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 @item thread apply [@var{threadno}] [@var{all}] @var{args}
2390 The @code{thread apply} command allows you to apply a command to one or
2391 more threads. Specify the numbers of the threads that you want affected
2392 with the command argument @var{threadno}. @var{threadno} is the internal
2393 @value{GDBN} thread number, as shown in the first field of the @samp{info
2394 threads} display. To apply a command to all threads, use
2395 @code{thread apply all} @var{args}.
2398 @cindex automatic thread selection
2399 @cindex switching threads automatically
2400 @cindex threads, automatic switching
2401 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2402 signal, it automatically selects the thread where that breakpoint or
2403 signal happened. @value{GDBN} alerts you to the context switch with a
2404 message of the form @samp{[Switching to @var{systag}]} to identify the
2407 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2408 more information about how @value{GDBN} behaves when you stop and start
2409 programs with multiple threads.
2411 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2412 watchpoints in programs with multiple threads.
2415 @section Debugging programs with multiple processes
2417 @cindex fork, debugging programs which call
2418 @cindex multiple processes
2419 @cindex processes, multiple
2420 On most systems, @value{GDBN} has no special support for debugging
2421 programs which create additional processes using the @code{fork}
2422 function. When a program forks, @value{GDBN} will continue to debug the
2423 parent process and the child process will run unimpeded. If you have
2424 set a breakpoint in any code which the child then executes, the child
2425 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2426 will cause it to terminate.
2428 However, if you want to debug the child process there is a workaround
2429 which isn't too painful. Put a call to @code{sleep} in the code which
2430 the child process executes after the fork. It may be useful to sleep
2431 only if a certain environment variable is set, or a certain file exists,
2432 so that the delay need not occur when you don't want to run @value{GDBN}
2433 on the child. While the child is sleeping, use the @code{ps} program to
2434 get its process ID. Then tell @value{GDBN} (a new invocation of
2435 @value{GDBN} if you are also debugging the parent process) to attach to
2436 the child process (@pxref{Attach}). From that point on you can debug
2437 the child process just like any other process which you attached to.
2439 On some systems, @value{GDBN} provides support for debugging programs that
2440 create additional processes using the @code{fork} or @code{vfork} functions.
2441 Currently, the only platforms with this feature are HP-UX (11.x and later
2442 only?) and GNU/Linux (kernel version 2.5.60 and later).
2444 By default, when a program forks, @value{GDBN} will continue to debug
2445 the parent process and the child process will run unimpeded.
2447 If you want to follow the child process instead of the parent process,
2448 use the command @w{@code{set follow-fork-mode}}.
2451 @kindex set follow-fork-mode
2452 @item set follow-fork-mode @var{mode}
2453 Set the debugger response to a program call of @code{fork} or
2454 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2455 process. The @var{mode} argument can be:
2459 The original process is debugged after a fork. The child process runs
2460 unimpeded. This is the default.
2463 The new process is debugged after a fork. The parent process runs
2468 @kindex show follow-fork-mode
2469 @item show follow-fork-mode
2470 Display the current debugger response to a @code{fork} or @code{vfork} call.
2473 If you ask to debug a child process and a @code{vfork} is followed by an
2474 @code{exec}, @value{GDBN} executes the new target up to the first
2475 breakpoint in the new target. If you have a breakpoint set on
2476 @code{main} in your original program, the breakpoint will also be set on
2477 the child process's @code{main}.
2479 When a child process is spawned by @code{vfork}, you cannot debug the
2480 child or parent until an @code{exec} call completes.
2482 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2483 call executes, the new target restarts. To restart the parent process,
2484 use the @code{file} command with the parent executable name as its
2487 You can use the @code{catch} command to make @value{GDBN} stop whenever
2488 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2489 Catchpoints, ,Setting catchpoints}.
2492 @chapter Stopping and Continuing
2494 The principal purposes of using a debugger are so that you can stop your
2495 program before it terminates; or so that, if your program runs into
2496 trouble, you can investigate and find out why.
2498 Inside @value{GDBN}, your program may stop for any of several reasons,
2499 such as a signal, a breakpoint, or reaching a new line after a
2500 @value{GDBN} command such as @code{step}. You may then examine and
2501 change variables, set new breakpoints or remove old ones, and then
2502 continue execution. Usually, the messages shown by @value{GDBN} provide
2503 ample explanation of the status of your program---but you can also
2504 explicitly request this information at any time.
2507 @kindex info program
2509 Display information about the status of your program: whether it is
2510 running or not, what process it is, and why it stopped.
2514 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2515 * Continuing and Stepping:: Resuming execution
2517 * Thread Stops:: Stopping and starting multi-thread programs
2521 @section Breakpoints, watchpoints, and catchpoints
2524 A @dfn{breakpoint} makes your program stop whenever a certain point in
2525 the program is reached. For each breakpoint, you can add conditions to
2526 control in finer detail whether your program stops. You can set
2527 breakpoints with the @code{break} command and its variants (@pxref{Set
2528 Breaks, ,Setting breakpoints}), to specify the place where your program
2529 should stop by line number, function name or exact address in the
2532 On some systems, you can set breakpoints in shared libraries before
2533 the executable is run. There is a minor limitation on HP-UX systems:
2534 you must wait until the executable is run in order to set breakpoints
2535 in shared library routines that are not called directly by the program
2536 (for example, routines that are arguments in a @code{pthread_create}
2540 @cindex memory tracing
2541 @cindex breakpoint on memory address
2542 @cindex breakpoint on variable modification
2543 A @dfn{watchpoint} is a special breakpoint that stops your program
2544 when the value of an expression changes. You must use a different
2545 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2546 watchpoints}), but aside from that, you can manage a watchpoint like
2547 any other breakpoint: you enable, disable, and delete both breakpoints
2548 and watchpoints using the same commands.
2550 You can arrange to have values from your program displayed automatically
2551 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2555 @cindex breakpoint on events
2556 A @dfn{catchpoint} is another special breakpoint that stops your program
2557 when a certain kind of event occurs, such as the throwing of a C@t{++}
2558 exception or the loading of a library. As with watchpoints, you use a
2559 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2560 catchpoints}), but aside from that, you can manage a catchpoint like any
2561 other breakpoint. (To stop when your program receives a signal, use the
2562 @code{handle} command; see @ref{Signals, ,Signals}.)
2564 @cindex breakpoint numbers
2565 @cindex numbers for breakpoints
2566 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2567 catchpoint when you create it; these numbers are successive integers
2568 starting with one. In many of the commands for controlling various
2569 features of breakpoints you use the breakpoint number to say which
2570 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2571 @dfn{disabled}; if disabled, it has no effect on your program until you
2574 @cindex breakpoint ranges
2575 @cindex ranges of breakpoints
2576 Some @value{GDBN} commands accept a range of breakpoints on which to
2577 operate. A breakpoint range is either a single breakpoint number, like
2578 @samp{5}, or two such numbers, in increasing order, separated by a
2579 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2580 all breakpoint in that range are operated on.
2583 * Set Breaks:: Setting breakpoints
2584 * Set Watchpoints:: Setting watchpoints
2585 * Set Catchpoints:: Setting catchpoints
2586 * Delete Breaks:: Deleting breakpoints
2587 * Disabling:: Disabling breakpoints
2588 * Conditions:: Break conditions
2589 * Break Commands:: Breakpoint command lists
2590 * Breakpoint Menus:: Breakpoint menus
2591 * Error in Breakpoints:: ``Cannot insert breakpoints''
2592 * Breakpoint related warnings:: ``Breakpoint address adjusted...''
2596 @subsection Setting breakpoints
2598 @c FIXME LMB what does GDB do if no code on line of breakpt?
2599 @c consider in particular declaration with/without initialization.
2601 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2604 @kindex b @r{(@code{break})}
2605 @vindex $bpnum@r{, convenience variable}
2606 @cindex latest breakpoint
2607 Breakpoints are set with the @code{break} command (abbreviated
2608 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2609 number of the breakpoint you've set most recently; see @ref{Convenience
2610 Vars,, Convenience variables}, for a discussion of what you can do with
2611 convenience variables.
2613 You have several ways to say where the breakpoint should go.
2616 @item break @var{function}
2617 Set a breakpoint at entry to function @var{function}.
2618 When using source languages that permit overloading of symbols, such as
2619 C@t{++}, @var{function} may refer to more than one possible place to break.
2620 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2622 @item break +@var{offset}
2623 @itemx break -@var{offset}
2624 Set a breakpoint some number of lines forward or back from the position
2625 at which execution stopped in the currently selected @dfn{stack frame}.
2626 (@xref{Frames, ,Frames}, for a description of stack frames.)
2628 @item break @var{linenum}
2629 Set a breakpoint at line @var{linenum} in the current source file.
2630 The current source file is the last file whose source text was printed.
2631 The breakpoint will stop your program just before it executes any of the
2634 @item break @var{filename}:@var{linenum}
2635 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2637 @item break @var{filename}:@var{function}
2638 Set a breakpoint at entry to function @var{function} found in file
2639 @var{filename}. Specifying a file name as well as a function name is
2640 superfluous except when multiple files contain similarly named
2643 @item break *@var{address}
2644 Set a breakpoint at address @var{address}. You can use this to set
2645 breakpoints in parts of your program which do not have debugging
2646 information or source files.
2649 When called without any arguments, @code{break} sets a breakpoint at
2650 the next instruction to be executed in the selected stack frame
2651 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2652 innermost, this makes your program stop as soon as control
2653 returns to that frame. This is similar to the effect of a
2654 @code{finish} command in the frame inside the selected frame---except
2655 that @code{finish} does not leave an active breakpoint. If you use
2656 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2657 the next time it reaches the current location; this may be useful
2660 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2661 least one instruction has been executed. If it did not do this, you
2662 would be unable to proceed past a breakpoint without first disabling the
2663 breakpoint. This rule applies whether or not the breakpoint already
2664 existed when your program stopped.
2666 @item break @dots{} if @var{cond}
2667 Set a breakpoint with condition @var{cond}; evaluate the expression
2668 @var{cond} each time the breakpoint is reached, and stop only if the
2669 value is nonzero---that is, if @var{cond} evaluates as true.
2670 @samp{@dots{}} stands for one of the possible arguments described
2671 above (or no argument) specifying where to break. @xref{Conditions,
2672 ,Break conditions}, for more information on breakpoint conditions.
2675 @item tbreak @var{args}
2676 Set a breakpoint enabled only for one stop. @var{args} are the
2677 same as for the @code{break} command, and the breakpoint is set in the same
2678 way, but the breakpoint is automatically deleted after the first time your
2679 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2682 @cindex hardware breakpoints
2683 @item hbreak @var{args}
2684 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2685 @code{break} command and the breakpoint is set in the same way, but the
2686 breakpoint requires hardware support and some target hardware may not
2687 have this support. The main purpose of this is EPROM/ROM code
2688 debugging, so you can set a breakpoint at an instruction without
2689 changing the instruction. This can be used with the new trap-generation
2690 provided by SPARClite DSU and most x86-based targets. These targets
2691 will generate traps when a program accesses some data or instruction
2692 address that is assigned to the debug registers. However the hardware
2693 breakpoint registers can take a limited number of breakpoints. For
2694 example, on the DSU, only two data breakpoints can be set at a time, and
2695 @value{GDBN} will reject this command if more than two are used. Delete
2696 or disable unused hardware breakpoints before setting new ones
2697 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2698 For remote targets, you can restrict the number of hardware
2699 breakpoints @value{GDBN} will use, see @ref{set remote
2700 hardware-breakpoint-limit}.
2704 @item thbreak @var{args}
2705 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2706 are the same as for the @code{hbreak} command and the breakpoint is set in
2707 the same way. However, like the @code{tbreak} command,
2708 the breakpoint is automatically deleted after the
2709 first time your program stops there. Also, like the @code{hbreak}
2710 command, the breakpoint requires hardware support and some target hardware
2711 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2712 See also @ref{Conditions, ,Break conditions}.
2715 @cindex regular expression
2716 @cindex breakpoints in functions matching a regexp
2717 @cindex set breakpoints in many functions
2718 @item rbreak @var{regex}
2719 Set breakpoints on all functions matching the regular expression
2720 @var{regex}. This command sets an unconditional breakpoint on all
2721 matches, printing a list of all breakpoints it set. Once these
2722 breakpoints are set, they are treated just like the breakpoints set with
2723 the @code{break} command. You can delete them, disable them, or make
2724 them conditional the same way as any other breakpoint.
2726 The syntax of the regular expression is the standard one used with tools
2727 like @file{grep}. Note that this is different from the syntax used by
2728 shells, so for instance @code{foo*} matches all functions that include
2729 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2730 @code{.*} leading and trailing the regular expression you supply, so to
2731 match only functions that begin with @code{foo}, use @code{^foo}.
2733 @cindex non-member C@t{++} functions, set breakpoint in
2734 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2735 breakpoints on overloaded functions that are not members of any special
2738 @cindex set breakpoints on all functions
2739 The @code{rbreak} command can be used to set breakpoints in
2740 @strong{all} the functions in a program, like this:
2743 (@value{GDBP}) rbreak .
2746 @kindex info breakpoints
2747 @cindex @code{$_} and @code{info breakpoints}
2748 @item info breakpoints @r{[}@var{n}@r{]}
2749 @itemx info break @r{[}@var{n}@r{]}
2750 @itemx info watchpoints @r{[}@var{n}@r{]}
2751 Print a table of all breakpoints, watchpoints, and catchpoints set and
2752 not deleted, with the following columns for each breakpoint:
2755 @item Breakpoint Numbers
2757 Breakpoint, watchpoint, or catchpoint.
2759 Whether the breakpoint is marked to be disabled or deleted when hit.
2760 @item Enabled or Disabled
2761 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2762 that are not enabled.
2764 Where the breakpoint is in your program, as a memory address. If the
2765 breakpoint is pending (see below for details) on a future load of a shared library, the address
2766 will be listed as @samp{<PENDING>}.
2768 Where the breakpoint is in the source for your program, as a file and
2769 line number. For a pending breakpoint, the original string passed to
2770 the breakpoint command will be listed as it cannot be resolved until
2771 the appropriate shared library is loaded in the future.
2775 If a breakpoint is conditional, @code{info break} shows the condition on
2776 the line following the affected breakpoint; breakpoint commands, if any,
2777 are listed after that. A pending breakpoint is allowed to have a condition
2778 specified for it. The condition is not parsed for validity until a shared
2779 library is loaded that allows the pending breakpoint to resolve to a
2783 @code{info break} with a breakpoint
2784 number @var{n} as argument lists only that breakpoint. The
2785 convenience variable @code{$_} and the default examining-address for
2786 the @code{x} command are set to the address of the last breakpoint
2787 listed (@pxref{Memory, ,Examining memory}).
2790 @code{info break} displays a count of the number of times the breakpoint
2791 has been hit. This is especially useful in conjunction with the
2792 @code{ignore} command. You can ignore a large number of breakpoint
2793 hits, look at the breakpoint info to see how many times the breakpoint
2794 was hit, and then run again, ignoring one less than that number. This
2795 will get you quickly to the last hit of that breakpoint.
2798 @value{GDBN} allows you to set any number of breakpoints at the same place in
2799 your program. There is nothing silly or meaningless about this. When
2800 the breakpoints are conditional, this is even useful
2801 (@pxref{Conditions, ,Break conditions}).
2803 @cindex pending breakpoints
2804 If a specified breakpoint location cannot be found, it may be due to the fact
2805 that the location is in a shared library that is yet to be loaded. In such
2806 a case, you may want @value{GDBN} to create a special breakpoint (known as
2807 a @dfn{pending breakpoint}) that
2808 attempts to resolve itself in the future when an appropriate shared library
2811 Pending breakpoints are useful to set at the start of your
2812 @value{GDBN} session for locations that you know will be dynamically loaded
2813 later by the program being debugged. When shared libraries are loaded,
2814 a check is made to see if the load resolves any pending breakpoint locations.
2815 If a pending breakpoint location gets resolved,
2816 a regular breakpoint is created and the original pending breakpoint is removed.
2818 @value{GDBN} provides some additional commands for controlling pending
2821 @kindex set breakpoint pending
2822 @kindex show breakpoint pending
2824 @item set breakpoint pending auto
2825 This is the default behavior. When @value{GDBN} cannot find the breakpoint
2826 location, it queries you whether a pending breakpoint should be created.
2828 @item set breakpoint pending on
2829 This indicates that an unrecognized breakpoint location should automatically
2830 result in a pending breakpoint being created.
2832 @item set breakpoint pending off
2833 This indicates that pending breakpoints are not to be created. Any
2834 unrecognized breakpoint location results in an error. This setting does
2835 not affect any pending breakpoints previously created.
2837 @item show breakpoint pending
2838 Show the current behavior setting for creating pending breakpoints.
2841 @cindex operations allowed on pending breakpoints
2842 Normal breakpoint operations apply to pending breakpoints as well. You may
2843 specify a condition for a pending breakpoint and/or commands to run when the
2844 breakpoint is reached. You can also enable or disable
2845 the pending breakpoint. When you specify a condition for a pending breakpoint,
2846 the parsing of the condition will be deferred until the point where the
2847 pending breakpoint location is resolved. Disabling a pending breakpoint
2848 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
2849 shared library load. When a pending breakpoint is re-enabled,
2850 @value{GDBN} checks to see if the location is already resolved.
2851 This is done because any number of shared library loads could have
2852 occurred since the time the breakpoint was disabled and one or more
2853 of these loads could resolve the location.
2855 @cindex negative breakpoint numbers
2856 @cindex internal @value{GDBN} breakpoints
2857 @value{GDBN} itself sometimes sets breakpoints in your program for
2858 special purposes, such as proper handling of @code{longjmp} (in C
2859 programs). These internal breakpoints are assigned negative numbers,
2860 starting with @code{-1}; @samp{info breakpoints} does not display them.
2861 You can see these breakpoints with the @value{GDBN} maintenance command
2862 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
2865 @node Set Watchpoints
2866 @subsection Setting watchpoints
2868 @cindex setting watchpoints
2869 You can use a watchpoint to stop execution whenever the value of an
2870 expression changes, without having to predict a particular place where
2873 @cindex software watchpoints
2874 @cindex hardware watchpoints
2875 Depending on your system, watchpoints may be implemented in software or
2876 hardware. @value{GDBN} does software watchpointing by single-stepping your
2877 program and testing the variable's value each time, which is hundreds of
2878 times slower than normal execution. (But this may still be worth it, to
2879 catch errors where you have no clue what part of your program is the
2882 On some systems, such as HP-UX, @sc{gnu}/Linux and most other
2883 x86-based targets, @value{GDBN} includes support for hardware
2884 watchpoints, which do not slow down the running of your program.
2888 @item watch @var{expr}
2889 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
2890 is written into by the program and its value changes.
2893 @item rwatch @var{expr}
2894 Set a watchpoint that will break when the value of @var{expr} is read
2898 @item awatch @var{expr}
2899 Set a watchpoint that will break when @var{expr} is either read from
2900 or written into by the program.
2902 @kindex info watchpoints
2903 @item info watchpoints
2904 This command prints a list of watchpoints, breakpoints, and catchpoints;
2905 it is the same as @code{info break} (@pxref{Set Breaks}).
2908 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
2909 watchpoints execute very quickly, and the debugger reports a change in
2910 value at the exact instruction where the change occurs. If @value{GDBN}
2911 cannot set a hardware watchpoint, it sets a software watchpoint, which
2912 executes more slowly and reports the change in value at the next
2913 @emph{statement}, not the instruction, after the change occurs.
2915 @cindex use only software watchpoints
2916 You can force @value{GDBN} to use only software watchpoints with the
2917 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
2918 zero, @value{GDBN} will never try to use hardware watchpoints, even if
2919 the underlying system supports them. (Note that hardware-assisted
2920 watchpoints that were set @emph{before} setting
2921 @code{can-use-hw-watchpoints} to zero will still use the hardware
2922 mechanism of watching expressiion values.)
2925 @item set can-use-hw-watchpoints
2926 @kindex set can-use-hw-watchpoints
2927 Set whether or not to use hardware watchpoints.
2929 @item show can-use-hw-watchpoints
2930 @kindex show can-use-hw-watchpoints
2931 Show the current mode of using hardware watchpoints.
2934 For remote targets, you can restrict the number of hardware
2935 watchpoints @value{GDBN} will use, see @ref{set remote
2936 hardware-breakpoint-limit}.
2938 When you issue the @code{watch} command, @value{GDBN} reports
2941 Hardware watchpoint @var{num}: @var{expr}
2945 if it was able to set a hardware watchpoint.
2947 Currently, the @code{awatch} and @code{rwatch} commands can only set
2948 hardware watchpoints, because accesses to data that don't change the
2949 value of the watched expression cannot be detected without examining
2950 every instruction as it is being executed, and @value{GDBN} does not do
2951 that currently. If @value{GDBN} finds that it is unable to set a
2952 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
2953 will print a message like this:
2956 Expression cannot be implemented with read/access watchpoint.
2959 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
2960 data type of the watched expression is wider than what a hardware
2961 watchpoint on the target machine can handle. For example, some systems
2962 can only watch regions that are up to 4 bytes wide; on such systems you
2963 cannot set hardware watchpoints for an expression that yields a
2964 double-precision floating-point number (which is typically 8 bytes
2965 wide). As a work-around, it might be possible to break the large region
2966 into a series of smaller ones and watch them with separate watchpoints.
2968 If you set too many hardware watchpoints, @value{GDBN} might be unable
2969 to insert all of them when you resume the execution of your program.
2970 Since the precise number of active watchpoints is unknown until such
2971 time as the program is about to be resumed, @value{GDBN} might not be
2972 able to warn you about this when you set the watchpoints, and the
2973 warning will be printed only when the program is resumed:
2976 Hardware watchpoint @var{num}: Could not insert watchpoint
2980 If this happens, delete or disable some of the watchpoints.
2982 The SPARClite DSU will generate traps when a program accesses some data
2983 or instruction address that is assigned to the debug registers. For the
2984 data addresses, DSU facilitates the @code{watch} command. However the
2985 hardware breakpoint registers can only take two data watchpoints, and
2986 both watchpoints must be the same kind. For example, you can set two
2987 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
2988 @strong{or} two with @code{awatch} commands, but you cannot set one
2989 watchpoint with one command and the other with a different command.
2990 @value{GDBN} will reject the command if you try to mix watchpoints.
2991 Delete or disable unused watchpoint commands before setting new ones.
2993 If you call a function interactively using @code{print} or @code{call},
2994 any watchpoints you have set will be inactive until @value{GDBN} reaches another
2995 kind of breakpoint or the call completes.
2997 @value{GDBN} automatically deletes watchpoints that watch local
2998 (automatic) variables, or expressions that involve such variables, when
2999 they go out of scope, that is, when the execution leaves the block in
3000 which these variables were defined. In particular, when the program
3001 being debugged terminates, @emph{all} local variables go out of scope,
3002 and so only watchpoints that watch global variables remain set. If you
3003 rerun the program, you will need to set all such watchpoints again. One
3004 way of doing that would be to set a code breakpoint at the entry to the
3005 @code{main} function and when it breaks, set all the watchpoints.
3008 @cindex watchpoints and threads
3009 @cindex threads and watchpoints
3010 @emph{Warning:} In multi-thread programs, watchpoints have only limited
3011 usefulness. With the current watchpoint implementation, @value{GDBN}
3012 can only watch the value of an expression @emph{in a single thread}. If
3013 you are confident that the expression can only change due to the current
3014 thread's activity (and if you are also confident that no other thread
3015 can become current), then you can use watchpoints as usual. However,
3016 @value{GDBN} may not notice when a non-current thread's activity changes
3019 @c FIXME: this is almost identical to the previous paragraph.
3020 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
3021 have only limited usefulness. If @value{GDBN} creates a software
3022 watchpoint, it can only watch the value of an expression @emph{in a
3023 single thread}. If you are confident that the expression can only
3024 change due to the current thread's activity (and if you are also
3025 confident that no other thread can become current), then you can use
3026 software watchpoints as usual. However, @value{GDBN} may not notice
3027 when a non-current thread's activity changes the expression. (Hardware
3028 watchpoints, in contrast, watch an expression in all threads.)
3031 @xref{set remote hardware-watchpoint-limit}.
3033 @node Set Catchpoints
3034 @subsection Setting catchpoints
3035 @cindex catchpoints, setting
3036 @cindex exception handlers
3037 @cindex event handling
3039 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3040 kinds of program events, such as C@t{++} exceptions or the loading of a
3041 shared library. Use the @code{catch} command to set a catchpoint.
3045 @item catch @var{event}
3046 Stop when @var{event} occurs. @var{event} can be any of the following:
3049 @cindex stop on C@t{++} exceptions
3050 The throwing of a C@t{++} exception.
3053 The catching of a C@t{++} exception.
3056 @cindex break on fork/exec
3057 A call to @code{exec}. This is currently only available for HP-UX.
3060 A call to @code{fork}. This is currently only available for HP-UX.
3063 A call to @code{vfork}. This is currently only available for HP-UX.
3066 @itemx load @var{libname}
3067 @cindex break on load/unload of shared library
3068 The dynamic loading of any shared library, or the loading of the library
3069 @var{libname}. This is currently only available for HP-UX.
3072 @itemx unload @var{libname}
3073 The unloading of any dynamically loaded shared library, or the unloading
3074 of the library @var{libname}. This is currently only available for HP-UX.
3077 @item tcatch @var{event}
3078 Set a catchpoint that is enabled only for one stop. The catchpoint is
3079 automatically deleted after the first time the event is caught.
3083 Use the @code{info break} command to list the current catchpoints.
3085 There are currently some limitations to C@t{++} exception handling
3086 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3090 If you call a function interactively, @value{GDBN} normally returns
3091 control to you when the function has finished executing. If the call
3092 raises an exception, however, the call may bypass the mechanism that
3093 returns control to you and cause your program either to abort or to
3094 simply continue running until it hits a breakpoint, catches a signal
3095 that @value{GDBN} is listening for, or exits. This is the case even if
3096 you set a catchpoint for the exception; catchpoints on exceptions are
3097 disabled within interactive calls.
3100 You cannot raise an exception interactively.
3103 You cannot install an exception handler interactively.
3106 @cindex raise exceptions
3107 Sometimes @code{catch} is not the best way to debug exception handling:
3108 if you need to know exactly where an exception is raised, it is better to
3109 stop @emph{before} the exception handler is called, since that way you
3110 can see the stack before any unwinding takes place. If you set a
3111 breakpoint in an exception handler instead, it may not be easy to find
3112 out where the exception was raised.
3114 To stop just before an exception handler is called, you need some
3115 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3116 raised by calling a library function named @code{__raise_exception}
3117 which has the following ANSI C interface:
3120 /* @var{addr} is where the exception identifier is stored.
3121 @var{id} is the exception identifier. */
3122 void __raise_exception (void **addr, void *id);
3126 To make the debugger catch all exceptions before any stack
3127 unwinding takes place, set a breakpoint on @code{__raise_exception}
3128 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
3130 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
3131 that depends on the value of @var{id}, you can stop your program when
3132 a specific exception is raised. You can use multiple conditional
3133 breakpoints to stop your program when any of a number of exceptions are
3138 @subsection Deleting breakpoints
3140 @cindex clearing breakpoints, watchpoints, catchpoints
3141 @cindex deleting breakpoints, watchpoints, catchpoints
3142 It is often necessary to eliminate a breakpoint, watchpoint, or
3143 catchpoint once it has done its job and you no longer want your program
3144 to stop there. This is called @dfn{deleting} the breakpoint. A
3145 breakpoint that has been deleted no longer exists; it is forgotten.
3147 With the @code{clear} command you can delete breakpoints according to
3148 where they are in your program. With the @code{delete} command you can
3149 delete individual breakpoints, watchpoints, or catchpoints by specifying
3150 their breakpoint numbers.
3152 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3153 automatically ignores breakpoints on the first instruction to be executed
3154 when you continue execution without changing the execution address.
3159 Delete any breakpoints at the next instruction to be executed in the
3160 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
3161 the innermost frame is selected, this is a good way to delete a
3162 breakpoint where your program just stopped.
3164 @item clear @var{function}
3165 @itemx clear @var{filename}:@var{function}
3166 Delete any breakpoints set at entry to the named @var{function}.
3168 @item clear @var{linenum}
3169 @itemx clear @var{filename}:@var{linenum}
3170 Delete any breakpoints set at or within the code of the specified
3171 @var{linenum} of the specified @var{filename}.
3173 @cindex delete breakpoints
3175 @kindex d @r{(@code{delete})}
3176 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3177 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3178 ranges specified as arguments. If no argument is specified, delete all
3179 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3180 confirm off}). You can abbreviate this command as @code{d}.
3184 @subsection Disabling breakpoints
3186 @cindex enable/disable a breakpoint
3187 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3188 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3189 it had been deleted, but remembers the information on the breakpoint so
3190 that you can @dfn{enable} it again later.
3192 You disable and enable breakpoints, watchpoints, and catchpoints with
3193 the @code{enable} and @code{disable} commands, optionally specifying one
3194 or more breakpoint numbers as arguments. Use @code{info break} or
3195 @code{info watch} to print a list of breakpoints, watchpoints, and
3196 catchpoints if you do not know which numbers to use.
3198 A breakpoint, watchpoint, or catchpoint can have any of four different
3199 states of enablement:
3203 Enabled. The breakpoint stops your program. A breakpoint set
3204 with the @code{break} command starts out in this state.
3206 Disabled. The breakpoint has no effect on your program.
3208 Enabled once. The breakpoint stops your program, but then becomes
3211 Enabled for deletion. The breakpoint stops your program, but
3212 immediately after it does so it is deleted permanently. A breakpoint
3213 set with the @code{tbreak} command starts out in this state.
3216 You can use the following commands to enable or disable breakpoints,
3217 watchpoints, and catchpoints:
3221 @kindex dis @r{(@code{disable})}
3222 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3223 Disable the specified breakpoints---or all breakpoints, if none are
3224 listed. A disabled breakpoint has no effect but is not forgotten. All
3225 options such as ignore-counts, conditions and commands are remembered in
3226 case the breakpoint is enabled again later. You may abbreviate
3227 @code{disable} as @code{dis}.
3230 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3231 Enable the specified breakpoints (or all defined breakpoints). They
3232 become effective once again in stopping your program.
3234 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3235 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3236 of these breakpoints immediately after stopping your program.
3238 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3239 Enable the specified breakpoints to work once, then die. @value{GDBN}
3240 deletes any of these breakpoints as soon as your program stops there.
3241 Breakpoints set by the @code{tbreak} command start out in this state.
3244 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3245 @c confusing: tbreak is also initially enabled.
3246 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3247 ,Setting breakpoints}), breakpoints that you set are initially enabled;
3248 subsequently, they become disabled or enabled only when you use one of
3249 the commands above. (The command @code{until} can set and delete a
3250 breakpoint of its own, but it does not change the state of your other
3251 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3255 @subsection Break conditions
3256 @cindex conditional breakpoints
3257 @cindex breakpoint conditions
3259 @c FIXME what is scope of break condition expr? Context where wanted?
3260 @c in particular for a watchpoint?
3261 The simplest sort of breakpoint breaks every time your program reaches a
3262 specified place. You can also specify a @dfn{condition} for a
3263 breakpoint. A condition is just a Boolean expression in your
3264 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3265 a condition evaluates the expression each time your program reaches it,
3266 and your program stops only if the condition is @emph{true}.
3268 This is the converse of using assertions for program validation; in that
3269 situation, you want to stop when the assertion is violated---that is,
3270 when the condition is false. In C, if you want to test an assertion expressed
3271 by the condition @var{assert}, you should set the condition
3272 @samp{! @var{assert}} on the appropriate breakpoint.
3274 Conditions are also accepted for watchpoints; you may not need them,
3275 since a watchpoint is inspecting the value of an expression anyhow---but
3276 it might be simpler, say, to just set a watchpoint on a variable name,
3277 and specify a condition that tests whether the new value is an interesting
3280 Break conditions can have side effects, and may even call functions in
3281 your program. This can be useful, for example, to activate functions
3282 that log program progress, or to use your own print functions to
3283 format special data structures. The effects are completely predictable
3284 unless there is another enabled breakpoint at the same address. (In
3285 that case, @value{GDBN} might see the other breakpoint first and stop your
3286 program without checking the condition of this one.) Note that
3287 breakpoint commands are usually more convenient and flexible than break
3289 purpose of performing side effects when a breakpoint is reached
3290 (@pxref{Break Commands, ,Breakpoint command lists}).
3292 Break conditions can be specified when a breakpoint is set, by using
3293 @samp{if} in the arguments to the @code{break} command. @xref{Set
3294 Breaks, ,Setting breakpoints}. They can also be changed at any time
3295 with the @code{condition} command.
3297 You can also use the @code{if} keyword with the @code{watch} command.
3298 The @code{catch} command does not recognize the @code{if} keyword;
3299 @code{condition} is the only way to impose a further condition on a
3304 @item condition @var{bnum} @var{expression}
3305 Specify @var{expression} as the break condition for breakpoint,
3306 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3307 breakpoint @var{bnum} stops your program only if the value of
3308 @var{expression} is true (nonzero, in C). When you use
3309 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3310 syntactic correctness, and to determine whether symbols in it have
3311 referents in the context of your breakpoint. If @var{expression} uses
3312 symbols not referenced in the context of the breakpoint, @value{GDBN}
3313 prints an error message:
3316 No symbol "foo" in current context.
3321 not actually evaluate @var{expression} at the time the @code{condition}
3322 command (or a command that sets a breakpoint with a condition, like
3323 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3325 @item condition @var{bnum}
3326 Remove the condition from breakpoint number @var{bnum}. It becomes
3327 an ordinary unconditional breakpoint.
3330 @cindex ignore count (of breakpoint)
3331 A special case of a breakpoint condition is to stop only when the
3332 breakpoint has been reached a certain number of times. This is so
3333 useful that there is a special way to do it, using the @dfn{ignore
3334 count} of the breakpoint. Every breakpoint has an ignore count, which
3335 is an integer. Most of the time, the ignore count is zero, and
3336 therefore has no effect. But if your program reaches a breakpoint whose
3337 ignore count is positive, then instead of stopping, it just decrements
3338 the ignore count by one and continues. As a result, if the ignore count
3339 value is @var{n}, the breakpoint does not stop the next @var{n} times
3340 your program reaches it.
3344 @item ignore @var{bnum} @var{count}
3345 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3346 The next @var{count} times the breakpoint is reached, your program's
3347 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3350 To make the breakpoint stop the next time it is reached, specify
3353 When you use @code{continue} to resume execution of your program from a
3354 breakpoint, you can specify an ignore count directly as an argument to
3355 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3356 Stepping,,Continuing and stepping}.
3358 If a breakpoint has a positive ignore count and a condition, the
3359 condition is not checked. Once the ignore count reaches zero,
3360 @value{GDBN} resumes checking the condition.
3362 You could achieve the effect of the ignore count with a condition such
3363 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3364 is decremented each time. @xref{Convenience Vars, ,Convenience
3368 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3371 @node Break Commands
3372 @subsection Breakpoint command lists
3374 @cindex breakpoint commands
3375 You can give any breakpoint (or watchpoint or catchpoint) a series of
3376 commands to execute when your program stops due to that breakpoint. For
3377 example, you might want to print the values of certain expressions, or
3378 enable other breakpoints.
3383 @item commands @r{[}@var{bnum}@r{]}
3384 @itemx @dots{} @var{command-list} @dots{}
3386 Specify a list of commands for breakpoint number @var{bnum}. The commands
3387 themselves appear on the following lines. Type a line containing just
3388 @code{end} to terminate the commands.
3390 To remove all commands from a breakpoint, type @code{commands} and
3391 follow it immediately with @code{end}; that is, give no commands.
3393 With no @var{bnum} argument, @code{commands} refers to the last
3394 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3395 recently encountered).
3398 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3399 disabled within a @var{command-list}.
3401 You can use breakpoint commands to start your program up again. Simply
3402 use the @code{continue} command, or @code{step}, or any other command
3403 that resumes execution.
3405 Any other commands in the command list, after a command that resumes
3406 execution, are ignored. This is because any time you resume execution
3407 (even with a simple @code{next} or @code{step}), you may encounter
3408 another breakpoint---which could have its own command list, leading to
3409 ambiguities about which list to execute.
3412 If the first command you specify in a command list is @code{silent}, the
3413 usual message about stopping at a breakpoint is not printed. This may
3414 be desirable for breakpoints that are to print a specific message and
3415 then continue. If none of the remaining commands print anything, you
3416 see no sign that the breakpoint was reached. @code{silent} is
3417 meaningful only at the beginning of a breakpoint command list.
3419 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3420 print precisely controlled output, and are often useful in silent
3421 breakpoints. @xref{Output, ,Commands for controlled output}.
3423 For example, here is how you could use breakpoint commands to print the
3424 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3430 printf "x is %d\n",x
3435 One application for breakpoint commands is to compensate for one bug so
3436 you can test for another. Put a breakpoint just after the erroneous line
3437 of code, give it a condition to detect the case in which something
3438 erroneous has been done, and give it commands to assign correct values
3439 to any variables that need them. End with the @code{continue} command
3440 so that your program does not stop, and start with the @code{silent}
3441 command so that no output is produced. Here is an example:
3452 @node Breakpoint Menus
3453 @subsection Breakpoint menus
3455 @cindex symbol overloading
3457 Some programming languages (notably C@t{++} and Objective-C) permit a
3458 single function name
3459 to be defined several times, for application in different contexts.
3460 This is called @dfn{overloading}. When a function name is overloaded,
3461 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3462 a breakpoint. If you realize this is a problem, you can use
3463 something like @samp{break @var{function}(@var{types})} to specify which
3464 particular version of the function you want. Otherwise, @value{GDBN} offers
3465 you a menu of numbered choices for different possible breakpoints, and
3466 waits for your selection with the prompt @samp{>}. The first two
3467 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3468 sets a breakpoint at each definition of @var{function}, and typing
3469 @kbd{0} aborts the @code{break} command without setting any new
3472 For example, the following session excerpt shows an attempt to set a
3473 breakpoint at the overloaded symbol @code{String::after}.
3474 We choose three particular definitions of that function name:
3476 @c FIXME! This is likely to change to show arg type lists, at least
3479 (@value{GDBP}) b String::after
3482 [2] file:String.cc; line number:867
3483 [3] file:String.cc; line number:860
3484 [4] file:String.cc; line number:875
3485 [5] file:String.cc; line number:853
3486 [6] file:String.cc; line number:846
3487 [7] file:String.cc; line number:735
3489 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3490 Breakpoint 2 at 0xb344: file String.cc, line 875.
3491 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3492 Multiple breakpoints were set.
3493 Use the "delete" command to delete unwanted
3499 @c @ifclear BARETARGET
3500 @node Error in Breakpoints
3501 @subsection ``Cannot insert breakpoints''
3503 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3505 Under some operating systems, breakpoints cannot be used in a program if
3506 any other process is running that program. In this situation,
3507 attempting to run or continue a program with a breakpoint causes
3508 @value{GDBN} to print an error message:
3511 Cannot insert breakpoints.
3512 The same program may be running in another process.
3515 When this happens, you have three ways to proceed:
3519 Remove or disable the breakpoints, then continue.
3522 Suspend @value{GDBN}, and copy the file containing your program to a new
3523 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3524 that @value{GDBN} should run your program under that name.
3525 Then start your program again.
3528 Relink your program so that the text segment is nonsharable, using the
3529 linker option @samp{-N}. The operating system limitation may not apply
3530 to nonsharable executables.
3534 A similar message can be printed if you request too many active
3535 hardware-assisted breakpoints and watchpoints:
3537 @c FIXME: the precise wording of this message may change; the relevant
3538 @c source change is not committed yet (Sep 3, 1999).
3540 Stopped; cannot insert breakpoints.
3541 You may have requested too many hardware breakpoints and watchpoints.
3545 This message is printed when you attempt to resume the program, since
3546 only then @value{GDBN} knows exactly how many hardware breakpoints and
3547 watchpoints it needs to insert.
3549 When this message is printed, you need to disable or remove some of the
3550 hardware-assisted breakpoints and watchpoints, and then continue.
3552 @node Breakpoint related warnings
3553 @subsection ``Breakpoint address adjusted...''
3554 @cindex breakpoint address adjusted
3556 Some processor architectures place constraints on the addresses at
3557 which breakpoints may be placed. For architectures thus constrained,
3558 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3559 with the constraints dictated by the architecture.
3561 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3562 a VLIW architecture in which a number of RISC-like instructions may be
3563 bundled together for parallel execution. The FR-V architecture
3564 constrains the location of a breakpoint instruction within such a
3565 bundle to the instruction with the lowest address. @value{GDBN}
3566 honors this constraint by adjusting a breakpoint's address to the
3567 first in the bundle.
3569 It is not uncommon for optimized code to have bundles which contain
3570 instructions from different source statements, thus it may happen that
3571 a breakpoint's address will be adjusted from one source statement to
3572 another. Since this adjustment may significantly alter @value{GDBN}'s
3573 breakpoint related behavior from what the user expects, a warning is
3574 printed when the breakpoint is first set and also when the breakpoint
3577 A warning like the one below is printed when setting a breakpoint
3578 that's been subject to address adjustment:
3581 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3584 Such warnings are printed both for user settable and @value{GDBN}'s
3585 internal breakpoints. If you see one of these warnings, you should
3586 verify that a breakpoint set at the adjusted address will have the
3587 desired affect. If not, the breakpoint in question may be removed and
3588 other breakpoints may be set which will have the desired behavior.
3589 E.g., it may be sufficient to place the breakpoint at a later
3590 instruction. A conditional breakpoint may also be useful in some
3591 cases to prevent the breakpoint from triggering too often.
3593 @value{GDBN} will also issue a warning when stopping at one of these
3594 adjusted breakpoints:
3597 warning: Breakpoint 1 address previously adjusted from 0x00010414
3601 When this warning is encountered, it may be too late to take remedial
3602 action except in cases where the breakpoint is hit earlier or more
3603 frequently than expected.
3605 @node Continuing and Stepping
3606 @section Continuing and stepping
3610 @cindex resuming execution
3611 @dfn{Continuing} means resuming program execution until your program
3612 completes normally. In contrast, @dfn{stepping} means executing just
3613 one more ``step'' of your program, where ``step'' may mean either one
3614 line of source code, or one machine instruction (depending on what
3615 particular command you use). Either when continuing or when stepping,
3616 your program may stop even sooner, due to a breakpoint or a signal. (If
3617 it stops due to a signal, you may want to use @code{handle}, or use
3618 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3622 @kindex c @r{(@code{continue})}
3623 @kindex fg @r{(resume foreground execution)}
3624 @item continue @r{[}@var{ignore-count}@r{]}
3625 @itemx c @r{[}@var{ignore-count}@r{]}
3626 @itemx fg @r{[}@var{ignore-count}@r{]}
3627 Resume program execution, at the address where your program last stopped;
3628 any breakpoints set at that address are bypassed. The optional argument
3629 @var{ignore-count} allows you to specify a further number of times to
3630 ignore a breakpoint at this location; its effect is like that of
3631 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3633 The argument @var{ignore-count} is meaningful only when your program
3634 stopped due to a breakpoint. At other times, the argument to
3635 @code{continue} is ignored.
3637 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3638 debugged program is deemed to be the foreground program) are provided
3639 purely for convenience, and have exactly the same behavior as
3643 To resume execution at a different place, you can use @code{return}
3644 (@pxref{Returning, ,Returning from a function}) to go back to the
3645 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3646 different address}) to go to an arbitrary location in your program.
3648 A typical technique for using stepping is to set a breakpoint
3649 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3650 beginning of the function or the section of your program where a problem
3651 is believed to lie, run your program until it stops at that breakpoint,
3652 and then step through the suspect area, examining the variables that are
3653 interesting, until you see the problem happen.
3657 @kindex s @r{(@code{step})}
3659 Continue running your program until control reaches a different source
3660 line, then stop it and return control to @value{GDBN}. This command is
3661 abbreviated @code{s}.
3664 @c "without debugging information" is imprecise; actually "without line
3665 @c numbers in the debugging information". (gcc -g1 has debugging info but
3666 @c not line numbers). But it seems complex to try to make that
3667 @c distinction here.
3668 @emph{Warning:} If you use the @code{step} command while control is
3669 within a function that was compiled without debugging information,
3670 execution proceeds until control reaches a function that does have
3671 debugging information. Likewise, it will not step into a function which
3672 is compiled without debugging information. To step through functions
3673 without debugging information, use the @code{stepi} command, described
3677 The @code{step} command only stops at the first instruction of a source
3678 line. This prevents the multiple stops that could otherwise occur in
3679 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3680 to stop if a function that has debugging information is called within
3681 the line. In other words, @code{step} @emph{steps inside} any functions
3682 called within the line.
3684 Also, the @code{step} command only enters a function if there is line
3685 number information for the function. Otherwise it acts like the
3686 @code{next} command. This avoids problems when using @code{cc -gl}
3687 on MIPS machines. Previously, @code{step} entered subroutines if there
3688 was any debugging information about the routine.
3690 @item step @var{count}
3691 Continue running as in @code{step}, but do so @var{count} times. If a
3692 breakpoint is reached, or a signal not related to stepping occurs before
3693 @var{count} steps, stepping stops right away.
3696 @kindex n @r{(@code{next})}
3697 @item next @r{[}@var{count}@r{]}
3698 Continue to the next source line in the current (innermost) stack frame.
3699 This is similar to @code{step}, but function calls that appear within
3700 the line of code are executed without stopping. Execution stops when
3701 control reaches a different line of code at the original stack level
3702 that was executing when you gave the @code{next} command. This command
3703 is abbreviated @code{n}.
3705 An argument @var{count} is a repeat count, as for @code{step}.
3708 @c FIX ME!! Do we delete this, or is there a way it fits in with
3709 @c the following paragraph? --- Vctoria
3711 @c @code{next} within a function that lacks debugging information acts like
3712 @c @code{step}, but any function calls appearing within the code of the
3713 @c function are executed without stopping.
3715 The @code{next} command only stops at the first instruction of a
3716 source line. This prevents multiple stops that could otherwise occur in
3717 @code{switch} statements, @code{for} loops, etc.
3719 @kindex set step-mode
3721 @cindex functions without line info, and stepping
3722 @cindex stepping into functions with no line info
3723 @itemx set step-mode on
3724 The @code{set step-mode on} command causes the @code{step} command to
3725 stop at the first instruction of a function which contains no debug line
3726 information rather than stepping over it.
3728 This is useful in cases where you may be interested in inspecting the
3729 machine instructions of a function which has no symbolic info and do not
3730 want @value{GDBN} to automatically skip over this function.
3732 @item set step-mode off
3733 Causes the @code{step} command to step over any functions which contains no
3734 debug information. This is the default.
3736 @item show step-mode
3737 Show whether @value{GDBN} will stop in or step over functions without
3738 source line debug information.
3742 Continue running until just after function in the selected stack frame
3743 returns. Print the returned value (if any).
3745 Contrast this with the @code{return} command (@pxref{Returning,
3746 ,Returning from a function}).
3749 @kindex u @r{(@code{until})}
3750 @cindex run until specified location
3753 Continue running until a source line past the current line, in the
3754 current stack frame, is reached. This command is used to avoid single
3755 stepping through a loop more than once. It is like the @code{next}
3756 command, except that when @code{until} encounters a jump, it
3757 automatically continues execution until the program counter is greater
3758 than the address of the jump.
3760 This means that when you reach the end of a loop after single stepping
3761 though it, @code{until} makes your program continue execution until it
3762 exits the loop. In contrast, a @code{next} command at the end of a loop
3763 simply steps back to the beginning of the loop, which forces you to step
3764 through the next iteration.
3766 @code{until} always stops your program if it attempts to exit the current
3769 @code{until} may produce somewhat counterintuitive results if the order
3770 of machine code does not match the order of the source lines. For
3771 example, in the following excerpt from a debugging session, the @code{f}
3772 (@code{frame}) command shows that execution is stopped at line
3773 @code{206}; yet when we use @code{until}, we get to line @code{195}:
3777 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
3779 (@value{GDBP}) until
3780 195 for ( ; argc > 0; NEXTARG) @{
3783 This happened because, for execution efficiency, the compiler had
3784 generated code for the loop closure test at the end, rather than the
3785 start, of the loop---even though the test in a C @code{for}-loop is
3786 written before the body of the loop. The @code{until} command appeared
3787 to step back to the beginning of the loop when it advanced to this
3788 expression; however, it has not really gone to an earlier
3789 statement---not in terms of the actual machine code.
3791 @code{until} with no argument works by means of single
3792 instruction stepping, and hence is slower than @code{until} with an
3795 @item until @var{location}
3796 @itemx u @var{location}
3797 Continue running your program until either the specified location is
3798 reached, or the current stack frame returns. @var{location} is any of
3799 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
3800 ,Setting breakpoints}). This form of the command uses breakpoints, and
3801 hence is quicker than @code{until} without an argument. The specified
3802 location is actually reached only if it is in the current frame. This
3803 implies that @code{until} can be used to skip over recursive function
3804 invocations. For instance in the code below, if the current location is
3805 line @code{96}, issuing @code{until 99} will execute the program up to
3806 line @code{99} in the same invocation of factorial, i.e. after the inner
3807 invocations have returned.
3810 94 int factorial (int value)
3812 96 if (value > 1) @{
3813 97 value *= factorial (value - 1);
3820 @kindex advance @var{location}
3821 @itemx advance @var{location}
3822 Continue running the program up to the given @var{location}. An argument is
3823 required, which should be of the same form as arguments for the @code{break}
3824 command. Execution will also stop upon exit from the current stack
3825 frame. This command is similar to @code{until}, but @code{advance} will
3826 not skip over recursive function calls, and the target location doesn't
3827 have to be in the same frame as the current one.
3831 @kindex si @r{(@code{stepi})}
3833 @itemx stepi @var{arg}
3835 Execute one machine instruction, then stop and return to the debugger.
3837 It is often useful to do @samp{display/i $pc} when stepping by machine
3838 instructions. This makes @value{GDBN} automatically display the next
3839 instruction to be executed, each time your program stops. @xref{Auto
3840 Display,, Automatic display}.
3842 An argument is a repeat count, as in @code{step}.
3846 @kindex ni @r{(@code{nexti})}
3848 @itemx nexti @var{arg}
3850 Execute one machine instruction, but if it is a function call,
3851 proceed until the function returns.
3853 An argument is a repeat count, as in @code{next}.
3860 A signal is an asynchronous event that can happen in a program. The
3861 operating system defines the possible kinds of signals, and gives each
3862 kind a name and a number. For example, in Unix @code{SIGINT} is the
3863 signal a program gets when you type an interrupt character (often @kbd{C-c});
3864 @code{SIGSEGV} is the signal a program gets from referencing a place in
3865 memory far away from all the areas in use; @code{SIGALRM} occurs when
3866 the alarm clock timer goes off (which happens only if your program has
3867 requested an alarm).
3869 @cindex fatal signals
3870 Some signals, including @code{SIGALRM}, are a normal part of the
3871 functioning of your program. Others, such as @code{SIGSEGV}, indicate
3872 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
3873 program has not specified in advance some other way to handle the signal.
3874 @code{SIGINT} does not indicate an error in your program, but it is normally
3875 fatal so it can carry out the purpose of the interrupt: to kill the program.
3877 @value{GDBN} has the ability to detect any occurrence of a signal in your
3878 program. You can tell @value{GDBN} in advance what to do for each kind of
3881 @cindex handling signals
3882 Normally, @value{GDBN} is set up to let the non-erroneous signals like
3883 @code{SIGALRM} be silently passed to your program
3884 (so as not to interfere with their role in the program's functioning)
3885 but to stop your program immediately whenever an error signal happens.
3886 You can change these settings with the @code{handle} command.
3889 @kindex info signals
3893 Print a table of all the kinds of signals and how @value{GDBN} has been told to
3894 handle each one. You can use this to see the signal numbers of all
3895 the defined types of signals.
3897 @code{info handle} is an alias for @code{info signals}.
3900 @item handle @var{signal} @var{keywords}@dots{}
3901 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
3902 can be the number of a signal or its name (with or without the
3903 @samp{SIG} at the beginning); a list of signal numbers of the form
3904 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
3905 known signals. The @var{keywords} say what change to make.
3909 The keywords allowed by the @code{handle} command can be abbreviated.
3910 Their full names are:
3914 @value{GDBN} should not stop your program when this signal happens. It may
3915 still print a message telling you that the signal has come in.
3918 @value{GDBN} should stop your program when this signal happens. This implies
3919 the @code{print} keyword as well.
3922 @value{GDBN} should print a message when this signal happens.
3925 @value{GDBN} should not mention the occurrence of the signal at all. This
3926 implies the @code{nostop} keyword as well.
3930 @value{GDBN} should allow your program to see this signal; your program
3931 can handle the signal, or else it may terminate if the signal is fatal
3932 and not handled. @code{pass} and @code{noignore} are synonyms.
3936 @value{GDBN} should not allow your program to see this signal.
3937 @code{nopass} and @code{ignore} are synonyms.
3941 When a signal stops your program, the signal is not visible to the
3943 continue. Your program sees the signal then, if @code{pass} is in
3944 effect for the signal in question @emph{at that time}. In other words,
3945 after @value{GDBN} reports a signal, you can use the @code{handle}
3946 command with @code{pass} or @code{nopass} to control whether your
3947 program sees that signal when you continue.
3949 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
3950 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
3951 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
3954 You can also use the @code{signal} command to prevent your program from
3955 seeing a signal, or cause it to see a signal it normally would not see,
3956 or to give it any signal at any time. For example, if your program stopped
3957 due to some sort of memory reference error, you might store correct
3958 values into the erroneous variables and continue, hoping to see more
3959 execution; but your program would probably terminate immediately as
3960 a result of the fatal signal once it saw the signal. To prevent this,
3961 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
3965 @section Stopping and starting multi-thread programs
3967 When your program has multiple threads (@pxref{Threads,, Debugging
3968 programs with multiple threads}), you can choose whether to set
3969 breakpoints on all threads, or on a particular thread.
3972 @cindex breakpoints and threads
3973 @cindex thread breakpoints
3974 @kindex break @dots{} thread @var{threadno}
3975 @item break @var{linespec} thread @var{threadno}
3976 @itemx break @var{linespec} thread @var{threadno} if @dots{}
3977 @var{linespec} specifies source lines; there are several ways of
3978 writing them, but the effect is always to specify some source line.
3980 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
3981 to specify that you only want @value{GDBN} to stop the program when a
3982 particular thread reaches this breakpoint. @var{threadno} is one of the
3983 numeric thread identifiers assigned by @value{GDBN}, shown in the first
3984 column of the @samp{info threads} display.
3986 If you do not specify @samp{thread @var{threadno}} when you set a
3987 breakpoint, the breakpoint applies to @emph{all} threads of your
3990 You can use the @code{thread} qualifier on conditional breakpoints as
3991 well; in this case, place @samp{thread @var{threadno}} before the
3992 breakpoint condition, like this:
3995 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4000 @cindex stopped threads
4001 @cindex threads, stopped
4002 Whenever your program stops under @value{GDBN} for any reason,
4003 @emph{all} threads of execution stop, not just the current thread. This
4004 allows you to examine the overall state of the program, including
4005 switching between threads, without worrying that things may change
4008 @cindex thread breakpoints and system calls
4009 @cindex system calls and thread breakpoints
4010 @cindex premature return from system calls
4011 There is an unfortunate side effect. If one thread stops for a
4012 breakpoint, or for some other reason, and another thread is blocked in a
4013 system call, then the system call may return prematurely. This is a
4014 consequence of the interaction between multiple threads and the signals
4015 that @value{GDBN} uses to implement breakpoints and other events that
4018 To handle this problem, your program should check the return value of
4019 each system call and react appropriately. This is good programming
4022 For example, do not write code like this:
4028 The call to @code{sleep} will return early if a different thread stops
4029 at a breakpoint or for some other reason.
4031 Instead, write this:
4036 unslept = sleep (unslept);
4039 A system call is allowed to return early, so the system is still
4040 conforming to its specification. But @value{GDBN} does cause your
4041 multi-threaded program to behave differently than it would without
4044 Also, @value{GDBN} uses internal breakpoints in the thread library to
4045 monitor certain events such as thread creation and thread destruction.
4046 When such an event happens, a system call in another thread may return
4047 prematurely, even though your program does not appear to stop.
4049 @cindex continuing threads
4050 @cindex threads, continuing
4051 Conversely, whenever you restart the program, @emph{all} threads start
4052 executing. @emph{This is true even when single-stepping} with commands
4053 like @code{step} or @code{next}.
4055 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4056 Since thread scheduling is up to your debugging target's operating
4057 system (not controlled by @value{GDBN}), other threads may
4058 execute more than one statement while the current thread completes a
4059 single step. Moreover, in general other threads stop in the middle of a
4060 statement, rather than at a clean statement boundary, when the program
4063 You might even find your program stopped in another thread after
4064 continuing or even single-stepping. This happens whenever some other
4065 thread runs into a breakpoint, a signal, or an exception before the
4066 first thread completes whatever you requested.
4068 On some OSes, you can lock the OS scheduler and thus allow only a single
4072 @item set scheduler-locking @var{mode}
4073 @cindex scheduler locking mode
4074 @cindex lock scheduler
4075 Set the scheduler locking mode. If it is @code{off}, then there is no
4076 locking and any thread may run at any time. If @code{on}, then only the
4077 current thread may run when the inferior is resumed. The @code{step}
4078 mode optimizes for single-stepping. It stops other threads from
4079 ``seizing the prompt'' by preempting the current thread while you are
4080 stepping. Other threads will only rarely (or never) get a chance to run
4081 when you step. They are more likely to run when you @samp{next} over a
4082 function call, and they are completely free to run when you use commands
4083 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4084 thread hits a breakpoint during its timeslice, they will never steal the
4085 @value{GDBN} prompt away from the thread that you are debugging.
4087 @item show scheduler-locking
4088 Display the current scheduler locking mode.
4093 @chapter Examining the Stack
4095 When your program has stopped, the first thing you need to know is where it
4096 stopped and how it got there.
4099 Each time your program performs a function call, information about the call
4101 That information includes the location of the call in your program,
4102 the arguments of the call,
4103 and the local variables of the function being called.
4104 The information is saved in a block of data called a @dfn{stack frame}.
4105 The stack frames are allocated in a region of memory called the @dfn{call
4108 When your program stops, the @value{GDBN} commands for examining the
4109 stack allow you to see all of this information.
4111 @cindex selected frame
4112 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4113 @value{GDBN} commands refer implicitly to the selected frame. In
4114 particular, whenever you ask @value{GDBN} for the value of a variable in
4115 your program, the value is found in the selected frame. There are
4116 special @value{GDBN} commands to select whichever frame you are
4117 interested in. @xref{Selection, ,Selecting a frame}.
4119 When your program stops, @value{GDBN} automatically selects the
4120 currently executing frame and describes it briefly, similar to the
4121 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
4124 * Frames:: Stack frames
4125 * Backtrace:: Backtraces
4126 * Selection:: Selecting a frame
4127 * Frame Info:: Information on a frame
4132 @section Stack frames
4134 @cindex frame, definition
4136 The call stack is divided up into contiguous pieces called @dfn{stack
4137 frames}, or @dfn{frames} for short; each frame is the data associated
4138 with one call to one function. The frame contains the arguments given
4139 to the function, the function's local variables, and the address at
4140 which the function is executing.
4142 @cindex initial frame
4143 @cindex outermost frame
4144 @cindex innermost frame
4145 When your program is started, the stack has only one frame, that of the
4146 function @code{main}. This is called the @dfn{initial} frame or the
4147 @dfn{outermost} frame. Each time a function is called, a new frame is
4148 made. Each time a function returns, the frame for that function invocation
4149 is eliminated. If a function is recursive, there can be many frames for
4150 the same function. The frame for the function in which execution is
4151 actually occurring is called the @dfn{innermost} frame. This is the most
4152 recently created of all the stack frames that still exist.
4154 @cindex frame pointer
4155 Inside your program, stack frames are identified by their addresses. A
4156 stack frame consists of many bytes, each of which has its own address; each
4157 kind of computer has a convention for choosing one byte whose
4158 address serves as the address of the frame. Usually this address is kept
4159 in a register called the @dfn{frame pointer register}
4160 (@pxref{Registers, $fp}) while execution is going on in that frame.
4162 @cindex frame number
4163 @value{GDBN} assigns numbers to all existing stack frames, starting with
4164 zero for the innermost frame, one for the frame that called it,
4165 and so on upward. These numbers do not really exist in your program;
4166 they are assigned by @value{GDBN} to give you a way of designating stack
4167 frames in @value{GDBN} commands.
4169 @c The -fomit-frame-pointer below perennially causes hbox overflow
4170 @c underflow problems.
4171 @cindex frameless execution
4172 Some compilers provide a way to compile functions so that they operate
4173 without stack frames. (For example, the @value{GCC} option
4175 @samp{-fomit-frame-pointer}
4177 generates functions without a frame.)
4178 This is occasionally done with heavily used library functions to save
4179 the frame setup time. @value{GDBN} has limited facilities for dealing
4180 with these function invocations. If the innermost function invocation
4181 has no stack frame, @value{GDBN} nevertheless regards it as though
4182 it had a separate frame, which is numbered zero as usual, allowing
4183 correct tracing of the function call chain. However, @value{GDBN} has
4184 no provision for frameless functions elsewhere in the stack.
4187 @kindex frame@r{, command}
4188 @cindex current stack frame
4189 @item frame @var{args}
4190 The @code{frame} command allows you to move from one stack frame to another,
4191 and to print the stack frame you select. @var{args} may be either the
4192 address of the frame or the stack frame number. Without an argument,
4193 @code{frame} prints the current stack frame.
4195 @kindex select-frame
4196 @cindex selecting frame silently
4198 The @code{select-frame} command allows you to move from one stack frame
4199 to another without printing the frame. This is the silent version of
4207 @cindex call stack traces
4208 A backtrace is a summary of how your program got where it is. It shows one
4209 line per frame, for many frames, starting with the currently executing
4210 frame (frame zero), followed by its caller (frame one), and on up the
4215 @kindex bt @r{(@code{backtrace})}
4218 Print a backtrace of the entire stack: one line per frame for all
4219 frames in the stack.
4221 You can stop the backtrace at any time by typing the system interrupt
4222 character, normally @kbd{C-c}.
4224 @item backtrace @var{n}
4226 Similar, but print only the innermost @var{n} frames.
4228 @item backtrace -@var{n}
4230 Similar, but print only the outermost @var{n} frames.
4232 @item backtrace full
4233 Print the values of the local variables also.
4239 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4240 are additional aliases for @code{backtrace}.
4242 Each line in the backtrace shows the frame number and the function name.
4243 The program counter value is also shown---unless you use @code{set
4244 print address off}. The backtrace also shows the source file name and
4245 line number, as well as the arguments to the function. The program
4246 counter value is omitted if it is at the beginning of the code for that
4249 Here is an example of a backtrace. It was made with the command
4250 @samp{bt 3}, so it shows the innermost three frames.
4254 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4256 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4257 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4259 (More stack frames follow...)
4264 The display for frame zero does not begin with a program counter
4265 value, indicating that your program has stopped at the beginning of the
4266 code for line @code{993} of @code{builtin.c}.
4268 @cindex value optimized out, in backtrace
4269 @cindex function call arguments, optimized out
4270 If your program was compiled with optimizations, some compilers will
4271 optimize away arguments passed to functions if those arguments are
4272 never used after the call. Such optimizations generate code that
4273 passes arguments through registers, but doesn't store those arguments
4274 in the stack frame. @value{GDBN} has no way of displaying such
4275 arguments in stack frames other than the innermost one. Here's what
4276 such a backtrace might look like:
4280 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4282 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4283 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4285 (More stack frames follow...)
4290 The values of arguments that were not saved in their stack frames are
4291 shown as @samp{<value optimized out>}.
4293 If you need to display the values of such optimized-out arguments,
4294 either deduce that from other variables whose values depend on the one
4295 you are interested in, or recompile without optimizations.
4297 @cindex backtrace beyond @code{main} function
4298 @cindex program entry point
4299 @cindex startup code, and backtrace
4300 Most programs have a standard user entry point---a place where system
4301 libraries and startup code transition into user code. For C this is
4302 @code{main}. When @value{GDBN} finds the entry function in a backtrace
4303 it will terminate the backtrace, to avoid tracing into highly
4304 system-specific (and generally uninteresting) code.
4306 If you need to examine the startup code, or limit the number of levels
4307 in a backtrace, you can change this behavior:
4310 @item set backtrace past-main
4311 @itemx set backtrace past-main on
4312 @kindex set backtrace
4313 Backtraces will continue past the user entry point.
4315 @item set backtrace past-main off
4316 Backtraces will stop when they encounter the user entry point. This is the
4319 @item show backtrace past-main
4320 @kindex show backtrace
4321 Display the current user entry point backtrace policy.
4323 @item set backtrace past-entry
4324 @itemx set backtrace past-entry on
4325 Backtraces will continue past the internal entry point of an application.
4326 This entry point is encoded by the linker when the application is built,
4327 and is likely before the user entry point @code{main} (or equivalent) is called.
4329 @item set backtrace past-entry off
4330 Backtraces will stop when they encouter the internal entry point of an
4331 application. This is the default.
4333 @item show backtrace past-entry
4334 Display the current internal entry point backtrace policy.
4336 @item set backtrace limit @var{n}
4337 @itemx set backtrace limit 0
4338 @cindex backtrace limit
4339 Limit the backtrace to @var{n} levels. A value of zero means
4342 @item show backtrace limit
4343 Display the current limit on backtrace levels.
4347 @section Selecting a frame
4349 Most commands for examining the stack and other data in your program work on
4350 whichever stack frame is selected at the moment. Here are the commands for
4351 selecting a stack frame; all of them finish by printing a brief description
4352 of the stack frame just selected.
4355 @kindex frame@r{, selecting}
4356 @kindex f @r{(@code{frame})}
4359 Select frame number @var{n}. Recall that frame zero is the innermost
4360 (currently executing) frame, frame one is the frame that called the
4361 innermost one, and so on. The highest-numbered frame is the one for
4364 @item frame @var{addr}
4366 Select the frame at address @var{addr}. This is useful mainly if the
4367 chaining of stack frames has been damaged by a bug, making it
4368 impossible for @value{GDBN} to assign numbers properly to all frames. In
4369 addition, this can be useful when your program has multiple stacks and
4370 switches between them.
4372 On the SPARC architecture, @code{frame} needs two addresses to
4373 select an arbitrary frame: a frame pointer and a stack pointer.
4375 On the MIPS and Alpha architecture, it needs two addresses: a stack
4376 pointer and a program counter.
4378 On the 29k architecture, it needs three addresses: a register stack
4379 pointer, a program counter, and a memory stack pointer.
4380 @c note to future updaters: this is conditioned on a flag
4381 @c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date
4382 @c as of 27 Jan 1994.
4386 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4387 advances toward the outermost frame, to higher frame numbers, to frames
4388 that have existed longer. @var{n} defaults to one.
4391 @kindex do @r{(@code{down})}
4393 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4394 advances toward the innermost frame, to lower frame numbers, to frames
4395 that were created more recently. @var{n} defaults to one. You may
4396 abbreviate @code{down} as @code{do}.
4399 All of these commands end by printing two lines of output describing the
4400 frame. The first line shows the frame number, the function name, the
4401 arguments, and the source file and line number of execution in that
4402 frame. The second line shows the text of that source line.
4410 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4412 10 read_input_file (argv[i]);
4416 After such a printout, the @code{list} command with no arguments
4417 prints ten lines centered on the point of execution in the frame.
4418 You can also edit the program at the point of execution with your favorite
4419 editing program by typing @code{edit}.
4420 @xref{List, ,Printing source lines},
4424 @kindex down-silently
4426 @item up-silently @var{n}
4427 @itemx down-silently @var{n}
4428 These two commands are variants of @code{up} and @code{down},
4429 respectively; they differ in that they do their work silently, without
4430 causing display of the new frame. They are intended primarily for use
4431 in @value{GDBN} command scripts, where the output might be unnecessary and
4436 @section Information about a frame
4438 There are several other commands to print information about the selected
4444 When used without any argument, this command does not change which
4445 frame is selected, but prints a brief description of the currently
4446 selected stack frame. It can be abbreviated @code{f}. With an
4447 argument, this command is used to select a stack frame.
4448 @xref{Selection, ,Selecting a frame}.
4451 @kindex info f @r{(@code{info frame})}
4454 This command prints a verbose description of the selected stack frame,
4459 the address of the frame
4461 the address of the next frame down (called by this frame)
4463 the address of the next frame up (caller of this frame)
4465 the language in which the source code corresponding to this frame is written
4467 the address of the frame's arguments
4469 the address of the frame's local variables
4471 the program counter saved in it (the address of execution in the caller frame)
4473 which registers were saved in the frame
4476 @noindent The verbose description is useful when
4477 something has gone wrong that has made the stack format fail to fit
4478 the usual conventions.
4480 @item info frame @var{addr}
4481 @itemx info f @var{addr}
4482 Print a verbose description of the frame at address @var{addr}, without
4483 selecting that frame. The selected frame remains unchanged by this
4484 command. This requires the same kind of address (more than one for some
4485 architectures) that you specify in the @code{frame} command.
4486 @xref{Selection, ,Selecting a frame}.
4490 Print the arguments of the selected frame, each on a separate line.
4494 Print the local variables of the selected frame, each on a separate
4495 line. These are all variables (declared either static or automatic)
4496 accessible at the point of execution of the selected frame.
4499 @cindex catch exceptions, list active handlers
4500 @cindex exception handlers, how to list
4502 Print a list of all the exception handlers that are active in the
4503 current stack frame at the current point of execution. To see other
4504 exception handlers, visit the associated frame (using the @code{up},
4505 @code{down}, or @code{frame} commands); then type @code{info catch}.
4506 @xref{Set Catchpoints, , Setting catchpoints}.
4512 @chapter Examining Source Files
4514 @value{GDBN} can print parts of your program's source, since the debugging
4515 information recorded in the program tells @value{GDBN} what source files were
4516 used to build it. When your program stops, @value{GDBN} spontaneously prints
4517 the line where it stopped. Likewise, when you select a stack frame
4518 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4519 execution in that frame has stopped. You can print other portions of
4520 source files by explicit command.
4522 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4523 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4524 @value{GDBN} under @sc{gnu} Emacs}.
4527 * List:: Printing source lines
4528 * Edit:: Editing source files
4529 * Search:: Searching source files
4530 * Source Path:: Specifying source directories
4531 * Machine Code:: Source and machine code
4535 @section Printing source lines
4538 @kindex l @r{(@code{list})}
4539 To print lines from a source file, use the @code{list} command
4540 (abbreviated @code{l}). By default, ten lines are printed.
4541 There are several ways to specify what part of the file you want to print.
4543 Here are the forms of the @code{list} command most commonly used:
4546 @item list @var{linenum}
4547 Print lines centered around line number @var{linenum} in the
4548 current source file.
4550 @item list @var{function}
4551 Print lines centered around the beginning of function
4555 Print more lines. If the last lines printed were printed with a
4556 @code{list} command, this prints lines following the last lines
4557 printed; however, if the last line printed was a solitary line printed
4558 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4559 Stack}), this prints lines centered around that line.
4562 Print lines just before the lines last printed.
4565 @cindex @code{list}, how many lines to display
4566 By default, @value{GDBN} prints ten source lines with any of these forms of
4567 the @code{list} command. You can change this using @code{set listsize}:
4570 @kindex set listsize
4571 @item set listsize @var{count}
4572 Make the @code{list} command display @var{count} source lines (unless
4573 the @code{list} argument explicitly specifies some other number).
4575 @kindex show listsize
4577 Display the number of lines that @code{list} prints.
4580 Repeating a @code{list} command with @key{RET} discards the argument,
4581 so it is equivalent to typing just @code{list}. This is more useful
4582 than listing the same lines again. An exception is made for an
4583 argument of @samp{-}; that argument is preserved in repetition so that
4584 each repetition moves up in the source file.
4587 In general, the @code{list} command expects you to supply zero, one or two
4588 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4589 of writing them, but the effect is always to specify some source line.
4590 Here is a complete description of the possible arguments for @code{list}:
4593 @item list @var{linespec}
4594 Print lines centered around the line specified by @var{linespec}.
4596 @item list @var{first},@var{last}
4597 Print lines from @var{first} to @var{last}. Both arguments are
4600 @item list ,@var{last}
4601 Print lines ending with @var{last}.
4603 @item list @var{first},
4604 Print lines starting with @var{first}.
4607 Print lines just after the lines last printed.
4610 Print lines just before the lines last printed.
4613 As described in the preceding table.
4616 Here are the ways of specifying a single source line---all the
4621 Specifies line @var{number} of the current source file.
4622 When a @code{list} command has two linespecs, this refers to
4623 the same source file as the first linespec.
4626 Specifies the line @var{offset} lines after the last line printed.
4627 When used as the second linespec in a @code{list} command that has
4628 two, this specifies the line @var{offset} lines down from the
4632 Specifies the line @var{offset} lines before the last line printed.
4634 @item @var{filename}:@var{number}
4635 Specifies line @var{number} in the source file @var{filename}.
4637 @item @var{function}
4638 Specifies the line that begins the body of the function @var{function}.
4639 For example: in C, this is the line with the open brace.
4641 @item @var{filename}:@var{function}
4642 Specifies the line of the open-brace that begins the body of the
4643 function @var{function} in the file @var{filename}. You only need the
4644 file name with a function name to avoid ambiguity when there are
4645 identically named functions in different source files.
4647 @item *@var{address}
4648 Specifies the line containing the program address @var{address}.
4649 @var{address} may be any expression.
4653 @section Editing source files
4654 @cindex editing source files
4657 @kindex e @r{(@code{edit})}
4658 To edit the lines in a source file, use the @code{edit} command.
4659 The editing program of your choice
4660 is invoked with the current line set to
4661 the active line in the program.
4662 Alternatively, there are several ways to specify what part of the file you
4663 want to print if you want to see other parts of the program.
4665 Here are the forms of the @code{edit} command most commonly used:
4669 Edit the current source file at the active line number in the program.
4671 @item edit @var{number}
4672 Edit the current source file with @var{number} as the active line number.
4674 @item edit @var{function}
4675 Edit the file containing @var{function} at the beginning of its definition.
4677 @item edit @var{filename}:@var{number}
4678 Specifies line @var{number} in the source file @var{filename}.
4680 @item edit @var{filename}:@var{function}
4681 Specifies the line that begins the body of the
4682 function @var{function} in the file @var{filename}. You only need the
4683 file name with a function name to avoid ambiguity when there are
4684 identically named functions in different source files.
