protocol
23266 The other special case in this protocol is the @code{system} call which
23267 is implemented as its own call, too. @value{GDBN} is taking over the full
23268 task of calling the necessary host calls to perform the @code{system}
23269 call. The return value of @code{system} is simplified before it's returned
23270 to the target. Basically, the only signal transmitted back is @code{EINTR}
23271 in case the user pressed @kbd{Ctrl-C}. Otherwise the return value consists
23272 entirely of the exit status of the called command.
23274 Due to security concerns, the @code{system} call is by default refused
23275 by @value{GDBN}. The user has to allow this call explicitly with the
23276 @kbd{set remote system-call-allowed 1} command.
23279 @item set remote system-call-allowed
23280 @kindex set remote system-call-allowed
23281 Control whether to allow the @code{system} calls in the File I/O
23282 protocol for the remote target. The default is zero (disabled).
23284 @item show remote system-call-allowed
23285 @kindex show remote system-call-allowed
23286 Show the current setting of system calls for the remote File I/O
23290 @node List of supported calls
23291 @subsection List of supported calls
23292 @cindex list of supported file-i/o calls
23309 @unnumberedsubsubsec open
23310 @cindex open, file-i/o system call
23314 int open(const char *pathname, int flags);
23315 int open(const char *pathname, int flags, mode_t mode);
23318 Fopen,pathptr/len,flags,mode
23322 @code{flags} is the bitwise or of the following values:
23326 If the file does not exist it will be created. The host
23327 rules apply as far as file ownership and time stamps
23331 When used with O_CREAT, if the file already exists it is
23332 an error and open() fails.
23335 If the file already exists and the open mode allows
23336 writing (O_RDWR or O_WRONLY is given) it will be
23337 truncated to length 0.
23340 The file is opened in append mode.
23343 The file is opened for reading only.
23346 The file is opened for writing only.
23349 The file is opened for reading and writing.
23352 Each other bit is silently ignored.
23357 @code{mode} is the bitwise or of the following values:
23361 User has read permission.
23364 User has write permission.
23367 Group has read permission.
23370 Group has write permission.
23373 Others have read permission.
23376 Others have write permission.
23379 Each other bit is silently ignored.
23384 @exdent Return value:
23385 open returns the new file descriptor or -1 if an error
23393 pathname already exists and O_CREAT and O_EXCL were used.
23396 pathname refers to a directory.
23399 The requested access is not allowed.
23402 pathname was too long.
23405 A directory component in pathname does not exist.
23408 pathname refers to a device, pipe, named pipe or socket.
23411 pathname refers to a file on a read-only filesystem and
23412 write access was requested.
23415 pathname is an invalid pointer value.
23418 No space on device to create the file.
23421 The process already has the maximum number of files open.
23424 The limit on the total number of files open on the system
23428 The call was interrupted by the user.
23432 @unnumberedsubsubsec close
23433 @cindex close, file-i/o system call
23442 @exdent Return value:
23443 close returns zero on success, or -1 if an error occurred.
23450 fd isn't a valid open file descriptor.
23453 The call was interrupted by the user.
23457 @unnumberedsubsubsec read
23458 @cindex read, file-i/o system call
23462 int read(int fd, void *buf, unsigned int count);
23465 Fread,fd,bufptr,count
23467 @exdent Return value:
23468 On success, the number of bytes read is returned.
23469 Zero indicates end of file. If count is zero, read
23470 returns zero as well. On error, -1 is returned.
23477 fd is not a valid file descriptor or is not open for
23481 buf is an invalid pointer value.
23484 The call was interrupted by the user.
23488 @unnumberedsubsubsec write
23489 @cindex write, file-i/o system call
23493 int write(int fd, const void *buf, unsigned int count);
23496 Fwrite,fd,bufptr,count
23498 @exdent Return value:
23499 On success, the number of bytes written are returned.
23500 Zero indicates nothing was written. On error, -1
23508 fd is not a valid file descriptor or is not open for
23512 buf is an invalid pointer value.