4686 @item edit *@var{address}
4687 Specifies the line containing the program address @var{address}.
4688 @var{address} may be any expression.
4691 @subsection Choosing your editor
4692 You can customize @value{GDBN} to use any editor you want
4694 The only restriction is that your editor (say @code{ex}), recognizes the
4695 following command-line syntax:
4697 ex +@var{number} file
4699 The optional numeric value +@var{number} specifies the number of the line in
4700 the file where to start editing.}.
4701 By default, it is @file{@value{EDITOR}}, but you can change this
4702 by setting the environment variable @code{EDITOR} before using
4703 @value{GDBN}. For example, to configure @value{GDBN} to use the
4704 @code{vi} editor, you could use these commands with the @code{sh} shell:
4710 or in the @code{csh} shell,
4712 setenv EDITOR /usr/bin/vi
4717 @section Searching source files
4718 @cindex searching source files
4720 There are two commands for searching through the current source file for a
4725 @kindex forward-search
4726 @item forward-search @var{regexp}
4727 @itemx search @var{regexp}
4728 The command @samp{forward-search @var{regexp}} checks each line,
4729 starting with the one following the last line listed, for a match for
4730 @var{regexp}. It lists the line that is found. You can use the
4731 synonym @samp{search @var{regexp}} or abbreviate the command name as
4734 @kindex reverse-search
4735 @item reverse-search @var{regexp}
4736 The command @samp{reverse-search @var{regexp}} checks each line, starting
4737 with the one before the last line listed and going backward, for a match
4738 for @var{regexp}. It lists the line that is found. You can abbreviate
4739 this command as @code{rev}.
4743 @section Specifying source directories
4746 @cindex directories for source files
4747 Executable programs sometimes do not record the directories of the source
4748 files from which they were compiled, just the names. Even when they do,
4749 the directories could be moved between the compilation and your debugging
4750 session. @value{GDBN} has a list of directories to search for source files;
4751 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4752 it tries all the directories in the list, in the order they are present
4753 in the list, until it finds a file with the desired name.
4755 For example, suppose an executable references the file
4756 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
4757 @file{/mnt/cross}. The file is first looked up literally; if this
4758 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
4759 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
4760 message is printed. @value{GDBN} does not look up the parts of the
4761 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
4762 Likewise, the subdirectories of the source path are not searched: if
4763 the source path is @file{/mnt/cross}, and the binary refers to
4764 @file{foo.c}, @value{GDBN} would not find it under
4765 @file{/mnt/cross/usr/src/foo-1.0/lib}.
4767 Plain file names, relative file names with leading directories, file
4768 names containing dots, etc.@: are all treated as described above; for
4769 instance, if the source path is @file{/mnt/cross}, and the source file
4770 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
4771 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
4772 that---@file{/mnt/cross/foo.c}.
4774 Note that the executable search path is @emph{not} used to locate the
4775 source files. Neither is the current working directory, unless it
4776 happens to be in the source path.
4778 Whenever you reset or rearrange the source path, @value{GDBN} clears out
4779 any information it has cached about where source files are found and where
4780 each line is in the file.
4784 When you start @value{GDBN}, its source path includes only @samp{cdir}
4785 and @samp{cwd}, in that order.
4786 To add other directories, use the @code{directory} command.
4789 @item directory @var{dirname} @dots{}
4790 @item dir @var{dirname} @dots{}
4791 Add directory @var{dirname} to the front of the source path. Several
4792 directory names may be given to this command, separated by @samp{:}
4793 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4794 part of absolute file names) or
4795 whitespace. You may specify a directory that is already in the source
4796 path; this moves it forward, so @value{GDBN} searches it sooner.
4800 @vindex $cdir@r{, convenience variable}
4801 @vindex $cwdr@r{, convenience variable}
4802 @cindex compilation directory
4803 @cindex current directory
4804 @cindex working directory
4805 @cindex directory, current
4806 @cindex directory, compilation
4807 You can use the string @samp{$cdir} to refer to the compilation
4808 directory (if one is recorded), and @samp{$cwd} to refer to the current
4809 working directory. @samp{$cwd} is not the same as @samp{.}---the former
4810 tracks the current working directory as it changes during your @value{GDBN}
4811 session, while the latter is immediately expanded to the current
4812 directory at the time you add an entry to the source path.
4815 Reset the source path to empty again. This requires confirmation.
4817 @c RET-repeat for @code{directory} is explicitly disabled, but since
4818 @c repeating it would be a no-op we do not say that. (thanks to RMS)
4820 @item show directories
4821 @kindex show directories
4822 Print the source path: show which directories it contains.
4825 If your source path is cluttered with directories that are no longer of
4826 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4827 versions of source. You can correct the situation as follows:
4831 Use @code{directory} with no argument to reset the source path to empty.
4834 Use @code{directory} with suitable arguments to reinstall the
4835 directories you want in the source path. You can add all the
4836 directories in one command.
4840 @section Source and machine code
4841 @cindex source line and its code address
4843 You can use the command @code{info line} to map source lines to program
4844 addresses (and vice versa), and the command @code{disassemble} to display
4845 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
4846 mode, the @code{info line} command causes the arrow to point to the
4847 line specified. Also, @code{info line} prints addresses in symbolic form as
4852 @item info line @var{linespec}
4853 Print the starting and ending addresses of the compiled code for
4854 source line @var{linespec}. You can specify source lines in any of
4855 the ways understood by the @code{list} command (@pxref{List, ,Printing
4859 For example, we can use @code{info line} to discover the location of
4860 the object code for the first line of function
4861 @code{m4_changequote}:
4863 @c FIXME: I think this example should also show the addresses in
4864 @c symbolic form, as they usually would be displayed.
4866 (@value{GDBP}) info line m4_changequote
4867 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4871 @cindex code address and its source line
4872 We can also inquire (using @code{*@var{addr}} as the form for
4873 @var{linespec}) what source line covers a particular address:
4875 (@value{GDBP}) info line *0x63ff
4876 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4879 @cindex @code{$_} and @code{info line}
4880 @cindex @code{x} command, default address
4881 @kindex x@r{(examine), and} info line
4882 After @code{info line}, the default address for the @code{x} command
4883 is changed to the starting address of the line, so that @samp{x/i} is
4884 sufficient to begin examining the machine code (@pxref{Memory,
4885 ,Examining memory}). Also, this address is saved as the value of the
4886 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4891 @cindex assembly instructions
4892 @cindex instructions, assembly
4893 @cindex machine instructions
4894 @cindex listing machine instructions
4896 This specialized command dumps a range of memory as machine
4897 instructions. The default memory range is the function surrounding the
4898 program counter of the selected frame. A single argument to this
4899 command is a program counter value; @value{GDBN} dumps the function
4900 surrounding this value. Two arguments specify a range of addresses
4901 (first inclusive, second exclusive) to dump.
4904 The following example shows the disassembly of a range of addresses of
4905 HP PA-RISC 2.0 code:
4908 (@value{GDBP}) disas 0x32c4 0x32e4
4909 Dump of assembler code from 0x32c4 to 0x32e4:
4910 0x32c4 <main+204>: addil 0,dp
4911 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
4912 0x32cc <main+212>: ldil 0x3000,r31
4913 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
4914 0x32d4 <main+220>: ldo 0(r31),rp
4915 0x32d8 <main+224>: addil -0x800,dp
4916 0x32dc <main+228>: ldo 0x588(r1),r26
4917 0x32e0 <main+232>: ldil 0x3000,r31
4918 End of assembler dump.
4921 Some architectures have more than one commonly-used set of instruction
4922 mnemonics or other syntax.
4925 @kindex set disassembly-flavor
4926 @cindex Intel disassembly flavor
4927 @cindex AT&T disassembly flavor
4928 @item set disassembly-flavor @var{instruction-set}
4929 Select the instruction set to use when disassembling the
4930 program via the @code{disassemble} or @code{x/i} commands.
4932 Currently this command is only defined for the Intel x86 family. You
4933 can set @var{instruction-set} to either @code{intel} or @code{att}.
4934 The default is @code{att}, the AT&T flavor used by default by Unix
4935 assemblers for x86-based targets.
4937 @kindex show disassembly-flavor
4938 @item show disassembly-flavor
4939 Show the current setting of the disassembly flavor.
4944 @chapter Examining Data
4946 @cindex printing data
4947 @cindex examining data
4950 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
4951 @c document because it is nonstandard... Under Epoch it displays in a
4952 @c different window or something like that.
4953 The usual way to examine data in your program is with the @code{print}
4954 command (abbreviated @code{p}), or its synonym @code{inspect}. It
4955 evaluates and prints the value of an expression of the language your
4956 program is written in (@pxref{Languages, ,Using @value{GDBN} with
4957 Different Languages}).
4960 @item print @var{expr}
4961 @itemx print /@var{f} @var{expr}
4962 @var{expr} is an expression (in the source language). By default the
4963 value of @var{expr} is printed in a format appropriate to its data type;
4964 you can choose a different format by specifying @samp{/@var{f}}, where
4965 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
4969 @itemx print /@var{f}
4970 @cindex reprint the last value
4971 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
4972 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
4973 conveniently inspect the same value in an alternative format.
4976 A more low-level way of examining data is with the @code{x} command.
4977 It examines data in memory at a specified address and prints it in a
4978 specified format. @xref{Memory, ,Examining memory}.
4980 If you are interested in information about types, or about how the
4981 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
4982 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
4986 * Expressions:: Expressions
4987 * Variables:: Program variables
4988 * Arrays:: Artificial arrays
4989 * Output Formats:: Output formats
4990 * Memory:: Examining memory
4991 * Auto Display:: Automatic display
4992 * Print Settings:: Print settings
4993 * Value History:: Value history
4994 * Convenience Vars:: Convenience variables
4995 * Registers:: Registers
4996 * Floating Point Hardware:: Floating point hardware
4997 * Vector Unit:: Vector Unit
4998 * OS Information:: Auxiliary data provided by operating system
4999 * Memory Region Attributes:: Memory region attributes
5000 * Dump/Restore Files:: Copy between memory and a file
5001 * Core File Generation:: Cause a program dump its core
5002 * Character Sets:: Debugging programs that use a different
5003 character set than GDB does
5004 * Caching Remote Data:: Data caching for remote targets
5008 @section Expressions
5011 @code{print} and many other @value{GDBN} commands accept an expression and
5012 compute its value. Any kind of constant, variable or operator defined
5013 by the programming language you are using is valid in an expression in
5014 @value{GDBN}. This includes conditional expressions, function calls,
5015 casts, and string constants. It also includes preprocessor macros, if
5016 you compiled your program to include this information; see
5019 @cindex arrays in expressions
5020 @value{GDBN} supports array constants in expressions input by
5021 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5022 you can use the command @code{print @{1, 2, 3@}} to build up an array in
5023 memory that is @code{malloc}ed in the target program.
5025 Because C is so widespread, most of the expressions shown in examples in
5026 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5027 Languages}, for information on how to use expressions in other
5030 In this section, we discuss operators that you can use in @value{GDBN}
5031 expressions regardless of your programming language.
5033 @cindex casts, in expressions
5034 Casts are supported in all languages, not just in C, because it is so
5035 useful to cast a number into a pointer in order to examine a structure
5036 at that address in memory.
5037 @c FIXME: casts supported---Mod2 true?
5039 @value{GDBN} supports these operators, in addition to those common
5040 to programming languages:
5044 @samp{@@} is a binary operator for treating parts of memory as arrays.
5045 @xref{Arrays, ,Artificial arrays}, for more information.
5048 @samp{::} allows you to specify a variable in terms of the file or
5049 function where it is defined. @xref{Variables, ,Program variables}.
5051 @cindex @{@var{type}@}
5052 @cindex type casting memory
5053 @cindex memory, viewing as typed object
5054 @cindex casts, to view memory
5055 @item @{@var{type}@} @var{addr}
5056 Refers to an object of type @var{type} stored at address @var{addr} in
5057 memory. @var{addr} may be any expression whose value is an integer or
5058 pointer (but parentheses are required around binary operators, just as in
5059 a cast). This construct is allowed regardless of what kind of data is
5060 normally supposed to reside at @var{addr}.
5064 @section Program variables
5066 The most common kind of expression to use is the name of a variable
5069 Variables in expressions are understood in the selected stack frame
5070 (@pxref{Selection, ,Selecting a frame}); they must be either:
5074 global (or file-static)
5081 visible according to the scope rules of the
5082 programming language from the point of execution in that frame
5085 @noindent This means that in the function
5100 you can examine and use the variable @code{a} whenever your program is
5101 executing within the function @code{foo}, but you can only use or
5102 examine the variable @code{b} while your program is executing inside
5103 the block where @code{b} is declared.
5105 @cindex variable name conflict
5106 There is an exception: you can refer to a variable or function whose
5107 scope is a single source file even if the current execution point is not
5108 in this file. But it is possible to have more than one such variable or
5109 function with the same name (in different source files). If that
5110 happens, referring to that name has unpredictable effects. If you wish,
5111 you can specify a static variable in a particular function or file,
5112 using the colon-colon (@code{::}) notation:
5114 @cindex colon-colon, context for variables/functions
5116 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5117 @cindex @code{::}, context for variables/functions
5120 @var{file}::@var{variable}
5121 @var{function}::@var{variable}
5125 Here @var{file} or @var{function} is the name of the context for the
5126 static @var{variable}. In the case of file names, you can use quotes to
5127 make sure @value{GDBN} parses the file name as a single word---for example,
5128 to print a global value of @code{x} defined in @file{f2.c}:
5131 (@value{GDBP}) p 'f2.c'::x
5134 @cindex C@t{++} scope resolution
5135 This use of @samp{::} is very rarely in conflict with the very similar
5136 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5137 scope resolution operator in @value{GDBN} expressions.
5138 @c FIXME: Um, so what happens in one of those rare cases where it's in
5141 @cindex wrong values
5142 @cindex variable values, wrong
5143 @cindex function entry/exit, wrong values of variables
5144 @cindex optimized code, wrong values of variables
5146 @emph{Warning:} Occasionally, a local variable may appear to have the
5147 wrong value at certain points in a function---just after entry to a new
5148 scope, and just before exit.
5150 You may see this problem when you are stepping by machine instructions.
5151 This is because, on most machines, it takes more than one instruction to
5152 set up a stack frame (including local variable definitions); if you are
5153 stepping by machine instructions, variables may appear to have the wrong
5154 values until the stack frame is completely built. On exit, it usually
5155 also takes more than one machine instruction to destroy a stack frame;
5156 after you begin stepping through that group of instructions, local
5157 variable definitions may be gone.
5159 This may also happen when the compiler does significant optimizations.
5160 To be sure of always seeing accurate values, turn off all optimization
5163 @cindex ``No symbol "foo" in current context''
5164 Another possible effect of compiler optimizations is to optimize
5165 unused variables out of existence, or assign variables to registers (as
5166 opposed to memory addresses). Depending on the support for such cases
5167 offered by the debug info format used by the compiler, @value{GDBN}
5168 might not be able to display values for such local variables. If that
5169 happens, @value{GDBN} will print a message like this:
5172 No symbol "foo" in current context.
5175 To solve such problems, either recompile without optimizations, or use a
5176 different debug info format, if the compiler supports several such
5177 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5178 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5179 produces debug info in a format that is superior to formats such as
5180 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5181 an effective form for debug info. @xref{Debugging Options,,Options
5182 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
5183 @xref{C, , Debugging C++}, for more info about debug info formats
5184 that are best suited to C@t{++} programs.
5187 @section Artificial arrays
5189 @cindex artificial array
5191 @kindex @@@r{, referencing memory as an array}
5192 It is often useful to print out several successive objects of the
5193 same type in memory; a section of an array, or an array of
5194 dynamically determined size for which only a pointer exists in the
5197 You can do this by referring to a contiguous span of memory as an
5198 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5199 operand of @samp{@@} should be the first element of the desired array
5200 and be an individual object. The right operand should be the desired length
5201 of the array. The result is an array value whose elements are all of
5202 the type of the left argument. The first element is actually the left
5203 argument; the second element comes from bytes of memory immediately
5204 following those that hold the first element, and so on. Here is an
5205 example. If a program says
5208 int *array = (int *) malloc (len * sizeof (int));
5212 you can print the contents of @code{array} with
5218 The left operand of @samp{@@} must reside in memory. Array values made
5219 with @samp{@@} in this way behave just like other arrays in terms of
5220 subscripting, and are coerced to pointers when used in expressions.
5221 Artificial arrays most often appear in expressions via the value history
5222 (@pxref{Value History, ,Value history}), after printing one out.
5224 Another way to create an artificial array is to use a cast.
5225 This re-interprets a value as if it were an array.
5226 The value need not be in memory:
5228 (@value{GDBP}) p/x (short[2])0x12345678
5229 $1 = @{0x1234, 0x5678@}
5232 As a convenience, if you leave the array length out (as in
5233 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5234 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5236 (@value{GDBP}) p/x (short[])0x12345678
5237 $2 = @{0x1234, 0x5678@}
5240 Sometimes the artificial array mechanism is not quite enough; in
5241 moderately complex data structures, the elements of interest may not
5242 actually be adjacent---for example, if you are interested in the values
5243 of pointers in an array. One useful work-around in this situation is
5244 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5245 variables}) as a counter in an expression that prints the first
5246 interesting value, and then repeat that expression via @key{RET}. For
5247 instance, suppose you have an array @code{dtab} of pointers to
5248 structures, and you are interested in the values of a field @code{fv}
5249 in each structure. Here is an example of what you might type:
5259 @node Output Formats
5260 @section Output formats
5262 @cindex formatted output
5263 @cindex output formats
5264 By default, @value{GDBN} prints a value according to its data type. Sometimes
5265 this is not what you want. For example, you might want to print a number
5266 in hex, or a pointer in decimal. Or you might want to view data in memory
5267 at a certain address as a character string or as an instruction. To do
5268 these things, specify an @dfn{output format} when you print a value.
5270 The simplest use of output formats is to say how to print a value
5271 already computed. This is done by starting the arguments of the
5272 @code{print} command with a slash and a format letter. The format
5273 letters supported are:
5277 Regard the bits of the value as an integer, and print the integer in
5281 Print as integer in signed decimal.
5284 Print as integer in unsigned decimal.
5287 Print as integer in octal.
5290 Print as integer in binary. The letter @samp{t} stands for ``two''.
5291 @footnote{@samp{b} cannot be used because these format letters are also
5292 used with the @code{x} command, where @samp{b} stands for ``byte'';
5293 see @ref{Memory,,Examining memory}.}
5296 @cindex unknown address, locating
5297 @cindex locate address
5298 Print as an address, both absolute in hexadecimal and as an offset from
5299 the nearest preceding symbol. You can use this format used to discover
5300 where (in what function) an unknown address is located:
5303 (@value{GDBP}) p/a 0x54320
5304 $3 = 0x54320 <_initialize_vx+396>
5308 The command @code{info symbol 0x54320} yields similar results.
5309 @xref{Symbols, info symbol}.
5312 Regard as an integer and print it as a character constant.
5315 Regard the bits of the value as a floating point number and print
5316 using typical floating point syntax.
5319 For example, to print the program counter in hex (@pxref{Registers}), type
5326 Note that no space is required before the slash; this is because command
5327 names in @value{GDBN} cannot contain a slash.
5329 To reprint the last value in the value history with a different format,
5330 you can use the @code{print} command with just a format and no
5331 expression. For example, @samp{p/x} reprints the last value in hex.
5334 @section Examining memory
5336 You can use the command @code{x} (for ``examine'') to examine memory in
5337 any of several formats, independently of your program's data types.
5339 @cindex examining memory
5341 @kindex x @r{(examine memory)}
5342 @item x/@var{nfu} @var{addr}
5345 Use the @code{x} command to examine memory.
5348 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5349 much memory to display and how to format it; @var{addr} is an
5350 expression giving the address where you want to start displaying memory.
5351 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5352 Several commands set convenient defaults for @var{addr}.
5355 @item @var{n}, the repeat count
5356 The repeat count is a decimal integer; the default is 1. It specifies
5357 how much memory (counting by units @var{u}) to display.
5358 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5361 @item @var{f}, the display format
5362 The display format is one of the formats used by @code{print},
5363 @samp{s} (null-terminated string), or @samp{i} (machine instruction).
5364 The default is @samp{x} (hexadecimal) initially.
5365 The default changes each time you use either @code{x} or @code{print}.
5367 @item @var{u}, the unit size
5368 The unit size is any of
5374 Halfwords (two bytes).
5376 Words (four bytes). This is the initial default.
5378 Giant words (eight bytes).
5381 Each time you specify a unit size with @code{x}, that size becomes the
5382 default unit the next time you use @code{x}. (For the @samp{s} and
5383 @samp{i} formats, the unit size is ignored and is normally not written.)
5385 @item @var{addr}, starting display address
5386 @var{addr} is the address where you want @value{GDBN} to begin displaying
5387 memory. The expression need not have a pointer value (though it may);
5388 it is always interpreted as an integer address of a byte of memory.
5389 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5390 @var{addr} is usually just after the last address examined---but several
5391 other commands also set the default address: @code{info breakpoints} (to
5392 the address of the last breakpoint listed), @code{info line} (to the
5393 starting address of a line), and @code{print} (if you use it to display
5394 a value from memory).
5397 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5398 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5399 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5400 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5401 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5403 Since the letters indicating unit sizes are all distinct from the
5404 letters specifying output formats, you do not have to remember whether
5405 unit size or format comes first; either order works. The output
5406 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5407 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5409 Even though the unit size @var{u} is ignored for the formats @samp{s}
5410 and @samp{i}, you might still want to use a count @var{n}; for example,
5411 @samp{3i} specifies that you want to see three machine instructions,
5412 including any operands. The command @code{disassemble} gives an
5413 alternative way of inspecting machine instructions; see @ref{Machine
5414 Code,,Source and machine code}.
5416 All the defaults for the arguments to @code{x} are designed to make it
5417 easy to continue scanning memory with minimal specifications each time
5418 you use @code{x}. For example, after you have inspected three machine
5419 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5420 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5421 the repeat count @var{n} is used again; the other arguments default as
5422 for successive uses of @code{x}.
5424 @cindex @code{$_}, @code{$__}, and value history
5425 The addresses and contents printed by the @code{x} command are not saved
5426 in the value history because there is often too much of them and they
5427 would get in the way. Instead, @value{GDBN} makes these values available for
5428 subsequent use in expressions as values of the convenience variables
5429 @code{$_} and @code{$__}. After an @code{x} command, the last address
5430 examined is available for use in expressions in the convenience variable
5431 @code{$_}. The contents of that address, as examined, are available in
5432 the convenience variable @code{$__}.
5434 If the @code{x} command has a repeat count, the address and contents saved
5435 are from the last memory unit printed; this is not the same as the last
5436 address printed if several units were printed on the last line of output.
5438 @cindex remote memory comparison
5439 @cindex verify remote memory image
5440 When you are debugging a program running on a remote target machine
5441 (@pxref{Remote}), you may wish to verify the program's image in the
5442 remote machine's memory against the executable file you downloaded to
5443 the target. The @code{compare-sections} command is provided for such
5447 @kindex compare-sections
5448 @item compare-sections @r{[}@var{section-name}@r{]}
5449 Compare the data of a loadable section @var{section-name} in the
5450 executable file of the program being debugged with the same section in
5451 the remote machine's memory, and report any mismatches. With no
5452 arguments, compares all loadable sections. This command's
5453 availability depends on the target's support for the @code{"qCRC"}
5458 @section Automatic display
5459 @cindex automatic display
5460 @cindex display of expressions
5462 If you find that you want to print the value of an expression frequently
5463 (to see how it changes), you might want to add it to the @dfn{automatic
5464 display list} so that @value{GDBN} prints its value each time your program stops.
5465 Each expression added to the list is given a number to identify it;
5466 to remove an expression from the list, you specify that number.
5467 The automatic display looks like this:
5471 3: bar[5] = (struct hack *) 0x3804
5475 This display shows item numbers, expressions and their current values. As with
5476 displays you request manually using @code{x} or @code{print}, you can
5477 specify the output format you prefer; in fact, @code{display} decides
5478 whether to use @code{print} or @code{x} depending on how elaborate your
5479 format specification is---it uses @code{x} if you specify a unit size,
5480 or one of the two formats (@samp{i} and @samp{s}) that are only
5481 supported by @code{x}; otherwise it uses @code{print}.
5485 @item display @var{expr}
5486 Add the expression @var{expr} to the list of expressions to display
5487 each time your program stops. @xref{Expressions, ,Expressions}.
5489 @code{display} does not repeat if you press @key{RET} again after using it.
5491 @item display/@var{fmt} @var{expr}
5492 For @var{fmt} specifying only a display format and not a size or
5493 count, add the expression @var{expr} to the auto-display list but
5494 arrange to display it each time in the specified format @var{fmt}.
5495 @xref{Output Formats,,Output formats}.
5497 @item display/@var{fmt} @var{addr}
5498 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5499 number of units, add the expression @var{addr} as a memory address to
5500 be examined each time your program stops. Examining means in effect
5501 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5504 For example, @samp{display/i $pc} can be helpful, to see the machine
5505 instruction about to be executed each time execution stops (@samp{$pc}
5506 is a common name for the program counter; @pxref{Registers, ,Registers}).
5509 @kindex delete display
5511 @item undisplay @var{dnums}@dots{}
5512 @itemx delete display @var{dnums}@dots{}
5513 Remove item numbers @var{dnums} from the list of expressions to display.
5515 @code{undisplay} does not repeat if you press @key{RET} after using it.
5516 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5518 @kindex disable display
5519 @item disable display @var{dnums}@dots{}
5520 Disable the display of item numbers @var{dnums}. A disabled display
5521 item is not printed automatically, but is not forgotten. It may be
5522 enabled again later.
5524 @kindex enable display
5525 @item enable display @var{dnums}@dots{}
5526 Enable display of item numbers @var{dnums}. It becomes effective once
5527 again in auto display of its expression, until you specify otherwise.
5530 Display the current values of the expressions on the list, just as is
5531 done when your program stops.
5533 @kindex info display
5535 Print the list of expressions previously set up to display
5536 automatically, each one with its item number, but without showing the
5537 values. This includes disabled expressions, which are marked as such.
5538 It also includes expressions which would not be displayed right now
5539 because they refer to automatic variables not currently available.
5542 @cindex display disabled out of scope
5543 If a display expression refers to local variables, then it does not make
5544 sense outside the lexical context for which it was set up. Such an
5545 expression is disabled when execution enters a context where one of its
5546 variables is not defined. For example, if you give the command
5547 @code{display last_char} while inside a function with an argument
5548 @code{last_char}, @value{GDBN} displays this argument while your program
5549 continues to stop inside that function. When it stops elsewhere---where
5550 there is no variable @code{last_char}---the display is disabled
5551 automatically. The next time your program stops where @code{last_char}
5552 is meaningful, you can enable the display expression once again.
5554 @node Print Settings
5555 @section Print settings
5557 @cindex format options
5558 @cindex print settings
5559 @value{GDBN} provides the following ways to control how arrays, structures,
5560 and symbols are printed.
5563 These settings are useful for debugging programs in any language:
5567 @item set print address
5568 @itemx set print address on
5569 @cindex print/don't print memory addresses
5570 @value{GDBN} prints memory addresses showing the location of stack
5571 traces, structure values, pointer values, breakpoints, and so forth,
5572 even when it also displays the contents of those addresses. The default
5573 is @code{on}. For example, this is what a stack frame display looks like with
5574 @code{set print address on}:
5579 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5581 530 if (lquote != def_lquote)
5585 @item set print address off
5586 Do not print addresses when displaying their contents. For example,
5587 this is the same stack frame displayed with @code{set print address off}:
5591 (@value{GDBP}) set print addr off
5593 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5594 530 if (lquote != def_lquote)
5598 You can use @samp{set print address off} to eliminate all machine
5599 dependent displays from the @value{GDBN} interface. For example, with
5600 @code{print address off}, you should get the same text for backtraces on
5601 all machines---whether or not they involve pointer arguments.
5604 @item show print address
5605 Show whether or not addresses are to be printed.
5608 When @value{GDBN} prints a symbolic address, it normally prints the
5609 closest earlier symbol plus an offset. If that symbol does not uniquely
5610 identify the address (for example, it is a name whose scope is a single
5611 source file), you may need to clarify. One way to do this is with
5612 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5613 you can set @value{GDBN} to print the source file and line number when
5614 it prints a symbolic address:
5617 @item set print symbol-filename on
5618 @cindex source file and line of a symbol
5619 @cindex symbol, source file and line
5620 Tell @value{GDBN} to print the source file name and line number of a
5621 symbol in the symbolic form of an address.
5623 @item set print symbol-filename off
5624 Do not print source file name and line number of a symbol. This is the
5627 @item show print symbol-filename
5628 Show whether or not @value{GDBN} will print the source file name and
5629 line number of a symbol in the symbolic form of an address.
5632 Another situation where it is helpful to show symbol filenames and line
5633 numbers is when disassembling code; @value{GDBN} shows you the line
5634 number and source file that corresponds to each instruction.
5636 Also, you may wish to see the symbolic form only if the address being
5637 printed is reasonably close to the closest earlier symbol:
5640 @item set print max-symbolic-offset @var{max-offset}
5641 @cindex maximum value for offset of closest symbol
5642 Tell @value{GDBN} to only display the symbolic form of an address if the
5643 offset between the closest earlier symbol and the address is less than
5644 @var{max-offset}. The default is 0, which tells @value{GDBN}
5645 to always print the symbolic form of an address if any symbol precedes it.
5647 @item show print max-symbolic-offset
5648 Ask how large the maximum offset is that @value{GDBN} prints in a
5652 @cindex wild pointer, interpreting
5653 @cindex pointer, finding referent
5654 If you have a pointer and you are not sure where it points, try
5655 @samp{set print symbol-filename on}. Then you can determine the name
5656 and source file location of the variable where it points, using
5657 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5658 For example, here @value{GDBN} shows that a variable @code{ptt} points
5659 at another variable @code{t}, defined in @file{hi2.c}:
5662 (@value{GDBP}) set print symbol-filename on
5663 (@value{GDBP}) p/a ptt
5664 $4 = 0xe008 <t in hi2.c>
5668 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5669 does not show the symbol name and filename of the referent, even with
5670 the appropriate @code{set print} options turned on.
5673 Other settings control how different kinds of objects are printed:
5676 @item set print array
5677 @itemx set print array on
5678 @cindex pretty print arrays
5679 Pretty print arrays. This format is more convenient to read,
5680 but uses more space. The default is off.
5682 @item set print array off
5683 Return to compressed format for arrays.
5685 @item show print array
5686 Show whether compressed or pretty format is selected for displaying
5689 @item set print elements @var{number-of-elements}
5690 @cindex number of array elements to print
5691 @cindex limit on number of printed array elements
5692 Set a limit on how many elements of an array @value{GDBN} will print.
5693 If @value{GDBN} is printing a large array, it stops printing after it has
5694 printed the number of elements set by the @code{set print elements} command.
5695 This limit also applies to the display of strings.
5696 When @value{GDBN} starts, this limit is set to 200.
5697 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5699 @item show print elements
5700 Display the number of elements of a large array that @value{GDBN} will print.
5701 If the number is 0, then the printing is unlimited.
5703 @item set print repeats
5704 @cindex repeated array elements
5705 Set the threshold for suppressing display of repeated array
5706 elelments. When the number of consecutive identical elements of an
5707 array exceeds the threshold, @value{GDBN} prints the string
5708 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
5709 identical repetitions, instead of displaying the identical elements
5710 themselves. Setting the threshold to zero will cause all elements to
5711 be individually printed. The default threshold is 10.
5713 @item show print repeats
5714 Display the current threshold for printing repeated identical
5717 @item set print null-stop
5718 @cindex @sc{null} elements in arrays
5719 Cause @value{GDBN} to stop printing the characters of an array when the first
5720 @sc{null} is encountered. This is useful when large arrays actually
5721 contain only short strings.
5724 @item show print null-stop
5725 Show whether @value{GDBN} stops printing an array on the first
5726 @sc{null} character.
5728 @item set print pretty on
5729 @cindex print structures in indented form
5730 @cindex indentation in structure display
5731 Cause @value{GDBN} to print structures in an indented format with one member
5732 per line, like this:
5747 @item set print pretty off
5748 Cause @value{GDBN} to print structures in a compact format, like this:
5752 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5753 meat = 0x54 "Pork"@}
5758 This is the default format.
5760 @item show print pretty
5761 Show which format @value{GDBN} is using to print structures.
5763 @item set print sevenbit-strings on
5764 @cindex eight-bit characters in strings
5765 @cindex octal escapes in strings
5766 Print using only seven-bit characters; if this option is set,
5767 @value{GDBN} displays any eight-bit characters (in strings or
5768 character values) using the notation @code{\}@var{nnn}. This setting is
5769 best if you are working in English (@sc{ascii}) and you use the
5770 high-order bit of characters as a marker or ``meta'' bit.
5772 @item set print sevenbit-strings off
5773 Print full eight-bit characters. This allows the use of more
5774 international character sets, and is the default.
5776 @item show print sevenbit-strings
5777 Show whether or not @value{GDBN} is printing only seven-bit characters.
5779 @item set print union on
5780 @cindex unions in structures, printing
5781 Tell @value{GDBN} to print unions which are contained in structures
5782 and other unions. This is the default setting.
5784 @item set print union off
5785 Tell @value{GDBN} not to print unions which are contained in
5786 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
5789 @item show print union
5790 Ask @value{GDBN} whether or not it will print unions which are contained in
5791 structures and other unions.
5793 For example, given the declarations
5796 typedef enum @{Tree, Bug@} Species;
5797 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5798 typedef enum @{Caterpillar, Cocoon, Butterfly@}
5809 struct thing foo = @{Tree, @{Acorn@}@};
5813 with @code{set print union on} in effect @samp{p foo} would print
5816 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5820 and with @code{set print union off} in effect it would print
5823 $1 = @{it = Tree, form = @{...@}@}
5827 @code{set print union} affects programs written in C-like languages
5833 These settings are of interest when debugging C@t{++} programs:
5836 @cindex demangling C@t{++} names
5837 @item set print demangle
5838 @itemx set print demangle on
5839 Print C@t{++} names in their source form rather than in the encoded
5840 (``mangled'') form passed to the assembler and linker for type-safe
5841 linkage. The default is on.
5843 @item show print demangle
5844 Show whether C@t{++} names are printed in mangled or demangled form.
5846 @item set print asm-demangle
5847 @itemx set print asm-demangle on
5848 Print C@t{++} names in their source form rather than their mangled form, even
5849 in assembler code printouts such as instruction disassemblies.
5852 @item show print asm-demangle
5853 Show whether C@t{++} names in assembly listings are printed in mangled
5856 @cindex C@t{++} symbol decoding style
5857 @cindex symbol decoding style, C@t{++}
5858 @kindex set demangle-style
5859 @item set demangle-style @var{style}
5860 Choose among several encoding schemes used by different compilers to
5861 represent C@t{++} names. The choices for @var{style} are currently:
5865 Allow @value{GDBN} to choose a decoding style by inspecting your program.
5868 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
5869 This is the default.
5872 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
5875 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
5878 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
5879 @strong{Warning:} this setting alone is not sufficient to allow
5880 debugging @code{cfront}-generated executables. @value{GDBN} would
5881 require further enhancement to permit that.
5884 If you omit @var{style}, you will see a list of possible formats.
5886 @item show demangle-style
5887 Display the encoding style currently in use for decoding C@t{++} symbols.
5889 @item set print object
5890 @itemx set print object on
5891 @cindex derived type of an object, printing
5892 @cindex display derived types
5893 When displaying a pointer to an object, identify the @emph{actual}
5894 (derived) type of the object rather than the @emph{declared} type, using
5895 the virtual function table.
5897 @item set print object off
5898 Display only the declared type of objects, without reference to the
5899 virtual function table. This is the default setting.
5901 @item show print object
5902 Show whether actual, or declared, object types are displayed.
5904 @item set print static-members
5905 @itemx set print static-members on
5906 @cindex static members of C@t{++} objects
5907 Print static members when displaying a C@t{++} object. The default is on.
5909 @item set print static-members off
5910 Do not print static members when displaying a C@t{++} object.
5912 @item show print static-members
5913 Show whether C@t{++} static members are printed or not.
5915 @item set print pascal_static-members
5916 @itemx set print pascal_static-members on
5917 @cindex static members of Pacal objects
5918 @cindex Pacal objects, static members display
5919 Print static members when displaying a Pascal object. The default is on.
5921 @item set print pascal_static-members off
5922 Do not print static members when displaying a Pascal object.
5924 @item show print pascal_static-members
5925 Show whether Pascal static members are printed or not.
5927 @c These don't work with HP ANSI C++ yet.
5928 @item set print vtbl
5929 @itemx set print vtbl on
5930 @cindex pretty print C@t{++} virtual function tables
5931 @cindex virtual functions (C@t{++}) display
5932 @cindex VTBL display
5933 Pretty print C@t{++} virtual function tables. The default is off.
5934 (The @code{vtbl} commands do not work on programs compiled with the HP
5935 ANSI C@t{++} compiler (@code{aCC}).)
5937 @item set print vtbl off
5938 Do not pretty print C@t{++} virtual function tables.
5940 @item show print vtbl
5941 Show whether C@t{++} virtual function tables are pretty printed, or not.
5945 @section Value history
5947 @cindex value history
5948 @cindex history of values printed by @value{GDBN}
5949 Values printed by the @code{print} command are saved in the @value{GDBN}
5950 @dfn{value history}. This allows you to refer to them in other expressions.
5951 Values are kept until the symbol table is re-read or discarded
5952 (for example with the @code{file} or @code{symbol-file} commands).
5953 When the symbol table changes, the value history is discarded,
5954 since the values may contain pointers back to the types defined in the
5959 @cindex history number
5960 The values printed are given @dfn{history numbers} by which you can
5961 refer to them. These are successive integers starting with one.
5962 @code{print} shows you the history number assigned to a value by
5963 printing @samp{$@var{num} = } before the value; here @var{num} is the
5966 To refer to any previous value, use @samp{$} followed by the value's
5967 history number. The way @code{print} labels its output is designed to
5968 remind you of this. Just @code{$} refers to the most recent value in
5969 the history, and @code{$$} refers to the value before that.
5970 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
5971 is the value just prior to @code{$$}, @code{$$1} is equivalent to
5972 @code{$$}, and @code{$$0} is equivalent to @code{$}.
5974 For example, suppose you have just printed a pointer to a structure and
5975 want to see the contents of the structure. It suffices to type
5981 If you have a chain of structures where the component @code{next} points
5982 to the next one, you can print the contents of the next one with this:
5989 You can print successive links in the chain by repeating this
5990 command---which you can do by just typing @key{RET}.
5992 Note that the history records values, not expressions. If the value of
5993 @code{x} is 4 and you type these commands:
6001 then the value recorded in the value history by the @code{print} command
6002 remains 4 even though the value of @code{x} has changed.
6007 Print the last ten values in the value history, with their item numbers.
6008 This is like @samp{p@ $$9} repeated ten times, except that @code{show
6009 values} does not change the history.
6011 @item show values @var{n}
6012 Print ten history values centered on history item number @var{n}.
6015 Print ten history values just after the values last printed. If no more
6016 values are available, @code{show values +} produces no display.
6019 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
6020 same effect as @samp{show values +}.
6022 @node Convenience Vars
6023 @section Convenience variables
6025 @cindex convenience variables
6026 @cindex user-defined variables
6027 @value{GDBN} provides @dfn{convenience variables} that you can use within
6028 @value{GDBN} to hold on to a value and refer to it later. These variables
6029 exist entirely within @value{GDBN}; they are not part of your program, and
6030 setting a convenience variable has no direct effect on further execution
6031 of your program. That is why you can use them freely.
6033 Convenience variables are prefixed with @samp{$}. Any name preceded by
6034 @samp{$} can be used for a convenience variable, unless it is one of
6035 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
6036 (Value history references, in contrast, are @emph{numbers} preceded
6037 by @samp{$}. @xref{Value History, ,Value history}.)
6039 You can save a value in a convenience variable with an assignment
6040 expression, just as you would set a variable in your program.
6044 set $foo = *object_ptr
6048 would save in @code{$foo} the value contained in the object pointed to by
6051 Using a convenience variable for the first time creates it, but its
6052 value is @code{void} until you assign a new value. You can alter the
6053 value with another assignment at any time.
6055 Convenience variables have no fixed types. You can assign a convenience
6056 variable any type of value, including structures and arrays, even if
6057 that variable already has a value of a different type. The convenience
6058 variable, when used as an expression, has the type of its current value.
6061 @kindex show convenience
6062 @cindex show all user variables
6063 @item show convenience
6064 Print a list of convenience variables used so far, and their values.
6065 Abbreviated @code{show conv}.
6068 One of the ways to use a convenience variable is as a counter to be
6069 incremented or a pointer to be advanced. For example, to print
6070 a field from successive elements of an array of structures:
6074 print bar[$i++]->contents
6078 Repeat that command by typing @key{RET}.
6080 Some convenience variables are created automatically by @value{GDBN} and given
6081 values likely to be useful.
6084 @vindex $_@r{, convenience variable}
6086 The variable @code{$_} is automatically set by the @code{x} command to
6087 the last address examined (@pxref{Memory, ,Examining memory}). Other
6088 commands which provide a default address for @code{x} to examine also
6089 set @code{$_} to that address; these commands include @code{info line}
6090 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
6091 except when set by the @code{x} command, in which case it is a pointer
6092 to the type of @code{$__}.
6094 @vindex $__@r{, convenience variable}
6096 The variable @code{$__} is automatically set by the @code{x} command
6097 to the value found in the last address examined. Its type is chosen
6098 to match the format in which the data was printed.
6101 @vindex $_exitcode@r{, convenience variable}
6102 The variable @code{$_exitcode} is automatically set to the exit code when
6103 the program being debugged terminates.
6106 On HP-UX systems, if you refer to a function or variable name that
6107 begins with a dollar sign, @value{GDBN} searches for a user or system
6108 name first, before it searches for a convenience variable.
6114 You can refer to machine register contents, in expressions, as variables
6115 with names starting with @samp{$}. The names of registers are different
6116 for each machine; use @code{info registers} to see the names used on
6120 @kindex info registers
6121 @item info registers
6122 Print the names and values of all registers except floating-point
6123 and vector registers (in the selected stack frame).
6125 @kindex info all-registers
6126 @cindex floating point registers
6127 @item info all-registers
6128 Print the names and values of all registers, including floating-point
6129 and vector registers (in the selected stack frame).
6131 @item info registers @var{regname} @dots{}
6132 Print the @dfn{relativized} value of each specified register @var{regname}.
6133 As discussed in detail below, register values are normally relative to
6134 the selected stack frame. @var{regname} may be any register name valid on
6135 the machine you are using, with or without the initial @samp{$}.
6138 @cindex stack pointer register
6139 @cindex program counter register
6140 @cindex process status register
6141 @cindex frame pointer register
6142 @cindex standard registers
6143 @value{GDBN} has four ``standard'' register names that are available (in
6144 expressions) on most machines---whenever they do not conflict with an
6145 architecture's canonical mnemonics for registers. The register names
6146 @code{$pc} and @code{$sp} are used for the program counter register and
6147 the stack pointer. @code{$fp} is used for a register that contains a
6148 pointer to the current stack frame, and @code{$ps} is used for a
6149 register that contains the processor status. For example,
6150 you could print the program counter in hex with
6157 or print the instruction to be executed next with
6164 or add four to the stack pointer@footnote{This is a way of removing
6165 one word from the stack, on machines where stacks grow downward in
6166 memory (most machines, nowadays). This assumes that the innermost
6167 stack frame is selected; setting @code{$sp} is not allowed when other
6168 stack frames are selected. To pop entire frames off the stack,
6169 regardless of machine architecture, use @code{return};
6170 see @ref{Returning, ,Returning from a function}.} with
6176 Whenever possible, these four standard register names are available on
6177 your machine even though the machine has different canonical mnemonics,
6178 so long as there is no conflict. The @code{info registers} command
6179 shows the canonical names. For example, on the SPARC, @code{info
6180 registers} displays the processor status register as @code{$psr} but you
6181 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6182 is an alias for the @sc{eflags} register.
6184 @value{GDBN} always considers the contents of an ordinary register as an
6185 integer when the register is examined in this way. Some machines have
6186 special registers which can hold nothing but floating point; these
6187 registers are considered to have floating point values. There is no way
6188 to refer to the contents of an ordinary register as floating point value
6189 (although you can @emph{print} it as a floating point value with
6190 @samp{print/f $@var{regname}}).
6192 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6193 means that the data format in which the register contents are saved by
6194 the operating system is not the same one that your program normally
6195 sees. For example, the registers of the 68881 floating point
6196 coprocessor are always saved in ``extended'' (raw) format, but all C
6197 programs expect to work with ``double'' (virtual) format. In such
6198 cases, @value{GDBN} normally works with the virtual format only (the format
6199 that makes sense for your program), but the @code{info registers} command
6200 prints the data in both formats.
6202 Normally, register values are relative to the selected stack frame
6203 (@pxref{Selection, ,Selecting a frame}). This means that you get the
6204 value that the register would contain if all stack frames farther in
6205 were exited and their saved registers restored. In order to see the
6206 true contents of hardware registers, you must select the innermost
6207 frame (with @samp{frame 0}).
6209 However, @value{GDBN} must deduce where registers are saved, from the machine
6210 code generated by your compiler. If some registers are not saved, or if
6211 @value{GDBN} is unable to locate the saved registers, the selected stack
6212 frame makes no difference.
6214 @node Floating Point Hardware
6215 @section Floating point hardware
6216 @cindex floating point
6218 Depending on the configuration, @value{GDBN} may be able to give
6219 you more information about the status of the floating point hardware.
6224 Display hardware-dependent information about the floating
6225 point unit. The exact contents and layout vary depending on the
6226 floating point chip. Currently, @samp{info float} is supported on
6227 the ARM and x86 machines.
6231 @section Vector Unit
6234 Depending on the configuration, @value{GDBN} may be able to give you
6235 more information about the status of the vector unit.
6240 Display information about the vector unit. The exact contents and
6241 layout vary depending on the hardware.
6244 @node OS Information
6245 @section Operating system auxiliary information
6246 @cindex OS information
6248 @value{GDBN} provides interfaces to useful OS facilities that can help
6249 you debug your program.
6251 @cindex @code{ptrace} system call
6252 @cindex @code{struct user} contents
6253 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
6254 machines), it interfaces with the inferior via the @code{ptrace}
6255 system call. The operating system creates a special sata structure,
6256 called @code{struct user}, for this interface. You can use the
6257 command @code{info udot} to display the contents of this data
6263 Display the contents of the @code{struct user} maintained by the OS
6264 kernel for the program being debugged. @value{GDBN} displays the
6265 contents of @code{struct user} as a list of hex numbers, similar to
6266 the @code{examine} command.
6269 @cindex auxiliary vector
6270 @cindex vector, auxiliary
6271 Some operating systems supply an @dfn{auxiliary vector} to programs at
6272 startup. This is akin to the arguments and environment that you
6273 specify for a program, but contains a system-dependent variety of
6274 binary values that tell system libraries important details about the
6275 hardware, operating system, and process. Each value's purpose is
6276 identified by an integer tag; the meanings are well-known but system-specific.
6277 Depending on the configuration and operating system facilities,
6278 @value{GDBN} may be able to show you this information. For remote
6279 targets, this functionality may further depend on the remote stub's
6280 support of the @samp{qPart:auxv:read} packet, see @ref{Remote
6281 configuration, auxiliary vector}.
6286 Display the auxiliary vector of the inferior, which can be either a
6287 live process or a core dump file. @value{GDBN} prints each tag value
6288 numerically, and also shows names and text descriptions for recognized
6289 tags. Some values in the vector are numbers, some bit masks, and some
6290 pointers to strings or other data. @value{GDBN} displays each value in the
6291 most appropriate form for a recognized tag, and in hexadecimal for
6292 an unrecognized tag.
6296 @node Memory Region Attributes
6297 @section Memory region attributes
6298 @cindex memory region attributes
6300 @dfn{Memory region attributes} allow you to describe special handling
6301 required by regions of your target's memory. @value{GDBN} uses attributes
6302 to determine whether to allow certain types of memory accesses; whether to
6303 use specific width accesses; and whether to cache target memory.
6305 Defined memory regions can be individually enabled and disabled. When a
6306 memory region is disabled, @value{GDBN} uses the default attributes when
6307 accessing memory in that region. Similarly, if no memory regions have
6308 been defined, @value{GDBN} uses the default attributes when accessing
6311 When a memory region is defined, it is given a number to identify it;
6312 to enable, disable, or remove a memory region, you specify that number.
6316 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6317 Define a memory region bounded by @var{lower} and @var{upper} with
6318 attributes @var{attributes}@dots{}, and add it to the list of regions
6319 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
6320 case: it is treated as the the target's maximum memory address.
6321 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6324 @item delete mem @var{nums}@dots{}
6325 Remove memory regions @var{nums}@dots{} from the list of regions
6326 monitored by @value{GDBN}.
6329 @item disable mem @var{nums}@dots{}
6330 Disable monitoring of memory regions @var{nums}@dots{}.
6331 A disabled memory region is not forgotten.
6332 It may be enabled again later.
6335 @item enable mem @var{nums}@dots{}
6336 Enable monitoring of memory regions @var{nums}@dots{}.
6340 Print a table of all defined memory regions, with the following columns
6344 @item Memory Region Number
6345 @item Enabled or Disabled.
6346 Enabled memory regions are marked with @samp{y}.
6347 Disabled memory regions are marked with @samp{n}.
6350 The address defining the inclusive lower bound of the memory region.
6353 The address defining the exclusive upper bound of the memory region.
6356 The list of attributes set for this memory region.
6361 @subsection Attributes
6363 @subsubsection Memory Access Mode
6364 The access mode attributes set whether @value{GDBN} may make read or
6365 write accesses to a memory region.
6367 While these attributes prevent @value{GDBN} from performing invalid
6368 memory accesses, they do nothing to prevent the target system, I/O DMA,
6369 etc. from accessing memory.
6373 Memory is read only.
6375 Memory is write only.
6377 Memory is read/write. This is the default.
6380 @subsubsection Memory Access Size
6381 The acccess size attributes tells @value{GDBN} to use specific sized
6382 accesses in the memory region. Often memory mapped device registers
6383 require specific sized accesses. If no access size attribute is
6384 specified, @value{GDBN} may use accesses of any size.
6388 Use 8 bit memory accesses.
6390 Use 16 bit memory accesses.
6392 Use 32 bit memory accesses.
6394 Use 64 bit memory accesses.
6397 @c @subsubsection Hardware/Software Breakpoints
6398 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6399 @c will use hardware or software breakpoints for the internal breakpoints
6400 @c used by the step, next, finish, until, etc. commands.
6404 @c Always use hardware breakpoints
6405 @c @item swbreak (default)
6408 @subsubsection Data Cache
6409 The data cache attributes set whether @value{GDBN} will cache target
6410 memory. While this generally improves performance by reducing debug
6411 protocol overhead, it can lead to incorrect results because @value{GDBN}
6412 does not know about volatile variables or memory mapped device
6417 Enable @value{GDBN} to cache target memory.
6419 Disable @value{GDBN} from caching target memory. This is the default.
6422 @c @subsubsection Memory Write Verification
6423 @c The memory write verification attributes set whether @value{GDBN}
6424 @c will re-reads data after each write to verify the write was successful.
6428 @c @item noverify (default)
6431 @node Dump/Restore Files
6432 @section Copy between memory and a file
6433 @cindex dump/restore files
6434 @cindex append data to a file
6435 @cindex dump data to a file
6436 @cindex restore data from a file
6438 You can use the commands @code{dump}, @code{append}, and
6439 @code{restore} to copy data between target memory and a file. The
6440 @code{dump} and @code{append} commands write data to a file, and the
6441 @code{restore} command reads data from a file back into the inferior's
6442 memory. Files may be in binary, Motorola S-record, Intel hex, or
6443 Tektronix Hex format; however, @value{GDBN} can only append to binary
6449 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6450 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6451 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6452 or the value of @var{expr}, to @var{filename} in the given format.
6454 The @var{format} parameter may be any one of:
6461 Motorola S-record format.
6463 Tektronix Hex format.
6466 @value{GDBN} uses the same definitions of these formats as the
6467 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
6468 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
6472 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6473 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
6474 Append the contents of memory from @var{start_addr} to @var{end_addr},
6475 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
6476 (@value{GDBN} can only append data to files in raw binary form.)
6479 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
6480 Restore the contents of file @var{filename} into memory. The
6481 @code{restore} command can automatically recognize any known @sc{bfd}
6482 file format, except for raw binary. To restore a raw binary file you
6483 must specify the optional keyword @code{binary} after the filename.
6485 If @var{bias} is non-zero, its value will be added to the addresses
6486 contained in the file. Binary files always start at address zero, so
6487 they will be restored at address @var{bias}. Other bfd files have
6488 a built-in location; they will be restored at offset @var{bias}
6491 If @var{start} and/or @var{end} are non-zero, then only data between
6492 file offset @var{start} and file offset @var{end} will be restored.
6493 These offsets are relative to the addresses in the file, before
6494 the @var{bias} argument is applied.
6498 @node Core File Generation
6499 @section How to Produce a Core File from Your Program
6500 @cindex dump core from inferior
6502 A @dfn{core file} or @dfn{core dump} is a file that records the memory
6503 image of a running process and its process status (register values
6504 etc.). Its primary use is post-mortem debugging of a program that
6505 crashed while it ran outside a debugger. A program that crashes
6506 automatically produces a core file, unless this feature is disabled by
6507 the user. @xref{Files}, for information on invoking @value{GDBN} in
6508 the post-mortem debugging mode.
6510 Occasionally, you may wish to produce a core file of the program you
6511 are debugging in order to preserve a snapshot of its state.
6512 @value{GDBN} has a special command for that.
6516 @kindex generate-core-file
6517 @item generate-core-file [@var{file}]
6518 @itemx gcore [@var{file}]
6519 Produce a core dump of the inferior process. The optional argument
6520 @var{file} specifies the file name where to put the core dump. If not
6521 specified, the file name defaults to @file{core.@var{pid}}, where
6522 @var{pid} is the inferior process ID.
6524 Note that this command is implemented only for some systems (as of
6525 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
6528 @node Character Sets
6529 @section Character Sets
6530 @cindex character sets
6532 @cindex translating between character sets
6533 @cindex host character set
6534 @cindex target character set
6536 If the program you are debugging uses a different character set to
6537 represent characters and strings than the one @value{GDBN} uses itself,
6538 @value{GDBN} can automatically translate between the character sets for
6539 you. The character set @value{GDBN} uses we call the @dfn{host
6540 character set}; the one the inferior program uses we call the
6541 @dfn{target character set}.
6543 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
6544 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
6545 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
6546 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
6547 then the host character set is Latin-1, and the target character set is
6548 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
6549 target-charset EBCDIC-US}, then @value{GDBN} translates between
6550 @sc{ebcdic} and Latin 1 as you print character or string values, or use
6551 character and string literals in expressions.
6553 @value{GDBN} has no way to automatically recognize which character set
6554 the inferior program uses; you must tell it, using the @code{set
6555 target-charset} command, described below.
6557 Here are the commands for controlling @value{GDBN}'s character set
6561 @item set target-charset @var{charset}
6562 @kindex set target-charset
6563 Set the current target character set to @var{charset}. We list the
6564 character set names @value{GDBN} recognizes below, but if you type
6565 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6566 list the target character sets it supports.
6570 @item set host-charset @var{charset}
6571 @kindex set host-charset
6572 Set the current host character set to @var{charset}.
6574 By default, @value{GDBN} uses a host character set appropriate to the
6575 system it is running on; you can override that default using the
6576 @code{set host-charset} command.
6578 @value{GDBN} can only use certain character sets as its host character
6579 set. We list the character set names @value{GDBN} recognizes below, and
6580 indicate which can be host character sets, but if you type
6581 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6582 list the host character sets it supports.
6584 @item set charset @var{charset}
6586 Set the current host and target character sets to @var{charset}. As
6587 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
6588 @value{GDBN} will list the name of the character sets that can be used
6589 for both host and target.
6593 @kindex show charset
6594 Show the names of the current host and target charsets.
6596 @itemx show host-charset
6597 @kindex show host-charset
6598 Show the name of the current host charset.
6600 @itemx show target-charset
6601 @kindex show target-charset
6602 Show the name of the current target charset.
6606 @value{GDBN} currently includes support for the following character
6612 @cindex ASCII character set
6613 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6617 @cindex ISO 8859-1 character set
6618 @cindex ISO Latin 1 character set
6619 The ISO Latin 1 character set. This extends @sc{ascii} with accented
6620 characters needed for French, German, and Spanish. @value{GDBN} can use
6621 this as its host character set.
6625 @cindex EBCDIC character set
6626 @cindex IBM1047 character set
6627 Variants of the @sc{ebcdic} character set, used on some of IBM's
6628 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6629 @value{GDBN} cannot use these as its host character set.
6633 Note that these are all single-byte character sets. More work inside
6634 GDB is needed to support multi-byte or variable-width character
6635 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6637 Here is an example of @value{GDBN}'s character set support in action.
6638 Assume that the following source code has been placed in the file
6639 @file{charset-test.c}:
6645 = @{72, 101, 108, 108, 111, 44, 32, 119,
6646 111, 114, 108, 100, 33, 10, 0@};
6647 char ibm1047_hello[]
6648 = @{200, 133, 147, 147, 150, 107, 64, 166,
6649 150, 153, 147, 132, 90, 37, 0@};
6653 printf ("Hello, world!\n");
6657 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6658 containing the string @samp{Hello, world!} followed by a newline,
6659 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6661 We compile the program, and invoke the debugger on it:
6664 $ gcc -g charset-test.c -o charset-test
6665 $ gdb -nw charset-test
6666 GNU gdb 2001-12-19-cvs
6667 Copyright 2001 Free Software Foundation, Inc.
6672 We can use the @code{show charset} command to see what character sets
6673 @value{GDBN} is currently using to interpret and display characters and
6677 (@value{GDBP}) show charset
6678 The current host and target character set is `ISO-8859-1'.
6682 For the sake of printing this manual, let's use @sc{ascii} as our
6683 initial character set:
6685 (@value{GDBP}) set charset ASCII
6686 (@value{GDBP}) show charset
6687 The current host and target character set is `ASCII'.
6691 Let's assume that @sc{ascii} is indeed the correct character set for our
6692 host system --- in other words, let's assume that if @value{GDBN} prints
6693 characters using the @sc{ascii} character set, our terminal will display
6694 them properly. Since our current target character set is also
6695 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
6698 (@value{GDBP}) print ascii_hello
6699 $1 = 0x401698 "Hello, world!\n"
6700 (@value{GDBP}) print ascii_hello[0]
6705 @value{GDBN} uses the target character set for character and string
6706 literals you use in expressions:
6709 (@value{GDBP}) print '+'
6714 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
6717 @value{GDBN} relies on the user to tell it which character set the
6718 target program uses. If we print @code{ibm1047_hello} while our target
6719 character set is still @sc{ascii}, we get jibberish:
6722 (@value{GDBP}) print ibm1047_hello
6723 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
6724 (@value{GDBP}) print ibm1047_hello[0]
6729 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
6730 @value{GDBN} tells us the character sets it supports:
6733 (@value{GDBP}) set target-charset
6734 ASCII EBCDIC-US IBM1047 ISO-8859-1
6735 (@value{GDBP}) set target-charset
6738 We can select @sc{ibm1047} as our target character set, and examine the
6739 program's strings again. Now the @sc{ascii} string is wrong, but
6740 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
6741 target character set, @sc{ibm1047}, to the host character set,
6742 @sc{ascii}, and they display correctly:
6745 (@value{GDBP}) set target-charset IBM1047
6746 (@value{GDBP}) show charset
6747 The current host character set is `ASCII'.
6748 The current target character set is `IBM1047'.
6749 (@value{GDBP}) print ascii_hello
6750 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
6751 (@value{GDBP}) print ascii_hello[0]
6753 (@value{GDBP}) print ibm1047_hello
6754 $8 = 0x4016a8 "Hello, world!\n"
6755 (@value{GDBP}) print ibm1047_hello[0]
6760 As above, @value{GDBN} uses the target character set for character and
6761 string literals you use in expressions:
6764 (@value{GDBP}) print '+'
6769 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
6772 @node Caching Remote Data
6773 @section Caching Data of Remote Targets
6774 @cindex caching data of remote targets
6776 @value{GDBN} can cache data exchanged between the debugger and a
6777 remote target (@pxref{Remote}). Such caching generally improves
6778 performance, because it reduces the overhead of the remote protocol by
6779 bundling memory reads and writes into large chunks. Unfortunately,
6780 @value{GDBN} does not currently know anything about volatile
6781 registers, and thus data caching will produce incorrect results when
6782 volatile registers are in use.
6785 @kindex set remotecache
6786 @item set remotecache on
6787 @itemx set remotecache off
6788 Set caching state for remote targets. When @code{ON}, use data
6789 caching. By default, this option is @code{OFF}.
6791 @kindex show remotecache
6792 @item show remotecache
6793 Show the current state of data caching for remote targets.
6797 Print the information about the data cache performance. The
6798 information displayed includes: the dcache width and depth; and for
6799 each cache line, how many times it was referenced, and its data and
6800 state (dirty, bad, ok, etc.). This command is useful for debugging
6801 the data cache operation.
6806 @chapter C Preprocessor Macros
6808 Some languages, such as C and C@t{++}, provide a way to define and invoke
6809 ``preprocessor macros'' which expand into strings of tokens.
6810 @value{GDBN} can evaluate expressions containing macro invocations, show
6811 the result of macro expansion, and show a macro's definition, including
6812 where it was defined.
6814 You may need to compile your program specially to provide @value{GDBN}
6815 with information about preprocessor macros. Most compilers do not
6816 include macros in their debugging information, even when you compile
6817 with the @option{-g} flag. @xref{Compilation}.
6819 A program may define a macro at one point, remove that definition later,
6820 and then provide a different definition after that. Thus, at different
6821 points in the program, a macro may have different definitions, or have
6822 no definition at all. If there is a current stack frame, @value{GDBN}
6823 uses the macros in scope at that frame's source code line. Otherwise,
6824 @value{GDBN} uses the macros in scope at the current listing location;
6827 At the moment, @value{GDBN} does not support the @code{##}
6828 token-splicing operator, the @code{#} stringification operator, or
6829 variable-arity macros.
6831 Whenever @value{GDBN} evaluates an expression, it always expands any
6832 macro invocations present in the expression. @value{GDBN} also provides
6833 the following commands for working with macros explicitly.
6837 @kindex macro expand
6838 @cindex macro expansion, showing the results of preprocessor
6839 @cindex preprocessor macro expansion, showing the results of
6840 @cindex expanding preprocessor macros
6841 @item macro expand @var{expression}
6842 @itemx macro exp @var{expression}
6843 Show the results of expanding all preprocessor macro invocations in
6844 @var{expression}. Since @value{GDBN} simply expands macros, but does
6845 not parse the result, @var{expression} need not be a valid expression;
6846 it can be any string of tokens.
6849 @item macro expand-once @var{expression}
6850 @itemx macro exp1 @var{expression}
6851 @cindex expand macro once
6852 @i{(This command is not yet implemented.)} Show the results of
6853 expanding those preprocessor macro invocations that appear explicitly in
6854 @var{expression}. Macro invocations appearing in that expansion are
6855 left unchanged. This command allows you to see the effect of a
6856 particular macro more clearly, without being confused by further
6857 expansions. Since @value{GDBN} simply expands macros, but does not
6858 parse the result, @var{expression} need not be a valid expression; it
6859 can be any string of tokens.
6862 @cindex macro definition, showing
6863 @cindex definition, showing a macro's
6864 @item info macro @var{macro}
6865 Show the definition of the macro named @var{macro}, and describe the
6866 source location where that definition was established.
6868 @kindex macro define
6869 @cindex user-defined macros
6870 @cindex defining macros interactively
6871 @cindex macros, user-defined
6872 @item macro define @var{macro} @var{replacement-list}
6873 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
6874 @i{(This command is not yet implemented.)} Introduce a definition for a
6875 preprocessor macro named @var{macro}, invocations of which are replaced
6876 by the tokens given in @var{replacement-list}. The first form of this
6877 command defines an ``object-like'' macro, which takes no arguments; the
6878 second form defines a ``function-like'' macro, which takes the arguments
6879 given in @var{arglist}.
6881 A definition introduced by this command is in scope in every expression
6882 evaluated in @value{GDBN}, until it is removed with the @command{macro
6883 undef} command, described below. The definition overrides all
6884 definitions for @var{macro} present in the program being debugged, as
6885 well as any previous user-supplied definition.
6888 @item macro undef @var{macro}
6889 @i{(This command is not yet implemented.)} Remove any user-supplied
6890 definition for the macro named @var{macro}. This command only affects
6891 definitions provided with the @command{macro define} command, described
6892 above; it cannot remove definitions present in the program being
6897 @i{(This command is not yet implemented.)} List all the macros
6898 defined using the @code{macro define} command.
6901 @cindex macros, example of debugging with
6902 Here is a transcript showing the above commands in action. First, we
6903 show our source files:
6911 #define ADD(x) (M + x)
6916 printf ("Hello, world!\n");
6918 printf ("We're so creative.\n");
6920 printf ("Goodbye, world!\n");
6927 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
6928 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
6929 compiler includes information about preprocessor macros in the debugging
6933 $ gcc -gdwarf-2 -g3 sample.c -o sample
6937 Now, we start @value{GDBN} on our sample program:
6941 GNU gdb 2002-05-06-cvs
6942 Copyright 2002 Free Software Foundation, Inc.
6943 GDB is free software, @dots{}
6947 We can expand macros and examine their definitions, even when the
6948 program is not running. @value{GDBN} uses the current listing position
6949 to decide which macro definitions are in scope:
6952 (@value{GDBP}) list main
6955 5 #define ADD(x) (M + x)
6960 10 printf ("Hello, world!\n");
6962 12 printf ("We're so creative.\n");
6963 (@value{GDBP}) info macro ADD
6964 Defined at /home/jimb/gdb/macros/play/sample.c:5
6965 #define ADD(x) (M + x)
6966 (@value{GDBP}) info macro Q
6967 Defined at /home/jimb/gdb/macros/play/sample.h:1
6968 included at /home/jimb/gdb/macros/play/sample.c:2
6970 (@value{GDBP}) macro expand ADD(1)
6971 expands to: (42 + 1)
6972 (@value{GDBP}) macro expand-once ADD(1)
6973 expands to: once (M + 1)
6977 In the example above, note that @command{macro expand-once} expands only
6978 the macro invocation explicit in the original text --- the invocation of
6979 @code{ADD} --- but does not expand the invocation of the macro @code{M},
6980 which was introduced by @code{ADD}.
6982 Once the program is running, GDB uses the macro definitions in force at
6983 the source line of the current stack frame:
6986 (@value{GDBP}) break main
6987 Breakpoint 1 at 0x8048370: file sample.c, line 10.
6989 Starting program: /home/jimb/gdb/macros/play/sample
6991 Breakpoint 1, main () at sample.c:10
6992 10 printf ("Hello, world!\n");
6996 At line 10, the definition of the macro @code{N} at line 9 is in force:
6999 (@value{GDBP}) info macro N
7000 Defined at /home/jimb/gdb/macros/play/sample.c:9
7002 (@value{GDBP}) macro expand N Q M
7004 (@value{GDBP}) print N Q M
7009 As we step over directives that remove @code{N}'s definition, and then
7010 give it a new definition, @value{GDBN} finds the definition (or lack
7011 thereof) in force at each point:
7016 12 printf ("We're so creative.\n");
7017 (@value{GDBP}) info macro N
7018 The symbol `N' has no definition as a C/C++ preprocessor macro
7019 at /home/jimb/gdb/macros/play/sample.c:12
7022 14 printf ("Goodbye, world!\n");
7023 (@value{GDBP}) info macro N
7024 Defined at /home/jimb/gdb/macros/play/sample.c:13
7026 (@value{GDBP}) macro expand N Q M
7027 expands to: 1729 < 42
7028 (@value{GDBP}) print N Q M
7035 @chapter Tracepoints
7036 @c This chapter is based on the documentation written by Michael
7037 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
7040 In some applications, it is not feasible for the debugger to interrupt
7041 the program's execution long enough for the developer to learn
7042 anything helpful about its behavior. If the program's correctness
7043 depends on its real-time behavior, delays introduced by a debugger
7044 might cause the program to change its behavior drastically, or perhaps
7045 fail, even when the code itself is correct. It is useful to be able
7046 to observe the program's behavior without interrupting it.
7048 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
7049 specify locations in the program, called @dfn{tracepoints}, and
7050 arbitrary expressions to evaluate when those tracepoints are reached.
7051 Later, using the @code{tfind} command, you can examine the values
7052 those expressions had when the program hit the tracepoints. The
7053 expressions may also denote objects in memory---structures or arrays,
7054 for example---whose values @value{GDBN} should record; while visiting
7055 a particular tracepoint, you may inspect those objects as if they were
7056 in memory at that moment. However, because @value{GDBN} records these
7057 values without interacting with you, it can do so quickly and
7058 unobtrusively, hopefully not disturbing the program's behavior.
7060 The tracepoint facility is currently available only for remote
7061 targets. @xref{Targets}. In addition, your remote target must know how
7062 to collect trace data. This functionality is implemented in the remote
7063 stub; however, none of the stubs distributed with @value{GDBN} support
7064 tracepoints as of this writing.
7066 This chapter describes the tracepoint commands and features.
7070 * Analyze Collected Data::
7071 * Tracepoint Variables::
7074 @node Set Tracepoints
7075 @section Commands to Set Tracepoints
7077 Before running such a @dfn{trace experiment}, an arbitrary number of
7078 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
7079 tracepoint has a number assigned to it by @value{GDBN}. Like with
7080 breakpoints, tracepoint numbers are successive integers starting from
7081 one. Many of the commands associated with tracepoints take the
7082 tracepoint number as their argument, to identify which tracepoint to
7085 For each tracepoint, you can specify, in advance, some arbitrary set
7086 of data that you want the target to collect in the trace buffer when
7087 it hits that tracepoint. The collected data can include registers,
7088 local variables, or global data. Later, you can use @value{GDBN}
7089 commands to examine the values these data had at the time the
7092 This section describes commands to set tracepoints and associated
7093 conditions and actions.
7096 * Create and Delete Tracepoints::
7097 * Enable and Disable Tracepoints::
7098 * Tracepoint Passcounts::
7099 * Tracepoint Actions::
7100 * Listing Tracepoints::
7101 * Starting and Stopping Trace Experiment::
7104 @node Create and Delete Tracepoints
7105 @subsection Create and Delete Tracepoints
7108 @cindex set tracepoint
7111 The @code{trace} command is very similar to the @code{break} command.
7112 Its argument can be a source line, a function name, or an address in
7113 the target program. @xref{Set Breaks}. The @code{trace} command
7114 defines a tracepoint, which is a point in the target program where the
7115 debugger will briefly stop, collect some data, and then allow the
7116 program to continue. Setting a tracepoint or changing its commands
7117 doesn't take effect until the next @code{tstart} command; thus, you
7118 cannot change the tracepoint attributes once a trace experiment is
7121 Here are some examples of using the @code{trace} command:
7124 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
7126 (@value{GDBP}) @b{trace +2} // 2 lines forward
7128 (@value{GDBP}) @b{trace my_function} // first source line of function
7130 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
7132 (@value{GDBP}) @b{trace *0x2117c4} // an address
7136 You can abbreviate @code{trace} as @code{tr}.
7139 @cindex last tracepoint number
7140 @cindex recent tracepoint number
7141 @cindex tracepoint number
7142 The convenience variable @code{$tpnum} records the tracepoint number
7143 of the most recently set tracepoint.
7145 @kindex delete tracepoint
7146 @cindex tracepoint deletion
7147 @item delete tracepoint @r{[}@var{num}@r{]}
7148 Permanently delete one or more tracepoints. With no argument, the
7149 default is to delete all tracepoints.
7154 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
7156 (@value{GDBP}) @b{delete trace} // remove all tracepoints
7160 You can abbreviate this command as @code{del tr}.
7163 @node Enable and Disable Tracepoints
7164 @subsection Enable and Disable Tracepoints
7167 @kindex disable tracepoint
7168 @item disable tracepoint @r{[}@var{num}@r{]}
7169 Disable tracepoint @var{num}, or all tracepoints if no argument
7170 @var{num} is given. A disabled tracepoint will have no effect during
7171 the next trace experiment, but it is not forgotten. You can re-enable
7172 a disabled tracepoint using the @code{enable tracepoint} command.
7174 @kindex enable tracepoint
7175 @item enable tracepoint @r{[}@var{num}@r{]}
7176 Enable tracepoint @var{num}, or all tracepoints. The enabled
7177 tracepoints will become effective the next time a trace experiment is
7181 @node Tracepoint Passcounts
7182 @subsection Tracepoint Passcounts
7186 @cindex tracepoint pass count
7187 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
7188 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
7189 automatically stop a trace experiment. If a tracepoint's passcount is
7190 @var{n}, then the trace experiment will be automatically stopped on
7191 the @var{n}'th time that tracepoint is hit. If the tracepoint number
7192 @var{num} is not specified, the @code{passcount} command sets the
7193 passcount of the most recently defined tracepoint. If no passcount is
7194 given, the trace experiment will run until stopped explicitly by the
7200 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
7201 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
7203 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
7204 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
7205 (@value{GDBP}) @b{trace foo}
7206 (@value{GDBP}) @b{pass 3}
7207 (@value{GDBP}) @b{trace bar}
7208 (@value{GDBP}) @b{pass 2}
7209 (@value{GDBP}) @b{trace baz}
7210 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
7211 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
7212 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
7213 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
7217 @node Tracepoint Actions
7218 @subsection Tracepoint Action Lists
7222 @cindex tracepoint actions
7223 @item actions @r{[}@var{num}@r{]}
7224 This command will prompt for a list of actions to be taken when the
7225 tracepoint is hit. If the tracepoint number @var{num} is not
7226 specified, this command sets the actions for the one that was most
7227 recently defined (so that you can define a tracepoint and then say
7228 @code{actions} without bothering about its number). You specify the
7229 actions themselves on the following lines, one action at a time, and
7230 terminate the actions list with a line containing just @code{end}. So
7231 far, the only defined actions are @code{collect} and
7232 @code{while-stepping}.
7234 @cindex remove actions from a tracepoint
7235 To remove all actions from a tracepoint, type @samp{actions @var{num}}
7236 and follow it immediately with @samp{end}.
7239 (@value{GDBP}) @b{collect @var{data}} // collect some data
7241 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
7243 (@value{GDBP}) @b{end} // signals the end of actions.
7246 In the following example, the action list begins with @code{collect}
7247 commands indicating the things to be collected when the tracepoint is
7248 hit. Then, in order to single-step and collect additional data
7249 following the tracepoint, a @code{while-stepping} command is used,
7250 followed by the list of things to be collected while stepping. The
7251 @code{while-stepping} command is terminated by its own separate
7252 @code{end} command. Lastly, the action list is terminated by an
7256 (@value{GDBP}) @b{trace foo}
7257 (@value{GDBP}) @b{actions}
7258 Enter actions for tracepoint 1, one per line:
7267 @kindex collect @r{(tracepoints)}
7268 @item collect @var{expr1}, @var{expr2}, @dots{}
7269 Collect values of the given expressions when the tracepoint is hit.
7270 This command accepts a comma-separated list of any valid expressions.
7271 In addition to global, static, or local variables, the following
7272 special arguments are supported:
7276 collect all registers
7279 collect all function arguments
7282 collect all local variables.
7285 You can give several consecutive @code{collect} commands, each one
7286 with a single argument, or one @code{collect} command with several
7287 arguments separated by commas: the effect is the same.
7289 The command @code{info scope} (@pxref{Symbols, info scope}) is
7290 particularly useful for figuring out what data to collect.
7292 @kindex while-stepping @r{(tracepoints)}
7293 @item while-stepping @var{n}
7294 Perform @var{n} single-step traces after the tracepoint, collecting
7295 new data at each step. The @code{while-stepping} command is
7296 followed by the list of what to collect while stepping (followed by
7297 its own @code{end} command):
7301 > collect $regs, myglobal
7307 You may abbreviate @code{while-stepping} as @code{ws} or
7311 @node Listing Tracepoints
7312 @subsection Listing Tracepoints
7315 @kindex info tracepoints
7317 @cindex information about tracepoints
7318 @item info tracepoints @r{[}@var{num}@r{]}
7319 Display information about the tracepoint @var{num}. If you don't specify
7320 a tracepoint number, displays information about all the tracepoints
7321 defined so far. For each tracepoint, the following information is
7328 whether it is enabled or disabled
7332 its passcount as given by the @code{passcount @var{n}} command
7334 its step count as given by the @code{while-stepping @var{n}} command
7336 where in the source files is the tracepoint set
7338 its action list as given by the @code{actions} command
7342 (@value{GDBP}) @b{info trace}
7343 Num Enb Address PassC StepC What
7344 1 y 0x002117c4 0 0 <gdb_asm>
7345 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
7346 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
7351 This command can be abbreviated @code{info tp}.
7354 @node Starting and Stopping Trace Experiment
7355 @subsection Starting and Stopping Trace Experiment
7359 @cindex start a new trace experiment
7360 @cindex collected data discarded
7362 This command takes no arguments. It starts the trace experiment, and
7363 begins collecting data. This has the side effect of discarding all
7364 the data collected in the trace buffer during the previous trace
7368 @cindex stop a running trace experiment
7370 This command takes no arguments. It ends the trace experiment, and
7371 stops collecting data.
7373 @strong{Note}: a trace experiment and data collection may stop
7374 automatically if any tracepoint's passcount is reached
7375 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
7378 @cindex status of trace data collection
7379 @cindex trace experiment, status of
7381 This command displays the status of the current trace data
7385 Here is an example of the commands we described so far:
7388 (@value{GDBP}) @b{trace gdb_c_test}
7389 (@value{GDBP}) @b{actions}
7390 Enter actions for tracepoint #1, one per line.
7391 > collect $regs,$locals,$args
7396 (@value{GDBP}) @b{tstart}
7397 [time passes @dots{}]
7398 (@value{GDBP}) @b{tstop}
7402 @node Analyze Collected Data
7403 @section Using the collected data
7405 After the tracepoint experiment ends, you use @value{GDBN} commands
7406 for examining the trace data. The basic idea is that each tracepoint
7407 collects a trace @dfn{snapshot} every time it is hit and another
7408 snapshot every time it single-steps. All these snapshots are
7409 consecutively numbered from zero and go into a buffer, and you can
7410 examine them later. The way you examine them is to @dfn{focus} on a
7411 specific trace snapshot. When the remote stub is focused on a trace
7412 snapshot, it will respond to all @value{GDBN} requests for memory and
7413 registers by reading from the buffer which belongs to that snapshot,
7414 rather than from @emph{real} memory or registers of the program being
7415 debugged. This means that @strong{all} @value{GDBN} commands
7416 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
7417 behave as if we were currently debugging the program state as it was
7418 when the tracepoint occurred. Any requests for data that are not in
7419 the buffer will fail.
7422 * tfind:: How to select a trace snapshot
7423 * tdump:: How to display all data for a snapshot
7424 * save-tracepoints:: How to save tracepoints for a future run
7428 @subsection @code{tfind @var{n}}
7431 @cindex select trace snapshot
7432 @cindex find trace snapshot
7433 The basic command for selecting a trace snapshot from the buffer is
7434 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
7435 counting from zero. If no argument @var{n} is given, the next
7436 snapshot is selected.
7438 Here are the various forms of using the @code{tfind} command.
7442 Find the first snapshot in the buffer. This is a synonym for
7443 @code{tfind 0} (since 0 is the number of the first snapshot).
7446 Stop debugging trace snapshots, resume @emph{live} debugging.
7449 Same as @samp{tfind none}.
7452 No argument means find the next trace snapshot.
7455 Find the previous trace snapshot before the current one. This permits
7456 retracing earlier steps.
7458 @item tfind tracepoint @var{num}
7459 Find the next snapshot associated with tracepoint @var{num}. Search
7460 proceeds forward from the last examined trace snapshot. If no
7461 argument @var{num} is given, it means find the next snapshot collected
7462 for the same tracepoint as the current snapshot.
7464 @item tfind pc @var{addr}
7465 Find the next snapshot associated with the value @var{addr} of the
7466 program counter. Search proceeds forward from the last examined trace
7467 snapshot. If no argument @var{addr} is given, it means find the next
7468 snapshot with the same value of PC as the current snapshot.
7470 @item tfind outside @var{addr1}, @var{addr2}
7471 Find the next snapshot whose PC is outside the given range of
7474 @item tfind range @var{addr1}, @var{addr2}
7475 Find the next snapshot whose PC is between @var{addr1} and
7476 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
7478 @item tfind line @r{[}@var{file}:@r{]}@var{n}
7479 Find the next snapshot associated with the source line @var{n}. If
7480 the optional argument @var{file} is given, refer to line @var{n} in
7481 that source file. Search proceeds forward from the last examined
7482 trace snapshot. If no argument @var{n} is given, it means find the
7483 next line other than the one currently being examined; thus saying
7484 @code{tfind line} repeatedly can appear to have the same effect as
7485 stepping from line to line in a @emph{live} debugging session.
7488 The default arguments for the @code{tfind} commands are specifically
7489 designed to make it easy to scan through the trace buffer. For
7490 instance, @code{tfind} with no argument selects the next trace
7491 snapshot, and @code{tfind -} with no argument selects the previous
7492 trace snapshot. So, by giving one @code{tfind} command, and then
7493 simply hitting @key{RET} repeatedly you can examine all the trace
7494 snapshots in order. Or, by saying @code{tfind -} and then hitting
7495 @key{RET} repeatedly you can examine the snapshots in reverse order.
7496 The @code{tfind line} command with no argument selects the snapshot
7497 for the next source line executed. The @code{tfind pc} command with
7498 no argument selects the next snapshot with the same program counter
7499 (PC) as the current frame. The @code{tfind tracepoint} command with
7500 no argument selects the next trace snapshot collected by the same
7501 tracepoint as the current one.
7503 In addition to letting you scan through the trace buffer manually,
7504 these commands make it easy to construct @value{GDBN} scripts that
7505 scan through the trace buffer and print out whatever collected data
7506 you are interested in. Thus, if we want to examine the PC, FP, and SP
7507 registers from each trace frame in the buffer, we can say this:
7510 (@value{GDBP}) @b{tfind start}
7511 (@value{GDBP}) @b{while ($trace_frame != -1)}
7512 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
7513 $trace_frame, $pc, $sp, $fp
7517 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
7518 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
7519 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
7520 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
7521 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
7522 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
7523 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
7524 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
7525 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
7526 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
7527 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
7530 Or, if we want to examine the variable @code{X} at each source line in
7534 (@value{GDBP}) @b{tfind start}
7535 (@value{GDBP}) @b{while ($trace_frame != -1)}
7536 > printf "Frame %d, X == %d\n", $trace_frame, X
7546 @subsection @code{tdump}
7548 @cindex dump all data collected at tracepoint
7549 @cindex tracepoint data, display
7551 This command takes no arguments. It prints all the data collected at
7552 the current trace snapshot.
7555 (@value{GDBP}) @b{trace 444}
7556 (@value{GDBP}) @b{actions}
7557 Enter actions for tracepoint #2, one per line:
7558 > collect $regs, $locals, $args, gdb_long_test
7561 (@value{GDBP}) @b{tstart}
7563 (@value{GDBP}) @b{tfind line 444}
7564 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
7566 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
7568 (@value{GDBP}) @b{tdump}
7569 Data collected at tracepoint 2, trace frame 1:
7570 d0 0xc4aa0085 -995491707
7574 d4 0x71aea3d 119204413
7579 a1 0x3000668 50333288
7582 a4 0x3000698 50333336
7584 fp 0x30bf3c 0x30bf3c
7585 sp 0x30bf34 0x30bf34
7587 pc 0x20b2c8 0x20b2c8
7591 p = 0x20e5b4 "gdb-test"
7598 gdb_long_test = 17 '\021'
7603 @node save-tracepoints
7604 @subsection @code{save-tracepoints @var{filename}}
7605 @kindex save-tracepoints
7606 @cindex save tracepoints for future sessions
7608 This command saves all current tracepoint definitions together with
7609 their actions and passcounts, into a file @file{@var{filename}}
7610 suitable for use in a later debugging session. To read the saved
7611 tracepoint definitions, use the @code{source} command (@pxref{Command
7614 @node Tracepoint Variables
7615 @section Convenience Variables for Tracepoints
7616 @cindex tracepoint variables
7617 @cindex convenience variables for tracepoints
7620 @vindex $trace_frame
7621 @item (int) $trace_frame
7622 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
7623 snapshot is selected.
7626 @item (int) $tracepoint
7627 The tracepoint for the current trace snapshot.
7630 @item (int) $trace_line
7631 The line number for the current trace snapshot.
7634 @item (char []) $trace_file
7635 The source file for the current trace snapshot.
7638 @item (char []) $trace_func
7639 The name of the function containing @code{$tracepoint}.
7642 Note: @code{$trace_file} is not suitable for use in @code{printf},
7643 use @code{output} instead.
7645 Here's a simple example of using these convenience variables for
7646 stepping through all the trace snapshots and printing some of their
7650 (@value{GDBP}) @b{tfind start}
7652 (@value{GDBP}) @b{while $trace_frame != -1}
7653 > output $trace_file
7654 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7660 @chapter Debugging Programs That Use Overlays
7663 If your program is too large to fit completely in your target system's
7664 memory, you can sometimes use @dfn{overlays} to work around this
7665 problem. @value{GDBN} provides some support for debugging programs that
7669 * How Overlays Work:: A general explanation of overlays.
7670 * Overlay Commands:: Managing overlays in @value{GDBN}.
7671 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7672 mapped by asking the inferior.
7673 * Overlay Sample Program:: A sample program using overlays.
7676 @node How Overlays Work
7677 @section How Overlays Work
7678 @cindex mapped overlays
7679 @cindex unmapped overlays
7680 @cindex load address, overlay's
7681 @cindex mapped address
7682 @cindex overlay area
7684 Suppose you have a computer whose instruction address space is only 64
7685 kilobytes long, but which has much more memory which can be accessed by
7686 other means: special instructions, segment registers, or memory
7687 management hardware, for example. Suppose further that you want to
7688 adapt a program which is larger than 64 kilobytes to run on this system.
7690 One solution is to identify modules of your program which are relatively
7691 independent, and need not call each other directly; call these modules
7692 @dfn{overlays}. Separate the overlays from the main program, and place
7693 their machine code in the larger memory. Place your main program in
7694 instruction memory, but leave at least enough space there to hold the
7695 largest overlay as well.
7697 Now, to call a function located in an overlay, you must first copy that
7698 overlay's machine code from the large memory into the space set aside
7699 for it in the instruction memory, and then jump to its entry point
7702 @c NB: In the below the mapped area's size is greater or equal to the
7703 @c size of all overlays. This is intentional to remind the developer
7704 @c that overlays don't necessarily need to be the same size.
7708 Data Instruction Larger
7709 Address Space Address Space Address Space
7710 +-----------+ +-----------+ +-----------+
7712 +-----------+ +-----------+ +-----------+<-- overlay 1
7713 | program | | main | .----| overlay 1 | load address
7714 | variables | | program | | +-----------+
7715 | and heap | | | | | |
7716 +-----------+ | | | +-----------+<-- overlay 2
7717 | | +-----------+ | | | load address
7718 +-----------+ | | | .-| overlay 2 |
7720 mapped --->+-----------+ | | +-----------+
7722 | overlay | <-' | | |
7723 | area | <---' +-----------+<-- overlay 3
7724 | | <---. | | load address
7725 +-----------+ `--| overlay 3 |
7732 @anchor{A code overlay}A code overlay
7736 The diagram (@pxref{A code overlay}) shows a system with separate data
7737 and instruction address spaces. To map an overlay, the program copies
7738 its code from the larger address space to the instruction address space.
7739 Since the overlays shown here all use the same mapped address, only one
7740 may be mapped at a time. For a system with a single address space for
7741 data and instructions, the diagram would be similar, except that the
7742 program variables and heap would share an address space with the main
7743 program and the overlay area.
7745 An overlay loaded into instruction memory and ready for use is called a
7746 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
7747 instruction memory. An overlay not present (or only partially present)
7748 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
7749 is its address in the larger memory. The mapped address is also called
7750 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
7751 called the @dfn{load memory address}, or @dfn{LMA}.
7753 Unfortunately, overlays are not a completely transparent way to adapt a
7754 program to limited instruction memory. They introduce a new set of
7755 global constraints you must keep in mind as you design your program:
7760 Before calling or returning to a function in an overlay, your program
7761 must make sure that overlay is actually mapped. Otherwise, the call or
7762 return will transfer control to the right address, but in the wrong
7763 overlay, and your program will probably crash.
7766 If the process of mapping an overlay is expensive on your system, you
7767 will need to choose your overlays carefully to minimize their effect on
7768 your program's performance.
7771 The executable file you load onto your system must contain each
7772 overlay's instructions, appearing at the overlay's load address, not its
7773 mapped address. However, each overlay's instructions must be relocated
7774 and its symbols defined as if the overlay were at its mapped address.
7775 You can use GNU linker scripts to specify different load and relocation
7776 addresses for pieces of your program; see @ref{Overlay Description,,,
7777 ld.info, Using ld: the GNU linker}.
7780 The procedure for loading executable files onto your system must be able
7781 to load their contents into the larger address space as well as the
7782 instruction and data spaces.
7786 The overlay system described above is rather simple, and could be
7787 improved in many ways:
7792 If your system has suitable bank switch registers or memory management
7793 hardware, you could use those facilities to make an overlay's load area
7794 contents simply appear at their mapped address in instruction space.
7795 This would probably be faster than copying the overlay to its mapped
7796 area in the usual way.
7799 If your overlays are small enough, you could set aside more than one
7800 overlay area, and have more than one overlay mapped at a time.
7803 You can use overlays to manage data, as well as instructions. In
7804 general, data overlays are even less transparent to your design than
7805 code overlays: whereas code overlays only require care when you call or
7806 return to functions, data overlays require care every time you access
7807 the data. Also, if you change the contents of a data overlay, you
7808 must copy its contents back out to its load address before you can copy a
7809 different data overlay into the same mapped area.
7814 @node Overlay Commands
7815 @section Overlay Commands
7817 To use @value{GDBN}'s overlay support, each overlay in your program must
7818 correspond to a separate section of the executable file. The section's
7819 virtual memory address and load memory address must be the overlay's
7820 mapped and load addresses. Identifying overlays with sections allows
7821 @value{GDBN} to determine the appropriate address of a function or
7822 variable, depending on whether the overlay is mapped or not.
7824 @value{GDBN}'s overlay commands all start with the word @code{overlay};
7825 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
7830 Disable @value{GDBN}'s overlay support. When overlay support is
7831 disabled, @value{GDBN} assumes that all functions and variables are
7832 always present at their mapped addresses. By default, @value{GDBN}'s
7833 overlay support is disabled.
7835 @item overlay manual
7836 @cindex manual overlay debugging
7837 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
7838 relies on you to tell it which overlays are mapped, and which are not,
7839 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
7840 commands described below.
7842 @item overlay map-overlay @var{overlay}
7843 @itemx overlay map @var{overlay}
7844 @cindex map an overlay
7845 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
7846 be the name of the object file section containing the overlay. When an
7847 overlay is mapped, @value{GDBN} assumes it can find the overlay's
7848 functions and variables at their mapped addresses. @value{GDBN} assumes
7849 that any other overlays whose mapped ranges overlap that of
7850 @var{overlay} are now unmapped.
7852 @item overlay unmap-overlay @var{overlay}
7853 @itemx overlay unmap @var{overlay}
7854 @cindex unmap an overlay
7855 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
7856 must be the name of the object file section containing the overlay.
7857 When an overlay is unmapped, @value{GDBN} assumes it can find the
7858 overlay's functions and variables at their load addresses.
7861 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
7862 consults a data structure the overlay manager maintains in the inferior
7863 to see which overlays are mapped. For details, see @ref{Automatic
7866 @item overlay load-target
7868 @cindex reloading the overlay table
7869 Re-read the overlay table from the inferior. Normally, @value{GDBN}
7870 re-reads the table @value{GDBN} automatically each time the inferior
7871 stops, so this command should only be necessary if you have changed the
7872 overlay mapping yourself using @value{GDBN}. This command is only
7873 useful when using automatic overlay debugging.
7875 @item overlay list-overlays
7877 @cindex listing mapped overlays
7878 Display a list of the overlays currently mapped, along with their mapped
7879 addresses, load addresses, and sizes.
7883 Normally, when @value{GDBN} prints a code address, it includes the name
7884 of the function the address falls in:
7887 (@value{GDBP}) print main
7888 $3 = @{int ()@} 0x11a0 <main>
7891 When overlay debugging is enabled, @value{GDBN} recognizes code in
7892 unmapped overlays, and prints the names of unmapped functions with
7893 asterisks around them. For example, if @code{foo} is a function in an
7894 unmapped overlay, @value{GDBN} prints it this way:
7897 (@value{GDBP}) overlay list
7898 No sections are mapped.
7899 (@value{GDBP}) print foo
7900 $5 = @{int (int)@} 0x100000 <*foo*>
7903 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
7907 (@value{GDBP}) overlay list
7908 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
7909 mapped at 0x1016 - 0x104a
7910 (@value{GDBP}) print foo
7911 $6 = @{int (int)@} 0x1016 <foo>
7914 When overlay debugging is enabled, @value{GDBN} can find the correct
7915 address for functions and variables in an overlay, whether or not the
7916 overlay is mapped. This allows most @value{GDBN} commands, like
7917 @code{break} and @code{disassemble}, to work normally, even on unmapped
7918 code. However, @value{GDBN}'s breakpoint support has some limitations:
7922 @cindex breakpoints in overlays
7923 @cindex overlays, setting breakpoints in
7924 You can set breakpoints in functions in unmapped overlays, as long as
7925 @value{GDBN} can write to the overlay at its load address.
7927 @value{GDBN} can not set hardware or simulator-based breakpoints in
7928 unmapped overlays. However, if you set a breakpoint at the end of your
7929 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
7930 you are using manual overlay management), @value{GDBN} will re-set its
7931 breakpoints properly.
7935 @node Automatic Overlay Debugging
7936 @section Automatic Overlay Debugging
7937 @cindex automatic overlay debugging
7939 @value{GDBN} can automatically track which overlays are mapped and which
7940 are not, given some simple co-operation from the overlay manager in the
7941 inferior. If you enable automatic overlay debugging with the
7942 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
7943 looks in the inferior's memory for certain variables describing the
7944 current state of the overlays.
7946 Here are the variables your overlay manager must define to support
7947 @value{GDBN}'s automatic overlay debugging:
7951 @item @code{_ovly_table}:
7952 This variable must be an array of the following structures:
7957 /* The overlay's mapped address. */
7960 /* The size of the overlay, in bytes. */
7963 /* The overlay's load address. */
7966 /* Non-zero if the overlay is currently mapped;
7968 unsigned long mapped;
7972 @item @code{_novlys}:
7973 This variable must be a four-byte signed integer, holding the total
7974 number of elements in @code{_ovly_table}.
7978 To decide whether a particular overlay is mapped or not, @value{GDBN}
7979 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
7980 @code{lma} members equal the VMA and LMA of the overlay's section in the
7981 executable file. When @value{GDBN} finds a matching entry, it consults
7982 the entry's @code{mapped} member to determine whether the overlay is
7985 In addition, your overlay manager may define a function called
7986 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
7987 will silently set a breakpoint there. If the overlay manager then
7988 calls this function whenever it has changed the overlay table, this
7989 will enable @value{GDBN} to accurately keep track of which overlays
7990 are in program memory, and update any breakpoints that may be set
7991 in overlays. This will allow breakpoints to work even if the
7992 overlays are kept in ROM or other non-writable memory while they
7993 are not being executed.
7995 @node Overlay Sample Program
7996 @section Overlay Sample Program
7997 @cindex overlay example program
7999 When linking a program which uses overlays, you must place the overlays
8000 at their load addresses, while relocating them to run at their mapped
8001 addresses. To do this, you must write a linker script (@pxref{Overlay
8002 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
8003 since linker scripts are specific to a particular host system, target
8004 architecture, and target memory layout, this manual cannot provide
8005 portable sample code demonstrating @value{GDBN}'s overlay support.
8007 However, the @value{GDBN} source distribution does contain an overlaid
8008 program, with linker scripts for a few systems, as part of its test
8009 suite. The program consists of the following files from
8010 @file{gdb/testsuite/gdb.base}:
8014 The main program file.
8016 A simple overlay manager, used by @file{overlays.c}.
8021 Overlay modules, loaded and used by @file{overlays.c}.
8024 Linker scripts for linking the test program on the @code{d10v-elf}
8025 and @code{m32r-elf} targets.
8028 You can build the test program using the @code{d10v-elf} GCC
8029 cross-compiler like this:
8032 $ d10v-elf-gcc -g -c overlays.c
8033 $ d10v-elf-gcc -g -c ovlymgr.c
8034 $ d10v-elf-gcc -g -c foo.c
8035 $ d10v-elf-gcc -g -c bar.c
8036 $ d10v-elf-gcc -g -c baz.c
8037 $ d10v-elf-gcc -g -c grbx.c
8038 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
8039 baz.o grbx.o -Wl,-Td10v.ld -o overlays
8042 The build process is identical for any other architecture, except that
8043 you must substitute the appropriate compiler and linker script for the
8044 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
8048 @chapter Using @value{GDBN} with Different Languages
8051 Although programming languages generally have common aspects, they are
8052 rarely expressed in the same manner. For instance, in ANSI C,
8053 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
8054 Modula-2, it is accomplished by @code{p^}. Values can also be
8055 represented (and displayed) differently. Hex numbers in C appear as
8056 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
8058 @cindex working language
8059 Language-specific information is built into @value{GDBN} for some languages,
8060 allowing you to express operations like the above in your program's
8061 native language, and allowing @value{GDBN} to output values in a manner
8062 consistent with the syntax of your program's native language. The
8063 language you use to build expressions is called the @dfn{working
8067 * Setting:: Switching between source languages
8068 * Show:: Displaying the language
8069 * Checks:: Type and range checks
8070 * Supported languages:: Supported languages
8071 * Unsupported languages:: Unsupported languages
8075 @section Switching between source languages
8077 There are two ways to control the working language---either have @value{GDBN}
8078 set it automatically, or select it manually yourself. You can use the
8079 @code{set language} command for either purpose. On startup, @value{GDBN}
8080 defaults to setting the language automatically. The working language is
8081 used to determine how expressions you type are interpreted, how values
8084 In addition to the working language, every source file that
8085 @value{GDBN} knows about has its own working language. For some object
8086 file formats, the compiler might indicate which language a particular
8087 source file is in. However, most of the time @value{GDBN} infers the
8088 language from the name of the file. The language of a source file
8089 controls whether C@t{++} names are demangled---this way @code{backtrace} can
8090 show each frame appropriately for its own language. There is no way to
8091 set the language of a source file from within @value{GDBN}, but you can
8092 set the language associated with a filename extension. @xref{Show, ,
8093 Displaying the language}.
8095 This is most commonly a problem when you use a program, such
8096 as @code{cfront} or @code{f2c}, that generates C but is written in
8097 another language. In that case, make the
8098 program use @code{#line} directives in its C output; that way
8099 @value{GDBN} will know the correct language of the source code of the original
8100 program, and will display that source code, not the generated C code.
8103 * Filenames:: Filename extensions and languages.
8104 * Manually:: Setting the working language manually
8105 * Automatically:: Having @value{GDBN} infer the source language
8109 @subsection List of filename extensions and languages
8111 If a source file name ends in one of the following extensions, then
8112 @value{GDBN} infers that its language is the one indicated.
8133 Objective-C source file
8140 Modula-2 source file
8144 Assembler source file. This actually behaves almost like C, but
8145 @value{GDBN} does not skip over function prologues when stepping.
8148 In addition, you may set the language associated with a filename
8149 extension. @xref{Show, , Displaying the language}.
8152 @subsection Setting the working language
8154 If you allow @value{GDBN} to set the language automatically,
8155 expressions are interpreted the same way in your debugging session and
8158 @kindex set language
8159 If you wish, you may set the language manually. To do this, issue the
8160 command @samp{set language @var{lang}}, where @var{lang} is the name of
8162 @code{c} or @code{modula-2}.
8163 For a list of the supported languages, type @samp{set language}.
8165 Setting the language manually prevents @value{GDBN} from updating the working
8166 language automatically. This can lead to confusion if you try
8167 to debug a program when the working language is not the same as the
8168 source language, when an expression is acceptable to both
8169 languages---but means different things. For instance, if the current
8170 source file were written in C, and @value{GDBN} was parsing Modula-2, a
8178 might not have the effect you intended. In C, this means to add
8179 @code{b} and @code{c} and place the result in @code{a}. The result
8180 printed would be the value of @code{a}. In Modula-2, this means to compare
8181 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
8184 @subsection Having @value{GDBN} infer the source language
8186 To have @value{GDBN} set the working language automatically, use
8187 @samp{set language local} or @samp{set language auto}. @value{GDBN}
8188 then infers the working language. That is, when your program stops in a
8189 frame (usually by encountering a breakpoint), @value{GDBN} sets the
8190 working language to the language recorded for the function in that
8191 frame. If the language for a frame is unknown (that is, if the function
8192 or block corresponding to the frame was defined in a source file that
8193 does not have a recognized extension), the current working language is
8194 not changed, and @value{GDBN} issues a warning.
8196 This may not seem necessary for most programs, which are written
8197 entirely in one source language. However, program modules and libraries
8198 written in one source language can be used by a main program written in
8199 a different source language. Using @samp{set language auto} in this
8200 case frees you from having to set the working language manually.
8203 @section Displaying the language
8205 The following commands help you find out which language is the
8206 working language, and also what language source files were written in.
8210 @kindex show language
8211 Display the current working language. This is the
8212 language you can use with commands such as @code{print} to
8213 build and compute expressions that may involve variables in your program.
8216 @kindex info frame@r{, show the source language}
8217 Display the source language for this frame. This language becomes the
8218 working language if you use an identifier from this frame.
8219 @xref{Frame Info, ,Information about a frame}, to identify the other
8220 information listed here.
8223 @kindex info source@r{, show the source language}
8224 Display the source language of this source file.
8225 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
8226 information listed here.
8229 In unusual circumstances, you may have source files with extensions
8230 not in the standard list. You can then set the extension associated
8231 with a language explicitly:
8234 @item set extension-language @var{ext} @var{language}
8235 @kindex set extension-language
8236 Tell @value{GDBN} that source files with extension @var{ext} are to be
8237 assumed as written in the source language @var{language}.
8239 @item info extensions
8240 @kindex info extensions
8241 List all the filename extensions and the associated languages.
8245 @section Type and range checking
8248 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
8249 checking are included, but they do not yet have any effect. This
8250 section documents the intended facilities.
8252 @c FIXME remove warning when type/range code added
8254 Some languages are designed to guard you against making seemingly common
8255 errors through a series of compile- and run-time checks. These include
8256 checking the type of arguments to functions and operators, and making
8257 sure mathematical overflows are caught at run time. Checks such as
8258 these help to ensure a program's correctness once it has been compiled
8259 by eliminating type mismatches, and providing active checks for range
8260 errors when your program is running.
8262 @value{GDBN} can check for conditions like the above if you wish.
8263 Although @value{GDBN} does not check the statements in your program,
8264 it can check expressions entered directly into @value{GDBN} for
8265 evaluation via the @code{print} command, for example. As with the
8266 working language, @value{GDBN} can also decide whether or not to check
8267 automatically based on your program's source language.
8268 @xref{Supported languages, ,Supported languages}, for the default
8269 settings of supported languages.
8272 * Type Checking:: An overview of type checking
8273 * Range Checking:: An overview of range checking
8276 @cindex type checking
8277 @cindex checks, type
8279 @subsection An overview of type checking
8281 Some languages, such as Modula-2, are strongly typed, meaning that the
8282 arguments to operators and functions have to be of the correct type,
8283 otherwise an error occurs. These checks prevent type mismatch
8284 errors from ever causing any run-time problems. For example,
8292 The second example fails because the @code{CARDINAL} 1 is not
8293 type-compatible with the @code{REAL} 2.3.
8295 For the expressions you use in @value{GDBN} commands, you can tell the
8296 @value{GDBN} type checker to skip checking;
8297 to treat any mismatches as errors and abandon the expression;
8298 or to only issue warnings when type mismatches occur,
8299 but evaluate the expression anyway. When you choose the last of
8300 these, @value{GDBN} evaluates expressions like the second example above, but
8301 also issues a warning.
8303 Even if you turn type checking off, there may be other reasons
8304 related to type that prevent @value{GDBN} from evaluating an expression.
8305 For instance, @value{GDBN} does not know how to add an @code{int} and
8306 a @code{struct foo}. These particular type errors have nothing to do
8307 with the language in use, and usually arise from expressions, such as
8308 the one described above, which make little sense to evaluate anyway.
8310 Each language defines to what degree it is strict about type. For
8311 instance, both Modula-2 and C require the arguments to arithmetical
8312 operators to be numbers. In C, enumerated types and pointers can be
8313 represented as numbers, so that they are valid arguments to mathematical
8314 operators. @xref{Supported languages, ,Supported languages}, for further
8315 details on specific languages.
8317 @value{GDBN} provides some additional commands for controlling the type checker:
8319 @kindex set check type
8320 @kindex show check type
8322 @item set check type auto
8323 Set type checking on or off based on the current working language.
8324 @xref{Supported languages, ,Supported languages}, for the default settings for
8327 @item set check type on
8328 @itemx set check type off
8329 Set type checking on or off, overriding the default setting for the
8330 current working language. Issue a warning if the setting does not
8331 match the language default. If any type mismatches occur in
8332 evaluating an expression while type checking is on, @value{GDBN} prints a
8333 message and aborts evaluation of the expression.
8335 @item set check type warn
8336 Cause the type checker to issue warnings, but to always attempt to
8337 evaluate the expression. Evaluating the expression may still
8338 be impossible for other reasons. For example, @value{GDBN} cannot add
8339 numbers and structures.
8342 Show the current setting of the type checker, and whether or not @value{GDBN}
8343 is setting it automatically.
8346 @cindex range checking
8347 @cindex checks, range
8348 @node Range Checking
8349 @subsection An overview of range checking
8351 In some languages (such as Modula-2), it is an error to exceed the
8352 bounds of a type; this is enforced with run-time checks. Such range
8353 checking is meant to ensure program correctness by making sure
8354 computations do not overflow, or indices on an array element access do
8355 not exceed the bounds of the array.
8357 For expressions you use in @value{GDBN} commands, you can tell
8358 @value{GDBN} to treat range errors in one of three ways: ignore them,
8359 always treat them as errors and abandon the expression, or issue
8360 warnings but evaluate the expression anyway.
8362 A range error can result from numerical overflow, from exceeding an
8363 array index bound, or when you type a constant that is not a member
8364 of any type. Some languages, however, do not treat overflows as an
8365 error. In many implementations of C, mathematical overflow causes the
8366 result to ``wrap around'' to lower values---for example, if @var{m} is
8367 the largest integer value, and @var{s} is the smallest, then
8370 @var{m} + 1 @result{} @var{s}
8373 This, too, is specific to individual languages, and in some cases
8374 specific to individual compilers or machines. @xref{Supported languages, ,
8375 Supported languages}, for further details on specific languages.
8377 @value{GDBN} provides some additional commands for controlling the range checker:
8379 @kindex set check range
8380 @kindex show check range
8382 @item set check range auto
8383 Set range checking on or off based on the current working language.
8384 @xref{Supported languages, ,Supported languages}, for the default settings for
8387 @item set check range on
8388 @itemx set check range off
8389 Set range checking on or off, overriding the default setting for the
8390 current working language. A warning is issued if the setting does not
8391 match the language default. If a range error occurs and range checking is on,
8392 then a message is printed and evaluation of the expression is aborted.
8394 @item set check range warn
8395 Output messages when the @value{GDBN} range checker detects a range error,
8396 but attempt to evaluate the expression anyway. Evaluating the
8397 expression may still be impossible for other reasons, such as accessing
8398 memory that the process does not own (a typical example from many Unix
8402 Show the current setting of the range checker, and whether or not it is
8403 being set automatically by @value{GDBN}.
8406 @node Supported languages
8407 @section Supported languages
8409 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
8410 assembly, Modula-2, and Ada.
8411 @c This is false ...
8412 Some @value{GDBN} features may be used in expressions regardless of the
8413 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
8414 and the @samp{@{type@}addr} construct (@pxref{Expressions,
8415 ,Expressions}) can be used with the constructs of any supported
8418 The following sections detail to what degree each source language is
8419 supported by @value{GDBN}. These sections are not meant to be language
8420 tutorials or references, but serve only as a reference guide to what the
8421 @value{GDBN} expression parser accepts, and what input and output
8422 formats should look like for different languages. There are many good
8423 books written on each of these languages; please look to these for a
8424 language reference or tutorial.
8428 * Objective-C:: Objective-C
8431 * Modula-2:: Modula-2
8436 @subsection C and C@t{++}
8438 @cindex C and C@t{++}
8439 @cindex expressions in C or C@t{++}
8441 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
8442 to both languages. Whenever this is the case, we discuss those languages
8446 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
8447 @cindex @sc{gnu} C@t{++}
8448 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
8449 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
8450 effectively, you must compile your C@t{++} programs with a supported
8451 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
8452 compiler (@code{aCC}).
8454 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
8455 format; if it doesn't work on your system, try the stabs+ debugging
8456 format. You can select those formats explicitly with the @code{g++}
8457 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
8458 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
8459 CC, gcc.info, Using @sc{gnu} CC}.
8462 * C Operators:: C and C@t{++} operators
8463 * C Constants:: C and C@t{++} constants
8464 * C plus plus expressions:: C@t{++} expressions
8465 * C Defaults:: Default settings for C and C@t{++}
8466 * C Checks:: C and C@t{++} type and range checks
8467 * Debugging C:: @value{GDBN} and C
8468 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
8472 @subsubsection C and C@t{++} operators
8474 @cindex C and C@t{++} operators
8476 Operators must be defined on values of specific types. For instance,
8477 @code{+} is defined on numbers, but not on structures. Operators are
8478 often defined on groups of types.
8480 For the purposes of C and C@t{++}, the following definitions hold:
8485 @emph{Integral types} include @code{int} with any of its storage-class
8486 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
8489 @emph{Floating-point types} include @code{float}, @code{double}, and
8490 @code{long double} (if supported by the target platform).
8493 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
8496 @emph{Scalar types} include all of the above.
8501 The following operators are supported. They are listed here
8502 in order of increasing precedence:
8506 The comma or sequencing operator. Expressions in a comma-separated list
8507 are evaluated from left to right, with the result of the entire
8508 expression being the last expression evaluated.
8511 Assignment. The value of an assignment expression is the value
8512 assigned. Defined on scalar types.
8515 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
8516 and translated to @w{@code{@var{a} = @var{a op b}}}.
8517 @w{@code{@var{op}=}} and @code{=} have the same precedence.
8518 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
8519 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
8522 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
8523 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
8527 Logical @sc{or}. Defined on integral types.
8530 Logical @sc{and}. Defined on integral types.
8533 Bitwise @sc{or}. Defined on integral types.
8536 Bitwise exclusive-@sc{or}. Defined on integral types.
8539 Bitwise @sc{and}. Defined on integral types.
8542 Equality and inequality. Defined on scalar types. The value of these
8543 expressions is 0 for false and non-zero for true.
8545 @item <@r{, }>@r{, }<=@r{, }>=
8546 Less than, greater than, less than or equal, greater than or equal.
8547 Defined on scalar types. The value of these expressions is 0 for false
8548 and non-zero for true.
8551 left shift, and right shift. Defined on integral types.
8554 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8557 Addition and subtraction. Defined on integral types, floating-point types and
8560 @item *@r{, }/@r{, }%
8561 Multiplication, division, and modulus. Multiplication and division are
8562 defined on integral and floating-point types. Modulus is defined on
8566 Increment and decrement. When appearing before a variable, the
8567 operation is performed before the variable is used in an expression;
8568 when appearing after it, the variable's value is used before the
8569 operation takes place.
8572 Pointer dereferencing. Defined on pointer types. Same precedence as
8576 Address operator. Defined on variables. Same precedence as @code{++}.
8578 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
8579 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
8580 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
8581 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
8585 Negative. Defined on integral and floating-point types. Same
8586 precedence as @code{++}.
8589 Logical negation. Defined on integral types. Same precedence as
8593 Bitwise complement operator. Defined on integral types. Same precedence as
8598 Structure member, and pointer-to-structure member. For convenience,
8599 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
8600 pointer based on the stored type information.
8601 Defined on @code{struct} and @code{union} data.
8604 Dereferences of pointers to members.
8607 Array indexing. @code{@var{a}[@var{i}]} is defined as
8608 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
8611 Function parameter list. Same precedence as @code{->}.
8614 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
8615 and @code{class} types.
8618 Doubled colons also represent the @value{GDBN} scope operator
8619 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
8623 If an operator is redefined in the user code, @value{GDBN} usually
8624 attempts to invoke the redefined version instead of using the operator's
8632 @subsubsection C and C@t{++} constants
8634 @cindex C and C@t{++} constants
8636 @value{GDBN} allows you to express the constants of C and C@t{++} in the
8641 Integer constants are a sequence of digits. Octal constants are
8642 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
8643 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
8644 @samp{l}, specifying that the constant should be treated as a
8648 Floating point constants are a sequence of digits, followed by a decimal
8649 point, followed by a sequence of digits, and optionally followed by an
8650 exponent. An exponent is of the form:
8651 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8652 sequence of digits. The @samp{+} is optional for positive exponents.
8653 A floating-point constant may also end with a letter @samp{f} or
8654 @samp{F}, specifying that the constant should be treated as being of
8655 the @code{float} (as opposed to the default @code{double}) type; or with
8656 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8660 Enumerated constants consist of enumerated identifiers, or their
8661 integral equivalents.
8664 Character constants are a single character surrounded by single quotes
8665 (@code{'}), or a number---the ordinal value of the corresponding character
8666 (usually its @sc{ascii} value). Within quotes, the single character may
8667 be represented by a letter or by @dfn{escape sequences}, which are of
8668 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8669 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8670 @samp{@var{x}} is a predefined special character---for example,
8671 @samp{\n} for newline.
8674 String constants are a sequence of character constants surrounded by
8675 double quotes (@code{"}). Any valid character constant (as described
8676 above) may appear. Double quotes within the string must be preceded by
8677 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8681 Pointer constants are an integral value. You can also write pointers
8682 to constants using the C operator @samp{&}.
8685 Array constants are comma-separated lists surrounded by braces @samp{@{}
8686 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8687 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8688 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8692 * C plus plus expressions::
8699 @node C plus plus expressions
8700 @subsubsection C@t{++} expressions
8702 @cindex expressions in C@t{++}
8703 @value{GDBN} expression handling can interpret most C@t{++} expressions.
8705 @cindex debugging C@t{++} programs
8706 @cindex C@t{++} compilers
8707 @cindex debug formats and C@t{++}
8708 @cindex @value{NGCC} and C@t{++}
8710 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
8711 proper compiler and the proper debug format. Currently, @value{GDBN}
8712 works best when debugging C@t{++} code that is compiled with
8713 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
8714 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
8715 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
8716 stabs+ as their default debug format, so you usually don't need to
8717 specify a debug format explicitly. Other compilers and/or debug formats
8718 are likely to work badly or not at all when using @value{GDBN} to debug
8724 @cindex member functions
8726 Member function calls are allowed; you can use expressions like
8729 count = aml->GetOriginal(x, y)
8732 @vindex this@r{, inside C@t{++} member functions}
8733 @cindex namespace in C@t{++}
8735 While a member function is active (in the selected stack frame), your
8736 expressions have the same namespace available as the member function;
8737 that is, @value{GDBN} allows implicit references to the class instance
8738 pointer @code{this} following the same rules as C@t{++}.
8740 @cindex call overloaded functions
8741 @cindex overloaded functions, calling
8742 @cindex type conversions in C@t{++}
8744 You can call overloaded functions; @value{GDBN} resolves the function
8745 call to the right definition, with some restrictions. @value{GDBN} does not
8746 perform overload resolution involving user-defined type conversions,
8747 calls to constructors, or instantiations of templates that do not exist
8748 in the program. It also cannot handle ellipsis argument lists or
8751 It does perform integral conversions and promotions, floating-point
8752 promotions, arithmetic conversions, pointer conversions, conversions of
8753 class objects to base classes, and standard conversions such as those of
8754 functions or arrays to pointers; it requires an exact match on the
8755 number of function arguments.
8757 Overload resolution is always performed, unless you have specified
8758 @code{set overload-resolution off}. @xref{Debugging C plus plus,
8759 ,@value{GDBN} features for C@t{++}}.
8761 You must specify @code{set overload-resolution off} in order to use an
8762 explicit function signature to call an overloaded function, as in
8764 p 'foo(char,int)'('x', 13)
8767 The @value{GDBN} command-completion facility can simplify this;
8768 see @ref{Completion, ,Command completion}.
8770 @cindex reference declarations
8772 @value{GDBN} understands variables declared as C@t{++} references; you can use
8773 them in expressions just as you do in C@t{++} source---they are automatically
8776 In the parameter list shown when @value{GDBN} displays a frame, the values of
8777 reference variables are not displayed (unlike other variables); this
8778 avoids clutter, since references are often used for large structures.
8779 The @emph{address} of a reference variable is always shown, unless
8780 you have specified @samp{set print address off}.
8783 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
8784 expressions can use it just as expressions in your program do. Since
8785 one scope may be defined in another, you can use @code{::} repeatedly if
8786 necessary, for example in an expression like
8787 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
8788 resolving name scope by reference to source files, in both C and C@t{++}
8789 debugging (@pxref{Variables, ,Program variables}).
8792 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
8793 calling virtual functions correctly, printing out virtual bases of
8794 objects, calling functions in a base subobject, casting objects, and
8795 invoking user-defined operators.
8798 @subsubsection C and C@t{++} defaults
8800 @cindex C and C@t{++} defaults
8802 If you allow @value{GDBN} to set type and range checking automatically, they
8803 both default to @code{off} whenever the working language changes to
8804 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
8805 selects the working language.
8807 If you allow @value{GDBN} to set the language automatically, it
8808 recognizes source files whose names end with @file{.c}, @file{.C}, or
8809 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
8810 these files, it sets the working language to C or C@t{++}.
8811 @xref{Automatically, ,Having @value{GDBN} infer the source language},
8812 for further details.
8814 @c Type checking is (a) primarily motivated by Modula-2, and (b)
8815 @c unimplemented. If (b) changes, it might make sense to let this node
8816 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
8819 @subsubsection C and C@t{++} type and range checks
8821 @cindex C and C@t{++} checks
8823 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
8824 is not used. However, if you turn type checking on, @value{GDBN}
8825 considers two variables type equivalent if:
8829 The two variables are structured and have the same structure, union, or
8833 The two variables have the same type name, or types that have been
8834 declared equivalent through @code{typedef}.
8837 @c leaving this out because neither J Gilmore nor R Pesch understand it.
8840 The two @code{struct}, @code{union}, or @code{enum} variables are
8841 declared in the same declaration. (Note: this may not be true for all C
8846 Range checking, if turned on, is done on mathematical operations. Array
8847 indices are not checked, since they are often used to index a pointer
8848 that is not itself an array.
8851 @subsubsection @value{GDBN} and C
8853 The @code{set print union} and @code{show print union} commands apply to
8854 the @code{union} type. When set to @samp{on}, any @code{union} that is
8855 inside a @code{struct} or @code{class} is also printed. Otherwise, it
8856 appears as @samp{@{...@}}.
8858 The @code{@@} operator aids in the debugging of dynamic arrays, formed
8859 with pointers and a memory allocation function. @xref{Expressions,
8863 * Debugging C plus plus::
8866 @node Debugging C plus plus
8867 @subsubsection @value{GDBN} features for C@t{++}
8869 @cindex commands for C@t{++}
8871 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
8872 designed specifically for use with C@t{++}. Here is a summary:
8875 @cindex break in overloaded functions
8876 @item @r{breakpoint menus}
8877 When you want a breakpoint in a function whose name is overloaded,
8878 @value{GDBN} breakpoint menus help you specify which function definition
8879 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
8881 @cindex overloading in C@t{++}
8882 @item rbreak @var{regex}
8883 Setting breakpoints using regular expressions is helpful for setting
8884 breakpoints on overloaded functions that are not members of any special
8886 @xref{Set Breaks, ,Setting breakpoints}.
8888 @cindex C@t{++} exception handling
8891 Debug C@t{++} exception handling using these commands. @xref{Set
8892 Catchpoints, , Setting catchpoints}.
8895 @item ptype @var{typename}
8896 Print inheritance relationships as well as other information for type
8898 @xref{Symbols, ,Examining the Symbol Table}.
8900 @cindex C@t{++} symbol display
8901 @item set print demangle
8902 @itemx show print demangle
8903 @itemx set print asm-demangle
8904 @itemx show print asm-demangle
8905 Control whether C@t{++} symbols display in their source form, both when
8906 displaying code as C@t{++} source and when displaying disassemblies.
8907 @xref{Print Settings, ,Print settings}.
8909 @item set print object
8910 @itemx show print object
8911 Choose whether to print derived (actual) or declared types of objects.
8912 @xref{Print Settings, ,Print settings}.
8914 @item set print vtbl
8915 @itemx show print vtbl
8916 Control the format for printing virtual function tables.
8917 @xref{Print Settings, ,Print settings}.
8918 (The @code{vtbl} commands do not work on programs compiled with the HP
8919 ANSI C@t{++} compiler (@code{aCC}).)
8921 @kindex set overload-resolution
8922 @cindex overloaded functions, overload resolution
8923 @item set overload-resolution on
8924 Enable overload resolution for C@t{++} expression evaluation. The default
8925 is on. For overloaded functions, @value{GDBN} evaluates the arguments
8926 and searches for a function whose signature matches the argument types,
8927 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
8928 expressions}, for details). If it cannot find a match, it emits a
8931 @item set overload-resolution off
8932 Disable overload resolution for C@t{++} expression evaluation. For
8933 overloaded functions that are not class member functions, @value{GDBN}
8934 chooses the first function of the specified name that it finds in the
8935 symbol table, whether or not its arguments are of the correct type. For
8936 overloaded functions that are class member functions, @value{GDBN}
8937 searches for a function whose signature @emph{exactly} matches the
8940 @kindex show overload-resolution
8941 @item show overload-resolution
8942 Show the current setting of overload resolution.
8944 @item @r{Overloaded symbol names}
8945 You can specify a particular definition of an overloaded symbol, using
8946 the same notation that is used to declare such symbols in C@t{++}: type
8947 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
8948 also use the @value{GDBN} command-line word completion facilities to list the
8949 available choices, or to finish the type list for you.
8950 @xref{Completion,, Command completion}, for details on how to do this.
8954 @subsection Objective-C
8957 This section provides information about some commands and command
8958 options that are useful for debugging Objective-C code. See also
8959 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
8960 few more commands specific to Objective-C support.
8963 * Method Names in Commands::
8964 * The Print Command with Objective-C::
8967 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
8968 @subsubsection Method Names in Commands
8970 The following commands have been extended to accept Objective-C method
8971 names as line specifications:
8973 @kindex clear@r{, and Objective-C}
8974 @kindex break@r{, and Objective-C}
8975 @kindex info line@r{, and Objective-C}
8976 @kindex jump@r{, and Objective-C}
8977 @kindex list@r{, and Objective-C}
8981 @item @code{info line}
8986 A fully qualified Objective-C method name is specified as
8989 -[@var{Class} @var{methodName}]
8992 where the minus sign is used to indicate an instance method and a
8993 plus sign (not shown) is used to indicate a class method. The class
8994 name @var{Class} and method name @var{methodName} are enclosed in
8995 brackets, similar to the way messages are specified in Objective-C
8996 source code. For example, to set a breakpoint at the @code{create}
8997 instance method of class @code{Fruit} in the program currently being
9001 break -[Fruit create]
9004 To list ten program lines around the @code{initialize} class method,
9008 list +[NSText initialize]
9011 In the current version of @value{GDBN}, the plus or minus sign is
9012 required. In future versions of @value{GDBN}, the plus or minus
9013 sign will be optional, but you can use it to narrow the search. It
9014 is also possible to specify just a method name:
9020 You must specify the complete method name, including any colons. If
9021 your program's source files contain more than one @code{create} method,
9022 you'll be presented with a numbered list of classes that implement that
9023 method. Indicate your choice by number, or type @samp{0} to exit if
9026 As another example, to clear a breakpoint established at the
9027 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
9030 clear -[NSWindow makeKeyAndOrderFront:]
9033 @node The Print Command with Objective-C
9034 @subsubsection The Print Command With Objective-C
9035 @cindex Objective-C, print objects
9036 @kindex print-object
9037 @kindex po @r{(@code{print-object})}
9039 The print command has also been extended to accept methods. For example:
9042 print -[@var{object} hash]
9045 @cindex print an Objective-C object description
9046 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
9048 will tell @value{GDBN} to send the @code{hash} message to @var{object}
9049 and print the result. Also, an additional command has been added,
9050 @code{print-object} or @code{po} for short, which is meant to print
9051 the description of an object. However, this command may only work
9052 with certain Objective-C libraries that have a particular hook
9053 function, @code{_NSPrintForDebugger}, defined.
9057 @cindex Fortran-specific support in @value{GDBN}
9060 @cindex @code{COMMON} blocks, Fortran
9062 @item info common @r{[}@var{common-name}@r{]}
9063 This command prints the values contained in the Fortran @code{COMMON}
9064 block whose name is @var{common-name}. With no argument, the names of
9065 all @code{COMMON} blocks visible at current program location are
9069 Fortran symbols are usually case-insensitive, so @value{GDBN} by
9070 default uses case-insensitive matches for Fortran symbols. You can
9071 change that with the @samp{set case-insensitive} command, see
9072 @ref{Symbols}, for the details.
9077 @cindex Pascal support in @value{GDBN}, limitations
9078 Debugging Pascal programs which use sets, subranges, file variables, or
9079 nested functions does not currently work. @value{GDBN} does not support
9080 entering expressions, printing values, or similar features using Pascal
9083 The Pascal-specific command @code{set print pascal_static-members}
9084 controls whether static members of Pascal objects are displayed.
9085 @xref{Print Settings, pascal_static-members}.
9088 @subsection Modula-2
9090 @cindex Modula-2, @value{GDBN} support
9092 The extensions made to @value{GDBN} to support Modula-2 only support
9093 output from the @sc{gnu} Modula-2 compiler (which is currently being
9094 developed). Other Modula-2 compilers are not currently supported, and
9095 attempting to debug executables produced by them is most likely
9096 to give an error as @value{GDBN} reads in the executable's symbol
9099 @cindex expressions in Modula-2
9101 * M2 Operators:: Built-in operators
9102 * Built-In Func/Proc:: Built-in functions and procedures
9103 * M2 Constants:: Modula-2 constants
9104 * M2 Defaults:: Default settings for Modula-2
9105 * Deviations:: Deviations from standard Modula-2
9106 * M2 Checks:: Modula-2 type and range checks
9107 * M2 Scope:: The scope operators @code{::} and @code{.}
9108 * GDB/M2:: @value{GDBN} and Modula-2
9112 @subsubsection Operators
9113 @cindex Modula-2 operators
9115 Operators must be defined on values of specific types. For instance,
9116 @code{+} is defined on numbers, but not on structures. Operators are
9117 often defined on groups of types. For the purposes of Modula-2, the
9118 following definitions hold:
9123 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
9127 @emph{Character types} consist of @code{CHAR} and its subranges.
9130 @emph{Floating-point types} consist of @code{REAL}.
9133 @emph{Pointer types} consist of anything declared as @code{POINTER TO
9137 @emph{Scalar types} consist of all of the above.
9140 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
9143 @emph{Boolean types} consist of @code{BOOLEAN}.
9147 The following operators are supported, and appear in order of
9148 increasing precedence:
9152 Function argument or array index separator.
9155 Assignment. The value of @var{var} @code{:=} @var{value} is
9159 Less than, greater than on integral, floating-point, or enumerated
9163 Less than or equal to, greater than or equal to
9164 on integral, floating-point and enumerated types, or set inclusion on
9165 set types. Same precedence as @code{<}.
9167 @item =@r{, }<>@r{, }#
9168 Equality and two ways of expressing inequality, valid on scalar types.
9169 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
9170 available for inequality, since @code{#} conflicts with the script
9174 Set membership. Defined on set types and the types of their members.
9175 Same precedence as @code{<}.
9178 Boolean disjunction. Defined on boolean types.
9181 Boolean conjunction. Defined on boolean types.
9184 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9187 Addition and subtraction on integral and floating-point types, or union
9188 and difference on set types.
9191 Multiplication on integral and floating-point types, or set intersection
9195 Division on floating-point types, or symmetric set difference on set
9196 types. Same precedence as @code{*}.
9199 Integer division and remainder. Defined on integral types. Same
9200 precedence as @code{*}.
9203 Negative. Defined on @code{INTEGER} and @code{REAL} data.
9206 Pointer dereferencing. Defined on pointer types.
9209 Boolean negation. Defined on boolean types. Same precedence as
9213 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
9214 precedence as @code{^}.
9217 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
9220 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
9224 @value{GDBN} and Modula-2 scope operators.
9228 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
9229 treats the use of the operator @code{IN}, or the use of operators
9230 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
9231 @code{<=}, and @code{>=} on sets as an error.
9235 @node Built-In Func/Proc
9236 @subsubsection Built-in functions and procedures
9237 @cindex Modula-2 built-ins
9239 Modula-2 also makes available several built-in procedures and functions.
9240 In describing these, the following metavariables are used:
9245 represents an @code{ARRAY} variable.
9248 represents a @code{CHAR} constant or variable.
9251 represents a variable or constant of integral type.
9254 represents an identifier that belongs to a set. Generally used in the
9255 same function with the metavariable @var{s}. The type of @var{s} should
9256 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
9259 represents a variable or constant of integral or floating-point type.
9262 represents a variable or constant of floating-point type.
9268 represents a variable.
9271 represents a variable or constant of one of many types. See the
9272 explanation of the function for details.
9275 All Modula-2 built-in procedures also return a result, described below.
9279 Returns the absolute value of @var{n}.
9282 If @var{c} is a lower case letter, it returns its upper case
9283 equivalent, otherwise it returns its argument.
9286 Returns the character whose ordinal value is @var{i}.
9289 Decrements the value in the variable @var{v} by one. Returns the new value.
9291 @item DEC(@var{v},@var{i})
9292 Decrements the value in the variable @var{v} by @var{i}. Returns the
9295 @item EXCL(@var{m},@var{s})
9296 Removes the element @var{m} from the set @var{s}. Returns the new
9299 @item FLOAT(@var{i})
9300 Returns the floating point equivalent of the integer @var{i}.
9303 Returns the index of the last member of @var{a}.
9306 Increments the value in the variable @var{v} by one. Returns the new value.
9308 @item INC(@var{v},@var{i})
9309 Increments the value in the variable @var{v} by @var{i}. Returns the
9312 @item INCL(@var{m},@var{s})
9313 Adds the element @var{m} to the set @var{s} if it is not already
9314 there. Returns the new set.
9317 Returns the maximum value of the type @var{t}.
9320 Returns the minimum value of the type @var{t}.
9323 Returns boolean TRUE if @var{i} is an odd number.
9326 Returns the ordinal value of its argument. For example, the ordinal
9327 value of a character is its @sc{ascii} value (on machines supporting the
9328 @sc{ascii} character set). @var{x} must be of an ordered type, which include
9329 integral, character and enumerated types.
9332 Returns the size of its argument. @var{x} can be a variable or a type.
9334 @item TRUNC(@var{r})
9335 Returns the integral part of @var{r}.
9337 @item VAL(@var{t},@var{i})
9338 Returns the member of the type @var{t} whose ordinal value is @var{i}.
9342 @emph{Warning:} Sets and their operations are not yet supported, so
9343 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
9347 @cindex Modula-2 constants
9349 @subsubsection Constants
9351 @value{GDBN} allows you to express the constants of Modula-2 in the following
9357 Integer constants are simply a sequence of digits. When used in an
9358 expression, a constant is interpreted to be type-compatible with the
9359 rest of the expression. Hexadecimal integers are specified by a
9360 trailing @samp{H}, and octal integers by a trailing @samp{B}.
9363 Floating point constants appear as a sequence of digits, followed by a
9364 decimal point and another sequence of digits. An optional exponent can
9365 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
9366 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
9367 digits of the floating point constant must be valid decimal (base 10)
9371 Character constants consist of a single character enclosed by a pair of
9372 like quotes, either single (@code{'}) or double (@code{"}). They may
9373 also be expressed by their ordinal value (their @sc{ascii} value, usually)
9374 followed by a @samp{C}.
9377 String constants consist of a sequence of characters enclosed by a
9378 pair of like quotes, either single (@code{'}) or double (@code{"}).
9379 Escape sequences in the style of C are also allowed. @xref{C
9380 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
9384 Enumerated constants consist of an enumerated identifier.
9387 Boolean constants consist of the identifiers @code{TRUE} and
9391 Pointer constants consist of integral values only.
9394 Set constants are not yet supported.
9398 @subsubsection Modula-2 defaults
9399 @cindex Modula-2 defaults
9401 If type and range checking are set automatically by @value{GDBN}, they
9402 both default to @code{on} whenever the working language changes to
9403 Modula-2. This happens regardless of whether you or @value{GDBN}
9404 selected the working language.
9406 If you allow @value{GDBN} to set the language automatically, then entering
9407 code compiled from a file whose name ends with @file{.mod} sets the
9408 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
9409 the language automatically}, for further details.
9412 @subsubsection Deviations from standard Modula-2
9413 @cindex Modula-2, deviations from
9415 A few changes have been made to make Modula-2 programs easier to debug.
9416 This is done primarily via loosening its type strictness:
9420 Unlike in standard Modula-2, pointer constants can be formed by
9421 integers. This allows you to modify pointer variables during
9422 debugging. (In standard Modula-2, the actual address contained in a
9423 pointer variable is hidden from you; it can only be modified
9424 through direct assignment to another pointer variable or expression that
9425 returned a pointer.)
9428 C escape sequences can be used in strings and characters to represent
9429 non-printable characters. @value{GDBN} prints out strings with these
9430 escape sequences embedded. Single non-printable characters are
9431 printed using the @samp{CHR(@var{nnn})} format.
9434 The assignment operator (@code{:=}) returns the value of its right-hand
9438 All built-in procedures both modify @emph{and} return their argument.
9442 @subsubsection Modula-2 type and range checks
9443 @cindex Modula-2 checks
9446 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
9449 @c FIXME remove warning when type/range checks added
9451 @value{GDBN} considers two Modula-2 variables type equivalent if:
9455 They are of types that have been declared equivalent via a @code{TYPE
9456 @var{t1} = @var{t2}} statement
9459 They have been declared on the same line. (Note: This is true of the
9460 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
9463 As long as type checking is enabled, any attempt to combine variables
9464 whose types are not equivalent is an error.
9466 Range checking is done on all mathematical operations, assignment, array
9467 index bounds, and all built-in functions and procedures.
9470 @subsubsection The scope operators @code{::} and @code{.}
9472 @cindex @code{.}, Modula-2 scope operator
9473 @cindex colon, doubled as scope operator
9475 @vindex colon-colon@r{, in Modula-2}
9476 @c Info cannot handle :: but TeX can.
9479 @vindex ::@r{, in Modula-2}
9482 There are a few subtle differences between the Modula-2 scope operator
9483 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
9488 @var{module} . @var{id}
9489 @var{scope} :: @var{id}
9493 where @var{scope} is the name of a module or a procedure,
9494 @var{module} the name of a module, and @var{id} is any declared
9495 identifier within your program, except another module.
9497 Using the @code{::} operator makes @value{GDBN} search the scope
9498 specified by @var{scope} for the identifier @var{id}. If it is not
9499 found in the specified scope, then @value{GDBN} searches all scopes
9500 enclosing the one specified by @var{scope}.
9502 Using the @code{.} operator makes @value{GDBN} search the current scope for
9503 the identifier specified by @var{id} that was imported from the
9504 definition module specified by @var{module}. With this operator, it is
9505 an error if the identifier @var{id} was not imported from definition
9506 module @var{module}, or if @var{id} is not an identifier in
9510 @subsubsection @value{GDBN} and Modula-2
9512 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
9513 Five subcommands of @code{set print} and @code{show print} apply
9514 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
9515 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
9516 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
9517 analogue in Modula-2.
9519 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
9520 with any language, is not useful with Modula-2. Its
9521 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
9522 created in Modula-2 as they can in C or C@t{++}. However, because an
9523 address can be specified by an integral constant, the construct
9524 @samp{@{@var{type}@}@var{adrexp}} is still useful.
9526 @cindex @code{#} in Modula-2
9527 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
9528 interpreted as the beginning of a comment. Use @code{<>} instead.
9534 The extensions made to @value{GDBN} for Ada only support
9535 output from the @sc{gnu} Ada (GNAT) compiler.
9536 Other Ada compilers are not currently supported, and
9537 attempting to debug executables produced by them is most likely
9541 @cindex expressions in Ada
9543 * Ada Mode Intro:: General remarks on the Ada syntax
9544 and semantics supported by Ada mode
9546 * Omissions from Ada:: Restrictions on the Ada expression syntax.
9547 * Additions to Ada:: Extensions of the Ada expression syntax.
9548 * Stopping Before Main Program:: Debugging the program during elaboration.
9549 * Ada Glitches:: Known peculiarities of Ada mode.
9552 @node Ada Mode Intro
9553 @subsubsection Introduction
9554 @cindex Ada mode, general
9556 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
9557 syntax, with some extensions.
9558 The philosophy behind the design of this subset is
9562 That @value{GDBN} should provide basic literals and access to operations for
9563 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
9564 leaving more sophisticated computations to subprograms written into the
9565 program (which therefore may be called from @value{GDBN}).
9568 That type safety and strict adherence to Ada language restrictions
9569 are not particularly important to the @value{GDBN} user.
9572 That brevity is important to the @value{GDBN} user.
9575 Thus, for brevity, the debugger acts as if there were
9576 implicit @code{with} and @code{use} clauses in effect for all user-written
9577 packages, making it unnecessary to fully qualify most names with
9578 their packages, regardless of context. Where this causes ambiguity,
9579 @value{GDBN} asks the user's intent.
9581 The debugger will start in Ada mode if it detects an Ada main program.
9582 As for other languages, it will enter Ada mode when stopped in a program that
9583 was translated from an Ada source file.
9585 While in Ada mode, you may use `@t{--}' for comments. This is useful
9586 mostly for documenting command files. The standard @value{GDBN} comment
9587 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
9588 middle (to allow based literals).
9590 The debugger supports limited overloading. Given a subprogram call in which
9591 the function symbol has multiple definitions, it will use the number of
9592 actual parameters and some information about their types to attempt to narrow
9593 the set of definitions. It also makes very limited use of context, preferring
9594 procedures to functions in the context of the @code{call} command, and
9595 functions to procedures elsewhere.
9597 @node Omissions from Ada
9598 @subsubsection Omissions from Ada
9599 @cindex Ada, omissions from
9601 Here are the notable omissions from the subset:
9605 Only a subset of the attributes are supported:
9609 @t{'First}, @t{'Last}, and @t{'Length}
9610 on array objects (not on types and subtypes).
9613 @t{'Min} and @t{'Max}.
9616 @t{'Pos} and @t{'Val}.
9622 @t{'Range} on array objects (not subtypes), but only as the right
9623 operand of the membership (@code{in}) operator.
9626 @t{'Access}, @t{'Unchecked_Access}, and
9627 @t{'Unrestricted_Access} (a GNAT extension).
9635 @code{Characters.Latin_1} are not available and
9636 concatenation is not implemented. Thus, escape characters in strings are
9637 not currently available.
9640 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
9641 equality of representations. They will generally work correctly
9642 for strings and arrays whose elements have integer or enumeration types.
9643 They may not work correctly for arrays whose element
9644 types have user-defined equality, for arrays of real values
9645 (in particular, IEEE-conformant floating point, because of negative
9646 zeroes and NaNs), and for arrays whose elements contain unused bits with
9647 indeterminate values.
9650 The other component-by-component array operations (@code{and}, @code{or},
9651 @code{xor}, @code{not}, and relational tests other than equality)
9652 are not implemented.
9655 There are no record or array aggregates.
9658 Calls to dispatching subprograms are not implemented.
9661 The overloading algorithm is much more limited (i.e., less selective)
9662 than that of real Ada. It makes only limited use of the context in which a subexpression
9663 appears to resolve its meaning, and it is much looser in its rules for allowing
9664 type matches. As a result, some function calls will be ambiguous, and the user
9665 will be asked to choose the proper resolution.
9668 The @code{new} operator is not implemented.
9671 Entry calls are not implemented.
9674 Aside from printing, arithmetic operations on the native VAX floating-point
9675 formats are not supported.
9678 It is not possible to slice a packed array.
9681 @node Additions to Ada
9682 @subsubsection Additions to Ada
9683 @cindex Ada, deviations from
9685 As it does for other languages, @value{GDBN} makes certain generic
9686 extensions to Ada (@pxref{Expressions}):
9690 If the expression @var{E} is a variable residing in memory
9691 (typically a local variable or array element) and @var{N} is
9692 a positive integer, then @code{@var{E}@@@var{N}} displays the values of
9693 @var{E} and the @var{N}-1 adjacent variables following it in memory as an array.
9694 In Ada, this operator is generally not necessary, since its prime use
9695 is in displaying parts of an array, and slicing will usually do this in Ada.
9696 However, there are occasional uses when debugging programs
9697 in which certain debugging information has been optimized away.
9700 @code{@var{B}::@var{var}} means ``the variable named @var{var} that appears
9701 in function or file @var{B}.'' When @var{B} is a file name, you must typically
9702 surround it in single quotes.
9705 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
9706 @var{type} that appears at address @var{addr}.''
9709 A name starting with @samp{$} is a convenience variable
9710 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
9713 In addition, @value{GDBN} provides a few other shortcuts and outright additions specific
9718 The assignment statement is allowed as an expression, returning
9719 its right-hand operand as its value. Thus, you may enter
9723 print A(tmp := y + 1)
9727 The semicolon is allowed as an ``operator,'' returning as its value
9728 the value of its right-hand operand.
9729 This allows, for example,
9730 complex conditional breaks:
9734 condition 1 (report(i); k += 1; A(k) > 100)
9738 Rather than use catenation and symbolic character names to introduce special
9739 characters into strings, one may instead use a special bracket notation,
9740 which is also used to print strings. A sequence of characters of the form
9741 @samp{["@var{XX}"]} within a string or character literal denotes the
9742 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
9743 sequence of characters @samp{["""]} also denotes a single quotation mark
9744 in strings. For example,
9746 "One line.["0a"]Next line.["0a"]"
9749 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF}) after each
9753 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
9754 @t{'Max} is optional (and is ignored in any case). For example, it is valid
9762 When printing arrays, @value{GDBN} uses positional notation when the
9763 array has a lower bound of 1, and uses a modified named notation otherwise.
9764 For example, a one-dimensional array of three integers with a lower bound of 3 might print as
9771 That is, in contrast to valid Ada, only the first component has a @code{=>}
9775 You may abbreviate attributes in expressions with any unique,
9776 multi-character subsequence of
9777 their names (an exact match gets preference).
9778 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
9779 in place of @t{a'length}.
9782 @cindex quoting Ada internal identifiers
9783 Since Ada is case-insensitive, the debugger normally maps identifiers you type
9784 to lower case. The GNAT compiler uses upper-case characters for
9785 some of its internal identifiers, which are normally of no interest to users.
9786 For the rare occasions when you actually have to look at them,
9787 enclose them in angle brackets to avoid the lower-case mapping.
9790 @value{GDBP} print <JMPBUF_SAVE>[0]
9794 Printing an object of class-wide type or dereferencing an
9795 access-to-class-wide value will display all the components of the object's
9796 specific type (as indicated by its run-time tag). Likewise, component
9797 selection on such a value will operate on the specific type of the
9802 @node Stopping Before Main Program
9803 @subsubsection Stopping at the Very Beginning
9805 @cindex breakpointing Ada elaboration code
9806 It is sometimes necessary to debug the program during elaboration, and
9807 before reaching the main procedure.
9808 As defined in the Ada Reference
9809 Manual, the elaboration code is invoked from a procedure called
9810 @code{adainit}. To run your program up to the beginning of
9811 elaboration, simply use the following two commands:
9812 @code{tbreak adainit} and @code{run}.
9815 @subsubsection Known Peculiarities of Ada Mode
9816 @cindex Ada, problems
9818 Besides the omissions listed previously (@pxref{Omissions from Ada}),
9819 we know of several problems with and limitations of Ada mode in
9821 some of which will be fixed with planned future releases of the debugger
9822 and the GNU Ada compiler.
9826 Currently, the debugger
9827 has insufficient information to determine whether certain pointers represent
9828 pointers to objects or the objects themselves.
9829 Thus, the user may have to tack an extra @code{.all} after an expression
9830 to get it printed properly.
9833 Static constants that the compiler chooses not to materialize as objects in
9834 storage are invisible to the debugger.
9837 Named parameter associations in function argument lists are ignored (the
9838 argument lists are treated as positional).
9841 Many useful library packages are currently invisible to the debugger.
9844 Fixed-point arithmetic, conversions, input, and output is carried out using
9845 floating-point arithmetic, and may give results that only approximate those on
9849 The type of the @t{'Address} attribute may not be @code{System.Address}.
9852 The GNAT compiler never generates the prefix @code{Standard} for any of
9853 the standard symbols defined by the Ada language. @value{GDBN} knows about
9854 this: it will strip the prefix from names when you use it, and will never
9855 look for a name you have so qualified among local symbols, nor match against
9856 symbols in other packages or subprograms. If you have
9857 defined entities anywhere in your program other than parameters and
9858 local variables whose simple names match names in @code{Standard},
9859 GNAT's lack of qualification here can cause confusion. When this happens,
9860 you can usually resolve the confusion
9861 by qualifying the problematic names with package
9862 @code{Standard} explicitly.
9865 @node Unsupported languages
9866 @section Unsupported languages
9868 @cindex unsupported languages
9869 @cindex minimal language
9870 In addition to the other fully-supported programming languages,
9871 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
9872 It does not represent a real programming language, but provides a set
9873 of capabilities close to what the C or assembly languages provide.
9874 This should allow most simple operations to be performed while debugging
9875 an application that uses a language currently not supported by @value{GDBN}.
9877 If the language is set to @code{auto}, @value{GDBN} will automatically
9878 select this language if the current frame corresponds to an unsupported
9882 @chapter Examining the Symbol Table
9884 The commands described in this chapter allow you to inquire about the
9885 symbols (names of variables, functions and types) defined in your
9886 program. This information is inherent in the text of your program and
9887 does not change as your program executes. @value{GDBN} finds it in your
9888 program's symbol table, in the file indicated when you started @value{GDBN}
9889 (@pxref{File Options, ,Choosing files}), or by one of the
9890 file-management commands (@pxref{Files, ,Commands to specify files}).
9892 @cindex symbol names
9893 @cindex names of symbols
9894 @cindex quoting names
9895 Occasionally, you may need to refer to symbols that contain unusual
9896 characters, which @value{GDBN} ordinarily treats as word delimiters. The
9897 most frequent case is in referring to static variables in other
9898 source files (@pxref{Variables,,Program variables}). File names
9899 are recorded in object files as debugging symbols, but @value{GDBN} would
9900 ordinarily parse a typical file name, like @file{foo.c}, as the three words
9901 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
9902 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
9909 looks up the value of @code{x} in the scope of the file @file{foo.c}.
9912 @cindex case-insensitive symbol names
9913 @cindex case sensitivity in symbol names
9914 @kindex set case-sensitive
9915 @item set case-sensitive on
9916 @itemx set case-sensitive off
9917 @itemx set case-sensitive auto
9918 Normally, when @value{GDBN} looks up symbols, it matches their names
9919 with case sensitivity determined by the current source language.
9920 Occasionally, you may wish to control that. The command @code{set
9921 case-sensitive} lets you do that by specifying @code{on} for
9922 case-sensitive matches or @code{off} for case-insensitive ones. If
9923 you specify @code{auto}, case sensitivity is reset to the default
9924 suitable for the source language. The default is case-sensitive
9925 matches for all languages except for Fortran, for which the default is
9926 case-insensitive matches.