23515 An attempt was made to write a file that exceeds the
23516 host specific maximum file size allowed.
23519 No space on device to write the data.
23522 The call was interrupted by the user.
23526 @unnumberedsubsubsec lseek
23527 @cindex lseek, file-i/o system call
23531 long lseek (int fd, long offset, int flag);
23534 Flseek,fd,offset,flag
23537 @code{flag} is one of:
23541 The offset is set to offset bytes.
23544 The offset is set to its current location plus offset
23548 The offset is set to the size of the file plus offset
23553 @exdent Return value:
23554 On success, the resulting unsigned offset in bytes from
23555 the beginning of the file is returned. Otherwise, a
23556 value of -1 is returned.
23563 fd is not a valid open file descriptor.
23566 fd is associated with the @value{GDBN} console.
23569 flag is not a proper value.
23572 The call was interrupted by the user.
23576 @unnumberedsubsubsec rename
23577 @cindex rename, file-i/o system call
23581 int rename(const char *oldpath, const char *newpath);
23584 Frename,oldpathptr/len,newpathptr/len
23586 @exdent Return value:
23587 On success, zero is returned. On error, -1 is returned.
23594 newpath is an existing directory, but oldpath is not a
23598 newpath is a non-empty directory.
23601 oldpath or newpath is a directory that is in use by some
23605 An attempt was made to make a directory a subdirectory
23609 A component used as a directory in oldpath or new
23610 path is not a directory. Or oldpath is a directory
23611 and newpath exists but is not a directory.
23614 oldpathptr or newpathptr are invalid pointer values.
23617 No access to the file or the path of the file.
23621 oldpath or newpath was too long.
23624 A directory component in oldpath or newpath does not exist.
23627 The file is on a read-only filesystem.
23630 The device containing the file has no room for the new
23634 The call was interrupted by the user.
23638 @unnumberedsubsubsec unlink
23639 @cindex unlink, file-i/o system call
23643 int unlink(const char *pathname);
23646 Funlink,pathnameptr/len
23648 @exdent Return value:
23649 On success, zero is returned. On error, -1 is returned.
23656 No access to the file or the path of the file.
23659 The system does not allow unlinking of directories.
23662 The file pathname cannot be unlinked because it's
23663 being used by another process.
23666 pathnameptr is an invalid pointer value.
23669 pathname was too long.
23672 A directory component in pathname does not exist.
23675 A component of the path is not a directory.
23678 The file is on a read-only filesystem.
23681 The call was interrupted by the user.
23685 @unnumberedsubsubsec stat/fstat
23686 @cindex fstat, file-i/o system call
23687 @cindex stat, file-i/o system call
23691 int stat(const char *pathname, struct stat *buf);
23692 int fstat(int fd, struct stat *buf);
23695 Fstat,pathnameptr/len,bufptr
23698 @exdent Return value:
23699 On success, zero is returned. On error, -1 is returned.
23706 fd is not a valid open file.
23709 A directory component in pathname does not exist or the
23710 path is an empty string.
23713 A component of the path is not a directory.
23716 pathnameptr is an invalid pointer value.
23719 No access to the file or the path of the file.
23722 pathname was too long.
23725 The call was interrupted by the user.
23729 @unnumberedsubsubsec gettimeofday
23730 @cindex gettimeofday, file-i/o system call
23734 int gettimeofday(struct timeval *tv, void *tz);
23737 Fgettimeofday,tvptr,tzptr
23739 @exdent Return value:
23740 On success, 0 is returned, -1 otherwise.
23747 tz is a non-NULL pointer.
23750 tvptr and/or tzptr is an invalid pointer value.