9928 @kindex show case-sensitive
9929 @item show case-sensitive
9930 This command shows the current setting of case sensitivity for symbols
9933 @kindex info address
9934 @cindex address of a symbol
9935 @item info address @var{symbol}
9936 Describe where the data for @var{symbol} is stored. For a register
9937 variable, this says which register it is kept in. For a non-register
9938 local variable, this prints the stack-frame offset at which the variable
9941 Note the contrast with @samp{print &@var{symbol}}, which does not work
9942 at all for a register variable, and for a stack local variable prints
9943 the exact address of the current instantiation of the variable.
9946 @cindex symbol from address
9947 @cindex closest symbol and offset for an address
9948 @item info symbol @var{addr}
9949 Print the name of a symbol which is stored at the address @var{addr}.
9950 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
9951 nearest symbol and an offset from it:
9954 (@value{GDBP}) info symbol 0x54320
9955 _initialize_vx + 396 in section .text
9959 This is the opposite of the @code{info address} command. You can use
9960 it to find out the name of a variable or a function given its address.
9963 @item whatis @var{expr}
9964 Print the data type of expression @var{expr}. @var{expr} is not
9965 actually evaluated, and any side-effecting operations (such as
9966 assignments or function calls) inside it do not take place.
9967 @xref{Expressions, ,Expressions}.
9970 Print the data type of @code{$}, the last value in the value history.
9973 @item ptype @var{typename}
9974 Print a description of data type @var{typename}. @var{typename} may be
9975 the name of a type, or for C code it may have the form @samp{class
9976 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
9977 @var{union-tag}} or @samp{enum @var{enum-tag}}.
9979 @item ptype @var{expr}
9981 Print a description of the type of expression @var{expr}. @code{ptype}
9982 differs from @code{whatis} by printing a detailed description, instead
9983 of just the name of the type.
9985 For example, for this variable declaration:
9988 struct complex @{double real; double imag;@} v;
9992 the two commands give this output:
9996 (@value{GDBP}) whatis v
9997 type = struct complex
9998 (@value{GDBP}) ptype v
9999 type = struct complex @{
10007 As with @code{whatis}, using @code{ptype} without an argument refers to
10008 the type of @code{$}, the last value in the value history.
10011 @item info types @var{regexp}
10013 Print a brief description of all types whose names match the regular
10014 expression @var{regexp} (or all types in your program, if you supply
10015 no argument). Each complete typename is matched as though it were a
10016 complete line; thus, @samp{i type value} gives information on all
10017 types in your program whose names include the string @code{value}, but
10018 @samp{i type ^value$} gives information only on types whose complete
10019 name is @code{value}.
10021 This command differs from @code{ptype} in two ways: first, like
10022 @code{whatis}, it does not print a detailed description; second, it
10023 lists all source files where a type is defined.
10026 @cindex local variables
10027 @item info scope @var{location}
10028 List all the variables local to a particular scope. This command
10029 accepts a @var{location} argument---a function name, a source line, or
10030 an address preceded by a @samp{*}, and prints all the variables local
10031 to the scope defined by that location. For example:
10034 (@value{GDBP}) @b{info scope command_line_handler}
10035 Scope for command_line_handler:
10036 Symbol rl is an argument at stack/frame offset 8, length 4.
10037 Symbol linebuffer is in static storage at address 0x150a18, length 4.
10038 Symbol linelength is in static storage at address 0x150a1c, length 4.
10039 Symbol p is a local variable in register $esi, length 4.
10040 Symbol p1 is a local variable in register $ebx, length 4.
10041 Symbol nline is a local variable in register $edx, length 4.
10042 Symbol repeat is a local variable at frame offset -8, length 4.
10046 This command is especially useful for determining what data to collect
10047 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
10050 @kindex info source
10052 Show information about the current source file---that is, the source file for
10053 the function containing the current point of execution:
10056 the name of the source file, and the directory containing it,
10058 the directory it was compiled in,
10060 its length, in lines,
10062 which programming language it is written in,
10064 whether the executable includes debugging information for that file, and
10065 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
10067 whether the debugging information includes information about
10068 preprocessor macros.
10072 @kindex info sources
10074 Print the names of all source files in your program for which there is
10075 debugging information, organized into two lists: files whose symbols
10076 have already been read, and files whose symbols will be read when needed.
10078 @kindex info functions
10079 @item info functions
10080 Print the names and data types of all defined functions.
10082 @item info functions @var{regexp}
10083 Print the names and data types of all defined functions
10084 whose names contain a match for regular expression @var{regexp}.
10085 Thus, @samp{info fun step} finds all functions whose names
10086 include @code{step}; @samp{info fun ^step} finds those whose names
10087 start with @code{step}. If a function name contains characters
10088 that conflict with the regular expression language (eg.
10089 @samp{operator*()}), they may be quoted with a backslash.
10091 @kindex info variables
10092 @item info variables
10093 Print the names and data types of all variables that are declared
10094 outside of functions (i.e.@: excluding local variables).
10096 @item info variables @var{regexp}
10097 Print the names and data types of all variables (except for local
10098 variables) whose names contain a match for regular expression
10101 @kindex info classes
10102 @cindex Objective-C, classes and selectors
10104 @itemx info classes @var{regexp}
10105 Display all Objective-C classes in your program, or
10106 (with the @var{regexp} argument) all those matching a particular regular
10109 @kindex info selectors
10110 @item info selectors
10111 @itemx info selectors @var{regexp}
10112 Display all Objective-C selectors in your program, or
10113 (with the @var{regexp} argument) all those matching a particular regular
10117 This was never implemented.
10118 @kindex info methods
10120 @itemx info methods @var{regexp}
10121 The @code{info methods} command permits the user to examine all defined
10122 methods within C@t{++} program, or (with the @var{regexp} argument) a
10123 specific set of methods found in the various C@t{++} classes. Many
10124 C@t{++} classes provide a large number of methods. Thus, the output
10125 from the @code{ptype} command can be overwhelming and hard to use. The
10126 @code{info-methods} command filters the methods, printing only those
10127 which match the regular-expression @var{regexp}.
10130 @cindex reloading symbols
10131 Some systems allow individual object files that make up your program to
10132 be replaced without stopping and restarting your program. For example,
10133 in VxWorks you can simply recompile a defective object file and keep on
10134 running. If you are running on one of these systems, you can allow
10135 @value{GDBN} to reload the symbols for automatically relinked modules:
10138 @kindex set symbol-reloading
10139 @item set symbol-reloading on
10140 Replace symbol definitions for the corresponding source file when an
10141 object file with a particular name is seen again.
10143 @item set symbol-reloading off
10144 Do not replace symbol definitions when encountering object files of the
10145 same name more than once. This is the default state; if you are not
10146 running on a system that permits automatic relinking of modules, you
10147 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
10148 may discard symbols when linking large programs, that may contain
10149 several modules (from different directories or libraries) with the same
10152 @kindex show symbol-reloading
10153 @item show symbol-reloading
10154 Show the current @code{on} or @code{off} setting.
10157 @cindex opaque data types
10158 @kindex set opaque-type-resolution
10159 @item set opaque-type-resolution on
10160 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
10161 declared as a pointer to a @code{struct}, @code{class}, or
10162 @code{union}---for example, @code{struct MyType *}---that is used in one
10163 source file although the full declaration of @code{struct MyType} is in
10164 another source file. The default is on.
10166 A change in the setting of this subcommand will not take effect until
10167 the next time symbols for a file are loaded.
10169 @item set opaque-type-resolution off
10170 Tell @value{GDBN} not to resolve opaque types. In this case, the type
10171 is printed as follows:
10173 @{<no data fields>@}
10176 @kindex show opaque-type-resolution
10177 @item show opaque-type-resolution
10178 Show whether opaque types are resolved or not.
10180 @kindex maint print symbols
10181 @cindex symbol dump
10182 @kindex maint print psymbols
10183 @cindex partial symbol dump
10184 @item maint print symbols @var{filename}
10185 @itemx maint print psymbols @var{filename}
10186 @itemx maint print msymbols @var{filename}
10187 Write a dump of debugging symbol data into the file @var{filename}.
10188 These commands are used to debug the @value{GDBN} symbol-reading code. Only
10189 symbols with debugging data are included. If you use @samp{maint print
10190 symbols}, @value{GDBN} includes all the symbols for which it has already
10191 collected full details: that is, @var{filename} reflects symbols for
10192 only those files whose symbols @value{GDBN} has read. You can use the
10193 command @code{info sources} to find out which files these are. If you
10194 use @samp{maint print psymbols} instead, the dump shows information about
10195 symbols that @value{GDBN} only knows partially---that is, symbols defined in
10196 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
10197 @samp{maint print msymbols} dumps just the minimal symbol information
10198 required for each object file from which @value{GDBN} has read some symbols.
10199 @xref{Files, ,Commands to specify files}, for a discussion of how
10200 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
10202 @kindex maint info symtabs
10203 @kindex maint info psymtabs
10204 @cindex listing @value{GDBN}'s internal symbol tables
10205 @cindex symbol tables, listing @value{GDBN}'s internal
10206 @cindex full symbol tables, listing @value{GDBN}'s internal
10207 @cindex partial symbol tables, listing @value{GDBN}'s internal
10208 @item maint info symtabs @r{[} @var{regexp} @r{]}
10209 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
10211 List the @code{struct symtab} or @code{struct partial_symtab}
10212 structures whose names match @var{regexp}. If @var{regexp} is not
10213 given, list them all. The output includes expressions which you can
10214 copy into a @value{GDBN} debugging this one to examine a particular
10215 structure in more detail. For example:
10218 (@value{GDBP}) maint info psymtabs dwarf2read
10219 @{ objfile /home/gnu/build/gdb/gdb
10220 ((struct objfile *) 0x82e69d0)
10221 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
10222 ((struct partial_symtab *) 0x8474b10)
10225 text addresses 0x814d3c8 -- 0x8158074
10226 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
10227 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
10228 dependencies (none)
10231 (@value{GDBP}) maint info symtabs
10235 We see that there is one partial symbol table whose filename contains
10236 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
10237 and we see that @value{GDBN} has not read in any symtabs yet at all.
10238 If we set a breakpoint on a function, that will cause @value{GDBN} to
10239 read the symtab for the compilation unit containing that function:
10242 (@value{GDBP}) break dwarf2_psymtab_to_symtab
10243 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
10245 (@value{GDBP}) maint info symtabs
10246 @{ objfile /home/gnu/build/gdb/gdb
10247 ((struct objfile *) 0x82e69d0)
10248 @{ symtab /home/gnu/src/gdb/dwarf2read.c
10249 ((struct symtab *) 0x86c1f38)
10252 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
10253 debugformat DWARF 2
10262 @chapter Altering Execution
10264 Once you think you have found an error in your program, you might want to
10265 find out for certain whether correcting the apparent error would lead to
10266 correct results in the rest of the run. You can find the answer by
10267 experiment, using the @value{GDBN} features for altering execution of the
10270 For example, you can store new values into variables or memory
10271 locations, give your program a signal, restart it at a different
10272 address, or even return prematurely from a function.
10275 * Assignment:: Assignment to variables
10276 * Jumping:: Continuing at a different address
10277 * Signaling:: Giving your program a signal
10278 * Returning:: Returning from a function
10279 * Calling:: Calling your program's functions
10280 * Patching:: Patching your program
10284 @section Assignment to variables
10287 @cindex setting variables
10288 To alter the value of a variable, evaluate an assignment expression.
10289 @xref{Expressions, ,Expressions}. For example,
10296 stores the value 4 into the variable @code{x}, and then prints the
10297 value of the assignment expression (which is 4).
10298 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
10299 information on operators in supported languages.
10301 @kindex set variable
10302 @cindex variables, setting
10303 If you are not interested in seeing the value of the assignment, use the
10304 @code{set} command instead of the @code{print} command. @code{set} is
10305 really the same as @code{print} except that the expression's value is
10306 not printed and is not put in the value history (@pxref{Value History,
10307 ,Value history}). The expression is evaluated only for its effects.
10309 If the beginning of the argument string of the @code{set} command
10310 appears identical to a @code{set} subcommand, use the @code{set
10311 variable} command instead of just @code{set}. This command is identical
10312 to @code{set} except for its lack of subcommands. For example, if your
10313 program has a variable @code{width}, you get an error if you try to set
10314 a new value with just @samp{set width=13}, because @value{GDBN} has the
10315 command @code{set width}:
10318 (@value{GDBP}) whatis width
10320 (@value{GDBP}) p width
10322 (@value{GDBP}) set width=47
10323 Invalid syntax in expression.
10327 The invalid expression, of course, is @samp{=47}. In
10328 order to actually set the program's variable @code{width}, use
10331 (@value{GDBP}) set var width=47
10334 Because the @code{set} command has many subcommands that can conflict
10335 with the names of program variables, it is a good idea to use the
10336 @code{set variable} command instead of just @code{set}. For example, if
10337 your program has a variable @code{g}, you run into problems if you try
10338 to set a new value with just @samp{set g=4}, because @value{GDBN} has
10339 the command @code{set gnutarget}, abbreviated @code{set g}:
10343 (@value{GDBP}) whatis g
10347 (@value{GDBP}) set g=4
10351 The program being debugged has been started already.
10352 Start it from the beginning? (y or n) y
10353 Starting program: /home/smith/cc_progs/a.out
10354 "/home/smith/cc_progs/a.out": can't open to read symbols:
10355 Invalid bfd target.
10356 (@value{GDBP}) show g
10357 The current BFD target is "=4".
10362 The program variable @code{g} did not change, and you silently set the
10363 @code{gnutarget} to an invalid value. In order to set the variable
10367 (@value{GDBP}) set var g=4
10370 @value{GDBN} allows more implicit conversions in assignments than C; you can
10371 freely store an integer value into a pointer variable or vice versa,
10372 and you can convert any structure to any other structure that is the
10373 same length or shorter.
10374 @comment FIXME: how do structs align/pad in these conversions?
10375 @comment /doc@cygnus.com 18dec1990
10377 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
10378 construct to generate a value of specified type at a specified address
10379 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
10380 to memory location @code{0x83040} as an integer (which implies a certain size
10381 and representation in memory), and
10384 set @{int@}0x83040 = 4
10388 stores the value 4 into that memory location.
10391 @section Continuing at a different address
10393 Ordinarily, when you continue your program, you do so at the place where
10394 it stopped, with the @code{continue} command. You can instead continue at
10395 an address of your own choosing, with the following commands:
10399 @item jump @var{linespec}
10400 Resume execution at line @var{linespec}. Execution stops again
10401 immediately if there is a breakpoint there. @xref{List, ,Printing
10402 source lines}, for a description of the different forms of
10403 @var{linespec}. It is common practice to use the @code{tbreak} command
10404 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
10407 The @code{jump} command does not change the current stack frame, or
10408 the stack pointer, or the contents of any memory location or any
10409 register other than the program counter. If line @var{linespec} is in
10410 a different function from the one currently executing, the results may
10411 be bizarre if the two functions expect different patterns of arguments or
10412 of local variables. For this reason, the @code{jump} command requests
10413 confirmation if the specified line is not in the function currently
10414 executing. However, even bizarre results are predictable if you are
10415 well acquainted with the machine-language code of your program.
10417 @item jump *@var{address}
10418 Resume execution at the instruction at address @var{address}.
10421 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
10422 On many systems, you can get much the same effect as the @code{jump}
10423 command by storing a new value into the register @code{$pc}. The
10424 difference is that this does not start your program running; it only
10425 changes the address of where it @emph{will} run when you continue. For
10433 makes the next @code{continue} command or stepping command execute at
10434 address @code{0x485}, rather than at the address where your program stopped.
10435 @xref{Continuing and Stepping, ,Continuing and stepping}.
10437 The most common occasion to use the @code{jump} command is to back
10438 up---perhaps with more breakpoints set---over a portion of a program
10439 that has already executed, in order to examine its execution in more
10444 @section Giving your program a signal
10445 @cindex deliver a signal to a program
10449 @item signal @var{signal}
10450 Resume execution where your program stopped, but immediately give it the
10451 signal @var{signal}. @var{signal} can be the name or the number of a
10452 signal. For example, on many systems @code{signal 2} and @code{signal
10453 SIGINT} are both ways of sending an interrupt signal.
10455 Alternatively, if @var{signal} is zero, continue execution without
10456 giving a signal. This is useful when your program stopped on account of
10457 a signal and would ordinary see the signal when resumed with the
10458 @code{continue} command; @samp{signal 0} causes it to resume without a
10461 @code{signal} does not repeat when you press @key{RET} a second time
10462 after executing the command.
10466 Invoking the @code{signal} command is not the same as invoking the
10467 @code{kill} utility from the shell. Sending a signal with @code{kill}
10468 causes @value{GDBN} to decide what to do with the signal depending on
10469 the signal handling tables (@pxref{Signals}). The @code{signal} command
10470 passes the signal directly to your program.
10474 @section Returning from a function
10477 @cindex returning from a function
10480 @itemx return @var{expression}
10481 You can cancel execution of a function call with the @code{return}
10482 command. If you give an
10483 @var{expression} argument, its value is used as the function's return
10487 When you use @code{return}, @value{GDBN} discards the selected stack frame
10488 (and all frames within it). You can think of this as making the
10489 discarded frame return prematurely. If you wish to specify a value to
10490 be returned, give that value as the argument to @code{return}.
10492 This pops the selected stack frame (@pxref{Selection, ,Selecting a
10493 frame}), and any other frames inside of it, leaving its caller as the
10494 innermost remaining frame. That frame becomes selected. The
10495 specified value is stored in the registers used for returning values
10498 The @code{return} command does not resume execution; it leaves the
10499 program stopped in the state that would exist if the function had just
10500 returned. In contrast, the @code{finish} command (@pxref{Continuing
10501 and Stepping, ,Continuing and stepping}) resumes execution until the
10502 selected stack frame returns naturally.
10505 @section Calling program functions
10508 @cindex calling functions
10509 @cindex inferior functions, calling
10510 @item print @var{expr}
10511 Evaluate the expression @var{expr} and display the resuling value.
10512 @var{expr} may include calls to functions in the program being
10516 @item call @var{expr}
10517 Evaluate the expression @var{expr} without displaying @code{void}
10520 You can use this variant of the @code{print} command if you want to
10521 execute a function from your program that does not return anything
10522 (a.k.a.@: @dfn{a void function}), but without cluttering the output
10523 with @code{void} returned values that @value{GDBN} will otherwise
10524 print. If the result is not void, it is printed and saved in the
10528 It is possible for the function you call via the @code{print} or
10529 @code{call} command to generate a signal (e.g., if there's a bug in
10530 the function, or if you passed it incorrect arguments). What happens
10531 in that case is controlled by the @code{set unwindonsignal} command.
10534 @item set unwindonsignal
10535 @kindex set unwindonsignal
10536 @cindex unwind stack in called functions
10537 @cindex call dummy stack unwinding
10538 Set unwinding of the stack if a signal is received while in a function
10539 that @value{GDBN} called in the program being debugged. If set to on,
10540 @value{GDBN} unwinds the stack it created for the call and restores
10541 the context to what it was before the call. If set to off (the
10542 default), @value{GDBN} stops in the frame where the signal was
10545 @item show unwindonsignal
10546 @kindex show unwindonsignal
10547 Show the current setting of stack unwinding in the functions called by
10551 @cindex weak alias functions
10552 Sometimes, a function you wish to call is actually a @dfn{weak alias}
10553 for another function. In such case, @value{GDBN} might not pick up
10554 the type information, including the types of the function arguments,
10555 which causes @value{GDBN} to call the inferior function incorrectly.
10556 As a result, the called function will function erroneously and may
10557 even crash. A solution to that is to use the name of the aliased
10561 @section Patching programs
10563 @cindex patching binaries
10564 @cindex writing into executables
10565 @cindex writing into corefiles
10567 By default, @value{GDBN} opens the file containing your program's
10568 executable code (or the corefile) read-only. This prevents accidental
10569 alterations to machine code; but it also prevents you from intentionally
10570 patching your program's binary.
10572 If you'd like to be able to patch the binary, you can specify that
10573 explicitly with the @code{set write} command. For example, you might
10574 want to turn on internal debugging flags, or even to make emergency
10580 @itemx set write off
10581 If you specify @samp{set write on}, @value{GDBN} opens executable and
10582 core files for both reading and writing; if you specify @samp{set write
10583 off} (the default), @value{GDBN} opens them read-only.
10585 If you have already loaded a file, you must load it again (using the
10586 @code{exec-file} or @code{core-file} command) after changing @code{set
10587 write}, for your new setting to take effect.
10591 Display whether executable files and core files are opened for writing
10592 as well as reading.
10596 @chapter @value{GDBN} Files
10598 @value{GDBN} needs to know the file name of the program to be debugged,
10599 both in order to read its symbol table and in order to start your
10600 program. To debug a core dump of a previous run, you must also tell
10601 @value{GDBN} the name of the core dump file.
10604 * Files:: Commands to specify files
10605 * Separate Debug Files:: Debugging information in separate files
10606 * Symbol Errors:: Errors reading symbol files
10610 @section Commands to specify files
10612 @cindex symbol table
10613 @cindex core dump file
10615 You may want to specify executable and core dump file names. The usual
10616 way to do this is at start-up time, using the arguments to
10617 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
10618 Out of @value{GDBN}}).
10620 Occasionally it is necessary to change to a different file during a
10621 @value{GDBN} session. Or you may run @value{GDBN} and forget to specify
10622 a file you want to use. In these situations the @value{GDBN} commands
10623 to specify new files are useful.
10626 @cindex executable file
10628 @item file @var{filename}
10629 Use @var{filename} as the program to be debugged. It is read for its
10630 symbols and for the contents of pure memory. It is also the program
10631 executed when you use the @code{run} command. If you do not specify a
10632 directory and the file is not found in the @value{GDBN} working directory,
10633 @value{GDBN} uses the environment variable @code{PATH} as a list of
10634 directories to search, just as the shell does when looking for a program
10635 to run. You can change the value of this variable, for both @value{GDBN}
10636 and your program, using the @code{path} command.
10638 On systems with memory-mapped files, an auxiliary file named
10639 @file{@var{filename}.syms} may hold symbol table information for
10640 @var{filename}. If so, @value{GDBN} maps in the symbol table from
10641 @file{@var{filename}.syms}, starting up more quickly. See the
10642 descriptions of the file options @samp{-mapped} and @samp{-readnow}
10643 (available on the command line, see @ref{File Options, , -readnow},
10644 and with the commands @code{file}, @code{symbol-file}, or
10645 @code{add-symbol-file}, described below), for more information.
10648 @code{file} with no argument makes @value{GDBN} discard any information it
10649 has on both executable file and the symbol table.
10652 @item exec-file @r{[} @var{filename} @r{]}
10653 Specify that the program to be run (but not the symbol table) is found
10654 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
10655 if necessary to locate your program. Omitting @var{filename} means to
10656 discard information on the executable file.
10658 @kindex symbol-file
10659 @item symbol-file @r{[} @var{filename} @r{]}
10660 Read symbol table information from file @var{filename}. @code{PATH} is
10661 searched when necessary. Use the @code{file} command to get both symbol
10662 table and program to run from the same file.
10664 @code{symbol-file} with no argument clears out @value{GDBN} information on your
10665 program's symbol table.
10667 The @code{symbol-file} command causes @value{GDBN} to forget the contents
10668 of its convenience variables, the value history, and all breakpoints and
10669 auto-display expressions. This is because they may contain pointers to
10670 the internal data recording symbols and data types, which are part of
10671 the old symbol table data being discarded inside @value{GDBN}.
10673 @code{symbol-file} does not repeat if you press @key{RET} again after
10676 When @value{GDBN} is configured for a particular environment, it
10677 understands debugging information in whatever format is the standard
10678 generated for that environment; you may use either a @sc{gnu} compiler, or
10679 other compilers that adhere to the local conventions.
10680 Best results are usually obtained from @sc{gnu} compilers; for example,
10681 using @code{@value{GCC}} you can generate debugging information for
10684 For most kinds of object files, with the exception of old SVR3 systems
10685 using COFF, the @code{symbol-file} command does not normally read the
10686 symbol table in full right away. Instead, it scans the symbol table
10687 quickly to find which source files and which symbols are present. The
10688 details are read later, one source file at a time, as they are needed.
10690 The purpose of this two-stage reading strategy is to make @value{GDBN}
10691 start up faster. For the most part, it is invisible except for
10692 occasional pauses while the symbol table details for a particular source
10693 file are being read. (The @code{set verbose} command can turn these
10694 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
10695 warnings and messages}.)
10697 We have not implemented the two-stage strategy for COFF yet. When the
10698 symbol table is stored in COFF format, @code{symbol-file} reads the
10699 symbol table data in full right away. Note that ``stabs-in-COFF''
10700 still does the two-stage strategy, since the debug info is actually
10704 @cindex reading symbols immediately
10705 @cindex symbols, reading immediately
10707 @cindex memory-mapped symbol file
10708 @cindex saving symbol table
10709 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10710 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10711 You can override the @value{GDBN} two-stage strategy for reading symbol
10712 tables by using the @samp{-readnow} option with any of the commands that
10713 load symbol table information, if you want to be sure @value{GDBN} has the
10714 entire symbol table available.
10716 If memory-mapped files are available on your system through the
10717 @code{mmap} system call, you can use another option, @samp{-mapped}, to
10718 cause @value{GDBN} to write the symbols for your program into a reusable
10719 file. Future @value{GDBN} debugging sessions map in symbol information
10720 from this auxiliary symbol file (if the program has not changed), rather
10721 than spending time reading the symbol table from the executable
10722 program. Using the @samp{-mapped} option has the same effect as
10723 starting @value{GDBN} with the @samp{-mapped} command-line option.
10725 You can use both options together, to make sure the auxiliary symbol
10726 file has all the symbol information for your program.
10728 The auxiliary symbol file for a program called @var{myprog} is called
10729 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
10730 than the corresponding executable), @value{GDBN} always attempts to use
10731 it when you debug @var{myprog}; no special options or commands are
10734 The @file{.syms} file is specific to the host machine where you run
10735 @value{GDBN}. It holds an exact image of the internal @value{GDBN}
10736 symbol table. It cannot be shared across multiple host platforms.
10738 @c FIXME: for now no mention of directories, since this seems to be in
10739 @c flux. 13mar1992 status is that in theory GDB would look either in
10740 @c current dir or in same dir as myprog; but issues like competing
10741 @c GDB's, or clutter in system dirs, mean that in practice right now
10742 @c only current dir is used. FFish says maybe a special GDB hierarchy
10743 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
10747 @item core-file @r{[}@var{filename}@r{]}
10749 Specify the whereabouts of a core dump file to be used as the ``contents
10750 of memory''. Traditionally, core files contain only some parts of the
10751 address space of the process that generated them; @value{GDBN} can access the
10752 executable file itself for other parts.
10754 @code{core-file} with no argument specifies that no core file is
10757 Note that the core file is ignored when your program is actually running
10758 under @value{GDBN}. So, if you have been running your program and you
10759 wish to debug a core file instead, you must kill the subprocess in which
10760 the program is running. To do this, use the @code{kill} command
10761 (@pxref{Kill Process, ,Killing the child process}).
10763 @kindex add-symbol-file
10764 @cindex dynamic linking
10765 @item add-symbol-file @var{filename} @var{address}
10766 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10767 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
10768 The @code{add-symbol-file} command reads additional symbol table
10769 information from the file @var{filename}. You would use this command
10770 when @var{filename} has been dynamically loaded (by some other means)
10771 into the program that is running. @var{address} should be the memory
10772 address at which the file has been loaded; @value{GDBN} cannot figure
10773 this out for itself. You can additionally specify an arbitrary number
10774 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
10775 section name and base address for that section. You can specify any
10776 @var{address} as an expression.
10778 The symbol table of the file @var{filename} is added to the symbol table
10779 originally read with the @code{symbol-file} command. You can use the
10780 @code{add-symbol-file} command any number of times; the new symbol data
10781 thus read keeps adding to the old. To discard all old symbol data
10782 instead, use the @code{symbol-file} command without any arguments.
10784 @cindex relocatable object files, reading symbols from
10785 @cindex object files, relocatable, reading symbols from
10786 @cindex reading symbols from relocatable object files
10787 @cindex symbols, reading from relocatable object files
10788 @cindex @file{.o} files, reading symbols from
10789 Although @var{filename} is typically a shared library file, an
10790 executable file, or some other object file which has been fully
10791 relocated for loading into a process, you can also load symbolic
10792 information from relocatable @file{.o} files, as long as:
10796 the file's symbolic information refers only to linker symbols defined in
10797 that file, not to symbols defined by other object files,
10799 every section the file's symbolic information refers to has actually
10800 been loaded into the inferior, as it appears in the file, and
10802 you can determine the address at which every section was loaded, and
10803 provide these to the @code{add-symbol-file} command.
10807 Some embedded operating systems, like Sun Chorus and VxWorks, can load
10808 relocatable files into an already running program; such systems
10809 typically make the requirements above easy to meet. However, it's
10810 important to recognize that many native systems use complex link
10811 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
10812 assembly, for example) that make the requirements difficult to meet. In
10813 general, one cannot assume that using @code{add-symbol-file} to read a
10814 relocatable object file's symbolic information will have the same effect
10815 as linking the relocatable object file into the program in the normal
10818 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
10820 You can use the @samp{-mapped} and @samp{-readnow} options just as with
10821 the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
10822 table information for @var{filename}.
10824 @kindex add-symbol-file-from-memory
10825 @cindex @code{syscall DSO}
10826 @cindex load symbols from memory
10827 @item add-symbol-file-from-memory @var{address}
10828 Load symbols from the given @var{address} in a dynamically loaded
10829 object file whose image is mapped directly into the inferior's memory.
10830 For example, the Linux kernel maps a @code{syscall DSO} into each
10831 process's address space; this DSO provides kernel-specific code for
10832 some system calls. The argument can be any expression whose
10833 evaluation yields the address of the file's shared object file header.
10834 For this command to work, you must have used @code{symbol-file} or
10835 @code{exec-file} commands in advance.
10837 @kindex add-shared-symbol-files
10839 @item add-shared-symbol-files @var{library-file}
10840 @itemx assf @var{library-file}
10841 The @code{add-shared-symbol-files} command can currently be used only
10842 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
10843 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
10844 @value{GDBN} automatically looks for shared libraries, however if
10845 @value{GDBN} does not find yours, you can invoke
10846 @code{add-shared-symbol-files}. It takes one argument: the shared
10847 library's file name. @code{assf} is a shorthand alias for
10848 @code{add-shared-symbol-files}.
10851 @item section @var{section} @var{addr}
10852 The @code{section} command changes the base address of the named
10853 @var{section} of the exec file to @var{addr}. This can be used if the
10854 exec file does not contain section addresses, (such as in the
10855 @code{a.out} format), or when the addresses specified in the file
10856 itself are wrong. Each section must be changed separately. The
10857 @code{info files} command, described below, lists all the sections and
10861 @kindex info target
10864 @code{info files} and @code{info target} are synonymous; both print the
10865 current target (@pxref{Targets, ,Specifying a Debugging Target}),
10866 including the names of the executable and core dump files currently in
10867 use by @value{GDBN}, and the files from which symbols were loaded. The
10868 command @code{help target} lists all possible targets rather than
10871 @kindex maint info sections
10872 @item maint info sections
10873 Another command that can give you extra information about program sections
10874 is @code{maint info sections}. In addition to the section information
10875 displayed by @code{info files}, this command displays the flags and file
10876 offset of each section in the executable and core dump files. In addition,
10877 @code{maint info sections} provides the following command options (which
10878 may be arbitrarily combined):
10882 Display sections for all loaded object files, including shared libraries.
10883 @item @var{sections}
10884 Display info only for named @var{sections}.
10885 @item @var{section-flags}
10886 Display info only for sections for which @var{section-flags} are true.
10887 The section flags that @value{GDBN} currently knows about are:
10890 Section will have space allocated in the process when loaded.
10891 Set for all sections except those containing debug information.
10893 Section will be loaded from the file into the child process memory.
10894 Set for pre-initialized code and data, clear for @code{.bss} sections.
10896 Section needs to be relocated before loading.
10898 Section cannot be modified by the child process.
10900 Section contains executable code only.
10902 Section contains data only (no executable code).
10904 Section will reside in ROM.
10906 Section contains data for constructor/destructor lists.
10908 Section is not empty.
10910 An instruction to the linker to not output the section.
10911 @item COFF_SHARED_LIBRARY
10912 A notification to the linker that the section contains
10913 COFF shared library information.
10915 Section contains common symbols.
10918 @kindex set trust-readonly-sections
10919 @cindex read-only sections
10920 @item set trust-readonly-sections on
10921 Tell @value{GDBN} that readonly sections in your object file
10922 really are read-only (i.e.@: that their contents will not change).
10923 In that case, @value{GDBN} can fetch values from these sections
10924 out of the object file, rather than from the target program.
10925 For some targets (notably embedded ones), this can be a significant
10926 enhancement to debugging performance.
10928 The default is off.
10930 @item set trust-readonly-sections off
10931 Tell @value{GDBN} not to trust readonly sections. This means that
10932 the contents of the section might change while the program is running,
10933 and must therefore be fetched from the target when needed.
10935 @item show trust-readonly-sections
10936 Show the current setting of trusting readonly sections.
10939 All file-specifying commands allow both absolute and relative file names
10940 as arguments. @value{GDBN} always converts the file name to an absolute file
10941 name and remembers it that way.
10943 @cindex shared libraries
10944 @value{GDBN} supports GNU/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
10945 and IBM RS/6000 AIX shared libraries.
10947 @value{GDBN} automatically loads symbol definitions from shared libraries
10948 when you use the @code{run} command, or when you examine a core file.
10949 (Before you issue the @code{run} command, @value{GDBN} does not understand
10950 references to a function in a shared library, however---unless you are
10951 debugging a core file).
10953 On HP-UX, if the program loads a library explicitly, @value{GDBN}
10954 automatically loads the symbols at the time of the @code{shl_load} call.
10956 @c FIXME: some @value{GDBN} release may permit some refs to undef
10957 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
10958 @c FIXME...lib; check this from time to time when updating manual
10960 There are times, however, when you may wish to not automatically load
10961 symbol definitions from shared libraries, such as when they are
10962 particularly large or there are many of them.
10964 To control the automatic loading of shared library symbols, use the
10968 @kindex set auto-solib-add
10969 @item set auto-solib-add @var{mode}
10970 If @var{mode} is @code{on}, symbols from all shared object libraries
10971 will be loaded automatically when the inferior begins execution, you
10972 attach to an independently started inferior, or when the dynamic linker
10973 informs @value{GDBN} that a new library has been loaded. If @var{mode}
10974 is @code{off}, symbols must be loaded manually, using the
10975 @code{sharedlibrary} command. The default value is @code{on}.
10977 @cindex memory used for symbol tables
10978 If your program uses lots of shared libraries with debug info that
10979 takes large amounts of memory, you can decrease the @value{GDBN}
10980 memory footprint by preventing it from automatically loading the
10981 symbols from shared libraries. To that end, type @kbd{set
10982 auto-solib-add off} before running the inferior, then load each
10983 library whose debug symbols you do need with @kbd{sharedlibrary
10984 @var{regexp}}, where @var{regexp} is a regular expresion that matches
10985 the libraries whose symbols you want to be loaded.
10987 @kindex show auto-solib-add
10988 @item show auto-solib-add
10989 Display the current autoloading mode.
10992 @cindex load shared library
10993 To explicitly load shared library symbols, use the @code{sharedlibrary}
10997 @kindex info sharedlibrary
11000 @itemx info sharedlibrary
11001 Print the names of the shared libraries which are currently loaded.
11003 @kindex sharedlibrary
11005 @item sharedlibrary @var{regex}
11006 @itemx share @var{regex}
11007 Load shared object library symbols for files matching a
11008 Unix regular expression.
11009 As with files loaded automatically, it only loads shared libraries
11010 required by your program for a core file or after typing @code{run}. If
11011 @var{regex} is omitted all shared libraries required by your program are
11014 @item nosharedlibrary
11015 @kindex nosharedlibrary
11016 @cindex unload symbols from shared libraries
11017 Unload all shared object library symbols. This discards all symbols
11018 that have been loaded from all shared libraries. Symbols from shared
11019 libraries that were loaded by explicit user requests are not
11023 Sometimes you may wish that @value{GDBN} stops and gives you control
11024 when any of shared library events happen. Use the @code{set
11025 stop-on-solib-events} command for this:
11028 @item set stop-on-solib-events
11029 @kindex set stop-on-solib-events
11030 This command controls whether @value{GDBN} should give you control
11031 when the dynamic linker notifies it about some shared library event.
11032 The most common event of interest is loading or unloading of a new
11035 @item show stop-on-solib-events
11036 @kindex show stop-on-solib-events
11037 Show whether @value{GDBN} stops and gives you control when shared
11038 library events happen.
11041 Shared libraries are also supported in many cross or remote debugging
11042 configurations. A copy of the target's libraries need to be present on the
11043 host system; they need to be the same as the target libraries, although the
11044 copies on the target can be stripped as long as the copies on the host are
11047 You need to tell @value{GDBN} where the target libraries are, so that it can
11048 load the correct copies---otherwise, it may try to load the host's libraries.
11049 @value{GDBN} has two variables to specify the search directories for target
11053 @kindex set solib-absolute-prefix
11054 @item set solib-absolute-prefix @var{path}
11055 If this variable is set, @var{path} will be used as a prefix for any
11056 absolute shared library paths; many runtime loaders store the absolute
11057 paths to the shared library in the target program's memory. If you use
11058 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
11059 out in the same way that they are on the target, with e.g.@: a
11060 @file{/usr/lib} hierarchy under @var{path}.
11062 You can set the default value of @samp{solib-absolute-prefix} by using the
11063 configure-time @samp{--with-sysroot} option.
11065 @kindex show solib-absolute-prefix
11066 @item show solib-absolute-prefix
11067 Display the current shared library prefix.
11069 @kindex set solib-search-path
11070 @item set solib-search-path @var{path}
11071 If this variable is set, @var{path} is a colon-separated list of directories
11072 to search for shared libraries. @samp{solib-search-path} is used after
11073 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
11074 the library is relative instead of absolute. If you want to use
11075 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
11076 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
11077 @value{GDBN} from finding your host's libraries.
11079 @kindex show solib-search-path
11080 @item show solib-search-path
11081 Display the current shared library search path.
11085 @node Separate Debug Files
11086 @section Debugging Information in Separate Files
11087 @cindex separate debugging information files
11088 @cindex debugging information in separate files
11089 @cindex @file{.debug} subdirectories
11090 @cindex debugging information directory, global
11091 @cindex global debugging information directory
11093 @value{GDBN} allows you to put a program's debugging information in a
11094 file separate from the executable itself, in a way that allows
11095 @value{GDBN} to find and load the debugging information automatically.
11096 Since debugging information can be very large --- sometimes larger
11097 than the executable code itself --- some systems distribute debugging
11098 information for their executables in separate files, which users can
11099 install only when they need to debug a problem.
11101 If an executable's debugging information has been extracted to a
11102 separate file, the executable should contain a @dfn{debug link} giving
11103 the name of the debugging information file (with no directory
11104 components), and a checksum of its contents. (The exact form of a
11105 debug link is described below.) If the full name of the directory
11106 containing the executable is @var{execdir}, and the executable has a
11107 debug link that specifies the name @var{debugfile}, then @value{GDBN}
11108 will automatically search for the debugging information file in three
11113 the directory containing the executable file (that is, it will look
11114 for a file named @file{@var{execdir}/@var{debugfile}},
11116 a subdirectory of that directory named @file{.debug} (that is, the
11117 file @file{@var{execdir}/.debug/@var{debugfile}}, and
11119 a subdirectory of the global debug file directory that includes the
11120 executable's full path, and the name from the link (that is, the file
11121 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
11122 @var{globaldebugdir} is the global debug file directory, and
11123 @var{execdir} has been turned into a relative path).
11126 @value{GDBN} checks under each of these names for a debugging
11127 information file whose checksum matches that given in the link, and
11128 reads the debugging information from the first one it finds.
11130 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
11131 which has a link containing the name @file{ls.debug}, and the global
11132 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
11133 for debug information in @file{/usr/bin/ls.debug},
11134 @file{/usr/bin/.debug/ls.debug}, and
11135 @file{/usr/lib/debug/usr/bin/ls.debug}.
11137 You can set the global debugging info directory's name, and view the
11138 name @value{GDBN} is currently using.
11142 @kindex set debug-file-directory
11143 @item set debug-file-directory @var{directory}
11144 Set the directory which @value{GDBN} searches for separate debugging
11145 information files to @var{directory}.
11147 @kindex show debug-file-directory
11148 @item show debug-file-directory
11149 Show the directory @value{GDBN} searches for separate debugging
11154 @cindex @code{.gnu_debuglink} sections
11155 @cindex debug links
11156 A debug link is a special section of the executable file named
11157 @code{.gnu_debuglink}. The section must contain:
11161 A filename, with any leading directory components removed, followed by
11164 zero to three bytes of padding, as needed to reach the next four-byte
11165 boundary within the section, and
11167 a four-byte CRC checksum, stored in the same endianness used for the
11168 executable file itself. The checksum is computed on the debugging
11169 information file's full contents by the function given below, passing
11170 zero as the @var{crc} argument.
11173 Any executable file format can carry a debug link, as long as it can
11174 contain a section named @code{.gnu_debuglink} with the contents
11177 The debugging information file itself should be an ordinary
11178 executable, containing a full set of linker symbols, sections, and
11179 debugging information. The sections of the debugging information file
11180 should have the same names, addresses and sizes as the original file,
11181 but they need not contain any data --- much like a @code{.bss} section
11182 in an ordinary executable.
11184 As of December 2002, there is no standard GNU utility to produce
11185 separated executable / debugging information file pairs. Ulrich
11186 Drepper's @file{elfutils} package, starting with version 0.53,
11187 contains a version of the @code{strip} command such that the command
11188 @kbd{strip foo -f foo.debug} removes the debugging information from
11189 the executable file @file{foo}, places it in the file
11190 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
11192 Since there are many different ways to compute CRC's (different
11193 polynomials, reversals, byte ordering, etc.), the simplest way to
11194 describe the CRC used in @code{.gnu_debuglink} sections is to give the
11195 complete code for a function that computes it:
11197 @kindex gnu_debuglink_crc32
11200 gnu_debuglink_crc32 (unsigned long crc,
11201 unsigned char *buf, size_t len)
11203 static const unsigned long crc32_table[256] =
11205 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
11206 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
11207 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
11208 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
11209 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
11210 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
11211 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
11212 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
11213 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
11214 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
11215 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
11216 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
11217 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
11218 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
11219 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
11220 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
11221 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
11222 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
11223 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
11224 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
11225 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
11226 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
11227 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
11228 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
11229 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
11230 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
11231 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
11232 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
11233 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
11234 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
11235 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
11236 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
11237 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
11238 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
11239 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
11240 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
11241 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
11242 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
11243 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
11244 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
11245 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
11246 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
11247 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
11248 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
11249 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
11250 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
11251 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
11252 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
11253 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
11254 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
11255 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
11258 unsigned char *end;
11260 crc = ~crc & 0xffffffff;
11261 for (end = buf + len; buf < end; ++buf)
11262 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
11263 return ~crc & 0xffffffff;
11268 @node Symbol Errors
11269 @section Errors reading symbol files
11271 While reading a symbol file, @value{GDBN} occasionally encounters problems,
11272 such as symbol types it does not recognize, or known bugs in compiler
11273 output. By default, @value{GDBN} does not notify you of such problems, since
11274 they are relatively common and primarily of interest to people
11275 debugging compilers. If you are interested in seeing information
11276 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
11277 only one message about each such type of problem, no matter how many
11278 times the problem occurs; or you can ask @value{GDBN} to print more messages,
11279 to see how many times the problems occur, with the @code{set
11280 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
11283 The messages currently printed, and their meanings, include:
11286 @item inner block not inside outer block in @var{symbol}
11288 The symbol information shows where symbol scopes begin and end
11289 (such as at the start of a function or a block of statements). This
11290 error indicates that an inner scope block is not fully contained
11291 in its outer scope blocks.
11293 @value{GDBN} circumvents the problem by treating the inner block as if it had
11294 the same scope as the outer block. In the error message, @var{symbol}
11295 may be shown as ``@code{(don't know)}'' if the outer block is not a
11298 @item block at @var{address} out of order
11300 The symbol information for symbol scope blocks should occur in
11301 order of increasing addresses. This error indicates that it does not
11304 @value{GDBN} does not circumvent this problem, and has trouble
11305 locating symbols in the source file whose symbols it is reading. (You
11306 can often determine what source file is affected by specifying
11307 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
11310 @item bad block start address patched
11312 The symbol information for a symbol scope block has a start address
11313 smaller than the address of the preceding source line. This is known
11314 to occur in the SunOS 4.1.1 (and earlier) C compiler.
11316 @value{GDBN} circumvents the problem by treating the symbol scope block as
11317 starting on the previous source line.
11319 @item bad string table offset in symbol @var{n}
11322 Symbol number @var{n} contains a pointer into the string table which is
11323 larger than the size of the string table.
11325 @value{GDBN} circumvents the problem by considering the symbol to have the
11326 name @code{foo}, which may cause other problems if many symbols end up
11329 @item unknown symbol type @code{0x@var{nn}}
11331 The symbol information contains new data types that @value{GDBN} does
11332 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
11333 uncomprehended information, in hexadecimal.
11335 @value{GDBN} circumvents the error by ignoring this symbol information.
11336 This usually allows you to debug your program, though certain symbols
11337 are not accessible. If you encounter such a problem and feel like
11338 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
11339 on @code{complain}, then go up to the function @code{read_dbx_symtab}
11340 and examine @code{*bufp} to see the symbol.
11342 @item stub type has NULL name
11344 @value{GDBN} could not find the full definition for a struct or class.
11346 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
11347 The symbol information for a C@t{++} member function is missing some
11348 information that recent versions of the compiler should have output for
11351 @item info mismatch between compiler and debugger
11353 @value{GDBN} could not parse a type specification output by the compiler.
11358 @chapter Specifying a Debugging Target
11360 @cindex debugging target
11361 A @dfn{target} is the execution environment occupied by your program.
11363 Often, @value{GDBN} runs in the same host environment as your program;
11364 in that case, the debugging target is specified as a side effect when
11365 you use the @code{file} or @code{core} commands. When you need more
11366 flexibility---for example, running @value{GDBN} on a physically separate
11367 host, or controlling a standalone system over a serial port or a
11368 realtime system over a TCP/IP connection---you can use the @code{target}
11369 command to specify one of the target types configured for @value{GDBN}
11370 (@pxref{Target Commands, ,Commands for managing targets}).
11372 @cindex target architecture
11373 It is possible to build @value{GDBN} for several different @dfn{target
11374 architectures}. When @value{GDBN} is built like that, you can choose
11375 one of the available architectures with the @kbd{set architecture}
11379 @kindex set architecture
11380 @kindex show architecture
11381 @item set architecture @var{arch}
11382 This command sets the current target architecture to @var{arch}. The
11383 value of @var{arch} can be @code{"auto"}, in addition to one of the
11384 supported architectures.
11386 @item show architecture
11387 Show the current target architecture.
11389 @item set processor
11391 @kindex set processor
11392 @kindex show processor
11393 These are alias commands for, respectively, @code{set architecture}
11394 and @code{show architecture}.
11398 * Active Targets:: Active targets
11399 * Target Commands:: Commands for managing targets
11400 * Byte Order:: Choosing target byte order
11401 * Remote:: Remote debugging
11402 * KOD:: Kernel Object Display
11406 @node Active Targets
11407 @section Active targets
11409 @cindex stacking targets
11410 @cindex active targets
11411 @cindex multiple targets
11413 There are three classes of targets: processes, core files, and
11414 executable files. @value{GDBN} can work concurrently on up to three
11415 active targets, one in each class. This allows you to (for example)
11416 start a process and inspect its activity without abandoning your work on
11419 For example, if you execute @samp{gdb a.out}, then the executable file
11420 @code{a.out} is the only active target. If you designate a core file as
11421 well---presumably from a prior run that crashed and coredumped---then
11422 @value{GDBN} has two active targets and uses them in tandem, looking
11423 first in the corefile target, then in the executable file, to satisfy
11424 requests for memory addresses. (Typically, these two classes of target
11425 are complementary, since core files contain only a program's
11426 read-write memory---variables and so on---plus machine status, while
11427 executable files contain only the program text and initialized data.)
11429 When you type @code{run}, your executable file becomes an active process
11430 target as well. When a process target is active, all @value{GDBN}
11431 commands requesting memory addresses refer to that target; addresses in
11432 an active core file or executable file target are obscured while the
11433 process target is active.
11435 Use the @code{core-file} and @code{exec-file} commands to select a new
11436 core file or executable target (@pxref{Files, ,Commands to specify
11437 files}). To specify as a target a process that is already running, use
11438 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
11441 @node Target Commands
11442 @section Commands for managing targets
11445 @item target @var{type} @var{parameters}
11446 Connects the @value{GDBN} host environment to a target machine or
11447 process. A target is typically a protocol for talking to debugging
11448 facilities. You use the argument @var{type} to specify the type or
11449 protocol of the target machine.
11451 Further @var{parameters} are interpreted by the target protocol, but
11452 typically include things like device names or host names to connect
11453 with, process numbers, and baud rates.
11455 The @code{target} command does not repeat if you press @key{RET} again
11456 after executing the command.
11458 @kindex help target
11460 Displays the names of all targets available. To display targets
11461 currently selected, use either @code{info target} or @code{info files}
11462 (@pxref{Files, ,Commands to specify files}).
11464 @item help target @var{name}
11465 Describe a particular target, including any parameters necessary to
11468 @kindex set gnutarget
11469 @item set gnutarget @var{args}
11470 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
11471 knows whether it is reading an @dfn{executable},
11472 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
11473 with the @code{set gnutarget} command. Unlike most @code{target} commands,
11474 with @code{gnutarget} the @code{target} refers to a program, not a machine.
11477 @emph{Warning:} To specify a file format with @code{set gnutarget},
11478 you must know the actual BFD name.
11482 @xref{Files, , Commands to specify files}.
11484 @kindex show gnutarget
11485 @item show gnutarget
11486 Use the @code{show gnutarget} command to display what file format
11487 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
11488 @value{GDBN} will determine the file format for each file automatically,
11489 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
11492 @cindex common targets
11493 Here are some common targets (available, or not, depending on the GDB
11498 @item target exec @var{program}
11499 @cindex executable file target
11500 An executable file. @samp{target exec @var{program}} is the same as
11501 @samp{exec-file @var{program}}.
11503 @item target core @var{filename}
11504 @cindex core dump file target
11505 A core dump file. @samp{target core @var{filename}} is the same as
11506 @samp{core-file @var{filename}}.
11508 @item target remote @var{dev}
11509 @cindex remote target
11510 Remote serial target in GDB-specific protocol. The argument @var{dev}
11511 specifies what serial device to use for the connection (e.g.
11512 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
11513 supports the @code{load} command. This is only useful if you have
11514 some other way of getting the stub to the target system, and you can put
11515 it somewhere in memory where it won't get clobbered by the download.
11518 @cindex built-in simulator target
11519 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
11527 works; however, you cannot assume that a specific memory map, device
11528 drivers, or even basic I/O is available, although some simulators do
11529 provide these. For info about any processor-specific simulator details,
11530 see the appropriate section in @ref{Embedded Processors, ,Embedded
11535 Some configurations may include these targets as well:
11539 @item target nrom @var{dev}
11540 @cindex NetROM ROM emulator target
11541 NetROM ROM emulator. This target only supports downloading.
11545 Different targets are available on different configurations of @value{GDBN};
11546 your configuration may have more or fewer targets.
11548 Many remote targets require you to download the executable's code once
11549 you've successfully established a connection. You may wish to control
11550 various aspects of this process, such as the size of the data chunks
11551 used by @value{GDBN} to download program parts to the remote target.
11554 @kindex set download-write-size
11555 @item set download-write-size @var{size}
11556 Set the write size used when downloading a program. Only used when
11557 downloading a program onto a remote target. Specify zero or a
11558 negative value to disable blocked writes. The actual size of each
11559 transfer is also limited by the size of the target packet and the
11562 @kindex show download-write-size
11563 @item show download-write-size
11564 @kindex show download-write-size
11565 Show the current value of the write size.
11568 @kindex set hash@r{, for remote monitors}
11569 @cindex hash mark while downloading
11570 This command controls whether a hash mark @samp{#} is displayed while
11571 downloading a file to the remote monitor. If on, a hash mark is
11572 displayed after each S-record is successfully downloaded to the
11576 @kindex show hash@r{, for remote monitors}
11577 Show the current status of displaying the hash mark.
11579 @item set debug monitor
11580 @kindex set debug monitor
11581 @cindex display remote monitor communications
11582 Enable or disable display of communications messages between
11583 @value{GDBN} and the remote monitor.
11585 @item show debug monitor
11586 @kindex show debug monitor
11587 Show the current status of displaying communications between
11588 @value{GDBN} and the remote monitor.
11593 @kindex load @var{filename}
11594 @item load @var{filename}
11595 Depending on what remote debugging facilities are configured into
11596 @value{GDBN}, the @code{load} command may be available. Where it exists, it
11597 is meant to make @var{filename} (an executable) available for debugging
11598 on the remote system---by downloading, or dynamic linking, for example.
11599 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
11600 the @code{add-symbol-file} command.
11602 If your @value{GDBN} does not have a @code{load} command, attempting to
11603 execute it gets the error message ``@code{You can't do that when your
11604 target is @dots{}}''
11606 The file is loaded at whatever address is specified in the executable.
11607 For some object file formats, you can specify the load address when you
11608 link the program; for other formats, like a.out, the object file format
11609 specifies a fixed address.
11610 @c FIXME! This would be a good place for an xref to the GNU linker doc.
11612 @code{load} does not repeat if you press @key{RET} again after using it.
11616 @section Choosing target byte order
11618 @cindex choosing target byte order
11619 @cindex target byte order
11621 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
11622 offer the ability to run either big-endian or little-endian byte
11623 orders. Usually the executable or symbol will include a bit to
11624 designate the endian-ness, and you will not need to worry about
11625 which to use. However, you may still find it useful to adjust
11626 @value{GDBN}'s idea of processor endian-ness manually.
11630 @item set endian big
11631 Instruct @value{GDBN} to assume the target is big-endian.
11633 @item set endian little
11634 Instruct @value{GDBN} to assume the target is little-endian.
11636 @item set endian auto
11637 Instruct @value{GDBN} to use the byte order associated with the
11641 Display @value{GDBN}'s current idea of the target byte order.
11645 Note that these commands merely adjust interpretation of symbolic
11646 data on the host, and that they have absolutely no effect on the
11650 @section Remote debugging
11651 @cindex remote debugging
11653 If you are trying to debug a program running on a machine that cannot run
11654 @value{GDBN} in the usual way, it is often useful to use remote debugging.
11655 For example, you might use remote debugging on an operating system kernel,
11656 or on a small system which does not have a general purpose operating system
11657 powerful enough to run a full-featured debugger.
11659 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
11660 to make this work with particular debugging targets. In addition,
11661 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
11662 but not specific to any particular target system) which you can use if you
11663 write the remote stubs---the code that runs on the remote system to
11664 communicate with @value{GDBN}.
11666 Other remote targets may be available in your
11667 configuration of @value{GDBN}; use @code{help target} to list them.
11669 Once you've connected to the remote target, @value{GDBN} allows you to
11670 send arbitrary commands to the remote monitor:
11673 @item remote @var{command}
11674 @kindex remote@r{, a command}
11675 @cindex send command to remote monitor
11676 Send an arbitrary @var{command} string to the remote monitor.
11681 @section Kernel Object Display
11682 @cindex kernel object display
11685 Some targets support kernel object display. Using this facility,
11686 @value{GDBN} communicates specially with the underlying operating system
11687 and can display information about operating system-level objects such as
11688 mutexes and other synchronization objects. Exactly which objects can be
11689 displayed is determined on a per-OS basis.
11692 Use the @code{set os} command to set the operating system. This tells
11693 @value{GDBN} which kernel object display module to initialize:
11696 (@value{GDBP}) set os cisco
11700 The associated command @code{show os} displays the operating system
11701 set with the @code{set os} command; if no operating system has been
11702 set, @code{show os} will display an empty string @samp{""}.
11704 If @code{set os} succeeds, @value{GDBN} will display some information
11705 about the operating system, and will create a new @code{info} command
11706 which can be used to query the target. The @code{info} command is named
11707 after the operating system:
11711 (@value{GDBP}) info cisco
11712 List of Cisco Kernel Objects
11714 any Any and all objects
11717 Further subcommands can be used to query about particular objects known
11720 There is currently no way to determine whether a given operating
11721 system is supported other than to try setting it with @kbd{set os
11722 @var{name}}, where @var{name} is the name of the operating system you
11726 @node Remote Debugging
11727 @chapter Debugging remote programs
11730 * Connecting:: Connecting to a remote target
11731 * Server:: Using the gdbserver program
11732 * NetWare:: Using the gdbserve.nlm program
11733 * Remote configuration:: Remote configuration
11734 * remote stub:: Implementing a remote stub
11738 @section Connecting to a remote target
11740 On the @value{GDBN} host machine, you will need an unstripped copy of
11741 your program, since @value{GDBN} needs symobl and debugging information.
11742 Start up @value{GDBN} as usual, using the name of the local copy of your
11743 program as the first argument.
11745 @cindex serial line, @code{target remote}
11746 If you're using a serial line, you may want to give @value{GDBN} the
11747 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
11748 (@pxref{Remote configuration, set remotebaud}) before the
11749 @code{target} command.
11751 After that, use @code{target remote} to establish communications with
11752 the target machine. Its argument specifies how to communicate---either
11753 via a devicename attached to a direct serial line, or a TCP or UDP port
11754 (possibly to a terminal server which in turn has a serial line to the
11755 target). For example, to use a serial line connected to the device
11756 named @file{/dev/ttyb}:
11759 target remote /dev/ttyb
11762 @cindex TCP port, @code{target remote}
11763 To use a TCP connection, use an argument of the form
11764 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
11765 For example, to connect to port 2828 on a
11766 terminal server named @code{manyfarms}:
11769 target remote manyfarms:2828
11772 If your remote target is actually running on the same machine as
11773 your debugger session (e.g.@: a simulator of your target running on
11774 the same host), you can omit the hostname. For example, to connect
11775 to port 1234 on your local machine:
11778 target remote :1234
11782 Note that the colon is still required here.
11784 @cindex UDP port, @code{target remote}
11785 To use a UDP connection, use an argument of the form
11786 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
11787 on a terminal server named @code{manyfarms}:
11790 target remote udp:manyfarms:2828
11793 When using a UDP connection for remote debugging, you should keep in mind
11794 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
11795 busy or unreliable networks, which will cause havoc with your debugging
11798 Now you can use all the usual commands to examine and change data and to
11799 step and continue the remote program.
11801 @cindex interrupting remote programs
11802 @cindex remote programs, interrupting
11803 Whenever @value{GDBN} is waiting for the remote program, if you type the
11804 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
11805 program. This may or may not succeed, depending in part on the hardware
11806 and the serial drivers the remote system uses. If you type the
11807 interrupt character once again, @value{GDBN} displays this prompt:
11810 Interrupted while waiting for the program.
11811 Give up (and stop debugging it)? (y or n)
11814 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
11815 (If you decide you want to try again later, you can use @samp{target
11816 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
11817 goes back to waiting.
11820 @kindex detach (remote)
11822 When you have finished debugging the remote program, you can use the
11823 @code{detach} command to release it from @value{GDBN} control.
11824 Detaching from the target normally resumes its execution, but the results
11825 will depend on your particular remote stub. After the @code{detach}
11826 command, @value{GDBN} is free to connect to another target.
11830 The @code{disconnect} command behaves like @code{detach}, except that
11831 the target is generally not resumed. It will wait for @value{GDBN}
11832 (this instance or another one) to connect and continue debugging. After
11833 the @code{disconnect} command, @value{GDBN} is again free to connect to
11836 @cindex send command to remote monitor
11838 @item monitor @var{cmd}
11839 This command allows you to send commands directly to the remote
11844 @section Using the @code{gdbserver} program
11847 @cindex remote connection without stubs
11848 @code{gdbserver} is a control program for Unix-like systems, which
11849 allows you to connect your program with a remote @value{GDBN} via
11850 @code{target remote}---but without linking in the usual debugging stub.
11852 @code{gdbserver} is not a complete replacement for the debugging stubs,
11853 because it requires essentially the same operating-system facilities
11854 that @value{GDBN} itself does. In fact, a system that can run
11855 @code{gdbserver} to connect to a remote @value{GDBN} could also run
11856 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
11857 because it is a much smaller program than @value{GDBN} itself. It is
11858 also easier to port than all of @value{GDBN}, so you may be able to get
11859 started more quickly on a new system by using @code{gdbserver}.
11860 Finally, if you develop code for real-time systems, you may find that
11861 the tradeoffs involved in real-time operation make it more convenient to
11862 do as much development work as possible on another system, for example
11863 by cross-compiling. You can use @code{gdbserver} to make a similar
11864 choice for debugging.
11866 @value{GDBN} and @code{gdbserver} communicate via either a serial line
11867 or a TCP connection, using the standard @value{GDBN} remote serial
11871 @item On the target machine,
11872 you need to have a copy of the program you want to debug.
11873 @code{gdbserver} does not need your program's symbol table, so you can
11874 strip the program if necessary to save space. @value{GDBN} on the host
11875 system does all the symbol handling.
11877 To use the server, you must tell it how to communicate with @value{GDBN};
11878 the name of your program; and the arguments for your program. The usual
11882 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
11885 @var{comm} is either a device name (to use a serial line) or a TCP
11886 hostname and portnumber. For example, to debug Emacs with the argument
11887 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
11891 target> gdbserver /dev/com1 emacs foo.txt
11894 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
11897 To use a TCP connection instead of a serial line:
11900 target> gdbserver host:2345 emacs foo.txt
11903 The only difference from the previous example is the first argument,
11904 specifying that you are communicating with the host @value{GDBN} via
11905 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
11906 expect a TCP connection from machine @samp{host} to local TCP port 2345.
11907 (Currently, the @samp{host} part is ignored.) You can choose any number
11908 you want for the port number as long as it does not conflict with any
11909 TCP ports already in use on the target system (for example, @code{23} is
11910 reserved for @code{telnet}).@footnote{If you choose a port number that
11911 conflicts with another service, @code{gdbserver} prints an error message
11912 and exits.} You must use the same port number with the host @value{GDBN}
11913 @code{target remote} command.
11915 On some targets, @code{gdbserver} can also attach to running programs.
11916 This is accomplished via the @code{--attach} argument. The syntax is:
11919 target> gdbserver @var{comm} --attach @var{pid}
11922 @var{pid} is the process ID of a currently running process. It isn't necessary
11923 to point @code{gdbserver} at a binary for the running process.
11926 @cindex attach to a program by name
11927 You can debug processes by name instead of process ID if your target has the
11928 @code{pidof} utility:
11931 target> gdbserver @var{comm} --attach `pidof @var{PROGRAM}`
11934 In case more than one copy of @var{PROGRAM} is running, or @var{PROGRAM}
11935 has multiple threads, most versions of @code{pidof} support the
11936 @code{-s} option to only return the first process ID.
11938 @item On the host machine,
11939 connect to your target (@pxref{Connecting,,Connecting to a remote target}).
11940 For TCP connections, you must start up @code{gdbserver} prior to using
11941 the @code{target remote} command. Otherwise you may get an error whose
11942 text depends on the host system, but which usually looks something like
11943 @samp{Connection refused}. You don't need to use the @code{load}
11944 command in @value{GDBN} when using gdbserver, since the program is
11945 already on the target.
11950 @section Using the @code{gdbserve.nlm} program
11952 @kindex gdbserve.nlm
11953 @code{gdbserve.nlm} is a control program for NetWare systems, which
11954 allows you to connect your program with a remote @value{GDBN} via
11955 @code{target remote}.
11957 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
11958 using the standard @value{GDBN} remote serial protocol.
11961 @item On the target machine,
11962 you need to have a copy of the program you want to debug.
11963 @code{gdbserve.nlm} does not need your program's symbol table, so you
11964 can strip the program if necessary to save space. @value{GDBN} on the
11965 host system does all the symbol handling.
11967 To use the server, you must tell it how to communicate with
11968 @value{GDBN}; the name of your program; and the arguments for your
11969 program. The syntax is:
11972 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
11973 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
11976 @var{board} and @var{port} specify the serial line; @var{baud} specifies
11977 the baud rate used by the connection. @var{port} and @var{node} default
11978 to 0, @var{baud} defaults to 9600@dmn{bps}.
11980 For example, to debug Emacs with the argument @samp{foo.txt}and
11981 communicate with @value{GDBN} over serial port number 2 or board 1
11982 using a 19200@dmn{bps} connection:
11985 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
11989 On the @value{GDBN} host machine, connect to your target (@pxref{Connecting,,
11990 Connecting to a remote target}).
11994 @node Remote configuration
11995 @section Remote configuration
11998 @kindex show remote
11999 This section documents the configuration options available when
12000 debugging remote programs. For the options related to the File I/O
12001 extensions of the remote protocol, see @ref{The system call,
12002 system-call-allowed}.
12005 @item set remoteaddresssize @var{bits}
12006 @cindex adress size for remote targets
12007 @cindex bits in remote address
12008 Set the maximum size of address in a memory packet to the specified
12009 number of bits. @value{GDBN} will mask off the address bits above
12010 that number, when it passes addresses to the remote target. The
12011 default value is the number of bits in the target's address.
12013 @item show remoteaddresssize
12014 Show the current value of remote address size in bits.
12016 @item set remotebaud @var{n}
12017 @cindex baud rate for remote targets
12018 Set the baud rate for the remote serial I/O to @var{n} baud. The
12019 value is used to set the speed of the serial port used for debugging
12022 @item show remotebaud
12023 Show the current speed of the remote connection.
12025 @item set remotebreak
12026 @cindex interrupt remote programs
12027 @cindex BREAK signal instead of Ctrl-C
12028 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
12029 when you press the @key{Ctrl-C} key to interrupt the program running
12030 on the remote. If set to off, @value{GDBN} sends the @samp{Strl-C}
12031 character instead. The default is off, since most remote systems
12032 expect to see @samp{Ctrl-C} as the interrupt signal.
12034 @item show remotebreak
12035 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
12036 interrupt the remote program.
12038 @item set remotedebug
12039 @cindex debug remote protocol
12040 @cindex remote protocol debugging
12041 @cindex display remote packets
12042 Control the debugging of the remote protocol. When enabled, each
12043 packet sent to or received from the remote target is displayed. The
12046 @item show remotedebug
12047 Show the current setting of the remote protocol debugging.
12049 @item set remotedevice @var{device}
12050 @cindex serial port name
12051 Set the name of the serial port through which to communicate to the
12052 remote target to @var{device}. This is the device used by
12053 @value{GDBN} to open the serial communications line to the remote
12054 target. There's no default, so you must set a valid port name for the
12055 remote serial communications to work. (Some varieties of the
12056 @code{target} command accept the port name as part of their
12059 @item show remotedevice
12060 Show the current name of the serial port.
12062 @item set remotelogbase @var{base}
12063 Set the base (a.k.a.@: radix) of logging serial protocol
12064 communications to @var{base}. Supported values of @var{base} are:
12065 @code{ascii}, @code{octal}, and @code{hex}. The default is
12068 @item show remotelogbase
12069 Show the current setting of the radix for logging remote serial
12072 @item set remotelogfile @var{file}
12073 @cindex record serial communications on file
12074 Record remote serial communications on the named @var{file}. The
12075 default is not to record at all.
12077 @item show remotelogfile.
12078 Show the current setting of the file name on which to record the
12079 serial communications.
12081 @item set remotetimeout @var{num}
12082 @cindex timeout for serial communications
12083 @cindex remote timeout
12084 Set the timeout limit to wait for the remote target to respond to
12085 @var{num} seconds. The default is 2 seconds.
12087 @item show remotetimeout
12088 Show the current number of seconds to wait for the remote target
12091 @cindex limit hardware breakpoints and watchpoints
12092 @cindex remote target, limit break- and watchpoints
12093 @anchor{set remote hardware-watchpoint-limit}
12094 @anchor{set remote hardware-breakpoint-limit}
12095 @item set remote hardware-watchpoint-limit @var{limit}
12096 @itemx set remote hardware-breakpoint-limit @var{limit}
12097 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
12098 watchpoints. A limit of -1, the default, is treated as unlimited.
12100 @item set remote fetch-register-packet
12101 @itemx set remote set-register-packet
12102 @itemx set remote P-packet
12103 @itemx set remote p-packet
12105 @cindex fetch registers from remote targets
12106 @cindex set registers in remote targets
12107 Determine whether @value{GDBN} can set and fetch registers from the
12108 remote target using the @samp{P} packets. The default depends on the
12109 remote stub's support of the @samp{P} packets (@value{GDBN} queries
12110 the stub when this packet is first required).
12112 @item show remote fetch-register-packet
12113 @itemx show remote set-register-packet
12114 @itemx show remote P-packet
12115 @itemx show remote p-packet
12116 Show the current setting of using the @samp{P} packets for setting and
12117 fetching registers from the remote target.
12119 @cindex binary downloads
12121 @item set remote binary-download-packet
12122 @itemx set remote X-packet
12123 Determine whether @value{GDBN} sends downloads in binary mode using
12124 the @samp{X} packets. The default is on.
12126 @item show remote binary-download-packet
12127 @itemx show remote X-packet
12128 Show the current setting of using the @samp{X} packets for binary
12131 @item set remote read-aux-vector-packet
12132 @cindex auxiliary vector of remote target
12133 @cindex @code{auxv}, and remote targets
12134 Set the use of the remote protocol's @samp{qPart:auxv:read} (target
12135 auxiliary vector read) request. This request is used to fetch the
12136 remote target's @dfn{auxiliary vector}, see @ref{OS Information,
12137 Auxiliary Vector}. The default setting depends on the remote stub's
12138 support of this request (@value{GDBN} queries the stub when this
12139 request is first required). @xref{General Query Packets, qPart}, for
12140 more information about this request.
12142 @item show remote read-aux-vector-packet
12143 Show the current setting of use of the @samp{qPart:auxv:read} request.
12145 @item set remote symbol-lookup-packet
12146 @cindex remote symbol lookup request
12147 Set the use of the remote protocol's @samp{qSymbol} (target symbol
12148 lookup) request. This request is used to communicate symbol
12149 information to the remote target, e.g., whenever a new shared library
12150 is loaded by the remote (@pxref{Files, shared libraries}). The
12151 default setting depends on the remote stub's support of this request
12152 (@value{GDBN} queries the stub when this request is first required).
12153 @xref{General Query Packets, qSymbol}, for more information about this
12156 @item show remote symbol-lookup-packet
12157 Show the current setting of use of the @samp{qSymbol} request.
12159 @item set remote verbose-resume-packet
12160 @cindex resume remote target
12161 @cindex signal thread, and remote targets
12162 @cindex single-step thread, and remote targets
12163 @cindex thread-specific operations on remote targets
12164 Set the use of the remote protocol's @samp{vCont} (descriptive resume)
12165 request. This request is used to resume specific threads in the
12166 remote target, and to single-step or signal them. The default setting
12167 depends on the remote stub's support of this request (@value{GDBN}
12168 queries the stub when this request is first required). This setting
12169 affects debugging of multithreaded programs: if @samp{vCont} cannot be
12170 used, @value{GDBN} might be unable to single-step a specific thread,
12171 especially under @code{set scheduler-locking off}; it is also
12172 impossible to pause a specific thread. @xref{Packets, vCont}, for
12175 @item show remote verbose-resume-packet
12176 Show the current setting of use of the @samp{vCont} request
12178 @item set remote software-breakpoint-packet
12179 @itemx set remote hardware-breakpoint-packet
12180 @itemx set remote write-watchpoint-packet
12181 @itemx set remote read-watchpoint-packet
12182 @itemx set remote access-watchpoint-packet
12183 @itemx set remote Z-packet
12185 @cindex remote hardware breakpoints and watchpoints
12186 These commands enable or disable the use of @samp{Z} packets for
12187 setting breakpoints and watchpoints in the remote target. The default
12188 depends on the remote stub's support of the @samp{Z} packets
12189 (@value{GDBN} queries the stub when each packet is first required).
12190 The command @code{set remote Z-packet}, kept for back-compatibility,
12191 turns on or off all the features that require the use of @samp{Z}
12194 @item show remote software-breakpoint-packet
12195 @itemx show remote hardware-breakpoint-packet
12196 @itemx show remote write-watchpoint-packet
12197 @itemx show remote read-watchpoint-packet
12198 @itemx show remote access-watchpoint-packet
12199 @itemx show remote Z-packet
12200 Show the current setting of @samp{Z} packets usage.
12202 @item set remote get-thread-local-storage-address
12203 @kindex set remote get-thread-local-storage-address
12204 @cindex thread local storage of remote targets
12205 This command enables or disables the use of the @samp{qGetTLSAddr}
12206 (Get Thread Local Storage Address) request packet. The default
12207 depends on whether the remote stub supports this request.
12208 @xref{General Query Packets, qGetTLSAddr}, for more details about this
12211 @item show remote get-thread-local-storage-address
12212 @kindex show remote get-thread-local-storage-address
12213 Show the current setting of @samp{qGetTLSAddr} packet usage.
12217 @section Implementing a remote stub
12219 @cindex debugging stub, example
12220 @cindex remote stub, example
12221 @cindex stub example, remote debugging
12222 The stub files provided with @value{GDBN} implement the target side of the
12223 communication protocol, and the @value{GDBN} side is implemented in the
12224 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
12225 these subroutines to communicate, and ignore the details. (If you're
12226 implementing your own stub file, you can still ignore the details: start
12227 with one of the existing stub files. @file{sparc-stub.c} is the best
12228 organized, and therefore the easiest to read.)
12230 @cindex remote serial debugging, overview
12231 To debug a program running on another machine (the debugging
12232 @dfn{target} machine), you must first arrange for all the usual
12233 prerequisites for the program to run by itself. For example, for a C
12238 A startup routine to set up the C runtime environment; these usually
12239 have a name like @file{crt0}. The startup routine may be supplied by
12240 your hardware supplier, or you may have to write your own.
12243 A C subroutine library to support your program's
12244 subroutine calls, notably managing input and output.
12247 A way of getting your program to the other machine---for example, a
12248 download program. These are often supplied by the hardware
12249 manufacturer, but you may have to write your own from hardware
12253 The next step is to arrange for your program to use a serial port to
12254 communicate with the machine where @value{GDBN} is running (the @dfn{host}
12255 machine). In general terms, the scheme looks like this:
12259 @value{GDBN} already understands how to use this protocol; when everything
12260 else is set up, you can simply use the @samp{target remote} command
12261 (@pxref{Targets,,Specifying a Debugging Target}).
12263 @item On the target,
12264 you must link with your program a few special-purpose subroutines that
12265 implement the @value{GDBN} remote serial protocol. The file containing these
12266 subroutines is called a @dfn{debugging stub}.
12268 On certain remote targets, you can use an auxiliary program
12269 @code{gdbserver} instead of linking a stub into your program.
12270 @xref{Server,,Using the @code{gdbserver} program}, for details.
12273 The debugging stub is specific to the architecture of the remote
12274 machine; for example, use @file{sparc-stub.c} to debug programs on
12277 @cindex remote serial stub list
12278 These working remote stubs are distributed with @value{GDBN}:
12283 @cindex @file{i386-stub.c}
12286 For Intel 386 and compatible architectures.
12289 @cindex @file{m68k-stub.c}
12290 @cindex Motorola 680x0
12292 For Motorola 680x0 architectures.
12295 @cindex @file{sh-stub.c}
12298 For Renesas SH architectures.
12301 @cindex @file{sparc-stub.c}
12303 For @sc{sparc} architectures.
12305 @item sparcl-stub.c
12306 @cindex @file{sparcl-stub.c}
12309 For Fujitsu @sc{sparclite} architectures.
12313 The @file{README} file in the @value{GDBN} distribution may list other
12314 recently added stubs.
12317 * Stub Contents:: What the stub can do for you
12318 * Bootstrapping:: What you must do for the stub
12319 * Debug Session:: Putting it all together
12322 @node Stub Contents
12323 @subsection What the stub can do for you
12325 @cindex remote serial stub
12326 The debugging stub for your architecture supplies these three
12330 @item set_debug_traps
12331 @findex set_debug_traps
12332 @cindex remote serial stub, initialization
12333 This routine arranges for @code{handle_exception} to run when your
12334 program stops. You must call this subroutine explicitly near the
12335 beginning of your program.
12337 @item handle_exception
12338 @findex handle_exception
12339 @cindex remote serial stub, main routine
12340 This is the central workhorse, but your program never calls it
12341 explicitly---the setup code arranges for @code{handle_exception} to
12342 run when a trap is triggered.
12344 @code{handle_exception} takes control when your program stops during
12345 execution (for example, on a breakpoint), and mediates communications
12346 with @value{GDBN} on the host machine. This is where the communications
12347 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
12348 representative on the target machine. It begins by sending summary
12349 information on the state of your program, then continues to execute,
12350 retrieving and transmitting any information @value{GDBN} needs, until you
12351 execute a @value{GDBN} command that makes your program resume; at that point,
12352 @code{handle_exception} returns control to your own code on the target
12356 @cindex @code{breakpoint} subroutine, remote
12357 Use this auxiliary subroutine to make your program contain a
12358 breakpoint. Depending on the particular situation, this may be the only
12359 way for @value{GDBN} to get control. For instance, if your target
12360 machine has some sort of interrupt button, you won't need to call this;
12361 pressing the interrupt button transfers control to
12362 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
12363 simply receiving characters on the serial port may also trigger a trap;
12364 again, in that situation, you don't need to call @code{breakpoint} from
12365 your own program---simply running @samp{target remote} from the host
12366 @value{GDBN} session gets control.
12368 Call @code{breakpoint} if none of these is true, or if you simply want
12369 to make certain your program stops at a predetermined point for the
12370 start of your debugging session.
12373 @node Bootstrapping
12374 @subsection What you must do for the stub
12376 @cindex remote stub, support routines
12377 The debugging stubs that come with @value{GDBN} are set up for a particular
12378 chip architecture, but they have no information about the rest of your
12379 debugging target machine.
12381 First of all you need to tell the stub how to communicate with the
12385 @item int getDebugChar()
12386 @findex getDebugChar
12387 Write this subroutine to read a single character from the serial port.
12388 It may be identical to @code{getchar} for your target system; a
12389 different name is used to allow you to distinguish the two if you wish.
12391 @item void putDebugChar(int)
12392 @findex putDebugChar
12393 Write this subroutine to write a single character to the serial port.
12394 It may be identical to @code{putchar} for your target system; a
12395 different name is used to allow you to distinguish the two if you wish.
12398 @cindex control C, and remote debugging
12399 @cindex interrupting remote targets
12400 If you want @value{GDBN} to be able to stop your program while it is
12401 running, you need to use an interrupt-driven serial driver, and arrange
12402 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
12403 character). That is the character which @value{GDBN} uses to tell the
12404 remote system to stop.
12406 Getting the debugging target to return the proper status to @value{GDBN}
12407 probably requires changes to the standard stub; one quick and dirty way
12408 is to just execute a breakpoint instruction (the ``dirty'' part is that
12409 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
12411 Other routines you need to supply are:
12414 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
12415 @findex exceptionHandler
12416 Write this function to install @var{exception_address} in the exception
12417 handling tables. You need to do this because the stub does not have any
12418 way of knowing what the exception handling tables on your target system
12419 are like (for example, the processor's table might be in @sc{rom},
12420 containing entries which point to a table in @sc{ram}).
12421 @var{exception_number} is the exception number which should be changed;
12422 its meaning is architecture-dependent (for example, different numbers
12423 might represent divide by zero, misaligned access, etc). When this
12424 exception occurs, control should be transferred directly to
12425 @var{exception_address}, and the processor state (stack, registers,
12426 and so on) should be just as it is when a processor exception occurs. So if
12427 you want to use a jump instruction to reach @var{exception_address}, it
12428 should be a simple jump, not a jump to subroutine.
12430 For the 386, @var{exception_address} should be installed as an interrupt
12431 gate so that interrupts are masked while the handler runs. The gate
12432 should be at privilege level 0 (the most privileged level). The
12433 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
12434 help from @code{exceptionHandler}.
12436 @item void flush_i_cache()
12437 @findex flush_i_cache
12438 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
12439 instruction cache, if any, on your target machine. If there is no
12440 instruction cache, this subroutine may be a no-op.
12442 On target machines that have instruction caches, @value{GDBN} requires this
12443 function to make certain that the state of your program is stable.
12447 You must also make sure this library routine is available:
12450 @item void *memset(void *, int, int)
12452 This is the standard library function @code{memset} that sets an area of
12453 memory to a known value. If you have one of the free versions of
12454 @code{libc.a}, @code{memset} can be found there; otherwise, you must
12455 either obtain it from your hardware manufacturer, or write your own.
12458 If you do not use the GNU C compiler, you may need other standard
12459 library subroutines as well; this varies from one stub to another,
12460 but in general the stubs are likely to use any of the common library
12461 subroutines which @code{@value{GCC}} generates as inline code.
12464 @node Debug Session
12465 @subsection Putting it all together
12467 @cindex remote serial debugging summary
12468 In summary, when your program is ready to debug, you must follow these
12473 Make sure you have defined the supporting low-level routines
12474 (@pxref{Bootstrapping,,What you must do for the stub}):
12476 @code{getDebugChar}, @code{putDebugChar},
12477 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
12481 Insert these lines near the top of your program:
12489 For the 680x0 stub only, you need to provide a variable called
12490 @code{exceptionHook}. Normally you just use:
12493 void (*exceptionHook)() = 0;
12497 but if before calling @code{set_debug_traps}, you set it to point to a
12498 function in your program, that function is called when
12499 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
12500 error). The function indicated by @code{exceptionHook} is called with
12501 one parameter: an @code{int} which is the exception number.
12504 Compile and link together: your program, the @value{GDBN} debugging stub for
12505 your target architecture, and the supporting subroutines.
12508 Make sure you have a serial connection between your target machine and
12509 the @value{GDBN} host, and identify the serial port on the host.
12512 @c The "remote" target now provides a `load' command, so we should
12513 @c document that. FIXME.
12514 Download your program to your target machine (or get it there by
12515 whatever means the manufacturer provides), and start it.
12518 Start @value{GDBN} on the host, and connect to the target
12519 (@pxref{Connecting,,Connecting to a remote target}).
12523 @node Configurations
12524 @chapter Configuration-Specific Information
12526 While nearly all @value{GDBN} commands are available for all native and
12527 cross versions of the debugger, there are some exceptions. This chapter
12528 describes things that are only available in certain configurations.
12530 There are three major categories of configurations: native
12531 configurations, where the host and target are the same, embedded
12532 operating system configurations, which are usually the same for several
12533 different processor architectures, and bare embedded processors, which
12534 are quite different from each other.
12539 * Embedded Processors::
12546 This section describes details specific to particular native
12551 * BSD libkvm Interface:: Debugging BSD kernel memory images
12552 * SVR4 Process Information:: SVR4 process information
12553 * DJGPP Native:: Features specific to the DJGPP port
12554 * Cygwin Native:: Features specific to the Cygwin port
12555 * Hurd Native:: Features specific to @sc{gnu} Hurd
12556 * Neutrino:: Features specific to QNX Neutrino
12562 On HP-UX systems, if you refer to a function or variable name that
12563 begins with a dollar sign, @value{GDBN} searches for a user or system
12564 name first, before it searches for a convenience variable.
12567 @node BSD libkvm Interface
12568 @subsection BSD libkvm Interface
12571 @cindex kernel memory image
12572 @cindex kernel crash dump
12574 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
12575 interface that provides a uniform interface for accessing kernel virtual
12576 memory images, including live systems and crash dumps. @value{GDBN}
12577 uses this interface to allow you to debug live kernels and kernel crash
12578 dumps on many native BSD configurations. This is implemented as a
12579 special @code{kvm} debugging target. For debugging a live system, load
12580 the currently running kernel into @value{GDBN} and connect to the
12584 (@value{GDBP}) @b{target kvm}
12587 For debugging crash dumps, provide the file name of the crash dump as an
12591 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
12594 Once connected to the @code{kvm} target, the following commands are
12600 Set current context from the @dfn{Process Control Block} (PCB) address.
12603 Set current context from proc address. This command isn't available on
12604 modern FreeBSD systems.
12607 @node SVR4 Process Information
12608 @subsection SVR4 process information
12610 @cindex examine process image
12611 @cindex process info via @file{/proc}
12613 Many versions of SVR4 and compatible systems provide a facility called
12614 @samp{/proc} that can be used to examine the image of a running
12615 process using file-system subroutines. If @value{GDBN} is configured
12616 for an operating system with this facility, the command @code{info
12617 proc} is available to report information about the process running
12618 your program, or about any process running on your system. @code{info
12619 proc} works only on SVR4 systems that include the @code{procfs} code.
12620 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
12621 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
12627 @itemx info proc @var{process-id}
12628 Summarize available information about any running process. If a
12629 process ID is specified by @var{process-id}, display information about
12630 that process; otherwise display information about the program being
12631 debugged. The summary includes the debugged process ID, the command
12632 line used to invoke it, its current working directory, and its
12633 executable file's absolute file name.
12635 On some systems, @var{process-id} can be of the form
12636 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
12637 within a process. If the optional @var{pid} part is missing, it means
12638 a thread from the process being debugged (the leading @samp{/} still
12639 needs to be present, or else @value{GDBN} will interpret the number as
12640 a process ID rather than a thread ID).
12642 @item info proc mappings
12643 @cindex memory address space mappings
12644 Report the memory address space ranges accessible in the program, with
12645 information on whether the process has read, write, or execute access
12646 rights to each range. On @sc{gnu}/Linux systems, each memory range
12647 includes the object file which is mapped to that range, instead of the
12648 memory access rights to that range.
12650 @item info proc stat
12651 @itemx info proc status
12652 @cindex process detailed status information
12653 These subcommands are specific to @sc{gnu}/Linux systems. They show
12654 the process-related information, including the user ID and group ID;
12655 how many threads are there in the process; its virtual memory usage;
12656 the signals that are pending, blocked, and ignored; its TTY; its
12657 consumption of system and user time; its stack size; its @samp{nice}
12658 value; etc. For more information, see the @samp{proc} man page
12659 (type @kbd{man 5 proc} from your shell prompt).
12661 @item info proc all
12662 Show all the information about the process described under all of the
12663 above @code{info proc} subcommands.
12666 @comment These sub-options of 'info proc' were not included when
12667 @comment procfs.c was re-written. Keep their descriptions around
12668 @comment against the day when someone finds the time to put them back in.
12669 @kindex info proc times
12670 @item info proc times
12671 Starting time, user CPU time, and system CPU time for your program and
12674 @kindex info proc id
12676 Report on the process IDs related to your program: its own process ID,
12677 the ID of its parent, the process group ID, and the session ID.
12680 @item set procfs-trace
12681 @kindex set procfs-trace
12682 @cindex @code{procfs} API calls
12683 This command enables and disables tracing of @code{procfs} API calls.
12685 @item show procfs-trace
12686 @kindex show procfs-trace
12687 Show the current state of @code{procfs} API call tracing.
12689 @item set procfs-file @var{file}
12690 @kindex set procfs-file
12691 Tell @value{GDBN} to write @code{procfs} API trace to the named
12692 @var{file}. @value{GDBN} appends the trace info to the previous
12693 contents of the file. The default is to display the trace on the
12696 @item show procfs-file
12697 @kindex show procfs-file
12698 Show the file to which @code{procfs} API trace is written.
12700 @item proc-trace-entry
12701 @itemx proc-trace-exit
12702 @itemx proc-untrace-entry
12703 @itemx proc-untrace-exit
12704 @kindex proc-trace-entry
12705 @kindex proc-trace-exit
12706 @kindex proc-untrace-entry
12707 @kindex proc-untrace-exit
12708 These commands enable and disable tracing of entries into and exits
12709 from the @code{syscall} interface.
12712 @kindex info pidlist
12713 @cindex process list, QNX Neutrino
12714 For QNX Neutrino only, this command displays the list of all the
12715 processes and all the threads within each process.
12718 @kindex info meminfo
12719 @cindex mapinfo list, QNX Neutrino
12720 For QNX Neutrino only, this command displays the list of all mapinfos.
12724 @subsection Features for Debugging @sc{djgpp} Programs
12725 @cindex @sc{djgpp} debugging
12726 @cindex native @sc{djgpp} debugging
12727 @cindex MS-DOS-specific commands
12730 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
12731 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
12732 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
12733 top of real-mode DOS systems and their emulations.
12735 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
12736 defines a few commands specific to the @sc{djgpp} port. This
12737 subsection describes those commands.
12742 This is a prefix of @sc{djgpp}-specific commands which print
12743 information about the target system and important OS structures.
12746 @cindex MS-DOS system info
12747 @cindex free memory information (MS-DOS)
12748 @item info dos sysinfo
12749 This command displays assorted information about the underlying
12750 platform: the CPU type and features, the OS version and flavor, the
12751 DPMI version, and the available conventional and DPMI memory.
12756 @cindex segment descriptor tables
12757 @cindex descriptor tables display
12759 @itemx info dos ldt
12760 @itemx info dos idt
12761 These 3 commands display entries from, respectively, Global, Local,
12762 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
12763 tables are data structures which store a descriptor for each segment
12764 that is currently in use. The segment's selector is an index into a
12765 descriptor table; the table entry for that index holds the
12766 descriptor's base address and limit, and its attributes and access
12769 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
12770 segment (used for both data and the stack), and a DOS segment (which
12771 allows access to DOS/BIOS data structures and absolute addresses in
12772 conventional memory). However, the DPMI host will usually define
12773 additional segments in order to support the DPMI environment.
12775 @cindex garbled pointers
12776 These commands allow to display entries from the descriptor tables.
12777 Without an argument, all entries from the specified table are
12778 displayed. An argument, which should be an integer expression, means
12779 display a single entry whose index is given by the argument. For
12780 example, here's a convenient way to display information about the
12781 debugged program's data segment:
12784 @exdent @code{(@value{GDBP}) info dos ldt $ds}
12785 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
12789 This comes in handy when you want to see whether a pointer is outside
12790 the data segment's limit (i.e.@: @dfn{garbled}).
12792 @cindex page tables display (MS-DOS)
12794 @itemx info dos pte
12795 These two commands display entries from, respectively, the Page
12796 Directory and the Page Tables. Page Directories and Page Tables are
12797 data structures which control how virtual memory addresses are mapped
12798 into physical addresses. A Page Table includes an entry for every
12799 page of memory that is mapped into the program's address space; there
12800 may be several Page Tables, each one holding up to 4096 entries. A
12801 Page Directory has up to 4096 entries, one each for every Page Table
12802 that is currently in use.
12804 Without an argument, @kbd{info dos pde} displays the entire Page
12805 Directory, and @kbd{info dos pte} displays all the entries in all of
12806 the Page Tables. An argument, an integer expression, given to the
12807 @kbd{info dos pde} command means display only that entry from the Page
12808 Directory table. An argument given to the @kbd{info dos pte} command
12809 means display entries from a single Page Table, the one pointed to by
12810 the specified entry in the Page Directory.
12812 @cindex direct memory access (DMA) on MS-DOS
12813 These commands are useful when your program uses @dfn{DMA} (Direct
12814 Memory Access), which needs physical addresses to program the DMA
12817 These commands are supported only with some DPMI servers.
12819 @cindex physical address from linear address
12820 @item info dos address-pte @var{addr}
12821 This command displays the Page Table entry for a specified linear
12822 address. The argument @var{addr} is a linear address which should
12823 already have the appropriate segment's base address added to it,
12824 because this command accepts addresses which may belong to @emph{any}
12825 segment. For example, here's how to display the Page Table entry for
12826 the page where a variable @code{i} is stored:
12829 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
12830 @exdent @code{Page Table entry for address 0x11a00d30:}
12831 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
12835 This says that @code{i} is stored at offset @code{0xd30} from the page
12836 whose physical base address is @code{0x02698000}, and shows all the
12837 attributes of that page.
12839 Note that you must cast the addresses of variables to a @code{char *},
12840 since otherwise the value of @code{__djgpp_base_address}, the base
12841 address of all variables and functions in a @sc{djgpp} program, will
12842 be added using the rules of C pointer arithmetics: if @code{i} is
12843 declared an @code{int}, @value{GDBN} will add 4 times the value of
12844 @code{__djgpp_base_address} to the address of @code{i}.
12846 Here's another example, it displays the Page Table entry for the
12850 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
12851 @exdent @code{Page Table entry for address 0x29110:}
12852 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
12856 (The @code{+ 3} offset is because the transfer buffer's address is the
12857 3rd member of the @code{_go32_info_block} structure.) The output
12858 clearly shows that this DPMI server maps the addresses in conventional
12859 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
12860 linear (@code{0x29110}) addresses are identical.
12862 This command is supported only with some DPMI servers.
12865 @cindex DOS serial data link, remote debugging
12866 In addition to native debugging, the DJGPP port supports remote
12867 debugging via a serial data link. The following commands are specific
12868 to remote serial debugging in the DJGPP port of @value{GDBN}.
12871 @kindex set com1base
12872 @kindex set com1irq
12873 @kindex set com2base
12874 @kindex set com2irq
12875 @kindex set com3base
12876 @kindex set com3irq
12877 @kindex set com4base
12878 @kindex set com4irq
12879 @item set com1base @var{addr}
12880 This command sets the base I/O port address of the @file{COM1} serial
12883 @item set com1irq @var{irq}
12884 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
12885 for the @file{COM1} serial port.
12887 There are similar commands @samp{set com2base}, @samp{set com3irq},
12888 etc.@: for setting the port address and the @code{IRQ} lines for the
12891 @kindex show com1base
12892 @kindex show com1irq
12893 @kindex show com2base
12894 @kindex show com2irq
12895 @kindex show com3base
12896 @kindex show com3irq
12897 @kindex show com4base
12898 @kindex show com4irq
12899 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
12900 display the current settings of the base address and the @code{IRQ}
12901 lines used by the COM ports.
12904 @kindex info serial
12905 @cindex DOS serial port status
12906 This command prints the status of the 4 DOS serial ports. For each
12907 port, it prints whether it's active or not, its I/O base address and
12908 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
12909 counts of various errors encountered so far.
12913 @node Cygwin Native
12914 @subsection Features for Debugging MS Windows PE executables
12915 @cindex MS Windows debugging
12916 @cindex native Cygwin debugging
12917 @cindex Cygwin-specific commands
12919 @value{GDBN} supports native debugging of MS Windows programs, including
12920 DLLs with and without symbolic debugging information. There are various
12921 additional Cygwin-specific commands, described in this subsection. The
12922 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
12923 that have no debugging symbols.
12929 This is a prefix of MS Windows specific commands which print
12930 information about the target system and important OS structures.
12932 @item info w32 selector
12933 This command displays information returned by
12934 the Win32 API @code{GetThreadSelectorEntry} function.
12935 It takes an optional argument that is evaluated to
12936 a long value to give the information about this given selector.
12937 Without argument, this command displays information
12938 about the the six segment registers.
12942 This is a Cygwin specific alias of info shared.
12944 @kindex dll-symbols
12946 This command loads symbols from a dll similarly to
12947 add-sym command but without the need to specify a base address.
12949 @kindex set new-console
12950 @item set new-console @var{mode}
12951 If @var{mode} is @code{on} the debuggee will
12952 be started in a new console on next start.
12953 If @var{mode} is @code{off}i, the debuggee will
12954 be started in the same console as the debugger.
12956 @kindex show new-console
12957 @item show new-console
12958 Displays whether a new console is used
12959 when the debuggee is started.
12961 @kindex set new-group
12962 @item set new-group @var{mode}
12963 This boolean value controls whether the debuggee should
12964 start a new group or stay in the same group as the debugger.
12965 This affects the way the Windows OS handles
12968 @kindex show new-group
12969 @item show new-group
12970 Displays current value of new-group boolean.
12972 @kindex set debugevents
12973 @item set debugevents
12974 This boolean value adds debug output concerning events seen by the debugger.
12976 @kindex set debugexec
12977 @item set debugexec
12978 This boolean value adds debug output concerning execute events
12979 seen by the debugger.
12981 @kindex set debugexceptions
12982 @item set debugexceptions
12983 This boolean value adds debug ouptut concerning exception events
12984 seen by the debugger.
12986 @kindex set debugmemory
12987 @item set debugmemory
12988 This boolean value adds debug ouptut concerning memory events
12989 seen by the debugger.
12993 This boolean values specifies whether the debuggee is called
12994 via a shell or directly (default value is on).
12998 Displays if the debuggee will be started with a shell.
13003 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
13006 @node Non-debug DLL symbols
13007 @subsubsection Support for DLLs without debugging symbols
13008 @cindex DLLs with no debugging symbols
13009 @cindex Minimal symbols and DLLs
13011 Very often on windows, some of the DLLs that your program relies on do
13012 not include symbolic debugging information (for example,
13013 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
13014 symbols in a DLL, it relies on the minimal amount of symbolic
13015 information contained in the DLL's export table. This subsubsection
13016 describes working with such symbols, known internally to @value{GDBN} as
13017 ``minimal symbols''.
13019 Note that before the debugged program has started execution, no DLLs
13020 will have been loaded. The easiest way around this problem is simply to
13021 start the program --- either by setting a breakpoint or letting the
13022 program run once to completion. It is also possible to force
13023 @value{GDBN} to load a particular DLL before starting the executable ---
13024 see the shared library information in @pxref{Files} or the
13025 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
13026 explicitly loading symbols from a DLL with no debugging information will
13027 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
13028 which may adversely affect symbol lookup performance.
13030 @subsubsection DLL name prefixes
13032 In keeping with the naming conventions used by the Microsoft debugging
13033 tools, DLL export symbols are made available with a prefix based on the
13034 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
13035 also entered into the symbol table, so @code{CreateFileA} is often
13036 sufficient. In some cases there will be name clashes within a program
13037 (particularly if the executable itself includes full debugging symbols)
13038 necessitating the use of the fully qualified name when referring to the
13039 contents of the DLL. Use single-quotes around the name to avoid the
13040 exclamation mark (``!'') being interpreted as a language operator.
13042 Note that the internal name of the DLL may be all upper-case, even
13043 though the file name of the DLL is lower-case, or vice-versa. Since
13044 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
13045 some confusion. If in doubt, try the @code{info functions} and
13046 @code{info variables} commands or even @code{maint print msymbols} (see
13047 @pxref{Symbols}). Here's an example:
13050 (@value{GDBP}) info function CreateFileA
13051 All functions matching regular expression "CreateFileA":
13053 Non-debugging symbols:
13054 0x77e885f4 CreateFileA
13055 0x77e885f4 KERNEL32!CreateFileA
13059 (@value{GDBP}) info function !
13060 All functions matching regular expression "!":
13062 Non-debugging symbols:
13063 0x6100114c cygwin1!__assert
13064 0x61004034 cygwin1!_dll_crt0@@0
13065 0x61004240 cygwin1!dll_crt0(per_process *)
13069 @subsubsection Working with minimal symbols
13071 Symbols extracted from a DLL's export table do not contain very much
13072 type information. All that @value{GDBN} can do is guess whether a symbol
13073 refers to a function or variable depending on the linker section that
13074 contains the symbol. Also note that the actual contents of the memory
13075 contained in a DLL are not available unless the program is running. This
13076 means that you cannot examine the contents of a variable or disassemble
13077 a function within a DLL without a running program.
13079 Variables are generally treated as pointers and dereferenced
13080 automatically. For this reason, it is often necessary to prefix a
13081 variable name with the address-of operator (``&'') and provide explicit
13082 type information in the command. Here's an example of the type of
13086 (@value{GDBP}) print 'cygwin1!__argv'
13091 (@value{GDBP}) x 'cygwin1!__argv'
13092 0x10021610: "\230y\""
13095 And two possible solutions:
13098 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
13099 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
13103 (@value{GDBP}) x/2x &'cygwin1!__argv'
13104 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
13105 (@value{GDBP}) x/x 0x10021608
13106 0x10021608: 0x0022fd98
13107 (@value{GDBP}) x/s 0x0022fd98
13108 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
13111 Setting a break point within a DLL is possible even before the program
13112 starts execution. However, under these circumstances, @value{GDBN} can't
13113 examine the initial instructions of the function in order to skip the
13114 function's frame set-up code. You can work around this by using ``*&''
13115 to set the breakpoint at a raw memory address:
13118 (@value{GDBP}) break *&'python22!PyOS_Readline'
13119 Breakpoint 1 at 0x1e04eff0
13122 The author of these extensions is not entirely convinced that setting a
13123 break point within a shared DLL like @file{kernel32.dll} is completely
13127 @subsection Commands specific to @sc{gnu} Hurd systems
13128 @cindex @sc{gnu} Hurd debugging
13130 This subsection describes @value{GDBN} commands specific to the
13131 @sc{gnu} Hurd native debugging.
13136 @kindex set signals@r{, Hurd command}
13137 @kindex set sigs@r{, Hurd command}
13138 This command toggles the state of inferior signal interception by
13139 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
13140 affected by this command. @code{sigs} is a shorthand alias for
13145 @kindex show signals@r{, Hurd command}
13146 @kindex show sigs@r{, Hurd command}
13147 Show the current state of intercepting inferior's signals.
13149 @item set signal-thread
13150 @itemx set sigthread
13151 @kindex set signal-thread
13152 @kindex set sigthread
13153 This command tells @value{GDBN} which thread is the @code{libc} signal
13154 thread. That thread is run when a signal is delivered to a running
13155 process. @code{set sigthread} is the shorthand alias of @code{set
13158 @item show signal-thread
13159 @itemx show sigthread
13160 @kindex show signal-thread
13161 @kindex show sigthread
13162 These two commands show which thread will run when the inferior is
13163 delivered a signal.
13166 @kindex set stopped@r{, Hurd command}
13167 This commands tells @value{GDBN} that the inferior process is stopped,
13168 as with the @code{SIGSTOP} signal. The stopped process can be
13169 continued by delivering a signal to it.
13172 @kindex show stopped@r{, Hurd command}
13173 This command shows whether @value{GDBN} thinks the debuggee is
13176 @item set exceptions
13177 @kindex set exceptions@r{, Hurd command}
13178 Use this command to turn off trapping of exceptions in the inferior.
13179 When exception trapping is off, neither breakpoints nor
13180 single-stepping will work. To restore the default, set exception
13183 @item show exceptions
13184 @kindex show exceptions@r{, Hurd command}
13185 Show the current state of trapping exceptions in the inferior.
13187 @item set task pause
13188 @kindex set task@r{, Hurd commands}
13189 @cindex task attributes (@sc{gnu} Hurd)
13190 @cindex pause current task (@sc{gnu} Hurd)
13191 This command toggles task suspension when @value{GDBN} has control.
13192 Setting it to on takes effect immediately, and the task is suspended
13193 whenever @value{GDBN} gets control. Setting it to off will take
13194 effect the next time the inferior is continued. If this option is set
13195 to off, you can use @code{set thread default pause on} or @code{set
13196 thread pause on} (see below) to pause individual threads.
13198 @item show task pause
13199 @kindex show task@r{, Hurd commands}
13200 Show the current state of task suspension.
13202 @item set task detach-suspend-count
13203 @cindex task suspend count
13204 @cindex detach from task, @sc{gnu} Hurd
13205 This command sets the suspend count the task will be left with when
13206 @value{GDBN} detaches from it.
13208 @item show task detach-suspend-count
13209 Show the suspend count the task will be left with when detaching.
13211 @item set task exception-port
13212 @itemx set task excp
13213 @cindex task exception port, @sc{gnu} Hurd
13214 This command sets the task exception port to which @value{GDBN} will
13215 forward exceptions. The argument should be the value of the @dfn{send
13216 rights} of the task. @code{set task excp} is a shorthand alias.
13218 @item set noninvasive
13219 @cindex noninvasive task options
13220 This command switches @value{GDBN} to a mode that is the least
13221 invasive as far as interfering with the inferior is concerned. This
13222 is the same as using @code{set task pause}, @code{set exceptions}, and
13223 @code{set signals} to values opposite to the defaults.
13225 @item info send-rights
13226 @itemx info receive-rights
13227 @itemx info port-rights
13228 @itemx info port-sets
13229 @itemx info dead-names
13232 @cindex send rights, @sc{gnu} Hurd
13233 @cindex receive rights, @sc{gnu} Hurd
13234 @cindex port rights, @sc{gnu} Hurd
13235 @cindex port sets, @sc{gnu} Hurd
13236 @cindex dead names, @sc{gnu} Hurd
13237 These commands display information about, respectively, send rights,
13238 receive rights, port rights, port sets, and dead names of a task.
13239 There are also shorthand aliases: @code{info ports} for @code{info
13240 port-rights} and @code{info psets} for @code{info port-sets}.
13242 @item set thread pause
13243 @kindex set thread@r{, Hurd command}
13244 @cindex thread properties, @sc{gnu} Hurd
13245 @cindex pause current thread (@sc{gnu} Hurd)
13246 This command toggles current thread suspension when @value{GDBN} has
13247 control. Setting it to on takes effect immediately, and the current
13248 thread is suspended whenever @value{GDBN} gets control. Setting it to
13249 off will take effect the next time the inferior is continued.
13250 Normally, this command has no effect, since when @value{GDBN} has
13251 control, the whole task is suspended. However, if you used @code{set
13252 task pause off} (see above), this command comes in handy to suspend
13253 only the current thread.
13255 @item show thread pause
13256 @kindex show thread@r{, Hurd command}
13257 This command shows the state of current thread suspension.
13259 @item set thread run
13260 This comamnd sets whether the current thread is allowed to run.
13262 @item show thread run
13263 Show whether the current thread is allowed to run.
13265 @item set thread detach-suspend-count
13266 @cindex thread suspend count, @sc{gnu} Hurd
13267 @cindex detach from thread, @sc{gnu} Hurd
13268 This command sets the suspend count @value{GDBN} will leave on a
13269 thread when detaching. This number is relative to the suspend count
13270 found by @value{GDBN} when it notices the thread; use @code{set thread
13271 takeover-suspend-count} to force it to an absolute value.
13273 @item show thread detach-suspend-count
13274 Show the suspend count @value{GDBN} will leave on the thread when
13277 @item set thread exception-port
13278 @itemx set thread excp
13279 Set the thread exception port to which to forward exceptions. This
13280 overrides the port set by @code{set task exception-port} (see above).
13281 @code{set thread excp} is the shorthand alias.
13283 @item set thread takeover-suspend-count
13284 Normally, @value{GDBN}'s thread suspend counts are relative to the
13285 value @value{GDBN} finds when it notices each thread. This command
13286 changes the suspend counts to be absolute instead.
13288 @item set thread default
13289 @itemx show thread default
13290 @cindex thread default settings, @sc{gnu} Hurd
13291 Each of the above @code{set thread} commands has a @code{set thread
13292 default} counterpart (e.g., @code{set thread default pause}, @code{set
13293 thread default exception-port}, etc.). The @code{thread default}
13294 variety of commands sets the default thread properties for all
13295 threads; you can then change the properties of individual threads with
13296 the non-default commands.
13301 @subsection QNX Neutrino
13302 @cindex QNX Neutrino
13304 @value{GDBN} provides the following commands specific to the QNX
13308 @item set debug nto-debug
13309 @kindex set debug nto-debug
13310 When set to on, enables debugging messages specific to the QNX
13313 @item show debug nto-debug
13314 @kindex show debug nto-debug
13315 Show the current state of QNX Neutrino messages.
13320 @section Embedded Operating Systems
13322 This section describes configurations involving the debugging of
13323 embedded operating systems that are available for several different
13327 * VxWorks:: Using @value{GDBN} with VxWorks
13330 @value{GDBN} includes the ability to debug programs running on
13331 various real-time operating systems.
13334 @subsection Using @value{GDBN} with VxWorks
13340 @kindex target vxworks
13341 @item target vxworks @var{machinename}
13342 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
13343 is the target system's machine name or IP address.
13347 On VxWorks, @code{load} links @var{filename} dynamically on the
13348 current target system as well as adding its symbols in @value{GDBN}.
13350 @value{GDBN} enables developers to spawn and debug tasks running on networked
13351 VxWorks targets from a Unix host. Already-running tasks spawned from
13352 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
13353 both the Unix host and on the VxWorks target. The program
13354 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
13355 installed with the name @code{vxgdb}, to distinguish it from a
13356 @value{GDBN} for debugging programs on the host itself.)
13359 @item VxWorks-timeout @var{args}
13360 @kindex vxworks-timeout
13361 All VxWorks-based targets now support the option @code{vxworks-timeout}.
13362 This option is set by the user, and @var{args} represents the number of
13363 seconds @value{GDBN} waits for responses to rpc's. You might use this if
13364 your VxWorks target is a slow software simulator or is on the far side
13365 of a thin network line.
13368 The following information on connecting to VxWorks was current when
13369 this manual was produced; newer releases of VxWorks may use revised
13372 @findex INCLUDE_RDB
13373 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
13374 to include the remote debugging interface routines in the VxWorks
13375 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
13376 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
13377 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
13378 source debugging task @code{tRdbTask} when VxWorks is booted. For more
13379 information on configuring and remaking VxWorks, see the manufacturer's
13381 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
13383 Once you have included @file{rdb.a} in your VxWorks system image and set
13384 your Unix execution search path to find @value{GDBN}, you are ready to
13385 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
13386 @code{vxgdb}, depending on your installation).
13388 @value{GDBN} comes up showing the prompt:
13395 * VxWorks Connection:: Connecting to VxWorks
13396 * VxWorks Download:: VxWorks download
13397 * VxWorks Attach:: Running tasks
13400 @node VxWorks Connection
13401 @subsubsection Connecting to VxWorks
13403 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
13404 network. To connect to a target whose host name is ``@code{tt}'', type:
13407 (vxgdb) target vxworks tt
13411 @value{GDBN} displays messages like these:
13414 Attaching remote machine across net...
13419 @value{GDBN} then attempts to read the symbol tables of any object modules
13420 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
13421 these files by searching the directories listed in the command search
13422 path (@pxref{Environment, ,Your program's environment}); if it fails
13423 to find an object file, it displays a message such as:
13426 prog.o: No such file or directory.
13429 When this happens, add the appropriate directory to the search path with
13430 the @value{GDBN} command @code{path}, and execute the @code{target}
13433 @node VxWorks Download
13434 @subsubsection VxWorks download
13436 @cindex download to VxWorks
13437 If you have connected to the VxWorks target and you want to debug an
13438 object that has not yet been loaded, you can use the @value{GDBN}
13439 @code{load} command to download a file from Unix to VxWorks
13440 incrementally. The object file given as an argument to the @code{load}
13441 command is actually opened twice: first by the VxWorks target in order
13442 to download the code, then by @value{GDBN} in order to read the symbol
13443 table. This can lead to problems if the current working directories on
13444 the two systems differ. If both systems have NFS mounted the same
13445 filesystems, you can avoid these problems by using absolute paths.
13446 Otherwise, it is simplest to set the working directory on both systems
13447 to the directory in which the object file resides, and then to reference
13448 the file by its name, without any path. For instance, a program
13449 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
13450 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
13451 program, type this on VxWorks:
13454 -> cd "@var{vxpath}/vw/demo/rdb"
13458 Then, in @value{GDBN}, type:
13461 (vxgdb) cd @var{hostpath}/vw/demo/rdb
13462 (vxgdb) load prog.o
13465 @value{GDBN} displays a response similar to this:
13468 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
13471 You can also use the @code{load} command to reload an object module
13472 after editing and recompiling the corresponding source file. Note that
13473 this makes @value{GDBN} delete all currently-defined breakpoints,
13474 auto-displays, and convenience variables, and to clear the value
13475 history. (This is necessary in order to preserve the integrity of
13476 debugger's data structures that reference the target system's symbol
13479 @node VxWorks Attach
13480 @subsubsection Running tasks
13482 @cindex running VxWorks tasks
13483 You can also attach to an existing task using the @code{attach} command as
13487 (vxgdb) attach @var{task}
13491 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
13492 or suspended when you attach to it. Running tasks are suspended at
13493 the time of attachment.
13495 @node Embedded Processors
13496 @section Embedded Processors
13498 This section goes into details specific to particular embedded
13501 @cindex send command to simulator
13502 Whenever a specific embedded processor has a simulator, @value{GDBN}
13503 allows to send an arbitrary command to the simulator.
13506 @item sim @var{command}
13507 @kindex sim@r{, a command}
13508 Send an arbitrary @var{command} string to the simulator. Consult the
13509 documentation for the specific simulator in use for information about
13510 acceptable commands.
13516 * H8/300:: Renesas H8/300
13517 * H8/500:: Renesas H8/500
13518 * M32R/D:: Renesas M32R/D
13519 * M68K:: Motorola M68K
13520 * MIPS Embedded:: MIPS Embedded
13521 * OpenRISC 1000:: OpenRisc 1000
13522 * PA:: HP PA Embedded
13525 * Sparclet:: Tsqware Sparclet
13526 * Sparclite:: Fujitsu Sparclite
13527 * ST2000:: Tandem ST2000
13528 * Z8000:: Zilog Z8000
13531 * Super-H:: Renesas Super-H
13532 * WinCE:: Windows CE child processes
13541 @item target rdi @var{dev}
13542 ARM Angel monitor, via RDI library interface to ADP protocol. You may
13543 use this target to communicate with both boards running the Angel
13544 monitor, or with the EmbeddedICE JTAG debug device.
13547 @item target rdp @var{dev}
13552 @value{GDBN} provides the following ARM-specific commands:
13555 @item set arm disassembler
13557 This commands selects from a list of disassembly styles. The
13558 @code{"std"} style is the standard style.
13560 @item show arm disassembler
13562 Show the current disassembly style.
13564 @item set arm apcs32
13565 @cindex ARM 32-bit mode
13566 This command toggles ARM operation mode between 32-bit and 26-bit.
13568 @item show arm apcs32
13569 Display the current usage of the ARM 32-bit mode.
13571 @item set arm fpu @var{fputype}
13572 This command sets the ARM floating-point unit (FPU) type. The
13573 argument @var{fputype} can be one of these:
13577 Determine the FPU type by querying the OS ABI.
13579 Software FPU, with mixed-endian doubles on little-endian ARM
13582 GCC-compiled FPA co-processor.
13584 Software FPU with pure-endian doubles.
13590 Show the current type of the FPU.
13593 This command forces @value{GDBN} to use the specified ABI.
13596 Show the currently used ABI.
13598 @item set debug arm
13599 Toggle whether to display ARM-specific debugging messages from the ARM
13600 target support subsystem.
13602 @item show debug arm
13603 Show whether ARM-specific debugging messages are enabled.
13606 The following commands are available when an ARM target is debugged
13607 using the RDI interface:
13610 @item rdilogfile @r{[}@var{file}@r{]}
13612 @cindex ADP (Angel Debugger Protocol) logging
13613 Set the filename for the ADP (Angel Debugger Protocol) packet log.
13614 With an argument, sets the log file to the specified @var{file}. With
13615 no argument, show the current log file name. The default log file is
13618 @item rdilogenable @r{[}@var{arg}@r{]}
13619 @kindex rdilogenable
13620 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
13621 enables logging, with an argument 0 or @code{"no"} disables it. With
13622 no arguments displays the current setting. When logging is enabled,
13623 ADP packets exchanged between @value{GDBN} and the RDI target device
13624 are logged to a file.
13626 @item set rdiromatzero
13627 @kindex set rdiromatzero
13628 @cindex ROM at zero address, RDI
13629 Tell @value{GDBN} whether the target has ROM at address 0. If on,
13630 vector catching is disabled, so that zero address can be used. If off
13631 (the default), vector catching is enabled. For this command to take
13632 effect, it needs to be invoked prior to the @code{target rdi} command.
13634 @item show rdiromatzero
13635 @kindex show rdiromatzero
13636 Show the current setting of ROM at zero address.
13638 @item set rdiheartbeat
13639 @kindex set rdiheartbeat
13640 @cindex RDI heartbeat
13641 Enable or disable RDI heartbeat packets. It is not recommended to
13642 turn on this option, since it confuses ARM and EPI JTAG interface, as
13643 well as the Angel monitor.
13645 @item show rdiheartbeat
13646 @kindex show rdiheartbeat
13647 Show the setting of RDI heartbeat packets.
13652 @subsection Renesas H8/300
13656 @kindex target hms@r{, with H8/300}
13657 @item target hms @var{dev}
13658 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
13659 Use special commands @code{device} and @code{speed} to control the serial
13660 line and the communications speed used.
13662 @kindex target e7000@r{, with H8/300}
13663 @item target e7000 @var{dev}
13664 E7000 emulator for Renesas H8 and SH.
13666 @kindex target sh3@r{, with H8/300}
13667 @kindex target sh3e@r{, with H8/300}
13668 @item target sh3 @var{dev}
13669 @itemx target sh3e @var{dev}
13670 Renesas SH-3 and SH-3E target systems.
13674 @cindex download to H8/300 or H8/500
13675 @cindex H8/300 or H8/500 download
13676 @cindex download to Renesas SH
13677 @cindex Renesas SH download
13678 When you select remote debugging to a Renesas SH, H8/300, or H8/500
13679 board, the @code{load} command downloads your program to the Renesas
13680 board and also opens it as the current executable target for
13681 @value{GDBN} on your host (like the @code{file} command).
13683 @value{GDBN} needs to know these things to talk to your
13684 Renesas SH, H8/300, or H8/500:
13688 that you want to use @samp{target hms}, the remote debugging interface
13689 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
13690 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
13691 the default when @value{GDBN} is configured specifically for the Renesas SH,
13692 H8/300, or H8/500.)
13695 what serial device connects your host to your Renesas board (the first
13696 serial device available on your host is the default).
13699 what speed to use over the serial device.
13703 * Renesas Boards:: Connecting to Renesas boards.
13704 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
13705 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
13708 @node Renesas Boards
13709 @subsubsection Connecting to Renesas boards
13711 @c only for Unix hosts
13713 @cindex serial device, Renesas micros
13714 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
13715 need to explicitly set the serial device. The default @var{port} is the
13716 first available port on your host. This is only necessary on Unix
13717 hosts, where it is typically something like @file{/dev/ttya}.
13720 @cindex serial line speed, Renesas micros
13721 @code{@value{GDBN}} has another special command to set the communications
13722 speed: @samp{speed @var{bps}}. This command also is only used from Unix
13723 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
13724 the DOS @code{mode} command (for instance,
13725 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
13727 The @samp{device} and @samp{speed} commands are available only when you
13728 use a Unix host to debug your Renesas microprocessor programs. If you
13730 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
13731 called @code{asynctsr} to communicate with the development board
13732 through a PC serial port. You must also use the DOS @code{mode} command
13733 to set up the serial port on the DOS side.
13735 The following sample session illustrates the steps needed to start a
13736 program under @value{GDBN} control on an H8/300. The example uses a
13737 sample H8/300 program called @file{t.x}. The procedure is the same for
13738 the Renesas SH and the H8/500.
13740 First hook up your development board. In this example, we use a
13741 board attached to serial port @code{COM2}; if you use a different serial
13742 port, substitute its name in the argument of the @code{mode} command.
13743 When you call @code{asynctsr}, the auxiliary comms program used by the
13744 debugger, you give it just the numeric part of the serial port's name;
13745 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
13749 C:\H8300\TEST> asynctsr 2
13750 C:\H8300\TEST> mode com2:9600,n,8,1,p
13752 Resident portion of MODE loaded
13754 COM2: 9600, n, 8, 1, p
13759 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
13760 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
13761 disable it, or even boot without it, to use @code{asynctsr} to control
13762 your development board.
13765 @kindex target hms@r{, and serial protocol}
13766 Now that serial communications are set up, and the development board is
13767 connected, you can start up @value{GDBN}. Call @code{@value{GDBN}} with
13768 the name of your program as the argument. @code{@value{GDBN}} prompts
13769 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
13770 commands to begin your debugging session: @samp{target hms} to specify
13771 cross-debugging to the Renesas board, and the @code{load} command to
13772 download your program to the board. @code{load} displays the names of
13773 the program's sections, and a @samp{*} for each 2K of data downloaded.
13774 (If you want to refresh @value{GDBN} data on symbols or on the
13775 executable file without downloading, use the @value{GDBN} commands
13776 @code{file} or @code{symbol-file}. These commands, and @code{load}
13777 itself, are described in @ref{Files,,Commands to specify files}.)
13780 (eg-C:\H8300\TEST) @value{GDBP} t.x
13781 @value{GDBN} is free software and you are welcome to distribute copies
13782 of it under certain conditions; type "show copying" to see
13784 There is absolutely no warranty for @value{GDBN}; type "show warranty"
13786 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
13787 (@value{GDBP}) target hms
13788 Connected to remote H8/300 HMS system.
13789 (@value{GDBP}) load t.x
13790 .text : 0x8000 .. 0xabde ***********
13791 .data : 0xabde .. 0xad30 *
13792 .stack : 0xf000 .. 0xf014 *
13795 At this point, you're ready to run or debug your program. From here on,
13796 you can use all the usual @value{GDBN} commands. The @code{break} command
13797 sets breakpoints; the @code{run} command starts your program;
13798 @code{print} or @code{x} display data; the @code{continue} command
13799 resumes execution after stopping at a breakpoint. You can use the
13800 @code{help} command at any time to find out more about @value{GDBN} commands.
13802 Remember, however, that @emph{operating system} facilities aren't
13803 available on your development board; for example, if your program hangs,
13804 you can't send an interrupt---but you can press the @sc{reset} switch!
13806 Use the @sc{reset} button on the development board
13809 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
13810 no way to pass an interrupt signal to the development board); and
13813 to return to the @value{GDBN} command prompt after your program finishes
13814 normally. The communications protocol provides no other way for @value{GDBN}
13815 to detect program completion.
13818 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
13819 development board as a ``normal exit'' of your program.
13822 @subsubsection Using the E7000 in-circuit emulator
13824 @kindex target e7000@r{, with Renesas ICE}
13825 You can use the E7000 in-circuit emulator to develop code for either the
13826 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
13827 e7000} command to connect @value{GDBN} to your E7000:
13830 @item target e7000 @var{port} @var{speed}
13831 Use this form if your E7000 is connected to a serial port. The
13832 @var{port} argument identifies what serial port to use (for example,
13833 @samp{com2}). The third argument is the line speed in bits per second
13834 (for example, @samp{9600}).
13836 @item target e7000 @var{hostname}
13837 If your E7000 is installed as a host on a TCP/IP network, you can just
13838 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
13841 The following special commands are available when debugging with the
13845 @item e7000 @var{command}
13847 @cindex send command to E7000 monitor
13848 This sends the specified @var{command} to the E7000 monitor.
13850 @item ftplogin @var{machine} @var{username} @var{password} @var{dir}
13851 @kindex ftplogin@r{, E7000}
13852 This command records information for subsequent interface with the
13853 E7000 monitor via the FTP protocol: @value{GDBN} will log into the
13854 named @var{machine} using specified @var{username} and @var{password},
13855 and then chdir to the named directory @var{dir}.
13857 @item ftpload @var{file}
13858 @kindex ftpload@r{, E7000}
13859 This command uses credentials recorded by @code{ftplogin} to fetch and
13860 load the named @var{file} from the E7000 monitor.
13863 @kindex drain@r{, E7000}
13864 This command drains any pending text buffers stored on the E7000.
13866 @item set usehardbreakpoints
13867 @itemx show usehardbreakpoints
13868 @kindex set usehardbreakpoints@r{, E7000}
13869 @kindex show usehardbreakpoints@r{, E7000}
13870 @cindex hardware breakpoints, and E7000
13871 These commands set and show the use of hardware breakpoints for all
13872 breakpoints. @xref{Set Breaks, hardware-assisted breakpoint}, for
13873 more information about using hardware breakpoints selectively.
13876 @node Renesas Special
13877 @subsubsection Special @value{GDBN} commands for Renesas micros
13879 Some @value{GDBN} commands are available only for the H8/300:
13883 @kindex set machine
13884 @kindex show machine
13885 @item set machine h8300
13886 @itemx set machine h8300h
13887 Condition @value{GDBN} for one of the two variants of the H8/300
13888 architecture with @samp{set machine}. You can use @samp{show machine}
13889 to check which variant is currently in effect.
13898 @kindex set memory @var{mod}
13899 @cindex memory models, H8/500
13900 @item set memory @var{mod}
13902 Specify which H8/500 memory model (@var{mod}) you are using with
13903 @samp{set memory}; check which memory model is in effect with @samp{show
13904 memory}. The accepted values for @var{mod} are @code{small},
13905 @code{big}, @code{medium}, and @code{compact}.
13910 @subsection Renesas M32R/D and M32R/SDI
13913 @kindex target m32r
13914 @item target m32r @var{dev}
13915 Renesas M32R/D ROM monitor.
13917 @kindex target m32rsdi
13918 @item target m32rsdi @var{dev}
13919 Renesas M32R SDI server, connected via parallel port to the board.
13922 The following @value{GDBN} commands are specific to the M32R monitor:
13925 @item set download-path @var{path}
13926 @kindex set download-path
13927 @cindex find downloadable @sc{srec} files (M32R)
13928 Set the default path for finding donwloadable @sc{srec} files.
13930 @item show download-path
13931 @kindex show download-path
13932 Show the default path for downloadable @sc{srec} files.
13934 @item set board-address @var{addr}
13935 @kindex set board-address
13936 @cindex M32-EVA target board address
13937 Set the IP address for the M32R-EVA target board.
13939 @item show board-address
13940 @kindex show board-address
13941 Show the current IP address of the target board.
13943 @item set server-address @var{addr}
13944 @kindex set server-address
13945 @cindex download server address (M32R)
13946 Set the IP address for the download server, which is the @value{GDBN}'s
13949 @item show server-address
13950 @kindex show server-address
13951 Display the IP address of the download server.
13953 @item upload @r{[}@var{file}@r{]}
13954 @kindex upload@r{, M32R}
13955 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
13956 upload capability. If no @var{file} argument is given, the current
13957 executable file is uploaded.
13959 @item tload @r{[}@var{file}@r{]}
13960 @kindex tload@r{, M32R}
13961 Test the @code{upload} command.
13964 The following commands are available for M32R/SDI:
13969 @cindex reset SDI connection, M32R
13970 This command resets the SDI connection.
13974 This command shows the SDI connection status.
13977 @kindex debug_chaos
13978 @cindex M32R/Chaos debugging
13979 Instructs the remote that M32R/Chaos debugging is to be used.
13981 @item use_debug_dma
13982 @kindex use_debug_dma
13983 Instructs the remote to use the DEBUG_DMA method of accessing memory.
13986 @kindex use_mon_code
13987 Instructs the remote to use the MON_CODE method of accessing memory.
13990 @kindex use_ib_break
13991 Instructs the remote to set breakpoints by IB break.
13993 @item use_dbt_break
13994 @kindex use_dbt_break
13995 Instructs the remote to set breakpoints by DBT.
14001 The Motorola m68k configuration includes ColdFire support, and
14002 target command for the following ROM monitors.
14006 @kindex target abug
14007 @item target abug @var{dev}
14008 ABug ROM monitor for M68K.
14010 @kindex target cpu32bug
14011 @item target cpu32bug @var{dev}
14012 CPU32BUG monitor, running on a CPU32 (M68K) board.
14014 @kindex target dbug
14015 @item target dbug @var{dev}
14016 dBUG ROM monitor for Motorola ColdFire.
14019 @item target est @var{dev}
14020 EST-300 ICE monitor, running on a CPU32 (M68K) board.
14022 @kindex target rom68k
14023 @item target rom68k @var{dev}
14024 ROM 68K monitor, running on an M68K IDP board.
14030 @kindex target rombug
14031 @item target rombug @var{dev}
14032 ROMBUG ROM monitor for OS/9000.
14036 @node MIPS Embedded
14037 @subsection MIPS Embedded
14039 @cindex MIPS boards
14040 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
14041 MIPS board attached to a serial line. This is available when
14042 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
14045 Use these @value{GDBN} commands to specify the connection to your target board:
14048 @item target mips @var{port}
14049 @kindex target mips @var{port}
14050 To run a program on the board, start up @code{@value{GDBP}} with the
14051 name of your program as the argument. To connect to the board, use the
14052 command @samp{target mips @var{port}}, where @var{port} is the name of
14053 the serial port connected to the board. If the program has not already
14054 been downloaded to the board, you may use the @code{load} command to
14055 download it. You can then use all the usual @value{GDBN} commands.
14057 For example, this sequence connects to the target board through a serial
14058 port, and loads and runs a program called @var{prog} through the
14062 host$ @value{GDBP} @var{prog}
14063 @value{GDBN} is free software and @dots{}
14064 (@value{GDBP}) target mips /dev/ttyb
14065 (@value{GDBP}) load @var{prog}
14069 @item target mips @var{hostname}:@var{portnumber}
14070 On some @value{GDBN} host configurations, you can specify a TCP
14071 connection (for instance, to a serial line managed by a terminal
14072 concentrator) instead of a serial port, using the syntax
14073 @samp{@var{hostname}:@var{portnumber}}.
14075 @item target pmon @var{port}
14076 @kindex target pmon @var{port}
14079 @item target ddb @var{port}
14080 @kindex target ddb @var{port}
14081 NEC's DDB variant of PMON for Vr4300.
14083 @item target lsi @var{port}
14084 @kindex target lsi @var{port}
14085 LSI variant of PMON.
14087 @kindex target r3900
14088 @item target r3900 @var{dev}
14089 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
14091 @kindex target array
14092 @item target array @var{dev}
14093 Array Tech LSI33K RAID controller board.
14099 @value{GDBN} also supports these special commands for MIPS targets:
14102 @item set mipsfpu double
14103 @itemx set mipsfpu single
14104 @itemx set mipsfpu none
14105 @itemx set mipsfpu auto
14106 @itemx show mipsfpu
14107 @kindex set mipsfpu
14108 @kindex show mipsfpu
14109 @cindex MIPS remote floating point
14110 @cindex floating point, MIPS remote
14111 If your target board does not support the MIPS floating point
14112 coprocessor, you should use the command @samp{set mipsfpu none} (if you
14113 need this, you may wish to put the command in your @value{GDBN} init
14114 file). This tells @value{GDBN} how to find the return value of
14115 functions which return floating point values. It also allows
14116 @value{GDBN} to avoid saving the floating point registers when calling
14117 functions on the board. If you are using a floating point coprocessor
14118 with only single precision floating point support, as on the @sc{r4650}
14119 processor, use the command @samp{set mipsfpu single}. The default
14120 double precision floating point coprocessor may be selected using
14121 @samp{set mipsfpu double}.
14123 In previous versions the only choices were double precision or no
14124 floating point, so @samp{set mipsfpu on} will select double precision
14125 and @samp{set mipsfpu off} will select no floating point.
14127 As usual, you can inquire about the @code{mipsfpu} variable with
14128 @samp{show mipsfpu}.
14130 @item set timeout @var{seconds}
14131 @itemx set retransmit-timeout @var{seconds}
14132 @itemx show timeout
14133 @itemx show retransmit-timeout
14134 @cindex @code{timeout}, MIPS protocol
14135 @cindex @code{retransmit-timeout}, MIPS protocol
14136 @kindex set timeout
14137 @kindex show timeout
14138 @kindex set retransmit-timeout
14139 @kindex show retransmit-timeout
14140 You can control the timeout used while waiting for a packet, in the MIPS
14141 remote protocol, with the @code{set timeout @var{seconds}} command. The
14142 default is 5 seconds. Similarly, you can control the timeout used while
14143 waiting for an acknowledgement of a packet with the @code{set
14144 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
14145 You can inspect both values with @code{show timeout} and @code{show
14146 retransmit-timeout}. (These commands are @emph{only} available when
14147 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
14149 The timeout set by @code{set timeout} does not apply when @value{GDBN}
14150 is waiting for your program to stop. In that case, @value{GDBN} waits
14151 forever because it has no way of knowing how long the program is going
14152 to run before stopping.
14154 @item set syn-garbage-limit @var{num}
14155 @kindex set syn-garbage-limit@r{, MIPS remote}
14156 @cindex synchronize with remote MIPS target
14157 Limit the maximum number of characters @value{GDBN} should ignore when
14158 it tries to synchronize with the remote target. The default is 10
14159 characters. Setting the limit to -1 means there's no limit.
14161 @item show syn-garbage-limit
14162 @kindex show syn-garbage-limit@r{, MIPS remote}
14163 Show the current limit on the number of characters to ignore when
14164 trying to synchronize with the remote system.
14166 @item set monitor-prompt @var{prompt}
14167 @kindex set monitor-prompt@r{, MIPS remote}
14168 @cindex remote monitor prompt
14169 Tell @value{GDBN} to expect the specified @var{prompt} string from the
14170 remote monitor. The default depends on the target:
14180 @item show monitor-prompt
14181 @kindex show monitor-prompt@r{, MIPS remote}
14182 Show the current strings @value{GDBN} expects as the prompt from the
14185 @item set monitor-warnings
14186 @kindex set monitor-warnings@r{, MIPS remote}
14187 Enable or disable monitor warnings about hardware breakpoints. This
14188 has effect only for the @code{lsi} target. When on, @value{GDBN} will
14189 display warning messages whose codes are returned by the @code{lsi}
14190 PMON monitor for breakpoint commands.
14192 @item show monitor-warnings
14193 @kindex show monitor-warnings@r{, MIPS remote}
14194 Show the current setting of printing monitor warnings.
14196 @item pmon @var{command}
14197 @kindex pmon@r{, MIPS remote}
14198 @cindex send PMON command
14199 This command allows sending an arbitrary @var{command} string to the
14200 monitor. The monitor must be in debug mode for this to work.
14203 @node OpenRISC 1000
14204 @subsection OpenRISC 1000
14205 @cindex OpenRISC 1000
14207 @cindex or1k boards
14208 See OR1k Architecture document (@uref{www.opencores.org}) for more information
14209 about platform and commands.
14213 @kindex target jtag
14214 @item target jtag jtag://@var{host}:@var{port}
14216 Connects to remote JTAG server.
14217 JTAG remote server can be either an or1ksim or JTAG server,
14218 connected via parallel port to the board.
14220 Example: @code{target jtag jtag://localhost:9999}
14223 @item or1ksim @var{command}
14224 If connected to @code{or1ksim} OpenRISC 1000 Architectural
14225 Simulator, proprietary commands can be executed.
14227 @kindex info or1k spr
14228 @item info or1k spr
14229 Displays spr groups.
14231 @item info or1k spr @var{group}
14232 @itemx info or1k spr @var{groupno}
14233 Displays register names in selected group.
14235 @item info or1k spr @var{group} @var{register}
14236 @itemx info or1k spr @var{register}
14237 @itemx info or1k spr @var{groupno} @var{registerno}
14238 @itemx info or1k spr @var{registerno}
14239 Shows information about specified spr register.
14242 @item spr @var{group} @var{register} @var{value}
14243 @itemx spr @var{register @var{value}}
14244 @itemx spr @var{groupno} @var{registerno @var{value}}
14245 @itemx spr @var{registerno @var{value}}
14246 Writes @var{value} to specified spr register.
14249 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
14250 It is very similar to @value{GDBN} trace, except it does not interfere with normal
14251 program execution and is thus much faster. Hardware breakpoints/watchpoint
14252 triggers can be set using:
14255 Load effective address/data
14257 Store effective address/data
14259 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
14264 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
14265 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
14267 @code{htrace} commands:
14268 @cindex OpenRISC 1000 htrace
14271 @item hwatch @var{conditional}
14272 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
14273 or Data. For example:
14275 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14277 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14281 Display information about current HW trace configuration.
14283 @item htrace trigger @var{conditional}
14284 Set starting criteria for HW trace.
14286 @item htrace qualifier @var{conditional}
14287 Set acquisition qualifier for HW trace.
14289 @item htrace stop @var{conditional}
14290 Set HW trace stopping criteria.
14292 @item htrace record [@var{data}]*
14293 Selects the data to be recorded, when qualifier is met and HW trace was
14296 @item htrace enable
14297 @itemx htrace disable
14298 Enables/disables the HW trace.
14300 @item htrace rewind [@var{filename}]
14301 Clears currently recorded trace data.
14303 If filename is specified, new trace file is made and any newly collected data
14304 will be written there.
14306 @item htrace print [@var{start} [@var{len}]]
14307 Prints trace buffer, using current record configuration.
14309 @item htrace mode continuous
14310 Set continuous trace mode.
14312 @item htrace mode suspend
14313 Set suspend trace mode.
14318 @subsection PowerPC
14321 @kindex target dink32
14322 @item target dink32 @var{dev}
14323 DINK32 ROM monitor.
14325 @kindex target ppcbug
14326 @item target ppcbug @var{dev}
14327 @kindex target ppcbug1
14328 @item target ppcbug1 @var{dev}
14329 PPCBUG ROM monitor for PowerPC.
14332 @item target sds @var{dev}
14333 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
14336 @cindex SDS protocol
14337 The following commands specifi to the SDS protocol are supported
14341 @item set sdstimeout @var{nsec}
14342 @kindex set sdstimeout
14343 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
14344 default is 2 seconds.
14346 @item show sdstimeout
14347 @kindex show sdstimeout
14348 Show the current value of the SDS timeout.
14350 @item sds @var{command}
14351 @kindex sds@r{, a command}
14352 Send the specified @var{command} string to the SDS monitor.
14357 @subsection HP PA Embedded
14361 @kindex target op50n
14362 @item target op50n @var{dev}
14363 OP50N monitor, running on an OKI HPPA board.
14365 @kindex target w89k
14366 @item target w89k @var{dev}
14367 W89K monitor, running on a Winbond HPPA board.
14372 @subsection Renesas SH
14376 @kindex target hms@r{, with Renesas SH}
14377 @item target hms @var{dev}
14378 A Renesas SH board attached via serial line to your host. Use special
14379 commands @code{device} and @code{speed} to control the serial line and
14380 the communications speed used.
14382 @kindex target e7000@r{, with Renesas SH}
14383 @item target e7000 @var{dev}
14384 E7000 emulator for Renesas SH.
14386 @kindex target sh3@r{, with SH}
14387 @kindex target sh3e@r{, with SH}
14388 @item target sh3 @var{dev}
14389 @item target sh3e @var{dev}
14390 Renesas SH-3 and SH-3E target systems.
14395 @subsection Tsqware Sparclet
14399 @value{GDBN} enables developers to debug tasks running on
14400 Sparclet targets from a Unix host.
14401 @value{GDBN} uses code that runs on
14402 both the Unix host and on the Sparclet target. The program
14403 @code{@value{GDBP}} is installed and executed on the Unix host.
14406 @item remotetimeout @var{args}
14407 @kindex remotetimeout
14408 @value{GDBN} supports the option @code{remotetimeout}.
14409 This option is set by the user, and @var{args} represents the number of
14410 seconds @value{GDBN} waits for responses.
14413 @cindex compiling, on Sparclet
14414 When compiling for debugging, include the options @samp{-g} to get debug
14415 information and @samp{-Ttext} to relocate the program to where you wish to
14416 load it on the target. You may also want to add the options @samp{-n} or
14417 @samp{-N} in order to reduce the size of the sections. Example:
14420 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
14423 You can use @code{objdump} to verify that the addresses are what you intended:
14426 sparclet-aout-objdump --headers --syms prog
14429 @cindex running, on Sparclet
14431 your Unix execution search path to find @value{GDBN}, you are ready to
14432 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
14433 (or @code{sparclet-aout-gdb}, depending on your installation).
14435 @value{GDBN} comes up showing the prompt:
14442 * Sparclet File:: Setting the file to debug
14443 * Sparclet Connection:: Connecting to Sparclet
14444 * Sparclet Download:: Sparclet download
14445 * Sparclet Execution:: Running and debugging
14448 @node Sparclet File
14449 @subsubsection Setting file to debug
14451 The @value{GDBN} command @code{file} lets you choose with program to debug.
14454 (gdbslet) file prog
14458 @value{GDBN} then attempts to read the symbol table of @file{prog}.
14459 @value{GDBN} locates
14460 the file by searching the directories listed in the command search
14462 If the file was compiled with debug information (option "-g"), source
14463 files will be searched as well.
14464 @value{GDBN} locates
14465 the source files by searching the directories listed in the directory search
14466 path (@pxref{Environment, ,Your program's environment}).
14468 to find a file, it displays a message such as:
14471 prog: No such file or directory.
14474 When this happens, add the appropriate directories to the search paths with
14475 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
14476 @code{target} command again.
14478 @node Sparclet Connection
14479 @subsubsection Connecting to Sparclet
14481 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
14482 To connect to a target on serial port ``@code{ttya}'', type:
14485 (gdbslet) target sparclet /dev/ttya
14486 Remote target sparclet connected to /dev/ttya
14487 main () at ../prog.c:3
14491 @value{GDBN} displays messages like these:
14497 @node Sparclet Download
14498 @subsubsection Sparclet download
14500 @cindex download to Sparclet
14501 Once connected to the Sparclet target,
14502 you can use the @value{GDBN}
14503 @code{load} command to download the file from the host to the target.
14504 The file name and load offset should be given as arguments to the @code{load}
14506 Since the file format is aout, the program must be loaded to the starting
14507 address. You can use @code{objdump} to find out what this value is. The load
14508 offset is an offset which is added to the VMA (virtual memory address)
14509 of each of the file's sections.
14510 For instance, if the program
14511 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
14512 and bss at 0x12010170, in @value{GDBN}, type:
14515 (gdbslet) load prog 0x12010000
14516 Loading section .text, size 0xdb0 vma 0x12010000
14519 If the code is loaded at a different address then what the program was linked
14520 to, you may need to use the @code{section} and @code{add-symbol-file} commands
14521 to tell @value{GDBN} where to map the symbol table.
14523 @node Sparclet Execution
14524 @subsubsection Running and debugging
14526 @cindex running and debugging Sparclet programs
14527 You can now begin debugging the task using @value{GDBN}'s execution control
14528 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
14529 manual for the list of commands.
14533 Breakpoint 1 at 0x12010000: file prog.c, line 3.
14535 Starting program: prog
14536 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
14537 3 char *symarg = 0;
14539 4 char *execarg = "hello!";
14544 @subsection Fujitsu Sparclite
14548 @kindex target sparclite
14549 @item target sparclite @var{dev}
14550 Fujitsu sparclite boards, used only for the purpose of loading.
14551 You must use an additional command to debug the program.
14552 For example: target remote @var{dev} using @value{GDBN} standard
14558 @subsection Tandem ST2000
14560 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
14563 To connect your ST2000 to the host system, see the manufacturer's
14564 manual. Once the ST2000 is physically attached, you can run:
14567 target st2000 @var{dev} @var{speed}
14571 to establish it as your debugging environment. @var{dev} is normally
14572 the name of a serial device, such as @file{/dev/ttya}, connected to the
14573 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
14574 connection (for example, to a serial line attached via a terminal
14575 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
14577 The @code{load} and @code{attach} commands are @emph{not} defined for
14578 this target; you must load your program into the ST2000 as you normally
14579 would for standalone operation. @value{GDBN} reads debugging information
14580 (such as symbols) from a separate, debugging version of the program
14581 available on your host computer.
14582 @c FIXME!! This is terribly vague; what little content is here is
14583 @c basically hearsay.
14585 @cindex ST2000 auxiliary commands
14586 These auxiliary @value{GDBN} commands are available to help you with the ST2000
14590 @item st2000 @var{command}
14591 @kindex st2000 @var{cmd}
14592 @cindex STDBUG commands (ST2000)
14593 @cindex commands to STDBUG (ST2000)
14594 Send a @var{command} to the STDBUG monitor. See the manufacturer's
14595 manual for available commands.
14598 @cindex connect (to STDBUG)
14599 Connect the controlling terminal to the STDBUG command monitor. When
14600 you are done interacting with STDBUG, typing either of two character
14601 sequences gets you back to the @value{GDBN} command prompt:
14602 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
14603 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
14607 @subsection Zilog Z8000
14610 @cindex simulator, Z8000
14611 @cindex Zilog Z8000 simulator
14613 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
14616 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
14617 unsegmented variant of the Z8000 architecture) or the Z8001 (the
14618 segmented variant). The simulator recognizes which architecture is
14619 appropriate by inspecting the object code.
14622 @item target sim @var{args}
14624 @kindex target sim@r{, with Z8000}
14625 Debug programs on a simulated CPU. If the simulator supports setup
14626 options, specify them via @var{args}.
14630 After specifying this target, you can debug programs for the simulated
14631 CPU in the same style as programs for your host computer; use the
14632 @code{file} command to load a new program image, the @code{run} command
14633 to run your program, and so on.
14635 As well as making available all the usual machine registers
14636 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
14637 additional items of information as specially named registers:
14642 Counts clock-ticks in the simulator.
14645 Counts instructions run in the simulator.
14648 Execution time in 60ths of a second.
14652 You can refer to these values in @value{GDBN} expressions with the usual
14653 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
14654 conditional breakpoint that suspends only after at least 5000
14655 simulated clock ticks.
14658 @subsection Atmel AVR
14661 When configured for debugging the Atmel AVR, @value{GDBN} supports the
14662 following AVR-specific commands:
14665 @item info io_registers
14666 @kindex info io_registers@r{, AVR}
14667 @cindex I/O registers (Atmel AVR)
14668 This command displays information about the AVR I/O registers. For
14669 each register, @value{GDBN} prints its number and value.
14676 When configured for debugging CRIS, @value{GDBN} provides the
14677 following CRIS-specific commands:
14680 @item set cris-version @var{ver}
14681 @cindex CRIS version
14682 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
14683 The CRIS version affects register names and sizes. This command is useful in
14684 case autodetection of the CRIS version fails.
14686 @item show cris-version
14687 Show the current CRIS version.
14689 @item set cris-dwarf2-cfi
14690 @cindex DWARF-2 CFI and CRIS
14691 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
14692 Change to @samp{off} when using @code{gcc-cris} whose version is below
14695 @item show cris-dwarf2-cfi
14696 Show the current state of using DWARF-2 CFI.
14698 @item set cris-mode @var{mode}
14700 Set the current CRIS mode to @var{mode}. It should only be changed when
14701 debugging in guru mode, in which case it should be set to
14702 @samp{guru} (the default is @samp{normal}).
14704 @item show cris-mode
14705 Show the current CRIS mode.
14709 @subsection Renesas Super-H
14712 For the Renesas Super-H processor, @value{GDBN} provides these
14717 @kindex regs@r{, Super-H}
14718 Show the values of all Super-H registers.
14722 @subsection Windows CE
14725 The following commands are available for Windows CE:
14728 @item set remotedirectory @var{dir}
14729 @kindex set remotedirectory
14730 Tell @value{GDBN} to upload files from the named directory @var{dir}.
14731 The default is @file{/gdb}, i.e.@: the root directory on the current
14734 @item show remotedirectory
14735 @kindex show remotedirectory
14736 Show the current value of the upload directory.
14738 @item set remoteupload @var{method}
14739 @kindex set remoteupload
14740 Set the method used to upload files to remote device. Valid values
14741 for @var{method} are @samp{always}, @samp{newer}, and @samp{never}.
14742 The default is @samp{newer}.
14744 @item show remoteupload
14745 @kindex show remoteupload
14746 Show the current setting of the upload method.
14748 @item set remoteaddhost
14749 @kindex set remoteaddhost
14750 Tell @value{GDBN} whether to add this host to the remote stub's
14751 arguments when you debug over a network.
14753 @item show remoteaddhost
14754 @kindex show remoteaddhost
14755 Show whether to add this host to remote stub's arguments when
14756 debugging over a network.
14760 @node Architectures
14761 @section Architectures
14763 This section describes characteristics of architectures that affect
14764 all uses of @value{GDBN} with the architecture, both native and cross.
14771 * HPPA:: HP PA architecture
14775 @subsection x86 Architecture-specific issues.
14778 @item set struct-convention @var{mode}
14779 @kindex set struct-convention
14780 @cindex struct return convention
14781 @cindex struct/union returned in registers
14782 Set the convention used by the inferior to return @code{struct}s and
14783 @code{union}s from functions to @var{mode}. Possible values of
14784 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
14785 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
14786 are returned on the stack, while @code{"reg"} means that a
14787 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
14788 be returned in a register.