23754 @unnumberedsubsubsec isatty
23755 @cindex isatty, file-i/o system call
23759 int isatty(int fd);
23764 @exdent Return value:
23765 Returns 1 if fd refers to the @value{GDBN} console, 0 otherwise.
23772 The call was interrupted by the user.
23776 @unnumberedsubsubsec system
23777 @cindex system, file-i/o system call
23781 int system(const char *command);
23784 Fsystem,commandptr/len
23786 @exdent Return value:
23787 The value returned is -1 on error and the return status
23788 of the command otherwise. Only the exit status of the
23789 command is returned, which is extracted from the hosts
23790 system return value by calling WEXITSTATUS(retval).
23791 In case /bin/sh could not be executed, 127 is returned.
23798 The call was interrupted by the user.
23801 @node Protocol specific representation of datatypes
23802 @subsection Protocol specific representation of datatypes
23803 @cindex protocol specific representation of datatypes, in file-i/o protocol
23806 * Integral datatypes::
23812 @node Integral datatypes
23813 @unnumberedsubsubsec Integral datatypes
23814 @cindex integral datatypes, in file-i/o protocol
23816 The integral datatypes used in the system calls are
23819 int@r{,} unsigned int@r{,} long@r{,} unsigned long@r{,} mode_t @r{and} time_t
23822 @code{Int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
23823 implemented as 32 bit values in this protocol.
23825 @code{Long} and @code{unsigned long} are implemented as 64 bit types.
23827 @xref{Limits}, for corresponding MIN and MAX values (similar to those
23828 in @file{limits.h}) to allow range checking on host and target.
23830 @code{time_t} datatypes are defined as seconds since the Epoch.
23832 All integral datatypes transferred as part of a memory read or write of a
23833 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
23836 @node Pointer values
23837 @unnumberedsubsubsec Pointer values
23838 @cindex pointer values, in file-i/o protocol
23840 Pointers to target data are transmitted as they are. An exception
23841 is made for pointers to buffers for which the length isn't
23842 transmitted as part of the function call, namely strings. Strings
23843 are transmitted as a pointer/length pair, both as hex values, e.g.@:
23850 which is a pointer to data of length 18 bytes at position 0x1aaf.
23851 The length is defined as the full string length in bytes, including
23852 the trailing null byte. Example:
23855 ``hello, world'' at address 0x123456
23866 @unnumberedsubsubsec struct stat
23867 @cindex struct stat, in file-i/o protocol
23869 The buffer of type struct stat used by the target and @value{GDBN} is defined
23874 unsigned int st_dev; /* device */
23875 unsigned int st_ino; /* inode */
23876 mode_t st_mode; /* protection */
23877 unsigned int st_nlink; /* number of hard links */
23878 unsigned int st_uid; /* user ID of owner */
23879 unsigned int st_gid; /* group ID of owner */
23880 unsigned int st_rdev; /* device type (if inode device) */
23881 unsigned long st_size; /* total size, in bytes */
23882 unsigned long st_blksize; /* blocksize for filesystem I/O */
23883 unsigned long st_blocks; /* number of blocks allocated */
23884 time_t st_atime; /* time of last access */
23885 time_t st_mtime; /* time of last modification */
23886 time_t st_ctime; /* time of last change */
23890 The integral datatypes are conforming to the definitions given in the
23891 approriate section (see @ref{Integral datatypes}, for details) so this
23892 structure is of size 64 bytes.
23894 The values of several fields have a restricted meaning and/or
23901 st_ino: No valid meaning for the target. Transmitted unchanged.
23903 st_mode: Valid mode bits are described in Appendix C. Any other
23904 bits have currently no meaning for the target.
23906 st_uid: No valid meaning for the target. Transmitted unchanged.
23908 st_gid: No valid meaning for the target. Transmitted unchanged.
23910 st_rdev: No valid meaning for the target. Transmitted unchanged.
23912 st_atime, st_mtime, st_ctime:
23913 These values have a host and file system dependent
23914 accuracy. Especially on Windows hosts the file systems
23915 don't support exact timing values.