14790 @item show struct-convention
14791 @kindex show struct-convention
14792 Show the current setting of the convention to return @code{struct}s
14801 @kindex set rstack_high_address
14802 @cindex AMD 29K register stack
14803 @cindex register stack, AMD29K
14804 @item set rstack_high_address @var{address}
14805 On AMD 29000 family processors, registers are saved in a separate
14806 @dfn{register stack}. There is no way for @value{GDBN} to determine the
14807 extent of this stack. Normally, @value{GDBN} just assumes that the
14808 stack is ``large enough''. This may result in @value{GDBN} referencing
14809 memory locations that do not exist. If necessary, you can get around
14810 this problem by specifying the ending address of the register stack with
14811 the @code{set rstack_high_address} command. The argument should be an
14812 address, which you probably want to precede with @samp{0x} to specify in
14815 @kindex show rstack_high_address
14816 @item show rstack_high_address
14817 Display the current limit of the register stack, on AMD 29000 family
14825 See the following section.
14830 @cindex stack on Alpha
14831 @cindex stack on MIPS
14832 @cindex Alpha stack
14834 Alpha- and MIPS-based computers use an unusual stack frame, which
14835 sometimes requires @value{GDBN} to search backward in the object code to
14836 find the beginning of a function.
14838 @cindex response time, MIPS debugging
14839 To improve response time (especially for embedded applications, where
14840 @value{GDBN} may be restricted to a slow serial line for this search)
14841 you may want to limit the size of this search, using one of these
14845 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
14846 @item set heuristic-fence-post @var{limit}
14847 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
14848 search for the beginning of a function. A value of @var{0} (the
14849 default) means there is no limit. However, except for @var{0}, the
14850 larger the limit the more bytes @code{heuristic-fence-post} must search
14851 and therefore the longer it takes to run. You should only need to use
14852 this command when debugging a stripped executable.
14854 @item show heuristic-fence-post
14855 Display the current limit.
14859 These commands are available @emph{only} when @value{GDBN} is configured
14860 for debugging programs on Alpha or MIPS processors.
14862 Several MIPS-specific commands are available when debugging MIPS
14866 @item set mips saved-gpreg-size @var{size}
14867 @kindex set mips saved-gpreg-size
14868 @cindex MIPS GP register size on stack
14869 Set the size of MIPS general-purpose registers saved on the stack.
14870 The argument @var{size} can be one of the following:
14874 32-bit GP registers
14876 64-bit GP registers
14878 Use the target's default setting or autodetect the saved size from the
14879 information contained in the executable. This is the default
14882 @item show mips saved-gpreg-size
14883 @kindex show mips saved-gpreg-size
14884 Show the current size of MIPS GP registers on the stack.
14886 @item set mips stack-arg-size @var{size}
14887 @kindex set mips stack-arg-size
14888 @cindex MIPS stack space for arguments
14889 Set the amount of stack space reserved for arguments to functions.
14890 The argument can be one of @code{"32"}, @code{"64"} or @code{"auto"}
14893 @item set mips abi @var{arg}
14894 @kindex set mips abi
14895 @cindex set ABI for MIPS
14896 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
14897 values of @var{arg} are:
14901 The default ABI associated with the current binary (this is the
14912 @item show mips abi
14913 @kindex show mips abi
14914 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
14917 @itemx show mipsfpu
14918 @xref{MIPS Embedded, set mipsfpu}.
14920 @item set mips mask-address @var{arg}
14921 @kindex set mips mask-address
14922 @cindex MIPS addresses, masking
14923 This command determines whether the most-significant 32 bits of 64-bit
14924 MIPS addresses are masked off. The argument @var{arg} can be
14925 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
14926 setting, which lets @value{GDBN} determine the correct value.
14928 @item show mips mask-address
14929 @kindex show mips mask-address
14930 Show whether the upper 32 bits of MIPS addresses are masked off or
14933 @item set remote-mips64-transfers-32bit-regs
14934 @kindex set remote-mips64-transfers-32bit-regs
14935 This command controls compatibility with 64-bit MIPS targets that
14936 transfer data in 32-bit quantities. If you have an old MIPS 64 target
14937 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
14938 and 64 bits for other registers, set this option to @samp{on}.
14940 @item show remote-mips64-transfers-32bit-regs
14941 @kindex show remote-mips64-transfers-32bit-regs
14942 Show the current setting of compatibility with older MIPS 64 targets.
14944 @item set debug mips
14945 @kindex set debug mips
14946 This command turns on and off debugging messages for the MIPS-specific
14947 target code in @value{GDBN}.
14949 @item show debug mips
14950 @kindex show debug mips
14951 Show the current setting of MIPS debugging messages.
14957 @cindex HPPA support
14959 When @value{GDBN} is debugging te HP PA architecture, it provides the
14960 following special commands:
14963 @item set debug hppa
14964 @kindex set debug hppa
14965 THis command determines whether HPPA architecture specific debugging
14966 messages are to be displayed.
14968 @item show debug hppa
14969 Show whether HPPA debugging messages are displayed.
14971 @item maint print unwind @var{address}
14972 @kindex maint print unwind@r{, HPPA}
14973 This command displays the contents of the unwind table entry at the
14974 given @var{address}.
14979 @node Controlling GDB
14980 @chapter Controlling @value{GDBN}
14982 You can alter the way @value{GDBN} interacts with you by using the
14983 @code{set} command. For commands controlling how @value{GDBN} displays
14984 data, see @ref{Print Settings, ,Print settings}. Other settings are
14989 * Editing:: Command editing
14990 * History:: Command history
14991 * Screen Size:: Screen size
14992 * Numbers:: Numbers
14993 * ABI:: Configuring the current ABI
14994 * Messages/Warnings:: Optional warnings and messages
14995 * Debugging Output:: Optional messages about internal happenings
15003 @value{GDBN} indicates its readiness to read a command by printing a string
15004 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
15005 can change the prompt string with the @code{set prompt} command. For
15006 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
15007 the prompt in one of the @value{GDBN} sessions so that you can always tell
15008 which one you are talking to.
15010 @emph{Note:} @code{set prompt} does not add a space for you after the
15011 prompt you set. This allows you to set a prompt which ends in a space
15012 or a prompt that does not.
15016 @item set prompt @var{newprompt}
15017 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
15019 @kindex show prompt
15021 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
15025 @section Command editing
15027 @cindex command line editing
15029 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
15030 @sc{gnu} library provides consistent behavior for programs which provide a
15031 command line interface to the user. Advantages are @sc{gnu} Emacs-style
15032 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
15033 substitution, and a storage and recall of command history across
15034 debugging sessions.
15036 You may control the behavior of command line editing in @value{GDBN} with the
15037 command @code{set}.
15040 @kindex set editing
15043 @itemx set editing on
15044 Enable command line editing (enabled by default).
15046 @item set editing off
15047 Disable command line editing.
15049 @kindex show editing
15051 Show whether command line editing is enabled.
15054 @xref{Command Line Editing}, for more details about the Readline
15055 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
15056 encouraged to read that chapter.
15059 @section Command history
15060 @cindex command history
15062 @value{GDBN} can keep track of the commands you type during your
15063 debugging sessions, so that you can be certain of precisely what
15064 happened. Use these commands to manage the @value{GDBN} command
15067 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
15068 package, to provide the history facility. @xref{Using History
15069 Interactively}, for the detailed description of the History library.
15071 Here is the description of @value{GDBN} commands related to command
15075 @cindex history substitution
15076 @cindex history file
15077 @kindex set history filename
15078 @cindex @env{GDBHISTFILE}, environment variable
15079 @item set history filename @var{fname}
15080 Set the name of the @value{GDBN} command history file to @var{fname}.
15081 This is the file where @value{GDBN} reads an initial command history
15082 list, and where it writes the command history from this session when it
15083 exits. You can access this list through history expansion or through
15084 the history command editing characters listed below. This file defaults
15085 to the value of the environment variable @code{GDBHISTFILE}, or to
15086 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
15089 @cindex save command history
15090 @kindex set history save
15091 @item set history save
15092 @itemx set history save on
15093 Record command history in a file, whose name may be specified with the
15094 @code{set history filename} command. By default, this option is disabled.
15096 @item set history save off
15097 Stop recording command history in a file.
15099 @cindex history size
15100 @kindex set history size
15101 @cindex @env{HISTSIZE}, environment variable
15102 @item set history size @var{size}
15103 Set the number of commands which @value{GDBN} keeps in its history list.
15104 This defaults to the value of the environment variable
15105 @code{HISTSIZE}, or to 256 if this variable is not set.
15108 History expansion assigns special meaning to the character @kbd{!}.
15109 @xref{Event Designators}, for more details.
15111 @cindex history expansion, turn on/off
15112 Since @kbd{!} is also the logical not operator in C, history expansion
15113 is off by default. If you decide to enable history expansion with the
15114 @code{set history expansion on} command, you may sometimes need to
15115 follow @kbd{!} (when it is used as logical not, in an expression) with
15116 a space or a tab to prevent it from being expanded. The readline
15117 history facilities do not attempt substitution on the strings
15118 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
15120 The commands to control history expansion are:
15123 @item set history expansion on
15124 @itemx set history expansion
15125 @kindex set history expansion
15126 Enable history expansion. History expansion is off by default.
15128 @item set history expansion off
15129 Disable history expansion.
15132 @kindex show history
15134 @itemx show history filename
15135 @itemx show history save
15136 @itemx show history size
15137 @itemx show history expansion
15138 These commands display the state of the @value{GDBN} history parameters.
15139 @code{show history} by itself displays all four states.
15144 @kindex show commands
15145 @cindex show last commands
15146 @cindex display command history
15147 @item show commands
15148 Display the last ten commands in the command history.
15150 @item show commands @var{n}
15151 Print ten commands centered on command number @var{n}.
15153 @item show commands +
15154 Print ten commands just after the commands last printed.
15158 @section Screen size
15159 @cindex size of screen
15160 @cindex pauses in output
15162 Certain commands to @value{GDBN} may produce large amounts of
15163 information output to the screen. To help you read all of it,
15164 @value{GDBN} pauses and asks you for input at the end of each page of
15165 output. Type @key{RET} when you want to continue the output, or @kbd{q}
15166 to discard the remaining output. Also, the screen width setting
15167 determines when to wrap lines of output. Depending on what is being
15168 printed, @value{GDBN} tries to break the line at a readable place,
15169 rather than simply letting it overflow onto the following line.
15171 Normally @value{GDBN} knows the size of the screen from the terminal
15172 driver software. For example, on Unix @value{GDBN} uses the termcap data base
15173 together with the value of the @code{TERM} environment variable and the
15174 @code{stty rows} and @code{stty cols} settings. If this is not correct,
15175 you can override it with the @code{set height} and @code{set
15182 @kindex show height
15183 @item set height @var{lpp}
15185 @itemx set width @var{cpl}
15187 These @code{set} commands specify a screen height of @var{lpp} lines and
15188 a screen width of @var{cpl} characters. The associated @code{show}
15189 commands display the current settings.
15191 If you specify a height of zero lines, @value{GDBN} does not pause during
15192 output no matter how long the output is. This is useful if output is to a
15193 file or to an editor buffer.
15195 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
15196 from wrapping its output.
15198 @item set pagination on
15199 @itemx set pagination off
15200 @kindex set pagination
15201 Turn the output pagination on or off; the default is on. Turning
15202 pagination off is the alternative to @code{set height 0}.
15204 @item show pagination
15205 @kindex show pagination
15206 Show the current pagination mode.
15211 @cindex number representation
15212 @cindex entering numbers
15214 You can always enter numbers in octal, decimal, or hexadecimal in
15215 @value{GDBN} by the usual conventions: octal numbers begin with
15216 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
15217 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
15218 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
15219 10; likewise, the default display for numbers---when no particular
15220 format is specified---is base 10. You can change the default base for
15221 both input and output with the commands described below.
15224 @kindex set input-radix
15225 @item set input-radix @var{base}
15226 Set the default base for numeric input. Supported choices
15227 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15228 specified either unambiguously or using the current input radix; for
15232 set input-radix 012
15233 set input-radix 10.
15234 set input-radix 0xa
15238 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
15239 leaves the input radix unchanged, no matter what it was, since
15240 @samp{10}, being without any leading or trailing signs of its base, is
15241 interpreted in the current radix. Thus, if the current radix is 16,
15242 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
15245 @kindex set output-radix
15246 @item set output-radix @var{base}
15247 Set the default base for numeric display. Supported choices
15248 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15249 specified either unambiguously or using the current input radix.
15251 @kindex show input-radix
15252 @item show input-radix
15253 Display the current default base for numeric input.
15255 @kindex show output-radix
15256 @item show output-radix
15257 Display the current default base for numeric display.
15259 @item set radix @r{[}@var{base}@r{]}
15263 These commands set and show the default base for both input and output
15264 of numbers. @code{set radix} sets the radix of input and output to
15265 the same base; without an argument, it resets the radix back to its
15266 default value of 10.
15271 @section Configuring the current ABI
15273 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
15274 application automatically. However, sometimes you need to override its
15275 conclusions. Use these commands to manage @value{GDBN}'s view of the
15282 One @value{GDBN} configuration can debug binaries for multiple operating
15283 system targets, either via remote debugging or native emulation.
15284 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
15285 but you can override its conclusion using the @code{set osabi} command.
15286 One example where this is useful is in debugging of binaries which use
15287 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
15288 not have the same identifying marks that the standard C library for your
15293 Show the OS ABI currently in use.
15296 With no argument, show the list of registered available OS ABI's.
15298 @item set osabi @var{abi}
15299 Set the current OS ABI to @var{abi}.
15302 @cindex float promotion
15304 Generally, the way that an argument of type @code{float} is passed to a
15305 function depends on whether the function is prototyped. For a prototyped
15306 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
15307 according to the architecture's convention for @code{float}. For unprototyped
15308 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
15309 @code{double} and then passed.
15311 Unfortunately, some forms of debug information do not reliably indicate whether
15312 a function is prototyped. If @value{GDBN} calls a function that is not marked
15313 as prototyped, it consults @kbd{set coerce-float-to-double}.
15316 @kindex set coerce-float-to-double
15317 @item set coerce-float-to-double
15318 @itemx set coerce-float-to-double on
15319 Arguments of type @code{float} will be promoted to @code{double} when passed
15320 to an unprototyped function. This is the default setting.
15322 @item set coerce-float-to-double off
15323 Arguments of type @code{float} will be passed directly to unprototyped
15326 @kindex show coerce-float-to-double
15327 @item show coerce-float-to-double
15328 Show the current setting of promoting @code{float} to @code{double}.
15332 @kindex show cp-abi
15333 @value{GDBN} needs to know the ABI used for your program's C@t{++}
15334 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
15335 used to build your application. @value{GDBN} only fully supports
15336 programs with a single C@t{++} ABI; if your program contains code using
15337 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
15338 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
15339 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
15340 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
15341 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
15342 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
15347 Show the C@t{++} ABI currently in use.
15350 With no argument, show the list of supported C@t{++} ABI's.
15352 @item set cp-abi @var{abi}
15353 @itemx set cp-abi auto
15354 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
15357 @node Messages/Warnings
15358 @section Optional warnings and messages
15360 @cindex verbose operation
15361 @cindex optional warnings
15362 By default, @value{GDBN} is silent about its inner workings. If you are
15363 running on a slow machine, you may want to use the @code{set verbose}
15364 command. This makes @value{GDBN} tell you when it does a lengthy
15365 internal operation, so you will not think it has crashed.
15367 Currently, the messages controlled by @code{set verbose} are those
15368 which announce that the symbol table for a source file is being read;
15369 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
15372 @kindex set verbose
15373 @item set verbose on
15374 Enables @value{GDBN} output of certain informational messages.
15376 @item set verbose off
15377 Disables @value{GDBN} output of certain informational messages.
15379 @kindex show verbose
15381 Displays whether @code{set verbose} is on or off.
15384 By default, if @value{GDBN} encounters bugs in the symbol table of an
15385 object file, it is silent; but if you are debugging a compiler, you may
15386 find this information useful (@pxref{Symbol Errors, ,Errors reading
15391 @kindex set complaints
15392 @item set complaints @var{limit}
15393 Permits @value{GDBN} to output @var{limit} complaints about each type of
15394 unusual symbols before becoming silent about the problem. Set
15395 @var{limit} to zero to suppress all complaints; set it to a large number
15396 to prevent complaints from being suppressed.
15398 @kindex show complaints
15399 @item show complaints
15400 Displays how many symbol complaints @value{GDBN} is permitted to produce.
15404 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
15405 lot of stupid questions to confirm certain commands. For example, if
15406 you try to run a program which is already running:
15410 The program being debugged has been started already.
15411 Start it from the beginning? (y or n)
15414 If you are willing to unflinchingly face the consequences of your own
15415 commands, you can disable this ``feature'':
15419 @kindex set confirm
15421 @cindex confirmation
15422 @cindex stupid questions
15423 @item set confirm off
15424 Disables confirmation requests.
15426 @item set confirm on
15427 Enables confirmation requests (the default).
15429 @kindex show confirm
15431 Displays state of confirmation requests.
15435 @node Debugging Output
15436 @section Optional messages about internal happenings
15437 @cindex optional debugging messages
15439 @value{GDBN} has commands that enable optional debugging messages from
15440 various @value{GDBN} subsystems; normally these commands are of
15441 interest to @value{GDBN} maintainers, or when reporting a bug. This
15442 section documents those commands.
15445 @kindex set exec-done-display
15446 @item set exec-done-display
15447 Turns on or off the notification of asynchronous commands'
15448 completion. When on, @value{GDBN} will print a message when an
15449 asynchronous command finishes its execution. The default is off.
15450 @kindex show exec-done-display
15451 @item show exec-done-display
15452 Displays the current setting of asynchronous command completion
15455 @cindex gdbarch debugging info
15456 @cindex architecture debugging info
15457 @item set debug arch
15458 Turns on or off display of gdbarch debugging info. The default is off
15460 @item show debug arch
15461 Displays the current state of displaying gdbarch debugging info.
15462 @item set debug aix-thread
15463 @cindex AIX threads
15464 Display debugging messages about inner workings of the AIX thread
15466 @item show debug aix-thread
15467 Show the current state of AIX thread debugging info display.
15468 @item set debug event
15469 @cindex event debugging info
15470 Turns on or off display of @value{GDBN} event debugging info. The
15472 @item show debug event
15473 Displays the current state of displaying @value{GDBN} event debugging
15475 @item set debug expression
15476 @cindex expression debugging info
15477 Turns on or off display of debugging info about @value{GDBN}
15478 expression parsing. The default is off.
15479 @item show debug expression
15480 Displays the current state of displaying debugging info about
15481 @value{GDBN} expression parsing.
15482 @item set debug frame
15483 @cindex frame debugging info
15484 Turns on or off display of @value{GDBN} frame debugging info. The
15486 @item show debug frame
15487 Displays the current state of displaying @value{GDBN} frame debugging
15489 @item set debug infrun
15490 @cindex inferior debugging info
15491 Turns on or off display of @value{GDBN} debugging info for running the inferior.
15492 The default is off. @file{infrun.c} contains GDB's runtime state machine used
15493 for implementing operations such as single-stepping the inferior.
15494 @item show debug infrun
15495 Displays the current state of @value{GDBN} inferior debugging.
15496 @item set debug lin-lwp
15497 @cindex @sc{gnu}/Linux LWP debug messages
15498 @cindex Linux lightweight processes
15499 Turns on or off debugging messages from the Linux LWP debug support.
15500 @item show debug lin-lwp
15501 Show the current state of Linux LWP debugging messages.
15502 @item set debug observer
15503 @cindex observer debugging info
15504 Turns on or off display of @value{GDBN} observer debugging. This
15505 includes info such as the notification of observable events.
15506 @item show debug observer
15507 Displays the current state of observer debugging.
15508 @item set debug overload
15509 @cindex C@t{++} overload debugging info
15510 Turns on or off display of @value{GDBN} C@t{++} overload debugging
15511 info. This includes info such as ranking of functions, etc. The default
15513 @item show debug overload
15514 Displays the current state of displaying @value{GDBN} C@t{++} overload
15516 @cindex packets, reporting on stdout
15517 @cindex serial connections, debugging
15518 @item set debug remote
15519 Turns on or off display of reports on all packets sent back and forth across
15520 the serial line to the remote machine. The info is printed on the
15521 @value{GDBN} standard output stream. The default is off.
15522 @item show debug remote
15523 Displays the state of display of remote packets.
15524 @item set debug serial
15525 Turns on or off display of @value{GDBN} serial debugging info. The
15527 @item show debug serial
15528 Displays the current state of displaying @value{GDBN} serial debugging
15530 @item set debug solib-frv
15531 @cindex FR-V shared-library debugging
15532 Turns on or off debugging messages for FR-V shared-library code.
15533 @item show debug solib-frv
15534 Display the current state of FR-V shared-library code debugging
15536 @item set debug target
15537 @cindex target debugging info
15538 Turns on or off display of @value{GDBN} target debugging info. This info
15539 includes what is going on at the target level of GDB, as it happens. The
15540 default is 0. Set it to 1 to track events, and to 2 to also track the
15541 value of large memory transfers. Changes to this flag do not take effect
15542 until the next time you connect to a target or use the @code{run} command.
15543 @item show debug target
15544 Displays the current state of displaying @value{GDBN} target debugging
15546 @item set debugvarobj
15547 @cindex variable object debugging info
15548 Turns on or off display of @value{GDBN} variable object debugging
15549 info. The default is off.
15550 @item show debugvarobj
15551 Displays the current state of displaying @value{GDBN} variable object
15556 @chapter Canned Sequences of Commands
15558 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
15559 command lists}), @value{GDBN} provides two ways to store sequences of
15560 commands for execution as a unit: user-defined commands and command
15564 * Define:: User-defined commands
15565 * Hooks:: User-defined command hooks
15566 * Command Files:: Command files
15567 * Output:: Commands for controlled output
15571 @section User-defined commands
15573 @cindex user-defined command
15574 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
15575 which you assign a new name as a command. This is done with the
15576 @code{define} command. User commands may accept up to 10 arguments
15577 separated by whitespace. Arguments are accessed within the user command
15578 via @var{$arg0@dots{}$arg9}. A trivial example:
15582 print $arg0 + $arg1 + $arg2
15586 To execute the command use:
15593 This defines the command @code{adder}, which prints the sum of
15594 its three arguments. Note the arguments are text substitutions, so they may
15595 reference variables, use complex expressions, or even perform inferior
15601 @item define @var{commandname}
15602 Define a command named @var{commandname}. If there is already a command
15603 by that name, you are asked to confirm that you want to redefine it.
15605 The definition of the command is made up of other @value{GDBN} command lines,
15606 which are given following the @code{define} command. The end of these
15607 commands is marked by a line containing @code{end}.
15613 Takes a single argument, which is an expression to evaluate.
15614 It is followed by a series of commands that are executed
15615 only if the expression is true (nonzero).
15616 There can then optionally be a line @code{else}, followed
15617 by a series of commands that are only executed if the expression
15618 was false. The end of the list is marked by a line containing @code{end}.
15622 The syntax is similar to @code{if}: the command takes a single argument,
15623 which is an expression to evaluate, and must be followed by the commands to
15624 execute, one per line, terminated by an @code{end}.
15625 The commands are executed repeatedly as long as the expression
15629 @item document @var{commandname}
15630 Document the user-defined command @var{commandname}, so that it can be
15631 accessed by @code{help}. The command @var{commandname} must already be
15632 defined. This command reads lines of documentation just as @code{define}
15633 reads the lines of the command definition, ending with @code{end}.
15634 After the @code{document} command is finished, @code{help} on command
15635 @var{commandname} displays the documentation you have written.
15637 You may use the @code{document} command again to change the
15638 documentation of a command. Redefining the command with @code{define}
15639 does not change the documentation.
15641 @kindex dont-repeat
15642 @cindex don't repeat command
15644 Used inside a user-defined command, this tells @value{GDBN} that this
15645 command should not be repeated when the user hits @key{RET}
15646 (@pxref{Command Syntax, repeat last command}).
15648 @kindex help user-defined
15649 @item help user-defined
15650 List all user-defined commands, with the first line of the documentation
15655 @itemx show user @var{commandname}
15656 Display the @value{GDBN} commands used to define @var{commandname} (but
15657 not its documentation). If no @var{commandname} is given, display the
15658 definitions for all user-defined commands.
15660 @cindex infinite recusrion in user-defined commands
15661 @kindex show max-user-call-depth
15662 @kindex set max-user-call-depth
15663 @item show max-user-call-depth
15664 @itemx set max-user-call-depth
15665 The value of @code{max-user-call-depth} controls how many recursion
15666 levels are allowed in user-defined commands before GDB suspects an
15667 infinite recursion and aborts the command.
15671 When user-defined commands are executed, the
15672 commands of the definition are not printed. An error in any command
15673 stops execution of the user-defined command.
15675 If used interactively, commands that would ask for confirmation proceed
15676 without asking when used inside a user-defined command. Many @value{GDBN}
15677 commands that normally print messages to say what they are doing omit the
15678 messages when used in a user-defined command.
15681 @section User-defined command hooks
15682 @cindex command hooks
15683 @cindex hooks, for commands
15684 @cindex hooks, pre-command
15687 You may define @dfn{hooks}, which are a special kind of user-defined
15688 command. Whenever you run the command @samp{foo}, if the user-defined
15689 command @samp{hook-foo} exists, it is executed (with no arguments)
15690 before that command.
15692 @cindex hooks, post-command
15694 A hook may also be defined which is run after the command you executed.
15695 Whenever you run the command @samp{foo}, if the user-defined command
15696 @samp{hookpost-foo} exists, it is executed (with no arguments) after
15697 that command. Post-execution hooks may exist simultaneously with
15698 pre-execution hooks, for the same command.
15700 It is valid for a hook to call the command which it hooks. If this
15701 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
15703 @c It would be nice if hookpost could be passed a parameter indicating
15704 @c if the command it hooks executed properly or not. FIXME!
15706 @kindex stop@r{, a pseudo-command}
15707 In addition, a pseudo-command, @samp{stop} exists. Defining
15708 (@samp{hook-stop}) makes the associated commands execute every time
15709 execution stops in your program: before breakpoint commands are run,
15710 displays are printed, or the stack frame is printed.
15712 For example, to ignore @code{SIGALRM} signals while
15713 single-stepping, but treat them normally during normal execution,
15718 handle SIGALRM nopass
15722 handle SIGALRM pass
15725 define hook-continue
15726 handle SIGLARM pass
15730 As a further example, to hook at the begining and end of the @code{echo}
15731 command, and to add extra text to the beginning and end of the message,
15739 define hookpost-echo
15743 (@value{GDBP}) echo Hello World
15744 <<<---Hello World--->>>
15749 You can define a hook for any single-word command in @value{GDBN}, but
15750 not for command aliases; you should define a hook for the basic command
15751 name, e.g. @code{backtrace} rather than @code{bt}.
15752 @c FIXME! So how does Joe User discover whether a command is an alias
15754 If an error occurs during the execution of your hook, execution of
15755 @value{GDBN} commands stops and @value{GDBN} issues a prompt
15756 (before the command that you actually typed had a chance to run).
15758 If you try to define a hook which does not match any known command, you
15759 get a warning from the @code{define} command.
15761 @node Command Files
15762 @section Command files
15764 @cindex command files
15765 A command file for @value{GDBN} is a text file made of lines that are
15766 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
15767 also be included. An empty line in a command file does nothing; it
15768 does not mean to repeat the last command, as it would from the
15771 You can request the execution of a command file with the @code{source}
15776 @item source @var{filename}
15777 Execute the command file @var{filename}.
15780 The lines in a command file are executed sequentially. They are not
15781 printed as they are executed. An error in any command terminates
15782 execution of the command file and control is returned to the console.
15784 Commands that would ask for confirmation if used interactively proceed
15785 without asking when used in a command file. Many @value{GDBN} commands that
15786 normally print messages to say what they are doing omit the messages
15787 when called from command files.
15789 @value{GDBN} also accepts command input from standard input. In this
15790 mode, normal output goes to standard output and error output goes to
15791 standard error. Errors in a command file supplied on standard input do
15792 not terminate execution of the command file---execution continues with
15796 gdb < cmds > log 2>&1
15799 (The syntax above will vary depending on the shell used.) This example
15800 will execute commands from the file @file{cmds}. All output and errors
15801 would be directed to @file{log}.
15804 @section Commands for controlled output
15806 During the execution of a command file or a user-defined command, normal
15807 @value{GDBN} output is suppressed; the only output that appears is what is
15808 explicitly printed by the commands in the definition. This section
15809 describes three commands useful for generating exactly the output you
15814 @item echo @var{text}
15815 @c I do not consider backslash-space a standard C escape sequence
15816 @c because it is not in ANSI.
15817 Print @var{text}. Nonprinting characters can be included in
15818 @var{text} using C escape sequences, such as @samp{\n} to print a
15819 newline. @strong{No newline is printed unless you specify one.}
15820 In addition to the standard C escape sequences, a backslash followed
15821 by a space stands for a space. This is useful for displaying a
15822 string with spaces at the beginning or the end, since leading and
15823 trailing spaces are otherwise trimmed from all arguments.
15824 To print @samp{@w{ }and foo =@w{ }}, use the command
15825 @samp{echo \@w{ }and foo = \@w{ }}.
15827 A backslash at the end of @var{text} can be used, as in C, to continue
15828 the command onto subsequent lines. For example,
15831 echo This is some text\n\
15832 which is continued\n\
15833 onto several lines.\n
15836 produces the same output as
15839 echo This is some text\n
15840 echo which is continued\n
15841 echo onto several lines.\n
15845 @item output @var{expression}
15846 Print the value of @var{expression} and nothing but that value: no
15847 newlines, no @samp{$@var{nn} = }. The value is not entered in the
15848 value history either. @xref{Expressions, ,Expressions}, for more information
15851 @item output/@var{fmt} @var{expression}
15852 Print the value of @var{expression} in format @var{fmt}. You can use
15853 the same formats as for @code{print}. @xref{Output Formats,,Output
15854 formats}, for more information.
15857 @item printf @var{string}, @var{expressions}@dots{}
15858 Print the values of the @var{expressions} under the control of
15859 @var{string}. The @var{expressions} are separated by commas and may be
15860 either numbers or pointers. Their values are printed as specified by
15861 @var{string}, exactly as if your program were to execute the C
15863 @c FIXME: the above implies that at least all ANSI C formats are
15864 @c supported, but it isn't true: %E and %G don't work (or so it seems).
15865 @c Either this is a bug, or the manual should document what formats are
15869 printf (@var{string}, @var{expressions}@dots{});
15872 For example, you can print two values in hex like this:
15875 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
15878 The only backslash-escape sequences that you can use in the format
15879 string are the simple ones that consist of backslash followed by a
15884 @chapter Command Interpreters
15885 @cindex command interpreters
15887 @value{GDBN} supports multiple command interpreters, and some command
15888 infrastructure to allow users or user interface writers to switch
15889 between interpreters or run commands in other interpreters.
15891 @value{GDBN} currently supports two command interpreters, the console
15892 interpreter (sometimes called the command-line interpreter or @sc{cli})
15893 and the machine interface interpreter (or @sc{gdb/mi}). This manual
15894 describes both of these interfaces in great detail.
15896 By default, @value{GDBN} will start with the console interpreter.
15897 However, the user may choose to start @value{GDBN} with another
15898 interpreter by specifying the @option{-i} or @option{--interpreter}
15899 startup options. Defined interpreters include:
15903 @cindex console interpreter
15904 The traditional console or command-line interpreter. This is the most often
15905 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
15906 @value{GDBN} will use this interpreter.
15909 @cindex mi interpreter
15910 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
15911 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
15912 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
15916 @cindex mi2 interpreter
15917 The current @sc{gdb/mi} interface.
15920 @cindex mi1 interpreter
15921 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
15925 @cindex invoke another interpreter
15926 The interpreter being used by @value{GDBN} may not be dynamically
15927 switched at runtime. Although possible, this could lead to a very
15928 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
15929 enters the command "interpreter-set console" in a console view,
15930 @value{GDBN} would switch to using the console interpreter, rendering
15931 the IDE inoperable!
15933 @kindex interpreter-exec
15934 Although you may only choose a single interpreter at startup, you may execute
15935 commands in any interpreter from the current interpreter using the appropriate
15936 command. If you are running the console interpreter, simply use the
15937 @code{interpreter-exec} command:
15940 interpreter-exec mi "-data-list-register-names"
15943 @sc{gdb/mi} has a similar command, although it is only available in versions of
15944 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
15947 @chapter @value{GDBN} Text User Interface
15949 @cindex Text User Interface
15952 * TUI Overview:: TUI overview
15953 * TUI Keys:: TUI key bindings
15954 * TUI Single Key Mode:: TUI single key mode
15955 * TUI Commands:: TUI specific commands
15956 * TUI Configuration:: TUI configuration variables
15959 The @value{GDBN} Text User Interface, TUI in short, is a terminal
15960 interface which uses the @code{curses} library to show the source
15961 file, the assembly output, the program registers and @value{GDBN}
15962 commands in separate text windows.
15964 The TUI is enabled by invoking @value{GDBN} using either
15966 @samp{gdbtui} or @samp{gdb -tui}.
15969 @section TUI overview
15971 The TUI has two display modes that can be switched while
15976 A curses (or TUI) mode in which it displays several text
15977 windows on the terminal.
15980 A standard mode which corresponds to the @value{GDBN} configured without
15984 In the TUI mode, @value{GDBN} can display several text window
15989 This window is the @value{GDBN} command window with the @value{GDBN}
15990 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
15991 managed using readline but through the TUI. The @emph{command}
15992 window is always visible.
15995 The source window shows the source file of the program. The current
15996 line as well as active breakpoints are displayed in this window.
15999 The assembly window shows the disassembly output of the program.
16002 This window shows the processor registers. It detects when
16003 a register is changed and when this is the case, registers that have
16004 changed are highlighted.
16008 The source and assembly windows show the current program position
16009 by highlighting the current line and marking them with the @samp{>} marker.
16010 Breakpoints are also indicated with two markers. A first one
16011 indicates the breakpoint type:
16015 Breakpoint which was hit at least once.
16018 Breakpoint which was never hit.
16021 Hardware breakpoint which was hit at least once.
16024 Hardware breakpoint which was never hit.
16028 The second marker indicates whether the breakpoint is enabled or not:
16032 Breakpoint is enabled.
16035 Breakpoint is disabled.
16039 The source, assembly and register windows are attached to the thread
16040 and the frame position. They are updated when the current thread
16041 changes, when the frame changes or when the program counter changes.
16042 These three windows are arranged by the TUI according to several
16043 layouts. The layout defines which of these three windows are visible.
16044 The following layouts are available:
16054 source and assembly
16057 source and registers
16060 assembly and registers
16064 On top of the command window a status line gives various information
16065 concerning the current process begin debugged. The status line is
16066 updated when the information it shows changes. The following fields
16071 Indicates the current gdb target
16072 (@pxref{Targets, ,Specifying a Debugging Target}).
16075 Gives information about the current process or thread number.
16076 When no process is being debugged, this field is set to @code{No process}.
16079 Gives the current function name for the selected frame.
16080 The name is demangled if demangling is turned on (@pxref{Print Settings}).
16081 When there is no symbol corresponding to the current program counter
16082 the string @code{??} is displayed.
16085 Indicates the current line number for the selected frame.
16086 When the current line number is not known the string @code{??} is displayed.
16089 Indicates the current program counter address.
16094 @section TUI Key Bindings
16095 @cindex TUI key bindings
16097 The TUI installs several key bindings in the readline keymaps
16098 (@pxref{Command Line Editing}).
16099 They allow to leave or enter in the TUI mode or they operate
16100 directly on the TUI layout and windows. The TUI also provides
16101 a @emph{SingleKey} keymap which binds several keys directly to
16102 @value{GDBN} commands. The following key bindings
16103 are installed for both TUI mode and the @value{GDBN} standard mode.
16112 Enter or leave the TUI mode. When the TUI mode is left,
16113 the curses window management is left and @value{GDBN} operates using
16114 its standard mode writing on the terminal directly. When the TUI
16115 mode is entered, the control is given back to the curses windows.
16116 The screen is then refreshed.
16120 Use a TUI layout with only one window. The layout will
16121 either be @samp{source} or @samp{assembly}. When the TUI mode
16122 is not active, it will switch to the TUI mode.
16124 Think of this key binding as the Emacs @kbd{C-x 1} binding.
16128 Use a TUI layout with at least two windows. When the current
16129 layout shows already two windows, a next layout with two windows is used.
16130 When a new layout is chosen, one window will always be common to the
16131 previous layout and the new one.
16133 Think of it as the Emacs @kbd{C-x 2} binding.
16137 Change the active window. The TUI associates several key bindings
16138 (like scrolling and arrow keys) to the active window. This command
16139 gives the focus to the next TUI window.
16141 Think of it as the Emacs @kbd{C-x o} binding.
16145 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
16146 (@pxref{TUI Single Key Mode}).
16150 The following key bindings are handled only by the TUI mode:
16155 Scroll the active window one page up.
16159 Scroll the active window one page down.
16163 Scroll the active window one line up.
16167 Scroll the active window one line down.
16171 Scroll the active window one column left.
16175 Scroll the active window one column right.
16179 Refresh the screen.
16183 In the TUI mode, the arrow keys are used by the active window
16184 for scrolling. This means they are available for readline when the
16185 active window is the command window. When the command window
16186 does not have the focus, it is necessary to use other readline
16187 key bindings such as @key{C-p}, @key{C-n}, @key{C-b} and @key{C-f}.
16189 @node TUI Single Key Mode
16190 @section TUI Single Key Mode
16191 @cindex TUI single key mode
16193 The TUI provides a @emph{SingleKey} mode in which it installs a particular
16194 key binding in the readline keymaps to connect single keys to
16198 @kindex c @r{(SingleKey TUI key)}
16202 @kindex d @r{(SingleKey TUI key)}
16206 @kindex f @r{(SingleKey TUI key)}
16210 @kindex n @r{(SingleKey TUI key)}
16214 @kindex q @r{(SingleKey TUI key)}
16216 exit the @emph{SingleKey} mode.
16218 @kindex r @r{(SingleKey TUI key)}
16222 @kindex s @r{(SingleKey TUI key)}
16226 @kindex u @r{(SingleKey TUI key)}
16230 @kindex v @r{(SingleKey TUI key)}
16234 @kindex w @r{(SingleKey TUI key)}
16240 Other keys temporarily switch to the @value{GDBN} command prompt.
16241 The key that was pressed is inserted in the editing buffer so that
16242 it is possible to type most @value{GDBN} commands without interaction
16243 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
16244 @emph{SingleKey} mode is restored. The only way to permanently leave
16245 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
16249 @section TUI specific commands
16250 @cindex TUI commands
16252 The TUI has specific commands to control the text windows.
16253 These commands are always available, that is they do not depend on
16254 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
16255 is in the standard mode, using these commands will automatically switch
16261 List and give the size of all displayed windows.
16265 Display the next layout.
16268 Display the previous layout.
16271 Display the source window only.
16274 Display the assembly window only.
16277 Display the source and assembly window.
16280 Display the register window together with the source or assembly window.
16282 @item focus next | prev | src | asm | regs | split
16284 Set the focus to the named window.
16285 This command allows to change the active window so that scrolling keys
16286 can be affected to another window.
16290 Refresh the screen. This is similar to using @key{C-L} key.
16292 @item tui reg float
16294 Show the floating point registers in the register window.
16296 @item tui reg general
16297 Show the general registers in the register window.
16300 Show the next register group. The list of register groups as well as
16301 their order is target specific. The predefined register groups are the
16302 following: @code{general}, @code{float}, @code{system}, @code{vector},
16303 @code{all}, @code{save}, @code{restore}.
16305 @item tui reg system
16306 Show the system registers in the register window.
16310 Update the source window and the current execution point.
16312 @item winheight @var{name} +@var{count}
16313 @itemx winheight @var{name} -@var{count}
16315 Change the height of the window @var{name} by @var{count}
16316 lines. Positive counts increase the height, while negative counts
16320 @kindex tabset @var{nchars}
16321 Set the width of tab stops to be @var{nchars} characters.
16325 @node TUI Configuration
16326 @section TUI configuration variables
16327 @cindex TUI configuration variables
16329 The TUI has several configuration variables that control the
16330 appearance of windows on the terminal.
16333 @item set tui border-kind @var{kind}
16334 @kindex set tui border-kind
16335 Select the border appearance for the source, assembly and register windows.
16336 The possible values are the following:
16339 Use a space character to draw the border.
16342 Use ascii characters + - and | to draw the border.
16345 Use the Alternate Character Set to draw the border. The border is
16346 drawn using character line graphics if the terminal supports them.
16350 @item set tui active-border-mode @var{mode}
16351 @kindex set tui active-border-mode
16352 Select the attributes to display the border of the active window.
16353 The possible values are @code{normal}, @code{standout}, @code{reverse},
16354 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
16356 @item set tui border-mode @var{mode}
16357 @kindex set tui border-mode
16358 Select the attributes to display the border of other windows.
16359 The @var{mode} can be one of the following:
16362 Use normal attributes to display the border.
16368 Use reverse video mode.
16371 Use half bright mode.
16373 @item half-standout
16374 Use half bright and standout mode.
16377 Use extra bright or bold mode.
16379 @item bold-standout
16380 Use extra bright or bold and standout mode.
16387 @chapter Using @value{GDBN} under @sc{gnu} Emacs
16390 @cindex @sc{gnu} Emacs
16391 A special interface allows you to use @sc{gnu} Emacs to view (and
16392 edit) the source files for the program you are debugging with
16395 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
16396 executable file you want to debug as an argument. This command starts
16397 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
16398 created Emacs buffer.
16399 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
16401 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
16406 All ``terminal'' input and output goes through the Emacs buffer.
16409 This applies both to @value{GDBN} commands and their output, and to the input
16410 and output done by the program you are debugging.
16412 This is useful because it means that you can copy the text of previous
16413 commands and input them again; you can even use parts of the output
16416 All the facilities of Emacs' Shell mode are available for interacting
16417 with your program. In particular, you can send signals the usual
16418 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
16423 @value{GDBN} displays source code through Emacs.
16426 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
16427 source file for that frame and puts an arrow (@samp{=>}) at the
16428 left margin of the current line. Emacs uses a separate buffer for
16429 source display, and splits the screen to show both your @value{GDBN} session
16432 Explicit @value{GDBN} @code{list} or search commands still produce output as
16433 usual, but you probably have no reason to use them from Emacs.
16435 If you specify an absolute file name when prompted for the @kbd{M-x
16436 gdb} argument, then Emacs sets your current working directory to where
16437 your program resides. If you only specify the file name, then Emacs
16438 sets your current working directory to to the directory associated
16439 with the previous buffer. In this case, @value{GDBN} may find your
16440 program by searching your environment's @code{PATH} variable, but on
16441 some operating systems it might not find the source. So, although the
16442 @value{GDBN} input and output session proceeds normally, the auxiliary
16443 buffer does not display the current source and line of execution.
16445 The initial working directory of @value{GDBN} is printed on the top
16446 line of the @value{GDBN} I/O buffer and this serves as a default for
16447 the commands that specify files for @value{GDBN} to operate
16448 on. @xref{Files, ,Commands to specify files}.
16450 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
16451 need to call @value{GDBN} by a different name (for example, if you
16452 keep several configurations around, with different names) you can
16453 customize the Emacs variable @code{gud-gdb-command-name} to run the
16456 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
16457 addition to the standard Shell mode commands:
16461 Describe the features of Emacs' @value{GDBN} Mode.
16464 Execute to another source line, like the @value{GDBN} @code{step} command; also
16465 update the display window to show the current file and location.
16468 Execute to next source line in this function, skipping all function
16469 calls, like the @value{GDBN} @code{next} command. Then update the display window
16470 to show the current file and location.
16473 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
16474 display window accordingly.
16477 Execute until exit from the selected stack frame, like the @value{GDBN}
16478 @code{finish} command.
16481 Continue execution of your program, like the @value{GDBN} @code{continue}
16485 Go up the number of frames indicated by the numeric argument
16486 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
16487 like the @value{GDBN} @code{up} command.
16490 Go down the number of frames indicated by the numeric argument, like the
16491 @value{GDBN} @code{down} command.
16494 In any source file, the Emacs command @kbd{C-x SPC} (@code{gud-break})
16495 tells @value{GDBN} to set a breakpoint on the source line point is on.
16497 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
16498 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
16499 point to any frame in the stack and type @key{RET} to make it become the
16500 current frame and display the associated source in the source buffer.
16501 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
16504 If you accidentally delete the source-display buffer, an easy way to get
16505 it back is to type the command @code{f} in the @value{GDBN} buffer, to
16506 request a frame display; when you run under Emacs, this recreates
16507 the source buffer if necessary to show you the context of the current
16510 The source files displayed in Emacs are in ordinary Emacs buffers
16511 which are visiting the source files in the usual way. You can edit
16512 the files with these buffers if you wish; but keep in mind that @value{GDBN}
16513 communicates with Emacs in terms of line numbers. If you add or
16514 delete lines from the text, the line numbers that @value{GDBN} knows cease
16515 to correspond properly with the code.
16517 The description given here is for GNU Emacs version 21.3 and a more
16518 detailed description of its interaction with @value{GDBN} is given in
16519 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
16521 @c The following dropped because Epoch is nonstandard. Reactivate
16522 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
16524 @kindex Emacs Epoch environment
16528 Version 18 of @sc{gnu} Emacs has a built-in window system
16529 called the @code{epoch}
16530 environment. Users of this environment can use a new command,
16531 @code{inspect} which performs identically to @code{print} except that
16532 each value is printed in its own window.
16537 @chapter The @sc{gdb/mi} Interface
16539 @unnumberedsec Function and Purpose
16541 @cindex @sc{gdb/mi}, its purpose
16542 @sc{gdb/mi} is a line based machine oriented text interface to
16543 @value{GDBN} and is activated by specifying using the
16544 @option{--interpreter} command line option (@pxref{Mode Options}). It
16545 is specifically intended to support the development of systems which
16546 use the debugger as just one small component of a larger system.
16548 This chapter is a specification of the @sc{gdb/mi} interface. It is written
16549 in the form of a reference manual.
16551 Note that @sc{gdb/mi} is still under construction, so some of the
16552 features described below are incomplete and subject to change.
16554 @unnumberedsec Notation and Terminology
16556 @cindex notational conventions, for @sc{gdb/mi}
16557 This chapter uses the following notation:
16561 @code{|} separates two alternatives.
16564 @code{[ @var{something} ]} indicates that @var{something} is optional:
16565 it may or may not be given.
16568 @code{( @var{group} )*} means that @var{group} inside the parentheses
16569 may repeat zero or more times.
16572 @code{( @var{group} )+} means that @var{group} inside the parentheses
16573 may repeat one or more times.
16576 @code{"@var{string}"} means a literal @var{string}.
16580 @heading Dependencies
16583 @heading Acknowledgments
16585 In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
16589 * GDB/MI Command Syntax::
16590 * GDB/MI Compatibility with CLI::
16591 * GDB/MI Output Records::
16592 * GDB/MI Command Description Format::
16593 * GDB/MI Breakpoint Table Commands::
16594 * GDB/MI Data Manipulation::
16595 * GDB/MI Program Control::
16596 * GDB/MI Miscellaneous Commands::
16598 * GDB/MI Kod Commands::
16599 * GDB/MI Memory Overlay Commands::
16600 * GDB/MI Signal Handling Commands::
16602 * GDB/MI Stack Manipulation::
16603 * GDB/MI Symbol Query::
16604 * GDB/MI Target Manipulation::
16605 * GDB/MI Thread Commands::
16606 * GDB/MI Tracepoint Commands::
16607 * GDB/MI Variable Objects::
16610 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16611 @node GDB/MI Command Syntax
16612 @section @sc{gdb/mi} Command Syntax
16615 * GDB/MI Input Syntax::
16616 * GDB/MI Output Syntax::
16617 * GDB/MI Simple Examples::
16620 @node GDB/MI Input Syntax
16621 @subsection @sc{gdb/mi} Input Syntax
16623 @cindex input syntax for @sc{gdb/mi}
16624 @cindex @sc{gdb/mi}, input syntax
16626 @item @var{command} @expansion{}
16627 @code{@var{cli-command} | @var{mi-command}}
16629 @item @var{cli-command} @expansion{}
16630 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
16631 @var{cli-command} is any existing @value{GDBN} CLI command.
16633 @item @var{mi-command} @expansion{}
16634 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
16635 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
16637 @item @var{token} @expansion{}
16638 "any sequence of digits"
16640 @item @var{option} @expansion{}
16641 @code{"-" @var{parameter} [ " " @var{parameter} ]}
16643 @item @var{parameter} @expansion{}
16644 @code{@var{non-blank-sequence} | @var{c-string}}
16646 @item @var{operation} @expansion{}
16647 @emph{any of the operations described in this chapter}
16649 @item @var{non-blank-sequence} @expansion{}
16650 @emph{anything, provided it doesn't contain special characters such as
16651 "-", @var{nl}, """ and of course " "}
16653 @item @var{c-string} @expansion{}
16654 @code{""" @var{seven-bit-iso-c-string-content} """}
16656 @item @var{nl} @expansion{}
16665 The CLI commands are still handled by the @sc{mi} interpreter; their
16666 output is described below.
16669 The @code{@var{token}}, when present, is passed back when the command
16673 Some @sc{mi} commands accept optional arguments as part of the parameter
16674 list. Each option is identified by a leading @samp{-} (dash) and may be
16675 followed by an optional argument parameter. Options occur first in the
16676 parameter list and can be delimited from normal parameters using
16677 @samp{--} (this is useful when some parameters begin with a dash).
16684 We want easy access to the existing CLI syntax (for debugging).
16687 We want it to be easy to spot a @sc{mi} operation.
16690 @node GDB/MI Output Syntax
16691 @subsection @sc{gdb/mi} Output Syntax
16693 @cindex output syntax of @sc{gdb/mi}
16694 @cindex @sc{gdb/mi}, output syntax
16695 The output from @sc{gdb/mi} consists of zero or more out-of-band records
16696 followed, optionally, by a single result record. This result record
16697 is for the most recent command. The sequence of output records is
16698 terminated by @samp{(@value{GDBP})}.
16700 If an input command was prefixed with a @code{@var{token}} then the
16701 corresponding output for that command will also be prefixed by that same
16705 @item @var{output} @expansion{}
16706 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(@value{GDBP})" @var{nl}}
16708 @item @var{result-record} @expansion{}
16709 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
16711 @item @var{out-of-band-record} @expansion{}
16712 @code{@var{async-record} | @var{stream-record}}
16714 @item @var{async-record} @expansion{}
16715 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
16717 @item @var{exec-async-output} @expansion{}
16718 @code{[ @var{token} ] "*" @var{async-output}}
16720 @item @var{status-async-output} @expansion{}
16721 @code{[ @var{token} ] "+" @var{async-output}}
16723 @item @var{notify-async-output} @expansion{}
16724 @code{[ @var{token} ] "=" @var{async-output}}
16726 @item @var{async-output} @expansion{}
16727 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
16729 @item @var{result-class} @expansion{}
16730 @code{"done" | "running" | "connected" | "error" | "exit"}
16732 @item @var{async-class} @expansion{}
16733 @code{"stopped" | @var{others}} (where @var{others} will be added
16734 depending on the needs---this is still in development).
16736 @item @var{result} @expansion{}
16737 @code{ @var{variable} "=" @var{value}}
16739 @item @var{variable} @expansion{}
16740 @code{ @var{string} }
16742 @item @var{value} @expansion{}
16743 @code{ @var{const} | @var{tuple} | @var{list} }
16745 @item @var{const} @expansion{}
16746 @code{@var{c-string}}
16748 @item @var{tuple} @expansion{}
16749 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
16751 @item @var{list} @expansion{}
16752 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
16753 @var{result} ( "," @var{result} )* "]" }
16755 @item @var{stream-record} @expansion{}
16756 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
16758 @item @var{console-stream-output} @expansion{}
16759 @code{"~" @var{c-string}}
16761 @item @var{target-stream-output} @expansion{}
16762 @code{"@@" @var{c-string}}
16764 @item @var{log-stream-output} @expansion{}
16765 @code{"&" @var{c-string}}
16767 @item @var{nl} @expansion{}
16770 @item @var{token} @expansion{}
16771 @emph{any sequence of digits}.
16779 All output sequences end in a single line containing a period.
16782 The @code{@var{token}} is from the corresponding request. If an execution
16783 command is interrupted by the @samp{-exec-interrupt} command, the
16784 @var{token} associated with the @samp{*stopped} message is the one of the
16785 original execution command, not the one of the interrupt command.
16788 @cindex status output in @sc{gdb/mi}
16789 @var{status-async-output} contains on-going status information about the
16790 progress of a slow operation. It can be discarded. All status output is
16791 prefixed by @samp{+}.
16794 @cindex async output in @sc{gdb/mi}
16795 @var{exec-async-output} contains asynchronous state change on the target
16796 (stopped, started, disappeared). All async output is prefixed by
16800 @cindex notify output in @sc{gdb/mi}
16801 @var{notify-async-output} contains supplementary information that the
16802 client should handle (e.g., a new breakpoint information). All notify
16803 output is prefixed by @samp{=}.
16806 @cindex console output in @sc{gdb/mi}
16807 @var{console-stream-output} is output that should be displayed as is in the
16808 console. It is the textual response to a CLI command. All the console
16809 output is prefixed by @samp{~}.
16812 @cindex target output in @sc{gdb/mi}
16813 @var{target-stream-output} is the output produced by the target program.
16814 All the target output is prefixed by @samp{@@}.
16817 @cindex log output in @sc{gdb/mi}
16818 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
16819 instance messages that should be displayed as part of an error log. All
16820 the log output is prefixed by @samp{&}.
16823 @cindex list output in @sc{gdb/mi}
16824 New @sc{gdb/mi} commands should only output @var{lists} containing
16830 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
16831 details about the various output records.
16833 @node GDB/MI Simple Examples
16834 @subsection Simple Examples of @sc{gdb/mi} Interaction
16835 @cindex @sc{gdb/mi}, simple examples
16837 This subsection presents several simple examples of interaction using
16838 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
16839 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
16840 the output received from @sc{gdb/mi}.
16842 @subsubheading Target Stop
16843 @c Ummm... There is no "-stop" command. This assumes async, no?
16844 Here's an example of stopping the inferior process:
16855 <- *stop,reason="stop",address="0x123",source="a.c:123"
16859 @subsubheading Simple CLI Command
16861 Here's an example of a simple CLI command being passed through
16862 @sc{gdb/mi} and on to the CLI.
16872 @subsubheading Command With Side Effects
16875 -> -symbol-file xyz.exe
16876 <- *breakpoint,nr="3",address="0x123",source="a.c:123"
16880 @subsubheading A Bad Command
16882 Here's what happens if you pass a non-existent command:
16886 <- ^error,msg="Undefined MI command: rubbish"
16890 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16891 @node GDB/MI Compatibility with CLI
16892 @section @sc{gdb/mi} Compatibility with CLI
16894 @cindex compatibility, @sc{gdb/mi} and CLI
16895 @cindex @sc{gdb/mi}, compatibility with CLI
16896 To help users familiar with @value{GDBN}'s existing CLI interface, @sc{gdb/mi}
16897 accepts existing CLI commands. As specified by the syntax, such
16898 commands can be directly entered into the @sc{gdb/mi} interface and @value{GDBN} will
16901 This mechanism is provided as an aid to developers of @sc{gdb/mi}
16902 clients and not as a reliable interface into the CLI. Since the command
16903 is being interpreteted in an environment that assumes @sc{gdb/mi}
16904 behaviour, the exact output of such commands is likely to end up being
16905 an un-supported hybrid of @sc{gdb/mi} and CLI output.
16907 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16908 @node GDB/MI Output Records
16909 @section @sc{gdb/mi} Output Records
16912 * GDB/MI Result Records::
16913 * GDB/MI Stream Records::
16914 * GDB/MI Out-of-band Records::
16917 @node GDB/MI Result Records
16918 @subsection @sc{gdb/mi} Result Records
16920 @cindex result records in @sc{gdb/mi}
16921 @cindex @sc{gdb/mi}, result records
16922 In addition to a number of out-of-band notifications, the response to a
16923 @sc{gdb/mi} command includes one of the following result indications:
16927 @item "^done" [ "," @var{results} ]
16928 The synchronous operation was successful, @code{@var{results}} are the return
16933 @c Is this one correct? Should it be an out-of-band notification?
16934 The asynchronous operation was successfully started. The target is
16937 @item "^error" "," @var{c-string}
16939 The operation failed. The @code{@var{c-string}} contains the corresponding
16943 @node GDB/MI Stream Records
16944 @subsection @sc{gdb/mi} Stream Records
16946 @cindex @sc{gdb/mi}, stream records
16947 @cindex stream records in @sc{gdb/mi}
16948 @value{GDBN} internally maintains a number of output streams: the console, the
16949 target, and the log. The output intended for each of these streams is
16950 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
16952 Each stream record begins with a unique @dfn{prefix character} which
16953 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
16954 Syntax}). In addition to the prefix, each stream record contains a
16955 @code{@var{string-output}}. This is either raw text (with an implicit new
16956 line) or a quoted C string (which does not contain an implicit newline).
16959 @item "~" @var{string-output}
16960 The console output stream contains text that should be displayed in the
16961 CLI console window. It contains the textual responses to CLI commands.
16963 @item "@@" @var{string-output}
16964 The target output stream contains any textual output from the running
16967 @item "&" @var{string-output}
16968 The log stream contains debugging messages being produced by @value{GDBN}'s
16972 @node GDB/MI Out-of-band Records
16973 @subsection @sc{gdb/mi} Out-of-band Records
16975 @cindex out-of-band records in @sc{gdb/mi}
16976 @cindex @sc{gdb/mi}, out-of-band records
16977 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
16978 additional changes that have occurred. Those changes can either be a
16979 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
16980 target activity (e.g., target stopped).
16982 The following is a preliminary list of possible out-of-band records.
16983 In particular, the @var{exec-async-output} records.
16986 @item *stopped,reason="@var{reason}"
16989 @var{reason} can be one of the following:
16992 @item breakpoint-hit
16993 A breakpoint was reached.
16994 @item watchpoint-trigger
16995 A watchpoint was triggered.
16996 @item read-watchpoint-trigger
16997 A read watchpoint was triggered.
16998 @item access-watchpoint-trigger
16999 An access watchpoint was triggered.
17000 @item function-finished
17001 An -exec-finish or similar CLI command was accomplished.
17002 @item location-reached
17003 An -exec-until or similar CLI command was accomplished.
17004 @item watchpoint-scope
17005 A watchpoint has gone out of scope.
17006 @item end-stepping-range
17007 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
17008 similar CLI command was accomplished.
17009 @item exited-signalled
17010 The inferior exited because of a signal.
17012 The inferior exited.
17013 @item exited-normally
17014 The inferior exited normally.
17015 @item signal-received
17016 A signal was received by the inferior.
17020 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17021 @node GDB/MI Command Description Format
17022 @section @sc{gdb/mi} Command Description Format
17024 The remaining sections describe blocks of commands. Each block of
17025 commands is laid out in a fashion similar to this section.
17027 Note the the line breaks shown in the examples are here only for
17028 readability. They don't appear in the real output.
17029 Also note that the commands with a non-available example (N.A.@:) are
17030 not yet implemented.
17032 @subheading Motivation
17034 The motivation for this collection of commands.
17036 @subheading Introduction
17038 A brief introduction to this collection of commands as a whole.
17040 @subheading Commands
17042 For each command in the block, the following is described:
17044 @subsubheading Synopsis
17047 -command @var{args}@dots{}
17050 @subsubheading @value{GDBN} Command
17052 The corresponding @value{GDBN} CLI command.
17054 @subsubheading Result
17056 @subsubheading Out-of-band
17058 @subsubheading Notes
17060 @subsubheading Example
17063 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17064 @node GDB/MI Breakpoint Table Commands
17065 @section @sc{gdb/mi} Breakpoint table commands
17067 @cindex breakpoint commands for @sc{gdb/mi}
17068 @cindex @sc{gdb/mi}, breakpoint commands
17069 This section documents @sc{gdb/mi} commands for manipulating
17072 @subheading The @code{-break-after} Command
17073 @findex -break-after
17075 @subsubheading Synopsis
17078 -break-after @var{number} @var{count}
17081 The breakpoint number @var{number} is not in effect until it has been
17082 hit @var{count} times. To see how this is reflected in the output of
17083 the @samp{-break-list} command, see the description of the
17084 @samp{-break-list} command below.
17086 @subsubheading @value{GDBN} Command
17088 The corresponding @value{GDBN} command is @samp{ignore}.
17090 @subsubheading Example
17095 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",line="5"@}
17102 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17103 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17104 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17105 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17106 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17107 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17108 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17109 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17110 addr="0x000100d0",func="main",file="hello.c",line="5",times="0",
17116 @subheading The @code{-break-catch} Command
17117 @findex -break-catch
17119 @subheading The @code{-break-commands} Command
17120 @findex -break-commands
17124 @subheading The @code{-break-condition} Command
17125 @findex -break-condition
17127 @subsubheading Synopsis
17130 -break-condition @var{number} @var{expr}
17133 Breakpoint @var{number} will stop the program only if the condition in
17134 @var{expr} is true. The condition becomes part of the
17135 @samp{-break-list} output (see the description of the @samp{-break-list}
17138 @subsubheading @value{GDBN} Command
17140 The corresponding @value{GDBN} command is @samp{condition}.
17142 @subsubheading Example
17146 -break-condition 1 1
17150 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17151 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17152 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17153 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17154 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17155 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17156 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17157 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17158 addr="0x000100d0",func="main",file="hello.c",line="5",cond="1",
17159 times="0",ignore="3"@}]@}
17163 @subheading The @code{-break-delete} Command
17164 @findex -break-delete
17166 @subsubheading Synopsis
17169 -break-delete ( @var{breakpoint} )+
17172 Delete the breakpoint(s) whose number(s) are specified in the argument
17173 list. This is obviously reflected in the breakpoint list.
17175 @subsubheading @value{GDBN} command
17177 The corresponding @value{GDBN} command is @samp{delete}.
17179 @subsubheading Example
17187 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17188 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17189 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17190 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17191 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17192 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17193 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17198 @subheading The @code{-break-disable} Command
17199 @findex -break-disable
17201 @subsubheading Synopsis
17204 -break-disable ( @var{breakpoint} )+
17207 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
17208 break list is now set to @samp{n} for the named @var{breakpoint}(s).
17210 @subsubheading @value{GDBN} Command
17212 The corresponding @value{GDBN} command is @samp{disable}.
17214 @subsubheading Example
17222 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17223 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17224 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17225 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17226 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17227 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17228 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17229 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
17230 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
17234 @subheading The @code{-break-enable} Command
17235 @findex -break-enable
17237 @subsubheading Synopsis
17240 -break-enable ( @var{breakpoint} )+
17243 Enable (previously disabled) @var{breakpoint}(s).
17245 @subsubheading @value{GDBN} Command
17247 The corresponding @value{GDBN} command is @samp{enable}.
17249 @subsubheading Example
17257 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17258 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17259 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17260 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17261 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17262 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17263 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17264 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17265 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
17269 @subheading The @code{-break-info} Command
17270 @findex -break-info
17272 @subsubheading Synopsis
17275 -break-info @var{breakpoint}
17279 Get information about a single breakpoint.
17281 @subsubheading @value{GDBN} command
17283 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
17285 @subsubheading Example
17288 @subheading The @code{-break-insert} Command
17289 @findex -break-insert
17291 @subsubheading Synopsis
17294 -break-insert [ -t ] [ -h ] [ -r ]
17295 [ -c @var{condition} ] [ -i @var{ignore-count} ]
17296 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
17300 If specified, @var{line}, can be one of:
17307 @item filename:linenum
17308 @item filename:function
17312 The possible optional parameters of this command are:
17316 Insert a tempoary breakpoint.
17318 Insert a hardware breakpoint.
17319 @item -c @var{condition}
17320 Make the breakpoint conditional on @var{condition}.
17321 @item -i @var{ignore-count}
17322 Initialize the @var{ignore-count}.
17324 Insert a regular breakpoint in all the functions whose names match the
17325 given regular expression. Other flags are not applicable to regular
17329 @subsubheading Result
17331 The result is in the form:
17334 ^done,bkptno="@var{number}",func="@var{funcname}",
17335 file="@var{filename}",line="@var{lineno}"
17339 where @var{number} is the @value{GDBN} number for this breakpoint, @var{funcname}
17340 is the name of the function where the breakpoint was inserted,
17341 @var{filename} is the name of the source file which contains this
17342 function, and @var{lineno} is the source line number within that file.
17344 Note: this format is open to change.
17345 @c An out-of-band breakpoint instead of part of the result?
17347 @subsubheading @value{GDBN} Command
17349 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
17350 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
17352 @subsubheading Example
17357 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
17359 -break-insert -t foo
17360 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",line="11"@}
17363 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17364 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17365 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17366 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17367 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17368 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17369 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17370 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17371 addr="0x0001072c", func="main",file="recursive2.c",line="4",times="0"@},
17372 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
17373 addr="0x00010774",func="foo",file="recursive2.c",line="11",times="0"@}]@}
17375 -break-insert -r foo.*
17376 ~int foo(int, int);
17377 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c",line="11"@}
17381 @subheading The @code{-break-list} Command
17382 @findex -break-list
17384 @subsubheading Synopsis
17390 Displays the list of inserted breakpoints, showing the following fields:
17394 number of the breakpoint
17396 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
17398 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
17401 is the breakpoint enabled or no: @samp{y} or @samp{n}
17403 memory location at which the breakpoint is set
17405 logical location of the breakpoint, expressed by function name, file
17408 number of times the breakpoint has been hit
17411 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
17412 @code{body} field is an empty list.
17414 @subsubheading @value{GDBN} Command
17416 The corresponding @value{GDBN} command is @samp{info break}.
17418 @subsubheading Example
17423 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17424 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17425 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17426 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17427 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17428 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17429 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17430 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17431 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
17432 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17433 addr="0x00010114",func="foo",file="hello.c",line="13",times="0"@}]@}
17437 Here's an example of the result when there are no breakpoints:
17442 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17443 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17444 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17445 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17446 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17447 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17448 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17453 @subheading The @code{-break-watch} Command
17454 @findex -break-watch
17456 @subsubheading Synopsis
17459 -break-watch [ -a | -r ]
17462 Create a watchpoint. With the @samp{-a} option it will create an
17463 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
17464 read from or on a write to the memory location. With the @samp{-r}
17465 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
17466 trigger only when the memory location is accessed for reading. Without
17467 either of the options, the watchpoint created is a regular watchpoint,
17468 i.e. it will trigger when the memory location is accessed for writing.
17469 @xref{Set Watchpoints, , Setting watchpoints}.
17471 Note that @samp{-break-list} will report a single list of watchpoints and
17472 breakpoints inserted.
17474 @subsubheading @value{GDBN} Command
17476 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
17479 @subsubheading Example
17481 Setting a watchpoint on a variable in the @code{main} function:
17486 ^done,wpt=@{number="2",exp="x"@}
17490 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
17491 value=@{old="-268439212",new="55"@},
17492 frame=@{func="main",args=[],file="recursive2.c",
17493 fullname="/home/foo/bar/devo/myproject/recursive2.c",line="5"@}
17497 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
17498 the program execution twice: first for the variable changing value, then
17499 for the watchpoint going out of scope.
17504 ^done,wpt=@{number="5",exp="C"@}
17508 ^done,reason="watchpoint-trigger",
17509 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
17510 frame=@{func="callee4",args=[],
17511 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17512 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
17516 ^done,reason="watchpoint-scope",wpnum="5",
17517 frame=@{func="callee3",args=[@{name="strarg",
17518 value="0x11940 \"A string argument.\""@}],
17519 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17520 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
17524 Listing breakpoints and watchpoints, at different points in the program
17525 execution. Note that once the watchpoint goes out of scope, it is
17531 ^done,wpt=@{number="2",exp="C"@}
17534 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17535 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17536 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17537 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17538 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17539 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17540 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17541 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17542 addr="0x00010734",func="callee4",
17543 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
17544 bkpt=@{number="2",type="watchpoint",disp="keep",
17545 enabled="y",addr="",what="C",times="0"@}]@}
17549 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
17550 value=@{old="-276895068",new="3"@},
17551 frame=@{func="callee4",args=[],
17552 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17553 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
17556 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17557 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17558 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17559 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17560 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17561 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17562 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17563 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17564 addr="0x00010734",func="callee4",
17565 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
17566 bkpt=@{number="2",type="watchpoint",disp="keep",
17567 enabled="y",addr="",what="C",times="-5"@}]@}
17571 ^done,reason="watchpoint-scope",wpnum="2",
17572 frame=@{func="callee3",args=[@{name="strarg",
17573 value="0x11940 \"A string argument.\""@}],
17574 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17575 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
17578 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17579 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17580 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17581 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17582 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17583 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17584 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17585 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17586 addr="0x00010734",func="callee4",
17587 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@}]@}
17591 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17592 @node GDB/MI Data Manipulation
17593 @section @sc{gdb/mi} Data Manipulation
17595 @cindex data manipulation, in @sc{gdb/mi}
17596 @cindex @sc{gdb/mi}, data manipulation
17597 This section describes the @sc{gdb/mi} commands that manipulate data:
17598 examine memory and registers, evaluate expressions, etc.
17600 @c REMOVED FROM THE INTERFACE.
17601 @c @subheading -data-assign
17602 @c Change the value of a program variable. Plenty of side effects.
17603 @c @subsubheading GDB command
17605 @c @subsubheading Example
17608 @subheading The @code{-data-disassemble} Command
17609 @findex -data-disassemble
17611 @subsubheading Synopsis
17615 [ -s @var{start-addr} -e @var{end-addr} ]
17616 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
17624 @item @var{start-addr}
17625 is the beginning address (or @code{$pc})
17626 @item @var{end-addr}
17628 @item @var{filename}
17629 is the name of the file to disassemble
17630 @item @var{linenum}
17631 is the line number to disassemble around
17633 is the the number of disassembly lines to be produced. If it is -1,
17634 the whole function will be disassembled, in case no @var{end-addr} is
17635 specified. If @var{end-addr} is specified as a non-zero value, and
17636 @var{lines} is lower than the number of disassembly lines between
17637 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
17638 displayed; if @var{lines} is higher than the number of lines between
17639 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
17642 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
17646 @subsubheading Result
17648 The output for each instruction is composed of four fields:
17657 Note that whatever included in the instruction field, is not manipulated
17658 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
17660 @subsubheading @value{GDBN} Command
17662 There's no direct mapping from this command to the CLI.
17664 @subsubheading Example
17666 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
17670 -data-disassemble -s $pc -e "$pc + 20" -- 0
17673 @{address="0x000107c0",func-name="main",offset="4",
17674 inst="mov 2, %o0"@},
17675 @{address="0x000107c4",func-name="main",offset="8",
17676 inst="sethi %hi(0x11800), %o2"@},
17677 @{address="0x000107c8",func-name="main",offset="12",
17678 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
17679 @{address="0x000107cc",func-name="main",offset="16",
17680 inst="sethi %hi(0x11800), %o2"@},
17681 @{address="0x000107d0",func-name="main",offset="20",
17682 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
17686 Disassemble the whole @code{main} function. Line 32 is part of
17690 -data-disassemble -f basics.c -l 32 -- 0
17692 @{address="0x000107bc",func-name="main",offset="0",
17693 inst="save %sp, -112, %sp"@},
17694 @{address="0x000107c0",func-name="main",offset="4",
17695 inst="mov 2, %o0"@},
17696 @{address="0x000107c4",func-name="main",offset="8",
17697 inst="sethi %hi(0x11800), %o2"@},
17699 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
17700 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
17704 Disassemble 3 instructions from the start of @code{main}:
17708 -data-disassemble -f basics.c -l 32 -n 3 -- 0
17710 @{address="0x000107bc",func-name="main",offset="0",
17711 inst="save %sp, -112, %sp"@},
17712 @{address="0x000107c0",func-name="main",offset="4",
17713 inst="mov 2, %o0"@},
17714 @{address="0x000107c4",func-name="main",offset="8",
17715 inst="sethi %hi(0x11800), %o2"@}]
17719 Disassemble 3 instructions from the start of @code{main} in mixed mode:
17723 -data-disassemble -f basics.c -l 32 -n 3 -- 1
17725 src_and_asm_line=@{line="31",
17726 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
17727 testsuite/gdb.mi/basics.c",line_asm_insn=[
17728 @{address="0x000107bc",func-name="main",offset="0",
17729 inst="save %sp, -112, %sp"@}]@},
17730 src_and_asm_line=@{line="32",
17731 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
17732 testsuite/gdb.mi/basics.c",line_asm_insn=[
17733 @{address="0x000107c0",func-name="main",offset="4",
17734 inst="mov 2, %o0"@},
17735 @{address="0x000107c4",func-name="main",offset="8",
17736 inst="sethi %hi(0x11800), %o2"@}]@}]
17741 @subheading The @code{-data-evaluate-expression} Command
17742 @findex -data-evaluate-expression
17744 @subsubheading Synopsis
17747 -data-evaluate-expression @var{expr}
17750 Evaluate @var{expr} as an expression. The expression could contain an
17751 inferior function call. The function call will execute synchronously.
17752 If the expression contains spaces, it must be enclosed in double quotes.
17754 @subsubheading @value{GDBN} Command
17756 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
17757 @samp{call}. In @code{gdbtk} only, there's a corresponding
17758 @samp{gdb_eval} command.
17760 @subsubheading Example
17762 In the following example, the numbers that precede the commands are the
17763 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
17764 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
17768 211-data-evaluate-expression A
17771 311-data-evaluate-expression &A
17772 311^done,value="0xefffeb7c"
17774 411-data-evaluate-expression A+3
17777 511-data-evaluate-expression "A + 3"
17783 @subheading The @code{-data-list-changed-registers} Command
17784 @findex -data-list-changed-registers
17786 @subsubheading Synopsis
17789 -data-list-changed-registers
17792 Display a list of the registers that have changed.
17794 @subsubheading @value{GDBN} Command
17796 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
17797 has the corresponding command @samp{gdb_changed_register_list}.
17799 @subsubheading Example
17801 On a PPC MBX board:
17809 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
17810 args=[],file="try.c",fullname="/home/foo/bar/devo/myproject/try.c",line="5"@}
17812 -data-list-changed-registers
17813 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
17814 "10","11","13","14","15","16","17","18","19","20","21","22","23",
17815 "24","25","26","27","28","30","31","64","65","66","67","69"]
17820 @subheading The @code{-data-list-register-names} Command
17821 @findex -data-list-register-names
17823 @subsubheading Synopsis
17826 -data-list-register-names [ ( @var{regno} )+ ]
17829 Show a list of register names for the current target. If no arguments
17830 are given, it shows a list of the names of all the registers. If
17831 integer numbers are given as arguments, it will print a list of the
17832 names of the registers corresponding to the arguments. To ensure
17833 consistency between a register name and its number, the output list may
17834 include empty register names.
17836 @subsubheading @value{GDBN} Command
17838 @value{GDBN} does not have a command which corresponds to
17839 @samp{-data-list-register-names}. In @code{gdbtk} there is a
17840 corresponding command @samp{gdb_regnames}.
17842 @subsubheading Example
17844 For the PPC MBX board:
17847 -data-list-register-names
17848 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
17849 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
17850 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
17851 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
17852 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
17853 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
17854 "", "pc","ps","cr","lr","ctr","xer"]
17856 -data-list-register-names 1 2 3
17857 ^done,register-names=["r1","r2","r3"]
17861 @subheading The @code{-data-list-register-values} Command
17862 @findex -data-list-register-values
17864 @subsubheading Synopsis
17867 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
17870 Display the registers' contents. @var{fmt} is the format according to
17871 which the registers' contents are to be returned, followed by an optional
17872 list of numbers specifying the registers to display. A missing list of
17873 numbers indicates that the contents of all the registers must be returned.
17875 Allowed formats for @var{fmt} are:
17892 @subsubheading @value{GDBN} Command
17894 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
17895 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
17897 @subsubheading Example
17899 For a PPC MBX board (note: line breaks are for readability only, they
17900 don't appear in the actual output):
17904 -data-list-register-values r 64 65
17905 ^done,register-values=[@{number="64",value="0xfe00a300"@},
17906 @{number="65",value="0x00029002"@}]
17908 -data-list-register-values x
17909 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
17910 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
17911 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
17912 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
17913 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
17914 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
17915 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
17916 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
17917 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
17918 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
17919 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
17920 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
17921 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
17922 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
17923 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
17924 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
17925 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
17926 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
17927 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
17928 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
17929 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
17930 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
17931 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
17932 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
17933 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
17934 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
17935 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
17936 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
17937 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
17938 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
17939 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
17940 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
17941 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
17942 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
17943 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
17944 @{number="69",value="0x20002b03"@}]
17949 @subheading The @code{-data-read-memory} Command
17950 @findex -data-read-memory
17952 @subsubheading Synopsis
17955 -data-read-memory [ -o @var{byte-offset} ]
17956 @var{address} @var{word-format} @var{word-size}
17957 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
17964 @item @var{address}
17965 An expression specifying the address of the first memory word to be
17966 read. Complex expressions containing embedded white space should be
17967 quoted using the C convention.
17969 @item @var{word-format}
17970 The format to be used to print the memory words. The notation is the
17971 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
17974 @item @var{word-size}
17975 The size of each memory word in bytes.
17977 @item @var{nr-rows}
17978 The number of rows in the output table.
17980 @item @var{nr-cols}
17981 The number of columns in the output table.
17984 If present, indicates that each row should include an @sc{ascii} dump. The
17985 value of @var{aschar} is used as a padding character when a byte is not a
17986 member of the printable @sc{ascii} character set (printable @sc{ascii}
17987 characters are those whose code is between 32 and 126, inclusively).
17989 @item @var{byte-offset}
17990 An offset to add to the @var{address} before fetching memory.
17993 This command displays memory contents as a table of @var{nr-rows} by
17994 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
17995 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
17996 (returned as @samp{total-bytes}). Should less than the requested number
17997 of bytes be returned by the target, the missing words are identified
17998 using @samp{N/A}. The number of bytes read from the target is returned
17999 in @samp{nr-bytes} and the starting address used to read memory in
18002 The address of the next/previous row or page is available in
18003 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
18006 @subsubheading @value{GDBN} Command
18008 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
18009 @samp{gdb_get_mem} memory read command.
18011 @subsubheading Example
18013 Read six bytes of memory starting at @code{bytes+6} but then offset by
18014 @code{-6} bytes. Format as three rows of two columns. One byte per
18015 word. Display each word in hex.
18019 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
18020 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
18021 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
18022 prev-page="0x0000138a",memory=[
18023 @{addr="0x00001390",data=["0x00","0x01"]@},
18024 @{addr="0x00001392",data=["0x02","0x03"]@},
18025 @{addr="0x00001394",data=["0x04","0x05"]@}]
18029 Read two bytes of memory starting at address @code{shorts + 64} and
18030 display as a single word formatted in decimal.
18034 5-data-read-memory shorts+64 d 2 1 1
18035 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
18036 next-row="0x00001512",prev-row="0x0000150e",
18037 next-page="0x00001512",prev-page="0x0000150e",memory=[
18038 @{addr="0x00001510",data=["128"]@}]
18042 Read thirty two bytes of memory starting at @code{bytes+16} and format
18043 as eight rows of four columns. Include a string encoding with @samp{x}
18044 used as the non-printable character.
18048 4-data-read-memory bytes+16 x 1 8 4 x
18049 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
18050 next-row="0x000013c0",prev-row="0x0000139c",
18051 next-page="0x000013c0",prev-page="0x00001380",memory=[
18052 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
18053 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
18054 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
18055 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
18056 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
18057 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
18058 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
18059 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
18063 @subheading The @code{-display-delete} Command
18064 @findex -display-delete
18066 @subsubheading Synopsis
18069 -display-delete @var{number}
18072 Delete the display @var{number}.
18074 @subsubheading @value{GDBN} Command
18076 The corresponding @value{GDBN} command is @samp{delete display}.
18078 @subsubheading Example
18082 @subheading The @code{-display-disable} Command
18083 @findex -display-disable
18085 @subsubheading Synopsis
18088 -display-disable @var{number}
18091 Disable display @var{number}.
18093 @subsubheading @value{GDBN} Command
18095 The corresponding @value{GDBN} command is @samp{disable display}.
18097 @subsubheading Example
18101 @subheading The @code{-display-enable} Command
18102 @findex -display-enable
18104 @subsubheading Synopsis
18107 -display-enable @var{number}
18110 Enable display @var{number}.
18112 @subsubheading @value{GDBN} Command
18114 The corresponding @value{GDBN} command is @samp{enable display}.
18116 @subsubheading Example
18120 @subheading The @code{-display-insert} Command
18121 @findex -display-insert
18123 @subsubheading Synopsis
18126 -display-insert @var{expression}
18129 Display @var{expression} every time the program stops.
18131 @subsubheading @value{GDBN} Command
18133 The corresponding @value{GDBN} command is @samp{display}.
18135 @subsubheading Example
18139 @subheading The @code{-display-list} Command
18140 @findex -display-list
18142 @subsubheading Synopsis
18148 List the displays. Do not show the current values.
18150 @subsubheading @value{GDBN} Command
18152 The corresponding @value{GDBN} command is @samp{info display}.
18154 @subsubheading Example
18158 @subheading The @code{-environment-cd} Command
18159 @findex -environment-cd
18161 @subsubheading Synopsis
18164 -environment-cd @var{pathdir}
18167 Set @value{GDBN}'s working directory.
18169 @subsubheading @value{GDBN} Command
18171 The corresponding @value{GDBN} command is @samp{cd}.
18173 @subsubheading Example
18177 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18183 @subheading The @code{-environment-directory} Command
18184 @findex -environment-directory
18186 @subsubheading Synopsis
18189 -environment-directory [ -r ] [ @var{pathdir} ]+
18192 Add directories @var{pathdir} to beginning of search path for source files.
18193 If the @samp{-r} option is used, the search path is reset to the default
18194 search path. If directories @var{pathdir} are supplied in addition to the
18195 @samp{-r} option, the search path is first reset and then addition
18197 Multiple directories may be specified, separated by blanks. Specifying
18198 multiple directories in a single command
18199 results in the directories added to the beginning of the
18200 search path in the same order they were presented in the command.
18201 If blanks are needed as
18202 part of a directory name, double-quotes should be used around
18203 the name. In the command output, the path will show up separated
18204 by the system directory-separator character. The directory-seperator
18205 character must not be used
18206 in any directory name.
18207 If no directories are specified, the current search path is displayed.
18209 @subsubheading @value{GDBN} Command
18211 The corresponding @value{GDBN} command is @samp{dir}.
18213 @subsubheading Example
18217 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18218 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18220 -environment-directory ""
18221 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18223 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
18224 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
18226 -environment-directory -r
18227 ^done,source-path="$cdir:$cwd"
18232 @subheading The @code{-environment-path} Command
18233 @findex -environment-path
18235 @subsubheading Synopsis
18238 -environment-path [ -r ] [ @var{pathdir} ]+
18241 Add directories @var{pathdir} to beginning of search path for object files.
18242 If the @samp{-r} option is used, the search path is reset to the original
18243 search path that existed at gdb start-up. If directories @var{pathdir} are
18244 supplied in addition to the
18245 @samp{-r} option, the search path is first reset and then addition
18247 Multiple directories may be specified, separated by blanks. Specifying
18248 multiple directories in a single command
18249 results in the directories added to the beginning of the
18250 search path in the same order they were presented in the command.
18251 If blanks are needed as
18252 part of a directory name, double-quotes should be used around
18253 the name. In the command output, the path will show up separated
18254 by the system directory-separator character. The directory-seperator
18255 character must not be used
18256 in any directory name.
18257 If no directories are specified, the current path is displayed.
18260 @subsubheading @value{GDBN} Command
18262 The corresponding @value{GDBN} command is @samp{path}.
18264 @subsubheading Example
18269 ^done,path="/usr/bin"
18271 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
18272 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
18274 -environment-path -r /usr/local/bin
18275 ^done,path="/usr/local/bin:/usr/bin"
18280 @subheading The @code{-environment-pwd} Command
18281 @findex -environment-pwd
18283 @subsubheading Synopsis
18289 Show the current working directory.
18291 @subsubheading @value{GDBN} command
18293 The corresponding @value{GDBN} command is @samp{pwd}.
18295 @subsubheading Example
18300 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
18304 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18305 @node GDB/MI Program Control
18306 @section @sc{gdb/mi} Program control
18308 @subsubheading Program termination
18310 As a result of execution, the inferior program can run to completion, if
18311 it doesn't encounter any breakpoints. In this case the output will
18312 include an exit code, if the program has exited exceptionally.
18314 @subsubheading Examples
18317 Program exited normally:
18325 *stopped,reason="exited-normally"
18330 Program exited exceptionally:
18338 *stopped,reason="exited",exit-code="01"
18342 Another way the program can terminate is if it receives a signal such as
18343 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
18347 *stopped,reason="exited-signalled",signal-name="SIGINT",
18348 signal-meaning="Interrupt"
18352 @subheading The @code{-exec-abort} Command
18353 @findex -exec-abort
18355 @subsubheading Synopsis
18361 Kill the inferior running program.
18363 @subsubheading @value{GDBN} Command
18365 The corresponding @value{GDBN} command is @samp{kill}.
18367 @subsubheading Example
18371 @subheading The @code{-exec-arguments} Command
18372 @findex -exec-arguments
18374 @subsubheading Synopsis
18377 -exec-arguments @var{args}
18380 Set the inferior program arguments, to be used in the next
18383 @subsubheading @value{GDBN} Command
18385 The corresponding @value{GDBN} command is @samp{set args}.
18387 @subsubheading Example
18390 Don't have one around.
18393 @subheading The @code{-exec-continue} Command
18394 @findex -exec-continue
18396 @subsubheading Synopsis
18402 Asynchronous command. Resumes the execution of the inferior program
18403 until a breakpoint is encountered, or until the inferior exits.
18405 @subsubheading @value{GDBN} Command
18407 The corresponding @value{GDBN} corresponding is @samp{continue}.
18409 @subsubheading Example
18416 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
18417 file="hello.c",fullname="/home/foo/bar/devo/myproject/hello.c",line="13"@}
18422 @subheading The @code{-exec-finish} Command
18423 @findex -exec-finish
18425 @subsubheading Synopsis
18431 Asynchronous command. Resumes the execution of the inferior program
18432 until the current function is exited. Displays the results returned by
18435 @subsubheading @value{GDBN} Command
18437 The corresponding @value{GDBN} command is @samp{finish}.
18439 @subsubheading Example
18441 Function returning @code{void}.
18448 *stopped,reason="function-finished",frame=@{func="main",args=[],
18449 file="hello.c",fullname="/home/foo/bar/devo/myproject/hello.c",line="7"@}
18453 Function returning other than @code{void}. The name of the internal
18454 @value{GDBN} variable storing the result is printed, together with the
18461 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
18462 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
18463 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
18464 gdb-result-var="$1",return-value="0"
18469 @subheading The @code{-exec-interrupt} Command
18470 @findex -exec-interrupt
18472 @subsubheading Synopsis
18478 Asynchronous command. Interrupts the background execution of the target.
18479 Note how the token associated with the stop message is the one for the
18480 execution command that has been interrupted. The token for the interrupt
18481 itself only appears in the @samp{^done} output. If the user is trying to
18482 interrupt a non-running program, an error message will be printed.
18484 @subsubheading @value{GDBN} Command
18486 The corresponding @value{GDBN} command is @samp{interrupt}.
18488 @subsubheading Example
18499 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
18500 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
18501 fullname="/home/foo/bar/devo/myproject/try.c",line="13"@}
18506 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
18511 @subheading The @code{-exec-next} Command
18514 @subsubheading Synopsis
18520 Asynchronous command. Resumes execution of the inferior program, stopping
18521 when the beginning of the next source line is reached.
18523 @subsubheading @value{GDBN} Command
18525 The corresponding @value{GDBN} command is @samp{next}.
18527 @subsubheading Example
18533 *stopped,reason="end-stepping-range",line="8",file="hello.c"
18538 @subheading The @code{-exec-next-instruction} Command
18539 @findex -exec-next-instruction
18541 @subsubheading Synopsis
18544 -exec-next-instruction
18547 Asynchronous command. Executes one machine instruction. If the
18548 instruction is a function call continues until the function returns. If
18549 the program stops at an instruction in the middle of a source line, the
18550 address will be printed as well.
18552 @subsubheading @value{GDBN} Command
18554 The corresponding @value{GDBN} command is @samp{nexti}.
18556 @subsubheading Example
18560 -exec-next-instruction
18564 *stopped,reason="end-stepping-range",
18565 addr="0x000100d4",line="5",file="hello.c"
18570 @subheading The @code{-exec-return} Command
18571 @findex -exec-return
18573 @subsubheading Synopsis
18579 Makes current function return immediately. Doesn't execute the inferior.
18580 Displays the new current frame.
18582 @subsubheading @value{GDBN} Command
18584 The corresponding @value{GDBN} command is @samp{return}.
18586 @subsubheading Example
18590 200-break-insert callee4
18591 200^done,bkpt=@{number="1",addr="0x00010734",
18592 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18597 000*stopped,reason="breakpoint-hit",bkptno="1",
18598 frame=@{func="callee4",args=[],
18599 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18600 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18606 111^done,frame=@{level="0",func="callee3",
18607 args=[@{name="strarg",
18608 value="0x11940 \"A string argument.\""@}],
18609 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18610 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18615 @subheading The @code{-exec-run} Command
18618 @subsubheading Synopsis
18624 Asynchronous command. Starts execution of the inferior from the
18625 beginning. The inferior executes until either a breakpoint is
18626 encountered or the program exits.
18628 @subsubheading @value{GDBN} Command
18630 The corresponding @value{GDBN} command is @samp{run}.
18632 @subsubheading Example
18637 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
18642 *stopped,reason="breakpoint-hit",bkptno="1",
18643 frame=@{func="main",args=[],file="recursive2.c",
18644 fullname="/home/foo/bar/devo/myproject/recursive2.c",line="4"@}
18649 @subheading The @code{-exec-show-arguments} Command
18650 @findex -exec-show-arguments
18652 @subsubheading Synopsis
18655 -exec-show-arguments
18658 Print the arguments of the program.
18660 @subsubheading @value{GDBN} Command
18662 The corresponding @value{GDBN} command is @samp{show args}.
18664 @subsubheading Example
18667 @c @subheading -exec-signal
18669 @subheading The @code{-exec-step} Command
18672 @subsubheading Synopsis
18678 Asynchronous command. Resumes execution of the inferior program, stopping
18679 when the beginning of the next source line is reached, if the next
18680 source line is not a function call. If it is, stop at the first
18681 instruction of the called function.
18683 @subsubheading @value{GDBN} Command
18685 The corresponding @value{GDBN} command is @samp{step}.
18687 @subsubheading Example
18689 Stepping into a function:
18695 *stopped,reason="end-stepping-range",
18696 frame=@{func="foo",args=[@{name="a",value="10"@},
18697 @{name="b",value="0"@}],file="recursive2.c",
18698 fullname="/home/foo/bar/devo/myproject/recursive2.c",line="11"@}
18708 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
18713 @subheading The @code{-exec-step-instruction} Command
18714 @findex -exec-step-instruction
18716 @subsubheading Synopsis
18719 -exec-step-instruction
18722 Asynchronous command. Resumes the inferior which executes one machine
18723 instruction. The output, once @value{GDBN} has stopped, will vary depending on
18724 whether we have stopped in the middle of a source line or not. In the
18725 former case, the address at which the program stopped will be printed as
18728 @subsubheading @value{GDBN} Command
18730 The corresponding @value{GDBN} command is @samp{stepi}.
18732 @subsubheading Example
18736 -exec-step-instruction
18740 *stopped,reason="end-stepping-range",
18741 frame=@{func="foo",args=[],file="try.c",
18742 fullname="/home/foo/bar/devo/myproject/try.c",line="10"@}
18744 -exec-step-instruction
18748 *stopped,reason="end-stepping-range",
18749 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
18750 fullname="/home/foo/bar/devo/myproject/try.c",line="10"@}
18755 @subheading The @code{-exec-until} Command
18756 @findex -exec-until
18758 @subsubheading Synopsis
18761 -exec-until [ @var{location} ]
18764 Asynchronous command. Executes the inferior until the @var{location}
18765 specified in the argument is reached. If there is no argument, the inferior
18766 executes until a source line greater than the current one is reached.
18767 The reason for stopping in this case will be @samp{location-reached}.
18769 @subsubheading @value{GDBN} Command
18771 The corresponding @value{GDBN} command is @samp{until}.
18773 @subsubheading Example
18777 -exec-until recursive2.c:6
18781 *stopped,reason="location-reached",frame=@{func="main",args=[],
18782 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="6"@}
18787 @subheading -file-clear
18788 Is this going away????
18792 @subheading The @code{-file-exec-and-symbols} Command
18793 @findex -file-exec-and-symbols
18795 @subsubheading Synopsis
18798 -file-exec-and-symbols @var{file}
18801 Specify the executable file to be debugged. This file is the one from
18802 which the symbol table is also read. If no file is specified, the
18803 command clears the executable and symbol information. If breakpoints
18804 are set when using this command with no arguments, @value{GDBN} will produce
18805 error messages. Otherwise, no output is produced, except a completion
18808 @subsubheading @value{GDBN} Command
18810 The corresponding @value{GDBN} command is @samp{file}.
18812 @subsubheading Example
18816 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18822 @subheading The @code{-file-exec-file} Command
18823 @findex -file-exec-file
18825 @subsubheading Synopsis
18828 -file-exec-file @var{file}
18831 Specify the executable file to be debugged. Unlike
18832 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
18833 from this file. If used without argument, @value{GDBN} clears the information
18834 about the executable file. No output is produced, except a completion
18837 @subsubheading @value{GDBN} Command
18839 The corresponding @value{GDBN} command is @samp{exec-file}.
18841 @subsubheading Example
18845 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18851 @subheading The @code{-file-list-exec-sections} Command
18852 @findex -file-list-exec-sections
18854 @subsubheading Synopsis
18857 -file-list-exec-sections
18860 List the sections of the current executable file.
18862 @subsubheading @value{GDBN} Command
18864 The @value{GDBN} command @samp{info file} shows, among the rest, the same
18865 information as this command. @code{gdbtk} has a corresponding command
18866 @samp{gdb_load_info}.
18868 @subsubheading Example
18872 @subheading The @code{-file-list-exec-source-file} Command
18873 @findex -file-list-exec-source-file
18875 @subsubheading Synopsis
18878 -file-list-exec-source-file
18881 List the line number, the current source file, and the absolute path
18882 to the current source file for the current executable.
18884 @subsubheading @value{GDBN} Command
18886 There's no @value{GDBN} command which directly corresponds to this one.
18888 @subsubheading Example
18892 123-file-list-exec-source-file
18893 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
18898 @subheading The @code{-file-list-exec-source-files} Command
18899 @findex -file-list-exec-source-files
18901 @subsubheading Synopsis
18904 -file-list-exec-source-files
18907 List the source files for the current executable.
18909 It will always output the filename, but only when GDB can find the absolute
18910 file name of a source file, will it output the fullname.
18912 @subsubheading @value{GDBN} Command
18914 There's no @value{GDBN} command which directly corresponds to this one.
18915 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
18917 @subsubheading Example
18920 -file-list-exec-source-files
18922 @{file=foo.c,fullname=/home/foo.c@},
18923 @{file=/home/bar.c,fullname=/home/bar.c@},
18924 @{file=gdb_could_not_find_fullpath.c@}]
18928 @subheading The @code{-file-list-shared-libraries} Command
18929 @findex -file-list-shared-libraries
18931 @subsubheading Synopsis
18934 -file-list-shared-libraries
18937 List the shared libraries in the program.
18939 @subsubheading @value{GDBN} Command
18941 The corresponding @value{GDBN} command is @samp{info shared}.
18943 @subsubheading Example
18947 @subheading The @code{-file-list-symbol-files} Command
18948 @findex -file-list-symbol-files
18950 @subsubheading Synopsis
18953 -file-list-symbol-files
18958 @subsubheading @value{GDBN} Command
18960 The corresponding @value{GDBN} command is @samp{info file} (part of it).
18962 @subsubheading Example
18966 @subheading The @code{-file-symbol-file} Command
18967 @findex -file-symbol-file
18969 @subsubheading Synopsis
18972 -file-symbol-file @var{file}
18975 Read symbol table info from the specified @var{file} argument. When
18976 used without arguments, clears @value{GDBN}'s symbol table info. No output is
18977 produced, except for a completion notification.
18979 @subsubheading @value{GDBN} Command
18981 The corresponding @value{GDBN} command is @samp{symbol-file}.
18983 @subsubheading Example
18987 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18992 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18993 @node GDB/MI Miscellaneous Commands
18994 @section Miscellaneous @value{GDBN} commands in @sc{gdb/mi}
18996 @c @subheading -gdb-complete
18998 @subheading The @code{-gdb-exit} Command
19001 @subsubheading Synopsis
19007 Exit @value{GDBN} immediately.
19009 @subsubheading @value{GDBN} Command
19011 Approximately corresponds to @samp{quit}.
19013 @subsubheading Example
19020 @subheading The @code{-gdb-set} Command
19023 @subsubheading Synopsis
19029 Set an internal @value{GDBN} variable.
19030 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
19032 @subsubheading @value{GDBN} Command
19034 The corresponding @value{GDBN} command is @samp{set}.
19036 @subsubheading Example
19046 @subheading The @code{-gdb-show} Command
19049 @subsubheading Synopsis
19055 Show the current value of a @value{GDBN} variable.
19057 @subsubheading @value{GDBN} command
19059 The corresponding @value{GDBN} command is @samp{show}.
19061 @subsubheading Example
19070 @c @subheading -gdb-source
19073 @subheading The @code{-gdb-version} Command
19074 @findex -gdb-version
19076 @subsubheading Synopsis
19082 Show version information for @value{GDBN}. Used mostly in testing.
19084 @subsubheading @value{GDBN} Command
19086 There's no equivalent @value{GDBN} command. @value{GDBN} by default shows this
19087 information when you start an interactive session.
19089 @subsubheading Example
19091 @c This example modifies the actual output from GDB to avoid overfull
19097 ~Copyright 2000 Free Software Foundation, Inc.
19098 ~GDB is free software, covered by the GNU General Public License, and
19099 ~you are welcome to change it and/or distribute copies of it under
19100 ~ certain conditions.
19101 ~Type "show copying" to see the conditions.
19102 ~There is absolutely no warranty for GDB. Type "show warranty" for
19104 ~This GDB was configured as
19105 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
19110 @subheading The @code{-interpreter-exec} Command
19111 @findex -interpreter-exec
19113 @subheading Synopsis
19116 -interpreter-exec @var{interpreter} @var{command}
19119 Execute the specified @var{command} in the given @var{interpreter}.
19121 @subheading @value{GDBN} Command
19123 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
19125 @subheading Example
19129 -interpreter-exec console "break main"
19130 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
19131 &"During symbol reading, bad structure-type format.\n"
19132 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
19138 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19139 @node GDB/MI Kod Commands
19140 @section @sc{gdb/mi} Kod Commands
19142 The Kod commands are not implemented.
19144 @c @subheading -kod-info
19146 @c @subheading -kod-list
19148 @c @subheading -kod-list-object-types
19150 @c @subheading -kod-show
19152 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19153 @node GDB/MI Memory Overlay Commands
19154 @section @sc{gdb/mi} Memory Overlay Commands
19156 The memory overlay commands are not implemented.
19158 @c @subheading -overlay-auto
19160 @c @subheading -overlay-list-mapping-state
19162 @c @subheading -overlay-list-overlays
19164 @c @subheading -overlay-map
19166 @c @subheading -overlay-off
19168 @c @subheading -overlay-on
19170 @c @subheading -overlay-unmap
19172 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19173 @node GDB/MI Signal Handling Commands
19174 @section @sc{gdb/mi} Signal Handling Commands
19176 Signal handling commands are not implemented.
19178 @c @subheading -signal-handle
19180 @c @subheading -signal-list-handle-actions
19182 @c @subheading -signal-list-signal-types
19186 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19187 @node GDB/MI Stack Manipulation
19188 @section @sc{gdb/mi} Stack Manipulation Commands
19190 @subheading The @code{-stack-info-depth} Command
19191 @findex -stack-info-depth
19193 @subsubheading Synopsis
19196 -stack-info-depth [ @var{max-depth} ]
19199 Return the depth of the stack. If the integer argument @var{max-depth}
19200 is specified, do not count beyond @var{max-depth} frames.
19202 @subsubheading @value{GDBN} Command
19204 There's no equivalent @value{GDBN} command.
19206 @subsubheading Example
19208 For a stack with frame levels 0 through 11:
19215 -stack-info-depth 4
19218 -stack-info-depth 12
19221 -stack-info-depth 11
19224 -stack-info-depth 13
19229 @subheading The @code{-stack-list-arguments} Command
19230 @findex -stack-list-arguments
19232 @subsubheading Synopsis
19235 -stack-list-arguments @var{show-values}
19236 [ @var{low-frame} @var{high-frame} ]
19239 Display a list of the arguments for the frames between @var{low-frame}
19240 and @var{high-frame} (inclusive). If @var{low-frame} and
19241 @var{high-frame} are not provided, list the arguments for the whole call
19244 The @var{show-values} argument must have a value of 0 or 1. A value of
19245 0 means that only the names of the arguments are listed, a value of 1
19246 means that both names and values of the arguments are printed.
19248 @subsubheading @value{GDBN} Command
19250 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19251 @samp{gdb_get_args} command which partially overlaps with the
19252 functionality of @samp{-stack-list-arguments}.
19254 @subsubheading Example
19261 frame=@{level="0",addr="0x00010734",func="callee4",
19262 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19263 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19264 frame=@{level="1",addr="0x0001076c",func="callee3",
19265 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19266 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19267 frame=@{level="2",addr="0x0001078c",func="callee2",
19268 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19269 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19270 frame=@{level="3",addr="0x000107b4",func="callee1",
19271 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19272 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19273 frame=@{level="4",addr="0x000107e0",func="main",
19274 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19275 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19277 -stack-list-arguments 0
19280 frame=@{level="0",args=[]@},
19281 frame=@{level="1",args=[name="strarg"]@},
19282 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19283 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19284 frame=@{level="4",args=[]@}]
19286 -stack-list-arguments 1
19289 frame=@{level="0",args=[]@},
19291 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19292 frame=@{level="2",args=[
19293 @{name="intarg",value="2"@},
19294 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19295 @{frame=@{level="3",args=[
19296 @{name="intarg",value="2"@},
19297 @{name="strarg",value="0x11940 \"A string argument.\""@},
19298 @{name="fltarg",value="3.5"@}]@},
19299 frame=@{level="4",args=[]@}]
19301 -stack-list-arguments 0 2 2
19302 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19304 -stack-list-arguments 1 2 2
19305 ^done,stack-args=[frame=@{level="2",
19306 args=[@{name="intarg",value="2"@},
19307 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19311 @c @subheading -stack-list-exception-handlers
19314 @subheading The @code{-stack-list-frames} Command
19315 @findex -stack-list-frames
19317 @subsubheading Synopsis
19320 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19323 List the frames currently on the stack. For each frame it displays the
19328 The frame number, 0 being the topmost frame, i.e. the innermost function.
19330 The @code{$pc} value for that frame.
19334 File name of the source file where the function lives.
19336 Line number corresponding to the @code{$pc}.
19339 If invoked without arguments, this command prints a backtrace for the
19340 whole stack. If given two integer arguments, it shows the frames whose
19341 levels are between the two arguments (inclusive). If the two arguments
19342 are equal, it shows the single frame at the corresponding level.
19344 @subsubheading @value{GDBN} Command
19346 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19348 @subsubheading Example
19350 Full stack backtrace:
19356 [frame=@{level="0",addr="0x0001076c",func="foo",
19357 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="11"@},
19358 frame=@{level="1",addr="0x000107a4",func="foo",
19359 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19360 frame=@{level="2",addr="0x000107a4",func="foo",
19361 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19362 frame=@{level="3",addr="0x000107a4",func="foo",
19363 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19364 frame=@{level="4",addr="0x000107a4",func="foo",
19365 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19366 frame=@{level="5",addr="0x000107a4",func="foo",
19367 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19368 frame=@{level="6",addr="0x000107a4",func="foo",
19369 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19370 frame=@{level="7",addr="0x000107a4",func="foo",
19371 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19372 frame=@{level="8",addr="0x000107a4",func="foo",
19373 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19374 frame=@{level="9",addr="0x000107a4",func="foo",
19375 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19376 frame=@{level="10",addr="0x000107a4",func="foo",
19377 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19378 frame=@{level="11",addr="0x00010738",func="main",
19379 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="4"@}]
19383 Show frames between @var{low_frame} and @var{high_frame}:
19387 -stack-list-frames 3 5
19389 [frame=@{level="3",addr="0x000107a4",func="foo",
19390 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19391 frame=@{level="4",addr="0x000107a4",func="foo",
19392 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19393 frame=@{level="5",addr="0x000107a4",func="foo",
19394 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@}]
19398 Show a single frame:
19402 -stack-list-frames 3 3
19404 [frame=@{level="3",addr="0x000107a4",func="foo",
19405 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@}]
19410 @subheading The @code{-stack-list-locals} Command
19411 @findex -stack-list-locals
19413 @subsubheading Synopsis
19416 -stack-list-locals @var{print-values}
19419 Display the local variable names for the current frame. With an
19420 argument of 0 or @code{--no-values}, prints only the names of the variables.
19421 With argument of 1 or @code{--all-values}, prints also their values. With
19422 argument of 2 or @code{--simple-values}, prints the name, type and value for
19423 simple data types and the name and type for arrays, structures and
19424 unions. In this last case, the idea is that the user can see the
19425 value of simple data types immediately and he can create variable
19426 objects for other data types if he wishes to explore their values in
19429 @subsubheading @value{GDBN} Command
19431 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
19433 @subsubheading Example
19437 -stack-list-locals 0
19438 ^done,locals=[name="A",name="B",name="C"]
19440 -stack-list-locals --all-values
19441 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
19442 @{name="C",value="@{1, 2, 3@}"@}]
19443 -stack-list-locals --simple-values
19444 ^done,locals=[@{name="A",type="int",value="1"@},
19445 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
19450 @subheading The @code{-stack-select-frame} Command
19451 @findex -stack-select-frame
19453 @subsubheading Synopsis
19456 -stack-select-frame @var{framenum}
19459 Change the current frame. Select a different frame @var{framenum} on
19462 @subsubheading @value{GDBN} Command
19464 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
19465 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
19467 @subsubheading Example
19471 -stack-select-frame 2
19476 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19477 @node GDB/MI Symbol Query
19478 @section @sc{gdb/mi} Symbol Query Commands
19481 @subheading The @code{-symbol-info-address} Command
19482 @findex -symbol-info-address
19484 @subsubheading Synopsis
19487 -symbol-info-address @var{symbol}
19490 Describe where @var{symbol} is stored.
19492 @subsubheading @value{GDBN} Command
19494 The corresponding @value{GDBN} command is @samp{info address}.
19496 @subsubheading Example
19500 @subheading The @code{-symbol-info-file} Command
19501 @findex -symbol-info-file
19503 @subsubheading Synopsis
19509 Show the file for the symbol.
19511 @subsubheading @value{GDBN} Command
19513 There's no equivalent @value{GDBN} command. @code{gdbtk} has
19514 @samp{gdb_find_file}.
19516 @subsubheading Example
19520 @subheading The @code{-symbol-info-function} Command
19521 @findex -symbol-info-function
19523 @subsubheading Synopsis
19526 -symbol-info-function
19529 Show which function the symbol lives in.
19531 @subsubheading @value{GDBN} Command
19533 @samp{gdb_get_function} in @code{gdbtk}.
19535 @subsubheading Example
19539 @subheading The @code{-symbol-info-line} Command
19540 @findex -symbol-info-line
19542 @subsubheading Synopsis
19548 Show the core addresses of the code for a source line.
19550 @subsubheading @value{GDBN} Command
19552 The corresponding @value{GDBN} command is @samp{info line}.
19553 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
19555 @subsubheading Example
19559 @subheading The @code{-symbol-info-symbol} Command
19560 @findex -symbol-info-symbol
19562 @subsubheading Synopsis
19565 -symbol-info-symbol @var{addr}
19568 Describe what symbol is at location @var{addr}.
19570 @subsubheading @value{GDBN} Command
19572 The corresponding @value{GDBN} command is @samp{info symbol}.
19574 @subsubheading Example
19578 @subheading The @code{-symbol-list-functions} Command
19579 @findex -symbol-list-functions
19581 @subsubheading Synopsis
19584 -symbol-list-functions
19587 List the functions in the executable.
19589 @subsubheading @value{GDBN} Command
19591 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
19592 @samp{gdb_search} in @code{gdbtk}.
19594 @subsubheading Example
19598 @subheading The @code{-symbol-list-lines} Command
19599 @findex -symbol-list-lines
19601 @subsubheading Synopsis
19604 -symbol-list-lines @var{filename}
19607 Print the list of lines that contain code and their associated program
19608 addresses for the given source filename. The entries are sorted in
19609 ascending PC order.
19611 @subsubheading @value{GDBN} Command
19613 There is no corresponding @value{GDBN} command.
19615 @subsubheading Example
19618 -symbol-list-lines basics.c
19619 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
19624 @subheading The @code{-symbol-list-types} Command
19625 @findex -symbol-list-types
19627 @subsubheading Synopsis
19633 List all the type names.
19635 @subsubheading @value{GDBN} Command
19637 The corresponding commands are @samp{info types} in @value{GDBN},
19638 @samp{gdb_search} in @code{gdbtk}.
19640 @subsubheading Example
19644 @subheading The @code{-symbol-list-variables} Command
19645 @findex -symbol-list-variables
19647 @subsubheading Synopsis
19650 -symbol-list-variables
19653 List all the global and static variable names.
19655 @subsubheading @value{GDBN} Command
19657 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
19659 @subsubheading Example
19663 @subheading The @code{-symbol-locate} Command
19664 @findex -symbol-locate
19666 @subsubheading Synopsis
19672 @subsubheading @value{GDBN} Command
19674 @samp{gdb_loc} in @code{gdbtk}.
19676 @subsubheading Example
19680 @subheading The @code{-symbol-type} Command
19681 @findex -symbol-type
19683 @subsubheading Synopsis
19686 -symbol-type @var{variable}
19689 Show type of @var{variable}.
19691 @subsubheading @value{GDBN} Command
19693 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
19694 @samp{gdb_obj_variable}.
19696 @subsubheading Example
19700 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19701 @node GDB/MI Target Manipulation
19702 @section @sc{gdb/mi} Target Manipulation Commands
19705 @subheading The @code{-target-attach} Command
19706 @findex -target-attach
19708 @subsubheading Synopsis
19711 -target-attach @var{pid} | @var{file}
19714 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
19716 @subsubheading @value{GDBN} command
19718 The corresponding @value{GDBN} command is @samp{attach}.
19720 @subsubheading Example
19724 @subheading The @code{-target-compare-sections} Command
19725 @findex -target-compare-sections
19727 @subsubheading Synopsis
19730 -target-compare-sections [ @var{section} ]
19733 Compare data of section @var{section} on target to the exec file.
19734 Without the argument, all sections are compared.
19736 @subsubheading @value{GDBN} Command
19738 The @value{GDBN} equivalent is @samp{compare-sections}.
19740 @subsubheading Example
19744 @subheading The @code{-target-detach} Command
19745 @findex -target-detach
19747 @subsubheading Synopsis
19753 Disconnect from the remote target. There's no output.
19755 @subsubheading @value{GDBN} command
19757 The corresponding @value{GDBN} command is @samp{detach}.
19759 @subsubheading Example
19769 @subheading The @code{-target-disconnect} Command
19770 @findex -target-disconnect
19772 @subsubheading Synopsis
19778 Disconnect from the remote target. There's no output.
19780 @subsubheading @value{GDBN} command
19782 The corresponding @value{GDBN} command is @samp{disconnect}.
19784 @subsubheading Example
19794 @subheading The @code{-target-download} Command
19795 @findex -target-download
19797 @subsubheading Synopsis
19803 Loads the executable onto the remote target.
19804 It prints out an update message every half second, which includes the fields:
19808 The name of the section.
19810 The size of what has been sent so far for that section.
19812 The size of the section.
19814 The total size of what was sent so far (the current and the previous sections).
19816 The size of the overall executable to download.
19820 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
19821 @sc{gdb/mi} Output Syntax}).
19823 In addition, it prints the name and size of the sections, as they are
19824 downloaded. These messages include the following fields:
19828 The name of the section.
19830 The size of the section.
19832 The size of the overall executable to download.
19836 At the end, a summary is printed.
19838 @subsubheading @value{GDBN} Command
19840 The corresponding @value{GDBN} command is @samp{load}.
19842 @subsubheading Example
19844 Note: each status message appears on a single line. Here the messages
19845 have been broken down so that they can fit onto a page.
19850 +download,@{section=".text",section-size="6668",total-size="9880"@}
19851 +download,@{section=".text",section-sent="512",section-size="6668",
19852 total-sent="512",total-size="9880"@}
19853 +download,@{section=".text",section-sent="1024",section-size="6668",
19854 total-sent="1024",total-size="9880"@}
19855 +download,@{section=".text",section-sent="1536",section-size="6668",
19856 total-sent="1536",total-size="9880"@}
19857 +download,@{section=".text",section-sent="2048",section-size="6668",
19858 total-sent="2048",total-size="9880"@}
19859 +download,@{section=".text",section-sent="2560",section-size="6668",
19860 total-sent="2560",total-size="9880"@}
19861 +download,@{section=".text",section-sent="3072",section-size="6668",
19862 total-sent="3072",total-size="9880"@}
19863 +download,@{section=".text",section-sent="3584",section-size="6668",
19864 total-sent="3584",total-size="9880"@}
19865 +download,@{section=".text",section-sent="4096",section-size="6668",
19866 total-sent="4096",total-size="9880"@}
19867 +download,@{section=".text",section-sent="4608",section-size="6668",
19868 total-sent="4608",total-size="9880"@}
19869 +download,@{section=".text",section-sent="5120",section-size="6668",
19870 total-sent="5120",total-size="9880"@}
19871 +download,@{section=".text",section-sent="5632",section-size="6668",
19872 total-sent="5632",total-size="9880"@}
19873 +download,@{section=".text",section-sent="6144",section-size="6668",
19874 total-sent="6144",total-size="9880"@}
19875 +download,@{section=".text",section-sent="6656",section-size="6668",
19876 total-sent="6656",total-size="9880"@}
19877 +download,@{section=".init",section-size="28",total-size="9880"@}
19878 +download,@{section=".fini",section-size="28",total-size="9880"@}
19879 +download,@{section=".data",section-size="3156",total-size="9880"@}
19880 +download,@{section=".data",section-sent="512",section-size="3156",
19881 total-sent="7236",total-size="9880"@}
19882 +download,@{section=".data",section-sent="1024",section-size="3156",
19883 total-sent="7748",total-size="9880"@}
19884 +download,@{section=".data",section-sent="1536",section-size="3156",
19885 total-sent="8260",total-size="9880"@}
19886 +download,@{section=".data",section-sent="2048",section-size="3156",
19887 total-sent="8772",total-size="9880"@}
19888 +download,@{section=".data",section-sent="2560",section-size="3156",
19889 total-sent="9284",total-size="9880"@}
19890 +download,@{section=".data",section-sent="3072",section-size="3156",
19891 total-sent="9796",total-size="9880"@}
19892 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
19898 @subheading The @code{-target-exec-status} Command
19899 @findex -target-exec-status
19901 @subsubheading Synopsis
19904 -target-exec-status
19907 Provide information on the state of the target (whether it is running or
19908 not, for instance).
19910 @subsubheading @value{GDBN} Command
19912 There's no equivalent @value{GDBN} command.
19914 @subsubheading Example
19918 @subheading The @code{-target-list-available-targets} Command
19919 @findex -target-list-available-targets
19921 @subsubheading Synopsis
19924 -target-list-available-targets
19927 List the possible targets to connect to.
19929 @subsubheading @value{GDBN} Command
19931 The corresponding @value{GDBN} command is @samp{help target}.
19933 @subsubheading Example
19937 @subheading The @code{-target-list-current-targets} Command
19938 @findex -target-list-current-targets
19940 @subsubheading Synopsis
19943 -target-list-current-targets
19946 Describe the current target.
19948 @subsubheading @value{GDBN} Command
19950 The corresponding information is printed by @samp{info file} (among
19953 @subsubheading Example
19957 @subheading The @code{-target-list-parameters} Command
19958 @findex -target-list-parameters
19960 @subsubheading Synopsis
19963 -target-list-parameters
19968 @subsubheading @value{GDBN} Command
19972 @subsubheading Example
19976 @subheading The @code{-target-select} Command
19977 @findex -target-select
19979 @subsubheading Synopsis
19982 -target-select @var{type} @var{parameters @dots{}}
19985 Connect @value{GDBN} to the remote target. This command takes two args:
19989 The type of target, for instance @samp{async}, @samp{remote}, etc.
19990 @item @var{parameters}
19991 Device names, host names and the like. @xref{Target Commands, ,
19992 Commands for managing targets}, for more details.
19995 The output is a connection notification, followed by the address at
19996 which the target program is, in the following form:
19999 ^connected,addr="@var{address}",func="@var{function name}",
20000 args=[@var{arg list}]
20003 @subsubheading @value{GDBN} Command
20005 The corresponding @value{GDBN} command is @samp{target}.
20007 @subsubheading Example
20011 -target-select async /dev/ttya
20012 ^connected,addr="0xfe00a300",func="??",args=[]
20016 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20017 @node GDB/MI Thread Commands
20018 @section @sc{gdb/mi} Thread Commands
20021 @subheading The @code{-thread-info} Command
20022 @findex -thread-info
20024 @subsubheading Synopsis
20030 @subsubheading @value{GDBN} command
20034 @subsubheading Example
20038 @subheading The @code{-thread-list-all-threads} Command
20039 @findex -thread-list-all-threads
20041 @subsubheading Synopsis
20044 -thread-list-all-threads
20047 @subsubheading @value{GDBN} Command
20049 The equivalent @value{GDBN} command is @samp{info threads}.
20051 @subsubheading Example
20055 @subheading The @code{-thread-list-ids} Command
20056 @findex -thread-list-ids
20058 @subsubheading Synopsis
20064 Produces a list of the currently known @value{GDBN} thread ids. At the
20065 end of the list it also prints the total number of such threads.
20067 @subsubheading @value{GDBN} Command
20069 Part of @samp{info threads} supplies the same information.
20071 @subsubheading Example
20073 No threads present, besides the main process:
20078 ^done,thread-ids=@{@},number-of-threads="0"
20088 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20089 number-of-threads="3"
20094 @subheading The @code{-thread-select} Command
20095 @findex -thread-select
20097 @subsubheading Synopsis
20100 -thread-select @var{threadnum}
20103 Make @var{threadnum} the current thread. It prints the number of the new
20104 current thread, and the topmost frame for that thread.
20106 @subsubheading @value{GDBN} Command
20108 The corresponding @value{GDBN} command is @samp{thread}.
20110 @subsubheading Example
20117 *stopped,reason="end-stepping-range",thread-id="2",line="187",
20118 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
20122 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20123 number-of-threads="3"
20126 ^done,new-thread-id="3",
20127 frame=@{level="0",func="vprintf",
20128 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
20129 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
20133 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20134 @node GDB/MI Tracepoint Commands
20135 @section @sc{gdb/mi} Tracepoint Commands
20137 The tracepoint commands are not yet implemented.
20139 @c @subheading -trace-actions
20141 @c @subheading -trace-delete
20143 @c @subheading -trace-disable
20145 @c @subheading -trace-dump
20147 @c @subheading -trace-enable
20149 @c @subheading -trace-exists
20151 @c @subheading -trace-find
20153 @c @subheading -trace-frame-number
20155 @c @subheading -trace-info
20157 @c @subheading -trace-insert
20159 @c @subheading -trace-list
20161 @c @subheading -trace-pass-count
20163 @c @subheading -trace-save
20165 @c @subheading -trace-start
20167 @c @subheading -trace-stop
20170 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20171 @node GDB/MI Variable Objects
20172 @section @sc{gdb/mi} Variable Objects
20175 @subheading Motivation for Variable Objects in @sc{gdb/mi}
20177 For the implementation of a variable debugger window (locals, watched
20178 expressions, etc.), we are proposing the adaptation of the existing code
20179 used by @code{Insight}.
20181 The two main reasons for that are:
20185 It has been proven in practice (it is already on its second generation).
20188 It will shorten development time (needless to say how important it is
20192 The original interface was designed to be used by Tcl code, so it was
20193 slightly changed so it could be used through @sc{gdb/mi}. This section
20194 describes the @sc{gdb/mi} operations that will be available and gives some
20195 hints about their use.
20197 @emph{Note}: In addition to the set of operations described here, we
20198 expect the @sc{gui} implementation of a variable window to require, at
20199 least, the following operations:
20202 @item @code{-gdb-show} @code{output-radix}
20203 @item @code{-stack-list-arguments}
20204 @item @code{-stack-list-locals}
20205 @item @code{-stack-select-frame}
20208 @subheading Introduction to Variable Objects in @sc{gdb/mi}
20210 @cindex variable objects in @sc{gdb/mi}
20211 The basic idea behind variable objects is the creation of a named object
20212 to represent a variable, an expression, a memory location or even a CPU
20213 register. For each object created, a set of operations is available for
20214 examining or changing its properties.
20216 Furthermore, complex data types, such as C structures, are represented
20217 in a tree format. For instance, the @code{struct} type variable is the
20218 root and the children will represent the struct members. If a child
20219 is itself of a complex type, it will also have children of its own.
20220 Appropriate language differences are handled for C, C@t{++} and Java.
20222 When returning the actual values of the objects, this facility allows
20223 for the individual selection of the display format used in the result
20224 creation. It can be chosen among: binary, decimal, hexadecimal, octal
20225 and natural. Natural refers to a default format automatically
20226 chosen based on the variable type (like decimal for an @code{int}, hex
20227 for pointers, etc.).
20229 The following is the complete set of @sc{gdb/mi} operations defined to
20230 access this functionality:
20232 @multitable @columnfractions .4 .6
20233 @item @strong{Operation}
20234 @tab @strong{Description}
20236 @item @code{-var-create}
20237 @tab create a variable object
20238 @item @code{-var-delete}
20239 @tab delete the variable object and its children
20240 @item @code{-var-set-format}
20241 @tab set the display format of this variable
20242 @item @code{-var-show-format}
20243 @tab show the display format of this variable
20244 @item @code{-var-info-num-children}
20245 @tab tells how many children this object has
20246 @item @code{-var-list-children}
20247 @tab return a list of the object's children
20248 @item @code{-var-info-type}
20249 @tab show the type of this variable object
20250 @item @code{-var-info-expression}
20251 @tab print what this variable object represents
20252 @item @code{-var-show-attributes}
20253 @tab is this variable editable? does it exist here?
20254 @item @code{-var-evaluate-expression}
20255 @tab get the value of this variable
20256 @item @code{-var-assign}
20257 @tab set the value of this variable
20258 @item @code{-var-update}
20259 @tab update the variable and its children
20262 In the next subsection we describe each operation in detail and suggest
20263 how it can be used.
20265 @subheading Description And Use of Operations on Variable Objects
20267 @subheading The @code{-var-create} Command
20268 @findex -var-create
20270 @subsubheading Synopsis
20273 -var-create @{@var{name} | "-"@}
20274 @{@var{frame-addr} | "*"@} @var{expression}
20277 This operation creates a variable object, which allows the monitoring of
20278 a variable, the result of an expression, a memory cell or a CPU
20281 The @var{name} parameter is the string by which the object can be
20282 referenced. It must be unique. If @samp{-} is specified, the varobj
20283 system will generate a string ``varNNNNNN'' automatically. It will be
20284 unique provided that one does not specify @var{name} on that format.
20285 The command fails if a duplicate name is found.
20287 The frame under which the expression should be evaluated can be
20288 specified by @var{frame-addr}. A @samp{*} indicates that the current
20289 frame should be used.
20291 @var{expression} is any expression valid on the current language set (must not
20292 begin with a @samp{*}), or one of the following:
20296 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
20299 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
20302 @samp{$@var{regname}} --- a CPU register name
20305 @subsubheading Result
20307 This operation returns the name, number of children and the type of the
20308 object created. Type is returned as a string as the ones generated by
20309 the @value{GDBN} CLI:
20312 name="@var{name}",numchild="N",type="@var{type}"
20316 @subheading The @code{-var-delete} Command
20317 @findex -var-delete
20319 @subsubheading Synopsis
20322 -var-delete @var{name}
20325 Deletes a previously created variable object and all of its children.
20327 Returns an error if the object @var{name} is not found.
20330 @subheading The @code{-var-set-format} Command
20331 @findex -var-set-format
20333 @subsubheading Synopsis
20336 -var-set-format @var{name} @var{format-spec}
20339 Sets the output format for the value of the object @var{name} to be
20342 The syntax for the @var{format-spec} is as follows:
20345 @var{format-spec} @expansion{}
20346 @{binary | decimal | hexadecimal | octal | natural@}
20350 @subheading The @code{-var-show-format} Command
20351 @findex -var-show-format
20353 @subsubheading Synopsis
20356 -var-show-format @var{name}
20359 Returns the format used to display the value of the object @var{name}.
20362 @var{format} @expansion{}
20367 @subheading The @code{-var-info-num-children} Command
20368 @findex -var-info-num-children
20370 @subsubheading Synopsis
20373 -var-info-num-children @var{name}
20376 Returns the number of children of a variable object @var{name}:
20383 @subheading The @code{-var-list-children} Command
20384 @findex -var-list-children
20386 @subsubheading Synopsis
20389 -var-list-children [@var{print-values}] @var{name}
20392 Returns a list of the children of the specified variable object. With
20393 just the variable object name as an argument or with an optional
20394 preceding argument of 0 or @code{--no-values}, prints only the names of the
20395 variables. With an optional preceding argument of 1 or @code{--all-values},
20396 also prints their values.
20398 @subsubheading Example
20402 -var-list-children n
20403 numchild=@var{n},children=[@{name=@var{name},
20404 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
20406 -var-list-children --all-values n
20407 numchild=@var{n},children=[@{name=@var{name},
20408 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
20412 @subheading The @code{-var-info-type} Command
20413 @findex -var-info-type
20415 @subsubheading Synopsis
20418 -var-info-type @var{name}
20421 Returns the type of the specified variable @var{name}. The type is
20422 returned as a string in the same format as it is output by the
20426 type=@var{typename}
20430 @subheading The @code{-var-info-expression} Command
20431 @findex -var-info-expression
20433 @subsubheading Synopsis
20436 -var-info-expression @var{name}
20439 Returns what is represented by the variable object @var{name}:
20442 lang=@var{lang-spec},exp=@var{expression}
20446 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
20448 @subheading The @code{-var-show-attributes} Command
20449 @findex -var-show-attributes
20451 @subsubheading Synopsis
20454 -var-show-attributes @var{name}
20457 List attributes of the specified variable object @var{name}:
20460 status=@var{attr} [ ( ,@var{attr} )* ]
20464 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
20466 @subheading The @code{-var-evaluate-expression} Command
20467 @findex -var-evaluate-expression
20469 @subsubheading Synopsis
20472 -var-evaluate-expression @var{name}
20475 Evaluates the expression that is represented by the specified variable
20476 object and returns its value as a string in the current format specified
20483 Note that one must invoke @code{-var-list-children} for a variable
20484 before the value of a child variable can be evaluated.
20486 @subheading The @code{-var-assign} Command
20487 @findex -var-assign
20489 @subsubheading Synopsis
20492 -var-assign @var{name} @var{expression}
20495 Assigns the value of @var{expression} to the variable object specified
20496 by @var{name}. The object must be @samp{editable}. If the variable's
20497 value is altered by the assign, the variable will show up in any
20498 subsequent @code{-var-update} list.
20500 @subsubheading Example
20508 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
20512 @subheading The @code{-var-update} Command
20513 @findex -var-update
20515 @subsubheading Synopsis
20518 -var-update @{@var{name} | "*"@}
20521 Update the value of the variable object @var{name} by evaluating its
20522 expression after fetching all the new values from memory or registers.
20523 A @samp{*} causes all existing variable objects to be updated.
20527 @chapter @value{GDBN} Annotations
20529 This chapter describes annotations in @value{GDBN}. Annotations were
20530 designed to interface @value{GDBN} to graphical user interfaces or other
20531 similar programs which want to interact with @value{GDBN} at a
20532 relatively high level.
20534 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
20538 This is Edition @value{EDITION}, @value{DATE}.
20542 * Annotations Overview:: What annotations are; the general syntax.
20543 * Server Prefix:: Issuing a command without affecting user state.
20544 * Prompting:: Annotations marking @value{GDBN}'s need for input.
20545 * Errors:: Annotations for error messages.
20546 * Invalidation:: Some annotations describe things now invalid.
20547 * Annotations for Running::
20548 Whether the program is running, how it stopped, etc.
20549 * Source Annotations:: Annotations describing source code.
20552 @node Annotations Overview
20553 @section What is an Annotation?
20554 @cindex annotations
20556 Annotations start with a newline character, two @samp{control-z}
20557 characters, and the name of the annotation. If there is no additional
20558 information associated with this annotation, the name of the annotation
20559 is followed immediately by a newline. If there is additional
20560 information, the name of the annotation is followed by a space, the
20561 additional information, and a newline. The additional information
20562 cannot contain newline characters.
20564 Any output not beginning with a newline and two @samp{control-z}
20565 characters denotes literal output from @value{GDBN}. Currently there is
20566 no need for @value{GDBN} to output a newline followed by two
20567 @samp{control-z} characters, but if there was such a need, the
20568 annotations could be extended with an @samp{escape} annotation which
20569 means those three characters as output.
20571 The annotation @var{level}, which is specified using the
20572 @option{--annotate} command line option (@pxref{Mode Options}), controls
20573 how much information @value{GDBN} prints together with its prompt,
20574 values of expressions, source lines, and other types of output. Level 0
20575 is for no anntations, level 1 is for use when @value{GDBN} is run as a
20576 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
20577 for programs that control @value{GDBN}, and level 2 annotations have
20578 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
20579 Interface, annotate, GDB's Obsolete Annotations}).
20582 @kindex set annotate
20583 @item set annotate @var{level}
20584 The @value{GDBN} command @code{set annotate} sets the level of
20585 annotations to the specified @var{level}.
20587 @item show annotate
20588 @kindex show annotate
20589 Show the current annotation level.
20592 This chapter describes level 3 annotations.
20594 A simple example of starting up @value{GDBN} with annotations is:
20597 $ @kbd{gdb --annotate=3}
20599 Copyright 2003 Free Software Foundation, Inc.
20600 GDB is free software, covered by the GNU General Public License,
20601 and you are welcome to change it and/or distribute copies of it
20602 under certain conditions.
20603 Type "show copying" to see the conditions.
20604 There is absolutely no warranty for GDB. Type "show warranty"
20606 This GDB was configured as "i386-pc-linux-gnu"
20617 Here @samp{quit} is input to @value{GDBN}; the rest is output from
20618 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
20619 denotes a @samp{control-z} character) are annotations; the rest is
20620 output from @value{GDBN}.
20622 @node Server Prefix
20623 @section The Server Prefix
20624 @cindex server prefix for annotations
20626 To issue a command to @value{GDBN} without affecting certain aspects of
20627 the state which is seen by users, prefix it with @samp{server }. This
20628 means that this command will not affect the command history, nor will it
20629 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
20630 pressed on a line by itself.
20632 The server prefix does not affect the recording of values into the value
20633 history; to print a value without recording it into the value history,
20634 use the @code{output} command instead of the @code{print} command.
20637 @section Annotation for @value{GDBN} Input
20639 @cindex annotations for prompts
20640 When @value{GDBN} prompts for input, it annotates this fact so it is possible
20641 to know when to send output, when the output from a given command is
20644 Different kinds of input each have a different @dfn{input type}. Each
20645 input type has three annotations: a @code{pre-} annotation, which
20646 denotes the beginning of any prompt which is being output, a plain
20647 annotation, which denotes the end of the prompt, and then a @code{post-}
20648 annotation which denotes the end of any echo which may (or may not) be
20649 associated with the input. For example, the @code{prompt} input type
20650 features the following annotations:
20658 The input types are
20663 @findex post-prompt
20665 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
20667 @findex pre-commands
20669 @findex post-commands
20671 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
20672 command. The annotations are repeated for each command which is input.
20674 @findex pre-overload-choice
20675 @findex overload-choice
20676 @findex post-overload-choice
20677 @item overload-choice
20678 When @value{GDBN} wants the user to select between various overloaded functions.
20684 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
20686 @findex pre-prompt-for-continue
20687 @findex prompt-for-continue
20688 @findex post-prompt-for-continue
20689 @item prompt-for-continue
20690 When @value{GDBN} is asking the user to press return to continue. Note: Don't
20691 expect this to work well; instead use @code{set height 0} to disable
20692 prompting. This is because the counting of lines is buggy in the
20693 presence of annotations.
20698 @cindex annotations for errors, warnings and interrupts
20705 This annotation occurs right before @value{GDBN} responds to an interrupt.
20712 This annotation occurs right before @value{GDBN} responds to an error.
20714 Quit and error annotations indicate that any annotations which @value{GDBN} was
20715 in the middle of may end abruptly. For example, if a
20716 @code{value-history-begin} annotation is followed by a @code{error}, one
20717 cannot expect to receive the matching @code{value-history-end}. One
20718 cannot expect not to receive it either, however; an error annotation
20719 does not necessarily mean that @value{GDBN} is immediately returning all the way
20722 @findex error-begin
20723 A quit or error annotation may be preceded by
20729 Any output between that and the quit or error annotation is the error
20732 Warning messages are not yet annotated.
20733 @c If we want to change that, need to fix warning(), type_error(),
20734 @c range_error(), and possibly other places.
20737 @section Invalidation Notices
20739 @cindex annotations for invalidation messages
20740 The following annotations say that certain pieces of state may have
20744 @findex frames-invalid
20745 @item ^Z^Zframes-invalid
20747 The frames (for example, output from the @code{backtrace} command) may
20750 @findex breakpoints-invalid
20751 @item ^Z^Zbreakpoints-invalid
20753 The breakpoints may have changed. For example, the user just added or
20754 deleted a breakpoint.
20757 @node Annotations for Running
20758 @section Running the Program
20759 @cindex annotations for running programs
20763 When the program starts executing due to a @value{GDBN} command such as
20764 @code{step} or @code{continue},
20770 is output. When the program stops,
20776 is output. Before the @code{stopped} annotation, a variety of
20777 annotations describe how the program stopped.
20781 @item ^Z^Zexited @var{exit-status}
20782 The program exited, and @var{exit-status} is the exit status (zero for
20783 successful exit, otherwise nonzero).
20786 @findex signal-name
20787 @findex signal-name-end
20788 @findex signal-string
20789 @findex signal-string-end
20790 @item ^Z^Zsignalled
20791 The program exited with a signal. After the @code{^Z^Zsignalled}, the
20792 annotation continues:
20798 ^Z^Zsignal-name-end
20802 ^Z^Zsignal-string-end
20807 where @var{name} is the name of the signal, such as @code{SIGILL} or
20808 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
20809 as @code{Illegal Instruction} or @code{Segmentation fault}.
20810 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
20811 user's benefit and have no particular format.
20815 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
20816 just saying that the program received the signal, not that it was
20817 terminated with it.
20820 @item ^Z^Zbreakpoint @var{number}
20821 The program hit breakpoint number @var{number}.
20824 @item ^Z^Zwatchpoint @var{number}
20825 The program hit watchpoint number @var{number}.
20828 @node Source Annotations
20829 @section Displaying Source
20830 @cindex annotations for source display
20833 The following annotation is used instead of displaying source code:
20836 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
20839 where @var{filename} is an absolute file name indicating which source
20840 file, @var{line} is the line number within that file (where 1 is the
20841 first line in the file), @var{character} is the character position
20842 within the file (where 0 is the first character in the file) (for most
20843 debug formats this will necessarily point to the beginning of a line),
20844 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
20845 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
20846 @var{addr} is the address in the target program associated with the
20847 source which is being displayed. @var{addr} is in the form @samp{0x}
20848 followed by one or more lowercase hex digits (note that this does not
20849 depend on the language).
20852 @chapter Reporting Bugs in @value{GDBN}
20853 @cindex bugs in @value{GDBN}
20854 @cindex reporting bugs in @value{GDBN}
20856 Your bug reports play an essential role in making @value{GDBN} reliable.
20858 Reporting a bug may help you by bringing a solution to your problem, or it
20859 may not. But in any case the principal function of a bug report is to help
20860 the entire community by making the next version of @value{GDBN} work better. Bug
20861 reports are your contribution to the maintenance of @value{GDBN}.
20863 In order for a bug report to serve its purpose, you must include the
20864 information that enables us to fix the bug.
20867 * Bug Criteria:: Have you found a bug?
20868 * Bug Reporting:: How to report bugs
20872 @section Have you found a bug?
20873 @cindex bug criteria
20875 If you are not sure whether you have found a bug, here are some guidelines:
20878 @cindex fatal signal
20879 @cindex debugger crash
20880 @cindex crash of debugger
20882 If the debugger gets a fatal signal, for any input whatever, that is a
20883 @value{GDBN} bug. Reliable debuggers never crash.
20885 @cindex error on valid input
20887 If @value{GDBN} produces an error message for valid input, that is a
20888 bug. (Note that if you're cross debugging, the problem may also be
20889 somewhere in the connection to the target.)
20891 @cindex invalid input
20893 If @value{GDBN} does not produce an error message for invalid input,
20894 that is a bug. However, you should note that your idea of
20895 ``invalid input'' might be our idea of ``an extension'' or ``support
20896 for traditional practice''.
20899 If you are an experienced user of debugging tools, your suggestions
20900 for improvement of @value{GDBN} are welcome in any case.
20903 @node Bug Reporting
20904 @section How to report bugs
20905 @cindex bug reports
20906 @cindex @value{GDBN} bugs, reporting
20908 A number of companies and individuals offer support for @sc{gnu} products.
20909 If you obtained @value{GDBN} from a support organization, we recommend you
20910 contact that organization first.
20912 You can find contact information for many support companies and
20913 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
20915 @c should add a web page ref...
20917 In any event, we also recommend that you submit bug reports for
20918 @value{GDBN}. The prefered method is to submit them directly using
20919 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
20920 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
20923 @strong{Do not send bug reports to @samp{info-gdb}, or to
20924 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
20925 not want to receive bug reports. Those that do have arranged to receive
20928 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
20929 serves as a repeater. The mailing list and the newsgroup carry exactly
20930 the same messages. Often people think of posting bug reports to the
20931 newsgroup instead of mailing them. This appears to work, but it has one
20932 problem which can be crucial: a newsgroup posting often lacks a mail
20933 path back to the sender. Thus, if we need to ask for more information,
20934 we may be unable to reach you. For this reason, it is better to send
20935 bug reports to the mailing list.
20937 The fundamental principle of reporting bugs usefully is this:
20938 @strong{report all the facts}. If you are not sure whether to state a
20939 fact or leave it out, state it!
20941 Often people omit facts because they think they know what causes the
20942 problem and assume that some details do not matter. Thus, you might
20943 assume that the name of the variable you use in an example does not matter.
20944 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
20945 stray memory reference which happens to fetch from the location where that
20946 name is stored in memory; perhaps, if the name were different, the contents
20947 of that location would fool the debugger into doing the right thing despite
20948 the bug. Play it safe and give a specific, complete example. That is the
20949 easiest thing for you to do, and the most helpful.
20951 Keep in mind that the purpose of a bug report is to enable us to fix the
20952 bug. It may be that the bug has been reported previously, but neither
20953 you nor we can know that unless your bug report is complete and
20956 Sometimes people give a few sketchy facts and ask, ``Does this ring a
20957 bell?'' Those bug reports are useless, and we urge everyone to
20958 @emph{refuse to respond to them} except to chide the sender to report
20961 To enable us to fix the bug, you should include all these things:
20965 The version of @value{GDBN}. @value{GDBN} announces it if you start
20966 with no arguments; you can also print it at any time using @code{show
20969 Without this, we will not know whether there is any point in looking for
20970 the bug in the current version of @value{GDBN}.
20973 The type of machine you are using, and the operating system name and
20977 What compiler (and its version) was used to compile @value{GDBN}---e.g.
20978 ``@value{GCC}--2.8.1''.
20981 What compiler (and its version) was used to compile the program you are
20982 debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
20983 C Compiler''. For GCC, you can say @code{gcc --version} to get this
20984 information; for other compilers, see the documentation for those
20988 The command arguments you gave the compiler to compile your example and
20989 observe the bug. For example, did you use @samp{-O}? To guarantee
20990 you will not omit something important, list them all. A copy of the
20991 Makefile (or the output from make) is sufficient.
20993 If we were to try to guess the arguments, we would probably guess wrong
20994 and then we might not encounter the bug.
20997 A complete input script, and all necessary source files, that will
21001 A description of what behavior you observe that you believe is
21002 incorrect. For example, ``It gets a fatal signal.''
21004 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
21005 will certainly notice it. But if the bug is incorrect output, we might
21006 not notice unless it is glaringly wrong. You might as well not give us
21007 a chance to make a mistake.
21009 Even if the problem you experience is a fatal signal, you should still
21010 say so explicitly. Suppose something strange is going on, such as, your
21011 copy of @value{GDBN} is out of synch, or you have encountered a bug in
21012 the C library on your system. (This has happened!) Your copy might
21013 crash and ours would not. If you told us to expect a crash, then when
21014 ours fails to crash, we would know that the bug was not happening for
21015 us. If you had not told us to expect a crash, then we would not be able
21016 to draw any conclusion from our observations.
21019 @cindex recording a session script
21020 To collect all this information, you can use a session recording program
21021 such as @command{script}, which is available on many Unix systems.
21022 Just run your @value{GDBN} session inside @command{script} and then
21023 include the @file{typescript} file with your bug report.
21025 Another way to record a @value{GDBN} session is to run @value{GDBN}
21026 inside Emacs and then save the entire buffer to a file.
21029 If you wish to suggest changes to the @value{GDBN} source, send us context
21030 diffs. If you even discuss something in the @value{GDBN} source, refer to
21031 it by context, not by line number.
21033 The line numbers in our development sources will not match those in your
21034 sources. Your line numbers would convey no useful information to us.
21038 Here are some things that are not necessary:
21042 A description of the envelope of the bug.
21044 Often people who encounter a bug spend a lot of time investigating
21045 which changes to the input file will make the bug go away and which
21046 changes will not affect it.
21048 This is often time consuming and not very useful, because the way we
21049 will find the bug is by running a single example under the debugger
21050 with breakpoints, not by pure deduction from a series of examples.
21051 We recommend that you save your time for something else.
21053 Of course, if you can find a simpler example to report @emph{instead}
21054 of the original one, that is a convenience for us. Errors in the
21055 output will be easier to spot, running under the debugger will take
21056 less time, and so on.
21058 However, simplification is not vital; if you do not want to do this,
21059 report the bug anyway and send us the entire test case you used.
21062 A patch for the bug.
21064 A patch for the bug does help us if it is a good one. But do not omit
21065 the necessary information, such as the test case, on the assumption that
21066 a patch is all we need. We might see problems with your patch and decide
21067 to fix the problem another way, or we might not understand it at all.
21069 Sometimes with a program as complicated as @value{GDBN} it is very hard to
21070 construct an example that will make the program follow a certain path
21071 through the code. If you do not send us the example, we will not be able
21072 to construct one, so we will not be able to verify that the bug is fixed.
21074 And if we cannot understand what bug you are trying to fix, or why your
21075 patch should be an improvement, we will not install it. A test case will
21076 help us to understand.
21079 A guess about what the bug is or what it depends on.
21081 Such guesses are usually wrong. Even we cannot guess right about such
21082 things without first using the debugger to find the facts.
21085 @c The readline documentation is distributed with the readline code
21086 @c and consists of the two following files:
21088 @c inc-hist.texinfo
21089 @c Use -I with makeinfo to point to the appropriate directory,
21090 @c environment var TEXINPUTS with TeX.
21091 @include rluser.texinfo
21092 @include inc-hist.texinfo
21095 @node Formatting Documentation
21096 @appendix Formatting Documentation
21098 @cindex @value{GDBN} reference card
21099 @cindex reference card
21100 The @value{GDBN} 4 release includes an already-formatted reference card, ready
21101 for printing with PostScript or Ghostscript, in the @file{gdb}
21102 subdirectory of the main source directory@footnote{In
21103 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
21104 release.}. If you can use PostScript or Ghostscript with your printer,
21105 you can print the reference card immediately with @file{refcard.ps}.
21107 The release also includes the source for the reference card. You
21108 can format it, using @TeX{}, by typing:
21114 The @value{GDBN} reference card is designed to print in @dfn{landscape}
21115 mode on US ``letter'' size paper;
21116 that is, on a sheet 11 inches wide by 8.5 inches
21117 high. You will need to specify this form of printing as an option to
21118 your @sc{dvi} output program.
21120 @cindex documentation
21122 All the documentation for @value{GDBN} comes as part of the machine-readable
21123 distribution. The documentation is written in Texinfo format, which is
21124 a documentation system that uses a single source file to produce both
21125 on-line information and a printed manual. You can use one of the Info
21126 formatting commands to create the on-line version of the documentation
21127 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
21129 @value{GDBN} includes an already formatted copy of the on-line Info
21130 version of this manual in the @file{gdb} subdirectory. The main Info
21131 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
21132 subordinate files matching @samp{gdb.info*} in the same directory. If
21133 necessary, you can print out these files, or read them with any editor;
21134 but they are easier to read using the @code{info} subsystem in @sc{gnu}
21135 Emacs or the standalone @code{info} program, available as part of the
21136 @sc{gnu} Texinfo distribution.
21138 If you want to format these Info files yourself, you need one of the
21139 Info formatting programs, such as @code{texinfo-format-buffer} or
21142 If you have @code{makeinfo} installed, and are in the top level
21143 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
21144 version @value{GDBVN}), you can make the Info file by typing:
21151 If you want to typeset and print copies of this manual, you need @TeX{},
21152 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
21153 Texinfo definitions file.
21155 @TeX{} is a typesetting program; it does not print files directly, but
21156 produces output files called @sc{dvi} files. To print a typeset
21157 document, you need a program to print @sc{dvi} files. If your system
21158 has @TeX{} installed, chances are it has such a program. The precise
21159 command to use depends on your system; @kbd{lpr -d} is common; another
21160 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
21161 require a file name without any extension or a @samp{.dvi} extension.
21163 @TeX{} also requires a macro definitions file called
21164 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
21165 written in Texinfo format. On its own, @TeX{} cannot either read or
21166 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
21167 and is located in the @file{gdb-@var{version-number}/texinfo}
21170 If you have @TeX{} and a @sc{dvi} printer program installed, you can
21171 typeset and print this manual. First switch to the the @file{gdb}
21172 subdirectory of the main source directory (for example, to
21173 @file{gdb-@value{GDBVN}/gdb}) and type:
21179 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
21181 @node Installing GDB
21182 @appendix Installing @value{GDBN}
21183 @cindex configuring @value{GDBN}
21184 @cindex installation
21185 @cindex configuring @value{GDBN}, and source tree subdirectories
21187 @value{GDBN} comes with a @code{configure} script that automates the process
21188 of preparing @value{GDBN} for installation; you can then use @code{make} to
21189 build the @code{gdb} program.
21191 @c irrelevant in info file; it's as current as the code it lives with.
21192 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
21193 look at the @file{README} file in the sources; we may have improved the
21194 installation procedures since publishing this manual.}
21197 The @value{GDBN} distribution includes all the source code you need for
21198 @value{GDBN} in a single directory, whose name is usually composed by
21199 appending the version number to @samp{gdb}.
21201 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
21202 @file{gdb-@value{GDBVN}} directory. That directory contains:
21205 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
21206 script for configuring @value{GDBN} and all its supporting libraries
21208 @item gdb-@value{GDBVN}/gdb
21209 the source specific to @value{GDBN} itself
21211 @item gdb-@value{GDBVN}/bfd
21212 source for the Binary File Descriptor library
21214 @item gdb-@value{GDBVN}/include
21215 @sc{gnu} include files
21217 @item gdb-@value{GDBVN}/libiberty
21218 source for the @samp{-liberty} free software library
21220 @item gdb-@value{GDBVN}/opcodes
21221 source for the library of opcode tables and disassemblers
21223 @item gdb-@value{GDBVN}/readline
21224 source for the @sc{gnu} command-line interface
21226 @item gdb-@value{GDBVN}/glob
21227 source for the @sc{gnu} filename pattern-matching subroutine
21229 @item gdb-@value{GDBVN}/mmalloc
21230 source for the @sc{gnu} memory-mapped malloc package
21233 The simplest way to configure and build @value{GDBN} is to run @code{configure}
21234 from the @file{gdb-@var{version-number}} source directory, which in
21235 this example is the @file{gdb-@value{GDBVN}} directory.