23918 The target gets a struct stat of the above representation and is
23919 responsible to coerce it to the target representation before
23922 Note that due to size differences between the host and target
23923 representation of stat members, these members could eventually
23924 get truncated on the target.
23926 @node struct timeval
23927 @unnumberedsubsubsec struct timeval
23928 @cindex struct timeval, in file-i/o protocol
23930 The buffer of type struct timeval used by the target and @value{GDBN}
23931 is defined as follows:
23935 time_t tv_sec; /* second */
23936 long tv_usec; /* microsecond */
23940 The integral datatypes are conforming to the definitions given in the
23941 approriate section (see @ref{Integral datatypes}, for details) so this
23942 structure is of size 8 bytes.
23945 @subsection Constants
23946 @cindex constants, in file-i/o protocol
23948 The following values are used for the constants inside of the
23949 protocol. @value{GDBN} and target are resposible to translate these
23950 values before and after the call as needed.
23961 @unnumberedsubsubsec Open flags
23962 @cindex open flags, in file-i/o protocol
23964 All values are given in hexadecimal representation.
23976 @node mode_t values
23977 @unnumberedsubsubsec mode_t values
23978 @cindex mode_t values, in file-i/o protocol
23980 All values are given in octal representation.
23997 @unnumberedsubsubsec Errno values
23998 @cindex errno values, in file-i/o protocol
24000 All values are given in decimal representation.
24025 EUNKNOWN is used as a fallback error value if a host system returns
24026 any error value not in the list of supported error numbers.
24029 @unnumberedsubsubsec Lseek flags
24030 @cindex lseek flags, in file-i/o protocol
24039 @unnumberedsubsubsec Limits
24040 @cindex limits, in file-i/o protocol
24042 All values are given in decimal representation.
24045 INT_MIN -2147483648
24047 UINT_MAX 4294967295
24048 LONG_MIN -9223372036854775808
24049 LONG_MAX 9223372036854775807
24050 ULONG_MAX 18446744073709551615
24053 @node File-I/O Examples
24054 @subsection File-I/O Examples
24055 @cindex file-i/o examples
24057 Example sequence of a write call, file descriptor 3, buffer is at target
24058 address 0x1234, 6 bytes should be written:
24061 <- @code{Fwrite,3,1234,6}
24062 @emph{request memory read from target}
24065 @emph{return "6 bytes written"}
24069 Example sequence of a read call, file descriptor 3, buffer is at target
24070 address 0x1234, 6 bytes should be read:
24073 <- @code{Fread,3,1234,6}
24074 @emph{request memory write to target}
24075 -> @code{X1234,6:XXXXXX}
24076 @emph{return "6 bytes read"}
24080 Example sequence of a read call, call fails on the host due to invalid
24081 file descriptor (EBADF):
24084 <- @code{Fread,3,1234,6}
24088 Example sequence of a read call, user presses Ctrl-C before syscall on
24092 <- @code{Fread,3,1234,6}
24097 Example sequence of a read call, user presses Ctrl-C after syscall on
24101 <- @code{Fread,3,1234,6}
24102 -> @code{X1234,6:XXXXXX}
24106 @include agentexpr.texi
24120 % I think something like @colophon should be in texinfo. In the
24122 \long\def\colophon{\hbox to0pt{}\vfill
24123 \centerline{The body of this manual is set in}
24124 \centerline{\fontname\tenrm,}
24125 \centerline{with headings in {\bf\fontname\tenbf}}
24126 \centerline{and examples in {\tt\fontname\tentt}.}
24127 \centerline{{\it\fontname\tenit\/},}
24128 \centerline{{\bf\fontname\tenbf}, and}
24129 \centerline{{\sl\fontname\tensl\/}}
24130 \centerline{are used for emphasis.}\vfill}
24132 % Blame: doc@cygnus.com, 1991.