21237 First switch to the @file{gdb-@var{version-number}} source directory
21238 if you are not already in it; then run @code{configure}. Pass the
21239 identifier for the platform on which @value{GDBN} will run as an
21245 cd gdb-@value{GDBVN}
21246 ./configure @var{host}
21251 where @var{host} is an identifier such as @samp{sun4} or
21252 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
21253 (You can often leave off @var{host}; @code{configure} tries to guess the
21254 correct value by examining your system.)
21256 Running @samp{configure @var{host}} and then running @code{make} builds the
21257 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
21258 libraries, then @code{gdb} itself. The configured source files, and the
21259 binaries, are left in the corresponding source directories.
21262 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
21263 system does not recognize this automatically when you run a different
21264 shell, you may need to run @code{sh} on it explicitly:
21267 sh configure @var{host}
21270 If you run @code{configure} from a directory that contains source
21271 directories for multiple libraries or programs, such as the
21272 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
21273 creates configuration files for every directory level underneath (unless
21274 you tell it not to, with the @samp{--norecursion} option).
21276 You should run the @code{configure} script from the top directory in the
21277 source tree, the @file{gdb-@var{version-number}} directory. If you run
21278 @code{configure} from one of the subdirectories, you will configure only
21279 that subdirectory. That is usually not what you want. In particular,
21280 if you run the first @code{configure} from the @file{gdb} subdirectory
21281 of the @file{gdb-@var{version-number}} directory, you will omit the
21282 configuration of @file{bfd}, @file{readline}, and other sibling
21283 directories of the @file{gdb} subdirectory. This leads to build errors
21284 about missing include files such as @file{bfd/bfd.h}.
21286 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
21287 However, you should make sure that the shell on your path (named by
21288 the @samp{SHELL} environment variable) is publicly readable. Remember
21289 that @value{GDBN} uses the shell to start your program---some systems refuse to
21290 let @value{GDBN} debug child processes whose programs are not readable.
21293 * Separate Objdir:: Compiling @value{GDBN} in another directory
21294 * Config Names:: Specifying names for hosts and targets
21295 * Configure Options:: Summary of options for configure
21298 @node Separate Objdir
21299 @section Compiling @value{GDBN} in another directory
21301 If you want to run @value{GDBN} versions for several host or target machines,
21302 you need a different @code{gdb} compiled for each combination of
21303 host and target. @code{configure} is designed to make this easy by
21304 allowing you to generate each configuration in a separate subdirectory,
21305 rather than in the source directory. If your @code{make} program
21306 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
21307 @code{make} in each of these directories builds the @code{gdb}
21308 program specified there.
21310 To build @code{gdb} in a separate directory, run @code{configure}
21311 with the @samp{--srcdir} option to specify where to find the source.
21312 (You also need to specify a path to find @code{configure}
21313 itself from your working directory. If the path to @code{configure}
21314 would be the same as the argument to @samp{--srcdir}, you can leave out
21315 the @samp{--srcdir} option; it is assumed.)
21317 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
21318 separate directory for a Sun 4 like this:
21322 cd gdb-@value{GDBVN}
21325 ../gdb-@value{GDBVN}/configure sun4
21330 When @code{configure} builds a configuration using a remote source
21331 directory, it creates a tree for the binaries with the same structure
21332 (and using the same names) as the tree under the source directory. In
21333 the example, you'd find the Sun 4 library @file{libiberty.a} in the
21334 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
21335 @file{gdb-sun4/gdb}.
21337 Make sure that your path to the @file{configure} script has just one
21338 instance of @file{gdb} in it. If your path to @file{configure} looks
21339 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
21340 one subdirectory of @value{GDBN}, not the whole package. This leads to
21341 build errors about missing include files such as @file{bfd/bfd.h}.
21343 One popular reason to build several @value{GDBN} configurations in separate
21344 directories is to configure @value{GDBN} for cross-compiling (where
21345 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
21346 programs that run on another machine---the @dfn{target}).
21347 You specify a cross-debugging target by
21348 giving the @samp{--target=@var{target}} option to @code{configure}.
21350 When you run @code{make} to build a program or library, you must run
21351 it in a configured directory---whatever directory you were in when you
21352 called @code{configure} (or one of its subdirectories).
21354 The @code{Makefile} that @code{configure} generates in each source
21355 directory also runs recursively. If you type @code{make} in a source
21356 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
21357 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
21358 will build all the required libraries, and then build GDB.
21360 When you have multiple hosts or targets configured in separate
21361 directories, you can run @code{make} on them in parallel (for example,
21362 if they are NFS-mounted on each of the hosts); they will not interfere
21366 @section Specifying names for hosts and targets
21368 The specifications used for hosts and targets in the @code{configure}
21369 script are based on a three-part naming scheme, but some short predefined
21370 aliases are also supported. The full naming scheme encodes three pieces
21371 of information in the following pattern:
21374 @var{architecture}-@var{vendor}-@var{os}
21377 For example, you can use the alias @code{sun4} as a @var{host} argument,
21378 or as the value for @var{target} in a @code{--target=@var{target}}
21379 option. The equivalent full name is @samp{sparc-sun-sunos4}.
21381 The @code{configure} script accompanying @value{GDBN} does not provide
21382 any query facility to list all supported host and target names or
21383 aliases. @code{configure} calls the Bourne shell script
21384 @code{config.sub} to map abbreviations to full names; you can read the
21385 script, if you wish, or you can use it to test your guesses on
21386 abbreviations---for example:
21389 % sh config.sub i386-linux
21391 % sh config.sub alpha-linux
21392 alpha-unknown-linux-gnu
21393 % sh config.sub hp9k700
21395 % sh config.sub sun4
21396 sparc-sun-sunos4.1.1
21397 % sh config.sub sun3
21398 m68k-sun-sunos4.1.1
21399 % sh config.sub i986v
21400 Invalid configuration `i986v': machine `i986v' not recognized
21404 @code{config.sub} is also distributed in the @value{GDBN} source
21405 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
21407 @node Configure Options
21408 @section @code{configure} options
21410 Here is a summary of the @code{configure} options and arguments that
21411 are most often useful for building @value{GDBN}. @code{configure} also has
21412 several other options not listed here. @inforef{What Configure
21413 Does,,configure.info}, for a full explanation of @code{configure}.
21416 configure @r{[}--help@r{]}
21417 @r{[}--prefix=@var{dir}@r{]}
21418 @r{[}--exec-prefix=@var{dir}@r{]}
21419 @r{[}--srcdir=@var{dirname}@r{]}
21420 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
21421 @r{[}--target=@var{target}@r{]}
21426 You may introduce options with a single @samp{-} rather than
21427 @samp{--} if you prefer; but you may abbreviate option names if you use
21432 Display a quick summary of how to invoke @code{configure}.
21434 @item --prefix=@var{dir}
21435 Configure the source to install programs and files under directory
21438 @item --exec-prefix=@var{dir}
21439 Configure the source to install programs under directory
21442 @c avoid splitting the warning from the explanation:
21444 @item --srcdir=@var{dirname}
21445 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
21446 @code{make} that implements the @code{VPATH} feature.}@*
21447 Use this option to make configurations in directories separate from the
21448 @value{GDBN} source directories. Among other things, you can use this to
21449 build (or maintain) several configurations simultaneously, in separate
21450 directories. @code{configure} writes configuration specific files in
21451 the current directory, but arranges for them to use the source in the
21452 directory @var{dirname}. @code{configure} creates directories under
21453 the working directory in parallel to the source directories below
21456 @item --norecursion
21457 Configure only the directory level where @code{configure} is executed; do not
21458 propagate configuration to subdirectories.
21460 @item --target=@var{target}
21461 Configure @value{GDBN} for cross-debugging programs running on the specified
21462 @var{target}. Without this option, @value{GDBN} is configured to debug
21463 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
21465 There is no convenient way to generate a list of all available targets.
21467 @item @var{host} @dots{}
21468 Configure @value{GDBN} to run on the specified @var{host}.
21470 There is no convenient way to generate a list of all available hosts.
21473 There are many other options available as well, but they are generally
21474 needed for special purposes only.
21476 @node Maintenance Commands
21477 @appendix Maintenance Commands
21478 @cindex maintenance commands
21479 @cindex internal commands
21481 In addition to commands intended for @value{GDBN} users, @value{GDBN}
21482 includes a number of commands intended for @value{GDBN} developers,
21483 that are not documented elsewhere in this manual. These commands are
21484 provided here for reference. (For commands that turn on debugging
21485 messages, see @ref{Debugging Output}.)
21488 @kindex maint agent
21489 @item maint agent @var{expression}
21490 Translate the given @var{expression} into remote agent bytecodes.
21491 This command is useful for debugging the Agent Expression mechanism
21492 (@pxref{Agent Expressions}).
21494 @kindex maint info breakpoints
21495 @item @anchor{maint info breakpoints}maint info breakpoints
21496 Using the same format as @samp{info breakpoints}, display both the
21497 breakpoints you've set explicitly, and those @value{GDBN} is using for
21498 internal purposes. Internal breakpoints are shown with negative
21499 breakpoint numbers. The type column identifies what kind of breakpoint
21504 Normal, explicitly set breakpoint.
21507 Normal, explicitly set watchpoint.
21510 Internal breakpoint, used to handle correctly stepping through
21511 @code{longjmp} calls.
21513 @item longjmp resume
21514 Internal breakpoint at the target of a @code{longjmp}.
21517 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
21520 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
21523 Shared library events.
21527 @kindex maint check-symtabs
21528 @item maint check-symtabs
21529 Check the consistency of psymtabs and symtabs.
21531 @kindex maint cplus first_component
21532 @item maint cplus first_component @var{name}
21533 Print the first C@t{++} class/namespace component of @var{name}.
21535 @kindex maint cplus namespace
21536 @item maint cplus namespace
21537 Print the list of possible C@t{++} namespaces.
21539 @kindex maint demangle
21540 @item maint demangle @var{name}
21541 Demangle a C@t{++} or Objective-C manled @var{name}.
21543 @kindex maint deprecate
21544 @kindex maint undeprecate
21545 @cindex deprecated commands
21546 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
21547 @itemx maint undeprecate @var{command}
21548 Deprecate or undeprecate the named @var{command}. Deprecated commands
21549 cause @value{GDBN} to issue a warning when you use them. The optional
21550 argument @var{replacement} says which newer command should be used in
21551 favor of the deprecated one; if it is given, @value{GDBN} will mention
21552 the replacement as part of the warning.
21554 @kindex maint dump-me
21555 @item maint dump-me
21556 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
21557 Cause a fatal signal in the debugger and force it to dump its core.
21558 This is supported only on systems which support aborting a program
21559 with the @code{SIGQUIT} signal.
21561 @kindex maint internal-error
21562 @kindex maint internal-warning
21563 @item maint internal-error @r{[}@var{message-text}@r{]}
21564 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
21565 Cause @value{GDBN} to call the internal function @code{internal_error}
21566 or @code{internal_warning} and hence behave as though an internal error
21567 or internal warning has been detected. In addition to reporting the
21568 internal problem, these functions give the user the opportunity to
21569 either quit @value{GDBN} or create a core file of the current
21570 @value{GDBN} session.
21572 These commands take an optional parameter @var{message-text} that is
21573 used as the text of the error or warning message.
21575 Here's an example of using @code{indernal-error}:
21578 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
21579 @dots{}/maint.c:121: internal-error: testing, 1, 2
21580 A problem internal to GDB has been detected. Further
21581 debugging may prove unreliable.
21582 Quit this debugging session? (y or n) @kbd{n}
21583 Create a core file? (y or n) @kbd{n}
21587 @kindex maint packet
21588 @item maint packet @var{text}
21589 If @value{GDBN} is talking to an inferior via the serial protocol,
21590 then this command sends the string @var{text} to the inferior, and
21591 displays the response packet. @value{GDBN} supplies the initial
21592 @samp{$} character, the terminating @samp{#} character, and the
21595 @kindex maint print architecture
21596 @item maint print architecture @r{[}@var{file}@r{]}
21597 Print the entire architecture configuration. The optional argument
21598 @var{file} names the file where the output goes.
21600 @kindex maint print dummy-frames
21601 @item maint print dummy-frames
21602 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
21605 (@value{GDBP}) @kbd{b add}
21607 (@value{GDBP}) @kbd{print add(2,3)}
21608 Breakpoint 2, add (a=2, b=3) at @dots{}
21610 The program being debugged stopped while in a function called from GDB.
21612 (@value{GDBP}) @kbd{maint print dummy-frames}
21613 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
21614 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
21615 call_lo=0x01014000 call_hi=0x01014001
21619 Takes an optional file parameter.
21621 @kindex maint print registers
21622 @kindex maint print raw-registers
21623 @kindex maint print cooked-registers
21624 @kindex maint print register-groups
21625 @item maint print registers @r{[}@var{file}@r{]}
21626 @itemx maint print raw-registers @r{[}@var{file}@r{]}
21627 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
21628 @itemx maint print register-groups @r{[}@var{file}@r{]}
21629 Print @value{GDBN}'s internal register data structures.
21631 The command @code{maint print raw-registers} includes the contents of
21632 the raw register cache; the command @code{maint print cooked-registers}
21633 includes the (cooked) value of all registers; and the command
21634 @code{maint print register-groups} includes the groups that each
21635 register is a member of. @xref{Registers,, Registers, gdbint,
21636 @value{GDBN} Internals}.
21638 These commands take an optional parameter, a file name to which to
21639 write the information.
21641 @kindex maint print reggroups
21642 @item maint print reggroups @r{[}@var{file}@r{]}
21643 Print @value{GDBN}'s internal register group data structures. The
21644 optional argument @var{file} tells to what file to write the
21647 The register groups info looks like this:
21650 (@value{GDBP}) @kbd{maint print reggroups}
21663 This command forces @value{GDBN} to flush its internal register cache.
21665 @kindex maint print objfiles
21666 @cindex info for known object files
21667 @item maint print objfiles
21668 Print a dump of all known object files. For each object file, this
21669 command prints its name, address in memory, and all of its psymtabs
21672 @kindex maint print statistics
21673 @cindex bcache statistics
21674 @item maint print statistics
21675 This command prints, for each object file in the program, various data
21676 about that object file followed by the byte cache (@dfn{bcache})
21677 statistics for the object file. The objfile data includes the number
21678 of minimal, partical, full, and stabs symbols, the number of types
21679 defined by the objfile, the number of as yet unexpanded psym tables,
21680 the number of line tables and string tables, and the amount of memory
21681 used by the various tables. The bcache statistics include the counts,
21682 sizes, and counts of duplicates of all and unique objects, max,
21683 average, and median entry size, total memory used and its overhead and
21684 savings, and various measures of the hash table size and chain
21687 @kindex maint print type
21688 @cindex type chain of a data type
21689 @item maint print type @var{expr}
21690 Print the type chain for a type specified by @var{expr}. The argument
21691 can be either a type name or a symbol. If it is a symbol, the type of
21692 that symbol is described. The type chain produced by this command is
21693 a recursive definition of the data type as stored in @value{GDBN}'s
21694 data structures, including its flags and contained types.
21696 @kindex maint set dwarf2 max-cache-age
21697 @kindex maint show dwarf2 max-cache-age
21698 @item maint set dwarf2 max-cache-age
21699 @itemx maint show dwarf2 max-cache-age
21700 Control the DWARF 2 compilation unit cache.
21702 @cindex DWARF 2 compilation units cache
21703 In object files with inter-compilation-unit references, such as those
21704 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
21705 reader needs to frequently refer to previously read compilation units.
21706 This setting controls how long a compilation unit will remain in the
21707 cache if it is not referenced. A higher limit means that cached
21708 compilation units will be stored in memory longer, and more total
21709 memory will be used. Setting it to zero disables caching, which will
21710 slow down @value{GDBN} startup, but reduce memory consumption.
21712 @kindex maint set profile
21713 @kindex maint show profile
21714 @cindex profiling GDB
21715 @item maint set profile
21716 @itemx maint show profile
21717 Control profiling of @value{GDBN}.
21719 Profiling will be disabled until you use the @samp{maint set profile}
21720 command to enable it. When you enable profiling, the system will begin
21721 collecting timing and execution count data; when you disable profiling or
21722 exit @value{GDBN}, the results will be written to a log file. Remember that
21723 if you use profiling, @value{GDBN} will overwrite the profiling log file
21724 (often called @file{gmon.out}). If you have a record of important profiling
21725 data in a @file{gmon.out} file, be sure to move it to a safe location.
21727 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
21728 compiled with the @samp{-pg} compiler option.
21730 @kindex maint show-debug-regs
21731 @cindex x86 hardware debug registers
21732 @item maint show-debug-regs
21733 Control whether to show variables that mirror the x86 hardware debug
21734 registers. Use @code{ON} to enable, @code{OFF} to disable. If
21735 enabled, the debug registers values are shown when GDB inserts or
21736 removes a hardware breakpoint or watchpoint, and when the inferior
21737 triggers a hardware-assisted breakpoint or watchpoint.
21739 @kindex maint space
21740 @cindex memory used by commands
21742 Control whether to display memory usage for each command. If set to a
21743 nonzero value, @value{GDBN} will display how much memory each command
21744 took, following the command's own output. This can also be requested
21745 by invoking @value{GDBN} with the @option{--statistics} command-line
21746 switch (@pxref{Mode Options}).
21749 @cindex time of command execution
21751 Control whether to display the execution time for each command. If
21752 set to a nonzero value, @value{GDBN} will display how much time it
21753 took to execute each command, following the command's own output.
21754 This can also be requested by invoking @value{GDBN} with the
21755 @option{--statistics} command-line switch (@pxref{Mode Options}).
21757 @kindex maint translate-address
21758 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
21759 Find the symbol stored at the location specified by the address
21760 @var{addr} and an optional section name @var{section}. If found,
21761 @value{GDBN} prints the name of the closest symbol and an offset from
21762 the symbol's location to the specified address. This is similar to
21763 the @code{info address} command (@pxref{Symbols}), except that this
21764 command also allows to find symbols in other sections.
21768 The following command is useful for non-interactive invocations of
21769 @value{GDBN}, such as in the test suite.
21772 @item set watchdog @var{nsec}
21773 @kindex set watchdog
21774 @cindex watchdog timer
21775 @cindex timeout for commands
21776 Set the maximum number of seconds @value{GDBN} will wait for the
21777 target operation to finish. If this time expires, @value{GDBN}
21778 reports and error and the command is aborted.
21780 @item show watchdog
21781 Show the current setting of the target wait timeout.
21784 @node Remote Protocol
21785 @appendix @value{GDBN} Remote Serial Protocol
21790 * Stop Reply Packets::
21791 * General Query Packets::
21792 * Register Packet Format::
21794 * File-I/O remote protocol extension::
21800 There may be occasions when you need to know something about the
21801 protocol---for example, if there is only one serial port to your target
21802 machine, you might want your program to do something special if it
21803 recognizes a packet meant for @value{GDBN}.
21805 In the examples below, @samp{->} and @samp{<-} are used to indicate
21806 transmitted and received data respectfully.
21808 @cindex protocol, @value{GDBN} remote serial
21809 @cindex serial protocol, @value{GDBN} remote
21810 @cindex remote serial protocol
21811 All @value{GDBN} commands and responses (other than acknowledgments) are
21812 sent as a @var{packet}. A @var{packet} is introduced with the character
21813 @samp{$}, the actual @var{packet-data}, and the terminating character
21814 @samp{#} followed by a two-digit @var{checksum}:
21817 @code{$}@var{packet-data}@code{#}@var{checksum}
21821 @cindex checksum, for @value{GDBN} remote
21823 The two-digit @var{checksum} is computed as the modulo 256 sum of all
21824 characters between the leading @samp{$} and the trailing @samp{#} (an
21825 eight bit unsigned checksum).
21827 Implementors should note that prior to @value{GDBN} 5.0 the protocol
21828 specification also included an optional two-digit @var{sequence-id}:
21831 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
21834 @cindex sequence-id, for @value{GDBN} remote
21836 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
21837 has never output @var{sequence-id}s. Stubs that handle packets added
21838 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
21840 @cindex acknowledgment, for @value{GDBN} remote
21841 When either the host or the target machine receives a packet, the first
21842 response expected is an acknowledgment: either @samp{+} (to indicate
21843 the package was received correctly) or @samp{-} (to request
21847 -> @code{$}@var{packet-data}@code{#}@var{checksum}
21852 The host (@value{GDBN}) sends @var{command}s, and the target (the
21853 debugging stub incorporated in your program) sends a @var{response}. In
21854 the case of step and continue @var{command}s, the response is only sent
21855 when the operation has completed (the target has again stopped).
21857 @var{packet-data} consists of a sequence of characters with the
21858 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
21861 Fields within the packet should be separated using @samp{,} @samp{;} or
21862 @cindex remote protocol, field separator
21863 @samp{:}. Except where otherwise noted all numbers are represented in
21864 @sc{hex} with leading zeros suppressed.
21866 Implementors should note that prior to @value{GDBN} 5.0, the character
21867 @samp{:} could not appear as the third character in a packet (as it
21868 would potentially conflict with the @var{sequence-id}).
21870 Response @var{data} can be run-length encoded to save space. A @samp{*}
21871 means that the next character is an @sc{ascii} encoding giving a repeat count
21872 which stands for that many repetitions of the character preceding the
21873 @samp{*}. The encoding is @code{n+29}, yielding a printable character
21874 where @code{n >=3} (which is where rle starts to win). The printable
21875 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
21876 value greater than 126 should not be used.
21883 means the same as "0000".
21885 The error response returned for some packets includes a two character
21886 error number. That number is not well defined.
21888 For any @var{command} not supported by the stub, an empty response
21889 (@samp{$#00}) should be returned. That way it is possible to extend the
21890 protocol. A newer @value{GDBN} can tell if a packet is supported based
21893 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
21894 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
21900 The following table provides a complete list of all currently defined
21901 @var{command}s and their corresponding response @var{data}.
21902 @xref{File-I/O remote protocol extension}, for details about the File
21903 I/O extension of the remote protocol.
21907 @item @code{!} --- extended mode
21908 @cindex @code{!} packet
21910 Enable extended mode. In extended mode, the remote server is made
21911 persistent. The @samp{R} packet is used to restart the program being
21917 The remote target both supports and has enabled extended mode.
21920 @item @code{?} --- last signal
21921 @cindex @code{?} packet
21923 Indicate the reason the target halted. The reply is the same as for
21927 @xref{Stop Reply Packets}, for the reply specifications.
21929 @item @code{a} --- reserved
21931 Reserved for future use.
21933 @item @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,@dots{}} --- set program arguments @strong{(reserved)}
21934 @cindex @code{A} packet
21936 Initialized @samp{argv[]} array passed into program. @var{arglen}
21937 specifies the number of bytes in the hex encoded byte stream @var{arg}.
21938 See @code{gdbserver} for more details.
21946 @item @code{b}@var{baud} --- set baud @strong{(deprecated)}
21947 @cindex @code{b} packet
21949 Change the serial line speed to @var{baud}.
21951 JTC: @emph{When does the transport layer state change? When it's
21952 received, or after the ACK is transmitted. In either case, there are
21953 problems if the command or the acknowledgment packet is dropped.}
21955 Stan: @emph{If people really wanted to add something like this, and get
21956 it working for the first time, they ought to modify ser-unix.c to send
21957 some kind of out-of-band message to a specially-setup stub and have the
21958 switch happen "in between" packets, so that from remote protocol's point
21959 of view, nothing actually happened.}
21961 @item @code{B}@var{addr},@var{mode} --- set breakpoint @strong{(deprecated)}
21962 @cindex @code{B} packet
21964 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
21965 breakpoint at @var{addr}.
21967 This packet has been replaced by the @samp{Z} and @samp{z} packets
21968 (@pxref{insert breakpoint or watchpoint packet}).
21970 @item @code{c}@var{addr} --- continue
21971 @cindex @code{c} packet
21973 @var{addr} is address to resume. If @var{addr} is omitted, resume at
21977 @xref{Stop Reply Packets}, for the reply specifications.
21979 @item @code{C}@var{sig}@code{;}@var{addr} --- continue with signal
21980 @cindex @code{C} packet
21982 Continue with signal @var{sig} (hex signal number). If
21983 @code{;}@var{addr} is omitted, resume at same address.
21986 @xref{Stop Reply Packets}, for the reply specifications.
21988 @item @code{d} --- toggle debug @strong{(deprecated)}
21989 @cindex @code{d} packet
21993 @item @code{D} --- detach
21994 @cindex @code{D} packet
21996 Detach @value{GDBN} from the remote system. Sent to the remote target
21997 before @value{GDBN} disconnects via the @code{detach} command.
22001 @item @emph{no response}
22002 @value{GDBN} does not check for any response after sending this packet.
22005 @item @code{e} --- reserved
22007 Reserved for future use.
22009 @item @code{E} --- reserved
22011 Reserved for future use.
22013 @item @code{f} --- reserved
22015 Reserved for future use.
22017 @item @code{F}@var{RC}@code{,}@var{EE}@code{,}@var{CF}@code{;}@var{XX} --- Reply to target's F packet.
22018 @cindex @code{F} packet
22020 This packet is send by @value{GDBN} as reply to a @code{F} request packet
22021 sent by the target. This is part of the File-I/O protocol extension.
22022 @xref{File-I/O remote protocol extension}, for the specification.
22024 @item @code{g} --- read registers
22025 @anchor{read registers packet}
22026 @cindex @code{g} packet
22028 Read general registers.
22032 @item @var{XX@dots{}}
22033 Each byte of register data is described by two hex digits. The bytes
22034 with the register are transmitted in target byte order. The size of
22035 each register and their position within the @samp{g} @var{packet} are
22036 determined by the @value{GDBN} internal macros
22037 @var{DEPRECATED_REGISTER_RAW_SIZE} and @var{REGISTER_NAME} macros. The
22038 specification of several standard @code{g} packets is specified below.
22043 @item @code{G}@var{XX@dots{}} --- write regs
22044 @cindex @code{G} packet
22046 @xref{read registers packet}, for a description of the @var{XX@dots{}}
22057 @item @code{h} --- reserved
22059 Reserved for future use.
22061 @item @code{H}@var{c}@var{t@dots{}} --- set thread
22062 @cindex @code{H} packet
22064 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
22065 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
22066 should be @samp{c} for step and continue operations, @samp{g} for other
22067 operations. The thread designator @var{t@dots{}} may be -1, meaning all
22068 the threads, a thread number, or zero which means pick any thread.
22079 @c 'H': How restrictive (or permissive) is the thread model. If a
22080 @c thread is selected and stopped, are other threads allowed
22081 @c to continue to execute? As I mentioned above, I think the
22082 @c semantics of each command when a thread is selected must be
22083 @c described. For example:
22085 @c 'g': If the stub supports threads and a specific thread is
22086 @c selected, returns the register block from that thread;
22087 @c otherwise returns current registers.
22089 @c 'G' If the stub supports threads and a specific thread is
22090 @c selected, sets the registers of the register block of
22091 @c that thread; otherwise sets current registers.
22093 @item @code{i}@var{addr}@code{,}@var{nnn} --- cycle step @strong{(draft)}
22094 @anchor{cycle step packet}
22095 @cindex @code{i} packet
22097 Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
22098 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
22099 step starting at that address.
22101 @item @code{I} --- signal then cycle step @strong{(reserved)}
22102 @cindex @code{I} packet
22104 @xref{step with signal packet}. @xref{cycle step packet}.
22106 @item @code{j} --- reserved
22108 Reserved for future use.
22110 @item @code{J} --- reserved
22112 Reserved for future use.
22114 @item @code{k} --- kill request
22115 @cindex @code{k} packet
22117 FIXME: @emph{There is no description of how to operate when a specific
22118 thread context has been selected (i.e.@: does 'k' kill only that
22121 @item @code{K} --- reserved
22123 Reserved for future use.
22125 @item @code{l} --- reserved
22127 Reserved for future use.
22129 @item @code{L} --- reserved
22131 Reserved for future use.
22133 @item @code{m}@var{addr}@code{,}@var{length} --- read memory
22134 @cindex @code{m} packet
22136 Read @var{length} bytes of memory starting at address @var{addr}.
22137 Neither @value{GDBN} nor the stub assume that sized memory transfers are
22138 assumed using word aligned accesses. FIXME: @emph{A word aligned memory
22139 transfer mechanism is needed.}
22143 @item @var{XX@dots{}}
22144 @var{XX@dots{}} is mem contents. Can be fewer bytes than requested if able
22145 to read only part of the data. Neither @value{GDBN} nor the stub assume
22146 that sized memory transfers are assumed using word aligned
22147 accesses. FIXME: @emph{A word aligned memory transfer mechanism is
22153 @item @code{M}@var{addr},@var{length}@code{:}@var{XX@dots{}} --- write mem
22154 @cindex @code{M} packet
22156 Write @var{length} bytes of memory starting at address @var{addr}.
22157 @var{XX@dots{}} is the data.
22164 for an error (this includes the case where only part of the data was
22168 @item @code{n} --- reserved
22170 Reserved for future use.
22172 @item @code{N} --- reserved
22174 Reserved for future use.
22176 @item @code{o} --- reserved
22178 Reserved for future use.
22180 @item @code{O} --- reserved
22182 @item @code{p}@var{hex number of register} --- read register packet
22183 @cindex @code{p} packet
22185 @xref{read registers packet}, for a description of how the returned
22186 register value is encoded.
22190 @item @var{XX@dots{}}
22191 the register's value
22195 Indicating an unrecognized @var{query}.
22198 @item @code{P}@var{n@dots{}}@code{=}@var{r@dots{}} --- write register
22199 @anchor{write register packet}
22200 @cindex @code{P} packet
22202 Write register @var{n@dots{}} with value @var{r@dots{}}, which contains two hex
22203 digits for each byte in the register (target byte order).
22213 @item @code{q}@var{query} --- general query
22214 @anchor{general query packet}
22215 @cindex @code{q} packet
22217 Request info about @var{query}. In general @value{GDBN} queries have a
22218 leading upper case letter. Custom vendor queries should use a company
22219 prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may optionally
22220 be followed by a @samp{,} or @samp{;} separated list. Stubs must ensure
22221 that they match the full @var{query} name.
22225 @item @var{XX@dots{}}
22226 Hex encoded data from query. The reply can not be empty.
22230 Indicating an unrecognized @var{query}.
22233 @item @code{Q}@var{var}@code{=}@var{val} --- general set
22234 @cindex @code{Q} packet
22236 Set value of @var{var} to @var{val}.
22238 @xref{general query packet}, for a discussion of naming conventions.
22240 @item @code{r} --- reset @strong{(deprecated)}
22241 @cindex @code{r} packet
22243 Reset the entire system.
22245 @item @code{R}@var{XX} --- remote restart
22246 @cindex @code{R} packet
22248 Restart the program being debugged. @var{XX}, while needed, is ignored.
22249 This packet is only available in extended mode.
22253 @item @emph{no reply}
22254 The @samp{R} packet has no reply.
22257 @item @code{s}@var{addr} --- step
22258 @cindex @code{s} packet
22260 @var{addr} is address to resume. If @var{addr} is omitted, resume at
22264 @xref{Stop Reply Packets}, for the reply specifications.
22266 @item @code{S}@var{sig}@code{;}@var{addr} --- step with signal
22267 @anchor{step with signal packet}
22268 @cindex @code{S} packet
22270 Like @samp{C} but step not continue.
22273 @xref{Stop Reply Packets}, for the reply specifications.
22275 @item @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} --- search
22276 @cindex @code{t} packet
22278 Search backwards starting at address @var{addr} for a match with pattern
22279 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
22280 @var{addr} must be at least 3 digits.
22282 @item @code{T}@var{XX} --- thread alive
22283 @cindex @code{T} packet
22285 Find out if the thread XX is alive.
22290 thread is still alive
22295 @item @code{u} --- reserved
22297 Reserved for future use.
22299 @item @code{U} --- reserved
22301 Reserved for future use.
22303 @item @code{v} --- verbose packet prefix
22305 Packets starting with @code{v} are identified by a multi-letter name,
22306 up to the first @code{;} or @code{?} (or the end of the packet).
22308 @item @code{vCont}[;@var{action}[@code{:}@var{tid}]]... --- extended resume
22309 @cindex @code{vCont} packet
22311 Resume the inferior. Different actions may be specified for each thread.
22312 If an action is specified with no @var{tid}, then it is applied to any
22313 threads that don't have a specific action specified; if no default action is
22314 specified then other threads should remain stopped. Specifying multiple
22315 default actions is an error; specifying no actions is also an error.
22316 Thread IDs are specified in hexadecimal. Currently supported actions are:
22322 Continue with signal @var{sig}. @var{sig} should be two hex digits.
22326 Step with signal @var{sig}. @var{sig} should be two hex digits.
22329 The optional @var{addr} argument normally associated with these packets is
22330 not supported in @code{vCont}.
22333 @xref{Stop Reply Packets}, for the reply specifications.
22335 @item @code{vCont?} --- extended resume query
22336 @cindex @code{vCont?} packet
22338 Query support for the @code{vCont} packet.
22342 @item @code{vCont}[;@var{action}]...
22343 The @code{vCont} packet is supported. Each @var{action} is a supported
22344 command in the @code{vCont} packet.
22346 The @code{vCont} packet is not supported.
22349 @item @code{V} --- reserved
22351 Reserved for future use.
22353 @item @code{w} --- reserved
22355 Reserved for future use.
22357 @item @code{W} --- reserved
22359 Reserved for future use.
22361 @item @code{x} --- reserved
22363 Reserved for future use.
22365 @item @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX@dots{}} --- write mem (binary)
22366 @cindex @code{X} packet
22368 @var{addr} is address, @var{length} is number of bytes, @var{XX@dots{}}
22369 is binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
22370 escaped using @code{0x7d}, and then XORed with @code{0x20}.
22371 For example, @code{0x7d} would be transmitted as @code{0x7d 0x5d}.
22381 @item @code{y} --- reserved
22383 Reserved for future use.
22385 @item @code{Y} reserved
22387 Reserved for future use.
22389 @item @code{z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- remove breakpoint or watchpoint @strong{(draft)}
22390 @itemx @code{Z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- insert breakpoint or watchpoint @strong{(draft)}
22391 @anchor{insert breakpoint or watchpoint packet}
22392 @cindex @code{z} packet
22393 @cindex @code{Z} packets
22395 Insert (@code{Z}) or remove (@code{z}) a @var{type} breakpoint or
22396 watchpoint starting at address @var{address} and covering the next
22397 @var{length} bytes.
22399 Each breakpoint and watchpoint packet @var{type} is documented
22402 @emph{Implementation notes: A remote target shall return an empty string
22403 for an unrecognized breakpoint or watchpoint packet @var{type}. A
22404 remote target shall support either both or neither of a given
22405 @code{Z}@var{type}@dots{} and @code{z}@var{type}@dots{} packet pair. To
22406 avoid potential problems with duplicate packets, the operations should
22407 be implemented in an idempotent way.}
22409 @item @code{z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- remove memory breakpoint @strong{(draft)}
22410 @item @code{Z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- insert memory breakpoint @strong{(draft)}
22411 @cindex @code{z0} packet
22412 @cindex @code{Z0} packet
22414 Insert (@code{Z0}) or remove (@code{z0}) a memory breakpoint at address
22415 @code{addr} of size @code{length}.
22417 A memory breakpoint is implemented by replacing the instruction at
22418 @var{addr} with a software breakpoint or trap instruction. The
22419 @code{length} is used by targets that indicates the size of the
22420 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
22421 @sc{mips} can insert either a 2 or 4 byte breakpoint).
22423 @emph{Implementation note: It is possible for a target to copy or move
22424 code that contains memory breakpoints (e.g., when implementing
22425 overlays). The behavior of this packet, in the presence of such a
22426 target, is not defined.}
22438 @item @code{z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- remove hardware breakpoint @strong{(draft)}
22439 @item @code{Z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- insert hardware breakpoint @strong{(draft)}
22440 @cindex @code{z1} packet
22441 @cindex @code{Z1} packet
22443 Insert (@code{Z1}) or remove (@code{z1}) a hardware breakpoint at
22444 address @code{addr} of size @code{length}.
22446 A hardware breakpoint is implemented using a mechanism that is not
22447 dependant on being able to modify the target's memory.
22449 @emph{Implementation note: A hardware breakpoint is not affected by code
22462 @item @code{z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- remove write watchpoint @strong{(draft)}
22463 @item @code{Z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- insert write watchpoint @strong{(draft)}
22464 @cindex @code{z2} packet
22465 @cindex @code{Z2} packet
22467 Insert (@code{Z2}) or remove (@code{z2}) a write watchpoint.
22479 @item @code{z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- remove read watchpoint @strong{(draft)}
22480 @item @code{Z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- insert read watchpoint @strong{(draft)}
22481 @cindex @code{z3} packet
22482 @cindex @code{Z3} packet
22484 Insert (@code{Z3}) or remove (@code{z3}) a read watchpoint.
22496 @item @code{z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- remove access watchpoint @strong{(draft)}
22497 @item @code{Z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- insert access watchpoint @strong{(draft)}
22498 @cindex @code{z4} packet
22499 @cindex @code{Z4} packet
22501 Insert (@code{Z4}) or remove (@code{z4}) an access watchpoint.
22515 @node Stop Reply Packets
22516 @section Stop Reply Packets
22517 @cindex stop reply packets
22519 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
22520 receive any of the below as a reply. In the case of the @samp{C},
22521 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
22522 when the target halts. In the below the exact meaning of @samp{signal
22523 number} is poorly defined. In general one of the UNIX signal numbering
22524 conventions is used.
22529 @var{AA} is the signal number
22531 @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
22532 @cindex @code{T} packet reply
22534 @var{AA} = two hex digit signal number; @var{n...} = register number
22535 (hex), @var{r...} = target byte ordered register contents, size defined
22536 by @code{DEPRECATED_REGISTER_RAW_SIZE}; @var{n...} = @samp{thread},
22537 @var{r...} = thread process ID, this is a hex integer; @var{n...} =
22538 (@samp{watch} | @samp{rwatch} | @samp{awatch}, @var{r...} = data
22539 address, this is a hex integer; @var{n...} = other string not starting
22540 with valid hex digit. @value{GDBN} should ignore this @var{n...},
22541 @var{r...} pair and go on to the next. This way we can extend the
22546 The process exited, and @var{AA} is the exit status. This is only
22547 applicable to certain targets.
22551 The process terminated with signal @var{AA}.
22553 @item O@var{XX@dots{}}
22555 @var{XX@dots{}} is hex encoding of @sc{ascii} data. This can happen at
22556 any time while the program is running and the debugger should continue
22557 to wait for @samp{W}, @samp{T}, etc.
22559 @item F@var{call-id}@code{,}@var{parameter@dots{}}
22561 @var{call-id} is the identifier which says which host system call should
22562 be called. This is just the name of the function. Translation into the
22563 correct system call is only applicable as it's defined in @value{GDBN}.
22564 @xref{File-I/O remote protocol extension}, for a list of implemented
22567 @var{parameter@dots{}} is a list of parameters as defined for this very
22570 The target replies with this packet when it expects @value{GDBN} to call
22571 a host system call on behalf of the target. @value{GDBN} replies with
22572 an appropriate @code{F} packet and keeps up waiting for the next reply
22573 packet from the target. The latest @samp{C}, @samp{c}, @samp{S} or
22574 @samp{s} action is expected to be continued.
22575 @xref{File-I/O remote protocol extension}, for more details.
22579 @node General Query Packets
22580 @section General Query Packets
22581 @cindex remote query requests
22583 The following set and query packets have already been defined.
22587 @item @code{q}@code{C} --- current thread
22588 @cindex current thread, remote request
22589 @cindex @code{qC} packet
22590 Return the current thread id.
22594 @item @code{QC}@var{pid}
22595 Where @var{pid} is an unsigned hexidecimal process id.
22597 Any other reply implies the old pid.
22600 @item @code{q}@code{fThreadInfo} -- all thread ids
22601 @cindex list active threads, remote request
22602 @cindex @code{qfThreadInfo} packet
22603 @code{q}@code{sThreadInfo}
22605 Obtain a list of active thread ids from the target (OS). Since there
22606 may be too many active threads to fit into one reply packet, this query
22607 works iteratively: it may require more than one query/reply sequence to
22608 obtain the entire list of threads. The first query of the sequence will
22609 be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
22610 sequence will be the @code{qs}@code{ThreadInfo} query.
22612 NOTE: replaces the @code{qL} query (see below).
22616 @item @code{m}@var{id}
22618 @item @code{m}@var{id},@var{id}@dots{}
22619 a comma-separated list of thread ids
22621 (lower case 'el') denotes end of list.
22624 In response to each query, the target will reply with a list of one or
22625 more thread ids, in big-endian unsigned hex, separated by commas.
22626 @value{GDBN} will respond to each reply with a request for more thread
22627 ids (using the @code{qs} form of the query), until the target responds
22628 with @code{l} (lower-case el, for @code{'last'}).
22630 @item @code{q}@code{ThreadExtraInfo}@code{,}@var{id} --- extra thread info
22631 @cindex thread attributes info, remote request
22632 @cindex @code{qThreadExtraInfo} packet
22633 Where @var{id} is a thread-id in big-endian hex. Obtain a printable
22634 string description of a thread's attributes from the target OS. This
22635 string may contain anything that the target OS thinks is interesting for
22636 @value{GDBN} to tell the user about the thread. The string is displayed
22637 in @value{GDBN}'s @samp{info threads} display. Some examples of
22638 possible thread extra info strings are ``Runnable'', or ``Blocked on
22643 @item @var{XX@dots{}}
22644 Where @var{XX@dots{}} is a hex encoding of @sc{ascii} data, comprising
22645 the printable string containing the extra information about the thread's
22649 @item @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} --- query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
22651 Obtain thread information from RTOS. Where: @var{startflag} (one hex
22652 digit) is one to indicate the first query and zero to indicate a
22653 subsequent query; @var{threadcount} (two hex digits) is the maximum
22654 number of threads the response packet can contain; and @var{nextthread}
22655 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
22656 returned in the response as @var{argthread}.
22658 NOTE: this query is replaced by the @code{q}@code{fThreadInfo} query
22663 @item @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread@dots{}}
22664 Where: @var{count} (two hex digits) is the number of threads being
22665 returned; @var{done} (one hex digit) is zero to indicate more threads
22666 and one indicates no further threads; @var{argthreadid} (eight hex
22667 digits) is @var{nextthread} from the request packet; @var{thread@dots{}}
22668 is a sequence of thread IDs from the target. @var{threadid} (eight hex
22669 digits). See @code{remote.c:parse_threadlist_response()}.
22672 @item @code{q}@code{CRC:}@var{addr}@code{,}@var{length} --- compute CRC of memory block
22673 @cindex CRC of memory block, remote request
22674 @cindex @code{qCRC} packet
22677 @item @code{E}@var{NN}
22678 An error (such as memory fault)
22679 @item @code{C}@var{CRC32}
22680 A 32 bit cyclic redundancy check of the specified memory region.
22683 @item @code{q}@code{Offsets} --- query sect offs
22684 @cindex section offsets, remote request
22685 @cindex @code{qOffsets} packet
22686 Get section offsets that the target used when re-locating the downloaded
22687 image. @emph{Note: while a @code{Bss} offset is included in the
22688 response, @value{GDBN} ignores this and instead applies the @code{Data}
22689 offset to the @code{Bss} section.}
22693 @item @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
22696 @item @code{q}@code{P}@var{mode}@var{threadid} --- thread info request
22697 @cindex thread information, remote request
22698 @cindex @code{qP} packet
22699 Returns information on @var{threadid}. Where: @var{mode} is a hex
22700 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
22707 See @code{remote.c:remote_unpack_thread_info_response()}.
22709 @item @code{q}@code{Rcmd,}@var{command} --- remote command
22710 @cindex execute remote command, remote request
22711 @cindex @code{qRcmd} packet
22712 @var{command} (hex encoded) is passed to the local interpreter for
22713 execution. Invalid commands should be reported using the output string.
22714 Before the final result packet, the target may also respond with a
22715 number of intermediate @code{O}@var{output} console output packets.
22716 @emph{Implementors should note that providing access to a stubs's
22717 interpreter may have security implications}.
22722 A command response with no output.
22724 A command response with the hex encoded output string @var{OUTPUT}.
22725 @item @code{E}@var{NN}
22726 Indicate a badly formed request.
22728 When @samp{q}@samp{Rcmd} is not recognized.
22731 @item @code{qSymbol::} --- symbol lookup
22732 @cindex symbol lookup, remote request
22733 @cindex @code{qSymbol} packet
22734 Notify the target that @value{GDBN} is prepared to serve symbol lookup
22735 requests. Accept requests from the target for the values of symbols.
22740 The target does not need to look up any (more) symbols.
22741 @item @code{qSymbol:}@var{sym_name}
22742 The target requests the value of symbol @var{sym_name} (hex encoded).
22743 @value{GDBN} may provide the value by using the
22744 @code{qSymbol:}@var{sym_value}:@var{sym_name} message, described below.
22747 @item @code{qSymbol:}@var{sym_value}:@var{sym_name} --- symbol value
22749 Set the value of @var{sym_name} to @var{sym_value}.
22751 @var{sym_name} (hex encoded) is the name of a symbol whose value the
22752 target has previously requested.
22754 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
22755 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
22761 The target does not need to look up any (more) symbols.
22762 @item @code{qSymbol:}@var{sym_name}
22763 The target requests the value of a new symbol @var{sym_name} (hex
22764 encoded). @value{GDBN} will continue to supply the values of symbols
22765 (if available), until the target ceases to request them.
22768 @item @code{qPart}:@var{object}:@code{read}:@var{annex}:@var{offset},@var{length} --- read special data
22769 @cindex read special object, remote request
22770 @cindex @code{qPart} packet
22771 Read uninterpreted bytes from the target's special data area
22772 identified by the keyword @code{object}.
22773 Request @var{length} bytes starting at @var{offset} bytes into the data.
22774 The content and encoding of @var{annex} is specific to the object;
22775 it can supply additional details about what data to access.
22777 Here are the specific requests of this form defined so far.
22778 All @samp{@code{qPart}:@var{object}:@code{read}:@dots{}}
22779 requests use the same reply formats, listed below.
22782 @item @code{qPart}:@code{auxv}:@code{read}::@var{offset},@var{length}
22783 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
22784 auxiliary vector}, and see @ref{Remote configuration,
22785 read-aux-vector-packet}. Note @var{annex} must be empty.
22791 The @var{offset} in the request is at the end of the data.
22792 There is no more data to be read.
22794 @item @var{XX@dots{}}
22795 Hex encoded data bytes read.
22796 This may be fewer bytes than the @var{length} in the request.
22799 The request was malformed, or @var{annex} was invalid.
22801 @item @code{E}@var{nn}
22802 The offset was invalid, or there was an error encountered reading the data.
22803 @var{nn} is a hex-encoded @code{errno} value.
22805 @item @code{""} (empty)
22806 An empty reply indicates the @var{object} or @var{annex} string was not
22807 recognized by the stub.
22810 @item @code{qPart}:@var{object}:@code{write}:@var{annex}:@var{offset}:@var{data@dots{}}
22811 @cindex write data into object, remote request
22812 Write uninterpreted bytes into the target's special data area
22813 identified by the keyword @code{object},
22814 starting at @var{offset} bytes into the data.
22815 @var{data@dots{}} is the hex-encoded data to be written.
22816 The content and encoding of @var{annex} is specific to the object;
22817 it can supply additional details about what data to access.
22819 No requests of this form are presently in use. This specification
22820 serves as a placeholder to document the common format that new
22821 specific request specifications ought to use.
22826 @var{nn} (hex encoded) is the number of bytes written.
22827 This may be fewer bytes than supplied in the request.
22830 The request was malformed, or @var{annex} was invalid.
22832 @item @code{E}@var{nn}
22833 The offset was invalid, or there was an error encountered writing the data.
22834 @var{nn} is a hex-encoded @code{errno} value.
22836 @item @code{""} (empty)
22837 An empty reply indicates the @var{object} or @var{annex} string was not
22838 recognized by the stub, or that the object does not support writing.
22841 @item @code{qPart}:@var{object}:@var{operation}:@dots{}
22842 Requests of this form may be added in the future. When a stub does
22843 not recognize the @var{object} keyword, or its support for
22844 @var{object} does not recognize the @var{operation} keyword,
22845 the stub must respond with an empty packet.
22847 @item @code{qGetTLSAddr}:@var{thread-id},@var{offset},@var{lm} --- get thread local storage address
22848 @cindex get thread-local storage address, remote request
22849 @cindex @code{qGetTLSAddr} packet
22850 Fetch the address associated with thread local storage specified
22851 by @var{thread-id}, @var{offset}, and @var{lm}.
22853 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
22854 thread for which to fetch the TLS address.
22856 @var{offset} is the (big endian, hex encoded) offset associated with the
22857 thread local variable. (This offset is obtained from the debug
22858 information associated with the variable.)
22860 @var{lm} is the (big endian, hex encoded) OS/ABI specific encoding of the
22861 the load module associated with the thread local storage. For example,
22862 a @sc{gnu}/Linux system will pass the link map address of the shared
22863 object associated with the thread local storage under consideration.
22864 Other operating environments may choose to represent the load module
22865 differently, so the precise meaning of this parameter will vary.
22869 @item @var{XX@dots{}}
22870 Hex encoded (big endian) bytes representing the address of the thread
22871 local storage requested.
22873 @item @code{E}@var{nn} (where @var{nn} are hex digits)
22876 @item @code{""} (empty)
22877 An empty reply indicates that @code{qGetTLSAddr} is not supported by the stub.
22880 Use of this request packet is controlled by the @code{set remote
22881 get-thread-local-storage-address} command (@pxref{Remote
22882 configuration, set remote get-thread-local-storage-address}).
22886 @node Register Packet Format
22887 @section Register Packet Format
22889 The following @samp{g}/@samp{G} packets have previously been defined.
22890 In the below, some thirty-two bit registers are transferred as
22891 sixty-four bits. Those registers should be zero/sign extended (which?)
22892 to fill the space allocated. Register bytes are transfered in target
22893 byte order. The two nibbles within a register byte are transfered
22894 most-significant - least-significant.
22900 All registers are transfered as thirty-two bit quantities in the order:
22901 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
22902 registers; fsr; fir; fp.
22906 All registers are transfered as sixty-four bit quantities (including
22907 thirty-two bit registers such as @code{sr}). The ordering is the same
22915 Example sequence of a target being re-started. Notice how the restart
22916 does not get any direct output:
22921 @emph{target restarts}
22924 <- @code{T001:1234123412341234}
22928 Example sequence of a target being stepped by a single instruction:
22931 -> @code{G1445@dots{}}
22936 <- @code{T001:1234123412341234}
22940 <- @code{1455@dots{}}
22944 @node File-I/O remote protocol extension
22945 @section File-I/O remote protocol extension
22946 @cindex File-I/O remote protocol extension
22949 * File-I/O Overview::
22950 * Protocol basics::
22951 * The F request packet::
22952 * The F reply packet::
22953 * Memory transfer::
22954 * The Ctrl-C message::
22956 * The isatty call::
22957 * The system call::
22958 * List of supported calls::
22959 * Protocol specific representation of datatypes::
22961 * File-I/O Examples::
22964 @node File-I/O Overview
22965 @subsection File-I/O Overview
22966 @cindex file-i/o overview
22968 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
22969 target to use the host's file system and console I/O when calling various
22970 system calls. System calls on the target system are translated into a
22971 remote protocol packet to the host system which then performs the needed
22972 actions and returns with an adequate response packet to the target system.
22973 This simulates file system operations even on targets that lack file systems.
22975 The protocol is defined host- and target-system independent. It uses
22976 its own independent representation of datatypes and values. Both,
22977 @value{GDBN} and the target's @value{GDBN} stub are responsible for
22978 translating the system dependent values into the unified protocol values
22979 when data is transmitted.
22981 The communication is synchronous. A system call is possible only
22982 when GDB is waiting for the @samp{C}, @samp{c}, @samp{S} or @samp{s}
22983 packets. While @value{GDBN} handles the request for a system call,
22984 the target is stopped to allow deterministic access to the target's
22985 memory. Therefore File-I/O is not interuptible by target signals. It
22986 is possible to interrupt File-I/O by a user interrupt (Ctrl-C), though.
22988 The target's request to perform a host system call does not finish
22989 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
22990 after finishing the system call, the target returns to continuing the
22991 previous activity (continue, step). No additional continue or step
22992 request from @value{GDBN} is required.
22995 (@value{GDBP}) continue
22996 <- target requests 'system call X'
22997 target is stopped, @value{GDBN} executes system call
22998 -> GDB returns result
22999 ... target continues, GDB returns to wait for the target
23000 <- target hits breakpoint and sends a Txx packet
23003 The protocol is only used for files on the host file system and
23004 for I/O on the console. Character or block special devices, pipes,
23005 named pipes or sockets or any other communication method on the host
23006 system are not supported by this protocol.
23008 @node Protocol basics
23009 @subsection Protocol basics
23010 @cindex protocol basics, file-i/o
23012 The File-I/O protocol uses the @code{F} packet, as request as well
23013 as as reply packet. Since a File-I/O system call can only occur when
23014 @value{GDBN} is waiting for the continuing or stepping target, the
23015 File-I/O request is a reply that @value{GDBN} has to expect as a result
23016 of a former @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
23017 This @code{F} packet contains all information needed to allow @value{GDBN}
23018 to call the appropriate host system call:
23022 A unique identifier for the requested system call.
23025 All parameters to the system call. Pointers are given as addresses
23026 in the target memory address space. Pointers to strings are given as
23027 pointer/length pair. Numerical values are given as they are.
23028 Numerical control values are given in a protocol specific representation.
23032 At that point @value{GDBN} has to perform the following actions.
23036 If parameter pointer values are given, which point to data needed as input
23037 to a system call, @value{GDBN} requests this data from the target with a
23038 standard @code{m} packet request. This additional communication has to be
23039 expected by the target implementation and is handled as any other @code{m}
23043 @value{GDBN} translates all value from protocol representation to host
23044 representation as needed. Datatypes are coerced into the host types.
23047 @value{GDBN} calls the system call
23050 It then coerces datatypes back to protocol representation.
23053 If pointer parameters in the request packet point to buffer space in which
23054 a system call is expected to copy data to, the data is transmitted to the
23055 target using a @code{M} or @code{X} packet. This packet has to be expected
23056 by the target implementation and is handled as any other @code{M} or @code{X}
23061 Eventually @value{GDBN} replies with another @code{F} packet which contains all
23062 necessary information for the target to continue. This at least contains
23069 @code{errno}, if has been changed by the system call.
23076 After having done the needed type and value coercion, the target continues
23077 the latest continue or step action.
23079 @node The F request packet
23080 @subsection The @code{F} request packet
23081 @cindex file-i/o request packet
23082 @cindex @code{F} request packet
23084 The @code{F} request packet has the following format:
23089 @code{F}@var{call-id}@code{,}@var{parameter@dots{}}
23092 @var{call-id} is the identifier to indicate the host system call to be called.
23093 This is just the name of the function.
23095 @var{parameter@dots{}} are the parameters to the system call.
23099 Parameters are hexadecimal integer values, either the real values in case
23100 of scalar datatypes, as pointers to target buffer space in case of compound
23101 datatypes and unspecified memory areas or as pointer/length pairs in case
23102 of string parameters. These are appended to the call-id, each separated
23103 from its predecessor by a comma. All values are transmitted in ASCII
23104 string representation, pointer/length pairs separated by a slash.
23106 @node The F reply packet
23107 @subsection The @code{F} reply packet
23108 @cindex file-i/o reply packet
23109 @cindex @code{F} reply packet
23111 The @code{F} reply packet has the following format:
23116 @code{F}@var{retcode}@code{,}@var{errno}@code{,}@var{Ctrl-C flag}@code{;}@var{call specific attachment}
23119 @var{retcode} is the return code of the system call as hexadecimal value.
23121 @var{errno} is the errno set by the call, in protocol specific representation.
23122 This parameter can be omitted if the call was successful.
23124 @var{Ctrl-C flag} is only send if the user requested a break. In this
23125 case, @var{errno} must be send as well, even if the call was successful.
23126 The @var{Ctrl-C flag} itself consists of the character 'C':
23133 or, if the call was interupted before the host call has been performed:
23140 assuming 4 is the protocol specific representation of @code{EINTR}.
23144 @node Memory transfer
23145 @subsection Memory transfer
23146 @cindex memory transfer, in file-i/o protocol
23148 Structured data which is transferred using a memory read or write as e.g.@:
23149 a @code{struct stat} is expected to be in a protocol specific format with
23150 all scalar multibyte datatypes being big endian. This should be done by
23151 the target before the @code{F} packet is sent resp.@: by @value{GDBN} before
23152 it transfers memory to the target. Transferred pointers to structured
23153 data should point to the already coerced data at any time.
23155 @node The Ctrl-C message
23156 @subsection The Ctrl-C message
23157 @cindex ctrl-c message, in file-i/o protocol
23159 A special case is, if the @var{Ctrl-C flag} is set in the @value{GDBN}
23160 reply packet. In this case the target should behave, as if it had
23161 gotten a break message. The meaning for the target is ``system call
23162 interupted by @code{SIGINT}''. Consequentially, the target should actually stop
23163 (as with a break message) and return to @value{GDBN} with a @code{T02}
23164 packet. In this case, it's important for the target to know, in which
23165 state the system call was interrupted. Since this action is by design
23166 not an atomic operation, we have to differ between two cases:
23170 The system call hasn't been performed on the host yet.
23173 The system call on the host has been finished.
23177 These two states can be distinguished by the target by the value of the
23178 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
23179 call hasn't been performed. This is equivalent to the @code{EINTR} handling
23180 on POSIX systems. In any other case, the target may presume that the
23181 system call has been finished --- successful or not --- and should behave
23182 as if the break message arrived right after the system call.
23184 @value{GDBN} must behave reliable. If the system call has not been called
23185 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
23186 @code{errno} in the packet. If the system call on the host has been finished
23187 before the user requests a break, the full action must be finshed by
23188 @value{GDBN}. This requires sending @code{M} or @code{X} packets as they fit.
23189 The @code{F} packet may only be send when either nothing has happened
23190 or the full action has been completed.
23193 @subsection Console I/O
23194 @cindex console i/o as part of file-i/o
23196 By default and if not explicitely closed by the target system, the file
23197 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
23198 on the @value{GDBN} console is handled as any other file output operation
23199 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
23200 by @value{GDBN} so that after the target read request from file descriptor
23201 0 all following typing is buffered until either one of the following
23206 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, the
23208 system call is treated as finished.
23211 The user presses @kbd{Enter}. This is treated as end of input with a trailing
23215 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
23216 character, especially no Ctrl-D is appended to the input.
23220 If the user has typed more characters as fit in the buffer given to
23221 the read call, the trailing characters are buffered in @value{GDBN} until
23222 either another @code{read(0, @dots{})} is requested by the target or debugging
23223 is stopped on users request.
23225 @node The isatty call
23226 @subsection The @samp{isatty} function call
23227 @cindex isatty call, file-i/o protocol
23229 A special case in this protocol is the library call @code{isatty} which
23230 is implemented as its own call inside of this protocol. It returns
23231 1 to the target if the file descriptor given as parameter is attached
23232 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
23233 would require implementing @code{ioctl} and would be more complex than
23236 @node The system call
23237 @subsection The @samp{system} function call
23238 @cindex system call, file-i/o protocol
23240 The other special case in this protocol is the @code{system} call which
23241 is implemented as its own call, too. @value{GDBN} is taking over the full
23242 task of calling the necessary host calls to perform the @code{system}
23243 call. The return value of @code{system} is simplified before it's returned
23244 to the target. Basically, the only signal transmitted back is @code{EINTR}
23245 in case the user pressed @kbd{Ctrl-C}. Otherwise the return value consists
23246 entirely of the exit status of the called command.
23248 Due to security concerns, the @code{system} call is by default refused
23249 by @value{GDBN}. The user has to allow this call explicitly with the
23250 @kbd{set remote system-call-allowed 1} command.
23253 @item set remote system-call-allowed
23254 @kindex set remote system-call-allowed
23255 Control whether to allow the @code{system} calls in the File I/O
23256 protocol for the remote target. The default is zero (disabled).
23258 @item show remote system-call-allowed
23259 @kindex show remote system-call-allowed
23260 Show the current setting of system calls for the remote File I/O
23264 @node List of supported calls
23265 @subsection List of supported calls
23266 @cindex list of supported file-i/o calls
23283 @unnumberedsubsubsec open
23284 @cindex open, file-i/o system call
23288 int open(const char *pathname, int flags);
23289 int open(const char *pathname, int flags, mode_t mode);
23292 Fopen,pathptr/len,flags,mode
23296 @code{flags} is the bitwise or of the following values:
23300 If the file does not exist it will be created. The host
23301 rules apply as far as file ownership and time stamps
23305 When used with O_CREAT, if the file already exists it is
23306 an error and open() fails.
23309 If the file already exists and the open mode allows
23310 writing (O_RDWR or O_WRONLY is given) it will be
23311 truncated to length 0.
23314 The file is opened in append mode.
23317 The file is opened for reading only.
23320 The file is opened for writing only.
23323 The file is opened for reading and writing.
23326 Each other bit is silently ignored.
23331 @code{mode} is the bitwise or of the following values:
23335 User has read permission.
23338 User has write permission.
23341 Group has read permission.
23344 Group has write permission.
23347 Others have read permission.
23350 Others have write permission.
23353 Each other bit is silently ignored.
23358 @exdent Return value:
23359 open returns the new file descriptor or -1 if an error
23367 pathname already exists and O_CREAT and O_EXCL were used.
23370 pathname refers to a directory.
23373 The requested access is not allowed.
23376 pathname was too long.
23379 A directory component in pathname does not exist.
23382 pathname refers to a device, pipe, named pipe or socket.
23385 pathname refers to a file on a read-only filesystem and
23386 write access was requested.
23389 pathname is an invalid pointer value.
23392 No space on device to create the file.
23395 The process already has the maximum number of files open.
23398 The limit on the total number of files open on the system
23402 The call was interrupted by the user.
23406 @unnumberedsubsubsec close
23407 @cindex close, file-i/o system call
23416 @exdent Return value:
23417 close returns zero on success, or -1 if an error occurred.
23424 fd isn't a valid open file descriptor.
23427 The call was interrupted by the user.
23431 @unnumberedsubsubsec read
23432 @cindex read, file-i/o system call
23436 int read(int fd, void *buf, unsigned int count);
23439 Fread,fd,bufptr,count
23441 @exdent Return value:
23442 On success, the number of bytes read is returned.
23443 Zero indicates end of file. If count is zero, read
23444 returns zero as well. On error, -1 is returned.
23451 fd is not a valid file descriptor or is not open for
23455 buf is an invalid pointer value.
23458 The call was interrupted by the user.
23462 @unnumberedsubsubsec write
23463 @cindex write, file-i/o system call
23467 int write(int fd, const void *buf, unsigned int count);
23470 Fwrite,fd,bufptr,count
23472 @exdent Return value:
23473 On success, the number of bytes written are returned.
23474 Zero indicates nothing was written. On error, -1
23482 fd is not a valid file descriptor or is not open for
23486 buf is an invalid pointer value.
23489 An attempt was made to write a file that exceeds the
23490 host specific maximum file size allowed.
23493 No space on device to write the data.
23496 The call was interrupted by the user.
23500 @unnumberedsubsubsec lseek
23501 @cindex lseek, file-i/o system call
23505 long lseek (int fd, long offset, int flag);
23508 Flseek,fd,offset,flag
23511 @code{flag} is one of:
23515 The offset is set to offset bytes.
23518 The offset is set to its current location plus offset
23522 The offset is set to the size of the file plus offset
23527 @exdent Return value:
23528 On success, the resulting unsigned offset in bytes from
23529 the beginning of the file is returned. Otherwise, a
23530 value of -1 is returned.
23537 fd is not a valid open file descriptor.
23540 fd is associated with the @value{GDBN} console.
23543 flag is not a proper value.
23546 The call was interrupted by the user.
23550 @unnumberedsubsubsec rename
23551 @cindex rename, file-i/o system call
23555 int rename(const char *oldpath, const char *newpath);
23558 Frename,oldpathptr/len,newpathptr/len
23560 @exdent Return value:
23561 On success, zero is returned. On error, -1 is returned.
23568 newpath is an existing directory, but oldpath is not a
23572 newpath is a non-empty directory.
23575 oldpath or newpath is a directory that is in use by some
23579 An attempt was made to make a directory a subdirectory
23583 A component used as a directory in oldpath or new
23584 path is not a directory. Or oldpath is a directory
23585 and newpath exists but is not a directory.
23588 oldpathptr or newpathptr are invalid pointer values.
23591 No access to the file or the path of the file.
23595 oldpath or newpath was too long.
23598 A directory component in oldpath or newpath does not exist.
23601 The file is on a read-only filesystem.
23604 The device containing the file has no room for the new
23608 The call was interrupted by the user.
23612 @unnumberedsubsubsec unlink
23613 @cindex unlink, file-i/o system call
23617 int unlink(const char *pathname);
23620 Funlink,pathnameptr/len
23622 @exdent Return value:
23623 On success, zero is returned. On error, -1 is returned.
23630 No access to the file or the path of the file.
23633 The system does not allow unlinking of directories.
23636 The file pathname cannot be unlinked because it's
23637 being used by another process.
23640 pathnameptr is an invalid pointer value.
23643 pathname was too long.
23646 A directory component in pathname does not exist.
23649 A component of the path is not a directory.
23652 The file is on a read-only filesystem.
23655 The call was interrupted by the user.
23659 @unnumberedsubsubsec stat/fstat
23660 @cindex fstat, file-i/o system call
23661 @cindex stat, file-i/o system call
23665 int stat(const char *pathname, struct stat *buf);
23666 int fstat(int fd, struct stat *buf);
23669 Fstat,pathnameptr/len,bufptr
23672 @exdent Return value:
23673 On success, zero is returned. On error, -1 is returned.
23680 fd is not a valid open file.
23683 A directory component in pathname does not exist or the
23684 path is an empty string.
23687 A component of the path is not a directory.
23690 pathnameptr is an invalid pointer value.
23693 No access to the file or the path of the file.
23696 pathname was too long.
23699 The call was interrupted by the user.
23703 @unnumberedsubsubsec gettimeofday
23704 @cindex gettimeofday, file-i/o system call
23708 int gettimeofday(struct timeval *tv, void *tz);
23711 Fgettimeofday,tvptr,tzptr
23713 @exdent Return value:
23714 On success, 0 is returned, -1 otherwise.
23721 tz is a non-NULL pointer.
23724 tvptr and/or tzptr is an invalid pointer value.
23728 @unnumberedsubsubsec isatty
23729 @cindex isatty, file-i/o system call
23733 int isatty(int fd);
23738 @exdent Return value:
23739 Returns 1 if fd refers to the @value{GDBN} console, 0 otherwise.
23746 The call was interrupted by the user.
23750 @unnumberedsubsubsec system
23751 @cindex system, file-i/o system call
23755 int system(const char *command);
23758 Fsystem,commandptr/len
23760 @exdent Return value:
23761 The value returned is -1 on error and the return status
23762 of the command otherwise. Only the exit status of the
23763 command is returned, which is extracted from the hosts
23764 system return value by calling WEXITSTATUS(retval).
23765 In case /bin/sh could not be executed, 127 is returned.
23772 The call was interrupted by the user.
23775 @node Protocol specific representation of datatypes
23776 @subsection Protocol specific representation of datatypes
23777 @cindex protocol specific representation of datatypes, in file-i/o protocol
23780 * Integral datatypes::
23786 @node Integral datatypes
23787 @unnumberedsubsubsec Integral datatypes
23788 @cindex integral datatypes, in file-i/o protocol
23790 The integral datatypes used in the system calls are
23793 int@r{,} unsigned int@r{,} long@r{,} unsigned long@r{,} mode_t @r{and} time_t
23796 @code{Int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
23797 implemented as 32 bit values in this protocol.
23799 @code{Long} and @code{unsigned long} are implemented as 64 bit types.
23801 @xref{Limits}, for corresponding MIN and MAX values (similar to those
23802 in @file{limits.h}) to allow range checking on host and target.
23804 @code{time_t} datatypes are defined as seconds since the Epoch.
23806 All integral datatypes transferred as part of a memory read or write of a
23807 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
23810 @node Pointer values
23811 @unnumberedsubsubsec Pointer values
23812 @cindex pointer values, in file-i/o protocol
23814 Pointers to target data are transmitted as they are. An exception
23815 is made for pointers to buffers for which the length isn't
23816 transmitted as part of the function call, namely strings. Strings
23817 are transmitted as a pointer/length pair, both as hex values, e.g.@:
23824 which is a pointer to data of length 18 bytes at position 0x1aaf.
23825 The length is defined as the full string length in bytes, including
23826 the trailing null byte. Example:
23829 ``hello, world'' at address 0x123456
23840 @unnumberedsubsubsec struct stat
23841 @cindex struct stat, in file-i/o protocol
23843 The buffer of type struct stat used by the target and @value{GDBN} is defined
23848 unsigned int st_dev; /* device */
23849 unsigned int st_ino; /* inode */
23850 mode_t st_mode; /* protection */
23851 unsigned int st_nlink; /* number of hard links */
23852 unsigned int st_uid; /* user ID of owner */
23853 unsigned int st_gid; /* group ID of owner */
23854 unsigned int st_rdev; /* device type (if inode device) */
23855 unsigned long st_size; /* total size, in bytes */
23856 unsigned long st_blksize; /* blocksize for filesystem I/O */
23857 unsigned long st_blocks; /* number of blocks allocated */
23858 time_t st_atime; /* time of last access */
23859 time_t st_mtime; /* time of last modification */
23860 time_t st_ctime; /* time of last change */
23864 The integral datatypes are conforming to the definitions given in the
23865 approriate section (see @ref{Integral datatypes}, for details) so this
23866 structure is of size 64 bytes.
23868 The values of several fields have a restricted meaning and/or
23875 st_ino: No valid meaning for the target. Transmitted unchanged.
23877 st_mode: Valid mode bits are described in Appendix C. Any other
23878 bits have currently no meaning for the target.
23880 st_uid: No valid meaning for the target. Transmitted unchanged.
23882 st_gid: No valid meaning for the target. Transmitted unchanged.
23884 st_rdev: No valid meaning for the target. Transmitted unchanged.
23886 st_atime, st_mtime, st_ctime:
23887 These values have a host and file system dependent
23888 accuracy. Especially on Windows hosts the file systems
23889 don't support exact timing values.
23892 The target gets a struct stat of the above representation and is
23893 responsible to coerce it to the target representation before
23896 Note that due to size differences between the host and target
23897 representation of stat members, these members could eventually
23898 get truncated on the target.
23900 @node struct timeval
23901 @unnumberedsubsubsec struct timeval
23902 @cindex struct timeval, in file-i/o protocol
23904 The buffer of type struct timeval used by the target and @value{GDBN}
23905 is defined as follows:
23909 time_t tv_sec; /* second */
23910 long tv_usec; /* microsecond */
23914 The integral datatypes are conforming to the definitions given in the
23915 approriate section (see @ref{Integral datatypes}, for details) so this
23916 structure is of size 8 bytes.
23919 @subsection Constants
23920 @cindex constants, in file-i/o protocol
23922 The following values are used for the constants inside of the
23923 protocol. @value{GDBN} and target are resposible to translate these
23924 values before and after the call as needed.
23935 @unnumberedsubsubsec Open flags
23936 @cindex open flags, in file-i/o protocol
23938 All values are given in hexadecimal representation.
23950 @node mode_t values
23951 @unnumberedsubsubsec mode_t values
23952 @cindex mode_t values, in file-i/o protocol
23954 All values are given in octal representation.
23971 @unnumberedsubsubsec Errno values
23972 @cindex errno values, in file-i/o protocol
23974 All values are given in decimal representation.
23999 EUNKNOWN is used as a fallback error value if a host system returns
24000 any error value not in the list of supported error numbers.
24003 @unnumberedsubsubsec Lseek flags
24004 @cindex lseek flags, in file-i/o protocol
24013 @unnumberedsubsubsec Limits
24014 @cindex limits, in file-i/o protocol
24016 All values are given in decimal representation.
24019 INT_MIN -2147483648
24021 UINT_MAX 4294967295
24022 LONG_MIN -9223372036854775808
24023 LONG_MAX 9223372036854775807
24024 ULONG_MAX 18446744073709551615
24027 @node File-I/O Examples
24028 @subsection File-I/O Examples
24029 @cindex file-i/o examples
24031 Example sequence of a write call, file descriptor 3, buffer is at target
24032 address 0x1234, 6 bytes should be written:
24035 <- @code{Fwrite,3,1234,6}
24036 @emph{request memory read from target}
24039 @emph{return "6 bytes written"}
24043 Example sequence of a read call, file descriptor 3, buffer is at target
24044 address 0x1234, 6 bytes should be read:
24047 <- @code{Fread,3,1234,6}
24048 @emph{request memory write to target}
24049 -> @code{X1234,6:XXXXXX}
24050 @emph{return "6 bytes read"}
24054 Example sequence of a read call, call fails on the host due to invalid
24055 file descriptor (EBADF):
24058 <- @code{Fread,3,1234,6}
24062 Example sequence of a read call, user presses Ctrl-C before syscall on
24066 <- @code{Fread,3,1234,6}
24071 Example sequence of a read call, user presses Ctrl-C after syscall on
24075 <- @code{Fread,3,1234,6}
24076 -> @code{X1234,6:XXXXXX}
24080 @include agentexpr.texi
24094 % I think something like @colophon should be in texinfo. In the
24096 \long\def\colophon{\hbox to0pt{}\vfill
24097 \centerline{The body of this manual is set in}
24098 \centerline{\fontname\tenrm,}
24099 \centerline{with headings in {\bf\fontname\tenbf}}
24100 \centerline{and examples in {\tt\fontname\tentt}.}
24101 \centerline{{\it\fontname\tenit\/},}
24102 \centerline{{\bf\fontname\tenbf}, and}
24103 \centerline{{\sl\fontname\tensl\/}}
24104 \centerline{are used for emphasis.}\vfill}
24106 % Blame: doc@cygnus.com, 1991.